Are circulating microRNAs peripheral biomarkers for Alzheimer's disease?

Abstract

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by memory loss, multiple cognitive abnormalities and intellectual impairments. Currently, there are no drugs or agents that can delay and/or prevent the progression of disease in elderly individuals, and there are no peripheral biomarkers that can detect AD early in its pathogenesis. Research has focused on identifying biomarkers for AD so that treatment can be begun as soon as possible in order to restrict or prevent intellectual impairments, memory loss, and other cognitive abnormalities that are associated with the disease. One such potential biomarker is microRNAs that are found in circulatory biofluids, such as blood and blood components, serum and plasma. Blood and blood components are primary sources where miRNAs are released in either cell-free form and then bind to protein components, or are in an encapsulated form with microvesicle particles. Exosomal miRNAs are known to be stable in biofluids and can be detected by high throughput techniques, like microarray and RNA sequencing. In AD brain, enriched miRNAs encapsulated with exosomes crosses the blood brain barrier and secreted in the CSF and blood circulations. This review summarizes recent studies that have identified miRNAs in the blood, serum, plasma, exosomes, cerebral spinal fluids, and extracellular fluids as potential biomarkers of AD. Recent research has revealed only six miRNAs–miR-9, miR-125b, miR-146a, miR-181c, let-7g-5p, and miR-191-5p – that were reported by multiple investigators. Some studies analyzed the diagnostic potential of these six miRNAs through receiver operating curve analysis which indicates the significant area-under-curve values in different biofluid samples. miR-191-5p was found to have the maximum area-under-curve value (0.95) only in plasma and serum samples while smaller area-under-curve values were found for miR-125, miR-181c, miR-191-5p, miR-146a, and miR-9. This article shortlisted the promising miRNA candidates and discussed their diagnostic properties and cellular functions in order to search for potential biomarker for AD.

A critical evaluation of neuroprotective and neurodegenerative MicroRNAs in Alzheimer's disease

“…miRNAs play a central role in the post-transcriptional regulation of gene expression [20,22]. In mammals, miRNAs are believed to control about 50% of all protein-coding genes [23].…”

“…Recent molecular biology discoveries (Kumar and Reddy 2016) have revealed a notable number of miRNAs in peripheral tissues, such as serum, plasma, ECF and CSF [20]. The levels of miRNAs in these fluids change with age, body physiology, diet, and disease state.…”

“…Recently, Kumar and Reddy (2016) assessed miRNAs in the blood and CSF from patients with AD in order to inform the development of miRNAs as possible peripheral biomarkers for AD [20]. They found a small number of changes in miRNAs associated with cognition in non-demented healthy humans and in humans with mild cognitive impairment and with AD.…”

“…Well-studied miRNAs in human diseases include cancer [9,10], cardiovascular diseases [11], hypertension [12], nephropathy [13], stroke [14], and neurodegenerative diseases such as schizophrenia [15], Huntington’s [16], Parkinson’s [17], and AD [18–20]. …”

Epigenetic Alterations in Aging and Aging-Associated Diseases: Review

“…Alzheimer miR-26b-3p, miR-28-3p, miR-30c-5p, miR-30d-5p, miR-148b-5p, miR-151a-3p, miR-186-5p, [69,70] miR-425-5p, miR-550a-5p, miR-1468, miR-4781-3p, miR-5001-3p, and miR-6513-3p seviyesinin artması, let-7a-5p, let-7e-5p, let-7f-5p, let-7g-5p, miR-15a-5p, miR-17-3p, miR-29b-3p, miR-98-5p, miR-144-5p, miR-148a-3p, miR-502-3p, miR-660-5p, miR-1294, and miR-3200-3p mir-103, mir-107 seviyesinin azalması Parkinson mir-34b, mir-34c aberasyonu, miR-10b-5p [71,72] Şizofreni mir-132, miR-195, miR-212 [73] Epilepsi mir-34a, mir-194-5p, mir-301a-3p, mir-30b-5p, mir-342-5p, mir-4446-3p [74,75] Miyokard İnfarktüsü miR-17, mir-19, mir-92a, mir-126, mir-133a, mir-145, mir-155, mir-208a [73] Obezite miR-17-5p, miR-34a, miR-99a, miR-100, miR-125b, miR-130b, miR-132, miR-134, miR-143, [76,77] miR-145, miR-181a, miR-185, miR-197, miR-210, miR-221…”