RANK/RANKL/OPG pathway: Genetic associations with stress fracture period prevalence in elite athletes

ContextThe RANK/RANKL/OPG signalling pathway is important in the regulation of bone turnover, with single nucleotide polymorphisms (SNPs) in genes within this pathway associated with bone phenotypic adaptations.ObjectiveTo determine whether four SNPs associated with genes in the RANK/RANKL/OPG signalling pathway were associated with stress fracture injury in elite athletes.Design, participants, and methodsRadiologically confirmed stress fracture history was reported in 518 elite athletes, forming the Stress Fracture Elite Athlete (SFEA) cohort. Data were analysed for the whole group and were sub-stratified into male and cases of multiple stress fracture groups. Genotypes were determined using proprietary fluorescence-based competitive allele-specific PCR assays.ResultsSNPs rs3018362 (RANK) and rs1021188 (RANKL) were associated with stress fracture injury (P < 0.05). 8.1% of the stress fracture group and 2.8% of the non-stress fracture group were homozygote for the rare allele of rs1021188. Allele frequency, heterozygotes and homozygotes for the rare allele of rs3018362 were associated with stress fracture period prevalence (P < 0.05). Analysis of the male only group showed 8.2% of rs1021188 rare allele homozygotes had suffered a stress fracture whilst 2.5% of the non-stress fracture group were homozygous. In cases of multiple stress fractures, homozygotes for the rare allele of rs1021188 and individuals possessing at least one copy of the rare allele of rs4355801 (OPG) were shown to be associated with stress fracture injury (P < 0.05).ConclusionsThe data support an association between SNPs in the RANK/RANKL/OPG signalling pathway and the development of stress fracture injury. The association of rs3018362 (RANK) and rs1021188 (RANKL) with stress fracture injury susceptibility supports their role in the maintenance of bone health and offers potential targets for therapeutic interventions.     

Quantitative Ultrasound of Bone and Markers of Bone Turnover in Cushing’s Syndrome

Quantitative ultrasound (QUS) of bone is a valuable tool in the assessment of postmenopausal osteoporosis. QUS and new markers of bone turnover have been poorly assessed in Cushing’s syndrome, however. Twenty-five patients with Cushing’s syndrome (20 women, 3 men; mean age ± SEM: 38 ± 2 years) were studied and compared with 35 age- and sex-matched control patients (mean age ± SEM: 38 ± 2 years). The following variables were measured in both groups: QUS parameters at the heel (BUA; SOS; Stiffness Index, SI); bone mineral density (BMD) at both the lumbar spine (LS) and femoral neck (FN) by dual-energy X-ray absorptiometry; and serum markers of bone turnover (osteocalcin, procollagen type I N- and C-terminal propeptides (PINP and PICP), bone alkaline phosphatase (BAP), procollagen type I C-terminal telopeptide (ICTP) and urinary type I collagen C-telopepetide breakdown products (CTX)). Both BUA and SI were decreased in patients with Cushing’s syndrome (p<0.01) but not SOS (p=0.08). BMD was also strongly decreased in Cushing’s syndrome, at both the LS and FN (p<0.005). The two markers of bone turnover statistically significantly different between the two groups were osteocalcin (mean ± SEM: 3.5 ± 0.7 ng/ml (Cushing’s syndrome) vs 6.4 ± 0.5 ng/ml (controls, p<0.01)) and CTX (mean ± SEM: 148.7 ± 17.1 μg/mmol Cr (Cushing’s syndrome) vs 220.8 ± 22.9 μg/mmol Cr (controls), p<0.05). The areas under the receiver operating characteristic curve (AUC) were 0.72 (BUA), 0.73 (SI), 0.90 (BMD_LS), 0.81 (BMD_FN), 0.83 (osteocalcin) and 0.64 (CTX) respectively. AUC was significantly higher for BMD_LS than for both BUA and SI (p<0.05). Conversely AUC was not statistically significantly different for BMD_FN as compared with either BUA or SI. AUC was also higher for osteocalcin than for other markers of bone turnover. In conclusion, QUS of bone seems to be a relevant tool for assessing bone involvement in Cushing’s syndrome. QUS does have a lower sensitivity compared with DXA, however, and the relevance of QUS cannot be ascertained until some longitudinal data are forthcoming. Except for CTX, the other new markers of bone turnover assessed in this study (PINP, PICP, BAP and ICTP) do not seem of interest in Cushing’s syndrome. Received: February 2000 / Accepted: 24 August 2000     

