Susceptibility genes for osteoporotic fracture in postmenopausal chinese women

To identify the susceptibility genes for osteoporotic fracture in postmenopausal Chinese women, a two‐stage case‐control association study using joint analysis was conducted in 1046 patients with nontraumatic vertebra, hip, or distal radius fractures and 2303 healthy controls. First, 113 single‐nucleotide polymorphisms (SNPs) in 16 potential osteoporosis candidate genes reported in recent genomewide association studies, meta‐analyses studies, large‐scale association studies, and functional studies were genotyped in a small‐sample‐size subgroup consisting of 541 patients with osteoporotic fractures and 554 healthy controls. Variants and haplotypes in SPTBN1, TNFRSF11B, CNR2, LRP4, and ESR1 that have been identified as being associated with osteoporotic fractures were further reanalyzed in the entire case‐control group. We identified one SNP in TNFRSF11B (rs3102734), three SNPs in ESR1 (rs9397448, rs2234693, and rs1643821), two SNPs in LRP4 (rs17790156 and rs898604), and four SNPs in SPTBN1 (rs2971886, rs2941583, rs2941584, and rs12475342) were associated with all of the broadly defined osteoporotic fractures. The most significant polymorphism was rs3102734, with increased risk of osteoporotic fractures (odds ratio, 1.35; 95% confidence interval [CI], 1.17–1.55, Bonferroni p = 2.6 × 10^?4). Furthermore, rs3102734, rs2941584, rs12475342, rs9397448, rs2234693, and rs898604 exhibited significant allelic, genotypic, and/or haplotypic associations with vertebral fractures. SNPs rs12475342, rs9397448, and rs2234693 showed significant genotypic associations with hip fractures, whereas rs3102734, rs2073617, rs1643821, rs12475342, and rs2971886 exhibited significant genotypic and/or haplotypic associations with distal radius fractures. Accordingly, we suggest that in addition to the clinical risk factors, the variants in TNFRSF11B, SPTBN1, ESR1, and LRP4 are susceptibility genetic loci for osteoporotic fracture in postmenopausal Chinese women. © 2012 American Society for Bone and Mineral Research © 2012 American Society for Bone and Mineral Research     

Rare EN1 Variants and Pediatric Bone Mass

A recent whole‐genome sequencing study in search of variation associated with adult areal bone mineral density (aBMD) identified rare variants near EN1, with markedly large effect sizes, and a common variant near SOX6. To understand the developmental effects of these loci, we sought to determine if they were associated with pediatric dual‐energy X‐ray absorptiometry–derived aBMD and bone mineral content (BMC) and if the associations were modified by sex. Our sample comprised 733 females and 685 males of European ancestry enrolled in the longitudinal Bone Mineral Density in Childhood Study (up to 7 annual study visits). Sex‐ and age‐specific Z‐scores, adjusted for height, were calculated for the total hip, femoral neck, spine, and distal radius. Total body less head (TBLH) BMC Z‐scores were also calculated. The previously reported single nucleotide polymorphisms (SNPs) near EN1 and SOX6 were derived from our imputed data set. Linear mixed‐effects models were used to test associations between each SNP and bone Z‐scores, plus interactions with sex were explored. The rare T allele of lead EN1 SNP rs11692564 was associated with higher aBMD Z‐score for total hip (beta = 0.62, p = 9.0 × 10^?4) and femoral neck (beta = 0.53, p = 0.010). In sex‐stratified analyses, this variant was associated with higher bone Z‐scores in females only, with the associations being strongest for total hip (sex interaction p = 1.9 × 10^?4; beta females = 0.86, p = 6.6 × 10^?6) and femoral neck (sex interaction p = 0.016; beta females = 0.73, p = 0.001). The common G allele of SOX6 SNP rs11024028 was associated with higher aBMD Z‐score for total hip (beta = 0.12, p = 0.009), femoral neck (beta = 0.13, p = 0.003), and TBLH‐BMC (beta = 0.09, p = 0.007); furthermore, this association strengthened in males in the sex‐stratified analyses. Our findings reveal that rare genetic variation near EN1 and common variation near SOX6 operates in childhood and has implications for the lifelong risk of osteoporosis and fracture. The sex differences observed need to be independently replicated. © 2016 American Society for Bone and Mineral Research.     

