title: Hyperhomocyst(e)inemia is associated with impaired endothelium-dependent vasodilation in humans.
abstract: BACKGROUND
  Hyperhomocyst(e)inemia is a risk factor for atherosclerosis and is prevalent in the elderly. The objective of this study was to determine whether hyperhomocyst(e)inemia is associated with impaired endothelium-dependent vasodilation in humans.
  
  
  RESULTS
  High-resolution vascular ultrasonography was used to study endothelium-dependent and -independent vasodilation in a nonatherosclerotic peripheral conduit artery of 26 elderly hyperhomocyst(e)inemic subjects and 15 age- and sex-matched subjects with normal homocysteine levels. Flow-mediated, endothelium-dependent (nitric oxide-mediated) vasodilation was assessed by measuring the percent change in brachial artery diameter during reactive hyperemia. Endothelium-independent vasodilation was assessed after the administration of 0.4 mg sublingual nitroglycerin. Endothelium-dependent vasodilation was significantly impaired in the hyperhomocyst(e)inemic subjects compared with control subjects (3.7 +/- 0.6% versus 8.1 +/- 1.2%; P = .004), whereas endothelium-independent vasodilation was not different between the two groups (10.1 +/- 1.6% versus 9.3 +/- 1.5%; P = NS). In a linear regression analysis with serum homocysteine concentration, folic acid, age, sex, cholesterol (serum total, LDL, or HDL cholesterol), mean arterial blood pressure, use of antihypertensive medication, and baseline brachial artery diameter included as covariates, serum homocysteine concentration emerged as the only significant predictor of flow-mediated vasodilation.
  
  
  CONCLUSIONS
  These data indicate that hyperhomocyst(e)inemia is associated with impaired endothelium-dependent vasodilation in humans and suggest that the bioavailability of nitric oxide is decreased in hyperhomocyst(e)inemic humans.
authors.affiliation: Vascular Medicine and Atherosclerosis Unit, Cardiovascular Division, Brigham and Women's Hospital, Boston, Mass 02115, USA.
authors.forename: A
authors.initials: A
authors.lastname: Tawakol
authors.forename: T
authors.initials: T
authors.lastname: Omland
authors.forename: M
authors.initials: M
authors.lastname: Gerhard
authors.forename: J T
authors.initials: JT
authors.lastname: Wu
authors.forename: M A
authors.initials: MA
authors.lastname: Creager
mesh_terms: D000368:Aged; D001161:Arteriosclerosis / Q000097:blood / Q000453:epidemiology; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000502:physiology / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000502:physiology / Q000503:physiopathology*; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006711:Homocystine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000000981:diagnostic imaging / Q000502:physiology / Q000503:physiopathology*; D009569:Nitric Oxide / Q000502:physiology; D005996:Nitroglycerin; D011237:Predictive Value of Tests; D012016:Reference Values; D012044:Regression Analysis; D012307:Risk Factors; D018608:Ultrasonography, Doppler; D014664:Vasodilation; D014665:Vasodilator Agents
chemical_list: D014665:Vasodilator Agents; D006710:Homocysteine; D009569:Nitric Oxide; D006711:Homocystine; D005996:Nitroglycerin