MiRNAs during the aging process

As we age, the levels of expression of some miRNAs vary: they are either over-expressed or under-expressed. These changes affect their functions, and changes in their expression profile have been described in several diseases, including cancers. This is the case of miR-31, over-expressed in breast cancer cells, and probably responsible for the production of reactive species that damage DNA[8]. Another study[9] highlighted 158 deregulated miRNAs in humans associated with metabolic and signal transduction pathways involved in the pathogenesis of type 2 diabetes. These results suggest that these miRNAs may play a role in the development of the disease. In addition, abnormalities in the expression of multiple miRNAs are found in neurodegenerative diseases. Many miRNA levels are altered in the brains of Alzheimer’s disease patients, and more than 60 miRNAs are altered in the cerebrospinal fluid. It appears that some of these miRNAs contribute to the pathogenesis of Alzheimer’s disease by influencing the production of proteins that aggregate in cells, including proteins Aβ[10]. Aberrant levels of miRNA have also been found in the brains of Parkinson’s disease patients, including miR-133 and miR-34, as have 75 miRNA in Huntington’s syndrome[10]. Finally, aberrations in the expression level of miRNAs are found in most cardiovascular diseases, such as coronary heart disease, myocardial infarction and heart failure[11].

These differences in levels can also have positive consequences on longevity. It has been shown that in dwarf long-lived mice, miR-27α in the liver and miR-470, miR-669b and miR-681 in the brain are high[12]. These changes are measurable and their association with aging has led to a new concept: miRNAs can be used as biomarkers of aging. From the early 2000s to the present, knowledge of non-coding RNAs has evolved considerably, and over the past decade or so, many publications have highlighted the use of miRNAs as biomarkers. Recently, these studies have increased in humans, extending knowledge and applications on age-related human diseases, including cardiovascular diseases[11], cancers[12] and neurodegenerative diseases[13,14].