title: Cardiomyocyte glucagon receptor signaling modulates outcomes in mice with experimental myocardial infarction.
abstract: OBJECTIVE
  Glucagon is a hormone with metabolic actions that maintains normoglycemia during the fasting state. Strategies enabling either inhibition or activation of glucagon receptor (Gcgr) signaling are being explored for the treatment of diabetes or obesity. However, the cardiovascular consequences of manipulating glucagon action are poorly understood.
  
  
  METHODS
  We assessed infarct size and the following outcomes following left anterior descending (LAD) coronary artery ligation; cardiac gene and protein expression, acylcarnitine profiles, and cardiomyocyte survival in normoglycemic non-obese wildtype mice, and in newly generated mice with selective inactivation of the cardiomyocyte Gcgr. Complementary experiments analyzed Gcgr signaling and cell survival in cardiomyocyte cultures and cell lines, in the presence or absence of exogenous glucagon.
  
  
  RESULTS
  Exogenous glucagon administration directly impaired recovery of ventricular pressure in ischemic mouse hearts ex vivo, and increased mortality from myocardial infarction after LAD coronary artery ligation in mice in a p38 MAPK-dependent manner. In contrast, cardiomyocyte-specific reduction of glucagon action in adult Gcgr (CM-/-) mice significantly improved survival, and reduced hypertrophy and infarct size following myocardial infarction. Metabolic profiling of hearts from Gcgr (CM-/-) mice revealed a marked reduction in long chain acylcarnitines in both aerobic and ischemic hearts, and following high fat feeding, consistent with an essential role for Gcgr signaling in the control of cardiac fatty acid utilization.
  
  
  CONCLUSIONS
  Activation or reduction of cardiac Gcgr signaling in the ischemic heart produces substantial cardiac phenotypes, findings with implications for therapeutic strategies designed to augment or inhibit Gcgr signaling for the treatment of metabolic disorders.
authors: Department of Laboratory Medicine and Pathobiology, Department of Medicine, Toronto, Ontario, Canada ; Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, ON, Canada.
authors: Safina
authors: S
authors: Ali
authors: Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, ON, Canada.
authors: John R
authors: JR
authors: Ussher
authors: Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, ON, Canada.
authors: Laurie L
authors: LL
authors: Baggio
authors: Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, ON, Canada.
authors: M Golam
authors: MG
authors: Kabir
authors: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors: Maureen J
authors: MJ
authors: Charron
authors: Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA ; Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Department of Medicine, Duke University Medical Center, Durham, NC, USA.
authors: Olga
authors: O
authors: Ilkayeva
authors: Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA ; Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Department of Medicine, Duke University Medical Center, Durham, NC, USA.
authors: Christopher B
authors: CB
authors: Newgard
authors: Department of Laboratory Medicine and Pathobiology, Department of Medicine, Toronto, Ontario, Canada ; Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, ON, Canada ; Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors: Daniel J
authors: DJ
authors: Drucker
keywords: Cardiomyocytes; Diabetes; Fatty acid metabolism; Glucagon; Glucagon receptor; Heart; Myocardial infarction