Efficient coupling of energy production to energy needs is critical for the beating heart, and factors disrupting this relationship are likely to promote injury. Glycolytic oscillations have been characterized extensively in yeast and pancreatic ?-cells, but conditions promoting their occurrence in cardiac myocytes are less established, compared to reactive oxygen species (ROS)-induced metabolic oscillations arising from the mitochondrial network. Our preliminary studies in rabbit ventricular myocytes show that the normally tight buffering of the ATP/ADP ratio by oxidative phosphorylation and the creatine kinase (CK) shuttle prevents glycolysis from oscillating, but under conditions in which this buffering is disrupted, glycolytic oscillations, manifested as large scale action potential duration (APD) oscillations via activation of ATP-sensitive K channels, develop in 90% of cardiac myocytes, as predicted by theoretical predictions. In this multi-PI proposal, our goal is to combine experimental and mathematical biology approaches to address two questions: 1) how are glycolytic oscillations regulated/modulated by physiological factors such as Cai cycling, autonomic tone, insulin, and signaling pathways relevant to cardioprotection? 2) do glycolytic oscillations occur during acute myocardial ischemia, in which the ability of oxidative phosphorylation and the CK shuttle to buffer cellular ATP/ADP ratio is markedly compromised? These questions will be addressed in three Specific Aims which integrate computer simulations and nonlinear dynamics with experimental patch-clamp and imaging studies in isolated myocytes from rabbits, wild-type and genetically-altered mice and neonatal rat ventricular myocyte monolayers subjected to coverslip ischemia/reperfusion. In addition, a novel fluorescent bioprobe designed for subcellular imaging of ATP will be further developed to study metabolism dynamics. These studies will increase our understanding of how cardiac metabolism functions at the systems level during metabolic stress, which may lead to new therapeutic insights towards preventing ischemia/reperfusion injury.
Since heart disease is the major cause of death in industrialized societies, understanding how to protect the heart from injury has major implications for the health care mission of the NIH/NHLBI and for society as a whole. To facilitate this understanding, this interdisciplinary project will integrate experimental physiology and mathematical biology to study the pathophysiology of oscillations in glycolysis, the key metabolic pathway for energy production during ischemia, and how they may contribute to ischemic cardiac injury by uncoupling energy production from energy needs in this critical situation. These insights may suggest novel therapies to protect the heart from injury during metabolic stresses such as heart attacks.
