The peroxisome proliferator-activated receptors (PPARs), belonging to the nuclear receptor superfamily, are a group of nuclear receptor proteins that are composed of three isoforms, including PPARγ, PPARα and PPARδ, encoded by separate genes. PPARs have a modular structure characterized by the presence of two highly conserved domains, including the DNA binding domain (DBD) of two zinc fingers and the ligand binding domain (LBD) of 13 α-helices and a small 4-stranded β-sheet. PPARs are ligand-regulated transcription factors controlling gene expression by binding to specific response elements (PPREs) within promoters, where PPARs bind as heterodimers with a retinoid X receptor and interact with cofactors upon binding leading to the increasing of rate of transcription initiation.