Bone mineral density (BMD), a diagnostic parameter for osteoporosis and a clinical predictor of fracture, is a polygenic trait with high heritability. To identify genetic variants that influence BMD in different ethnic groups, we performed a genome-wide association study (GWAS) on 800 unrelated Southern Chinese women with extreme BMD and carried out follow-up replication studies in six independent study populations of European descent and Asian populations including 18,098 subjects. In the meta-analysis, rs2273061 of the Jagged1 (JAG1) gene was associated with high BMD (p = 5.27 x 10(-8) for lumbar spine [LS] and p = 4.15 x 10(-5) for femoral neck [FN], n = 18,898). This SNP was further found to be associated with the low risk of osteoporotic fracture (p = 0.009, OR = 0.7, 95% CI 0.57-0.93, n = 1881). Region-wide and haplotype analysis showed that the strongest association evidence was from the linkage disequilibrium block 5, which included rs2273061 of the JAG1 gene (p = 8.52 x 10(-9) for LS and 3.47 x 10(-5) at FN). To assess the function of identified variants, an electrophoretic mobility shift assay demonstrated the binding of c-Myc to the "G" but not "A" allele of rs2273061. A mRNA expression study in both human bone-derived cells and peripheral blood mononuclear cells confirmed association of the high BMD-related allele G of rs2273061 with higher JAG1 expression. Our results identify the JAG1 gene as a candidate for BMD regulation in different ethnic groups, and it is a potential key factor for fracture pathogenesis.

Several genome-wide scans have been performed to detect loci that regulate BMD, but these have yielded inconsistent results, with limited replication of linkage peaks in different studies. In an effort to improve statistical power for detection of these loci, we performed a meta-analysis of genome-wide scans in which spine or hip BMD were studied. Evidence was gained to suggest that several chromosomal loci regulate BMD in a site-specific and sex-specific manner.Introduction: BMD is a heritable trait and an important predictor of osteoporotic fracture risk. Several genome-wide scans have been performed in an attempt to detect loci that regulate BMD, but there has been limited replication of linkage peaks between studies. In an attempt to resolve these inconsistencies, we conducted a collaborative meta-analysis of genome-wide linkage scans in which femoral neck BMD (FN-BMD) or lumbar spine BMD (LS-BMD) had been studied. Materials and Methods: Data were accumulated from nine genome-wide scans involving 11,842 subjects. Data were analyzed separately for LS-BMD and FN-BMD and by sex. For each study, genomic bins of 30 cM were defined and ranked according to the maximum LOD score they contained. While various densitometers were used in different studies, the ranking approach that we used means that the results are not confounded by the fact that different measurement devices were used. Significance for high average rank and heterogeneity was obtained through Monte Carlo testing. Results: For LS-BMD, the quantitative trait locus (QTL) with greatest significance was on chromosome 1p13.3-q23.3 (p ‫ס‬ 0.004), but this exhibited high heterogeneity and the effect was specific for women. Other significant LS-BMD QTLs were on chromosomes 12q24. 31-qter, 3p25.3-p22.1, 11p12-q13.3, and 1q32-q42.3, including one on 18p11-q12.3 that had not been detected by individual studies. For FN-BMD, the strongest QTL was on chromosome 9q31.1-q33.3 (p ‫ס‬ 0.002). Other significant QTLs were identified on chromosomes 17p12-q21.33, 14q13.1-q24.1, 9q21.32-q31.1, and 5q14.3-q23.2. There was no correlation in average ranks of bins between men and women and the loci that regulated BMD in men and women and at different sites were largely distinct.

The prevalence of chronic diseases has risen along with increased longevity. Co-occurrence of two or more chronic diseases in an individual (multimorbidity) is prevalent and poses a huge burden to individuals and the society. However, determinants of multimorbidity are largely unknown. Handgrip strength is a general indicator of muscle strength and linked with premature mortality. However, its role in multimorbidity has never been evaluated. To investigate the relationships between handgrip strength and multiple chronic diseases and multimorbidity, and to assess the usefulness of age and handgrip as a marker of chronic diseases and multimorbidity in a community dwelling sample of men and women, we analyzed a cross-sectional cohort with 1,145 subjects (748 men and 397 women) aged 50 years and older living in Hong Kong. Low handgrip strength was significantly associated with increased odds of having five and three chronic diseases in men and women, respectively, after controlling for age, body mass index, history of smoking, educational level, marital level and comorbidity. Multivariable-adjusted handgrip strength was significantly decreased with the number of chronic diseases in men (trend, P = 0.001), but the trend in women was marginal (trend, P = 0.06). Conversely, multivariable-adjusted age was significantly increased with the number of chronic diseases in women (trend, P = 0.033), but not in men (trend, P = 0.118). In conclusion, handgrip strength is associated with multiple chronic diseases and multimorbidity in men and women after adjustment of confounding factors. It shows a linear trend of association with the number of chronic diseases in men, but not in women. Since handgrip strength is a biomarker of multiple physiological systems, its augmentation may be a feasible strategy to improve general health and decrease likelihood of having multiple chronic diseases and hence, premature mortality.Electronic supplementary materialThe online version of this article (doi:10.1007/s11357-012-9385-y) contains supplementary material, which is available to authorized users.