Novel Genetic Variants Associated With Increased Vertebral Volumetric BMD,Reduced Vertebral Fracture Risk,and Increased Expression of SLC1A3 and EPHB2

Genome‐wide association studies (GWASs) have revealed numerous loci for areal bone mineral density (aBMD). We completed the first GWAS meta‐analysis (n = 15,275) of lumbar spine volumetric BMD (vBMD) measured by quantitative computed tomography (QCT), allowing for examination of the trabecular bone compartment. SNPs that were significantly associated with vBMD were also examined in two GWAS meta‐analyses to determine associations with morphometric vertebral fracture (n = 21,701) and clinical vertebral fracture (n = 5893). Expression quantitative trait locus (eQTL) analyses of iliac crest biopsies were performed in 84 postmenopausal women, and murine osteoblast expression of genes implicated by eQTL or by proximity to vBMD‐associated SNPs was examined. We identified significant vBMD associations with five loci, including: 1p36.12, containing WNT4 and ZBTB40; 8q24, containing TNFRSF11B; and 13q14, containing AKAP11 and TNFSF11. Two loci (5p13 and 1p36.12) also contained associations with radiographic and clinical vertebral fracture, respectively. In 5p13, rs2468531 (minor allele frequency [MAF] = 3%) was associated with higher vBMD (β = 0.22, p = 1.9 × 10^–8) and decreased risk of radiographic vertebral fracture (odds ratio [OR] = 0.75; false discovery rate [FDR] p = 0.01). In 1p36.12, rs12742784 (MAF = 21%) was associated with higher vBMD (β = 0.09, p = 1.2 × 10^–10) and decreased risk of clinical vertebral fracture (OR = 0.82; FDR p = 7.4 × 10^–4). Both SNPs are noncoding and were associated with increased mRNA expression levels in human bone biopsies: rs2468531 with SLC1A3 (β = 0.28, FDR p = 0.01, involved in glutamate signaling and osteogenic response to mechanical loading) and rs12742784 with EPHB2 (β = 0.12, FDR p = 1.7 × 10^–3, functions in bone‐related ephrin signaling). Both genes are expressed in murine osteoblasts. This is the first study to link SLC1A3 and EPHB2 to clinically relevant vertebral osteoporosis phenotypes. These results may help elucidate vertebral bone biology and novel approaches to reducing vertebral fracture incidence. © 2016 American Society for Bone and Mineral Research.     

A Rare Haplotype in the Upstream Regulatory Region of COL1A1 Is Associated With Reduced Bone Quality and Hip Fracture

Three polymorphisms have been identified in the 5′ regulatory region of the COL1A1 gene at positions −1997 (rs1107946), −1663 (rs2412298), and +1245G/T (rs1800012), which combine to form haplotypes that have been associated with BMD in several populations. These polymorphisms and haplotypes have not thus far been studied in relation to biomechanical properties of bone or fracture risk. Genotypes and haplotypes of the COL1A1 gene were related to the biomechanical properties of bone ex vivo in samples of bone tissue obtained from the femoral head of 98 consecutive patients undergoing surgery for low-trauma hip fractures. Genotype and haplotype frequencies in the hip fracture cases were compared with 3418 population-based controls recruited from the same region. All three polymorphisms were associated with material density of the bone core, yield strength, and toughness. The association between −1663InsdelT and +1245G/T alleles, yield strength, and toughness remained significant after adjusting for material density of the core and other confounding factors. A haplotype comprising the unfavorable allele at all three polymorphic sites (−1997T/−1663delT/+1245T) was also associated with yield strength, modulus, and toughness after adjusting for confounding factors. This haplotype was carried by 19/94 (20.2%) patients with hip fracture compared with only 2/3399 (0.06%) female controls drawn from the general population (p < 0.0001). In contrast, there was no significant difference between cases and controls in genotype distribution for the individual polymorphisms. This study shows that common genetic variants in the 5′ regulatory region of COL1A1 are associated with biomechanical properties of bone and reduced bone quality by mechanisms independent of their effects on BMD. The biomechanically unfavorable allele at each polymorphic site defines a haplotype that is extremely rare in the general population but that is ∼400-fold enriched in hip fracture patients. This haplotype may have clinical value as a genetic marker for susceptibility to hip fracture, and further studies to investigate this possibility would be of interest.     

