Asymmetric dimethylarginine, smoking, and risk of coronary heart disease in apparently healthy men: prospective analysis from the population-based Monitoring of Trends and Determinants in Cardiovascular Disease/Kooperative Gesundheitsforschung in der Region Augsburg study and experimental data.

BACKGROUND: An increased plasma concentration of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) predicts adverse clinical outcome in patients with coronary heart disease. We investigated the association between plasma concentrations of ADMA and risk in initially healthy smoking and nonsmoking men.
METHODS: Participants for this nested case-control study came from the population-based Monitoring of Trends and Determinants in Cardiovascular Disease/Kooperative Gesundheitsforschung in der Region Augsburg study. ADMA was measured by liquid chromatography-tandem mass spectrometry in 88 men with incident coronary events (fatal and nonfatal myocardial infarction and sudden cardiac death) and 254 age-matched controls, with a median (interquartile range) follow-up of 6.2 (3.3-7.9) years.
RESULTS: After adjustment for potential confounders, the relative risk for a future coronary event was 2.00 [95% confidence interval (CI) 1.27-3.16; P = 0.003] for smokers compared with nonsmokers and 1.35 (95% CI 0.78-2.33; P = 0.282) for the top vs the bottom tertile of the ADMA distribution. In cases and controls, lower ADMA plasma concentrations were observed in smokers. Analysis of ADMA-associated risk in smokers and nonsmokers separately revealed substantial differences: the adjusted relative risk for future coronary events (top vs bottom tertile of the ADMA distribution) was 0.48 (95% CI 0.16-1.46; P = 0.198) in smokers and 2.40 (95% CI 1.14-5.08; P = 0.021) in nonsmokers. Exposure of human endothelium-derived EAhy 926 cells to tobacco smoke enhanced expression of the ADMA metabolizing enzyme dimethylarginine dimethylaminohydrolase 2 and reduced ADMA concentration.
CONCLUSIONS: In apparently healthy men, increased ADMA predicts the risk for coronary events in nonsmokers, but not in smokers. This may be explained in part by an alteration of ADMA metabolism by tobacco smoke.