The gut insulin receptor acts as gatekeeper of intestinal barrier integrity

An impaired gut barrier has emerged as a potential driver of the low-grade inflammation that accompanies obesity and its complications. Among these, hyperglycemia per se has been proposed to sustain such increased intestinal permeability and subsequent translocation of bacterial endotoxins in the systemic circulation. Because reduced insulin signaling in the gut epithelium has also been reported upon obese conditions, we hypothesized that, beyond hyperglycemia, defective intestinal insulin signaling could directly comrpomise epithelial integrity. To mimic this diabesity feature, we induced deletion of the insulin receptor (IR) in the adult gut epithelium of IRΔGUT mice. Remarkably, gut IR loss persistently maintained normal body weight and glucose homeostasis, thereby allowing the specific role of insulin action to be investigated. While IRΔGUT mice exhibited increased intestinal paracellular permeability, mechanistic characterization of this gut leakiness revealed that IRΔGUT mice displayed a rapid and drastic decline in Paneth cells anti-microbial defenses. This paralleled the onset of a cecal dysbiosis, as characterized by increased abundance of Pseudomonadota, and enhanced microbiota encroachment. Of note, IRΔGUT mice exhibited intestinal stem cell (ISC) defects, as evidenced by reduced expression of ISC markers and ISC-mediated growth of intestinal organoids. Although expression of niche factors such as Wnt3a was diminished in Paneth cells isolated from IRΔGUT mice, pharmacological activation of the canonical Wnt pathway failed to rescue the growth defects of IR-deleted gut organoids. The direct contribution of IR-downstream signaling to ISCs homeostasis was confirmed by the transcriptional reprogramming of FACS-sorted ISCs from IRΔISC mice. Finally, while gut IR loss did not worsen endotoxemia or impaired glycemic control upon HFD-feeding, IRΔGUT displayed a higher susceptibility to chemically induced colitis and enteric infections (S. typhimurium, C. rodentium), underscoring intestinal insulin signaling as a key determinant of barrier integrity and epithelial homeostasis.