Role of Glutamate Dehydrogenase in Carbohydrate, Amino Acid and Energy Metabolism of Neurons

脑神经元控制着身体的所有功能。尽管神经元健康的重要性得到了普遍认可，但令人惊讶的是，人们对神经元新陈代谢知之甚少。谷氨酸脱氢酶是一种连接细胞内碳水化合物、氨基酸和能量代谢的线粒体酶。这项拟议的研究项目将调查中心酶GDH在神经元新陈代谢中的作用。最近产生了一只中枢神经系统(CNS)特异性缺失GDH基因Glud1的小鼠(CNS-Glud1-/-小鼠)，并证实了这些小鼠脑内GDH的消融。体外小脑颗粒神经元培养、神经元-星形胶质细胞共培养和CNS-Glud1-/-小鼠脑片将作为模型系统。从CNS-Glud1-/-小鼠的细胞培养或脑片上获得的数据与对照组小鼠的数据进行比较，将为GDH在神经元代谢中的作用提供信息。利用13C和15N标记的底物(如葡萄糖或谷氨酸)的代谢图谱，通过质谱学和核磁共振波谱分析代谢，将揭示GDH在神经元中的作用。对神经元-星形胶质细胞共培养和CNS-Glud1-/-小鼠脑片中神经元代谢的分析将阐明神经元GDH在神经元和星形胶质细胞代谢相互作用中的作用。此外，还将研究谷氨酸脱氢酶对糖酵解和线粒体神经元能量产生的重要性，以及含有谷氨酸的抗氧化剂谷胱甘肽的神经元含量。此外，对神经递质谷氨酸的释放和再摄取的研究将揭示GDH在神经元之间神经传递中的作用。综上所述，该项目将提供有关谷氨酸脱氢酶在神经元能量代谢中的作用的基本信息，这也将是进一步研究谷氨酸脱氢酶功能障碍在神经系统疾病和影响大脑的疾病中的作用所必需的。

Brain neurons are controlling all functions of the body. Although the importance of neuronal health is generally acknowledged, surprisingly little is known about neuronal metabolism. Glutamate dehydrogenase (GDH) is a mitochondrial enzyme that links carbohydrate, amino acid and energy metabolism of cells. The proposed research project will investigate the role of the central enzyme GDH in neuronal metabolism. A mouse with a central nervous system (CNS) specific deletion of the GDH gene Glud1 (CNS-Glud1-/-mice) has been generated recently and the ablation of GDH in the brain of these mice has been confirmed. In vitro cerebellar granule neuron cultures, neuron-astrocyte co-cultures and brain slices from CNS-Glud1-/-mice will be used as model systems. The comparison of data obtained on cell cultures or brain slices from CNS-Glud1-/-mice with control mice will provide information of the role of GDH in neuronal metabolism. Analysis of the metabolism by metabolic mapping employing 13C- and 15N-labeled substrates (e.g. glucose or glutamate) by mass spectrometry and nuclear magnetic resonance spectroscopy will reveal a detailed picture about the role of GDH in neurons. Analysis of the metabolism of neurons in neuron-astrocyte co-cultures and brain slices from CNS-Glud1-/-mice will clarify the role of the neuronal GDH in the metabolic interactions of neurons and astrocytes. Moreover, the importance of GDH for both the glycolytic and mitochondrial neuronal energy production and the neuronal content of the glutamate-containing antioxidant glutathione will be studied. Also, investigations of release and reuptake of the neurotransmitter glutamate will reveal valuable insights into the role of GDH in neurotransmission between neurons. In summary, this project will supply fundamental informations of the role of GDH in neuronal energy metabolism, which will also be essential for further investigations of the contribution of GDH-malfunction in neurological diseases and diseases affecting the brain.