MC4R and obesity due to melanocortin 4 receptor deficiency: It was recently reported that mice with homozygous Gαs deficiency in MC4R-expressing cells developed obesity due to both increased food intake and decreased energy expenditure, and the ability of the MC4R agonist MTII to stimulate energy expenditure as well as to inhibit food intake was significantly impaired in these animals (Podyma et al., 2018).