PPARA and metabolic disease: Some of the synthetic PPAR ligands are currently usedto treat metabolic diseases: fibrates, which bind to PPARα, are hypolipidemicagents; thiazolidinediones (TZDs), which bind to PPARγ, are insulin sensitizers.A recent report shows that retinoic acid, depending on the ratio of cellularretinoic acid binding protein 2 (CRABP-II)and fatty acid binding protein 5 (FABP5), may function as a PPARδ ligand [16].