Benjamin E. Garfield

Stanford Seven-Day Physical Activity Recall questionnaire in COPD

Quantification of daily physical activity is of clinical interest in chronic obstructive pulmonary disease (COPD). Objective measures using activity monitors may take several days to obtain reliable results. The aim of our study was to evaluate the Stanford Seven-Day Physical Activity Recall questionnaire (PAR) against the SenseWear armband (SWA) and compare its validity with three other physical activity questionnaires. 43 COPD patients wore the SWA for 7 days. Patients completed the PAR, Baecke, Physical Activity Scale for the Elderly (PASE) and Zutphen questionnaires. Spearman rank correlation, intraclass correlation coefficients (ICC) and receiver-operating characteristics (ROC) curves were used to assess the relationship between the questionnaires and SWA. Assessed by PAR, time spent at ≥3.0 metabolic equivalents (METs) correlated significantly (r=0.54, p<0.001) with equivalent measures from SWA, with an ICC of 0.40. No relationship was seen between the other questionnaires and the SWA. The PAR predicted active patients (≥30 min at ≥3.0 METs or a physical activity level (PAL) ≥1.55) and very inactive patients (PAL <1.40) with an area under ROC curve of 0.83, 0.77 and 0.70, respectively. While the PAR did not measure physical activity sufficiently accurately to make individual recommendations, it was able to identify COPD patients at extremes of the physical activity spectrum, potentially reducing the number of patients requiring direct measurement.

Growth differentiation factor-15 is associated with muscle mass in chronic obstructive pulmonary disease and promotes muscle wasting in vivo.

Loss of muscle mass is a co‐morbidity common to a range of chronic diseases including chronic obstructive pulmonary disease (COPD). Several systemic features of COPD including increased inflammatory signalling, oxidative stress, and hypoxia are known to increase the expression of growth differentiation factor‐15 (GDF‐15), a protein associated with muscle wasting in other diseases. We therefore hypothesized that GDF‐15 may contribute to muscle wasting in COPD.

MicroRNA-542 Promotes Mitochondrial Dysfunction and SMAD Activity and Is Elevated in Intensive Care Unit–acquired Weakness

Rationale: Loss of skeletal muscle mass and function is a common consequence of critical illness and a range of chronic diseases, but the mechanisms by which this occurs are unclear. Objectives: To identify microRNAs (miRNAs) that were increased in the quadriceps of patients with muscle wasting and to determine the molecular pathways by which they contributed to muscle dysfunction. Methods: miRNA‐542‐3p/5p (miR‐542‐3p/5p) were quantified in the quadriceps of patients with chronic obstructive pulmonary disease and intensive care unit‐acquired weakness (ICUAW). The effect of miR‐542‐3p/5p was determined on mitochondrial function and transforming growth factor‐&bgr; signaling in vitro and in vivo. Measurements and Main Results: miR‐542‐3p/5p were elevated in patients with chronic obstructive pulmonary disease but more markedly in patients with ICUAW. In vitro, miR‐542‐3p suppressed the expression of the mitochondrial ribosomal protein MRPS10 and reduced 12S ribosomal RNA (rRNA) expression, suggesting mitochondrial ribosomal stress. miR‐542‐5p increased nuclear phospho‐SMAD2/3 and suppressed expression of SMAD7, SMURF1, and PPP2CA, proteins that inhibit or reduce SMAD2/3 phosphorylation, suggesting that miR‐542‐5p increased transforming growth factor‐&bgr; signaling. In mice, miR‐542 overexpression caused muscle wasting, and reduced mitochondrial function, 12S rRNA expression, and SMAD7 expression, consistent with the effects of the miRNAs in vitro. Similarly, in patients with ICUAW, the expression of 12S rRNA and of the inhibitors of SMAD2/3 phosphorylation were reduced, indicative of mitochondrial ribosomal stress and increased transforming growth factor‐&bgr; signaling. In patients undergoing aortic surgery, preoperative levels of miR‐542‐3p/5p were positively correlated with muscle loss after surgery. Conclusions: Elevated miR‐542‐3p/5p may cause muscle atrophy in intensive care unit patients through the promotion of mitochondrial dysfunction and activation of SMAD2/3 phosphorylation.

miR-322-5p targets IGF-1 and is suppressed in the heart of rats with pulmonary hypertension.

Pulmonary arterial hypertension (PAH) is characterised by remodelling of the pulmonary vasculature leading to right ventricular hypertrophy. Here, we show that miR‐322‐5p (the rodent orthologue of miR‐424‐5p) expression is decreased in the right ventricle of monocrotaline‐treated rats, a model of PAH, whereas a putative target insulin‐like growth factor 1 (IGF‐1) is increased. IGF‐1 mRNA was enriched 16‐fold in RNA immunoprecipitated with Ago2, indicating binding to miR‐322‐5p. In cell transfection experiments, miR‐322‐5p suppressed the activity of a luciferase reporter containing a section of the IGF‐1 3′ untranslated region (UTR) as well as IGF‐1 mRNA and protein levels. Taken together, these data suggest that miR‐322 targets IGF‐1, a process downregulated in PAH‐related RV hypertrophy.

