Effects Of Multi-electrode Renal Denervation On Insulin Sensitivity And Glucose Metabolism In A Canine Model Of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus(T2DM)is often accompanied with one or more clinical symptoms of the metabolic syndrome,such as hypertension,dyslipidemia,obesity,etc.,and the risk and development of complications of T2 DM will increase significantly with an increase in blood glucose,blood pressure,blood lipid or body weight.Therefore,the treatment for T2 DM should follow evidence-based medical evidence and be comprehensive,including hypoglycemic,antihypertensive,anticoagulation,weight control,etc.Hypoglycemic therapy includes diet control,suitable exercise,blood glucose monitoring,education and hypoglycemic drugs,but it is difficult to control the process of T2 DM and its complications due to hunger and irregular habit.In 2009,Krum firstly reported that catheter-based renal denervation(RDN)could cause substantial and sustained blood-pressure reduction,and renal noradrenaline spillover decreased in some patients,showing that RDN could reduce the activity of the sympathetic nervous system.In some other researches,RDN could be used to treat arrhythmia,heart failure,and obstructive sleep apnea syndrome.Interestingly,when treating hypertensive patients with T2 DM,an improvement of glucose metabolism and insulin sensitivity was also found.However,the accurate mechanism remains unclear.In this study,we applied the six-electrode RDN catheter to a canine model of T2 DM to explore its feasibility and effect,and we explored the relevant mechanism to provide theoretical and experimental basis for clinical application.Part ? Establishment of a canine model of type 2 diabetes mellitusObjective: Recently,researchers reported that catheter-based renal denervation(RDN)could cause substantial and sustained blood-pressure reduction,and an improvement of glucose metabolism and insulin sensitivity was also found when treating hypertensive patients with type 2 diabetes mellitus(T2DM).However,the accurate mechanism remains unclear.In this study,we applied the six-electrode RDN catheter to a canine model of T2 DM to explore its feasibility and effect,and we explored the relevant mechanism to provide theoretical and experimental basis for clinical application.In this part,the objective is to establish a canine model of T2 DM.Methods: Thirty-three canines were enrolled,and body weight and blood biochemistry were measured at baseline.The canines then were fed a high-fat diet(HFD)for 16 weeks.Subsequently,animals received 18.5 mg/kg streptozotocin(STZ)solution via intravenous injection and reduced food intake for the following week.Canines were fed an HFD for an additional 3 weeks,followed by an intravenous glucose tolerance test at 4 weeks post-STZ to confirm that the T2 DM model developed successfully.Plasma triglyceride(TG),total cholesterol(TC),low-density lipoprotein(LDL),blood urine nitrogen(BUN),creatinine(Cr),noradrenaline(NE),angiotensin II(Ang II),fasting plasma glucose(FPG),fasting insulin(FIns),etc.were measured.Results: During the 20 weeks of HFD diet and intravenous STZ injection,compared with animals at baseline,canines showed significantly increased body weight,TG,TC,LDL,NE and Ang II(12.03 ± 0.58 kg vs.19.16 ± 2.12 kg,P < 0.001 for body weight;0.44 ± 0.10 mmol/L vs.2.53 ± 0.35 mmol/L,P < 0.001 for TG;5.07 ± 0.47 mmol/L vs.7.78 ± 0.89 mmol/L,P < 0.001 for TC;2.10 ± 0.19 mmol/L vs.3.94 ± 0.51 mmol/L,P < 0.001 for LDL;161.30 ± 23.98 pg/m L vs.571.73 ± 80.19 pg/m L,P < 0.001 for NE;and 1.47 ± 0.08 pg/m L vs.2.25 ± 0.27 pg/m L,P < 0.001 for Ang II).In addition,FPG,FIns and HOMA-IR increased significantly(4.22 ± 0.65 mmol/L vs.9.99 ± 1.72 mmol/L,P < 0.001 for FPG;2.69 ± 0.40 m IU/m L vs.18.29 ± 2.24 m IU/m L,P < 0.001 for FIns;and 0.50 ± 0.10 vs.8.09 ± 1.57,P < 0.001 for HOMA-IR).Conclusion: At 20 weeks,HFD feeding and STZ injection succeeded leading to a canine model with T2 DM,which is a new kind of large T2 DM animal model like metabolic patients' characteristics.Part II An acute