Pipes Output http://pipes.yahoo.com/pipes/pipe.info?_id=9f9d8b24eee6f920ac6285f05e0d9c73 Tue, 21 May 2013 10:57:30 +0000 http://pipes.yahoo.com/pipes/ http://feedproxy.google.com/~r/JbmrFeed/~3/nkKOR5uUl0M/doi Mon, 20 May 2013 16:35:51 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1982 http://feedproxy.google.com/~r/JbmrFeed/~3/1kFa4srjDwc/doi Osteoporosis is increasingly reported in the aging HIV-positive population, and co-infection with hepatitis C virus (HCV) may further increase the risk of osteoporosis. However, it remains unclear whether HCV-related increased fracture risk is a function of the severity of liver disease. We calculated the time-updated APRI score (an indirect marker of hepatic fibrosis) in all HIV infected patients enrolled in the Veterans Affairs' Clinical Case Registry between 1984 and 2009. The association between HCV co-infection and incident osteoporotic fracture (defined as closed wrist, vertebral or hip fracture) was assessed in univariate and multivariate Cox survival models adjusting for traditional risk factors for osteoporosis and APRI score or the presence of cirrhosis. 772 osteoporotic fractures were identified among 56,660 HIV-infected patients (98.1% male; 31.3% HCV co-infected; median age: 44.0 years) contributing 305,237 patient-years of follow-up. Fracture rates were significantly higher among HIV/HCV patients than HIV-only patients (2.57 vs. 2.07/1000 patient-years, relative risk: 1.24, p < 0.0001). In a Cox multi-variable model including age, race, smoking, drug use, BMI and antiretroviral therapy, HCV co-infection remained an independent predictor of osteoporotic fractures after controlling for presence of cirrhosis (hazard ratio [HR]: 1.32; p < 0.001) or APRI score (HR: 1.30; p = 0.003). Among HIV/HCV co-infected patients, cirrhosis strongly predicted osteoporotic fractures (HR: 1.65; 95% CI: 1.11-2.44; p = 0.012), but APRI score was a weaker predictor (HR: 1.008; 95% CI: 1.002-1.014; p = 0.015). In conclusion, among HIV-infected patients, severity of liver disease partly explains the HCV-associated increased risk of osteoporotic fractures. Other determinants of this increased risk remain to be defined. Wed, 15 May 2013 07:32:37 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1988 http://feedproxy.google.com/~r/JbmrFeed/~3/ncbtw7R5Dss/doi Siglecs are a family of sialic acid-binding immunoglobulin-like lectins that regulate the functions of cells in the innate and adaptive immune systems through glycan recognition. Here we show that Siglec-15 regulates osteoclast development and bone resorption by modulating receptor activator of nuclear factor κB ligand (RANKL) signaling in association with DNAX-activating protein 12kDa (DAP12), an adaptor protein bearing an immunoreceptor tyrosine-based activation motif (ITAM). Among the known Siglecs expressed in myeloid lineage cells, only Siglec-15 was upregulated by RANKL in mouse primary bone marrow macrophages. Siglec-15 deficient mice exhibit mild osteopetrosis due to impaired osteoclast development. Consistently, cells lacking Siglec-15 exhibit defective osteoclast development and resorptive activity in vitro. RANKL-induced activation of phosphatidylinositol 3-kinase (PI3K)/Akt and Erk pathways were impaired in Siglec-15 deficient cells. Retroviral transduction of Siglec-15 null osteoclast precursors with wild-type Siglec-15 or mutant Siglec-15 revealed that the association of Siglec15 with DAP12 is involved in the downstream signal transduction of RANK. Furthermore, we found that the ability of osteoclast formation is preserved in the region adjacent to the growth plate in Siglec-15 deficient mice, indicating that there is a compensatory mechanism for Siglec-15-mediated osteoclastogenesis in the primary spongiosa. To clarify the mechanism of this compensation, we examined whether osteoclast-associated receptor (OSCAR)/Fc receptor common γ (FcRγ) signaling, an alternative ITAM-mediated signaling pathway to DAP12, rescues impaired osteoclastogenesis in Siglec-15 deficient cells. The ligands in type II collagen activate OSCAR and rescue impaired osteoclastogenesis in Siglec-15 deficient cells when cultured on bone slices, indicating that Siglec-15 mediated signaling can be compensated for by signaling activated by type II collagen and other bone matrix components in the primary spongiosa. Our findings indicate that Siglec-15 plays an important role in physiologic bone remodeling by modulating RANKL signaling, especially in the secondary spongiosa. Wed, 15 May 2013 07:31:59 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1989 http://feedproxy.google.com/~r/JbmrFeed/~3/LS58gvqAsHQ/doi Normal mineral metabolism is critical for skeletal integrity and recently serum fibroblast Growth factor 23 (FGF23) levels were found to be directly related to overall fracture risk in elderly Swedish Men. To confirm this association, we performed a prospective case-cohort study to understand the relation of FGF23 and fracture risk in older Caucasian men enrolled in the Osteoporotic Fractures in Men (MrOS) Study. Methods In the cohort of 5994 men attending the baseline MrOS examination, we evaluated a subgroup of 387 men with incident nonvertebral fracture including 73 hip fractures and a sample of 1385 men randomly selected from the cohort with baseline mineral and calcium hormone measurements. FGF23 was measured in baseline serum samples by ELISA (Millipore, Billerica, MA). Modified Cox proportional hazards models that account for case cohort study design were used to estimate the relative hazards (RH) of fracture in men across quartiles of FGF23. Subjects were also stratified by renal function and RH per strata was estimated in men with the highest quartile of FGF23 compared to quartile 3, 2 and 1. Results Overall, there was no difference in risk of nonspine or hip fracture by baseline FGF23. However, associations differed by strata of eGFRCrCy. Among men with eGFRCrCys < 60ml/min/1.73m2 (n = 73/313 non-spine fractures), the RH in the highest quartile of FGF23 compared to the rest was 2.02 (95% CI: 1.07–3.79), but in men with eGFRCrCy, > 60ml/min/1.73m2 (304/1370 fractures) the RH was 0.91 (95% CI: 0.66–1.25) after adjustment for age, clinic site, BMI, race, total hip BMD, vitamin D, PTH, alcohol use, physical activity, fracture history and serum phosphorus. Summary Serum FGF23 levels are not associated with incident fractures in elderly men overall. However, higher levels of serum FGF23 are associated with fracture risk in those with poor renal function. Wed, 15 May 2013 07:31:47 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1985 http://feedproxy.google.com/~r/JbmrFeed/~3/45G_L9xxAvY/doi Radiographic texture analysis has been developed lately to improve the assessment of bone architecture as a determinant of bone quality. We validate here an algorithm for the evaluation of trabecular homogeneity index (HI) in the proximal femur from hip radiographs, with a focus on the impact of the principal compressive system of the trabecular bone, and evaluate its correlation with femoral strength, bone mineral density (BMD), and volumetric trabecular structure parameters. A semi-automatic custom-made algorithm was applied to calculate the HI in the femoral neck and trochanteric areas from radiographs of 178 femoral bone specimens (mean age 79.3 ± 10.4 years). Corresponding neck region was selected in CT scans to calculate volumetric parameters of trabecular structure. The site-specific BMDs were assessed from DXA, and the femoral strength was experimentally tested in side-impact configuration. Regression analysis was performed between the HI and biomechanical femoral strength, BMD, and volumetric parameters. The correlation between HI and failure load was R2 = 0.50; this result was improved to R2 = 0.58 for cervical fractures alone. The discrimination of bones with high risk of fractures (load < 3000N) were similar for HI and BMD (AUC = 0.87). Regression analysis between the HIs versus site-specific BMDs yielded R2 = 0.66 in neck area, R2 = 0.60 in trochanteric area, and an overall of R2 = 0.66 for the total hip. Neck HI and BMD correlated significantly with volumetric structure parameters. We present here a method to assess HI that can explain itself 50% of an experimental failure load and determines bones with high fracture risk with similar accuracy than BMD. The HI had also good correlation with DXA and CT-derived data. Wed, 15 May 2013 07:28:57 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1987 http://feedproxy.google.com/~r/JbmrFeed/~3/n1pXjsIYK4Q/doi Osteogenesis imperfecta (OI) is typically caused by mutations in type 1 collagen genes, but in recent years new recessive and dominant forms caused by mutations in a plethora of different genes have been characterized. OI type V is a dominant form caused by the recurrent (c.-14C > T) mutation in the 5'UTR of the IFITM5 gene. The mutation adds 5 residues to the N-terminus of the IFITM5 but the pathophysiology of the disease still remains to be elucidated. Typical clinical features present in the majority of OI type V patients include interosseous membrane calcification between the radius and ulna, and the tibia and fibula, radial head dislocation and significant hyperplastic callus formation at the site of fractures. We report a 5 year-old child with clinical features of OI type III or severe OI type IV (characteristic facies, grey sclerae, typical fractures) and absence of classical features of OI type V with a de novo recurrent IFITM5 mutation (c.-14C > T), now typical of OI type V. This highlights the variability of OI caused by IFITM5 mutations and suggests screening for mutations in this gene in most cases of OI where type 1 collagen mutations are absent. Tue, 14 May 2013 09:33:05 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1983 http://feedproxy.google.com/~r/JbmrFeed/~3/RVzJFP9iFzQ/doi Oxidative stress contributes to the pathogenesis of age-related diseases as well as bone fragility. Our previous study demonstrated that copper/zinc superoxide dismutase (Sod1)-deficient mice exhibit the induction of intracellular reactive oxygen species (ROS) and bone fragility due to low-turnover bone loss and impaired collagen cross-linking (Nojiri, H., Saita, Y., Morikawa, D., Kobayashi, K., Tsuda, C., Miyazaki, T., Saito, M., Marumo, K., Yonezawa, I., Kaneko, K., Shirasawa, T., Shimizu, T. (2011) J. Bone. Miner. Res. 26, 2682–2694). Mechanical stress also plays an important role in the maintenance of homeostasis in bone tissue. However, the molecular links between oxidative and mechanical stresses in bone tissue have not been fully elucidated. We herein report that mechanical unloading significantly increased intracellular ROS production and the specific up-regulation of Sod1 in bone tissue in a tail-suspension experiment. We also reveal that Sod1 loss exacerbated bone loss via reduced osteoblastic abilities during mechanical unloading. Interestingly, we found that the administration of an antioxidant, vitamin C, significantly attenuated bone loss during unloading. These results indicate that mechanical unloading, in part, regulates bone mass via intracellular ROS generation and the Sod1 expression, suggesting that activating Sod1 may be a preventive strategy for ameliorating mechanical unloading-induced bone loss. Tue, 14 May 2013 09:32:41 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1981 http://feedproxy.google.com/~r/JbmrFeed/~3/4JdBVJ9ZY5c/doi Annual costs are enormous for musculoskeletal diseases such as osteoporosis and sarcopenia and for bone and muscle injuries, costing billions annually in health care. While it is clear that muscle and bone development, growth and function are connected, and that muscle loads bone, little is known regarding cellular and molecular interactions between these two tissues. A conference supported by the National Institutes of Health, NIH, and the American Society for Bone and Mineral Research, ASBMR, was held in July 2012 to address the enormous burden of musculoskeletal disease. National and international experts in either bone or muscle presented their findings and their novel hypotheses regarding muscle-bone interactions in order to stimulate the exchange of ideas between these two fields. The immediate goal of the conference was to identify critical research themes that would lead to collaborative research interactions and grant applications focusing on interactions between muscle and bone. The ultimate goal of the meeting was to generate a better understanding of how these two tissues integrate and crosstalk in both health and disease in order to stimulate new therapeutic strategies to enhance and maintain musculoskeletal health. Mon, 13 May 2013 23:34:08 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1980 http://feedproxy.google.com/~r/JbmrFeed/~3/zMLKd3QaJEQ/doi Parathyroid hormone-related protein (PTHrP)(1–36) increases lumbar spine (LS) bone mineral density (BMD), acting as an anabolic agent when injected intermittently, but has not been directly compared to parathyroid hormone (PTH)(1–34). We performed a three month, randomized, prospective study in 105 postmenopausal women with low bone density or osteoporosis comparing daily subcutaneous injections of PTHrP(1–36) to PTH(1–34). Thirty-five women were randomized to each of three groups: PTHrP(1–36) 400 µg/d; PTHrP(1–36) 600 µg/d; and PTH(1–34) 20 µg/d. The primary outcomes measures were changes in amino-terminal telopeptides of procollagen 1 (PINP) and carboxy-terminal telopeptides of collagen 1 (CTX). Secondary measures included safety parameters, 1,25(OH)2vitamin D and BMD. The increase in bone resorption (CTX) by PTH(1–34) (92%) (p < 0.005) was greater than for PTHrP(1–36) (30%) (p < 0.05). PTH(1–34) also increased bone formation (PINP) (171%) (p < 0.0005) more than either dose of PTHrP(1–36) (46 & 87%). The increase in PINP was earlier (day 15) and greater than the increase in CTX for all three groups. LS BMD increased equivalently in each group (p < 0.05 for all). Total hip (TH) and femoral neck (FN) BMD increased equivalently in each group but were only significant for the two doses of PTHrP(1–36) (p < 0.05) at the TH, and for PTHrP(1–36) 400 (p < 0.05) at the FN. PTHrP(1–36) 400 induced mild, transient (day 15) hypercalcemia. PTHrP(1–36) 600 required a dose reduction for hypercalcemia in three subjects. PTH(1–34) was not associated with hypercalcemia. Each peptide induced a marked biphasic increase in 1,25(OH)2D. Adverse events (AE) were similar among the three groups. This study demonstrates that PTHrP(1–36) and PTH(1–34) cause similar increases in LS BMD. PTHrP(1–36) also increased hip BMD. PTH(1–34) induced greater changes in bone turnover than PTHrP(1–36). PTHrP(1–36) was associated with mild transient hypercalcemia. Longer term studies using lower doses of PTHrP(1–36) are needed to define both the optimal dose and full clinical benefits of PTHrP. Thu, 09 May 2013 10:40:54 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1978 http://feedproxy.google.com/~r/JbmrFeed/~3/Fq5NftpSbEg/doi We aimed to identify all patients with post-surgical hypoparathyroidism (HypoPT) and to evaluate their risks of renal complications and cardiovascular disease in relation to their disease and its treatment. We identified possible patients through the Danish National Patient Registry and a prescription database. Case status was adjudicated by review of individual patients hospital records. For each patients with post-surgical HypoPT due to surgery for non-malignant diseases between 1988 and 2012, three age (± 2 yrs) and gender matched controls were selected from the general background population. The prevalence of postsurgical HypoPT was 22/100,000. We identified 688 patients who had undergone neck surgery since 1988 with subsequent hypocalcaemia and inappropriate low PTH levels that necessitated treatment with calcium and/or vitamin D supplementation for more than 6 months. The average age at diagnosis was 49 years (range 17–87 yrs), and 88% were women. 16% of all patients had had neck surgery prior to the operation causing HypoPT. Compared with controls, patients with HypoPT had an increased risk of renal complications (HR 3.67, 95% CI 2.41;5.59) and hospitalization due to seizures (HR 3.82; 95% CI, 2.15–6.79), whereas there was no increased risk of cardiac arrhythmias (HR 1.11; 95% CI, 0.79–1.57) or cardiovascular disease or death (HR 0.89, 95% CI 0.73;1.09). In conclusion, while risk of seizures and renal complications is increased, mortality and risk of cardiovascular diseases or arrhythmias is not increased in patients with HypoPT. Further studies should try to determine how to reduce risk seizures and renal complications in HypoPT. Thu, 09 May 2013 10:03:37 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1979 http://feedproxy.google.com/~r/JbmrFeed/~3/H0uxs4NSPTI/doi The osteoclast is a giant cell that resorbs calcified matrix by secreting acids and collagenolytic enzymes. The molecular mechanisms underlying metabolic adaptation to the increased biomass and energetic demands of osteoclastic bone resorption remain elusive. Here we show that during osteoclastogenesis the expression of both Glut1 and glycolytic genes is increased, while the knockdown of HIF1α, as well as glucose deprivation, inhibits the bone-resorbing function of osteoclasts, along with a suppression of Glut1 and glycolytic gene expression. Furthermore, the expression of the glutamine transporter Slc1a5 and glutaminase 1 was increased early in differentiation, and a depletion of L-glutamine or pharmacological inhibition of the Slc1a5 transporter suppressed osteoclast differentiation and function. Inhibition of c-Myc function abrogated osteoclast differentiation and function, along with a suppression of Slc1a5 and glutaminase 1 gene expression. Genetic and pharmacological inhibition of mTOR, as well as the activation of AMPK, inhibited osteoclastogenesis. Thus, the uptake of glucose and glutamine and utilization of the carbon sources derived from them, coordinated by HIF1α and c-Myc, are essential for osteoclast development and bone-resorbing activity through a balanced regulation of the nutrient and energy sensors, mTOR and AMPK. Thu, 09 May 2013 10:03:18 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1976 http://feedproxy.google.com/~r/JbmrFeed/~3/h4H6jHPNrEw/doi Recently, safety concerns about calcium supplementation have arisen. In this situation, ensuring appropriateness of use is highly important. We aimed to describe the use of calcium and vitamin D supplements, the factors related to it, and to assess the appropriateness of calcium prescription among men and women of fifty or older. We performed a cross-sectional study in 2009–2010 including 11,035 adults who belong to the ESOSVAL cohort and attend 272 primary healthcare centres in the Valencia region (Spain). Criteria for the inappropriateness of calcium prescription, based on guidelines and recent evidence, were: excessive or insufficient daily total intake (diet plus supplements), excessive single doses of supplements, excessive or insufficient association with vitamin D, and overall inappropriateness. Calcium and/or vitamin D were prescribed to about 17% of the population. Older age, antiosteoporotic treatment, use of glucocorticoids and a diagnosis of osteoporosis were related to prescription. The presence of other secondary causes of osteoporosis determined supplementation only in men. Calcium dietary intake was not related to the prescription of supplements. Among calcium users, 85.8% met at least one criterion of inappropriate prescription; 29% had an inappropriate daily total intake mainly due to excessive consumption (>2000 mg/d); 53.8% of patients were given calcium supplements in quantities higher than 500 mg per dose; and 38.9% of individuals receiving calcium supplements had inappropriate (absent or below 800 UI/d) vitamin D supplementation (all of them at high risk). In conclusion, we found high inappropriateness of calcium supplementation, mainly due to calcium overdosing, and also to undertreatment and underdosing of Vitamin D in high-risk patients. Physicians should be encouraged to assess calcium dietary intakes before supplementation, recommending intake from food whenever possible, and to prescribe low calcium doses and high vitamin D doses when given in fixed-dose combinations, or Vitamin D alone when calcium is not necessary. Thu, 09 May 2013 08:56:32 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1977 http://feedproxy.google.com/~r/JbmrFeed/~3/80akh-ODPcg/doi It has been suggested that fracture during childhood could be a predictor of low peak bone mass, and thereby a potential risk factor for osteoporosis and fragility fractures later in life. The aim of this cross-sectional, population-based study was to investigate whether prevalent fractures, occurring from birth to young adulthood, were related to HR-pQCT derived trabecular and cortical microstructure, and bone strength estimated by finite element (FEA) analysis of the radius and tibia, in 833 young adult men around the time of peak bone mass (23–25 yrs). In total, 292 subjects with prevalent X-ray verified fractures were found. Men with prevalent fractures had lower trabecular bone volume fraction (BV/TV) at the radius (5.5%, p < 0.001) and tibia (3.7%, p < 0.001), as well as lower cortical thickness (5.1%, p < 0.01) and cortical cross-sectional area (4.1%, p < 0.01) at the tibia. No significant differences were seen for the cortical porosity or mean pore diameter. Using a logistic regression model (including age, smoking, physical activity, calcium intake, height and weight as covariates), every SD decrease of FEA estimated failure load was associated with an increased prevalence of fractures at both the radius (OR 1.22 (1.03–1.45)) and tibia (OR 1.32 (1.11–1.56)). Including DXA derived radius areal bone mineral density (aBMD), cortical thickness and trabecular BV/TV simultaneously in a logistic regression model (with age, smoking, physical activity, calcium intake, height and weight as covariates), BV/TV was inversely and independently associated with prevalent fractures (OR 1.28 (1.04–1.59)), whereas aBMD and cortical thickness were not (OR 1.19 (0.92–1.55) and OR 0.91 (0.73–1.12), respectively). In conclusion, prevalent fractures in young adult men were associated with impaired trabecular BV/TV at the radius, independently of aBMD and cortical thickness, indicating that primarily trabecular bone deficits are of greatest importance for prevalent fracture in this population. Wed, 08 May 2013 09:23:43 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1974 http://feedproxy.google.com/~r/JbmrFeed/~3/bLZaXZqdsvg/doi Background Paget's disease of bone (PDB) has a strong genetic component. Here we investigated possible associations between genetic variants that predispose to PDB and disease severity. Methods Allelic variants identified as predictors of PDB from genome wide association studies were analysed in 1940 PDB patients from the UK, Italy, Western Australia and Spain. A cumulative risk allele score was constructed by adding the variants together and related to markers of disease severity, alone and in combination with SQSTM1 mutations. Results In SQSTM1 negative patients, risk allele scores in the highest tertile were associated with a 27% increase in disease extent, compared with the lowest tertile (p < 0.00001) with intermediate values in the middle tertile (20% increase; p = 0.0007). The effects were similar for disease severity score which was 15% (p = 0.01) and 25% (p < 0.00001) higher in the middle and upper tertiles, respectively. Risk allele score remained a significant predictor of extent and severity when SQSTM1 positive individuals were included, with an effect size approximately one-third of that observed with SQSTM1 mutations. A genetic risk score was developed by combining information from