Purpose: We tested the hypothesis that a critical biologic determinant of T2D disparities is based on ethnicity-related differences in pancreatic islet function.
Methods: Utilizing donor tissues from the NIDDK-funded Human Pancreas Analysis Program (HPAP) , we examined both insulin and glucagon secretion from nondiabetic and diabetic Caucasian and African American donor islets. Initially, a physiological amino acid mixture was used to stimulate glucagon secretion, followed by low and high glucose to stimulate insulin secretion and suppress glucagon secretion. During the high glucose step, IBMX (0.1 mM) is added to potentiate secretion of both hormones. Insulin and glucagon concentration in perifusates and islet extracts was measured by radioimmunoassay or ELISA. Statistical comparisons were drawn by repeated measures ANOVA.
Results: Comparing nondiabetic islets, we observed overlapping insulin secretion profiles between both ethnicities; however, glucagon secretion was distinctly greater in both nondiabetic African American (+111%) islets compared to nondiabetic Caucasian islets, under all interventions. In T2D, the reduction in insulin secretion was significantly greater in African American T2D donors (high glucose -76%; IBMX -76%) compared to Caucasian T2D donors (high glucose -47%; IBMX -50%) . More strikingly, glucagon secretion in T2D donors was markedly different based on ethnicity. Whereas Caucasian T2D islets exhibited a similar baseline of glucagon secretion compared to Caucasian controls, there was a marked reduction of glucagon secretion overall in African American T2D donors (-70%) compared to their corresponding controls. The largest detected difference was in IBMX-potentiation of glucagon secretion, which is higher in Caucasian T2D donors (+103%) but significantly decreased in African American T2D donors (-76%) . Preliminary analysis of hormone content in a subset of the donor islet preparations revealed no differences according to ethnicity.
Conclusions: We propose that ethnicity-related differences in nondiabetic islet function may contribute to the enhanced risk of T2D.
N. M. Doliba: None. M. Brissova: None. K. H. Kaestner: None. D. A. Stoffers: Other Relationship; Biomarin, Correlagen. J. Roman: None. A. V. Rozo: None. W. Qin: None. C. Liu: None. A. Naji: None. M. R. Rickels: Advisory Panel; Sernova, Corp., Vertex Pharmaceuticals Incorporated, Zealand Pharma A/S, Consultant; L-Nutra Inc. M. A. Atkinson: None. A. C. Powers: None.
This work is supported by 3UC4-112217-01S1 and U01-DK123594-02, UC4-DK-112217, UC4-DK-112232, and U01-DK-123716.