Malus toringoides Polysaccharide Alleviates DSS-Induced Colitis in Mice and Is Associated with Gut Microbiota–Metabolite Remodeling and Nrf2/HO-1–NF-κB Signaling

Plant polysaccharides have garnered an increasing amount of attention as potential natural candidates for enhancing intestinal health in animals.The protective effects of Malus toringoides polysaccharide (MTK) against dextran sulphate sodium (DSS) induced colitis in mice were assessed in this study.During a seven-day period of exposure to 3% DSS, sixty male BALB/c rodents were divided into six groups (n=10 per group) and administered MTK at doses of 50, 100, or 200 mg/kg/day.Animals were randomly selected within each group for subset analyses, regardless of disease severity or treatment response.In the CON, MOD, and MTK-H (200 mg/kg/day) groups, histological analyses were undertaken on six mice per group (n=6), while 16S rRNA sequencing and untargeted metabolomics were conducted on three mice per group (n=3).The data were analyzed using one-way ANOVA, followed by Tukey's test or the appropriate nonparametric test.MTK decreased disease activity, body weight loss, and colon shortening, increased IL-10 and SOD, and decreased TNF-α, IL-6, MPO, and MDA (P<0.05).MTK also enhanced the expression of ZO-1, Occludin, and Claudin-3, as well as the PAS-positive area and colonic histopathology.This was accompanied by an increase in the expression of Nrf2 and HO-1 proteins, as well as a decrease in the p-p65/p65 and p-IκBα/IκBα ratios.MTK-associated changes in gut microbial composition and faecal metabolites related to amino acid, bile acid, lipid, and tryptophan/indole metabolism were identified through multi-omics analyses.Additionally, associations among microbial, metabolic, inflammatory, oxidative, and barrier-related variables were identified through integrated analyses.These discoveries substantiate the intestinal protective effectiveness of MTK and establish a foundation for additional mechanistic and veterinary investigations.