Bone

Editorial Board

2012-06-01

Editorial Board

2012-06-01

IBMS Board of Directors

2012-06-01

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2012-06-01

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2012-06-01

Ginsenoside Rh2 inhibits osteoclastogenesis through down-regulation of NF-κB, NFATc1 and c-Fos

2012-06-01

Abstract: Ginsenoside Rh2 is one of the most active components of red ginseng, controlling cancer and other metabolic diseases including osteoclast differentiation. However, the molecular mechanism underlying the inhibition of osteoclast differentiation by ginsenoside Rh2 remains poorly understood. In the present study, it was found that ginsenoside Rh2 suppressed osteoclast differentiation from bone marrow macrophages (BMMs) treated with receptor activator of nuclear factor κB ligand (RANKL) without any cytotoxicity. Ginsenoside Rh2 significantly reduced RANKL-induced expression of transcription factors, c-Fos and nuclear factor of activated T-cells (NFATc1), as well as osteoclast markers, TRAP and OSCAR. In defining the signaling pathways, ginsenoside Rh2 was shown to moderately inhibit NF-κB activation and ERK phosphorylation in response to RANKL stimulation in BMM cells without any effect on p38 and c-Jun N-terminal kinase (JNK). Finally, ginsenoside Rh2 blocked osteoporosis in vivo as confirmed by restored bone mineral density (BMD) and other markers associated osteoclast differentiation. Hence, it is suggested that ginsenoside Rh2 could suppress RANKL-induced osteoclast differentiation in vitro and in vivo through the regulation of c-Fos and NFATc1 expressions, not excluding the involvement of NF-κB and ERK. Ginsenoside Rh2 is also suggested to be developed as a therapeutic drug for prevention and treatment of osteoporosis.Highlights: ► Ginsenoside Rh2 inhibits RANKL induced osteoclast formation. ► ERK and NF-κB pathways were related with this inhibitory mechanism. ► Ginsenoside Rh2 prevents bone destruction in mouse model.

Chronic exposure to methylphenidate impairs appendicular bone quality in young rats

2012-06-01

Abstract: Methylphenidate (MP) is a psychostimulant widely prescribed to treat Attention Deficit Hyperactivity Disorder (ADHD). Although generally well tolerated, growth deficits have been reported in children and adolescents undergoing MP treatment. This study was designed to elucidate the skeletal effects of chronic MP administration in adolescent rats. Male, 4-week-old rats received one of two doses of MP (MP-Low or MP-High) delivered for 8h a day via drinking water, or were untreated (water only). After 13weeks, half were sacrificed (N=12/group) and the remaining rats were left to recover, untreated for 5 additional weeks. Femora, tibiae, and L5 vertebra were analyzed using calipers, DXA, and mechanical testing. Immediately following treatment, MP decreased femoral anterior–posterior diameter (5% and 9% for MP-Low and MP-High, respectively), femoral and tibial bone mineral density (BMD) (6% and 5% for MP-High femora and tibiae, respectively), and bone mineral content (BMC) (9% for MP-High femora and tibiae). In addition, femora from MP treated rats had reduced ultimate force (20% for MP-High) and energy to failure (20% and 33% for MP-Low and MP-High, respectively). However, after recovery, there were no statistically significant differences for any measured parameters. Despite these effects on the appendicular skeleton, no differences were identified between vertebral samples at either time-point. In summary, MP treatment resulted in smaller, less mineralized, and weaker bones at appendicular sites, but did not affect the axial site. Although these effects were ameliorated within 5weeks, these data suggest that adolescents undergoing MP treatment may be at an increased risk for long bone fractures.Highlights: ► Chronic administration of methylphenidate to young rats adversely affects appendicular skeletal development. ► Chronic administration of methylphenidate to young rats does not affect axial skeletal development. ► The adverse effects of methylphenidate administration to young rats were eliminated within 5weeks of treatment cessation. ► Adolescents taking methylphenidate may have an increased risk for skeletal problems.

Attenuated Wnt/β-catenin signalling mediates methotrexate chemotherapy-induced bone loss and marrow adiposity in rats

2012-06-01

Abstract: Cancer chemotherapy often causes significant bone loss, marrow adiposity and haematopoietic defects, yet the underlying mechanisms and recovery potential remain unclear. Wnt/β-catenin signalling is integral to the regulation of osteogenesis, adipogenesis and haematopoiesis; using a rat model, the current study investigated roles of this signalling pathway in changes to bone marrow stromal and haematopoietic cell differentiation after chemotherapy with methotrexate (MTX), a commonly used antimetabolite. MTX treatment in rats (5 daily administrations at 0.75mg/kg) has previously been found to decrease bone volume and increase marrow fat, which was associated with increased osteoclastogenesis in haematopoietic cells and with an osteogenesis to adipogenesis switch in bone marrow stromal cells of treated rats. In the current study, on day 6 after the first MTX dose we found that accompanying these changes as well as a suppressed haematopoietic cellularity but increased granulocyte/macrophage differentiation potential, there was an increase in mRNA expression of Wnt antagonists sFRP-1 and Dkk-1 in bone, a reduction in nuclear β-catenin protein in bone marrow stromal cells, and decreased mRNA levels of β-catenin target genes lef-1, cyclin D1 and survivin, suggesting reduced activation of Wnt/β-catenin signalling in the bone during MTX-induced damage. Concurrent administration of BIO, a GSK-3β inhibitor that stabilises β-catenin, partially abrogated the MTX-induced transient changes in osteogenic/adipogenic commitment, granulocyte/macrophage lineage differentiation and osteoclast number. These findings demonstrate a potentially important role of Wnt/β-catenin signalling in MTX chemotherapy-induced cellular changes to the bone marrow microenvironment.Highlights: ►Cancer chemotherapy often causes bone loss, marrow adiposity and haematopoietic defects, yet the underlying mechanisms remain unclear. ►This study investigated roles of Wnt/β-catenin signalling in changes to bone marrow cell differentiation in rats after antimetabolite methotrexate chemotherapy. ►Changes in bone marrow adipogenic, osteogenic, haematopoietic and osteoclastogenic differentiation potential after MTX chemotherapy are associated with attenuated Wnt/β-catenin signalling. ►Concurrent administration of BIO, a GSK-3β inhibitor that activates Wnt/β-catenin signalling, partially abrogates MTX-induced changes in the bone marrow. ►These findings suggest a potentially important role of Wnt/β-catenin signalling in MTX chemotherapy-induced cellular changes to the bone marrow microenvironment.

Risk factors for osteoporosis in Caucasian patients with moderate chronic obstructive pulmonary disease: A case control study

2012-06-01

Abstract: The prevalence of osteoporosis is high in chronic obstructive pulmonary disease (COPD) patients. The gold standard for the diagnosis of osteoporosis is bone mineral density (BMD) measurements as assessed by dual energy absorptiometry (DXA) scanning as well as vertebral fractures as assessed by instant vertebral assessment (IVA). The aim of this study was to compare COPD GOLD II patients (that is, patients with moderate COPD, stage II, according to the GOLD classification) with osteoporosis (cases) to COPD GOLD II patients without osteoporosis (controls) to identify risk factors for osteoporosis.The diagnosis of osteoporosis was based on BMD and vertebral fractures. Cases (n=49) were matched for gender, age and forced expiratory volume in the first second to controls (n=49). We assessed pulmonary function, body composition, vitamin D, emphysema score (by high-resolution computer tomography), medical history and medication use in all patients. Variables that were significantly different between the cases and controls were included in a logistic regression analysis.COPD patients with osteoporosis had a significantly lower body mass index (BMI) and higher residual volume as the percentage of total lung capacity (RV%TLC) compared to COPD patients without osteoporosis. Decreasing BMI and increasing RV%TLC increased the odds ratio for osteoporosis. Overweight and obese BMI values were protective for osteoporosis.Screening for osteoporosis should be performed even in moderate COPD patients, especially in those with a low BMI and/or a high RV%TLC.Highlights: ► COPD patients with and without osteoporosis based on bone mineral density and vertebral fractures were compared. ► Decreasing body mass index and increasing RV%TLC increased the odds ratio for osteoporosis. ► Overweight and obese body mass index were protective of osteoporosis. ► Even in moderate COPD screening for osteoporosis should be done.

