Efficacy of vitamin D supplementation according to vitamin D-binding protein polymorphisms

Objectives: The aim of this study was to determine the influence of vitamin D-binding protein (DBP) gene polymorphisms in vitamin D metabolites before and after vitamin D supplementation. Methods: In all, 234 participants (126 women; 108 men) with vitamin D deficiency [25(OH)D <50 nmol/L] were given 50 000 IU of vitamin D supplements for 8 wk followed by daily maintenance of 1000 IU for 4 mo. Two single-nucleotide polymorphisms (rs4588 and rs7041) in DBP coding gene were assessed. Results: Baseline 25(OH)D was significantly in higher in participants with homozygous major genotype of rs7041 than other genotypes (P = 0.02). Postsupplementation 25(OH)D was significantly higher in participants with homozygous major genotypes of either rs4588 and rs7041 than other genotypes (P < 0.001). Participants with the minor allele of either rs4588 or rs7041 were 2.9 (1.9-4.5) times and 3.7 (2.1-6.6) times, respectively, more likely to be non-responders (postsupplementation 25 OHD <50 nmol/L) than those homo-zygous for the major allele at these locations (P < 0.001). Furthermore, participants with homozygous minor and heterozygous genotype of rs7041 were 6.2 and 4.2 times more likely to be non-responders than those with the homozygous major genotype (P < 0.001) even after adjustments for age, sex, body mass index, base-line 25(OH)D concentration, and other alleles. Participants with homozygous minor and heterozygous geno-types of rs4588 were 4.1 and 12.4 times more likely to be non-responders than those with homozygous major genotypes. These significant risks, however, were lost after adjustment. Conclusions: rs7041 and rs4588 variants of the DBP gene are associated with variations in 25(OH)D levels and efficacy of response to vitamin D supplementation in Saudi Arabian adults. (C) 2019 The Authors. Published by Elsevier Inc.