São Carlos Physics Institute, University of São Paulo, São Carlos, Sao Paulo, Brazil.
PLoS One. 2012;7(5):e36297. doi: 10.1371/journal.pone.0036297. Epub 2012 May 23.
Thiazolidinediones (TZDs) act through peroxisome proliferator activated receptor (PPAR) γ to increase insulin sensitivity in type 2 diabetes (T2DM), but deleterious effects of these ligands mean that selective modulators with improved clinical profiles are needed. We obtained a crystal structure of PPARγ ligand binding domain (LBD) and found that the ligand binding pocket (LBP) is occupied by bacterial medium chain fatty acids (MCFAs). We verified that MCFAs (C8-C10) bind the PPARγ LBD in vitro and showed that they are low-potency partial agonists that display assay-specific actions relative to TZDs; they act as very weak partial agonists in transfections with PPARγ LBD, stronger partial agonists with full length PPARγ and exhibit full blockade of PPARγ phosphorylation by cyclin-dependent kinase 5 (cdk5), linked to reversal of adipose tissue insulin resistance. MCFAs that bind PPARγ also antagonize TZD-dependent adipogenesis in vitro. X-ray structure B-factor analysis and molecular dynamics (MD) simulations suggest that MCFAs weakly stabilize C-terminal activation helix (H) 12 relative to TZDs and this effect is highly dependent on chain length. By contrast, MCFAs preferentially stabilize the H2-H3/β-sheet region and the helix (H) 11-H12 loop relative to TZDs and we propose that MCFA assay-specific actions are linked to their unique binding mode and suggest that it may be possible to identify selective PPARγ modulators with useful clinical profiles among natural products.
噻唑烷二酮类药物（TZDs）通过过氧化物酶体增殖物激活受体（PPAR）γ 增加 2 型糖尿病（T2DM）的胰岛素敏感性，但这些配体的有害作用意味着需要具有改善临床特征的选择性调节剂。我们获得了 PPARγ 配体结合域（LBD）的晶体结构，发现配体结合口袋（LBP）被细菌中链脂肪酸（MCFAs）占据。我们验证了 MCFAs（C8-C10）在体外与 PPARγ LBD 结合，并表明它们是低效力的部分激动剂，与 TZDs 相比具有特定于测定的作用；它们在 PPARγ LBD 的转染中作为非常弱的部分激动剂，在全长 PPARγ 中作为更强的部分激动剂，并表现出对细胞周期依赖性激酶 5（cdk5）磷酸化的完全阻断，与脂肪组织胰岛素抵抗的逆转有关。与 TZD 相关的体外脂肪生成，与 TZD 相关的体外脂肪生成。X 射线结构 B 因子分析和分子动力学（MD）模拟表明，MCFAs 与 TZDs 相比，弱稳定 C 端激活螺旋（H）12，这种效应高度依赖于链长。相比之下，MCFAs 优先稳定 H2-H3/β-折叠区和 H11-H12 环，与 TZDs 相比，我们提出 MCFAs 测定特异性作用与其独特的结合模式有关，并表明可能有可能从天然产物中识别具有有用临床特征的选择性 PPARγ 调节剂。
