When seleno-protein is found in high serum levels, it is associated with metabolic diseases, insulin resistance, and increased ROS via the activation of AMPK, and it influences the drop in concentrations of irisin, meteorin-like (METRNL), and β-aminoisobutyric acid (BAIBA), which consequently attenuates the loss of fat mass induced by physical exercises [11]. Here, FNDC5 is linked to metabolic disease.