both markers, which identified subgroups of individuals with low, medium and high levels severity with a specificity of 70% and sensitivity of 55%. Conclusions Risk allele scores and SQSTM1 mutations both predict extent and severity of PDB. It is possible that with further refinement, genetic profiling may be of clinical value in identifying individuals at high risk of severe disease who might benefit from enhanced surveillance and early intervention. Wed, 08 May 2013 09:17:59 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1975 http://feedproxy.google.com/~r/JbmrFeed/~3/qoN2HwlxOmo/doi Activating transcription factor 4 (ATF4) is a critical transcription factor for bone remodeling; however, its role in bone angiogenesis has not been established. Here we show that ablation of the Atf4 gene expression in mice severely impaired skeletal vasculature and reduced microvascular density of the bone associated with dramatically decreased expression of hypoxia inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) in osteoblasts located on bone surfaces. Results from in vivo studies revealed that hypoxia/reoxygenation induction of HIF-1α and VEGF expression leading to bone angiogenesis, a key adaptive response to hypoxic conditions, was severely compromised in mice lacking the Atf4 gene. Loss of ATF4 completely prevented endothelial sprouting from embryonic metatarsals, which was restored by addition of recombinant human VEGF protein. In vitro studies revealed that ATF4 promotion of HIF-1α and VEGF expression in osteoblasts was highly dependent upon the presence of hypoxia. ATF4 interacted with HIF-1α in hypoxic osteoblasts and loss of ATF4 increased HIF-1α ubiquitination and reduced its protein stability without affecting HIF-1α mRNA stability and protein translation. Loss of ATF4 increased the binding of HIF-1α to prolyl hydroxylases, the enzymes that hydroxylate HIF-1α protein and promote its proteasomal degradation via the pVHL pathway. Furthermore, parathyroid hormone-related protein (PTHrP) and receptor activator of NF-kappaB ligand (RANKL), both well-known activators of osteoclasts, increased release of VEGF from the bone matrix and promoted angiogenesis through the protein kinase C- and ATF4-dependent activation of osteoclast differentiation and bone resorption. Thus, ATF4 is a new key regulator of the HIF/VEGF axis in osteoblasts in response to hypoxia and of VEGF release from bone matrix, two critical steps for bone angiogenesis. Fri, 03 May 2013 07:14:06 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1958 http://feedproxy.google.com/~r/JbmrFeed/~3/U1nX6OC2EcM/doi Reduced bone mineral density and hip fracture are frequently observed in patients of Alzheimer's disease (AD). However, mechanisms underlying their association remain poorly understood. Amyloid precursor protein (APP) is a transmembrane protein that is ubiquitously expressed, including bone marrow stromal cells (BMSCs), osteoblasts (OBs), macrophages (BMMs), and osteoclasts (OCs). Mutations in APP gene identified in early-onset AD patients are believed to cause AD. But, little is known about APP's role in bone remodeling. Here, we present evidence for Swedish mutant APP (APPswe) in suppression of OB differentiation and function in culture and in mouse. APP expression in BMSCs increases during ageing. Ubiquitous expression of APPswe in young adult Tg2576 (under the control of prion promoter) recaptured skeletal “ageing-like” deficits, including decreased OB genesis and bone formation, increased adipogenesis and bone marrow fat, enhanced OC genesis and bone resorption. Remarkably, selective expression of APPswe in mature OB-lineage cells in TgAPPswe-Ocn mice [under the control of osteocalcin (Ocn) promoter driven Cre] also decreased OB genesis and increased OC formation, resulting in a trabecular bone loss. These results thus suggest a cell autonomous role for APPswe in suppressing OB formation and function, but a non-autonomous effect on OC genesis. Notably, increased adipogenesis and elevated bone marrow fat were detected in young adult Tg2576, but not TgAPPswe-Ocn, mice, implicating that APPswe in BMSCs and/or multi-cell types in bone marrow promotes bone marrow adipogenesis. Intriguingly, the skeletal ageing-like deficits in young adult Tg2576 mice were prevented by treatment with NAC (n-acetyl-l-cysteine), an anti-oxidant, suggesting that reactive oxygen species (ROS) may underlie APPswe-induced osteoporotic deficits. Taken together, these results demonstrate a role for APPswe in suppressing OB differentiation and bone formation, implicate APPswe as a detrimental factor for AD associated osteoporotic deficit, and reveal a potential clinical value of NAC in the treatment of osteoporotic deficits. Fri, 03 May 2013 07:12:58 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1954 http://feedproxy.google.com/~r/JbmrFeed/~3/Z8Acfy2gpQQ/doi Untreated, hypoparathyroidism (hypoPT) is a state of hypocalcemia with inappropriate low plasma parathyroid hormone (PTH) levels and hyperphosphatemia. PTH administration normalizes plasma calcium and phosphate levels and reduces the doses of calcium and active vitamin D analogues needed. In order to develop an evidence based clinical algorithm on how to monitor hypoPT patients treated with recombinant human rhPTH(1–84) injected subcutaneously in the thigh, we performed a 24h monitoring of pharmacokinetic and pharmacodynamic effects in a group of 38 patients who had completed a six-month randomized study on effects of treatment with a fixed rhPTH(1–84) dose of 100 µg/d or similar placebo, as an add-on to conventional treatment. PTH levels rose immediately, reaching a median peak level of 26.5 (interquartile range [IQR]: 20.1;42.5) pmol/l 15 min following injection. Thereafter, levels gradually decreased until reaching pre-dosing levels after 16h, with a plasma half-life of 2.2 (1.7;2.5)h. rhPTH(1–84) changed the diurnal rhythms of ionized calcium- and 1,25(OH)2D-levels, with rising levels following injection. Ionized calcium peaked after 7.0 (5.0;10.0) h. Asymptomatic hypercalcemia was present in 71% of the rhPTH(1–84)-treated patients. Compared with placebo, 24h urinary calcium, phosphate, and magnesium did not change, although the diurnal variation in renal excretion rates changed significantly in response to treatment. In conclusion, as a safety precaution we recommend measuring calcium levels at approximately 7h after administration occasionally in order to reveal episodes of hypercalcemia. A daily dose of rhPTH(1–84) 100 µg appears to be too high in some patients suggesting a need for a device allowing for individual dose adjustments. Fri, 03 May 2013 07:06:43 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1964 http://feedproxy.google.com/~r/JbmrFeed/~3/GTP5ZQcLTlk/doi Bone metastasis, the leading cause of breast cancer-related deaths, is characterized by bone degradation due to increased osteoclastic activity. In contrast, mechanical stimulation in healthy individuals upregulates osteoblastic activity, leading to new bone formation. However, the effect of mechanical loading on the development and progression of metastatic breast cancer in bone remains unclear. Here, we developed a new in vivo model to investigate the role of skeletal mechanical stimuli on the development and osteolytic capability of secondary breast tumors. Specifically, we applied compressive loading to the tibia following intratibial injection of metastatic breast cancer cells (MDA-MB231) into the proximal compartment of female immuno-compromised (SCID) mice. In the absence of loading, tibiae developed histologically-detectable tumors with associated osteolysis and excessive degradation of the proximal bone tissue. In contrast, mechanical loading dramatically reduced osteolysis and tumor formation and increased tibial cancellous mass due to trabecular thickening. These loading effects were similar to the baseline response we observed in non-injected SCID mice. In vitro mechanical loading of MDA-MB231 in a pathologically relevant 3-D culture model suggested that the observed effects were not due to loading-induced tumor cell death, but rather mediated via decreased expression of genes interfering with bone homeostasis. Collectively, our results suggest that mechanical loading inhibits the growth and osteolytic capability of secondary breast tumors following their homing to the bone, which may inform future treatment of breast cancer patients with advanced disease. Fri, 03 May 2013 07:03:59 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1966 http://feedproxy.google.com/~r/JbmrFeed/~3/I6ARQPMwM4w/doi Sarcopenia is associated with a greater fracture risk; this relationship was originally thought to be explained by an increased risk of falls in sarcopenic individuals. However, in addition, there is growing evidence of a functional muscle-bone unit in which bone health may be directly influenced by muscle function. Since a definition of sarcopenia encompasses muscle size, strength and physical performance, we investigated relationships for each of these with bone size, bone density and bone strength to interrogate these hypotheses further in participants from the Hertfordshire Cohort Study. 313 men and 318 women underwent baseline assessment of health and detailed anthropometric measurements. Muscle strength was measured by grip strength and physical performance was determined by gait speed. Peripheral quantitative computed tomography (pQCT) examination of the calf and forearm was performed to assess muscle cross-sectional area (mCSA) at the 66% level, and bone structure (radius and tibia, 4% and 66% levels). Muscle size was positively associated with bone size (distal radius total bone area β = 17.5mm2/SD [12.0, 22.9]) and strength (strength strain index (β = 23.3mm3/SD [18.2, 28.4]) amongst women (p < 0.001). These associations were also seen in men and were maintained after adjustment for age, height, weight-adjusted-for-height, limb length-adjusted-for-height, social class, smoking status, alcohol consumption, calcium intake, physical activity, diabetes mellitus, and in women, years since menopause and estrogen replacement therapy. While grip strength showed similar associations with bone size and strength in both sexes, these were substantially attenuated after similar adjustment. Consistent relationships between gait speed and bone structure were not seen. We conclude that while muscle size and grip strength are associated with bone size and strength, relationships between gait speed and bone structure and strength were not apparent in this cohort, supporting a role for the muscle-bone unit. Tue, 30 Apr 2013 07:25:21 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1972 http://feedproxy.google.com/~r/JbmrFeed/~3/73Ge0atZLRY/doi Autophagy is a conserved lysosomal degradation process that has important roles in both normal human physiology and disease. However, the function of autophagy in bone homeostasis is not well understood. Here, we report that autophagy is activated during osteoblast differentiation. Ablation of FIP200 (focal adhesion kinase family interacting protein of 200 kD), an essential component of mammalian autophagy, led to multiple autophagic defects in osteoblasts including aberrantly increased p62 expression, deficient LC3-II conversion, defective autophagy flux, absence of GFP-LC3 puncta in FIP200-null osteoblasts expressing transgenic GFP-LC3 and absence of autophagosome-like structures by electron microscope examination. Osteoblast-specific deletion of FIP200 led to osteopenia in mice. Histomorphometric analysis revealed that the osteopenia was due to cell-autonomous effects of FIP200 deletion on osteoblasts. FIP200 deletion led to defective osteoblast terminal differentiation in both primary bone marrow and calvarial osteoblasts in vitro. Interestingly, both proliferation and differentiation were not adversely affected by FIP200 deletion in early cultures. However, FIP200 deletion led to defective osteoblast nodule formation after initial proliferation and differentiation. Furthermore, treatment with autophagy inhibitors recapitulated the effects of FIP200 deletion on osteoblast differentiation. Taken together, these data identify FIP200 as an important regulator of bone development and reveal a novel role of autophagy in osteoblast function through its positive role in supporting osteoblast nodule formation and differentiation. Tue, 30 Apr 2013 07:22:10 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1971 http://feedproxy.google.com/~r/JbmrFeed/~3/nxisTRnNHAU/doi Bacterial infection can cause inflammatory bone diseases accompanied by the bone destruction due to excess generation of osteoclasts. Although lipoproteins are one of the major immuno-stimulating components of bacteria, little is known about their effects on bone metabolism. In this study, we investigated the role of lipoproteins in bacteria-induced bone destruction using Staphylococcus aureus wild-type, its lipoprotein-deficient mutant, and synthetic lipopeptides Pam2CSK4 and Pam3CSK4 known to mimic bacterial lipoproteins. Formaldehyde-inactivated S. aureus or the synthetic lipopeptides induced severe bone loss in the femurs of mice after intraperitoneal administration and in a calvarial bone implantation model, while the lipoprotein-deficient S. aureus did not show such effects. Mechanism studies further identified three action mechanisms for the lipopeptide-induced osteoclast differentiation and bone resorption via (i) enhancement of osteoclast differentiation through Toll-like receptor 2 and MyD88-dependent signaling pathways, (ii) induction of pro-inflammatory cytokines, TNF-α and IL-6, and (iii) up-regulation of RANKL expression with down-regulation of osteoprotegerin expression in osteoblasts. Taken together, these results suggest that lipoprotein might be an important bacterial component responsible for bone destruction during bacterial infections through augmentation of osteoclast differentiation and activation. Tue, 30 Apr 2013 07:20:52 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1973 http://feedproxy.google.com/~r/JbmrFeed/~3/QlkSPhEpVEM/doi With the advent of effective antiretroviral therapy (ART) more than 15 years ago, HIV has been transformed from a fatal illness into a manageable chronic condition and the HIV-infected population is aging into their 60s and 70s and beyond. There is concern, however, that the burden of co-morbid conditions normally seen with increased prevalence with aging, such as cardiovascular disease, chronic obstructive pulmonary disease, neurocognitive decline, is higher among HIV-infected populations and that these conditions, rather than HIV-infection, pose the greatest threat to longevity and quality of life for HIV-infected patients. Since early in the era of effective ART (sometimes referred to as highly active antiretroviral therapy (HAART)), a higher prevalence of low bone mineral density (BMD) and osteoporosis has been described among HIV-infected persons compared to their HIV-uninfected peers. © 2013 American Society for Bone and Mineral Research Mon, 29 Apr 2013 08:30:10 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1967 http://feedproxy.google.com/~r/JbmrFeed/~3/d2SXzJ_ODMI/doi The musculoskeletal system evolved in mammals to perform diverse functions that include locomotion, facilitating breathing, protecting internal organs, and coordinating global energy expenditure. Bone and skeletal muscles involved with locomotion are both derived from somitic mesoderm and accumulate peak tissue mass synchronously, according to genetic information and environmental stimuli. Aging results in the progressive and parallel loss of bone (osteopenia) and skeletal muscle (sarcopenia) with profound consequences for quality of life. Age-associated sarcopenia results in reduced endurance, poor balance and reduced mobility that predispose elderly individuals to falls, which more frequently result in fracture because of concomitant osteoporosis. Thus, a better understanding of the mechanisms underlying the parallel development and involution of these tissues is critical to developing new and more effective means to combat osteoporosis and sarcopenia in our increasingly aged population. This perspective will highlight recent advances in our understanding of mechanisms coupling bone and skeletal muscle mass, and identify critical areas where further work is needed. © 2013 American Society for Bone and Mineral Research Mon, 29 Apr 2013 08:28:57 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1969 http://feedproxy.google.com/~r/JbmrFeed/~3/DLUUMMeUZHY/doi Context Following fracture there is increased risk of re-fracture and premature mortality. These outcomes, particularly premature mortality following re-fracture, have not previously been studied together to understand overall mortality risk. Objectives This study examined the long-term cumulative incidence of subsequent fracture and total mortality with mortality calculated as a compound risk and separated according to initial and re-fracture. Design Community dwelling participants aged 60+ from Dubbo Osteoporosis Epidemiology Study with incident fractures, followed prospectively for further fractures and deaths from 1989–2010. Outcome Measures Subsequent fracture and mortality ascertained using cumulative incidence competing risk models allowing 4 possible outcomes: death without re-fracture, death following re-fracture, re-fracture but alive and event–free. Results There were 952 women and 343 men with incident fracture. Within five years following initial fracture, 24% women and 20% men re-fractured; and 26% women and 37% men died without re-fracture. Of those who re-fractured, a further 50% of women and 75% of men died, so total five-year mortality was 39% in women and 51% in men. Excess mortality was 24% in women and 27% in men. While mortality following re-fracture occurred predominantly in the first five years post initial fracture, total mortality (post initial and re-fracture) was elevated for 10 years. Most of the 5–10 year excess mortality was associated with re-fracture. The long term (>10 yr) re-fracture rate was reduced, particularly in the elderly due to their high mortality rate. The 30% alive beyond 10 years post fracture were at low risk of further adverse outcomes. Conclusion Re-fractures contribute substantially to overall mortality associated with fracture. The majority of the mortality and re-fractures occurred in the first 5 years following the initial fracture. However, excess mortality was observed for up to 10 years post fracture, predominantly related to that following re-fracture. Wed, 24 Apr 2013 09:39:21 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1968 http://feedproxy.google.com/~r/JbmrFeed/~3/OKZMU66vbw4/doi Farnesoid X receptor (FXR) is a nuclear receptor, which functions as a bile acid sensor controlling bile acid homeostasis. We investigated the role of FXR in regulating bone metabolism. We identified the expression of FXR in calvaria and bone marrow cells, which gradually increased during osteoblastic differentiation in vitro. In male mice, deletion of FXR (FXR−/−) in vivo resulted in a significant reduction in bone mineral density by 4.3∼6.6% in mice 8 to 20 weeks of age compared with FXR+/+ mice. Histological analysis of the lumbar spine showed that FXR deficiency reduced the bone formation rate as well as the trabecular bone volume and thickness. Moreover, TRACP staining of the femurs revealed that both the osteoclast number and osteoclast surface were significantly increased in FXR−/− mice compared with FXR+/+ mice. At the cellular level, induction of alkaline phosphatase (ALP) activities was blunted in primary calvarial cells in FXR−/− mice compared with FXR+/+ mice in concert with a significant reduction in Col1a1, ALP, and Runx2 gene expressions. Cultures of bone marrow derived macrophages from FXR−/− mice exhibited an increased number of osteoclast formations and protein expression of NFATc1. In female FXR−/− mice, although BMD was not significantly different from that in FXR+/+ mice, bone loss was accelerated after an ovariectomy compared with FXR+/+ mice. In vitro, activation of FXR by bile acids (CDCA or 6-ECDCA) or FXR agonists (GW4064 or Fexaramine) significantly enhanced osteoblastic differentiation through the upregulation of Runx2 and enhanced ERK and β-catenin signaling. FXR agonists also suppressed osteoclast differentiation from bone marrow macrophages. Finally, administration of a farnesol diet (1%) marginally prevented OVX-induced bone loss and enhanced bone mass gain in growing C57BL/6J mice. Taken together, these results suggest that FXR positively regulates bone metabolism through both arms of the bone remodeling pathways, i.e. bone formation and resorption. Mon, 22 Apr 2013 08:11:57 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1961 http://feedproxy.google.com/~r/JbmrFeed/~3/QW56UcVIDhI/doi Mutations in Low-density lipoprotein receptor-related protein 6 (LRP6) are associated with human skeletal disorders. LRP6 is required for parathyroid hormone (PTH)-stimulated signaling pathways in osteoblasts. We investigated whether LRP6 in osteoblasts directly regulates bone remodeling and mediates the bone anabolic effects of PTH by specifically deleting LRP6 in mature osteoblasts in mice (LRP6 KO). Three month-old LRP6 KO mice had a significant reduction in bone mass in the femora secondary spongiosa relative to their wild type littermates, whereas marginal changes were seen in femoral tissue of 1 month-old LRP6 KO mice. The remodeling area of the 3 month-old LRP6 KO mice showed a decreased bone formation rate as detected by Goldner's Trichrome staining and calcein double labeling. Bone histomorphometric and immumohistochemical analysis revealed a reduction in osteoblasts but little change in the numbers of osteoclasts and osteoprogenitors/osteoblast precursors in LRP6 KO mice compared to wild type littermates. In addition, the percentage of the apoptotic osteoblasts on the bone surface was higher in LRP6 KO mice compared to wild type littermates. Intermittent injection of PTH had no effect on bone mass nor osteoblastic bone formation in either trabecular and cortical bone in LRP6 KO mice, whereas all were enhanced in wild type littermates. Additionally, the anti-apoptotic effect of PTH on osteoblasts in LRP6 KO mice was less significant compared to wild type mice. Therefore, our findings demonstrate that LRP6 in osteoblasts is essential for osteoblastic differentiation during bone remodeling and the anabolic effects of PTH. Mon, 22 Apr 2013 07:45:40 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1962 http://feedproxy.google.com/~r/JbmrFeed/~3/o752pvrTILY/doi The risk of hip fracture rises rapidly with age, and is notably higher in women. After falls and prior fragility fractures, the main clinically recognized risk factor for hip fracture is reduced bone density. To better understand the extent to which femoral neck density and structure change with age in each sex, we have carried out a longitudinal study in subjects not treated with agents known to influence bone mineral density to investigate changes in regional cortical thickness, as well as cortical and trabecular bone mineral density at the mid-femoral neck. Segmental QCT analysis was used to assess bone measurements in two anatomic sub-regions, the supero-lateral (superior) and infero-medial (inferior). A total of 400 older individuals (100 men and 300 women, aged 66-90 years) who were participants in the AGES-Reykjavik study, were studied. Participants had two QCT scans of the hip over a median follow-up of 5.1 yr. (mean baseline age 74 yr.). Changes in bone values during follow-up were estimated from mixed effects regression models. At baseline women had lower bone values in the superior region than men. At follow-up all bone values were lower in women, except cortical