miR‐181b expression as a potential biomarker in Alzheimer’s Disease

Abstract Background Alzheimer’s Disease (AD) is a multifactorial neurodegenerative disorder with complex molecular pathophysiology at the cellular level. Despite intensive research to decipher genetic and molecular players, non‐invasive markers of early diagnosis and progression are yet to be discovered. MicroRNAs (miRNAs) regulate post‐transcriptional gene expression and hold the potential to act as biomarkers for disease prediction, diagnosis and prognosis. Identification of differentially expressed circulating miRNAs in late‐onset AD will serve for the establishment of non‐invasive biomarker panels for disease prediction at earlier ages. In this regard, miR‐181b may serve as a candidate molecule. Here we aimed to evaluate the expression pattern of hsa‐miR‐181b in the serum samples of late‐onset AD patients and healthy controls. Method Blood samples were collected from 33 late‐onset AD patients and 34 healthy individuals. Samples were processed immediately for plasma isolation and kept at ‐80°C. Following total RNA extraction and cDNA synthesis, expression levels of hsa‐miR‐181b‐5p were determined in all samples via qRT‐PCR using SyberGreen. Cel‐miR39 was used as a spike‐in control and all samples were processed in duplicates. Data were analyzed by the ∆∆C T method. p<0,05 was considered to be significant. Result The average ages of AD patients and healthy controls were 82 and 59 years, respectively. Females constituted 60% of the samples in both groups. Patients were being treated with Donepezil or Donepezil and Memantine. According to the qPCR results, miR181b levels were found to be significantly reduced by 3 folds in AD patients, compared to controls. Conclusion There are conflicting data in the literature regarding up or down regulation of miR181b in AD. This may be due to different experimental set‐ups, ethnicities of the study populations, sample characteristics or other confounding factors. To the best of our knowledge, this is the first study evaluating the expression pattern of miR181b in the plasma samples of Turkish AD patients. Our results indicate that hsa‐miR‐181b‐5p can be regarded as a potential blood biomarker for the prediction of AD. miR181 was shown to be involved in immune response regulation and neuroinflammation in the literature, therefore it is of high importance in AD.