The Role Of Proteasome In AD Like Pathological Changes In Diabetic Brain

Object:Diabetes is an important risk factor for Alzheimer's disease,which can cause AD like pathological changes and cognitive decline in the brain.Abnormal aggregation of specific proteins is a typical AD like pathological changes,affecting neuronal function and even leading to neuronal cell death.Proteasome is an important organelle of abnormal protein metabolism in cells,which participates in the regulation of "protein homeostasis" in cells.In this study,the role of proteasome in the pathological process of diabetic susceptible AD was investigated by detecting the changes of proteasome function in the brain and the effect of proteasome activity on AD like pathology.The understanding of the mechanism of AD was deepened from the perspective of metabolism.Content: The experiment used high-sugar and high-fat diet feeding combined with low-dose intraperitoneal injection of streptozotocin to establish a model of human type 2 diabetes in rats,the systematically detected diabetes related indicators to confirm that the experimental animal model is established successfully.After successful modeling,diabetic rats and normal rats were given intracerebral intervention of proteasome inhibitors,and detected the inhibitory effect of proteasome to confirm the effect of the proteasome intervention.A variety of detection methods to detect changes in the structure and function of the proteasome in the brain and the effects of the proteasome on AD like pathological changes,including proteasome activity detection kit,Western-blotting for detection of proteasome subunits,immunohistochemistry and immunofluorescence for detection of proteasome changes in rat brain.Results:1 This experiment successfully established a human model of type 2 diabetes by using high-sugar and high-fat diet feeding combined with low-dose intraperitoneal injection of streptozotocin.2 Study on the changes of proteasome structure and function in brain2.1 Detection of the content of each subunit of 20 S proteasome in cerebral cortex and hippocampus: The content of ?2 and ?5 subunits in 20 S proteasome subunit of DM group was lower than that of Ctrl group(P >0.05),and recombinant 20 S protease subunit protein i?2 The content of i?5 has an increasing trend(P>0.05).2.2 Changes of three hydrolase activities in 20 S proteasome: T-L and CT-L in DM group were higher than Ctrl group in brain cerebral cortex and hippocampus(P>0.05).3 Study on the relationship between proteasome function and AD like pathological changes in diabetic brain3.1 Detection of proteasome inhibitors and their effects: The activities of three proteases in the DM+Lac group and the Ctrl+Lac group in the hippocampus were significantly higher than those in the DM group(P<0.05);the content of Ubiquitin conjugated protein in brain of DM and Ctrl groups was significantly higher than that of untreated rats(P<0.05).3.2 Detection of proteasome inhibitors on A? production pathway and Tau protein phosphorylation pathway in hippocampus: There was no significant change in the content of A? production pathway-related protein in the brain of rats in each group.The protein related to Tau phosphorylation pathway increased after proteasome inhibition,but it was not statistically significant(P>0.05).3.3 Detection of the effect of proteasome on oxidative damage protein in hippocampus of brain: DNP and 3-NT in DM+Lac group,Ctrl+Lac group and DM group were significantly higher than those in Ctrl group(P<0.05).4 Changes of proteasome regulation related proteins in hippocampus of the brain4.1 Detection of 11 S proteasome subunit protein content in brain: The content of 11 S protease subunit protein PSME2 in DM group was significantly higher than that in Ctrl group(P<0.05).4.2 Changes of proteasome-associated proteinss in brain: The structure of neurons and11 S proteasome subunit protein PSME2 in DM group changed.Conclusion: Long-term high-fat diet feeding combined with low-dose STZ can induce a non-genetic background rat model of diabetes.The model shows symptoms of hyperglycemia,hyperlipidemia,weight loss,fatty liver,polydipsia and polyuria.,and was able to simulate some typical characteristics of human type 2 diabetes mellitus.Diabetes has a tendency to increase the proteasome immunotype subunits i?2,i?5 in the rat cerebral cortex and hippocampus,but there is no statistical difference.Diabetes has a tendency to increase the activity of the proteasome T-L and CT-L hydrolase.Proteasome inhibition has different effects on AD like pathological changesin hippocampus of diabetic rats.The key protein of A? production pathway is not affected by proteasome inhibition;phosphorylated Tau protein has an increasing tendency after proteasome inhibition;oxidatively modified protein accumulation is affected by proteasome inhibition.