The objective of this study was to determine whether patients with
chronic obstructive lung disease (
COPD) display differences in organization of the metabolic pathways and segments involved in energy supply compared with healthy control subjects. Metabolic pathway potential, based on the measurement of the maximal activity (V(max)) of representative
enzymes, was assessed in tissue extracted from the vastus lateralis in seven patients with
COPD (age 67 +/- 4 yr; FEV(1)/FVC = 44 +/- 3%, where FEV(1) is forced expiratory volume in 1 s and FVC is forced vital capacity; means +/- SE) and nine healthy age-matched controls (age 68 +/- 2 yr; FEV(1)/FVC = 75 +/- 2%). Compared with control, the
COPD patients displayed lower (P < 0.05) V(max) (mol.kg protein(-1).h(-1)) for
cytochrome c oxidase (COX; 21.2 +/- 2.0 vs. 28.7 +/- 2.2) and
3-hydroxyacyl-CoA dehydrogenase (HADH; 2.54 +/- 0.14 vs. 3.74 +/- 0.12) but not
citrate synthase (CS; 2.20 +/- 0.16 vs. 3.19 +/- 0.5). While no differences between groups were observed in V(max) for
creatine phosphokinase,
phosphorylase (PHOSPH),
phosphofructokinase (PFK),
pyruvate kinase, and
lactate dehydrogenase,
hexokinase (HEX) was elevated in
COPD (P < 0.05).
Enzyme activity ratios were higher (P < 0.05) for HEX/CS, HEX/COX, PHOSPH/HADH and PFK/HADH in
COPD compared with control. It is concluded that
COPD patients exhibit a reduced potential for both the electron transport system and fat oxidation and an increased potential for
glucose phosphorylation while the potential for glycogenolysis and glycolysis remains normal. A comparison of
enzyme ratios indicated greater potentials for
glucose phosphorylation relative to the citric acid cycle and the electron transport chain and glycogenolysis and glycolysis relative to beta-oxidation.