Aims: Lipotoxicity increases oxidative stress and induces mitochondrial alterations in cardiomyocytes, contributing to left ventricular dysfunction in diabetic cardiomyopathy. GLP-1 is an incretin reported to have anti-oxidant actions in different cellular models. We investigated whether GLP-1 inhibits oxidative stress, mitochondrial dysfunction and DNA oxidative damage in murine HL-1 cardiomyocytes stimulated with palmitate.
Methods: Studies were performed in HL-1 cardiomyocytes incubated with palmitate (750 μM) for 6 hours in the absence or the presence of GLP-1 (100 nM and 200 nM). Total and mitochondrial DNA oxidative damage and parameters evaluating cytosolic and mitochondrial oxidative stress were assessed. In addition, cytochrome c (cyt c) oxidase activity and ATP synthase (ATPs) expression, as well as mitochondrial membrane potential and permeability were estimated. Finally, intracellular ATP was quantified and release of creatine to the extracellular medium was evaluated as an indicator of intracellular energy state.
Results: In HL-1 cardiomyocytes, palmitate alters all parameters indicative of increased oxidative stress, diminishes cyt c oxidase activity and ATPs expression, enhances mitochondrial membrane depolarization and permeability, increases ATP decrement and creatine leakage, and induces total and mitochondrial DNA oxidative damage, as compared with control HL-1 cells. GLP-1 reduced cytosolic and mitochondrial oxidative stress, increased the expression of the mitochondrial ATPs, partially restored mitochondrial membrane permeability, cyt c oxidase activity and ATP production, blunted leakage of creatine to the extracellular medium, and inhibited oxidative damage in total and mitochondrial DNA, in palmitate-stimulated HL-1 cardiomyocytes. However, GLP-1 failed to prevent palmitate-induced depolarization of the mitochondrial membrane in this model.
Conclusion: GLP-1 protects HL-1 cardiomyocytes against lipotoxicity induced by an excess of palmitate. This cytoprotective ability is mediated by the antioxidant effects of the incretin at the cytosolic and mitochondrial levels. It is proposed that therapies aimed to increase GLP-1 may contribute to prevent mitochondrial dysfunction in the context of cardiac diseases with excessive intracellular lipid accumulation.