Role of Carnitine Acetyltransferase in Defending Mitochondrial and Metabolic Func

肉碱乙酰转移酶在保护线粒体和代谢功能中的作用

• 批准号: 7977269
• 负责人: DEBORAH M MUOIO
• 金额: $ 44.96万
• 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/7977269
• 关键词: Acetyl Coenzyme A; Acetylcarnitine; Address; Adenoviruses; Advertising; Aging; Animals; Antidiabetic Drugs; Arts; 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）：本项目旨在阐明肉毒碱乙酰转移酶（CrAT）作为线粒体功能和葡萄糖耐量的重要调节剂以及L-肉毒碱治疗的抗糖尿病作用的主要介体的作用。肉毒碱乙酰转移酶（CrAT）是一种线粒体基质酶，在短链肉毒碱缀合物（如乙酰肉毒碱）的合成和流出中起关键作用。这种酶在富含肉毒碱的组织如骨骼肌和心脏中含量最丰富，但其精确的代谢功能在很大程度上仍未被探索。CrAT活性主要由L-肉毒碱的可用性调节，L-肉毒碱是一种条件性必需营养素，其在允许长链脂肪酸的线粒体摄取和氧化中的强制性作用是众所周知的。除了其在脂肪氧化中的必要作用外，肉毒碱还允许酰基肉毒碱缀合物的线粒体内形成，从而促进过量碳燃料的线粒体流出。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毒碱不足损害燃料代谢和胰岛素作用，损害CrAT活性。值得注意的是，膳食肉碱补充剂改善了这些模型中的代谢结果，并与血浆和尿乙酰肉碱水平的强劲增加有关。乙酰肉毒碱的生产和流出的生理相关性是知之甚少，令人惊讶的研究不足。我们试图了解的具体作用CrAT作为肉毒碱效应，捍卫代谢稳态。我们将解决两个中心假设：1）CrAT在调节葡萄糖和脂肪酸燃料之间的线粒体底物转换中起关键作用，和2）CrAT衍生的酰基肉毒碱的线粒体流出提供针对由慢性营养过剩引起的肌肉胰岛素抵抗和氧化应激的保护。这些假设将在原代人骨骼肌细胞以及基因敲除小鼠模型中使用功能获得和功能丧失基因工程方法进行测试。主要结果测量将包括间接热量测定、胰岛素作用和代谢通量的多种测量，以及沿着最先进的基于质谱的代谢分析。 公共卫生相关性：这个项目研究了肉毒碱不足的作用，肉毒碱不足是代谢紊乱如胰岛素抵抗和2型糖尿病的发展和进展的一个促成因素。左旋肉碱是一种条件性必需氨基酸衍生物，经常被宣传为能量增强营养素。我们实验室最近的动物研究表明，全身肉毒碱稳态受到衰老和肥胖的影响，而肉毒碱补充剂改善了代谢调节和葡萄糖耐量。肉毒碱治疗的有益效果与被称为肉毒碱乙酰转移酶（CrAT）的线粒体酶的活性增加有关。该项目的总体目标是阐明补充L-肉碱改善葡萄糖耐量的机制，并确定CrAT酶在调节能量代谢中的确切作用。拟议研究的结果可能会产生关于L-肉碱治疗特性的新见解，同时也促进了对线粒体功能和胰岛素作用之间相互作用的理解。这些都是具有强烈科学兴趣和争议的临床相关主题。