Macrophage Migration Inhibitory Factor (MIF) Knockout Preserves Cardiac Homeostasis through Alleviating Akt-Mediated Myocardial Autophagy Suppression in High Fat Diet-Induced Obesity

BACKGROUND: Macrophage migration inhibitory factor (MIF) plays a role in the development of obesity and diabetes. However, whether MIF plays a role in fat diet-induced obesity and associated cardiac anomalies still remains unknown. The aim of this study was to examine the impact of MIF knockout on high fat diet-induced obesity, obesity-associated cardiac anomalies and the underlying mechanisms involved with a focus on Akt-mediated autophagy. METHODS: Adult male wild-type (WT) and MIF knockout (MIF(−/−)) mice were placed on 45% high fat diet for 5 months. Oxygen consumption, CO(2) production, respiratory exchange ratio (RER), locomotor activity, and heat generation were measured using energy calorimeter. Echocardiographic, cardiomyocyte mechanical and intracellular Ca(2+) properties were assessed. Apoptosis was examined using TUNEL staining and western blot analysis. Akt signaling pathway and autophagy markers were evaluated. Cardiomyocytes isolated from WT and MIF(−/−) mice were treated with recombinant mouse MIF (rmMIF). RESULTS: High fat diet feeding elicited increased body weight gain, insulin resistance, and caloric disturbance in WT and MIF(−/−) mice. High fat diet induced unfavorable geometric, contractile and histological changes in the heart, the effects of which were alleviated by MIF knockout. In addition, fat diet-induced cardiac anomalies were associated with Akt activation and autophagy suppression, which were nullified by MIF deficiency. In cardiomyocytes from WT mice, autophagy was inhibited by exogenous rmMIF through Akt activation. In addition, MIF knockout rescued palmitic acid-induced suppression of cardiomyocyte autophagy, the effect of which was nullified by rmMIF. CONCLUSIONS: These results indicate that MIF knockout preserved obesity-associated cardiac anomalies without affecting fat diet-induced obesity, probably through restoring myocardial autophagy in an Akt-dependent manner. Our findings provide new insights for the role of MIF in obesity and associated cardiac anomalies.