Association Analysis of BMD‐associated SNPs with Knee Osteoarthritis

Osteoarthritis (OA) risk is widely recognized to be heritable but few loci have been identified. Observational studies have identified higher systemic bone mineral density (BMD) to be associated with an increased risk of radiographic knee osteoarthritis. With this in mind, we sought to evaluate whether well‐established genetic loci for variance in BMD are associated with risk for radiographic OA in the Osteoarthritis Initiative (OAI) and the Johnston County Osteoarthritis (JoCo) Project. Cases had at least one knee with definite radiographic OA, defined as the presence of definite osteophytes with or without joint space narrowing (Kellgren‐Lawrence [KL] grade ≥ 2) and controls were absent for definite radiographic OA in both knees (KL grade ≤ 1 bilaterally). There were 2014 and 658 Caucasian cases, respectively, in the OAI and JoCo Studies, and 953 and 823 controls. Single nucleotide polymorphisms (SNPs) were identified for association analysis from the literature. Genotyping was carried out on Illumina 2.5M and 1M arrays in Genetic Components of Knee OA (GeCKO) and JoCo, respectively and imputation was done. Association analyses were carried out separately in each cohort with adjustments for age, body mass index (BMI), and sex, and then parameter estimates were combined across the two cohorts by meta‐analysis. We identified four SNPs significantly associated with prevalent radiographic knee OA. The strongest signal (p = 0.0009; OR = 1.22; 95% CI, 1.08–1.37) maps to 12q3, which contains a gene coding for SP7. Additional loci map to 7p14.1 (TXNDC3), 11q13.2 (LRP5), and 11p14.1 (LIN7C). For all four loci the allele associated with higher BMD was associated with higher odds of OA. A BMD risk allele score was not significantly associated with OA risk. This meta‐analysis demonstrates that several genomewide association studies (GWAS)‐identified BMD SNPs are nominally associated with prevalent radiographic knee OA and further supports the hypothesis that BMD, or its determinants, may be a risk factor contributing to OA development. © 2014 American Society for Bone and Mineral Research.     

Genetic Association and Gene Expression Profiles of TGFB1 and the Contribution of TGFB1 to Otosclerosis Susceptibility

Otosclerosis (OTSC) is a common form of acquired hearing loss resulting from disturbed bone remodeling in the otic capsule of the middle ear. Transforming growth factor‐beta1 (TGFB1) produced by osteoblasts is the most abundant growth factor in human bone. Previous studies have shown the contribution of single‐nucleotide polymorphisms (SNPs) in TGFB1 toward the risk of developing OTSC in some ethnic populations. The present study was aimed at investigating the genetic association and expression profiles of TGFB1 in OTSC patients. Two SNPs (c.–800G > A and c.–509C > T) in the promoter region and three SNPs (c.29T > C, c.74G > C, and c.788C > T) in the coding region were genotyped in 170 cases and 170 controls. The genetic association analysis revealed the significant association between c.–509C > T (p = 0.0067; odds ratio [OR] = 1.562; 95% confidence interval [CI], 1.140–2.139) and OTSC. The increased minor allele “T” frequency in cases (0.42) compared to controls (0.31) indicates its possible role in the etiology of the disease. The minor allele frequencies for the SNPs c.–800G > A, c.29T > C, and c.74G > C were similar among the cases (0.04, 0.47, and 0.08, respectively) and controls (0.05, 0.42, 0.07, respectively). We found that c.788C > T was monomorphic in this population. Interestingly, a four‐locus haplotype (G‐T‐T‐G) from these SNPs was found to be significantly associated with OTSC (p = 0.0077). We identified a de novo heterozygous mutation c.–832G > A in the promoter region of TGFB1 in 1 patient. In a secondary analysis, we investigated the possibility of abnormal TGFB1 expression and irregular bone growth in OTSC by expression analysis of TGFB1 mRNA in disease tissue compared to control. We found relatively increased expression of TGFB1 mRNA in the stapes tissues of cases compared to controls (p = 0.0057). In conclusion, this study identified a risk variant c.–509C > T and a risk haplotype G‐T‐T‐G in the TGFB1 gene that contribute toward the susceptibility to OTSC. © 2013 American Society for Bone and Mineral Research.     

