Effect of Vitamin D Supplementation on Obesity-Induced Insulin Resistance: A Double-Blind, Randomized,Placebo-Controlled Trial (Studien/Vitamin D)

Chiara M.A. Cefalo1*, Caterina Conte1,2*, Gian Pio Sorice1, Simona Moffa1, Vinsin A. Sun1, Francesca Cinti1, Enrica Salomone1,3, Giovanna Muscogiuri1,4, Alex A.G. Brocchi1, Alfredo Pontecorvi1, Teresa Mezza 1, and Andrea Giaccari1

1 Center for Endocrine and Metabolic Diseases, Gemelli University Polyclinic Foundation, Catholic University of the Sacred Heart, Rome, Italy. Correspondence: Teresa Mezza (teresa.mezza@gmail.com)
2 Internal Medicine and Transplant Unit, San Raffaele Hospital, Milan, Italy
3 Center for Diabetes and Metabolic Diseases, Association of Italian Knights of the Sovereign Military Order of Malta, Rome, Italy
4 Division of Endocrinology, Department of Clinical Medicine and Surgery, Federic II University, Naples, Italy.

Objective: The aim was to investigate whether vitamin D supplementation, combined with a hypocaloric diet, could have an independent effect on insulin sensitivity in subjects with both overweight and hypovitaminosis D. Changes from baseline in anthropometric parameters, body composition, glucose tolerance, and insulin secretion were considered as secondary outcomes.
Methods: Eighteen volunteers who were nondiabetic and vitamin D deficient and had BMI>25 kg/m2 were randomized (1:1) in a double-blind manner to a hypocaloric diet1either oral cholecalciferol at 25,000 IU/wk or placebo for 3 months. Hyperinsulinemic-euglycemic clamp to measure insulin sensitivity was performed at baseline and after intervention.
Results: Body weight in both groups decreased significantly (27.5% in the vitamin D group and 210% in the placebo group; P<0.05 for both), with no between-group differences. Serum 25-hydroxyvitamin D levels in the vitamin D group increased considerably (from 36.7613.2 nmol/L to 74.8618.7 nmol/L; P<0.001). Insulin sensitivity in the vitamin D group improved (from 4.662.0 to 6.963.3mgkg21min21; P<0.001), whereas no changes were observed in the placebo group (from 4.961.1 to 5.160.3mgkg21min21; P50.84).
Conclusions: Cholecalciferol supplementation, combined with a weight loss program, significantly improves insulin sensitivity in healthy subjects with obesity and might represent a personalized approach for insulin-resistant subjects with obesity. (…)