Study On The Mechanism Of Regulation On Serum Cholesterol Level By Pea Protein And Pork Protein In Differential Ways

Proteins from different sources,especially plant protein and animal protein,exert distinctly different effects on human health.As the dietary structures changed in the recent decades,the incidence of cardiovascular diseases(CVD)caused by lipid metabolism disorders is on the rise in China,even globally.Although the lipids lowering drugs show obvious efficiency,the side effects on human health cannot be ignored.Gut,the vital place where cholesterol can be absorbed,converted and excreted,plays essential role in maintaining the cholesterol homeostasis.However,the exact role of gut microbiota in proteins modulating host cholesterol has not been well established.The effects of plant and animal proteins on fermentation characteristics by human fecal microbiota was determined firstly.The casein,rice,oat,chicken,pork and beef proteins were selected as the substrates for simulated gastrointestinal digestion,and human fecal samples were collected from healthy donors as the inoculum of fermentation.The correlations of amino acids compositions,fermentation productions and gut microbiota were further analyzed.As the results,the animal protein groups had higher degree of hydrolysis(DH)after digestion and higher levels of ammonia nitrogen(NH₃-N)after fermentation than cereal proteins.The pH value of fermentation liquid declined as proteins were added during fermentation.Cereal protein groups promoted the gut microbiota to produce more short chain fatty acids(SCFAs)with the high proportion of acetate,propionate and butyrate by lowering the pH than red meat proteins.The abundance of Firmicutes at phylum level in cereal protein groups was lower than red meat proteins after fermentation.The cereal protein groups enhanced the growth of Bacteroides and Bifidobacterium while red meat proteins stimulated the growth of Peptoclostridium.The hamsters were treated with antibiotics(Abx)to study the difference between pea protein and pork protein in regulating cholesterol after elimination of intestinal flora.The decisive roles of gut microbiota in regulating host cholesterol were illustrated by the findings that the differences in serum cholesterol level between pea protein and pork protein disappeared in the hamsters treated with antibiotics.To further investigate the effects of different dietary proteins on gut microbiota and host cholesterol levels,hamsters were fed with different proteins in different period.The experimental results of cross-over intervention of pea and pork protein showed that the serum cholesterol level was reversed with dietary exchange.Most interestingly,the corresponded changes in abundance of dominant bacteria suggested that the“beneficial”microbe Muribaculaceae were responsible for the inhibitory effect of pea protein on serum cholesterol level,while the opposite effect of pork protein was due to the“harmful”microbe Erysipelotrichaceae.Moreover,dietary pea protein supplement altered cecal metabolites including changes in arginine/histidine pathway,primary bile acid biosynthesis,SCFA or other lipid-like molecules,which involved in cholesterol metabolism.In conclusion,this study indicated that plant protein showed better fermentation characteristics than red meat protein.The decisive role of gut microbiota was confirmed by that no differences in serum or liver cholesterol were observed after the gut microbiota were eliminating using Abx.The substitution of pork protein with pea protein could reshape the gut microbiota,affect the contents of metabolites in caecum,and thus regulate cholesterol metabolism.The difference between pea protein and pork protein in regulating cholesterol can be attributed to the improvement of gut microbiota and amino acid metabolism.