A Poly Adenosine Repeat in the Human Vitamin D Receptor Gene is Associated with Bone Mineral Density in Young Swedish Women

Peak bone mass (PBM) and subsequent bone loss are important risk factors for development of osteoporosis later in life, and twin studies have reported strong genetic influence on PBM. The genetic factor influencing PBM is polygenetic, and many genes most likely exert relatively small effects on bone mass. The poly adenosine (A) microsatellite in the 3′ untranslated region (UTR) of the VDR gene has been associated with both prostate and breast cancer risk but little is known about the effect of bone mineral density (BMD). In this report the poly A microsatellite and the linked BsmI SNP have been investigated in a population-based cohort of 343 Swedish women, aged 20–39. BMD was measured by dual x-ray absorptiometry at the spine, proximal femur, total body and heel and by quantitative ultrasound at the heel. Correlations were found between VDR genotypes and BMD at lumbar spine L2-L4, (ss versus LL , P = 0.03 and BB versus bb, P = 0.02, respectively), with a similar pattern concerning total hip (ss versus LL, P = 0.12 and BB versus bb, P = 0.16 respectively). After corrections for age, height, fat and lean mass, the VDR BsmI genotype was still associated to BMD at the lumbar spine (BB versus bb, P = 0.03). The polymorphisms were in linkage disequilibrium (Chi-square = 566, P < 0.0001). In conclusion, genetic variation in the VDR is associated with BMD in premenopausal women, and further studies are needed to evaluate a possible functional role of the VDR 3′UTR poly A repeat, a region that has shown to be of important for mRNA stability.