The regulatory response level of bile acids related to the intestinal flora

Abstract

Crohn's disease (CD) is a complex chronic transmural inflammatory bowel disease. Although vedolizumab (VDZ) markedly improves clinical outcomes in CD, treatment non-response remains a significant limitation, constraining its broader utility. Elucidating the mechanisms underlying VDZ responsiveness is thus critically needed. In this research, we employed a humanized mouse model of 2,4,6-trinitrobenzene sulfonic acid-induced colitis to investigate VDZ treatment response in CD. Our findings indicate that VDZ significantly alleviated disease phenotypes in a portion of CD mice. Integrated metagenomic and metabolomic profiling identified baseline gut microbiota-derived secondary bile acids as potential predictors of VDZ efficacy. Subsequent fecal microbiota transplantation from clinical donors into pseudo-germ-free mice confirmed that gut microbial composition critically influences VDZ responsiveness. Targeted metabolomics further pinpointed lithocholic acid (LCA) as a key microbially derived metabolite correlated with therapeutic remission. Single-cell RNA sequencing also revealed that intestinal macrophages serve as pivotal mediators of LCA-driven modulation of treatment outcomes. Furthermore, transcriptomic analyses demonstrated that LCA polarizes macrophages toward an M2-resolutive phenotype via concurrent engagement of the TGR5/FXR and their downstream nuclear factor kappa-B (NF-κB) pathways. Ultimately, using a conditioned medium co-culture system, we established that the regulatory effects of pro-resolutive macrophage niche on treatment response in a manner dependent on the TGR5/FXR-NF-κB axis. Taken together, our study elucidates a microbiota-immune circuit in which gut microbial metabolite LCA augments VDZ responsiveness in CD by reprogramming macrophages toward a pro-resolutive phenotype via the TGR5/FXR-NF-κB signaling network. These insights provide a mechanistic foundation for biomarker development and personalized therapeutic strategies in inflammatory bowel disease.