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 Maddocks, Matthew
A1 Shrikrishna, Dinesh
A1 Natanek, Samantha
A1 Vitoriano, Simone
A1 Tanner, Rebecca
A1 Hart, Nicholas
A1 Kemp, Paul
A1 Moxham, John
A1 Polkey, Michael
A1 Hopkinson, Nicholas
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.