Vitamin D receptor gene polymorphisms modify the association of serum 25-hydroxyvitamin D levels with handgrip strength in the elderly in Northern China

Objectives: The aim of this cross-sectional study was to investigate the association of serum 25-hydroxyvitamin D (25[OH]D) levels and vitamin D receptor (VDR) genotypes with skeletal muscle mass and function in elderly subjects in northern China. Methods: A total of 275 men and 510 women, ages 63.1 to 72.5 y, in two randomly selected communities in Beijing were investigated. The investigation included a questionnaire, physical measurements, muscle mass and function measurements, serum 25(OH)D levels, and VDR gene polymorphisms analysis. Results: In the group with 25(OH)D levels <10.0 ng/mL, the proportion with low handgrip strength was 3.04 times higher than that in the group with 25(OH)D levels >20.0 ng/mL for men (odds ratio: 3.04; 95% confidence interval, 1.13-8.20) but not for women. The general linear model showed that higher 25(OH)D levels and having T allele of Fok1 and the bb genotype of Bsm1 were significantly associated with more hand grip strength. The regression coefficients (beta) were 1.80 (P < 0.01), 1.26 (P < 0.01), and 2.90 (P < 0.01), respectively. There was a significant interaction between 25(OH)D and VDR gene polymorphisms for handgrip strength for both Fok1 (beta = 2.86; P < 0.01) and Bsm1 (beta = 3.14; P=0.02) after adjustment for potential confounders (sex, age, body mass index, fat mass, physical activity, sun exposure, energy, and protein intake). Conclusions: 25(OH)D levels are associated with handgrip strength for men and this relationship could be modified with the interaction between 25(OH)D and VDR gene polymorphisms (Fok1 and Bsml). (C) 2018 Published by Elsevier Inc.