Evaluation of selected polymorphisms of the Mendelian hypertensive disease genes in the Japanese population.

It remains to be defined whether molecular variants of the genes underlying Mendelian forms of hypertension play some etiological role in essential hypertension. To pursue this issue, we focused on the following three genes: the epithelial sodium channel (ENaC), 11beta-hydroxysteroid dehydrogenase type 2, and mineralocorticoid receptor genes. Five sequence variations of these genes, which were either previously reported to show significant association with hypertension or identified as "mild" molecular variants, were chosen for our study. Each variation was screened in 247 severe hypertensive patients with early onset (<45 years) and any detectable variations were subsequently characterized in 291 older normotensive subjects (>60 years) for the case-control comparison. We also investigated the significance of association between the tested variants and biochemical parameters reflecting sodium-water homeostasis, such as plasma aldosterone concentration (PAC) and renin activity (PRA). Only the T663A variant (alpha-subunit of ENaC) turned out to be polymorphic in the Japanese population. In disagreement with positive associations previously reported in white and black subjects, we observed no significant association between T663A and hypertension, while allele frequencies of A663 were higher in Japanese (58-64%) compared with a reported prevalence of 29% in whites and 15% in blacks. T663A showed a borderline association (p=0.02) with the PAC/PRA ratio but not with PAC or PRA in the multivariate analysis. Our data did not support the association between Mendelian disease gene variants and essential hypertension in the Japanese. However, the present study did not definitively resolve this issue and further investigation is certainly warranted.