animal experiment with multi-electrode catheter-based radiofrequency denervationObjective: The Symplicity catheter is equipped with a single-electrode,which made the denervation procedure highly operator-dependent,so researchers are trying to develope new denervation catheters.Since 2012,Shanghai Golden Leaf Med Tec Co.,Ltd.has developed a new catheter,which possesses six helically arranged electrodes on a net.When the net is expended,the helically placed electrodes are evenly placed and touched four quadrants of the arterial wall.This unique design makes the denervation operation much easier and time saving,which greatly reduces operators' dependency,and denervation was controlled by setting the temperature limit at 60 ?C and the time at 2 minutes for each electrode.In this part,the objective is to explore the safety,feasibility and effect of this new catheter.Methods: Five canines were enrolled,and RDN was controlled by setting the temperature limit at 60 ?C and the time at 2 minutes for each electrode.Euthanasia was performed immediately after RDN,then samples of renal arteries,kidneys,and the surrounding tissue were taken,and histopathological analyses were made to evaluate the effect of RDN.Results: Renal angiography immediately after RDN revealed no significant changes in the shape or inner walls of the renal arteries.No dissection,aneurysm,thrombus or artery rupture was observed.Histopathological analyses showed that the nerve bundles had a hypercellular appearance and the perineurium thickened after RDNConclusion: This new six-electrode catheter could be safely and effectively used for RDN,which provided a new option for doctors when performing the RDN procedure.Part III Effects of multi-electrode renal denervation on insulin sensitivity and glucose metabolism in a canine model of type 2 diabetes mellitusObjective: Recently,a research reported the effects of multi-electrode renal denervation(RDN)on patients with metabolic syndrome,and the authors clarified that multi-electrode RDN could reduce elevated sympathetic nerve activity and restore the normal neural response to oral glucose loading.However,the accurate mechanism remains unclear.In this part,the objective is to evaluate the effects of multi-electrode RDN on insulin sensitivity and glucose metabolism in a type 2 diabetes mellitus(T2DM)canine model.Methods: Thirty-three T2 DM canines were divided equally into three groups: bilateral renal denervation(BRDN)group,left renal denervation(LRDN)group,and the sham operation(SHAM)group.Body weight,plasma triglyceride(TG),total cholesterol(TC),low-density lipoprotein(LDL),blood urine nitrogen(BUN),creatinine(Cr),noradrenaline(NE),angiotensin II(Ang II),fasting plasma glucose(FPG),fasting insulin(FIns)were measured before and 3 months after RDN.Renal angiography and computerized tomographic angiography(CTA)were determined before the procedure and 1 month,2 months,and 3 months after the procedure.Western blot was performed to identify the activities of gluconeogenic enzymes and insulin signaling proteins.Results: Compared with the SHAM group,FPG,FIns,homeostasis model assessmentinsulin resistance(HOMA-IR),NE and Ang II in the BRDN group had significantly decreased at the 3-month follow-up(9.64 ± 1.57 mmol/L vs.5.12 ± 1.08 mmol/L,P < 0.0001 for FPG;16.19 ± 1.43 m IU/m L vs.5.07 ± 1.13 m IU/m L,P < 0.0001 for FIns;6.95 ± 1.33 vs.1.15 ± 0.33,P < 0.0001 for HOMA-IR;600.6 ± 93.6 pg/m L vs.364.2 ± 47.5 pg/m L,P < 0.0001 for NE;and 2.54 ± 0.28 pg/m L vs.1.78 ± 0.20 pg/m L,P < 0.0001 for Ang II).CTA and histopathological analyses did not show any dissection,aneurysm,thrombus,or rupture in any of the renal arteries.Western blot analyses showed RDN suppressed the gluconeogenetic genes,modulated insulin action,and activated insulin receptors-AKT signaling cascade in the liver.Conclusion: These findings identified that multi-electrode catheter-based RDN could effectively decrease gluconeogenesis and glycogenolysis,resulting in improvements in insulin sensitivity and glucose metabolism in a T2 DM canine model.