Expression of osteoblastic and osteoclastic genes during spontaneous regeneration and autotransplantation of goldfish scale: A new tool to study intramembranous bone regeneration

2012-06-01

Abstract: Complementary DNA of osteoblast-specific genes (dlx5, runx2a, runx2b, osterix, RANKL, type I collagen, ALP, and osteocalcin) was cloned from goldfish (Carassius auratus) scale. Messenger RNA expressions were analyzed during spontaneous scale regeneration. Dlx5 had an early peak of expression on day 7, whereas osterix was constantly expressed during days 7–21. Runx2, a major osteoblastic transcription factor in mammalian bone, did not show any significant expression. The expressions of two functional genes, type I collagen and ALP, continually increased after day 7, while that of osteocalcin increased on day 14. As for osteoclastic markers, in addition to the cloning of two functional genes, TRAP and cathepsin K, in our previous study, we here cloned the transcription factor NFATc1 to use as an early osteoclastic marker. Using these bone markers, we investigate the signal key that controls the onset of scale resorption and regeneration by performing intra-scale-pocket autotransplantation of five groups of modified scales, namely, 1) methanol-fixed scale, 2) proteinase K-treated cell-free scale, 3) polarity reversal (upside-down) scale, 4) U-shape trimmed scale, and 5) circular-hole perforated scale. In this autotransplantation, each ontogenic scale was pulled out, modified, and then re-inserted into the same scale pocket. At post-transplant, inside the pockets of all modified transplant groups, new regenerating scales formed, attaching to the ongoing resorbed transplants. Autotransplantation of methanol-fixed scale, proteinase K-treated cell-free scale, and polarity reversal (upside-down) scale triggered scale resorption and scale regeneration. These two processes of scale resorption and regeneration occurred in accordance with osteoclastic and osteoblastic marker gene expressions. These results were microscopically confirmed using TRAP and ALP staining. Regarding the autotransplantation of U-shape trimmed and circular-hole perforated scales, new scales regenerated and grew at the trimmed/perforated part of each transplant, while scale resorption occurred apparently only around the trimmed/perforated area. In contrast, no scale resorption or regeneration was detected in sham transplantations. Our finding suggests that loss of correct cell-to-cell contact between the scale-pocket lining cells and the scale cortex cells is the key to switch on the onset of scale resorption and regeneration. Overall, the present study shows that goldfish scale regeneration shares similarities in gene expression with intramembranous bone regeneration. Improved understanding of goldfish scale regeneration will help elucidate the process of intramembranous bone regeneration and make goldfish scale a possible new tool to study bone regeneration.Highlights: ► Goldfish scale regeneration shares similarities in gene expression and morphology with intramembranous bone regeneration. ► During scale regeneration, osteoblastic genes; dlx5, osterix, collagen, ALP, and osteocalcin, show similar patterns of expression as intramembranous bone regeneration. ► Dlx5 is expressed in the early stage of scale regeneration. ► Loss of correct cell-to-cell contact between the scale-pocket and the scale cortex triggers scale resorption and regeneration. ► Scale regeneration starts and finishes in the area that lacks cell-to-cell contact; U-shape trimmed/circular-hole perforated part, of transplanted scales.

Inhibition of cathepsin K reduces cartilage degeneration in the anterior cruciate ligament transection rabbit and murine models of osteoarthritis

Tadashi Hayami, Ya Zhuo, Gregg A. Wesolowski, Maureen Pickarski, Le T. Duong — 2012-06-01

Abstract: Objective: To investigate the disease modifying effects of cathepsin K (CatK) inhibitor L-006235 compared to alendronate (ALN) in two preclinical models of osteoarthritis (OA).Methods: Skeletally mature rabbits underwent sham or anterior cruciate ligament transection (ACLT)-surgery and were treated with L-006235 (L-235, 10mg/kg or 50mg/kg, PO, daily) or ALN (0.6mg/kg, s.c., weekly) for 8-weeks. ACLT joint instability was also induced in CatK−/− versus wild type (wt) mice and treated for 16-weeks. Changes in cartilage degeneration, subchondral bone volume and osteophyte area were determined by histology and μ-CT. Collagen type I helical peptide (HP-I), a bone resorption marker and collagen type II C-telopeptide (CTX-II), a cartilage degradation marker were measured.Results: L-235 (50mg/kg) and ALN treatment resulted in significant chondroprotective effects, reducing CTX-II by 60% and the histological Mankin score for cartilage damage by 46% in the ACLT-rabbits. Both doses of L-235 were more potent than ALN in protecting against focal subchondral bone loss, and reducing HP-I by 70% compared to vehicle. L-235 (50mg/kg) and ALN significantly reduced osteophyte formation in histomorphometric analysis by 55%. The Mankin score in ACLT-CatK−/− mice was ~2.5-fold lower than the ACLT-wt mice and was not different from sham-CatK−/−. Osteophyte development was not different among the groups.Conclusion: Inhibition of CatK provides significant benefits in ACLT-model of OA, including: 1) protection of subchondral bone integrity, 2) protection against cartilage degradation and 3) reduced osteophytosis. Preclinical evidence supports the role of CatK as a potential therapeutic target for the treatment of OA.Highlights: ► Disease modifying effects of the cathepsin K inhibitor L-235 were evaluated in ACLT-induced OA in rabbits and CatK-null mice. ► Lack of CatK activity in these models reduced cartilage degradation demonstrated by histological Mankin scores and CTX-II levels. ► Inhibition of CatK also protected subchondral bone integrity and reduced osteophyte formation as determined by histomorphometry and μ-CT.

5-HIAA excretion is not associated with bone metabolism in carcinoid syndrome patients

2012-03-26

Abstract: In patients with a carcinoid syndrome and neuroendocrine tumors of the digestive tract (carcinoids), elevated circulating serotonin (5-hydroxytryptamine, 5-HT) levels can be demonstrated. It can be hypothesized that bone metabolism will be affected in these patients, since serotonin receptors are expressed on bone cells and serotonin effects on bone have been demonstrated. However, to date, no data are available on bone metabolism parameters in patients with neuroendocrine tumors of the digestive tract (carcinoids). In the current retrospective study we have measured serum bone formation markers P1CP (pro-collagen type I C-terminal), and osteocalcin, and the bone resorption marker NTx (collagen breakdown product N-terminal), in a group of 61 carcinoid patients with increased circulating serotonin levels as demonstrated by increased excretion of the serotonin breakdown product, 5-hydroxy indole acetic acid (5-HIAA), in the urine (>50μmol/24h, so-called “hyper-secretors”) and a control group of 23 carcinoid patients, without increased 5-HIAA excretion (so-called non-secretors). The 24-h urinary excretion of 5-HIAA reflects the 24-h production of serotonin. Measurements of markers of bone metabolism were performed in serum samples obtained before the start of medical treatment. The hypersecretor group had on average a 10-fold higher urinary 5-HIAA excretion than the control (non-secretor) group. No significant differences in bone metabolism parameters could be demonstrated between hyper-secretors and controls (non-secretors). Correlation and regression analyses could not demonstrate significant age- and sex-adjusted correlations between urinary 5-HIAA excretion and any of the markers for bone turnover. A limitation is that the exposure time to elevated levels of serotonin is unknown, which might have been too short to induce effects on bone metabolism. Treatment of human pre-osteoblasts SV-HFO with serotonin didn't change alkaline phosphatase activity throughout differentiation as well as mineralization.In conclusion, the current study in a unique group of untreated carcinoid patients could not demonstrate a major role for circulating serotonin in the control of bone metabolism.Highlights: ► Unaltered bone turnover markers in carcinoid patients with serotonin hypersecretion. ► No effect of serotonin on differentiation and mineralization of human osteoblasts. ► Question the clinical relevance of serotonin in the control of human bone turnover.

