RT Journal Article
SR Electronic
T1 Mid-thigh intramuscular fat is associated with physical inactivity and quadriceps fibre type profile in patients with COPD
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP 1985
VO 42
IS Suppl 57
A1 Matthew Maddocks
A1 Dinesh Shrikrishna
A1 Samantha Natanek
A1 Simone Vitoriano
A1 Rebecca Tanner
A1 Nicholas Hart
A1 Paul Kemp
A1 John Moxham
A1 Michael Polkey
A1 Nicholas Hopkinson
YR 2013
UL http://erj.ersjournals.com/content/42/Suppl_57/1985.abstract
AB Introduction: Quadriceps muscle dysfunction is an important complication of COPD occurring in mild and more advanced disease. It is largely driven by physical inactivity and is characterised by atrophy and a shift towards a less aerobic phenotype, with reduced Type I fibre proportions and oxidative enzymes. We hypothesised that physical inactivity and fibre type shift would be associated with intramuscular fat and that this could be a non-invasive and non-volitional marker of muscle quality.Methods: Mid-thigh cross-sectional area (MTCSA) and percentage intramuscular fat were assessed using computed tomography (CT) image analysis. Tissues were differentiated using standard attenuation ranges; fat -190 to -30 and skeletal muscle -29 to 150 Hounsfield Units. Daily step count and physical activity level (PAL) were recorded using an armband accelerometer (SenseWear, Bodymedia). Type I and II fibre proportions were determined from vastus lateralis samples using immunohistochemistry. Associations were determined using multivariate regression models incorporating MTCSA and age.Results: CT data were available for 102 patients (61 male, mean (SD) age 65(8) years, FEV1 41(20)% predicted) and 10 age-matched healthy controls. Accelerometer and biopsy data were obtained in 69 and 58 participants respectively. Percentage intramuscular fat was higher in the patient group (6.7(3.5) vs 4.3(1.2)%, p<0.01) and was independently associated with PAL (r=-0.33, p=0.02) and Type I fibre proportion (r=-0.33, p<0.01).Conclusion: Intramuscular fat assessed using CT reflects multiple aspects of muscle dysfunction in patients with COPD and may provide a valuable biomarker in this group.