IRS1 and Alzheimer disease: There is a growing interest in understanding the status and function of insulin signaling in AD brain, especially since defects in insulin, insulin receptor (IR), insulin receptor substrate (IRS-1)11 and, increased insulin-like growth factor-I (IGF-1) levels in astrocytes12,13 as well as decreased IGF-1/IGF-II levels14 have been reported in AD.