Selective peroxisome proliferator-activated receptor gamma (PPARgamma) modulation as a strategy for safer therapeutic PPARgamma activation

Abstract

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a clinically validated target for treatment of insulin resistance. PPARgamma activation by full agonists such as thiazolidinediones has shown potent and durable glucose-lowering activity in patients with type 2 diabetes without the concern for hypoglycemia or gastrointestinal toxicities associated with some other medications used to treat this disease. However, thiazolidinediones are linked to safety and tolerability issues such as weight gain, fluid retention, edema, congestive heart failure, and bone fracture. Distinctive properties of PPARgamma provide the opportunity for selective modulation of the receptor such that desirable therapeutic effects may be attained without the unwanted effects of full activation. PPARgamma is a nuclear receptor that forms a complex with coreceptor RXR and a cell type- and cell state-specific array of coregulators to control gene transcription. PPARgamma affinity for these components, and hence transcriptional response, is determined by the conformational changes induced by ligand binding within a complex pocket with multiple interaction points. This molecular mechanism thereby offers the opportunity for selective modulation. A desirable selective PPARgamma modulator profile would include high-affinity interaction with the PPARgamma-binding pocket in a manner that leads to retention of the insulin-sensitizing activity that is characteristic of full agonists as well as mitigation of the effects leading to increased adiposity, fluid retention, congestive heart failure, and bone fracture. Examples of endogenous and synthetic selective PPARgamma modulator (SPPARM) ligands have been identified. SPPARM drug candidates are being tested clinically and provide support for this strategy.