Effect of endurance training on skeletal muscle myokine expression in obese men: identification of apelin as a novel myokine.

1] Inserm, UMR1048, Obesity Research Laboratory, I2MC, Institute of Metabolic and Cardiovascular Diseases, Toulouse, France [2] University of Toulouse, UMR1048, Paul Sabatier University, Toulouse, France.
International journal of obesity (2005) (Impact Factor: 5.22). 08/2013; DOI: 10.1038/ijo.2013.158
Source: PubMed

ABSTRACT IntroductionIt has been suggested that metabolic benefits of physical exercise could be mediated by myokines. We examined here the effect of exercise training on skeletal muscle expression of a panel of myokines in humans. Pathways regulating myokine expression were investigated in human myotubes.Methods
Eleven obese non diabetic male subjects were enrolled in an 8-week endurance training program. Insulin sensitivity was assessed by oral glucose tolerance test. Subcutaneous adipose tissue and Vastus Lateralis muscle biopsies were collected before and after training. RNAs were prepared from adipose tissue and skeletal muscle. Primary culture of myoblasts was established.ResultsAs expected, exercise training improved aerobic capacity and decreased fat mass. No significant change in interleukin 6, fibroblast growth factor 21, myostatin or irisin mRNA level was found in muscle after training. A 2-fold increase in apelin mRNA level was found in muscle but not in adipose tissue. No change in circulating myokine and adipokine plasma levels was observed in the resting state in response to training. Interestingly, apelin was significantly expressed and secreted in primary human myotubes. Apelin gene expression was up-regulated by cyclic AMP and calcium unlike the other myokines investigated. Importantly, muscle apelin mRNA levels were positively related to whole-body insulin sensitivity.Conclusion
Collectively, our data show that exercise training up-regulates muscle apelin expression in obese subjects. Apelin expression is induced by exercise signalling pathways and secreted in vitro in human primary myotubes, and may behave as a novel exercise-regulated myokine with autocrine/paracrine action.International Journal of Obesity accepted article preview online, 27 August 2013. doi:10.1038/ijo.2013.158.

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May 27, 2014