Race/ethnicity-specific association of Vitamin D and global DNA methylation: Cross-sectional and interventional findings

Objectives: Understanding of the influence of vitamin D deficiency on epigenome will provide novel insights into the chronic disease risk. We tested our hypotheses that 1) vitamin D deficiency is associated with global hypomethylation and this association may be race/ethnicity dependent; and 2) vitamin D supplementation will increase global DNA methylation level. Methods: A two-stage design, cross-sectional observation followed by a 16 week randomized, doubleblinded, placebo-controlled trial (RCT) of vitamin D3 supplementation, was undertaken. Global DNA methylation level (percentage of 5-methylcytosine, %5-mC) was quantified using leukocyte DNA with the MethylFlash^™ Methylated DNA Quantification kit (Epigentek). Global methylation data was obtained from 454 Caucasians and African Americans (42%) in the observation cohort and 58 African Americans with vitamin D deficiency in the dose responsive RCT. Results: In the cross-sectional study, African Americans had lower %5-mC than Caucasians (P = 0.04). A significant interaction was detected between plasma 25(OH)D and race on %5-mC (P = 0.05), as a positive association was observed between plasma 25(OH)D and %5-mC in African Americans (β = 0.20, p<0.01), but not in Caucasians (β = 0.03, p = 0.62). In the 16-week RCT, a dose-response benefit of vitamin D₃ supplementation was observed for % 5-mC, as indicated by a significant linear upward trend (-0.01 ± 0.01%, placebo; 0.11 ± 0.01%, ∼600 IU/day; 0.30 ± 0.01%, ∼2,000 IU/day; and 0.65 ± 0.01%, ∼4,000 IU/day group; P-trend = 0.04). Conclusions: Vitamin D deficiency is associated with global hypomethylation in African Americans. Vitamin D3 supplementation increases global DNA methylation in a dose-response manner in African Americans with vitamin D deficiency.