Genetic Polymorphisms of OPG, RANK, and ESR1 and Bone Mineral Density in Korean Postmenopausal Women

To evaluate the effects of genetic polymorphisms of OPG, RANK, and ESR1, which regulate osteoclastogenesis, on bone mineral density (BMD), a cross-sectional study was conducted in 650 Korean postmenopausal women. BMDs of the distal radius and the calcaneus were measured by dual energy X-ray absorptiometry (DXA). Genetic polymorphisms of OPG 163 A > G, 1181 G > C; RANK 421 C > T, 575 T > C; and ESR1 1335 C > T, 2142 G > A were determined by matrix-assisted laser desorption/ionization—time of flight (MALDI-ToF) mass spectrometry. The differences between the BMDs of the genotypes of OPG, RANK, and ESR1 were analyzed by multiple linear regression model adjusted for age and body mass index. Women with the OPG 1181 CC genotype had higher BMDs at the distal radius (7%) and calcaneus (10%) than those with the GG genotype; and these differences were statistically significant (P = 0.001 and P = 0.007, respectively). A significant association was also observed between RANK 575 T > C and calcaneus BMD (P for trend = 0.017). No significant association was observed between BMDs and the polymorphisms of ESR1. The association between OPG 1181 G > C and BMD was profound in subjects with the RANK 575 TT or ESR1 2142 GG genotypes; women with OPG 1181 CC had higher BMDs at the distal radius (11%) and calcaneus (11%) than those with OPG 1181 GG only in women with RANK 575 TT genotype (P = 0.002 and P = 0.021, respectively). These results suggest that OPG genetic polymorphisms, especially with the RANK 575 TT or ESR1 2142 GG genotypes, are related to low BMD in postmenopausal Korean women.     

Does Bone Resorption Stimulate Periosteal Expansion? A Cross‐Sectional Analysis of β‐C‐telopeptides of Type I Collagen (CTX), Genetic Markers of the RANKL Pathway,and Periosteal Circumference as Measured by pQCT

We hypothesized that bone resorption acts to increase bone strength through stimulation of periosteal expansion. Hence, we examined whether bone resorption, as reflected by serum β‐C‐telopeptides of type I collagen (CTX), is positively associated with periosteal circumference (PC), in contrast to inverse associations with parameters related to bone remodeling such as cortical bone mineral density (BMD_C). CTX and mid‐tibial peripheral quantitative computed tomography (pQCT) scans were available in 1130 adolescents (mean age 15.5 years) from the Avon Longitudinal Study of Parents and Children (ALSPAC). Analyses were adjusted for age, gender, time of sampling, tanner stage, lean mass, fat mass, and height. CTX was positively related to PC (β = 0.19 [0.13, 0.24]) (coefficient = SD change per SD increase in CTX, 95% confidence interval)] but inversely associated with BMD_C (β = –0.46 [–0.52,–0.40]) and cortical thickness [β = –0.11 (–0.18, –0.03)]. CTX was positively related to bone strength as reflected by the strength‐strain index (SSI) (β = 0.09 [0.03, 0.14]). To examine the causal nature of this relationship, we then analyzed whether single‐nucleotide polymorphisms (SNPs) within key osteoclast regulatory genes, known to reduce areal/cortical BMD, conversely increase PC. Fifteen such genetic variants within or proximal to genes encoding receptor activator of NF‐κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) were identified by literature search. Six of the 15 alleles that were inversely related to BMD were positively related to CTX (p < 0.05 cut‐off) (n = 2379). Subsequently, we performed a meta‐analysis of associations between these SNPs and PC in ALSPAC (n = 3382), Gothenburg Osteoporosis and Obesity Determinants (GOOD) (n = 938), and the Young Finns Study (YFS) (n = 1558). Five of the 15 alleles that were inversely related to BMD were positively related to PC (p < 0.05 cut‐off). We conclude that despite having lower BMD, individuals with a genetic predisposition to higher bone resorption have greater bone size, suggesting that higher bone resorption is permissive for greater periosteal expansion. © 2014 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.     

