Total Calcium Intake Is Associated With Trabecular Bone Density in Adolescent Girls With Type 1 Diabetes

Type 1 diabetes (T1D) confers an increased risk of fracture and is associated with lower bone mineral density (BMD) and altered microarchitecture compared with controls. Adequate calcium (Ca) intake promotes bone mineralization, thereby increasing BMD. The objective of this analysis was to evaluate the associations of total daily Ca intake with bone outcomes among youth with T1D. This was a cross-sectional analysis of girls ages 10-16 years with (n = 62) and without (n = 60) T1D. We measured Ca intake with a validated food-frequency questionnaire and BMD, microarchitecture, and strength estimates with dual-energy X-ray absorptiometry and high-resolution peripheral quantitative computed tomography. Total daily Ca intake did not differ between groups (950 ± 488 in T1D versus 862 ± 461 mg/d in controls, p = 0.306). Serum 25OHD was lower in T1D (26.3 ± 7.6 versus 32.6 ± 9.0 ng/mL, p = <0.001), and parathyroid hormone (PTH) was higher in T1D (38.9 ± 11 versus 33.4 ± 9.7 pg/mL, p = 0.004). Trabecular volumetric BMD and thickness at the tibia were lower in T1D (p = 0.013, p = 0.030). Ca intake correlated with trabecular BMD at the radius and tibia among T1D participants (β = 0.27, p = 0.047, and β = 0.28, p = 0.027, β = 0.28, respectively) but not among controls (pinteraction = 0.009 at the radius, pinteraction = 0.010 at the tibia). Similarly, Ca intake was associated with estimated failure load at the tibia in T1D but not control participants (p = 0.038, β = 0.18; pinteraction = 0.051). We observed the expected negative association of Ca intake with parathyroid hormone in controls (p = 0.022, β = -0.29) but not in T1D participants (pinteraction = 0.022). Average glycemia as measured by hemoglobin A1c did not influence the relationship of Ca and PTH among participants with T1D (pinteraction = 0.138). These data suggest that youth with T1D may be particularly vulnerable to dietary Ca insufficiency. Increasing Ca intake may be an effective strategy to optimize bone health in this population. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

A Population-Based Registry Study of Extended Bisphosphonate Use: Minimal Shift After Landmark Publications About Shorter Treatment Duration

Optimal duration of bisphosphonate therapy was unknown until the FLEX study was published in 2006 showing a 5-year course to be adequate for most women. In 2008, a link between long-term bisphosphonate and atypical femoral fractures was reported and confirmed in later studies. We hypothesized these landmark observations should have led to a decrease in use of bisphosphonates for >5 or 10 years, from 2010 onward. The Manitoba Bone Mineral Density (BMD) Registry with linkage to provincial pharmacy data was used to determine the percentage of long- and very long-term bisphosphonate users from therapy start. The cohort comprised women aged >50 years with BMD between 1995 and 2018 with oral bisphosphonate first prescribed for >90 days with adherence >75% in the first year. For each calendar year of continued therapy, the percentage of patients and medication possession rate was tabulated. The percentage of users beyond 5 years was compared among patients who started therapy in 1998-2004 (those taking 5 years of therapy still finish before 2010) versus 2005-2012 (all new therapy starts overlap 2010 in those taking ≥5 years of treatment). The cohort included 2991 women with mean follow-up 8.8 (1.3) years, 64.9% of whom took continuous oral bisphosphonate for >5 years and 41.9% for >10 years. In the earlier versus later era, there were 74.4% versus 70.2% who completed 5 years. With respect to longer treatment, there were 68.0% and 60.5% of patients treated for 6 or more years (p < 0.0001) and 46.6% versus 33.5% treated for >10 years (p = 0.08). Medication possession rate was >79% in every year of therapy. Landmark studies leading to more limited bisphosphonate courses may have slightly reduced longer-term treatment, but up to one-third of adherent patients in the modern era still receive continuous bisphosphonate therapy for >10 years. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Measurements of the Vitamin D Metabolome in the Calgary Vitamin D Study: Relationship of Vitamin D Metabolites to Bone Loss

In a 36-month randomized controlled trial examining the effect of high-dose vitamin D3 on radial and tibial total bone mineral density (TtBMD), measured by high-resolution peripheral quantitative tomography (HR-pQCT), participants (311 healthy males and females aged 55-70 years with dual-energy X-ray absorptiometry T-scores > -2.5 without vitamin D deficiency) were randomized to receive 400 IU (N = 109), 4000 IU (N = 100), or 10,000 IU (N = 102) daily. Participants had HR-pQCT radius and tibia scans and blood sampling at baseline, 6, 12, 24, and 36 months. This secondary analysis examined the effect of vitamin D dose on plasma measurements of the vitamin D metabolome by liquid chromatography-tandem mass spectrometry (LC-MS/MS), exploring whether the observed decline in TtBMD was associated with changes in four key metabolites [25-(OH)D3 ; 24,25-(OH)2 D3 ; 1,25-(OH)2 D3 ; and 1,24,25-(OH)3 D3 ]. The relationship between peak values in vitamin D metabolites and changes in TtBMD over 36 months was assessed using linear regression, controlling for sex. Increasing vitamin D dose was associated with a marked increase in 25-(OH)D3 , 24,25-(OH)2 D3 and 1,24,25-(OH)3 D3 , but no dose-related change in plasma 1,25-(OH)2 D3 was observed. There was a significant negative slope for radius TtBMD and 1,24,25-(OH)3 D3 (-0.05, 95% confidence interval [CI] -0.08, -0.03, p < 0.001) after controlling for sex. A significant interaction between TtBMD and sex was seen for 25-(OH)D3 (female: -0.01, 95% CI -0.12, -0.07; male: -0.04, 95% CI -0.06, -0.01, p = 0.001) and 24,25-(OH)2 D3 (female: -0.75, 95% CI -0.98, -0.52; male: -0.35, 95% CI -0.59, -0.11, p < 0.001). For the tibia there was a significant negative slope for 25-(OH)D3 (-0.03, 95% CI -0.05, -0.01, p < 0.001), 24,25-(OH)2 D3 (-0.30, 95% CI -0.44, -0.16, p < 0.001), and 1,24,25-(OH)3 D3 (-0.03, 95% CI -0.05, -0.01, p = 0.01) after controlling for sex. These results suggest vitamin D metabolites other than 1,25-(OH)2 D3 may be responsible for the bone loss seen in the Calgary Vitamin D Study. Although plasma 1,25-(OH)2 D3 did not change with vitamin D dose, it is possible rapid catabolism to 1,24,25-(OH)3 D3 prevented the detection of a dose-related rise in plasma 1,25-(OH)2 D3 . © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Association of Preterm Birth and Low Birthweight with Bone Fractures during Childhood

