Patterns of circulating piRNAs in the context of a single bout of exercise: Potential biomarkers of exercise-induced adaptation?

Background. Physical activity induces a range of physiological and molecular adaptations, particularly affecting skeletal muscle and the cardiovascular system, regulating both tissue architecture and metabolic pathways. Emerging evidence suggests that PIWI-interacting RNAs (piRNAs) may serve as potential biomarkers for these adaptations. Methods. This study selected eight participants of the iReAct study (DRKS00017446) for piRNA analysis. Baseline assessments included demographic profiling and fitness evaluation, particularly maximal oxygen uptake (V̇O2max) assessment. In addition, blood samples were collected pre and post a standard reference training session. Subsequently, subjects underwent 6-week training protocols, employing standardized high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) regimens. RNA sequencing was conducted to identify differentially expressed piRNAs, and correlation analyses were performed between piRNA expression patterns and training-associated changes in V̇O2max. Different screening procedures were applied to identify piRNAs potentially of interest in the context of exercise. Results. Specific piRNAs exhibited characteristic changes in expression levels in response to exercise. There were no significant correlations of piRNA patterns with changes in V̇O2max, but some interesting trends, that might be verified in larger studies. Conclusions. This hypothesis-generating study identifies characteristic piRNA patterns in the context of exercise. Their significance as biomarkers is yet to be determined.