Intact fibroblast growth factor 23 levels predict incident cardiovascular event before but not after the start of dialysis

2012-03-26

Abstract: Purpose: Low 25-hydroxyvitamin D (25D), increased levels of fibroblast growth factor 23 (FGF23), parathyroid hormone (PTH), and alkaline phosphatase (ALP) were reported to be risk factors for mortality in chronic kidney disease (CKD). However, the independent associations of these factors with cardiovascular disease (CVD), the leading cause of death among CKD patients, remain unclear. Our purpose was to identify which of these factors predict incident CVD in CKD.Methods: In this prospective cohort study, we enrolled 738 predialysis outpatients in the two nephrology departments. We employed Cox proportional hazards analyses to elucidate predictors of the endpoint, defined as fatal or non-fatal cardiovascular event requiring hospitalization. Multiple imputation was performed for missing values.Results: Mean estimated glomerular filtration rate (eGFR) was 35mL/min/1.73m2. During a median duration of 4.4years, 86 patients developed the endpoint, of whom 62 patients achieved it before the initiation of dialysis. Multivariable analyses revealed that high serum intact FGF23 levels predicted the outcome preceding dialysis initiation (hazard ratio (HR) per lnFGF23 (SD), 1.64 (1.27–2.30)), while 25D, PTH, and bone-specific ALP did not. Adding FGF23 to the conventional model of age, sex, diabetes, prior CVD, pulse pressure, and eGFR, led to a net reclassification improvement of 6.87% (P=0.04). Not censoring the patients at the start of dialysis and continuing follow-up even after dialysis, FGF23 levels did not predict the outcome (HR, 1.16 (0.91–1.48)). Complete case analyses yielded similar results.Conclusions: Intact FGF23 levels in predialysis CKD predicted incident cardiovascular events requiring hospitalization before starting dialysis, but did not predict events during the entire follow-up period, including post dialysis initiation.Highlights: ► A prospective cohort study to identify a predictor of cardiovascular events (CVD). ► We enrolled 738 predialysis outpatients with chronic kidney disease (CKD). ► Serum bone markers, 25-hydroxyvitamin D, phosphaturic hormones were measured. ► Only intact fibroblast growth factor-23 (FGF23) predicted CVD before dialysis onset. ► FGF23 levels did not predict CVD if we continued follow-up after dialysis onset.

Effects of mineral content on the fracture properties of equine cortical bone in double-notched beams

Jordan McCormack, Susan M. Stover, Jeffery C. Gibeling, David P. Fyhrie — 2012-03-27

Abstract: We recently developed a method to measure cortical bone fracture initiation toughness using a double-notched beam in four-point bending. This method was used to test the hypothesis that mineralization around the two notch roots is correlated with fracture toughness and crack extension (physical damage). Total energy absorbed to failure negatively correlated with average mineralization of the beam (r2=0.62), but not with notch root mineralization. Fracture initiation toughness was positively correlated to mineralization at the broken notch root (r2=0.34). Crack length extension at the unbroken notch was strongly negatively correlated with the average mineralization of the notch roots (r2=0.81) whereas crack length extension at the broken notch did not correlate with any of the mineralization measurements. Mineralization at the notch roots and the average mineralization contributed independently to the mechanical and damage properties. The data are consistent with a hypothesis that a) high notch root mineralization results in less stable crack length extension but high force to initiate unstable crack propagation while b) higher average mineralization leads to low post-yield (and total) energy absorption to failure.Highlights: ► Fracture initiation toughness was measured using a double-notched beam in four-point bending and mineral quantified using backscattered electron imaging. ► Mineralization around the two notch roots was positively correlated with fracture toughness (r2=0.34) and negatively with crack extension (r2=0.81). ► Energy absorbed was negatively correlated with average mineralization of the beam (r2=0.62), but not with notch root mineralization. ► High notch root mineralization decreases stable crack growth and increases the force to initiate unstable crack growth. ► High average mineralization reduces energy absorption to failure.

Mechanical failure begins preferentially near resorption cavities in human vertebral cancellous bone under compression

2012-03-30

Abstract: The amount of bone turnover in the body has been implicated as a factor that can influence fracture risk and bone strength. Here we test the idea that remodeling cavities promote local tissue failure by determining if microscopic tissue damage (microdamage) caused by controlled loading in vitro is more likely to form near resorption cavities. Specimens of human vertebral cancellous bone (L4, 7 male and 2 female, age 70±10, mean±SD) were loaded in compression to the yield point, stained for microscopic tissue damage and submitted to three-dimensional fluorescent imaging using serial milling (image voxel size 0.7×0.7×5.0μm). We found the resulting damage volume per bone volume (DV/BV) was correlated with percent eroded surface (p<0.01, r2=0.65), demonstrating that whole specimen measures of resorption cavities and microdamage are related. Locations of microdamage were more than two times as likely to have a neighboring resorption cavity than randomly selected sites without microdamage (relative risk 2.39, 95% confidence interval of relative risk: 2.09–2.73), indicating a spatial association between resorption cavities and microdamage at the local level. Individual microdamage sites were 48,700 (40,100; 62,700) μm3 in size (median, 25th and 75th percentiles). That microdamage was associated with resorption cavities when measured at the whole specimen level as well as at the local level provides strong evidence that resorption cavities play a role in mechanical failure processes of cancellous bone and therefore have the potential to influence resistance to clinical fracture.Highlights: ► We examine microdamage caused by compressive loading of cancellous bone. ► We found that microdamage is much more likely to form around resorption cavities. ► Damage volume fraction (DV/BV) was strongly correlated with eroded surface. ► Resorption cavities promote local mechanical failure and may impair bone strength.

