Importantly, due to insulin resistance and elevated ratio of glucagon/insulin in obesity and T2DM [159,160,161,162], lipolysis would be increased in adipose tissue and a glycerol flux to the liver would occur, glycerol will be used as a preferred gluconeogenic precursor (Figure 4) [170]. The gene discussed is GCG; the disease is obesity due to melanocortin 4 receptor deficiency.