Biochemical Markers of Bone Turnover,Hip Bone Loss,and Fracture in Older Men: The MrOS Study

We used data from the Osteoporotic Fractures in Men (MrOS) study to test the hypothesis that men with higher levels of bone turnover would have accelerated bone loss and an elevated risk of fracture. MrOS enrolled 5995 subjects >65 yr; hip BMD was measured at baseline and after a mean follow‐up of 4.6 yr. Nonspine fractures were documented during a mean follow‐up of 5.0 yr. Using fasting serum collected at baseline and stored at ?190°C, bone turnover measurements (type I collagen N‐propeptide [PINP]; β C‐terminal cross‐linked telopeptide of type I collagen [βCTX]; and TRACP5b) were obtained on 384 men with nonspine fracture (including 72 hip fractures) and 947 men selected at random. Among randomly selected men, total hip bone loss was 0.5%/yr among those in the highest quartile of PINP (>44.3 ng/ml) and 0.3%/yr among those in the lower three quartiles (p = 0.01). Fracture risk was elevated among men in the highest quartile of PINP (hip fracture relative hazard = 2.13; 95% CI: 1.23, 3.68; nonspine relative hazard = 1.57, 95% CI: 1.21, 2.05) or βCTX (hip fracture relative hazard = 1.76, 95 CI: 1.04, 2.98; nonspine relative hazard = 1.29, 95% CI: 0.99, 1.69) but not TRACP5b. Further adjustment for baseline hip BMD eliminated all associations between bone turnover and fracture. We conclude that higher levels of bone turnover are associated with greater hip bone loss in older men, but increased turnover is not independently associated with the risk of hip or nonspine fracture.     

促胰液素对去卵巢骨质疏松大鼠血清骨转换指标和骨密度的影响

目的 观察促胰液素(secretin,SCT)对去卵巢骨质疏松大鼠骨转换指标和骨密度的影响。方法 采用双侧卵巢去除法制备绝经后骨质疏松大鼠模型,将60只SD大鼠随机分为假手术组、模型对照组、雌激素治疗组和促胰液素治疗组,每组各15只。干预3个月后,测定腰椎骨密度(bone mineral density,BMD),采取ELISA法测定血清I型胶原N前端肽(procollagen I N-Terminal propeptide,PINP)和I型胶原C末端肽(collagen type I C-terminal cross-linked telopeptide,CTX),另使用STRING10.0蛋白相互作用网络分析工具分析骨质疏松相关差异蛋白。结果 与假手术组比较,模型对照组、雌激素治疗组、促胰液素治疗组的PINP含量升高（P＜0.05）,模型对照组的CTX含量升高（P＜0.05）,模型对照组的BMD下降（P＜0.05）,雌激素治疗组和促胰液素治疗组的CTX、BMD含量无显著差异（P＞0.05）;与模型对照组比较,雌激素治疗组、促胰液素治疗组PINP、CTX含量有所下降,而BMD含量升高（P＜0.05）;雌激素组与促胰液素组之间PINP、CTX、BMD含量无显著差异（P＞0.05）。结论 促胰液素能改善去卵巢骨质疏松大鼠的PINP和CTX含量,增加骨密度,抑制骨质丢失,具有较好的抗骨质疏松效果。     

Meta‐analysis of genome‐wide studies identifies WNT16 and ESR1 SNPs associated with bone mineral density in premenopausal women