Preterm birth and low birthweight have been associated with increased fracture risk in children. Our aim was to analyze bone fractures during childhood in preterm, and low-birthweight newborns compared to full-term and normal-birthweight newborns. We conducted a nationwide register-based cohort study in Finland from 1998 to 2017 and utilized the Medical Birth Register and Care Register for Health Care. All newborns alive 28 days after birth were included, and data on all fracture visits in specialized healthcare units were gathered. Incidences per 100,000 person-years with 95% confidence intervals (CI) were calculated, and comparisons were made by incidence rate ratios (IRRs). Kaplan-Meier analysis was used to analyze the timing of fractures during childhood (0-20 years). We included a total of 997,468 newborns and 95,869 fractures; the mean follow-up was 10.0 years, and the overall incidence of fractures was 963 per 100,000 person-years. Very preterm (<32 gestational weeks) newborns had 23% lower fracture incidence than term newborns (IRR 0.77; CI: 0.70-0.85). Preterm newborns (32 to 36 gestational weeks) had a fracture rate (IRR 0.98; CI: 0.95-1.01) similar to that of term newborns. Birthweight showed a linear increase in the fracture rates as newborns with birthweight less than 1000 g had the lowest fracture incidence of 773 per 100,000 person-years and the highest incidence (966 per 100,000 person-years) was among newborns with birthweight 2500 g or more. Children born very preterm or with extremely low birthweight have in general a lower fracture incidence during childhood compared to children born full term and with normal birthweight. These findings possibly reflect, in addition to improvements of neonatal intensive care and early nutrition, the fact that childhood fracture incidences are more dependent on issues other than early life events. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Increased Bone Formation and Accelerated Bone Mass Accrual in a Man Presenting with Diffuse Osteosclerosis/High Bone Mass Phenotype and Adenocarcinoma of Unknown Primary

A 71-year-old man was referred for evaluation of incidental generalized osteosclerosis. He was found to have a high bone mass (HBM) with an elevated lumbar spine bone mineral density (BMD) Z-score of +5.3. Over an 18-month period, his lumbar spine BMD measured by dual energy X-ray absorptiometry (DXA) had increased by +64% from 1.09 to 1.79 g/cm2 and femoral neck by +21% from 0.83 to 1.01 g/cm2. Biochemical markers of bone turnover were markedly increased (serum propeptide of type 1 collagen and urine telopeptides greater than 10-times normal). The high bone formation and increased skeletal calcium acquisition resulted in profound hypocalcemia (low serum calcium 1.88 mmol/L) and hypocalciuria (low urinary calcium <0.2 mmol/day). Positron emission tomography (PET) with 2-deoxy-2-[fluorine-18] fluoro-D-glucose (FDG) confirmed diffuse osteosclerosis without focal areas of abnormal FDG uptake in the skeleton or elsewhere to suggest either an underlying primary malignancy or metastatic disease. Bone biopsy showed markedly sclerotic woven and lamellar bone. The marrow space was devoid of typical bone cells and adipocytes and instead was filled by fibromyxoid stroma, infiltrated by small clusters of tumor cells. Bone histomorphometry and micro-computed tomography demonstrated an elevated trabecular bone volume and trabecular plate thickness. The bone disorder in this case is unique and raises the possibility of a new yet undefined novel anabolic paracrine factor (or factors) secreted by an adenocarcinoma of unknown primary that resulted in dramatic increases in BMD, HBM, and radiological osteosclerosis. The differential diagnosis and potential mechanisms responsible for the HBM are discussed. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Calcitriol-Dependent and -Independent Regulation of Intestinal Calcium Absorption, Osteoblast Function, and Skeletal Mineralization during Lactation and Recovery in Mice

Recovery from lactation-induced bone loss appears to be calcitriol-independent, since mice lacking 1-alpha-hydroxylase or vitamin D receptor (VDR) exhibit full skeletal recovery. However, in those studies mice consumed a calcium-, phosphorus-, and lactose-enriched "rescue" diet. Here we assessed whether postweaning skeletal recovery of Vdr null mice required that rescue diet. Wild type (WT) and Vdr null mice were raised on the rescue diet and switched to a normal (1% calcium) diet at Day 21 of lactation until 28 days after weaning. Unmated mice received the same regimen. In WT mice, cortical thickness was significantly reduced by 25% at 21 days of lactation and was completely restored by 28 days after weaning. Three-point bending tests similarly showed a significant reduction during lactation and full recovery of ultimate load and energy absorbed. Although Vdr null mice exhibited a similar lactational reduction in cortical thickness and mechanical strength, neither was even partially restored after weaning. Unmated mice showed no significant changes. In micro-computed tomography scans, diaphyses of Vdr null femora at 28 days after weaning were highly porous and exhibited abundant low-density bone extending into the marrow space from the endocortical surface. To quantify, we segregated bone into low-, mid-, and high-density components. In WT diaphyses, high-density bone was lost during lactation and restored after weaning. Vdr null mice also lost high-density bone during lactation but did not replace it; instead, they demonstrated a threefold increase in low-density bone mass. Histology revealed that intracortical and endocortical surfaces of Vdr null bones after weaning contained very thick (up to 20 micron) osteoid seams, covered with multiple layers of osteoblasts and precursors. We conclude that during the postweaning period, osteoblasts are potently stimulated to produce osteoid despite lacking VDRs, and that either calcitriol or a calcium-enriched diet are needed for this immature bone to become mineralized. © 2022 American Society for Bone and Mineral Research (ASBMR).

Response to High-Dose Vitamin D Supplementation Is Specific to Imaging Modality and Skeletal Site

High-dose vitamin D supplementation (4000 or 10,000 IU/d) in vitamin D-sufficient individuals results in a dose-dependent decrease in radius and tibia total bone mineral density (Tt.BMD) compared with 400 IU/d. This exploratory analysis examined whether the response to high-dose vitamin D supplementation depends on imaging modality and skeletal site. Participants were aged 55 to 70 years, not osteoporotic, with serum 25(OH)D 30 to 125 nM. Participants' radius and tibia were scanned on high-resolution peripheral quantitative computed tomography (HR-pQCT) to measure Tt.BMD, trabecular bone volume fraction (Tb.BV/TV), trabecular separation (Tb.Sp), cortical thickness (Ct.Th), and finite element analysis (FEA) estimated failure load. Three-dimensional image registration was used. Dual-energy X-ray absorptiometry (DXA) scans of the hip, spine, and radius measured areal BMD (aBMD) and trabecular bone score (TBS). Constrained linear mixed-effects models determined treatment group-by-time and treatment group-by-time-by-sex interactions. The treatment group-by-time interaction previously observed for radial Tt.BMD was observed at both ultradistal (UD, p < 0.001) and 33% (p < 0.001) aBMD sites. However, the treatment group-by-time-by-sex interaction observed for radial Tt.BMD was not observed with aBMD at either the UD or 33% site, and the 4000 and 400 groups did not differ. Registered radial FEA results mirrored Tt.BMD. An increase in Tb.Sp and decrease in Ct.Th underpinned dose-dependent changes in radial BMD and strength. We observed no effects in DXA-based aBMD at the hip or spine or TBS. At the tibia, we observed a time-by-treatment group effect for Tb.BV/TV. Given that DXA measures at the radius did not detect sex differences or differences between the 4000 and 400 groups, HR-pQCT at the radius may be more sensitive for examining bone changes after vitamin D supplementation. Although DXA did not reveal treatment effects at the hip or spine, whether that is a true skeletal site difference or a lack of modality sensitivity remains unclear. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Persistent Musculoskeletal Deficits in Pediatric, Adolescent and Young Adult Survivors of Allogeneic Hematopoietic Stem-Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a common therapy for pediatric hematologic malignancies. With improved supportive care, addressing treatment-related late effects is at the forefront of survivor long-term health and quality of life. We previously demonstrated that alloHSCT survivors had increased adiposity, decreased lean mass, and lower bone density and strength, 7 years (median) from alloHSCT compared to their healthy peers. Yet it is unknown whether these deficits persist. Our longitudinal study characterized changes in muscle and bone over a period of 3.4 (range, 2.0 to 4.9) years in 47 childhood alloHSCT survivors, age 5-26 years at baseline (34% female). Tibia cortical bone geometry and volumetric density and lower leg muscle cross-sectional area (MCSA) were assessed via peripheral quantitative computed tomography (pQCT). Anthropometric and pQCT measurements were converted to age, sex, and ancestry-specific standard deviation scores, adjusted for leg length. Muscle-specific force was assessed as strength relative to MCSA adjusted for leg length (strength Z-score). Measurements were compared to a healthy reference cohort (n = 921), age 5-30 years (52% female). At baseline and follow-up, alloHSCT survivors demonstrated lower height Z-scores, weight Z-scores, and leg length Z-scores compared to the healthy reference cohort. Deficits in MCSA, trabecular volumetric bone density, and cortical bone size and estimated strength (section modulus) were evident in survivors (all p < 0.05). Between the two study time points, anthropometric, muscle, and bone Z-scores did not change significantly in alloHSCT survivors. Approximately 15% and 17% of alloHSCT survivors had MCSA and section modulus Z-score < -2.0, at baseline and follow-up, respectively. Furthermore, those with a history of total body irradiation compared to those without demonstrated lower MCSA at follow-up. The persistent muscle and bone deficits in pediatric alloHSCT survivors support the need for strategies to improve bone and muscle health in this at-risk population. © 2022 American Society for Bone and Mineral Research (ASBMR).

