DAla2GIP-Glu-PAL对阿尔茨海默病APP/PS1转基因鼠的神经保护效应研究

Alzheimer's disease (AD) is the most common type of dementia, which seriously affects the life quality of the elderly, but no effective treatment is found up to now. Epidemiological studies have shown that type 2 diabetes mellitus is an important risk factor of AD, and the both diseases show the common impairments in central insulin receptor and its signal transduction. It is reported that Glucose-dependent insulinotropic polypeptide (GIP), an incretin hormone, plays an important role in memory formation, synaptic plasticity and cell proliferation. However, GIP is quickly degraded by the enzyme dipeptidyl peptidase IV, and the half-life of GIP is less than 2 minutes, which is nearly useless for the long-term treatment of AD. DAla2GIP-Glu-PAL is a newly synthetic novel enzyme-resistant GIP analogue, with 5-6h of longer half-life, but the neuroprotective roles of DAla2GIP-Glu-PAL especially its anti-AD effects are still not reported up to now. The present study will test the neuroprotective effects of DAla2GIP-Glu-PAL against the cerebral pathological impairments and cognitive deficits in APP/PS1 transgenic mice. Further, the cellular and molecular mechanisms of DAla2GIP-Glu-PAL will be examined by recording in vivo hippocampal field potential, brain slice ion channel currents, and cerebral inflammatory factors in the brain. The study will try to provide a novel and effective strategy for the treatment of neurodegenerative diseases such as AD.

阿尔茨海默病（AD）是导致老年人寿命降低和生活质量下降的主要疾病，目前仍缺乏有效治疗措施。研究表明，Ⅱ型糖尿病是AD重要的危险因素，肠促胰岛素（GIP）可以通过血脑屏障进入脑内，调节胰岛素信号、促进神经再生，但其生物半衰期很短，不能用于AD的长期治疗。DAla2GIP-Glu-PAL是最新设计的GIP类似物，可免受二肽酶Ⅳ裂解，使半衰期大大延长。然而，DAla2GIP-Glu-PAL的在体神经保护作用特别是抗AD效应还未见研究报道。本研究将利用APP/PS1转基因小鼠，结合行为、电生理、分子生物及非损伤微测定技术，系统观察DAla2GIP-Glu-PAL是否能够有效逆转AD小鼠病理性脑损伤及认知功能伤害，并通过检测在体海马场电位、跨膜离子电流、炎性反应因子和相关信号转导通路，阐明DAla2GIP-Glu-PAL神经保护作用的可能机制，为AD治疗寻找新的突破点。

阿尔茨海默病（AD）是导致老年人寿命降低和生活质量下降的主要疾病，目前仍缺乏有效治疗措施。研究表明，Ⅱ型糖尿病是AD重要的危险因素，两者在脑内的胰岛素信号转导系统均有异常。肠促胰岛素（GIP）可以通过血脑屏障进入脑内，调节胰岛素信号、促进神经再生，但其生物半衰期很短，不能用于AD的长期治疗。DAla2GIP-Glu-PAL是最新设计的GIP类似物，可免受二肽酶Ⅳ裂解，使半衰期大大延长。本研究利用APP/PS1转基因小鼠，结合行为学、电生理、跨膜离子流和分子生物学等技术，系统观察了DAla2GIP-Glu-PAL有效逆转AD小鼠病理性脑损伤及认知功能伤害的神经保护作用，并通过检测在体海马场电位、脑片跨膜离子流、炎性反应因子和相关信号转导通路，以期阐明DAla2GIP-Glu-PAL神经保护作用的可能机制，为AD治疗提供一个新的突破口。实验结果表明：DAla2GIP-Glu-PAL慢性腹腔注射治疗可以逆转APP/PS1双转基因小鼠以上认知功能的伤害；慢性腹腔注射DAla2GIP-Glu-PAL可以减弱APP/PS1双转基因小鼠脑内出现的Aβ斑块、磷酸化Tau沉积、以及胶质细胞增生等病理学特征；慢性腹腔注射DAla2GIP-Glu-PAL可以经突触后机制逆转APP/PS1双转基因小鼠的海马突触可塑性伤害；DAla2GIP-Glu-PAL改善APP/PS1双转基因小鼠突触可塑性和脑内病理特征的神经保护作用可能是通过增强cAMP-PKA-CREB信号转导，提高PI3K和AKT2的磷酸化水平，同时压抑GSK3β和NF-κB的磷酸化实现的。这些结果证实了DAla2GIP-Glu-PAL在治疗AD动物中的有效性。对淀粉样蛋白假说提供了有力的支持。提示DAla2GIP-Glu-PAL有可能成为一种新的、安全有效的AD治疗策略。此外，我们还利用非损伤微测定技术检测了海马脑片钙离子跨膜流动的情况，发现：急性给予Glu 及Aβ31-35 引起海马脑片CA1 区神经元钙离子内流；Aβ31-35 预处理剂量依赖性增强Glu 诱发的海马脑片神经元钙离子内流；NMDA 受体阻断剂D-APV 可逆转Aβ31-35 对海马脑片神经元跨膜钙离子内流的易化作用。特别是发现了：Aβ31-35 预处理还可抑制海马脑片CA1区神经元低钙人工脑脊液诱发的钙离子外排。从而为AD发病机制提供了进一步的证据。