title: Mice with cardiac overexpression of peroxisome proliferator-activated receptor γ have impaired repolarization and spontaneous fatal ventricular arrhythmias.
abstract: BACKGROUND
  Diabetes mellitus and obesity, which confer an increased risk of sudden cardiac death, are associated with cardiomyocyte lipid accumulation and altered cardiac electric properties, manifested by prolongation of the QRS duration and QT interval. It is difficult to distinguish the contribution of cardiomyocyte lipid accumulation from the contribution of global metabolic defects to the increased incidence of sudden death and electric abnormalities.
  
  
  RESULTS
  In order to study the effects of metabolic abnormalities on arrhythmias without the complex systemic effects of diabetes mellitus and obesity, we studied transgenic mice with cardiac-specific overexpression of peroxisome proliferator-activated receptor γ 1 (PPARγ1) via the cardiac α-myosin heavy-chain promoter. The PPARγ transgenic mice develop abnormal accumulation of intracellular lipids and die as young adults before any significant reduction in systolic function. Using implantable ECG telemeters, we found that these mice have prolongation of the QRS and QT intervals and spontaneous ventricular arrhythmias, including polymorphic ventricular tachycardia and ventricular fibrillation. Isolated cardiomyocytes demonstrated prolonged action potential duration caused by reduced expression and function of the potassium channels responsible for repolarization. Short-term exposure to pioglitazone, a PPARγ agonist, had no effect on mortality or rhythm in WT mice but further exacerbated the arrhythmic phenotype and increased the mortality in the PPARγ transgenic mice.
  
  
  CONCLUSIONS
  Our findings support an important link between PPARγ activation, cardiomyocyte lipid accumulation, ion channel remodeling, and increased cardiac mortality.
authors: Columbia University, Division of Cardiology, PH 10-203, 622 W.168th St, New York, NY, USA. jpm46@columbia.edu
authors: John P
authors: JP
authors: Morrow
authors: Alexander
authors: A
authors: Katchman
authors: Ni-Huiping
authors: NH
authors: Son
authors: Chad M
authors: CM
authors: Trent
authors: Raffay
authors: R
authors: Khan
authors: Takayuki
authors: T
authors: Shiomi
authors: Haiyan
authors: H
authors: Huang
authors: Vaibhav
authors: V
authors: Amin
authors: Joshua M
authors: JM
authors: Lader
authors: Carolina
authors: C
authors: Vasquez
authors: Gregory E
authors: GE
authors: Morley
authors: Jeanine
authors: J
authors: D'Armiento
authors: Shunichi
authors: S
authors: Homma
authors: Ira J
authors: IJ
authors: Goldberg
authors: Steven O
authors: SO
authors: Marx
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D016757:Death, Sudden, Cardiac / Q000453:epidemiology; D004195:Disease Models, Animal; D004562:Electrocardiography; D007004:Hypoglycemic Agents / Q000494:pharmacology; D015994:Incidence; D008050:Lipid A / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology; D047495:PPAR gamma / Q000235:genetics* / Q000502:physiology; D010641:Phenotype; D000077205:Pioglitazone; D011188:Potassium / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000502:physiology; D012032:Refractory Period, Electrophysiological / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D017180:Tachycardia, Ventricular / Q000235:genetics / Q000401:mortality / Q000503:physiopathology*; D045162:Thiazolidinediones / Q000494:pharmacology; D014693:Ventricular Fibrillation / Q000235:genetics / Q000401:mortality / Q000503:physiopathology*; D020257:Ventricular Remodeling / Q000502:physiology
chemical_list: D018031:Connexin 43; C543076:GJA1 protein, mouse; D007004:Hypoglycemic Agents; D008050:Lipid A; D047495:PPAR gamma; D024642:Potassium Channels, Voltage-Gated; D045162:Thiazolidinediones; D012964:Sodium; D011188:Potassium; D002118:Calcium; D000077205:Pioglitazone