Prediction of Bone Mineral Density and Fragility Fracture by Genetic Profiling

Although the susceptibility to fracture is partly determined by genetic factors, the contribution of newly discovered genetic variants to fracture prediction is still unclear. This study sought to define the predictive value of a genetic profiling for fracture prediction. Sixty‐two bone mineral density (BMD)‐associated single‐nucleotide polymorphisms (SNPs) were genotyped in 557 men and 902 women who had participated in the Dubbo Osteoporosis Epidemiology Study. The incidence of fragility fracture was ascertained from X‐ray reports between 1990 and 2015. Femoral neck BMD was measured by dual‐energy X‐ray absorptiometry. A weighted polygenic risk score (genetic risk score [GRS]) was created as a function of the number of risk alleles and their BMD‐associated regression coefficients for each SNP. The association between GRS and fracture risk was assessed by the Cox proportional hazards model. Individuals with greater GRS had lower femoral neck BMD (p < 0.01), but the variation in GRS accounted for less than 2% of total variance in BMD. Each unit increase in GRS was associated with a hazard ratio of 1.20 (95% CI, 1.04 to 1.38) for fracture, and this association was independent of age, prior fracture, fall, and in a subset of 33 SNPs, independent of femoral neck BMD. The significant association between GRS and fracture was observed for the vertebral and wrist fractures, but not for hip fracture. The area under the receiver‐operating characteristic (ROC) curve (AUC) for the model with GRS and clinical risk factors was 0.71 (95% CI, 0.68 to 0.74). With GRS, the correct reclassification of fracture versus nonfracture ranged from 12% for hip fracture to 23% for wrist fracture. A genetic profiling of BMD‐ associated genetic variants could improve the accuracy of fracture prediction over and above that of clinical risk factors alone, and help stratify individuals by fracture status. © 2016 American Society for Bone and Mineral Research.     

Genetic Risk Scores Implicated in Adult Bone Fragility Associate With Pediatric Bone Density

Using adult identified bone mineral density (BMD) loci, we calculated genetic risk scores (GRS) to determine if they were associated with changes in BMD during childhood. Longitudinal data from the Bone Mineral Density in Childhood Study were analyzed (N = 798, 54% female, all European ancestry). Participants had up to 6 annual dual energy X‐ray scans, from which areal BMD (aBMD) Z‐scores for the spine, total hip, and femoral neck were estimated, as well as total body less head bone mineral content (TBLH‐BMC) Z‐scores. Sixty‐three single‐nucleotide polymorphisms (SNPs) were genotyped, and the percentage of BMD‐lowering alleles carried was calculated (overall adult GRS). Subtype GRS that include SNPs associated with fracture risk, pediatric BMD, WNT signaling, RANK‐RANKL‐OPG, and mesenchymal stem cell differentiation were also calculated. Linear mixed effects models were used to test associations between each GRS and bone Z‐scores, and if any association differed by sex and/or chronological age. The overall adult, fracture, and WNT signaling GRS were associated with lower Z‐scores (eg, spine aBMD Z‐score: β_adult = –0.04, p = 3.4 × 10^?7; β_fracture = –0.02, p = 8.9 × 10^?6; β_WNT = –0.01, p = 3.9 × 10^?4). The overall adult GRS was more strongly associated with lower Z‐scores in females (p‐interaction ≤ 0.05 for all sites). The fracture GRS was more strongly associated with lower Z‐scores with increasing age (p‐interaction ≤ 0.05 for all sites). The WNT GRS associations remained consistent for both sexes and all ages (p‐interaction > 0.05 for all sites). The RANK‐RANKL‐OPG GRS was more strongly associated in females with increasing age (p‐interaction < 0.05 for all sites). The mesenchymal stem cell GRS was associated with lower total hip and femoral neck Z‐scores, in both boys and girls, across all ages. No associations were observed between the pediatric GRS and bone Z‐scores. In conclusion, adult identified BMD loci associated with BMD and BMC in the pediatric setting, especially in females and in loci involved in fracture risk and WNT signaling. © 2015 American Society for Bone and Mineral Research.     

