A healthy brain aging strategy to restore insulin signaling and Ca homeostasis

 描述(由申请人提供)： 外周代谢失调似乎增加了随着年龄的增长而导致认知能力下降的风险，以及对阿尔茨海默病等痴呆性神经退行性疾病的易感性。然而，代谢紊乱和年龄相关性认知障碍之间的关系的途径和机制还没有明确的定义。在这里，我们认为，大脑中的胰岛素抵抗可以破坏严格调控的过程的稳定，这些过程维持神经元中正常的钙稳态，导致神经元功能障碍和认知受损。与年龄相关的神经细胞钙调节失调是一种公认的导致神经功能障碍和认知功能下降的机制，我们和其他人已经广泛地表征了这种功能障碍在大脑结构中对学习和记忆至关重要。有趣的是，胰岛素抵抗的外周组织也表现出钙调节失调，并为大脑中类似的关系提供了支持证据。在前一个资金周期中，我们 发现了以前未知的代谢失调和海马神经元钙信号改变之间的联系。总之，这些发现支持了这样一种观点，即通过提高胰岛素的策略克服海马体中的胰岛素抵抗将重新建立神经元钙稳态。几种创新的方法将被用来在衰老过程中增加大脑胰岛素信号。具体地说，我们将1)利用胰岛素鼻腔给药来增加体内脑内胰岛素受体的胰岛素利用率，2)通过腺病毒介导的人胰岛素受体突变体(β亚单位)的表达来增加脑内胰岛素受体的信号转导，以及3)通过使用新的药理策略来增加内源性胰岛素受体的转运。在F344大鼠的衰老模型中使用这些方法，我们将使用不同的行为范式来研究认知功能。在这些动物的海马区组织中，我们将使用单细胞电生理学/成像来直接测量钙状态(记录钙依赖电位和钙成像)，并用分子/生化分析来补充这些研究。为了确定大脑中增加的胰岛素是否会影响其他独立于钙离子的途径，我们还将对p-Akt信号、酪氨酸磷酸化、葡萄糖稳态(葡萄糖成像)和脂联素水平进行量化。2型糖尿病在老年人中已经达到流行的程度，约有2600万人，给我们的医疗保健系统造成了1750亿美元的损失(CDC统计数据)。我们的研究旨在确定增强大脑中的胰岛素作用是否可以减轻衰老过程中认知能力下降的负担，并有助于保持健康的认知功能。我们的研究结果将为相关的临床研究提供参考，并可能对老龄化人口产生重大影响，特别是对阿尔茨海默病等神经退行性疾病风险增加的人。这项工作是以临床为导向的，并通过建立新的靶点来治疗脑老化中的认知衰退和/或痴呆症，直接解决了NIA的任务之一。

 DESCRIPTION (provided by applicant): Peripheral metabolic dysregulation appears to increase the risk for cognitive decline with aging and susceptibility to dementing neurodegenerative disorders such as Alzheimer's disease. However, the pathways and mechanisms underlying the relationship between metabolic dysregulation and age-related cognitive impairment are not clearly defined. Here we propose that insulin resistance in the brain can destabilize tightly regulated processes which maintain normal calcium homeostasis in neurons resulting in neuronal dysfunction and impaired cognition. Age-related neuronal calcium dysregulation is a well-recognized mechanism contributing to neurologic dysfunction and cognitive decline and we and others have extensively characterized this dysfunction in brain structures important for learning and memory. Interestingly, peripheral tissues that are insulin resistant also show calcium dysregulation and provide supporting evidence for a similar relationship in the brain. In the prior funding cycle, we identified a previously unrecognized link between metabolic dysregulation and altered calcium signaling in hippocampal neurons. Together, these findings provide support for the notion that overcoming insulin resistance in the hippocampus with insulin-raising strategies will reestablish neuronal calcium homeostasis. Several innovative approaches will be used to increase brain insulin signaling in aging. Specifically, we will 1) utilize intranasal insulin delivery to increas insulin availability at the brain insulin receptor in vivo, 2) increase insulin receptor signaling n the brain via AAV-mediated expression of a constitutively active human insulin receptor mutant (β subunit), and 3) increase endogenous insulin receptor trafficking through the use of a novel pharmacologic strategy. Using these approaches in the F344 rat model of aging, we will investigate cognitive functions using different behavioral paradigms. In hippocampal tissue from these animals, we will use single cell electrophysiology/imaging to directly measure calcium status (recordings of calcium-dependent potentials and calcium imaging), and complement these studies with molecular/biochemical assays. To determine whether increasing insulin in the brain affects other pathways independent of Ca2+, we will also quantify p-Akt signaling, tyrosine phosphorylation, glucose homeostasis (glucose imaging), and adiponectin levels. Type 2 diabetes has reached epidemic proportions among older adults accounting for approximately 26 million people and a $175 billion dollar toll to our health care system (CDC statistics). Our studies are designed to determine whether enhancing insulin action in the brain reduces the burden of cognitive decline in aging and helps to maintain healthy cognitive function. The outcomes from our studies will inform related clinical studies and may have significant impact for the aging population, especially for those at increased risk for neurodegenerative diseases such as Alzheimer's disease. This work is clinically-oriented and directly addresses one of the missions of the NIA by establishing novel targets for the treatment of cognitive decline and/or dementia in brain aging.