Endothelial nitric oxide synthase -786T>C, but not 894G>T and 4a4b, polymorphism influences plasma homocysteine concentrations in persons with normal vitamin status.

Background: Nitric oxide (NO) plays a relevant role in various events during atherogenesis. In vitro data suggest that NO may modulate homocysteine (Hcy) concentrations. The aim of this study was to investigate the role of endothelial nitric oxide synthase (eNOS) -786T>C, 894G>T, and 4a4b polymorphisms in influencing Hcy concentrations.

Methods: Blood samples were obtained from 1287 unrelated persons. Plasma Hcy was measured by fluorescence polarization immunoassay, folate and vitamin B(12) by RIA, vitamin B(6) by HPLC, and eNOS and methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms by PCR with restriction fragment length polymorphism analysis.

Results: MTHFR 677C>T polymorphism significantly influenced Hcy concentrations after adjustment for all confounding variables (P <0.0001 for trend). Univariate analysis showed that the eNOS -786T>C polymorphism, but not 894G>T and 4a4b, was significantly associated with the risk of having Hcy in the third tertile [>13.4 micromol/L; odds ratio (OR) = 1.2; 95% confidence interval (CI), 1.02-1.5; P = 0.03]. After adjustment for all variables known to influence Hcy, the -786T>C polymorphism still influenced Hcy concentrations (OR = 1.9; 95% CI, 1.1-3.2; P = 0.01). By analyzing the influence of eNOS polymorphisms on plasma Hcy concentrations according to vitamin concentrations (folate, vitamin B(6), and vitamin B(12)), age, and smoking habits, we found a significant association between the eNOS -786T>C polymorphism and Hcy in nonsmokers, in persons with normal vitamin status, and in persons <60 years.

Conclusion: The eNOS -786T>C polymorphism, but not 894G>T and 4a4b, influences plasma Hcy concentrations mildly but significantly and independently.