title: Vitamin D improves endothelial function in patients with Type 2 diabetes mellitus and low vitamin D levels.
abstract: 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.
authors.affiliation: Department of Clinical Pharmacology, Division of Medicine and Therapeutics, Ninewells Hospital and Medical School, Dundee, UK. j.a.sugden@dundee.ac.uk
authors.forename: J A
authors.initials: JA
authors.lastname: Sugden
authors.forename: J I
authors.initials: JI
authors.lastname: Davies
authors.forename: M D
authors.initials: MD
authors.lastname: Witham
authors.forename: A D
authors.initials: AD
authors.lastname: Morris
authors.forename: A D
authors.initials: AD
authors.lastname: Struthers
mesh_terms: 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
chemical_list: D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2