Effects Of GPR109A On Intestinal Flora And Colonization Of ETEC In Mice

Existing studies have shown that GPR109A plays a critical role in maintaining intestinal health.It mediates the anti-inflammatory effects of butyric acid and beta-hydroxybutyric acid,as well as regulates the expression of tight junction proteins in the body and improves intestinal permeability.However,the effect and mechanism of GPR109A in the infection of exogenous pathogenic microorganisms is still unclear.In this article,we established an animal model of infection by oral ETEC gavage to observe the protect effect of GPR109A on the intestinal tract and mechanisms underlying.Experimental GPR109A^-/-and WT mice were administered with 1×10⁹cfu ETEC by oral administration.The colonization and translocation of ETEC in the intestine were detected by plate counting method.The expression of tight junction protein,inflammatory factor and SIgA in the intestine were detected by q-PCR,western blot,ELISA and Immunohistochemistry.The results showed that GPR109A^-/-mice were more susceptible to ETEC infection,showing more severe inflammatory reactions and intestinal damage.It is worth noting that the secretion of IgA in the intestinal tract of WT mice was significantly increased after ETEC infection,but this change was not observed in GPR109A^-/-mice.Adding 5g/L butyrate into drinking water can pre-protect WT mice against ETEC infection,but has no effect on GPR109A^-/-mice.Similarly,butyrate increased the SIgA content in the gut of the WT mice,but not GPR109A^-/-mice.In conclusion,activated GPR109A is effective against colonization and translocation of ETEC in the gut and maintains intestinal barrier integrity,possibly by the promotion of intestinal IgA secretion.The communication between the intestinal flora and the host on the surface of the intestinal mucosa promotes the establishment and development of the immune system and becomes an important immune barrier for the animal body.Studies have shown that GPR109A can affect the structure of the intestinal flora,but the specific mechanism is not clear.GPR109A can regulate lipid metabolism in the body.We reasonably assume that GPR109A affects the flora structure through this function.Therefore,we used high-throughput sequencing technology to detect the structure of WT and GPR109A-/-mouse intestinal flora,GC-MS to detect in mouse feces and intestinal epithelium,and the Correlation between metabolites and flora was analyzed。The results show that the absence of GPR109A can cause changes in the relative abundance of various bacterial genera in the intestinal tract,such as the genus Mycoplasma,Roseburia,Paraprevotella,and Anaerovorax.At the same time,the absence of GPR109A led to intestinal epithelial metabolites 3-Hydroxypropionic acid 1,sulfuric acid,dihydroxyacetone,d-glyceric acid,taurine and stigmasterol were significantly reduced.In contrast,Pyruvic acid,Phenylpyruvate,Galactinol 3,and Raffinose increased significantly.The content of Cholesterol,2-Hydroxy-3-methylbutyric acid,Alanine,2-Hydroxy-3-methylvaleric acid,Campesterol,γ-Tocopherol,Lactic acid,Fructose,Epephrine increased significantly in fecal metabolites,while the content of glycerol,Ethanolamine,d-Glucose,d-Galactose,Alpha-Lactose,and N-Acetyl-D-glucosamine significantly reduced.The correlation analysis showed that there was a significant correlation between the differential flora and differential metabolites,which indicates that the effect of GPR109A on the intestinal flora and metabolites may be the result of interaction between the host and intestinal microorganisms.