| Background and Objectives:Diabetes mellitus(DM)is a common endocrine metabolic disease characterized by hyperglycemia caused by defective insulin secretion or insulin resistance,which seriously endangers human health.The pathogenesis of DM is complex and has not yet been fully elucidated.Its pathogenesis may be related to multiple factors such as genetics,abnormal glucose and lipid metabolism,hemodynamic changes,inflammatory mediators,and cytokines.Type 2 diabetes mellitus(T2DM)accounts for about 90% of DM patients,and once it develops,it lasts a lifetime.Damage to the heart,brain,liver,kidney,and other systemic organs caused by long-term hyperglycemia is its most significant complication.Among them,21%-78% of T2DM patients will develop a liver injury.Therefore,the study of the pathogenesis and prevention of liver injury in T2DM is one of the popular areas in the field of biomedicine.Liver injury in T2DM may be caused by various factors such as insulin resistance(IR),dyslipidemia,oxidative stress,inflammation,and apoptosis,and autophagy is closely related to these factors.At present,the pathogenesis of T2DM liver injury is still unclear,and there is no ideal prevention method in clinical practice.Therefore,it is of great theoretical and practical significance to explore the pathogenesis and new drugs for its prevention and treatment of liver injury in T2DM.Astragalus membranaceus is a common drug used in the clinical treatment of DM heart,brain,liver,and kidney injury.Astragaloside Ⅳ(AS-Ⅳ)is the active ingredient of Astragalus membranaceus,which has a wide range of pharmacological effects.Previous studies in our group have confirmed that AS-Ⅳ can improve T2DM nephropathy and cardiac injury,but little is known about its role in T2DM liver injury.Therefore,we propose to investigate whether AS-Ⅳ has a role in preventing liver injury in T2DM and its possible molecular mechanisms by examining the AMPK/mTOR signaling pathway and its autophagy.Methods:After one week of adaptive feeding,SD rats were randomly divided into normal(Control,Con)group and T2DM group,and were given normal diet and high-sugar and high-fat diet,respectively.After feeding high-sugar and high-fat feed for 6 weeks,all rats in the T2DM group were intraperitoneally injected with 35 mg/kg STZ.72 hours and 7days after STZ injection,the tail vein FBG value measured with a blood glucose meter should not be less than 16.7 mmol/L,which means that the SD rat model for T2DM was successfully established.According to different treatment methods,T2DM SD rats were randomly divided into the model group(Mod),AS-Ⅳ(80 mg/kg)group,and metformin(Met,120 mg/kg)group.The rats were continuously treated with drugs(once/day)for 8weeks,and their general condition was examined,and the FBG value of the tail vein was measured with a blood glucose meter.After the drug treatment,blood was taken from the abdominal aorta and the liver was collected to calculate the liver index;the serum ALT,AST,FBG,FINS,GSP,TNF-α,IL-6,and blood lipid-related indexes were detected;HE,Masson,TUNEL and Oil red O staining were used to observe the pathological changes of liver tissues in rats;western blotting and immunohistochemistry were used to detect liver-related protein expression levels;transmission electron microscopy was used to observe liver autophagosomes.Results:1.The water intake,food intake,and urine volume of rats in the Mod group rats were significantly increased,while their body weight was significantly decreased;the FBG level of blood taken from the tail vein of rats in the Mod group was significantly increased from 0 to 8 weeks of drug administration.In addition,serum levels of ALT,AST,FBG,FINS,GSP,and liver indices were significantly increased in the Mod group rats;HE and Masson staining results showed pathological changes in the liver of the Mod group rats,including hepatocellular disorders and significant lipid deposition and fibrosis in the liver.This confirms that the T2DM rat model was successfully induced and accompanied by the development of liver injury.However,after AS-Ⅳ treatment,the above indicators were significantly improved.2.The serum HOMA-IR value of the Mod group rats was significantly increased,indicating that T2DM rats showed obvious IR;the serum lipid-related indexes of the Mod group rats were disordered,and the Oil red O staining showed significant lipid deposition in the liver of the Mod group rats,indicating that T2DM rats showed obvious dyslipidemia;The results of western blotting and serological experiments showed that the liver and serum levels of TNF-α and IL-6 were significantly increased in the Mod group rats,indicating significant inflammation was shown in the liver of T2DM rats;the results of western blotting showed that the expression level of HO-1 in the liver of Mod group rats was significantly increased,indicating significant oxidative stress was shown in the liver of T2DM rats;The results of TUNEL staining showed that the hepatocytes in the Mod group rats showed significant apoptosis.However,after AS-Ⅳ treatment,the above indicators were significantly improved.3.The results of western blotting and immunohistochemistry showed that the level of autophagy in the liver of rats in the Mod group was inhibited;the results of transmission electron microscopy showed that the formation of autophagic vesicles in the liver of rats in the Mod group was inhibited.However,AS-Ⅳ treatment restored the inhibited autophagy level in the liver of T2DM rats.4.The results of western blotting showed that the AMPK/mTOR pathway was inhibited in Mod group rats.However,AS-Ⅳ treatment activated the inhibited AMPK/mTOR pathway in the liver of T2DM rats.Conclusion:In this experiment,a T2DM SD rat model was successfully prepared and accompanied by liver injury.AS-Ⅳ has a protective effect on T2DM liver injury,and the mechanism may be that AS-Ⅳ restores the inhibited autophagy level in the liver of T2DM rats by activating the AMPK/mTOR signaling pathway,which ameliorates IR and dyslipidemia and inhibits hepatic oxidative stress,inflammation,and apoptosis levels. |
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