Bone architecture, bone material properties, and bone turnover in non-osteoporotic post-menopausal women with fragility fracture.

Macro- and microarchitectural, bone material property, dynamic histomorphometric, and bone turnover marker data were studied in normal bone mineral density (BMD) post-menopausal women with fragility fracture. Women with fracture had thinner iliac cortices and more homogeneous bone material properties in cortical bone than age/BMD-matched non-fracture women. Low cortical thickness and bone tissue heterogeneity in normal BMD women are associated with prevalent fragility fracture. INTRODUCTION: Bone mass (bone mineral density, (BMD)) of the spine and hip is today's best single measurement for evaluating future fragility fracture risk. However, the majority of fragility fractures occur in women with BMD T-score above the WHO osteoporotic BMD threshold of - 2.5, indicating that non-BMD endpoints may play a role in their fragility fractures. We hypothesize that in non-osteoporotic women, bone micoarchitecture, bone material properties, dynamic histomorphometric endpoints, and bone turnover markers are related to fragility fracture. METHODS: Two groups (N = 60 each) of post-menopausal women with total hip BMD T-score ranging from + 0.3 to -2.49 were recruited: fragility fracture and age/BMD-matched, non-fragility fracture women. Normal (T-score > - 0.99) and osteopenic (T-score ≤ - 1.0) BMD cohorts were designated within both the fracture and non-fracture groups. Transiliac biopsy specimens were obtained to evaluate dynamic histomorphometric and microarchitectural endpoints and bone material properties by static and dynamic nanoindentation testing. All variables for fracture and non-fracture women within each BMD cohort were compared by the Wilcoxon signed-rank test (P < 0.01). RESULTS: Compared to non-fracture/normal BMD women, fracture/normal BMD women display lower iliac cortical thickness (- 12%, P = 0.0041) and lower heterogeneity of hardness (- 27%, P = 0.0068), elastic modulus (- 35%, P = 0.0009), and storage modulus (- 23%, P = 0.0054) in the cortical bone tissue, and lower heterogeneity of hardness (- 13%, P = 0.0088) in the trabecular bone tissue. Osteopenic women had no abnormalities related to fracture status. CONCLUSION: Post-menopausal women with normal BMD and fragility fracture have low cortical thickness and heterogeneity of several bone material properties in cortical and trabecular mineralized bone tissue. These differences may explain a portion of the excess bone fragility in women with normal BMD and fragility fracture.

In premenopausal women with idiopathic osteoporosis, lower bone formation rate is associated with higher body fat and higher IGF-1.

We examined serum IGF-1 in premenopausal IOP, finding relationships that were opposite to those expected: higher IGF-1 was associated with lower bone formation and higher body fat, and lower BMD response to teriparatide. These paradoxical relationships between serum IGF-1, bone, and fat may contribute to the mechanism of idiopathic osteoporosis in premenopausal women. INTRODUCTION: Premenopausal women with idiopathic osteoporosis (IOP) have marked deficits in bone microarchitecture but variable bone remodeling. We previously reported that those with low tissue-level bone formation rate (BFR) are less responsive to teriparatide and have higher serum IGF-1, a hormone anabolic for osteoblasts and other tissues. The IGF-1 data were unexpected because IGF-1 is low in other forms of low turnover osteoporosis-leading us to hypothesize that IGF-1 relationships are paradoxical in IOP. This study aimed to determine whether IOP women with low BFR have higher IGF-1 and paradoxical IGF-1 relationships in skeletal and non-skeletal tissues, and whether IGF-1 and the related measures predict teriparatide response. METHODS: This research is an ancillary study to a 24 month clinical trial of teriparatide for IOP. Baseline assessments were related to trial outcomes: BMD, bone remodeling. SUBJECTS:  Premenopausal women with IOP(n = 34); bone remodeling status was defined by baseline cancellous BFR/BS on bone biopsy. MEASURES:  Serum IGF-1 parameters, compartmental adiposity (DXA, CT, MRI), serum hormones, and cardiovascular-risk-markers related to fat distribution. RESULTS: As seen in other populations, lower BFR was associated with higher body fat and poorer teriparatide response. However, in contrast to observations in other populations, low BFR, higher body fat, and poorer teriparatide response were all related to higher IGF-1: IGF-1 Z-score was inversely related to BFR at all bone surfaces (r = - 0.39 to - 0.46; p < 0.05), directly related to central fat (p = 0.05) and leptin (p = 0.03). IGF-1 inversely related to 24 month hip BMD %change (r = - 0.46; p = 0.01). CONCLUSIONS: Paradoxical IGF-1 relationships suggest that abnormal or atypical regulation of bone and fat may contribute to osteoporosis mechanisms in premenopausal IOP.

