Vitamin D improves endothelial function in patients with Type 2 diabetes mellitus and low vitamin D levels

J. A. Sugden, J. I. Davies, M. D. Witham*, A. D. Morris† and A. D. Struthers

Department of Clinical Pharmacology, Division of Medicine and Therapeutics, *Section of Ageing and Health, Division of Medicine and Therapeutics and †Division of Medicine and Therapeutics, Ninewells Hospital and Medical School, Dundee, UK

Aims—To test whether a single large dose of vitamin D2 can improve endothelial function in patients with Type 2 diabetes mellitus and low serum 25-hydroxyvitamin D levels.
Methods—Double-blind, parallel group, placebo-controlled randomized trial. A single dose of 100 000 IU vitamin D2 or placebo was administered to patients with Type 2 diabetes over the winter, when levels of circulating 25-hydroxyvitamin D were likely to be lowest. Patients were enrolled if their baseline 25-hydroxyvitamin D level was < 50 nmol/l. Endothelial function and blood pressure were measured and fasting blood samples were taken at baseline and 8 weeks after administration of vitamin D.
Results—Forty-nine per cent of subjects screened had 25-hydroxyvitamin D levels < 50 nmol/l. Thirty-four subjects completed the study, with a mean age of 64 years and a baseline 25-hydroxyvitamin D level of 38.3 nmol/l. Vitamin D supplementation increased 25-hydroxyvitamin D levels by 15.3 nmol/l relative to placebo and significantly improved flow mediated vasodilatation (FMD) of the brachial artery by 2.3%. The improvement in FMD remained significant after adjusting for changes in blood pressure. Vitamin D supplementation significantly decreased systolic blood pressure by 14 mmHg compared with placebo; this did not correlate with change in FMD.
Conclusions— Vitamin D insufficiency is common in patients with Type 2 diabetes during winter in Scotland. A single large dose of oral vitamin D2 improves endothelial function in patients with Type 2 diabetes and vitamin D insufficiency. Diabet. Med. 25, 320–325 (2008)

blood pressure, endothelial function, vitamin D (…)