Imperial College London

DrPaulKemp

Faculty of MedicineNational Heart & Lung Institute

Reader in the Molecular Biology of Muscles
 
 
 
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+44 (0)20 7594 1716p.kemp

 
 
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Sir Alexander Fleming BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
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125 results found

Kemp P, Paul R, Neil D, Russell A, Hinken A, Griffiths Met al., Metabolic profiling shows pre-existing mitochondrial dysfunction contributes to muscle loss in a model of ICU acquired weakness Journal of Cachexia, Sarcopenia and Muscle, Journal of Cachexia, Sarcopenia and Muscle, ISSN: 2190-6009

Journal article

Connolly M, Garfield B, Crosby A, Morrell N, Wort S, Kemp Pet al., 2020, miR-1-5p targets TGF-βR1 and is suppressed in the hypertrophying hearts of rats with pulmonary arterial hypertension, PLoS One, Vol: 15, ISSN: 1932-6203

The microRNA miR-1 is an important regulator of muscle phenotype including cardiac muscle. Down-regulation of miR-1 has been shown to occur in left ventricular hypertrophy but its contribution to right ventricular hypertrophy in pulmonary arterial hypertension are not known. Previous studies have suggested that miR-1 may suppress transforming growth factor-beta (TGF-β) signalling, an important pro-hypertrophic pathway but only indirect mechanisms of regulation have been identified. We identified the TGF-β type 1 receptor (TGF-βR1) as a putative miR-1 target. We therefore hypothesized that miR-1 and TGF-βR1 expression would be inversely correlated in hypertrophying right ventricle of rats with pulmonary arterial hypertension and that miR-1 would inhibit TGF-β signalling by targeting TGF-βR1 expression. Quantification of miR-1 and TGF-βR1 in rats treated with monocrotaline to induce pulmonary arterial hypertension showed appropriate changes in miR-1 and TGF-βR1 expression in the hypertrophying right ventricle. A miR-1-mimic reduced enhanced green fluorescent protein expression from a reporter vector containing the TGF-βR1 3’- untranslated region and knocked down endogenous TGF-βR1. Lastly, miR-1 reduced TGF-β activation of a (mothers against decapentaplegic homolog) SMAD2/3-dependent reporter. Taken together, these data suggest that miR-1 targets TGF-βR1 and reduces TGF-β signalling, so a reduction in miR-1 expression may increase TGF-β signalling and contribute to cardiac hypertrophy.

Journal article

Band M, Hume C, Pilvynte K, Aitchison M, Smith K, Avenell A, Kemp P, Donnan P, Hapca A, Struthers A, Sumukadas D, George J, Witham Met al., 2019, Recruitment methods for sarcopenia trials - lessons from the LACE randomised controlled trial, Publisher: BMC

Conference paper

Connolly M, Wort S, Garfield B, Crosby A, Morrell N, Kemp Pet al., 2019, MiR-1-5p targets TGF-beta R1 and is suppressed in the hypertrophying hearts of rats with pulmonary arterial hypertension, European-Respiratory-Society (ERS) International Congress, Publisher: EUROPEAN RESPIRATORY SOC JOURNALS LTD, ISSN: 0903-1936

Conference paper

Ciano M, Mantellato G, Connolly M, Paul-Clark M, Mitchell J, Wilson-Owen S, Cookson W, Moffatt M, Hughes S, Polkey M, Kemp P, Natanek Set al., 2019, EGF receptor (EGFR) inhibition promotes a slow-twitch oxidative, over a fast-twitch, muscle phenotype, Scientific Reports, Vol: 9, ISSN: 2045-2322

A low quadriceps slow-twitch (ST), oxidative (relative to fast-twitch) fiber proportion is prevalent in chronic diseases such Chronic Obstructive Pulmonary Disease (COPD) and is associated with exercise limitation and poor outcomes. Benefits of an increased ST fiber proportion are demonstrated in genetically modified animals. Pathway analysis of published data of differentially expressed genes in mouse ST and FT fibers, mining of our microarray data and a qPCR analysis of quadriceps specimens from COPD patients and controls were performed. ST markers were quantified in C2C12 myotubes with EGF-neutralizing antibody, EGFR inhibitor or an EGFR-silencing RNA added. A zebrafish egfra mutant was generated by genome editing and ST fibers counted. EGF signaling was (negatively) associated with the ST muscle phenotype in mice and humans, and muscle EGF transcript levels were raised in COPD. In C2C12 myotubes, EGFR inhibition/silencing increased ST, including mitochondrial, markers. In zebrafish, egfra depletion increased ST fibers and mitochondrial content. EGF is negatively associated with ST muscle phenotype in mice, healthy humans and COPD patients. EGFR blockade promotes the ST phenotype in myotubes and zebrafish embryos. EGF signaling suppresses the ST phenotype, therefore EGFR inhibitors may be potential treatments for COPD-related muscle ST fiber loss.

