Heritability of angiotensin-converting enzyme and angiotensinogen - A comparison of US blacks and Nigerians

Angiotensinogen (AGT) and angiotensin I-converting enzyme (ACE) are heritab le traits, but whether the environmental context influences heritability ha s not been examined. Known genetic factors explain only a portion of variat ion in AGT and ACE, and levels of both proteins are influenced by the envir onment. The African diaspora provides an opportunity to compare these trait s in genetically related populations in contrasting environments. As part o f a study of the genetics of hypertension, we examined families that includ ed 1449 Nigerians and 1147 African Americans. Body mass index (weight [kg]/ height [m](2)) was 21 kg/m(2) in Nigeria and 29 kg/m(2) in the United State s, which is consistent with a large environmental contrast. AGT was conside rably higher among African Americans (1919 versus 1396, P<0.01), whereas AC E was higher in Nigerians (630 versus 517, P<0.01), A household effect was observed among the Nigerian families (spouse correlations 0.30 for AGT, 0.1 8 for ACE), and correlations among first-degree relatives were large (0.42 to 0.51 and 0.36 to 0.38 for AGT and ACE, respectively). Among African Amer icans, the familial aggregations of AGT and ACE were very limited, and the familial correlation for AGT was not different from zero. Heritability was 77% for AGT and 67% for ACE in Nigeria and 18% for AGT and ACE in the Unite d States. The familial patterns of body mass index and blood pressure were similar among both family sets. In conclusion, less familial aggregation wa s observed for AGT and ACE in the United States than in Nigeria, most likel y reflecting a greater random individual environmental effect on these trai ts. Variation in heritability of traits could influence the power of epidem iological studies to identify genetic effects.