Attenuation of Glucolipotoxicity-Evoked Dysfunction and Insulin Resistance by Amentoflavone Involves in AMPK/Nrf2 Signaling in Cardiomyocytes

Abstract

Background: Diabetic cardiomyopathy (DCM) is becoming a proverbial diabetes mellitus-induced clinical entity due to the increased risk of heart failure. Glucolipotoxicity is a key feature of DCM. A recent study corroborates the critical roles of amentoflavone in cardiac injury. However, its function in DCM remains unclear. Purpose: To explore the role of amentoflavone in DCM. Methods: Cardiomyocytes were treated with amentoflavone under exposure to high glucose and high palmitic acid to mimic glucolipotoxicity environment of DCM. Cells were divided into control groups, glucolipotoxicity groups, and glucolipotoxicity and amentoflavone groups at the indicated doses. Then, cell viability, apoptosis and caspase-3 activity were determined using the commercial kits. The effects on glucolipotoxicity-induced oxidative damage, insulin resistance and fibrosis-related protein expression were detected. Results: Amentoflavone had little cytotoxicity to rat H9C2 cardiomyocytes (p > 0.05). Subsequently, cardiomyocytes were exposed to glucolipotoxicity conditions and confirmed that amentoflavone reversed glucolipotoxicity-inhibited cell viability (p < 0.05) and reduced cell apoptosis (p < 0.05) and activity of caspase-3 (p < 0.05). Amentoflavone inhibited glucolipotoxicity-triggered oxidative stress insult by increasing levels of antioxidant superoxide dismutase (SOD), glutathione (GSH) and glutathione peroxidase (GSH-Px), and decreasing contents of reactive oxygen species (ROS), malondialdehyde (MDA) and lactate dehydrogenase (LDH) (all p < 0.05). Furthermore, glucolipotoxicity restrained insulin-stimulated glucose uptake and glucose transporter 4 (Glut4) expression (p < 0.05), which were reversed after amentoflavone treatment (p < 0.05). Concomitantly, amentoflavone suppressed glucolipotoxicity-elevated transcripts and protein expression of fibrosis-related collagen I (p < 0.05) and fibronectin (p < 0.05). Mechanistically, glucolipotoxicity inhibited the activation of the adenosine monophosphate-activated protein kinase (AMPK)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling (p < 0.05), which was offset following amentoflavone treatment (p < 0.05). Moreover, blockage of the AMPK pathway overturned the protective effects of amentoflavone on glucolipotoxicity-induced oxidative injury (p < 0.05), insulin resistance (p < 0.05) and fibrosis protein expression (p < 0.05). Conclusions: Amentoflavone may protect against glucolipotoxicity-evoked cardiomyocyte oxidative damage, insulin resistance and fibrosis by reactivating the AMPK/Nrf2 signaling. Thus, this study may support amentoflavone as a promising therapeutic agent for DCM.