LETTERS TO THE EDITOR
doi:10.1093/eurjhf/hfq190
Myostatin serum levels in heart failure We have carefully read the interesting article of George et al.1 and found some similarities, but also some differences, compared with our results.2,3 We assessed myostatin (MYOS) and MYOS pro-peptide precursor (pro-MYOS) serum levels by commercial ELISA in 70 heart failure (HF) patients [30 NYHA class I–II and 40 class III–IV; 66% of ischaemic aetiology, 10% with dilated cardiomyopathy; left ventricular ejection fraction (LVEF) 31.9 + 12.3%] and analysed the relationship between these peptides and clinical parameters and prognosis.2,3 Similar to George et al.,1 we found no relationship between MYOS or pro-MYOS and clinical/ demographic variables such as age, sex, LVEF, body mass index, HF duration, and treatment. In addition, we found no relationship between MYOS or pro-MYOS and NYHA functional class. Furthermore, mortality was not related with the serum levels of these peptides during a mean follow-up of 17.9 + 1.3 months. In contrast, NT-proBNP and r2-TNF-alpha showed a highly significant relationship both with NYHA functional class and survival. Once more, no correlation was observed between these two markers and MYOS or pro-MYOS. We also assessed changes in MYOS serum levels over a median period of 225 days in 35 HF patients (NYHA functional class III, 94% and IV, 6%), and we found that changes in MYOS also showed no prognostic predictive value after a median follow-up of 893 days.4 In the absence of established normal levels of MYOS, we also analysed a pool of 11 healthy controls (63% male, mean age 66.9 + 9.8 years).3 In contrast to the findings observed by George et al.1 assessing latent complex serum levels in healthy controls and patients with dilated cardiomyopathy, our HF patients had lower MYOS and pro-MYOS levels than controls. It may be that latent complex levels assessed by western blot1 and MYOS serum levels determined by ELISA2 – 4 actually measure different fragments of the protein that have different implications. On the other hand, it remains unclear how much MYOS serum levels correlate with cardiac and/or peripheral muscle
tissue MYOS expression. As George et al. reported,1 we also observed very low propeptide levels in patients and healthy controls and found no correlation between MYOS and pro-MYOS. The absence of a relationship between serum MYOS and pro-MYOS levels and classical parameters of HF severity suggests that although this protein may actually participate in the muscle wasting secondary to HF, it cannot be considered a biomarker of HF severity. Further studies are needed to clarify the role of MYOS in HF patients.
References 1. George I, Bish LT, Kamalakkannan G, Petrilli CM, Oz MC, Naka Y, Sweeney HL, Maybaum S. Myostatin activation in patients with advanced heart failure and after mechanical unloading. Eur J Heart Fail 2010;12: 444 –453. 2. Zamora E, Lupo´n J, Simo´ R, Gala´n A, Urrutia A, Mas D, Gonza´lez B, Valle V. Myostatin serum levels in heart failure. Eur J Heart Fail 2008;7(suppl. 1):98 (abstract). 3. Zamora E, Simo´ R, Lupo´n J, Gala´n A, Urrutia A, Gonza´lez B, Mas D, Valle V. Serum myostatin levels in chronic heart failure. Rev Esp Cardiol 2010; 63:992 – 996. 4. Zamora E, Lupo´n J, Simo´ R, Gala´n A, Urrutia A, Mas D, Gonza´lez B, Valle V. Changes in myostatin serum levels and prognosis in heart failure. Eur J Heart Fail 2009;8(suppl. 2): ii492.