Journal article

Farre-Garros R, Lee J, Natanek S, Connolly M, Sayer A, Patel H, Cooper C, Polkey M, Kemp Pet al., 2019, Quadriceps miR-542-3p and 5p are elevated in COPD and reduce function by inhibiting ribosomal and protein synthesis, Journal of Applied Physiology, Vol: 126, Pages: 1514-1524, ISSN: 8750-7587

Reduced physical performance reduces quality of life in patients with COPD. Impaired physical performance is, in part, a consequence of reduced muscle mass and function, which is accompanied by mitochondrial dysfunction. We recently showed that miR-542-3p and miR-542-5p were elevated in a small cohort of COPD patients and more markedly in critical care patients. In mice these miRNAs promoted mitochondrial dysfunction suggesting that they would affect physical performance in patients with COPD but we did not explore the association of these miRNAs with disease severity or physical performance further. We therefore quantified miR-542-3p/5p and mitochondrial rRNA expression in RNA extracted from quadriceps muscle of patients with COPD and determined their association with physical performance. As miR-542-3p inhibits ribosomal protein synthesis its ability to inhibit protein synthesis was also determined in vitro.Both miR-542-3p and -5p expression were elevated in patients with COPD (5-fold p<0.001) and the degree of elevation associated with impaired lung function (TLCO% and FEV1%) and physical performance (6-minute walk distance %). In COPD patients, the ratio of 12S rRNA to 16S rRNA was suppressed suggesting mitochondrial ribosomal stress and mitochondrial dysfunction and miR-542-3p/5p expression was inversely associated with mitochondrial gene expression and positively associated with p53 activity. miR-542-3p suppressed RPS23 expression and maximal protein synthesis in vitro. Our data show that miR-542-3p and -5p expression is elevated in COPD patients and may suppress physical performance at least in part by inhibiting mitochondrial and cytoplasmic ribosome synthesis and suppressing protein synthesis.

Journal article

Sharanya A, Ciano M, Withana S, Polkey M, Kemp P, Natanek Set al., 2019, Sex differences in COPD-related quadriceps muscle dysfunction and fibre abnormalities, Chronic Respiratory Disease, Vol: 16, Pages: 1-13, ISSN: 1479-9723

Background: In COPD, lower limb dysfunction is associated with reduced exercise capacity, increased hospitalisations and mortality. We investigated sex differences in the prevalence of quadriceps dysfunction and fibre abnormalities in a large COPD cohort, controlling for the normal sex differences in health. Methods: We compared existing data from 76 male and 38 female COPD patients where each variable was expressed as a function of gender-specific normal values (obtained from 16 male and 14 female controls). Results: Female COPD patients had lower quadriceps muscle strength and peak workload on a maximal incremental cycle ergometry protocol compared to male patients. Female patients had a smaller type II fibre cross-sectional area (CSA) compared to male patients, suggesting a greater female preponderance to fibre atrophy, although this result was largely driven by a few male patients with increased type II fibre CSA. Female patients had significantly higher concentrations of a number of plasma pro-inflammatory cytokines including tumor necrosis factor alpha (TNFα) and interleukin 8 (IL8), but not lower levels of physical activity or arterial oxygenation, compared to males. Conclusions: Our data confirms results from a previous small study and suggests that female COPD patients have a greater prevalence of muscle wasting and weakness. Larger studies investigating sex differences in COPD-related muscle atrophy and weakness are needed, as the results will have implications for monitoring in clinical practice and for design of clinical trials evaluating novel muscle anabolic agents.

