黄连解毒汤对2型糖尿病大鼠Alzheimer病样tau蛋白磷酸化修饰及机制研究

Insulin resistance is considered as the core lesion of type 2 diabetes,and the insulin signaling pathway is a downstream mechanism.It has been confirmed that IR is correlated with the Alzheimer's disease and the insulin is involved in regulating the hyperphosphorylation of tau and the metabolism of Aβ. Our preliminary research shows that Huanglian Jiedu Decoction could optimize the learning and memory abilities of rats with dementia by reducing Aβ deposition in Hippocampus of the rats through modifying the phosphorylation Based on Chinese medicine theory, we put forward the hypothesis that since PI-3K-Akt/PKB signal transduction pathway is regulated through Huanglian Jiedu Decoction, modified the the hyperphosphorylation of tau in Alzheimer-like of type 2 diabetes mellitus. Taking Huanglian Jiedu Decoction as the research object, our study is designed to observe the change of tau protein phosphorylation in type 2 diabetic rats' hippocampus for the first time, and then do research on 2 aspects, insulin transduction signal reduction and glucose metabolism impairment caused by insulin resistance, to explore the mechanism of reversing the hyperphosphorylation of tau protein by Huanglian Jiedu Decoction.Through this study, we would reveal the specific mechanisms of T2DM, which is considered as a risk factor for AD pathogenesis,. It not only provides a new potential therapeutic approach for the type 2 diabetics, but also provides the scientific evidence of Huanglian Jiedu Decoction for cognition impairment caused by T2DM from molecular level.

胰岛素抵抗(IR)是2型糖尿病(T2DM)的核心病变，胰岛素信号通路是其发生的下游机制。已经证实IR与阿尔茨海默病(AD)也有关联，胰岛素参与调节tau蛋白磷酸化和Aβ的代谢。我们前期研究发现，黄连解毒汤可通过对tau蛋白磷酸化修饰，减轻AD大鼠海马内Aβ沉积，改善其学习记忆能力。基于消渴从毒论治的中医理论，本项目提出"黄连解毒汤通过调控PI-3K-Akt/PKB信号转导通路修饰2型糖尿病Alzheimer病样tau蛋白过度磷酸化"的假说，拟以黄连解毒汤为研究对象，首次观察其对T2DM大鼠海马tau蛋白磷酸化修饰，从IR致胰岛素转导信号下调及葡萄糖代谢受损两方面对tau蛋白磷酸化机制进行研究，从分子学水平揭示T2DM作为AD发病的危险因子的具体原因，不仅为T2DM中已发生AD的患者找到新的治疗途径，并且为黄连解毒汤临床用于治疗糖尿病所致的认知功能障碍提供科学依据。

本项目基于消渴呆病从“毒”论治的中医理论，提出“黄连解毒汤通过调控PI3K-Akt/PKB信号转导通路修饰2型糖尿病Alzheimer病样tau蛋白过度磷酸化”的假说，以黄连解毒汤为研究对象，以链脲佐菌素（STZ）诱导T2DM大鼠模型为研究载体，通过观察大鼠的学习记忆能力、脑组织形态学、PI3K-Akt/PKB信号通路、脑内葡萄糖代谢以及脑内tau蛋白磷酸化的变化，探讨黄连解毒汤对T2DM并发AD的治疗作用及可能机制。研究发现，黄连解毒汤可有效降低T2DM大鼠空腹胰岛素水平、空腹血糖和胰岛素抵抗指数，有效改善T2DM大鼠学习记忆能力下降，对T2DM大鼠脑组织神经元退行性形态改变有较好的治疗作用，其作用机制可能通过作用于脑内PI3K-Akt/PKB信号通路，进一步激活GSK-3β的活性，抑制海马中tau蛋白在Ser199、Ser202、Thr231、Ser396等多位点上的磷酸化水平有关，但此途径不是抑制tau蛋白Alzheimer病样过度磷酸化修饰的唯一方式。同时黄连解毒汤可以调节T2DM大鼠脑内葡萄糖代谢，增加其海马中GLUT3的表达，提高海马中tau蛋白O-GlcNAc糖基化修饰水平，进而负向调节tau蛋白磷酸化修饰。综上所述，项目从胰岛素抵抗致胰岛素转导信号下调及葡萄糖代谢受损两方面对tau蛋白磷酸化机制进行研究，从分子水平揭示T2DM作为AD发病的风险因子及黄连解毒汤治疗T2DM并发AD的具体机制，不仅对预防T2DM并发AD的发生具有重大意义，而且为T2DM中已发生AD的患者找到新的可能的治疗途径。