Adverse Effects of High-Dose Vitamin D Supplementation on Volumetric Bone Density Are Greater in Females than Males

Three years of high-dose vitamin D supplementation (400 IU, 4000 IU, 10,000 IU) in healthy vitamin D-sufficient individuals aged 55 to 70 years (serum 25(OH)D 30-125 nmol/L at baseline), resulted in a negative dose-response relationship for bone density and strength. This study examined whether response differed between males and females. A total of 311 participants (53% male) were randomized to 400 IU (male = 61, female = 48), 4000 IU (male = 51, female = 49), or 10,000 IU (male = 53, female = 49) daily vitamin D₃ . Participants were scanned with high-resolution peripheral quantitative computed tomography (HR-pQCT) to measure total volumetric BMD (TtBMD) at baseline, 6, 12, 24, and 36 months. Finite element analysis estimated bone strength. Balance, physical function, and clinical biochemistry parameters were also assessed. Constrained linear mixed effects models determined time-by-treatment group-by-sex interactions. Baseline, 3-month, and 3-year levels of 25(OH)D were 76.3, 76.7, and 77.4 nmol/L (400 IU); 81.3, 115.3, and 132.2 (4000 IU); and 78.4, 188.0, and 144.4 (10,000 IU), respectively. There were significant time-by-treatment group-by-sex interactions for TtBMD at the radius (p = .002) and tibia (p = .005). Treatment with 4000 IU or 10,000 IU compared to 400 IU resulted in TtBMD losses in females, but this was not observed with males. After 3 years, females lost 1.8% (400 IU), 3.8% (4000 IU), and 5.5% (10,000 IU), whereas males lost 0.9% (400 IU), 1.3% (4000 IU), and 1.9% (10,000 IU) at the radius. At the tibia, losses in TtBMD were smaller, but followed a similar trend. There were no significant bone strength interactions. Vitamin D supplementation with 4000 IU or 10,000 IU, compared with 400 IU daily, resulted in greater losses of TtBMD over 3 years in healthy vitamin D-sufficient females, but not males. These results are clinically relevant, because vitamin D supplementation is widely administered to postmenopausal females for osteoporosis prevention. Our findings do not support a benefit of high-dose vitamin D supplementation for bone health, and raise the possibility of harm for females. © 2020 American Society for Bone and Mineral Research (ASBMR).

Bone Density and Trabecular Morphology at Least 10 Years After Gastric Bypass and Gastric Banding

Roux-en-Y gastric bypass (RYGB) instigates high-turnover bone loss in the initial 5 years after surgery, whereas skeletal changes after adjustable gastric banding (AGB) are less pronounced. Long-term skeletal data are scarce, and the mechanisms of bone loss remain unclear. We sought to examine bone density and microarchitecture in RYGB and AGB patients a decade after surgery and to determine whether prior published reports of bone loss represent an appropriate adaptation to new postsurgical weight. In this cross-sectional study, 25 RYGB and 25 AGB subjects who had bariatric surgery ≥10 years ago were matched 1:1 with nonsurgical controls for age, sex, and current body mass index (BMI). We obtained bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA), volumetric BMD and microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT), trabecular morphology by individual trabecular segmentation, and metabolic bone laboratory results. As compared with BMI-matched controls, RYGB subjects had significantly lower hip BMD, and lower total volumetric BMD at the distal radius and tibia. Substantial deficits in cortical and trabecular microarchitecture were observed in the RYGB group compared to controls, with reduced trabecular plate bone volume fraction and estimated failure load at both the radius and tibia, respectively. Bone turnover markers CTX and P1NP were 99% and 77% higher in the RYGB group than controls, respectively, with no differences in serum calcium, 25-hydroxyvitamin D, or parathyroid hormone. In contrast, the AGB group did not differ from their BMI-matched controls in any measured bone density, microarchitecture, or laboratory parameter. Thus, RYGB, but not AGB, is associated with lower than expected hip and peripheral BMD for the new weight setpoint, as well as deleterious changes in bone microarchitecture. These findings suggest that pathophysiologic processes other than mechanical unloading or secondary hyperparathyroidism contribute to bone loss after RYGB, and have important clinical implications for the long-term care of RYGB patients. © 2020 American Society for Bone and Mineral Research.

Nitrates Do Not Affect Bone Density or Bone Turnover in Postmenopausal Women: A Randomized Controlled Trial

Organic nitrates have been reported to have significant effects on bone mineral density (BMD) and bone turnover in previous clinical trials. However, results are inconsistent and some trials with strikingly positive results have been retracted because of scientific misconduct. As preparation for a potential fracture prevention study, we set out to determine the lowest effective dose and the most effective and acceptable nitrate preparation. We undertook a 1-year, double-blind, randomized, placebo-controlled trial of three different nitrate preparations and two different doses in osteopenic postmenopausal women, with a planned 1-year observational extension. The primary endpoint was change in BMD at the lumbar spine, and secondary endpoints included BMD changes at other sites, changes in bone turnover markers, and adverse events. A total of 240 eligible women who tolerated low-dose oral nitrate treatment in a 2-week run-in period were randomized to five different treatment groups or placebo. Over 12 months, there were no statistically significant between-group differences in changes in BMD at any site and no consistent differences in bone turnover markers. When the active treatment groups were pooled, there were also no differences in changes in BMD or bone turnover markers between nitrate treatment and placebo. Eighty-eight (27%) women withdrew during the run-in phase, with the majority because of nitrate-induced headache, and 41 of 200 (21%) women randomized to nitrate treatment withdrew or stopped study medication during the 1-year study compared with 1 of 40 (2.5%) in the placebo group. In summary, organic nitrates do not have clinically relevant effects on BMD or bone turnover in postmenopausal women and were poorly tolerated. These results call into question the validity of previous clinical research reporting large positive effects of nitrates on BMD and bone turnover. © 2020 American Society for Bone and Mineral Research.

