Frontotemporal dementia (FTD) is amongst the most prevalent early onset dementias and even though it is clinically, pathologically and genetically heterogeneous, a crucial involvement of metabolic perturbations in FTD pathology is being recognized. However, changes in metabolism at the cellular level, implicated in FTD and in neurodegeneration in general, are still poorly understood. Here we generate induced human pluripotent stem cells (hiPSCs) from patients carrying mutations in CHMP2B (FTD3) and isogenic controls generated via CRISPR/Cas9 gene editing with subsequent neuronal and glial differentiation and characterization. FTD3 neurons show a dysregulation of glutamate-glutamine related metabolic pathways mapped by 13C-labelling coupled to mass spectrometry. FTD3 astrocytes show increased uptake of glutamate whilst glutamate metabolism is largely maintained. Using quantitative proteomics and live-cell metabolic analyses, we elucidate molecular determinants and functional alterations of neuronal and glial energy metabolism in FTD3. Importantly, correction of the mutations rescues such pathological phenotypes. Notably, these findings implicate dysregulation of key enzymes crucial for glutamate-glutamine homeostasis in FTD3 pathogenesis which may underlie vulnerability to neurodegeneration. Neurons derived from human induced pluripotent stem cells (hiPSCs) of patients carrying mutations in CHMP2B (FTD3) display major metabolic alterations compared to CRISPR/Cas9 generated isogenic controls. Using quantitative proteomics, 13C-labelling coupled to mass spectrometry metabolic mapping and seahorse analyses, molecular determinants and functional alterations of neuronal and astrocytic energy metabolism in FTD3 were characterized. Our findings implicate dysregulation of glutamate-glutamine homeostasis in FTD3 pathogenesis. In addition, FTD3 neurons recapitulate glucose hypometabolism observed in FTD patient brains. The impaired mitochondria function found here is concordant with disturbed TCA cycle activity and decreased glycolysis in FTD3 neurons. FTD3 neuronal glutamine hypermetabolism is associated with up-regulation of PAG expression and, possibly, ROS production. Distinct compartments of glutamate metabolism can be suggested for the FTD3 neurons. Endogenous glutamate generated from glutamine via PAG may enter the TCA cycle via AAT (left side of neuron) while exogenous glutamate taken up from the extracellular space may be incorporated into the TCA cycle via GDH (right side of the neuron) FTD3 astrocytic glutamate uptake is upregulated whilst glutamate metabolism is largely maintained. Finally, pharmacological reversal of glutamate hypometabolism manifesting from decreased GDH expression should be explored as a novel therapeutic intervention for treating FTD3.

中文翻译：

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谷氨酸-谷氨酰胺稳态在源自额颞痴呆患者iPSC模型的神经元和星形胶质细胞中受到干扰。

额颞痴呆（FTD）是最普遍的早期发作性痴呆之一，尽管它在临床，病理和遗传上都是异质的，但人们已经认识到代谢紊乱在FTD​​病理学中的关键作用。然而，仍然很少了解与FTD和神经退行性疾病有关的细胞水平的代谢变化。在这里，我们从携带CHMP2B（FTD3）突变的患者和通过CRISPR / Cas9基因编辑产生的同基因对照以及随后的神经元和神经胶质分化和表征中产生的人多能干细胞（hiPSC）生成。FTD3神经元显示谷氨酸-谷氨酰胺相关的代谢途径失调，其通过13C标记与质谱联用绘制。FTD3星形胶质细胞显示出谷氨酸的摄取增加，而谷氨酸的代谢被大部分维持。使用定量蛋白质组学和活细胞代谢分析，我们阐明了FTD3中分子决定因素以及神经元和神经胶质能量代谢的功能改变。重要的是，突变的纠正可以挽救这种病理表型。值得注意的是，这些发现暗示在FTD3发病机理中对谷氨酸-谷氨酰胺稳态至关重要的关键酶失调可能是神经退行性变弱的基础。与CRISPR / Cas9生成的等基因对照相比，携带CHMP2B（FTD3）突变的患者的人诱导多能干细胞（hiPSC）衍生的神经元显示出主要的代谢改变。使用定量蛋白质组学，13C标记结合质谱代谢图谱和海马分析，表征了FTD3的分子决定因素和神经元和星形细胞能量代谢的功能改变。我们的发现暗示FTD3发病机制中的谷氨酸-谷氨酰胺稳态失调。另外，FTD3神经元概括了在FTD患者大脑中观察到的葡萄糖代谢低下。此处发现的线粒体功能受损与FCA3神经元的TCA循环活性受损和糖酵解降低有关。FTD3神经元谷氨酰胺过度代谢与PAG表达的上调以及可能与ROS的产生有关。对于FTD3神经元，可以建议谷氨酸代谢的不同区室。谷氨酰胺通过PAG产生的内源性谷氨酸可通过AAT（神经元的左侧）进入TCA循环，而从细胞外空间吸收的外源谷氨酸可通过GDH（神经元的右侧）并入TCA循环，FTD3星形胶质谷氨酸的摄取为在很大程度上维持谷氨酸代谢的同时上调。最后，应探索由降低的GDH表达所表现出的谷氨酸低新陈代谢的药理学逆转，作为治疗FTD3的新型治疗手段。