Polymorphisms in the Osteoprotegrin Gene with Risk of Osteoporosis and Urinary Calcium Level in a Chinese Population

Abstract

Osteoporosis is an age-related disease caused by imbalanced calcium metabolism identified to be associated with genetic variations of multiple genes including osteoprotegrin (OPG). While bone mineral density (BMD) predicts the risk of osteoporotic fractures, the urinary calcium level (UCL) may reflect calcium metabolism, which thereby indicates osteoporotic trends. BMD of 1,206 local Chinese geriatrics in Shanghai was measured by dual X-ray absorptionmetry. UCL were examined in 728 fasting geriatric urine samples by photometry. Genotyping of the OPG SNPs rs1032128, rs334061 and rs3134063 in 481 subjects including healthy controls, osteopenia and osteoporosis patients was performed and the association between the OPG SNP variations and UCL was assessed among all comparative groups. Differences in age and BMD were statistically significant between males and females with either normal BMD or osteopenia, but were not between those with osteoporosis. Significant correlations were found between BMD and genotypes of rs1032128 in males, and between BMD and age in females. The genotypes of rs1032128 were significantly correlated with BMD in males, but were correlated with UCL in females. UCL was significantly correlated with BMD in males but was associated with rs1032128 genotypes in females. The AA type of rs1032128 was independently associated with risk of osteoporosis in males. The GG type of rs1032128 was negatively associated with UCL in males but was positively associated with UCL in females. Our data suggest that the genotypes of the OPG SNP rs1032128 may protect old males from osteoporosis development, and that UCL may be useful to predict osteoporosis if combined with the genotypes of the OPG SNP, at least in some local Chinese geriatrics.