Lactobacillus reuteri-Enriched Eicosatrienoic Acid Regulates Glucose Homeostasis by Promoting GLP-1 Secretion to Protect Intestinal Barrier Integrity

Lactobacillus reuteri is a well-known probiotic with beneficial effects, such as anti-insulin resistance, anti-inflammatory, and improvement of the intestinal barrier. However, the underlying mechanisms remain unclear. Here, we found that gavage of L. reuteri improved the intestinal barrier and glucose homeostasis in HFD-fed mice. Analysis of lipid metabolomics reveals a significant increase in eicosatrienoic acid (ETA) levels in mouse feces after L. reuteri gavage. We found that ETA maintain intestinal barrier integrity and improve glucose homeostasis by promoting GLP-1 secretion. Mechanistically, by using CD36 inhibitor in vivo and CD36 knockdown STC-1 cells in vitro, we elucidate that ETA activates intestinal CD36-activated PLC/IP3R/Ca²⁺ signaling to promote GLP-1 secretion. In vivo administration of GLP-1R inhibitor and in vitro intestinal organoid experiments demonstrate that GLP-1 upregulates the PI3K/AKT/HIF-1α pathway by GLP-1R and increases intestinal tight junction protein expressions, which in turn enhance the intestinal barrier integrity, reduce serum LPS level, attenuate inflammation in white adipose tissue (WAT), and ultimately improve glucose homeostasis in HFD and db/db mice. Our study elucidates for the first time the mechanism by which L. reuteri and its enriched metabolite ETA inhibit WAT inflammation by ameliorating the intestinal barrier, ultimately improving glucose homeostasis, and provides a new treatment strategy for T2D.