Investigating Increased Insulin Secretion Upon Casp1/Ripk3 Inhibition/Deletion

Abstract

Inflammation and intrinsic cell death pathways contribute to the pathology of type 2 diabetes (T2D) by promoting β-cell dysfunction and impairing insulin secretion. In its canonical form, Caspase-1 (Casp1) and other inflammasome components work together to activate proinflammatory cytokine release, while receptor-interacting protein kinase 3 (Ripk3) participates in the programmed cell death pathway, necroptosis. Our previous work demonstrated that male and female whole-body Casp1/11 and Ripk3 double knockout (DKO) mice fed a low-fat diet (LFD) exhibited improved glucose tolerance and enhanced glucose-stimulated insulin secretion (GSIS). Here, we investigated mechanisms underlying this phenotype using genetic and pharmacological approaches. Firstly, despite minimal differences in transcriptomic changes in key β-cell target genes between genotypes, immunofluorescence staining of DKO pancreatic sections revealed a reduction in urocortin-3 (UCN3) area. This suggests a potential disruption of the UCN3-somatostatin negative feedback loop, which normally inhibits insulin secretion. We then determined that the non-canonical pyroptosis mediator Casp11 does not contribute to the observed glucose phenotype in DKO mice. Next, using selective Casp1 and Ripk3 inhibitors in mice and isolated islets, we observed increased glucose tolerance and GSIS, similar to those observed in the genetic model. Finally, we found that administration of exogenous UCN3 produced a blunted response in DKO mice, an effect not observed with the addition of the somatostatin analogue octreotide, suggesting that deletion of Casp1 and Ripk3 alters δ-cell function. Understanding how Casp1 and Ripk3 together contribute to glucose metabolism and islet function under LFD conditions can help define their non-canonical roles in the absence of chronic inflammation.