Molecular Characterization of Novel Insulin Sensitizers

 描述(申请人提供)：糖尿病的发病率随着人口老龄化和肥胖比例的增加而迅速增加。根据国家健康统计中心的数据，糖尿病现在是美国第七大死亡原因。随着人们对TZD类胰岛素增敏剂使用安全性的担忧增加，2型糖尿病(T2 DM)的一线治疗方法已经不再使用TZD类胰岛素增敏剂。这是不幸的，因为TZDS一直显示出治疗T2 DM的强大的胰岛素增敏效果。虽然体重增加与使用TZD有关，但主要的安全性问题包括浮肿、血浆容量膨胀(PVE/血液稀释)，这与心脏肥大和心力衰竭有关，增加骨折的风险，尤其是吡格列酮，增加膀胱癌的风险。在动物模型和人体中的研究表明，体重增加和PVE的指标虽然没有被消除，但可以通过使用PPARG的部分激动剂(与TZDS相比，受体的最小激动度，无论化合物的浓度)来最小化胰岛素增敏。虽然目前尚不清楚使用此类药物是否可以将骨折风险降至最低，但这些研究清楚地表明，PPARG配体提供的胰岛素敏化与它们诱导的经典兴奋性(AF2介导的兴奋性)水平无关。我们证明，部分激动剂和TZD治疗提供的胰岛素敏化与这些药物阻断肥胖诱导的PPARG在S273的磷酸化的能力相关(PS273)。2011年，我们发现PPARG配体SR1664不会引起经典的兴奋性反应，但可以有效地阻断pS273，并且在糖尿病啮齿动物模型中作为胰岛素增敏剂是有效的。最近，我们在SR1664的类药物特性方面取得了重大进展，产生了SR11023和SR10171等化合物，这些化合物在每天口服一次后显示出对肥胖小鼠的疗效。这些化合物代表着朝着开发具有改善的治疗指数的PPARG调节剂的方向迈进了一大步；然而，仍然存在几个问题：1)PPARG的pS273是如何抑制与肥胖和糖尿病相关的基因的，以及其他哪些PTM参与其中？我们预计，PPARG复合体中的因子会被pS273招募或移位，这些因子会影响靶基因的子集的表达。因此，当配体阻断pS273时，这些因子与复合体的相互作用就会改变。我们将确定这些因素是什么，以及它们是否有助于我们新化合物的作用机制；2)促进SR11023和SR10171作用的结构决定因素是什么。我们将使用成熟的技术来回答这个问题；以及3)缺乏经典的激动剂是否会完全将疗效与PPARG调节剂的主要副作用，特别是它们对骨骼的影响分开？在这里，我们将使用化学和结构生物学以及适当的细胞和动物模型，并结合全面的蛋白质组和基因组分析来解决这些问题。这项拟议的研究将深入了解PPARG信号通路的分子组成，产生阻断pS273的高亲和力非激动剂配体的结构决定因素，并更好地理解调节PPARG对骨骼的影响。虽然吡格列酮很快就会成为仿制药，但它与膀胱癌风险的关联及其对骨骼的负面影响最终将限制其使用。因此，需要一种更安全有效的胰岛素增敏剂来治疗T2 DM。

 DESCRIPTION (provided by applicant): The incidence of diabetes is increasing rapidly as the percentage of the population ages and becomes more obese. According to the National Center for Health Statistics diabetes is now the seventh leading cause of death in the US. The approach for first-line treatment of type 2 diabetes mellitus (T2DM) has moved away from the use of the TZD class of insulin sensitizers as safety concerns over their use have grown. This is unfortunate as TZDs have consistently shown robust insulin sensitization efficacy for treatment of T2DM. While weight gain is associated with use of TZDs, the major safety concerns include edema, plasma volume expansion (PVE/hemodilution) which is linked to cardiomegaly and heart failure, increased risk of bone fractures and specific to pioglitazone, increased risk in bladder cancer. Studies in animal models and in man have shown that indicators of weight gain and PVE, while not eliminated, can be minimized without loss of insulin sensitization by the use of partial agonists of PPARG (minimal agonism of the receptor as compared to TZDs regardless of concentration of compound). While it is unclear if the bone fracture risk can be minimized with use of such agents, these studies clearly demonstrate that insulin sensitization afforded by PPARG ligands does not correlate with the level of classical agonism they induce (AF2-mediated agonism). We demonstrated that the insulin sensitization afforded by partial agonist and TZD treatment correlates with the ability of these drugs to block the obesity-induced phosphorylation of PPARG at S273 (pS273). In 2011, we showed that the PPARG ligand SR1664 does not induce classical agonism yet potently blocks pS273, and is efficacious as an insulin sensitizer in rodent models of diabetes. Recently, we have made significant advances on the drug-like properties of SR1664 resulting in compounds such as SR11023 and SR10171 that demonstrate efficacy in obese mice following once-a-day oral administration. These compounds represent a significant advancement towards developing PPARG modulators with an improved therapeutic index; however, several questions remain; 1) how does pS273 of PPARG repress genes linked with obesity and diabetes, and what other PTMs are involved? We anticipate that factors are recruited to or displaced from the PPARG complex in response to pS273 and these factors influence expression of a subset of target genes. Thus, when ligands block pS273, the interaction of these factors with the complex is altered. We will determine what these factors are and if they contribute to the mechanism of action of our novel compounds; 2) what are the structural determinants that facilitate the action of SR11023 and SR10171. We will use proven technologies to answer this; and 3) will the lack of classical agonism fully dissociate efficacy from the major side effects of PPARG modulators, particularly their effects on bone? Here we will use chemical and structural biology with appropriate cell and animal models coupled with comprehensive proteomic and genomic analysis to address these questions. The proposed research will provide insight into the molecular components of the PPARG signaling pathway, structural determinants for generating high affinity non-agonist ligands that block pS273, and a better understanding of the impact of modulating PPARG on bone. While pioglitazone will become generic soon, its association with bladder cancer risk and its negative effects on bone will ultimately limit its use. Therefore, a significant need exists for a safer yet efficacious inslin sensitizer for treatment of T2DM.