噻唑烷二酮通过Wnt通路改善2型糖尿病大鼠海马阿尔茨海默病样病变

Thiazolidinedione improves Alzheimer-like changes in the hippocampus of type 2 diabetic rats by Wnt pathway

目的:2型糖尿病(T2DM)是阿尔茨海默病(AD)发病的重要风险因子。本研究运用噻唑烷二酮类药物(TZD)对T2DM大鼠进行干预,检测W nt途径在用药前后变化,探讨TZD降低T2DM大鼠AD发生风险的可能机制。方法:造T2DM大鼠模型,TZD分别灌胃2周(TZD2W)及4周(TZD4W)。葡萄糖氧化酶法检测血浆葡萄糖水平,放免法检测血浆胰岛素水平,免疫印迹技术检测大鼠海马tau蛋白、tau蛋白上部分磷酸化位点及β淀粉样蛋白(Aβ)前体APP水平,W nt途径中β-联蛋白(β-caten in)和糖原合成激酶3β(GSK-3β)水平,及TZD作用物PPARγ水平。免疫组化技术检测各组大鼠海马Aβ沉积程度。结果:T2DM组及TZD2W组血糖、胰岛素水平及胰岛素抵抗程度显著高于对照组,TZD4W组虽胰岛素水平仍显著高于对照组,但血糖及胰岛素抵抗程度已明显下降,与对照组比较无显著差别。T2DM组大鼠海马tau蛋白上位点Ser199/202、Ser422磷酸化程度及Aβ前体APP水平均显著高于对照组,经TZD干预后,tau蛋白上上述位点磷酸化程度逐渐下降,Aβ沉积逐渐减少;T2DM组大鼠大脑PPAR-γ水平与对照组比较无差异,但运用TZD后,PPAR-γ水平显著升高;T2DM组大鼠大脑W nt途径中β-caten in水平下降,GSK-3β活性升高,运用TZD干预2周和4周大鼠大脑β-caten in水平显著升高,GSK-3β活性显著下降。结论:TZD干预可降低T2DM时AD发病风险。TZD通过上调W nt通路改善2型糖尿病大鼠海马AD样病变。该作用先于胰岛素信号转导通路。

AIM：The abnormal level of insulin and glycemia in type 2 diabetes mellitus（T2DM） are important risk factors of Alzheimer＇s disease（AD）.To explore the mechanism that thiazolidinedione（TZD） decreases the incidence of AD in T2DM,we use TZD on T2DM rats for an intervention and detect the change of Wnt pathway before and after the intervention.METHODS： To establish a T2DM model,the rats were fed with high glucose,high fat and high protein for 8 weeks,and then injected with STZ.TZD was administered intragastrically for 2 and 4 weeks and the rats were divided into TZD2W and TZD4W groups,respectively.Plasma insulin level was measured by RIA method,and the plasma glucose was detected by glucose-oxidase method.Total tau level,the phosphorylation level of tau at individual phosphorylation sites and the level of amyloid β precursor protein（APP）,β-catenin,glycogen synthase kinase-3β（GSK-3β） and PPARγ in rat hippocampus were analyzed by Western blotting.The activity of GSK-3β in the hippocampus of rats was determined using γ——ATP and the specific peptide substrate.The level of APP was also determined by immunochemistry.The insulin resistant（IR） degree was valued by HOMA-IR.RESULTS： Glycemia level in T2DM and TZD2W groups was obviously higher than that in control group.No significant difference of glycemia level between TZD4W and control group was observed.Plasma insulin levels in all groups were evidently higher than that in control group.The IR degree in T2DM and TZD2W groups increased significantly as compared to control group,but no obvious difference between TZD4W and control group was observed.The level of phosphorylated tau protein at site Ser199/202 and Ser422,and APP level in hippocampus of T2DM rats were found to be notably raised as compared to control group,but the level of phosphorylated tau protein at those sites and APP level were decreased gradually.No change of the PPARγ level was found in the hippocampus in T2DM and control group,but a notable increase was observed after TZD intervention.There was a decrease in β-catenin level in hippocampus of T2DM rats,which increased after TZD intervention for 2 and 4 weeks.There was a rise of GSK-3β activity in T2DM rats,which decreased after intervention.CONCLUSION： These findings suggest that TZD may improve the AD-like changes in the hippocampus of T2DM rats by up-regulation of Wnt pathway,which acts before the insulin signal transduction in the contribution of AD-like changes in T2DM rats.