GLP-1 Alleviated Diabetic Kidney Disease Through Activation Of Autophagy By Inhibiting MTOR Signaling Pathway

BackgroundNowadays,as the population of the diabetic patients is more than 100 million in China,diabetic has been a major public health problem and the economic burden of chronic diabetic complications to the family and society.Diabetic kidney disease is one of the most serious and harmful chronic complications of diabetes,which has been the main causes of end-stage renal disease.Requiring long-term renal replacement therapy,end-stage renal disease not only has a heavy burden on family,society and economy,but also leads to a significant decline in quality of life and long-term survival rate.New research reports that among the people with diabetic kidney disease,60.5%of the patients are at the early stage of diabetic kidney disease,which is accompanied with a slight increase in proteinuria with normal renal function.It is urgent to use effective methods to intervene early diabetic kidney disease and block the progression of chronic kidney disease to end-stage renal disease.GLP-1,a significant gastrointestinal hormone,can regulate autophagy and reduce reactive oxygen species(ROS)through activating GLP-1R.It has been reported,the suppression of autophagy in renal tubular epithelial cells can damage cell organelle and cellular homeostasis in high glucose environment.Consequently,it can lead to renal dysfunction.The activation of autophagy moderately can inhibit the injure of renal tubular epithelial cell by reducing oxidative stress.We hypothesis there is a autophagy protection mechanism to protect diabetic kidney disease in our body.While,whether GLP-1 play a protect role through this way had not been repoted.Objective1.To assess the protective effect of GLP-1 on renal injury in type 2 diabetic rats;2.To study the possible mechanism of GLP-1 in alleviating diabetic kidney disease through activation of autophagy by inhibiting mTOR signaling pathway;MethodsTo induce type 2 diabetic rat model,we fed the 8 week old ZDF rats with high-fat diet for 2 weeks.Rats were randomly divided into non-diabetic group,diabetic group,insulin group,Saxagliptin group and Liraglutide group.All the groups were fed with high-fat diet for 9 weeks and were given corresponding processing.During the experimental period,we detected the food intake,blood glucose and body weight weekly.The HbA1c was measured to realise the recently blood glucose level,the oral glucose tolerance test was performed before the end of the experiment to assess the islet function,and 24h urine was collected to detect the urine microalbumin.After killing the rats,we collected serum to detect blood lipids,blood urea,serum creatinine and cystatin C.Renal tissues were removed for HE staining to observe renal morphological changes.PAS staining was used to observe the morphology of basement membrane and mesangial matrix,and Masson staining was used to observe the renal fibrosis.The expression of autophagy related protein LC3B and P62 was detected by immunohistochemistry.Western Blot method was adopted to examine the expression of mTOR pathway and autophagy related protein in renal tissues.mTOR and Beclin-1 mRNA levels were detected by Quantitation RT-PCR method.The kits radical detected the scavenging of kidney tissue including SOD activity and GSH levels.Results1.The pathological results of type 2 diabetic rats were remarkable proliferation and hypertrophy of glomerulus,diffused thickness of BGM,slight proliferation of mesangial cell and increase of mesangial matrix with obvious fibrosis.2.Compared with diabetic control group,Saxagliptin and Liraglutide can improve the food intake,blood glucose,body weight,blood lipid and renal function of type 2 diabetic rats,as well as the pathological changes of diabetic kidney disease rats under light microscope.And the treatment effect of Liraglutide group was more significant.3.Compared with the insulin group,Liraglutide aslo can improve the renal function of type 2 diabetic rats in the same blood glucose level,especially the reducing of 24h urinary microalbumin was significantly superior to insulin group.4.Compared with diabetic control group,pS6K,pS6 and P62 protein expression in renal tissues of Liraglutide group were significantly decreased,and the expressions of beclin-1 mRNA in renal tissues were markedly increased.5.Compared with diabetic control group,the treatment of Liraglutide significantly decreased ROS by increasing the free radical scavenging of kidney tissue including GSH levels.ConclusionIn conclusion,GLP-1 has hypoglycemic action,at the same time can obviously improve the type 2 diabetic rats kidney damage and delay the progress of diabetic kidney disease;GLP-1 plays a role in renal protective effect through activation of autophagy by inhibiting mTOR signaling pathway,and then alleviating ROS.The Liraglutide is superior to saxagliptin in improving type 2 diabetic rats endocrine metabolic disorder and the renal protective effect.