Long-Term Vitamin D Supplementation Affects Metabolic Status in Vitamin D-Deficient Type 2 Diabetic Patients with Coronary Artery Disease

Abstract

Background: Vitamin D might be beneficial in diabetic patients with coronary artery disease (CAD) through its favorable effects on metabolic profiles and biomarkers of inflammation and oxidative stress. Objective: This study was performed to examine the effects of 60 of vitamin D supplementation on metabolic status in diabetic patients with CAD. Methods: This randomized, double-blind, placebo-controlled clinical trial was conducted in 60 vitamin D-deficient diabetic patients with CAD aged 40-85 y. Subjects were randomly assigned into 2 groups to take either 50,000-IU vitamin D supplements (n = 30) or placebo (n = 30) every 2 wk for+/-mo. Fasting blood samples were obtained at the beginning of the study and after the 6-mo intervention to quantify glycemic indicators, lipid concentrations, and biomarkers of inflammation and oxidative stress. Results: Compared with placebo, vitamin D supplementation resulted in significant reductions in fasting plasma glucose (214.9+/-7.1 compared with + 19.3+/-7.1 mg/dL; P = 0.001), serum insulin (22.7+/-1.1 compared with + 1.8+/-1.1 mIU/mL; P = 0.006), homeostasis model assessment of insulin resistance (20.76 0.3 comparedwith + 0.56 0.3; P = 0.01), and b cell function (29.164.2 comparedwith + 5.764.2; P = 0.01) and a significant increase in serumvitamin D (+ 6.860.9 compared with + 0.1+/-0.9 ng/mL; P < 0.001) and the Quantitative Insulin Sensitivity Check Index (+ 0.008+/-0.004 compared with 20.007+/-0.004; P = 0.01). In addition, changes in serum high-sensitivity C-reactive protein (hs-CRP; 21.0+/-0.5 compared with + 0.66 0.5 mg/mL; P = 0.02), plasma nitric oxide (NO; + 7.06 2.0 comparedwith24.66 2.0 mmol/L; P < 0.001), total reduced glutathione (GSH; + 104+/-16.4 compared with + 24.8+/-16.4 mmol/L; P = 0.001), and malondialdehyde concentrations (20.2+/-0.1 compared with + 0.2+/-0.1 mmol/L; P < 0.001) in the supplemented group were significantly different fromthe changes in these indicators in the placebo group. Conclusions: Overall, 6mo of vitamin D supplementation among vitamin D-deficient diabetic patients with CAD had beneficial effects on glycemic control and serum hs-CRP, NO, GSH, and malondialdehyde concentrations. This trial was registered on the Iranian website (www. irct. ir) for registration of clinical trials as IRCT201510315623N56.