Regulation of Glial Function by Insulin Peptides

The best characterized insulin peptides (ILPs) in the brain are insulin and insulin-like growth factor I (IGF-I), with most attention given to their role in relation to neurons. With the advent of glial biology as a key player in brain physiology, actions of ILPs in glial function are now gradually emerging. Because of their time-honored role as neuronal adjuvants, most studies of ILPs in glia have been focused on astrocytes. For the other two major types of glial cells, oligodendrocytes and microglia, most studies dealt with IGF-I, while the potential role of insulin has been comparatively neglected. Due to the classical assignment of ILPs as neuroprotective agents, research has been biased toward their role in the response of glial cells to brain injury, while their impact on the physiological roles of glial cells is somewhat less studied. In this chapter, we will review the most significant recent observations in glial biology in health and disease that relate to insulin and IGF-I.