High-glucose condition reduces cardioprotective effects of insulin against mechanical stress-induced cell injury

Aims: Mechanical stress induces cardiomyocyte injury and contributes to the progression of heart failure in patients with hypertension. In this study, we investigated whether insulin exerts cardioprotective effects against mechanical stretching-induced cell injury, and whether the protective effect is influenced by high-glucose condition. Main methods: Cultured neonatal rat cardiomyocytes were plated on silicone chambers, and the cells were mechanically stretched by 15% to induce cell injury. Key findings: Mechanical stretching increased reactive oxygen species (ROS) and decreased mitochondrial inner membrane potential (Delta Psi(m)), eventually leading to cell death by apoptosis and necrosis. Insulin activated the phosphoinositide 3 (PI3) kinase/Akt pathway and reduced apoptosis and necrosis by suppressing ROS increase and preserving Delta Psi(m). However, high-glucose condition attenuated the insulin-induced Akt phosphorylation and cardioprotection. To investigate the mechanisms that attenuated the effects of insulin in high-glucose condition, we examined the expression of tensin homologue deleted on chromosome 10 (PTEN), which is a negative regulator of the PI3 kinase/Akt pathway. The expressions of PTEN and phosphorylated PTEN were significantly decreased by insulin, and those effects were attenuated in high-glucose condition. Significance: The present results suggest that insulin prevents mechanical stress-induced cell injury which otherwise lead to heart failure. Furthermore, we found that high-glucose condition prevented the decrease in PTEN expression and the cardioprotective effects induced by insulin. (C) 2010 Elsevier Inc. All rights reserved.