Modulation of neural function in energy failure

描述（由申请人提供）：人葡萄糖转运蛋白i型缺乏（G1D）导致脑葡萄糖流减少和神经功能障碍，主要表现为癫痫。正常情况下，大多数葡萄糖通过三羧酸（TCA）循环被完全降解为二氧化碳和水，用于大脑能量的产生，这也是神经递质谷氨酸和GABA的合成和利用的核心。重要的是，一小部分葡萄糖并不直接产生能量，而是通过一种被称为修复的反应来补充天然TCA循环前体的损失。尽管有这些长期建立的生化原理，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在脑组织内（而不是体外）破坏兴奋性的，包括导致尖波癫痫的G1D。这种机制上的知识差距严重限制了治疗，正如G1D的抗惊厥药耐药性所表明的那样，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在患者和小鼠模型中机械地了解这些脑代谢-兴奋性关系，以开发药理学和饮食疗法。本应用的目的是在一种新型的、稳健的G1D小鼠模型中表征高兴奋性，并通过饮食底物刺激过敏和TCA循环来减轻高兴奋性。我们的人体数据和初步实验室结果，如在G1D小鼠中发现TCA循环前体耗竭和新皮层和丘脑异常兴奋性，证明了更深入地研究这些机制，以了解癫痫过度同步是人类和小鼠G1D的核心特征。这导致了突触功能障碍对疾病病理生理至关重要的主要假设。该建议还包括治疗性考虑，即使是由普通膳食脂肪或生酮饮食产生的碳酮，也可以促进TCA循环并改善G1D的癫痫发作，但不会逆转。相比之下，我们的数据打开了一个新的治疗机会，因为给药的奇碳脂肪在G1D中有效地重新填充脑TCA循环前体；这导致了另一个假设，即它甚至比碳脂肪通过复位更有效地恢复神经功能。这些假设将在三个方面得到验证：1)研究G1D皮层高兴奋性的基础；2)将这种机械方法扩展到丘脑；3)通过修复恢复脑代谢和功能。该建议意义重大，因为它关注的是代谢-兴奋性关系和脑组织中的骨质疏松，使用了一个非常信息丰富的小鼠模型，代表了神经代谢性疾病方法的转变，其中电生理学，13C NMR和质谱提供了对有助于潜在治疗的机制的补充理解。特别创新的是结合对神经回路或大脑关键区域突触功能的研究

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.