Potato Protein Hydrolysate Interferes With Colon Inflammation In Mice And Its Mechanism

Intestinal tract is the main organ of food digestion,absorption and metabolism.Oxidative stresses which are caused by exogenous harmful factors such as antigens and microorganisms usually lead to tissue damage and persistent inflammation of intestine.In severe case,these may result in occurrence of cancer.Currently,inflammatory bowel disease is mainly treated with anti-inflammatory drugs and immunomodulators.However,these drugs have great side effects.To search safe and effective substances,bioactive peptides from food source are focused recently.Some peptides from food proteins hydrolysates have been demonstrated to be the potential substance to relieve inflammatory bowel disease（IBD）because of their antioxidant properties.Potato protein which has high nutrition value is usually recovered from juice of starch industry.The harsh heat treatment during potato protein processing resulted in loss of its solubility.That limited its application in food.It has been indicated that hydrolysis of potato protein can improve its antioxidative capacity in vitro.However,the antioxidant properties of potato protein hydrosate after digestion and its ability to relieve IBD are not clear.The aim of the present works is to investigate the antioxidant capacity of PPH in food model emulsion during digestion,oxidative stresses inhibition capacity of PPH in Caco-2 model induced by H₂O₂,potential application of PPH in relieving IBD and its mechanism.The main results were as follow:In trial 1,the effect of PPH with different hydrolysis time（0.5,1,6 h）on retarding lipid oxidation of food model emulsions was investigated by temperature speeding up trials.The results showed that PPH can improve the oxidation stability of emulsion.PPH with hydrolysis time of 1 h exhibited was more effective in retarding lipid oxidation of emulsions.In trial 2,the effect of PPH on retarding lipid oxidation of food model emulsions during digestion was investigated in in vitro stimulated digestion model.The results showed that PPH can decrease the lipid oxidation of food model emulsions during digestion.And PPH was able to inhibit the lipid oxidation of emulsions catalyzed by Fe²⁺from dietary during digestion.In trial 3,the effect digestion on antioxidant capacity of PPH in inhibiting H₂O₂-induced oxidative stresses in Caco-2 model was investigated.The results showed that PPH digesta from gastro-intestinal digestion was able to scavenge ROS produced in Caco-2 cell,inhibit lipid and protein oxidation of and enhance the activity of CAT,SOD and GSH-Px in Caco-2 cell（p<0.05）.The mechanism that PPH can retard oxidative stresses in Caco-2 model might be because PPH was able to regulate the gene expression of PDE4D,GPX2,PLB1,MYL12B,HSPA4L and KCNJ8.In trial 4,antioxidant peptides in PPH were fractionated and separated by ultrafiltration and gel filtration,followed by purification with preparative-HPLC.The amino acid sequence of antioxidant peptides in PPH was identified using UPLC-MS/MS.Five antioxidant peptides were identified,including Phe-Tyr,Tyr-Tyr,Leu-Asp-Ala-Lys,Tyr-Phe-Glu and Pro-Pro-His-Tyr-Phe.The selected peptide Tyr-Phe-Glu（YFE）was demonstrated to show good cell antioxidant activity and be absorbed by Caco-2 cell intact.In trial 5,the potential role of PPH in inhibiting dextran sulfate sodium（DSS）-induced oxidative stresses and intestinal inflammation in Babc mice was investigated.The results showed that PPH was able to retard the body weight loss,alleviate clinical symptoms,inhibit the shortening tendency of colon and relieve pathological changes of colon tissue of mice（p<0.05）.Also,PPH was able to alleviate oxidation damages of colon and liver,improve the antioxidant capacity of mice and decrease expression level of inflammatory factors.These might be related to signal pathway regulations of MAPK和NF-kB.In trial 6,the effect of PPH on diversity and abundance of intestinal microflora which indicated the changes in micro ecology of intestine were investigated using high throughput sequencing analysis.The results showed that PPH was able to change the diversity and richness of intestinal microflora.And PPH might interfere intestinal oxidation stresses and inflammation by increasing the abundance of intestinal microflora that produce short chain fatty acid.In trial 7,metabolite changes of colon tissues in mice with PPH treatment were investigated with UPLC-Q-TOF/MS.It was demonstrated that PPH might alleviate inflammation by regulating the metabolite of L-arginine,L-aspartic acid,DPA,glutathione and glycerophospholipids in inflammatory mice.