vBMD inferiorly. The relative losses in all bone values estimated in the superior region were substantially (about threefold) and significantly greater compared to those estimated in the inferior region in both sexes. Women lost cortical thickness and cortical vBMD more rapidly than men in both regions; and this was only weakly reflected in total femoral neck DXA-like results. The higher rate of bone loss in women at critical locations may contribute materially to the greater femoral neck fracture incidence among women than men. Mon, 22 Apr 2013 07:09:24 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1960 http://feedproxy.google.com/~r/JbmrFeed/~3/ZdS4VZ0XgV0/doi Low levels of physical activity or sun exposure and limitations to physical functioning (or disability) have been identified as possible risk factors for hip fracture. However, these factors are closely related and data on their independent and joint association with risk of hip fracture are limited. A total of 158 057 individuals aged ≥45 years sampled from the general population of New South Wales, Australia, from the prospective 45 and Up Study completed a baseline postal questionnaire in 2006-9 including data on physical activity (Active Australia questionnaire); sun exposure (usual time outdoors); and physical functioning (Medical Outcomes Score-Physical Functioning; scored 0-100). Incident first hip fractures were ascertained by linkage to administrative hospital data (n = 293; average follow-up 2.3 years). The Relative Risk (RR) of hip fracture was estimated using Cox proportional hazards. Poorer physical functioning, lower physical activity and less time outdoors were positively related to each other at baseline and individually associated with significantly increased hip fracture risk. However, physical activity and time outdoors were not significantly related to hip fracture risk after adjustment for baseline physical functioning or when analysis was restricted to those with no or mild baseline physical limitation. In contrast, physical functioning remained strongly related to hip fracture risk after adjustment for the other two factors; compared with the group without limitation (100) the RR of hip fracture among those with mild (75–95), moderate (50–70), severe (25–45) and greatest (0–20) level of physical limitation were 1.38 (95%CI 0.88–2.14), 2.14 (1.29–3.53), 3.87 (2.31–6.44), and 5.61 (3.33–9.42), respectively. The findings suggest that limitation in physical functioning, but not physical activity or time outdoors, is strongly related to hip fracture risk. The apparent increased risk of hip fracture previously described for low physical activity or sun exposure may be, at least in part, due to uncontrolled confounding. Mon, 22 Apr 2013 07:07:06 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1963 http://feedproxy.google.com/~r/JbmrFeed/~3/ezxpKBZODeo/doi We previously isolated a low bone mass mouse, Gja1Jrt/ + , with a mutation in the gap junction protein, alpha 1 gene (Gja1), encoding for a dominant negative G60S Connexin 43 (Cx43) mutant protein. Similarly to other Cx43 mutant mouse models described, including a global Cx43 deletion, four skeletal cell conditional-deletion mutants and a Cx43 missense mutant (G138R/ +), a reduction in Cx43 gap junction formation and/or function resulted in mice with early onset osteopenia. In contrast to other Cx43 mutants, however, we found that Gja1Jrt/+ mice have both higher bone marrow stromal osteoprogenitor numbers and increased appendicular skeleton osteoblast activity leading to cell autonomous upregulation of both matrix bone sialoprotein (BSP) and membrane-bound receptor activator of nuclear factor kappa-B ligand (mbRANKL). In younger Gja1Jrt/+ mice, these contributed to increased osteoclast number and activity resulting in early onset osteopenia. In older animals, however, this effect was abrogated by increased osteoprotegerin (OPG) levels and serum alkaline phosphatase (ALP) so that differences in mutant and wild type (WT) bone parameters and mechanical properties lessened or disappeared with age. Our study is the first to describe a Cx43 mutation in which osteopenia is caused by increased rather than decreased osteoblast function and where activation of osteoclasts occurs not only through increased mbRANKL but an increase in a matrix protein that affects bone resorption, which together abrogate age-related bone loss in older animals. Fri, 19 Apr 2013 07:10:37 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1965 http://feedproxy.google.com/~r/JbmrFeed/~3/L1FSgAxgBFQ/doi A huge number of risk assessment tools have been developed. Far from all have been validated in external studies, more of them have absence of methodological and transparent evidence and few are integrated in national guidelines. Therefore, we performed a systematic review to provide an overview of existing valid and reliable risk assessment tools for prediction of osteoporotic fractures. Additionally, we aimed to determine if the performance each tool was sufficient for practical use and lastly to examine whether the complexity of the tools influenced their discriminative power. We searched PubMed, Embase and Cochrane databases for papers and evaluated these with respect to methodological quality using the QUADAS checklist. A total of 48 tools were identified, 20 had been externally validated, however only 6 tools had been tested more than once in a population-based setting with acceptable methodological quality. None of the tools performed consistently better than others and simple tools (i.e. OST, ORAI and Garvan) often did as well or better than more complex tools (i.e. SCORE, FRAX, Qfracture). No studies determined the effectiveness of tools in selecting patients for therapy and thus improving fracture outcomes. High quality studies in randomized design with population-based cohorts with different case mixes are needed. © 2013 American Society for Bone and Mineral Research Tue, 16 Apr 2013 08:45:05 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1956 http://feedproxy.google.com/~r/JbmrFeed/~3/e8I4fZ3fuxE/doi Few year-long vitamin D supplementation trials exist that match seasonal changes. The aim of this study was to determine whether daily oral vitamin D3 at 400 IU or 1000 IU compared with placebo affects annual BMD change in postmenopausal women in a 1-year double blind placebo controlled trial in Scotland. Caucasian women aged 60-70 y (n = 305) were randomized to one of two doses of vitamin D or placebo. All participants started simultaneously in January/February 2009, attending visits at bi-monthly intervals with 265 (87%) women attending the final visit; and an additional visit 1 month after treatment cessation. BMD (Lunar iDXA) and 1,25-dihydroxyvitamin D[1,25(OH)2D], N-terminal propeptide of type 1 collagen [P1NP], C-terminal telopeptide of type I collagen [CTX] and fibroblast growth factor-23 [FGF23] were measured by immunoassay at the start and end of treatment. Circulating PTH, serum Ca and total 25-hydroxyvitamin D [25(OH)D] (latter by tandem mass spectrometry) were measured at each visit. Mean BMD loss at the hip was significantly less for the 1000 IU vitamin D group (0.05 ± 1.46%), compared to the 400 IU vitamin D or placebo groups (0.57 ± 1.33% and 0.60 ± 1.67%, respectively) (p < 0.05). Mean(± SD) baseline 25(OH)D was 33.8 ± 14.6 nmol/L; comparative 25(OH)D change for the placebo, 400 IU and 1000 IU vitamin D groups was: −4.1 ± 11.5 nmol/L, +31. 6 ± 19.8 nmol/L and +42.6 ± 18.9 nmol/L respectively. Treatment did not change markers of bone metabolism, except for small reductions in PTH and serum calcium (latter with 1000 IU dose only). The discordance between the incremental increase in 25(OH)D between the 400IU and 1000 IU vitamin D and effect on BMD suggests that 25(OH)D may not accurately reflect clinical outcome, nor how much vitamin D is being stored. Sat, 13 Apr 2013 02:10:19 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1959 http://feedproxy.google.com/~r/JbmrFeed/~3/HcrIZCU80U8/doi Parathyroid hormone (PTH) and PTH(1–34) have been shown to promote bone healing in several animal studies. It is known that the mechanical environment is important in fracture healing. Furthermore, PTH and mechanical loading has been suggested to have synergistic effects on intact bone. The aim of the present study was to investigate whether the effect of PTH(1–34) on fracture healing in rats was influenced by reduced mechanical loading. For this purpose we used female, 25-week-old ovariectomized rats. Animals were subjected to closed midshaft fracture of the right tibia ten weeks after ovariectomy. Five days before fracture, half of the animals received Botulinum Toxin A-injections in the muscles of the fractured leg to induce muscle paralysis (unloaded group), while the other half received saline injections (control group). For the following eight weeks, half of the animals in each group received injections of hPTH(1–34) (20 µg/kg/day) and the other half received vehicle treatment. Fracture healing was assessed by radiology, DXA, histology and bone strength analysis. We found that unloading reduced callus area significantly, while no effects of PTH(1–34) on callus area were seen in neither normally nor unloaded animals. PTH(1–34) increased callus bone mineral density (BMD) and bone mineral content (BMC) significantly, while unloading decreased callus BMD and BMC significantly. PTH(1–34)-treatment increased bone volume of the callus in both unloaded and control animals. PTH(1–34)-treatment increased ultimate force of the fracture by 63% in both control and unloaded animals and no interaction of the two interventions could be detected. PTH(1–34) was able to stimulate bone formation in normally loaded as well as unloaded intact bone. In conclusion, the study confirms the stimulatory effect of PTH(1–34) on fracture healing and our data suggest that PTH(1–34) is able to promote fracture healing, as well as intact bone formation during conditions of reduced mechanical loading. Sat, 13 Apr 2013 01:07:50 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1957 http://feedproxy.google.com/~r/JbmrFeed/~3/XDcMaPG80KM/doi The risk of subsequent fracture is increased following initial fractures, however, proper understanding of its magnitude is lacking. This population-based study examines the subsequent fracture risk in women and men by age and type of initial incident fracture. All incident non-vertebral fractures between 1994 and 2009 were registered in 27,158 participants in the Tromsø Study, Norway. The analysis included 3,108 subjects with an initial incident fracture after the age of 49 years. Subsequent fracture (n = 664) risk was expressed as rate ratios (RR) and absolute proportions irrespective of death. The rates of both initial and subsequent fractures increased with age, the latter with the steepest curve. Compared with initial incident fracture rate of 30.8 per 1000 in women and 12.9 per 1000 in men, the overall age-adjusted RR of subsequent fracture was 1.3 (95% CI 1.2–1.5) in women, and 2.0 (95% CI 1.6–2.4) in men. Although the RRs decreased with age, the absolute proportions of those with initial fracture who suffered a subsequent fracture increased with age; from 9% to 30% in women and from 10% to 26% in men, between the age groups 50–59 to 80+ years, respectively. The type of subsequent fracture varied by age from mostly minor fractures in the youngest to hip or other major fractures in the oldest age groups, irrespective of type and severity of initial fracture. In women and men respectively, 45% and 38% of the subsequent hip or other major fractures, were preceded by initial minor fractures. The risk of subsequent fracture is high in all age groups. At older age, severe subsequent fracture types follow both clinically severe and minor initial incident fractures. Any fragility fracture in the elderly reflects the need for specific osteoporosis management to reduce further fracture risk. Tue, 09 Apr 2013 08:29:53 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1952 http://feedproxy.google.com/~r/JbmrFeed/~3/pjb43zDBiI4/doi Clinical risk factors (CRFs), with or without bone mineral density (BMD), are used to determine the risk of osteoporotic fracture (OF), which has a heritable component. This study investigated whether genetic profiling can additionally improve the ability to predict OF. Using 1,229 unrelated Korean postmenopausal women, 39 single-nucleotide polymorphisms (SNPs) in 30 human genomic loci were tested for association with osteoporosis-related traits, such as BMD, osteoporosis, vertebral fracture (VF), non-vertebral fracture (NVF), and any fracture. To estimate the effects of genetic profiling, the genetic risk score (GRS) was calculated using five prediction models: (model I) GRSs only; (model II) BMD only; (model III) CRFs only; (model IV) CRFs and BMD; and (model V) CRFs, BMD and GRS. A total of 21 SNPs within 19 genes associated with one or more osteoporosis-related traits and were included for GRS calculation. GRS associated with BMD before and after adjustment for CRFs (P = < 0.001 to 0.018). GRS associated with NVF before and after adjustment for CRFs and BMD (P = 0.017 to 0.045), and with any fracture after adjustment for CRFs and femur neck BMD (P = 0.049). In terms of predicting NVF, the area under the receptor-operator characteristics curve (AUC) for model I was 0.55, which was lower than the AUCs of models II (0.60), III (0.64), and IV (0.65). Adding GRS to model IV (in model V) increased the AUC to 0.67, and improved the accuracy of NVF classification by 11.5% (P = 0.014). In terms of predicting any fracture, the AUC of model V (0.68) was similar to that of model IV (0.68), and model V did not significantly improve the accuracy of any fracture classification (P = 0.39). Thus, genetic profiling may enhance the accuracy of NVF predictions and help to delineate the intervention threshold. Tue, 09 Apr 2013 08:23:14 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1955 http://feedproxy.google.com/~r/JbmrFeed/~3/OFZUQUG2E-8/doi African-American women have a lower risk of fracture than Caucasian women, and this difference is only partially explained by differences in DXA areal bone mineral density (aBMD). Little is known about racial differences in skeletal microarchitecture and the consequences for bone strength. To evaluate potential factors underlying this racial difference in fracture rates, we used high-resolution peripheral quantitative computed tomography (HR-pQCT) to assess cortical and trabecular bone microarchitecture and estimate bone strength using micro-finite element analysis in African-American (n = 100) and Caucasian (n = 173) women participating in the Study of Women's Health Across the Nation (SWAN). African-American women had larger and denser bones than Caucasians, with greater total area, aBMD, and total volumetric BMD (vBMD) at the radius and tibia metaphysis (p < 0.05 for all). African-Americans had greater trabecular vBMD at the radius, but higher cortical vBMD at the tibia. Cortical microarchitecture tended to show the most pronounced racial differences, with higher cortical area, thickness, and volumes in African-Americans at both skeletal sites (p < 0.05 for all), and lower cortical porosity in African-Americans at the tibia (p < 0.05). African-American women also had greater estimated bone stiffness and failure load at both the radius and tibia. Differences in skeletal microarchitecture and estimated stiffness and failure load persisted even after adjustment for DXA aBMD. The densitometric and microarchitectural predictors of failure load at the radius and tibia were the same in African-American and Caucasian women. In conclusion, differences in bone microarchitecture and density contribute to greater estimated bone strength in African-Americans and probably explain, at least in part, the lower fracture risk of African-American women. Tue, 09 Apr 2013 08:22:59 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1953 http://feedproxy.google.com/~r/JbmrFeed/~3/1h2Tns9efsU/doi hbdPRELP is a peptide corresponding to the N-terminal heparin binding domain of the matrix protein Proline/aRginine-rich End Leucine-rich repeat Protein (PRELP). hbdPRELP inhibits osteoclastogenesis entering pre-fusion osteoclasts through a chondroitin sulfate- and annexin 2-dependent mechanism and reducing the nuclear factor-κB transcription factor activity. In this work we hypothesized that hbdPRELP could have a pharmacological relevance counteracting bone loss in a variety of in vivo models of bone diseases induced by exacerbated osteoclast activity. In healthy mice, we demonstrated that the peptide targeted the bone and increased trabecular bone mass over basal level. In mice treated with retinoic acid to induce an acute increase of osteoclast formation, the peptide consistently antagonized osteoclastogenesis and prevented the increase of the serum levels of the osteoclast-specific marker tartrate-resistant acid phosphatase. In ovariectomized mice, in which osteoclast activity was chronically enhanced by estrogen deficiency, hbdPRELP counteracted exacerbated osteoclast activity and bone loss. In mice carrying osteolytic bone metastases, in which osteoclastogenesis and bone resorption were enhanced by tumor cell derived factors, hbdPRELP reduced the incidence of osteolytic lesions, both preventively and curatively, with mechanisms involving impaired tumor cell homing to bone and tumor growth in the bone microenvironment. Interestingly, in tumor-bearing mice, hbdPRELP also inhibited breast tumor growth in orthotopic sites and development of metastatic disease in visceral organs, reducing cachexia and improving survival especially when administered preventively. hbdPRELP was retained in the tumor tissue and appeared to affect tumor growth by interacting with the microenvironment rather than by directly affecting the tumor cells. Since safety studies and high dose treatments revealed no adverse effects, hbdPRELP could be employed as novel biological agent to combat experimentally induced bone loss and breast cancer metastases, with a potential translational impact. © 2013 American Society for Bone and Mineral Research. Thu, 04 Apr 2013 09:06:50 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1951 http://feedproxy.google.com/~r/JbmrFeed/~3/pbPuoeU_vNo/doi The goal of this MR-imaging study was to quantify vertebral bone marrow fat content and composition in diabetic and non-diabetic postmenopausal women with fragility fractures and to compare them with non-fracture controls with and without type-2 diabetes mellitus. Sixty-nine postmenopausal women (mean age 63 ± 5 years) were recruited. Thirty-six patients (47.8%) had spinal and/or peripheral fragility fractures. Seventeen fracture patients were diabetic. Thirty-three women (52.2%) were non-fracture controls. Sixteen women were diabetic non-fracture controls. To quantify vertebral bone marrow fat content and composition, patients underwent MR-spectroscopy (MRS) of the lumbar spine at 3 Tesla. Bone mineral density (BMD) was determined by dual-energy X-Ray-absorptiometry (DXA) of the hip and lumbar spine (LS) and quantitative computed tomography (QCT) of the LS. To evaluate associations of vertebral marrow fat content and composition with spinal and/or peripheral fragility fractures and diabetes, we used linear regression models adjusted for age, race, and spine vBMD by QCT. At the LS, non-diabetic and diabetic fracture patients had lower vBMD than controls and diabetics without fractures (p = 0.018; p = 0.005). However, aBMD by DXA did not differ between fracture and non-fracture patients. After adjustment for age, race, and spinal vBMD, the prevalence of fragility fractures was associated with −1.7% lower unsaturation levels (confidence interval [CI] −2.8% to −0.5%, p = 0.005) and +2.9% higher saturation levels (CI 0.5% to 5.3%, p = 0.017). Diabetes was associated with −1.3% (CI −2.3% to −0.2%, p = 0.018) lower unsaturation and +3.3% (CI 1.1% to 5.4%. p = 0.004) higher saturation levels. Diabetics with fractures had the lowest marrow unsaturation and highest saturation. There were no associations of marrow fat content with diabetes or fracture. Our results suggest that altered bone marrow fat composition is linked with fragility fractures and diabetes. MRS of spinal bone marrow fat may therefore serve as a novel tool for BMD-independent fracture risk assessment. © 2013 American Society for Bone and Mineral Research. Thu, 04 Apr 2013 09:06:41 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1950 http://feedproxy.google.com/~r/JbmrFeed/~3/mZvntAKefxo/doi There is an ongoing debate over the role of serum 25(OH) vitamin D [25(OH)D] levels in maintaining or improving physical performance and muscle strength. Much of the controversy is due to the variability between studies in participants' characteristics, baseline serum 25(OH)D levels, and baseline physical functioning. The aim of this ancillary study conducted within a randomized controlled clinical trial was to investigate whether supplementation with 400 or 2000 IU vitamin D3 daily for 6 months would improve measures of physical performance and muscle strength in a community-dwelling elderly population aged 65 to 95. Those with the slowest gait speed improved their ability to do chair-stand tests after vitamin D supplementation. This finding remained significant after controlling for potential confounding variables. There was also an inverse correlation between serum 25(OH)D levels and fat mass index (FMI) among women, suggesting that higher supplementation with vitamin D is needed as weight increases. The results of this study suggest that supplementation with vitamin D may be most beneficial in older populations who have low baseline physical functioning. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:18:42 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1949 http://feedproxy.google.com/~r/JbmrFeed/~3/n832_OLgxGA/doi Concern about the risk of bone loss in astronauts due to prolonged exposure to microgravity prompted the National Aeronautics and Space Administration to convene a Bone Summit with a panel of experts at the Johnson Space Center to review the medical data and research evidence from astronauts who have had prolonged exposure to spaceflight. Data were reviewed from 35 astronauts who had served on spaceflight missions lasting between 120 and 180 days with attention focused on astronauts who (a) were repeat fliers on long-duration missions, (b) were users of an Advanced Resistive Exercise Device, (c) were scanned by quantitative computed tomography (QCT) at the hip, (d) had hip bone strength estimated by finite element modeling, or (e) had lost > 10% of areal bone mineral density at the hip or lumbar spine as measured by dual-energy X-ray absorptiometry (DXA). Because of the limitations of DXA in describing the effects of spaceflight on bone strength, the panel recommended that the U.S. space program use QCT and finite element modeling to further study the unique effects of spaceflight (and recovery) on bone health in order to better inform clinical decisions. