转录因子AP-2α在特丁基对苯二酚增强胰岛素敏感性中的作用及机制研究

Deficiency of either AMP-activated protein kinase (AMPK) or β-arrestin-2 contributes to insulin resistance. The molecular link between AMPK and β-arrestin-2 remains unknown. Tert-butylhydroquinone (tBHQ), as a food additive, effectively activates AMPK in hepatocytes. Previous studies have shown that activation of AMPK upregulates the transcriptional activity of transcriptional factor activator protein 2 alpha (AP-2α) in vascular cells. Our exciting preliminary data indicated that administration of tBHQ improved insulin sensitivity in Apoe-/- mice. Oppositely, knockdown of AP-2α impaired glucose tolerance and decreased insulin sensitivity, companied with decreased β-arrestin-2 gene expression. Bioinformatics analysis revealed that β-arrestin-2 gene promoter has two AP-2α binding sites, and this potential binding between AP-2α and β-arrestin-2 gene promoter was confirmed by using chromatin-immunoprecipitation (ChIP) assay in cultured cells. Thus, we hypothesized that tBHQ, via activation of AMPK, upregulates AP-2α-dependent β-arrestin-2 gene expression, leading to the improvement of insulin sensitivity. In order to test this hypothesis, we plan to identity AP-2α as a new transactional factor of β-arrestin-2 gene, to illuminate the molecular mechanism how tBHQ enhances insulin sensitivity, and to determine the role of AP-2α in tBHQ-improved insulin resistance. Completion of the proposal by the powerful combination of in vitro and in vivo studies will provide novel insights into whether AP-2α is a potential target for therapy in type 2 diabetic mice.

胰岛素的降糖作用与β-arrestin-2所介导的Akt磷酸化密切相关。特丁基对苯二酚（tBHQ）是一种食物添加剂，能增加Akt的磷酸化，但tBHQ能否改善胰岛素抵抗，目前并不明确。研究发现tBHQ能激活AMPK，而活化的AMPK能增加AP-2α的转录活性。前期工作发现tBHQ能改善小鼠糖耐量，而沉默AP-2α则降低胰岛素敏感性，且β-arrestin-2的基因转录依赖于AP-2α。故我们推测tBHQ可能经AMPK激活AP-2α，上调β-arrestin-2的基因转录，进而增加Akt的磷酸化，最终增强了胰岛素的敏感性。本课题拟用相应的生物学实验方法，体外体内研究相结合，明确AP-2α是β-arrestin-2的转录因子及其在tBHQ增强胰岛素敏感性中的作用，确立AP-2α是tBHQ改善胰岛素抵抗的关键分子。通过解析tBHQ改善胰岛素抵抗的分子机制，旨在为开发抗2型糖尿病药物提供新靶点。

特丁基对苯二酚（tBHQ）是一种食物添加剂，增加Akt的磷酸化。胰岛素通过β-arrestin-2所介导的信号复合物促进Akt的磷酸化而降糖，但tBHQ能否增强胰岛素的敏感性，目前并不清楚。研究发现tBHQ能激活AMPK，而AMPK能上调AP-2α的转录活性。预实验发现tBHQ能增强胰岛素敏感性，而抑制AP-2α引起糖耐量异常，且β-arrestin-2的基因转录依赖于AP-2α。因此我们推测tBHQ可能经AMPK增加AP-2α的活性而上调β-arrestin-2的基因转录，从而改善胰岛素抵抗。我们通过用先进的生物学实验方法，体外体内研究相结合，发现AP-2α是β-arrestin-2基因的转录因子，AMPK活化增加了AP-2α与β-arrestin-2启动子的结合并增强胰岛素敏感性。反之，抑制AP-2α的表达阻断了tBHQ所引起的β-arrestin-2基因表达及改善胰岛素抵抗作用，沉默AP-2α基因表达在胰岛素抵抗或2型糖尿病模型抑制了tBHQ改善胰岛素抵抗的作用。本课题解析了tBHQ改善胰岛素抵抗的分子机制，为开发抗2型糖尿病药物提供新靶点。