In skeletal muscle, training-induced irisin regulates glucose metabolism by upregulating the AMPK pathway and GLUT-4 translocation [20], whereas FGF-21 enhances glucose uptake, GLUT-1, and phosphoinositide-3-kinase–protein kinase/Akt1 (PI3K/Akt1) [21,22], thereby preventing T2D. This evidence concerns the gene FGF21 and type 2 diabetes mellitus.