Mice with cardiac overexpression of peroxisome proliferator-activated receptor ? have impaired repolarization and spontaneous fatal ventricular arrhythmias.

ABSTRACT: 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.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 ? 1 (PPAR?1) via the cardiac ?-myosin heavy-chain promoter. The PPAR? 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 PPAR? agonist, had no effect on mortality or rhythm in WT mice but further exacerbated the arrhythmic phenotype and increased the mortality in the PPAR? transgenic mice.Our findings support an important link between PPAR? activation, cardiomyocyte lipid accumulation, ion channel remodeling, and increased cardiac mortality.

SUBMITTER: Morrow JP 

PROVIDER: S-EPMC3258098 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature