1474-P: Testosterone Amplifies Glucose-Stimulated Insulin Secretion from Male ß-Cells via Soluble Adenylate Cyclase

Male mice with elimination of the androgen receptor (AR) in islet β cells (βARKO) exhibit blunted glucose-stimulated insulin secretion (GSIS) , leading to hypoinsulinemia and hyperglycemia. We showed that dihydrotestosterone (DHT) activation of an extranuclear AR in β cells potentiates GSIS by amplifying the insulinotropic action of islet-derived and exogenous GLP-1 via GLP-1R in mouse and human islets. Using electron microscopy, we observe that DHT increases the size of granules and the frequency of multivesicular granules, suggesting that DHT promotes multivesicular exocytosis. Using live β cell models expressing organelle-specific cAMP sensors and novel allosteric inhibitors in human islets, we show that DHT enhances the ability of GLP-1 to produce cAMP at the plasma membrane and endosomes and enhances islet GSIS via the bicarbonate (HCO₃^-) sensor, soluble adenylate cyclase (sAC) . The end-products of glucose metabolism in the TCA cycle are CO₂ and H₂O, which is followed by rapid conversion of CO₂ to HCO₃^- and H⁺ by carbonic anhydrase (CA) . Therefore, CO₂ production is translated to HCO₃^- and specifically sensed by sAC. Bioenergetics analysis of DHT-stimulated respiration in mouse islets using a Seahorse Analyser revealed that DHT decreases glycolytic acidification and increases mitochondrial acidification (H⁺ efflux rate) , suggesting that DHT increases mitochondrial production of CO₂ followed by conversion to HCO₃^- and H⁺, allowing HCO₃^- to stimulate sAC. We discuss experiments of single-cell transcriptomics, proteomics and metabolomics dissecting the impact of DHT on human islets glycolysis and mitochondrial CO₂ production. Consistent with DHT increasing production of CO₂ followed by conversion to HCO₃^- by CAand activation of sAC, in cultured human male islets, the CA inhibitor acetazolamide blunted DHT-enhancement of GSIS. Together these experiments provide novel insights into the role of DHT action via an extranuclear AR in enhancing GSIS.