APP and Alzheimer disease: In addition, APOE ε4 had a greater effect than other APOE alleles on enhancing APP transcription, promoting transformation of Aβ peptide into neurotoxic Aβ oligomer and fibrils, prolongating half‐life of Aβ and inhibiting enzymatic degradation of Aβ in the brain of AD animal models33, 34 and AD patients.8