Association between -786TC polymorphism in the endothelial nitric oxide synthase gene and hypertension in the Tunisian population

Background: Nitric oxide (NO) is produced by endothelial cells and serves as a potent vasodilator. Several lines of evidence have shown that NO plays an important role in the regulation of blood pressure and regional blood flow. Recent genetic studies have shown an association between the -786TC polymorphism in the endothelial nitric oxide synthase gene (NOS3) and coronary artery diseases, but any possible association with hypertension has been controversial. In the present study, we examined a possible association between the -786TC polymorphism of the NOS3 gene and hypertension in a sample of the Tunisian population.

Methods: A total of 288 unrelated Tunisian patients with hypertension and 373 normotensive subjects were included in the study. The -786TC gene polymorphism was analyzed by PCR-RFLP.

Results: A significant difference in genotype distribution and allele frequency was observed between patients and controls. Patients with hypertension had a frequency of 19.7% for CC genotype, 52.9% for TC genotype and 27.3% for TT genotype. The control had a frequency of 14.7% for the CC genotype, 47.2% for the TC genotype and 38.1% for the TT genotype (χ²=9.09, p=0.01). The hypertension patient group showed a significant higher frequency of the C allele compared to the controls (0.46 vs. 0.38; χ²=8.26, p=0.004). The odds ratio of hypertension for C vs. T allele frequencies was statistically significant 1.59 (1.14-2.21) at 95% CI, p = 0.004 in men, whereas it was non-significant in women 1.21 (0.87-1.67), p=0.23.

Conclusion: The present study showed a significant and independent association between the -786TC gene polymorphism (presence of C allele) and hypertension in the Tunisian population.