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.     

A Haplotype‐Based Analysis of the LRP5 Gene in Relation to Osteoporosis Phenotypes in Spanish Postmenopausal Women

LRP5 encodes the low‐density lipoprotein receptor‐related protein 5, a transmembrane protein involved in Wnt signaling. LRP5 is an important regulator of osteoblast growth and differentiation, affecting bone mass in vertebrates. Whether common variations in LRP5 are associated with normal BMD variation or osteoporotic phenotypes is of great relevance. We used a haplotype‐based approach to search for common disease‐associated variants in LRP5 in a cohort of 964 Spanish postmenopausal women. Twenty‐four SNPs were selected, covering the LRP5 region, including the missense changes p.V667M and p.A1330V. The SNPs were genotyped and evaluated for association with BMD at the lumbar spine (LS) or femoral neck (FN) and with osteoporotic fracture, at single SNP and haplotype levels, by regression methods. Association with LS BMD was found for SNP 1, rs312009, located in the 5′‐flanking region (p = 0.011, recessive model). SNP 6, rs2508836, in intron 1, was also associated with BMD, both at LS (p = 0.025, additive model) and FN (p = 0.031, recessive model). Two polymorphisms were associated with fracture: SNP 11, rs729635, in intron 1, and SNP 15, rs643892, in intron 5 (p = 0.007 additive model and p = 0.019 recessive model, respectively). Haplotype analyses did not provide additional information, except for haplotype “GC” of the block located at the 3′end of the gene. This haplotype spans intron 22 and the 3′ untranslated region and was associated with FN BMD (p = 0.029, one copy of the haplotype versus none). In silico analyses showed that SNP 1 (rs312009) lies in a putative RUNX2 binding site. Electro‐mobility shift assays confirmed RUNX2 binding to this site.     

SIRT1/HERC4 Locus Associated With Bisphosphonate‐Induced Osteonecrosis of the Jaw: An Exome‐Wide Association Analysis

Osteonecrosis of the jaw (ONJ) is a rare, but serious drug side effect, mainly associated with the use of intravenous (iv) bisphosphonates (BPs). The purpose of this study was to identify genetic variants associated with ONJ in patients of European ancestry treated with iv BPs using whole‐exome sequencing (WES). The WES phase 1 included 44 multiple myeloma patients (22 ONJ cases and 22 controls) and WES phase 2 included 17 ONJ patients with solid tumors. Multivariable logistic regression analysis was performed to estimate the odds ratios (ORs) and 95% confidence intervals (CI), adjusting for age, sex, and principal components for ancestry. Meta‐analysis of WES phase 1 and 2 was performed to estimate the combined ORs. In silico analyses were then performed to identify expression quantitative loci (eQTL) single‐nucleotide polymorphisms (SNPs) that are in high linkage disequilibrium (LD) with the top SNPs. The associations of the potentially functional SNPs were replicated and validated in an independent case‐control study of 48 patients of European ancestry treated with iv BPs (19 ONJ cases and 29 controls). The top SNPs in the exome‐wide association meta‐analysis were two SNPs on chromosome 10: SIRT1 SNP rs7896005 and HERC4 SNP rs3758392 with identical OR of 0.07 (0.01–0.46; p = 3.83 × 10^?5). In the in silico functional analyses, two promoter region SNPs (rs7894483 and rs3758391) were identified to be in high LD with the index SNPs and are eQTLs for SIRT1 gene in whole blood in the GTEx database. The ORs were 0.30 (0.10–0.88), 0.26 (0.12–0.55), and 0.26 (0.12–0.55) for the WES top SNP rs7896005 and two promoter SNPs rs7894483 and rs3758391, respectively, in the replication sample. In summary, we identified the SIRT1/HERC4 locus on chromosome 10 to be associated with iv BP‐induced ONJ and two promoter SNPs that might be the potential genetic markers for this association. © 2017 The Authors.Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.     