Most genome-wide association (GWA) studies have focused on populations of European ancestry with limited assessment of the influence of the sequence variants on populations of other ethnicities. To determine whether markers that we have recently shown to associate with Bone Mineral Density (BMD) in Europeans also associate with BMD in East-Asians we analysed 50 markers from 23 genomic loci in samples from Korea (n = 1,397) and two Chinese Hong Kong sample sets (n = 3,869 and n = 785). Through this effort we identified fourteen loci that associated with BMD in East-Asian samples using a false discovery rate (FDR) of 0.05; 1p36 (ZBTB40, P = 4.3×10−9), 1p31 (GPR177, P = 0.00012), 3p22 (CTNNB1, P = 0.00013), 4q22 (MEPE, P = 0.0026), 5q14 (MEF2C, P = 1.3×10−5), 6q25 (ESR1, P = 0.0011), 7p14 (STARD3NL, P = 0.00025), 7q21 (FLJ42280, P = 0.00017), 8q24 (TNFRSF11B, P = 3.4×10−5), 11p15 (SOX6, P = 0.00033), 11q13 (LRP5, P = 0.0033), 13q14 (TNFSF11, P = 7.5×10−5), 16q24 (FOXL1, P = 0.0010) and 17q21 (SOST, P = 0.015). Our study marks an early effort towards the challenge of cataloguing bone density variants shared by many ethnicities by testing BMD variants that have been established in Europeans, in East-Asians.

Independent risk factors for osteoporotic fracture were identified for a Southern Chinese postmenopausal population. Clinical risk factor assessment with or without BMD measurement was shown to be an effective predictor of 10-yr risk of osteoporotic fracture and provides a more accessible tool for patient evaluation.Introduction: Asian-specific data on risk factors for osteoporosis remain sparse. However, risk factor assessment, in addition to BMD measurement, is increasingly recognized as a reliable predictor of absolute osteoporotic fracture risk. The purpose of this prospective study was to determine the specific independent risk factors for osteoporotic fracture and to predict the 10-yr risk of osteoporotic fracture in the postmenopausal Southern Chinese population. Materials and Methods: A total of 1435 community-dwelling, postmenopausal, treatment-naive women were recruited. Baseline demographic characteristics and clinical risk factors were obtained, and BMD at the spine and hip was measured. Subjects were followed for outcomes of incident low trauma fracture. Ten-year risk of osteoporotic fracture was predicted from the risk factor assessment and BMD measurement by Cox proportional hazards models. Results: The mean age of subjects was 63.4 ± 8.3 yr. After 5.0 ± 2.3 yr (range, 1.0-11.0 yr) of follow-up, 80 nontraumatic new fractures were reported during follow-up. Eight independent clinical risk factors identified at baseline were found to be significant predictors of osteoporotic fracture, with the most important being use of walking aids (RR, 4.2; 95% CI, 2.7-6.7; p < 0.001) and a history of fall (RR, 4.0; 95% CI, 2.5-6.2; p < 0.001). Other predictive factors included being homebound, calcium intake < 400 mg/d, age > 65 yr, history of fracture, and BMI < 19 kg/cm

The findings support a sustained anti-fracture effect of bazedoxifene on new vertebral fractures in postmenopausal osteoporotic women and on non-vertebral fractures in the higher-risk subgroup of women.

Handgrip strength (HGS) is a potentially useful objective parameter to predict fracture since it is an indicator of general muscle strength and is associated with fragility and propensity to fall. Our objective was to examine the association of HGS with fracture, to evaluate the accuracy of HGS in predicting incident fracture, and to identify subjects at risk of fracture. We analyzed a cross-sectional cohort with 2,793 subjects (1,217 men and 1,576 women aged 50–101 years) and a subset of 1,702 subjects which were followed for a total of 4,855 person-years. The primary outcome measures were prevalent fractures and incident major fragility fractures. Each standard deviation (SD) reduction in HGS was associated with a 1.24-fold increased odds for major clinical fractures even after adjustment for other clinical factors. A similar result was obtained in the prospective cohort with each SD reduction in HGS being associated with a 1.57-fold increased hazard ratio of fracture even after adjustment for clinical factors. A combination of HGS and femoral neck bone mineral density (FN BMD) T-score values (combined T-score), together with other clinical factors, had a better predictive power of incident fractures than FN BMD or HGS T-score alone with clinical factors. In addition, combined T-score has better sensitivity and specificity in predicting incidence fractures than FN BMD alone. This study is the first study to compare the predictive ability of HGS and BMD. We showed that HGS is an independent risk factor for major clinical fractures. Compared with using FN BMD T-score of −2.5 alone, HGS alone has a comparable predictive power to BMD, and the combined T-score may be useful to identify extra subjects at risk of clinical fractures with improved specificity.Electronic supplementary materialThe online version of this article (doi:10.1007/s11357-011-9297-2) contains supplementary material, which is available to authorized users.

Thyrotoxic (hypokalemic) periodic paralysis (TPP) is a frequent complication of thyrotoxicosis among Chinese men. To determine the genetic association of TPP, we studied 97 male TPP patients, 77 Graves' disease patients without TPP, and 100 normal male subjects. Mutations of the voltage-dependent calcium channel (Ca(v)1.1), sodium channel (Na(v)1.4), and potassium channel (K(v)3.4), and association of the microsatellite markers on chromosome 1 in the region of the Na/K-ATPase subunits alpha1, alpha2, and beta1 were studied. None of the TPP patients carried the known mutations in Ca(v)1.1, Na(v)1.4, and K(v)3.4 genes. There was no association of TPP with the microsatellite markers that mapped to 1p13, 1q21-23, and 1q22-25. We detected 12 single nucleotide polymorphisms (SNPs) in Ca(v)1.1 in our population, of which three were novel. Significant differences in the SNP genotype distribution between TPP compared with Graves' disease controls and normal controls were seen at the 5' flanking region nucleotide (nt) -476 (P = 0.02), intron 2 nt 57 (P < 0.01), and intron 26 nt 67 (P < 0.001). Because these SNPs lie at or near the thyroid hormone responsive element, it is possible that they may affect the binding affinity of the thyroid hormone responsive element and modulate the stimulation of thyroid hormone on the Ca(v)1.1 gene.