Ameliorating Effects And Mechanism Of Galacto-oligosaccharides On The Colonic Barrier Damage Induced By Dietary AGEs

The availability and consumption of heat-treated processed foods has increased dramatically over the past few decades,in line with the prevalence of microvascular diseases such as chronic kidney disease and diabetes.Inhibition of the glycosylation pathway reversed intestinal barrier damage and reduced the risk of microvascular disease(e.g.,chronic kidney disease).Improving intestinal barrier damage may be beneficial in intervening in the development of related diseases.Advanced glycation end products(AGEs)are recognized as potentially pathogenic components of processed foods.The cross-linking properties of AGEs,as well as the fact that AGEs glycosylation sites occupy trypsin sites(lysine and arginine),make them resistant to digestion in the upper gastrointestinal tract,resulting in most of AGEs being able to reach the colon and disrupt the intestinal microbiota.Compared to mucincovered colonic epithelial cells,AGEs are more likely to be exposed to the intestinal microbiota in the intestinal lumen.Current in vivo studies on dietary AGEs have mostly focused on the improvement of AGEs-related diseases.There are fewer studies on nutritional interventions for AGEs-induced intestinal barrier damage.Currently,the intake of indigestible food components represents an effective way to influence the composition of the intestinal microbiota,resulting in host health benefits.Galacto-oligosaccharides(GOS),as a prebiotic composed of galactose chains,can selectively increase the abundance of bacteria containing specific glycosidases in the colon to play a role in regulating the intestinal microbiota and alleviate intestinal barrier damage.In this study,C57BL6 mice fed with high AGEs chow(AGE group,fluorescent AGEs of 50306.34 AU/g,about 7 times of the control chow)were gavaged with low(100 mg/kg BW,LGOS group)and high(500 mg/kg BW,HGOS group)doses of GOS(based on the reported dietary intake of GOS)to analyze the effects of GOS on intestinal barrier damage induced by dietary AGEs in mice and its mechanisms.The main results were as follows:(1)Compared with the LGOS group,the HGOS group was more effective in regulating OGTT,ITT and serum LPS levels in dietary AGEs-fed mice.Meanwhile,high-dose GOS ameliorated the increase in colonic barrier permeability caused by dietary AGEs by increasing the neutral mucin area(37.86%),the number of goblet cell(30.97%),the level of Muc2 m RNA expression(137.83%),up-regulating the protein expression of the tight junction proteins occludin and claudin-1,and down-regulating the level of the transcription of the antimicrobial peptide Reg3γ(64.40%).(2)High doses of GOS upregulated the transcript levels of AGER2(involved in the clearance of AGEs,27.19%),decreased the transcript levels of Fut2(33.64%),and increased the transcript levels of St3gal1(64.71%)and St3gal3(59.04%),which contributed to the maintenance of the integrity of the colonic mucus layer.In addition,GOS reversed the reduction of colonic goblet cell caused by AGEs by inhibiting the activation of p38(26.21%)and ERK(46.20%)of MAPK pathway.However,it did not affect the changes in the transcript levels of proliferation and differentiation-related Wnt,BMP and Notch-related genes,as well as the apoptosis-related CHOP pathway.(3)Compared with the AGE group,supplementation with high-dose GOS moderated the perturbation of the gut microbiota caused by dietary AGEs,significantly decreasing the relative abundance of Akkermansia,Faecalibacterium,Megamonas,Oscillospira,and Lachnospiraceae＿UCG-004,as well as increasing fecal levels of propionate,butyrate,and pentanoate(by 20.55%,116.75%,and 82.59%).(4)The FMT showed that the short-chain fatty acid content was increased in the feces of recipient mice that received fecal bacterial transplants from the HGOS group(FG group,fed AGE chow).Meanwhile,the perturbation of colonic mucin synthesis due to dietary AGEs was ameliorated in FG group mice,such as increased transcript levels of Gcnt4(mucin elongationassociated,469.23%)and St3gal1(associated with termination of mucin elongation,69.84%).In addition,activation of ERK(43.88%)in the MAPK signaling pathway was suppressed and mucus barrier damage was ameliorated(increase in the number of goblet cell and the area of neutral mucin)in the colon of AGEs-fed recipient mice after receiving fecal transplantation from the HGOS group.The above results demonstrated that GOS ameliorates AGEs-induced intestinal barrier damage by regulating the structure of the intestinal microbiota and the expression of metabolites.The molecular mechanism may be related to the regulation of MAPK signaling pathway.The study provides a theoretical basis for precise nutritional intervention for AGEsinduced intestinal barrier damage.