Apolipoprotein E and immunometabolism in Alzheimer's disease

总结：慢性神经炎症和代谢功能障碍是神经退行性疾病的特征， 包括阿尔茨海默病（AD）。已知的最早的AD生物标志物之一是AD的改变模式。 大脑局部葡萄糖代谢载脂蛋白E（APOE）ε4等位基因的携带者表现出这一点， 从年轻时就改变了大脑葡萄糖代谢模式， 收购AD。同时，ε4个体也被认为具有适应不良和有害的 神经炎性表型，在ε4小胶质细胞中具有增加的促炎性信号传导。此外，它是很好的- 建立了小胶质细胞炎症表型是由精确的代谢重编程驱动的， 需要增加有氧糖酵解的炎性细胞因子产生-一种称为 “免疫代谢”。该建议旨在研究ε4中的神经炎性表型是否 小胶质细胞可能是由ε4对葡萄糖代谢的影响内在驱动的。目标1将调查 糖酵解前体基因表达增强驱动神经炎性ε4转录的假说 通过利用靶向单细胞RNA测序的能力来询问表型的基因表达， 一组预先选择的代谢、神经炎症和疾病相关基因，结果在 蛋白质和翻译后水平。目的2将解决ε4小胶质细胞显示增加的假设。 由于中枢碳代谢的潜在损伤而引起的促炎表型。我们将使用稳定 同位素解析代谢组学（SIRM），使用13 C-葡萄糖示踪剂测量ε2、ε3和ε4中的代谢通量 对促炎和抗炎治疗有反应的原发性小胶质细胞。我们将比较氧化 磷酸化和糖酵解活性。这些代谢指标将被 通过平行评估细胞因子释放和吞噬活性，将其与小胶质细胞功能的读数联系起来。目标3 将评估靶向关键代谢节点以重新编程ε4炎症反应的有效性。我们 假设在本发明中鉴定特异性代谢酶的药理学抑制或病毒过表达 我们的初步数据表明，受APOE基因型的干扰，ε4小胶质细胞中细胞因子的产生将重新平衡。 并提高淀粉样β肽的吞噬作用。本研究的最终目的是：（1）了解 APOE基因型如何影响小胶质细胞对炎症刺激的代谢反应，（2）确定 代谢基因表达的改变是否驱动了有利于神经炎症的转录谱， AD风险增加，以及（3）确定由APOE基因型改变的免疫代谢途径， 神经退行性疾病治疗的靶向途径。该提案将创新 转录组学和代谢组学技术与小胶质细胞的功能读数，以统一我们对 ε4风险的两个主要方面：代谢功能障碍和慢性神经炎症。针对这两个 这些方面串联在一起可能在开发用于治疗AD的成功疗法中具有更大的希望。

Summary: Chronic neuroinflammation and metabolic dysfunction characterize neurodegenerative diseases, including Alzheimer's disease (AD). One of the earliest known biomarkers of AD is an altered pattern of regional glucose metabolism in the brain. Carriers of the ε4 allele of apolipoprotein E (APOE) exhibit this pattern of altered cerebral glucose metabolism from a young age and suffer from a dramatically increased risk of acquiring AD. Meanwhile, ε4 individuals are also considered to have a maladaptive and detrimental neuroinflammatory phenotype, with increased pro-inflammatory signaling in ε4 microglia. Additionally, it is well- established that microglial inflammatory phenotypes are driven by precise metabolic reprogramming, with pro- inflammatory cytokine production requiring increased aerobic glycolysis – a phenomenon known as `immunometabolism'. This proposal aims to investigate whether the neuroinflammatory phenotype in ε4 microglia could be intrinsically driven by ε4’s effects on glucose metabolism. Aim 1 will investigate the hypothesis that enhanced pro-glycolytic gene expression drives neuroinflammatory ε4 transcriptional phenotypes by leveraging the power of targeted single-cell RNA sequencing to interrogate gene expression of a panel of pre-selected metabolic, neuroinflammatory, and disease-associated genes, with results validated at the protein and post-translational level. Aim 2 will address the hypothesis that ε4 microglia show an increased pro-inflammatory phenotype due to underlying impairments in central carbon metabolism. We will use Stable Isotope Resolved Metabolomics (SIRM) with a 13C-glucose tracer to measure metabolic flux in ε2, ε3, and ε4 primary microglia responding to pro- and anti-inflammatory treatments. We will compare oxidative phosphorylation and glycolytic activity in response to these treatments. These metabolic measures will then be linked to readouts of microglial function by assessing cytokine release and phagocytic activity in parallel. Aim 3 will evaluate the efficacy of targeting key metabolic nodes to reprogram the ε4 inflammatory response. We hypothesize that pharmacological inhibition or viral overexpression of specific metabolic enzymes identified in our preliminary data as being perturbed by APOE genotype will rebalance cytokine production in ε4 microglia and improve phagocytosis of amyloid beta peptide. Our ultimate goals for this research are to: (1) understand how APOE genotype influences the metabolic response to inflammatory stimuli in microglia, (2) determine whether altered metabolic gene expression drives a transcriptional profile that favors neuroinflammation and increased AD risk, and (3) identify immunometabolic pathways altered by APOE genotype that could represent avenues to target in the treatment of neurodegenerative disease. This proposal integrates innovative transcriptomic and metabolomic techniques with functional readouts of microglia to unify our understanding of two major facets of ε4’s risk: metabolic dysfunction and chronic neuroinflammation. Targeting both of these aspects in tandem may hold greater promise in developing successful therapeutics for the treatment of AD.