Effect of co-morbidities on fracture risk: Findings from the Global Longitudinal Study of Osteoporosis in Women (GLOW)

2012-03-30

Abstract: Introduction: Greater awareness of the relationship between co-morbidities and fracture risk may improve fracture-prediction algorithms such as FRAX.Materials and methods: We used a large, multinational cohort study (GLOW) to investigate the effect of co-morbidities on fracture risk. Women completed a baseline questionnaire detailing past medical history, including co-morbidity history and fracture. They were re-contacted annually to determine incident clinical fractures. A co-morbidity index, defined as number of baseline co-morbidities, was derived. The effect of adding the co-morbidity index to FRAX risk factors on fracture prevention was examined using chi-squared tests, the May–Hosmer test, c index and comparison of predicted versus observed fracture rates.Results: Of 52,960 women with follow-up data, enrolled between October 2006 and February 2008, 3224 (6.1%) sustained an incident fracture over 2years. All recorded co-morbidities were significantly associated with fracture, except for high cholesterol, hypertension, celiac disease, and cancer. The strongest association was seen with Parkinson's disease (age-adjusted hazard ratio [HR]: 2.2; 95% CI: 1.6–3.1; P<0.001). Co-morbidities that contributed most to fracture prediction in a Cox regression model with FRAX risk factors as additional predictors were: Parkinson's disease, multiple sclerosis, chronic obstructive pulmonary disease, osteoarthritis, and heart disease.Conclusion: Co-morbidities, as captured in a co-morbidity index, contributed significantly to fracture risk in this study population. Parkinson's disease carried a particularly high risk of fracture; and increasing co-morbidity index was associated with increasing fracture risk. Addition of co-morbidity index to FRAX risk factors improved fracture prediction.Highlights: ► We investigated the effect of co-morbidities on fracture risk. ► 3224 of 52,960 women (6.1%) sustained an incident fracture over 2years. ► Parkinson's disease and multiple sclerosis had the greatest effect on fracture risk.

A novel library screen identifies immunosuppressors that promote osteoblast differentiation

2012-04-05

Abstract: Bone homeostasis can be compromised by an increase in osteoclast-mediated resorption and/or a decrease in osteoblast-mediated bone deposition. While many efforts have focused on treating osteoclast resorption, there has been less emphasis on identifying strategies for promoting osteoblast function. Herein, we describe a high-throughput screening assay to select for small molecules that augment bone morphogenetic protein-2 (BMP-2)-mediated osteoblast lineage commitment. After an initial screen of 5405 compounds; consisting of FDA-approved drugs, known bioactives, and compounds with novel chemical makeup, we identified 45 small molecules that promoted osteoblast commitment. Of the 45 candidates, there was a broad array of classes that included nine retinoid analogs/derivatives and four immunosuppressants, notably rapamycin and FK-506, which were chosen for further study. Treatment of osteoblast precursor cells with rapamycin or FK-506, either alone, or synergistically with BMP-2, increased levels of phospho-Smad 1/5/8 protein and transcription of Runx-2, Osx and Smad-7, consistent with a role in promoting osteoblast differentiation. Only FK-506 was able to enhance osteocalcin transcripts and Alizarin Red staining, both late markers for differentiation. When osteoblast differentiation was suppressed with exogenous TGF-β1 treatment, rapamycin (but not FK-506) was able to rescue expression of differentiation markers, indicating distinct but overlapping activity of these compounds. Collectively, these data add to an understanding of pathways engaged in osteoblastogenesis, support a role for non-redundant immunosuppressant signaling, and provide a novel approach for the discovery of potentially therapeutic compounds that affect bone remodeling.Graphical abstract: Highlights: ► High-throughput screen identifies osteogenic compounds. ► Two immunosuppressors among many selected for secondary analysis. ► Rapamycin and FK-506 promote osteogenesis. ► Pathway analysis supports different roles. ► Novel approach for identifying potential factors mitigating bone loss.

Quality control for bone quality parameters affected by subject motion in high-resolution peripheral quantitative computed tomography

2012-04-05

Abstract: Subject motion during high-resolution peripheral quantitative computed tomography (HR-pQCT) causes image artifacts that affect morphological analysis of bone quality. The aim of our study was to determine effectiveness of techniques for quality control in the presence of motion in vivo including automated and manual approaches. First, repeatability of manual grading was determined within and between laboratories. Given proper training using a standardized scale and training images (provided by the manufacturer), we found that manual grading is suitable for repeatable image quality grading within and across sites (ICC>0.7). Both a new automated technique providing motion measures based on projection moments, and traditional manual grading (1=best, 5=worst) were subsequently used to assess subject data for motion in N=137 image pairs (scan/re-scan) from the Canadian Multicentre Osteoporosis Study (CaMos) Calgary cohort. High quality image pairs were selected and measurement precision was estimated by calculating the coefficient of variation (CV). Consistent with previous data, density parameters (e.g. total bone mineral density) are more robust than structural (e.g. trabecular number) or finite element parameters (e.g. failure load). To obtain acceptable measurement precision, images should not exceed a manual grading of 3 (on a scale from 1 to 5) or an automatic (εT) grading of 1.2. Automatic and manual grading provide comparable quality control, but the advantage of the automated technique is its ability to provide a motion value at scan time (providing a basis for real time decision regarding re-scan requirements), and the assessment is objective. Notably, automatic motion measurement can be performed retrospectively based on original scan data, and is therefore well suited for multi-center studies as well as any research where objective quality control is paramount.Highlights: ►Presents manual and automatic grading for motion monitoring in HR-pQCT. ►Manual grading is reproducible across and between sites with training. ►Density parameters are more robust to motion than structural and FE parameters. ►Manual grade of 3 or automatic grade of 1.2 yield acceptable reproducibility. ►Tables are provided for determining appropriate grading thresholds.

Serum free estradiol and estrogen receptor-α mediated activity are related to decreased incident hip fractures in older women

2012-04-04

Abstract: There is paucity of data from Asian women on the association between serum estrogens and osteoporotic hip fracture risk. We conducted a case–control study nested within a population-based prospective cohort, The Singapore Chinese Health Study, to evaluate serum estrogens levels, ERα-mediated estrogenic activity and hip fracture risk in postmenopausal Asian women. Among 35,298 women who were recruited between 1993 and 1998, 15,410 women donated blood for research between 1999 and 2004. From this subcohort, we identified 140 cases who subsequently suffered hip fracture after blood donation, and 278 age-matched controls. Serum levels of total estrone, estradiol and sex hormone binding globulin levels were measured in a blinded fashion among cases and controls. ERα-mediated estrogenic activity of serum samples was quantified using a sensitive ERα-driven cell bioassay. Women with hip fracture had lower serum estrogens than control women. Compared to the lowest quintile, women in the highest quintile of free estradiol exhibited a statistically significant 57% reduction in risk of hip fracture (95% confidence interval (CI), 6–80%), with a dose-dependent relationship (p for trend=0.021). High levels of ERα-mediated estrogenic activity were also associated with decreased risk of hip fracture (p for trend=0.048). Overall, women with relatively high levels of both free estradiol and ERα-mediated estrogenic activity had a 55% reduction in hip fracture risk (95% CI, 17–76%) compared to women with low levels of both. High levels of free estradiol and ERα-mediated estrogen activity in sera were associated with reduced hip fracture risk in Chinese postmenopausal women.Highlights: ► Lack of population studies on serum estrogens and hip fracture risk in Asian women. ► We examine associations between estrogenic biomarkers hip fracture risk. ► High levels of free estradiol were associated with reduced hip fracture risk. ► ERα-mediated estrogen activity of serum was also associated with reduced hip fracture risk.

