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Entero-insular axis and postprandial insulin differences in African American and European American children^1,2,3,4

¹ From the Departments of Nutrition Sciences (PBH, JRF, WTG, and BAG) and Critical Care (WMG), and the Clinical Nutrition Research Center (PBH, JRF, WTG, WMG, and BAG), University of Alabama at Birmingham, Birmingham, AL

Background: African Americans have a greater insulin response after glucose challenge than do European Americans. Factors underlying this response are unknown.

Objective: We determined the insulin, C-peptide, and incretin responses to a mixed macronutrient meal in African American and European American children. We hypothesized that 1) African Americans would have greater postprandial insulin and C-peptide responses, 2) African Americans would have higher incretin responses, and 3) the greater β cell response among African Americans would be explained by greater incretin responses.

Design: Subjects were 34 African American and 18 European American children. Glucose, insulin, C-peptide, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured after the subjects consumed a liquid mixed meal. Insulin, C-peptide, and incretin responses were derived from the area under the curve (AUC) for minutes 0–30 (early response) and minutes 30–180 (late response) after meal ingestion.

Results: The early insulin response was higher in African American (14 565 ± 6840 pmol/L x 30 min) than in European American (7450 ± 4077 pmol/L x 30 min; P < 0.01) children. Early C-peptide AUC did not differ by ethnicity (African Americans: 34.8 ± 12.5; European Americans: 28.6 ± 12.5 nmol/L x 30 min; P = 0.10). Early and late GLP-1 responses were lower in African Americans than in European Americans: 108.1 ± 56.4 compared with 160.5 ± 90.8 pmol/L x 30 min and 509.4 ± 286.9 compared with 781.9 ± 483.4 pmol/L x 150 min, respectively (P < 0.05 for both). The GIP response did not differ between groups.

Conclusions: The greater early insulin response in African Americans than in European Americans is not due to differences in circulating GLP-1 or GIP and may be due to lesser insulin clearance. Further research is needed to determine the physiologic implications of lower GLP-1 among African Americans.