Insulin C-peptide secretion on-a-chip to measure the dynamics of secretion and metabolism from individual islets

Abstract

Summary: First-phase glucose-stimulated insulin secretion is mechanistically linked to type 2 diabetes, yet the underlying metabolism is difficult to discern due to significant islet-to-islet variability. Here, we miniaturize a fluorescence anisotropy immunoassay onto a microfluidic device to measure C-peptide secretion from individual islets as a surrogate for insulin (InsC-chip). This method measures secretion from up to four islets at a time with ∼7 s resolution while providing an optical window for real-time live-cell imaging. Using the InsC-chip, we reveal two glucose-dependent peaks of insulin secretion (i.e., a double peak) within the classically defined 1st phase (<10 min). By combining real-time secretion and live-cell imaging, we show islets transition from glycolytic to oxidative phosphorylation (OxPhos)-driven metabolism at the nadir of the peaks. Overall, these data validate the InsC-chip to measure glucose-stimulated insulin secretion while revealing new dynamics in secretion defined by a shift in glucose metabolism. Motivation: Insulin secretion dynamics reflect islet β cell function and dysfunction in disease. Measurement of individual islet responses relative to metabolism is critical since functional heterogeneity has been reported in both rodents and humans. Therefore, we designed the InsC-chip to measure insulin secretion from multiple individual islets with high temporal resolution while leaving the tissue optically accessible for live-cell metabolic imaging.

Keywords

• CP: Biotechnology
• CP: Metabolism