FA is elevated in the brains (He et al., 2010; Tong et al., 2011) and urine (Chen F. et al., 2022) of AD patients, in the brains of aged rats (Tong et al., 2013b), APP/PS1 mice (Yue et al., 2019) that expresses APP and a mutant human presenilin 1 (Lok et al., 2013), and in ALDH2–/– null mice (Tan et al., 2018; Ai et al., 2019). Here, ALDH2 is linked to Alzheimer disease.