Does vitamin D receptor polymorphism influence the response of bone to brisk walking in postmenopausal women?

Vitamin D receptor (VDR) polymorphism may be a genetic factor affecting bone mineral density (BMD). This study examined the interaction of VDR genotype with the effect of an exercise intervention on bone measurements in UK postmenopausal women. 33 walkers, who completed 20.4 +/- 3.9 (mean +/- SD) min day-1 of brisk walking over 1 year, and 36 controls agreed to give DNA samples. BMD was measured at the lumbar spine, femoral neck and calcaneus by dual energy X-ray absorptiometry and broadband ultrasonic attenuation (BUA) was measured at the calcaneus. VDR genotype was determined by BsmI restriction fragment length polymorphisms and the presence, or absence, of the restriction site was signified by 'b' or 'B', respectively. At baseline there was no significant difference in BMD between VDR genotypes, but BUA was significantly higher in the BB genotype than in the Bb or bb genotype. Although there was no significant difference in 1-year change (%) in BMD and BUA between the three genotypes, the 1-year changes in spinal BMD and BUA in the bb walkers (0.75 and 2.35%, respectively) were significantly different from those in the bb controls (-1.25 and -6.10%, respectively). These results suggest that in the bb genotype of VDR, bone may be more responsive to exercise than in other VDR genotypes in British postmenopausal women.