title: Antioxidant vitamin C improves endothelial function in obstructive sleep apnea.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) is associated with oxidative stress, endothelial dysfunction, and increased cardiovascular morbidity and mortality.
  
  
  OBJECTIVE
  We tested the hypothesis that endothelial dysfunction in patients with OSA is linked to oxidative stress.
  
  
  METHODS
  In the present study, we measured flow-mediated dilation (FMD) of the brachial artery by ultrasound in 10 otherwise healthy, untreated patients with OSA and 10 age-and sex-matched control subjects without sleep-disordered breathing before and after intravenous injection of the antioxidant vitamin C. The investigator performing the FMD measurements was blinded to the status of the patients.
  
  
  RESULTS
  When compared with control subjects, baseline FMD was significantly reduced in the patients with OSA. After intravenous injection of 0.5 g vitamin C, vasoreactivity remained unchanged in the control subjects. In the patients with OSA, ascorbate led to an increase in FMD to a level comparable to that observed in the control group.
  
  
  CONCLUSIONS
  The reduced endothelial-dependent vasodilation in untreated patients with OSA acutely improves by the free radical scavenger vitamin C. These results are in favor of oxidative stress being responsible for the endothelial dysfunction in OSA. Antioxidant strategies should be explored for the treatment of OSA-related cardiovascular disease.
authors.affiliation: Division of Cardiology and Angiology, Department of Internal Medicine, Justus-Liebig University, Giessen, Germany. mathias.grebe@innere.med.uni-giessen.de
authors.forename: Mathias
authors.initials: M
authors.lastname: Grebe
authors.forename: Hans Joachim
authors.initials: HJ
authors.lastname: Eisele
authors.forename: Norbert
authors.initials: N
authors.lastname: Weissmann
authors.forename: Christian
authors.initials: C
authors.lastname: Schaefer
authors.forename: Harald
authors.initials: H
authors.lastname: Tillmanns
authors.forename: Werner
authors.initials: W
authors.lastname: Seeger
authors.forename: Richard
authors.initials: R
authors.lastname: Schulz
mesh_terms: D000286:Administration, Sublingual; D000975:Antioxidants / Q000008:administration & dosage / Q000627:therapeutic use*; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000627:therapeutic use*; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin / Q000008:administration & dosage; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000188:drug therapy* / Q000503:physiopathology; D016896:Treatment Outcome; D014463:Ultrasonography; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000008:administration & dosage
chemical_list: D000975:Antioxidants; D014665:Vasodilator Agents; D005996:Nitroglycerin; D001205:Ascorbic Acid