Ultra-structural defects cause low bone matrix stiffness despite high mineralization in osteogenesis imperfecta mice

2012-04-05

Abstract: Bone is a complex material with a hierarchical multi-scale organization from the molecule to the organ scale. The genetic bone disease, osteogenesis imperfecta, is primarily caused by mutations in the collagen type I genes, resulting in bone fragility. Because the basis of the disease is molecular with ramifications at the whole bone level, it provides a platform for investigating the relationship between structure, composition, and mechanics throughout the hierarchy. Prior studies have individually shown that OI leads to: 1. increased bone mineralization, 2. decreased elastic modulus, and 3. smaller apatite crystal size. However, these have not been studied together and the mechanism for how mineral structure influences tissue mechanics has not been identified. This lack of understanding inhibits the development of more accurate models and therapies. To address this research gap, we used a mouse model of the disease (oim) to measure these outcomes together in order to propose an underlying mechanism for the changes in properties. Our main finding was that despite increased mineralization, oim bones have lower stiffness that may result from the poorly organized mineral matrix with significantly smaller, highly packed and disoriented apatite crystals. Using a composite framework, we interpret the lower oim bone matrix elasticity observed as the result of a change in the aspect ratio of apatite crystals and a disruption of the crystal connectivity.Highlights: ► We have investigated osteogenesis imperfecta mice (oim) bone matrix. ► oim mice have lower matrix stiffness and higher mineralization than wild type mice. ► Poor correlation found between stiffness and mineralization. ► Changes in apatite crystal structure and connectivity may play a role the degradation of material properties despite higher density.

Age and sex differences in tibia morphology in healthy adult Caucasians

Vanessa D. Sherk, Debra A. Bemben, Michael G. Bemben, Mark A. Anderson — 2012-04-05

Abstract: Variability in peripheral Quantitative Computed Tomography (pQCT) measurement sites limits direct comparisons of results between studies. Further, it is unclear what estimates of bone strength are most indicative of changes due to aging, disease, or interventions. The purpose of this study was to examine age group and sex differences in tibia morphology. Additional purposes of this study were to determine which tibia site or sites are most sensitive for detecting age and sex differences.Methods: Self-identifying Caucasian men (n=55) and women (n=59) ages 20–59years and separated by decades had their non-dominant tibias measured with pQCT (Stratec XCT 3000) at every 10% of the limb length from 5% to 85% (distal to proximal). Volumetric BMD and BMC of the total, cortical and trabecular bone were determined, as well as periosteal (PeriC) and endosteal (EndoC) circumferences, and cortical thickness (CTh).Results: There were significant (p<0.01) site effects for all BMC, vBMD, PeriC and EndoC measures. Large sex differences (men>women) in Tot.BMC (21–28%) were paralleled by differences in Cort.BMC (21–25%) (p<0.01). Site∗sex interaction effects were significant (p<0.05) for BMC (peak sex difference: 5%, 15%, 25%, 85% sites) and circumference (peak sex difference: 65% site) variables. CTh and total vBMD were lowest (p<0.05) in 50–59year group, and EndoC was highest in the 50–59year group. Site∗age interactions existed for Cort.vBMD, Tot.BMC (85% site), and EndoC (25%, 35%, 55%–85% sites). Correcting for bone free lean body mass (BFLBM) greatly reduced sex differences, eliminating sex∗site interaction effects, but sex main effects remained significant. Correcting for BFLBM did not eliminate age effects.Conclusion: The magnitude of age and sex differences in tibia variables varied by measurement site demonstrating the need for standardization of measurement sites.Highlights: ► Large sex differences in bone content; much smaller differences in vBMD. ► Sex differences largely accounted for by differences in lean mass. ► Age group and sex differences dependent on measurement site.

Pharmacodynamic Responses to combined treatment regimens with the calcium sensing receptor antagonist JTT-305/MK-5442 and alendronate in osteopenic ovariectomized rats

2012-04-05

Abstract: Parathyroid hormone (PTH) is the anabolic standard of care for patients with severe osteoporosis. The CaSR allosteric antagonist JTT-305/MK-5442, a PTH secretagogue, could offer an oral osteoanabolic treatment alternative for postmenopausal women with osteoporosis.Here we disclose the pharmacokinetic profile of JTT-305/MK-5442 and its activity on bone remodeling in ovariectomized (OVX) osteopenic rats. Daily treatments (0.3 to 2.4mg/kg/d) for 12weeks resulted in plateaued BMD increases (3.8 to 5.3%) at axial and appendicular skeletal sites. However, treatment effects were not statistically significant, in agreement with effects seen in animals treated with low dose PTH (1–84) (5μg/kg/d).In a consecutive study we tested JTT-305/MK-5442 effects on bone formation in OVX-rats challenged with combined alendronate (ALN) treatment paradigms. At 7month, JTT-305/MK-5442 treatment significantly increased BMD in lumbar vertebrae (LV), while no change in BMD was observed in femora or tibiae. ALN add-on co-treatment produced incremental increases in LV, distal femur (DF) and proximal tibia (PT) BMD over the respective ALN control. Histological analyses confirmed modest increases in mineralized surface (MS/BS) and bone formation rate (30.5±1.9%) on trabecular surfaces by JTT-305/MK-5442. As expected, ALN administration profoundly reduced bone formation, however, JTT-305/MK-5442 significantly stimulated MS/BS and BFR in ALN treated groups.In summary, JTT-305/MK-5442 acts as a PTH secretagogue in the osteopenic OVX-rat, eliciting consistent, though modest effects on remediation of BMD due to estrogen depletion. Induction of bone formation by JTT-305/MK-5442 at trabecular bone surfaces appears to be resilient to ALN-mediated suppression of bone formation. This study provides for the first time, a mechanistic evaluation of combination treatment of a PTH secretagogue with ALN.Highlights: ► We administered the PTH secretagogue, JTT-305/MK-5442, to osteopenic OVX-rats. ► JTT-305/MK-5442 treatment resulted in modest increases in BMD and bone formation. ► We evaluated combination treatments with the anti-resorptive agent alendronate (ALN). ► Bone formation rate increases were resilient to ALN-mediated suppression. ► There were no significant salutary effects on BMD vs. respective control treatments.

Prediction of survival, second fracture, and functional recovery following the first hip fracture surgery in elderly patients

2012-04-05

Abstract: This study was designed to investigate predictable factors of mortality, second fracture, and functional recovery within 24months of hip fracture surgery in elderly patients. In addition, the authors sought to identify differences in survival and functional outcomes according to fracture type. Four hundred and fifteen patients with acute, first-time and lower-energy trauma hip fractures were enrolled into this prospective cohort study and followed for a minimum of 24months. The potential risk factors of mortality and functional outcomes considered were; (1) age, gender, body mass index, previous fracture history, preoperative ambulatory ability and residency type; (2) 8 comorbidity items, cognitive impairment, smoking, and American Society of Anesthesiologists' classification; and (3) delay prior to surgery, fracture type, operation time, operation method, and postoperative fall history. Multivariate logistic regression and Cox regression models were used for analysis. One-year and 2-year mortality rates after hip fracture surgery were 14.7% and 24.3%, respectively. The 2-year second fracture rate was 9.2% and the 2-year functional recovery rate was 38.6%. Advanced age, cancer, a prior fracture history, and a solitary life were found to be significantly associated with the risk of increased 2-year mortality. A fall within 1year of surgery and a solitary life were found to be closely associated with the risk of a second fracture, and malignancy and cognitive impairment with a poor functional outcome. Operation time and the 2-year second fracture rate differed significantly between the two fracture groups. An understanding of the incidences and risk factors of mortality and postoperative outcomes following hip fracture surgery in elderly patients provides a valuable basis to improve in health care of geriatric population.Highlights: ► We investigated predictable factors of mortality and morbidity of the first hip fracture surgery in elderly patients. ► Advanced age, cancer, a prior fracture history, and a solitary life were associated with mortality. ► A fall within 1year of surgery and a solitary life were associated with second fracture. ► Malignancy and cognitive impairment were associated with functional recovery.

