PPIB and early-onset autosomal dominant Alzheimer disease: IDE, originally known as the main enzyme involved in the cleavage of insulin as well as other amyloidogenic peptides, such as the β-amyloid (Aβ) peptide, eliminates Aβ’s neurotoxic effects, one of the hallmarks of Alzheimer’s disease (AD), which shows the relationship between IDE, diabetes, and AD [171,172].