Limosilactobacillus reuteri Z-621 isolated from Hu lambs alleviates colitis by restoring intestinal barrier homeostasis and modulating the gut microbiota composition and lipid metabolism

Ulcerative colitis (UC) is a chronic and relapsing inflammatory bowel disease (IBD) accompanied by intestinal microbiota imbalance and intestinal barrier damage. Previous study has indicated that Hu lambs exhibit superior disease resistance in a dextran sulfate sodium (DSS)-induced model. Screening core probiotic microorganisms from such disease-resistant phenotypes may serve as new potential alternative prophylactic strategies. In this study, using multi-omics approaches, we isolated Lactobacillus strains from Hu lambs, and evaluated their prophylactic potential and mechanisms in a DSS-induced colitis mouse model. A novel Limosilactobacillus reuteri ( L. reuteri ) Z-621 strain was isolated from Hu lambs and exhibited favorable probiotic characteristics, including antimicrobial activity, acid and thermal tolerance, moderate bile salt tolerance, high hydrophobicity, and strong adhesion capacity. The strain was also safe in vivo and susceptible to common antibiotics. Prophylactic L. reuteri Z-621 supplementation significantly ameliorated colitis severity, as evidenced by attenuating weight loss (3.13% vs. 11.54% in the DSS group), reducing disease activity index (DAI) (6 vs. 9.5 in the DSS group), preventing colon shortening (5.20 cm vs. 4.38 cm in the DSS group), and improving histopathological damage. Mechanistically, L. reuteri Z-621 enhanced intestinal barrier function by downregulating proinflammatory cytokines (interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α) and increasing anti-inflammatory cytokines (IL-4 and IL-10) in both colon tissues and serum. The probiotic also promoted tight junction (TJ) protein (ZO-1 and occludin) expression and increased goblet cell numbers and mucin MUC2 production. Multi-omics analyses revealed that pre-supplementation with L. reuteri Z-621 modulated gut microbiota composition and corrected metabolic disturbances. Specifically, it reduced the relative abundance of potential pathogenic bacteria such as Clostridium , Segatella , and Faecalibaculum , increased the relative abundance of beneficial Bifidobacterium , and decreased glycerylphosphorylethanolamine (harmful metabolite involved in lipid metabolism pathways) levels. Spearman correlation analysis further highlighted significant interrelationships between altered microbiota, metabolites, and colitis clinical indicators. L. reuteri Z-621 from Hu lambs alleviates DSS-induced colitis by restoring gut microbial homeostasis, regulating lipid metabolism, reinforcing intestinal barrier integrity, and could be a promising probiotic candidate.