Journal article

Kemp P, Griffiths M, Polkey M, 2019, Muscle wasting in the presence of disease, why is it so variable?, Biological Reviews, Vol: 94, Pages: 1038-105, ISSN: 1464-7931

Skeletal muscle wasting is a common clinical feature of many chronic diseases and also occurs in response to single acute events. The accompanying loss of strength can lead to significant disability, increased care needs and have profound negative effects on quality of life. As muscle is the most abundant source of amino acids in the body, it appears to function as a buffer for fuel and substrates that can be used to repair damage elsewhere and to feed the immune system. In essence, the fundamentals of muscle wasting are simple: less muscle is made than is broken down. However, although well‐described mechanisms modulate muscle protein turnover, significant individual differences in the amount of muscle lost in the presence of a given severity of disease complicate the understanding of underlying mechanisms and suggest that individuals have different sensitivities to signals for muscle loss. Furthermore, the rate at which muscle protein is turned over under normal conditions means that clinically significant muscle loss can occur with changes in the rate of protein synthesis and/or breakdown that are too small to be measurable. Consequently, the changes in expression of factors regulating muscle turnover required to cause a decline in muscle mass are small and, except in cases of rapid wasting, there is no consistent pattern of change in the expression of factors that regulate muscle mass. MicroRNAs are fine tuners of cell phenotype and are therefore ideally suited to cause the subtle changes in proteome required to tilt the balance between synthesis and degradation in a way that causes clinically significant wasting. Herein we present a model in which muscle loss as a consequence of disease in non‐muscle tissue is modulated by a set of microRNAs, the muscle expression of which is associated with severity of disease in the non‐muscle tissue. These microRNAs alter fundamental biological processes including the synthesis of ribosomes and mitochondria leading to reduce

Journal article

Garfield B, Crosby A, Shao D, Yang P, Read C, Sawaik S, Moore S, Parfitt L, Harries C, Rice M, Paul R, Ormiston M, Morrell N, Polkey M, Wort SJ, Kemp Pet al., 2019, Growth/differentiation factor 15 causes TGFβ activated kinase 1 dependent muscle atrophy in pulmonary arterial hypertension, Thorax, Vol: 74, Pages: 164-176, ISSN: 1468-3296

Introduction Skeletal muscle dysfunction is a clinically important complication of pulmonary arterial hypertension (PAH). Growth/differentiation factor 15 (GDF-15), a prognostic marker in PAH, has been associated with muscle loss in other conditions. We aimed to define the associations of GDF-15 and muscle wasting in PAH, to assess its utility as a biomarker of muscle loss and to investigate its downstream signalling pathway as a therapeutic target.Methods GDF-15 levels and measures of muscle size and strength were analysed in the monocrotaline (MCT) rat, Sugen/hypoxia mouse and in 30 patients with PAH. In C2C12 myotubes the downstream targets of GDF-15 were identified. The pathway elucidated was then antagonised in vivo.Results Circulating GDF-15 levels correlated with tibialis anterior (TA) muscle fibre diameter in the MCT rat (Pearson r=−0.61, p=0.003). In patients with PAH, plasma GDF-15 levels of <564 pg/L predicted those with preserved muscle strength with a sensitivity and specificity of ≥80%. In vitro GDF-15 stimulated an increase in phosphorylation of TGFβ-activated kinase 1 (TAK1). Antagonising TAK1, with 5(Z)-7-oxozeaenol, in vitro and in vivo led to an increase in fibre diameter and a reduction in mRNA expression of atrogin-1 in both C2C12 cells and in the TA of animals who continued to grow. Circulating GDF-15 levels were also reduced in those animals which responded to treatment.Conclusions Circulating GDF-15 is a biomarker of muscle loss in PAH that is responsive to treatment. TAK1 inhibition shows promise as a method by which muscle atrophy may be directly prevented in PAH.

Journal article

Willis-Owen SAG, Thompson AR, Kemp P, Moffatt MF, Polkey M, Cookson W, Natanek Set al., 2018, COPD is accompanied by co-ordinated transcriptional perturbation in the quadriceps affecting the mitochondria and extracellular matrix, Scientific Reports, Vol: 8, ISSN: 2045-2322

Skeletal muscle dysfunction is a frequent extra-pulmonary manifestation of Chronic Obstructive Pulmonary Disease (COPD) with implications for both quality of life and survival. The underlying biology nevertheless remains poorly understood. We measured global gene transcription in the quadriceps using Affymetrix HuGene1.1ST arrays in an unselected cohort of 79 stable COPD patients in secondary care and 16 healthy age- and gender-matched controls. We detected 1,826 transcripts showing COPD-related variation. Eighteen exhibited ≥2fold changes (SLC22A3, FAM184B, CDKN1A, FST, LINC01405, MUSK, PANX1, ANKRD1, C12orf75, MYH1, POSTN, FRZB, TNC, ACTC1, LINC00310, MYH3, MYBPH and AREG). Thirty-one transcripts possessed previous reported evidence of involvement in COPD through genome-wide association, including FAM13A. Network analysis revealed a substructure comprising 6 modules of co-expressed genes. We identified modules with mitochondrial and extracellular matrix features, of which IDH2, a central component of the mitochondrial antioxidant pathway, and ABI3BP, a proposed switch between proliferation and differentiation, represent hubs respectively. COPD is accompanied by coordinated patterns of transcription in the quadriceps involving the mitochondria and extracellular matrix and including genes previously implicated in primary disease processes.