Effect of Macroanatomic Bone Type and Estrogen Loss on Osteocyte Lacunar Properties in Healthy Adult Women.

This is the first study to examine clinical human bone specimens by three-dimensional imaging to characterize osteocyte lacunar properties as a function of macroanatomic bone type and estrogen loss. We applied laboratory-based instrumentation [3D X-ray microscope (3DXRM), MicroXCT-200; Carl Zeiss/Xradia, Inc.] that reaches the same resolution as synchrotron microscopy. We used serial transiliac bone biopsy specimens to examine the effect of macroanatomic bone type and estrogen status on osteocyte lacunar properties. These properties include lacunar size (volume, axes lengths of the ellipsoidal lacunar voids), distribution (density, average near-neighbor lacunar distance), and shape factors (sphericity ratio, average eigenvalues, degree of equancy, elongation, and flatness) in both cortical and trabecular bone tissue. The lacunar properties (volume, surface area, density, near-neighbor distance, etc.) and the shape factors (E1, L1, L2, degree of equancy, degree of elongation) were different between cortical and trabecular bone regardless of estrogen status. In cortical bone and trabecular nodes, the lacunar void volume and surface area were either smaller or tended to be smaller in postmenopausal as compared to premenopausal women. The void volume-to-bone volume ratio of cortical bone showed declining trends with estrogen loss. While there were differences between trabecular and cortical bone tissue, the lacunar void sphericity ratio for trabecular struts shows decreasing trends in postmenopausal women. These data suggest that using 3DXRM can provide new insight into osteocyte lacunar properties in transiliac bone biopsies from patients with various skeletal disease/conditions and pharmaceutical treatments.

Baseline mineralizing surface determines the magnitude of the bisphosphonate effect on cortical bone mineralization in postmenopausal osteoporotic patients.

PURPOSE: To determine the effect of short- or long-term bisphosphonate treatment on cortical bone mineralization density distribution (BMDD). METHODS: BMDD was assessed by quantitative backscatter electron imaging in postmenopausal osteoporosis: in paired transiliac biopsy samples (n=36) at baseline and after 3 years risedronate treatment from a clinical study, in transiliac biopsy samples from patients who were treated with either risedronate (n=31) or alendronate (n=68) for 3 to 7 years from an observational study. Outcomes were related to premenopausal reference data (n=73) and to histomorphometric mineralizing surface per bone surface (MS/BS). RESULTS: In the clinical study, patients with lower (below cohort median) MS/BS had normal cortical CaMean at baseline. After 3 years risedronate, their CaMean was not different versus baseline but increased versus reference (+2.9%, p=0.003). Among the groups of the observational study, CaMean did not exceed reference level, was similar for alendronate versus risedronate and similar between 3 to 5 years versus longer than 5 years treatment duration. CONCLUSION: Baseline bone mineralizing surface appears to be important for the effect of bisphosphonate on cortical bone mineralization. In patients with lower baseline MS/BS, level of mineralization after treatment can exceed reference level. Whether this is beneficial in the long-term is unknown.

Bone safety with risedronate: histomorphometric studies at different dose levels and exposure.

UNLABELLED: This report describes bone safety and histomorphometric data across different dose levels and dosing frequencies of risedronate. Normal bone structure and histomorphometric data were observed, with ongoing bone remodeling and mineralization regardless of dose. These data are reassuring and do not suggest compromised bone remodeling during treatment with established risedronate regimens. INTRODUCTION: The efficacy and bone safety of risedronate 5 mg daily were established in pivotal phase III randomized, placebo-controlled clinical studies. Histomorphometric analysis of paired biopsies demonstrated bone safety as reflected by presence of fluorescent tetracycline double-labels in all evaluable biopsies. This report describes bone safety and histomorphometric data across studies of various dose regimens of risedronate. METHODS: Bridging studies, with bone mineral density as the primary endpoint, demonstrated non-inferiority of risedronate 35 mg and 50 mg once a week, risedronate 150 mg once a month, and a risedronate 75-mg dose on two consecutive days a month versus risedronate 5 mg daily. The low oral bioavailability and known dosing limitations due to food interactions of bisphosphonates have led to development of an oral delayed-release dose form of risedronate 35 mg to be taken weekly, before or after breakfast. Bone biopsies were collected at 24 months in studies involving these risedronate dosing regimens; bone safety and histomorphometric data were evaluated. RESULTS: Qualitative bone histology showed normal mineralization of newly formed bone without evidence of pathological findings, such as osteomalacia, bone marrow dyscrasia, or bone marrow fibrosis. Importantly, ongoing bone remodeling, based on fluorochrome labeling, was observed in all patients regardless of dose and exposure. Key histomorphometric variables were comparable to those observed with the risedronate 5 mg daily dose and were within the range seen in healthy pre- and post-menopausal women. CONCLUSIONS: Overall, the results are reassuring with respect to bone safety and histomorphometric data, and do not suggest oversuppression of bone remodeling during treatment with these established risedronate regimens.

