Fig. 4.

OSAS-induced low-grade systemic inflammation by mediating gut dysbiosis. The increased F/B ratio is a hallmark of gut microbiota dysbiosis, which is mainly characterized by a decrease in SCFA production-related bacteria and an increase in harmful bacteria. Decreased mucus secretion and mucin synthesis by dermal goblet cells disrupt the integrity of the intestinal barrier. The intestinal epithelium is dysfunctional due to inadequate nutrition, manifesting as reduced mucus production, decreased mucin secretion, and disrupted intestinal barrier integrity. Increased abundances of Prevotella and Desulfovibrio produce lipopolysaccharide and promote the degradation of mucin, increasing intestinal permeability and leading to a “leaky gut”, which triggers an intrinsic and adaptive immune response that induces low-grade inflammation in the body. Prevotella converts nutrients containing TMA into TMAO, which promotes inflammation. The reduced ability of SCFAs to activate GPR43, GPR109a, and HDAC results in diminished anti-inflammatory and increased proinflammatory capacity. GM gut microbiota, F/B Firmicutes/Bacteroidetes, SCFAs short-chain fatty acids, TMA trimethylamine, TMAO trimethylamine oxide, LPS lipopolysaccharide, HDAC histone deacetylase, GPR G-protein-coupled receptor, Blimp-1 maturation protein-1