Abstract: Ulcerative colitis is a chronic inflammatory bowel disease, and its incidence is increasing year by year in China. Current drug treatments have side effects, so the use of probiotics to regulate intestinal microbiota is emerging as an intervention method. Numerous studies have shown that bifidobacteria have a good clinical effect in alleviating symptoms of ulcerative colitis. However, the underlying mechanism has not been systematically elucidated. In recent years, with continuous breakthroughs in research on multi-omics, the gut microbiota, the gut-brain axis, and the gut-liver axis, significant progress has been made in understanding the action mechanism of bifidobacteria in alleviating ulcerative colitis. This article reviews the latest progress that has been made in the research and application of bifidobacteria in alleviating ulcerative colitis in the past decade, and introduces bifidobacteria alleviating ulcerative colitis, with a focus on the underlying mechanism. This review reports that bifidobacteria alleviates ulcerative colitis mainly by regulating the structure of the intestinal microbiota, restoring intestinal barrier function, improving intestinal immune response, regulating intestinal purine metabolism, inhibiting oxidative stress, and providing energy for the intestinal epithelium. It is our hope that this review will provide a reference for further elucidating the regulatory mechanism of bifidobacteria on life and health as well as for furthering the application and promotion of probiotic preparation.

Key words: bifidobacteria; ulcerative colitis; intestinal barrier; mechanism of action; inflammatory factors