Antidiabetic actions of a non-agonist PPARγ ligand blocking Cdk5-mediated phosphorylation

Abstract

The nuclear receptor PPARγ is the target of thiazolidinedione antidiabetics including rosiglitazone and pioglitazone. These full PPARγ agonists are effective and well tolerated in most patients, but cause fluid retention and weight gain in a minority. In this proof-of-concept study, Choi et al. show the development of specific PPARγ ligands that retain antidiabetic activity through blockade of Cdk5-mediated PPARγ phosphorylation, but that are not full PPARγ agonists. In mouse models, these ligands do not cause the side effects sometimes associated with full PPARγ agonists. PPARγ is the functioning receptor for the thiazolidinedione (TZD) class of antidiabetes drugs including rosiglitazone and pioglitazone1. These drugs are full classical agonists for this nuclear receptor, but recent data have shown that many PPARγ-based drugs have a separate biochemical activity, blocking the obesity-linked phosphorylation of PPARγ by Cdk5 (ref. 2). Here we describe novel synthetic compounds that have a unique mode of binding to PPARγ, completely lack classical transcriptional agonism and block the Cdk5-mediated phosphorylation in cultured adipocytes and in insulin-resistant mice. Moreover, one such compound, SR1664, has potent antidiabetic activity while not causing the fluid retention and weight gain that are serious side effects of many of the PPARγ drugs. Unlike TZDs, SR1664 also does not interfere with bone formation in culture. These data illustrate that new classes of antidiabetes drugs can be developed by specifically targeting the Cdk5-mediated phosphorylation of PPARγ.