Affiliation:
1. Clinical Endocrine Section, Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
Abstract
Abstract
Background
Primary insulin hypersecretion predicts type 2 diabetes (T2DM) independent of insulin resistance. Enhanced β-cell glucose responsivity contributes to insulin hypersecretion. African Americans (AAs) are at a higher risk for T2DM than non-Hispanic Whites (NHWs). Whether AAs manifest primary insulin hypersecretion is an important topic that has not been examined systematically.
Objective
To examine if nondiabetic AA adults have a higher β-cell glucose responsivity compared with NHWs.
Methods
Healthy nondiabetic AA (n = 18) and NHW (n=18) subjects were prospectively recruited. Indices of β-cell function, acute C-peptide secretion (X0); basal (Φ B), first-phase (Φ 1), second-phase (Φ 2), and total β-cell responsivity to glucose (Φ TOT), were derived from modeling of insulin, C-peptide, and glucose concentrations during an intravenous glucose tolerance test. Insulin sensitivity was assessed by the hyperinsulinemic–euglycemic glucose clamp technique.
Results
Glucose disposal rate (GDR) during clamp was similar in AAs and NHWs (GDR: [AA] 12.6 ± 3.2 vs [NHW] 12.6 ± 4.2 mg/kg fat free mass +17.7/min, P = .49). Basal insulin secretion rates were similar between the groups. AA had significantly higher X0 (4423 ± 593 vs 1807 ± 176 pmol/L, P = .007), Φ 1 [377.5 ± 59.0 vs 194.5 ± 26.6 (109) P = 0.03], and Φ TOT [76.7 ± 18.3 vs 29.6 ± 4.7 (109/min), P = 0.03], with no significant ethnic differences in Φ B and Φ 2.
Conclusions
Independent of insulin sensitivity, AAs showed significantly higher first-phase and total β-cell responsivity than NHWs. We propose that this difference reflects increased β-cell responsivity specifically to first-phase readily releasable insulin secretion. Future studies are warranted to identify mechanisms leading to primary β-cell hypersensitivity in AAs.
Funder
Intramural Research Program
National Institute of Diabetes and Digestive and Kidney Diseases
Subject
Biochemistry (medical),Clinical Biochemistry,Endocrinology,Biochemistry,Endocrinology, Diabetes and Metabolism
Cited by
10 articles.
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