Profound alterations in cardiac excitability and contractile function occur within minutes of inhibiting energy metabolism in the heart, whether the inhibition is by ischemia, hypoxia, or chemical poisoning. The arrhythmias accompanying such a decline in the metabolic rate, as well as during the restoration of energy flux, are often fatal. Intervention into the pathological consequences of abrupt changes in energy metabolism will require a detailed understanding of the relationship between substrate supply, the control of metabolism, and the sensitivity of ion channels to perturbations of energy metabolites. The project explores this relationship by studying a cellular experimental model which displays dynamic coupling between energy metabolism and ion channel activity. Specifically, a metabolic control loop in isolated ventricular cardiomyocytes that is prone to oscillation when substrate input is altered (as during the withdrawal or reintroduction of extracellular glucose) has been identified. This mild metabolic stress leads to cyclical increases in the activity of ATP-sensitive K+ channels (K,ATP channels) and a coordinated suppression of excitation-contraction coupling. Both of these functional events are synchronized with the transient oxidation of nicotinamide adenine dinucleotides that serve as markers of a primary metabolic oscillator. Preliminary data indicating that the oscillator is sensitive to the extracellular glucose concentration and to rapid perturbations of intracellular adenine nucleotides induced by flash photolysis suggest that the source of oscillation is in glycolysis, most likely as a result of the control properties of a single enzyme, phosphofructokinase.
The aims of the proposal are to elucidate the mechanism of the metabolic oscillations at the cellular level through biological experimentation and computer modeling; to study the molecular basis for energy-sensing by ion channels (L-type Ca2+ and K,ATP); and to determine the effects of the oscillations on the electrical excitability of cardiomyocytes. The ultimate goal of the work is to identify strategies for preventing or controlling cardiac electrical mechanical dysfunction during ischemia and reperfusion.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL054598-03
Application #
2714100
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Project Start
1996-06-01
Project End
2000-05-31
Budget Start
1998-06-01
Budget End
1999-05-31
Support Year
3
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Ma, Junfeng; Banerjee, Partha; Whelan, Stephen A et al. (2016) Comparative Proteomics Reveals Dysregulated Mitochondrial O-GlcNAcylation in Diabetic Hearts. J Proteome Res 15:2254-64
Tocchetti, Carlo G; Stanley, Brian A; Sivakumaran, Vidhya et al. (2015) Impaired mitochondrial energy supply coupled to increased H2O2 emission under energy/redox stress leads to myocardial dysfunction during Type I diabetes. Clin Sci (Lond) 129:561-74
Zhou, Lufang; Aon, Miguel A; Almas, Tabish et al. (2010) A reaction-diffusion model of ROS-induced ROS release in a mitochondrial network. PLoS Comput Biol 6:e1000657
Aon, Miguel Antonio; Cortassa, Sonia; Akar, Fadi Gabriel et al. (2006) Mitochondrial criticality: a new concept at the turning point of life or death. Biochim Biophys Acta 1762:232-40
Akar, Fadi G; Aon, Miguel A; Tomaselli, Gordon F et al. (2005) The mitochondrial origin of postischemic arrhythmias. J Clin Invest 115:3527-35
Cortassa, Sonia; Aon, Miguel A; Winslow, Raimond L et al. (2004) A mitochondrial oscillator dependent on reactive oxygen species. Biophys J 87:2060-73
O'Rourke, Brian (2004) Evidence for mitochondrial K+ channels and their role in cardioprotection. Circ Res 94:420-32
Cortassa, Sonia; Aon, Miguel A; Marban, Eduardo et al. (2003) An integrated model of cardiac mitochondrial energy metabolism and calcium dynamics. Biophys J 84:2734-55
Aon, Miguel A; Cortassa, Sonia; Marban, Eduardo et al. (2003) Synchronized whole cell oscillations in mitochondrial metabolism triggered by a local release of reactive oxygen species in cardiac myocytes. J Biol Chem 278:44735-44
Sasaki, N; Sato, T; Marban, E et al. (2001) ATP consumption by uncoupled mitochondria activates sarcolemmal K(ATP) channels in cardiac myocytes. Am J Physiol Heart Circ Physiol 280:H1882-8

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