Effects Of Dietary Fats On Colonic Barrier And Its Mechanism In Rats

In recent years,the relationship between dietary fats and health has attracted more and more attention.Dietary fats are the source of essential fatty acids and the carrier of fat-soluble vitamins.The main source of dietary fats is cooking oil.Different dietary fats have different effects on health due to the amount,type and fatty acid composition.There are a lot of researches on diet and health,including dietary protein,dietary fiber,high and low fat.And these researches mainly focus on the changes of gut microbes and liver metabolism.Several researches were also carried out on intestinal mucosa barrier by histological observation instead of molecular biology.In addition,most of the researches are based on the over intake or disease models,without considering the real need of fat.Lard and soybean oil are two major cooking oil in China,and fish oil is one of the most widely studied functional oil.The lard is rich in SFA and MUFA.Fish oil is rich in ?-3 PUFA(EPA and DHA).Soybean oil is rich in n-6 PUFA.Thirty-six middle-aged Sprague-Dawley rats were assigned to one of diets containing soybean oil,lard or fish oil,respectively(n=12 per group).All rats were euthanized by cervical dislocation after 5-week feeding.Blood and colon tissue samples were collected.Then the blood biochemical parameters were measured by automatic blood biochemical analyzer.The endotoxin content,D-lactic acid content and the activity of the DAO in plasma were measured by enzyme-linked immunosorbent assay(ELISA).Colon tissue was fixed in 4%(wt/vol)paraformaldehyde in PBS for fixation overnight.We examined the histological and morphological changes by Alcian blue-periodic acid-Schiff(AB-PAS).Quantitative real-time polymerase chain reaction(RT-qPCR)and western blotting were performed to measure the changes of Muc2 expression and other factors.This study was to investigate how intake of soybean oil,lard and fish oil affected the colonic barrier and its potential mechanism.The main contents and results are as follows.1.Effects of soybean oil,lard and fish oil on the growth status and blood parameters of ratsThe growth status,food intake,blood biochemical parameters,endotoxin content,D-lactic acid content and the activity of the DAO in plasma were measured and analyzed,for a preliminary understanding of the effects of different dietary fats on the health.The results showed that fish oil significantly reduced body weight gain,feed conversion rate,the blood glucose,triglyceride,total cholesterol,and high-density lipoprotein,but increased the endotoxin content,D-lactic acid content and the activity of the DAO in plasma.No significant difference existed between the soybean oil and lard group.Take together,the results indicated that fish oil can effectively control the weight gain,the level of glucose,triglyceride and cholesterol in the blood,making big improvements on the blood glucose and lipid.However,fish oil may impair the intestinal barrier.The moderate intake of lard(4%)caused more body weight gain,but there was no significant difference in the blood glucose and intestinal barrier when compared to soybean oil.2.Effects of soybean oil,lard and fish oil on colonic barrier in ratsThe rats were fed for 5 weeks and then the histological and morphological changes,goblet cells,Muc2 expression,inflammatory cytokines and TLRs expression in the colon were measured.The study aimed to illustrate the specific impacts of soybean oil,lard,fish oil on rats colonic intestinal barrier.The results showed that lard reduced the crypt depth,the mRNA level of Muc2 and MyD88,fewer significant differences were observes between rats in soybean oil and lard groups,except for the crypt depth,the mRNA level of Muc2 and MyD88.However,compared with the lard and soybean oil diet groups,intake of fish oil decreased the number of goblet cells,and inhibited Muc2 and TLRs expression in the colon of middle-aged rats,which would impair mucus barrier.3.Study on influential mechanism of soybean oil,lard and fish oil on colonic barrierTMT proteomics technology was used to determine and analyze the expression spectrum of colonic proteins in rats.Goblet cell-like LS174T cells were treated with SCFAs in vitro,after which cell number,Muc2 mRNA levels and TLRs expression were analyzed.The study aimed to investigate the influential mechanism of soybean oil,lard and fish oil on colonic barrier by both in vivo and in vitro methods.Proteome analysis showed the lowest abundance of Agr2 and Pdxdc1,Pfkp,Plch1,Gale,Gne,Cmpkl,Pmm2 and Rexo2 in the fish oil diet group,which could be involved in the glycosylation process.However,no statistical difference was observed between soybean oil and lard group.We hypothesized that the negative effect of fish oil could be associated with the suppression of Muc2 glycosylation process.Experiment in vitro showed that SCFAs differently changed the cell proliferation,Muc2 expression and TLRs gene expression.The differences resulted from the type and concentrations of SCFAs,as well as the cultured time.It indicated that SCFAs participate in the regulation of colonic barrier by influencing the cell number and Muc2 expression.