8704 A DREADD-base Chemogenetic Approach to Quiz the Impact of the Delta Cell Input on Islet Hormone Secretion

Abstract Disclosure: D. Hakim Rodriguez: None. A. Tamayo: None. R. Rodriguez Diaz: None. E. Pereira: None. O. Alcazar: None. M. Makhmutova: None. The utilization of DREADDs (Designer Receptors Exclusively Activated by Designer Drugs) that are gated by clozapine-N-oxide (CNO) enables the selective stimulation of genetically specified cell types in vivo. This chemogenetic technology has been successfully applied in various in vivo studies, including those using mice, to remotely control GPCR signaling in specific cells, such as neurons, glia cells, pancreatic β-cells, or cancer cells. Utilizing DREADDs in the study of pancreatic islets, particularly in the somatostatin-producing δ-cells, could offer insights into the complex role of this hormone. Somatostatin is known to inhibit the secretion of other islet hormones, such as insulin and glucagon, but the detailed mechanisms of its action have not been fully elucidated. To address this, we generated mice enabling the expression of either the activator-DREADD Gq or the inhibitor-DREADD Gi in the mouse somatostatin secreting cells, including the islet δ-cell. Immunohistochemical staining of pancreas sections showed that DREADD were expressed and translocated to the membrane of the islet δ-cells. Perifusion experiments with isolated islets showed that δ-cells responded to CNO stimulation as expected. Islets bearing the DREADD Gq secreted somatostatin in a dose-dependent manner, while somatostatin secretion was inhibited in those expressing DREADD Gi. Secretion of insulin and glucagon were modulated upon activation or inhibition of δ-cells via CNO/DREADD manipulation. CNO-driven pulses of somatostatin stimulation caused asynchronous off responses of neighboring α-and β-cells during the time lapses of somatostatin secretion falloff, resulting in a net increment in the magnitude of both insulin and glucagon secretion. Meanwhile, inhibition of somatostatin secretion surprisingly unleashed glucagon secretion in non-permissive 16mM glucose. These results encouraged us to explore the potential application of DREADD tools in isolated human islets. We will discuss our current approaches whilst using viral vectors to drive the expression of DREADDs in human δ-cells and its impact in the overall islet secretory output. Presentation: 6/2/2024