Hormones and Antiaging Medicine: Insulin and Antiaging

The signaling of insulin or its similar IGF-1 (insulin-like growth factor-1) is a positive regulator of cell proliferation, reproduction, and metabolism, and the signaling pathway is conserved from nematodes to mammals (Fig. 50.1). In nematodes and flies, it is thought to suppress stress resistance through various mechanisms. In nematodes and flies, although there are multiple insulin-like peptides (ILPs), orthologs of insulin or IGF-1, including those that show inhibitory effects on receptors, it is thought that a single receptor mediates both metabolic and proliferative effects, unlike in mammals. However, it is not entirely clear how these are regulated. On the other hand, in mammals, insulin mainly has a metabolic effect, and IGF-1 has a cell proliferative effect, but the two are somewhat complementary. This is thought to be because each hormone can bind not only to its own receptor, such as the insulin receptor (IR) or the IGF-1 receptor (IGF-1R), but also to different receptors with low affinity, and the two types of receptors can form hybrid receptors.