Cerebral glucose hypometabolism is consistently observed in individuals with Alzheimer’s disease (AD), as well as in young cognitively normal carriers of the Ε4 allele of Apolipoprotein E (APOE), the strongest genetic predictor of late-onset AD. While this clinical feature has been described for over two decades, the mechanism underlying these changes in cerebral glucose metabolism remains a critical knowledge gap in the field. Here, we undertook a multi-omic approach by combining single-cell RNA sequencing (scRNAseq) and stable isotope resolved metabolomics (SIRM) to define a metabolic rewiring across astrocytes, brain tissue, mice, and human subjects expressing APOE4. Single-cell analysis of brain tissue from mice expressing human APOE revealed E4-associated decreases in genes related to oxidative phosphorylation, particularly in astrocytes. This shift was confirmed on a metabolic level with isotopic tracing of 13C-glucose in E4 mice and astrocytes, which showed decreased pyruvate entry into the TCA cycle and increased lactate synthesis. Metabolic phenotyping of E4 astrocytes showed elevated glycolytic activity, decreased oxygen consumption, blunted oxidative flexibility, and a lower rate of glucose oxidation in the presence of lactate. Together, these cellular findings suggest an E4-associated increase in aerobic glycolysis (i.e. the Warburg effect). To test whether this phenomenon translated to APOE4 humans, we analyzed the plasma metabolome of young and middle-aged human participants with and without the Ε4 allele, and used indirect calorimetry to measure whole body oxygen consumption and energy expenditure. In line with data from E4-expressing female mice, a subgroup analysis revealed that young female E4 carriers showed a striking decrease in energy expenditure compared to non-carriers. This decrease in energy expenditure was primarily driven by a lower rate of oxygen consumption, and was exaggerated following a dietary glucose challenge. Further, the stunted oxygen consumption was accompanied by markedly increased lactate in the plasma of E4 carriers, and a pathway analysis of the plasma metabolome suggested an increase in aerobic glycolysis. Together, these results suggest astrocyte, brain and system-level metabolic reprogramming in the presence of APOE4, a ‘Warburg like’ endophenotype that is observable in young females decades prior to clinically manifest AD.

中文翻译：

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APO乙4通过有氧糖酵解增加通量来降低女性的能量消耗并损害葡萄糖氧化

在患有阿尔茨海默氏病 (AD) 的个体以及携带载脂蛋白 E (APOE) 的 ε4 等位基因（迟发性 AD 的最强遗传预测因子）的认知正常的年轻携带者中，始终观察到脑葡萄糖代谢减退。虽然这种临床特征已经被描述了 20 多年，但脑葡萄糖代谢的这些变化背后的机制仍然是该领域的一个关键知识缺口。在这里，我们通过结合单细胞 RNA 测序 (scRNAseq) 和稳定同位素解析代谢组学 (SIRM) 来采用多组学方法来定义星形胶质细胞、脑组织、小鼠和表达 APOE4 的人类受试者之间的代谢重新布线。对表达人类 APOE 的小鼠脑组织的单细胞分析显示，与氧化磷酸化相关的基因 E4 相关减少，特别是在星形胶质细胞中。这种转变在代谢水平上通过 E4 小鼠和星形胶质细胞中 13C-葡萄糖的同位素示踪得到证实，表明进入 TCA 循环的丙酮酸减少，乳酸合成增加。E4 星形胶质细胞的代谢表型显示糖酵解活性升高、耗氧量减少、氧化灵活性减弱以及在存在乳酸的情况下葡萄糖氧化率降低。总之，这些细胞发现表明 E4 相关的有氧糖酵解增加（即 Warburg 效应）。为了测试这种现象是否适用于 APOE4 人类，我们分析了有和没有 ε4 等位基因的青年和中年人类参与者的血浆代谢组，并使用间接量热法测量全身耗氧量和能量消耗。与表达 E4 的雌性小鼠的数据一致，一项亚组分析显示，与非携带者相比，年轻女性 E4 携带者的能量消耗显着下降。这种能量消耗的减少主要是由较低的氧气消耗率驱动的，并且在饮食葡萄糖挑战后被夸大了。此外，缺氧伴随着 E4 携带者血浆中乳酸的显着增加，血浆代谢组的途径分析表明有氧糖酵解增加。总之，这些结果表明在 APOE4 存在的情况下星形胶质细胞、大脑和系统水平的代谢重编程，APOE4 是一种“Warburg 样”内表型，在临床表现 AD 之前几十年可在年轻女性中观察到。这种能量消耗的减少主要是由较低的氧气消耗率驱动的，并且在饮食葡萄糖挑战后被夸大了。此外，缺氧伴随着 E4 携带者血浆中乳酸的显着增加，血浆代谢组的途径分析表明有氧糖酵解增加。总之，这些结果表明在 APOE4 存在的情况下星形胶质细胞、大脑和系统水平的代谢重编程，APOE4 是一种“Warburg 样”内表型，在临床表现 AD 之前几十年可在年轻女性中观察到。这种能量消耗的减少主要是由较低的氧气消耗率驱动的，并且在饮食葡萄糖挑战后被夸大了。此外，缺氧伴随着 E4 携带者血浆中乳酸的显着增加，血浆代谢组的途径分析表明有氧糖酵解增加。总之，这些结果表明在 APOE4 存在的情况下星形胶质细胞、大脑和系统水平的代谢重编程，APOE4 是一种“Warburg 样”内表型，在临床表现 AD 之前几十年可在年轻女性中观察到。血浆代谢组的途径分析表明有氧糖酵解增加。总之，这些结果表明在 APOE4 存在的情况下星形胶质细胞、大脑和系统水平的代谢重编程，APOE4 是一种“Warburg 样”内表型，在临床表现 AD 之前几十年可在年轻女性中观察到。血浆代谢组的途径分析表明有氧糖酵解增加。总之，这些结果表明在 APOE4 存在的情况下星形胶质细胞、大脑和系统水平的代谢重编程，APOE4 是一种“Warburg 样”内表型，在临床表现 AD 之前几十年可在年轻女性中观察到。