Self-reported calcium use in a cohort of postmenopausal women receiving osteoporosis therapy: results from POSSIBLE US™.

UNLABELLED: Calcium use was common and remained high among women on osteoporosis therapy. Use of calcium-supplemented pharmacologic therapy increased from 65.1 to 76.0% in these women (mean follow-up, 27.5 months). Over 12 months, calcium discontinuation was fairly similar among women using calcium only (23.7%) and women supplementing pharmacologic therapy with calcium (22.5%). INTRODUCTION: Calcium has an important role in bone health. This study describes calcium use and persistence in a postmenopausal osteoporosis treatment cohort. METHODS: Subject-reported calcium use was analyzed for 3,722 participants of the Prospective Observational Scientific Study Investigating Bone Loss Experience (POSSIBLE US(TM)) who used calcium either as their sole osteoporosis treatment (calcium only) or to supplement pharmacologic osteoporosis therapy (supplementers). Descriptive analyses were conducted. Kaplan-Meier methods were used to estimate the probability of discontinuing calcium therapy, and logistic regression was used to assess associations (age-adjusted odds ratios) between healthy behaviors and calcium use. RESULTS: At entry, there were 711 calcium-only subjects and 1,960 of 3,011 subjects on pharmacologic osteoporosis therapy also supplementing with calcium (supplementers). The percentage of supplementers increased from 65.1 to 76.0% during follow-up (mean, 27.5 months). During the first 12 months on study, the probability of calcium discontinuation was 23.7% (95 % confidence interval [CI], 20.7 - 27.0) among calcium-only subjects and 22.5% (95% CI, 20.7-24.5) among supplementers. Supplementers who discontinued pharmacologic therapy were more likely to discontinue calcium than supplementers who continued pharmacologic therapy (34.9 versus 14.8%). Overall 54.2% of calcium-only subjects who discontinued calcium and 42.3% of supplementers who discontinued calcium resumed calcium use during follow-up. Regular exercise was positively correlated with calcium use at study entry. CONCLUSIONS: Calcium supplementation in pharmacologically treated subjects increased over time. Persistence with calcium was high. Discontinuation of pharmacologic osteoporosis therapy was associated with an increased likelihood of discontinuing calcium use.

Marrow adiposity assessed on transiliac crest biopsy samples correlates with noninvasive measurement of marrow adiposity by proton magnetic resonance spectroscopy ((1)H-MRS) at the spine but not the femur.

UNLABELLED: Measurement of marrow fat (MF) is important to the study of bone fragility. We measured MF on iliac biopsies and by spine/hip magnetic resonance spectroscopy in the same subjects. Noninvasively assessed spine MF and histomorphometrically assessed MF correlated well. MF quantity and relationships with bone volume differed by measurement site. INTRODUCTION: Excess marrow fat has been implicated in the pathogenesis of osteoporosis in several populations. In the bone marrow, adipocytes and osteoblasts share a common precursor and are reciprocally regulated. In addition, adipocytes may secrete toxic fatty acids and adipokines that adversely affect osteoblasts. Measurement of marrow fat is important to the study of mechanisms of bone fragility. Marrow fat can be quantified on bone biopsy samples by histomorphometry and noninvasively by proton magnetic resonance spectroscopy ((1)H-MRS). In this study, we evaluate relationships between marrow fat assessed using both methods in the same subjects for the first time. METHODS: Sixteen premenopausal women, nine with idiopathic osteoporosis and seven normal controls, had marrow fat measured at the iliac crest by bone biopsy and at the lumbar spine (L3) and proximal femur by (1)H-MRS. RESULTS: At L3, fat fraction by (1)H-MRS correlated directly and significantly with marrow fat variables on iliac crest biopsies (r = 0.5-0.8). In contrast, there were no significant correlations between fat fraction at the femur and marrow fat on biopsies. Marrow fat quantity (%) was greater at the femur than at L3 and the iliac crest and correlated inversely with total hip and femoral neck BMD by DXA. CONCLUSIONS: In summary, measurement of marrow fat in transiliac crest biopsies correlates with marrow fat at the spine but not the proximal femur by (1)H-MRS. There were site-specific differences in marrow fat quantity and in the relationships between marrow fat and bone volume.

Long-term fracture rates seen with continued ibandronate treatment: pooled analysis of DIVA and MOBILE long-term extension studies.

