FNDC5 and type 2 diabetes mellitus: Although several metabolic glycemic control variables has been associated to FNDC5/ irisin levels, to our knowledge, it is the first time that neck circumference (a practice factor related to insulin resistance) (38) and a developing risk T2DM global index are inversely related to FNDC5/irisin levels, indicating, once again, that in humans, the levels of this peptides is fully combined with insulin resistance and glucose tolerance, as observed in animals and in vitro studies (1,39).