Biology of the PPAR family of receptors

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of transcription factors. PPARs respond to specific ligands by alternating gene expression in a cell-, developmental-, and sex-specific manner. Three subtypes of this receptor have been discovered (PPARα, β and γ), each apparently evolving to fulfill different biological niches. Although PPARs were initially characterized as being activated by xenobiotic peroxisome proliferators (PPs), subsequently it was shown these proteins respond to endogenous fatty acids, leukotrienes and prostaglandins. In addition, PPARs control a variety of target genes involved in lipid homeostasis, diabetes and cancer. In this review article the importance of the PPAR subtypes in lipid homeostasis is discussed in the context of physiologic effectors as well as phenotypes of transgenic mice in which PPAR expression is ablated.