Prevention of Intestinal Inflammation and Gut Dysbiosis by Prebiotic Grape Seed Flour in Mice with DSS-Induced Colitis.

Background: Inflammatory bowel disease is a complex intestinal inflammatory disorder linked to immune dysregulation, oxidative stress, and an imbalance in the gut microbiota. Grape seed flour (GSF), a winemaking by-product rich in polyphenols and fibres, displays antioxidant and anti-inflammatory properties and may help maintain gut homeostasis. Methods: The phenolic composition and antioxidant capacity of our GSF were evaluated. We assessed whether a diet containing 10% (w/w) GSF protects against dextran sulphate sodium (DSS)-induced acute colitis in BALB/c mice. Animals received either a standard diet or a GSF-supplemented diet before and during DSS exposure. Body weight and disease activity index were monitored. At sacrifice, colon length and colonic histology scoring were measured. The study of the faecal microbiota and predicted genome was performed using PICRUSt. Caecal metabolites, including short-chain fatty acids, were also quantified. Results: GSF is rich in fibres (64%) and exhibits a very high polyphenolic content and high antioxidant capacity. GSF supplementation attenuated DSS-induced weight loss and disease activity and limited colonic shortening and histological damage. It also improved biomarkers of colon, mesenteric lymph nodes (MLNs), and liver injury. At the molecular level, GSF downregulated key pro-inflammatory mediators in the colon and liver, while enhancing anti-inflammatory (e.g., IL-10) and antioxidant markers, indicating reinforcement of regulatory and redox-protective pathways along the gut-liver axis. At the gut microbiota level, GSF supplementation modulated α-diversity. Further analysis demonstrated that GSF reshaped the GM profile by preventing the blooming of some taxa, including UBA1819, Akkermansia, and Bacteroides caecimuris, and enriching butyrate-producing bacteria, such as Muribaculaceae and Ruminococcus. These shifts were accompanied by lower acetone and ethyl acetate levels and higher indole levels, which are known to support epithelial barrier integrity and mucosal homeostasis. Conclusions: Overall, GSF mitigates DSS-induced colitis through combined actions on inflammatory signalling, oxidative stress, immune regulation, microbiota composition and microbiota-derived metabolites, supporting its potential as a functional prebiotic ingredient for intestinal health.