The role of microRNAs in regulating inflammation and exercise-induced adaptations in rheumatoid arthritis

Lay Summary What does this mean for patients? In this review, we look at the role of microRNAs in rheumatoid arthritis (RA) and how exercise might affect them. MicroRNAs are very small molecules that travel around the body and help in a lot of biological functions, such as how cells work, when they multiply and when they die. In RA, many of these microRNAs are dysregulated (i.e. their levels might be different from those in people without RA). This might be associated with some of the symptoms of RA, such as joint pain and swelling, inflammation and disease activity. Exercise also affects microRNAs. After we have exercised, circulating levels of some microRNAs can increase, whereas others decrease. These changes help us to get fitter. What is currently not known is how microRNAs change when people with RA exercise. We believe that understanding this will help us to develop better exercise programmes that will improve health and overall quality of life for people with RA. MicroRNAs (miRNAs) are endogenously generated single-stranded RNAs that play crucial roles in numerous biological processes, such as cell development, proliferation, differentiation, metabolism and apoptosis. They negatively regulate target gene expression by repressing translation of messenger RNA into a functional protein. Several miRNAs have been implicated in the development and progression of RA. They are involved in inflammatory and immune processes and are associated with susceptibility to RA and disease activity. They are also considered to be potential markers of disease activity or even therapeutic targets. Likewise, several miRNAs are affected acutely by exercise and regulate exercise-related adaptations in the skeletal muscle and cardiovascular system and aerobic fitness. Interestingly, some miRNAs affected by exercise are also important in the context of RA. Investigating these might increase our understanding of the effects of exercise in RA and improve exercise prescription and, potentially, disease management. In this review, we focus on the miRNAs that are associated with both RA and exercise and discuss their roles in (and potential interactions between) RA and exercise-induced adaptations.