Protect Effects Of Myricitrin On Diabetic Cardiomyopathy And Its Underlying Mechanisms

Diabetes mellitus has been regarded as one of the most important chronic diseases in the world,and the number of diabetic patients has increased fast in recent years.Diabetic cardiomyopathy is a common cardiovascular complication of diabetes with a high mortality rate.It is mainly characterized by left ventricular diastolic dysfunction in the early stage and further developed into heart failure.Therefore,it is of great significance to study the pathogenesis of diabetic cardiomyopathy,and to explore new method and medicine for the treatment of the disease.Myricitrin is a flavonoid glycosides with polyphenol hydroxyl existing in many kinds of natural plants.It has many pharmacological activities,such as improving microcirculation,anti-inflammation,anti-oxidation,inhibiting apoptosis and so on.In this research,the protective effect of myricitrin on diabetic cardiomyopathy and its underlying mechanism were investigated.In vivo experiments,intraperitoneal injection of streptozotocin(STZ)combined with high fat diet was used to establish the diabetic animal model.Drugs were given to the mice by intragstric administration.Blood glucose concentration,body weight,food intake and water intake were measured during the administration.After 8 weeks,M-mode echocardiography was used to measure cardiac parameters.Hearts were weighted to calculate heart weight/ body weight(HB/BW)ratio.The level of myocardial enzymes(LDH,CK,AST)in serum,the content of the lipid peroxide(MDA)and the activity of antioxidant enzymes(SOD,CAT,GSH-PX)in myocardial tissue were measured by assay kits.The pathologic changes of the myocardial tissue and the fibrosis of the myocardial matrix were observed by HE and Masson staining.Further more,the expression of apoptosis-related proteins(Bcl-2,Bax,cleaved Casepase-3,cleaved Casepase-9)in myocardial tissue was analysed by Western blot assay.In vitro experiments,a cell injury model was established in which high glucose(HG)could induce damage to cardiac myoblasts H9c2.Then the cell viability was measured by MTT assay.The leakage of LDH,the content of MDA and the activity of SOD,CAT and GSH-PX were measured by assay kits.The intracellular level of ROS was detected by the fluorescence staining,the changes of mitochondrial membrane potential was detected by JC-1staining,and the cell apoptosis was detected by Hochest 33342/PI staining.Finally,theexpression of apoptosis-related proteins(Bcl-2,Bax,cleaved Casepase-3,cleaved Casepase-9)and Akt/Nrf2 signaling pathway related proteins(Akt,p-Akt,Nrf2,HO-1,NQO-1)was analysed by Western blot assay.In vivo study revealed that myricitrin had hypoglycemic effect,could alleviate body weight loss,and reduced food intake and water intake.M-mode echocardiography measurements showed that myricitrin could significantly improve left ventricular ejection fraction(EF)and fractional shortening(FS),and reduce HW/BW ratio of STZ-induced diabetic mice.Besides,myricitrin could reduce the level of LDH,CK and AST in serum,decrease the content of MDA and enhance the activity of SOD,CAT and GSH-PX in myocardial tissue.HE and Masson staining showed that myricitrin could reduce myocardial lesion and fibrosis in STZ-induced diabetic mice.The changes of apoptosis-related proteins expression indicated that Myricitrin could inhibit myocardial cell apoptosis induced by diabetes.In vitro study found that myricitrin could attenuate HG-induced H9c2 cells injury and improve cell viability and cell morphology.Myricitrin also could reduced LDH leakage and MDA content,and enhance SOD,CAT and GSH-PX activity in HG-induced H9c2 cells significantly.Further more,Myricitrin could inhibit HG-induced H9c2 cells apoptosis,decreased intracellular ROS level and increased mitochondrial membrane potential.Western blot analysis showed that myricitrin could up-regulate the expression of Bcl-2 and down-regulate the expression of Bax,cleaved Casepase-3 and cleaved Casepase-9.Besides,myricitrin could recover the phosphorylation of Akt and the expression of Nrf2,HO-1 and NQO-1which were inhibited by high glucose.Both in vivo and in vitro experiments suggested that myricitrin has a protective effect on diabetic cardiomypathy.It could reduce myocardial injury and dysfunction in the STZ-induced diabetic mice,and could inhibit HG-induced H9c2 cells apoptosis and oxidative stress damage.It indicated that myricetrin might inhibit myocardial apoptosis and oxidative stress by activating the Akt/Nrf2 signaling pathway.