New insights in gut microbiota and mucosal immunity of the small intestine

Beyond host genetics, the environment determines microbiota-immunity interactions. Most recent studies have focused on the interconnections between micronutrients, microbial and immune populations. However, the control of the gut oxidative stress and redox status has been neglected. Oxidative stress sensitive (Ox-S) prokaryotes include butyrate producers and minority mucosa-associated immunogenic symbionts, such as specific Lactobacillus strains, Bifidobacterium adolescentis, and segmented filamentous bacteria which exemplify the mucosal “minority report” paradigm. Butyrate, produced by Lachnospiraceae, Ruminococcaceae and Bacteroidetes, is the main microbiota-derived gut mucosal immunity regulator and the best functional marker of the healthy mature anaerobic gut microbiota (HMAGM). Oxidative stress during the “window of opportunity” around weaning is observed in severe acute malnutrition and results in Ox-S prokaryote depletion, HMAGM disruption, collapse of butyrate production and durable gut mucosal immunity alteration. High saturated-fat diet leads to oxidative stress, selection of oxidative stress-resistant (Ox-R) Lactobacillus reuteri strains in Peyer’s patches, secretion of pro-inflammatory cytokines, disruption of mucosal immune compartmentalization (leaky gut) and obesity. Beyond dietary micronutrient diversity and pathogen control, future research should focus on antioxidants, control of oxidative stress and Ox-S gut prokaryote preservation as new instrumental targets for maintenance of the gut microbiota-immunity symbiotic loop and prevention of malnutrition and obesity.