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.

METHODS AND 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: John P Morrow, Alexander Katchman, Ni-Huiping Son, Chad M Trent, Raffay Khan, Takayuki Shiomi, Haiyan Huang, Vaibhav Amin, Joshua M Lader, Carolina Vasquez, Gregory E Morley, Jeanine D'Armiento, Shunichi Homma, Ira J Goldberg, Steven O Marx
• Journal: Circulation (Circulation) Vol. 124 Issue 25 Pg. 2812-21 (Dec 20 2011) ISSN: 1524-4539 [Electronic] United States
• PMID: 22124376 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Connexin 43
• GJA1 protein, mouse
• Hypoglycemic Agents
• Lipid A
• PPAR gamma
• Potassium Channels, Voltage-Gated
• Thiazolidinediones
• Sodium
• Potassium
• Calcium
• Pioglitazone

Topics

• Action Potentials (physiology)
• Animals
• Calcium (metabolism)
• Connexin 43 (genetics, metabolism)
• Death, Sudden, Cardiac (epidemiology)
• Disease Models, Animal
• Electrocardiography
• Hypoglycemic Agents (pharmacology)
• Incidence
• Lipid A (metabolism)
• Mice
• Mice, Transgenic
• Myocardium (metabolism)
• Myocytes, Cardiac (cytology, physiology)
• PPAR gamma (genetics, physiology)
• Phenotype
• Pioglitazone
• Potassium (metabolism)
• Potassium Channels, Voltage-Gated (genetics, physiology)
• Refractory Period, Electrophysiological (drug effects, physiology)
• Sodium (metabolism)
• Tachycardia, Ventricular (genetics, mortality, physiopathology)
• Thiazolidinediones (pharmacology)
• Ventricular Fibrillation (genetics, mortality, physiopathology)
• Ventricular Remodeling (physiology)