Purpose: Intensive exercise is known to be accompanied by a rapid release of cell-free DNA (cfDNA). The physiological significance of cfDNA release for performance diagnostics has not been studied. The authors analyzed the release of cfDNA during bicycle exercise and its correlation with physiological parameters.
Methods: Eleven male athletes performed an incremental cycling test. Venous blood was collected before and immediately after exercise and after 90 min of recovery. Since the amount of cfDNA is influenced by preanalytical parameters like DNA extraction and quantification method, the authors applied different measurement approaches based on quantitative real-time polymerase chain reaction. They compared a direct measurement procedure not requiring cfDNA extraction for a short (L1PA290) and a long fragment (L1PA2222) and a procedure for extracted cfDNA for a short (LTR570) and long fragment (LTR5323) with primers targeting the repetitive sequences L1PA2 and LTR5 in both assays, respectively.
Results: With the exception of LTR5323, the procedures revealed significant increases of cfDNA postexercise, whereas the direct approach showed lower interindividual variance in cfDNA values. When linking cfDNA levels to parameters of exercise performance the authors observed that, especially, the measurement based on L1PA2222 correlated significantly with exercise markers. These correlations were similar to the relationship of the performance markers among themselves.
Conclusions: cfDNA is a possible physiological marker to assess and predict exercise performance in athletes. In addition, the results indicate that using cfDNA as a marker in exercise physiology requires careful selection of a suitable measurement technique, whether it is eluted DNA or directly quantified.
Keywords: cfDNA; cycle exercise; direct quantitative real-time PCR; exercise marker; exercise performance.