A critical role for peroxisomal proliferator-activated receptor-alpha nuclear receptors in the development of cardiomyocyte degeneration and necrosis.

Peroxisomal proliferator-activated receptor (PPAR)-alpha is a ligand-activated transcriptional factor that regulates genes involved in lipid metabolism and energy homeostasis. PPAR-alpha activators, including fibrates, have been used to treat dyslipidemia for several decades. In contrast to their known effects on lipids, the pharmacological consequences of PPAR-alpha activation on cardiac metabolism and function are not well understood. Therefore, we evaluated the role that PPAR-alpha receptors play in the heart. Our studies demonstrate that activation of PPAR-alpha receptors using a selective PPAR-alpha ligand results in cardiomyocyte necrosis in mice. Studies in PPAR-alpha-deficient mice demonstrated that cardiomyocyte necrosis is a consequence of the activation of PPAR-alpha receptors. Cardiac fatty acyl-CoA oxidase mRNA levels increased at doses in which cardiac damage was observed and temporally preceded cardiomyocyte degeneration, suggesting that peroxisomal beta-oxidation correlates with the appearance of microscopic injury and cardiac injury biomarkers. Increased myocardial oxidative stress was evident in mice treated with the PPAR-alpha agonists coinciding with increased peroxisomal biomarkers of fatty acid oxidation. These findings suggest that activation of PPAR-alpha leads to increased cardiac fatty acid oxidation and subsequent accumulation of oxidative stress intermediates resulting in cardiomyocyte necrosis.