Bacteroides intestinalis -Driven Arabinoxylan Fermentation Mitigates Inflammatory and Metabolic Dysfunction

Insufficient dietary fiber intake is closely linked to gut microbiome dysfunction and increased risk of noncommunicable diseases. Synergistic synbiotics, pairing defined microbes with their dietary substrates, offer a precise strategy to restore microbiome function. Here, we show that pairing the human colonic commensal Bacteroides intestinalis with insoluble wheat arabinoxylan (inWAX) yields pronounced metabolic and anti-inflammatory benefits. Using mono-associated gnotobiotic mice and high-fat diet-induced obese mice, we demonstrate that this synbiotic enhances resistance to intestinal inflammation and improves glucose homeostasis. Mechanistically, this synbiotic increases production of 6-hydroxylated bile acids with anti-diabetic and anti-steatotic effects. It also promotes microbial transformation of phenolic compounds and redirects protein metabolism toward neuroactive metabolites. These metabolic shifts are accompanied by transcriptional remodeling in the colon, spleen and liver, involving induction of genes essential for circadian rhythm, lipid metabolism, immune defense, and bile acid 6-hydroxylation. Notably, Y chromosome-linked genes associated with epigenetic regulation and protein turnover are also induced, suggesting a potential sex-specific response to synbiotics. Together, our findings establish a mechanistic framework for targeted synbiotic interventions to combat inflammatory and metabolic disorders.