| Objective: Glucagon like peptide-1 is secreted by endocrine cells of the gut when eating some food.It can regulate the metabolism of the body after feeding, such as appetite suppression, stable blood sugar, regulation of intestinal motility, etc.Liraglutide,as a GLP-1 receptor agonist, is currently developing new antidiabetic drugs, the stimulation of insulin secretion in a glucose concentration dependent mode, thereby reducing blood glucose.Compared with the traditional antidiabetic drugs, the incidence of adverse events significantly reduced,such as hypoglycemia, weight gain,and so on.It will bring a new hope for the treatment of diabetes.The prevalence rate increased significantly in type 2 diabetes, and insulin resistance is one of the pathological basis of type 2 diabetes.Studies have found that liraglutide can improve insulin resistance, but the mechanism is unknown. In this study, by giving high fat fed rats with different concentrations of liraglutide intervention, observe the effects on insulin sensitivity and lipid deposition in skeletal muscle of rats;by measuring the m RNA and protein expression of AKT and GLUT-4 in insulin signal transduction pathway and the m RNA and protein expression of FAT/CD36 and CPT-1 in fatty acid transport and oxidation,to explore new mechanisms for liraglutide improve IR and for the clinical application of liraglutide provides new theoretical basis.Method: 54 wistar male rats(230-260g) were divided into 16 normal diet group and 38 high fat food group.Insulin resistance was evaluated by hyperinsulinemic euglycemic clamp technique after 8 weeks.IR rat models were tested successful,then randomly divided into high-fat group,intervention group 1, intervention group 2,11 rats in each group.11 rats normal diet group was the normal contol group.The normal contol group and high-fat group:subcutaneous injection of normal saline;intervention group 1(liraglutide: 100ug/(kg·d)),intervention group 2(liraglutide:200ug/(kg·d)).After 2 weeks of liraglutide intervene,that GIR was examined again by hyperinsulinemic euglycemic clamp technique and the area under the curve of glucose tolerance(AUC) was calculated by oral glucose tolerance test in rats.The rest of the 6 rats in each group weighed the body mass, blood taken from abdominal aorta,FBG,FINS,FFA, TCH,TG,HDL-C and LDL-C were examined,then preserve skeletal muscle specimen,determinated of m TG 、 LCACo A in skeletal muscle.Meanwhile,skeletal muscle cell was observed by electron microscopy.Application of Real-time PCR and Western blot method to detect the expression of FAT/CD36,CPT-1,AKT and GLUT-4 in skeletal muscle.Results: 1 Comparison of the general situation in four groups of ratsCompared with contol group,the body mass,FBG,FINS,FFA,TCH,TG,LDL-C,m TG,LCACo A increased in HF group(P<0.05/P<0.01);Compared with HF group,the TG,FFA,LCACo A decreased in intervention group 1(P<0.05);while the body mass,FBG,FINS,FFA,TCH,TG,LDL-C,m TG,LCA Co A in intervention group 2 were significantly decreased compared with HF group(P<0.05/P<0.01);Compared with intervention group 1,the FFA,m TG,LCACo A in intervention group 2 were significantly decreased(P<0.05/P<0.01).2 Comparison of GIR in four groups of ratsBefore the drug intervention:Compared with contol group,the GIR of rats decreased in HF group(P<0.01). After drug intervention for two weeks,compared with contol group,the GIR decreased in HF group(P<0.01);while the GIR in intervention groups were increased compared with HF group(P<0.01);Compared with intervention group 1,the GIR in interv ention group 2 was significantly increased(P<0.01).3 Comparison of the results of oral glucose tolerance test(OGTT) in four groups of ratsCompared with contol group,the blood glucose of the rats in the HF group was increased, and the AUC was increased(P<0.01);Compared with HF group,the blood glucose and AUC was decreased in intervention group 2(P<0.05/P<0.01),while the blood glucose and AUC was decreased in intervention group 2,but the difference was statistically significant at 120min(P<0.05);Compared with intervention group 1, the blood glucosein at 0min,120 min and AUC were decreased intervention group 2(P<0.05).4 Electron microscope results of four groups of ratsThe contol group rats:Skeletal muscle cytoplasm without lipid droplets,mitochondria, myofilament stripes;in HF group rats:in cytoplasm there were many lipid droplets,mitochondrial swelling,even vacuolization,part of myofilament dissolved.In the intervention group 1 and 2:lipid dr oplets inthe intervention group were reduced, the structure of mitochondr ia was clear, but there was still partial dissolution and slight swelling o f mitochondria compared with the control group.5 The expression of mRNA in FAT/CD36, CPT-1 and AKT, GLU T-4 in skeletal muscle of four groups of rat were comparedCompared with contol group,the expression of m RNA in FAT/CD36 was increased,the expression of m RNA in CPT-1,AKT,GLUT-4 were d ecreased in HF group(P<0.01);Compared with HF group,the expression of m RNA in FAT/CD36 was decreased,and the expression of m RNA in CPT-1,GLUT-4,AKT were increased in intervention group 1 and 2(P<0.05,P<0.01). Compared with intervention group 1, the expression of m RNA in FAT/CD36 was decreased and the expression of CPT-1,AKT,G LUT-4m RNA were increased in intervention group2(P<0.05,P<0.01).6 The expression of protein in FAT/CD36, CPT-1 and AKT, GLU T-4 in skeletal muscle of four groups of rat were comparedCompared with contol group,the expression of protein in FAT/CD36 was increased,the expression of protein in CPT-1,AKT,GLUT-4 were de creased in HF group(P<0.01);Compared with HF group,the expression o f protein in FAT/CD36 was decreased,and the expression of protein in CPT-1,GLUT-4,AKT were increased in intervention group 1 and 2(P<0.05,P<0.01). Compared with intervention group 1, the expression of protei n in FAT/CD36 was decreased and the expression of CPT-1,AKT,GLUT-4 were increased in intervention group 2(P<0.05,P<0.01).7 Correlation analysis resultsGIR was significantly negatively correlated with FINS, FFA, m TG, LCACo A(r =-0.7842,-0.5241,-0.5371,-0.7091,P<0.05,P<0.01). Skeletal mu scle LCACo A was positively correlated with the expression of m RNA i n FAT/CD36(r =0.841, P<0.01), while was negatively correlated with the expression of m RNA in CPT-1(r=-0.6441, P<0.01), and was negatively c orrelated with the expression of m RNA in GLUT-4(r =-0.578, P<0.01).The expression of m RNA in GLUT-4 were significantly positively correl ated with GIR(r=0.8740,0.7139, P<0.01).Conclusion:1 High fat diet can result in the disorder of glucose and raised lipid metabolism in rats,and increase skeletal muscle ectopic lipid deposition, induced insulin resistance and impaires glucose tolerance.2 Liraglutide is concentration dependent improve glucose and lipid metabolism disorders with high-fat diet rats, reduce lipid deposition in skeletal muscle and reduce IR.3 Liraglutide is concentration dependence regulation the expression of fatty acid transport protein FAT/CD36 and fatty acid oxidation protein CPT-1, reduce muscle cells to fatty acid intake and accelerate the intracellular lipid oxidation, thereby reducing the intracellular lipid accumulation in skeletal muscle cells. At the same time,up regulation of the expression of insulin signaling pathway AKT, GLUT-4, promote the uptake of glucose by muscle cells and improve IR. |
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