Carnitine Acetyltransferase in Defending Mitochondrial and Metabolic Function

肉碱乙酰转移酶保护线粒体和代谢功能

• 批准号: 8309298
• 负责人: DEBORAH M MUOIO
• 金额: $ 35.32万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8309298
• 关键词: Acetyl Coenzyme A; Acetylcarnitine; Address; Adenoviruses; Advertising; Aging; Animals; Antidiabetic Drugs; Body fat; Carbohydrates; Carbon; Carnitine; Carnitine O-Acetyltransferase; Chronic; Coenzyme A; Data; Development; Diet; Elderly; Energy Metabolism; Enzymes; Esters; Exercise Tolerance; Fatty Acids; Fatty acid glycerol esters; Genetic Engineering; Glucose; Glucose Intolerance; Goals; Heart; Homeostasis; Human; Indirect Calorimetry; Insulin; Insulin Resistance; Knockout Mice; Laboratories; Levocarnitine; Link; Lipids; Mass Spectrum Analysis; Measures; Mediating; Mediator of activation protein; Metabolic; Metabolic Control; Metabolic Diseases; Metabolic stress; Metabolic syndrome; Metabolism; Mitochondria; Mitochondrial Matrix; Mitochondrial Proteins; Modeling; Muscle; Muscle Fibers; Non-Insulin-Dependent Diabetes Mellitus; Nutrient; Obesity; Outcome; Outcome Measure; Overnutrition; Oxidative Stress; Physiological; Plasma; Play; Production; Property; Proteomics; Publishing; Reaction; Recombinants; Regulation; Respiratory physiology; Rodent; Role; Skeletal Muscle; Stress; Supplementation; Technology; Testing; Therapeutic; Tissues; Urine; Work; acylcarnitine; base; clinically relevant; conditionally essential amino acid; diabetes mellitus genetics; diabetic; glucose tolerance; improved; insight; interest; long chain fatty acid; loss of function; mouse model; novel; oxidation; primary outcome; public health relevance; pyruvate dehydrogenase; research study; skeletal; small hairpin RNA; uptake; urinary

DESCRIPTION (provided by applicant): This project seeks to elucidate the role of carnitine acetyltransferase (CrAT) as an important regulator of mitochondrial function and glucose tolerance, and the principal mediator of the antidiabetic actions of L-carnitine therapy. Carnitine acetyltransferase (CrAT) is a mitochondrial matrix enzyme that plays a key role in the synthesis and efflux of short chain carnitine conjugates, such as acetyl-carnitine. This enzyme is most abundant in carnitine-rich tissues such as skeletal muscle and heart, but its precise metabolic function remains largely unexplored. CrAT activity is mainly regulated by availability of L-carnitine, a conditionally essential nutrient that is best known for its obligatory role in permitting mitochondrial uptake and oxidation of long chain fatty acids. In addition to its requisite role in fat oxidation, carnitine also permits the intramitochondrial formation of acylcarnitine conjugates, thereby facilitating mitochondrial efflux of excess carbon fuels. Recent studies by our laboratory suggest that carnitine insufficiency caused by aging and/or overnutrition impairs fuel metabolism and insulin action by compromising CrAT activity. Remarkably, dietary carnitine supplementation improved metabolic outcomes in these models in association with robust increases in plasma and urinary acetyl-carnitine levels. The physiological relevance of acetyl-carnitine production and efflux is poorly understood and surprisingly understudied. We seek to understand the specific role of CrAT as a carnitine effector that defends metabolic homeostasis. We will address two central hypotheses: 1) CrAT plays a key role in regulating mitochondrial substrate switching between glucose and fatty acid fuels, and 2) mitochondrial efflux of CrAT-derived acylcarnitines affords protection against muscle insulin resistance and oxidative stress caused by chronic overnutrition. These hypotheses will be tested using gain- and loss-of-function genetic engineering approaches in primary human skeletal myocytes as well as knockout mouse models. Primary outcome measures will include indirect calorimetry, multiple measures of insulin action and metabolic flux, along with state-of-the-art mass spectrometry-based metabolic profiling. PUBLIC HEALTH RELEVANCE: This project examines the role of carnitine insufficiency a contributing factor to the development and progression of metabolic disorders such as insulin resistance and type 2 diabetes. L- carnitine is a conditionally essential amino acid derivative that is often advertised as an energy enhancing nutrient. Recent animal studies by our laboratory have shown that systemic carnitine homeostasis is compromised by aging and obesity, whereas carnitine supplementation improved metabolic regulation and glucose tolerance. The salutary effects of carnitine therapy were linked to increased activity of a mitochondrial enzyme known as carnitine acetyltransferase (CrAT). The overarching goal of this project is to elucidate mechanisms through which supplemental L-carnitine improves glucose tolerance and to determine the precise role of the CrAT enzyme in regulating energy metabolism. Results from the proposed studies are likely to yield new insights regarding the therapeutic properties of L-carnitine while also advancing understanding of the interplay between mitochondrial function and insulin action. These are clinically relevant topics of intense scientific interest and controversy.

描述（由申请人提供）：本项目旨在阐明肉碱乙酰转移酶（CrAT）作为线粒体功能和葡萄糖耐量的重要调节因子的作用，以及左旋肉碱治疗降糖作用的主要介质。肉碱乙酰转移酶（Carnitine acetyltransferase, CrAT）是一种线粒体基质酶，在短链肉碱缀合物如乙酰肉碱的合成和外排中起关键作用。这种酶在骨骼肌和心脏等肉毒碱丰富的组织中最为丰富，但其精确的代谢功能在很大程度上仍未被探索。CrAT活性主要受左旋肉碱的调节，左旋肉碱是一种有条件的必需营养素，其最著名的作用是允许线粒体摄取和氧化长链脂肪酸。除了在脂肪氧化中必不可少的作用外，肉碱还允许线粒体内形成酰基肉碱偶联物，从而促进线粒体排出多余的碳燃料。我们实验室最近的研究表明，由衰老和/或营养过剩引起的肉碱不足通过损害CrAT活性来损害燃料代谢和胰岛素作用。值得注意的是，在这些模型中，饮食中补充肉碱可以改善代谢结果，并显著增加血浆和尿液中乙酰肉碱水平。乙酰-肉碱产生和外排的生理相关性了解甚少，令人惊讶的是研究不足。我们试图了解CrAT的具体作用，作为肉碱效应，捍卫代谢稳态。我们将解决两个中心假设：1)CrAT在调节线粒体底物在葡萄糖和脂肪酸燃料之间的转换中起关键作用；2)CrAT衍生的酰基肉碱的线粒体外排可防止肌肉胰岛素抵抗和慢性营养过剩引起的氧化应激。这些假设将在原代人骨骼肌细胞和敲除小鼠模型中使用获得和丧失功能的基因工程方法进行测试。主要结果测量将包括间接量热法、胰岛素作用和代谢通量的多重测量，以及最先进的基于质谱的代谢谱分析。