INS and Alzheimer disease: Growing evidence, mainly from in vivo experiments, reported that an altered mitochondrial bioenergetics in the brain occurred in association with brain insulin resistance, with an overproduction of mitochondrial reactive oxygen species, along with mitochondrial depolarization and swelling, and that these two events could lead to the development of cognitive decline and AD [105] (Fig. 2), so that AD is now emerging as type III diabetes mellitus [18].