Improvement of inflammatory bowel disease by lactic acid bacteria-derived metabolites: a review

Lactic acid bacteria (LAB) plays a crucial role in the establishment and maintenance of host health, as well as the improvement of some diseases. One of the major modes is the secretion of metabolites that may be intermediate or end products of the LAB's metabolism. In this review, we summarized some common metabolites (particularly short-chain fatty acids [SCFAs], bacteriocin, and exopolysaccharide [EPS]) from LAB in fermented foods and the gut for the first time. The effects of LAB-derived metabolites (LABM) on inflammation, oxidative stress, the intestinal barrier, and gut microbiota in inflammatory bowel disease (IBD) model are also discussed. The discovery of LABM and identification of IBD biomarkers are mainly attributed to the development of metabolomics technologies, especially nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography tandem mass spectrometry (LC-MS). The application of these metabolomics technologies in identification of LABM and IBD biomarkers are also summarized and analyzed. Although the beneficial effects of some LABM have been explored, undiscovered metabolites and their functions still need further investigations.