Downregulated serum miR-223 servers as biomarker in Alzheimer's disease.

Alzheimer's disease (AD) is an age-related neurodegenerative disorder that is characterized by progressive memory loss and deteriorated higher cognitive functions. An economical, rapid and noninvasive biomarker for AD has not been identified. We aimed to investigate the diagnostic value of serum miR-223 and miR-519 in AD. The expressions of miR-223 and miR-519, with previously reported AD-associated miR-29 and miR-125b, were measured by quantitative reverse transcription polymerase chain reaction in the serum of 84 probable sporadic AD patients (age onset > 65 years) and 62 healthy control populations in China. Analyses were undertaken to assess the specificity and sensitivity of miRNAs to predict AD. In addition, the relationship between miRNAs and mini mental state examination (MMSE) scores in AD patients was also assessed. Serum miR-29, miR-125b and miR-223 were significantly decreased, but serum miR-519 was significantly increased in AD patients compared with healthy blood donors. In addition, serum miR-223 was strongly positively correlated with MMSE score in AD patients but serum miR-519 was not. Importantly, the receiver operating characteristic (ROC) result of serum miR-223 for prediction of AD was 0.786, higher than those of serum miR-29 (0.734) or miR-125b (0.726). The combination of serum miR-223 and miR-125b gave improved sensitivity/specificity for AD prediction (area under the ROC curve, 0.879) than either miRNA alone. Our preliminary findings indicate that serum miR-223 might be a potential biomarker for AD evaluation.