Impaired amino acid metabolism in mitochondrial diseases

描述(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。到目前为止，治疗线粒体疾病的尝试一直令人失望，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。我们已经在携带与人类线粒体疾病相关的线粒体DNA突变的细胞中发现了以前未知的谷氨酰胺代谢缺陷。我们发现，在这些细胞中，谷氨酰胺通过谷氨酰胺-谷氨酸-β-酮戊二酸途径的能量利用受到损害。我们能够通过补充绕过酶阻断的化合物来挽救代谢缺陷。谷氨酰胺是一种含量最丰富、用途最广的循环氨基酸，主要在骨骼肌中合成并在血液中释放，在器官间作为氮、碳和能量的载体发挥着重要作用。体内谷氨酰胺的各种利用途径依赖于各组织的专门化代谢，在调节代谢产物动态平衡的器官间综合代谢中起着至关重要的作用。这项应用的目的是在体内确定改变的谷氨酰胺途径，并通过饮食补充绕过代谢障碍，从而确定治疗线粒体疾病的新方法。为此，我们提出了以下目标：1)COX10 KO小鼠体内代谢产物失衡。我们将在小鼠体内研究谷氨酰胺的利用和合成途径，该模型是由于细胞色素c氧化酶(COX)装配的遗传破坏而导致的RC缺陷，导致进行性线粒体病变。相关代谢物的水平将在血浆和组织中测定，并将与生物能量学、氧化还原、酸/碱和氮状态相关。将评估受影响组织的脆弱性，并将其与疾病进展相关联。2)COX10-KO小鼠饲喂饲料。在体外的初步研究中，已经确定了有效绕过RC缺陷细胞代谢障碍的代谢物。这些代谢物将被添加到COX10 KO小鼠的饮食中。将评估不同组织的专门化代谢、器官间代谢的动态平衡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，它将为基于饮食补充的临床试验提供理论基础，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.