Effect Of Corn Peptide On The Protective Effect Of Liver Fibrosis And Protein Synthesis Of Rats

ObjectiveTo solve the problem of protein malnutrition in patients with chronic liver disease and explore other biological effects of corn peptide,this study aims to study the effects of corn peptide on liver function and protein synthesis under the condition of sustained liver function impairment through rat liver fibrosis model,and explore its internal mechanism preliminarily.MethodsFifty eight-week-old healthy male Sprague-Dawley（SD）rats were randomly divided into 5 groups:control group,model group,whey protein group,low-dose corn peptide group and high-dose corn peptide group.Rats in control group were intraperitoneally injected with olive oil（1 m L/kg bw,twice/week）,and the other groups of rats were intraperitoneally injected with 50%CCl₄-olive oil solution（1 m L/kg bw,twice/week）to induce the liver fibrosis model.At the same time,the whey protein group rats were given500 mg/kg/d of whey protein by body weight,the rats in low-dose and high-dose corn peptide groups were given 250 mg/kg/d and 500 mg/kg/d of corn peptide,respectively.And the control and model group rats were severally given equal volume of distilled water,for8 weeks in total.The first part analyzed the protective effects of corn peptide on liver fibrosis and hepatic protein synthesis in rats.The weight,liver weight and spleen weight of rats were weighed by analytical balance.The liver function of rats in each group was measured by automatic biochemical analyzer,and the liver cell structure was analyzed by pathological staining.Gene expression levels of interleukin-6（IL-6）,tumor necrosis factor-α（TNF-α）and nuclear factor-kappa B（NF-κB）in liver tissue were determined by reverse transcription-polymerase chain reaction（RT-PCR）.Western Blot was performed to analyze the protein expression of mTOR,p-mTOR,p70S6K and p-p70S6K.The second part analyzed the effect of corn peptides on protein synthesis in skeletal muscle of hepatic fibrosis rats.The grasping force of the limbs of the rats was measured by an electronic grasping force meter,and the weight of the gastrocnemius was weighed by an analytical balance.The gastrocnemius was stained by pathological slices to analyze the morphology of muscle tissue.The gene expression of IL-6,TNF-αand NF-κB inflammatory factors in muscle tissue were analyzed by RT-PCR.The expression of Myosin,MYH2 and MYL2 in gastrocnemius and the protein synthesis related signal molecules mTOR and p70S6K and their phosphorylation levels were determined by Western Blot experiment.ResultsThe first part of the experimental results showed that after 8 weeks of intervention,there was no significant difference in body weight among the rats in each group（P>0.05）.The body weight of rats in the model group,whey protein group,low-dose and high-dose corn peptide group was slightly lower than that of the control group.Compared with the control group,the liver volume and the liver index of the rats in the model group increased,while the liver function decreased significantly（P<0.05）.Compared with the model group,the liver function of the corn peptide group was slightly improved,and the serum albumin level of the high-dose corn peptide group was significantly higher than that of the model group and the whey protein group（P<0.05）.The pathological images of liver tissue showed that the liver lobules in the control group were clear and complete,radially arranged,and no aggregation of inflammatory cells was observed.In the model group,the arrangement of hepatocytes was disordered,the ballooning degeneration of hepatocytes was obvious,the inflammatory cells were massively aggregated,and the deposition area of liver fibrosis was significantly higher than that of the control group（P<0.05）.Compared with the model group,the corn peptide groups had less ballooning degeneration of hepatocytes,a small amount of inflammatory cell infiltration,and the deposition area of liver fibrosis was significantly lower than the model group（P<0.05）.The expression of IL-6,TNF-α,NF-κB inflammatory factor genes in the liver tissue of the rats in the model group were higher than those in other groups,and the high-dose corn peptide group was significantly lower than the model group（P<0.05）.Western Blot results showed that the protein expression of p-mTOR/mTOR and p-p70S6K/p70S6K in the model group were significantly lower than those in the control group（P<0.05）,and the expression in the high-dose corn peptide group were higher than the model group（P<0.05）.The results of the second part showed that there was no significant difference in the grasping power and gastrocnemius muscle index among the rats in each group（P>0.05）.Compared with the control group,the limb grasping strength and gastrocnemius muscle index showed a downward trend in the model group.In the muscle tissue slices,the muscle fibers of the control group were arranged neatly and tightly,while the muscle fibers of the other four groups were relatively loosely arranged,and no obvious pathological changes were observed.The mRNA expression levels of inflammatory factors（IL-6,TNF-α,NF-κB）in the skeletal muscle of rats in the model group were significantly higher than those in the control group（P<0.05）,and the expression levels of inflammatory factors in the high-dose corn peptide group were significantly lower than those of the model group（P<0.05）.Compared with the control group,the protein expressions of Myosin,MYL2 and MYH2 in the skeletal muscle of the rats in the model group showed a downward trend,and the expression levels of Myosin and MYH2 in the high-dose corn peptide group were significantly higher than those in the model group（P<0.05）.The protein expression levels of p-mTOR/mTOR and p-p70S6K/p70S6K in the gastrocnemius muscle of rats in the model group were significantly lower than those in the control group（P<0.05）,while the protein phosphorylation level of high-dose corn peptides was higher than that in the model group（P<0.05）.Conclusion1.Corn peptides can inhibit the inflammatory state of rat liver tissue which induced by CCl₄,delay the progression of liver fibrosis,and have a certain protective effect on the liver function of rats.2.Corn peptides can activate mTOR signaling pathway,promote mTOR and p70S6K protein phosphorylation,improve protein transcription and translation efficiency,and improve serum protein levels better than whey protein.3.Corn peptide has the potential to promote skeletal muscle protein synthesis,which is related to the inhibition of inflammatory factor expression and the activation of mTOR signaling pathway by corn peptide.The research on its effect on skeletal muscle protein synthesis requires longer intervention.