LGG Enhances Gut Barrier Function by Modulating Arginine Metabolism and Vitamin B₃Synthesis

Gut barrier dysfunction is a hallmark of inflammatory bowel disease (IBD), characterized by increased intestinal permeability, epithelial disruption, and chronic inflammation. Despite growing insights into the gut microbiota’s role, the mechanisms underlying probiotic-driven metabolic reprogramming of gut barrier function remain elusive. This study hypothesizes that Lacticaseibacillus rhamnosus GG (LGG), in synergy with dietary tryptophan, reprograms host metabolism to restore intestinal homeostasis and enhance barrier integrity. Using germ-free mice colonized with LGG and fed tryptophan-deficient or -sufficient diets, we employed untargeted metabolomics, transcriptomics, and a novel metabolome-transcriptome correlation analysis (METRCA). Functional validation was performed via in vitro assays, ex vivo organoids, and DSS-induced colitis mouse models. LGG robustly enhanced gut barrier function through two complementary mechanisms. First, LGG significantly upregulated argininosuccinate lyase (ASL), a critical enzyme in arginine biosynthesis, alleviating the accumulation of argininosuccinate (ASA)—a barrier-disrupting metabolite that perturbs tight junction proteins such as Ocln and Tjp1. These effects were evident in both experimental colitis and human IBD, where reduced ASL expression correlated with disease severity. Second, LGG stimulated the production of methylnicotinamide (MNA), a vitamin B 3 derivative that exhibited potent barrier-protective effects by enhancing epithelial tight junctions and promoting healing in DSS-induced colitis. METRCA analyses revealed strong correlations between LGG-regulated metabolites, including indole derivatives and MNA, and genes associated with arginine metabolism and epithelial barrier integrity. Notably, MNA reduced intestinal permeability and inflammatory cytokine production, positioning it as a key effector in LGG’s mechanism of action. These findings were further validated by in silico analyses of human IBD datasets, demonstrating that LGG and dietary tryptophan synergistically modulate arginine biosynthesis and reduce ASA levels, ultimately mitigating gut barrier dysfunction. This study highlights LGG’s dual capacity to enhance gut barrier function by leveraging dietary tryptophan to drive arginine metabolism and vitamin B3 synthesis. By targeting the metabolic disruptions underlying IBD, LGG emerges as a transformative precision probiotic. These exciting findings establish a framework for microbiome-based therapeutic strategies, emphasizing the potential of dietary and probiotic interventions to restore intestinal barrier integrity in IBD and related disorders. (NIH R01-AT010243, R01-DK102934, R01-DK119198 and NSF 1754783) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.