Proteins in a family of ligand-activated transcription factors known as peroxisome proliferator-activated receptors (PPARs) respond to changes in dietary lipid by altering the expression of genes involved in fat and carbohydrate metabolism.

These transcription factors were first recognized for their roles in peroxisome synthesis—thus their name. They are a group of nuclear receptor proteins that function as transcription factors regulating the expression of genes.  PPARs play essential roles in the regulation of cellular differentiation, development, and metabolism (carbohydrate, lipid, protein), and tumorigenesis of higher organisms.

Their normal ligands are fatty acids or fatty acid derivatives, but they can also bind synthetic agonists and can be activated in the laboratory by genetic manipulation. PPARα, PPARδ, and PPARγ are members of this nuclear receptor superfamily.

They act in the nucleus by forming heterodimers with another nuclear receptor, RXR, then binding to regulatory regions of DNA near the genes under their control and changing the rate of transcription of those genes.