MAPT and Alzheimer disease: Previous studies suggested that these biometals may disrupt and retard the metabolism, and facilitate the aggregation, of β-amyloid (Aβ) peptide and tau protein (Ayton et al., 2013; Guo et al., 2013; Tong et al., 2014; Ward et al., 2014; Li et al., 2017; Takeda et al., 2017; Cheignon et al., 2018), but firm conclusions and mechanisms about the functional roles of these essential biometals in AD pathogenesis are not established.