Association Between Bat Vitamin D Receptor 3' Haplotypes and Vitamin D Levels at Baseline and a Lower Response After Increased Vitamin D Supplementation and Exposure to Sunlight.

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Objective: The aim of this study was to evaluate the relationship between vitamin D levels at baseline and after 12 weeks of supplementation/exposure to sunlight and VDR genotypes (BsmI, TaqI and ApaI) and haplotypes in a homogeneous population of postmenopausal women. Methods: We made a prospective study in which 151 women were randomized to two groups: One with 1000mg of calcium and 800 IU vitamin D supplementation (102 women) and a placebo group with neither calcium or vitamin D supplementation (49 women). The follow-up was from May to September 2012.Vitamin D was determined by chemiluminescent immunoassay. Genotypes were determined using the Sequenomi Plexplatform and haplotypes using PHASE software. Results: Baseline (25±10ng/mlvs.23±9ng/ml, p>0.05) and 12-week (32±8ng/mlvs.29±10ng/ml, p>0.05) vitamin D levels were similar between the two groups. The genetic study was made in the total population. There were no differences in baseline and final levels of vitamin D in terms of genotypes and haplotypes, except for the Bat haplotype, whose baseline values were lower (25OHD: 21±10 ng/mlvs. 21±10ng/ml, p=0.038). The rate of nonresponders in this group was 15% (p=0.001), compared with 9%, 2% and 3% in the other groups. Conclusions: The Bat haplotype was associated with lower baseline levels of vitamin D and a worse response to supplementation and, therefore, may be a risk factor for vitamin D deficiency.