RESUMEN
OBJECTIVE: Irisin is a muscle-secreted protein released into the circulation by cleavage of fibronectin type III domain containing protein 5(FNDC5). Since its discovery in 2012, it has been the subject of many researches due to its physiological role. It is believed that understanding irisin's function may be the key to comprehend many diseases and their development. The aim of this study is to perform a systematic review in order to establish whether there is an association of irisin's levels with obesity, diabetes mellitus, non-alcoholic steatohepatitis, chronic kidney disease and cancer in terms of prognosis. MATERIALS AND METHODS: The articles that support these findings were selected from Medline using the keyword "irisin" and filtered with "humans only". The selected articles were in English and with abstract. RESULTS: Higher baseline irisin concentrations are associated with greater reductions in glycemia and insulinemia after weight loss in obese subjects. Besides, it was observed that macrovascular disease, a complication of diabetes, was developed when there were lower levels of irisin. In addition, although not statistically significant, high levels of irisin were associated with portal inflammation and severity of histological lesions. Its concentrations decreased with increasing chronic kidney disease stage, and they were not only independently and positively predicted by renal function and insulin resistance but also associated with sarcopenia and carotid atherosclerosis in patients undergoing peritoneal dialysis. Regarding cancer, irisin reduced the proliferation, viability and migration of malignant breast cells. Finally, it is also related to bone health once its concentration is associated with previous osteoporotic fractures. CONCLUSIONS: In every condition studied, irisin's concentrations were related to the development of the disease.