Skeletal muscle oxidative capacity in amyotrophic lateral sclerosis

Mitochondrial dysfunction in the motor neuron has been suspected in amyotrophic lateral sclerosis (ALS). If mitochondrial abnormalities are also found in skeletal muscle, assessing skeletal muscle could serve as an important biomarker of disease progression.Using 31P magnetic resonance (31P-MRS) and near infrared (NIRS) spectroscopy, we compared the absolute values and reproducibility of skeletal muscle oxidative capacity in people with ALS (n = 6) and healthy adults (young, n = 7 and age-matched, n = 4).ALS patients had slower time constants for phosphocreatine (PCr) and muscle oxygen consumption (mVO2 ) compared with young, but not age-matched controls. The coefficient of variation for the time constant was 10% (SD = 2.8%) and 17% (SD = 6.2%) for PCr and mVO2 , respectively.People with ALS had, on average, a small but not statistically significant, impairment in skeletal muscle mitochondrial function measured by both 31P-MRS and NIRS. Both methods demonstrated good reproducibility.