Journal article

Band MM, Sumukadas D, Struthers AD, Avenell A, Donnan PT, Kemp PR, Smith KT, Hume CL, Hapca A, Witham MDet al., 2018, Leucine and ACE inhibitors as therapies for sarcopenia (LACE trial): study protocol for a randomised controlled trial, Trials, Vol: 19, ISSN: 1745-6215

Background:Sarcopenia (the age-related loss of muscle mass and function) is a major contributor to loss of mobility, falls, loss of independence, morbidity and mortality in older people. Although resistance training is effective in preventing and reversing sarcopenia, many older people are sedentary and either cannot or do not want to exercise. This trial examines the efficacy of supplementation with the amino acid leucine and/or angiotensin converting enzyme inhibition to potentially improve muscle mass and function in people with sarcopenia. Promising preliminary data exist from small studies for both interventions, but neither has yet been tested in adequately powered randomised trials in patients with sarcopenia.Methods:Leucine and ACE inhibitors in sarcopenia (LACE) is a multicentre, masked, placebo-controlled, 2 × 2 factorial randomised trial evaluating the efficacy of leucine and perindopril (angiotensin converting enzyme inhibitor (ACEi)) in patients with sarcopenia. The trial will recruit 440 patients from primary and secondary care services across the UK. Male and female patients aged 70 years and over with sarcopenia as defined by the European Working Group on Sarcopenia (based on low total skeletal muscle mass on bioimpedance analysis and either low gait speed or low handgrip strength) will be eligible for participation. Participants will be excluded if they have a contraindication to, or are already taking, an ACEi, angiotensin receptor blocker or leucine. The primary clinical outcome for the trial is the between-group difference in the Short Physical Performance Battery score at all points between baseline and 12 months. Secondary outcomes include appendicular muscle mass measured using dual-energy X-ray absorptiometry, muscle strength, activities of daily living, quality of life, activity using pedometer step counts and falls. Participants, clinical teams, outcomes assessors and trial analysts are masked to treatment allocation. A

Journal article

Connolly M, Garfield B, Crosby A, Morrell N, Wort SJ, Kemp Pet al., 2017, miR-322-5p targets IGF-1 and is suppressed in the heart of rats with pulmonary hypertension, FEBS Open Bio, Vol: 8, Pages: 339-348, ISSN: 2211-5463

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.

Journal article

Kemp P, Connolly, Paul R, Farre Garros R, Natanek, Bloch, Lee J, lorenzo, Patel H, Cooper C, Sayer A, Wort, Griffiths, Polkeyet al., 2017, miR-424-5p reduces ribosomal RNA and protein synthesis in muscle wasting, Journal of Cachexia, Sarcopenia and Muscle, Vol: 9, Pages: 400-416, ISSN: 2190-6009

Background: A loss of muscle mass occurs as a consequence of a range of chronic and acute diseases as well as in older age. This wasting results from an imbalance of protein synthesis and degradation with a reduction in synthesis and resistance to anabolic stimulation often reported features. Ribosomes are required for protein synthesis so changes in the control of ribosome synthesis is a potential contributor to muscle wasting. MicroRNAs (miRNAs) are known regulators of muscle phenotype and have been shown to modulate components of the protein synthetic pathway. One miRNA that is predicted to target a number of components of protein synthetic pathway is miR-424-5p, which is elevated in the quadriceps of patients with chronic obstructive pulmonary disease (COPD).Methods: Targets of miR-424-5p were identified by Ago2 pull-down and the effects of the miRNA on RNA and protein expression were determined by qPCR and western blotting in muscle cells in vitro. Protein synthesis was determined by puromycin incorporation in vitro. The miRNA was over-expressed in the tibialis anterior muscle of mice by electroporation and the effects quantified. Finally, quadriceps expression of the miRNA was determined by qPCR in patients with COPD, intensive care unit acquired weakness (ICUAW), and in patients undergoing aortic surgery as well as in individuals from the Hertfordshire Sarcopenia Study.Results: Pull-down assays showed that miR-424-5p bound to mRNAs encoding proteins associated with muscle protein synthesis. The most highly enriched mRNAs encoded proteins required for the Pol I RNA pre-initiation complex (PIC) required for rRNA transcription, (PolR1A and Upstream binding transcription factor, UBTF). In vitro, miR-424-5p reduced expression of these RNAs, reduced rRNA levels and inhibited protein synthesis. In mice, over-expression of miR-322 (rodent miR-424 orthologue) caused fibre atrophy and reduced UBTF expression and rRNA levels. In humans elevated miR-424-5p as

