AD patients carrying the ApoE4 allele have been reported to express reduced IDE protein and mRNA levels in the hippocampus (Biessels et al., 2005; Schipper, 2011), suggesting a causal link between impaired insulin metabolism, either hypoinsulinemia or insulin resistance, and the pathogenesis of AD (Schipper, 2011). Here, INS is linked to Alzheimer disease.