Androgen receptors blockage does not influence the expression of Irisin in myocardium of endurance trained rats

Abstract

Recently, skeletal muscle was identified as an endocrine organ that produces and releases myokines. These cytokines exert their effects in autocrine, paracrine, and endocrine manners and play an important role in driving adaptive changes to physical exercise. Irisin is a myokine considered as an `exercise protein`, which is a product of the transcriptional co-activator PGC-1α and is related to energy metabolism. Irisin was discovered in 2012 and there are very few experimental studies regarding its production by myocardium after endurance training while the role of androgens via their androgen receptors (AR) is not elucidated.The goal of the present study was to investigate the influence of androgens on Irisin expression in myocardium in endurance trained rats.Male Wistar rats were divided in two groups. The rats of one group were trained on treadmill with submaximal loading for 8 weeks and the other group was sedentary. Half of the trained and half of the sedentary rats were treated with an AR blocker Flutamide and the other half of the groups - with sesame oil for the same time period. At the end of the trial immunohistochemical reaction for Irisin was applied and morphometrically analyzed.Irisin expression was higher in the cardiomyocytes of left ventricle of both trained groups (P<0.001) in comparison with sedentary rats. Flutamide treatment had no significant effect.The results obtained show that AR blocker application did not influence Irisin expression in the cardiomyocytes, which indicates relative androgen independence of Irisin production in myocardium after endurance training. Probably, other signaling pathways, including p38 MAPK and extracellular-signal regulated kinase (ERK) are involved in the process of PGC-1α activation and Irisin secretion.