Differential effects of emphysema on skeletal muscle fibre atrophy in hamsters

Abstract

Patients afflicted with emphysema demonstrate altered peripheral skeletal muscle fibre composition and atrophy. It is unknown whether these alterations are general to all skeletal muscles independent of function, phenotype or oxidative capacity. Therefore, the purpose of this investigation was to determine whether emphysema induces alterations in muscle fibre composition or atrophy in respiratory and locomotory muscles with diverse fibre types and metabolic profiles.Fibre composition and cross-sectional area were measured in selected hindlimb muscles and diaphragm of hamsters following saline (control, n=7) or elastase (emphysema, n=15) instillation.Excised lung volume increased 145% with emphysema. Fibre composition was largely unaltered, with the exception of a 13% reduction in IIB fibres in the tibialis anterior muscle of emphysema animals. Type I fibre size was also mainly unaltered, except for a diminished cross-sectional area in plantaris muscle. However, fibre cross-sectional area of fast-twitch types IIA, IIX and/or IIB fibres was reduced in the caudal biceps femoris, vastus lateralis, tibialis anterior, gastrocnemius and plantaris muscles of emphysema animals. In contrast, there was a trend for emphysema to increase the cross-sectional area of type IIA fibres in the diaphragm.These data demonstrate that emphysema-induced atrophy primarily affects locomotory muscles, independent of phenotype or oxidative capacity.

Oxidative and proteolysis‐related parameters of skeletal muscle from hamsters with experimental pulmonary emphysema: a comparison between papain and elastase induction

“…The left gastrocnemius was divided: one portion was saved for morphometric histological procedures, and the other portion was pulverized, frozen in liquid nitrogen and stored at −86°C until used for proteolysis assays.The gastrocnemius muscle has previously been demonstrated as a good indicator of alterations in the skeletal muscle of emphysemic hamsters (Mattson et al . ), including in aspects related to oxidative parameters (Mattson et al . ; Tonon et al .…”

“…Mattson et al . () demonstrated that emphysema induces fibre atrophy and the response is not specific to locomotory muscles composed of a given fibre‐type or oxidative capacity, in hamsters after 180 days of pulmonary emphysema induced by elastase instillation (25 IU/100 g body weight). Rinaldi et al .…”

Lung injury-dependent oxidative status and chymotrypsin-like activity of skeletal muscles in hamsters with experimental emphysema

“…The gastrocnemius muscle was excised, weighed, frozen in liquid nitrogen, and stored at −86°C until use. The gastrocnemius muscle has previously been demonstrated as a good indicator of alterations in the skeletal muscle of emphysemic hamsters [22], including those in lipid peroxidation [2]. In hamsters, there is no obvious gross division of fibers in this muscle [23], and therefore, the whole muscle is typically analyzed.…”

Treatment with a corticotrophin releasing factor 2 receptor agonist modulates skeletal muscle mass and force production in aged and chronically ill animals

“…In COPD patients, respiratory muscle weakness and diaphragm fiber atrophy decreases respiratory muscle reserves increasing muscle fatigability/weakness thereby predisposing the patient to chronic hypercapnia [23]. The changes in diaphragm muscle that occur during EMP include muscle fiber shortening by loss of sarcomeres in series [24,25], increase in cross-sectional area of type I and II fibers [26,27], atrophy [28,29] and loss of oxidative enzyme capacity [30]. While the adaptive changes in diaphragm muscle are complex, ultimately EMP augments the energetic requirements of respiratory muscles which, concomitant with EMP-induced reductions in muscle mass, contributes to diaphragm weakness, increased fatigability and overall dysfunction.…”

“…In humans and animals with EMP, changes in peripheral skeletal muscles have been described including atrophy [27,31], reduced myocyte cross-sectional area [27,31], loss of type IIB fibers [27], increased fatigability [32,33], lipofuscin inclusions [33] and increased antioxidant enzyme levels [33]. Thus in EMP, overall skeletal muscle function is altered and therapies with the potential to improve skeletal muscle function may have beneficial effects.…”