In vitroandin vivocontractile properties of the vastus lateralis muscle in males with COPD

Abstract

Peripheral muscle weakness is common in chronic obstructive pulmonary disease (COPD) but it is still under debate whether weakness is due to atrophy or contractile dysfunction.In vitro and in vivo contractile properties of the vastus lateralis muscle were studied in 16 patients with stable COPD (forced expiratory volume in one second 39 ¡ 16% of predicted, age 67 ¡ 4 yrs (mean ¡ SD)) and nine sedentary control subjects. Isometric knee extensor strength was measured while mid-thigh muscle cross-sectional area (MTMCSA) was obtained using computed tomography. Muscle strips from the vastus lateralis obtained through open biopsy were rapidly suspended in an oxygenated KrebsRinger solution that was maintained at 35uC with a pH of 7.40 to study their contractile properties.The isometric knee extensors strength/MTMCSA ratio was 0.50¡0.08 versus 0.58¡0.06 kg?cm -2 for COPD and control subjects, respectively. The muscle bundle cross-sectional area (CSA) was 4.6¡2.1 and 4.4¡3.1 mm -2 , the length at which active tension was maximum was 15¡4 and 15¡3 mm, and maximal isometric peak forces normalised for CSA were 4.3¡2.7 and 4.8¡2.6 N?cm -2 for COPD and control subjects, respectively. The force/frequency relationship tended to be shifted to the right in patients with COPD, meaning that a higher stimulation frequency was necessary to produce the same relative force. Patients with COPD had a lower proportion of type I fibre than controls (26¡12% versus 39¡11%) with reciprocal significant increase in type IIb fibre proportion (20 ¡ 16% versus 8 ¡ 4%). The proportion of type IIa fibres was similar between the two groups.These results suggest that the contractile properties of the vastus lateralis are preserved in patients with chronic obstructive pulmonary disease. Therefore, the reduction in the quadriceps strength in patients with chronic obstructive pulmonary disease cannot be explained on the basis of an alteration of the contractile apparatus.

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

“…The technique most often used to assess the vastus lateralis muscle in patients with COPD or other chronic diseases is the Bergströ m semi-open biopsy, which is generally performed with 6-mm trocars and requires a 0.5-1-cm skin incision. Open biopsies are also feasible in these patients [6,7], but are even more invasive than the Bergströ m technique. Both approaches have the advantage of providing abundant muscle tissue for reliable biochemical, histochemical and histomorphometric analyses [24], but their major drawback is limited patient acceptance and the difficulty of obtaining serial biopsies in a given subject.…”

“…The percutaneous conchotome biopsy, also a semi-open muscle biopsy technique using an ''alligator forceps'', is an alternative to the Bergströ m technique used to biopsy muscle, such as the anterior tibialis [5]. Finally, open biopsy of the vastus lateralis [6,7] and the deltoid muscle [8] has recently been performed in COPD patients for in vitro contractility or biochemical studies.…”

Age-graded reductions in quadriceps muscle strength and peak aerobic capacity in COPD

“…Indeed, type I and IIA fi bers from older healthy men were generally stronger than similar fi bers from older women even after adjusting for size 31 . Whether and to what extent gender diff erences in muscle contractile properties are also present in COPD remains currently unknown 32 .…”

Alterations in Nutritional Status and Body Composition in COPD Patients

“…This cell corpuscle degrades proteins, with or without prior ubiquitination, and its activity is greatly increased in underweight COPD patients 50 . However, ubiquitination needs the intervention of atrogenin-1 and MuRF1, both regulated by FoxO transcription factors, which are overexpressed in skeletal muscles of COPD patients [51][52][53] . Calpains, proteolytic enzymes that are very abundant in skeletal muscles and can increase their action by factors such as a reduction in physical activity, also seem to be involved in the loss of muscle mass of these patients 54 .…”