| Diabetic cardiomyopathy, which develops in diabetic patients in the absence ofcoronary artery disease or hypertension, is a major cause of heart failure in diabeticpatients. It is mainly characterized by left ventricular diastolic dysfunction, systolicdysfunction and structural remodeling. Cardiac hypertrophy, which includes a seriesof changes in heart size, shape, and function, is characterized by a structuralrearrangement of the cardiac chamber wall that involves cardiomyocyte hypertrophyand eventually fibrosis. Although diabetic cardiomyopathy is increasing recognized,the underlying mechanisms of it are still poorly understood.5’-adenosine monophosphate-activated protein kinase (AMPK) is a heterogonousprotein trimer composed of three subunits; a functional subunit (α) and regulatorysubunits (β γ). AMPK plays an important role in various intracellular signalingpathways that regulate intracellular energy balance. Activated AMPK triggers glucoseuptake, glycolysis, fatty acid oxidation and mitochondria biogenesis, decreasesprotein synthesis, glycogen synthesis and fatty acid synthesis. In addition, increasedAMPK activity promotes the translocation of the glucose transporters onto the plasmamembrane and enhances glucose uptake.Berberine (BBR), an isoquinoline alkaloid, derived from medicinal herbs, hashypoglycemic and insulin-sensitizing activity in both animal models and in patientswith type2diabetes mellitus. Recently, the effect of berberine on cardiomyopathy hasattracted many researchers, our previous studies also demonstrated that berberinecould protect the myocardium from ischemia reperfusion injury, and reduce the areaof infarction. Although there has numerous evidence that proved the benefical effectsof berberine on heart, the mechanism of underlying it remains blunt, also, whether ithas a protective effects on diabetic cardiomyopathy rarely reported. In this case, ourpresent study reported the protective effect of berberine on diabetic cardiomyopathyboth in vivo and vitro studies, we hope that our works will provid a theoretical basis for prevention and treatment of diabetic complications.First of all, we studied the cardioprotective effect of berberine on diabetic rats.In our vivo studies, we used the type2diabetic models established by our lab,High-fat diet combined with multiple STZ injection were used to establish thisdiabetic mellitus model in rats, and after the diabetic model has been established, therats were divided into three groups, DM group treated with water and DM grouptreated with berberine (100mg/kg/d), after16weeks, blood glucose concentration,blood lipids, insulin, intraperitoneal glucose tolerance test, and cardiac function usedby echocardiography were examined, results showed that DM group showed moreslow in heart rate(HR), and increased in diastolic left ventricular internaldiameter(LVIDd), systolic left ventricular internal diameter(LVIDs), decreased insystolic septal thickness(IVSs), systolic left ventricular posterior wall thickness(LVPWs), E/A ratio, fracional shortening(%FS) and ejection fraction(EF%). Inaddition, morphology of HE stainings in myocardial tissue demonstrated that heartfrom DM group had a disorders of myocardial cells arrangement, Masson stainingsalso found that the occurrence of myocardial fibrosis; which were consistent withthose reported of the diabetic cardiomyopathy rat model. Berberine administeredcontinuously for16weeks, compared with DM group, BBR group significantlyimproved heart rate of type2diabetic rats, reduced LVIDd, LVIDs, increased E/A,%FS and EF%. Fasting glucose, triglycerides, cholesterol and fasting insulin levelswas significantly higher treatment by BBR, HE stainings and Masson stainings resultsalso showed that BBR treatment improved myocardial morphology and reducefibrosis. Western blot was used to examine the expression of protein in diabetic ratheart tissue, the expression of AMPK/AS160/GLUT4were upregulated andphosphorylation of AKT/GSK-3β were increased after BBR administration,suggesting that the protective effect of berberine on cardiac may be related toactivation of AMPK.Secondly, in vitro study, we explore the protection of berberine on cardiomyoc-ytes both in insulin resistance and cardiac hypertrophy.We first examined the glucose consumption in H9c2myocardial cells, the resultsshowed that berberine increased glucose consumption in a dose–dependent mannerin H9c2cells, and at the same time, increased AMPK expression in a dose-dependentmanner; we also observed the glucose consumption and glucose uptake after treated with agonist (AICAR)/inhibitor (Compound C) of AMPK alone or combined withBBR, the results showed that specific inhibitor of AMPK could diminish the glucoseconsumption and glucose uptake induced by BBR in normal H9c2cardiomyocytes;We further examined the glucose consumption and glucose uptake in insulin resistantH9c2cardiomyocytes induced by high insulin, we found that BBR could increasedthe glucose consumption and glucose uptake whether or not occurrence of insulinresistance in H9c2cardiomyocytes. Specific inhibitor of AMPK--Compound Cpartially diminished the glucose consumption induced by BBR as well as the glucoseuptake in insulin resistant H9C cardiomyocytes, and western blot showed that theexpression of AMPK was increased significantly in insulin resistant H9c2cellstreated with BBR, meanwhile, the expression of AKT and p-AKT was not increasedsignificantly, all above results showed that berberine improved the insulin resistance,at least in part,by activation of AMPK in H9c2cardiomyocytes.Cardiac hypertrophy is an important manifestation of diabetic cardiomyopathy,long-term cardiac hypertrophy can lead to myocardial cell apoptosis, which leading toheart failure and death. Therefore, in the second part, we primarily investigate theprotective effects and mechanisms of berberine on cardiomyocyte hypertrophy.inH9c2hypertrophic cells induced by palmitic acid. We established the hypertrophymodel induced by palmitic acid in H9c2cardiomyocytes to mimic the bodyenvironment of fat patients, the results showed that cardiomyocytes size of the modelgroup (PAL group) was increased significantly compared to the CON group, BBRgroup significantly reduced the size of cardiomyocyte. Further detection of AMPK inhypertrophy cells induced by palmitic acid showed that palmitic acid could reducedexpression of AMPK in a dose-dependent manner, intestingly, berberine reversed thereduction of AMPK levels in H9c2hypertrophy cells induced by palmitic acid, andwe next examined the expression of specific cardiac hypertrophy proteins, the resultsfound that the expression of α-MHC was significantly reduced in PAL group, and theexpression of β-MHC was significantly increased, indicating that shifting washappened in cardiac myosin Phenotypi, the cell hypertrophy could also been identifiedfrom the cell morphology. BBR could elevated α-MHC and reduced expression ofβ-MHC significantly; this was also observed in myocardial cell morphology.Interestingly, specific inhibitors of AMPK Compoud C could diminished the theprotective effect of berberine on cardiac myocyte hypertrophy, western blot also showed that phosphorylation of AKT/GSK-3β were reduced in hypertrophy group,and berberine could reversed these reduction, all above results showed that berberinecould protect cardiomyocytes from hypertrophy, at least in part, through theactivation of AMPK.In summary, berberine has a protective effect on heart function in diabeticcardiomyopathy rats, AMPK is one of the key targets of its protective role, berberinecould improve insulin resistance and cardiac hypertrophy through the activation ofAMPK in H9c2cardiomyocytes, and the underlying mechanism may be related toelevated expression of AMPK, which leading to increased GLUT-4translocationthereby increasing glucose consumption and glucose uptake, also reduce oxidativestress by increasing phosphorylation of GSK-3β. |
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