The BsmI vitamin D receptor restriction fragment length polymorphism (BB) predicts low bone density in premenopausal black and white women

Abstract

We conducted a study to determine whether a recently described restriction fragment length polymorphism in the vitamin D receptor gene (VDR‐RFLP) predicts bone mineral density (BMD) in unrelated, premenopausal women as well as to determine the racial contribution to any genotypic influences on BMD. White (n = 83) and black (n = 72) women between 20 and 40 years of age were genotyped based on the presence (b) or absence (B) of a Bsm1 restriction enzyme site in the VDR gene, and BMD in the lumbar spine and femur neck was determined for each subject. There were 16 BB, 73 Bb, and 66 bb women. No significant difference was observed in genotypic distribution between the racial groups. The interaction of race by genotype on age‐ and body mass index (BMI)‐adjusted BMD was not significant at either site. Age‐ and BMI‐adjusted BMD was higher in black women at the spine (by 7.2%, p = 0.046) and femur neck (7.3% higher, p = 0.004). In the group as a whole, mean BMD in the femur neck was lower in the BB women than the bb (by 8.1%, p = 0.034) or Bb women (by 9.3%, p = 0.015) after controlling for age, BMI, race, and the race by genotype interaction. Adjusted lumbar spine BMD was lower in the BB women than the Bb women (6.4% lower, p = 0.036) in the group as a whole. No differences were detected between Bb and bb women at either site. A similar pattern of low BMD at the femur neck and the lumbar spine was seen in BB women of both races. These data provide support for an association between low bone density and the BB genotype in a racially mixed, premenopausal population and suggests that this genotype may limit peak bone mass. Furthermore, racial differences in BMD appear to be independent from the VDR genotype.