The human calcium-sensing receptor and interleukin-6 genes are associated with bone mineral density in Chinese

Calcium sensing receptor (CASR) is a central factor involved in calcium metabolism. Interleukin-6 (IL-6) is a pleiotropic cytokine that plays an important role in osteoclast differentiation. Thus, both CASR and IL-6 are important in bone and mineral metabolism and are prominent candidate genes for osteoporosis. The study aimed to test association and/or linkage between the CASR and IL-6 genes with bone mineral density (BMD) variation in a Chinese population. A cytosine-adenine (CA)n repeat polymorphism in the CASR gene and the IL-6 gene was genotyped, respectively, in 1,263 subjects from 402 Chinese nuclear families. Employing tests implemented in the program QTDT (quantitative transmission disequilibrium tests), a significant total association of the CASR (CA)12 allele (P = 0.006) and (CA)18 allele (P = 0.02) with BMD at the femoral neck was found. For the IL-6 gene, significant within-family associations were found between the (CA)14 allele and BMD at the total hip (P = 0.021), the femoral neck (P = 0.041), and the intertrochanteric region (P = 0.029). A significant linkage was also observed between IL-6 CA repeat polymorphism and BMD at the spine (P = 0.001). The results suggest that the CASR gene and the IL-6 gene may have effects on BMD variation in Chinese.