title: Randomized controlled trial of vitamin D supplement on endothelial function in patients with type 2 diabetes.
abstract: BACKGROUND
  Suboptimal vitamin D status is associated with endothelial dysfunction and an increased risk of cardiovascular diseases but it is unclear whether vitamin D supplementation is beneficial. The aim was to investigate the effect of vitamin D supplementation on endothelial function in patients with type 2 diabetes mellitus (DM).
  
  
  METHODS
  In a double-blind, placebo-controlled trial, we randomized 100 type 2 DM patients to vitamin D supplement (5000 IU/day, n = 50) or placebo (controls, n = 50) for 12 weeks. Assessment of vascular function with brachial artery flow-mediated dilatation (FMD), circulating levels of endothelial progenitor cells (EPCs) and brachial-ankle pulse wave velocity, and metabolic parameter, high-sensitivity C-reactive protein (hsCRP) and oxidative stress markers were performed before and after the supplementation.
  
  
  RESULTS
  After 12 weeks, vitamin D treated patients had significant increases in serum 25-hydroxyvitamin D [25(OH)D] concentration (treatment effect 34.7 ng/mL, 95% CI 26.4-42.9, P < 0.001) and serum ionized calcium (treatment effect 0.037 mmol/L, 95% CI 0.007-0.067, P = 0.018); decreased serum parathyroid hormone concentration (treatment effect -0.55 pmol/L, 95% CI -1.08 to -0.02, P = 0.042) compared to patients who received placebo. Nevertheless, vitamin D supplementation did not improve vascular function as determined by FMD, circulating EPC count or baPWV (all P > 0.05). Furthermore, hsCRP, oxidative stress markers, low- and high-density lipoprotein and glycated hemoglobin were also similar between two groups (all P > 0.05).
  
  
  CONCLUSIONS
  In patients with type 2 DM, 12 weeks oral supplementation of vitamin D did not significantly affect vascular function or serum biomarkers of inflammation and oxidative stress.
  
  
  BACKGROUND
  HKCTR-867, www.hkclinicaltrials.com.
authors.affiliation: Cardiology Division, Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
authors.forename: Yuen-Fung
authors.initials: YF
authors.lastname: Yiu
authors.forename: Kai-Hang
authors.initials: KH
authors.lastname: Yiu
authors.forename: Chung-Wah
authors.initials: CW
authors.lastname: Siu
authors.forename: Yap-Hang
authors.initials: YH
authors.lastname: Chan
authors.forename: Sheung-Wai
authors.initials: SW
authors.lastname: Li
authors.forename: Lai-Yung
authors.initials: LY
authors.lastname: Wong
authors.forename: Stephen W L
authors.initials: SW
authors.lastname: Lee
authors.forename: Sidney
authors.initials: S
authors.lastname: Tam
authors.forename: Eric W K
authors.initials: EW
authors.lastname: Wong
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
authors.forename: Bernard M Y
authors.initials: BM
authors.lastname: Cheung
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D001916:Brachial Artery / Q000187:drug effects / Q000503:physiopathology; D002097:C-Reactive Protein / Q000378:metabolism; D002118:Calcium / Q000097:blood; D002762:Cholecalciferol / Q000008:administration & dosage*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000503:physiopathology; D004311:Double-Blind Method; D004730:Endothelium, Vascular / Q000187:drug effects / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress / Q000187:drug effects; D063177:Pulse Wave Analysis; D014664:Vasodilation / Q000187:drug effects; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D015415:Biomarkers; D014807:Vitamin D; D002762:Cholecalciferol; D002097:C-Reactive Protein; C104450:25-hydroxyvitamin D; D002118:Calcium