Vitamin D receptor gene polymorphisms are not related to bone turnover, rate of bone loss, and bone mass in postmenopausal women: the OFELY Study.

Vitamin D receptor (VDR) gene polymorphisms have been reported to account for most of the well established genetic influence on bone mineral density (BMD). However, discordant studies have been published and it is still not clear whether VDR genotypes influence bone mass accretion and/or postmenopausal bone loss. In this study, we analyzed VDR gene polymorphisms, i.e., that of BsmI, ApaI, and TaqI restriction enzymes in 268 untreated postmenopausal women 1-26 years postmenopausal. There were 37 BBAA homozygote (absence of BsmI and ApaI restriction sites on both alleles), 55 bbaa homozygote (presence of restriction sites on both alleles), and 176 heterozygotes. At baseline, women between the three genotypes did not differ significantly in age, years since menopause, body mass index (BMI), nor dietary calcium intake. We found no relationship between VDR genotypes and bone turnover assessed by three serum markers of bone formation and three urinary bone resorption markers, nor with BMD measured at the spine, hip, forearm, and whole body by dual-energy X-ray absorptiometry (DXA). Rates of bone loss assessed by repeated DXA measurements over 2 years were highly significant (p = 0.02-0.0001) at all skeletal sites except for the lumbar spine but did not differ between genotypes at any sites either before or after adjustment for potential confounding factors such as years since menopause, BMI, calcium intake, serum 25 hydroxyvitamin D levels, and baseline BMD. When we restricted the analysis to early postmenopausal women, within 10 years of menopause (n = 128), lumbar spine bone loss became significant, but no significant difference between VDR genotypes in the rate of bone loss measured at any site was found. We conclude that VDR genotypes are not predictive of bone turnover, rate of postmenopausal bone loss, and bone mass in either early or late postmenopausal women. In a subgroup of women with a low calcium intake (below 600 mg/day), we also found no significant differences between genotypes in BMD and the rate of bone loss measured at any site, although the sample size (n = 64) may be too small to detect small differences. In conclusion, these data, along with the absence of relationships between VDR gene polymorphisms and peak bone mass that we recently reported, suggest that the determination of VDR genotypes is probably not a useful clinical test for the risk assessment of osteoporosis.