Fiber Size and Energy Metabolites in Five Separate Muscles from Patients with Chronic Obstructive Lung Disease

Abstract

The purpose of this study was to examine whether morphologic abnormalities in human respiratory muscles are related to increased airway obstruction. 43 patients who were undergoing thoracotomy for suspected neoplasm had biopsies taken from one or more of the following muscles: external intercostal (EXT), internal intercostal (INT), diaphragm (DIA), latissimus dorsi (LAT), and quadriceps femoris (LEG). Mean FEV₁/FVC was 65% of predicted (range 43–90%). 21 of the 43 patients had a malignancy. Atrophy of type I fibers was found in 27% of respiratory and 11 % of nonrespiratory muscles. Type II fiber atrophy was more common, being found in 58% of all muscles studied. The degree of type II fiber atrophy correlated significantly with the amount of weight loss, but not with age or the presence of malignancy. A unique and significant relationship was found between type II fiber atrophy in the INT (an expiratory muscle) and all measured indices of airway obstruction. This relationship did not exist in the DIA, EXT, or LAT, ordinarily considered muscles of inspiration. The percentage of type I and type II fibers bore no relationship to indices of airway obstruction. Depletion of muscle metabolites was common to all muscles and could not be related to airway obstruction or fiber atrophy. These data suggest that fiber atrophy and metabolite depletion occur commonly in both respiratory and nonrespiratory muscles in patients with stable obstructive lung disease. These changes probably reflect a generalized disease process and may predispose to muscle fatigue. Whether or not airway obstruction produces fiber atrophy in expiratory muscles requires further investigation.

Differential effects of emphysema on skeletal muscle fibre atrophy in hamsters

“…In the patient population, COPD has been demonstrated to induce variable alterations in fibre composition of peripheral skeletal muscles. Similar to the present investigation, HUGHES et al [10] and JAKOBSSON et al [25] demonstrated no differences in fibre composition of vastus lateralis muscle biopsies from COPD patients, and SATO et al [11] found no difference in fibre composition in biceps brachii muscle biopsies. 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.…”

“…HUGHES et al [10] reported reductions in type II, but not type I fibres in vastus lateralis muscle biopsies from COPD patients. In contrast, two other investigations demonstrated reductions in both type I and type II fibre size in peripheral skeletal muscle biopsies from COPD patients [7,11].…”

“…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.…”

“…Based on previously reported alterations in muscle oxidative capacity [5], the authors hypothesised that EMP would induce muscle-specific reductions in the proportion of type I fibres and increases in type II fibres. Furthermore, based upon the work of HUGHES et al [10] suggesting an increased susceptibility of type II fibres to atrophy, the authors hypothesised muscle-specific atrophy of type II fibres.…”

Muscle Blood Flow and Oxygen Utilization Measured by Near-Infrared Spectroscopy during Handgrip Exercise in Chronic Respiratory Patients

“…Muscle biopsies during rest periods are often used to assess muscle metabolism [4][5][6][7] , as is magnetic resonance spectroscopy (MRS) during exercise 8,9) . To assess muscle oxygenation, arterial and venous blood sampling are used [10][11][12][13] .…”