Short Sleep Is Associated With Low Bone Mineral Density and Osteoporosis in the Women's Health Initiative

Short sleep duration, recognized as a public health epidemic, is associated with adverse health conditions, yet little is known about the association between sleep and bone health. We tested the associations of usual sleep behavior and bone mineral density (BMD) and osteoporosis. In a sample of 11,084 postmenopausal women from the Women's Health Initiative (WHI; mean age 63.3 years, SD = 7.4), we performed a cross-sectional study of the association of self-reported usual hours of sleep and sleep quality (WHI Insomnia Rating Score) with whole body, total hip, femoral neck, and spine BMD using linear regression models. We also studied the association of sleep duration and quality with dual-energy X-ray absorptiometry (DXA)-defined low bone mass (T-score < -2.5 to <-1) and osteoporosis (T-score ≤ -2.5) using multinomial regression models. We adjusted for age, DXA machine, race, menopausal symptoms, education, smoking, physical activity, body mass index, alcohol use, physical function, and sleep medication use. In adjusted linear regression models, women who reported sleeping 5 hours or less per night had on average 0.012 to 0.018 g/cm² significantly lower BMD at all four sites compared with women who reported sleeping 7 hours per night (reference). In adjusted multinomial models, women reporting 5 hours or less per night had higher odds of low bone mass and osteoporosis of the hip (odds ratio [OR] = 1.22; 95% confidence interval [CI] 1.03-1.45, and 1.63; 1.15-2.31, respectively). We observed a similar pattern for spine BMD, where women with 5 hours or less per night had higher odds of osteoporosis (adjusted OR = 1.28; 95% CI 1.02-1.60). Associations of sleep quality and DXA BMD failed to reach statistical significance. Short sleep duration was associated with lower BMD and higher risk of osteoporosis. Longitudinal studies are needed to confirm the cross-sectional effects of sleep duration on bone health and explore associated mechanisms. © 2019 American Society for Bone and Mineral Research.

Calcium Supplement Use Is Associated With Less Bone Mineral Density Loss, But Does Not Lessen the Risk of Bone Fracture Across the Menopause Transition: Data From the Study of Women's Health Across the Nation

Diet is a modifiable factor that is related to bone mass and risk for fractures; however, the use of calcium supplements for bone health is controversial, with little scientific agreement. The purpose of this analysis was to estimate the change in lumbar spine and femoral neck BMD and the risk of bone fracture by the use of calcium supplements among the Study of Women's Health Across the Nation (SWAN) participants. SWAN is a multicenter, multiethnic, community‐based longitudinal cohort designed to examine the health of women across the menopause transition (n = 1490; aged 42 to 52 years at baseline in 1996 to 1997 and followed annually until 2006 to 2008). A mixed‐effect model for repeated measures was used to estimate annualized BMD change across time between supplement users and nonusers, unadjusted or fully adjusted (age, race, height, weight, menopausal status [pre‐, early peri‐, late peri‐, and postmenopausal], DXA scanner mode, alcohol intake, vitamin D supplement use, smoking, and physical activity) and a log‐linear model with repeated measures was used to estimate the relative risk of fracture by calcium supplement use. All models were also stratified by baseline menopausal status. In fully adjusted models, calcium supplement use was associated with less annualized loss of femoral neck BMD (−0.0032 versus −0.0040 g/cm²/year; p < .001) and lumbar spine BMD (−0.0046 versus −0.0053 g/cm²/year, p = 0.021) in the complete cohort. However, this protective association of calcium supplement use with BMD loss was significant only among premenopausal women (femoral neck: −0.0032 versus −0.0042 g/cm²/year; p = 0.002; lumbar spine: −0.0038 versus −0.0050 g/cm²/year, p = 0.001); no significant differences in BMD were observed among women who were early perimenopausal by calcium supplement use at baseline. No significant differences in the relative risk of fracture were observed, regardless of baseline menopausal status. The use of calcium supplements was associated with less BMD loss over more than a decade, but was not related to the risk of incident bone fracture across the menopause transition. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Effects of Intravenous Zoledronate on Bone Turnover and Bone Density Persist for at Least 11 Years in HIV-Infected Men

Previously we reported the results of a 4-year extension of a 2-year randomized placebo-controlled trial showing that the antiresorptive effects of two annual 4-mg doses of zoledronate in HIV-infected men persisted for at least 5 years after the second dose. We set out to determine whether the effects on BMD and bone turnover persist beyond 10 years. We invited all participants in the original trial known to be alive and living in New Zealand to attend an additional visit approximately 12 years after trial entry and 11 years after their second dose of study medication. The outcome measures were BMD at the lumbar spine, proximal femur, and total body, and markers of bone turnover. Twenty-five of the 43 men originally enrolled in the trial attended the final visit, representing 25 of 31 (81%) participants alive and residing in New Zealand at the time. The average duration of follow-up was 12.4 years. At the final visit, BMD remained higher in the zoledronate group than the placebo group (lumbar spine 3.7%, 95% CI, 0.1 to 7.3; total hip 3.7%, 95% CI, 1.2 to 6.2; femoral neck 5.0%, 95% CI, 2.1 to 7.9; total body 2.4%, 95% CI, 0.7 to 4.0), and the between-group differences in BMD remained stable between 6 and 12 years. Serum CTx remained lower in the zoledronate group than the placebo group between 6 and 12 years and, at the final visit, was 45% lower (95% CI, 25 to 64) than the placebo group. P1NP was 26% (95% CI, 4 to 48) lower in the zoledronate group than the placebo group at the final visit. In summary, two annual 4-mg doses of zoledronate have effects on bone turnover and BMD in men that persist for at least 11 years after the second dose. © 2019 American Society for Bone and Mineral Research.

A Comparison of US and Canadian Osteoporosis Screening and Treatment Strategies in Postmenopausal Women

The optimal approach to osteoporosis screening and treatment in postmenopausal women is unclear. We compared (i) the United States Preventive Services Task Force (USPSTF) and Osteoporosis Canada osteoporosis screening strategies; and (ii) the National Osteoporosis Foundation (NOF) and Canadian treatment strategies. We used data from the prospective Women's Health Initiative Observational Study and Clinical Trials of women aged 50 to 79 years at baseline (n = 117,707 followed for self-reported fractures; n = 8134 in bone mineral density [BMD] subset). We determined the yield of the screening and treatment strategies in identifying women who experienced major osteoporotic fractures (MOFs) during a 10-year follow-up. Among women aged 50 to 64 years, 23.1% of women were identified for BMD testing under the USPSTF strategy and 52.3% under the Canadian strategy. For women ≥65 years, 100% were identified for testing under the USPSTF and Canadian strategies, 35% to 74% were identified for treatment under NOF, and 16% to 37% were identified for treatment under CAROC (range among 5-year age subgroups). Among women who experienced MOF during follow-up, the USPSTF strategy identified 6.7% of women 50 to 54 years-old and 49.5% of women 60 to 64 years-old for BMD testing (versus 54.4% and 60.6% for the Canadian strategy, respectively). However, the specificity of the USPSTF strategy was higher than that of the Canadian strategy among women 50 to 64 years-old. Among women who experienced MOF during follow-up, sensitivity for identifying women as treatment candidates was lowest for both strategies in women aged 50 to 64 (NOF 10% to 38%; CAROC 1% to 15%) and maximal in 75-year-old to 79-year-old women (NOF 82.8%; 51.6% CAROC); specificity declined with advancing age and was lower with the NOF compared to the CAROC strategy. Among women aged 50 to 64 years, the screening and treatment strategies examined had low sensitivity for identifying those who subsequently experience MOF; sensitivity was higher among women ≥65 years than among younger women. New screening and treatment algorithms are needed. © 2018 American Society for Bone and Mineral Research.

