Impaired Myocardial MIF/AMPK Activation Aggravates Myocardial Ischemia Reperfusion Injury in High-Fat Diet-Induced Obesity

Background: Obese patients are more sensitive to myocardial ischemia, which has been linked with high mortality rates. The following study investigates the effects of impaired macrophage Migration Inhibitory Factor (MIF)/AMP-Activated Protein Kinase (AMPK) activation on increased susceptibility to myocardial ischemia/reperfusion (I/R) in high-fat diet-induced obesity. Methods: Male C57BL/6J mice were fed with a normal diet (10% kcal as fat, lean group) or a high-fat diet (60kcal as fat, obese group) for 12 consecutive weeks. To detect the MIF expression and AMPK activation in response to I/R in isolated hearts from lean and obese mice, myocardial samples were collected from left ventricular areas at different time points. To determine whether MIF supplementation is protective against I/R injury, recombined MIF (10 ng/mL) was applied before ischemia. Myocardial infarct size was estimated by triphenyltetrazolium staining. Western blot was used to detect myocardial MIF expression, AMPK activation and membrane glucose transporter 4 (Glut4) expression. Results: The expression of MIF was remarkably higher in obese group compared to lean group. Ischemia increased myocardial MIF expression and phosphorylation of AMPK in lean mice, whereas it had no significant effect on obese mice. Furthermore, administration of recombinant MIF increased ischemic AMPK activation and membrane Glut4 expression in both lean and obese mice, while it reduced the infarct size in lean mice only. Conclusion: An impaired MIF/AMPK activation response and consequent reduced membrane Glut4 expression may play an important role in increasing myocardial susceptibility to I/R in obesity.