This study examined how genetic deletion or pharmacologic inhibition of caspase 1 (Casp1) and receptor interacting protein kinase 3 (Ripk3) affects metabolic function and islet insulin secretion in mice. The authors investigated whether loss of these proteins, which are canonically linked to inflammasome signaling and regulated cell death, alters glucose homeostasis and islet responses independently of overt inflammatory or cell‑death outcomes.
Researchers used male and female wild‑type (WT), Casp1/11 knockout (KO), Ripk3 KO and Casp1/11/Ripk3 double knockout (DKO) mice. Animals were fed either a matched low‑fat control diet or a 60% kcal high‑fat diet to induce obesity. Metabolic phenotyping included measurements relevant to adiposity, glucose tolerance and insulin sensitivity. Isolated pancreatic islets from WT and DKO mice were used for ex vivo secretion studies. Pharmacologic inhibition of Casp1 (Ac‑YVAD‑cmk) and Ripk3 (GSK872) was performed in isolated islets and by in vivo administration to corroborate genetic findings. Exogenous hormones were administered before glucose injection to test acute in vivo responses.
High‑fat feeding produced increased adiposity in male mice but not in females across single and double knockout genotypes. Mice with single or combined deletion of Casp1/11 and Ripk3 showed markers consistent with impaired glucose tolerance and reduced insulin sensitivity under high‑fat feeding conditions.
By contrast, when mice were maintained on the low‑fat diet, simultaneous genetic loss or pharmacologic inhibition of both Casp1 and Ripk3 led to reduced glucose excursion after glucose administration. This paradoxical improvement in glucose excursion was attributable to increased plasma insulin levels following glucose challenge rather than to changes in insulin sensitivity reported in the excerpt. Administration of exogenous hormones was used to probe mechanisms, and somatostatin (octreotide) but not Ucn3 restored the altered glucose excursion in vivo (see Islet signaling section).
Islets isolated from DKO mice secreted more insulin in response to glucose in dynamic ex vivo assays compared with WT islets, mirroring the in vivo elevation in plasma insulin after glucose challenge observed on the low‑fat diet. Pharmacologic blockade of Casp1 and Ripk3 (Ac‑YVAD‑cmk and GSK872, respectively) in WT islets and in vivo recapitulated the increased insulin secretion phenotype, supporting an islet‑intrinsic effect of these proteins on glucose‑stimulated insulin release.
The authors state that these effects occur independently of the classical inflammatory or cell‑death functions typically attributed to Casp1 and Ripk3, although detailed mechanistic steps linking kinase/caspase activity to exocytotic machinery were not reported in the source excerpt.
Immunofluorescent staining of intact pancreatic sections showed no change in the proportions of α‑, β‑ and δ‑cells between WT and DKO mice, indicating that altered insulin secretion was not explained by major shifts in islet cell composition.
However, DKO mice exhibited a significant reduction in the percentage of urocortin‑3 (Ucn3)‑positive β‑cells compared to controls, implicating perturbation of the Ucn3–somatostatin (Sst) paracrine axis within the islet. Functional testing with exogenous peptides revealed that somatostatin (octreotide) could correct the decreased glucose excursion in DKO animals, whereas exogenous Ucn3 did not, suggesting that changes downstream or parallel to Ucn3 signaling—potentially Sst release or somatostatin receptor responses—contribute to the phenotype.
The findings support a model in which endogenous Casp1 and Ripk3 contribute to regulation of normal glucose‑stimulated insulin secretion by pancreatic islets. Loss or inhibition of both proteins increased insulin release in response to glucose under low‑fat conditions, demonstrating that these factors perform roles in islet physiology beyond mediation of inflammation or programmed cell death. The effect was reproduced ex vivo and by pharmacologic inhibitors, consistent with an islet‑intrinsic mechanism.
Under high‑fat feeding, combined genotypes still displayed metabolic impairments such as increased adiposity (sex‑specific) and signs of impaired glucose tolerance and insulin sensitivity, indicating that the net metabolic outcome depends on dietary context and likely additional systemic influences.
The preprint excerpt does not provide detailed quantitative results, statistical values, effect sizes, or time courses for the reported metabolic and islet assays; those data were not reported in the source text provided here. Mechanistic pathways linking Casp1 and Ripk3 molecular activity to insulin secretory machinery were not fully delineated in the excerpt. Information on whether islet inflammation, β‑cell mass, or long‑term glycemic trajectories were assessed beyond the described experiments was not reported in the source material.
Taken together, the work identifies a previously underappreciated role for Casp1 and Ripk3 in coordinating homeostatic insulin secretion, with diet and sex influencing broader metabolic outcomes.