PPARα plays a central role in lipid transport and metabolism as well as in the response to xenobiotics. PPARα is since activated by a diverse array of ligands, including natural and synthetic compounds. The natural ligands free fatty acids (FFA) originate either from the catabolism of chylomicrons (CM), very-low-density lipoproteins (VLDL) or high-density lipoproteins (HDL) via the lipoprotein lipase (LPL), or from the degradation of glucose. They are also released in the cell from the fatty acid binding protein (FABP). Activated PPARα heterodimerizes with RXR and binds to PPRE to drive expression of target genes.