ABCB1/MDR1 gene polymorphism and colorectal cancer risk: a meta‐analysis of case–control studies

Aim ABCB1/MDR1 protein is found in high concentrations on the apical surfaces of colonic epithelial cells. It acts as an efflux pump by transporting toxic endogenous substances, drugs and xenobiotics out of cells. Polymorphisms in the ABCB1/MDR1 gene may either change expression of the ABCB1/MDR1 protein or alter its function, suggesting its possible association with colorectal cancer. Several studies have reported a relationship between ABCB1 gene polymorphisms and colorectal cancer risk, but no consistent conclusion has been reached. We therefore conducted a meta‐analysis to identify any association between the ABCB1 gene and CRC risk. Method PubMed, Embase, Google Scholar, Cbmdisc and CNKI were searched for studies on the relationship of ABCB1/MDR1 gene SNPs and the incidence of colorectal cancer. Eligible articles were included for data extraction. The main outcome was the frequency of ABCB1/MDR1 gene SNPs among cases and controls. Comparison of the distribution of SNPs was performed mainly using Review Manager 5.0. Results Ten, four and two trials were identified that focussed on the ABCB1 gene SNPs rs1045642, rs2032582 and rs3789243, respectively. A total of 3175 cases and 3715 controls were included. The meta‐analysis, stratified by ethnicity or population source, indicated no association between the ABCB1 gene rs1045642 polymorphism and colorectal cancer risk. However, when the study by Bae et al. was removed from the analysis, there was some evidence to indicate a higher T‐allele frequency in Asian colorectal cancer patients (OR = 1.30, 95% CI: 1.02–1.67, P = 0.03). Neither ABCB1 rs2032582 nor ABCB1 rs3789243 indicated an association with colorectal cancer risk. An increased frequency only of the wild‐type combined allele (rs2032582G/rs1045642C) was found in Caucasian patients (OR = 1.22, 95% CI: 1.03–1.44, P = 0.02). Conclusion There is some evidence to indicate an association between ABCB1 rs1045642T and colorectal cancer risk in Asians. Compared with the ABCB1 gene SNPs rs1045642, rs2032582 or rs3789243 alone, combined haplotypes of several SNPs might be a better marker to determine the genetic influence on the susceptibility to colorectal cancer among Caucasians.     