Previous genome‐wide association studies (GWAS) have identified common variants in genes associated with variation in bone mineral density (BMD), although most have been carried out in combined samples of older women and men. Meta‐analyses of these results have identified numerous single‐nucleotide polymorphisms (SNPs) of modest effect at genome‐wide significance levels in genes involved in both bone formation and resorption, as well as other pathways. We performed a meta‐analysis restricted to premenopausal white women from four cohorts (n = 4061 women, aged 20 to 45 years) to identify genes influencing peak bone mass at the lumbar spine and femoral neck. After imputation, age‐ and weight‐adjusted bone‐mineral density (BMD) values were tested for association with each SNP. Association of an SNP in the WNT16 gene (rs3801387; p = 1.7 × 10^?9) and multiple SNPs in the ESR1/C6orf97 region (rs4870044; p = 1.3 × 10^?8) achieved genome‐wide significance levels for lumbar spine BMD. These SNPs, along with others demonstrating suggestive evidence of association, were then tested for association in seven replication cohorts that included premenopausal women of European, Hispanic‐American, and African‐American descent (combined n = 5597 for femoral neck; n = 4744 for lumbar spine). When the data from the discovery and replication cohorts were analyzed jointly, the evidence was more significant (WNT16 joint p = 1.3 × 10^?11; ESR1/C6orf97 joint p = 1.4 × 10^?10). Multiple independent association signals were observed with spine BMD at the ESR1 region after conditioning on the primary signal. Analyses of femoral neck BMD also supported association with SNPs in WNT16 and ESR1/C6orf97 (p < 1 × 10^?5). Our results confirm that several of the genes contributing to BMD variation across a broad age range in both sexes have effects of similar magnitude on BMD of the spine in premenopausal women. These data support the hypothesis that variants in these genes of known skeletal function also affect BMD during the premenopausal period. © 2013 American Society for Bone and Mineral Research.     

Bone ultrasonometry and turnover markers in primary hyperparathyroidism

Quantitative ultrasound (QUS) of bone and new markers of bone remodeling have been poorly investigated in mild primary hyperparathyroidism (PHPT). In this study 26 patients (20 females and 6 males) were evaluated. BUA and SOS were measured by QUS at the heel. Markers of bone remodeling assessed were bone alkaline phosphatase (BAP), osteocalcin (OC), procollagen type I N- and C-terminal propeptides (PINP et PICP), and procollagen type I C-terminal telopeptide in blood and urine (ICTP and CTX). Bone mineral density (BMD) was measured at the lumbar spine (LS), femoral neck (FN), and Ward's triangle (WT). The control group comprised 35 sex- and age-matched subjects. The statistically significant variables between the two groups were (P < 0.05) BUA, BMD_LS, BMD_FN, BMD_WT, BAP, and OC. Corresponding z-scores were −0.55 ± 0.75, −0.66 ± 0.77, −0.66 ± 0.71, −0.67 ± 0.52, 1.87 ± 3.87, and 1.93 ± 3.53, respectively. Although PICP and PINP levels were higher in PHPT patients as compared with controls, the difference was not significant. Several markers of bone turnover were moderately correlated with both QUS (r =−0.39 to −0.55) and BMD (r =−0.48 to 0.63). In conclusion QUS seems to be a relevant tool in the assessment of bone status for patients with mild PHPT. Received: 1 October 1998 / Accepted: 1 July 1999     

Serum uric acid is associated with bone health in older men: A cross‐sectional population‐based study

Serum uric acid (UA) is a strong endogenous antioxidant. Since oxidative stress has been linked to osteoporosis, we examined the association between serum UA levels and bone mineral density (BMD), prevalent vertebral and nonvertebral fractures, and laboratory measures such as calcitropic hormones and bone turnover marker levels. This cross‐sectional analysis consisted of 1705 community‐dwelling men aged 70 years or over who participated in the baseline part of the Concord Health and Ageing in Men Project (CHAMP), a population‐based study of older men in Sydney, Australia. BMD at all sites was significantly higher among men with serum UA levels above the group median than among men with UA levels below the median. In multiple regression analyses adjusted for potential confounders, serum UA remained associated with BMD at all sites (β = 0.12 to 0.14, p < .001), serum calcium (β = 0.11, p = .001), parathyroid hormone (β = 0.09, p = .002), 25‐hydroxyvitamin D (β = 0.09, p = .005), and was negatively associated with urinary excretion amino‐terminal cross‐linked telopeptide of type 1 collagen (β = –0.09, p = .006). Overall, serum UA accounted for 1.0% to 1.44% of the variances in BMD (R² = 0.10 to 0.22). In multiple logistic regression analyses, above‐median serum UA levels were associated with a lower prevalence of osteoporosis at the femoral neck [odds ratio (OR) = 0.42, 95% confidence interval (CI) 0.22–0.81, p = .010) and lumbar spine (OR = 0.44, 95% CI 0.23–0.86, p = .016) and a lower prevalence of vertebral (OR = 0.62, 95% CI 0.43–0.91, p = .015) and nonvertebral (OR = 0.51, 95% CI 0.29–0.89, p = .018) fractures. In conclusion, higher serum UA levels are associated with higher BMD at all skeletal sites and with a lower prevalence of vertebral and nonvertebral fractures in older men. © 2011 American Society for Bone and Mineral Research.     

