Mitochondrial dysfunction by synthetic ligands of peroxisome proliferator activated receptors (PPARs)

PPARs are a class of nuclear receptors involved in lipid and glucidic metabolism, immune regulation and cell differentiation. This spectrum of biological activities stimulated pharmacological research to synthetize different molecules with PPARs binding activity with beneficial therapeutic effects. As a matter of fact, some synthetic PPAR-ligands have been already employed in pharmacotherapy: PPAR-alpha ligands, such as fibrates, are used in hyperlipidemias and thiazolidinediones, mainly PPAR-gamma ligands, are employed as insulin sensitizers. However, both classes of drugs showed pharmacotoxicological profiles which cannot be fully ascribed to activation of their specific receptors and which are causing a growing incidence of dramatic side effects (rhabdomyolysis, acute liver failure, heart failure, etc.). A re-evaluation of the biological activities of PPAR synthetic ligands, in particular of the mitochondrial dysfunction based on a rotenone-like Complex I partial inhibition and of its consequent metabolic adaptations, seems to explain some of the pathophysiologic aspects of PPARs allowing a better definition of the therapeutic properties of the so-called PPAR-ligands.