Fndc5/irisin is regulated by myogenesis stage, irisin, muscle type and training.

Objectives: Irisin, a novel myokine that responds to exercise, was initially identified as a regulator of fat tissue metabolism. We aimed to investigate fibronectin type III domain-containing protein 5 (Fndc5)/irisin, auto/para-crine role in different muscle fibers, different activities, and muscle cell differentiation.

Methods: Using , , and muscle models, Fndc5 was studied at the physiological and molecular levels.