title: Autophagy inhibition rescues against leptin-induced cardiac contractile dysfunction.
abstract: Leptin hormone plays a vital role in the pathophysiological changes in heart geometry and function. Nonetheless, the precise mechanism(s) triggering leptin-induced cardiomyocyte contractile dysfunction is not well understood. The present study was designed to examine if autophagy plays a role in leptin-induced cardiac contractile anomalies. Cardiomyocyte contractile function was evaluated using an IonOptix edge detection system in cardiomyocytes following treatment with leptin in the presence or absence of the autophagy inhibiting chemical 3-methyladenine (3-MA). Immunoblotting was employed to evaluate expression of AMPK, Beclin1, Atg 5, p62 and LC3-II. GFP-LC3 puncta was used to assess autophagosome formation. Leptin suppressed cardiac contractile function as evidenced by decreased peak shortening, maximal velocity of shortening and relengthening, increased time-to-90% relengthening, all the observed effects were reduced or obliterated by autophagy inhibition. Leptin promoted superoxide generation, AMPK activation and overt autophagy induction. Leptin promoted autophagy as evidenced by enhanced LC3-II, Beclin, Atg 5 and decreased p62 levels. Pharmacological inhibition of reactive oxygen species (ROS) using tempol significantly attenuated leptin-induced autophagosome formation and cardiac contractile anomalies. In addition, genetic deletion of AMPKα2 or pharmacological inhibition of AMPK using compound C abrogated leptin or superoxide induced cardiac contractile dysfunction and autophagosome formation. In summary, our data revealed that leptin impairs cardiac contractile function through a superoxide generation-AMPK activation-and autophagy dependent mechanism.
authors.forename: Machender R
authors.initials: MR
authors.lastname: Kandadi
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Roe
authors.affiliation: Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, Wyoming 82071. jren@uwyo.edu.
authors.forename: Jun
authors.initials: J
authors.lastname: Ren
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D020013:Calcium Signaling / Q000187:drug effects; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002460:Cell Line; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D020738:Leptin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010588:Phagosomes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051381:Rats; D017382:Reactive Oxygen Species / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D002316:Cardiotonic Agents; D020738:Leptin; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; C025946:3-methyladenine; C534978:Prkaa2 protein, mouse; D055372:AMP-Activated Protein Kinases; D000225:Adenine