Skeletal muscle fibre-type shifting and metabolic profile in patients with chronic obstructive pulmonary disease

Abstract

The aim of this study was to examine the nature of fibre-type redistribution in relation to fibre metabolic profile in the vastus lateralis in chronic obstructive pulmonary disease (COPD) and COPD subtypes. Fifteen COPD patients (eight with emphysema stratified by high-resolution computed tomography) and 15 healthy control subjects were studied. A combination of myofibrillar adenosine triphosphatase staining and immunohistochemistry was used to identify pure, as well as hybrid fibre types. For oxidative capacity, fibres were stained for cytochrome c oxidase and succinate dehydrogenase activities, and glycogen phosphorylase for glycolytic capacity. The proportion of type‐I fibres in COPD patients was markedly lower (16%versus 42%), especially in emphysema, and the proportion of hybrid fibres was higher (29%versus 16%) compared to controls. The proportion of fibres staining positive for oxidative enzymes was lower in COPD patients, which correlated with the proportion of type‐I fibres. In COPD oxidative capacity was lower within IIA fibres. The authors conclude that fibre-type transitions are involved in the fibre-type redistribution in chronic obstructive pulmonary disease. Low oxidative capacity is closely related to the proportion of type‐I fibres, but an additional reduction of oxidative enzyme activity is present within IIA fibres. Fibre-type abnormalities may be aggravated in emphysema.