Iron status and fibroblast growth factor-23 in Gambian children

Vickie Braithwaite, Landing M.A. Jarjou, Gail R. Goldberg, Ann Prentice — 2012-04-09

Abstract: A relationship between iron and fibroblast growth factor-23 (FGF23) metabolic pathways has been proposed. Iron deficiency anaemia is prevalent in The Gambia and concentrations of fibroblast growth factor-23 FGF23 are elevated in a large percentage of Gambian children with rickets-like bone deformity.We speculate that low iron status may be involved in the aetiology of Gambian rickets. The aim of this study was to determine if there was a relationship between haemoglobin, as a marker of iron status, and FGF23 in samples from children with and without a history of rickets-like bone deformities in The Gambia. We conducted a retrospective analysis of studies carried out from 2006 to 2008 in children from a rural community in The Gambia where iron deficiency anaemia is endemic and where elevated circulating concentrations of FGF23 have been found. To investigate the relationship between circulating FGF23 and haemoglobin concentrations we used an age-adjusted linear regression model on data from children <18y of age with a family or personal history of rickets-like bone deformity (BD) (n=108) and from the local community (LC) (n=382).We found that circulating concentration of FGF23 was inversely correlated with haemoglobin concentration. This effect was more pronounced in BD children compared with LC children (interaction: P≤0.0001). Anaemia and elevated FGF23 were more prevalent in BD children compared to LC children (P=0.0003 and P=0.0001 respectively).In conclusion, there is a stronger relationship between FGF23 and haemoglobin in Gambian children with a history of rickets compared to local community children. This study provides support for the contention that iron may be involved in FGF23 metabolic pathways.Highlights: ► We analysed data from Gambian children with and without a family history of rickets. ► Hb is negatively correlated with FGF23. ► This relationship is significantly steeper in children with a history of rickets. ► Iron status may be involved in FGF23 metabolic pathways. ► Iron status may contribute to the aetiology of Gambian rickets.

Micro-computed tomography assessment of the progression of fracture healing in mice

2012-04-09

Abstract: The mouse fracture model is ideal for research into the pathways of healing because of the availability of genetic and transgenic mice and the ability to create cell-specific genetic mutations. While biomechanical tests and histology are available to assess callus integrity and tissue differentiation, respectively, micro-computed tomography (μCT) analysis has increasingly been utilized in fracture studies because it is non-destructive and provides descriptions of the structural and compositional properties of the callus. However, the dynamic changes of μCT properties that occur during healing are not well defined. Thus, the purpose of this study was to determine which μCT properties change with the progression of fracture repair and converge to values similar to unfractured bone in the mouse femur fracture model. A unilateral femur fracture was performed in C57BL/6 mice and intramedullary fixation performed. Fractured and un-fractured contralateral specimens were harvested from groups of mice between 2 and 12weeks post-fracture. Parameters describing callus based on μCT were obtained, including polar moment of inertia (J), bending moment of inertia (I), total volume (TV), tissue mineral density (TMD), total bone volume fraction (BV/TV), and volumetric bone mineral density (vBMD). For comparison, plain radiographs were used to measure the callus diameter (D) and area (A); and biomechanical properties were evaluated using either three-point bending or torsion. The μCT parameters J, I, TV, and TMD converged toward their respective values of the un-fractured femurs over time, although significant differences existed between the two sides at every time point evaluated (p<0.05). Radiograph measurement D changed with repair progression in similar manner to TV. In contrast, BV/TV and BMD increased and decreased over time with statistical differences between callus and un-fractured bone occurring sporadically. Similarly, none of the biomechanical properties were found to distinguish consistently between the fractured and un-fractured femur. Micro-CT parameters assessing callus structure and size (J, I, and TV) were more sensitive to changes in callus over time post-fracture than those assessing callus substance (TMD, BV/TV, and BMD). Sample size estimates based on these results indicate that utilization of μCT requires fewer animals than biomechanics and thus is more practical for evaluating the healing femur in the mouse fracture model.Highlights: ► Mouse femur fracture healing described using CT, radiographs, and biomechanics. ► CT-derived assessment of callus size and structure more sensitive to changes. ► Biomechanics did not detect differences in callus strength and had high variance. ► CT allows few animals to be used for adequate power compared to biomechanics. ► Comprehensive description of normal healing provides valuable reference.

Changes in vitamin D metabolites during teriparatide treatment

Felicia Cosman, Bess Dawson-Hughes, Xiaohai Wan, John H. Krege — 2012-04-11

Abstract: Parathyroid hormone (PTH) increases the conversion of 25-hydroxyvitamin D [25(OH)D] to 1,25 dihydroxyvitamin D [1,25(OH)2D]. The purpose of this study was to assess the changes in serum concentration of vitamin D metabolites 1,25 dihydroxyvitamin D [1,25(OH)2D] and 25-hydroxyvitamin D [25(OH)D] during teriparatide 20μg/day (teriparatide) therapy in the double-blind Fracture Prevention Trial of postmenopausal women with osteoporosis and in the male study of men with osteoporosis. Patients were randomized to teriparatide or placebo and received daily supplements of calcium 1000mg and vitamin D 400–1200IU. Serum concentrations of 1,25(OH)2D and 25(OH)D were measured. In women (N=336), median 1,25(OH)2D concentrations at 1month increased from baseline by 27% (P<0.0001) in the teriparatide group versus −3% (P=0.87) in the placebo group (between group P<0.0001). At 12months, the increase was 19% (P<0.0001) in the teriparatide group versus −2% (P=0.23) in the placebo group (P<0.0001). Median 25(OH)D concentrations at 12months decreased by 19% (P<0.0001) in the teriparatide group versus 0% (P=0.13) in the placebo group (P<0.0001). In men (N=287), median 1,25(OH)2D concentrations at 1month increased by 22% (P<0.0001) in the teriparatide group versus 0% (P=0.99) in the placebo group (P<0.0001). At 12months, the increase was 14% (P<0.0001) in the teriparatide group versus 5% (P=0.004) in the placebo group (P=0.17). Median 25(OH)D concentrations at 12months decreased by 11% (P=0.001) in the teriparatide group versus an increase of 1% (P=0.20) in the placebo group (P=0.003). Therefore, treatment with teriparatide increases 1,25(OH)2D concentrations and decreases 25(OH)D concentrations.Highlights: ► Twelve months of teriparatide treatment (20μg/day) in men and postmenopausal women, significantly increased 1,25(OH)2D and significantly decreased 25(OH)D. ► 1,25(OH)2D levels peaked at 1month of treatment and persisted over 1year. ► Results suggest a conversion of 25(OH)D to biologically active 1,25(OH)2D. ► Increase of 1,25(OH)2D may contribute to the biological effect of teriparatide treatment.

