BACE1 and Alzheimer disease: In human serum, the up-regulated miR-24-3 and down-regulated miR-193a-3p may promote neuronal apoptosis [48,49]; miR-4422-5p can target gamma-secretase-activating protein (GSAP) and beta-site APP-cleaving enzyme-1 (BACE1) to exacerbate Aβ formation [50,51]; the down-regulated miR-148a-3p can trigger the neurotoxicity of Aβ to the nervous system [52]; the reduced levels of miR-222, miR-223, miR-29c-3p, and miR-19b-3p in blood samples of AD patients, and the increased level of miR-501-3p, have the potential to predict the occurrence and progression of AD [53,54,55,56].