Effects of endothelial nitric oxide synthase tagSNPs haplotypes on nitrite levels in black subjects.

Haplotypes formed by clinically relevant polymorphisms in the endothelial nitric oxide synthase (eNOS) gene have been associated with variations in endogenous nitric oxide (NO) formation in white and black subjects. We examined whether further genetic variation and haplotypes of the eNOS gene, represented by the rs3918188, rs743506 and rs7830 tagSNPs (polymorphisms that represent the information of neighboring SNPs in linkage disequilibrium) affect endogenous NO formation in 181 healthy black subjects. We measured whole blood nitrite concentration as a marker of endogenous NO formation for each subject. We found that the heterozygotes CA for the tagSNP rs7830 (P=0.0278, OR=0.4839, CI 95% 0.2567-0.9121), as well as the haplotype "C-G-A" (P=0.0068), were more common in subjects with low circulating whole blood nitrite concentrations compared with subjects with high circulating whole blood nitrite concentrations, although the genotype finding is not significant after correction for multiple comparisons. These findings suggest that these tagSNPs of the eNOS gene and haplotypes are associated with low levels of nitric oxide production in blacks, and could be used as a marker of cardiovascular risk.