Journal article

Kemp P, paul R, lee J, donaldson AV, connolly M, sharif M, natanek SA, rosendahl U, polkey M, griffiths Met al., 2017, miR-422a suppresses SMAD4 protein expression and promotes resistance to muscle loss, Journal of Cachexia Sarcopenia and Muscle, Vol: 9, Pages: 119-128, ISSN: 2190-5991

BackgroundLoss of muscle mass and strength are important sequelae of chronic disease, but the response of individuals is remarkably variable, suggesting important genetic and epigenetic modulators of muscle homeostasis. Such factors are likely to modify the activity of pathways that regulate wasting, but to date, few such factors have been identified.MethodsThe effect of miR-422a on SMAD4 expression and transforming growth factor (TGF)-β signalling were determined by western blotting and luciferase assay. miRNA expression was determined by qPCR in plasma and muscle biopsy samples from a cross-sectional study of patients with chronic obstructive pulmonary disease (COPD) and a longitudinal study of patients undergoing aortic surgery, who were subsequently admitted to the intensive care unit (ICU).ResultsmiR-422a was identified, by a screen, as a microRNA that was present in the plasma of patients with COPD and negatively associated with muscle strength as well as being readily detectable in the muscle of patients. In vitro, miR-422a suppressed SMAD4 expression and inhibited TGF-beta and bone morphogenetic protein-dependent luciferase activity in muscle cells. In male patients with COPD and those undergoing aortic surgery and on the ICU, a model of ICU-associated muscle weakness, quadriceps expression of miR-422a was positively associated with muscle strength (maximal voluntary contraction r = 0.59, P < 0.001 and r = 0.51, P = 0.004, for COPD and aortic surgery, respectively). Furthermore, pre-surgery levels of miR-422a were inversely associated with the amount of muscle that would be lost in the first post-operative week (r = −0.57, P < 0.001).ConclusionsThese data suggest that differences in miR-422a expression contribute to the susceptibility to muscle wasting associated with chronic and acute disease and that at least part of this activity may be mediated by reduced TGF-beta signalling in skeletal muscle.

Journal article

farre garros, paul R, connolly M, lewis A, natanek SA, garfield BE, BLoch S, Mouly V, griffiths M, polkey MI, Kemp Pet al., 2017, miR-542 promotes mitochondrial dysfunction and SMAD activity and is raised in ICU Acquired Weakness, American Journal of Respiratory and Critical Care Medicine, Vol: 196, ISSN: 1073-449X

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: We aimed to identify 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: miR-542-3p/-5p were quantified in the quadriceps of patients with COPD and intensive care unit acquired weakness (ICUAW). The effect of miR-542-3p/5p was determined on mitochondrial function and TGF-β signaling in vitro and in vivo. Measurements and main results: miR-542-3p/5p were elevated in patients with COPD but more markedly in patients with ICUAW. In vitro, miR-542-3p suppressed the expression of the mitochondrial ribosomal protein MRPS10, and reduced 12S 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 TGF-β signaling. In mice, miR-542 over-expression caused muscle wasting, 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 TGF-β signaling. In patients undergoing aortic surgery, pre-operative levels of miR-542-3p/5p were positively correlated with muscle loss following surgery. Conclusion; Elevated miR-542-3p/5p may cause muscle atrophy in ICU patients through the promotion of mitochondrial dysfunction and activation of SMAD2/3 phosphorylation.

Journal article

Lee J, Donaldson AV, Lewis A, Natanek A, Polkey, Kemp Pet al., 2017, Circulating miRNAs from imprinted genomic regions are associated with peripheral muscle strength in COPD patients, European Respiratory Journal, Vol: 49, ISSN: 1399-3003

Circulating levels of miR-485-3p, a maternally expressed miRNA, are associated with muscle strength in COPD patients http://ow.ly/Wq51309fQtK

Journal article

Kemp P, Natanek A, 2017, Epigenetics and susceptibility to muscle wasting in COPD, Archivos de Bronconeumología, Vol: 53, Pages: 364-365, ISSN: 0300-2896

