Age-related reduction of cardiac cellular metabolic reserve

In normal myocardium, the concentrations of the high-energy phosphate compounds ATP and phosphocreatine (PCr) are tightly controlled over a range of performance because ATP production by mitochondrial oxidative phosphorylation is closely coupled to ATP utilisation by cytosolic adenosine triphosphatases. ATP is the direct energy source for energy-consuming reactions in the cell, while PCr acts as an energy storage compound and, in addition, as an energy transport molecule in the ‘creatine kinase-PCr energy shuttle’. Previous clinical studies using phosphorus-31 magnetic resonance spectroscopy (³¹P-MRS) to measure PCr/ATP ratios in human myocardium have shown that this ratio is reduced in hypertrophied and, even more so, in failing human myocardium. In their Heart manuscript, Nathania1 investigated a possible relation between age and PCr/ATP ratio and cardiac power in healthy women by cardiac MRS with ³¹P spectroscopy and maximal graded cardiopulmonary exercise testing.1 PCr/ATP ratio, peak cardiac power, diastolic function and peak exercise oxygen consumption were significantly lower in old compared with young age group. PCr/ATP ratio showed a significant positive relationship with diastolic function, peak cardiac power output and peak oxygen consumption. These results indicate that high-energy phosphate metabolism and peak power of the heart decline with age. Additionally, based on the positive relationship between …