Increased telomerase activity and vitamin D supplementation in overweight African Americans

OBJECTIVE: We aimed to investigate whether vitamin D supplementation modulates peripheral blood mononuclear cell (PBMC) telomerase activity in overweight African Americans. DESIGN: A double blind, randomized and placebo-controlled clinical trial (#NCT01141192) was recently conducted. SUBJECTS AND METHODS: African-American adults were randomly assigned to either the placebo, or the vitamin D group (60000 IU per month (equivalent to similar to 2000 IU per day) oral vitamin D3 supplementation). Fresh PBMCs were collected from 37 subjects (18 in the placebo group and 19 in the vitamin D group), both at baseline and 16 weeks. PBMC telomerase activity was measured by the telomeric repeat amplification protocol. RESULTS: Serum 25 hydroxyvitamin D levels increased from 40.7 +/- 15.7 at baseline to 48.1 +/- 17.5 nmol l(-1) at posttest (P = 0.004) in the placebo group, and from 35.4 +/- 11.3 at baseline to 103.7 +/- 31.5 nmol l(-1) at posttests (P < 0.0001) in the vitamin D group. In the vitamin D group, PBMC telomerase activity increased by 19.2% from baseline (1.56 +/- 0.29 absorbance reading unit (AU)) to posttest (1.86 +/- 0.42 AU, P < 0.0001). The significance persisted after controlling for age, sex and body mass index (P = 0.039). PBMC telomerase activity in the placebo group did not change from baseline (1.43 +/- 0.26 AU) to posttest (1.46 +/- 0.27 AU, P = 0.157). CONCLUSION: Vitamin D supplementation significantly increased PBMC telomerase activity in overweight African Americans. Our data suggest that vitamin D may improve telomere maintenance and prevent cell senescence and counteract obesity-induced acceleration of cellular aging.