Enteroendocrine Cells Regulate Barrier Function and Protect Against DSS-Induced Outcomes

Enteroendocrine cells (EECs) are often dysregulated in metabolic and gastrointestinal diseases, such as inflammatory bowel disease (IBD), although their roles in disease pathogenesis remain unknown. EECs are rare sensory cells scattered throughout the gastrointestinal epithelium that respond to environmental stimuli like nutrients and microbes by secreting over 20 distinct hormones, neurotransmitters, and metabolites. EECs are well-known for their systemic effects in regulating endocrine and exocrine pancreas function and appetite, but the roles they play within their local environment of the intestine remain obscure. Many metabolic and gastrointestinal diseases are associated with impaired function of the intestinal epithelial barrier, allowing undigested food, microbes, metabolites, and toxins to cross the epithelium and enter the submucosa which triggers local and systemic inflammation. The objective of our study was to evaluate the role of EECs in barrier function and barrier function-mediated disease, with the hypothesis that EECs were required to maintain a healthy barrier. We found that EEC-deficient human intestinal organoids display increased barrier permeability and upregulate an inflammatory signature compared to healthy control organoids. The increased barrier permeability observed in EEC-deficient intestinal organoids was significantly exacerbated by addition of TNF-alpha and could be rescued to control levels by the administration of exogenous EEC-derived products in vitro. We found reduced expression of junctional proteins promoting a tight epithelial barrier alongside increased expression of Claudin-2, a pore-forming junctional protein, in EEC-deficient human intestinal organoids and EEC-deficient mouse intestine. Additionally, lipidomic analysis of murine intestinal epithelium revealed decreased abundance of several long-chain ceramide species in EEC-deficient jejunum. In support of this finding, we observed reduction of Cers4, a ceramide synthase enzyme that synthesizes long-chain ceramides, in intestinal crypts within EEC-deficient jejunum. Ceramides are sphingolipids that are important for maintaining barrier integrity and function in epithelial tissues, including the intestine, and are often misregulated in GI diseases like IBD which present with more permeable barriers. To test the role of EECs in barrier maintenance in disease, we exposed mice to dextran sodium sulfate (DSS) in the drinking water for seven days and observed more severe outcomes and impaired recovery in the small and large intestines of EEC-deficient mice compared to control. Studies are ongoing to define the mechanisms by which EECs protect against DSS-induced intestinal outcomes and whether that mechanism includes regulation of ceramides. These experiments define a new role for EECs in maintaining gastrointestinal homeostasis, uncover a novel mechanism regulating barrier integrity in health and disease, and provide a basis for future therapies aimed at repairing a leaky gut. This study was supported by K01DK125341 to H.A.M. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.