Irisin – a myokine potentially bridging muscle and fat tissue in cachexia

1. Matsuo Y, Gleitsmann K, Mangner N, Werner S, Fischer T, Bowen TS, et al. Fibronectin type III domain containing 5 expression in skeletal muscle in chronic heart failure-relevance of inflammatory cytokines. J Cachexia Sarcopenia Muscle 2015;6:62–72. 2. Evans WJ, Morley JE, Argiles J, Bales C, Baracos V, Guttridge D, et al. Cachexia: a new definition. Clin Nutr 2008;27:793–799. 3. von Haehling S, Lainscak M, Springer J, Anker SD. Cardiac cachexia: a systematic overview. Pharmacol Ther 2009;121: 227–252. 4. von Haehling S. The wasting continuum in heart failure: from sarcopenia to cachexia. Proc Nutr Soc 2015;12:1–11. 5. Josiak K, Jankowska EA, Piepoli MF, Banasiak W, Ponikowski P. Skeletal myopathy in patients with chronic heart failure: significance of anabolic-androgenic hormones. J Cachexia Sarcopenia Muscle 2014;5:287–296. 6. Loncar G, Fulster S, von Haehling S, Popovic V. Metabolism and the heart: an overview of muscle, fat, and bone metabolism in heart failure. Int J Cardiol 2013;162:77–85. 7. Nedergaard A, Sun S, Karsdal MA, Henriksen K, Kjaer M, Lou Y, et al. Type VI collagen turnover-related peptides-novel serological We read with great interest the recent article reporting muscle atrophy in heart failure animal models by Matsuo et al. Cachexia is characterized by loss of muscle mass with or without fat mass. Also, in patients with heart failure, muscle, fat and even bone loss were shown and reported to be associated with worse outcome. Although studies in muscle wasting attract much attention in heart failure, cross-talk among these three different tissues has been increasingly investigated and discussed as Matsuo et al. stated them in Introduction of this article. Large number of muscle biomarkers are in development and mentioned in several issues of Journal of Cachexia, Sarcopenia and Muscle. Under these circumstances, myokines including irisin, myostatin, interleukin-6, follistatin, and so on, which are produced by muscle tissue and affect other organs, are highlighted as both biomarkers and hormonal substances, which may have therapeutic implication. Irisin has been investigated as a key myokine, which has a bridging potential between muscle and fat. There are a number of articles reporting the plasma levels of irisin in patients with diabetes, chronic kidney disease, and myocardial infarction. However, there is almost no data about irisin levels in heart failure patients. In addition, recent reports have just been casting some doubt on the detection methods for human plasma irisin. In this context, further clinical studies in heart failure patients performed with improved assays are needed.