Protective Effect Of TCA On Diabetic Peripheral Neuropathy Via ENOS/NO Pathway

ObjectiveDiabetic peripheral neuropathy(DPN)is one of the most common complications of diabetes,and is often manifested as distal symmetric sensorimotor dysfunction in clinical practice.In this study.C57BL/6J mice were used as the research object.The DPN model was induced by intraperitoneal injection of streptozocin(STZ)to investigate the effect of transCinnamaldehyde(TCA)on DPN via eNOS/NO pathway.Methods1.Five days STZ(50mg/kg/d)continuous intraperitoneal injection for preparing type I diabetes mellitus(DM)mice to induce DPN.2.set up control group,and the mice with successful modeling were randomly divided into different groups according to fasting blood glucose:diabetic group(0.05%CMC-solution,ip.),TCA low dose group(25mg/kg/d,ip.),TCA middle dose group(50mg/kg/d,ip.),TCA high dose group(100mg/kg/d,ip.),TCA(50mg/kg/d.ip.)+NOS inhibitor(1mg/mL,po.);3.Laser Doppler Flowmetry was used to detect the blood flow of terminal microcirculation of mice in each group;4.Small animal ultrasound imaging was used to detect the femoral artery blood flow of lower extremity;5.Detection of sciatic nerve conduction velocity by using multichannel stimulator and Spike 2 recording software;6.YLS-6B intelligent hot plate was used to detect paw withdrawal latency(PWL);7.Vascular endothelium-dependent relaxation,smooth muscle-dependent relaxation and vasoconstriction function were detected by DMT620;8.Nitric oxide(NO)level was measured by nitrate reductase method;9.Vascular nitric oxide(NO)levels were detected by DAF-2DA fluorescent staining;10.The protein expression ratio of total endothelial nitric oxide(T-eNOS)and phosphorylated endothelial nitric oxide(p-eNOS)was detected by Western blotting.Results1.STZ-induced diabetic mice showed symptoms of slow or stopped weight growth and blood glucose continued to be higher than 250 mg/dl;2.When STZ induced diabetes lasted for 4 weeks,the decrease of microcirculation perfusion of diabetes mice was observed for the first time.At the 6th week of induction,the sciatic nerve conduction velocity slowed down,and the paw withdrawal latency was increased.3.Compared with the control group,the diabetes mellitus group(DM)performed with the microcirculation perfusion decreased(P<0.05),the blood flow of the lower extremity femoral artery decreased(P<0.05),the nerve conduction velocity decreased(P<0.05),the paw withdrawal latency(PWL)increased(P<0.05),and endothelium-dependent diastolic function decreased(P<0.05);The STZ also significantly reduced in vascular and serum nitric oxide levels in DM mice(P<0.05).4.Compared with the diabetes mellitus group(DM),TCA treatment for 2 weeks after STZ induction for 6 weeks can significantly improve neurological and blood vessels function,protect endothelial function,and increase NO production in serum and blood vessels without changing the blood glucose and body weight of diabetic mice;5.While intraperitoneal injection of TCA,providing L-NAME(NOS inhibitor)in drinking water was found to blocking NO production and reversing the protection of blood vessels and nerve caused by TCA;6.TCA significantly increased the protein ratio of p-eNOS/T-eNOS in vascular tissue caused by diabetes.(P<0.05).Conclusion1.DPN model was successfully established by intraperitoneal injection of STZ;2.TCA effectively improved neurological damage caused by diabetes;3.TCA effectively improved the vascular endothelial function damage which caused by diabetes;4.By increasing the activity of vascular endothelial eNOS of diabetic mice,TCA increases NO production and improves microcirculation damage,ultimately treating DPN.