UNLABELLED: Ibandronate reduces the risk of vertebral and non-vertebral fractures versus placebo in postmenopausal women with osteoporosis. This analysis, in which fractures were reported as safety events, showed that long-term use of ibandronate was associated with low fracture rates over 5 years of treatment. INTRODUCTION: A previous post-hoc meta-analysis of 2-3 year studies found that ibandronate regimens with annual cumulative exposure (ACE) of ≥10.8 mg reduced the risk of vertebral and nonvertebral fractures (NVFs) versus placebo in postmenopausal women. This post-hoc analysis used individual patient data from the 2-year monthly oral ibandronate in ladies (MOBILE) and dosing intravenous administration (DIVA) studies, including the 3-year long-term extensions (LTEs), to assess fracture risk in patients treated with ibandronate for 5 years. METHODS: Patients treated for 2 years in MOBILE with monthly oral ibandronate 150 mg (n = 176) and in DIVA with IV ibandronate every 2 months 2 mg (n = 253) or quarterly 3 mg (n = 263) who continued on the same regimens for 3 additional years in the LTEs were included. Three-year placebo data (n = 1,924) were obtained from the ibandronate osteoporosis vertebral fracture trial in North America and Europe (BONE) and IV Fracture Prevention trials. The primary endpoint was clinical fracture rate; clinical fracture data were collected as adverse events. Time to fracture was analyzed using Kaplan-Meier and statistical analysis was conducted using the log-rank test. All clinical fractures included all NVFs and symptomatic vertebral fractures. RESULTS: For ibandronate regimens with ACE ≥10.8 mg, time to fracture was significantly longer for all clinical fractures, NVFs, and clinical vertebral fractures versus placebo (P = 0.005). For all fracture types, the rate of fracture appeared stable during the 5-year treatment period. CONCLUSION: In women with postmenopausal osteoporosis, continuous treatment with ibandronate over 5 years results in low sustained clinical fracture rate.

Relationship of bone mineralization density distribution (BMDD) in cortical and cancellous bone within the iliac crest of healthy premenopausal women.

Bone mineralization density distribution (BMDD) is an important determinant of bone mechanical properties. The most available skeletal site for access to the BMDD is the iliac crest. Compared to cancellous bone much less information on BMDD is available for cortical bone. Hence, we analyzed complete transiliac crest bone biopsy samples from premenopausal women (n = 73) aged 25-48 years, clinically classified as healthy, by quantitative backscattered electron imaging for cortical (Ct.) and cancellous (Cn.) BMDD. The Ct.BMDD was characterized by the arithmetic mean of the BMDD of the cortical plates. We found correlations between Ct. and Cn. BMDD variables with correlation coefficients r between 0.42 and 0.73 (all p < 0.001). Additionally to this synchronous behavior of cortical and cancellous compartments, we found that the heterogeneity of mineralization densities (Ct.Ca(Width)), as well as the cortical porosity (Ct.Po) was larger for a lower average degree of mineralization (Ct.Ca(Mean)). Moreover, Ct.Po correlated negatively with the percentage of highly mineralized bone areas (Ct.Ca(High)) and positively with the percentage of lowly mineralized bone areas (Ct.Ca(Low)). In conclusion, the correlation of cortical with cancellous BMDD in the iliac crest of the study cohort suggests coordinated regulation of bone turnover between both bone compartments. Only in a few cases, there was a difference in the degree of mineralization of >1wt % between both cortices suggesting a possible modeling situation. This normative dataset of healthy premenopausal women will provide a reference standard by which disease- and treatment-specific effects can be assessed at the level of cortical bone BMDD.

Treatment of postmenopausal osteoporosis with delayed-release risedronate 35 mg weekly for 2 years.

UNLABELLED: Bone mineral density response to once weekly delayed-release formulation of risedronate, given before or following breakfast, was non-inferior to that seen with traditional immediate-release risedronate given daily before breakfast. Delayed-release risedronate is a convenient dosing regimen for oral bisphosphonate therapy that might avoid poor compliance. INTRODUCTION: This 2-year, randomized, controlled, non-inferiority study assessed the efficacy and safety of a delayed-release (DR) 35-mg weekly oral formulation of risedronate that allows subjects to take their weekly risedronate dose before or immediately after breakfast. Results from the first year of the study were published previously (McClung et al. Osteoporos Int 23(1):267-276, 2012); we now report the final results after 2 years. METHODS: Women with postmenopausal osteoporosis were randomly assigned to receive risedronate 5 mg immediate-release (IR) daily (n = 307) at least 30 min before breakfast, or risedronate 35 mg DR weekly, either immediately following breakfast (FB, n = 307) or at least 30 min before breakfast (BB, n = 308). Bone mineral density (BMD), bone turnover markers (BTMs), fractures, adverse events, and bone histomorphometry were evaluated. RESULTS: A total of 248 subjects (80.8 %) in the IR daily group, 234 subjects (76.2 %) in the DR FB weekly group, and 240 subjects (77.9 %) in the DR BB weekly group completed the 2-year study. After 2 years of treatment, BMD increases at the lumbar spine and total hip with the weekly DR doses similar to or greater than that with the IR daily dose. Decreases in BTMs were similar or significantly lower in the DR groups. Bone histomorphometry results did not differ among the DR weekly and the IR daily formulations. The three regimens were similarly well tolerated. CONCLUSIONS: Risedronate 35 mg DR weekly is as effective and as well tolerated as risedronate 5 mg IR daily, and will allow subjects to take their weekly risedronate dose immediately after breakfast.