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:18:33 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1948 http://feedproxy.google.com/~r/JbmrFeed/~3/e3WL-6OLPoc/doi Osteoporosis is frequently seen in patients with chronic obstructive pulmonary disease (COPD). Since research on bone structure and bone strength in COPD patients is limited, the objectives of this pilot study were: 1. To compare bone structure, stiffness and failure load, measured at the peripheral skeleton, between men with and without COPD after stratification for areal bone mineral density (aBMD), and 2. To relate clinical parameters with bone stiffness and failure load in men with COPD. We included 30 men with COPD (normal aBMD n = 18, osteoporosis n = 12) and 17 men without COPD (normal aBMD n = 9, osteoporosis n = 8). We assessed pack-years of smoking, body mass index (BMI), fat free mass index (FFMI), pulmonary function (FEV1, FEV1/FVC, DLCO and KCO) and extent of emphysema. Bone structure of the distal radius and tibia was assessed by high resolution peripheral quantitative computed tomography (HR-pQCT), and bone stiffness and failure load of the distal radius and tibia were estimated from micro finite element analysis (µFEA). After stratification for aBMD and COPD, men with osteoporosis showed abnormal bone structure (p < 0.01), lower bone stiffness (p < 0.01) and lower failure load (p < 0.01) compared with men with normal aBMD, and men with COPD had comparable bone structure, stiffness and failure load compared with men without COPD. In men with COPD, lower FFMI was related with lower bone stiffness and failure load of the radius and tibia and lower DLCO and KCO were related with lower bone stiffness and failure load of the tibia after normalization with respect to femoral neck aBMD. Thus, this pilot study could not detect differences in bone structure, stiffness and failure load between men with and without COPD after stratification for aBMD. FFMI and gas transfer capacity of the lung were significantly related with bone stiffness and failure load in men with COPD after normalization with respect to femoral neck aBMD. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:18:21 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1947 http://feedproxy.google.com/~r/JbmrFeed/~3/TXUYFgmLynk/doi Loss-of-function and certain missense mutations in the Wnt co-receptor LRP5 significantly decrease or increase bone mass, respectively. These human skeletal phenotypes have been recapitulated in mice harboring Lrp5 knockout and knockin mutations. We hypothesized that measuring mRNA expression in diaphyseal bone from mice with Lrp5 wild-type (Lrp5+/+), knockout (Lrp5-/-), and high bone mass (HBM)-causing (Lrp5p.A214V/+) alleles could identify genes and pathways that regulate or are regulated by LRP5 activity. We performed RNA-seq on pairs of tibial diaphyseal bones from four 16-week-old mice with each of the aforementioned genotypes. We then evaluated different methods for controlling for contaminating non-skeletal tissue (i.e., blood, bone marrow, and skeletal muscle) in our data. These methods included pre-digestion of diaphyseal bone with collagenase and separate transcriptional profiling of blood, skeletal muscle and bone marrow. We found that collagenase digestion reduced contamination, but also altered gene expression in the remaining cells. In contrast, in silico filtering of the diaphyseal bone RNA-seq data for highly expressed blood, skeletal muscle, and bone marrow transcripts significantly increased the correlation between RNA-seq data from an animal's right and left tibiae and from animals with the same Lrp5 genotype. We conclude that reliable and reproducible RNA-seq data can be obtained from mouse diaphyseal bone and that lack of LRP5 has a more pronounced effect on gene expression than the HBM-causing LRP5 missense mutation. We identified 84 differentially expressed protein-coding transcripts between LRP5 “sufficient” (i.e., Lrp5+/+ and Lrp5p.A214V/+) and “insufficient” (Lrp5-/-) diaphyseal bone, and far fewer differentially expressed genes between Lrp5p.A214V/+ and Lrp5+/+ diaphyseal bone. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:18:12 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1946 http://feedproxy.google.com/~r/JbmrFeed/~3/u7yQw5hqUm8/doi Global gene deletion studies in mice and humans have established the pivotal role of runt related transcription factor-2 (Runx2) in both intramembranous and endochondral ossification processes during skeletogenesis. In this study, we for the first time generated mice carrying a conditional Runx2 allele with exon 4, which encodes the Runt domain, flanked by loxP sites. These mice were crossed with α1(I)-collagen-Cre or α1(II)-collagen-Cre transgenic mice to obtain osteoblast- or chondrocyte-specific Runx2 deficient mice, respectively. As seen in Runx2-/- mice, perinatal lethality was observed in α1(II)-Cre;Runx2flox/flox mice, but this was not the case in animals in which α1(I)-collagen-Cre was used to delete Runx2. When using double staining with Alizarin red for mineralized matrix and Alcian blue for cartilaginous matrix, we observed previously that mineralization was totally absent at embryonic day 15.5 throughout the body in Runx2-/- mice, but was found in areas undergoing intramembranous ossification such as skull and clavicles in α1(II)-Cre;Runx2flox/flox mice. In newborn α1(II)-Cre;Runx2flox/flox mice, mineralization impairment was restricted to skeletal areas undergoing endochondral ossification including long bones and vertebrae. In contrast, no apparent skeletal abnormalities were seen in mutant embryo, newborn, and 3- to 6-week old-mice in which Runx2 had been deleted with the α1(I)-collagen-Cre driver. These results suggest that Runx2 is absolutely required for endochondral ossification during embryonic and postnatal skeletogenesis, but that disrupting its expression in already committed osteoblasts as achieved here with the α1(I)-collagen-Cre driver does not affect overtly intramembranous and endochondral ossification. The Runx2 floxed allele established here is undoubtedly useful for investigating the role of Runx2 in particular cells. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:18:03 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1945 http://feedproxy.google.com/~r/JbmrFeed/~3/eAdARyK8rws/doi A better understanding of osteogenesis at genetic and biochemical levels is yielding new molecular entities that can modulate bone regeneration and potentially act as novel therapies in a clinical setting. These new entities are motivating alternative approaches for bone repair by utilizing DNA-derived expression systems, as well as RNA-based regulatory molecules controlling the fate of cells involved in osteogenesis. These sophisticated mediators of osteogenesis, however, pose unique delivery challenges that are not obvious in deployment of conventional therapeutic agents. Viral and non-viral delivery systems are actively pursued in preclinical animal models to realize the potential of the gene-based medicines. This article will summarize promising bone-inducing molecular agents in the horizon as well as providing a critical review of delivery systems employed for their administration. Special attention was paid to synthetic (non-viral) delivery systems since they are more likely to be adopted for clinical testing due to safety considerations. We present a comparative analysis of dose-response relationships, as well as pharmacokinetics and pharmacodynamics features of various approaches, with the purpose of clearly defining the current frontier in the field. We conclude with the authors' perspective on the future of gene-based therapy of bone defects, articulating promising research avenues to advance the field to clinical bone repair. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:17:49 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1944 http://feedproxy.google.com/~r/JbmrFeed/~3/a4aN5-WipTI/doi Fat mass may be modulated by the number of brown-like adipocytes in white adipose tissue (WAT) in humans and rodents. Bone remodeling is dependent on systemic energy metabolism and, with age, bone remodeling becomes uncoupled and brown adipose tissue (BAT) function declines. To test the interaction between BAT and bone, we employed Misty (m/m) mice, which were reported be deficient in BAT. We found that Misty mice have accelerated age-related trabecular bone loss and impaired brown fat function (including reduced temperature, lower expression of Pgc1a, and less sympathetic innervation compared to wildtype (+/ +)). Despite reduced BAT function, Misty mice had normal core body temperature, suggesting heat is produced from other sources. Indeed, upon acute cold exposure (4°C for 6 hr), inguinal WAT from Misty mice compensated for BAT dysfunction by increasing expression of Acadl, Pgc1a, Dio2 and other thermogenic genes. Interestingly, acute cold exposure also decreased Runx2 and increased Rankl expression in Misty bone, but only Runx2 was decreased in wildtype. Browning of WAT is under the control of the sympathetic nervous system (SNS) and, if present at room temperature, could impact bone metabolism. To test whether SNS activity could be responsible for accelerated trabecular bone loss, we treated wildtype and Misty mice with the β-blocker, propranolol. As predicted, propranolol slowed trabecular BV/TV loss in the distal femur of Misty mice without affecting wildtype. Finally, the Misty mutation (a truncation of DOCK7) also has a significant cell-autonomous role. We found DOCK7 expression in whole bone and osteoblasts. Primary osteoblast differentiation from Misty calvaria was impaired, demonstrating a novel role for DOCK7 in bone remodeling. Despite the multifaceted effects of the Misty mutation, we have shown that impaired brown fat function leads to altered SNS activity and bone loss, and for the first time that cold exposure negatively affects bone remodeling. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:17:33 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1943 http://feedproxy.google.com/~r/JbmrFeed/~3/x-Et66zUBYU/doi Bone remodeling allows the conservation of normal bone mass despite constant changes in internal and external environments. The adaptation of the skeleton to these various stimuli led credence to the notion that bone remodeling is a true homeostatic function, and as such is under the control of specific centers in the central nervous system (CNS). Hypothalamic and brainstem centers, as well as the sympathetic nervous system (SNS), have been identified as regulators of bone remodeling. However, the nature of the afferent CNS stimuli that may modulate CNS centers involved in the control of bone remodeling, with the exception of leptin, remains unclear. Based on the partial efficacy of exercise and mechanical stimulation regimens to prevent microgravity-induced bone loss and the known alterations in vestibular functions associated with space flights, we hypothesized that inner ear vestibular signals may contribute to the regulation of bone remodeling. Using an established model of bilateral vestibular lesions and microtomographic and histomorphometric bone analyses, we show here that induction of bilateral vestibular lesion in rats generates significant bone loss, which is restricted to weight-bearing bones and associated with a significant reduction in bone formation, as observed in rats under microgravity conditions. Importantly, this bone loss was not associated with reduced locomotor activity or metabolic abnormalities, was accompanied with molecular signs of increased sympathetic outflow, and could be prevented by the β-blocker propranolol. Collectively, these data suggest that the homeostatic process of bone remodeling has a vestibulo-sympathetic regulatory component and that vestibular system pathologies might be accompanied by bone fragility. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:17:15 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1940 http://feedproxy.google.com/~r/JbmrFeed/~3/VYbr-z-a4os/doi Paradoxically, Asians have lower areal bone mineral density, but their rates of hip and wrist fractures are lower than Caucasians. Therefore, we used high-resolution pQCT (HR-pQCT) to determine whether differences in bone macro- and microstructure, BMD and bone strength at the distal radius are apparent in Asian (n = 91, 53 males, 38 females, 17.3 ± 1.5 yrs) and Caucasian (n = 89, 46 males, 43 females, 18.1 ± 1.8 yrs) adolescents and young adults. HR-pQCT outcomes included total BMD (Tt.BMD), trabecular bone volume fraction (BV/TV), trabecular number (Tb.N), thickness (Tb.Th) and separation (Tb.Sp). We used an automated segmentation algorithm to determine total bone area (Tt.Ar), cortical BMD (Ct.BMD), porosity (Ct.Po) and thickness (Ct.Th), and we applied finite element analysis to HR-pQCT scans to estimate bone strength. We fit sex-specific multivariable regression models to compare bone outcomes between Asians and Caucasians, adjusting for age, age at menarche (girls), lean mass, ulnar length, dietary calcium intake and physical activity. In males, after adjusting for covariates, Asians had 11% greater Tt.BMD, 8% greater Ct.BMD and 25% lower Ct.Po than Caucasians (p < 0.05). Also, Asians had 9% smaller Tt.Ar and 27% greater Ct.Th (p < 0.01). In females, Asians had smaller Tt.Ar than Caucasians (16%, p < 0.001), but this difference was not significant after adjusting for covariates. Asian females had 5% greater Ct.BMD, 12% greater Ct.Th and 11% lower Tb.Sp than Caucasians after adjusting for covariates (p < 0.05). Estimated bone strength did not differ between Asian and Caucasian males or females. Our study supports the notion of compensatory elements of bone structure that sustain bone strength; smaller bones as observed between those of Asian compared with Caucasian origin, have, on average, more dense, less porous and thicker cortices. Longitudinal studies are needed to determine whether ethnic differences in bone structure exist in childhood, persist into old age and whether they influence fracture risk. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:17:02 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1939 http://feedproxy.google.com/~r/JbmrFeed/~3/WC8asVqHzfU/doi Chemokines play crucial roles in the recruitment of specific hematopoetic cell types, and some of them have been suggested to be involved in the regulation of bone remodeling. Since we have previously observed that Ccl2 and Ccl5 are direct target genes of non-canonical Wnt signaling in osteoblasts, we analyzed the skeletal phenotypes of Ccl2- and Ccl5-deficient mice. In line with previous studies Ccl2-deficient mice display a moderate reduction of osteoclastogenesis at the age of 6 months. In contrast, 6 months old Ccl5-deficient mice display osteopenia associated with decreased bone formation and increased osteoclastogenesis. Moreover, unlike in wildtype and Ccl2-deficient mice, large areas of their trabecular and endocortical bone surfaces are not covered by osteoblasts or bone-lining cells, and this is associated with a severe reduction of endosteal bone formation. Although this phenotype diminishes with age, it is important that we could further identify a reduced number of osteal macrophages in 6 months old Ccl5-deficient mice, since this cell type has previously been reported to promote endosteal bone formation. As Ccl5-deficient mice also display increased osteoclastogenesis, we finally addressed the question, whether osteal macrophages could differentiate into osteoclasts and/or secrete inhibitors of osteoclastogenesis. For that purpose we isolated these cells by CD11b affinity purification from calvarial cultures and characterized them ex vivo. Here we found that they are unable to differentiate into osteoblasts or osteoclasts, but that their conditioned medium mediates an anti-osteoclastogenic effect, possibly caused by IL-18, an inhibitor of osteoclastogenesis expressed by osteal macrophages. Taken together, our data provide in vivo-evidence supporting the previously suggested role of Ccl5 in bone remodeling. Moreover, to the best of our knowledge, Ccl5-deficient mice represent the first model with a spontaneous partial deficiency of osteal macrophages, a recently identified cell type, whose impact on bone remodeling is just beginning to be understood. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:16:47 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1937 http://feedproxy.google.com/~r/JbmrFeed/~3/utriAXGp34k/doi Ubiquitin E3 ligase-mediated protein degradation promotes proteasomal degradation of key positive regulators of osteoblast functions. For example, the E3 ligases, Smurf1, Itch and Wwp1, promote degradation of Runx2, JunB, and CXCR4 proteins to inhibit their functions. However, the role of E3 ligases in age-associated bone loss is unknown. We found that the expression level of Wwp1, but not Smurf1 or Itch, was significantly increased in CD45- bone marrow-derived mesenchymal stem cells (MSCs) from 6- and 12-month-old WT mice. Wwp1-/- mice developed increased bone mass as they aged, associated with increased bone formation rates and normal bone resorption parameters. Bone marrow stromal cells (BMSCs) from Wwp1-/- mice formed increased numbers and areas of alkaline phosphatase+ and Alizarin Red+ nodules and had increased migration potential towards CXCL12 gradients. Runx2, JunB and CXCR4 protein levels were significantly increased in Wwp1-/- BMSCs. Wwp1-/- BMSCs had increased amount of ubiquitinated JunB protein, but Runx2 ubiquitination was no change. Knocking-down JunB in Wwp1-/- BMSCs returned Runx2 protein levels to that in WT cells. Thus, Wwp1 negatively regulates osteoblast functions by affecting both their migration and differentiation. Mechanisms designed to decrease Wwp1 levels in BMSCs may represent a new approach to prevent the decrease in osteoblastic bone formation associated with aging. © 2013 American Society for Bone and Mineral Research. Tue, 02 Apr 2013 13:16:30 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1938 http://feedproxy.google.com/~r/JbmrFeed/~3/fu4YVi7YBAc/doi COL1A1 haploinsufficiency mutations lead to the mildest form of osteogenesis imperfecta (OI), OI type I. The skeletal clinical characteristics resulting from such mutations have not been characterized in detail. In this study we assessed 86 patients (36 male, 50 female; mean age 13.3 years; range 0.6 to 54 years) with COL1A1 haploinsufficiency mutations, of whom 70 were aged 21 years or less (‘pediatric’ patients). Birth history was positive for fracture or long-bone deformity in 12% of patients. The average rate of long-bone fracture (femur, tibia/fibula, humerus, radius /ulna) in pediatric patients was 0.62 fractures per year, half of which affected the tibia/fibula. Long-bone fracture rate was negatively associated with age and lumbar spine areal bone mineral density. Vertebral compression fractures were observed in 71% of the 58 pediatric patients who had lateral spine radiographs. The median number of vertebral fractures was higher for females (median 4; range 0 to 14) than for males (median 1, range 0 to 8) (P = 0.03). Lumbar spine areal bone mineral density was negatively associated with the severity of vertebral compression fractures, as reflected in the spine deformity index. Scoliosis was present in about 30% of pediatric patients but the Cobb angle was <30 degrees in all cases. The average final height z-score was -1.1, representing a deficit of 8 to 10 cm compared to the general population. In summary, OI patients with COL1A1 haploinsufficiency mutations have high rates of significant skeletal involvement. Systematic follow up of growing patients with COL1A1 haploinsufficiency mutations including radiographic screening for vertebral compression fractures and scoliosis is warranted. © 2013 American Society for Bone and Mineral Research. Mon, 25 Mar 2013 17:10:51 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1942 http://feedproxy.google.com/~r/JbmrFeed/~3/mR4d9c7kPq0/doi The receptor activator of the NF-κB ligand (RANKL) is the central player in the regulation of osteoclastogenesis and the quantity of RANKL presented to osteoclast precursors is an important factor determining the magnitude of osteoclast formation. Since osteoblastic cells are thought to be a major source of RANKL, the regulatory mechanisms of RANKL subcellular trafficking have been studied in osteoblastic cells. However, recent reports showed that osteocytes are a major source of RANKL presentation to osteoclast precursors, prompting a need to reinvestigate RANKL subcellular trafficking in osteocytes. Investigation of molecular mechanisms in detail needs well-designed in vitro experimental systems. Thus, we developed a novel co-culture system of osteoclast precursors and osteocytes embedded in collagen gel. Experiments using this model revealed that osteocytic RANKL is provided as a membrane-bound form to osteoclast precursors through osteocyte dendritic processes and that the contribution of soluble RANKL to the osteoclastogenesis supported by osteocytes is minor. Moreover, the regulation of RANKL subcellular trafficking, such as OPG-mediated transport of newly synthesized RANKL molecules to lysosomal storage compartments, and the release of RANKL to the cell surface upon stimulation with RANK, are confirmed to be functional in osteocytes. These results provide a novel understanding of the regulation of osteoclastogenesis. © 2013 American Society for Bone and Mineral Research. Mon, 25 Mar 2013 17:10:33 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1941 http://feedproxy.google.com/~r/JbmrFeed/~3/Zy7VQiWqRzM/doi p130Cas, Crk-associated substrate (Cas), is an adaptor/scaffold protein that plays a central role in actin cytoskeletal reorganization. We previously reported that p130Cas is not tyrosine-phosphorylated in osteoclasts derived from Src-deficient mice, which are congenital osteopetrotic, suggesting that p130Cas serves as a downstream molecule of c-Src and is involved in osteoclastic bone resorption. However, the physiological role of p130Cas in osteoclasts has not yet been confirmed because the p130Cas-deficient mice displayed embryonic lethality. Osteoclast-specific p130Cas conditional knockout (p130CasΔOCL-) mice exhibit a high bone mass phenotype caused by defect in multinucleation and cytoskeleton organization causing bone resorption deficiency. Bone marrow cells from p130CasΔOCL- mice were able to differentiate into osteoclasts and wild-type cells in vitro. However, osteoclasts from p130CasΔOCL- mice failed to form actin rings and resorb pits on dentine slices. Although the initial events of osteoclast attachment, such as β3-integrin or Src phosphorylation, were intact, the Rac1 activity that organizes the actin cytoskeleton was reduced, and its distribution was disrupted in p130CasΔOCL- osteoclasts. Dock5, a Rho family guanine nucleotide exchanger, failed to associate with Src or Pyk2 in osteoclasts in the absence of p130Cas. These results strongly indicate that p130Cas plays pivotal roles in osteoclastic bone resorption. © 2013 American Society for Bone and Mineral Research. Fri, 22 Mar 2013 13:41:32 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1936 http://feedproxy.google.com/~r/JbmrFeed/~3/62FoAoT_8RQ/doi To assess the roles of Lrrk1 and Lrrk2, we examined skeletal phenotypes in Lrrk1 and Lrrk2 knockout (KO) mice. Lrrk1 KO mice exhibit severe osteopetrosis caused by dysfunction of multinucleated osteoclasts, reduced bone resorption in endocortical and trabecular regions, and increased bone mineralization. Lrrk1 KO mice have lifelong accumulation of bone and respond normally to the anabolic actions of teriparatide treatment, but are resistant to ovariectomy-induced bone boss. Precursors derived from Lrrk1 KO mice differentiate into multinucleated cells in response to M-CSF/RANKL treatment, but these cells fail to form peripheral sealing zones and ruffled borders, and fail to resorb bone. The phosphorylation of c-Src at Tyr-527 is significantly elevated whereas at Tyr-416 is decreased in Lrrk1 deficient osteoclasts. The defective osteoclast function is partially rescued by overexpression of the constitutively active form of Y527F c-Src. Immunoprecipitation assays in osteoclasts detected a physical interaction of Lrrk1 with Csk. Lrrk2 KO mice do not show obvious bone phenotypes. Precursors derived from Lrrk2 KO mice differentiate into functional multinucleated osteoclasts. Our finding of osteopetrosis in Lrrk1 KO mice provides convincing evidence that Lrrk1 plays a critical role in negative