Development of new biomarkers in alzheimer?s disease: MicroRNA analysis from serum

Alzheimer?s disease (AD) is the most common form of dementia in elderly. It?s characterized by progressive deterioration of cognitive functions. In clinic, current criteria for diagnosis of AD are still largely based on the exclusion of secondary causes and other dementive disorders. The golden standard of diagnosis is the identification of typical neuropathological changes in the brain of a patient who has suffered from clinical AD. These neuropathological changes are progressive synaptic and neuronal loss, presence of extracellular beta-amyloid plaques and intracellular neurofibrillary tangels contining hyperphosphorylated tau protein. Studies have shown that the accuracy of clinical diagnosis is between 65% and 96%. In view of this, the need for spesific AD marker is great. Biomarker research for AD are doing in peripheral blood samples, because that obtaining cerebrospinal fluid (CSF) sample is difficult and brain alternations in Alzheimer?s disease could be observed in peripheral blood.MicroRNAs (miRNAs) are non-coding, small RNAs which are post-transcriptional regulator of gene regulation. miRNAs can regulate gene expression through messenger RNA (mRNA) degradation or translation repression. It?s thought that miRNAs have a role in development, plasticity and neurodegeneration of the nervous system. Although dysregulation of miRNA expression has been characterized mostly in cancer, it has recently been studied in many other diseases. Specifically, miRNAs have been proposed as regulators of immune cell development, playing roles in the inflammatory response, and as key players in the pathogenesis of neurodegenerative diseases. Recent studies suggested circulating miRNAs as new diagnostic and prognostic biomarkers of diseases, because of their high stability in circulation and correlation compared to tissue profiles.In this study, we searched for miRNA expression differences in serum samples of both AD (n=10) and controls (n=10). Up to date studies that focused on the expression changes of miRNAs from brain tissue of the AD showed that different miRNAs could play an important role in pathogenesis of AD and could be used as diagnostic markers for AD. In this study we searched the potential of circulating miRNAs as new class of biomarkers for AD. According to miRNA array analysis, 20 most significantly changed miRNAs are detected.Key Words: Alzheimer?s disease, microRNA, biomarker