Pharmacological or genetic inhibition ofScn9aprotects beta-cells while reducing insulin secretion in type 1 diabetes

Abstract

AbstractPancreatic β-cells are critical for systemic glucose homeostasis, and most of them undergo cell death during the pathogenesis of type 1 diabetes. We previously showed that a Na+channel inhibitor, carbamazepine, could protect β-cellsin vitroandin vivo. Here, we confirmed the effects of carbamazepine and other Na+channel inhibitors on human islets and focused on the specific role of the Na+channel gene,Scn9a(Nav1.7), in β-cell function and survival. BecauseScn9acan be found in multiple human and mouse islet cell types, we generated a β-cell specific knockout ofScn9aon the non-obese diabetic (NOD) background. We crossed anScn9aflox/floxallele onto theIns1Creknock-in mouse line resulting in the following genotypes: knockout (NOD.Ins1Cre;Scn9aflox/flox), heterozygous (NOD.Ins1Cre;Scn9aflox/wt), and wildtype littermate controls (NOD.Ins1Cre;Scn9awt/wt). We observed near complete ablation of Na+currents in knockout β-cells, and intermediate Na+currents in the heterozygotes. Insulin secretion in response to 15 mM glucose, but not lower concentrations, was significantly reduced from NOD.Ins1Cre;Scn9aflox/floxand NOD.Ins1Cre;Scn9awt/wtislets from both male and female mice. These effects of carbamazepine on insulin secretionin vitrowere not additive to the effects ofScn9aknockout, suggesting thatScn9ais the main target of carbamazepine in β-cells that is relevant for insulin secretion. CompleteScn9adeletion also protected β-cells from deathin vitro, similarly and non-additively to carbamazepine treatment. Finally, we assessed diabetes incidence in Nod.Scn9aflox/floxmice and NOD.Ins1Cre;Scn9awt/wtmice injected with AAV8-Ins1Crevirus and a found significant reduction in diabetes incidence in β-cell specific knockout mice compared with littermate controls. Collectively, our data show theScn9aplays important roles in β-cell function, but also contributes to β-cell death and type 1 diabetes progression.Scn9ais a novel drug target to preserve β-cells in type 1 diabetes.