Peripheral Blood MicroRNA Expression Profiles in Alzheimer's Disease: Screening, Validation, Association with Clinical Phenotype and Implications for Molecular Mechanism

A series of investigations have been performed regarding microRNA (miRNA, miR) of Alzheimer's disease (AD) patients. However, most of these used microarray with neither validation by PCR nor any follow-up on the biological mechanism implicated by findings. Further, there were rarely any analyses linking clinical phenotype of de novo, drug-naive patients to cellular pathogenic mechanism(s) to date. Microarray screening followed by validation via quantitative PCR (Q-PCR) assays and the relationship between miRNAs and phenotypic indices were evaluated. Additionally, the cellular mechanism of miRNAs through effects of beta-site amyloid precursor protein (APP) cleaving enzyme (BACE1) was assessed. We identified 2 specific differentially expressed (DE) miRNAs (miR-339 and miR-425) as potential diagnostic biomarkers for AD and revealed that these DE miRNAs could be involved in modulating the pathogenesis of AD via BACE1 protein inhibition. The findings presented here reveal a detailed snapshot of the profile of peripheral blood mononuclear cells (PBMC) miRNA changes in AD patients, association with clinical phenotype, and potential roles in cellular pathogenesis.