Association Analysis of WNT10B With Bone Mass and Structure Among Individuals of African Ancestry

Wnts comprise a family of secreted growth factors that regulate the development and maintenance of many organs. Recently, Wnt10b was shown to stimulate osteoblastogenesis and bone formation in mice. To evaluate further the role of Wnt10b in bone health in humans, we performed bidirectional sequencing of ～8 kb of the WNT10B gene region in 192 individuals (96 African, 96 white) to identify single nucleotide polymorphisms (SNPs). We identified 19 SNPs with minor allele frequency (MAF) ≥0.01. Ten of these SNPs were not present in the NCBI dbSNP database (build 127), whereas 10 of the 20 SNPs (50%) reported in dbSNP were not verified. We initially genotyped seven tagging SNPs that captured common (MAF ≥ 0.05) variation in the region with r² > 0.80 and a potentially functional SNP in exon 5 in 1035 Afro‐Caribbean men ≥40 yr of age. Association analysis showed three SNPs in a 3′ region of linkage disequilibrium that were associated with DXA measures of hip BMD. Associations between two of these three SNPs (rs1051886, rs3741627) with hip BMD were replicated in an additional 980 Afro‐Caribbean men (p < 0.05), in the combined sample of 2015 men (p ≤ 0.006), and in 416 individuals ≥18 yr of age (mean, 44 yr) belonging to eight extended, multigenerational Afro‐Caribbean families with mean family size >50 (3535 relative pairs; p < 0.05). Further analysis showed that rs1051886 and rs3741627 were associated with cortical cross‐sectional area, periosteal circumference, and BMC in the radius, such that individuals with the minor alleles had lower biomechanical indices of long‐bone bending strength. This analysis implicates the WNT10B locus as a genetic element in the regulation of bone mass and structural geometry.     

Association Analyses of <Emphasis Type="Italic">RANKL/RANK/OPG</Emphasis> Gene Polymorphisms with Femoral Neck Compression Strength Index Variation in Caucasians

Femoral neck compression strength index (fCSI), a novel phenotypic parameter that integrates bone density, bone size, and body size, has significant potential to improve hip fracture risk assessment. The genetic factors underlying variations in fCSI, however, remain largely unknown. Given the important roles of the receptor activator of the nuclear factor-κB ligand/receptor activator of the nuclear factor-κB/osteoprotegerin (RANKL/RANK/OPG) pathway in the regulation of bone remodeling, we tested the associations between RANKL/RANK/OPG polymorphisms and variations in fCSI as well as its components (femoral neck bone mineral density [fBMD], femoral neck width [FNW], and weight). This was accomplished with a sample comprising 1873 subjects from 405 Caucasian nuclear families. Of the 37 total SNPs studied in these three genes, 3 SNPs, namely, rs12585014, rs7988338, and rs2148073, of RANKL were significantly associated with fCSI (P = 0.0007, 0.0007, and 0.0005, respectively) after conservative Bonferroni correction. Moreover, the three SNPs were approximately in complete linkage disequilibrium. Haplotype-based association tests corroborated the single-SNP results since haplotype 1 of block 1 of the RANKL gene achieved an even more significant association with fCSI (P = 0.0003) than any of the individual SNPs. However, we did not detect any significant associations of these genes with fBMD, FNW, or weight. In summary, our findings suggest that the RANKL gene may play an important role in variation in fCSI, independent of fBMD and non-fBMD components.     

