Impaired amino acid metabolism in mitochondrial diseases

描述（由申请人提供）：线粒体疾病是由呼吸链（RC）损伤引起的异质性遗传疾病。迄今为止，治疗线粒体疾病的尝试令人失望，主要是因为缺乏明确的目标。这一应用的主要假设是线粒体疾病的发病机制涉及器官间氨基酸代谢的关键步骤的阻断。我们已经在与人类线粒体疾病相关的线粒体DNA突变细胞中发现了以前未被认识到的谷氨酰胺代谢缺陷。我们发现通过谷氨酰胺-谷氨酸-酮戊二酸途径对谷氨酰胺的能量利用在这些细胞中受损。我们能够通过补充绕过酶阻塞的化合物来挽救代谢缺陷。谷氨酰胺是最丰富、用途最广的循环氨基酸，主要在骨骼肌中合成，并释放到血液中，作为器官间氮、碳和能量的载体发挥重要作用。谷氨酰胺在体内的各种利用途径依赖于各组织的特化代谢，在调节代谢物稳态的器官间综合代谢中起着至关重要的作用。本应用的目的是确定体内改变的谷氨酰胺途径，并通过膳食补充绕过代谢阻塞，从而确定线粒体疾病治疗的新方法。为此，我们提出以下目的：1)COX10 KO小鼠的代谢物失衡。我们将在细胞色素c氧化酶（COX）组装的遗传破坏引起的RC缺陷小鼠模型中研究谷氨酰胺的利用和合成途径，从而导致进行性线粒体病。相关代谢物的水平将在血浆和组织中确定，并将与生物能量学、氧化还原、酸碱和氮态相关。受影响组织的易损性将被评估并与疾病进展相关。2) COX10 KO小鼠的日粮补充。在体外初步研究中，已经确定了有效绕过RC缺陷细胞代谢阻滞的代谢物。这些代谢物将在COX10 KO小鼠的饮食中补充。将评估不同组织的特化代谢、器官间代谢稳态以及与疾病进展相关的生理变化。这一目标的潜在临床前影响是，它将为基于膳食补充剂的临床试验提供依据，使用生理化合物。

DESCRIPTION (provided by applicant): Mitochondrial diseases are heterogeneous genetic disorders caused by respiratory chain (RC) impairment. Attempts to treat mitochondrial diseases have been disappointing so far, mostly due to the lack of defined targets. The leading hypothesis of this application is that mitochondrial disease pathogenesis involves the blockage of crucial steps of the inter-organ amino acid metabolism. We have identified previously unrecognized defects in glutamine metabolism in cells harboring mitochondrial DNA mutations associated with human mitochondrial diseases. We found that the energetic utilization of glutamine through the glutamine-glutamate-¿-ketoglutarate pathway was impaired in these cells. We were able to rescue the metabolic defect by supplementation with compounds that bypass the enzymatic blockages. Glutamine is the most abundant and versatile circulating amino acid, mostly synthesized in skeletal muscle and released in the blood where it plays an important role as a carrier of nitrogen, carbon, and energy between organs. The various glutamine-utilization pathways in the body depend on the specialized metabolism of each tissue and play a crucial role in the inter-organs integrated metabolism that regulates metabolites homeostasis. The goal of this application is to define in vivo the altered glutamine pathways and to bypass the metabolic blockages with dietary supplementation, thus identifying new approaches to the therapy of mitochondrial diseases. To this end, we propose the following aims: 1) Metabolites imbalance in the COX10 KO mouse. We will investigate the glutamine utilization and synthesis pathways in vivo in a mouse model of RC defect caused by genetic disruption of cytochrome c oxidase (COX) assembly, resulting in a progressive mitochondriopathy. The levels of relevant metabolites will be determined in plasma and in tissues, and will be correlated with the bioenergetics, redox, acid/base and nitrogen states. The vulnerability of the affected tissues will be evaluated and correlated with disease progression. 2) Dietary supplementation in the COX10 KO mouse. In preliminary studies in vitro, metabolites that effectively bypass metabolic blocks in RC deficient cells have been identified. These metabolites will be supplemented in the diet of the COX10 KO mouse. The specialized metabolism of different tissues, the inter-organ metabolic homeostasis, and the physiological alterations in relation to disease progression will be assessed. The potential preclinical impact o this aim is that it will provide a rationale for clinical trials based on dietary supplementation, using physiological compounds.