MiR-29a, miR-29b-1, miR-29c, and miR-339-5p, which regulate BACE1, were found downregulated in AD, leading to BACE1 upregulation, with increased APP cleavage and Aβ accumulation in vitro, in vivo, and in the AD patients’ brain [61,159,160]. Here, APP is linked to Alzheimer disease.