Journal article

Garfield BE, Shao D, Parfitt L, Harries C, Price L, Dimopoulos K, Polkey MI, Kemp P, Wort SJet al., 2016, LOW SKELETAL MUSCLE STRENGTH AND PHYSICAL ACTIVITY ARE ASSOCIATED WITH POOR OUTCOMES IN PULMONARY ARTERIAL HYPERTENSION, THORAX, Vol: 71, Pages: A64-A64, ISSN: 0040-6376

Journal article

Polkey MI, Griffiths MJ, Kemp PR, 2016, Muscle regeneration after critical illness: are satellite cells the answer?, American Journal of Respiratory and Critical Care Medicine, Vol: 194, Pages: 780-782, ISSN: 1535-4970

Journal article

Mohan D, Lewis A, Patel MS, Curtis KJ, Lee JY, Hopkinson NS, Wilkinson IB, Kemp PR, Polkey MIet al., 2016, Using laser capture microdissection to study fiber specific signalling in locomotor muscle in COPD: A pilot study, Muscle & Nerve, Vol: 55, Pages: 902-912, ISSN: 1097-4598

INTRODUCTION: Quadriceps dysfunction is important in chronic obstructive pulmonary disease (COPD), with an associated increased proportion of type II fibers. Investigation of protein synthesis and degradation has yielded conflicting results, possibly due to study of whole biopsy samples, whereas signalling may be fiber-specific. Our objective was to develop a method for fiber-specific gene expression analysis. METHODS: 12 COPD and 6 healthy subjects underwent quadriceps biopsy. Cryosections were immunostained for type II fibers, which were separated using laser capture microdissection (LCM). Whole muscle and different fiber populations were subject to quantitative polymerase chain reaction (qPCR). RESULTS: Muscle-RING-finger-protein-1(MURF-1) and Atrogin-1 were lower in type II fibers of COPD versus healthy subjects (P=0.02 and P=0.03, respectively), but differences were not apparent in whole muscle or type I fibers. DISCUSSION: We describe a novel method for studying fiber-specific gene expression in optimum-cutting-temperature (OCT) compound-embedded muscle specimens. LCM offers a more sensitive way to identify molecular changes in COPD muscle. This article is protected by copyright. All rights reserved.

Journal article

Patel MS, Donaldson AV, Lewis A, Natanek SA, Lee JY, Andersson YM, Haji G, Jackson SG, Bolognese BJ, Foley JP, Podolin PL, Bruijnzeel PLB, Hart N, Hopkinson NS, Man WD-C, Kemp PR, Polkey MIet al., 2016, Klotho and smoking – An interplay influencing the skeletal muscle function deficits that occur in COPD, Respiratory Medicine, Vol: 113, Pages: 50-56, ISSN: 0954-6111

BackgroundKlotho is an ‘anti-ageing’ hormone and transmembrane protein; Klotho deficient mice develop a similar ageing phenotype to smokers including emphysema and muscle wasting. The objective of this study was to evaluate skeletal muscle and circulating Klotho protein in smokers and COPD patients and to relate Klotho levels to relevant skeletal muscle parameters. We sought to validate our findings by undertaking complimentary murine studies.MethodsFat free mass, quadriceps strength and spirometry were measured in 87 participants (61 COPD, 13 ‘healthy smokers’ and 13 never smoking controls) in whom serum and quadriceps Klotho protein levels were also measured. Immunohistochemistry was performed to demonstrate the location of Klotho protein in human skeletal muscle and in mouse skeletal muscle in which regeneration was occurring following injury induced by electroporation. In a separate study, gastrocnemius Klotho protein was measured in mice exposed to 77 weeks of smoke or sham air.ResultsQuadriceps Klotho levels were lower in those currently smoking (p = 0.01), irrespective of spirometry, but were not lower in patients with COPD. A regression analysis identified current smoking status as the only independent variable associated with human quadriceps Klotho levels, an observation supported by the finding that smoke exposed mice had lower gastrocnemius Klotho levels than sham exposed mice (p = 0.005). Quadriceps Klotho levels related to local oxidative stress but were paradoxically higher in patients with established muscle wasting or weakness; the unexpected relationship with low fat free mass was the only independent association. Within locomotor muscle, Klotho localized to the plasma membrane and to centralized nuclei in humans and in mice with induced muscle damage. Serum Klotho had an independent association with quadriceps strength but did not relate to quadriceps Klotho levels or to spirometric parameters.ConclusionsKlotho is expressed

Journal article

Lewis A, Donaldson AV, Natanek SA, Vaidyanathan S, Man WDC, Hopkinson NS, Sayer AA, Patel HP, Cooper C, Syddall H, Polkey MI, Kemp PRet al., 2016, Increased expression of H19/miR-675 is associated with a low fat free mass index in patients with COPD, Journal of Cachexia, Sarcopenia and Muscle, Vol: 7, Pages: 330-344, ISSN: 2190-6009