Elisabet Zamora 1,2 1
Unitat d’Insuficie`ncia Cardı´aca, Servei de Cardiologia, Hospital Universitari Germans Trias i Pujol, Crta. Canyet s/n, 08016 Badalona, Spain 2 Departament de Medicina, Universitat Auto`noma de Barcelona, Bellaterra, Barcelona, Spain
Josep Lupo´n 1,2 1
Unitat d’Insuficie`ncia Cardı´aca, Servei de Cardiologia, Hospital Universitari Germans Trias i Pujol, Crta. Canyet s/n, 08016 Badalona, Spain 2 Departament de Medicina, Universitat Auto`noma de Barcelona, Bellaterra, Barcelona, Spain
Rafael Simo´ 2,3 2
Departament de Medicina, Universitat Auto`noma de Barcelona, Bellaterra, Barcelona, Spain 3 Grupo de Investigacio´n en Diabetes y Metabolismo, Instituto de Investigacio´n Hospital Universitario Vall d’Hebro´n, Barcelona, Spain
Amparo Gala´n 2,4 2
Departament de Medicina, Universitat Auto`noma de Barcelona, Bellaterra, Barcelona, Spain
4 Servei de Bioquı´mica, Hospital Universitari Germans Trias i Pujol, Badalona, Spain Tel: +34 934 978 915; Fax: +34 934 978 939; Email:
[email protected]
doi:10.1093/eurjhf/hfq191
Myostatin serum levels in heart failure: reply We have read the letter from Dr Zamora et al. with great interest, comparing and contrasting the data from their study1 with that from ours2 with respect to serum myostatin levels in heart failure (HF). To our knowledge, these are the only two reports in the literature describing myostatin expression in HF patients. We would like to highlight important methodological differences between the two studies. In our study, we measured serum myostatin in patients diagnosed with HF of nonischaemic aetiology using western blot. The antibody used in our assay was raised against the N-terminal domain of myostatin and detected a predominant band at 75 kDa. This corresponds to the predicted size of the myostatin latent complex (two cleaved myostatin propeptides bound to C-dimer), which has been previously reported to circulate in mouse serum.3 We found that myostatin latent complex levels were increased in the serum of HF patients (n ¼ 28) compared with healthy controls (n ¼ 29). Dr Zamora et al. also measured serum myostatin in patients diagnosed with HF of mixed aetiology. They used two separate ELISA assays to measure serum myostatin. In the first assay, the antibody was raised against the N-terminal domain of myostatin and was therefore capable of detecting myostatin full-length precursor protein, myostatin latent complex, and free myostatin propeptide (dissociated from latent complex). In the second assay, the antibody was raised against myostatin full-length precursor protein and was therefore capable of detecting all forms of myostatin, including myostatin full-length precursor protein, myostatin latent complex, free myostatin propeptide, and free C-dimer. In contrast to our results, Zamora et al. found that serum myostatin levels in their HF patients (n ¼ 70), as measured by
Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2010. For permissions please email:
[email protected].
1380 both assays, were decreased compared with healthy controls (n ¼ 11). Zamora et al. found no association between myostatin levels and HF aetiology, so the difference in HF aetiology between the two studies is unlikely to explain the discordant results. As Zamora et al. note, it is possible that different results may have been obtained due to the fact that different assays were used to quantify myostatin in each study. The myostatin value obtained for each sample by ELISA represents a composite value, and the contribution of each form of myostatin is unknown. As proteins are separated by size via electrophoresis prior to western blot, western blot offers the advantage that each individual form of myostatin can be visualized and quantified. Another possibility is that the control myostatin value in Zamora’s study does not accurately
Letters to the Editor
reflect the true myostatin serum value in healthy humans due to sampling error associated with the small sample number. As described previously, we believe the isoforms of myostatin may have varying significance in the pathogenesis of HF; further investigation is needed to compare western blot and ELISA as methods of quantifying serum myostatin in HF and to define the relationship between myostatin and HF.
References 1. Zamora E, Simo R, Lupon J, Galan A, Urrutia A, Gonza´lez B, Mas D, Valle V. Serum myostatin levels in chronic heart failure. Rev Esp Cardiol 2010; 63:992 –996. 2. George I, Bish LT, Kamalakkannan G, Petrilli CM, Oz MC, Naka Y, Sweeney HL, Maybaum S. Myostatin activation in patients with advanced heart failure and
after mechanical unloading. Eur J Heart Fail 2010;12: 444 –453. 3. Lee SJ. Regulation of muscle mass by myostatin. Annu Rev Cell Dev Biol 2004;20:61–86.
Lawrence T. Bish Department of Physiology University of Pennsylvania Philadelphia PA 19104 USA Tel: +1 215 898 0046 Fax: +1 215 746 3884 Email:
[email protected]
Isaac George Department of Surgery Columbia University New York NY 10032 USA
