title: Skeletal muscle adiposity is associated with physical activity, exercise capacity and fibre shift in COPD.
abstract: Quadriceps muscle phenotype varies widely between patients with chronic obstructive pulmonary disease (COPD) and cannot be determined without muscle biopsy. We hypothesised that measures of skeletal muscle adiposity could provide noninvasive biomarkers of muscle quality in this population. In 101 patients and 10 age-matched healthy controls, mid-thigh cross-sectional area, percentage intramuscular fat and skeletal muscle attenuation were calculated using computed tomography images and standard tissue attenuation ranges: fat -190- -30 HU; skeletal muscle -29-150 HU. Mean±sd percentage intramuscular fat was higher in the patient group (6.7±3.5% versus 4.3±1.2%, p = 0.03). Both percentage intramuscular fat and skeletal muscle attenuation were associated with physical activity level, exercise capacity and type I fibre proportion, independent of age, mid-thigh cross-sectional area and quadriceps strength. Combined with transfer factor of the lung for carbon monoxide, these variables could identify >80% of patients with fibre type shift with >65% specificity (area under the curve 0.83, 95% CI 0.72-0.95). Skeletal muscle adiposity assessed by computed tomography reflects multiple aspects of COPD related muscle dysfunction and may help to identify patients for trials of interventions targeted at specific muscle phenotypes.
authors.affiliation: Dept of Palliative Care, Policy and Rehabilitation, King's College London, London, UK Dept of Asthma, Allergy and Lung Biology, King's College London, London, UK Both authors contributed equally.
authors.forename: Matthew
authors.initials: M
authors.lastname: Maddocks
authors.affiliation: National Heart and Lung Institute, NIHR Respiratory Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, UK Both authors contributed equally.
authors.forename: Dinesh
authors.initials: D
authors.lastname: Shrikrishna
authors.affiliation: Dept of Palliative Care, Policy and Rehabilitation, King's College London, London, UK Dept of Asthma, Allergy and Lung Biology, King's College London, London, UK.
authors.forename: Simone
authors.initials: S
authors.lastname: Vitoriano
authors.affiliation: National Heart and Lung Institute, NIHR Respiratory Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: Samantha A
authors.initials: SA
authors.lastname: Natanek
authors.affiliation: National Heart and Lung Institute, NIHR Respiratory Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Tanner
authors.affiliation: NIHR Comprehensive Biomedical Research Centre, Guy's and St Thomas' NHS Foundation Trust and King's College London, London, UK.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hart
authors.affiliation: National Heart and Lung Institute, NIHR Respiratory Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Kemp
authors.affiliation: Dept of Palliative Care, Policy and Rehabilitation, King's College London, London, UK Dept of Asthma, Allergy and Lung Biology, King's College London, London, UK.
authors.forename: John
authors.initials: J
authors.lastname: Moxham
authors.affiliation: National Heart and Lung Institute, NIHR Respiratory Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.affiliation: National Heart and Lung Institute, NIHR Respiratory Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, UK n.hopkinson@ic.ac.uk.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
mesh_terms: D000273:Adipose Tissue; D050154:Adiposity; D000368:Aged; D015415:Biomarkers; D002248:Carbon Monoxide / Q000737:chemistry; D016022:Case-Control Studies; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D015588:Observer Variation; D010641:Phenotype; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging / Q000503:physiopathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D015415:Biomarkers; D002248:Carbon Monoxide