Are bone mineral density loci associated with hip osteoporotic fractures? A validation study on previously reported genome-wide association loci in a Chinese population

Osteoporosis is a heritable disease characterized mainly by low bone mineral density (BMD) and/or osteoporotic fractures (OF). Most genome-wide association studies on osteoporosis have focused on BMD, whereas little effort has been expended to identify genetic variants directly linked to OF. To determine whether BMD-loci are also associated with OF risk, we performed a validation study to examine 23 BMD-loci reported by recent genome-wide association studies for association with hip OF risk. Our sample consisted of 700 elderly Chinese Han subjects, 350 with hip OF and 350 healthy matched controls. We identified four BMD-loci that were significantly associated with hip OF in this Chinese population, including 7q21 (FLJ42280, P = 1.17 x 10(-4) for rs4729260; P = 0.008 for rs7781370), 6p21 (MHC, P = 0.004 for rs3130340), 13q14 (TNFSF11, P = 0.012 for rs9533090; P = 0.018 for rs9594759; P = 0.020 for rs9594738; P = 0.044 for rs9594751), and 18q21 (TNFRSF11A, P = 0.015 for rs884205). The SNP rs4729260 at 7q21 remained significantly associated, even after conservative Bonferroni's correction. Our results further highlight the importance of these loci in the pathogenesis of osteoporosis, and demonstrate that it is feasible and useful to use OF as the direct phenotype to conduct genetic studies, to enhance our understanding of the genetic architecture of osteoporosis.