Mucus

Ulcerative colitis (UC) is a chronic recurrent intestinal inflammatory disease characterized by high incidence and young onset age. Recently, there have been some interesting findings in the pathogenesis of UC. The mucus barrier, which is composed of a mucin complex rich in O-glycosylation, not only provides nutrients and habitat for intestinal microbes but also orchestrates the taming of germs. In turn, the gut microbiota modulates the production and secretion of mucins and stratification of the mucus layers. Active bidirectional communication between the microbiota and its 'slimy' partner, the mucus barrier, seems to be a continually performed concerto, maintaining homeostasis of the gut ecological microenvironment. Any abnormalities may induce a disorder in the gut community, thereby causing inflammatory damage. Our review mainly focuses on the complicated communication between the mucus barrier and gut microbiome to explore a promising new avenue for UC therapy.

Intestinal mucus plays important roles in protecting the epithelial surfaces against pathogens, supporting the colonization with commensal bacteria, maintaining an appropriate environment for digestion, as well as facilitating nutrient transport from the lumen to the underlying epithelium. The mucus layer in the poultry gut is produced and preserved by mucin-secreting goblet cells that rapidly develop and mature after hatch as a response to external stimuli including environmental factors, intestinal microbiota as well as dietary factors. The ontogenetic development of goblet cells affects the mucin composition and secretion, causing an alteration in the physicochemical properties of the mucus layer. The intestinal mucus prevents the invasion of pathogens to the epithelium by its antibacterial properties (e.g. β-defensin, lysozyme, avidin and IgA) and creates a physical barrier with the ability to protect the epithelium from pathogens. Mucosal barrier is the first line of innate defense in the gastrointestinal tract. This barrier has a selective permeability that allows small particles and nutrients passing through. The structural components and functional properties of mucins have been reviewed extensively in humans and rodents, but it seems to be neglected in poultry. This review discusses the impact of age on development of goblet cells and their mucus production with relevance for the functional characteristics of mucus layer and its protective mechanism in the chicken's intestine. Dietary factors directly and indirectly (through modification of the gut bacteria and their metabolic activities) affect goblet cell proliferation and differentiation and can be used to manipulate mucosal integrity and dynamic. However, the mode of action and mechanisms behind these effects need to be studied further. As mucins resist to digestion processes, the sloughed mucins can be utilized by bacteria in the lower part of the gut and are considered as endogenous loss of protein and energy to animal. Hydrothermal processing of poultry feed may reduce this loss by reduction in mucus shedding into the lumen. Given the significance of this loss and the lack of precise data, this matter needs to be carefully investigated in the future and the nutritional strategies reducing this loss have to be defined better.

Preterm births are a global health priority that affects 15 million babies every year worldwide. There are no effective prognostic and therapeutic strategies relating to preterm delivery, but uterine infections appear to be a major cause. The vaginal epithelium is covered by the cervicovaginal mucus, which is essential to health because of its direct involvement in reproduction and functions as a selective barrier by sheltering the beneficial lactobacilli while helping to clear pathogens. During pregnancy, the cervical canal is sealed with a cervical mucus plug that prevents the vaginal flora from ascending toward the uterine compartment, which protects the fetus from pathogens. Abnormalities of the cervical mucus plug and bacterial vaginosis are associated with a higher risk of preterm delivery. This review addresses the current understanding of the cervicovaginal mucus and the cervical mucus plug and their interactions with the microbial communities in both the physiological state and bacterial vaginosis, with a focus on gel-forming mucins. We also review the current state of knowledge of gel-forming mucins contained in mouse cervicovaginal mucus and the mouse models used to study bacterial vaginosis.

ObjectiveThis study investigates whether live Akkermansia muciniphila MucT supplementation can counteract obesity and metabolic dysfunctions induced by a high-fat diet (HFD) by modulating intestinal mucus production, secretion and composition.DesignC57BL/6J mice were fed an HFD with or without live A. muciniphila MucT (2 × 108 CFU per day) supplementation or a control diet for 6 weeks. Body weight, fat mass gain and metabolic markers were measured. Intestinal mucus characteristics were assessed via gene expression analysis of mucins and analysed mucin glycosylation by tandem mass spectrometry (MS/MS).ResultsMice receiving live A. muciniphila MucT exhibited reduced body weight gain and fat mass accumulation compared to HFD controls, without changes in muscle mass. A. muciniphila improved gut barrier integrity by increasing antimicrobial peptide expression in the jejunum and in the colon of HFD-fed mice. Furthermore, live A. muciniphila MucT influenced markers of goblet cell differentiation and restored the expression of mucin markers altered by HFD. Specifically, live A. muciniphila MucT counteracted HFD-induced mucin 3 (Muc3) expression depletion in the colon. Although the overall mucus thickness was not affected by live A. muciniphila MucT, the bacteria significantly modulated mucin glycans composition. Live A. muciniphila MucT did not change the gut microbiota composition.ConclusionThese findings highlight the protective effects of live A. muciniphila MucT against diet-induced metabolic dysfunctions by modulating adiposity, mucus layer composition, and glycan profiles. This reinforces its potential as a therapeutic strategy for metabolic disorders associated with gut microbiota alterations.