Figure 1.

Energy production in the normal heart. Overview of the central metabolic pathways contributing to ATP production in the heart. Mitochondrial fatty acid oxidation (FAO) is the main source of energy (70%–80%). The remaining 20%–30% of ATP production largely derives from glucose oxidation. During this process, the pyruvate produced in the cytosol as result of glycolysis and lactate oxidation is transferred to the mitochondria and converted to acetyl-CoA by the pyruvate dehydrogenase complex (PDC). Acetyl-CoA, which is also the final product of fatty acid oxidation, enters the tricarboxylic acid cycle (TCA cycle) promoting the production of nicotinamide adenine dinucleotide (NADH), and thus providing a source of electrons for the electron transport chain (ETC), located at the inner mitochondrial membrane. Within the ETC, each complex contributes to the creation of a proton gradient fundamental to provide sufficient energy to generate ATP from adenosine diphosphate (ADP).