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S72 QUADRICEPS MUSCLE EXPRESSION OF MYOSTATIN IN PATIENTS WITH COPD
1W. D. Man, 2S. A. Sathyapala, 2J. Riddoch-Contreras, 2A. Lewis, 1G. Marsh, 1M. I. Polkey, 2P. R. Kemp. 1Royal Brompton & Harefield NHS Foundation Trust, London, UK, 2Molecular Medicine, Imperial College, London, UK
Introduction and Objectives Quadriceps muscle weakness is well recognised in chronic obstructive pulmonary disease (COPD), and is associated with reduced exercise capacity, impaired health status and increased mortality. The cause of quadriceps weakness in COPD is multifactorial, but chronic daily inactivity is a likely major contributor. Myostatin is a negative regulator of muscle mass as demonstrated in naturally occurring human and animal genetic mutations, and genetic rodent models. A recent cross-sectional study showed increased expression of vastus lateralis myostatin mRNA in cachexic patients with COPD compared with healthy controls (Plant et al 2009). We hypothesised that vastus lateralis expression of myostatin would negatively correlate with quadriceps strength.
Methods 18 patients with COPD were clinically phenotyped with measurements of lung function, quadriceps muscle strength (quadriceps maximum voluntary contraction normalised to body mass index: QMVC/BMI) and endurance (time for quadriceps force to fall to 80%: T80), exercise capacity (6 minute walk distance: 6MWD), daily physical activity (locomotion time measured by tri-axial accelerometry: Lo) and health status (St George’s Respiratory Questionnaire: SGRQ). Biopsy of the vastus lateralis muscle was performed using a Bergstrom needle. Real-time PCR for expression levels of transcripts for myostatin was performed in duplicate wells, and normalised to a housekeeping gene. The relationship between clinical variables and quadriceps myostatin expression was determined by Spearman rank correlation.
Results Baseline clinical characteristics are outlined in table 1. Quadriceps muscle myostatin mRNA expression was negatively correlated with QMVC/BMI (r = −0.50, p<0.04), T80 (r = −0.53, p<0.03), 6MWD (r = −0.62, p<0.01) and Lo (r = −0.54, p<0.04).
Conclusions Myostatin may play a role in the development of quadriceps muscle dysfunction in COPD.
Acknowledgements WDM is an NIHR Clinician Scientist, SAS is a Wellcome Trust Clinical Research Training Fellow.
WDM and SAS contributed equally to the study. MIP and PRK were joint senior investigators.
S73 SKELETAL MUSCLE GENE EXPRESSION IN PATIENTS WITH COPD WITH NORMAL AND LOW FFMI AND HEALTHY CONTROLS. A MICROARRAY GENE EXPRESSION ANALYSIS
1R. A. Rabinovich, 1E. M. Drost, 2D. Dunbar, 2J. Manning, 3R. Bastos, 1W. MacNee. 1ELEGI/Colt laboratory, UoE/MRC Centre for Inflammation Research, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, UK, 2Bioinformatics Team, UoE/MRC Centre for Inflammation Research, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, UK, 3Department of Pulmonary Medicine (IDIBAPS), Hospital Clínic University of Barcelona, Barcelona, Spain
Skeletal dysfunction is one of the most important systemic effects of chronic obstructive pulmonary disease (COPD), leading to disability and poor prognosis; however, its underlying mechanisms are not fully understood. To gain insight into the molecular basis of this phenomenon we have undertaken a microarray gene expression analysis. 30 Agilent Human Whole Genome 4x44K Microarrays were hybridised following Agilent standard protocols with total RNA isolated from vastus lateralis of 20 patients with COPD (10 low (FFML) and 10 normal (FFMIN) fat-free mass index) and 10 matched healthy controls (C).
Expression measures were normalised using rma methodology from the Affy package of the Bioconductor project. Data analysis was performed using Rank Products method. Our ongoing work indicates that 542 well characterised genes were differentially expressed between COPD and C. Statistically significant gene ontology terms associate with relevant biological processes such as oxygen transport, muscle morphogenesis and contraction, inflammatory response and response to reactive oxygen species, among others.
