Effect of high doses of vitamin D on arterial properties, adiponectin, leptin and glucose homeostasis in type 2 diabetic patients

Abstract

Background & aims: Vitamin D supplementation has the potential to alleviate the cardiovascular damage in diabetic patients. The present study was designed to evaluate long term impact of high doses of vitamin D on arterial properties, glucose homeostasis, adiponectin and leptin in patients with type 2 diabetes mellitus.

Methods and results: In randomized, placebo-controlled study 47 diabetic patients were assigned into two groups: Group 1 received oral daily supplementation with vitamin D at a dose of 1000 U/day for 12 months. Group 2 received matching placebo capsules. Blood sampling for metabolic parameters, including fasting glucose, lipid profile, HbA1C, insulin, hs-CRP, 25 OH Vit D, adiponectin and leptin was performed at baseline and at the end of the study. Insulin resistance was assessed by homeostasis model assessment (HOMA-IR). Central aortic augmentation index (AI) was evaluated using SphygmoCor.

Results: The two groups were similar at baseline in terms of hemodynamic parameters. After 12 months, AI decreased significantly during the treatment period in patients received vitamin D (p < 0.0001) and did not change in placebo group. Glucose homeostasis parameters, leptin as well as leptin adiponectin ratio did not change in both groups. 25 OH Vit D level significantly increased (p = 0.022) and circulating adiponectin marginally increased (p = 0.065) during 12 month treatment period in active treatment and did not change in placebo group.

Conclusions: High doses of vitamin D supplementation in diabetic patients was associated with significant decrease in AI during one year treatment. This beneficial vascular effect was not associated with improvement in glucose homeostasis parameters.

Keywords: Arterial stiffness; Circulating adiponectin; Glucose homeostasis parameters; Vitamin D.