Mitochondrial Metabolism in Primary Hyperoxaluria

原发性高草酸尿症的线粒体代谢

• 批准号: 8926129
• 负责人: ROSS P HOLMES
• 金额: $ 5.85万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-16 至 2017-12-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8926129
• 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; Health; 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; pyridoxine; research study; response; urinary

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，其特征是尿中草酸盐排泄增加，形成草酸钙肾结石，严重时肾功能衰竭。在最极端的情况下，一些婴儿发展为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起主要作用。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4-羟基-2-氧戊二酸醛缩酶（HOGA）的活性不足，这是降解途径的一个组成部分。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盐，并由于AGT的缺乏而在细胞质中还原回乙醇酸盐时，肝脏中发生乙醇酸-乙醛酸盐循环。我们假设这种循环产生的过氧化氢由于活性氧的增加而导致线粒体功能障碍。我们进一步假设，这些类型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。在这项提议中，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）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HOGA缺失时底物HOG是如何分裂的。我们假设一种替代醛缩酶在其浓度充分增加时能够分裂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。是否线粒体特异性药物如MitoQ可以抵消任何不利的变化将被研究。第三个具体目标是确定从这些小鼠中分离的线粒体在代谢羟脯氨酸和乙醛酸盐时发生的变化。这些实验将阐明与PH中草酸盐合成增加相关的代谢，强调线粒体在疾病过程中所起的作用，并说明肝脏和肾脏线粒体之间的重要差异。这项研究将为减少过量草酸合成和改变线粒体功能障碍提供新的途径。