Factors Influencing Post-exercise Plasma Protein Carbonyl Concentration

Exercise of sufficient intensity and duration can cause acute oxidative stress. Plasma protein
carbonyl (PC) moieties are abundant, chemically stable, and easily detectable markers of oxidative
stress that are widely used for the interpretation of exercise-induced changes in redox balance.
Despite many studies reporting acute increases in plasma PC concentration in response to exercise,
some studies, including those from our own laboratory have shown decreases. This review will
discuss the differences between studies reporting increases, decreases, and no change in plasma
PC concentration following exercise in humans; highlighting participant physiology (i.e. training
status) and study design (i.e. intensity, duration, and novelty of the exercise bout) as the main
factors driving the direction of the PC response to exercise. The role of the 20S proteasome system
is proposed as a possible mechanism mediating the clearance of plasma PC following exercise.
Resting and exercise-induced differences in plasma protein composition and balance between
tissues are also discussed. We suggest that exercise may stimulate the clearance of plasma PC
present at baseline, whereas simultaneously increasing reactive oxygen species production that
facilitates the formation of new PC groups. The balance between these two processes likely
explains why some studies have reported no change or even decreases in plasma PC level postexercise
when other biomarkers of oxidative stress (e.g. markers of lipid peroxidation) were
elevated. Future studies should determine factors that influence the balance between PC clearance
and formation following acute exercise.