MTOR and obesity due to melanocortin 4 receptor deficiency: Indeed, the inositol phosphate multikinase (IPMK), which generates IP4 and IP5 and functions as a PI3K, has been implicated in growth and metabolism.44 Interestingly, in mice fed a high-fat diet, genetic ablation of the inositol hexakisphosphate kinase 1 (IP6K1), which produces the inositol pyrophosphate IP7, leads to insulin-sensitivity (normal blood glucose, despite decreased circulating insulin), and resistance to obesity.45 This effect is mediated by the action of IP7 as an inhibitor of the Akt and mTOR signaling downstream of insulin.