Protective Effects Of AS-Ⅳ On Diabetic Cardiomyopathy By Improving Myocardial Lipid Metabolism In Rat Models Of T2DM

Objective: Based on the previous work,this study is to explore whether astragaloside Ⅳ can prevent myocardial damage induced by type 2 diabetes,and to focusing on the role of AS-Ⅳ in regulating myocardial lipid metabolism and its possible mechanism.Methods: In this paper,high-fat feeding was used to induce insulin resistance,and a small dose of STZ was used to induce islet β-cell dysfunction to construct a rat model of type 2 diabetes.Rats with successful modeling were randomly divided into normal group,model group,AS-Ⅳ(80 mg / kg)group,metformin(200 mg / kg)group,10 rats in each group,and intragastric administration.Hemodynamic tests were performed after 8 weeks of continuous administration to evaluate cardiac diastolic function.Serum CK-MB and LDH levels were measured to evaluate myocardial damage.Plasma glucose,insulin,cholesterol,triglycerides,high-density lipoprotein and free fatty acid levels were measured to evaluate the metabolic characteristics of the model.HE,masson and Sirius staining were used to observe the pathological changes of myocardial structure in each group of rats.Western blot was used to detect the expression levels of TNF-α,IL-1β,and IL-6 in myocardial tissue.Free fatty acid kit and oil red staining were used to detect the accumulation of free fatty acids and lipids in the myocardium.Immunohistochemistry and Western blot was used to analysis the LKB1/AMPK protein and downstream lipid metabolism related proteins ACC,CPT-1 and CD36 expression levels.On this basis,the metabolic therapy drug metformin was used to observe its effect on lipid metabolism in diabetic rats and its protective effect on the heart.Results: Compared with normal group,the model group are in a worse state: with a lack of energy,sluggish fur,sluggish movements,"three more and one less" symptoms,weight loss,and significant increases in blood glucose and insulin levels,proving that a type 2 diabetes model was successfully constructed.After 8 weeks of AS-Ⅳ treatment,the general condition of the rats began to improve,the symptoms of "three more and one less" were alleviated,and the body weight and blood glucose level were also significantly improved.From the perspective of hemodynamics,compared with the model group,AS-Ⅳ significantly improved cardiac contraction and diastolic function.Observed from the perspective of histomorphology and pathology,compared with the control group,pathological changes appeared in the model group as myocardial fiber disorder,nuclear lysis or loss of cardiomyocytes,unclear boundary between cardiomyocytes,interstitial inflammatory cell infiltration and increased collagen deposition.The extent of these pathological changes was significantly improved after 8 weeks of AS-Ⅳ treatment,as well as the myocardial collagen deposition was decreased significantly.From the perspective of inflammation,compared with the control group,the expression levels of TNF-α,IL-6 and IL-1βincreased significantly in the model group.After 8 weeks of AS-Ⅳ treatment,TNF-α,IL-6 and IL-1β expression of myocardial tissue decreased significantly.Analysis of serum and cardiac tissue biochemical indicators revealed that plasma TC,TG,HDL and myocardial tissue FFA levels were significantly increased in the model group compared to the control group.Compared with the model group,AS-Ⅳ can significantly improve circulating TC,TG,and HDL levels,as well as free fatty acid content and lipid accumulation in cardiomyocytes of T2 DM rats.Further examination of myocardial energy metabolism regulation key factors LKB1 / AMPK and lipid metabolism related proteins ACC / CPT-1,CD36 expression levels,compared with the control group,the expression of p-LKB1,p-AMPK,and CPT-1 proteins in the model group was significantly reduced,and the expressions of ACC and CD36 protein were significantly increased.Compared with the model group,the expression of p-LKB1,p-AMPK and CPT-1 protein in myocardial tissue of ASⅣ treatment group was significantly increased,and the expression of ACC and CD36 protein was significantly reduced.Conclusion: In summary,our results indicate that AS-Ⅳ has a protective effect on T2 DMinduced myocardial injury in rats,and its mechanism may be related to improving cardiomyocyte lipid metabolism by upregulating the AMPK signaling pathway.