Abstract 17038: Long-Acting Phosphodiesterase-5 Inhibitor Tadalafil Attenuates Oxidative Stress and Protects Against Myocardial Ischemia/Reperfusion Injury in Type 2 Diabetic Mice
Background: Diabetic patients exhibit increased risk for the development of cardiovascular diseases. Recent findings from our laboratory suggest that phosphodiesterase-5 (PDE-5) inhibitor, sildenafil, restores NO signaling and protects against ischemia/reperfusion injury. In this study, we determined the effect of long-acting PDE-5 inhibitor, tadalafil (TAD), on type 2 diabetes associated complications in db/db mice.
Methods and Results: Adult male db/db mice (n=24/group) were randomized to receive: DMSO (10%, 0.2 ml, i.p.) or TAD (1 mg/kg, i.p) for 28 days. The mice were sacrificed and blood was collected for assessment of biochemical parameters. Cardiomyocytes were isolated from the hearts and subjected to 40 min simulated ischemia followed by 1 h of reoxygenation. Dichlorodihydrofluorescein diacetate and JC-1 staining were used to measure ROS generation and mitochondrial membrane potential (Δψm), respectively. A second subset of mice hearts were subjected to 30 min global ischemia followed by 60 min reperfusion in Langendorff mode. Infarct size was measured using computer morphometry of tetrazolium stained sections. A third subset of mice hearts were used for the estimation of lipid peroxidation, GSSH/GSH and the expression of myocardial pAKT and pAMPK by Western blot. TAD treatment reduced the body weight (48.5±1.5 g vs 51.9±1.3 g), fasting plasma glucose levels (466.1±41.4 mg/dl vs 567.7±29.7 mg/dl), insulin (2.97±0.67 ng/ml vs 14.42±3.15 ng/ml; p<0.02) and triglycerides (91.2±12.3 mg/dl vs 190.5±38.5 mg/dl; p<0.05) as compared to control db/db mice. TAD-treated mice also showed reduced infarct size compared to the control db/db mice (21.2±1.8% vs 45.8±2.8%; p<0.01). Control db/db mice demonstrated enhanced oxidative stress as indicated by significantly increased ROS production, lipid peroxidation and GSSH/GSH ratio which were attenuated in TAD-treated mice. Furthermore, TAD treatment preserved the loss of Δψm and enhanced the expression of myocardial pAKT and pAMPK compared to the control (n=4/group; p<0.05).
Conclusion: Chronic treatment with TAD attenuates oxidative stress and improves mitochondrial integrity while providing powerful cardioprotective effects through Akt-AMPK signaling in type 2 diabetes.
- © 2011 by American Heart Association, Inc.