Association between the C825T polymorphism of the G protein beta 3-subunitgene and hypertension in blacks

A polymorphism (C825T) of the G protein beta 3-subunit gene has been associ ated with low renin hypertension in whites, The aim of this study was to ex amine the C825T polymorphism in relation to hypertension in a population-ba sed study of black people of African origin who have high prevalence of low renin, salt-sensitive hypertension. A total of 428 men and women, aged 40 to 59 years (270 Caribbeans and 158 West Africans), who took part in a popu lation-based survey were studied. All were blacks and first-generation immi grants. The C825T polymorphism was detected by polymerase chain reaction fo llowed by restriction-enzyme digestion. The prevalence of hypertension (sup ine blood pressures greater than or equal to 160 systolic and/or 95 mm Hg d iastolic or on drug therapy) was 43%. The distribution of the genotypes (CC , CT, and TT) was in Hardy-Weinberg equilibrium with observed frequencies o f 4.0% (n=17), 33.6% (n=144), and 62.4% (n=267), respectively. Allele frequ encies were 20.8% for C and 79.2% for T. No difference was detected between Caribbeans and West Africans. A 3-fold higher risk of hypertension was fou nd among the carriers of the T variant both as heterozygotes (odds ratio [O R], 3.43 [95% CI, 0.94 to 12.4]) and homozygotes (OR, 3.87 [95% CI, 1.09 to 13.8]). The estimate of effect and the blood pressure values in the groups carrying the T variant suggested a dominant model for the T allele, This w as confirmed by a significant association between the T allele and hyperten sion (OR, 3.71 [95% CI, 1.05 to 13.1]), even when adjusted for age,sex, and body mass index (OR, 4.14 [95% CI, 1.11 to 15.4]). The study shows, for th e first time, a high frequency of the 825T allele in black people, and it p rovides evidence that the T allele may be a susceptibility factor for the d evelopment of hypertension in blacks. Given the high frequency of the T all ele, even a 2-fold increased risk of hypertension among the carriers of the T allele might account for 44% of the cases of hypertension in blacks.