Correlation between vitamin D receptor genotypes and bone mineral density in Japanese patients with osteoporosis

In order to better understand the pathogenesis of osteoporosis, we investigated the correlation between the vitamin D receptor (VDR) genotypes defined by BsmI restriction enzyme, as well as other related factors, and the bone mineral density (BMD) at the lumbar spine in 90 Japanese patients with osteoporosis. The same study was performed in 36 patients with osteoarthrosis of the hip joint and 92 healthy volunteers. The majority of the VDR genotypes were bb, and a few of the population showed either the BB or Bb genotype in all three groups. There was no statistical difference in the frequencies of these VDR genotypes in the three groups. The mean age-matched value of BMD (Z scores) at the lumbar spine in patients with osteoporosis was significantly lower than that in patients with osteoarthrosis or healthy volunteers. The mean Z scores of the healthy volunteers with bb genotype were significantly higher than those with BB genotype, whereas those of the osteoporosis patients with BB genotype were significantly higher than those with Bb genotype. There was no significant difference in the mean Z scores between bb and Bb genotypes in patients with osteoporosis and healthy volunteers. No significant difference was seen in the mean Z scores in patients with osteoarthrosis regardless of genotype. On the other hand, body weight significantly correlated with BMD in patients with osteoporosis by simple- and multiple-regression analysis. These results indicate that the BMD at the lumbar spine in Japanese patients with osteoporosis is affected by body weight, and might be affected partially by the VDR genotypes defined by BsmI.