ACE2 and Alzheimer disease: Within the brain, it has been reported that ACE2 can affect Aβ42 synthesis [91], and SARS-CoV-2 infection is also able to change the expression of ACE2 [106], suggesting the possibility of SARS-CoV-2 as an additional AD regulatory factor by controlling ACE2 expression and subsequently affecting neurotoxic forms of Aβ.