African Americans (AA) have a greater post-glucose-challenge insulin response than European Americans (EA). Factors underlying this response are unknown.
To determine the insulin, C-peptide, and incretin responses to a mixed macronutrient meal in AA and EA children. We hypothesized that: 1) AA would have greater postprandial insulin and C-peptide responses; 2) AA would have higher incretin responses; 3) the greater β-cell response among AA would be explained by greater incretin responses.
Subjects were 34 AA and 18 EA children. Glucose, insulin, C-peptide, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured after consumption of 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”) following meal ingestion
The early insulin response was higher in AA (14,565 ±6,840 pmol/L × 30min) vs. EA (7,450 ±4,077 pmol/L × 30min, P<0.001). Early C-peptide AUC did not differ by ethnicity (34.8 ±12.5 vs. 28.6 ±12.5nmol/L ×30mins, for AA and EA, respectively; P=0.10). Early and late GLP-1 responses were lower in AA vs EA (108.1 ±56.4 vs. 160.5 ±90.8pmol/L ×30mins) and (509.4 ±286.9 vs. 781.9 ±483.4pmol/L ×150mins), respectively (P<0.05 for both). The GIP response did not differ between groups.
Greater early insulin response in AA vs. EA 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 AA.