Long-term administration of quarterly IV ibandronate is effective and well tolerated in postmenopausal osteoporosis: 5-year data from the DIVA study long-term extension.

UNLABELLED: Long-term bone mineral density (BMD) gains, bone marker levels, and safety of 3 mg quarterly intravenous (IV) ibandronate were studied in this 3-year extension to the Dosing IntraVenous Administration (DIVA) trial. Quarterly IV ibandronate consistently increased lumbar spine bone mineral density measured with dual-energy X-ray absorptiometry (DXA-BMD) over 5 years (8.1%) and was well tolerated in women with postmenopausal osteoporosis. INTRODUCTION: Treatment with IV ibandronate regimens, 2 mg bimonthly and 3 mg quarterly, has been studied for up to 5 years in a long-term extension (LTE) to the 2-year DIVA trial. METHODS: DIVA LTE is an open-label extension to a 2-year randomized, double-blind, double-dummy, noninferiority, phase III study (DIVA core). DIVA LTE involved postmenopausal women who had completed 2 years of DIVA core, comparing daily oral and IV ibandronate (≥75% adherence with IV ibandronate in year 2 of DIVA). Patients previously treated with 2 mg bimonthly or 3 mg quarterly IV ibandronate continued on the same regimen; patients who had received 2.5 mg daily oral ibandronate and placebo IV in DIVA core were switched to IV ibandronate. RESULTS: Pooled analysis of 497 intent-to-treat (ITT) patients receiving IV ibandronate from DIVA core baseline showed consistent increases over 5 years in lumbar spine DXA-BMD (8.4% [95% confidence interval (CI) = 7.5, 9.3] with 2 mg bimonthly and 8.1% [95% CI = 7.2, 8.9] with 3 mg quarterly). Three-year data relative to DIVA LTE baseline in the full ITT population (756 patients randomized or reallocated from DIVA, including those previously on daily treatment) showed maintenance of DXA-BMD gains from DIVA core with further gains in lumbar spine DXA-BMD. These benefits are supported by sustained reductions in markers of bone metabolism. No tolerability concerns or new safety signals were observed. CONCLUSIONS: Treatment with IV ibandronate 2 mg bimonthly or 3 mg quarterly is effective and well tolerated for up to 5 years in women with postmenopausal osteoporosis.

Efficacy of monthly oral ibandronate is sustained over 5 years: the MOBILE long-term extension study.

UNLABELLED: The long-term efficacy and safety of once-monthly ibandronate were studied in this extension to the 2-year Monthly Oral Ibandronate in Ladies (MOBILE) trial. Over 5 years, lumbar spine bone mineral density (BMD) increased from baseline with monthly ibandronate 150 mg (8.4%). Long-term monthly ibandronate is effective and well tolerated for up to 5 years in women with postmenopausal osteoporosis. INTRODUCTION: Once-monthly therapy with ibandronate has been studied for up to 5 years in a long-term extension (LTE) to the 2 year MOBILE trial. METHODS: This multicenter, double-blind extension study of monthly ibandronate involved postmenopausal women who had completed 2 years of the MOBILE core study, with ≥75% adherence. Patients were reallocated, or were randomized from daily therapy, to ibandronate 100 mg monthly or 150 mg monthly for a further 3 years. RESULTS: A pooled intent-to-treat (ITT) analysis of 344 patients receiving monthly ibandronate from the core MOBILE baseline showed increases over 5 years in lumbar spine BMD (8.2% with 100 mg and 8.4% with 150 mg). Three-year data relative to MOBILE LTE baseline in the full ITT population of all 698 patients randomized or reallocated from MOBILE (including those previously on daily treatment) showed, on average, maintenance of proximal femur BMD gains achieved in the core 2-year study, with further small gains in lumbar spine BMD. In general, maintenance of efficacy was also indicated by markers of bone metabolism. CONCLUSIONS: There were no tolerability concerns or new safety signals. Monthly treatment with ibandronate 100 and 150 mg is effective and well tolerated for up to 5 years in women with postmenopausal osteoporosis.

Efficacy and safety of a novel delayed-release risedronate 35 mg once-a-week tablet.

