Ant may well destroy a whole dam: glycans of colonic mucus barrier disintegrated by gut bacteria

The colonic mucus layer plays a critical role in maintaining the integrity of the colonic mucosal barrier, serving as the primary defense against colonic microorganisms. Predominantly composed of mucin 2 (MUC2), a glycosylation-rich protein, the mucus layer forms a gel-like coating that covers the colonic epithelium surface. This layer provides a habitat for intestinal microorganisms, which can utilize mucin glycans present in the mucus layer as a sustainable source of nutrients. Additionally, metabolites produced by the microbiota during the metabolism of mucus glycans have a profound impact on host health. Under normal conditions, the production and consumption of mucus maintain a dynamic balance. However, several studies have demonstrated that certain factors, such as dietary fiber deficiency, can enhance the metabolism of mucus glycans by gut bacteria, thereby disturbing this balance and weakening the mucus barrier function of the mucus layer. To better understand the occurrence and development of colon-related diseases, it is crucial to investigate the complex metabolic patterns of mucus glycosylation by intestinal microorganisms. Our objective was to comprehensively review these patterns in order to clarify the effects of mucus layer glycan metabolism by intestinal microorganisms on the host.