Antioxidant effect of creatine in cultured mammalian cells

Creatine (Cr) is the most popular supplement proposed to be an ergogenic aid. However, the potential mechanisms underlying this effect have not been fully clarified. Since oxidative stress can affect muscle fatigue, it has been recently proposed that Cr might exert antioxidant activity. However, to the best of our knowlege, no research has been aimed to directly test the antioxidant effect of Cr on cultured cells. In the present research the effects of Cr were studied using cultured human promonocytic (U937) and endothelial (HUVE) cells and murine muscular (C2C12) cells exposed to H2O2. Cr, at pharmacologically attainable concentrations, markedly attenuated the cytotoxic effects induced by H2O2 (as assessed with the trypan blue exclusion assay and morphologic analysis) in all cell lines. Cr-cytoprotection was independent of chelation of transition metals; Cr did not affect cellular antioxidant status; cytoprotection was invariably associated with elevation of the intracellular fractions of free and phosphorylated Cr; mass spectrometryexperiments showed that a 136 MW molecule, which is likely to represent an oxidation by-product of creatine, formed in reaction buffers containing Cr and H2O2, as well as in cellular extracts from H2O2/Cr-treated U937 cells. On the basis of these findings it is suggested that Cr exerts significant antioxidant activity in cultured cells via a pleiotropic mechanism involving direct scavenging of oxidative species and amelioration of the energy status of the cells.