UNLABELLED: Dosing regimens of oral bisphosphonates are inconvenient and contribute to poor compliance. The bone mineral density response to a once weekly delayed-release formulation of risedronate given before or following breakfast was non-inferior to traditional immediate-release risedronate given daily before breakfast. Delayed-release risedronate is a convenient regimen for oral bisphosphonate therapy. INTRODUCTION: We report the results of a randomized, controlled, clinical study assessing the efficacy and safety of a delayed-release (DR) 35 mg weekly oral formulation of risedronate that allows patients to take their weekly risedronate dose before or immediately after breakfast. METHODS: Women with postmenopausal osteoporosis were randomly assigned to receive risedronate 5 mg immediate-release (IR) daily (n = 307) at least 30 min before breakfast, or risedronate 35 mg DR weekly, either at least 30 min before breakfast (BB, n = 308) or immediately following breakfast (FB, n = 307). Bone mineral density (BMD), bone turnover markers (BTMs), fractures, and adverse events were evaluated. The primary efficacy variable was percent change from baseline in lumbar spine BMD at Endpoint. RESULTS: Two hundred fifty-seven subjects (83.7%) in the IR daily group, 252 subjects (82.1%) in the DR FB weekly group, and 258 subjects (83.8%) in the DR BB weekly group completed 1 year. Both DR weekly groups were determined to be non-inferior to the IR daily regimen. Mean percent changes in hip BMD were similar across groups. The magnitude of BTM response was similar across groups; some statistical differences were seen that were small and deemed by investigators to have no major clinical importance. The incidence of adverse events leading to withdrawal and serious adverse events were similar across treatment groups. All three regimens were well tolerated. CONCLUSIONS: Risedronate 35 mg DR weekly is similar in efficacy and safety to risedronate 5 mg IR daily, and will allow patients to take their weekly risedronate dose immediately after breakfast.

Premenopausal women with idiopathic low-trauma fractures and/or low bone mineral density.

INTRODUCTION: In men, idiopathic osteoporosis (IOP) is often associated with low serum insulin-like growth factor (IGF-1) and reduced bone formation. The characteristics of premenopausal women with IOP are not well defined. We aimed to define the clinical, reproductive, and biochemical characteristics of premenopausal women with unexplained osteoporosis. METHODS: This is a cross-sectional study of 64 women with unexplained osteoporosis, 45 with fragility fractures, 19 with low bone mineral density (BMD; Z-score less than or equal to -2.0) and 40 normal controls. The following are the main outcome measures: clinical and anthropometric characteristics, reproductive history, BMD, gonadal and calciotropic hormones, IGF-1, and bone turnover markers (BTMs). RESULTS: Subjects had lower BMI and BMD than controls, but serum and urinary calcium, serum estradiol, vitamin D metabolites, IGF-1, and most BTMs were similar. Serum parathyroid hormone (PTH) and the resorption marker, tartrate-resistant acid phosphatase (TRAP5b), were significantly higher in both groups of subjects than controls and directly associated in all groups. Serum IGF-1 and all BTMs were directly associated in controls, but the association was not significant after controlling for age. There was no relationship between serum IGF-1 and BTMs in subjects. There were few differences between women with fractures and low BMD. CONCLUSIONS: Higher serum TRAP5b and PTH suggest that increased bone turnover, possibly related to subclinical secondary hyperparathyroidism could contribute to the pathogenesis of IOP. The absence of differences between women with fractures and those with very low BMD indicates that this distinction may not be clinically useful to categorize young women with osteoporosis.

High resolution imaging in bone tissue research-review.

This review article focuses on imaging of bone tissue to understand skeletal health with regards to bone quality. Skeletal fragility fractures are due to bone diseases such as osteoporosis which result in low bone mass and bone mineral density (BMD) leading to high risk of fragility fractures. Recent advances in imaging and analysis technologies have highly benefitted the field of biological sciences. In particular, their application in skeletal health has been of significant importance in understanding bone mechanical behavior (structure and properties) at the tissue level. While synchrotron based microCT technique has remained the gold standard for non-destructive evaluation of structure in material and biological sciences, several lab based microCT systems have been developed to provide high resolution imaging of specimens with greater access, and ease of use in laboratory settings. Lab based microCT scanners are widely used in the bone field as a standard tool to evaluate three-dimensional (3D) morphologies of bone structure at image resolutions appropriate for bone samples from small animals to bone biopsy specimens from humans. Both synchrotron and standard lab based microCT systems provide high resolution imaging ex vivo for a small sized specimen. A few X-ray based systems are also commercially available for in vivo scanning at relatively low image resolutions. Synchrotron-based CT microscopy is being used for various ultra-high-resolution image analyses using complex 3D software. However, the synchrotron-based CT technology is in high demand, allows only limited numbers of specimens, expensive, requires complex additional instrumentation, and is not easily available to researchers as it requires access to a synchrotron source which is always limited. Therefore, desktop laboratory scanners (microXCT, Zeiss/Xradia, Scanco, SkyScan. etc.), mimicking the synchrotron based CT technology or image resolution, have been developed to solve the accessibility issues. These lab based scanners have helped both material science, and the bone field to investigate bone tissue morphologies at submicron mage resolutions. Considerable progress has been made in both in vivo and ex vivo imaging towards providing high resolution images of bone tissue. Both clinical and research imaging technologies will continue to improve and help understand osteoporosis and other related skeletal issues in order to develop targeted treatments for bone fragility. This review summarizes the high resolution imaging work in bone research.