Vitamin D Binding Protein Genotype and Osteoporosis

Osteoporosis is a bone disease leading to an increased fracture risk. It is considered a complex multifactorial genetic disorder with interaction of environmental and genetic factors. As a candidate gene for osteoporosis, we studied vitamin D binding protein (DBP, or group-specific component, Gc), which binds to and transports vitamin D to target tissues to maintain calcium homeostasis through the vitamin D endocrine system. DBP can also be converted to DBP-macrophage activating factor (DBP-MAF), which mediates bone resorption by directly activating osteoclasts. We summarized the genetic linkage structure of the DBP gene. We genotyped two single-nucleotide polymorphisms (SNPs, rs7041 = Glu416Asp and rs4588 = Thr420Lys) in 6,181 elderly Caucasians and investigated interactions of the DBP genotype with vitamin D receptor (VDR) genotype and dietary calcium intake in relation to fracture risk. Haplotypes of the DBP SNPs correspond to protein variations referred to as Gc1s (haplotype 1), Gc2 (haplotype 2), and Gc1f (haplotype3). In a subgroup of 1,312 subjects, DBP genotype was found to be associated with increased and decreased serum 25-(OH)D₃ for haplotype 1 (P = 3 × 10⁻⁴) and haplotype 2 (P = 3 × 10⁻⁶), respectively. Similar associations were observed for 1,25-(OH)₂D₃. The DBP genotype was not significantly associated with fracture risk in the entire study population. Yet, we observed interaction between DBP and VDR haplotypes in determining fracture risk. In the DBP haplotype 1-carrier group, subjects of homozygous VDR block 5-haplotype 1 had 33% increased fracture risk compared to noncarriers (P = 0.005). In a subgroup with dietary calcium intake <1.09 g/day, the hazard ratio (95% confidence interval) for fracture risk of DBP hap1-homozygote versus noncarrier was 1.47 (1.06–2.05). All associations were independent of age and gender. Our study demonstrated that the genetic effect of the DBP gene on fracture risk appears only in combination with other genetic and environmental risk factors for bone metabolism.     

Association between ADAMTS‐4 gene polymorphism and lumbar disc degeneration in Chinese Han population

Low back pain (LBP) is a common health problem and many LBP are caused by lumbar disc degeneration (LDD). ADAMTS‐4 (a disintegrin and metalloprotease with thrombospondin motifs‐4), also known as aggrecanse‐1, plays a core role in degeneration of extracellular matrix in LDD. To investigate the association between ADAMTS‐4 genetic polymorphism and LDD, we genotyped SNPs in and around ADAMTS‐4. We recruited 482 sporadic cases of LDD and 496 healthy controls from Chinese Han population. Five SNPs were selected and phenotyped by the Sequenom MassARRAY system. Allelic, genotypic, and haplotypic association was performed. Rs4233367 (c.1877 C>T), which located in exon of ADAMTS‐4 showed significant association with LDD. The T allele conferred a lower risk of LDD with an OR of 0.69 and TT genotype is at nearly one‐fifth of the risk compared to CC genotype. Other tested SNPs didn't show significant difference between the case and control groups. The SNP rs4233367 in the exon of ADAMTS‐4 gene may be associated with lumbar disc degeneration. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:860–864, 2016.     

Methylation of Bone SOST,Its mRNA,and Serum Sclerostin Levels Correlate Strongly With Fracture Risk in Postmenopausal Women

Inhibition of sclerostin, a glycoprotein secreted by osteocytes, offers a new therapeutic paradigm for treatment of osteoporosis (OP) through its critical role as Wnt/catenin signaling regulator. This study describes the epigenetic regulation of SOST expression in bone biopsies of postmenopausal women. We correlated serum sclerostin to bone mineral density (BMD), fractures, and bone remodeling parameters, and related these findings to epigenetic and genetic disease mechanisms. Serum sclerostin and bone remodeling biomarkers were measured in two postmenopausal groups: healthy (BMD T‐score > –1) and established OP (BMD T‐score < –2.5, with at least one low‐energy fracture). Bone specimens were used to analyze SOST mRNAs, single nucleotide polymorphisms (SNPs), and DNA methylation changes. The SOST gene promoter region showed increased CpG methylation in OP patients (n = 4) compared to age and body mass index (BMI) balanced controls (n = 4) (80.5% versus 63.2%, p = 0.0001) with replication in independent cohorts (n = 27 and n = 36, respectively). Serum sclerostin and bone SOST mRNA expression correlated positively with age‐adjusted and BMI‐adjusted total hip BMD (r = 0.47 and r = 0.43, respectively; both p < 0.0005), and inversely to serum bone turnover markers. Five SNPs, one of which replicates in an independent population‐based genomewide association study (GWAS), showed association with serum sclerostin or SOST mRNA levels under an additive model (p = 0.0016 to 0.0079). Genetic and epigenetic changes in SOST influence its bone mRNA expression and serum sclerostin levels in postmenopausal women. The observations suggest that increased SOST promoter methylation seen in OP is a compensatory counteracting mechanism, which lowers serum sclerostin concentrations and reduces inhibition of Wnt signaling in an attempt to promote bone formation. © 2014 American Society for Bone and Mineral Research.     

