Plasma branched-chain amino acid levels and muscle energy metabolism in patients with chronic obstructive pulmonary disease.

Background & Aims: Although several studies have shown that plasma concentrations of branched-chain amino acids (BCAAs) are reduced in patients with chronic obstructive pulmonary disease (COPD), little is understood about how low concentrations of BCAAs limit exercise in such patients. The present study investigated whether plasma BCAAs are related to energy metabolism in exercising muscle using (31)P-magnetic resonance spectroscopy (MRS).

Methods: We analyzed the plasma amino acid profiles of 23 male patients with COPD (aged 69.2+/-5.1 years) and of 7 healthy males (aged 64.1+/-6.0 years). We normalized the exercise intensity of repetitive lifting by adjusting the weight to 7% of the maximal grip power. The intracellular pH and the phosphocreatine (PCr) index (PCr/(PCr+Pi); Pi, inorganic phosphate) were calculated from MR spectra. We evaluated the relationship between intracellular pH and PCr index at the completion of exercise and the plasma BCAA concentration.

Results: Glutamine concentrations were elevated in patients with COPD compared with healthy individuals. Plasma concentrations of BCAAs correlated with intracellular pH and PCr index at the completion of exercise.

Conclusions: The findings are consistent with the notion that BCAAs affect muscle energy metabolism during exercise in patients with COPD.