title: Improvement of endothelial function and insulin sensitivity with vitamin C in patients with coronary spastic angina: possible role of reactive oxygen species.
abstract: OBJECTIVE
  This study was designed to examine the effect of antioxidant supplementation on the endothelial function and insulin sensitivity in patients with coronary spastic angina (CSA).
  
  
  BACKGROUND
  Insulin resistance may play a key role in coronary heart disease, and there is a possible link between acetylcholine-induced coronary vasoconstriction and hyperinsulinemia in patients with CSA. Endothelial dysfunction is present in the systemic arteries in CSA patients, and reactive oxygen species may cause inactivation of nitric oxide in these patients.
  
  
  METHODS
  We measured flow-mediated dilation of the brachial artery using ultrasound technique in 22 patients with CSA and 20 control subjects. We also evaluated glucose tolerance using a 75-g oral glucose tolerance test and insulin sensitivity using steady-state plasma glucose (SSPG) methods in the same patients.
  
  
  RESULTS
  The incidence of impaired glucose tolerance was higher in the CSA group than in the control group. Vitamin C infusion augmented flow-mediated dilation and decreased SSPG levels in the CSA group (from 3.27 +/- 0.77% to 7.00 +/- 0.59% [p < 0.001 by analysis of variance (ANOVA)] and from 177.3 +/- 13.3 to 143.1 +/- 14.9 mg/dl [p = 0.047 by ANOVA], respectively) but not in the control group (from 6.47 +/- 0.66% to 6.80 +/- 0.60% and from 119.8 +/- 11.7 mg/dl to 118.1 +/- 11.3 mg/dl, respectively). The steady-state plasma insulin levels were not affected by vitamin C infusion in either group.
  
  
  CONCLUSIONS
  Vitamin C improves both endothelial function and insulin sensitivity in patients with CSA. Thus, reactive oxygen species and/or decreased nitric oxide bioactivity may play an important role in the genesis of both endothelial dysfunction and insulin resistance in patients with CSA.
authors.affiliation: Department of Cardiovascular Medicine, Kumamoto University School of Medicine, Japan.
authors.forename: O
authors.initials: O
authors.lastname: Hirashima
authors.forename: H
authors.initials: H
authors.lastname: Kawano
authors.forename: T
authors.initials: T
authors.lastname: Motoyama
authors.forename: N
authors.initials: N
authors.lastname: Hirai
authors.forename: M
authors.initials: M
authors.lastname: Ohgushi
authors.forename: K
authors.initials: K
authors.lastname: Kugiyama
authors.forename: H
authors.initials: H
authors.lastname: Ogawa
authors.forename: H
authors.initials: H
authors.lastname: Yasue
mesh_terms: D000789:Angina, Unstable / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology*; D001205:Ascorbic Acid / Q000627:therapeutic use*; D001786:Blood Glucose; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000503:physiopathology*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D007328:Insulin; D001205:Ascorbic Acid