Factors Contributing to Alterations in Skeletal Muscle and Plasma Amino Acid Profiles in Patients with Chronic Obstructive Pulmonary Disease

Abstract

Background There is increasing evidence of abnormal protein metabolism in patients with chronic obstructive pulmonary disease (COPD), as reflected by lower plasma branched-chain amino acid (BCAA) concentrations and different muscle amino acid (AA) patterns than in age-matched control subjects. Objective We examined whether the low plasma BCAA concentrations in COPD reflect an imbalance between anabolic and catabolic processes as evidenced by a low fat-free mass (FFM) and alterations in the anabolic hormone insulin and whether discrepancies in muscle AA concentrations between studies are related to different patient characteristics. Design AA profiles in arterial plasma and quadriceps femoris muscle and insulin concentrations in venous plasma were analyzed in 28 postabsorptive COPD patients (14 with and 14 without macroscopic emphysema) and in 28 control subjects. FFM was measured by dual-energy X-ray absorptiometry. Results The lower sum of plasma BCAAs in the COPD group than in the control subjects was the result of a lower leucine concentration (P: Conclusions Leucine metabolism is altered in COPD patients and is associated with low FFM and high insulin concentrations. There were striking differences in the skeletal muscle AA profile between the COPD subtypes.