165 differentially expressed genes between FFML and FFMIN associate with muscle contraction, organ development, muscle morphogenesis, cell differentiation and blood vessel remodelling.
In conclusion, our results identified a set of differentially expressed genes in both comparisons COPD vs C and FFML vs FFMIN that are relevant to muscle dysfunction/wasting. They also highlight the relevance of gene expression analysis in human tissue samples to identify molecular pathways involved in clinical abnormalities.
Supported by Chief Scientist Office, Scotland 06/S1103/5 and FIS PIO80320.
S74 LOWER LIMB FUNCTION AND EXERCISE PERFORMANCE IN DIFFERENT MRC DYSPNOEA SCALE CATEGORIES OF COPD
M. K. Menon, L. Houchen, S. J. Singh, M. D. Morgan, M. C. Steiner. Pulmonary Rehabilitation Research Group, Glenfield Hospital, Leicester, UK
Background Wasting and weakness of the lower limb muscles, especially the quadriceps, is a clinically relevant systemic manifestation of chronic obstructive pulmonary disease (COPD). Although inactivity is believed to be an important aetiological factor, the level of disability at which lower limb dysfunction occurs is not clear. The Medical Research Council (MRC) dyspnoea scale is a simple and valid method of assessing disability due to breathlessness in COPD; increased scores are associated with worsening exercise capacity and health status. Our aim was to compare thigh muscle mass, quadriceps strength and whole-body exercise performance in patients with COPD and healthy controls, after they were assigned into groups based on the MRC dyspnoea scale.
Methods 61 patients with COPD and 18 age-matched healthy controls were included in this study (table 1). Subjects were asked to grade their level of perceived breathlessness according to the MRC dyspnoea scale. While controls graded themselves in MRC 1, patients were in grades 3, 4 or 5. Subjects underwent a dual energy x ray absorptiometry (DEXA) scan to measure whole-body (Tlean) and thigh (Qlean) lean mass (Lunar Prodigy Advance). Quadriceps strength was measured on an isokinetic dynamometer (Cybex II Norm) during a maximal static contraction with the knee at 70°. A symptom-limited incremental cycle ergometry test was also performed by all participants. For data analysis, patients in MRC grades 4 and 5 were grouped together as there were only four patients in MRC grade 5. Comparisons were made between controls, patients in MRC grade 3, and those in grades 4 and 5 combined.
Results When compared with healthy controls, Qlean and quadriceps strength were significantly lower in patients with MRC grade 4 and 5 dyspnoea, but not in MRC grade 3 (table 1). However, whole-body exercise performance was impaired in all patients with COPD irrespective of the MRC dyspnoea grade.
Conclusion Our data suggest that lower limb function in COPD is preserved in patients who are less disabled by breathlessness, despite having lower maximal whole-body exercise capacity.
S75 PULMONARY REHABILITATION IMPROVES CARDIOVASCULAR RISK FACTORS IN PATIENTS WITH COPD
1N. S. Gale, 2J. M. Duckers, 3D. Proud, 3T. Lines, 1S. Enright, 4J. R. Cockcroft, 2D. J. Shale, 2C. E. Bolton. 1School of Healthcare Studies, Cardiff University, Cardiff, UK, 2Department of Respiratory Medicine, University Hospital Llandough, Cardiff, UK, 3University Hospital Llandough, Cardiff, UK, 4Welsh Heart Research Institute, Cardiff University, Cardiff, UK
Background Cardiovascular disease (CVD) contributes significantly to the morbidity and mortality of patients with chronic obstructive pulmonary disease (COPD).1 We have previously identified increased arterial stiffness as determined by aortic pulse wave velocity (aPWV), an independent predictor of CVD in these patients.2 Pulmonary rehabilitation (rehab) includes exercise, education and nutritional therapy, which are also key in the prevention and treatment of CVD. We hypothesised that rehab would improve aPWV.
