Astrocyte Lipid Droplets as a Novel Mechanism for Impaired Glucose Metabolism in the E4 and AD Brain

项目摘要 阿尔茨海默病（AD）是一种社会负担，每年花费国家2770亿美元，是世界上最严重的疾病。 第六大死因。随着对AD的疾病修饰疗法的研究的继续， 了解AD大脑中的细胞代谢对于指导研究至关重要。载脂蛋白E（APOE） 基因是晚发性AD（LOAD）最强的遗传预测因子。在人类中，有三种主要的同种型 apoE：E2、E3和E4。E3是人类中表达的主要同种型（约占人群的60%）。E4赋予之间 与E3相比，LOAD风险增加2倍（杂合）至15倍（纯合）。载脂蛋白E（apoE） 主要由星形胶质细胞分泌，作为大脑中的主要脂质载体， 大脑代谢的影响例如，E4载体表现出降低的葡萄糖摄取，如通过18氟脱氧- 葡萄糖正电子发射断层扫描（FDG-PET）。FDG-PET在AD患者中同样较低，但E4 携带者在出现症状性认知能力下降前几十年表现出低FDG-PET。我们最近展示了 表达E4的星形胶质细胞以脂滴（LD）的形式积累的脂质显著多于表达E4的星形胶质细胞。 E3，根据1907年阿尔茨海默病的最初报告，这是一个有趣的发现，涉及神经胶质脂质积累 作为疾病的标志由于LD已被证明参与代谢疾病-包括调节 我们假设星形胶质细胞LD的过度积累导致葡萄糖摄取受损， 在E4和AD大脑中可见。因此，该提议测试了LD相关蛋白质 隔离葡萄糖转运蛋白运输的关键介质，导致星形胶质细胞葡萄糖减少 摄取。我们将在人E3和E4纯合子小鼠体内测试这种机制（Aim 1A），并在人E3和E4纯合子小鼠体内测试这种机制（Aim 1B-1A）。 C）在表达人E3和E4的原代星形胶质细胞中体外。我们还将把我们的发现（目标2）翻译为： 表征APOE基因分型的人死后脑组织中的LD形成， 来自英国阿尔茨海默病中心队列的临床数据。该奖学金的重点是揭示 驱动E4星形胶质细胞中葡萄糖摄取受损的细胞机制，以及使受训者具备以下技能： 质谱，共聚焦显微镜，免疫组织化学，放射性示踪，翻译人类 样品处理、数据分析等。这些技能和优秀的指导将有助于 学员的道路，成为一个独立的物理学家，科学家。

PROJECT SUMMARY Alzheimer’s disease (AD) is a societal burden, costing the nation 277 billion dollars per year and is the sixth leading cause of death. As the search for disease modifying therapies for AD continues, a deeper understanding of cellular metabolism in the AD brain is critical to guide research. The apolipoprotein E (APOE) gene is the strongest genetic predictor of late onset AD (LOAD). In humans, there are three major isoforms of apoE: E2, E3, and E4. E3 is the major isoform expressed in humans (~60% of population). E4 confers between a 2 (heterozygous) to 15-fold (homozygous) increase in risk of LOAD compared to E3. Apolipoprotein E (apoE) is primarily secreted by astrocytes as a primary lipid carrier in the brain, and has gained traction as a regulator of cerebral metabolism. For example, E4 carriers exhibit decreased glucose uptake as measured by 18fludeoxy- glucose positron emission tomography (FDG-PET). FDG-PET is similarly lower in AD individuals, however E4 carriers show low FDG-PET decades before the onset of symptomatic cognitive decline. We recently showed that E4 expressing astrocytes accumulate significantly more lipid in the form of lipid droplets (LDs) compared to E3, an intriguing finding in light of the initial 1907 report from Alzheimer that implicated glial lipid accumulation as a hallmark of disease. Since LDs have been shown to be involved in metabolic disease – including regulation of glucose uptake – we hypothesize that over accumulation of astrocyte LDs drive the impaired glucose uptake seen in E4 and AD brains. Therefore, this proposal tests a mechanism by which an LD-associated protein sequesters a critical mediator of glucose transporter trafficking, leading to a decrease in astrocyte glucose uptake. We will test this mechanism (Aim 1A) in vivo in mice homozygous for human E3 and E4, and (Aim 1B- C) in vitro in primary astrocytes that express human E3 and E4. We will also translate our findings (Aim 2) by characterizing LD formation in APOE genotyped human post-mortem brain tissue, correlating lipid abundance with clinical data from the UK Alzheimer’s Disease Center cohort. The key focus of this fellowship is to uncover a cellular mechanism driving impaired glucose uptake in E4 astrocytes, as well as equip the trainee with skills in mass spectrometry, confocal microscopy, immunohistochemistry, radioactive tracing, translational human specimen handling, data analysis, and more. These skills and excellent mentorship will be instrumental in the trainee’s path to become an independent physician-scientist.