Effects Of Telmisartan On The Expresion Of Cardiac Adiponectin And Its Receptors 1 In Type 2 Diabetic Rats

【Objective】Diabetic cardiomyopathy referred to be some damages including in extensive myocardial necrosis caused by cardiac microangiopathy and myocardial metabolic disorder. It is one of the main causes which lead to death in diabetic patients. Adiponectin is considered as one special cytokine, which is most closely related to insulin resistance, in many products secreted by adipose. Adiponectin accurately and effectively plays its roles after combining with its receptors. It remains to be clear whether adiponectin and its receptors are related to diabetic cardiomyopathy or not. Telmisartan is one of angiotensin II type 1 receptor blocker with regulated activity of selective peroxisome proliferator-activated receptor-γand has some functions of peroxisome proliferator-activated receptor-γagonist. Some recent studies showed that telmisartan had some preventive and therapeutic effect on diabetic cardiomyopathy. In this study, type 2 diabeteic model was induced by feeding Wistar rats with high-sugar and high-fat diet and then injection with a low dose of streptozotocin (STZ) by abdominal cavity.Then the serum adiponectin and the expression of the adiponectin receptor 1(AdipoR1)in myocardial tissue in experimental animals were detected in order to explore the association among serum adiponectin, AdipoR1 and diabetic cardiomyopathy and investigate the preventive and therapeutic effect of telmisartan on diabetic cardiomyopathy and its mechanism.【Methods】Ten of thirty-six Wistar rats were randomly taken out to be normal control group (group NC) and the rest were made for type 2 diabetic. The normal control rats were fed with standard diet while the diabetic rats were fed with high-sugar-high-fat diet (mixed 2.5%cholesterin, 20%suger, 15% cooked lard and standard diet together). Four weeks later, 30 mg/kg STZ was injected into diabetic vena caudalis to destroy pancreas while the normal control group was injected with equivalent volume of citric acid buffer by vena caudalis.At the end of 6 weeks The rats with fasting blood glucose (FBG)≥7.8mmol/l and insulin resistance were considered as type 2 diabetic models. Diabetic rats were divided randomly into 2 groups:diabetic model rats (group DC),diabetic model rats treated with Telmisartan (group DCT).The experiment lasted for 18 weeks.At the end of four and six weeks,body weight,FBG,fasting insulin(FINS), insulin sensitivity index(ISI),serum triglyceride(TG)and total cholesterol(TC)levels in different group rats were measured. At the end of this experiment, the body weight and heart function were measured. The rats were sacrificed after blood was obtained by abdominal cardinal vein. The heart was immediately taken out of thoracic cavity after the rat was sacrificed. The heart was rinsed with normal sodium and dried by filter-paper and then weighed. The apex of heart was fixed by formalin and then was dehydrated, imbedded by paraffin and sliced for HE and immunohistochemistry stain. The rest part of cardiac ventricle was immediately thrown into the liquid nitrogen and then stored in the﹣70C°refrigerator in use for detecting the adiponectin concentration, the mRNA and protein expression of adoponectin receptor 1, and the protein expression of GLUT4 and P-AMPK in the heart of the rats. FBG, TG and TC were detected by biochemistry method. FINS was measured by radioimmunity. Serum and myocardial adiponectin levels were measured by enzyme linked immunosorbent assay (ELISA). Cardiac mRNA expression of adiponectin receptor 1 was determined by RT-PCR. The expression of AdipoR1 in myocardium was detected by immunohistochemical staining.The protein expression of AdipoR1, P-AMPKand GLUT4 was detected by Western bloting.The results were analyzed with computer image-analysis system and the integral optical density (IOD) was calculated. The data were dealt with SPSS11.0.