A Glucagon-like Peptide 1 Analog Protects Mitochondria and Attenuates Hypoxia-Reoxygenation Injury in Cultured Cardiomyocytes.

Abstract

Glucagon-like peptide 1 (GLP-1) analogs improve glycemic control in diabetes and protect the heart against ischemia-reperfusion injury. However, the mechanisms underlying this protection remain unclear. Mitochondria are essential for myocyte homeostasis. Therefore, we herein examined the effects of a GLP-1 analog on mitochondria after the hypoxia-reoxygenation of rat neonatal cultured cardiomyocytes. Cardiomyocytes were subjected to hypoxia for 5 hours followed by reoxygenation for 30 minutes in the presence or absence of exendin-4 (50 nmol/L), a GLP-1 analog. Hypoxia-reoxygenation increased lactate dehydrogenase and caspase-3 activities, indicators of lethal myocyte injury and apoptosis, respectively, and exendin-4 attenuated these increases. The content of ATP in myocytes decreased after hypoxia-reoxygenation but was preserved by exendin-4. The membrane potential and shape of mitochondria were assessed using a fluorescent probe. Exendin-4 attenuated the hypoxia-reoxygenation-induced disruption of the mitochondrial membrane potential and shortening. Mitochondrial quality control-related factors, such as optic atrophy protein 1, mitofusin 2, dynamin-related protein 1, and parkin, were examined by Western blotting. Exendin-4 significantly increased the expression of the fusion proteins, optic atrophy protein 1 and mitofusin 2, and decreased that of the mitophagy-related protein, parkin, without altering dynamin-related protein 1 expression levels. Exendin-4 also preserved Akt phosphorylation levels after hypoxia-reoxygenation, whereas wortmannin, an inhibitor of the phosphoinositide 3-kinase-Akt pathway, blunted exendin-4-induced myocyte protection and its effects on mitochondrial quality control factors. In conclusion, exendin-4 protected mitochondria by preserving the phosphorylation of Akt and fusion proteins, leading to the attenuation of hypoxia-reoxygenation-induced injury in cultured myocytes.