Polymorphisms in BMP4 and FGFR1 genes are associated with fracture non‐union

Fracture healing is a complex process influenced by a multitude of factors and expression of several thousand genes. Polymorphisms in these genes can lead to an extended healing process and explain why certain patients are more susceptible to develop non‐union. A total of 16 SNPs within five genes involved in bone repair pathogenesis (FAM5C, BMP4, FGF3, FGF10, and FGFR1) were investigated in 167 patients with long bone fractures, 101 with uneventful healing, and 66 presenting aseptic non‐unions. Exclusion criteria were patients presenting pathological fractures, osteoporosis, hypertrophic and infected non‐unions, pregnancy, and children. All genetic markers were genotyped using TaqMan real‐time PCR. Chi‐square test was used to compare genotypes, allele frequencies, and haplotype differences between groups. Binary logistic regression analyzed the significance of many covariates and the incidence of non‐union. Statistical analysis revealed open fracture to be a risk factor for non‐union development (p < 0.001, OR 3.6 [1.70–7.67]). A significant association of haplotype GTAA in BMP4 (p = 0.01) and FGFR1 rs13317 (p = 0.005) with NU could be observed. Also, uneventful healing showed association with FAM5C rs1342913 (p = 0.04). Our work supported the role of BMP4 and FGFR1 in NU fracture independently of the presence of previously described risk factors. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1971–1979, 2013     

Potential influence of IL1B haplotype and IL1A-IL1B-IL1RN extended haplotype on hand osteoarthritis risk

OBJECTIVE: To assess osteoarthritis (OA) association with the human interleukin-1 (IL-1) region. DESIGN: Sixty-four European-descent cases with radiographic hand OA and 48 European-descent controls were genotyped at nine single nucleotide polymorphism (SNP), one variable-number-of-tandem-repeat (VNTR), and one microsatellite marker extending across loci for IL-1alpha (IL1A), IL-1beta (IL1B), and IL-1 receptor antagonist (IL1RN). The genotype data were used to reconstruct individual locus haplotypes, and then locus haplotypes were used as superalleles for extended haplotype reconstruction. RESULTS: Nine different extended IL1A-IL1B-IL1RN haplotypes occurred at a frequency 0.05 or greater in either cases or controls. Only two IL1A-IL1B-IL1RN extended haplotypes were consistent with previously described extended risk haplotypes and totaled n=9 in cases and n=3 in controls [odds ratio (OR) 2.1, Haldane's chi(2) 1.67, one-sided P 0.1]. Our prior report showed hand OA association with homozygous IL1B rs1143633 minor allele genotype. All except one extended risk haplotype copy also had the IL1B rs1143633 minor allele. The rs1143633 genotype association was explained by one common six-SNP IL1B haplotype bearing rs1143633 minor allele and also risk alleles at rs1143634, rs1143627, and rs16944, component markers of the previously described extended risk haplotypes. The IL1B haplotype bearing all three risk alleles was found in 16 haplotype-homozygous hand OA cases and in four haplotype-homozygous controls and conferred OR 3.4 among homozygotes (nominal P value 0.006). CONCLUSION: Our evidence broadly supports the genetic association of OA phenotypes with an IL-1 region extended risk haplotype and specifically IL1B genotype. The extended risk haplotype previously associated with hip OA appears to be less frequent and has weaker genetic effect in hand OA. Hand OA risk is conferred by homozygous state for the IL1B haplotype characteristic of the extended risk haplotype.