P268 The role of growth and differentiation factor 15 in smooth muscle cell proliferation in pulmonary hypertension

Introduction Growth and differentiation factor 15 (GDF-15) is a prognostic marker in pulmonary hypertension (PH). Its effects on endothelial cells have been documented, but its mechanism of action and role in the development of PH have not yet been fully investigated. We aimed to define the role and mechanism of action of GDF-15 in the development of PH. Methods Rats were treated with moncrotaline (MCT) or vehicle control and euthanized after undergoing cardiovascular monitoring 4 weeks later. The expression of GDF-15 mRNA in the lung was measured by qPCR. Total GDF-15 protein levels in serum and lung were analysed by ELISA. The distribution of GDF-15 in the lung was analysed by immunohistochemistry. GDF-15 signalling in human pulmonary artery smooth muscle cells (HPASMCs) was analysed using western blot, and its role on HPASMC proliferation was measured using a cyquant assay. Results GDF-15 mRNA and protein levels were raised in the lung homogenates of the MCT rat compared to controls (p < 0.05). Immunohistochemistry revealed GDF-15 was localised in the endothelial cells and to a lesser extent in the PASMCs of these animal. GDF-15 levels in the serum of the MCT treated rats was higher than that in those treated with vehicle control (771 ± 345 vs. 411 ± 305, p < 0.05). Serum GDF-15 was correlated with RV/LV+S weight in the MCT treated group (Pearson r = 0.66, p < 0.05). Immunohistochemistry also revealed an increase of phospho-TGFβ activated kinase 1 (TAK1) in PASMCs of the MCT rat. In HPASMCs GDF-15 (1 ng/ml) treatment resulted in an increase in proliferation over baseline at 72 h (Figure 1). GDF-15 was also able to induce phosphorylation of TAK1 in HPASMCs.Abstract P268 Figure 1 Conclusions GDF-15 is over-expressed in the lung vasculature of MCT rats, mimicking human disease. GDF-15 was associated with the degree of right ventricular hypertrophy in these animals. GDF-15 downstream signalling molecule phosphorylated TAK-1 is present in increased levels in the vasculature of the MCT rat. In vitro GDF-15 treatment caused proliferation of HPASMCs and activation of TAK-1. Further investigation of this pathway is required to determine its relevance to human disease.

S73 4-Metre gait speed as a functional outcome measure in patients with Chronic Obstructive Pulmonary Disease (COPD)

Introduction Well-established functional outcome measures in COPD include the 6-min walk test (6MW) and incremental shuttle walk test (ISW). However, these tests require space, repetition, and can be time-consuming. In the elderly population, gait speed alone has been shown to be a significant predictor of disability and mortality. We hypothesised that the 4-m gait speed in COPD patients would correlate well with the 6MW and ISW, and with validated COPD mortality composite scores such as BODE and ADO. Methods 26 well-characterised COPD patients were studied. Each underwent 6MW test as per ATS guidelines, ISW test and completed a 4-m walk in random order. For the 4-m walk, participants were instructed to walk at their usual speed along a marked, flat unobstructed course. Timing was stopped when the first foot completely crossed the 4-m mark. The faster of two timed walks was used for scoring purposes, and a gait speed was calculated in m/s. Data were analysed using Spearmans rank correlation to assess association between 4-m gait speed and 6MW, ISW, BODE score and ADO index. Results Baseline characteristics are presented as mean (SD) or median (25th, 75th percentile): 11M: 15 F; age=69 (8); FEV1% predicted=43 (20); 6MW=330 (83); ISW=291 (122.5); MRC dyspnoea 3 (2, 4); St Georges Respiratory Questionnaire (SGRQ)=49.6 (21.0); BMI=25.9 (4.9); BODE=4.5 (1.75, 6.0), ADO=5 (4, 6). Mean (SD) 4-m gait speed was 0.96 (0.20) m/s. There was a significant correlation between 4-m gait speed and 6MW (r=0.62, p=<0.001), ISW (r=0.80, p=<0.0001)—see Abstract S73 Figure 1, BODE score (r=−0.56, p=0.003) and ADO index (r=−0.43, p=0.03).Abstract S73 Figure 1 Conclusions 4-m gait speed correlates well with existing functional outcome measures and validated mortality composite scores used in COPD. It is an easy and quick to perform field test, and does not require specialist training or equipment. Further longitudinal and intervention studies are required to validate the 4-m gait speed as an assessment tool.