1731-P: Screening Human Islets to Identify Small Molecules Enhancing Glucagon Secretion under Hypoglycemia

In type 1 diabetes (T1D), α cell function is dysregulated with loss of glucagon secretion in response to hypoglycemia that precedes a secretory impairment of major α cell stimulus, epinephrine, produced by adrenal chromaffin cells. Recurrent hypoglycemic episodes, which correlate with progressive β cell loss in T1D, lead to an impairment of sympathoadrenal responses and the risk of a life-threatening hypoglycemia unawareness syndrome. To discover new molecules that activate signaling pathways in human α cells and promote glucagon secretion during hypoglycemia, we used our primary human pseudoislet system for screening of 1027 FDA-approved compounds from ion channel and GPCR compound library (APExBIO). The compound screen was optimized for pseudoislet formation in 96-well format including state-of-the-art liquid-handling platforms for compound addition and analysis of glucagon secretion from a single pseudoislet in the presence of carefully selected internal standards. Using this approach, we identified several ‘hit’ compounds targeting both ion channels and GPCRs that increased glucagon secretion above positive controls including 1.7 mM glucose + 20 mM arginine. Notably, nearly 30 compounds targeting GPCRs including opioid, oxytocin, histamine H1, dopamine, 5-HT, adrenergic, and muscarinic receptors elicited robust glucagon responses across multiple human islet donors (N=3). Additionally, we leveraged our single cell and bulk RNA-seq datasets to evaluate target specificity and facilitate the compound selection process based on target expression changes in T1D α cells. Overall, the primary human pseudoislet system is ideal for the screen because it maintains 3-D islet cell arrangement, islet microenvironment, and allows for generation of α cell-enriched, T1D-like pseudoislets as a model system for further compound validation. This could lead to repurposing of FDA-approved drugs for treatment of hypoglycemia and rapid translation for clinical testing.