Gestational Weight Gain and Offspring Bone Mass: Different Associations in Healthy Weight Versus Overweight Women

Weight management strategies during pregnancy reduce child cardiometabolic risk. However, because maternal weight has an overall positive correlation with offspring bone mass, pregnancy weight management could adversely affect child bone health. We aimed to estimate associations between gestational weight gain (GWG) and bone mineralization in the offspring at 7 years of age, and test early pregnancy body mass index (BMI) as an effect modifier. We analyzed prospective data from 2167 mother-child pairs from the Generation XXI birth cohort who underwent whole-body dual-energy X-ray absorptiometry at 7 years of age. GWG was analyzed as a continuous measure and using the Institute of Medicine categories. In the whole sample and for each early pregnancy BMI category (under/normal weight and overweight/obese), relationships between GWG and offspring bone measures (bone mineral content [BMC], bone areal density [aBMD], size-corrected BMC [scBMC], and height) at 7 years were fitted through local polynomial regression and smoothing splines. The magnitude of associations was estimated through linear regression coefficients (95% CIs), crude and adjusted for maternal age, height, educational level, and child gestational age. In under/normal weight mothers, GWG was associated with slightly increased bone measures at 7 years (per 5 kg of GWG, BMC: 0.07 SD [95% CI, 0.01 to 0.12]; aBMD: 0.10 SD [95% CI, 0.05 to 0.15], scBMC: 0.11SD [95% CI, 0.06 to 0.16], and height: 0.05 SD [95% CI, 0.00 to 0.10]), while in overweight/obese mothers no effect of GWG on bone was observed (BMC: 0.02 SD [95% CI, -0.04 to 0.09]; aBMD: 0.02 SD [95% CI, -0.04 to 0.08], scBMC: 0.01 SD [95% CI, -0.06 to 0.08], and height: 0.02 SD [95% CI, -0.04 to 0.08]). Also, no advantageous effect of gaining weight above the Institute of Medicine recommendations was observed in either early pregnancy BMI group. Our results suggest that adherence to Institute of Medicine recommendations for pregnancy weight gain is unlikely to have a negative repercussion on offspring bone health, particularly in women with excess weight in early pregnancy. © 2018 American Society for Bone and Mineral Research.

Effects of a Randomized Weight Loss Intervention Trial in Obese Adolescents on Tibia and Radius Bone Geometry and Volumetric Density

Obese adolescents have increased fracture risk, but effects of alterations in adiposity on bone accrual and strength in obese adolescents are not understood. We evaluated 12-month changes in trabecular and cortical volumetric bone mineral density (vBMD) and cortical geometry in obese adolescents undergoing a randomized weight management program, and investigated the effect of body composition changes on bone outcomes. Peripheral quantitative computed tomography (pQCT) of the radius and tibia, and whole-body dual-energy X-ray absorptiometry (DXA) scans were obtained at baseline, 6 months, and 12 months in 91 obese adolescents randomized to standard care versus behavioral intervention for weight loss. Longitudinal models assessed effects of body composition changes on bone outcomes, adjusted for age, bone length, and African-American ancestry, and stratified by sex. Secondary analyses included adjustment for physical activity, maturation, vitamin D, and inflammatory biomarkers. Baseline body mass index (BMI) was similar between intervention groups. Twelve-month change in BMI in the standard care group was 1.0 kg/m² versus -0.4 kg/m² in the behavioral intervention group (p < 0.01). Intervention groups were similar in bone outcomes, so they were combined for subsequent analyses. For the tibia, BMI change was not associated with change in vBMD or structure. Greater baseline lean body mass index (LBMI) associated with higher cortical vBMD in males, trabecular vBMD in females, and polar section modulus (pZ) and periosteal circumference (Peri-C) in both sexes. In females, change in LBMI positively associated with gains in pZ and Peri-C. Baseline visceral adipose tissue (VFAT) was inversely associated with pZ in males and cortical vBMD in females. Change in VFAT did not affect bone outcomes. For the radius, BMI and LBMI changes positively associated with pZ in males. Thus, in obese adolescents, weight loss intervention with modest changes in BMI was not detrimental to radius or tibia bone strength, and changes in lean, but not adiposity, measures were beneficial to bone development. © 2017 American Society for Bone and Mineral Research.

Moderate-to-Vigorous Physical Activity But Not Sedentary Time Is Associated With Musculoskeletal Health Outcomes in a Cohort of Australian Middle-Aged Women

Associations between physical activity and time spent sedentary and musculoskeletal outcomes remain unclear in middle-aged adults. This study aimed to describe associations between objectively-measured physical activity and sedentary time and musculoskeletal health outcomes in middle-aged women. This cross-sectional study from a population-based sample of 309 women (age 36 to 57 years) examined associations of total physical activity (accelerometer counts/min of wear time), and time spent sedentary, in light physical activities and moderate-to-vigorous physical activities (MVPA) (by Actigraph GT1M accelerometer) with lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) (by dual-energy X-ray absorptiometry), lower limb muscle strength (LMS), and functional mobility and balance tests (timed up and go test [TUG], functional reach test [FRT], lateral reach test [LRT], and step test [ST]) using linear regression. Total physical activity was beneficially associated with FN BMD (values are β; 95% CI) (0.011 g/cm² ; 95% CI, 0.003 to 0.019 g/cm² ), LMS (2.13 kg; 95% CI, 0.21 to 4.06 kg), and TUG (-0.080 s; 95% CI, -0.129 to -0.030 s), after adjustment for confounders. MVPA was also beneficially associated with FN BMD (0.0050 g/cm² ; 95% CI, 0.0007 to 0.0094 g/cm² ), LMS (1.48 kg; 95% CI, 0.45 to 2.52 kg), ST (0.12 steps; 95% CI, 0.02 to 0.23 steps), and TUG (-0.043 s; 95% CI, -0.070 to -0.016 s). Associations between MVPA and LMS, TUG and ST persisted after further adjustment for sedentary time. Only TUG was associated with sedentary time, with a detrimental effect (0.075 s; 95% CI, 0.013 to 0.137 s) and this did not persist after further adjustment for MVPA. Light physical activity was not associated with any outcome. MVPA appears more important than light physical activity or sedentary time for many musculoskeletal outcomes in middle-aged women. This needs to be considered when developing interventions to improve habitual physical activity that aim to improve musculoskeletal health. © 2016 American Society for Bone and Mineral Research.

Treatment Sequence Matters: Anabolic and Antiresorptive Therapy for Osteoporosis

The effects of anabolic medications (teriparatide [TPTD] and parathyroid hormone [PTH]) differ in patients who have received recent treatment with potent antiresorptives. This perspective reviews studies evaluating bone density (BMD) and histomorphometric effects of treatment sequences beginning with TPTD/PTH followed by potent antiresorptives and those beginning with potent antiresorptives followed by switching to or adding TPTD. Effect of treatment sequence on spine BMD outcome is minor, with modest quantitative differences. However, when individuals established on potent bisphosphonates are switched to TPTD, hip BMD declines below baseline for at least the first 12 months after the switch to TPTD. This transient hip BMD loss is more prominent when the antiresorptive is denosumab; in this setting, hip BMD remains below baseline for almost a full 24 months. In a controlled comparison of those who switched from alendronate to TPTD versus those who added TPTD to ongoing alendronate, the effect on hip BMD was improved with combination therapy. Furthermore, hip strength improved with the addition of TPTD to ongoing alendronate, whereas it was neutral after switching from alendronate to TPTD, primarily due to the effect on cortical bone. Bone biopsy studies indicate that TPTD stimulates bone formation in patients who have not been treated previously as well as in patients on prior and ongoing bisphosphonates. Histomorphometric evidence suggests that use of alendronate with TPTD blocks the TPTD-induced increase in cortical porosity. When possible, we suggest anabolic therapy first, followed by potent antiresorptive therapy. The common practice of switching to TPTD only after patients have an inadequate response to antiresorptives (intercurrent fracture or inadequate BMD effect) is not the optimal utilization of anabolic treatment. In fact, this may result in transient loss of hip BMD and strength. In this setting, continuing a potent antiresorptive while starting TPTD might improve hip outcomes. © 2017 American Society for Bone and Mineral Research.

