Limosilactobacillus reuteri SXDT-32-derived shikimic acid protects against colonic inflammation in piglets by inhibiting the PI3K-Akt pathway

Abstract

Colitis caused by bacterial infection is a major global health challenge. Unfortunately, current treatment options are limited. We previously disclosed that L. reuteri SXDT-32 was enriched in the feces of an ancient diarrhea-resistant pig breed (Mashen pig) in China over 2500 years old. As diarrhea is often closely associated with intestinal inflammation, L. reuteri SXDT-32 was identified as a potential beneficial bacterium to prevent intestinal inflammation. However, the precise mechanisms involved remained unclear. Our tests showed that L. reuteri SXDT-32 alleviated colonic damage induced by pathogenic E. coli SKLAN202302 in weaned pigs by enhancing barrier integrity and inhibiting inflammation. The transcriptomics revealed that L. reuteri SXDT-32 protected against inflammatory injury by inhibiting the PI3K-AKT signaling pathway. Metabolite analysis indicated that the content of shikimic acid (SA) was substantially elevated in the colonic mucosa of L. reuteri SXDT-32-fed piglets (P < 0.05). In addition, Liquid Chromatography-Mass Spectrometer (LC-MS) analysis showed significant increases in SA content in both the colonic chyme of L. reuteri SXDT-32-fed piglets and the supernatant of in vitro grown cultures of L. reuteri SXDT-32 (P < 0.05). Polymerase chain reaction (PCR) analysis identified gene aroE from L. reuteri SXDT-32, which is a key gene directly linked to SA synthesis, and elevated shikimate dehydrogenase (SD, encoded by aroE) was also detected in both L. reuteri SXDT-32 and the colonic mucosa of piglets fed L. reuteri SXDT-32 (P < 0.01). In vitro Caco-2 cell experiments demonstrated that SA, L. reuteri SXDT-32, and the supernatant from in vitro grown cultures of L. reuteri SXDT-32 exhibited comparable inhibitory effects on the PI3K-Akt pathway to those of the PI3K inhibitor LY294002. L. reuteri SXDT-32 alleviated intestinal inflammation in piglets by producing SA that inhibits the PI3K-Akt pathway. This study provides an innovative approach for the treatment and prevention of colitis caused by bacterial infection.