title: Heterogeneity of quadriceps muscle phenotype in chronic obstructive pulmonary disease (Copd); implications for stratified medicine?
abstract: BACKGROUND
  Quadriceps muscle dysfunction is common in COPD. Determining, and, if possible, predicting quadriceps phenotype in COPD is important for patient stratification for therapeutic trials.
  
  
  METHODS
  In biopsies from 114 COPD patients and 30 controls, we measured fiber size and proportion and assessed the relationship with quadriceps function (strength and endurance), clinical phenotype (lung function, physical activity, fat-free mass) and exercise performance. In a subset (n = 40) we measured muscle mid-thigh cross-sectional area by computed tomography.
  
  
  RESULTS
  Normal ranges for fiber proportions and fiber cross-sectional area were defined from controls; we found isolated fiber shift in 31% of patients, isolated fiber (predominantly type II) atrophy in 20%, both shift and atrophy in 25%, and normal fiber parameters in 24%. Clinical parameters related poorly to muscle biopsy appearances.
  
  
  CONCLUSIONS
  Quadriceps morphology is heterogeneous in COPD and cannot be predicted without biopsy, underlining the need for biomarkers.
authors.affiliation: NIHR Respiratory Biomedical Research Unit of the Royal Brompton, and Harefield NHS Foundation Trust and Imperial College London, London, SW3 6NP, United Kingdom; Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology & Metabolism, Maastricht University Medical Centre, AZ Maastricht, Netherlands; Molecular Medicine Section, National Heart & Lung Institute, Imperial College London, South Kensington Campus, London, United Kingdom.
authors.forename: Samantha A
authors.initials: SA
authors.lastname: Natanek
authors.forename: Harry R
authors.initials: HR
authors.lastname: Gosker
authors.forename: Ilse G M
authors.initials: IG
authors.lastname: Slot
authors.forename: Gemma S
authors.initials: GS
authors.lastname: Marsh
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
authors.forename: William D-C
authors.initials: WD
authors.lastname: Man
authors.forename: Ruth
authors.initials: R
authors.lastname: Tal-Singer
authors.forename: John
authors.initials: J
authors.lastname: Moxham
authors.forename: Paul R
authors.initials: PR
authors.lastname: Kemp
authors.forename: Annemie M W J
authors.initials: AM
authors.lastname: Schols
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
mesh_terms: D000367:Age Factors; D000368:Aged; D005080:Exercise Test; D005260:Female; D005819:Genetic Markers; D006801:Humans; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000473:pathology*; D010641:Phenotype; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D012720:Severity of Illness Index
chemical_list: D005819:Genetic Markers
keywords: COPD; fiber atrophy; fiber shift; muscle biopsy; muscle histology; quadriceps