The Influence Of Long-term Low-protein Diet On Nonspecific Inflammatory Response In Middle-aged Mice

Objective:To explore effects of long-term low-protein diet on nonspecific inflammatory response in middle-aged mice and explore the related mechanism through the detection of mTOR protein in liver.Methods:The 14-month-old female KM mice were randomly divided into control group,low-protein group,high-protein group and high-protein+rapamycin group.The middle-aged mice in control group received standard food and the others received special food.The middle-aged mice of high-protein+rapamycin group was injected intraperitoneally with rapamycin once every two days.Animals were sacrificed at the end of 3 months,then we obtained the liver,colon and spleen of them.Liver histology slices were prepared to observe the pathological changes and detect the expressions of CD68 and mTOR(the mechanistic target of rapamycin),colon histology slices were prepared to observe the pathological changes and the lymphocyte suspension of spleen were prepared to count the percentage of CD4~+T and CD8~+T cells.Results:1.Compared with control group,histology with HE staining showed that aging related changes were obviously relieved with liver cells arranging neatly and mild sinus hepaticus expansion in low-protein group and high-protein+rapamycin group.2.Compared with control group,the expression of CD68 in the liver was decreased in low-protein group and high protein+rapamycin group.On the contrary,the expression of CD68 in the liver of high protein group was increased.The Optical density from immunohistochemistry in control group,low-protein group,high protein group and high protein group+rapamycin were 0.21±0.01,0.18±0.01,0.29±0.02,0.15±0.02.3.Compared with control group,histology with HE staining showed that aging related changes were obviously relieved with colonic mucosal epithelial cells missing,crypts changing and goblet cells increasing in the colon of low-protein group and high-protein+rapamycin group,while it showed that lymphocytes in the colon of high-protein group were increase.4.Compared with control group,the percentage of CD4~+T and CD8~+T lymphocytes in the spleen were increased in low-protein group and high-protein+rapamycin group.The percentage of CD4~+T lymphocytes in the spleen of control group,low-protein group,high protein group and high protein group+rapamycin were 26.61%±2.92%,37.35%±1.53%,28.84%±2.83%,40.86%±1.13%.The percentage CD8~+T lymphocytes in the spleen of control group,low-protein group,high protein group and high protein group+rapamycin were 10.73%±1.30%,19.53%±2.61%,13.21%±0.98%,19.04%±0.61%.5.Compared with control group,the expression of mTOR in the liver was decreased in low-protein group and high protein+rapamycin group.The Optical density from immunohistochemistry in control group,low-protein group,high protein group and high protein group+rapamycin were 0.16±0.02,0.09±0.02,0.23±0.02,0.11±0.01.The rate of mTOR and GAPDH in control group,low-protein group,high protein group and high protein group+rapamycin were 1.11±0.15,0.70±0.05,1.17±0.37,0.45±0.14.Conclusion:Long-term low-protein diet in middle-aged mice can effectively alleviate the disturbance of liver tissue structure,the increase of nonspecific inflammatory cells,the deficiency of colonic mucosal epithelial cells,the extensive infiltration of lymphocytes and the decrease of the percentage of CD4~+T and CD8~+T lymphocytes in the spleen,so It helps to delay the aging related phenotype.The mechanism may be related to the low-protein diet down-regulated the expression of mTOR protein in the tissue.