Distinct Properties and Advantages of a Novel Peroxisome Proliferator-Activated Protein γ Selective Modulator

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Abstract
Antidiabetic thiazolidinediones (TZDs) and non-TZD compounds have been shown to serve as agonists of the peroxisome proliferator-activated receptor γ (PPARγ). Here, we report the identification and characterization of a novel non-TZD selective PPARγ modulator (nTZDpa). nTZDpa bound potently to PPARγ with high selectivity vs. PPARα or PPARδ. In cell-based assays for transcriptional activation, nTZDpa served as a selective, potent PPARγ partial agonist and was able to antagonize the activity of PPARγ full agonists. nTZDpa also displayed partial agonist effects when its ability to promote adipogenesis in 3T3-L1 cells was evaluated. Assessment of protein conformation using protease protection or solution nuclear magnetic resonance spectroscopy methods showed that nTZDpa produced altered PPARγ conformational stability vs. full agonists, thereby establishing a physical basis for its observed partial agonism. DNA microarray analysis of RNA from 3T3-L1 adipocytes treated with nTZDpa or several structurally diverse PPARγ full agonists demonstrated qualitative differences in the affected gene expression profile for nTZDpa. Chronic treatment of fat-fed, C57BL/6J mice with nTZDpa or a TZD full agonist ameliorated hyperglycemia and hyperinsulinemia. However, unlike the TZD, nTZDpa caused reductions in weight gain and adipose depot size. Feed efficiency was also substantially diminished. Unlike TZDs, nTZDpa did not cause cardiac hypertrophy in mice. When a panel of PPARγ target genes was examined in white adipose tissue, nTZDpa produced a different in vivo expression pattern vs. the full agonist. These findings establish that novel selective PPARγ modulators can produce altered receptor conformational stability leading to distinctive gene expression profiles, reduced adipogenic cellular effects, and potentially improved in vivo biological responses. Such compounds may lead to preferred therapies for diabetes, obesity, or metabolic syndrome.