A consideration of PPAR-gamma ligands with respect to lipophilicity: current trends and perspectives.

The fact that PPAR-gamma is expressed dramatically higher in fat, regulating gene transcription in response to small lipophilic ligands, supports an essential role of increased lipophilicity for those ligands. On the other hand, the skepticism concerning high lipophilicity as a characteristic associated with undesirable effects and formulation problems raises the question of how much lipophilicity should be incorporated in the ligand molecules so that they comply with generally accepted guidelines. A survey on the lipophilic behavior of thiazolidinediones and tyrosine-based derivatives with well-established PPAR-gamma affinity and functional activity suggests that excessive lipophilicity may not be favorable for their action.