Vitamin D supplementation increases adipokine concentrations in overweight or obese adults

Purpose: Vitamin D regulates adipokine production in vitro; however, clinical trials have been inconclusive. We conducted secondary analyses of a randomized controlled trial to examine whether vitamin D supplementation improves adipokine concentrations in overweight/obese and vitamin D-deficient adults. Methods: Sixty-five individuals with a BMI ≥ 25 kg/m² and 25-hydroxyvitamin D (25(OH)D) ≤ 50 nmol/L were randomized to oral cholecalciferol (100,000 IU single bolus followed by 4,000 IU daily) or matching placebo for 16 weeks. We measured BMI, waist-to-hip ratio, % body fat (dual X-ray absorptiometry), serum 25(OH)D (chemiluminescent immunoassay) and total adiponectin, leptin, resistin, and adipsin concentrations (multiplex assay; flow cytometry). Sun exposure, physical activity, and diet were assessed using questionnaires. Results: Fifty-four participants completed the study (35M/19F; mean age = 31.9 ± 8.5 years; BMI = 30.9 ± 4.4 kg/m²). After 16 weeks, vitamin D supplementation increased 25(OH)D concentrations compared with placebo (57.0 ± 21.3 versus 1.9 ± 15.1 nmol/L, p < 0.001). There were no differences between groups for changes in adiponectin, leptin, resistin, or adipsin in unadjusted analyses (all p > 0.05). After adjustment for baseline values, season, sun exposure, and dietary vitamin D intake, there was a greater increase in adiponectin (β[95%CI] = 13.7[2.0, 25.5], p = 0.02) and leptin (β[95%CI] = 22.3[3.8, 40.9], p = 0.02) in the vitamin D group compared with placebo. Results remained significant after additional adjustment for age, sex, and % body fat (p < 0.02). Conclusions: Vitamin D may increase adiponectin and leptin concentrations in overweight/obese and vitamin D-deficient adults. Further studies are needed to clarify the molecular interactions between vitamin D and adipokines and the clinical implications of these interactions in the context of obesity. Clinical trial registration: clinicaltrials.gov: NCT02112721.