| The dietary protein not only provides an important source of nitrogen nutrition,but also has a wide range of biological functions.Meat protein contains all of the essential amino acids necessary in the human diet.The short-term feeding experiments of rats in our laboratory showed that different sources of meat protein have different effects on physiology and metabolism,however,the long-term physiological effects of meat protein diet are still unclear.Its potential molecular mechanism remains to be proven.Therefore,in this study,casein protein was used as a comparison of non meat animal protein and soy protein as a comparison of plant protein.The difference of protein expression profile in rat liver were compared between fish,chicken,pork and beef protein after 90 days feeding.According to the differences in protein exploiting the differential metabolic pathways and potential regulatory factor and exploring the possible mechanism of differential regulation of dietary protein.It provides scientific basis for understanding physiological function of different source dietary proteins,which guides human rational diet as well as prevention of disease.Our research mainly divided into the following four parts:1.The effects of different meat protein intake on rat liver proteomeProtein was extracted from fish,chicken,pork and beef respectively,with casein and soybean protein as control.Diets were prepared in accordance with the AIN-93G diet formulation and rats were fed for 90 days.Blood and liver samples were collected at the end of feeding period.Liver protein was extracted and digested by trypsin,then liver proteomics was performed using iTRAQ and LC-ESI-MS/MS.Principal component analysis revealed a substantial inter-and intra-group variation of liver proteome as a response to dietary proteins.Fish protein group was similar to soybean/casein group,followed by chicken protein group.Pork and beef protein groups showed the greatest variation.Based on bioinformatics analysis of the differentially expressed protein revealed that the four kinds of meat protein diet than soybean/casein protein group had a significant change in amino acids and other organic nitrogen metabolism pathway.Comparing with casein group,there were significant differences of related protein expression in the process of ribosomal assembly and protein synthesis in pork,beef and chicken protein groups.Comparing with soybean/casein group,many nutrients metabolism enzyme were significantly reduced in all meat protein groups.Pork,chicken and fish protein groups had significant difference in lipid metabolism and PPAR signal pathway.Compared with soybean/casein group,four meat protein groups significantly reduced the biotransformation related enzyme and mitochondrial oxidative phosphorylation protein existed significant differences.2.The effects of different meat protein sources intake on rat liver amino acid metabolism and protein synthesisIn terms of the effects of dietary proteins on serum amino acid levels in rats,the serum amino acid content in chicken protein group was similar to casein group in general,while the fish,beef and pork groups were relatively low or significantly lower than that of casein group.Compared with soybean protein group,fish protein group had more essential amino acids levels,the serum content of amino acids in chicken protein group was higher than that of the soybean group,while no significant alteration was detected for serum amino acids levels between pork,beef and soybean protein groups.Compared with soybean/casein protein groups,multiple amino acids metabolism enzymes had lower abundances in pork and chicken protein groups.The situation of differential amino acid metabolizing enzymes was similar in beef protein group.Compared with soybean/casein protein group,glycolysis and nucleotide metabolism enzymes had lower abundances in pork,chicken and beef protein groups.The rate of urea cycle in soybean protein group was significantly higher than other groups.In liver protein metabolism,the protein involved in the process of transcription mRNA splicing,localization,nuclear export,ribosome assembly and translation initiation in various meat protein groups had differences from soybean/casein protein group.Compared with casein/soybean protein groups,the protein involved in chaperone-mediated protein folding,protein modification and transhipment were significantly lower in all meat protein groups.The protein level of protein degradation related enzymes in the meat protein groups were higher than that of casein group and lower than the soybean protein group.The mTOR signaling pathway was suggested to involve the diet-mediated regulation of ribosome assembly and protein synthesis.The mRNA level of mTOR and downstream regulators in pork,chicken and beef protein groups were significantly different from soybean protein group.3.The effects of different meat protein sources intake on rat liver fat oxidation and energy metabolismFish and pork protein groups significantly increased cholesterol synthesis and esterification related genes expression in rat liver.The mRNA expression of SR-BI and LDLR were significantly increased in pork protein group.Chicken,pork and beef protein groups significantly increased the reverse cholesterol transport and bile acid generated genes expression.Fish protein group had significantly higher cholesterol concentration in liver than the other groups,while the rat in chicken,beef and pork protein group had lower hepatic cholesterol levels.Hepatic triglyceride levels in chicken,beef and pork group were significantly lower than the control group.The mRNA expression of PGC1a were significantly increased in chicken,pork,beef protein groups.High expression of PGC1a promoted the metabolism of triglyceride degradation.The related protein of ?-oxidation in the meat groups(such as pork protein group)are significantly decreased.The PPARy mRNA expression was significantly decreased in pork and chicken protein groups.No significant alterations was detected for PPARa mRNA expression.Although the mRNA level of(mtDNA)-encoded genes were increased in chickens,pork and beef protein groups,its protein content was significantly lower,especially of ATP synthase in meat protein groups.Meat protein groups can promote uncoupling of oxidative phosphorylation,and then promote the body's adaptive thermogenesis.4.The effects of different meat protein sources intake on rat liver biotransformation and inflammatory responseNo significant alteration was detected for the total antioxidant capacity and lipid peroxidation level between the four meat groups and casein group,but lipid peroxidation were significantly higher than that of soybean protein group.The enzymatic antioxidants in the chicken and fish protein groups were superior to the soybean protein group,while the pork and beef protein groups were relatively lower than casein group in enzymatic antioxidants.In the terms of the non-enzymatic antioxidants,GSH levels were significantly higher in fish,chicken and beef protein groups,compared with soybean protein or casein group.Four kinds of meat protein dietary significantly decreased the liver phase I enzymes(CYP450s,etc.)and phase II enzymes(GSTs,UGTs,and SULTs)at both mRNA and protein levels,and Keapl-Nrf2-ARE pathways played an important role in the differentially expression of phase I and II enzymes between all meat protein groups and casein/soybean protein group.The effects of the four kinds of meat protein diets on the liver inflammatory response in rats were consistent with the casein/soybean protein group,which only significantly changed the expression of vascular permeability related factors,and meat proteins such as beef protein stimulated the liver to express several immune-related proteins. |
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