Irisin is a recently discovered exercise-induced myokine，which is secreted by skeletal muscles and produced by cleavage of the FNDC5. Studies show that Irisin stimulates mitochondria uncoupling protein-1 (UCP-1; a regulator of thermogenic capability of brown fat) expression，so Irisin can upregulate white to brown fat conversion and improve systemic metabolism by increasing energy expenditure. Hence，Irisin is a potential new drug target in the study of metabolic disorders，such as obesity and type 2 diabetes mellitus (T2DM). Moreover，FNDC5-like receptors are conserved in vertebrates and critical for neuronal development.
