For example, (1) insulin receptors (IRs) in the brain have been shown to be downregulated in AD models [8]; (2) the impairment of insulin signaling has been documented in the brain from both postmortem analysis of AD patients and in animal models of AD [6,7,8,9]; and (3) the deficit of memory function in AD patients has been shown to be associated with altered levels of circulating insulin, insulin levels in the brain, and defects in peripheral insulin signaling pathways [4,5,10]. Here, INS is linked to Alzheimer disease.