MicroRNAs (miRNAs) are short and noncoding RNA fragments that bind to the messenger RNA. They have different roles in many physiological or pathological processes. MicroRNA-21, one of the first miRNAs discovered, is encoded by the MIR21 gene and is located on the chromosomal positive strand 17q23.2. MicroRNA-21 is transcribed by polymerase II and has its own promoter sequence, although it is in an intron. It is intra-and extracellular and can be found in many body fluids, alone or combined with another molecule. It regulates many signalling pathways and therefore plays an important role in the cardiovascular system. Indeed, it is involved in the differentiation and migration of endothelial cells and angiogenesis. It contributes to the reconstruction of a myocardial infarction, and it can also act as a cellular connector or as an antagonist to cardiac cell apoptosis. By playing all these roles, it can be interesting to use it as a biomarker, especially for cardiovascular diseases.

Introduction The aim of work is to assess the usefulness of oxidative stress parameters in the differential diagnosis of dementia of the Alzheimer’s type and dementia of the Alzheimer’s type with coexisting depression. Methods The study involved three groups of people: patients with Alzheimer’s disease (AD) (AD; N=27), patients with Alzheimer’s disease and depression (D) (AD+D; N=30), and a control group that consisted of people without dementia and without depression (C; N=24). The assessment of cognitive functioning was carried out using among alia, Auditory Verbal Learning Test and Verbal Fluency Test. Furthermore, we determined the activity of superoxide dismutase (SOD-1) and superoxide anion radical. Results Multiple models with different combinations of independent variables showed that SOD together with Rey delayed recall were the best significant predictors of AD with the area under curve (AUC) of 0.893 (p = 0.001) and superoxide anion radical (O2 •− ) together with verbal fluency – sharp objects were the best significant predictors of AD +D diagnosis with the AUC of 0.689 (p = 0.034). Conclusion This study confirmed the value of neuropsychological diagnosis and analysis of oxidative stress markers in the diagnosis of AD and major depressive disorder (MDD) in the course of AD. The combination of the use of biochemical markers and neuropsychological tests seems particularly important for differential diagnosis.