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 bon e mineral density (BMD). This study examined the interaction of VDR genotyp e with the effect of an exercise intervention on bone measurements in UK po stmenopausal women. 33 walkers, who completed 20.4 +/- 3.9 (mean +/- SD) mi n 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 b y dual energy X-ray absorptiometry and broadband ultrasonic attenuation (BU A) was measured at the calcaneus. VDR genotype was determined by BsmI restr iction fragment length polymorphisms and the presence, or absence, of the r estriction site was signified by 'b' or 'B', respectively. At baseline ther e was no significant difference in BMD between VDR genotypes, but BUA was s ignificantly higher in the BE genotype than in the Bb or bb genotype. Altho ugh 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 t he bb walkers (0.75 and 2.35%, respectively) were significantly different f rom those in the bb controls (-1.25 and -6.10%, respectively). These result s suggest that in the bb genotype of VDR, bone may be more responsive to ex ercise than in other VDR genotypes in British postmenopausal women.