The Peroxisome Proliferator Activated Receptors (PPARs) are members of the nuclear hormone receptor subfamily of transcription factors. PPARs form heterodimers with retinoid X receptors (RXRs) and these heterodimers regulate transcription of various genes. There are 3 known subtypes of PPARs, PPAR alpha, PPAR delta and PPAR gamma. PPAR gamma is believed to be involved in adipocyte differentiation.