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Alzheimer disease (AD) is one of the most common neurodegenerative diseases, affecting middle-aged and elderly individuals worldwide. AD pathophysiology involves the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain, along with chronic neuroinflammation and neurodegeneration. Physical exercise (PE) is a beneficial non-pharmacological strategy and has been described as an ally to combat cognitive decline in individuals with AD. However, the molecular mechanisms that govern the beneficial adaptations induced by PE in AD are not fully elucidated. MicroRNAs are small non-coding RNAs involved in the post-transcriptional regulation of gene expression, inhibiting or degrading their target mRNAs. MicroRNAs are involved in physiological processes that govern normal brain function and deregulated microRNA profiles are associated with the development and progression of AD. It is also known that PE changes microRNA expression profile in the circulation and in target tissues and organs. Thus, this review aimed to identify the role of deregulated microRNAs in the pathophysiology of AD and explore the possible role of the modulation of microRNAs as a molecular mechanism involved in the beneficial actions of PE in AD.

Chagas disease (CD) affects approximately 6-7 million people worldwide, from which 30% develop chronic Chagas cardiomyopathy (CCC), usually after being asymptomatic for years. Currently available diagnostic methods are capable of adequately identifying infected patients, but do not provide information regarding the individual risk of developing the most severe form of the disease. The identification of biomarkers that predict the progression from asymptomatic or indeterminate form to CCC, may guide early implementation of pharmacological therapy. Here, six circulating microRNAs (miR-19a-3p, miR-21-5p, miR-29b-3p, miR-30a-5p, miR-199b-5p and miR-208a-3p) were evaluated and compared among patients with CCC ( n = 28), CD indeterminate form ( n = 10) and healthy controls ( n = 10). MiR-19a-3p, miR-21-5p, and miR-29b-3p were differentially expressed in CCC patients when compared to indeterminate form, showing a positive correlation with cardiac dysfunction, functional class, and fibrosis, and a negative correlation with ejection fraction and left ventricular strain. Cardiac tissue analysis confirmed increased expression of microRNAs in CCC patients. In vitro studies using human cells indicated the involvement of these microRNAs in the processes of cardiac hypertrophy and fibrosis. Our study suggests that miRNAs are involved in the process of cardiac fibrosis and remodeling presented in CD and indicate a group of miRNAs as potential biomarkers of disease progression in CCC.