Enhanced levels of whole-body protein turnover in patients with chronic obstructive pulmonary disease Academic Article uri icon

abstract

  • A substantial number of patients with chronic obstructive pulmonary disease (COPD) are characterized by fat-free mass wasting and altered muscle and plasma amino acid levels, suggesting changes in protein metabolism. In the present study, we examined whether whole-body protein breakdown (PB) and synthesis (PS) differ between 14 stable patients with COPD and 8 healthy controls. Whole-body PB, PS, and net PB (= PB-PS) were measured by the combined infusion of the stable isotopes L-[ring-2H5]phenylalanine (Phe) and L-[ring-2H2]tyrosine. Because there is evidence for specific disturbances in leucine (Leu) metabolism, the PB values were compared with those obtained when infusing L-[I-13C]Leu tracer. In arterialized-venous plasma and in vastus lateralis muscle, the isotope enrichment values and amino acid concentrations were measured. Whole-body PS and PB, assessed by Phe and Tyr tracer, were higher in the COPD group than in the control group (p < 0.05), indicating an elevated protein turnover. Net PB was increased in both groups, indicating a comparable degree of protein catabolism in the postabsorptive state. In contrast, whole-body PB determined by Leu tracer was not different between the groups. As a consequence, the ratio of Leu to Phe breakdown was reduced in the COPD group (p < 0.001). Moreover, in the COPD group a higher muscle-to-plasma gradient was found for Leu (p < 0.001) but not for Phe. The present study reveals elevated levels for protein turnover in patients with COPD, and indicates that infusion of the Leu tracer gives a reflection of Leu metabolism but not of whole-body protein metabolism in these patients.

published proceedings

  • American Journal of Respiratory and Critical Care Medicine

author list (cited authors)

  • Engelen, M., Deutz, N., Wouters, E., & Schols, A

citation count

  • 89

complete list of authors

  • Engelen, MPKJ||Deutz, NEP||Wouters, EFM||Schols, AMWJ

publication date

  • January 2000