Research On The Mechanism Of Ovalbumin And Its Maillard Reaction Products In Intestinal Barrier Repair

Inflammatory Bowel Disease(IBD)is a group of diseases characterized by chronic intestinal inflammation,including Ulcerative Colitis and Crohn’s Disease.The incidence of IBD has been increasing in recent decades.Patients with IBD may experience chronic abdominal pain,diarrhea,anemia,malnutrition,and other symptoms significantly impacting their quality of life.Despite progress,the exact causes of IBD remain unclear,posing challenges for research in prevention and treatment.The disruption of the intestinal barrier by IBD leads to tissue damage,impaired intestinal function,and difficulties in nutrient absorption.New guidelines from the European Society for Clinical Nutrition and Metabolism(ESPEN)recommend increasing the protein requirement for adults with IBD to 1.2–1.5 g/kg body weight/day compared to the recommended amount for the general population(0.83 g/kg body weight/day).Therefore,besides timely medical treatment,adjusting diet and nutritional intake is crucial for alleviating IBD symptoms and maintaining intestinal health.Understanding the role of dietary active proteins in regulating the intestinal barrier repair mechanism is essential for developing functional foods to assist in alleviating intestinal inflammation.Ovalbumin(OVA),the main protein in eggs with a rich amino acid composition,contributes to maintaining physiological functions and tissue repair in the body,making it an excellent raw material for developing functional foods.Research has shown that the primary stage of the Maillard reaction(MR)(protein glycation)of OVA can effectively improve protein processing characteristics.However,the impact of this reaction on the digestion and nutritional properties of ovalbumin is not yet clear.Therefore,research on Maillard reaction products(MRPs)guiding better food processing and cooking methods is of great significance for improving the quality of egg food and maintaining its nutritional value.This article focuses on OVA as the research object.Under mild heating conditions,the MRPs of OVA are prepared by glucose using a wet heat method.During the thermal processing,we investigate the influence of primary-stage MR on the OVA structure and the digestive characteristics changing rules.The study also explores the potential of OVA and its MRPs in restoring the intestinal barrier using a mouse model of colitis induced by dextran sulfate sodium(DSS).Finally,the research delves into the regulation patterns of gut microbiota and metabolites by OVA and its MRPs through 16 S rDNA microbial sequencing and un-targeted metabolomics,revealing the metabolic pathways and molecular mechanisms involved in the repair of the intestinal barrier during the process.It provides a theoretical foundation for the development of natural active ingredients in eggs and the exploration of the functions of food-derived active proteins.The main research content and results of this study are as follows:(1)We investigate the impact of different degrees of MR in the primary stage on the structure and digestion characteristics of OVA;We prepare MRPs in different reaction degrees by adjusting the ratio of glucose to protein.As the glucose ratio increased,protein turbidity decreased,hydrophobicity increased,while intrinsic fluorescence intensity decreased.Additionally,new infrared absorption peaks appeared after MR.The α-helix content decreased,while the β-sheet ratio increased significantly,which indicates a significant alteration in the protein’s structure.After in vitro simulated digestion,the content of free amino acids in the system decreased with increasing MR degree.Glucose modification leads to a reduction of released lysine,arginine,and other EAA after OVA digestion.Moreover,MR affects the cutting efficiency of pancreatic protease,resulting in differences in peptide sequences,including the ratio of long peptides to short peptides.(2)UC mouse model is used to explore the regulation effects of OVA and its MRPs on intestinal barrier and intestinal inflammation.After damaging the mouse intestinal barrier with DSS,the mice experienced weight loss,shortened colon length,and noticeable infiltration of inflammatory cells in the tissue.Upon ingestion of OVA and its MRPs,the colon length significantly increased.OVA and its MRPs also significantly reduced the levels of pro-inflammatory cytokines,effectively alleviating oxidative damage to intestinal tissues.Furthermore,the intestinal mucus layer is restored,and the expression of mucin protein MUC-2 and tight junction protein ZO-1 significantly increased.Intestinal permeability significantly decreased,indicating that OVA and its MRPs could alleviate intestinal inflammation and restore the integrity of the intestinal structure.(3)We evaluate the regulatory effects of OVA and its MRPs on the gut microbiota and short-chain fatty acids(SCFAs)in colitis mice through 16 S r DNA sequencing technology and targeted metabolomics.The disruption of the intestinal barrier leads to a significant decrease in the levels of EAA and NEAA in mouse serum.After ingesting OVA,the levels of both EAA and NEAA increased.Compared to OVA,MRPs with higher reaction degree cause a significant decrease in serum levels of lysine and arginine.There are differences in the regulation of the gut microbiota by OVA and its MRPs.In the OVA group,Muribaculaceae is the main factor.In L-MRPs and H-MRPs groups,Turicibacter and Clostridia replace.Both the OVA and its MRPs increased the levels of propionic acid and butyric acid in vivo.(4)The regulatory effects of OVA and its MRPs on the metabolites in colitis mice were investigated through un-targeted metabolomics.A total of 1322 metabolites were identified in all samples.Most of them enrich on the pathways related to metabolism.The intake of MRPs with different reaction degrees affects the abundance of short peptides in vivo,with a decrease in the abundance of Thr-Ala-Lys-Phe,Ile-Ile-Thr,ValVal-Glu,Val-Iel-Val,Arg-Leu-Glu,and Arg-Gly-Ile in the H-MRPs group.OVA regulated putrescine,inosine,cholic acid,and glycocholic acid abundance through pathways such as ABC transporters,lysine degradation,arginine and proline metabolism,and bile secretion.There are differences in the signaling pathways between the two MRPs groups.