Key result
Altering intracellular creatine levels via genetic over-expression or knockout did not influence the functional deterioration of isolated perfused mouse hearts exposed to acute oxidative stress.
Why the study?
Does altered intracellular creatine level improve or reduce cardiac function and oxidative damage in isolated perfused mouse hearts exposed to acute oxidative stress?
Does altered intracellular creatine level improve or reduce cardiac function and oxidative damage in isolated perfused mouse hearts exposed to acute oxidative stress?
Intracellular creatine levels do not influence the response to acute oxidative stress in the intact beating heart, arguing against a physiologically relevant anti-oxidant role for creatine in this setting.
Answers are grounded in this paper and cite their sources.
No impact of creatine levels on acute cardiac oxidative stress; hypothesis-generating against major antioxidant role, pending other models.
BACKGROUND: Multiple studies suggest creatine mediates anti-oxidant activity in addition to its established role in cellular energy metabolism. The functional significance for the heart has yet to be established, but antioxidant activity could contribute to the cardioprotective effect of creatine in ischaemia/reperfusion injury. OBJECTIVES: To determine whether intracellular creatine levels influence responses to acute reactive oxygen species (ROS) exposure in the intact beating heart. We hypothesised that mice with elevated creatine due to over-expression of the creatine transporter (CrT-OE) would be relatively protected, while mice with creatine-deficiency (GAMT KO) would fare worse. METHODS AND RESULTS: CrT-OE mice were pre-selected for creatine levels 20-100% above wild-type using in vivo (1)H-MRS. Hearts were perfused in isovolumic Langendorff mode and cardiac function monitored throughout. After 20 min equilibration, hearts were perfused with either H2O2 0.5 µM (30 min), or the anti-neoplastic drug doxorubicin 15 µM (100 min). Protein carbonylation, creatine kinase isoenzyme activities and phospho-PKCδ expression were quantified in perfused hearts as markers of oxidative damage and apoptotic signalling. Wild-type hearts responded to ROS challenge with a profound decline in contractile function that was ameliorated by co-administration of catalase or dexrazoxane as positive controls. In contrast, the functional deterioration in CrT-OE and GAMT KO hearts was indistinguishable from wild-type controls, as was the extent of oxidative damage and apoptosis. Exogenous creatine supplementation also failed to protect hearts from doxorubicin-induced dysfunction. CONCLUSIONS: Intracellular creatine levels do not influence the response to acute ROS challenge in the intact beating heart, arguing against creatine exerting (patho-)physiologically relevant anti-oxidant activity.
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Aksentijević et al. (2014) studied Acute oxidative stress. Altered intracellular creatine levels (CrT-OE or GAMT KO) vs. Wild-type controls was evaluated on Cardiac functional decline (Left ventricular developed pressure, Rate pressure product) in response to ROS challenge. Altering intracellular creatine levels via genetic over-expression or knockout did not influence the functional deterioration of isolated perfused mouse hearts exposed to acute oxidative stress.
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