Plasma microRNA vary in association with the progression of Alzheimer's disease

Early intervention in Alzheimer's disease (AD) requires the development of an easily administered test that is able to identify those at risk. Focusing on microRNA robustly detected in plasma and standardizing the analysis strategy, we sought to identify disease-stage specific biomarkers.Using TaqMan microfluidics arrays and a statistical consensus approach, we assessed plasma levels of 185 neurodegeneration-related microRNA, in cohorts of cognitively normal amyloid β-positive (CN-Aβ+), mild cognitive impairment (MCI), and Alzheimer's disease (AD) participants, relative to their respective controls.Distinct disease stage microRNA biomarkers were identified, shown to predict membership of the groups (area under the curve [AUC] >0.8) and were altered dynamically with AD progression in a longitudinal study. Bioinformatics demonstrated that these microRNA target known AD-related pathways, such as the Phosphoinositide 3-kinase (PI3K-Akt) signalling pathway. Furthermore, a significant correlation was found between miR-27a-3p, miR-27b-3p, and miR-324-5p and amyloid beta load.Our results show that microRNA signatures alter throughout the progression of AD, reflect the underlying disease pathology, and may prove to be useful diagnostic markers.