AKT1 and obesity due to melanocortin 4 receptor deficiency: To test whether glucose intolerance was the outcome of a metabolic imbalance, we selected two metabolic sensors associated with insulin resistance and obesity (the kinases AKT and mTOR), and two proteins associated with glycogen synthesis, glycogen synthase kinase-3 (GSK-3) and glycogen synthase (GS) (Supplementary Figure S1).