Therefore, since there is no previous data associating irisin plasma levels in T2DM in children and adolescents and considering the findings in the adult population, the lower irisin levels found in our cohort could be attributed to a reduced PGC-1α activity in muscle tissue with a consequent decrease in FNDC5 and irisin expression. This evidence concerns the gene PPARGC1A and type 2 diabetes mellitus.