regulation of bone mass in part through modulating the c-Src signaling pathway in mice. © 2013 American Society for Bone and Mineral Research. Fri, 22 Mar 2013 13:40:56 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1935 http://feedproxy.google.com/~r/JbmrFeed/~3/7D5KMrHn-dE/doi Taller women are at increased risk for fracture despite having wider bones that better tolerate bending. As wider bones require less material to achieve a given bending strength, we hypothesized that taller women assemble bones with relatively thinner and more porous cortices because excavation of a larger medullary canal may be accompanied by excavation of more intracortical canals. Three-dimensional images of distal tibia, fibula and radius were obtained in vivo using high-resolution peripheral quantitative computed tomography in a twin study of 345 females aged 40 to 61 years, 93 with at least one fracture. Cortical porosity below as well as above 100 microns, and microarchitecture were quantified using Strax1.0, a new algorithm. Multivariable linear and logistic regression using generalized estimating equation methods quantified associations between height and microarchitecture and estimated the associations with fracture risk. Each standard deviation (SD) greater height was associated with a 0.69 SD larger tibia total cross sectional area (CSA), 0.66 SD larger medullary CSA, 0.50 SD higher medullary CSA/total CSA (i.e., thinner cortices relative to the total CSA due to a proportionally larger medullary area) and 0.42 SD higher porosity (all p < 0.001). Cortical area was 0.45 SD larger in absolute terms but 0.50 SD smaller in relative terms. These observations were confirmed by examining trait correlations in twin pairs. Fracture risk was associated with height, total CSA, medullary CSA/total CSA and porosity in univariate analyses. In multivariable analyses, distal tibia, medullary CSA/total CSA and porosity predicted fracture independently; height was no longer significant. Each SD greater porosity was associated with fracture; odds ratios; distal tibia 1.55; 95% CI: 1.11–2.15, distal fibula 1.47; 95% CI 1.14–1.88, distal radius 1.22; 95% CI 0.96–1.55. Taller women assemble wider bones with relatively thinner and more porous cortices predisposing to fracture. © 2013 American Society for Bone and Mineral Research. Wed, 20 Mar 2013 10:11:47 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1934 http://feedproxy.google.com/~r/JbmrFeed/~3/TCD9yCWUMh0/doi Parathyroid hormone (PTH) has a significant role as an anabolic hormone in bone when administered by intermittent injection. Previous microarray studies in our laboratory have shown that the most highly regulated gene, monocyte chemoattractant protein-1 (MCP-1), is rapidly and transiently induced when hPTH(1–34) is injected intermittently in rats. Through further in vivo studies, we found that rats treated with hPTH(1–34) showed a significant increase in serum MCP-1 levels 2 hours after PTH injection compared to basal levels. Using immunohistochemistry, increased MCP-1 expression in osteoblasts and osteocytes is evident after PTH treatment. PTH also increased the number of marrow macrophages. MCP-1 knockout mice injected daily with hPTH(1–34) showed less trabecular bone mineral density and bone volume compared to wild type mice as measured by pQCT and microCT. Histomorphometric analysis revealed that the increase in osteoclast surface and osteoclast number observed with intermittent PTH treatment in the wild type mice was completely eliminated in the MCP-1 null mice, as well as much lower numbers of macrophages. Consequently, the lack of osteoclast and macrophage activity in the MCP-1 null mice was paralleled by a reduction in bone formation. We conclude that osteoblast and osteocyte MCP-1 expression is an important mediator for the anabolic effects of PTH on bone. © 2013 American Society for Bone and Mineral Research. Wed, 20 Mar 2013 10:11:33 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1933 http://feedproxy.google.com/~r/JbmrFeed/~3/nA5dFoaYvkU/doi Mouse embryonic fibroblasts (MEFs) differentiate into fully functional chondrocytes in response to bone morphogenetic protein-2 (BMP-2). However, the comprehensive proteomic aspect of BMP-2–induced chondrogenesis remains unknown. We took advantage of quantitative proteomic analysis based on isobaric tag for relative and absolute quantitation (iTRAQ) and on-line 2D nano-liquid chromatography/tandem mass spectrometry (LC/MS/MS) to identify proteins differentially expressed during BMP-2–induced chondrogenic differentiation of MEFs. We found 85 downregulated proteins, and Ingenuity Pathways Analysis (IPA) revealed a protein-protein network with chromodomain-helicase-DNA-binding protein 4 (Chd4) in the center. Chromatin immunoprecipitation (ChIP) and nuclease hypersensitivity assays showed that Chd4, interacting with Hdac1/2, cooperates with its related proteins Kap1 and Cbx1 to bind at −207/−148 of the Sox9 promoter. We also provided evidence that let-7a targets the 3'UTR of Chd4 to promote chondrogenesis of MEFs. Together, our findings indicate that BMP-2 induced the upregulation of let-7a, targeting Chd4 and positively controlling the chondrogenic differentiation of MEFs. These findings illustrate epigenetic regulation of the chondrogenic differentiation process and also expand the understanding of the involved intracellular mechanisms. © 2013 American Society for Bone and Mineral Research. Wed, 20 Mar 2013 10:11:18 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1932 http://feedproxy.google.com/~r/JbmrFeed/~3/38sXit13WvQ/doi This study assessed the ability of multisite quantitative ultrasound (mQUS) to predict fracture over a five-year follow-up. Participants were a subset of the Canadian Multicentre Osteoporosis Study. mQUS-assessed speed of sound (SOS in m/s) at three sites (distal radius, tibia and phalanx) and extensive questionnaires were completed, after which participants were followed for five years and incident fractures recorded. Two survival analyses were completed for each site – a univariate analysis and an adjusted multivariate analysis controlling for age, anti-resorptive use, femoral neck bone mineral density, number of diseases, previous fractures, BMI, parental history of hip fracture, current smoking, current alcoholic drinks >3 per day, current using glucocorticoids, and rheumatoid arthritis diagnosis (variables from the FRAX 10-year fracture risk assessment tool). The unit of change for regression analyses was one standard deviation for all measurement sites, specific to site and sex. Separate analyses were completed for all clinical fractures, non-vertebral fractures and hip fractures by sex. There were 2633 women and 1108 men included and they experienced 204 incident fractures over five years (5.5% fractured). Univariate models revealed statistically significant (p < 0.05) predictive ability of mQUS for all three measurement sites for women alone for all three fracture types (one standard deviation decrease in SOS was associated with a 52–130% increase in the risk of fracture), but not for the men's group. The adjusted model found that measures at the distal radius and tibia in the women's group could significantly (p < 0.05) predict all clinical fractures and non-vertebral fractures within the next five years (one standard deviation decrease in SOS was associated with a 25–31% increase in the risk of fracture). mQUS provided significant five-year clinical fracture prediction in women, independent of bone mineral density and other significant risk factors for fracture, when measured at the distal radius and tibia sites. © 2013 American Society for Bone and Mineral Research. Wed, 20 Mar 2013 10:11:05 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1931 http://feedproxy.google.com/~r/JbmrFeed/~3/OaLyDfZCN5w/doi Bisphosphonates are widely-prescribed to increase bone density in postmenopausal women with osteopenia or osteoporosis. Amino-bisphosphonates have numerous anticancer properties and reduce bone-metastases in cancer patients. Several studies, including the Women's Health Initiative (WHI), have found that use of oral bisphosphonates is associated with reduced risk of developing breast cancer, but less is known about associations with other common malignancies in women such as colorectal cancer (CRC). A few case-control and retrospective cohort studies have reported decreased risk of CRC among bisphosphonate users. In contrast, a prospective cohort study found no association. We evaluated the association between oral bisphosphonate use and CRC incidence in 156,826 postmenopausal women, ages 50–79, who participated in WHI clinical trials and observational study. A detailed health interview was conducted at baseline, and bisphosphonate use was ascertained from an inventory of regularly-used medications at baseline and over follow-up. A total of 1,931 women were diagnosed with incident invasive CRC during a median follow-up of 12 years. Alendronate was the most commonly used bisphosphonate, accounting for >90% of the total person-years of use. The association between oral bisphosphonate use and CRC risk did not reach statistical significance (hazard ratio [HR] from multivariable-adjusted models, 0.88; 95% confidence interval [CI], 0.72–1.07; P = 0.19). Furthermore, we did not observe greater risk reductions for women with longer duration of use. Uncontrolled confounding may explain why previous studies have observed an association. © 2013 American Society for Bone and Mineral Research. Wed, 20 Mar 2013 10:10:51 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1930 http://feedproxy.google.com/~r/JbmrFeed/~3/IstUMrX_gGk/doi Pregnancy invokes a doubling of intestinal calcium absorption while lactation programs skeletal resorption to provide calcium to milk. Post-weaning bone formation restores the skeleton's bone mineral content (BMC), but the factors that regulate this are not established. We used Pth null mice to test whether parathyroid hormone (PTH) is required for post-weaning skeletal recovery. On a normal 1% calcium diet, WT and Pth null mice each gained BMC during pregnancy, declined 15–18% below baseline during lactation, and restored the skeleton above baseline BMC within 14 days post-weaning. A 2% calcium diet reduced the lactational decline in BMC without altering the gains achieved during pregnancy and post-weaning. The hypocalcemia and hyperphosphatemia of Pth null mice normalized during lactation and serum calcium remained normal during post-weaning. Osteocalcin and P1NP each rose significantly after lactation to similar values in WT and Pth null. Serum calcitriol increased 5-fold during pregnancy in both genotypes while vitamin D binding protein levels were unchanged. Absence of PTH blocked a normal rise in fibroblast growth factor-23 (FGF23) during pregnancy despite high calcitriol. A 30-fold higher expression of Cyp27b1 in maternal kidneys vs. placenta suggests that the pregnancy-related increase in calcitriol comes from the kidneys. Conversely, substantial placental expression of Cyp24a1 may contribute significantly to the metabolism of calcitriol. In conclusion, PTH is not required to upregulate renal expression of Cyp27b1 during pregnancy or to stimulate recovery from loss of BMC caused by lactation. A calcium-rich diet in rodents suppresses skeletal losses during lactation, unlike clinical trials which showed no effect of supplemental calcium on lactational decline in BMC. © 2013 American Society for Bone and Mineral Research. Sun, 17 Mar 2013 18:26:03 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1925 http://feedproxy.google.com/~r/JbmrFeed/~3/MUZNylMOxN0/doi Vitamin D deficiency has been recognized as a major public health issue worldwide. Recent studies have indicated that genetic factors might play an important role in determining serum 25-hydroxy vitamin D [25(OH)D] levels in Caucasians and African Americans. However, the genes that contribute to the variation in serum 25(OH)D levels in Chinese are unknown. In this study, we screened 15 key genes within the vitamin D metabolic pathway using 96 single-nucleotide polymorphism (SNP) markers in a group of 2,897 unrelated healthy Chinese subjects. Significant confounding factors that may influence the variability in serum 25(OH)D levels were used as covariates for association analyses. An association test for quantitative traits was performed to evaluate the association between candidate genes and serum 25(OH)D levels. In the present study, variants and/or haplotypes in GC, CYP2R1 and DHCR7/NADSYN1 were identified as being associated with 25(OH)D levels. Participants with 3 or 4 risk alleles of the two variants (GC-rs4588 and CYP2R1-rs10766197) had an increased chance of presenting with a 25(OH)D concentration lower than 20 ng/mL (2.121, 1.586–2.836, p = 6.1 × 10−8) compared with those lacking the risk alleles. Each additional copy of a risk allele was significantly associated with a 0.12-fold decrease in the log-25(OH)D concentration (p = 3.7 × 10−12). Haplotype TGA of GC rs705117-rs2282679-rs1491710, haplotype GAGTAC of GC rs842999-rs705120-rs222040-rs4588-rs7041-rs10488854, haplotype CA of GC rs1155563-rs222029, and haplotype AAGA of CYP2R1 rs7936142-rs12794714-rs2060793-rs16930609 were genetic risk factors toward a lower 25(OH)D concentration. In contrary, haplotype TGGGCCC of DHCR7/NADSYN1 rs1790349-rs7122671-rs1790329-rs11606033-rs2276360-rs1629220-rs2282618 were genetic protective factors. The results suggest that the GC, CYP2R1 and DHCR7/NADSYN1 genes might contribute to variability in the serum 25(OH)D levels in a healthy Chinese population in Shanghai. These markers could be used as tools in Mendelian randomization analyses of vitamin D, and they could potentially be drug targets in the Chinese population in Shanghai. © 2013 American Society for Bone and Mineral Research. Sat, 16 Mar 2013 22:22:48 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1926 http://feedproxy.google.com/~r/JbmrFeed/~3/fxbsFyT03-0/doi Osteoblasts, which orchestrate the deposition of small apatite crystals through the expression of nucleating proteins, have been shown to also express clock genes associated with the circadian signaling pathway. We hypothesized that protein-mediated bone mineralization may be linked to circadian oscillator mechanisms functioning in peripheral bone tissue. In this study, Per1 expression in ex vivo neonatal murine calvaria organ cultures was monitored for 6 days using a Per1-luciferase transgene as a bioluminescent indicator of clock function. Fluctuations in Per1 expression had a period of 25 ± 4 hours (n = 14) with early expression at CT09:59 ± 03:37 (circadian time). We also established the kinetics of mineral deposition in developing bone by using non-invasive Raman microscopy to track mineral accumulation in calvarial tissue. The content and quality of newly deposited mineral was continually examined at the interparietal bone/fontanel boundary for a period of 6 days with 1 hour temporal resolution. Using this approach, mineralization over time exhibited bursts of mineral deposition followed by little or no deposition, which was recurrent with a periodicity of 26.8 ± 9.6 hours. As many as 6 near-daily mineralization events were observed in the calvaria before deposition ceased. Earliest mineralization events occurred at CT16:51 ± 03:45, which is 6 hours behind Per1 expression. These findings are consistent with the hypothesis that mineralization in developing bone tissue is regulated by a local circadian oscillator mechanism. © 2013 American Society for Bone and Mineral Research. Sat, 16 Mar 2013 22:22:29 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1924 http://feedproxy.google.com/~r/JbmrFeed/~3/mg-CYSPmFjs/doi Fibroblast growth factor 23 (FGF23) is an osteocyte-derived hormone that regulates phosphate and vitamin D homeostasis. Through unknown mechanisms, certain intravenous iron preparations induce acute, reversible increases in circulating FGF23 levels that lower serum phosphate in association with inappropriately low levels of calcitriol, similar to genetic diseases of primary FGF23 excess. In contrast, studies in wild-type mice suggest that iron deficiency stimulates fgf23 transcription but does not result in hypophosphatemia because FGF23 is cleaved within osteocytes by an unknown catabolic system. We tested the association of iron deficiency anemia with C-terminal FGF23 (cFGF23) and intact FGF23 (iFGF23) levels in 55 women with a history of heavy uterine bleeding, and assessed the longitudinal biochemical response over 35 days to equivalent doses of randomly-assigned, intravenous elemental iron in the form of ferric carboxymaltose (FCM) or iron dextran. Iron deficiency was associated with markedly elevated cFGF23 (807.8 ± 123.9 RU/ml) but normal iFGF23 (28.5 ± 1.1 pg/ml) levels at baseline. Within 24 hours of iron administration, cFGF23 levels fell by approximately 80% in both groups. In contrast, iFGF23 transiently increased in the FCM group alone, and was followed by a transient, asymptomatic reduction in serum phosphate <2.0 mg/dL in 10 women in the FCM group compared to none in the iron dextran group. Reduced serum phosphate was accompanied by increased urinary fractional excretion of phosphate, decreased calcitriol levels and increased parathyroid hormone levels. These findings suggest that iron deficiency increases cFGF23 levels, and that certain iron preparations temporarily increase iFGF23 levels. We propose that intravenous iron lowers cFGF23 in humans by reducing fgf23 transcription as it does in mice, whereas carbohydrate moieties in certain iron preparations may simultaneously inhibit FGF23 degradation in osteocytes leading to transient increases in iFGF23 and reduced serum phosphate. © 2013 American Society for Bone and Mineral Research. Sat, 16 Mar 2013 22:22:03 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1923 http://feedproxy.google.com/~r/JbmrFeed/~3/tkHbNsLgFEM/doi Bone mineral density (BMD) has been inversely associated with subclinical and clinical cardiovascular disease (CVD) in population studies, but the potential mechanisms underlying this relationship are unclear. To test if there is a genetic basis underlying this association, we determined the phenotypic and genetic correlations between BMD and carotid artery ultrasound measures in families. Dual-energy X-ray absorptiometry and peripheral quantitative computed tomography were used to measure BMD in 461 African ancestry individuals belonging to 7 large, multigenerational families (mean family size 66; 3,414 total relative pairs). Carotid artery ultrasound was used to measure adventitial diameter (AD) and intima-media thickness (IMT). Phenotypic and genetic correlations between BMD and carotid measures were determined using pedigree-based maximum likelihood methods. We adjusted for potential confounding factors, including age, sex, body weight, height, menopausal status, smoking, alcohol intake, walking for exercise, diabetes, hypertension, serum lipid and lipoprotein levels, inflammation markers and kidney function. We found statistically significant phenotypic (ρ = −0.19) and genetic (ρG = −0.70) correlations (P < 0.05 for both) between lumbar spine BMD and AD in fully adjusted models. There was also a significant genetic correlation between trabecular BMD at the radius and IMT in fully adjusted models (ρG = −0.398; P < 0.05). Our findings indicate that the previously observed association between osteoporosis and CVD in population-based studies may be partly mediated by genetic factors and that the pleiotropic effects of these genes may operate independently of traditional risk pathways. © 2013 American Society for Bone and Mineral Research. Sat, 16 Mar 2013 22:21:00 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1922 http://feedproxy.google.com/~r/JbmrFeed/~3/sOJJE46eqLw/doi Sclerostin is a potent inhibitor of bone formation but has been shown to correlate positively with areal bone mineral density (aBMD). Little is known about its relationship to parameters of bone strength and volumentric BMD (vBMD) as measured by peripheral quantitative computed tomography (pQCT). We measured both serum sclerostin and parameters of tibial bone size and strength by pQCT to characterize this relationship. Our study population consisted of 223 Caucasian and 35 African American women (mean age 87) from the Study of Osteoporotic Fractures (SOF) cohort, who had usable pQCT scans of the tibia at sites 4% (T4%), 33% (T33%), and 66% (T66%) from the ankle. Analysis of covariance was used to test for differences in age-adjusted means of aBMD, pQCT variables, and serum biomarkers across sclerostin quartiles. Black women had significantly lower median sclerostin (34.3 pmol/L) than white women (48.5 pmol/L) (p = 0.05). Women in the highest sclerostin quartile had 7–14.5% higher hip aBMD and pQCT parameters of vBMD and bone size than those in the lowest quartile in multivariate models adjusting for age, race, weight, height and diabetes. The association of sclerostin with parameters of bone strength differed dramatically between T33% and T66% sites. At T66%, women in the highest sclerostin quartile had pQCT strength parameters 9.4–15.3% greater than the lowest quartile, whereas no trend was found for the T33% site. Our results suggest paradoxical associations between circulating sclerostin and bone size, density and strength. © 2013 American Society for Bone and Mineral Research. Fri, 15 Mar 2013 12:03:40 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1929 http://feedproxy.google.com/~r/JbmrFeed/~3/wuzw4XCgu30/doi In biological tissues such as bone, cell function and activity crucially depend on the physical properties of the extracellular matrix which the cells synthesize and condition. During bone formation and remodeling, osteoblasts get embedded into the matrix they deposit and differentiate to osteocytes. These cells form a dense network throughout the entire bone material. Osteocytes are known to orchestrate bone remodeling. However, the precise role of osteocytes during mineral homeostasis and their potential influence on bone material quality remains unclear. To understand the mutual influence of osteocytes and extracellular matrix, it is crucial to reveal their network organization in relation to the properties of their surrounding material. Here we visualize and topologically quantify the osteocyte network in mineralized bone sections with confocal laser scanning microscopy. At the same region of the sample, synchrotron small angle x-ray scattering is used to determine nanoscopic bone mineral particle size and arrangement relative to the cell network. Major findings are that most of the mineral particles reside within less than a micrometer from the nearest cell network channel and that mineral particle characteristics depend on the distance from the cell network. The architecture of the network reveals optimization with respect to transport costs between cells and to blood vessels. In conclusion, these findings quantitatively show that the osteocyte network provides access to a huge mineral reservoir in bone due to its dense organization. The observed correlation between the architecture of osteocyte networks and bone material properties supports the hypothesis that osteocytes interact with their mineralized vicinity and thus, participate in bone mineral homeostasis. © 2013 American Society for Bone and Mineral Research. Wed, 13 Mar 2013 08:26:53 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1927 http://feedproxy.google.com/~r/JbmrFeed/~3/Ez8yG7I8iPw/doi The further development in research of bone regeneration is necessary to meet the clinical demand for bone reconstruction. Plasminogen is a critical factor of the tissue fibrinolytic system, which mediates tissue repair in the skin and liver. However, the role of the fibrinolytic system in bone regeneration