Association analyses of vitamin D-binding protein gene with compression strength index variation in Caucasian nuclear families.

UNLABELLED: This study was conducted to test whether there exists an association between vitamin D-binding protein (DBP) gene and compression strength index (CSI) phenotype. Candidate gene association analyses were conducted in total sample, male subgroup, and female subgroup, respectively. Two single-nucleotide polymorphisms (SNPs) with significant association results were found in males, suggesting the importance of DBP gene polymorphisms on the variation in CSI especially in Caucasian males. INTRODUCTION: CSI of the femoral neck (FN) is a newly developed phenotype integrating information about bone size, body size, and bone mineral density. It is considered to have the potential to improve the performance of risk assessment for hip fractures because it is based on a combination of phenotypic traits influencing hip fractures rather than a single trait. CSI is under moderate genetic determination (with a heritability of approximately 44% found in this study), but the relevant genetic study is still rather scarce. METHODS: Based on the known physiological role of DBP in bone biology and the relatively high heritability of CSI, we tested 12 SNPs of the DBP gene for association with CSI variation in 405 Caucasian nuclear families comprising 1,873 subjects from the Midwestern US. Association analyses were performed in the total sample, male and female subgroups, respectively. RESULTS: Significant associations with CSI were found with two SNPs (rs222029, P = 0.0019; rs222020, P = 0.0042) for the male subgroup. Haplotype-based association tests corroborated the single-SNP results. CONCLUSIONS: Our findings suggest that the DBP gene might be one of the genetic factors influencing CSI phenotype in Caucasians, especially in males.

Genome-wide copy number variation association study suggested VPS13B gene for osteoporosis in Caucasians.

UNLABELLED: Osteoporotic fracture (OF) is a serious outcome of osteoporosis. Important risk factors for OF include reduced bone mineral density and unstable bone structure. This genome-wide copy number variation association study suggested VPS13B gene for osteoporosis in Caucasians. INTRODUCTION: Bone mineral density (BMD) and femoral neck cross-sectional geometric parameters (FNCSGPs) are under strong genetic control. DNA copy number variation (CNV) is an important source of genetic diversity for human diseases. This study aims to identify CNVs associated with BMD and FNCSGPs. METHODS: Genome-wide CNV association analyses were conducted in 1,000 unrelated Caucasian subjects for BMD at the spine, hip, femoral neck, and for three FNCSGPs -cortical thickness (CT), cross-section area (CSA), and buckling ratio (BR). BMD was measured by dual energy X-ray absorptiometry (DEXA). CT, CSA, and BR were estimated using DEXA measurements. Affymetrix 500K arrays and copy number analysis tool was used to identify CNVs. RESULTS: A CNV in VPS13B gene was significantly associated with spine, hip and FN BMDs, and CT, CSA, and BR (p < 0.05). Compared to subjects with two copies of the CNV, carriers of one copy had an average of 14.6%, 12.4%, and 13.6% higher spine, hip, and FN BMD, 20.0% thicker CT, 10.6% larger CSA, and 12.4% lower BR. Thus, a decrease of the CNV consistently produced stronger bone, thereby reducing osteoporotic fracture risk. CONCLUSIONS: VPS13B gene, via affecting BMD and FNCSGPs, is a novel osteoporosis risk gene.

Assessment of trabecular and cortical architecture and mechanical competence of bone by high-resolution peripheral computed tomography: comparison with transiliac bone biopsy.