Associations between dietary cadmium exposure and bone mineral density and risk of osteoporosis and fractures among women

2012-04-13

Abstract: Osteoporosis and its main health outcome, fragility fractures, are large and escalating public health problems. Cadmium, a widespread food contaminant, is a proposed risk factor; still the association between estimated dietary cadmium exposure and bone mineral density (BMD) has never been assessed. Within a sub-cohort of the Swedish Mammography Cohort, we assessed dietary cadmium exposure based on a food frequency questionnaire (1997) and urinary cadmium (2004–2008) in relation to total-body BMD and risk of osteoporosis and fractures (1997–2009) among 2676 women (aged 56–69years). In multivariable-adjusted linear regression, dietary cadmium was inversely associated with BMD at the total body and lumbar spine. After further adjustment for dietary factors important for bone health and cadmium bioavailability—calcium, magnesium, iron and fiber, the associations became more pronounced. A 32% increased risk of osteoporosis (95% CI: 2–71%) and 31% increased risk for any first incident fracture (95% CI: 2–69%) were observed comparing high dietary cadmium exposure (≥13μg/day, median) with lower exposures (<13μg/day). By combining high dietary with high urinary cadmium (≥0.50μg/g creatinine), odds ratios among never-smokers were 2.65 (95% CI: 1.43–4.91) for osteoporosis and 3.05 (95% CI: 1.66–5.59) for fractures. In conclusion, even low-level cadmium exposure from food is associated with low BMD and an increased risk of osteoporosis and fractures. The partial masking of the associations by essential nutrients indicates important interplay between dietary factors and contaminants present in food. In separate analyses, dietary and urinary cadmium underestimated the association with bone effects.Highlights: ► Dietary cadmium exposure can be assessed via a food frequency questionnaire. ► Low-level dietary exposure to cadmium is associated with decreased BMD and increased risk of osteoporosis and fractures. ► The adverse associations were partly masked by dietary factors of importance for bone health or cadmium bioavailability. ► Combining high dietary and high urinary cadmium decreased exposure misclassification, resulting in stronger associations between cadmium and bone. ► The findings have obvious public health relevance as elevated cadmium concentrations in cereals and vegetables are prevalent.

Evaluation of high-resolution peripheral quantitative computed tomography, finite element analysis and biomechanical testing in a pre-clinical model of osteoporosis: A study with odanacatib treatment in the ovariectomized adult rhesus monkey

2012-04-13

Abstract: This study aimed to validate finite element analysis (FEA) estimation of strength, identify high-resolution peripheral quantitative computed tomography (HR-pQCT) measures correlating with strength, and evaluate the precision of HR-pQCT measurements to longitudinally monitor effects of osteoporosis treatment in ovariectomized (OVX) non-human primates (NHPs). HR-pQCT images were acquired in three groups of NHPs: Intact (n=10), OVX-odanacatib treated (OVX-ODN 30mg/kg, n=10) and OVX-vehicle treated (OVX-Veh, n=10) at the ultradistal (UD) and distal 1/3 radii and tibia at 12, 16 and 20months. FEA estimates of bone strength using the Pistoia criterion were validated by ex-vivo mechanical compression (r2=0.95) of the UD radius. Single linear regressions of FEA-determined ultimate stress showed high correlation with HR-pQCT derived parameters: integral vBMD (r2=0.86), bone volume fraction (r2=0.84) and cortical thickness (r2=0.79). Precision of HR-pQCT measurements, obtained from an excised radius and tibia, showed low variation (CV=0.005%–5.6%) and helped identify possible sources of error. Comparison of OVX-Veh and Intact groups showed decreases in bone parameters demonstrating trends consistent with bone loss. Comparison of OVX-ODN and OVX-Veh groups showed a treatment effect with increases in bone parameters: integral vBMD (477±27 vs. 364±22mgHA/cm3) and cortical thickness (Ct.Th) (0.90±0.07 vs. 0.64±0.04mm) at the UD radius, Ct.Th (2.15±0.28 vs. 1.56±0.08mm) at the distal 1/3 radius. Axial compression peak stress calculated and obtained experimentally showed the OVX-ODN group was 33% stronger than the OVX-Veh group. We conclude that HR-pQCT and FEA serve as robust techniques to longitudinally monitor bone parameters and strength in NHP's.Highlights: ► HR-pQCT-based FEA failure criterion developed by Pistoia et al. was validated in rhesus monkeys (r2=0.95, FEA vs. experimental measurements). ► Ultradistal radius integral vBMD (r2=0.86), total BV/TV (r2=0.84) and Ct.Th (r2=0.79) show excellent correlation with experimentally determined strength. ► HR-pQCT in rhesus monkeys has good precision to monitor changes in bone mass and quality due to osteoporosis therapy.

Five years of anti-resorptive activity after a single dose of zoledronate — Results from a randomized double-blind placebo-controlled trial

2012-04-12

Abstract: Intravenous zoledronate 5mg, administered annually, prevents fractures in people with osteoporosis, but the optimal dosing schedule is not known. Previously, we reported that a single dose of 5mg zoledronate stably decreased bone turnover and increased bone mineral density (BMD) for 3years in a randomized controlled trial in 50 postmenopausal women with osteopenia. We have now completed a 2-year double-blind extension of this trial, during which no additional treatment was administered. The primary endpoint was change in the bone turnover markers procollagen type-I N-terminal propeptide (P1NP) and β-C-terminal telopeptide of type I collagen (β-CTX); the secondary endpoint was change in BMD at lumbar spine, total hip and total body. Mean levels of the each of the bone turnover markers were lower in the zoledronate group throughout the study (P<0.0001 for each marker). After 5years, mean (95% CI) levels of β-CTX and P1NP were 277ng/L (150, 404) and 28μg/L (16, 40) lower in the zoledronate group, corresponding to reductions of 48% and 45%, respectively. BMD was higher in the zoledronate group during the study (P<0.0001 for each site). After 5years, BMD in the zoledronate group was higher by 4.2% (1.1, 7.2) at the lumbar spine, by 5.3% (2.7, 7.9) at the total hip, and by 2.7% (1.1, 4.2) at the total body. These findings suggest that the anti-resorptive effects of a single 5mg dose of zoledronate persist for at least 5years in postmenopausal women. Trials assessing the anti-fracture efficacy of dosing intervals of zoledronate of up to 5years are justified.Highlights: ► Intravenous zoledronate, 5mg, reduces fracture risk, but the optimal dosing regimen is uncertain. ► A 5mg dose of zoledronate stably reduced bone turnover and increased bone density for 5years in postmenopausal women. ► Investigation of the anti-fracture efficacy of dosing intervals of zoledronate of up to 5years is justified.

Different effects of age, adiposity and physical activity on the risk of ankle, wrist and hip fractures in postmenopausal women

2012-04-13

Abstract: While increasing age, decreasing body mass index (BMI), and physical inactivity are known to increase hip fracture risk, whether these factors have similar effects on other common fractures is not well established. We used prospectively-collected data from a large cohort to examine the role of these factors on the risk of incident ankle, wrist and hip fractures in postmenopausal women. 1,155,304 postmenopausal participants in the Million Women Study with a mean age of 56.0 (SD 4.8) years, provided information about lifestyle, anthropometric, and reproductive factors at recruitment in 1996–2001. All participants were linked to National Health Service cause-specific hospital records for day-case or overnight admissions. During follow-up for an average of 8.3years per woman, 6807 women had an incident ankle fracture, 9733 an incident wrist fracture, and 5267 an incident hip fracture. Adjusted absolute and relative risks (RRs) for incident ankle, wrist, and hip fractures were calculated using Cox regression models. Age-specific rates for wrist and hip fractures increased sharply with age, whereas rates for ankle fracture did not. Cumulative absolute risks from ages 50 to 84years per 100 women were 2.5 (95%CI 2.2–2.8) for ankle fracture, 5.0 (95%CI 4.4–5.5) for wrist fracture, and 6.2 (95%CI 5.5–7.0) for hip fracture. Compared with lean women (BMI<20kg/m2), obese women (BMI≥30kg/m2) had a three-fold increased risk of ankle fracture (RR=3.07; 95%CI 2.53–3.74), but a substantially reduced risk of wrist fracture and especially of hip fracture (RR=0.57; 0.51–0.64 and 0.23; 0.21–0.27, respectively). Physical activity was associated with a reduced risk of hip fracture but was not associated with ankle or wrist fracture risk. Ankle, wrist and hip fractures are extremely common in postmenopausal women, but the associations with age, adiposity, and physical activity differ substantially between the three fracture sites.Highlights: ► Risk factors for ankle, wrist, and hip fractures differ by age, adiposity, and physical activity in postmenopausal women. ► Age-specific rates for wrist and hip fractures increased sharply with age, whereas rates for ankle fracture did not. ► Obese women had a three-fold increased risk of ankle fracture, when compared with lean women. ► Compared with lean women, obese women had a 43% and 77% reduced risk of wrist and hip fractures, respectively. ► Physical inactivity was associated with increased risk of hip fracture, but had little association with ankle or wrist fracture.

