Metabolic characteristics of African descendants: a comparative study of African-Americans and Ghanaian immigrants using minimal model analysis

Abstract

We have previously demonstrated that glucose-tolerant American blacks manifest significantly higher insulin concentrations and a lower insulin sensitivity than native African blacks who reside in their respective countries. It is, however, unknown whether the serum glucose, beta-cell function and insulin sensitivity are different in native Africans and African-Americans who reside in the same environments. We have studied 68 healthy American blacks and age- and weight-matched 30 African blacks recently immigrated from Ghana residing in Franklin County, Ohio, USA. Each subject underwent a standard oral glucose tolerance test to determine glucose tolerance status. Insulin sensitivity index (Si) and glucose effectiveness (Sg) were measured by the insulin-modified, frequently-sampled intravenous glucose tolerance test. The body composition variables were measured by the bioelectrical impedance analyser and body fat distribution pattern by the waist-hip ratio. The clinical characteristics were identical in the African-American and the African blacks; the mean fasting serum glucose, insulin and C-peptide levels were not different. Following the oral and intravenous glucose administration, the mean peak and incremental areas of serum glucose, insulin and C-peptide were not different in the two groups. The mean Si (3.1±0.7 vs 2.4±0.3×10-4·(min/ΜU·l-1)-1 and Sg (2.5±0.3 vs 2.7±0.2×10-2·min-1) were not significantly different in the American and African blacks, respectively. In summary, the metabolic parameters measured in the American blacks and recent African immigrants were identical. We speculate that, in contrast to the indigenous Africans who reside in their native countries, migration to the western world results in rapid "adaptation" in glucoregulation, beta-cell function and insulin sensitivity, similar to those of American blacks. © 1995 Springer-Verlag.