The Influence Of Troxerutin On The Cognitive Impairment Of STZ-induced Diabetic Rats And The Expression Of Nrf2in Hippocampus

Objective: Diabetic encephalopathy also called diabetes-associatedcognitive decline,its main symptoms is impairment of both learning andmemory function. Recent researchs indicate that oxidative stress is a criticalfactor in the progress of the disease.Nrf2is the critical transcriptive factor toregulate the endogenous antioxidant defense system.SOD and MDA are thetypical indexes to test the level of tissue oxidative stress. The present studywas performed to observe the changes of hippocampal Nrf2ofStreptozotocin-induced diabetic rats with cognitive disfunction and whethertroxerutin could protect diabetic cognitive function。Methods： Seventy Healthy male Sprague Dawley(SD) rats (weight150-170g),were randomly divided into normal control group (NC group n=10), diabetes model group (DC group n=60). The diabetic rat models wereinduced by intraperitoneal injection of STZ (60mg／kg) after abrosia for12hours,while the rats of NC group received equal volume of citrate buffersolution by intrapertoneal injection.Random blood glucose monitored bytail-vein sampling≥16．7mmol／L was our criterion for experimental diabetes.At the1w and12w point after the models were established,all the rats weretested by the Morris water maze testing. At13w point，the rats of DC groupwere randomly divided into four groups:diabetic control group（DC）,diabeticgroup treated with physiological saline(DN),diabetic group treated withα-lipoic acid(DL),and diabetic group treated with troxerutin(DT)。Since13wpoint，the rats of DL and DT group were administered with ALA (60mg／kg)and troxerutin (60mg／kg) by intraperitoneal injection once daily for6weeksrespectively.The rats of NC and DN group were aDCinistered with equalvolume physiological saline for6weeks. All rats accepted the Morris water maze test at the18w point and then were sacrificed by decapitation，the wholehippocampus were took out quickly。The activity of SOD and MDA in thehippocampus were detected using the methods of xanthine oxidase andthiobarbituric acid respectively to evaluate the oxidative stress levels inhippocampus．The expression of Nrf2were detected by Real-time polymerasechain reaction(R-T PCR) and Western blotting in rats’hippocampus．All the Datas were dealed with statistical software packages SPSS13.0，the Datas were analyzed using repeated measures and multivariate analysis ofvariance(ANOVA) process and Oneway ANOVA of completely randomdesign，the results were expressed as the mean±standard deviation。Statisticalsignificance was set at p＜0.05。Results:1Generally observation,The rats of DC group appeared polyuria、polydipsia、polyphagia after thediabetic model was established, the blood glucoses of diabetic rats maintainedat high levels (＞20.0mmol/l).Followed with the progression of experiment,the diabetic rats gradually appeared weight lose、Loose stools、gloomy sparsefur and dull. While the NC group rats were in good shape with pure white andglossy fur and gain syeady growth.After intervention,the general conditionsof DT group were better than that of DL group.2Results of Morris water mazeAt1week point, there was no significant difference between DC groupand NC group (P>0.05).At12week point, the escape latency of DC group was prolonged thanNC group (P <0.05),and it indicates that DC group developed impairment ofcognition.At19week point, the escape latency of DL group and DT group wasshorter than DC group and DN group, but was still longer than NC group (P <0.05); There were no significant difference between DL Group and DTgroup,and also between DC Group and DN group(P＞0.05). 3R-T PCR：Compared with the NC group，the expression of hippocampalNrf2mRNA in the rats of group DC and DN was decresed(P＜0.05)；Therewas no statistical significanc（ep＞0.05）between group DC and DN.Comparedwith the DC/DN group, the expression of hippocampal Nrf2mRNA in the ratsof DL group and DT group was elevated(P＜0.01，P＜0.05). The expressionof hippocampal Nrf2mRNA in the rats of DL group was increased comparedwith DT group.4western blot：Total Nrf2protein:The expression of total Nrf2protein in hippocampusof rats in group DC and DN were lower than that in the NC group(P＜0.01).There was no statistical significance between DC group and DN group（P＞0.05）.The total Nrf2protein expression of DL group and DT groupwere increased comparede with DC/DN group(P＜0.01). There was nostatistical significance（p＞0.05）between DL and DT group.Nuclear Nrf2protein: The expression of nuclear Nrf2protein inhippocampus of rats in group DC and DN were lower than that in the NCgroup(P＜0.01). There was no statistical significanc（ep＞0.05）between groupDC and DN. The nuclear Nrf2protein expression of DL group and DT groupwere increased compared with DC/DN group(P＜0.01). The expression ofnuclear Nrf2protein of the rats in DL group are higher than that in DTgroup(P＜0.01).5SOD activity and MDA contentSOD activity: The SOD activity of NC group was higher than DC groupand DN group (P＜0.01）; The SOD activity of DL group and DT group wereenhanced comparede with DC/DN group(P＜0.01). There was no statisticalsignificanc（ep＞0.05）between group DC and DN，and also between group DLand DT.MDA content：The MDA content of NC group was lower than DC groupand DN group (P＜0.01）. There was no statistical significance（p＞0.05）between group DC and DN. The MDA content of DL group and DT group were decreased compared with DC/DN group(P＜0.01)。The MDA content ofDL group was lower than that of DT group(P＜0.01).Conclusion:1STZ-induced diabetic rats developed significant decilne in learning andmemory function at12-week point. Meanwhile the levels of oxidative stresswere elevated in the hippocampus and the expression of Nrf2was decreased.2Troxerutin can upregulate Nrf2expression，restore oxidative stress levelsin the hippocampus，and improve cognitive impairment in diabetic rats...