miR-133b is a potential diagnostic biomarker for Alzheimer's disease and has a neuroprotective role

MicroRNAs (miRNAs/miRs) are involved in post-transcriptional gene regulation and aberrant expression of miRNAs has been widely detected in various human diseases. The aim of the present study was to examine the serum levels of miR-133b in patients with Alzheimer's disease (AD), and to explore its diagnostic value and neuroprotective role in AD. Reverse transcription-quantitative PCR was applied to analyze the serum levels of miR-133b in 105 AD patients and 98 healthy controls. A cell model of AD was established by treating SH-SY5Y cells with amyloid beta (A beta)25-35, and the resulting effect on miR-133b expression was determined. Cell viability and apoptosis were also measured. A dual-luciferase assay was used to validate a target gene of miR-133b. Receiver operating characteristic (ROC) curve analysis was also applied to assess the specificity and sensitivity of miR-133b to diagnose AD. The results indicated that the serum levels of miR-133b were significantly downregulated in AD patients and SH-SY5Y cells treated with A beta 25-35 (all P<0.001). A positive correlation between the serum levels of miR-133b and the Mini-Mental State Examination score of AD patients was determined (r=0.8814, P<0.001). The area under the ROC curve for miR-133b regarding the diagnosis of AD was 0.907, with a sensitivity of 90.8% and specificity of 74.3% at the cutoff value of 1.70. Overexpression of miR-133b significantly attenuated the A beta 25-35-induced inhibition of cell viability (P<0.01) and induction of cell apoptosis (P<0.01). The luciferase reporter assay demonstrated that epidermal growth factor receptor (EGFR) is a target gene of miR-133b. In conclusion, miR-133b may serve as a novel diagnostic biomarker for AD and it may have a neuroprotective role in AD and targets EGFR.