STAT3 and obesity due to melanocortin 4 receptor deficiency: Investigations of Theurich et al. revealed that obesity is associated with an increase of an IL-6/Stat3-dependent expansion of a distinct IL-6Ra- and Csf1r (colony stimulating factor 1 receptor)-expressing NK cell subpopulation in mice and humans, which are important mediators of metaflammation and insulin resistance (84).