IRS2 and Alzheimer disease: Concerning AD, a recent hypothesis points towards the idea that AD is the “brain-type diabetes.” This is supported by decreased number or binding capacity of brain IR in both AD patients and mouse models, increased risk for type 2 diabetes in AD patients (and vice versa), and the accumulation of hyperphosphorylated tau in the CNS of IRS-2-disrupted mice, a model of type 2 diabetes.