APP and Alzheimer disease: Among the complex etiology of AD, Aβ peptides are derived from the successive cleavage of the amyloid protein precursor (APP) by the β-APP cleaving enzyme 1 (BACE1), or β-secretase, and gamma (γ)-secretase enzyme to form Aβ aggregates that have the potential to develop into Aβ plaques (Li et al., 2000).