Neuronal Enriched Extracellular Vesicle miR-122-5p as a Potential Biomarker for Alzheimer's Disease.

Alzheimer's disease (AD) is the leading cause of dementia and is often prefaced by mild cognitive impairment (MCI). Detection of AD-related changes via blood-based biomarkers would enable critical therapeutic interventions early in disease progression. Neuronal enriched extracellular vesicle (NEEV) miRNAs regulate peripheral genes as a response to early AD brain changes and hence may have biomarker potential. Plasma NEEVs were captured from plasma samples of Mexican Americans (MAs) and Non-Hispanic Whites (NHWs) using an antibody against the neuronal surface marker CD171. miRNAs isolated from NEEVs were sequenced and analyzed using miRDeep2/DEseq2 and QIAGEN RNA-seq portal for differential expression between cognitively impaired (CI) and cognitively unimpaired controls. hsa-miR-122-5p was significantly underrepresented in the CI group in both MAs and NHWs compared to the healthy control. Other population-specific miRNAs (MAs: hsa-miR-26a-5p, hsa-let-7f-5p, and hsa-miR-139-5p, NHWs: hsa-miR-133a-3p, hsa-miR-125b-5p, and hsa-miR-100-5p) identified may have biomarker potential in AD precision medicine. Some of these differentially expressed miRNAs were associated with key AD-related comorbidities such as APOE genotype, age, and metabolic burden and were predicted to target genes within NF-κB -regulated inflammatory pathways. Together, these findings suggest that dysregulated miRNA networks may serve as a mechanistic link between comorbidity burden and AD-related neuroinflammation and neurodegeneration.