Irisin, encoded by the FNDC5 (fibronectin type III domain containing 5) gene, is a novel myokine that has been implicated as an essential mediator of exercise benefits. Effects of irisin on heart physiology is still ambiguous. This study aimed to evaluate the impact of exogenous administration of irisin on heart physiology and the pharmacokinetic profile of pump-administered irisin. To do so, Sprague Dawley rats were implanted with an irisin-loaded osmotic pump (5 μg/kg/day) for 42 days, and other animals were administered with single bolus subcutaneous injections of irisin (5 µg/kg). Body weights and blood samples were collected weekly for 42 days for serum irisin quantification and histopathology. Clinical biochemistry analyses were performed. Heart mRNA expression was assessed in 26 selected genes. Chronic interventional exogenous irisin significantly reduced body weight without affecting the heart myocyte size and significantly reduced creatine kinase enzyme level. Blood CBC, serum biochemistry, and heart morphology were normal. Gene expression of FNCD5, Raf1, CPT1, IGF-1, and CALCIN, encoding for heart physiology, increased while PGC1, Nox4, and Mfn1 significantly decreased. Nevertheless, irisin increased the expression of cardioprotective genes and inhibited some genes that harm heart physiology. Administration of irisin promotes myocardial functions and could be translated into clinical settings after preclinical profiling.
Keywords: gene expression; heart physiology; irisin; myocytes.