【Result】1 Various indexes after 4 weeks: Been fed with high-sugar-fat diet for 4 weeks, test rats were heavier than normal control rats. FBG(7.80±0.23)mmol/L and FINS (29.9±0.53)IU/mL of test rats were higher than FBG(3.99±0.27)mmol/L and FINS (23.10±0.71)IU/mL of control rats(all P<0.05).At the same time, ISI(-5.35±0.42)in test rats was lower than ISI(-4.75±0.71)in control rats(P<0.05).2 Various indexes after 6 weeks: 2 weeks after STZ injection, FINS(23.40±1.99) IU/mL in group DC rats compared to FINS(24.10±0.31)IU/mL in group NC rats was unstatistics distinction (P>0.05). Other features were retained. FBG(18.23±0.57) mmol /L in group DC rats was higher than FBG(3.95±0.29)mmol/L in group NC rats and ISI (-6.05±0.19)in group DC rats was lower than ISI(-4.55±0.08) in group NC rats (both P<0.01).Thus far,the T2DM rat model was accomplished.3 Various biochemical indexes after 18 weeks:When the experiment was finished, FBG, FINS and ISI in group NC rats were(4.02±0.44)mmol/L, (23.44±1.47)IU/mL and (-4.55±0.14).FBG(17.55±0.76)mmol/L, FINS(43.06±1.24)IU/mL, TG and TC in group DC rats were all higher than those in group NC rats.ISI(-6.59±0.17)in group DC rats were lower than those in group NC(all P<0.05).FBG(10.62±0.77)mmol/L, FINS (30.78±0.72)IU/mL and foregoing items in group DCT rats were lower than those in group DC rats, ISI (-5.79±0.08)in group DCT rats were higher than those in group DC rats(all P<0.05).4 the serum and myocardial adiponectin after 18 weeks: serum adiponectin(1.09±0.03)μg/mL in group DC rats was lower than that(1.87±0.05)μg/mL in group NC rats(P<0.05).And foregoing item(1.41±0.02)μg/mL in group DCT rats was higher than that in group DC rats.(P<0.05).Related analysis showed that serum adiponectin had a negative correlation with FINS (r=-0.801 P<0.05), a positive correlation with ISI(r= 0.778, P<0.05) in experimental rats. myocardial adiponectin(0.12±0.02)μg/mg in group DC rats was lower than that(0.21±0.02)μg/mg in group NC rats (P<0.05).And myocardial adiponectin(0.14±0.02)μg/mg in group DCT rats was higher than that in group DC rats(P<0.05).5 the protein expression of myocardial adipoRl after 18 weeks: the protein expression of myocardial adipoRl(0.34±0.11) in group DC rats was lower than that(0.77±0.08) in group NC rats(P<0.05).And foregoing item(0.47±0.09) in group DCT rats was higher than that in group DC rats(P<0.05).6 the protein expression of myocardial GLUT4 after 18 weeks: the protein expression of myocardial GLUT4(0.41±0.09) in group DC rats was lower than that(0.79±0.08) in group NC rats(P<0.05).And the protein expression of myocardial GLUT4(0.52±0.10) in group DCT rats was higher than that in group DC rats(P<0.05).7 the protein expression of myocardial P-AMPK after 18 weeks: the protein expression of myocardial AMPK(0.47±0.12) in group DC rats was lower than that(0.7±0.10) in group NC rats(P<0.05).And the protein expression of myocardial AMPK(0.57±0.10) in group DCT rats was higher than that in group DC rats(P<0.05).8 Morphology: Group NC rats: cardiac muscle fibers were normal, nucleolus of myocardial cell was spherical or ellipse, and in the center of cell. Group DC rats: cardiac muscle fibers was in order, and there were focal necrosis and fibrocyte proliferation in the cardiac muscle fibers.There were much degeneration in the myocardial cell, and extent of cell was obfuscation. collagenoblast proliferation and collagen fibers accrescence between myocardial cell. intercellular space phlegmasia-ctye infiltrate.Group DCT rats were outweigh to Group DC rats,Cell degeneration had improved.【Conclusion】1 The T2DM rat model that was induced by high-sugar-fat diet and a low dose of STZ had some characteristics similar to human T2DM.It would be available to study T2DM and its complications.2 The heart fuction is decreased in diabetic rats. The serum and myocardial adiponectin levels, the myocardial protein and mRNA expression of AdipoR1, and the protein expression of P-AMPK and GLUT4 are decreased in diabetic rats, indicating that the decreased adiponectin and its receptor might be related to myocardial glucose metabolism dysfuction and the decreased heart function in type 2 diabetic.3 Telmisartan could increase serum adiponectin concentration and AdipoR1 protein expression in cardiac muscle, then lowered circulating levels of glucose and lipids and improved insulin sensitivity. Telmisartan treatment increase levels of myocardial adiponectin and its recaptors in type 2 diabetic rats. Telmisartan provide new treatment method for type 2 diabetes mellitus.