绝经后女性血清硒水平与骨质疏松骨密度和骨代谢指标相关性研究

目的探索血清硒水平与绝经后妇女骨代谢指标以及腰椎和髋部骨密度之间相关性。方法检测156例正常骨密度和162例骨质疏松症的血清硒、25-羟基维生素D、PTH、骨钙素、PINP、CTX和NTX/Cr等指标水平。腰椎和股骨颈的BMD通过双能X线吸收法测量。探索了血清硒水平与骨密度的关系。结果骨质疏松症女性的血清硒水平低于正常骨密度的女性(P0.05)。在骨质疏松症妇女中,血清硒水平与年龄、绝经年限、BMI、PTH、骨钙素、PINP、CTX和NTX/Cr水平呈负相关,与25-羟基维生素D水平呈正相关。在正常骨密度组,血清硒水平与这些参数均未发现明显的相关性。调整年龄和BMI后,腰椎和股骨颈骨密度与血清硒及25-羟基维生素D水平呈显著正相关,与绝经年限、PTH、骨钙素、PINP、CTX和NTX/Cr呈负相关。对年龄和BMI进行调整后,进行多元回归分析以确定BMD的预测因子,血清硒和PINP、CTX是腰椎和股骨颈骨密度的显著预测因子。结论绝经后女性患者血清硒水平降低与腰椎和股骨颈骨密度降低密切有关。     

Identification of IDUA and WNT16 Phosphorylation‐Related Non‐Synonymous Polymorphisms for Bone Mineral Density in Meta‐Analyses of Genome‐Wide Association Studies

Protein phosphorylation regulates a wide variety of cellular processes. Thus, we hypothesize that single‐nucleotide polymorphisms (SNPs) that may modulate protein phosphorylation could affect osteoporosis risk. Based on a previous conventional genome‐wide association (GWA) study, we conducted a three‐stage meta‐analysis targeting phosphorylation‐related SNPs (phosSNPs) for femoral neck (FN)‐bone mineral density (BMD), total hip (HIP)‐BMD, and lumbar spine (LS)‐BMD phenotypes. In stage 1, 9593 phosSNPs were meta‐analyzed in 11,140 individuals of various ancestries. Genome‐wide significance (GWS) and suggestive significance were defined by α = 5.21 × 10^–6 (0.05/9593) and 1.00 × 10^–4, respectively. In stage 2, nine stage 1–discovered phosSNPs (based on α = 1.00 × 10^–4) were in silico meta‐analyzed in Dutch, Korean, and Australian cohorts. In stage 3, four phosSNPs that replicated in stage 2 (based on α = 5.56 × 10^–3, 0.05/9) were de novo genotyped in two independent cohorts. IDUA rs3755955 and rs6831280, and WNT16 rs2707466 were associated with BMD phenotypes in each respective stage, and in three stages combined, achieving GWS for both FN‐BMD (p = 8.36 × 10^–10, p = 5.26 × 10^–10, and p = 3.01 × 10^–10, respectively) and HIP‐BMD (p = 3.26 × 10^–6, p = 1.97 × 10^–6, and p = 1.63 × 10^–12, respectively). Although in vitro studies demonstrated no differences in expressions of wild‐type and mutant forms of IDUA and WNT16B proteins, in silico analyses predicts that WNT16 rs2707466 directly abolishes a phosphorylation site, which could cause a deleterious effect on WNT16 protein, and that IDUA phosSNPs rs3755955 and rs6831280 could exert indirect effects on nearby phosphorylation sites. Further studies will be required to determine the detailed and specific molecular effects of these BMD‐associated non‐synonymous variants. © 2015 American Society for Bone and Mineral Research.     

IL21R and PTH may underlie variation of femoral neck bone mineral density as revealed by a genome‐wide association study

