The purpose of this study was to analyse key enzyme activities of the deltoid muscle (DM) in chronic obstructive pulmonary disease (COPD) patients.The activities of one oxidative enzyme (citrate synthase (CS)), two glycolytic enzymes (lacatate dehydrogenase (LD); and phosphofructokinase (PFK)) and one enzyme related to the use of energy stores (creatine kinase (CK)) were determined in the DM of 10 patients with COPD and nine controls. Exercise capacity (cycloergometry) and the handgrip strength were also evaluated.Although exercise capacity was markedly reduced in COPD (57¡20% predicted), their handgrip strength was relatively preserved (77¡19% pred). One of the main symptoms in patients with chronic obstructive pulmonary disease (COPD) is limitation to exercise [1]. This limitation was classically attributed to ventilatory factors, and the role of peripheral skeletal muscle dysfunction has only been recognized in recent years [1][2][3]. The potential causes of this functional impairment would include loss in muscle mass, fibre atrophy, and decreases in the percentage of oxidative fibres and enzyme activities [4,5]. However, it is unclear whether muscle weakness is a generalized problem, or if it only or predominately affects some muscle groups. In addition, the causes of skeletal muscle weakness, and the specific role for each, still remain controversial. However, it is worth noting that most of the previous studies were performed in muscles from the lower limbs, where deconditioning due to reduction in activity may be particularly relevant but could coexist with other factors. The study of muscles from other locations, such as the deltoid muscle (DM), could contribute not only to elucidate whether skeletal muscle changes in COPD are homogeneous, but also to clarify whether systemic or local aetiological factors play the predominant role in inducing such changes. The objectives of the study were, firstly, to evaluate the metabolic capacity of the DM in COPD patients, and secondly, to investigate the potential relationships between lung function and the activity of different key enzymes in DM.
Methods
PopulationTen patients with severe-to-mild COPD were included (table 1). The COPD diagnosis was based on smoking history and forced spirometry showing nonreversible airways obstruction. All patients were clinically stable, with absence of exacerbations during the 2 months prior to the study. Recruitment was carried out consecutively on COPD patients who consulted the authors9 department and subsequently agreed to participate in the study. In order to avoid bias due to hormonal factors, only males were included. At the same time, individuals with malnutrition (body mass index (BMI) v20 kg?m -2 ), alcoholism (w80 g?day -1 ), bronchial asthma, associated chronic respiratory failure, neuromuscular or metabolic diseases, undergoing chronic treatment with systemic steroids, systemic b-agonists, Ca zz antagonists or diuretics, and those undergoing rehabilitation were excluded. Nine subjects of similar age and an...