Modulation of neural function in energy failure

描述（由申请人提供）：人葡萄糖转运蛋白I型缺陷（G1 D）导致脑葡萄糖内流减少和神经功能障碍，主要表现为癫痫。通常情况下，大多数葡萄糖通过三羧酸（TCA）循环完全降解为CO2和水，用于大脑能量生成，这也是神经递质谷氨酸和GABA合成和利用的核心。重要的是，一部分葡萄糖不直接产生能量，而是通过称为回补的反应来补充天然TCA循环前体损失。尽管有这些早已确立的生化原理，但目前尚不清楚大多数损害脑代谢并导致癫痫发作的疾病是如何破坏脑组织内（而不是体外）的兴奋性的，包括导致棘波癫痫的G1 D。关于机制的知识差距严重限制了治疗，如G1 D中的抗惊厥药耐药性所示，这也是许多其他神经代谢疾病的规律。我们的实验室和临床长期目标是从机制上了解患者和小鼠模型中的这些脑代谢-兴奋性关系，以开发药理学和饮食疗法。本申请的目的是在一种新型、稳健的G1 D小鼠模型中表征过度兴奋性，并通过用膳食底物刺激回补和TCA循环来缓解过度兴奋性。我们的人类数据和初步实验室结果，如TCA循环前体耗竭和异常的新皮层和丘脑兴奋性在G1 D小鼠的发现，证明这些机制更深入地了解癫痫超同步化作为人类和小鼠G1 D的一个中心特征。这导致了突触功能障碍对疾病病理生理学至关重要的主要假设。该提案还包括治疗方面的考虑，即由普通膳食脂肪或生酮饮食产生的偶数碳酮可以促进TCA循环并改善G1 D中的癫痫发作，但不是回补性的。相比之下，我们的数据开辟了一个新的治疗机会，因为在G1 D中给予奇数碳脂肪有效地重新填充大脑TCA循环前体;导致额外的假设，即它通过回补比偶数碳脂肪更有效地恢复神经功能。这些假设将在三个目标中进行测试：1）研究G1 D中皮质过度兴奋的基础; 2）将这种机制方法扩展到丘脑; 3）通过回补恢复脑代谢和功能。该建议是重要的，因为它的重点是代谢兴奋性的关系和回补在脑组织中使用一个非常翔实的小鼠模型代表了一个转变的方法来神经代谢疾病，其中电生理学，13 C NMR和质谱提供了一个互补的理解机制，有利于潜在的治疗。特别创新的是将联合收割机与对神经回路或大脑区域的突触功能的研究结合起来， 用于癫痫、行为受损或精神发育迟滞，开发了对清醒小鼠脑代谢敏感的方法，广泛适用于其他脑病。总之，我们希望这个建议将有助于将G1 D定义为一种突触疾病，并使其易于兴奋或代谢靶点修饰。

DESCRIPTION (provided by applicant): Human glucose transporter type I-deficiency (G1D) leads to reduced brain glucose influx and neurological dysfunction principally manifested as epilepsy. Normally, most glucose is fully degraded into CO2 and water for brain energy generation via the tricarboxylic acid (TCA) cycle, which is also central to the synthesis and utilization of the neurotransmitters glutamate and GABA. Importantly, a fraction of glucose does not directly generate energy, but refills natural TCA cycle precursor loss through a reaction termed anaplerosis. Despite these long-established biochemical principles, it is unclear how most diseases that impair brain metabolism and cause seizures disrupt excitability within brain tissue (rather than in vitro), including G1D, which leads to spike-wave epilepsy. This knowledge gap about mechanisms critically limits treatment, as illustrated by anticonvulsant resistance in G1D, which is also the rule in many other neurometabolic disorders. Our laboratory and clinical long-term goal is to mechanistically understand these brain metabolism-excitability relationships in patients and mouse models to develop pharmacological and dietary therapies. The objectives of this application are to characterize hyperexcitability in a novel, robust G1D mouse model and to mitigate it by stimulating both anaplerosis and the TCA cycle with dietary substrates. Our human data and preliminary laboratory results, such as the finding of TCA cycle precursor depletion and of abnormal neocortical and thalamic excitability in G1D mice, justify investigating these mechanisms in more depth to understand epileptic hypersynchronization as a central feature of human and murine G1D. This leads to the main hypothesis that synaptic dysfunction is critical for disease pathophysiology. The proposal also includes the therapeutic consideration that even-carbon ketones, generated from common dietary fats or a ketogenic diet, can fuel the TCA cycle and ameliorate seizures in G1D, but are not anaplerotic. In contrast, our data open a new therapeutic opportunity because administered odd-carbon fat refills brain TCA cycle precursors efficiently in G1D; leading to the additional hypothesis that it restores neural functio more effectively than even-carbon fat via anaplerosis. The hypotheses will be tested in three aims: 1) Investigate the basis of cortical hyperexcitability in G1D; 2) Expand this mechanistic approach to the thalamus; 3) Restore brain metabolism and function via anaplerosis. The proposal is significant because its focus on metabolism-excitability relationships and anaplerosis in brain tissue using a very informative mouse model represents a shift in approach to neurometabolic diseases, where electrophysiology, 13C NMR and mass spectrometry offer a complementary understanding of mechanisms conducive to potential therapies. Particularly innovative is to combine an investigation of synaptic function in circuits or brain regions crucial for epilepsy, impaired behavior or mental retardation with the development of methodology sensitive to conscious mouse brain metabolism with broad applicability to other encephalopathies. In summary, we expect that this proposal will help define G1D as a synaptic disorder and render it amenable to excitable or metabolic target modification.