Altered expression of myosin heavy chain in the vastus lateralis muscle in patients with COPD

Abstract

This study was designed to further characterize peripheral skeletal muscle alterations in patients with chronic obstructive pulmonary disease (COPD) and to evaluate the possible relationship between myosin heavy chain (MyoHC) isoform expression and exercise tolerance in these individuals.MyoHC composition from biopsy of the vastus lateralis muscle was examined in 12 COPD patients (forced expiratory volume in one second (FEV1)=319% predicted, peak oxygen consumption (V 'O 2 )=154 mL . kg -1 . min -1 ) and 10 age-matched normal male subjects (peak). The proportion of MyoHC type I was smaller in COPD than in normals (2717% versus 419%, p<0.05) with an increase in MyoHC type IIa (5115% versus 399%, p<0.05) and the proportion of MyoHC type IIx being comparable between both groups. A significant relationship was found between peak V 'O 2 mL . kg -1 . min -1 and FEV1 % pred (r=0.91, p<0.0001) and the percentage of MyoHC type I (r=0.61, p=0.016). In stepwise multiple regression, only FEV1 % pred was found to be a significant determinant of peak V 'O 2 (p<0.0001). This variable explained 83% of the total variance of peak V 'O 2 .In summary, this study showed considerable modifications in the phenotypic expression of the myosin heavy chain in the vastus lateralis muscle in patients with chronic obstructive pulmonary disease. An independent effect of myosin heavy chain expression on exercise capacity was not found. These results suggest that chronic inactivity and muscle deconditioning may not be the sole factors explaining peripheral muscle dysfunction in patients with chronic obstructive pulmonary disease. Eur Respir J 1999; 13: 850±854.

Skeletal muscle microbiopsy: a validation study of a minimally invasive technique

“…The first inevitable requirement is the muscle biopsy, since research at the cellular level is essential [9,[26][27][28]. The second requirement, however, is to pursue research goals as noninvasively as possible in these patients [29], which compelled the current authors to search for an acceptable alternative to the Bergströ m technique.…”

Pulmonary Rehabilitation in lung cancer

“…As already remarked, in fact, NSCLC patients usually presented symptoms similar to those related to COPD such as dyspnea, reduced exercise capacity, respiratory distress and a deteriorated quality of life. However, while in COPD have been well identified anatomical, physiological and biochemical alterations that are the basis of muscular dysfunction, as well as the biological mechanisms that may be the cause, namely the inactivity, the use of corticosteroids, systemic inflammation and oxidative stress [30,31], this has not yet occurred in cancer patients.…”

Differential effects of emphysema on skeletal muscle fibre atrophy in hamsters

“…In contrast, other investigators [4,6,7] have reported that COPD patients have a lower proportion of type I fibres and an elevation in the per cent of type II fibres in the vastus lateralis muscle. In addition, two investigations [8,9] have demonstrated altered MyHC expression in vastus lateralis muscle biopsies from COPD patients. These investigations collectively indicate that alterations in muscle fibre composition induced by COPD may differ between humans and animals.…”

“…Such a shift would predispose skeletal muscle to greater fatigability and impair exercise tolerance. In addition, COPD patients with reduced work capacity present with alterations in peripheral skeletal muscle composition and structure, including altered fibre composition [4,6,7] and myosin heavy chain (MyHC) expression [8,9], atrophy of peripheral skeletal muscle type I and/or II fibres [7,10,11], and reductions in lean body mass [12]. Therefore, altered metabolic pathways, fibre transformation and fibre atrophy appear to underlie problems of enhanced skeletal muscle fatigability, reduced force production and exercise intolerance in patients with COPD.…”