| BackgroundAs the aging population and the improvement of people's living standard,the morbidity and mortality rates of diabetes mellitus are increasing in China recently.Diabetes associate with dysfunction of the autonomic nervous system,especially the parasympathetic nervous system activity attenuation,inducing diabetic cardiovascular disease.Diabetes mellitus patients often accompany cardiaovascular dysfunction,associating with hyperglycemia,hyperlipidemia,high blood viscosity and arterioscler-osis,which contributed to a variety of cardiovascular complications.Paeoniflorin is the active component of Radix Paeoniae Rubra,a traditional Chinese medicine that has cardiaovascular protective action through anti-inflammatory,anti-oxidant and vascular relaxation.However,the effect of paeoniflorin on the cardiaovascular system in diabetic mellitus has to be defined.ObjectiveThe effect of paeoniflorin on the cardiaovascular dysfunction induced by diabetic mellitus and its underlying mechanism related with parasympathetic nervous system activity will be determined in this study.This study will provide experience basis for the effects of paeoniflorin on treatment and the prevention of cardiovascular disease in diabetes mellitus.Methods1.Diabetic rats were induced by a single intraperitoneal injection of streptozoto-cin(STZ)at a dosage of 50 mg/kg body weight after feeding high fat diet for 45 days.The plasma glucose levels of rats were measured 3 days after injection.DM was confirmed by blood glucose level ? 16.7 mM.;;l2.Rats were randomly divided into six groups: control group,diabetic group,paeoniflorin(50 mg/kg)+ diabetic group,paeoniflorin(100 mg/kg)+ diabetes group,paeoniflorin(200 mg/kg)+ diabetic group,metformin + diabetic group(200 mg/kg).3.The plasma level of glucose and lipid were measured with glucose meter and lipid automatic biochemical analyzer respectively.The plasma levels of atrial natriuretic peptide,angiotensin II and endothelin-1 were measured by radioimmuno-assay,and nitric oxide was measured by nitrate reductase method.4.Blood pressure was measured by the tail-cuff method in rats,and it was monitored using Biological Laboratory System(Model BL-420S).5.HE staining and toluidine blue staining techniques were used to detect the change of cardaiac and thoracic aortic morphology.6.In order to investigate the effects of ACh on changes in atrial dynamics and ANP releas,isolated perfused atria beating experimental model and radioimmunoa-ssay technique were used in this study.Experiments were performed on anesthetized rats.Isolated left atrium fixed to the experimental model.The atrium was perfused with HEPES buffer for 90 min to stabilize ANP secretion and atrial dynamics.The perfusate was collected(30 samples)for ANP analysis at 2-min intervals at 4?.In order to observe the effects of ACh on atrial dynamic and ANP secretion,an initial control period of 48 min was followed by ACh infusion for 12 min.7.The survival rate of human umbilical vein endothelial cell was measured by MTT assay.8.ACh was examined for its vascular relaxant effect in isolated phenylephrineprecontracted rat thoracic aorta.The tension of aortic rings was monitored using Biological Laboratory System(Model BL-420S).Results1.The plasma levels of blood glucose,triglycerides,total cholesterol and homoc-ysteine were increased in diabetic rats(P<0.05),while treatment with paeoniflorin reversed this change(P<0.05).2.The plasma levels of atrial natriuretic peptide,angiotensin II and endothelin-1 were increased,and nitric oxide was decreased in diabetic rats(P<0.01),while treatment with paeoniflorin reversed this change(P<0.05).3.The blood pressure was increased in diabetic rats(P<0.05),while treatment with paeoniflorin reversed this change(P<0.05).4.The ratio of heart weight and body weight was increased in diabetic rats(P<0.05),while treatment with paeoniflorin reversed this change(P<0.05).5.HE staining result showed that myocardial gaps were bigger and cardio-myocytes were arranged disorderly in the cardiac section from diabetic rats,while treatment with paeoniflorin(200mg/kg)reversed this change.In the thoracic aortic section of diabetic rats,intimal endothelial layers were rougher and medial layers were impaired,with elastic fiber disappearment,and disordered arrangement of the nuclei,cavitation,while treatment with paeoniflorin(200mg/kg)reversed this change.Toluidine blue staining result showed that the number of mast cells was incereaed both in blood vessels of the heart and thoracic aorta from diabetic rats,while treatment with paeoniflorin(200mg/kg)reversed this change.6.Acetylcholine(0.3?M),a parasympathetic neurotransmitter,decreased atrial pulse pressure by-39.15 ± 6.82% and-3.41 ± 1.09% in control and diabetic rats(P<0.01),respectively.Acetylcholine(0.3?M)decreased atrial pulse pressure by-51.72±2.62% in paeoniflorin(200mg/kg)+ diabetic group.Compared to the diabetic group,paeoniflorin(200mg/kg)reversed this change(P<0.01).Acetylcholine(0.3?M)decreased atrial pulse pressure by-19.46 ± 4.2% in metformin(200mg/kg)+ diabetes group.Compared to the diabetic group,metformin(200mg/kg)reversed this change(P<0.05).7.Acetylcholine(0.3?M),a parasympathetic neurotransmitter,increased atrial natriuretic peptide secretion by 43.25 ± 8.95% and 13.47 ± 4.2% in control and diabetic rats(P<0.01),respectively.Acetylcholine(0.3?M)increased atrial natriure-tic peptide secretion by 40.12±6.75% in paeoniflorin(200mg/kg)+ diabetes group.Compared to the diabetic group,paeoniflorin(200mg/kg)reversed this effect(P<0.01).Acetylcholine(0.3 ?M)increased atrial natriuretic peptide secretion by 20.43 ± 6.75% in metformin(200 mg/kg)+ diabetes group.Compared to the diabetic group,metformin(200mg/kg)reversed this change(P<0.05).8.Paeoniflorin significantly promoted the survival rate of human umbilical vein endothelial cells(P<0.01),and high sugar(33mM)significantly decreased the survival rate of human umbilical vein endothelial cells(P<0.01).Paeoniflorin reversed the high sugar(33mM)-induced decrease in survival rate of human umbilical vein endothelial cells(P<0.01).9.Acetylcholine-induced relaxation of thoracic aorta was significantly attenuated in diabetic rats compared to control rats(P<0.01),while paeoniflorin and metformin significantly reversed this effect(P<0.01),respectively.Conclusions1.Paeoniflorin significantly reduced the levels of blood pressure and blood lipid,and exerted anti-inflammatory effect via inhibition of mast cells infiltration of the heart and blood vessels in diabetic rats.2.Acetylcholine-induced increase in atrial natriuretic peptide release was attenuated in diabetic rats,while paeoniflorin reversed this change.3.Acetylcholine-induced relaxation of thoracic aorta was attenuated in diabetic rats,while paeoniflorin reversed this change. |
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