APOE genetic variants and apoE, miR-107 and miR-650 levels in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative dementia in adults. Pathogenesis of AD depends on various factors, including APOE genetic variants, apolipoprotein E (apoE) phenotype and oxidative stress, which may promote both DNA and RNA damage, including non-coding RNA (ncRNA). Among ncRNAs, microRNA (miRNA) is known to contribute to pathologic processes in AD. The aim of the study was to analyse the plasma concentration of apoE by ELISA as well as the plasma levels of miR-107 and miR-650 by qPCR in relation to APOE genetic variants and clinical features including the age of onset and dementia severity in 64 AD patients and 132 controls. Our data showed that a low apoE plasma concentration was a risk factor for developing AD (OR = 5.18, p = 6.58E-06) and was particularly pronounced in severe dementia (p < 0.001) and correlated with cognitive functions (R = 0.295, p = 0.020), similarly as the level of miR-650 (R = 0.385, p = 0.033). The presence of APOE E4 allele in both AD patients and controls led to a reduction in apoE, while APOE E3/E3 genotype was associated with an increased apoE concentration and level of miR-107 in AD (p < 0.05) which was inversely correlated with the number of APOE E4 alleles (R = -0.448, p = 0.009). Additionally, patients with the onset at 60-69 years of age showed a reduced level of miR-107 (p < 0.05, as compared to AD above 80 years of age). Changed levels of plasma apoE, miR-107 and miR-650 may be a marker of the neurodegenerative process in the course of AD, associated with amyloid beta metabolism and inordinate cell cycle.