Methods Thirty-two patients with COPD (11 male) were recruited and commenced rehab. Blood pressure (BP), aPWV, fasting lipids, body mass index (BMI) and the inflammatory mediator interleukin-6 (IL-6) were measured in addition to standard outcome measures before and after rehab. The multidisciplinary rehab programme has previously been described. Twenty-two representative patients completed study assessments before and after rehab. Age- and gender-matched controls, n = 20, were also studied at baseline.
Results In the patients commencing rehab, median age (range) was 65 (49–80) years, mean (SD) forced expiratory volume in 1 s (FEV1) % predicted 42.5% (14.7%). The aPWV in patients (9.8 (2.7) m/s) was greater than in controls (8.5 (1.4) m/s), as was IL-6, both p<0.05. Mean metabolic parameters (BMI, BP and cholesterol) were similar (p>0.05); however 5 patients (0 controls) had low BMI and 8 patients (3 controls) had a BMI >30 kg/m2. More patients had hypercholesterolaemia (patients 69%, controls 35%) (p<0.05) and there was a trend of more patients (44%) meeting the criteria for hypertension than controls (25%). In the 22 patients completing rehab, aPWV, BP and cholesterol were all reduced along with an increase in incremental shuttle walk/ing test (ISWT) (p<0.05), (table 1). Using multiple regression, the change in aPWV was explained by the reduction in BP.
Conclusions Pulmonary rehabilitation has haemodynamic benefits for patients with COPD, in addition to improvements in function and quality of life which have already been established.
S76 EXTRAPULMONARY POLYPHARMACY AND CARDIOVASCULAR MEDICATIONS IN COPD
A. R. C. Patel, S. Karmali, J. J. P. Goldring, G. C. Donaldson, J. K. Quint, J. R. Hurst, J. A. Wedzicha. Academic Unit of Respiratory Medicine, UCL Medical School, Royal Free Campus, London, UK
Introduction Cardiovascular co-morbidities requiring pharmacological treatment are common in chronic obstructive pulmonary disease (COPD). However, there are no COPD-specific guidelines and this may lead to suboptimal drug prescribing. We investigated the prevalence and pattern of extrapulmonary medications in COPD and in control subjects.
Methods We retrospectively analysed the recruitment records of 353 patients with COPD and 44 controls (current and ex-smokers with normal lung function) enrolled into the London COPD Cohort. Self-reported co-morbid diagnoses, medication, age, gender and forced expiratory volume in 1 s (FEV1) % predicted were recorded, and comparisons were made using χ2 and Mann–Whitney U tests where appropriate.
Results Patients with COPD were prescribed more classes of extrapulmonary medication than controls: median (interquartile range) 3 (1–5) vs 1 (0–3) p = 0.009. 20% of COPD patients were prescribed ⩾5 classes of extrapulmonary medication, fulfilling a definition of polypharmacy, vs 7% of controls (p = 0.037). The use of angiotensin-converting enzyme (ACE) inhibitors, calcium channel antagonists, loop diuretics and nitrates was significantly more common in patients with COPD (see table 1), in keeping with a higher prevalence of cardiovascular disease in this group. Almost half of the patients with COPD reported taking at least one class of blood pressure-lowering medication compared with fewer than a third in the controls. Despite the difference in cardiovascular disease, there was a significantly lower use of β-blockers in patients with COPD compared with controls (4.5% vs 13.6%, p = 0.013). Aspirin and statins were commonly prescribed in both groups (see table 1). Analgesics, antidiabetic, antidepressant and anxiolytic medications were not significantly different in the COPD and control groups.
Conclusions Extrapulmonary polypharmacy is approximately three times more common in patients with COPD than in controls. There are clinically important differences in the pharmacological treatment of cardiovascular disease in COPD compared with controls. In particular, cardioselective β-blockers are significantly underprescribed despite good evidence of their safety and benefit in COPD.
Clear guidelines on the treatment of cardiovascular co-morbidities in COPD may help to reduce morbidity and mortality through the rational use of appropriate medication classes.