remains unknown. Herein, we investigated bone repair and ectopic bone formation using plasminogen deficient (Plg−/−) mice. Bone repair of the femur is delayed in Plg−/− mice, unlike that in the wild-type (Plg+/+) mice. The deposition of cartilage matrix and osteoblast formation were both decreased in Plg−/− mice. Vessel formation, macrophage accumulation, and the levels of vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGF-β) were decreased at the site of bone damage in Plg−/− mice. Conversely, heterotopic ossification was not significantly different between Plg+/+ and Plg−/− mice. Moreover, angiogenesis, macrophage accumulation, and the levels of VEGF and TGF-β were comparable between Plg+/+ and Plg−/− mice in heterotopic ossification. Our data provide novel evidence that plasminogen is essential for bone repair. The present study indicates that plasminogen contributes to angiogenesis related to macrophage accumulation, TGF-β, and VEGF, thereby leading to the enhancement of bone repair. © 2013 American Society for Bone and Mineral Research. Sun, 03 Mar 2013 15:44:14 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1921 http://feedproxy.google.com/~r/JbmrFeed/~3/75GbHCCN7ts/doi States of growth hormone (GH) resistance, such those observed in Laron's dwarf patients, are characterized by mutations in the GH receptor (GHR), decreased serum and tissue IGF-1 levels, impaired glucose tolerance, and impaired skeletal acquisition. IGF-1 replacement therapy in such patients increases growth velocity but does not normalize growth. Herein we combined the GH-resistant (GHR knockout, GHRKO) mouse model with mice expressing the hepatic Igf-1 transgene (HIT) to generate the GHRKO-HIT mouse model. In GHRKO-HIT mice, serum IGF-1 levels were restored via transgenic expression of Igf-1, allowing us to study how endocrine IGF-1 affects growth, metabolic homeostasis, and skeletal integrity. We show that in a GH-resistant state, normalization of serum IGF-1 improved body adiposity and restored glucose tolerance but was insufficient to support normal skeletal growth, resulting in an osteopenic skeletal phenotype. The inability of serum IGF-1 to restore skeletal integrity in the total absence of GHR likely resulted from reduced skeletal Igf-1 gene expression, blunted GH-mediated effects on the skeleton that are independent of serum or tissue IGF-1, and from poor delivery of IGF-1 to the tissues. These findings are consistent with clinical data showing that IGF-I replacement therapy in patients with Laron's syndrome does not achieve full skeletal growth. © 2013 American Society for Bone and Mineral Research. Sun, 03 Mar 2013 15:41:50 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1920 http://feedproxy.google.com/~r/JbmrFeed/~3/6XaKbztbKJo/doi While high-resolution peripheral quantitative computed tomography (HR-pQCT) has advanced clinical assessment of trabecular bone microstructure, nonlinear microstructural finite element (µFE) prediction of yield strength by HR-pQCT voxel model is impractical for clinical use due to its prohibitively high computational costs. The goal of this study was to develop an efficient HR-pQCT-based plate and rod (PR) modeling technique to fill the unmet clinical need for fast bone strength estimation. By using individual trabecula segmentation (ITS) technique to segment the trabecular structure into individual plates and rods, a patient-specific PR model was implemented by modeling each trabecular plate with multiple shell elements and each rod with a beam element. To validate this modeling technique, predictions by HR-pQCT PR model were compared with those of the registered high resolution µCT voxel model of 19 trabecular sub-volumes from human cadaveric tibiae samples. Both Young's modulus and yield strength of HR-pQCT PR models strongly correlated with those of µCT voxel models (r2=0.91 and 0.86). Notably, the HR-pQCT PR models achieved major reductions in element number (>40-fold) and CPU time (>1,200-fold). Then, we applied PR model µFE analysis to HR-pQCT images of 60 postmenopausal women with (n=30) and without (n=30) a history of vertebral fracture. HR-pQCT PR model revealed significantly lower Young's modulus and yield strength at the radius and tibia in fracture subjects compared to controls. Moreover, these mechanical measurements remained significantly lower in fracture subjects at both sites after adjustment for aBMD T-score at the ultradistal radius or total hip. In conclusion, we validated a novel HR-pQCT PR model of human trabecular bone against µCT voxel models and demonstrated its ability to discriminate vertebral fracture status in postmenopausal women. This accurate nonlinear µFE prediction of HR-pQCT PR model, which requires only seconds of desktop computer time, has tremendous promise for clinical assessment of bone strength. © 2013 American Society for Bone and Mineral Research. Sun, 03 Mar 2013 15:40:06 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1919 http://feedproxy.google.com/~r/JbmrFeed/~3/i7NNyRsbXEo/doi Rosiglitazone (RSG) is an anti-diabetic drug that has been associated with increased peripheral fractures primarily in postmenopausal women. In this report, we investigated the underlying mechanisms of RSG-associated bone loss in ovariectomized (OVX) rats and determine whether changes in bone parameters associated with RSG administration are reversible on treatment cessation or preventable by co-administration with an antiresorptive agent. Nine-month-old Sprague-Dawley rats underwent OVX or sham operation. Sham-operated rats received oral vehicle only; OVX animals were randomized to receive vehicle, RSG, alendronate (ALN) or RSG plus ALN for 12 weeks. All treatment started the day after ovariectomy. After the 12 week treatment period, the OVX and RSG groups also underwent an 8-week treatment-free recovery period. Bone densitometry measurements, bone turnover markers, biomechanical testing and histomorphometric analysis were conducted. Micro-computed tomography was also used to investigate changes in microarchitecture. RSG significantly increased deoxypyridinoline levels compared with OVX. Significant exacerbation of OVX-induced loss of bone mass, strength and microarchitectural deteriorations was observed in RSG-treated OVX animals compared with OVX controls. These effects were observed predominantly at sites rich in trabecular bone with less pronounced effects in cortical bone. Co-administration of RSG and ALN prevented the bone loss associated with RSG treatment. Following cessation of RSG treatment, effects on bone mass and strength showed evidence of reversal. Thus, treatment of OVX rats with RSG results in loss of bone mass and strength, primarily at sites rich in trabecular bone mainly due to increased bone resorption. These effects can be prevented by concomitant treatment with ALN and may be reversed following discontinuation of RSG. © 2013 American Society for Bone and Mineral Research. Sun, 03 Mar 2013 15:38:57 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1918 http://feedproxy.google.com/~r/JbmrFeed/~3/xtScnGfOo7I/doi The increased osteocyte death by oxidative stress (OS) during aging is a major cause contributing to the impairment of bone quality and bone loss. However, the underlying molecular mechanism is largely unknown. Here, we showed that H2O2 induced cell death of primary osteocytes and osteocytic MLO-Y4 cells, and also caused dose-dependent decrease expression of gap junction and hemichannel-forming connexin 43 (Cx43). The decrease of Cx43 expression was also demonstrated with the treatment of other oxidants, rotenone and menadione. Antioxidant reversed the effects of oxidants on Cx43 expression and osteocyte cell death. Cx43 protein was also much lower in the osteocytes from 20-month as opposed to the 5-week or 20-week old mice. Dye transfer assay showed that H2O2 reduced the gap junction intercellular communication (GJIC). In contrast to the effect on GJIC, there was a dose-dependent increase of hemichannel function by H2O2, which was correlated with the increased cell surface expression of Cx43. Cx43 (E2) antibody, an antibody which specifically blocks Cx43 hemichannel activity but not gap junctions completely blocked dye uptake induced by H2O2 and further exacerbated H2O2-induced osteocytic cell death. In addition, knockdown of Cx43 expression by siRNA increased the susceptibility of the cells to OS-induced death. Together, our study provides a novel cell protective mechanism mediated by osteocytic Cx43 channels against OS. © 2013 American Society for Bone and Mineral Research. Sat, 02 Mar 2013 23:10:17 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1917 http://feedproxy.google.com/~r/JbmrFeed/~3/n5E1K1-1czo/doi Chronic kidney disease (CKD) patients may have high rates of bone loss and fractures, but microarchitectural and biochemical mechanisms of bone loss in CKD patients have not been fully described. In this longitudinal study of 53 patients with CKD Stages 2-5D, we used dual energy X-ray absorptiometry (DXA), high resolution peripheral quantitative computed tomography (HRpQCT) and biochemical markers of bone metabolism to elucidate effects of CKD on the skeleton. Median follow-up was 1.5 years (Range 0.9 to 4.3 years); bone changes were annualized and compared to baseline. By DXA, there were significant declines in areal bone mineral density (BMD) of the total hip and ultradistal radius: -1.3% (95% CI: -2.1 to -0.6) and -2.4% (95% CI: -4.0 to -0.9), respectively. By HRpQCT at the distal radius, there were significant declines in cortical area, density and thickness, and increases in porosity: -2.9% (95% CI -3.7 to -2.2), -1.3% (95% CI -1.6 to -0.6), -2.8% (95% CI -3.6 to -1.9), and +4.2% (95% CI 2.0 to 6.4) respectively. Radius trabecular area increased significantly: +0.4% (95% CI 0.2 to 0.6), without significant changes in trabecular density or microarchitecture. Elevated time-averaged levels of parathyroid hormone (PTH) and bone turnover markers predicted cortical deterioration. Higher levels of serum 25-hydroxyvitamin D predicted decreases in trabecular network heterogeneity. These data suggest that significant cortical loss occurs with CKD, which is mediated by hyperparathyroidism and elevated turnover. Future investigations are required to determine whether these cortical losses can be attenuated by treatments that reduce PTH levels and remodeling rates. © 2013 American Society for Bone and Mineral Research. Sat, 02 Mar 2013 23:08:06 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1916 http://feedproxy.google.com/~r/JbmrFeed/~3/HmzkrpklS14/doi Higher levels of C-Reactive Protein (CRP), an inflammatory marker, are associated with increased fracture risk, although previous studies on CRP and bone mineral density (BMD) have yielded conflicting results. We aimed to test the hypotheses that composite indices of femoral neck strength relative to load, which are inversely associated with fracture risk, would also be inversely associated with CRP, and would explain part of the association between CRP and fracture risk. We analyzed data from a multi-site, multi-ethnic prospective cohort of 1872 community-dwelling women, pre- or early peri-menopausal at baseline. Femoral neck composite strength indices in three failure modes were calculated using DXA-derived femoral neck width (FNW), femoral neck axis length (FNAL), femoral neck BMD and body size at baseline, as BMD*FNW/weight for compression strength, BMD*(FNW)2/(FNAL*weight) for bending strength, and BMD*FNW*FNAL/(height*weight) for impact strength. Incident non-digital, non-craniofacial fractures were ascertained annually over median follow up of 9 years. In analyses adjusted for age, race/ethnicity, diabetes, menopause transition stage, body mass index, smoking, alcohol use, physical activity, medications, prior fracture and study site, CRP was associated inversely with each composite strength index (0.035 to 0.041SD decrement per doubling of CRP, all p<.001), but not associated with femoral neck or lumbar spine BMD. During the follow-up, 194 women (10.4%) had fractures. In Cox proportional hazards analyses, fracture hazard increased linearly with log(CRP), only for CRP levels ⇒ 3 mg/L. Addition of femoral neck or lumbar spine BMD to the model did not attenuate the CRP-fracture association. However, addition of any of the composite strength indices attenuated the CRP-fracture association and made it statistically non-significant. We conclude that fracture risk increases with increasing CRP, only above the threshold of 3mg/L. Unlike BMD, composite strength indices are inversely related to CRP levels, and partially explain the increased fracture risk associated with inflammation. © 2013 American Society for Bone and Mineral Research. Sat, 02 Mar 2013 23:06:31 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1915 http://feedproxy.google.com/~r/JbmrFeed/~3/jEGv-HifXLk/doi Introduction Distal forearm fractures are among the most common fractures during childhood, but it remains unclear whether they predict an increased fracture risk later in life. Methods We studied a population-based cohort of 1776 children ≤ 18 years of age, from Olmsted County, Minnesota, who had a distal forearm fracture in 1935-1992. Incident fractures occurring at age ≥ 35 years were identified through review of complete medical records using the linkage system of the Rochester Epidemiology Project. Observed non-pathologic fractures resulting from no more than moderate trauma (fragility fractures) were compared with expected numbers estimated from fracture site-specific incidence rates, based on age, sex and calendar year, for Olmsted County (standardized incidence ratios [SIR]). Results In 1086 boys (mean [± SD] age, 11 ± 4 years) and 690 girls (10 ± 4 years) followed for 27,292 person-years after age 35 years, subsequent fragility fractures were observed in 144 (13%) men and 74 (11%) women. There was an increased risk for future fragility fractures in boys who had a distal forearm fracture (SIR, 1.9; 95% CI, 1.6-2.3) but not girls (SIR, 1.0; 95% CI, 0.8-1.2). Fragility fractures at both major osteoporotic (hip, spine, wrist and shoulder) sites (SIR, 2.6; 95% CI, 2.1-3.3) and remaining sites (SIR, 1.7; 95% CI, 1.3-2.0) were increased in men, irrespective of age at distal forearm fracture as boys. Conclusions A distal forearm fracture in boys, but not girls, is associated with an increased risk for fragility fractures as older adults. It is necessary to determine whether the increased fractures observed in men is due to persistent deficits of bone strength, continued high fracture risk activity, or both. Until then, men should be asked about a childhood distal forearm fracture and, if so, warrant further screening and counseling on measures to optimize bone health and prevent fractures. © 2013 American Society for Bone and Mineral Research. Sat, 02 Mar 2013 22:52:27 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1914 http://feedproxy.google.com/~r/JbmrFeed/~3/2ld6TUVJ6mg/doi JTT-305/MK-5442 is a Calcium Sensing Receptor (CaSR) allosteric antagonist being investigated for the treatment of osteoporosis. JTT-305/MK-5442 binds to CaSRs, thus preventing receptor activation by Ca2+. In the parathyroid gland, this results in the release of parathyroid hormone (PTH). Sharp spikes in PTH secretion followed by rapid returns to baseline are associated with bone formation, while sustained elevation in PTH is associated with bone resorption. We have developed a semi-mechanistic, non-population model of the time-course relationship between JTT-305/MK-5442 and whole plasma PTH concentrations to describe both the secretion of PTH and the kinetics of its return to baseline levels. We obtained mean concentration data for JTT-305/MK-5442 and whole PTH from a multiple dose study in US postmenopausal women at doses of 5, 10, 15 and 20 mg. We hypothesized that PTH is released from two separate sources: a reservoir that is released rapidly (within minutes) in response to reduction in Ca2+ binding, and a second source released more slowly following hours of reduced Ca2+ binding. We modeled the release rates of these reservoirs as Emax functions of JTT-305/MK-5442 concentration. Our model describes both the dose-dependence of PTH Tmax and Cmax, and the extent and duration of the observed non-monotonic return of PTH to baseline levels following JTT-305/MK-5442 administration. © 2013 American Society for Bone and Mineral Research. Thu, 21 Feb 2013 11:47:23 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1900 http://feedproxy.google.com/~r/JbmrFeed/~3/sk7LofPIVOA/doi Age-standardized rates of hip fracture in Canada declined during the period 1985 to 2005. We investigated whether this incidence pattern is explained by period effects, cohort effects or both. All hospitalizations during the study period with primary diagnosis of hip fracture were identified. Age- and sex-specific hip fracture rates were calculated for nineteen 5-years age groups and four 5-years calendar periods, resulting in twenty births cohorts. The effect of age, calendar period, and birth cohort on hip fracture rates was assessed using age-period-cohort models as proposed by Clayton and Schiffers. From 1985 to 2005, a total of 570,872 hospitalizations for hip fracture were identified. Age-standardized rates for hip fracture have progressively declined for females and males. The annual linear decrease in rates per 5 year period were 12% for females and 7% for males (both p<0.0001). Significant birth cohort effects were also observed for both sexes (p<0.0001). Cohorts born prior to 1950 had a higher risk of hip fracture, while those born after 1954 had a lower risk. After adjusting for age and constant annual linear change (drift term common to both period and cohort effects), we observed a significant nonlinear birth cohort effect for males (p=0.0126) but not for females (p=0.9960). In contrast, the nonlinear period effect, after adjustment for age and drift term was significant for females (p=0.0373) but not for males (p=0.2515). For males, we observed no additional nonlinear period effect after adjusting for age and birth cohort whereas for females, we observed no additional nonlinear birth cohort effect after adjusting for age and period. Although hip fracture rates decreased in both sexes, different factors may explain these changes. In addition to the constant annual linear decrease, non-linear birth cohort effects were identified for males and calendar period effects were identified for females as possible explanations. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 13:49:24 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1863 http://feedproxy.google.com/~r/JbmrFeed/~3/waKOPYOmuUU/doi Functional ablation of tissue-nonspecific alkaline phosphatase (TNAP) (Alpl-/- mice) leads to hypophosphatasia, characterized by rickets/osteomalacia attributable to elevated levels of extracellular inorganic pyrophosphate, a potent mineralization inhibitor. Osteopontin (OPN) is also elevated in the plasma and skeleton of Alpl-/- mice. Phosphorylated OPN is known to inhibit mineralization, however, the phosphorylation status of the increased OPN found in Alpl-/- mice is unknown. Here, we generated a transgenic mouse line expressing human TNAP under control of an osteoblast-specific Col1a1 promoter (Col1a1-Tnap). The transgene is expressed in osteoblasts, periosteum, and cortical bones, and plasma levels of TNAP in mice expressing Col1a1-Tnap are 10-20 times higher than those of wild-type mice. The Col1a1-Tnap animals are healthy and exhibit increased bone mineralization by microCT analysis. Crossbreeding of Col1a1-Tnap transgenic mice to Alpl-/- mice rescues the lethal hypophosphatasia phenotype characteristic of this disease model. Osteoblasts from [Col1a1-Tnap] mice mineralize better than non-transgenic controls and osteoblasts from [Col1a1-Tnap+/-; Alpl-/-] mice are able to mineralize to the level of Alpl+/- heterozygous osteoblasts, while Alpl-/- osteoblasts show no mineralization. We found that the increased levels of OPN in bone tissue of Alpl-/- mice are comprised of phosphorylated forms of OPN while WT and [Col1a1-Tnap+/-; Alpl-/-] mice had both phosphorylated and dephosphorylated forms of OPN. OPN from [Col1a1-Tnap] osteoblasts were more phosphorylated than non-transgenic control cells. Titanium dioxide-liquid chromatography and tandem mass spectrometry analysis revealed that OPN peptides derived from Alpl-/- bone and osteoblasts yielded a higher proportion of phosphorylated peptides than samples from WT mice, and at least two phosphopeptides, p(S174FQVS178DEQY182PDAT186DEDLT191)SHMK and FRIp(S299HELES304S305S306S307)EVN, with one non-localized site each, appear to be preferred sites of TNAP action on OPN. Our data suggest that the pro-mineralization role of TNAP may be related not only to its accepted pyrophosphatase activity but also to its ability to modify the phosphorylation status of OPN. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 11:46:58 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1901 http://feedproxy.google.com/~r/JbmrFeed/~3/O0pk0kw1ISM/doi We have recently observed an increased risk for vertebral fractures (VF) in a randomized controlled trial comparing the analgesic effect of vertebroplasty (VP) versus conservative treatment in symptomatic VF. The aim of the present study was to evaluate the risk factors related to the development of VF after VP in these patients. We evaluated risk factors including age, gender, bone mineral density, the number, type and severity of vertebral deformities at baseline, the number of vertebral bodies treated, the presence and location of disk cement leakage, bone remodeling (determining bone turnover markers) and 25 hydroxyvitamin D (25OHD) levels at baseline in all patients.Twenty-nine radiologically new VF were observed in 17/57 patients undergoing VP, 72% adjacent to the VP. Patients developing VF after VP showed an increased prevalence of 25OHD deficiency (< 20 ng/ml) and higher PINP values. 25OHD levels < 20ng/ml was the principal factor related to the development of VF after VP in multivariate analysis (RR,15.47; 95% CI,2.99-79.86, P<0.0001), whereas age >80 years (RR,3.20;95%CI,1.70-6.03, P=0.0007) and glucocorticoid therapy (RR,3.64;95%CI,1.61-8.26,P=0.0055) constituted the principal factors in the overall study population. Increased risk of VF after VP was also associated with cement leakage into the inferior disk (RR,6.14;95%CI,1.65-22.78, P=0.044) and >1 vertebral body treated during VP (RR,4.19; 95% CI,1.03-34.3, P=0.044). In conclusion, nearly 30% of patients with osteoporotic VF treated with VP had a new VF after the procedure. Age, especially over 80 years, the presence of inferior disk cement leakage after the procedure, the number of cemented vertebrae and low 25OHD serum levels were related to the development of new VF in these patients; the latter indicating the need to correct vitamin D deficiency prior to performing VP. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 11:45:53 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1899 http://feedproxy.google.com/~r/JbmrFeed/~3/N5lhTEJ69DQ/doi Osteoporosis mainly affects postmenopausal women and older men. Gastrointestinal hormones released after meal ingestion, such as glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide (GLP)-2, have been shown to regulate bone turnover. However, whether GLP-1, another important gastrointestinal hormone, and its analogues also have anti-osteoporotic effects, especially in aged postmenopausal situation, is not confirmed yet. In the present study, we evaluated the effects of the GLP-1 receptor agonist exendin-4 on ovariectomy (OVX) induced osteoporosis in old rats. Twelve-month-old female Sprague-Dawley rats were subjected to OVX, and exendin-4 were administrated 4 weeks after the surgery and lasted for 16 weeks. Bone characters and related serum and gene biomarkers were analyzed. Sixteen weeks treatment of exendin-4 slowed down the body weight gain by decreasing fat mass and prevented the loss of bone mass in old OVX rats. Exendin-4 also enhanced the bone strength and prevented the deterioration of trabecular microarchitecture. Moreover, exendin-4 decreased urinary DPD/creatinine ratio and serum CTX-I and increased serum ALP, OC and P1NP levels, key biochemical markers of bone turnover. Interestingly, gene expression results further showed that exendin-4 not only inhibited bone resorption by increasing OPG/RANKL ratio, but also promoted bone formation by increasing the expressions of OC, Col1, Runx2, and ALP, which exhibited dual regulatory effects on bone turnover as compared with previous anti-osteoporotic agents. In conclusion, these findings demonstrated for the first time the anti-osteoporotic effects of exendin-4 in old OVX rats and that it might be a potential candidate for treatment of aged postmenopausal osteoporosis. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 11:44:37 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1898 http://feedproxy.google.com/~r/JbmrFeed/~3/PixVpR9cEqo/doi Zoledronic acid is used to treat bone disease in both multiple myeloma (MM) and breast cancer patients (pts) with bone metastasis (BC). However, bones of MM and BC pts show a difference in retention of the bisphosphonate used for bone scintigraphy. Therefore we hypothesized that disease-specific factors may differently influence Zol retention in MM and BC pts. We tested this hypothesis in an investigator initiated phase II clinical trial where we compared the whole body retention (WBrt) of Zol in a cohort of 30 multiple myeloma (MM) and 30 breast cancer (BC) (20 Zol naive and 40 with ≥6 previous administrations). On average, 62% of the administered Zol was retained in the skeleton of both MM and BC pts and independently of the number of treatments. WBrt of Zol did not correlate with CTX levels, but linear regression analyses showed correlation with bALP levels in BC (p=0.001), but rather with CTX/bALP in Zol naive MM pts (p=0.012). Especially in BC pts WBrt correlated with age (p=0.014) independently of kidney function. In MM pts WBrt was found to primarily correlate with the extent of bone disease (p=0.028). Multivariate linear regression analyses of the entire cohort pointed out that WBrt of Zol was best predicted by age (p<0.000), osseous lesions (p<0.001) and the preceding Zol dosing (p<0.005)(r2=0.97). Comparing bone scintigrams with CT/X-ray images showed a poor correlation between sites of active bone disease and binding of scintigraphy bisphosphonate in 36% of MM pts and in 13% of BC pts. We conclude that WBrt of Zol is primarily determined by non-disease related factors, but that there may be differences in retention or drug delivery at individual sites of bone disease between MM and BC pts. In order to find the optimal dosing of Zol these observations should be taken into account. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 11:42:46 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1897 http://feedproxy.google.com/~r/JbmrFeed/~3/Gnu4DOmiaq0/doi It is sometimes assumed that dietary fat is required for vitamin D absorption, although the impact of different amounts of dietary fat on vitamin D absorption is not established. This study was conducted to determine whether the presence of a meal and the fat content of the meal influences vitamin D absorption or the 25-hydroxyvitamin D (25OHD) response to supplemental vitamin D3. Based on earlier studies in rats we postulated that absorption would be greatest in the low-fat meal group. Sixty two healthy older men and women were randomly assigned to one of three meal groups: no meal, high-fat meal or low-fat meal; each was given a monthly 50,000 IU vitamin D3 supplement with the test breakfast meal (or after a fast for the no-meal group) and followed for 90 days. Plasma vitamin D3 was measured by LC/MS before and 12 hrs after the first dose; plasma 25OHD was measured by radioimmunoassay at baseline and after 30 and 90 days. The mean 12-hr increments in vitamin D3, after adjusting for age and sex, were 200.9 nmol/L in the no-meal group, 207.4 nmol/L in the high-fat meal group, and 241.1 nmol/L in the low-fat meal group (P = 0.038), with the increase in the low-fat group being significantly greater than the increases in the other two groups. However, increments in 25OHD levels at 30 and 90 days didn't differ significantly in the three groups. We conclude that absorption was increased when a 50,000 IU dose of vitamin D was taken with a low-fat meal, compared with a high-fat meal and no meal, but that the greater absorption didn't result in higher plasma 25OHD levels in the low-fat meal group. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 11:40:25 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1896 http://feedproxy.google.com/~r/JbmrFeed/~3/4aqCsyDft54/doi Intramembrane proteases are critically involved in signal transduction and membrane protein turnover. Signal-peptide-peptidase-like 2a (SPPL2A), a presenilin-homologue residing in lysosomes/late endosomes, cleaves type II-oriented transmembrane proteins. We recently identified SPPL2A as the enzyme controlling turnover and functions of the invariant chain (CD74) of the MHCII complex and demonstrated critical importance of this process for B cell development. Surprisingly, we found that SPPL2A is critical for formation of dental enamel. In Sppl2a knockout mice, enamel of the erupted incisors was chalky white and rapidly eroded after eruption. SPPL2A was found to be expressed in enamel epithelium during secretory and maturation stage amelogenesis. Mineral content of enamel in Sppl2a-/- incisors was inhomogeneous and reduced by ∼20% compared to wild type mice with the most pronounced reduction at the mesial side. Frequently, disruption of the enamel layer and localized detachment of the most superficial enamel layer was observed in the knockout incisors leading to an uneven enamel surface. In Sppl2a null mice, morphology and function of secretory stage ameloblasts were not noticeably different from that of wild type mice. However, maturation stage ameloblasts showed reduced height and a characteristic undulation of the ameloblast layer with localized adherence of the cells to the outer enamel. This was reflected in a delayed and incomplete resorption of the proteinaceous enamel matrix. Thus, we conclude that intramembrane proteolysis by SPPL2A is essential for maintaining cellular homeostasis of ameloblasts. Since modulation of SPPL2A activity appears to be an attractive therapeutic target to deplete B cells and treat autoimmunity, interference with tooth enamel formation should be investigated as a possible adverse effect of pharmacological SPPL2A inhibitors in humans. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 11:39:26 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1895 http://feedproxy.google.com/~r/JbmrFeed/~3/VcfTKdN2uoQ/doi Osteonecrosis of the jaw (ONJ) is a well-recognized complication of antiresorptive medications, such as bisphosphonates (BPs). Although ONJ is most common after tooth extractions in patients receiving high dose BPs, many patients do not experience oral trauma. Animal models utilizing tooth extractions and high BP doses recapitulate several clinical, radiographic and histologic findings of ONJ. We and others have reported on rat models of ONJ utilizing experimental dental disease in the absence of tooth extraction. These models emphasize the importance of dental infection/inflammation for ONJ development. Here, we extend our original report in the rat, and present a mouse model of ONJ in the presence of dental disease. Mice were injected with high dose zoledronic acid and pulpal exposure of mandibular molars was performed to induce periapical disease. After 8 weeks, quantitative and qualitative radiographic and histologic analyses of mouse mandibles were executed. Periapical lesions were larger in vehicle- vs. BP treated mice. Importantly, radiographic features resembling clinical ONJ, including thickening of the lamina dura, periosteal bone deposition and increased trabecular density, were seen in the drilled site of BP treated animals. Histologically, osteonecrosis, periosteal thickening, periosteal bone apposition, epithelial migration and bone exposure were present in the BP treated animals in the presence of periapical disease. No difference in TRAP+ cell numbers was observed, but round, detached, and removed from the bone surface cells were present in BP animals. Although 88% of the BP animals showed areas of osteonecrosis in the dental disease site, only 33% developed bone exposure, suggesting that osteonecrosis precedes bone exposure. Our data further emphasize the importance of dental disease in ONJ development, provide qualitative and quantitative measures of ONJ, and present a novel mouse ONJ model in the absence of tooth extraction that should be useful in further exploring ONJ pathophysiological mechanisms. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 11:38:35 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1894 http://feedproxy.google.com/~r/JbmrFeed/~3/mlFBvZeGL_0/doi Osteoclast (OCL) precursors from many Paget's disease (PD) patients express measles virus nucleocapsid protein (MVNP) and are hypersensitive to 1,25-(OH)2D3. The increased 1,25-(OH)2D3 sensitivity is mediated by TAF12, a co-activator of VDR, which is present at much higher levels in MVNP-expressing OCL precursors than normals. These results suggest that TAF12 plays an important role in the abnormal OCL activity in PD. However, the molecular mechanisms underlying both 1,25-(OH)2D3's effects on OCL formation and the contribution of TAF12 to these effects in both normals and PD patients are unclear. Inhibition of TAF12 with a specific TAF12 antisense construct decreased OCL formation and OCL precursors sensitivity to 1,25-(OH)2D3 in PD patient bone marrow samples. Further, OCL-precursors from transgenic mice in which TAF12 expression was targeted to the OCL lineage (TRAP-TAF12 mice), formed OCL at very low levels of 1,25-(OH)2D3, although the OCL failed to exhibit other hallmarks of PD OCL, including RANKL hyper-sensitivity and hyper-multinucleation. ChIP analysis of OCL precursors using an anti-TAF12 antibody demonstrated that TAF12 binds the 24-hydroxylase (CYP24A1) promoter, which contains two functional vitamin D response elements (VDRE), in the presence of 1,25-(OH)2D3. Since TAF12 directly interacts with the ATF7 transcription factor and potentiates ATF7-induced transcriptional activation of ATF7-driven genes in other cell types, we determined if TAF12 is a functional partner of ATF7 in OCL precursors. Immunoprecipitation of lysates from either WT or MVNP-expressing OCL with an anti-TAF12 antibody followed by blotting with an anti-ATF7 antibody, or vice versa, showed that TAF12 and ATF7 physically interact in OCL. Knockdown of ATF7 in MVNP-expressing cells decreased CYP24A1 induction by 1,25-(OH)2D3 as well as TAF12 binding to the CYP24A1 promoter. These results show that ATF7 interacts with TAF12 and contributes to the hyper-sensitivity of OCL precursors to 1,25-(OH)2D3 in PD. © 2013 American Society for Bone and Mineral Research. Wed, 20 Feb 2013 11:37:23 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1884 http://feedproxy.google.com/~r/JbmrFeed/~3/uUJHkeAJh1g/doi Osteogenesis imperfecta Type VI has recently be linked to a mutation in the SERPINF1 gene which encodes Pigment Epithelium-Derived Factor (PEDF), a ubiquitously expressed protein originally described for its neurotrophic and anti-angiogenic properties. In this study, we characterized the skeletal phenotype of a mouse with targeted disruption of Pedf. In normal mouse bone, Pedf was localized to osteoblasts and osteocytes. MicroCT and quantitative bone histomorphometry in femurs of mature Pedf null mutants revealed reduced trabecular bone volume and the accumulation of unmineralized bone matrix. Fourier transform infrared microscopy (FTIR) indicated an increased mineral:matrix ratio in mutant bones which were more brittle than controls. In vitro, osteoblasts from Pedf null mice exhibited enhanced mineral deposition as assessed by alizarin red staining and an increased mineral:matrix determined by FTIR analysis of calcified nodules. The findings in this mouse model mimic the principal structural and biochemical features of bone observed in humans with OI type VI and consequently provide a useful model with which to further investigate the role of PEDF in this bone disorder. © 2013 American Society for Bone and Mineral Research. Thu, 14 Feb 2013 10:54:11 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1892 http://feedproxy.google.com/~r/JbmrFeed/~3/ocQ_0DWQJSk/doi In a large cohort of osteogenesis imperfecta type V (OI type V) patients (17 individuals from 12 families), we identified the same mutation in the 5′ UTR of the IFITM5 gene by whole exome and Sanger sequencing (IFITM5 c.-14C>T) and provide a detailed description of their phenotype. This mutation leads to the creation of a novel start codon adding 5 residues to IFITM5 and was recently reported in several other OI type V families. The variability of the phenotype was quite large even within families. Whereas some patients presented with the typical calcification of the forearm interosseous membrane, radial head dislocation and hyperplastic callus (HPC) formation following fractures, others had only some of the typical OI type V findings. Thirteen had calcification of interosseous membranes, fourteen had radial head dislocations, ten had HPC, nine had long bone bowing, eleven could ambulate without assistance, and one had mild unilateral mixed hearing loss. The bone mineral density varied greatly, even within families. Our study thus highlights the phenotypic variability of OI type V caused by the IFITM5 mutation. © 2013 American Society for Bone and Mineral Research. Wed, 13 Feb 2013 15:37:44 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1891 http://feedproxy.google.com/~r/JbmrFeed/~3/UmJ5wo_1WuA/doi Bone remodeling, a physiological process characterized by bone formation by osteoblasts (OB) and resorption of pre-existing bone matrix by osteoclasts (OC), is vital for the maintenance of healthy bone tissue in adult humans. Imbalances in this vital process result in pathological conditions including osteoporosis. Owing to its initial asymptomatic nature, osteoporosis is often detected only after the patient has sustained significant bone loss or a fracture. Hence, anabolic therapeutics that stimulates bone accrual is in high clinical demand. Here we identify Ca2+/calmodulin (CaM)-dependent protein kinase kinase 2 (CaMKK2) as a potential target for such therapeutics, as its inhibition enhances OB differentiation and bone growth and suppresses OC differentiation. Mice null for CaMKK2 possess higher trabecular bone mass in their long bones, along with significantly more OBs and fewer multinuclear OCs. Whereas Camkk2 -/- MSCs yield significantly higher numbers of OBs, bone marrow cells from Camkk2 -/- mice produce fewer multinuclear OCs, in vitro. Acute inhibition of CaMKK2 by its selective, cell-permeable pharmacological inhibitor STO-609 also results in increased OB and diminished OC formation. Further, we find phospho-protein kinase A (PKA) and Ser133 phosphorylated form of cyclic adenosine monophosphate (cAMP) response element binding protein (pCREB) to be markedly elevated in OB progenitors deficient in CaMKK2. On the other hand, genetic ablation of CaMKK2 or its pharmacological inhibition in OC progenitors results in reduced pCREB as well as significantly reduced levels of its transcriptional target, nuclear factor of activated T cells c1 (NFATc1). Moreover, in vivo administration of STO-609 results in increased OBs and diminished OCs, conferring significant protection from ovariectomy (OVX)-induced osteoporosis in adult mice. Overall, our findings reveal a novel function for CaMKK2 in bone remodeling and highlight the potential for its therapeutic inhibition as a valuable bone anabolic strategy that also inhibits OC differentiation in the treatment of osteoporosis. © 2013 American Society for Bone and Mineral Research. Wed, 13 Feb 2013 15:37:12 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1890 http://feedproxy.google.com/~r/JbmrFeed/~3/EH-OzVk1hEw/doi While there is strong evidence that bisphosphonates prevent certain types of osteoporotic fractures, there are concerns that these medications may be associated with rare atypical femoral fractures (AFF). Recent published studies examining this potential association are conflicting in regards to the existence and strength of this association. We conducted a systematic review and meta-analysis of published studies examining the association of bisphosphonates with subtrochanteric, femoral shaft, and AFF. The random-effects model was used to calculate the pooled estimates of adjusted risk ratios (RR). Subgroup analysis was performed by study design, for studies that used validated outcome definitions for AFF, and for studies reporting on duration of bisphosphonate use. Eleven studies were included in the meta-analysis: five case-control and six cohort studies. Bisphosphonate exposure was associated with an increased risk of subtrochanteric, femoral shaft, and AFF with adjusted RR of 1.70 (95% CI 1.22-2.37). Subgroup analysis of studies using the ASBMR-criteria to define AFF suggests a higher risk of AFF with bisphosphonate use with RR of 11.78 (95% CI 0.39-359.69) as compared to studies using mainly diagnosis codes (RR 1.62, 95% CI 1.18-2.22), although there is a wide confidence interval and severe heterogeneity (I2=96.15%) in this subgroup analysis. Subgroup analysis of studies examining at least 5 years of bisphosphonate use showed adjusted RR of 1.62 (95% CI 1.29-2.04). This meta-analysis suggests there is an increased risk of subtrochanteric, femoral shaft, and AFF among bisphosphonate users. Further research examining the risk of AFF with long-term use of bisphosphonates is indicated as there was limited data in this subgroup. The public health implication of this observed increase in AFF risk is not clear. © 2013 American Society for Bone and Mineral Research. Wed, 13 Feb 2013 15:36:26 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1893 http://feedproxy.google.com/~r/JbmrFeed/~3/XicrQzDJen4/doi As new insights into the complexities of endochondral fracture repair emerge, the temporal role of osteoclast activity remains ambiguous. With numerous anti-resorptive agents available to treat bone disease, understanding their impact on bone repair is vital. Further, in light of recent work suggesting osteoclast activity may not be necessary during early endochondral fracture union, we hypothesize instead a pivotal role of MMP secreting cells in driving this process. While the role of MMPs in fracture healing has been examined, no directly comparative experiments exist. We examined a number of anti-resorptive treatments to either block osteoclast activity, including the potent bisphosphonates zoledronic acid (ZA) and clodronate (CLOD), which work via differing mechanisms, or antagonize osteoclastogenesis with recombinant OPG (HuOPG-Fc), comparing these directly to an inhibitor of matrix metalloproteinase (MMP) activity (MMI270). Endochondral ossification to union occurred normally in all anti-resorptive groups. In contrast, MMP inhibition greatly impaired endochondral union, significantly delaying cartilage callus removal. MMP inhibition also produced smaller, denser hard calluses. Hard callus remodeling was, as expected, delayed with ZA, CLOD and OPG treatment at 4 and 6 weeks, resulting in larger more mineralized calluses at 6 weeks. As a result of reduced hard callus turnover, bone formation was reduced with anti-resorptive agents at these time points. These results confirm that the achievement of endochondral fracture union occurs independently of osteoclast activity. Alternatively, MMP secretion by invading cells is obligatory to endochondral union. This study provides new insight into cellular contributions to bone repair and may abate concerns regarding anti-resorptive therapies impeding initial fracture union. © 2013 American Society for Bone and Mineral Research. Wed, 13 Feb 2013 14:29:57 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1889 http://feedproxy.google.com/~r/JbmrFeed/~3/ngLCEhk-iAc/doi Sclerostin is predominantly expressed by osteocytes. Serum sclerostin levels are positively correlated with areal bone mineral density (aBMD) measured by DXA and bone microarchitecture assessed by high resolution peripheral quantitative computed tomography (HR-pQCT) in small studies. We assessed the relation of serum sclerostin levels with aBMD and microarchitectural parameters based on HR-pQCT in 1134 men aged 20-87 years using multivariable models adjusted for confounders (age, body size, lifestyle, co-morbidities, hormones regulating bone metabolism, muscle mass and strength). The apparent age-related increase in serum sclerostin levels was faster before the age of 63 than afterwards (0.43SD vs 0.20SD per decade). In 446 men aged ≤63, aBMD (spine, hip, whole body), trabecular volumetric BMD (Tb.vBMD) and trabecular number (Tb.N) at the distal radius and tibia were higher in the highest sclerostin quartile vs the three lower quartiles combined. After adjustment for aBMD, men in the highest sclerostin quartile had higher Tb.vBMD (mainly in the central compartment) and Tb.N at both skeletal sites (p<0.05-0.001). In 688 men aged >63, aBMD was positively associated with serum sclerostin levels at all skeletal sites. Cortical vBMD (Ct.vBMD) and cortical thickness (Ct.Th) were lower in the first sclerostin quartile vs the three higher quartiles combined. Tb.vBMD increased across the sclerostin quartiles which was associated with lower Tb.N and more heterogeneous trabecular distribution (higher Tb.Sp.SD) in men in the lowest sclerostin quartile. After adjustment for aBMD, men in the lowest sclerostin quartile had lower Tb.vBMD and Tb.N, but higher Tb.Sp.SD (p<0.05-0.001) at both the skeletal sites. In conclusion, serum sclerostin levels in men are strongly positively associated with better bone microarchitectural parameters, mainly trabecular architecture, regardless of the potential confounders. © 2013 American Society for Bone and Mineral Research. Wed, 13 Feb 2013 14:29:10 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1888 http://feedproxy.google.com/~r/JbmrFeed/~3/hdoU_cK9-4I/doi Management of women discontinuing bisphosphonates after 3-5 years of treatment is controversial. Little is known about how much bone mineral density (BMD) is lost after discontinuation, or whether there are risk factors for greater rates of bone loss post-discontinuation. We report patterns of change in BMD and prediction models for the changes in BMD in postmenopausal women during a 5-year treatment-free period following alendronate (ALN) therapy. We studied 406 women enrolled in the Fracture Intervention Trial (FIT) who had taken ALN for a mean of 5 years and were then enrolled in the placebo arm of the FIT Long Term Extension (FLEX) trial for an additional 5 years, describing 5-year percent changes in total hip, femoral neck, and lumbar spine BMD over the treatment-free period. Prediction models of 5-year percent changes in BMD considered all linear combinations of candidate risk factors for bone loss such as BMD at the start of the treatment-free period, the change in BMD on ALN, age, and fracture history. Serum for three markers of bone turnover was available in 76 women, and these bone turnover markers were included as candidate predictors for these 76 women. Mean 5-year BMD changes were -3.6% at the total hip, -1.7% at the femoral neck, and 1.3% at the