Effect Of Renal Denervation On Ventricular CX43 In Diabetic Rats

OBJECTIVE: Diabetes as a common chronic metabolic disease that is associated with continuous increase in blood glucose levels.The metabolic disorders of the body caused by diabetes can cause long-term elevation of glucose levels in the blood and lead to degenerative complications of microvascular(blindness,kidney disease and neuropathy)and macrovascular(cardiovascular and stroke).It is closely linked to cardiovascular disease in the clinical.At present,it has been an important risk factor for coronary heart disease,heart failure,arrhythmia,hypertension,cardiomyopathy and other diseases.However,cardiac arrhythmia and heart failure occur clinically one after another,based on the same pathophysiological changes and pathogenesis--the abnormality of electromechanical coupling and the imbalance of neuro-humoral mechanism.Gap junction,an important way of electromechanical coupling between cardiomyocytes,which is a cluster of transmembrane channels connecting adjacent cells,and mediates the normal electrical activity of cardiomyocytes to cardiomyocytes.The constituent proteins of gap junction channels are called connexins.Among them,the three protein subtypes of Cx40,Cx43,and Cx45 are mainly expressed in the myocardium.The conductive pathways formed between cells are responsible for controlling the orderly diffusion of normal rhythmic currents,so their abnormal expression may lead to the tendency of arrhythmia.The abnormal expression includes Abnormal spatial distribution and changes of quantitative expression of connexins.Studies have shown that changes of connexin expression and gap junction remodelingunder sustained hyperglycemia conditions lead to a high incidence of arrhythmias and even sudden death.The Cx43 as an important structure,mainly exists in the connection pathways of ventricular myocytes.It plays a role in maintaining normal Electrophysiological activity of the heart and coordinating pump function.Its remodeling can cause ventricular current conduction disorders,which may cause life-threatening malignant ventricles arrhythmia occurs.As we all know,the core of the neuro-humoral mechanism is the renin-angiotensin-aldosterone system(RAAS)and the sympathetic nervous system(SNS).They cooperate with each other to maintain the normal physiological homeostasis of the human body,but in order to maintain sufficient perfusion when heart failure occurs,Neural-humoral mechanisms are activated to compensate.Energize SNS to stimulate renin increase,constrict blood vessels,and promote absorption of raw urine.Although it has a temporary effect,long-term activation of SNS will increase the symptoms of heart load.In terms of arrhythmias,SNS activation shortens the refractory period,shortens the duration of action potentials,increases the refractory period dispersion,increases repolarization heterogeneity,and causes early post-depolarization.More likely to induce ventricular arrhythmias.Therefore,the neuro-humoral mechanism,especially SNS,is an important factor in the development of arrhythmia and heart failure.Renal denervation(RDN)has been developed as a new method to reduce sympathetic nerve activity.According to research,it can effectively suppress some of the negative effects caused by the excessive activation of the SNS system,and according to further research,this new method also has positive effects on the following diseases related to sympathetic nervous excitement,such as hypertension,insulin Resistance,apnea syndrome and atrial fibrillation.This study aimed to investigate the effect of RDN on ventricular Cx43 in diabetic rats.Methods: Thirty-two adult male SD rats were randomly divided into a blank operationgroup(SHAM,n = 8)and a model group(n = 24).The blank operation group was fed with normal diet and drinking water,and the model group used streptozotocin(STZ)to make a diabetic rat model.After 3 days,the tail vein blood glucose was more than16.8mmol / l was a successful model.Unsuccessful rats continued to use STZ.Then the model group was randomly divided into diabetic cardiomyopathy group(DCM),metoprolol group(MET),and renal denervation group(RDN),eight per group.After 4weeks of normal rearing,the MET group was given 20 mg / kg / d of gavage;In the RDN group,fasting but not water before surgery.Renal desympathetic surgery was performed the next day.Anesthesia was injected intraperitoneally with 10% chloral hydrate(3ml / kg).Using a midline abdominal incision to expose the renal arteries