Visceral Adipose Tissue Is Associated With Bone Microarchitecture in the Framingham Osteoporosis Study

Obesity has been traditionally considered to protect the skeleton against osteoporosis and fracture. Recently, body fat, specifically visceral adipose tissue (VAT), has been associated with lower bone mineral density (BMD) and increased risk for some types of fractures. We studied VAT and bone microarchitecture in 710 participants (58% women, age 61.3 ± 7.7 years) from the Framingham Offspring cohort to determine whether cortical and trabecular BMD and microarchitecture differ according to the amount of VAT. VAT was measured from CT imaging of the abdomen. Cortical and trabecular BMD and microarchitecture were measured at the distal tibia and radius using high-resolution peripheral quantitative computed tomography (HR-pQCT). We focused on 10 bone parameters: cortical BMD (Ct.BMD), cortical tissue mineral density (Ct.TMD), cortical porosity (Ct.Po), cortical thickness (Ct.Th), cortical bone area fraction (Ct.A/Tt.A), trabecular density (Tb.BMD), trabecular number (Tb.N), trabecular thickness (Tb.Th), total area (Tt.Ar), and failure load (FL) from micro-finite element analysis. We assessed the association between sex-specific quartiles of VAT and BMD, microarchitecture, and strength in all participants and stratified by sex. All analyses were adjusted for age, sex, and in women, menopausal status, then repeated adjusting for body mass index (BMI) or weight. At the radius and tibia, Ct.Th, Ct.A/Tt.A, Tb.BMD, Tb.N, and FL were positively associated with VAT (all p-trend <0.05), but no other associations were statistically significant except for higher levels of cortical porosity with higher VAT in the radius. Most of these associations were only observed in women, and were no longer significant when adjusting for BMI or weight. Higher amounts of VAT are associated with greater BMD and better microstructure of the peripheral skeleton despite some suggestions of significant deleterious changes in cortical measures in the non-weight bearing radius. Associations were no longer significant after adjustment for BMI or weight, suggesting that the effects of VAT may not have a substantial effect on the skeleton independent of BMI or weight. © 2016 American Society for Bone and Mineral Research.

Bariatric Surgery: What the Rheumatologist Needs to Know

A staggering 76 million adults are obese in the United States. It is known that obesity contributes to increased incidence and worse disease outcomes in many rheumatic conditions. Bariatric surgery has emerged as the most effective treatment modality for the morbidly obese, leading to substantial and sustained weight loss. The purpose of this review article is to summarize the findings of studies investigating the effect of substantial weight loss achieved through bariatric surgery on rheumatic disease and outcomes. Second, with an increasing number of patients undergoing bariatric surgery, it is important for the rheumatologist to have a basic understanding of the commonly performed bariatric procedures and to be aware of important nutritional deficiencies and medication restrictions that apply to this patient population.

A Surrogate Measure of Cortical Bone Matrix Density by Long T2 -Suppressed MRI

Magnetic resonance has the potential to image and quantify two pools of water within bone: free water within the Haversian pore system (transverse relaxation time, T2 > 1 ms), and water hydrogen-bonded to matrix collagen (T2 ∼ 300 to 400 μs). Although total bone water concentration quantified by MRI has been shown to scale with porosity, greater insight into bone matrix density and porosity may be gained by relaxation-based separation of bound and pore water fractions. The objective of this study was to evaluate a recently developed surrogate measurement for matrix density, single adiabatic inversion recovery (SIR) zero echo-time (ZTE) MRI, in human bone. Specimens of tibial cortical bone from 15 donors (aged 27 to 97 years; 8 female and 7 male) were examined at 9.4T field strength using two methods: (1) (1)H ZTE MRI, to capture total (1)H signal, and (2) (1)H SIR-ZTE MRI, to selectively image matrix-associated (1)H signal. Total water, bone matrix, and bone mineral densities were also quantified gravimetrically, and porosity was measured by micro-CT. ZTE apparent total water (1)H concentration was 32.7 ± 3.2 M (range 28.5 to 40.3 M), and was correlated positively with porosity (R(2) = 0.80) and negatively with matrix and mineral densities (R(2) =  0.90 and 0.82, respectively). SIR-ZTE apparent bound water (1)H concentration was 32.9 ± 3.9 M (range 24.4 to 39.8 M), and its correlations were opposite to those of apparent total water: negative with porosity (R(2) = 0.73) and positive with matrix density (R(2) = 0.74) and mineral density (R(2) = 0.72). Porosity was strongly correlated with gravimetric matrix density (R(2) = 0.91, negative) and total water density (R(2) = 0.92, positive). The strong correlations of SIR-ZTE-derived apparent bound water (1)H concentration with ground-truth measurements suggest that this quantitative solid-state MRI method provides a nondestructive surrogate measure of bone matrix density.

Incident Vertebral Fractures and Risk Factors in the First Three Years Following Glucocorticoid Initiation Among Pediatric Patients With Rheumatic Disorders

Vertebral fractures are an important yet underrecognized manifestation of osteoporosis in children with chronic, glucocorticoid-treated illnesses. Our goal was to determine the incidence and clinical predictors of vertebral fractures in the 3 years following glucocorticoid initiation among pediatric patients with rheumatic disorders. Incident vertebral fractures were evaluated according to the Genant semiquantitative method on lateral radiographs at baseline and then annually in the 3 years following glucocorticoid initiation. Extended Cox models were used to assess the association between vertebral fractures and clinical risk predictors. A total of 134 children with rheumatic disorders were enrolled in the study (mean ± standard deviation (SD) age 9.9 ± 4.4 years; 65% girls). The unadjusted vertebral fracture incidence rate was 4.4 per 100 person-years, with a 3-year incidence proportion of 12.4%. The highest annual incidence occurred in the first year (6.0%; 95% confidence interval (CI) 2.9% to 11.7%). Almost one-half of the patients with fractures were asymptomatic. Every 0.5 mg/kg increase in average daily glucocorticoid (prednisone equivalents) dose was associated with a twofold increased fracture risk (hazard ratio (HR) 2.0; 95% CI 1.1 to 3.5). Other predictors of increased vertebral fracture risk included: (1) increases in disease severity scores between baseline and 12 months; (2) increases in body mass index Z-scores in the first 6 months of each 12-month period preceding the annual fracture assessment; and (3) decreases in lumbar spine bone mineral density Z-scores in the first 6 months of glucocorticoid therapy. As such, we observed that a clinically significant number of children with rheumatic disorders developed incident vertebral fractures in the 3 years following glucocorticoid initiation. Almost one-half of the children were asymptomatic and thereby would have been undiagnosed in the absence of radiographic monitoring. In addition, discrete clinical predictors of incident vertebral fractures were evident early in the course of glucocorticoid therapy.

