Role of Carnitine Acetyltransferase in Mitochondrial and Metabolic Function

 描述（由申请人提供）：我们在线粒体功能、能量稳态和代谢组学领域的工作使我们发现了不良心脏代谢结果与酰基肉毒碱缀合物的组织/血液水平之间的显著强关联。这些代谢产物来源于燃料催化剂的酰基辅酶A中间体，并允许线粒体输出过量的碳。我们的工作模型将酰基肉毒碱定位为线粒体应激的生物标志物和缓解应激的载体。为了验证这一假设，我们一直在研究肉毒碱乙酰转移酶（CrAT）的代谢和生理重要性，CrAT是一种线粒体基质酶，可将乙酰辅酶A和其他短链酰基辅酶A转化为膜渗透酰基肉毒碱。在上一个资助周期中，我们确定CrAT的酰基缓冲能力对于正常的燃料选择、葡萄糖控制和运动耐量是必要的。我们所做的最令人兴奋和潜在的重要发现之一是，在小鼠骨骼肌中CrAT的基因消融增加了乙酰辅酶A的组织浓度，并加剧了饮食诱导的线粒体蛋白乙酰化。赖氨酸乙酰化（AcK）是可逆的翻译后蛋白质修饰（PTM），其中两个碳乙酰基与赖氨酸残基的e-氨基共价结合。这种PTM主要存在于线粒体蛋白中，过量的AcK与缺乏sirtuin 3（SIRT 3）的小鼠的代谢疾病有关，SIRT 3是主要的脑内定位脱乙酰酶，可从特定的赖氨酸残基中去除乙酰基。我们的初步数据表明AcK可以在乙酰辅酶A的线粒体库扩增时非酶促发生。该项目采用最先进的蛋白质组学和代谢组学方法来验证我们的假设，即CrAT和SIRT 3协同作用以对抗线粒体碳应激，并且这些酶的功能中共存的不相容性有助于代谢疾病背景下的代谢失调。由于CrAT和SIRT 3依赖于必需微量营养素底物，L-肉碱和烟酰胺的可用性，我们还将确定一种新的组合营养策略，同时针对这两个系统可能会赋予添加剂或协同代谢的好处时，管理肥胖啮齿动物。

 DESCRIPTION (provided by applicant): Our work in the area of mitochondrial function, energy homeostasis and metabolomics has led us to discover a remarkably strong association between adverse cardiometabolic outcomes and tissue/blood levels of acylcarnitine conjugates. These metabolites derive from acyl-CoA intermediates of fuel catabolism and permit mitochondrial export of excess carbons. Our working model positions acylcarnitines as biomarkers of mitochondrial stress and vehicles of stress relief. To test this hypothesis we have been studying the metabolic and physiological importance of carnitine acetyltransferase (CrAT), the mitochondrial matrix enzyme that converts acetyl-CoA and other short chain acyl-CoA species to their membrane permeant acylcarnitine counterparts. During the previous funding cycle we determined that the acyl group buffering capacity of CrAT is necessary for normal fuel selection, glucose control and exercise tolerance. One of the most exciting and potentially important discoveries we made is that genetic ablation of CrAT in mouse skeletal muscle increases tissue concentrations of acetyl-CoA and exacerbates diet-induced acetylation of mitochondrial proteins. Lysine acetylation (AcK) is reversible post-translational protein modification (PTM) in which a two carbon acetyl group is covalently bound to the e-amino group of a lysine residue. This PTM is found prominently on mitochondrial proteins and excessive AcK has been linked to metabolic disease in mice lacking sirtuin 3 (SIRT3), the principal mitochondrial-localized deacetylase enzyme that removes acetyl groups from specific lysine residues. Our preliminary data suggest AcK can occur non- enzymatically when the mitochondrial pool of acetyl-CoA expands. The proposed project applies state-of-the-art proteomics and metabolomics approaches to test our hypothesis that CrAT and SIRT3 function cooperatively to oppose mitochondrial carbon stress, and that coexisting insufficiencies in the function of these enzymes contribute to metabolic dysregulation in the context of metabolic disease. Because CrAT and SIRT3 depend on availability of essential micronutrient substrates, L-carnitine and nicotinamide, we will also determine whether a new combinatorial nutraceutical strategy that targets the two systems simultaneously might confer additive or perhaps synergetic metabolic benefits when administered to obese rodents.