Creatine Kinase Metabolism in Failing Murine Hearts

描述（由申请人提供）：本提案旨在通过心肌肌酸激酶（CK）测量和操纵小鼠体内心通量，以验证心力衰竭（CHF）的能量饥饿假说。正常心脏收缩功能对ATP的需求是绝对的，CK反应是心脏的主要能量储存。CHF中CK代谢物减少并预测预后。最近对人类心脏中通过CK的ATP通量的第一次直接测量显示，甚至在全局[ATP]损失发生之前，CHF中的CK通量就急剧减少了50-70%。尽管有这些支持证据，传统的代谢干预措施未能增加衰竭心脏中的CK库或通量，无法直接验证能量饥饿假说。该应用建议使用研究者刚刚开发的新转染方法，通过基因过表达最有可能限制CHF中CK通量的因子，并在体内确定其能量和功能后果。具体目标是：1.)在小鼠研究中应用新的临床MR技术来评估体内心肌CK代谢物、通量和功能，2.)验证CHF中CK表达增加可增加体内心肌CK通量和改善心室功能的假设，3.)验证肌酸转运蛋白表达增加可增加CHF中心肌肌酸、CK通量和机械功能的假设。4.)验证条件性CK基因缺失会加剧CHF的发展，而CK抢救会提供保护的假设。该提案独特地汇集了新的非侵入性工具来测量体内心脏CK通量，执行遗传CK操作的新技术，显示人类CHF特征的相关动物模型，以及评估功能后果的复杂方法。这些小鼠研究提供了在人类CHF中无法实现的干预措施，并有望为这种流行的、日益增长的疾病提供新的见解。概要：心力衰竭是美国发病率和死亡率的一个重要且日益增长的原因。我们最近对人类心力衰竭的观察指导了这些目前只能在小鼠身上进行的研究。我们将使用最先进的技术来增加衰竭小鼠心脏的能量代谢，看看这是否能改善心脏收缩，减少心力衰竭。

DESCRIPTION (provided by applicant): This proposal aims to measure and manipulate in vivo cardiac flux through myocardial creatine kinase (CK) in mice to test the energy starvation hypothesis of heart failure (CHF). The requirement of ATP for normal cardiac contractile function is absolute and the CK reaction is the major energy reservoir of the heart. CK metabolites are reduced in CHF and predict outcomes. The first direct measures of ATP flux through CK in the human heart recently revealed dramatic 50-70% reductions in CK flux in CHF even before global [ATP] loss occurs. Despite this supporting evidence, conventional metabolic interventions have failed to augment CK pools or flux in failing hearts to directly test the energy starvation hypothesis. This application proposes the use of new transfection approaches, just developed by the investigators, to genetically over-express the factors most likely limiting CK flux in CHF and determine, in vivo, the energetic and functional consequences. The specific aims are: 1.) to implement new clinical MR techniques in mouse studies for assessing in vivo cardiac CK metabolites, flux and function, 2.) to test the hypothesis that increasing CK expression in CHF increases in vivo cardiac CK flux and improves ventricular function, 3.) to test the hypothesis that increasing creatine transport protein expression will increase myocardial creatine, CK flux, and mechanical function in CHF, 4.) to test the hypothesis that conditional CK gene deletion will exacerbate the development of CHF and that CK rescue will provide protection. This proposal uniquely brings together novel non-invasive tools to measure in vivo cardiac CK flux, new technology to perform genetic CK manipulations, relevant animal models that capitulate characteristics of human CHF, and finally, sophisticated means to assess the functional consequences. These mouse studies offer interventions not possible in human CHF and promise new insights for this prevalent, growing disease. Lay summary: Heart failure is an important and growing cause of morbidity and mortality in the United States. Our recent observations in human heart failure guide these studies that currently can only be performed in mice. We will use state-of-the-art techniques to increase energy metabolism in failing mouse hearts and see if that improves the contraction of the heart and reduces heart failure.