An Integrated Model of Cardiac Mitrochondrial Energy Metabolism and Calcium Dynamics

Model Status

This CellML model has been checked in both OpenCell and COR and the units are consistent. Unfortunately the model will not integrate at the moment. We are working with the model author to complete the curation of this model.

Model Structure

The high metabolic rate of cardiac tissue necessitates close agreement between the rates of energy production and consumption. About 2 percent of cellular ATP is consumed per heartbeat, and under normal conditions, almost all of this energy is provided by mitochondrial oxidative phosphorylation. Although the chemiosmotic theory of energy transduction was developed by Michell in 1961, remarkably little has since been elucidated about the mechanisms underlying the control of mitochondrial metabolism.

The thermokinetic model describes the tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and mitochondrial Ca²⁺ dynamics (see the figure below). The kinetic portion of the model includes effectors of the TCA cycle enzymes regulating production of NADH and FADH₂. In turn, these are used by the electron transport chain to establish a proton motive force driving the F₁F₀-ATPase. In addition, mitochondrial matrix Ca²⁺, determined by Ca²⁺ uniporter and Ca²⁺/Na⁺ exchanger activities, controls the activity of the TCA cycle enzymes isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase. Model simulations are used to predict the response of mitochondria to changes in substrate delivery, metabolic inhibition, the rate of ATP/ADP exchange, and Ca²⁺ concentration. Model simulations are able to reproduce experimental data, which was taken as supporting evidence for the validity of the model. The steady-state and time-dependent behaviour of the model supports the hypothesis that mitochondrial matrix Ca²⁺ plays an important role in matching energy supply with demand in cardiac myocytes.

Previously published models of mitochondrial energetics include the models of pancreatic beta-cell mitochondrial metabolism by Magnus and Keizer (see Mitochondrial Ca²⁺ Handling Model, 1997). An oxidative phosphorylation model has been developed by Korzeniewski (see The Oxidative Phosphorylation Pathway, 2001). However, these models, in common with other previously developed models of mitochondrial energetics, fail to include all the necessary variables. Together with the desire to improve understanding of mitochondrial metabolism, this has led Cortassa et al. to develop an integrated kinetic and thermodynamic model of cardiac mitochondrial energy metabolism. Their model has been described here in CellML (the raw CellML description of the Cortassa et al. model can be downloaded in various formats as described in ).

The complete original paper reference is cited below:

An Integrated Model of Cardiac Mitochondrial Energy Metabolism and Calcium Dynamics, Sonia Cortassa, Miguel A. Aon, Eduardo Marban, Raimond L. Winslow, and Brian O'Rourke, 2003, Biophysical Journal , 84, 2734-2755. (Full text (HTML) and PDF versions of the article are available on the Biophysical Journal website.) PubMed ID: 12668482

A schematic diagram of the reactions used in the model of the glycogenolysis pathway in skeletal muscle.