BackgroundLoss of muscle mass and strength is a significant comorbidity in patients with chronic obstructive pulmonary disease (COPD) that limits their quality of life and has prognostic implications but does not affect everyone equally. To identify mechanisms that may contribute to the susceptibility to a low muscle mass, we investigated microRNA (miRNA) expression, methylation status, and regeneration in quadriceps muscle from COPD patients and the effect of miRNAs on myoblast proliferation in vitro. The relationships of miRNA expression with muscle mass and strength was also determined in a group of healthy older men.MethodsWe identified miRNAs associated with a low fat-free mass (FFM) phenotype in a small group of patients with COPD using a PCR screen of 750 miRNAs. The expression of two differentially expressed miRNAs (miR-675 and miR-519a) was determined in an expanded group of COPD patients and their associations with FFM and strength identified. The association of these miRNAs with FFM and strength was also explored in a group of healthy community-dwelling older men. As the expression of the miRNAs associated with FFM could be regulated by methylation, the relative methylation of the H19 ICR was determined. Furthermore, the proportion of myofibres with centralized nuclei, as a marker of muscle regeneration, in the muscle of COPD patients was identified by immunofluorescence.ResultsImprinted miRNAs (miR-675 and from a cluster, C19MC which includes miR-519a) were differentially expressed in the quadriceps of patients with a low fat-free mass index (FFMI) compared to those with a normal FFMI. In larger cohorts, miR-675 and its host gene (H19) were higher in patients with a low FFMI and strength. The association of miR-519a expression with FFMI was present in male patients with severe COPD. Similar associations of miR expression with lean mass and strength were not observed in healthy community dwelling older men participating in the Hertfordshire Sarcopenia Stu

Journal article

Patel MS, Lee J, Baz M, Wells CE, Bloch S, Lewis A, Donaldson AV, Garfield B, Hopkinson NS, Natanek SA, Man W, Wells D, Baker EH, Polkey MI, Kemp Pet al., 2015, Growth differentiation factor-15 is associated with muscle mass in chronic obstructive pulmonary disease and promotes muscle wasting in vivo, Journal of Cachexia, Sarcopenia and Muscle, Vol: 7, Pages: 436-448, ISSN: 2190-6009

BackgroundLoss 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.MethodsWe determined the expression of GDF-15 in the serum and muscle of patients with COPD and analysed the association of GDF-15 expression with muscle mass and exercise performance. To determine whether GDF-15 had a direct effect on muscle, we also determined the effect of increased GDF-15 expression on the tibialis anterior of mice by electroporation.ResultsGrowth differentiation factor-15 was increased in the circulation and muscle of COPD patients compared with controls. Circulating GDF-15 was inversely correlated with rectus femoris cross-sectional area (P < 0.001) and exercise capacity (P < 0.001) in two separate cohorts of patients but was not associated with body mass index. GDF-15 levels were associated with 8-oxo-dG in the circulation of patients consistent with a role for oxidative stress in the production of this protein. Local over-expression of GDF-15 in mice caused wasting of the tibialis anterior muscle that expressed it but not in the contralateral muscle suggesting a direct effect of GDF-15 on muscle mass (P < 0.001).ConclusionsTogether, the data suggest that GDF-15 contributes to the loss of muscle mass in COPD.

Journal article

Garfield B, Shao D, Crosby A, Yang P, Morrell N, Polkey M, Kemp P, Wort SJet al., 2015, THE ROLE OF GROWTH AND DIFFERENTIATION FACTOR 15 IN SMOOTH MUSCLE CELL PROLIFERATION IN PULMONARY HYPERTENSION, Winter Meeting of the British-Thoracic-Society, Publisher: BMJ PUBLISHING GROUP, Pages: A213-A214, ISSN: 0040-6376

Conference paper

Paul RG, Polkey MI, Kemp PR, Griffiths MJDet al., 2015, GDF-15, THE MIR-542 CLUSTER AND MIR-422A ARE ASSOCIATED WITH MUSCLE WASTING IN INTENSIVE CARE UNIT ACQUIRED PARESIS, Winter Meeting of the British-Thoracic-Society, Publisher: BMJ PUBLISHING GROUP, Pages: A66-A67, ISSN: 0040-6376

