Abstract 14283: Brain-Mediated Cardioprotective Actions of Leptin: Potential Role of Brown Adipose Tissue and Its Release of Extracellular Vesicles

Abstract

Background: We recently demonstrated that leptin has powerful central nervous system (CNS) actions that dramatically improve cardiac function following ischemia/reperfusion (IR) injury. How the brain communicates with the heart during CNS leptin infusion to improve cardiac function is unknown. One potential mechanism is activation of brown adipose tissue (BAT) which may be an important source of extracellular vesicles (EVs) carrying cardioprotective microRNAs (miR), including miR-125b-5p. Hypothesis: We investigated whether BAT contributes to the cardioprotective effect of CNS leptin infusion and the potential role of EVs carrying the miR-125b-5p in this protection. Methods: Male Sprague-Dawley rats were submitted to interscapular BAT ablation (iBATx) and instrumented with an intracerebroventricular (ICV) cannula in the brain lateral ventricle. After recovery and baseline assessment of cardiac function by echocardiography (ECHO), myocardial IR was induced by temporary ligation of the left anterior descending coronary artery. Vehicle (saline, 0.5 μL/hr) or leptin (0.62 μg/hr) was infused ICV chronically for 28 days using osmotic pumps. Cardiac function was assessed weekly by ECHO. Another set of animals with intact iBAT was treated with ICV leptin or vehicle for 4 weeks and had their iBAT collected for EVs isolation and quantification. Expression of the miR-125b-5p was measured in the heart of leptin treated rats with intact iBAT or iBATx. Results: Compared to vehicle-treated animals, ICV leptin infusion increased iBAT-derived EVs and removal of iBAT prevented leptin’s CNS-mediated cardioprotective effects after IR injury as indicated by a lack of improvement in ejection fraction (26±6 vs 41±3%) and stroke volume (162±31 vs 275±19μL) at week 4 post-IR. Expression of the mature miR-125b-5p was increased in the heart of ICV leptin treated rats and iBATx abolished this effect. Conclusion: These results indicate that the BAT plays an important role in mediating the cardioprotective effect of CNS leptin administration after IR injury and suggest that iBAT-derived EVs may be involved in delivering the miR-125b-5p to the heart during central leptin infusion. AHA 835218, 1R01HL163076, P20GM104357, and P20GM104320-07