Identification of transcription factor which regulates obesity-linked downregulation of adiponectin gene and development of treatment modality for metabolic syndrome

为了阐明肥胖导致脂联素（Ad）基因下调的机制，我们首先在体外增生性脂肪细胞模型中，通过结合功能启动子研究和电泳迁移位移测定（EMSAs）技术，试图确定Ad基因对肥胖及其相关转录因子的启动子区域。我们确定了一个这样的启动子区域，我们将其命名为糖尿病/肥胖相关元件（DRE），以及它的结合蛋白（DRE结合蛋白；Deb）。酵母单杂交筛选证实Deb1基因为KLF家族转录因子。emsa和染色质免疫沉淀实验显示Deb1确实与DRE结合。Deb1剂量依赖性和特异性增强Ad启动子活性。Deb1 siRNA对内源性Ad mRNA的相应改变以及Deb1在体外的过表达证实了Deb1对Ad转录的调节作用。有针对性地破坏Deb1可引起部分但显著的Ad表达减少和血浆Ad水平降低。有趣的是，肥胖小鼠（如ob/ob小鼠）中Deb1的表达及其与DRE的结合减少。此外，我们发现，在肥厚脂肪细胞中观察到的氧化应激和炎症的增加以及激素受体信号的变化减少了Deb1和Ad，而这些细胞内改变的正常化增加了Deb1和Ad。综上所述，这些结果表明：1)肥胖通过氧化应激和炎症等多种途径降低Deb1，从而导致Ad减少；2)WAT中的Deb1激活剂可能为代谢综合征提供一种新的治疗方式（论文正在准备中）。此外，我们发现肥胖患者不仅血浆脂联素水平下降，而且AdipoR1/R2的表达水平也下降，这似乎在胰岛素抵抗的发展中发挥了因果作用。此外，我们发现不仅AdipoR1/R2的激动作用，而且在脂联素存在的情况下增加AdipoR1/R2的策略确实可以改善胰岛素抵抗和2型糖尿病（Nat. Med. 13:332,2007）。少

To clarify the mechanism by which obesity results in downregulation of Adiponectin (Ad) gene, we first tried to identify the promoter region of the Ad gene that confers the response to obesity and its responsible transcription factor(s) by using a combination of functional promoter studies and electrophoretic mobility shift assays (EMSAs) techniques in hypertrophic adipocytes model in vitro. We identified one such promoter region, which we named Diabetes/obesity-Related Element (DRE), and its binding protein(s) (Dre binding protein; Deb). Deb1 gene turned out to be a KLF family transcription factor by yeast one-hybrid screen.EMSAs and chromatin immunoprecipitation assays revealed that Deb1 indeed bound to DRE. Deb1 dose-dependently and specifically enhanced Ad promoter activity. Regulation of Ad transcription by Deb1 was confirmed by corresponding changes in endogenous Ad mRNA by Deb1 siRNA and Deb1 overexpression in vitro. Targeted disruption of Deb1 caused a partial but significant r … More eduction of Ad expression in WAT and plasma Ad levels. Interestingly, expression of Deb1 and its binding to DRE were reduced in obese mice such as ob/ob mice. Moreover, we found that increased oxidative stress and inflammation as well as changes in hormonal receptor signalling observed within hypertrophic adipocytes reduced Deb1 and Ad, and that normalization of these intracellular alterations increased Deb1 and Ad.Taken together, these results suggested that 1) obesity decreases Deb1 via multiple pathways such as oxidative stress and inflammation, which leads to Ad reduction, 2) Deb1 activators in WAT may provide a novel treatment modality for metabolic syndrome (manuscript in preparation).Moreover, we showed that not only plasma adiponectin levels but also expression levels of AdipoR1/R2 were decreased in obesity, which appeared to play causal roles in the development of insulin resistance. Furthermore, we showed that not only agonism of AdipoR1/R2 but also strategies to increase AdipoR1/R2 in the presence of adiponectin indeed resulted in amelioration of insulin resistance and type 2 diabetes (Nat. Med. 13:332,2007). Less