UGT1A1 and constipation disorder: Mechanistically, this study first elucidates how B. adolescentis alleviates post-long-haul constipation through three interacting pathways: (1) The arginine-urea cycle axis: colonization significantly upregulates colonic Ugt1a1, Gpt, and Otc expression in the colon (increased by 2.1, 1.8, and 2.3 fold, respectively; FDR < 0.01), accelerating ornithine-polyamine synthesis, restoring nitric oxide homeostasis, and promoting Lgr5+ intestinal stem cell proliferation, thereby accelerating mucosal renewal [33].