Abstract MP20: Vitamin D Supplementation Increases Global DNA Methylation in Overweight and Obese African Americans with Vitamin D Deficiency

Introduction: Vitamin D deficiency is associated with cardiovascular disease, diabetes and cancer. Individuals with obesity or darker skin are at risk for vitamin D deficiency. Our genome-wide methylation study has shown that African Americans with vitamin D deficiency have reduced levels of methylation compared with controls. Global decrease in DNA methylation, a common feature of cancer, is associated with genomic and chromosomal instability. Therefore, we aimed to test our hypothesis that vitamin D supplementation will increase global DNA methylation level in overweight and obese African Americans with vitamin D deficiency. Methods: We recently conducted a 16 weeks randomized, placebo controlled clinical trial of vitamin D3 supplementation (NCT01583621). A total of 65 young overweight and obese African Americans (13-45 years, 83% females) with vitamin D deficiency (25-hydroxyvitamin D3 [25(OH)D] < 20 ng/ml) were randomly assigned to receive a supervised monthly oral vitamin D3 dose of placebo (n=16), 18,000 IU (~600 IU/day, the current RDA; n=15), 60,000 IU (~2,000 IU/day; n=17), or 120,000 IU (~4,000 IU/day, the deemed tolerable upper intake level; n=17). Global DNA methylation level (percentage of 5-methylcytosine, %5-mC) was quantified using leukocyte DNA with the MethylFlash Methylated DNA Quantification kit (Epigentek) in a total of 58 participants. Results: At baseline, serum 25(OH)D levels were positively correlated with %5-mC (r=0.26, p=0.04) in the entire cohort. A significant increase was observed in the changes of serum 25(OH)D from baseline to 16 weeks (0.9 ± 2.0, placebo; 8.6 ± 2.1, 600 IU/day; 20.1 ± 2.0, 2,000 IU/day; and 21.2 ± 2.0 ng/ml, 4,000 IU/day; p<0.01). In addition, a significant dose-responsive increase was observed in the changes of %5-mC from baseline to 16 weeks (0.00 ± 0.18, placebo; 0.02 ± 0.20, 600 IU/day; 0.29 ± 0.17, 2,000 IU/day; and 0.66 ± 0.18%, 4,000 IU/day group; p<0.01). This response remained significant even after adjusting for age, sex and BMI. Moreover, the changes in %5-mC were significantly correlated with the changes in serum 25(OH)D (r=0.60, p=0.02) in the 4,000 IU group. Conclusions: Vitamin D supplementation increases global DNA methylation level in a dose-responsive manner. Increased global DNA methylation, subsequently increased genomic and chromosomal stability may be one of the underlying mechanisms by which vitamin D exerts its beneficial effects on cardiovascular disease, diabetes and cancer. Large scale vitamin D supplementation clinical trial is warranted to verify our findings.