PPARA and obesity due to melanocortin 4 receptor deficiency: Interestingly, considering both the important clinical use of well-known class of chemical derivatives of fibric acid, the peroxisome proliferator activated receptors (PPAR) ligands, and the growing role of the new class of their derivatives, the thiazolidinediones (TZDs), in the pathophysiology of various diseases (diabetes, obesity, hepatic dysfunctions, cognitive disorders and, most importantly, cancer) together with the intriguing pharmacotoxicological profiles of their putative ligands, we propose to better delineate the interrelationships existing between mitochondria and PPAR ligands.