Ligand-activated transcription factor. Key regulator of lipid metabolism. Activated by lipids. Receptor for peroxisome proliferators such as hypolipidemic drugs and fatty acids. Once activated by a ligand, the receptor binds to promoter elements of target genes. Regulates the peroxisomal beta-oxidation pathway of fatty acids (By similarity). Heterodimer with the retinoid X receptor. Ubiquitous. Oocytes, embryos, and adults. Belongs to the nuclear hormone receptor family. NR1 subfamily.