The association between plasma homocysteine levels, methylation capacity and incident osteoporotic fractures

2012-04-12

Abstract: Background: An elevated level of plasma homocysteine (Hcy) is a known risk factor for osteoporotic fractures. In addition, Hcy is related to DNA-methylation metabolism. To determine whether the association between Hcy and fractures is explained by an altered methylation capacity, we investigated the associations between levels of s-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) and fracture risk.Methods: We studied 503 females aged 55years and over from the Rotterdam Study (RS) in whom plasma Hcy, SAM and SAH levels were measured. Bone mineral density (BMD) at the hip was assessed using DXA. Incident fractures were recorded over a mean period of 7.0years. Cox proportional hazards analysis and linear regression were used to assess relationships between plasma metabolite levels, incident osteoporotic fractures and BMD.Results: Over a total of 3502 person-years of follow-up, 103 subjects sustained at least one osteoporotic fracture. Whereas incidence of osteoporotic fractures was associated with quartiles of Hcy (p=0.047), it was not associated with quartiles of SAM, SAH or SAM/SAH-ratio (all p for trend>0.6). Stepwise linear regression showed that SAM/SAH-ratio, but not Hcy, was independently associated with hip BMD (β=0.073, p=0.025).Conclusion: Since SAM, SAH and SAM/SAH-ratio were not associated with osteoporotic fractures, alterations in methylation capacity most likely do not appear to be an important factor in the association between Hcy and fractures.Highlights: ► Plasma Hcy predicts osteoporotic fractures, but not FN-BMD. ► Plasma SAM/SAH-ratio is associated with FN-BMD, but not with osteoporotic fracture incidence. ► Methylation capacity is not likely to be an important factor in the association between Hcy and osteoporotic fracture incidence.

Arsenic trioxide affects bone remodeling by effects on osteoblast differentiation and function

2012-04-13

Abstract: Arsenic trioxide (ATO) is widely used in tumor treatment, but excessive arsenic exposure can have adverse health effects. This study was to examine the association between ATO treatment and bone remodeling. The effects of ATO on osteoblast function were investigated in primary cell cultures and in an in vivo study in rats. Sprague–Dawley rats (n=30) were randomly assigned to 3 groups which were injected intraperitoneally with saline or 5 or 10mg/kg of ATO for 4weeks. In cell culture, ATO decreased osteoblast mineralization by decreasing alkaline phosphatase (ALP) expression and this effect was prevented by co-addition of inorganic phosphate (Pi). Moreover, levels of mRNAs for the transcription factors runt-related transcription factor 2 (Runx2) and osterix, the osteoblast osteogenic gene osteocalcin, and the adherence molecule vascular cell adhesion molecule-1 (VCAM-1) were decreased by ATO. Levels of mRNAs for the cytokine IL-6 were also decreased, whereas GM-CSF mRNA levels were increased. Similar effects of ATO on osteoblasts were seen in in vivo experiments in the rat. Moreover, decreases of bone turnover markers of osteocalcin, Procollagen type I N-terminal propeptide (PINP), and C-terminal cross-linked telopeptide (CTX) as well as bone mineral density (BMD) and trabecular bone volume of femur were observed in ATO-treated rats. These results suggest that ATO interferes with bone remodeling mostly through changes in osteoblast differentiation and function.Graphical abstract: Highlights: ► Arsenic trioxide decreases expressions of transcription factors, Runx2 and osterix, and of the osteogenic gene, osteocalcin and ALP cultured osteoblast. ► Osteoblast's mineralization is decreased. ► Bone mineral density and trabecular bone volume are decreased in arsenic trioxide-treated rats. ► Expressions of osteogenic genes Runx2, ALP, osteocalcin, RANKL and TRAP in femur are decreased in the arsenic trioxide-treated rat. ► Arsenic trioxide interferes with bone remodeling through changes in osteoblast differentiation and function.

Failure strength of human vertebrae: Prediction using bone mineral density measured by DXA and bone volume by micro-CT

2012-04-12

Abstract: Significant relationships exist between areal bone mineral density (BMD) derived from dual energy X-ray absorptiometry (DXA) and bone strength. However, the predictive validity of BMD for osteoporotic vertebral fractures remains suboptimal. The diagnostic sensitivity of DXA in the lumbar spine may be improved by assessing BMD from lateral-projection scans, as these might better approximate the objective of measuring the trabecular-rich bone in the vertebral body, compared to the commonly-used posterior–anterior (PA) projections. Nowadays, X-ray micro-computed tomography (μCT) allows non-destructive three-dimensional structural characterization of entire bone segments at high resolution. In this study, human lumbar cadaver spines were examined ex situ by DXA in lateral and PA projections, as well as by μCT, with the aims (1) to investigate the ability of bone quantity measurements obtained by DXA in the lateral projection and in the PA projection, to predict variations in bone quantity measurements obtained by μCT, and (2) to assess their respective capabilities to predict whole vertebral body strength, determined experimentally.Human cadaver spines were scanned by DXA in PA projections and lateral projections. Bone mineral content (BMC) and BMD for L2 and L3 vertebrae were determined. The L2 and L3 vertebrae were then dissected and entirely scanned by μCT. Total bone volume (BVtot=cortical+trabecular), trabecular bone volume (BV), and trabecular bone volume fraction (BV/TV) were calculated over the entire vertebrae. The vertebral bodies were then mechanically tested to failure in compression, to determine ultimate load.The variables BVtot, BV, and BV/TV measured by μCT were better predicted by BMC and BMD measured by lateral-projection DXA, with higher R2 values and smaller standard errors of the estimate (R2=0.65–0.90, SEE=11%–18%), compared to PA-projection DXA (R2=0.33–0.53, SEE=22%–34%). The best predictors of ultimate load were BVtot and BV assessed by μCT (R2=0.88 and R2=0.81, respectively), and BMC and BMD from lateral-projection DXA (R2=0.82 and R2=0.70, respectively). Conversely, BMC and BMD from PA-projection DXA were lower predictors of ultimate load (R2=0.49 and R2=0.37, respectively).This ex vivo study highlights greater capabilities of lateral-projection DXA to predict variations in vertebral body bone quantity as measured by μCT, and to predict vertebral strength as assessed experimentally, compared to PA-projection DXA. This provides basis for further exploring the clinical application of lateral-projection DXA analysis.Highlights: ► Vertebral BMC and BMD from lateral-projection DXA better predict BV and BV/TV from μCT, compared to PA-projection DXA. ► Vertebral BMC and BMD from lateral-projection DXA better predict failure load determined experimentally, compared to PA-projection DXA. ► BVtot measured by μCT is the best predictor of vertebral failure load determined experimentally. ► In conclusion, lateral-projection DXA has greater capability than PA-projection DXA to predict variations in vertebral bone quantity and strength. ► This provides basis for further exploring the clinical application of lateral-projection DXA analysis.