J Cardiovasc Pharmacol. 2021 Dec 31.
ABSTRACT: Glucagon-like peptide 1 (GLP-1) analogues 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 analogue 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 analogue. 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 (OPA1), mitofusin 2 (Mfn2), dynamin-related protein 1 (Drp1), and parkin, were examined by Western blotting. Exendin 4 significantly increased the expression of the fusion proteins, OPA1 and Mfn2, and decreased that of the mitophagy-related protein, parkin, without altering Drp1 expression levels. Exendin 4 also preserved Akt phosphorylation levels after hypoxia-reoxygenation, while wortmannin, an inhibitor of the PI3K-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.