PAT5A: A Partial Agonist of Peroxisome Proliferator-Activated Receptor γ Is a Potent Antidiabetic Thiazolidinedione Yet Weakly Adipogenic

PAT5A [5-[4-[ N -(2-pyridyl)-(2 S )-pyrrolidine-2-methoxyl]phenylmethylene[thiazolidine-2,4-dione, malic acid salt]], a chemically distinct unsaturated thiazolidinedione, activates peroxisome proliferator-activated receptor γ (PPARγ) submaximally in vitro with the binding affinity ∼10 times less than that of rosiglitazone, a highly potent thiazolidinedione. PAT5A reduces plasma glucose level and improves insulin sensitivity in insulin resistant db/db mice, similar to that of rosiglitazone, while exerting a relatively weak adipogenic effect. In contrast to rosiglitazone, PAT5A inhibits cholesterol and fatty acid biosynthesis suggesting that PAT5A possesses a unique receptor-independent non-PPAR related property. PAT5A induces qualitatively similar but quantitatively different protease digestion patterns and interacts with PPARγ differently than rosiglitazone. PAT5A shows differential cofactor recruitment and gene activation than that of rosiglitazone. Thus, the partial agonism of PAT5A to PPARγ together with its receptor independent effects may contribute to its antidiabetic potency similar to rosiglitazone in vivo despite reduced affinity for PPARγ. These biological effects suggest that PAT5A is a PPARγ modulator that activates some (insulin sensitization), but not all (adipogenesis), PPARγ-signaling pathways.