title: Vitamin C improves endothelium-dependent vasodilation in patients with insulin-dependent diabetes mellitus.
abstract: OBJECTIVE
  We sought to determine whether the antioxidant vitamin C improves endothelium-dependent vasodilation of forearm resistance vessels in patients with insulin-dependent diabetes mellitus.
  
  
  BACKGROUND
  Endothelium-dependent vasodilation is impaired in patients with diabetes mellitus. Oxidatively mediated degradation of endothelium-derived nitric oxide contributes to abnormal endothelium-dependent vasodilation in animal models of diabetes mellitus.
  
  
  METHODS
  The study group included 10 patients with insulin-dependent diabetes mellitus and 10 age-matched control subjects. Forearm blood flow was determined by venous occlusion plethysmography. Endothelium-dependent vasodilation was assessed by intraarterial infusion of methacholine (0.3 to 10 microg/min). Endothelium-independent vasodilation was assessed by intraarterial infusion of nitroprusside (0.3 to 10 microg/min). Forearm blood flow dose-response curves were determined for each drug infusion before and during concomitant infusion of vitamin C (24 mg/min).
  
  
  RESULTS
  In diabetic subjects, endothelium-dependent vasodilation was augmented by the concomitant infusion of vitamin C (p = 0.001). Endothelium-independent vasodilation was not affected by the concomitant infusion of vitamin C (p = NS). In control subjects, vitamin C infusion did not affect endothelium-dependent vasodilation (p = NS).
  
  
  CONCLUSIONS
  Vitamin C selectively restores the impaired endothelium-dependent vasodilation in the forearm resistance vessels of patients with insulin-dependent diabetes mellitus. These findings indicate that nitric oxide degradation by oxygen-derived free radicals contributes to abnormal vascular reactivity in humans with insulin-dependent diabetes mellitus.
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: F K
authors.initials: FK
authors.lastname: Timimi
authors.forename: H H
authors.initials: HH
authors.lastname: Ting
authors.forename: E A
authors.initials: EA
authors.lastname: Haley
authors.forename: M A
authors.initials: MA
authors.lastname: Roddy
authors.forename: P
authors.initials: P
authors.lastname: Ganz
authors.forename: M A
authors.initials: MA
authors.lastname: Creager
mesh_terms: D000328:Adult; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D004334:Drug Administration Schedule; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000503:physiopathology; D005260:Female; D005542:Forearm / Q000098:blood supply; D016166:Free Radical Scavengers / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007261:Infusions, Intra-Arterial; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D014655:Vascular Resistance / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D016166:Free Radical Scavengers; D001205:Ascorbic Acid