Reduction in growth hormone (GH) and insulin-like growth factor (IGF) and increased insulin responsiveness correlate with the prolonged life and an apparent reduction in the aging process.31–33 IGFs, insulin receptors (INSR), and insulin receptor substrate-1 (IRS-1) could regulate insulin resistance as well as contribute to metabolic syndrome (Fig. 5). Here, IRS1 is linked to metabolic syndrome.