Vitamin D improves endothelial function in patients with Type 2 diabetes mellitus and low vitamin D levels.
OBJECTIVE
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.
Sugden
J A
JA
Department of Clinical Pharmacology, Division of Medicine and Therapeutics, Ninewells Hospital and Medical School, Dundee, UK. j.a.sugden@dundee.ac.uk
Davies
J I
JI
Witham
M D
MD
Morris
A D
AD
Struthers
A D
AD
D015652:25-Hydroxyvitamin D 2 / Q000008:administration & dosage*; D000368:Aged; D001794:Blood Pressure / Q000187:drug effects*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy* / Q000503:physiopathology; D019587:Dietary Supplements; D004727:Endothelium / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013223:Statistics as Topic; D014807:Vitamin D / Q000008:administration & dosage*; D014808:Vitamin D Deficiency / Q000150:complications / Q000188:drug therapy
D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2