Macrophages promote osteoblastic differentiation in-vivo: implications in fracture repair and bone homeostasis

Macrophages are activated in inflammation and during early phases of repair processes. Interestingly, they are also present in bone during development, but their function during this process is unclear. Here, we explore the function of macrophages in bone development, growth, and repair using transgenic mice to constitutively or conditionally deplete macrophages. Depletion of macrophages led to early skeletal growth retardation and progressive osteoporosis. By 3 months of age, macrophage-deficient mice displayed a 25% reduction in bone mineral density and a 70% reduction in the number of trabecular bone compared to control littermates. Despite depletion of macrophages, functional osteoclasts were still present in bones, lining trabecular bone and the endosteal surface of the cortical bone. Furthermore, ablation of macrophages led to a 60% reduction in the number of bone marrow mesenchymal progenitor cells and a decrease in the ability of these cells to differentiate to osteoblasts. When macrophages were depleted during fracture repair, bone union was impaired. Calluses from macrophage-deficient animals were smaller, and contained less bone and more fibrotic tissue deposition. Taken together, this shows that macrophages are crucial for maintaining bone homeostasis and promoting fracture repair by enhancing the differentiation of mesenchymal progenitors.

Thalassemia bone disease: a 19-year longitudinal analysis

Thalassemia is an inherited disorder of alpha or beta globin chain synthesis leading to ineffective erythropoiesis requiring chronic transfusion therapy in its most severe form. This leads to iron overload, marrow expansion, and hormonal complications, which are implicated in bone deformity and loss of bone mineral density (BMD). In this 19-year retrospective longitudinal study, the relationships between BMD (determined by dual-energy X-ray absorptiometry) and risk factors for osteoporosis in 277 subjects with transfusion-dependent thalassemia were examined. The mean age at first review was 23.2 ± 11.9 years and 43.7% were male. Hypogonadism was present in 28.9%. Fractures were confirmed in 11.6% of subjects and were more frequent in males (16.5%) compared with females (7.7%). Lumbar spine (LS), femoral neck (FN), and total body (TB) Z-scores were derived. Patients with transfusion-dependent thalassemia had a significant longitudinal decline in BMD at the FN and TB. In the linear mixed-model analysis of BMD and risk factors for bone loss, FN Z-score was more significantly associated with risk factors compared with the LS and TB. The rate of decline at the FN was 0.02 Z-score per year and was 3.85-fold greater in males. The decline in FN Z-score over the last 5 years (years 15 to 19) was 2.5-fold that of the previous 7 years (years 8 to 14) and coincided with a change in iron chelator therapy from desferrioxamine to deferasirox. Hemoglobin (Hb) levels positively correlated with higher TB and LS Z-scores. In conclusion, the FN is the preferred site for follow-up of BMD. Male patients with β-thalassemia experienced a greater loss of BMD and had a higher prevalence of fractures compared with females. Transfusing patients (particularly males) to a higher Hb target may reduce the decline in BMD. Whether deferasirox is implicated in bone loss warrants further study.

Association of chronic obstructive pulmonary disease and smoking status with bone density and vertebral fractures in male lung cancer screening participants

We studied the vertebral fracture prevalence on low-dose chest computed tomography (CT) in male lung cancer screening participants and the association of fractures and bone density with chronic obstructive pulmonary disease (COPD) and smoking. 1140 male current and former smokers with ≥ 16.5 packyears from the NELSON lung cancer screening trial were included. Age, body mass index, and smoking status were registered. CT scans and pulmonary function tests were obtained on the same day. On CT, vertebral fractures and bone density were measured. The cohort had a mean age of 62.5 years (standard deviation 5.2) old; 531 (46.6%) had quit smoking; and 437 (38.3%) had COPD. Of the group, 100 (8.8%) participants had a vertebral fracture. Fracture prevalence was higher in current compared to former smokers (11.3% versus 5.8%, p = 0.001), but similar in participants with COPD compared to those without (9.6% versus 8.3%, p = 0.430). The multivariable adjusted odds ratio for fracture presence was 1.79 (95% CI: 1.13-2.84) in current smokers and 1.08 (95% CI: 0.69-1.67) in COPD participants. Bone density was lower in current compared to former smokers (103.2 HU versus 108.7 HU, p = 0.006) and in participants with COPD compared to those without [100.7 Hounsfield Units (HU) versus 108.9 HU, p < 0.001]. In multivariate analysis, smoking status and COPD status were independently associated with bone density, corrected for age and body mass index. In conclusion, our study shows that lung cancer screening participants have a substantial vertebral fracture burden. Fractures are more common in current smokers, who also have lower bone density. We could not confirm that COPD is independently associated with vertebral fractures.

High-resolution genome screen for bone mineral density in heterogeneous stock rat

We previously demonstrated that skeletal mass, structure, and biomechanical properties vary considerably in heterogeneous stock (HS) rat strains. In addition, we observed strong heritability for several of these skeletal phenotypes in the HS rat model, suggesting that it represents a unique genetic resource for dissecting the complex genetics underlying bone fragility. The purpose of this study was to identify and localize genes associated with bone mineral density in HS rats. We measured bone phenotypes from 1524 adult male and female HS rats between 17 and 20 weeks of age. Phenotypes included dual-energy X-ray absorptiometry (DXA) measurements for bone mineral content and areal bone mineral density (aBMD) for femur and lumbar spine (L3-L5), and volumetric BMD measurements by CT for the midshaft and distal femur, femur neck, and fifth lumbar vertebra (L5). A total of 70,000 polymorphic single-nucleotide polymorphisms (SNPs) distributed throughout the genome were selected from genotypes obtained from the Affymetrix rat custom SNPs array for the HS rat population. These SNPs spanned the HS rat genome with a mean linkage disequilibrium coefficient between neighboring SNPs of 0.95. Haplotypes were estimated across the entire genome for each rat using a multipoint haplotype reconstruction method, which calculates the probability of descent for each genotyped locus from each of the eight founder HS strains. The haplotypes were tested for association with each bone density phenotype via a mixed model with covariate adjustment. We identified quantitative trait loci (QTLs) for BMD phenotypes on chromosomes 2, 9, 10, and 13 meeting a conservative genomewide empiric significance threshold (false discovery rate [FDR] = 5%; p < 3 × 10(-6)). Importantly, most QTLs were localized to very small genomic regions (1-3 megabases [Mb]), allowing us to identify a narrow set of potential candidate genes including both novel genes and genes previously shown to have roles in skeletal development and homeostasis.

Association between polymorphisms in period genes and bone density in postmenopausal Korean women

OBJECTIVE

In the present study, we aimed to investigate the association between genetic polymorphisms in period (PER) genes and bone mineral density (BMD) in postmenopausal Korean women.

METHODS

The PER1 c.2247C> T and c.2884C> G polymorphisms; the PER2 c.661G> A and c.3731G> A polymorphisms; the PER3 c.2592G> A, c.3029C> T, c.3035C> T, and c.3083T> C polymorphisms, and the 54 bp variable number tandem repeats polymorphism were analyzed in 551 postmenopausal Korean women. Serum leptin, soluble leptin receptor, osteoprotegerin, soluble receptor activator of the nuclear factor-κB ligand, and bone markers including bone alkaline phosphatase and carboxy-terminal telopeptide of type I collagen were measured, and the lumbar spine and femoral neck BMDs were also determined.

RESULTS

The PER2 c.661G> A, PER3 c.3029C> T and c.3035C> T polymorphisms were not observed. The PER2 and PER3 polymorphisms evaluated were not related to BMD, whereas associations of the c.2247C> T and c.2884C> G polymorphisms in PER1 with the lumbar spine BMD were observed both singly and in combination. The CC haplotype homozygotes showed significantly lower lumbar spine BMD than participants with other genotypes. Additionally, 2.01-fold higher odds for osteoporosis of the lumbar spine were found in the CC haplotype homozygotes compared to women not carrying the haplotype CC allele. No significant differences in bone markers were detected according to the PER1 haplotype genotype.

CONCLUSIONS

Our results suggest that both the PER1 c.2247C> T and c.2884C> G polymorphisms may be genetic factors affecting the lumbar spine BMD in postmenopausal Korean women.

