Association of a 27-bp repeat polymorphism in intron 4 of endothelial constitutive nitric oxide synthase gene with myocardial infarction in Tunisian patients

Abstract

Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) mediates endothelium-dependent vasodilatation and antithrombotic action. Controversial results regarding the association of eNOS gene (NOS3) polymorphisms with myocardial infarction (MI) have been reported. In the present study, we examined a possible association between a 27-base pair (bp) repeat polymorphism in intron 4 of the NOS3 gene and MI in a subgroup of the Tunisian population. A total of 310 Tunisian patients with MI and 250 healthy controls were included in the study. The NOS3 gene intron 4a4b variable number of tandem repeats polymorphism was analyzed by PCR. A significant difference in genotype distribution and allele frequency was observed between patients and controls. Patients with MI had a frequency of 4.8% for the 4a4a genotype, 33.9% for the 4a4b genotype and 61.3% for the 4b4b genotype. Controls had a frequency of only 1.6% for the 4a4a genotype, 24.4% for the 4a4b genotype and 74.0% for the 4b4b genotype (chi2=11.81, p=0.003). The MI patient group showed a significant higher frequency of the 4a allele compared to controls (0.218 vs. 0.139; chi2=5.81, p=0.01). In the present study, a significant association between the NOS34a/4b gene polymorphism (presence of 4a allele) and MI in the Tunisian population was found.