F2-isoprostane formation, measurement and interpretation: The role of exercise

The level of F2-isoprostanes (F2-IsoP) in blood or urine is widely regarded as the reference marker for the assessment of oxidative stress. As a result, nowadays, F2-IsoP is the most frequently measured oxidative stress marker. Nevertheless, determining F2-IsoP is a challenging task and the measurement is neither free of mishaps nor straightforward. This review presents for the first time the effect of acute and chronic exercise on F2-IsoP levels in plasma, urine and skeletal muscle, placing emphasis on the origin, the methodological caveats and the interpretation of F2-IsoP alterations. From data analysis, the following effects of exercise have emerged: (i) acute exercise clearly increases F2-IsoP levels in plasma and this effect is generally short-lived, (ii) acute exercise and increased contractile activity markedly increase F2-IsoP levels in skeletal muscle, (iii) chronic exercise exhibits trend for decreased F2-IsoP levels in urine but further research is needed. Theoretically, it seems that significant amounts of F2-IsoP can be produced not only from phospholipids but from neutral lipids as well. The origin of F2-IsoP detected in plasma and urine (as done by almost all studies in humans) remains controversial, as a multitude of tissues (including skeletal muscle and plasma) can independently produce F2-IsoP.