Bone mineral density (BMD) measured at the femoral neck (FN) is the most important risk phenotype for osteoporosis and has been used as a reference standard for describing osteoporosis. The specific genes influencing FN BMD remain largely unknown. To identify such genes, we first performed a genome‐wide association (GWA) analysis for FN BMD in a discovery sample consisting of 983 unrelated white subjects. We then tested the top significant single‐nucleotide polymorphisms (SNPs; 175 SNPs with p < 5 × 10^?4) for replication in a family‐based sample of 2557 white subjects. Combing results from these two samples, we found that two genes, parathyroid hormone (PTH) and interleukin 21 receptor (IL21R), achieved consistent association results in both the discovery and replication samples. The PTH gene SNPs, rs9630182, rs2036417, and rs7125774, achieved p values of 1.10 × 10^?4, 3.24 × 10^?4, and 3.06 × 10^?4, respectively, in the discovery sample; p values of 6.50 × 10^?4, 5.08 × 10^?3, and 5.68 × 10^?3, respectively, in the replication sample; and combined p values of 3.98 × 10^?7, 9.52 × 10^?6, and 1.05 × 10^?5, respectively, in the total sample. The IL21R gene SNPs, rs8057551, rs8061992, and rs7199138, achieved p values of 1.51 × 10^?4, 1.53 × 10^?4, and 3.88 × 10^?4, respectively, in the discovery sample; p values of 2.36 × 10^?3, 6.74 × 10^?3, and 6.41 × 10^?3, respectively, in the replication sample; and combined p values of 2.31 × 10^?6, 8.62 × 10^?6, and 1.41 × 10^?5, respectively, in the total sample. The effect size of each SNP was approximately 0.11 SD estimated in the discovery sample. PTH and IL21R both have potential biologic functions important to bone metabolism. Overall, our findings provide some new clues to the understanding of the genetic architecture of osteoporosis. © 2010 American Society for Bone and Mineral Research     

Effects of denosumab on bone turnover markers in postmenopausal osteoporosis

Denosumab, a fully human monoclonal antibody to RANKL, decreases bone remodeling, increases bone density, and reduces fracture risk. This study evaluates the time course and determinants of bone turnover marker (BTM) response during denosumab treatment, the percentage of denosumab‐treated women with BTMs below the premenopausal reference interval, and the correlations between changes in BTMs and bone mineral density (BMD). The BTM substudy of the Fracture REduction Evaulation of Denosumab in Osteoporosis every 6 Months (FREEDOM) Trial included 160 women randomized to subcutaneous denosumab (60 mg) or placebo injections every 6 months for 3 years. Biochemical markers of bone resorption (serum C‐telopeptide of type I collagen [CTX] and tartrate‐resistant acid phosphatise [TRACP‐5b]) and bone formation (serum procollagen type I N‐terminal propeptide [PINP] and bone alkaline phosphatase [BALP]) were measured at baseline and at 1, 6, 12, 24, and 36 months. Decreases in CTX were more rapid and greater than decreases in PINP and BALP. One month after injection, CTX levels in all denosumab‐treated subjects decreased to levels below the premenopausal reference interval. CTX values at the end of the dosing period were influenced by baseline CTX values and the dosing interval. The percentage of subjects with CTX below the premenopausal reference interval before each subsequent injection decreased from 79% to 51% during the study. CTX and PINP remained below the premenopausal reference interval at all time points in 46% and 31% denosumab‐treated subjects, respectively. With denosumab, but not placebo, there were significant correlations between CTX reduction and BMD increase (r = ?0.24 to ?0.44). The BTM response pattern with denosumab is unique and should be appreciated by physicians to monitor this treatment effectively. © 2011 American Society for Bone and Mineral Research.     

Exercise training in obese older adults prevents increase in bone turnover and attenuates decrease in hip bone mineral density induced by weight loss despite decline in bone‐active hormones

Weight loss therapy to improve health in obese older adults is controversial because it causes further bone loss. Therefore, it is recommended that weight loss therapy should include an intervention such as exercise training (ET) to minimize bone loss. The purpose of this study was to determine the independent and combined effects of weight loss and ET on bone metabolism in relation to bone mineral density (BMD) in obese older adults. One‐hundred‐seven older (age >65 years) obese (body mass index [BMI] ≥30 kg/m²) adults were randomly assigned to a control group, diet group, exercise group, and diet‐exercise group for 1 year. Body weight decreased in the diet (?9.6%) and diet‐exercise (?9.4%) groups, not in the exercise (?1%) and control (?0.2%) groups (between‐group p < 0.001). However, despite comparable weight loss, bone loss at the total hip was relatively less in the diet‐exercise group (?1.1%) than in the diet group (?2.6%), whereas BMD increased in the exercise group (1.5%) (between‐group p < 0.001). Serum C‐terminal telopeptide (CTX) and osteocalcin concentrations increased in the diet group (31% and 24%, respectively), whereas they decreased in the exercise group (?13% and ?15%, respectively) (between‐group p < 0.001). In contrast, similar to the control group, serum CTX and osteocalcin concentrations did not change in the diet‐exercise group. Serum procollagen propeptide concentrations decreased in the exercise group (?15%) compared with the diet group (9%) (p = 0.04). Serum leptin and estradiol concentrations decreased in the diet (?25% and ?15%, respectively) and diet‐exercise (?38% and ?13%, respectively) groups, not in the exercise and control groups (between‐group p = 0.001). Multivariate analyses revealed that changes in lean body mass (β = 0.33), serum osteocalcin (β = ?0.24), and one‐repetition maximum (1‐RM) strength (β = 0.23) were independent predictors of changes in hip BMD (all p < 0.05). In conclusion, the addition of ET to weight loss therapy among obese older adults prevents weight loss–induced increase in bone turnover and attenuates weight loss–induced reduction in hip BMD despite weight loss–induced decrease in bone‐active hormones. © 2011 American Society for Bone and Mineral Research     