lumbar spine. Five-year BMD losses of > 5% were experienced by 29% of subjects at the total hip, 11% of subjects at the femoral neck, and 1% of subjects at the lumbar spine. Several risk factors such as age and BMI were associated with greater bone loss, but no models based on these risk factors predicted bone loss rates. Though about a third of women who discontinue ALN after 5 years experienced > 5% bone loss at the total hip, predicting which women will lose at a higher rate was not possible. © 2013 American Society for Bone and Mineral Research. Wed, 13 Feb 2013 14:26:28 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1864 http://feedproxy.google.com/~r/JbmrFeed/~3/J1vDGk0zkH8/doi Changes in trabecular morphology during un- and re-loading are marked by large variations between individuals, implicating a strong genetic influence on the magnitude of the response. Here, we subjected more than 350 second-generation (BALBxC3H) 4mo old adult female mice to 3wk of hindlimb unloading followed by 3wk of reambulation to identify the quantitative trait loci (QTLs) that define an individual's propensity to either lose trabecular bone when weightbearing is removed or to gain trabecular bone when weightbearing is reintroduced. Longitudinal in vivo µCT scans demonstrated that individual mice lost between 15% and 71% in trabecular BV/TV in the distal femur during unloading (average: -43%). Changes in trabecular BV/TV during the 3wk reambulation period ranged from a continuation of bone loss (-18%) to large additions (56%) of tissue (average: +10%). During unloading, six QTLs accounted for 21% of the total variability in changes in BV/TV while one QTL accounted for 6% of the variability in changes in BV/TV during reambulation. QTLs were also identified for changes in trabecular architecture. Most of the QTLs defining morphologic changes during unloading or reambulation did not overlap with those QTLs identified at baseline, suggesting that these QTLs harbor genes that are specific for sensing changes in the levels of weightbearing. The lack of overlap in QTLs between unloading and reambulation also emphasizes that the genes modulating the trabecular response to unloading are distinct from those regulating tissue recovery during reloading. The identified QTLs contain the regulatory genes underlying the strong genetic regulation of trabecular bone's sensitivity to weightbearing and may help to identify individuals that are most susceptible to unloading induced bone loss and/or the least capable of recovering. © 2013 American Society for Bone and Mineral Research. Thu, 07 Feb 2013 14:25:32 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1883 http://feedproxy.google.com/~r/JbmrFeed/~3/CLV6JcTB_N8/doi Obesity is associated with higher areal bone density (aBMD) but its protective effect on the risk of fracture is controversial. We aimed to analyse bone microarchitecture and biomechanical properties in obese (OB) postmenopausal French women compared with normal weight (NW) women. A matched case-control study from the OFELY cohort was conducted in 63 OB women (BMI>30, mean age69±8 years) age-matched with 126 NW women (19<25). Bone architecture was measured with high-resolution pQCT at the distal radius and tibia and bone strength was assessed by micro-finite element analysis (µFEA). aBMD, total body fat (FM) and lean (LM) masses were measured by DXA. aBMD was 15% higher at the total hip in OB compared with NW. At the radius, OB had 13 and 14% higher volumetric total and trabecular bone densities, 11% higher cortical thickness, 13% greater trabecular number, and 22% lower distribution of trabecular separation compared with NW (p adjusted for height, physical activity and medication use <0.01 for all). Differences of a similar magnitude were found at the distal tibia. At both sites, µFEA showed significant higher values of bone strength in OB compared to controls. After normalizing values for individual body weight, we observed that all the parameters were relatively lower in OB compared to NW women. The increase of FM was four fold greater than the increase of LM in OB. The effect of FM on bone parameters was more pronounced at the tibia than compared to the non-weight bearing site. Nevertheless, the coefficients of correlation were about half of those of LM for the biomechanical parameters. We conclude that higher absolute values of bone densities, cortical and trabecular architecture and strength indices were not in proportion to the excess of BMI and particularly of FM in obese postmenopausal French women. © 2013 American Society for Bone and Mineral Research. Thu, 31 Jan 2013 12:27:45 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1880 http://feedproxy.google.com/~r/JbmrFeed/~3/lsiGPu7wtLQ/doi OBJECTIVE A site-dependent association between obesity and fracture has been reported in postmenopausal women. In this study we investigated the relationship between body mass index (BMI) and fracture at different skeletal sites in older men (≥65 years). METHODS We carried out a population-based cohort study using data from the SIDIAPQ database. SIDIAPQ contains the primary care and hospital admission computerized medical records of >1,300 GPs in Catalonia (North-East Spain), with information on a representative 30% of the population (>2 million people). In 2007, 186,171 men ≥65 were eligible, of whom 139,419 (74.9%) had an available BMI measurement. For this analysis men were categorized as underweight/normal (<25 kg/m2, n=26,298), overweight (25 - <30 kg/m2, n=70,851), and obese (≥30 kg/m2, n=42,270). Incident fractures in the period 2007-2009 were ascertained using ICD codes. RESULTS A statistically significant reduction in clinical spine and hip fractures was observed in obese (RR 0.65; 95% CI 0.53,0.80 and RR 0.63; 95% CI 0.54,0.74), and overweight men (RR 0.77; 95% CI 0.64,0.92 and RR 0.63; 95% CI 0.55,0.72) when compared with underweight/normal men. Additionally, obese men had significantly fewer wrist/forearm (RR 0.77; 95% CI 0.61,0.97) and pelvic (RR 0.44; 95% CI 0.28,0.70) fractures than underweight/normal men. Conversely, multiple rib fractures were more frequent in overweight (RR 3.42; 95% CI 1.03,11.37) and obese (RR 3.96; 95% CI 1.16,13.52) men. CONCLUSIONS In this population-based cohort of older men, obesity was associated with a reduced risk of clinical spine, hip, pelvis and wrist/forearm fracture and increased risk of multiple rib fractures when compared to normal or underweight men. Further work is needed to identify the mechanisms underlying these associations. © 2013 American Society for Bone and Mineral Research. Thu, 31 Jan 2013 12:27:38 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1878 http://feedproxy.google.com/~r/JbmrFeed/~3/UGSoCVupzck/doi When bound to the vitamin D receptor (VDR), the active form of vitamin D, 1,25-dihydroxyvitamin D (1,25D) is a potent regulator of osteoblast transcription. Less clear is the impact of 1,25D on post-transcriptional events in osteoblasts, such as the generation and action of microRNAs (miRNAs). Microarray analysis using replicate (n = 3) primary cultures of human osteoblasts (HOB) identified human miRNAs that were differentially regulated by > 1.5-fold following treatment with 1,25D (10nM, 6 hrs), which included miRNAs 637 and 1228. RT-PCR analyses showed that the host gene for miR-1228, low density lipoprotein receptor-related protein 1 (LRP1), was co-induced with miR-1228 in a dose-dependent fashion following treatment with 1,25D (0.1 – 10nM, 6hrs). By contrast, the endogenous host gene for miR-637, death-associated protein kinase 3 (DAPK3), was transcriptionally repressed by following treatment with 1,25D. Analysis of two potential targets for miR-637 and miR-1228 in HOB, type IV collagen (COL4A1) and bone morphogenic protein 2 kinase (BMP2K) respectively, showed that 1,25D-mediates suppression of these targets via distinct mechanisms. In the case of miR-637, suppression of COL4A1 appears to occur via decreased levels of COL4A1 mRNA. By contrast, suppression of BMP2K by miR-1228 appears to occur by inhibition of protein translation. In mature HOBs, siRNA inactivation of miR-1228 alone was sufficient to abrogate 1,25D-mediated down regulation of BMP2K protein expression. This was associated with suppression of pro-differentiation responses to 1,25D in HOB, as represented by parallel decrease in osteocalcin and alkaline phosphatase expression. These data show for the first time that the effects of 1,25D on human bone cells are not restricted to classical VDR-mediated transcriptional responses but also involve miRNA-directed post-transcriptional mechanisms. © 2013 American Society for Bone and Mineral Research. Tue, 29 Jan 2013 13:53:38 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1882 http://feedproxy.google.com/~r/JbmrFeed/~3/vLCQYIr3k3s/doi Tumor-induced osteomalacia (TIO) is a rare disorder of phosphate wasting due to fibroblast growth factor-23 (FGF23)-secreting tumors that are often difficult to locate. We present a systematic approach to tumor localization and post-operative biochemical changes in 31 subjects with TIO. All had failed either initial, or re-localization (in case of recurrence or metastases at outside institutions). Functional imaging with 111Indium- octreotide with single photon emission computed tomography (octreo-SPECT or SPECT/CT), and 18fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT) were performed, followed by anatomic imaging (CT,MRI). Selective venous sampling (VS) was performed when multiple suspicious lesions were identified or high surgical risk was a concern. Tumors were localized in 20/31 subjects (64.5%). Nineteen of 20 subjects underwent octreo-SPECT imaging, and 16/20 FDG-PET/CT imaging. Eighteen of 19 (95%) were positive on octreo-SPECT, and 14/16 (88%) on FDG-PET/CT. Twelve of 20 subjects underwent VS; 10/12 (83%) were positive. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were: sensitivity=0.95, specificity=0.64, PPV=0.82 and NPV=0.88 for octreo-SPECT; sensitivity=0.88, specificity=0.36, PPV=0.62 and NPV=0.50 for FDG-PET/CT. Fifteen subjects had their tumor resected at our institution, and were disease-free at last follow-up. Serum phosphorus returned to normal in all subjects within 1-5 days. In 10 subjects who were followed for at least 7 days postoperatively, intact FGF23 (iFGF23) decreased to near undetectable within hours and returned to the normal range within 5 days. C-terminal FGF23 (cFGF23) decreased immediately but remained elevated, yielding a markedly elevated cFGF23/iFGF23 ratio. Serum 1,25-dihydroxyvitamin D3 (1,25D) rose and exceeded the normal range. In this systematic approach to TIO tumor localization Octreo-SPECT was more sensitive and specific, but in many cases FDG-PET/CT was complementary. VS can discriminate between multiple suspicious lesions and increase certainty prior to surgery. Sustained elevations in cFGF23 and 1,25D were observed, suggesting novel regulation of FGF23 processing and 1,25D generation. © 2013 American Society for Bone and Mineral Research. Tue, 29 Jan 2013 13:53:09 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1881 http://feedproxy.google.com/~r/JbmrFeed/~3/qSBZ_K3EuM8/doi Physiological systems like bone respond to many genetic and environmental factors by adjusting traits in a highly coordinated, compensatory manner to establish organ-level function. To be mechanically functional, a bone should be sufficiently stiff and strong to support physiological loads. Factors impairing this process are expected to compromise strength and increase fracture risk. We tested the hypotheses that individuals with reduced stiffness relative to body size will show an increased risk of fracturing and that reduced strength arises from the acquisition of biologically distinct sets of traits (i.e., different combinations of morphological and tissue-level mechanical properties). We assessed tibial functionality retrospectively for 336 young adult women and men engaged in military training, and calculated robustness (total area/ bone length), cortical area (Ct.Ar), and tissue-mineral density (TMD). These three traits explained 69-72% of the variation in tibial stiffness (p<0.0001). Having reduced stiffness relative to body size (body weight x bone length) was associated with odds ratios of 1.5 (95% CI = 0.5-4.3) and 7.0 (95% CI = 2.0-25.1) for women and men, respectively, for developing a stress fracture based on radiography and scintigraphy. K-means cluster analysis was used to segregate men and women into sub-groups based on robustness, Ct.Ar, and TMD adjusted for body size. Stiffness varied 37-42% among the clusters (p<0.0001, ANOVA). For men, 78% of stress fracture cases segregated to 3 clusters (p<0.03, Chi-square). Clusters showing reduced function exhibited either slender tibiae with the expected Ct.Ar and TMD relative to body size and robustness (i.e., well adapted bones) or robust tibiae with reduced residuals for Ct.Ar or TMD relative to body size and robustness (i.e., poorly adapted bones). Thus, we show there are multiple biomechanical and thus biological pathways leading to reduced function and increased fracture risk. Our results have important implications for developing personalized preventative diagnostics and treatments. © 2013 American Society for Bone and Mineral Research. Tue, 29 Jan 2013 10:35:52 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1879 http://feedproxy.google.com/~r/JbmrFeed/~3/FUY9NOtR7eU/doi ATP release and subsequent activation of purinergic receptors has been suggested to be one of the key transduction pathways activated by mechanical stimulation of bone. The P2Y13 receptor, recently found to be expressed by osteoblasts, has been suggested to provide a negative feedback pathway for ATP release in different cell types. Therefore, we hypothesised that the P2Y13 receptor may contribute to the mediation of osteogenic responses to mechanical stimulation by regulating ATP metabolism by osteoblasts. To test this hypothesis, wild type (WT) and P2Y13 receptor knock-out (P2Y13R-/-) mice were subject to non-invasive axial mechanical loading of the left tibiae to induce an osteogenic response. Micro-Computed Tomography analysis showed mechanical loading induced an osteogenic response in both strains of mice in terms of increased total bone volume and cortical bone volume, with the P2Y13R-/- mice having a significantly greater response. The extent of the increased osteogenic response was defined by dynamic histomorphometry data showing dramatically increased bone formation and mineral apposition rates in P2Y13R-/- mice compared with controls. In vitro, primary P2Y13R-/- osteoblasts had an accumulation of mechanically induced extracellular ATP and reduced levels of hydrolysis. In addition, P2Y13R-/- osteoblasts also had a reduction in their maximal alkaline phosphatase (ALP) activity, one of the main ecto-enzymes expressed by osteoblasts which hydrolyses extracellular ATP. In conclusion, deletion of the P2Y13 receptor leads to an enhanced osteogenic response to mechanical loading in vivo, possibly due to the reduced extracellular ATP degradation by ALP. The augmented osteogenic response to mechanical stimulation, combined with suppressed bone remodelling activities and protection from OVX-induced bone loss after P2Y13 receptor depletion as previously described, suggests a potential role for P2Y13 receptor antagonist-based therapy, possibly in combination with mechanical loading, for the treatment of osteoporosis. © 2013 American Society for Bone and Mineral Research. Tue, 29 Jan 2013 10:04:48 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1877 http://feedproxy.google.com/~r/JbmrFeed/~3/JHdsZU9qylw/doi Pre-clinical and clinical evidence from megakaryocyte (MK) related diseases suggest that MKs play a significant role in maintaining bone homeostasis. Findings from our laboratories reveal that MKs significantly increase osteoblast (OB) number through direct MK-OB contact and the activation of integrins. We therefore examined the role of Pyk2, a tyrosine kinase known to be regulated downstream of integrins, in the MK-mediated enhancement of OBs. When OBs were co-cultured with MKs, total Pyk2 levels in OBs were significantly enhanced primarily due to increased Pyk2 gene transcription. Additionally, p53 and Mdm2 were both decreased in OBs upon MK stimulation, which would be permissive of cell cycle entry. We then demonstrated that OB number was markedly reduced when Pyk2-/- OBs, as opposed to wild-type (WT) OBs, were co-cultured with MKs. We also determined that MKs inhibit OB differentiation in the presence and absence of Pyk2 expression. Finally, given that MK replete spleen cells from GATA-1 deficient mice can robustly stimulate OB proliferation and bone formation in WT mice, we adoptively transferred spleen cells from these mice into Pyk2-/- recipient mice. Importantly, GATA-1 deficient spleen cells failed to stimulate an increase in bone formation in Pyk2-/- mice, suggesting in vivo the important role of Pyk2 in the MK-induced increase in bone volume. Further understanding of the signaling pathways involved in the MK-mediated enhancement of OB number and bone formation will facilitate the development of novel anabolic therapies to treat bone loss diseases. © 2013 American Society for Bone and Mineral Research. Tue, 29 Jan 2013 10:04:14 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1876 http://feedproxy.google.com/~r/JbmrFeed/~3/R81RcbW6tJE/doi The mechanisms leading to colonization of metastatic breast cancer cells (BCa) in the skeleton are still not fully understood. Here, we demonstrate that mineralized extracellular matrices secreted by primary human osteoblasts (hOBM) modulate cellular processes associated with BCa colonization of bone. A panel of four BCa cell lines of different bone-metastatic potential, T47D, SUM1315, MDA-MB-231 and the bone-seeking subline MDA-MB-231BO, was cultured on hOBM. After three days, the metastatic BCa cells had undergone morphological changes on hOBM and were aligned along the hOBM's collagen type I fibrils that were decorated with bone-specific proteins. In contrast, non-metastatic BCa cells showed a random orientation on hOBM. Atomic Force Microscopy-based Single Cell Force Spectroscopy revealed that the metastatic cell lines adhered more strongly to hOBM compared to non-metastatic cells. Function-blocking experiments indicated that β1-integrins mediated cell adhesion to hOBM. In addition, metastatic BCa cells migrated directionally and invaded hOBM, which was accompanied by enhanced MMP-2 and -9 secretion. Furthermore, we observed gene expression changes associated with osteomimickry in BCa cultured on hOBM. As such, osteopontin mRNA levels were significantly increased in SUM1315 and MDA-MB-231BO cells in a β1-integrin dependent manner after growing for three days on hOBM compared to tissue culture plastic. In conclusion, our results show that extracellular matrices derived from human osteoblasts represent a powerful experimental platform to dissect mechanisms underlying critical steps in the development of bone metastases. © 2013 American Society for Bone and Mineral Research. Tue, 29 Jan 2013 10:03:23 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1875 http://feedproxy.google.com/~r/JbmrFeed/~3/S8DlliqrJTI/doi HIV infection and anti-retroviral therapies have detrimental effects on bone metabolism, but data on their impact on fracture risk are controversial. We conducted a population-based cohort study to explore the association between clinical diagnosis of HIV infection and hip and major osteoporotic fracture risk. Data was obtained from the SIDIAPQ Database, which contains clinical information for >2 million patients in Catalonia, Spain (30% of the population). We screened the database to identify participants with a clinical diagnosis of HIV infection, and ascertained incident hip and osteoporotic major fractures in the population aged 40 years or older in 2007-2009. In addition, data on incident fractures involving hospital admission were obtained from the Hospital Admissions database. Cox regression models were used to estimate Hazard Ratios (HRs) for the HIV-infected VS uninfected participants. Models were adjusted for age, gender, body mass index, smoking status, alcohol drinking, oral glucocorticoid use, and co-morbid conditions (Charlson Index). Among 1,118,156 eligible participants, we identified 2,489 (0.22%) subjects with a diagnosis of HIV/AIDS. Age and gender-adjusted HR for HIV/AIDS were 6.2 [95%CI 3.5-10.9; p<0.001] and 2.7 [2.01-3.5; p<0.001] for hip and major fractures respectively; this remained significant after adjustment for all mentioned potential confounders: HR 4.7 [2.4-9.5; p<0.001] and 1.8 [1.2-2.5; p=0.002]. After stratifying by age, the association between HIV infection and major fractures was attenuated for those aged <59 years (adjusted HR 1.35 [0.88-2.07], p=0.17), but appeared stronger in older patients (adjusted HR 2.11 [1.05-4.22], p=0.035). We report a strong association between HIV infection and hip fracture incidence, with an almost 5-fold increased risk in the HIV infected, independent of gender, age, smoking, alcohol drinking and co-morbidities. Similarly, we demonstrate a 75% higher risk of all clinical fractures and a 60% increase in risk of non-hip clinical fractures among patients with a diagnosis of HIV infection. © 2013 American Society for Bone and Mineral Research. Tue, 29 Jan 2013 10:02:41 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1874 http://feedproxy.google.com/~r/JbmrFeed/~3/eg3LiYFKYVg/doi Osteoporosis is highly prevalent in COPD patients and has been related to several clinical features. However, most studies have been in relatively small COPD cohorts. Therefore, the objectives of this study were to compare bone attenuation measured on low-dose chest computed tomography (CT) between COPD subjects, smoker and non-smoker controls, and to relate bone attenuation to clinical parameters, inflammatory biomarkers and outcomes in a large, well-characterized COPD cohort. We studied 1634 COPD subjects, 259 smoker controls and 186 non-smoker controls who participated in a large longitudinal study (ECLIPSE). We measured bone attenuation, extent of emphysema and coronary artery calcification (Agatston score) on baseline CT scans, and clinical parameters, inflammatory biomarkers and outcomes. Bone attenuation was lower in COPD subjects compared with smoker and non-smoker controls (164.9±49.5 HU versus 183.8±46.1 HU versus 212.1±54.4 HU, p<0.001). Bone attenuation was not significantly different between COPD subjects and smoker controls after adjustment for age, sex and pack-years of smoking(=). In the COPD subjects, bone attenuation correlated positively with FEV1 (r=0.062, p=0.014), FEV1/FVC ratio (r=0.102, p<0.001), body mass index (r=0.243, p<0.001), fat free mass index (FFMI, r=0.265, p<0.001) and C-reactive protein (r=0.104, p<0.001), and correlated negatively with extent of emphysema (r=-0.090, p<0.001), Agatston score (r=-0.177, p<0.001) and interleukin-8 (r=-0.054, p=0.035). In a multiple regression model, older age, lower FFMI and higher Agatston score were associated with lower bone attenuation. Lower bone attenuation was associated with higher exacerbation (r=-0.057, p=0.022) and hospitalization (r=-0.078, p=0.002) rates, but was not associated with all-cause mortality. In conclusion, CT measured bone attenuation was lower in COPD subjects compared with non-smoker controls but not compared with smoker controls, after adjustment for age, sex and pack-years of smoking. In the COPD subjects, bone attenuation was associated with age, body composition and coronary artery calcification, but was not associated with all-cause mortality. © 2013 American Society for Bone and Mineral Research. Tue, 29 Jan 2013 10:02:03 +0000 ]]> http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjbmr.1873