In Vivo Evaluation of the Effect of Limosilactobacillus fermentum MC1 and Its EPSs on the Microbiota and Inflammatory Processes in the Mouse Intestine

Limosilactobacillus fermentum MC1 is an exopolysaccharide (EPS)-producing strain with previously determined probiotic potential in vitro. This study aimed to investigate the in vivo capacity of the MC1 strain or its EPSs to modulate intestinal microbiota and assess its anti-inflammatory effects in both healthy and dysbiotic conditions. Therefore, Lb. fermentum MC1 and its EPSs were administered to a mouse model of dextran sulfate sodium (DSS)-induced colitis (DIC) and to a healthy group, and the effects were observed. Microbiome analysis was used to detect taxonomic differences between treatments. According to the results, administration of the MC1 strain and MC1-EPSs significantly altered gut microbiome composition at different taxonomic levels. The most notable effect was an increased relative abundance of Firmicutes and decreased levels of Candidatus saccharibacteria. Llb. fermentum MC1, and its EPS administration positively affected several disease parameters: reduced disease activity index (DAI), reduced mouse colitis histology index (MCHI), reduced expression of inflammation-related genes and levels of bleeding, and induced polarization of M1 macrophages to the M2-like macrophage phenotype in the DIC mice. These results, along with those related to the induction of antioxidant enzymes and changes in NF-κB-related gene expression, suggest that strain MC1 and MC1-EPSs could be further investigated for their capacity to alleviate DSS-induced histopathological changes and modulate pro-inflammatory cytokine gene expression in colon tissue, which positively correlates with the secretion of inflammatory cytokines, the delay of intestinal inflammation and the maintenance of intestinal barrier function. The obtained data provide a basis for further research into the potential application of intact or microencapsulated Llb. fermentum MC1 cells and its EPSs in colitis therapy.