Impacts Of Long-term Dietary AGEs Consumption On The Mice Gut Microta,Metabolites And Barrier Function

The mammalian gastrointestinal tract houses an expansive number of microorganisms,forming a microbial ecosystem with their microbial metabolites.More and more studies have demonstrated that the balance of the intestinal ecosystem is crucial for the maintenance of human health.One predominant relationship between the host and its resident microbiota is the production of microbiota metabolites.Among the numerous factors which affect intestinal microecology,dietary composition is one of the most important one.Advanced glycation end products(AGEs)are inevitably formed during thermal food processing through non-enzymatic reactions of reducing sugars with the free amino groups of proteins,nucleic acids or lipids.As a result of cross-linking and protein aggregation,AGEs become less digestible for they impair intestinal peptidase proteolysis.While gut microbiota are able to degrade selected glycated amino acids because there are deglycating enzyme systems present in bacteria.It had been estimated that only 10-30% of consumed dietary AGEs are absorbed and enter circulation,the whereabouts and its impacts on the host health of the rest of part of AGEs still need to be explored.In the present study,we fed healthy C57BL/6 mice heated-treated diet as a high AGEs diet(H-AGEs)or standard AIN-93 G diet(L-AGEs)for eight months,fecal microbiota composition was examined by 16 S r DNA sequencing,fecal metabolome profile was evaluated by gas chromatography tandem time-of-flight mass spectrometry(GC-TOF-MS)and short-chain fatty acids(SCFAs)were also measured.In addition,we investigated the influences of dietary AGEs on the intestinal tissue structure,inflammation level and intestinal barrier function.The results are as follows:(1)The average food intake of mice in the H-AGEs group was higher than L-AGEs group,while dietary AGEs consumption for more than 20 weeks significantly reduced the mouse body weight(p<0.05).8 months dietary AGEs consumption decreased fecal microbiota α-diversity(p<0.05)and obviously changed microbiota composition through PCo A.Compare with L-AGEs group,at the phylum level,the abundance of Firmicutes was significantly lower(p<0.05),whereas the level of Actinobacteria was significantly higher(p<0.05);At the family level,the following families were significantly increased(p<0.05)in the H-AGEs group: Porphyromonadaceae,Prevotellaceae and Helicobacteraceae.Conversely,Desulfovibrionaceae were significantly reduced(p<0.01);At the genus level,Parabacteroides,Alloprevotella and Helicobacter were significantly increased(p<0.05)in the H-AGEs group,whereas Desulfovibrio and Roseburia were markedly reduced(p<0.01).(2)Compared to the L-AGEs group,acetate and butyrate were significantly decreased(p<0.01 and p<0.05,respectively)after 8 months of AGEs intake,whereas isovalerate and isobutyrate were notably increased(p<0.05).AGEs intervention had a great modulating effect on metabolite profiles,causing a clear cluster separation and discrimination away from L-AGEs group.36 metabolites in the H-AGEs group were up-regulated,and 21 metabolites were down-regulated;Through pearson correlation analysis,some altered specific gut microflora-related metabolites were strongly associated with perturbed gut microbes;These significant perturbed metabolites participated instarch,sucrose and galactose metabolism,valine,leucine and isoleucine biosynthesis and glycine,serine and threonine metabolism,the citric acid(TCA)cycle,ascorbate and aldarate metabolism and glycerolipid metabolism.(3)8 months dietary AGEs consumption markedly increased cecal area and wet weight(p<0.01).In histological examination,the morphology of mouse ileum was basically intact,only part of the intestinal villi became shorter and the submucosa was slightly edema.The morphology of mouse colon was also basically intact,but a little inflammatory infiltration in the mucosa and submucosa,edema in submucosal increased,colon epithelial cells slightly atrophy.Compared to the L-AGEs group,the level of inflammatory cytokines had no obvious changes in ileum tissue,while IL-6、TNF-α and IL-1β contents and their m RNA level significantly increased in colon tissue(p<0.05).Moreover,the intestinal barrier function of H-AGEs group mice was impaired,serum fluorescence and LPS content increased(p<0.05),the expression on m RNA level of tight junction proteins(Occludin and ZO-1)in the colon decreased significantly(p<0.05).