Effect of early risedronate treatment on bone mineral density and bone turnover markers after liver transplantation: a prospective single‐center study

The aim of this study was to investigate the effect of risedronate (RIS) on bone loss and bone turnover markers after liver transplantation (LT). Patients with osteopenia or osteoporosis within the first month after LT were randomized to receive RIS 35 mg/week plus calcium 1000 mg/day and vitamin D₃ 800 IU/day (n = 45) or calcium and vitamin D₃ at same dosages (n = 44). Primary endpoint was change in bone mineral density (BMD) 6 and 12 months after LT. Secondary endpoints included changes in serum β‐CrossLaps (β‐CTX) and procollagen type 1 amino‐terminal peptide (P1NP) and fracture rate. Spine X‐rays were obtained at baseline and after 12 months. There was no significant difference in BMD changes between both treatment groups at any sites; either at 6 or 12 months. Spine BMD increased in both groups at 12 months vs. baseline (P = 0.001). RIS patients had a significant increase in intertrochanteric BMD at 12 months (P < 0.05 vs. baseline). Serum β‐CTX decreased in both groups (P < 0.01), with significant differences between groups at 3 months. No significant difference in vertebral fracture incidence was found. After 12 months, BMD improved at lumbar spine and did not change at hip in both groups. Significant differences between both groups were not found. Other factors (calcium and vitamin D replacement, early prednisone withdrawal) seem to have also positive effects in BMD.     

Genetic variation in the TNFRSF11A gene encoding RANK is associated with susceptibility to Paget's disease of bone

RANK (receptor activator of nuclear factor‐κB), encoded by TNFRSF11A, is a key protein in osteoclastogenesis. TNFRSF11A mutations cause Paget's disease of bone (PDB)–like diseases (ie, familial expansile osteolysis, expansile skeletal hyperphosphatasia, and early‐onset PDB) and an osteoclast‐poor form of osteopetrosis. However, no TNFRSF11A mutations have been found in classic PDB, neither in familial nor in isolated cases. To investigate the possible relationship between TNFRSF11A polymorphisms and sporadic PDB, we conducted an association study including 32 single‐nucleotide polymorphisms (SNPs) in 196 Belgian sporadic PDB patients and 212 control individuals. Thirteen SNPs and 3 multimarker tests (MMTs) turned out to have a p value of between .036 and 3.17 × 10^?4, with the major effect coming from females. Moreover, 6 SNPs and 1 MMT withstood the Bonferroni correction (p < .002). Replication studies were performed for 2 nonsynonymous SNPs (rs35211496 and rs1805034) in a Dutch and a British cohort. Interestingly, both SNPs resulted in p values ranging from .013 to 8.38 × 10^?5 in both populations. Meta‐analysis over three populations resulted in p = .002 for rs35211496 and p = 1.27 × 10^?8 for rs1805034, again mainly coming from the female subgroups. In an attempt to identify the underlying causative SNP, we performed functional studies for the coding SNPs as well as resequencing efforts of a 31‐kb region harboring a risk haplotype within the Belgian females. However, neither approach resulted in significant evidence for the causality of any of the tested genetic variants. Therefore, further studies are needed to identify the real cause of the increased risk to develop PDB shown to be present within TNFRSF11A. © 2010 American Society for Bone and Mineral Research.