Influence of the C242T Polymorphism of the p22-phox Gene (CYBA) on the Interaction between Urinary Sodium Excretion and Blood Pressure in an Urban Brazilian Population

BACKGROUND: Reactive oxygen species are implicated in the physiopathogenesis of salt-induced hypertension and the C242T polymorphism of the p22-phox gene has been associated with higher superoxide production. This study investigated the impact of this polymorphism on the relationship between urinary sodium excretion (USE) and blood pressure levels in an urban Brazilian population. METHODS: We cross-sectionally evaluated 1,298 subjects from the city of Vitoria-ES, located in the Southeast region of Brazil, by clinical history, physical examination, anthropometry, analysis of laboratory parameters, USE measurement and p22-phox C242T polymorphism genotyping. RESULTS: No significant differences in studied parameters were detected between the studied genotype groups (CC vs. CT+TT). Systolic blood pressure exhibited significant correlation with USE only in T allele carriers (r = 0.166; p<0.001), while diastolic blood pressure and hypertension status correlated with USE in both genotypes albeit more weakly in subjects with CC genotype (r = 0.098; p = 0.021 and r = 0.105; p = 0.013, respectively) than in T carriers (r = 0.236; p<0.001 and r = 0.213; p<0.001, respectively). Regression analyses adjusted for confounding factors showed that USE remained independently associated with systolic (p<0.001) and diastolic blood pressure (p<0.001) and hypertension status (p = 0.004) only in T allele carriers. Finally, higher diastolic and systolic blood pressure levels were detected in T allele carriers than in CC genotype individuals in the highest tertile of USE. CONCLUSIONS: The p22-phox 242T allele is associated with higher blood pressure levels among subjects with higher USE in an urban Brazilian population.