Circulating irisin concentrations decrease progressively with the worsening of glucose tolerance, are reduced in T2DM and are associated with compromised expression and secretion of irisin from skeletal muscle (Choi et al., 2013; Liu et al., 2013; Assyov et al., 2016; Shoukry et al., 2016). This evidence concerns the gene FNDC5 and type 2 diabetes mellitus.