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

大脑神经元控制着身体的所有功能。尽管人们普遍认识到神经元健康的重要性，但令人惊讶的是，人们对神经元代谢知之甚少。谷氨酸脱氢酶（GDH）是一种连接细胞碳水化合物、氨基酸和能量代谢的线粒体酶。拟议的研究项目将探讨中枢酶GDH在神经元代谢中的作用。最近已经产生了一种中枢神经系统（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-/-小鼠脑切片将作为模型系统。将CNS-Glud1-/-小鼠的细胞培养或脑切片数据与对照小鼠进行比较，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），通过质谱和核磁共振谱分析代谢图谱，将揭示GDH在神经元中的作用的详细图景。分析神经元-星形胶质细胞共培养和CNS-Glud1-/-小鼠脑切片中神经元的代谢将阐明神经元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GDH对糖酵解和线粒体神经元能量产生以及含谷氨酸的抗氧化剂谷胱甘肽的神经元含量的重要性。此外，对神经递质谷氨酸的释放和再摄取的研究将揭示GDH在神经元间神经传递中的作用。总之，该项目将提供GDH在神经元能量代谢中的作用的基础信息，这也将对进一步研究GDH功能障碍在神经系统疾病和影响大脑的疾病中的作用至关重要。

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.