The Effect Of GLP-1 On Hepatic Steatosis And Jnk Signaling Pathway In Type 2 Diabetic Rats

Objective:To investigate the effect of GLP-1 analogues(liraglutide)on hepatic steatosis and JNK signaling pathway in type 2 diabetic rats.Methods:90 normal SPF male rats were selected.20 of them were randomized as normal group(NC group),others were feeding on high-fat-high-glucose diet combined with a low-dose STZ injection to induce type 2 diabetic rat model.Type 2 diabetic rats were randomly divided into three groups:low dose lirglutide(400ug/kg)treatment group(LR-L,n=18),high dose liraglutide(800ug/kg)treatment group(LR-H,n=18),diabetic control group(DM,n=19),liraglutide was injected subcutaneously once a day for the treatment groups;NC group and DM control group were injected with normal saline in the same way.Body weight of the rats,fasting blood-glucose(FBG),diet condition and mental state were recorded.All of the rats were sacrificed at 4 weeks after giving medicine.The serum was collected to measure the blood glucose,blood lipid,liver enzyme and insulin resistance(IR).Liver tissue was collected to detect the TNF-a by enzyme-linked immunosorbent assay(ELASA).Hematoxylin-eosin(HE)staining was used to observe the pathological changes of liver tissue.The expression of JNK1 protein and P-JNK1 protein were detected by immunohistochemistry.The expression of JNK1mRNA was detected by fluorescence quantitative PCR.Results:after 4 weeks of treatment:?Body weight:NC group>DM group>LR-H,LR-L group(337.77±28.64,250.29±19.02,220.25±22.49,206.73±26.50,respectively,P<0.05);?Blood sugar and blood lipids:FBG:DM group>LR-H,LR-L group>NC group(0.64±0.10,0.51±0.17,0.51±0.13,0.24±0.08,respectively,P<0.05);TG:DM group>LR-H,LR-L,NC group(0.64±0.10,0.51±0.17,0.51±0.13,0.24+0.08,respectively,P<0.05);TC:DM group>LR-H,LR-L group>NC group(1.74±0.88,1.23+0.13,1.16±0.21,0.85±0.22,respectively,P<0.05;?HOMA-IR and ISI:before the treatment:HOMA-IR:DM,LR-H,LR-L group>NC group(33.37±8.74,32.58±5.42,32.09±5.20,5.82±1.13,respectively,P<0.05);ISI:NC group>DM,LR-H,LR-L group(-4.85±0.20,-6.59±0.26,-6.58+0.17,-6.57±0.17,respectively,P<0.05);After the treatment:HOMA-IR decreased and ISI increased statistically significantly(P<0.05),HOMA-IR:DM group>LR-H,LR-L group>NC group(33.79±6.74,26.46±4.01,26.32±5.27,6.16±1.87,respectively,P<0.05);ISI:NC group>LR-H,LR-L group>DM group(-4.88±0.33,-6.61±0.21,-6.34±0.17,-6.37±0.19,respectively,P<0.05);?ALT:DM group>NC group,LR-H group>LR-L group(153.33±51.32,103.80±40.17,109.44±36.24,144.75±45.91,respectively,P<0.05);? Pathological changes of liver tissue and NAS score under HE staining:under the microscope,NC group:Liver cells arranged neatly,liver lobular rules,the central cells have large and round nuclei,cytoplasmic uniform,no fat degeneration and inflammatory cell infiltration.The structure of hepatic cords was disorder,hepatocyte swelling,steatosis,inflammatory cell infiltration were found.There was some spotted and focal necrosis in liver lobules.LR-H group and LR-L groups:pathological alterations were significantly improved;NAS score:DM group>LR-H,LR-R group>NC group(4.29±0.95,2.13±0.99,2.18±1.25,0.92±0.64,respectively,P<0.05);? TNF-? level and JNK1mRNA expression:DM group>LR-H,LR-L group>NC group(TNF-a:1490.40+75.11,1282.09±133.31,1261.58±178.20,1108.11±110.41;JNK1mRNA:2.02±0.23,1.41±0.26,1.41±0.27,1.01±0.16,respectively,P<0.05);?JNK1 protein and P-JNK1 protein:The difference was not statistically significant among four groups(P>0.05).Conclusions:? The T2DM NAFLD rat model could be successfully induced by injecting STZ 35 mg kg-1 combined with high-fat-high-glucose feed for 5 weeks,and the model was characterized by hyperglycemia,hyperlipidemia,hyperinsulinemia and insulin resistance;? Liraglutide can reduce body weight,fasting blood glucose,improve insulin resistance,increase insulin sensitivity and decrease TC,TG levels in type 2 diabetic rats.? Liraglutide treatment can improve liver fatty degeneration and NAS score in rats with T2DM and NAFLD.? Liraglutide can reduce TNF-a level and down-regulate the expression of JNK1mRNA.?The role of liraglutide in improving hepatocyte fatty degeneration in T2DM may be achieved by reducing the TNF-a level,thereby inhibiting the activity of JNK signaling pathway.