BACE1 and Alzheimer disease: Although we did not examine the enzymatic activity of these three enzymes including BACE1, IDE, and NEP, accumulating evidences have shown that the expression levels of production (BACE1) and degradation (IDE or NEP) enzymes of Aβ were consistently regulated with the enzymatic activities in the AD brains (Fukumoto et al. 2002; Austin et al. 2010; McAllister et al. 2010; Marwarha et al. 2017; Li et al. 2018).