Polymorphisms in the vitamin D receptor gene are associated with muscle strength in men and women.

INTRODUCTION: Vitamin D receptor (VDR) polymorphisms have been associated with fracture risk and muscle strength, although evidence for the latter is limited and conflicting.
METHODS: BsmI, TaqI and FokI VDR polymorphisms were genotyped in 253 men (54.9 +/- 10.2 yr) and 240 women (41.5 +/- 13.2 yr). Haplotypes were constructed for BsmI and TaqI. Handgrip, isometric (at 60 degrees , 120 degrees and 180 degrees joint angle) and eccentric torques (60 degrees /s) of knee extension and flexion were analysed using AN(C)OVA. Torque-velocity curves were constructed for concentric torques at 60 degrees /s, 180 degrees /s and 240 degrees /s and analysed using multivariate AN(C)OVA. Age, height and fat-free mass were included as covariates.
RESULTS: Quadriceps isometric and concentric strength were higher in female f/f homozygotes compared to F allele carriers. Adjustment for confounding factors rendered results for quadriceps isometric strength at 120 degrees non-significant. No significant association was found with BsmI-TaqI haplotype in women. In contrast, male Bt/Bt homozygotes had higher isometric quadriceps strength at 150 degrees and higher concentric quadriceps strength than bT allele carriers without and with adjustment for confounding factors. No association was observed with FokI in men. In both genders, no interaction effect was present between BsmI-TaqI haplotype and FokI.
CONCLUSIONS: Different VDR gene polymorphisms are associated with quadriceps strength in men and women.