and veins from the aorta to the renal hilum,and carefully peel off the fascia and connective tissue covering the outer wall of the blood vessel,remove all the nerves visible to the naked eye next to the renal artery,and apply 20% phenol-containing ethanol solution around the renal artery to break the remaining nerves around the artery,then,electrical stimulation was used to verify the renal sympathetic effect.The blank surgery group also disinfected and closed the abdomen after the renal arteries and veins were exposed with saline smeared.Penicillin was routinely applied to prevent infection in the two groups,and blood glucose,weight,and mental status were regularly observed during the period.Eight weeks after drug and surgical intervention,ECG data was measured and recorded after anesthesia,and cardiac and blood samples were retained,and cardiac body mass index was recorded.Elisa method was used to measure the plasma norepinephrine(NE)content.HE staining was used to observe the myocardial tissue morphology and degree of fibrosis.Immunohistochemistry was used to determine the expression of Cx43.Western blotting was used to determine the relative expression of Cx43 and P-Cx43 proteins in rats.Results: 1.Except for the SHAM group,the other three groups of rats exhibited symptoms of weight loss,polyuria,poor spirit,and cataracts during the feeding period,and their blood glucose continued to be higher than normal.One died after the operation,and a total of 29 survived to the end of the experiment.2.In terms of cardiac mass and cardiac weight index,compared with sham group,the other three groups were significantly reduced(P < 0.05),compared with DCM group,met and RDN group were significantly reduced(P < 0.05).3.Compared with the SHAM group,the plasma NE concentration in the DCM group was significantly increased(P <0.05);Compared with the DCM group,plasma NE concentrations in the MET and RDN groups were significantly reduced(P <0.05);compared with the MET group,the plasma NE concentrations in the RDN group were significantly reduced(P <0.05).4.Compared with SHAM group,ECG showed that QRS wave width and QT interval increased in rats in DCM group(P <0.05)also ventricular premature beats,ventricular tachycardia and other arrhythmias were found;The RDN and MET groups improved the QRS wave width and QT interval,and the RDN was better than MET(P <0.05).5.The myocardial cells of the SHAM group were relatively neatly arranged,and there was no obvious interstitial fibrosis and cell edema;The cardiomyocytes in the DCM group were relatively disordered,with obvious cell edema,increased volume,obvious nuclear rupture and interstitial fibrosis;myocardial damage was reduced in the MET and RDN groups compared with the DCM group.6.Immunohistochemistry was used to determine the spatial expression of Cx43 in each group of rats.It was found that the expression of Cx43 in the diabetic group,metoprolol group,and kidney removed sympathetic nerve group gradually increased,and the distribution improved sequentially.7.Western blotting showed that compared with the SHAM group,the normal expressions of Cx43 and P-Cx43 in rat ventricles were significantly down-regulated(P <0.05),while the RDN and MET groups improved the ventricular Cx43 and P-Cx43 expression in diabetic rats(P <0.05).and RDN was better than that of metoprolol(P <0.05).Conclusions: 1.Diabetes significantly damages the normal structure and morphology of rat myocardium and increases the secretion of norepinephrine,which may be relatedto the hyperexcitation of sympathetic nerves caused by diabetes.2.RDN and metoprolol can improve the myocardial damage caused by diabetes,reduce myocardial remodeling and reduce the secretion of norepinephrine,and inhibit the sympathetic nerve activation to a certain extent.Among them,RDN can reduce norepinephrine excessive secretion more than metoprolol.3.Diabetes can down-regulate the normal expression of Cx43 and P-Cx43 in rat ventricles.RDN and metoprolol can improve the expression of ventricular Cx43 and P-Cx43 in diabetic rats,and RDN is better than metoprolol.4.The QRS wave width and QT interval of diabetic rats increase,and it is easy to induce ventricular arrhythmia.The two may be related to each other.RDN and metoprolol have certain effects on improving ECG stability,and RDN is better than metoprolol to a certain extent,and the mechanism may be related to the inhibition of sympathetic nerve over-activation,the regulation of Cx43 expression and the improvement of myocardial injury.