Key result
A computational model suggests that calcium is a potent activator of net ATP production in cardiac mitochondria, with energy production increasing almost linearly as pacing increases.
A computational model demonstrates that calcium acts as a potent activator of net ATP production in cardiac mitochondria during simulated pacing.
Hypothesis-generating for mitochondrial calcium signaling; leaves open in vivo validation before any clinical relevance.
The energy production of mitochondria in heart increases during exercise. Several works have suggested that calcium acts at multiple control points to activate net ATP production in what is termed "parallel activation". To study this, a computational model of mitochondrial energy metabolism in the heart has been developed that integrates the Dudycha-Jafri model for the tricarboxylic acid cycle with the Magnus-Keizer model for mitochondrial energy metabolism and calcium dynamics. The model improves upon the previous formulation by including an updated formulation for calcium dynamics, and new descriptions of sodium, hydrogen, phosphate, and ATP balance. To this end, it incorporates new formulations for the calcium uniporter, sodium-calcium exchange, sodium-hydrogen exchange, the F(1)F(0)-ATPase, and potassium-hydrogen exchange. The model simulates a wide range of experimental data, including steady-state and simulated pacing protocols. The model suggests that calcium is a potent activator of net ATP production and that as pacing increases energy production due to calcium goes up almost linearly. Furthermore, it suggests that during an extramitochondrial calcium transient, calcium entry and extrusion cause a transient depolarization that serve to increase NADH production by the tricarboxylic acid cycle and NADH consumption by the respiration driven proton pumps. The model suggests that activation of the F(1)F(0)-ATPase by calcium is essential to increase ATP production. In mitochondria very close to the release sites, the depolarization is more severe causing a temporary loss of ATP production. However, due to the short duration of the depolarization the net ATP production is also increased.
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Nguyen et al. (2007) studied Cardiac mitochondrial energy metabolism. Calcium was evaluated on Net ATP production. A computational model suggests that calcium is a potent activator of net ATP production in cardiac mitochondria, with energy production increasing almost linearly as pacing increases.
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