Spatial heterogeneity in the response of the proximal femur to two lower-body resistance exercise regimens

Understanding the skeletal effects of resistance exercise involves delineating the spatially heterogeneous response of bone to load distributions from different muscle contractions. Bone mineral density (BMD) analyses may obscure these patterns by averaging data from tissues with variable mechanoresponse. To assess the proximal femoral response to resistance exercise, we acquired pretraining and posttraining quantitative computed tomography (QCT) images in 22 subjects (25-55 years, 9 males, 13 females) performing two resistance exercises for 16 weeks. One group (SQDL, n = 7) performed 4 sets each of squats and deadlifts, a second group (ABADD, n = 8) performed 4 sets each of standing hip abductions and adductions, and a third group (COMBO, n = 7) performed two sets each of squat/deadlift and abduction/adduction exercise. Subjects exercised three times weekly, and the load was adjusted each session to maximum effort. We used voxel-based morphometry (VBM) to visualize BMD distributions. Hip strength computations used finite element modeling (FEM) with stance and fall loading conditions. We used QCT analysis for cortical and trabecular BMD, and cortical tissue volume. For muscle size and density, we analyzed the cross-sectional area (CSA) and mean Hounsfield unit (HU) in the hip extensor, flexor, abductor, and adductor muscle groups. Whereas SQDL increased vertebral BMD, femoral neck cortical BMD and volume, and stance hip strength, ABADD increased trochanteric cortical volume. The COMBO group showed no changes in any parameter. VBM showed different effects of ABADD and SQDL exercise, with the former causing focal changes of trochanteric cortical bone, and the latter showing diffuse changes in the femoral neck and head. ABADD exercise increased adductor CSA and HU, whereas SQDL exercise increased the hip extensor CSA and HU. In conclusion, we observed different proximal femoral bone and muscle tissue responses to SQDL and ABADD exercise. This study supports VBM and volumetric QCT (vQCT) to quantify the spatially heterogeneous effects of types of muscle contractions on bone.

Duration of antiresorptive effects of low-dose zoledronate in osteopenic postmenopausal women: a randomized, placebo-controlled trial

Annual intravenous administration of 5 mg zoledronate decreases fracture risk, but the optimal dosing regimen for zoledronate has not been determined. We set out to evaluate the antiresorptive effects of a single administration of lower doses of zoledronate. A total of 180 postmenopausal women with osteopenia enrolled in a double-blind, randomized, placebo-controlled trial over 2 years at an academic research center. Participants were randomized to a single baseline administration of intravenous zoledronate in doses of 1 mg, 2.5 mg, or 5 mg, or placebo. The primary endpoint was change in bone mineral density(BMD) at the lumbar spine. Secondary endpoints were change in BMD at the proximal femur and total body, and changes in biochemical markers of bone turnover. After 2 years, the change in spine BMD was greater in each of the zoledronate groups than in the placebo group; values are mean (95% confidence interval [CI]) difference versus placebo: zoledronate 1 mg 4.4% [2.7% to 6.1%]; 2.5 mg 5.5% [3.9% to 7.2%]; 5 mg 5.3% [3.8% to 6.7%], p < 0.001 for each dose). Change in BMD at the total hip was greater in each of the zoledronate groups than the placebo group (mean [95% CI] difference versus placebo: zoledronate 1 mg 2.6% [1.5% to 3.7%]; 2.5 mg 4.4% [3.5% to 5.3%]; 5 mg 4.7% [3.7% to 5.7%], p < 0.001 for each dose). Each of the bone turnover markers, β-C-terminal telopeptide of type I collagen (β-CTX) and procollagen type-I N-terminal propeptide (P1NP), was lower in each of the 2.5-mg and 5-mg zoledronate groups than the placebo group throughout the trial (p < 0.001 versus placebo for each marker for each dose at each time point). For each endpoint, changes were similar in the 2.5-mg and 5-mg zoledronate groups, whereas those in the 1-mg group were smaller than those in the other zoledronate groups. These data demonstrate that single administrations of zoledronate 1 mg or 2.5 mg produce antiresorptive effects that persist for at least 2 years. Trials assessing the antifracture efficacy of intermittent low doses of zoledronate, in particular the 2.5-mg dose, are justified.

A systematic review

OBJECTIVE

The effect of systemic sclerosis (SSc) on bone density is not well understood. Through systematic review of the literature, the objectives of this study were to synthesize data about the prevalence of low bone mineral density (BMD), risk factors for low BMD, and occurrence of fracture and fracture-related mortality in SSc.

METHODS

A search was conducted of MEDLINE (1948-2012), Evidence Based Medicine Reviews (1991-2012), EMBASE (1980-2012), and CINAHL (1981-2012). Abstracts were screened to identify studies that evaluated low BMD in patients with SSc. Two investigators independently used a standardized form to abstract prevalence of osteopenia and osteoporosis (OP); risk factors for low BMD, BMD measurements, frequency of fracture, and fracture-related mortality.

RESULTS

Screening of 1032 citations identified 19 articles. Fifteen studies compared patients with SSc to controls. Most patients were white, female (prevalence 74%-100%), and postmenopausal (prevalence 45.9%-100%). The prevalence of low BMD and OP was 27%-53.3% and 3%-51.1%, respectively. Ten studies reported a lower BMD in patients with SSc compared to matched controls, whereas 2 studies reported no difference. Candidate risk factors for low BMD in SSc include family history of OP, age, menopause, diffuse subtype, presence of internal organ involvement, low vitamin D levels, and calcinosis. However, the studies supporting these factors were conflicting. Fracture rate ranged between 0% and 38%. No study reported OP-related fracture mortality.

CONCLUSION

The data suggest that patients with SSc are at risk of low BMD and fracture, especially when other risk factors for OP are present. The interaction of SSc manifestations, traditional OP risk factors, and clinically relevant outcomes is complex and warrants further research.

Targeted disruption of leucine-rich repeat kinase 1 but not leucine-rich repeat kinase 2 in mice causes severe osteopetrosis

To assess the roles of Lrrk1 and Lrrk2, we examined skeletal phenotypes in Lrrk1 and Lrrk2 knockout (KO) mice. Lrrk1 KO mice exhibit severe osteopetrosis caused by dysfunction of multinucleated osteoclasts, reduced bone resorption in endocortical and trabecular regions, and increased bone mineralization. Lrrk1 KO mice have lifelong accumulation of bone and respond normally to the anabolic actions of teriparatide treatment, but are resistant to ovariectomy-induced bone boss. Precursors derived from Lrrk1 KO mice differentiate into multinucleated cells in response to macrophage colony-stimulating factor (M-CSF)/receptor activator of NF-κB ligand (RANKL) treatment, but these cells fail to form peripheral sealing zones and ruffled borders, and fail to resorb bone. The phosphorylation of cellular Rous sarcoma oncogene (c-Src) at Tyr-527 is significantly elevated whereas at Tyr-416 is decreased in Lrrk1-deficient osteoclasts. The defective osteoclast function is partially rescued by overexpression of the constitutively active form of Y527F c-Src. Immunoprecipitation assays in osteoclasts detected a physical interaction of Lrrk1 with C-terminal Src kinase (Csk). Lrrk2 KO mice do not show obvious bone phenotypes. Precursors derived from Lrrk2 KO mice differentiate into functional multinucleated osteoclasts. Our finding of osteopetrosis in Lrrk1 KO mice provides convincing evidence that Lrrk1 plays a critical role in negative regulation of bone mass in part through modulating the c-Src signaling pathway in mice.