Supplemental oxygen and muscle metabolism in mitochondrial myopathy patients

Patients with mitochondrial myopathy (MM) have a reduced capacity to perform exercise due to a reduced oxidative capacity. We undertook this study to determine whether skeletal muscle metabolism could be improved with oxygen therapy in patients with MM. Six patients with MM and six controls, matched for age, gender and physical activity, underwent ³¹P-magnetic resonance spectroscopy (³¹P-MRS) examination. ³¹P-MR spectra were collected at rest and in series during exercise and recovery whilst breathing normoxic (0.21 O₂) or hyperoxic (1.0 O₂) air. At rest, MM showed an elevated [ADP] (18 ± 3 μmol/l) and pH (7.03 ± 0.01) in comparison to the control group (12 ± 1 μmol/l, 7.01 ± 0.01) (P < 0.05) consistent with mitochondrial dysfunction. Oxygen supplementation did not change resting metabolites in either MM or the control group (P > 0.05). Inferred maximal ATP synthesis rate improved by 33% with oxygen in MM (21 ± 3 vs. 28 ± 5 mmol/(l min), P < 0.05) but only improved by 5% in controls (40 ± 3 vs. 42 ± 3 mmol/(l min), P > 0.05). We conclude that oxygen therapy is associated with significant improvements in muscle metabolism in patients with MM. These data suggest that patients with MM could benefit from therapies which improve the provision of oxygen.