title: Asymmetric dimethylarginine (ADMA): a novel risk factor for endothelial dysfunction: its role in hypercholesterolemia.
abstract: BACKGROUND
  Asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide (NO) synthase. Because endothelial NO elaboration is impaired in hypercholesterolemia, we investigated whether plasma concentrations of ADMA are elevated in young, clinically asymptomatic hypercholesterolemic adults. We further studied whether such elevation of ADMA levels was correlated with impaired endothelium-dependent, NO-mediated vasodilation and urinary nitrate excretion. In a randomized, double-blind, placebo-controlled study, we investigated whether these changes could be reversed with exogenous L-arginine.
  
  
  RESULTS
  We measured plasma levels of L-arginine, ADMA, and symmetrical dimethylarginine (SDMA) by high-performance liquid chromatography in 49 hypercholesterolemic (HC) and 31 normocholesterolemic (NC) humans. In 8 HC subjects, endothelium-dependent forearm vasodilation was assessed before and after an intravenous infusion of L-arginine or placebo and compared with 8 NC control subjects. ADMA levels were significantly elevated by >100% (2.17+/-0.15 versus 1.03+/-0.09 micromol/L; P<0.05) in HC subjects compared with NC adults. L-Arginine levels were similar, resulting in a significantly decreased L-arginine/ADMA ratio in HC subjects (27.7+/-2.4 versus 55. 7+/-5.4; P<0.05). In 8 HC subjects, intravenous infusion of L-arginine significantly increased the L-arginine/ADMA ratio and normalized endothelium-dependent vasodilation and urinary nitrate excretion. ADMA levels were inversely correlated with endothelium-mediated vasodilation (R=0.762, P<0.01) and urinary nitrate excretion rates (R=0.534, P<0.01).
  
  
  CONCLUSIONS
  We find that ADMA is elevated in young HC individuals. Elevation of ADMA is associated with impaired endothelium-dependent vasodilation and reduced urinary nitrate excretion. This abnormality is reversed by administration of L-arginine. ADMA may be a novel risk factor for endothelial dysfunction in humans.
authors.affiliation: Divisions of Cardiovascular Medicine, Clinical Pharmacology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: R H
authors.initials: RH
authors.lastname: Böger
authors.forename: S M
authors.initials: SM
authors.lastname: Bode-Böger
authors.forename: A
authors.initials: A
authors.lastname: Szuba
authors.forename: P S
authors.initials: PS
authors.lastname: Tsao
authors.forename: J R
authors.initials: JR
authors.lastname: Chan
authors.forename: O
authors.initials: O
authors.lastname: Tangphao
authors.forename: T F
authors.initials: TF
authors.lastname: Blaschke
authors.forename: J P
authors.initials: JP
authors.lastname: Cooke
mesh_terms: D001120:Arginine / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use; D004311:Double-Blind Method; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood* / Q000188:drug therapy / Q000201:enzymology / Q000503:physiopathology*; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D009994:Osmolar Concentration; D012307:Risk Factors
chemical_list: C018524:N,N-dimethylarginine; D001120:Arginine; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III