Conference paper

Bloch SAA, Donaldson AVJ, Lewis A, Banya WAS, Polkey MI, Griffiths MJD, Kemp PRet al., 2015, MiR-181a: a potential biomarker of acute muscle wasting following elective high-risk cardiothoracic surgery, Critical Care, Vol: 19, ISSN: 1364-8535

Journal article

Garfield B, Crosby A, Pieran Y, Jen L, Shao D, Parfitt L, Harries C, Morrell N, Polkey M, Kemp P, Wort SJet al., 2015, The role of growth and differentiation factor 15 (GDF-15) in the development of skeletal muscle wasting in pulmonary arterial hypertension (PAH), Publisher: EUROPEAN RESPIRATORY SOC JOURNALS LTD, ISSN: 0903-1936

Conference paper

Kemp P, Lee JY, lori O, Wells Det al., 2015, FHL1 activates myostatin signalling in skeletal muscle and promotes atrophy, FEBS Open Bio, Vol: 5, Pages: 753-762, ISSN: 2211-5463

Myostatin is a TGFβ family ligand that reduces muscle mass. In cancer cells, TGFβ signalling is increased by the protein FHL1. Consequently, FHL1 may promote signalling by myostatin. We therefore tested the ability of FHL1 to regulate myostatin function. FHL1 increased the myostatin activity on a SMAD reporter and increased myostatin dependent myotube wasting. In mice, independent expression of myostatin reduced fibre diameter whereas FHL1 increased fibre diameter, both consistent with previously identified effects of these proteins. However, co-expression of FHL1 and myostatin reduced fibre diameter to a greater extent than myostatin alone. Together, these data suggest that the expression of FHL1 may exacerbate muscle wasting under the appropriate conditions.Abbreviations FHL1, four and a half LIM domain protein 1; COPD, chronic obstructive pulmonary disease; TGF-β, transforming growth factor beta; MHC, myosin heavy chain; GDF-15, growth and differentiation factor 15; PAI-1, plasminogen activator inhibitor 1; TA, tibialis anterior; VEGF-C, vascular endothelial growth factor C

Journal article

Mohan D, Lewis A, Patel MS, Curtis KJ, Lee JY, Hopkinson NS, Wilkinson IB, Kemp PR, Polkey MIet al., 2015, Fiber Specific Signalling In Locomotor Muscle In Chronic Obstructive Pulmonary Disease (COPD), International Conference of the American-Thoracic-Society (ATS), Publisher: AMER THORACIC SOC, ISSN: 1073-449X

Conference paper

Bloch SAA, Lee JY, Syburra T, Rosendahl U, Griffiths MJD, Kemp PR, Polkey MIet al., 2014, Increased expression of GDF-15 may mediate ICU-acquired weakness by down-regulating muscle microRNAs, Thorax, Vol: 70, Pages: 219-228, ISSN: 0040-6376

Rationale The molecular mechanisms underlying the muscle atrophy of intensive care unit-acquired weakness (ICUAW) are poorly understood. We hypothesised that increased circulating and muscle growth and differentiation factor-15 (GDF-15) causes atrophy in ICUAW by changing expression of key microRNAs.Objectives To investigate GDF-15 and microRNA expression in patients with ICUAW and to elucidate possible mechanisms by which they cause muscle atrophy in vivo and in vitro.Methods In an observational study, 20 patients with ICUAW and seven elective surgical patients (controls) underwent rectus femoris muscle biopsy and blood sampling. mRNA and microRNA expression of target genes were examined in muscle specimens and GDF-15 protein concentration quantified in plasma. The effects of GDF-15 on C2C12 myotubes in vitro were examined.Measurements and main results Compared with controls, GDF-15 protein was elevated in plasma (median 7239 vs 2454 pg/mL, p=0.001) and GDF-15 mRNA in the muscle (median twofold increase p=0.006) of patients with ICUAW. The expression of microRNAs involved in muscle homeostasis was significantly lower in the muscle of patients with ICUAW. GDF-15 treatment of C2C12 myotubes significantly elevated expression of muscle atrophy-related genes and down-regulated the expression of muscle microRNAs. miR-181a suppressed transforming growth factor-β (TGF-β) responses in C2C12 cells, suggesting increased sensitivity to TGF-β in ICUAW muscle. Consistent with this suggestion, nuclear phospho-small mothers against decapentaplegic (SMAD) 2/3 was increased in ICUAW muscle.Conclusions GDF-15 may increase sensitivity to TGF-β signalling by suppressing the expression of muscle microRNAs, thereby promoting muscle atrophy in ICUAW. This study identifies both GDF-15 and associated microRNA as potential therapeutic targets.

Journal article

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