Mitochondrial Metabolism in Primary Hyperoxaluria

原发性高草酸尿症的线粒体代谢

基本信息

批准号：
8632089
负责人：
ROSS P HOLMES
金额：
$ 33.19万
依托单位：
UNIVERSITY OF ALABAMA AT BIRMINGHAM
依托单位国家：
美国
项目类别：
财政年份：
1999
资助国家：
美国
起止时间：
1999-05-01 至 2017-12-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8632089
关键词：
Address Alanine-glyoxylate aminotransferase Alcohols Aldehyde-Lyases Anions Antioxidants Back Bioenergetics Calcium Oxalate Cells Chinese Hamster Ovary Cell Culture Media Cultured Cells Cytoplasm Cytosol Degradation Pathway Diabetes Mellitus Disease End stage renal failure Enzymes Excretory function Experimental Animal Model Fatty Liver Functional disorder Generations Glycolates Glyoxylates Heart Diseases Hepatocyte Hereditary Disease Hydrogen Peroxide Hydroxyproline Impairment Individual Infant Infusion procedures Ions Kidney Kidney Calculi Kidney Failure Kidney Transplantation Knockout Mice Knowledge Label Lead Life Liver Measures Metabolic Metabolic Diseases Metabolism Mitochondria Modeling Mus Nephrocalcinosis Oxalates Oxidases Parkinson Disease Pathway interactions Patients Pharmaceutical Preparations Phenotype Plasma Play Primary Hyperoxaluria Process Production Property Proximal Kidney Tubules Rare Diseases Reactive Oxygen Species Renal function Research Rodent Model Role Sampling Source Stress Techniques Testing Therapeutic Tissues Tracer Transplantation Urine Wild Type Mouse alpha ketoglutarate design enzyme activity glyoxylate glyoxylate reductase insight mitochondrial dysfunction mouse model nervous system disorder novel novel strategies oxidation peroxisome public health relevance pyridoxine research study response urinary

项目摘要

DESCRIPTION (provided by applicant): Primary Hyperoxaluria (PH) is a rare, genetic disorder that is characterized by an increased urinary oxalate excretion, the formation of calcium oxalate kidney stones, and in severe cases renal failure. In the most extreme cases, some develop nephrocalcinosis and renal failure as infants with a poor survival outlook. Our research suggests that hydroxyproline metabolism makes a major contribution to the increased oxalate synthesis that occurs in PH. This metabolism occurs in the mitochondrion and is aberrant in a recently identified form of the disease, Type 3, where the activity of the enzyme, 4-hydroxy-2-oxoglutarate aldolase (HOGA), a component of the degradation pathway, is deficient. A deficiency in another mitochondrial enzyme, glyoxylate reductase, is associated with Type 2 disease. In Type 1 disease, glycolate-glyoxylate cycling occurs in the liver when glycolate produced in mitochondria from hydroxyproline metabolism is oxidized in peroxisomes to glyoxylate and reduced back to glycolate in the cytoplasm because of the absence of AGT. We hypothesize that the hydrogen peroxide produced with this cycling contributes to mitochondrial dysfunction due to an increased generation of reactive oxygen species. We further hypothesize that the altered metabolism in these types of PH may result in an altered concentration of oxalate, glyoxylate and glycolate in mitochondria and the cytosol. Changes in ion levels, particularly oxalate and calcium, could further modify mitochondrial properties. In this proposal, we will use genetically modified mice to determine how the changes in enzyme composition associated with PH alter mitochondrial properties in hepatocytes and renal proximal tubule cells (RPTC). The first specific aim will determine the phenotype of Hoga1 knock-out mice and examine how the substrate, HOG, is split when HOGA is absent. We hypothesize that an alternative aldolase is able to split HOG when its concentration increases sufficiently. The second specific aim will examine mitochondrial properties and metabolic changes that occur in intact hepatocytes and RTPC from normal and genetically modified mice using an XF-analyzer. Mitochondrial quality will also be assessed in liver and kidney tissue of the mouse models and in liver tissue from PH patients receiving a transplant. Whether a mitochondrial specific drug such as MitoQ can offset any adverse changes will be investigated. The third specific aim will identify changes that occur in mitochondria isolated from these mice when they metabolize hydroxyproline and glyoxylate. These experiments will illuminate the metabolism associated with the increased oxalate synthesis that occurs in PH, highlight the role played by mitochondria in the disease process, and illustrate important differences between liver and kidney mitochondria. This research should lead to novel approaches to decrease excessive oxalate synthesis and modify mitochondrial dysfunction in PH.

描述（由申请人提供）：原发性高草酸尿症（PH）是一种罕见的遗传性疾病，其特征是尿草酸排泄增加、草酸钙肾结石形成，严重时会出现肾功能衰竭。在最极端的情况下，一些婴儿在婴儿时期就出现肾钙质沉着症和肾功能衰竭，生存前景不佳。我们的研究表明，羟脯氨酸代谢对 PH 中草酸盐合成的增加做出了重大贡献。这种代谢发生在线粒体中，并且在最近发现的 3 型疾病中是异常的，其中降解途径的一个组成部分 4-羟基-2-酮戊二酸醛缩酶 (HOGA) 的活性缺陷。另一种线粒体酶乙醛酸还原酶的缺乏与 2 型疾病有关。在 1 型疾病中，当线粒体中羟脯氨酸代谢产生的乙醇酸在过氧化物酶体中氧化为乙醛酸，并由于缺乏 AGT 而在细胞质中还原回乙醇酸时，肝脏中会发生乙醇酸-乙醛酸循环。我们假设这种循环产生的过氧化氢由于活性氧的产生增加而导致线粒体功能障碍。我们进一步假设这些类型的 PH 代谢的改变可能导致线粒体和细胞质中草酸盐、乙醛酸盐和乙醇酸盐浓度的改变。离子水平的变化，特别是草酸盐和钙的变化，可以进一步改变线粒体的特性。在本提案中，我们将使用转基因小鼠来确定与 PH 相关的酶组成的变化如何改变肝细胞和肾近端小管细胞 (RPTC) 中的线粒体特性。第一个具体目标是确定 Hoga1 敲除小鼠的表型，并检查当 HOGA 不存在时底物 HOG 是如何分裂的。我们假设另一种醛缩酶在其浓度充分增加时能够分解 HOG。第二个具体目标是使用 XF 分析仪检查正常小鼠和转基因小鼠的完整肝细胞和 RTPC 中发生的线粒体特性和代谢变化。还将评估小鼠模型的肝脏和肾脏组织以及接受移植的 PH 患者的肝脏组织中的线粒体质量。将研究线粒体特异性药物（例如 MitoQ）是否可以抵消任何不利变化。第三个具体目标是确定从这些小鼠体内分离出的线粒体在代谢羟脯氨酸和乙醛酸时发生的变化。这些实验将阐明与 PH 中草酸合成增加相关的代谢，强调线粒体在疾病过程中所发挥的作用，并说明肝脏和肾脏线粒体之间的重要差异。这项研究应该会带来新的方法来减少过量的草酸盐合成并改变PH中的线粒体功能障碍。