PSEN1 and Alzheimer disease: In the specimens of AD patients and the APP/PS1 double transgenic mouse model, the α-secretase of the non-amyloidogenic pathway of APP is decreased, and the β-secretase of the amyloidogenic pathway of APP is increased, and the Aβ-degrading enzyme is decreased, which could lead to an imbalance in the production and degradation of Aβ (Holsinger et al., 2002; Kummer et al., 2012; Sogorb-Esteve et al., 2018; Yang et al., 2018; Sun et al., 2019b).