UNLABELLED: We compared microarchitecture and mechanical competence parameters measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) and finite-element analysis of radius and tibia to those measured by histomorphometry, micro-CT, and finite-element analysis of transiliac bone biopsies. Correlations were weak to moderate between parameters measured on biopsies and scans. INTRODUCTION: HR-pQCT is a new imaging technique that assesses trabecular and cortical bone microarchitecture of the radius and tibia in vivo. The purpose of this study was to determine the extent to which microarchitectural variables measured by HR-pQCT reflect those measured by the "gold standard," transiliac bone biopsy. METHODS: HR-pQCT scans (Xtreme CT, Scanco Medical AG) and iliac crest bone biopsies were performed in 54 subjects (aged 39 +/- 10 years). Biopsies were analyzed by 2D quantitative histomorphometry and 3D microcomputed tomography (microCT). Apparent Young's modulus, an estimate of mechanical competence or strength, was determined by micro-finite-element analysis (microFE) of biopsy microCT and HR-pQCT images. RESULTS: The strongest correlations observed were between trabecular parameters (bone volume fraction, number, separation) measured by microCT of biopsies and HR-pQCT of the radius (R 0.365-0.522; P < 0.01). Cortical width of biopsies correlated with cortical thickness by HR-pQCT, but only at the tibia (R = 0.360, P < 0.01). Apparent Young's modulus calculated by microFE of biopsies correlated with that calculated for both radius (R = 0.442; P < 0.001) and tibia (R = 0.380; P < 0.001) HR-pQCT scans. CONCLUSIONS: The associations between peripheral (HR-pQCT) and axial (transiliac biopsy) measures of microarchitecture and estimated mechanical competence are significant but modest.

Genome-wide association analyses suggested a novel mechanism for smoking behavior regulated by IL15.

Cigarette smoking is the leading preventable cause of death in the United States. Although smoking behavior has a significant genetic determination, the specific genes and associated mechanisms underlying the smoking behavior are largely unknown. Here, we carried out a genome-wide association study on smoking behavior in 840 Caucasians, including 417 males and 423 females, in which we examined approximately 380,000 single nucleotide polymorphisms (SNPs). We found that a cluster of nine SNPs upstream from the IL15 gene were associated with smoking status in males, with the most significant SNP, rs4956302, achieving a P-value (8.80 x 10(-8)) of genome-wide significance. Another SNP, rs17354547 that is highly conserved across multiple species achieved a P-value of 5.65 x 10(-5). These two SNPs, together with two additional SNPs (rs1402812 and rs4956396) were selected from the above nine SNPs for replication in an African-American sample containing 1251 subjects, including 412 males and 839 females. The SNP rs17354547 was replicated successfully in the male subgroup of the replication sample; it was associated with smoking quantity (SQ), the Heaviness of Smoking Index (HSI) and the Fagerstrom Test for Nicotine Dependence (FTND), with P-values of 0.031, 0.0046 and 0.019, respectively. In addition, a haplotype formed by rs17354547, rs1402812 and rs4956396 was also associated with SQ, HSI and FTND, achieving P-values of 0.039, 0.0093 and 0.0093, respectively. To further confirm our findings, we carried out an in silico replication study of the nine SNPs in a Framingham Heart Study sample containing 7623 Caucasians from 1731 families, among which, 3491 subjects were males and 4132 were females. Again, the male-specific association with smoking status was observed, for which seven of the nine SNPs achieved significant P-values (P<0.05) and two achieved marginally significant P-values (P<0.10) in males. Several of the nine SNPs, including the highly conserved one across species, rs17354547, are located at potential transcription factor binding sites, suggesting transcription regulation as a possible function for these SNPs. Through this function, the SNPs may modulate the gene expression of IL15, a key cytokine regulating immune function. As the immune system has long been recognized to influence drug addiction behavior, our association findings suggest a novel mechanism for smoking addiction involving immune modulation through the IL15 pathway.

Comparison of whole genome linkage scans in premenopausal and postmenopausal women: no bone-loss-specific QTLs were implicated.

UNLABELLED: This study was conducted to investigate if there exist bone-loss-specific quantitative trait loci (QTLs) for females. Genome-wide linkage scans were conducted in total, premenopausal, and postmenopausal women, respectively. No QTLs exclusively were found in postmenopausal women, suggesting that no bone-loss-specific QTL was implicated independent of BMD in our sample. INTRODUCTION: Bone mineral density (BMD) in elderly women is determined jointly by peak bone mass achieved before menopause and by subsequent bone loss upon and after menopause. Peak bone mass is under strong genetic control, but whether bone loss has genetic determination independent of peak BMD is unknown. MATERIALS AND METHODS: To investigate if there exist bone-loss-specific quantitative trait loci (QTLs) for females, we conducted genome-wide linkage scans in 2,582 Caucasian females from 451 pedigrees including 1,486 premenopausal and 1,096 postmenopausal women. Linkage analyses were performed in the total sample and premenopausal and postmenopausal women subgroups, respectively, and the results were compared. RESULTS: No linkage evidence was found exclusively in postmenopausal women. Linkage signals identified are largely consistent in the total, premenopausal, and postmenopausal samples. For example, for spine BMD, for the total sample, a significant linkage was obtained on 15q13 (LOD = 3.67), and LOD scores of 1.52 and 2.49 were achieved on 15q13 in premenopausal and postmenopausal women, respectively. CONCLUSIONS: We did not find any QTLs exclusively in postmenopausal women; hence, no specific QTL for bone loss was implicated independent of BMD in our female sample.