PPARGC1A and obesity due to melanocortin 4 receptor deficiency: Obesity is closely associated with mitochondrial dysfunction (i.e., decreased oxidation capacity and fatty acid oxidation), reduced expression in a cluster of nuclear genes responsible for oxidative metabolism (PGC-1α), and decreased mitochondrial biogenesis (i.e., the generation of new mtDNA and proteins) in skeletal muscle [5,6].