摘要
目的建立2型糖尿病(type 2diabetes,T2D)模型,检测大脑胰岛素水平及海马胰岛素信号转导途径活性,研究海马胰岛素信号传导途径改变与阿尔茨海默病(AD)样病变的关系,并用胰岛素增敏剂噻唑烷二酮类药物(吡格列酮)对T2D大鼠进行干预,检测上述指标在用药前后的变化,以明确吡格列酮能否降低T2D大鼠AD的发生风险,并探讨其可能的机制。方法建立T2D大鼠模型(T2D),吡格列酮灌胃4周。葡萄糖氧化酶法检测血浆血糖,放免法检测脑脊液及血浆胰岛素,免疫印迹技术检测大脑及肝脏组织胰岛素信号传导途径中磷脂酰肌醇3激酶(Phosphatidylinositol 3ki-nase,PI3K)/蛋白激酶B(Protein kinase B,Akt)、糖原合成激酶-3β(Glucogen synthase kinase-3β,GSK-3β)活性以及海马tau蛋白、tau蛋白上部分磷酸化位点水平。结果 T2D大鼠血浆葡萄糖水平及胰岛素水平显著升高,脑脊液胰岛素水平显著降低,大脑海马组织和外周组织(肝脏)胰岛素信号传导途径PI3K/Akt活性均显著下降,GSK-3β活性显著升高,海马tau蛋白上位点Ser199、Ser396磷酸化程度显著升高。经吡格列酮干预后,血浆胰岛素水平低于T2D组,仍高于对照组,血糖及胰岛素抵抗程度较T2D组已明显下降,与对照组比较差异无统计学意义;脑脊液胰岛素水平与T2D组相比无明显改变,但大脑海马组织和外周组织(肝脏)胰岛素信号传导途径PI3K/Akt活性均显著升高,GSK-3β活性降低,tau蛋白上述位点磷酸化程度下降。结论 T2D大鼠大脑与外周组织一样也存在胰岛素抵抗,但大脑胰岛素水平较对照组降低,同时大脑海马组织tau蛋白过度磷酸化,即AD样病变加重。吡格列酮干预后并未改变脑脊液胰岛素浓度,但改善了外周和大脑胰岛素抵抗,同时降低了海马组织tau蛋白磷酸化水平,即改善了AD样病变。因此,T2D大脑胰岛素抵抗可能是导致T2D时AD发病的重要原因,而脑脊液胰岛素浓度的变化在T2D大鼠AD样病变中的作用可能并不重要。
Objective To detect the insulin level in the cerebrospinal fluid（CSF）,hippocampus insulin signal transduetion activity and tau protein phosphorylation in type 2 diabetes（T2D） rats and to observe their changes after intervention with piogli- tazone（an insulin sensitizer） in an attemp to better understand the pathogenesis of Alzheimer＇ s disease（AD） in T2D. Methods Rat models of T2D were established by feeding on high protein,high glucose and high fat diet for 3 months and a streptozocin （STZ） injection. Pioglitazone was administered intragastrically for 4 weeks. Plasma insulin level was measured by radioimmuno- assay（RIA） and the plasma glucose by glucose-oxidase method. The activities of PI3K/Akt and glycogen synthase kinase-3i3 （GSK-3~） in insulin signal transduction pathway in the brain and liver tissues were determined by Western blot. The phospho- rylation of tau in brain tissues was also measured by Western blot. The insulin resistant（IR） degree was evaluated by HOMA- IR. Results The plasma insulin level was significantly higher and the CSF insulin level sinificantly lower in T2D rats than in control rats. The PI3K/Akt activity was significantly lower and the GSK-3[3 activity significantly higher in both brain and liver tissues of T2D rats than in those of control rats. The level of phosphorylated tau protein at site Ser199 and Ser396 in hippocam- pus of T2D rats was found to be notably raised as compared with control rats. For the pioglitazone group,the palsma insulin lev- el was evidently lower than that in T2D group, but still higher than in control rats. The glycemia level and the IR degree de- creased significantly in pioglitazone group as compared with T2D group, which were not significantly different from those in control rats. There was no significant difference in brain insulin level between pioglitazone group and T2D group. The PI3K/Akt activity in both brain and liver tissues was significantly up-regulated and the GSK-313 activity was down-regulated in pioglitazone group as compared with T2D group. The level of phosphorylated tau protein at site Ser199 and Ser396 in hippocampus of T2D rats was found to be notably decreased in pioglitazone as compared with T2D group. Conclusion Pioglitazone interventin can ameoliorate the cerebral insulin resistance and decrease which suggests that insulin resistance rather than brain tau protein hyperphosphorylation, but not increase brain insulin level, insulin level is responsible for Alzheimer-like changes（tau protein hyperphosphorylation）.
出处
《华中科技大学学报（医学版）》
CAS
CSCD
北大核心
2013年第2期137-142,共6页
Acta Medicinae Universitatis Scientiae et Technologiae Huazhong
基金
国家自然科学基金资助项目(No.NSFC81100582)
