FNDC5 and Insulin resistance: As another example of indirect evidence for effects of irisin on cardiac glucose metabolism, in an in vitro study, 500 μM of PA induced insulin resistance in the H9c2 cardiomyoblast cell line, while co-treatment with 200 ng/mL of irisin reversed it and significantly increased cellular insulin-stimulated glucose consumption by inhibiting autophagy through the PI3K/Akt signaling pathway [89].