title: Leptin Attenuates the Contractile Function of Adult Rat Cardiomyocytes Involved in Oxidative Stress and Autophagy.
abstract: BACKGROUND
  Leptin has been identified as an important protein involved in obesity. As a chronic metabolic disorder, obesity is associated with a high risk of developing cardiovascular and metabolic diseases, including heart failure. The aim of this paper was to investigate the effects and the mechanism of leptin on the contractile function of cardiomyocytes in the adult rat.
  
  
  METHODS
  Isolated adult rat cardiomyocytes were exposed to leptin (1, 10, and 100 nmol/L) for 1 hour. The calcium transients and the contraction of adult rat cardiomyocytes were recorded with SoftEdge MyoCam system. Apocynin, tempol and rapamycin were added respectively, and Western blotting was employed to evaluate the expression of LC3B and Beclin-1.
  
  
  RESULTS
  The peak shortening and maximal velocity of shortening/relengthening (± dL/dtmax) of cell shortening were significantly decreased, and the time to 50% relengthening was prolonged with leptin perfusion. Leptin also significantly reduced the baseline, peak and time to 50% baseline of calcium transient. Leptin attenuated autophagy as indicated by decreased LC3-II and Beclin-1. All of the abnormalities were significantly attenuated by apocynin, tempol or rapamycin.
  
  
  CONCLUSIONS
  Our results indicated that leptin depressed the intracellular free calcium and myocardial systolic function via increasing oxidative stress and inhibiting autophagy.
authors.affiliation: Department of Pharmacology, Guangzhou Medical University; ; The Fourth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436.
authors.forename: Liu-Jin
authors.initials: LJ
authors.lastname: Luo
authors.affiliation: Department of Pharmacology, Guangzhou Medical University; ; Guangzhou Huaxia Technical College, Guangzhou 510935, P.R. China.
authors.forename: Ying-Ping
authors.initials: YP
authors.lastname: Liu
authors.affiliation: Department of Pharmacology, Guangzhou Medical University.
authors.forename: Xun
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Department of Pharmacology, Guangzhou Medical University.
authors.forename: Gui-Ping
authors.initials: GP
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, Guangzhou Medical University.
authors.forename: Ning
authors.initials: N
authors.lastname: Hou
authors.affiliation: Department of Pharmacology, Guangzhou Medical University.
authors.forename: Xiao-Qian
authors.initials: XQ
authors.lastname: Wu
authors.affiliation: Department of Pharmacology, Guangzhou Medical University.
authors.forename: Jian-Dong
authors.initials: JD
authors.lastname: Luo
authors.affiliation: Department of Pharmacology, Guangzhou Medical University.
authors.forename: Gen-Shui
authors.initials: GS
authors.lastname: Zhang
keywords: Autophagy; Calcium transient; Cardiac function; Chronic heart failure; Leptin; Oxidative stress