The pathogenesis of AD is complex and unclear, but a large number of biological targets with potential therapeutic effects have been identified, such as Aβ, tau protein, cholinergic receptor, glutamate receptor, 5-hydroxytryptamine receptor, dopamine receptor, norepinephrine receptor, acetylcholinesterase, butyrylcholinesterase, α-, β-and γ-acetylcholinesterase, monoamine oxidase A, monoamine oxidase B, etc. (Hampel et al., 2018; Li et al., 2018; Long and Holtzman, 2019). Here, MAOA is linked to Alzheimer disease.