KLF11影响机体代谢的分子机理研究

Blood glucose levels in mammals must be maintained within a narrow range. Impaired insulin signaling together with abnormal hepatic glucose production result in type 2 diabetes.Type 2 diabetes is a major cause of morbidity and an important risk factor for cardiovascular disease, blindness and kidney failure, highlighting the urgent need for new therapeutic strategies. Our previous study suggests that the expression of the transcription factor KLF11 gene is dysregulated in the livers of db/db diabetic and high-fat diet-induced obese (DIO) mice. Adenovirus-mediated overexpression of KLF11 in the livers of db/db and DIO mice activates the PPARα signaling pathway, subsequently markedly improving the fatty liver phenotype. Conversely, knockdown of KLF11 by adenovirus (Ad-shKLF11) in livers of wild-type C57BL/6J and db/m mice increases hepatic triglyceride (TG) levels, owing to decreased fatty acid oxidation. Finally, the treatment of diabetic mice with Ad-shPPARα abolishes the KLF11 stimulatory effects on expression of genes involved in fatty acid oxidation and inhibitory effects on hepatic TG content. In contrast, PPARα rescue restores the increased hepatic TG levels in Ad-shKLF11-infected db/m mice to normal levels. These data indicate that KLF11 regulates hepatic lipids metabolism. These findings have been published in Journal of Hepatology (Mouse KLF11 regulates hepatic lipid metabolism; Huabing Zhang, Qi Chen, Min Yang, Bin Zhu, Ying Cui, Yuan Xue, Nin Gong, Anfang Cui, Min Wang, Lian Shen, Shutian Zhang, Fude Fang, and Yongsheng Chang; Journal of Hepatology，2013;58(4):763-70). Our further studies suggested that adenovirus-mediated overexpression of KLF11 in primary mouse hepatocytes decreased expression of key gluconeogenic genes, including PPARγ coactivator 1α (PGC-1α) and its target genes PEPCK and G6Pase, subsequently decreasing cellular glucose production. Although we previously showed that KLF11 regulated hepatic lipids metabolism, the physiological roles of KLF11 in regulation of hepatic glucose metabolism, insulin secretions in pancreas, adipocytes differentiation and adipose development remain unexplored. Thus, we plan to generate KLF11 conditional knockout mice to further study physiological function of KLF11 in different tissues, including liver, adipose and pancreas, from molecular, cellular and animal levels. We previously employed adenovirus systems to study the short-term effects of KLF11 deficiency on hepatic lipids metabolism. In the near future, we will also use KLF11 global knockout and tissue-specific knockout mice as animal models to study the long-term effects of KLF11 deficiency on systemic glucose and lipids metabolism, including different tissues such as liver, adipose and pancreas.

转录因子KLF11也被命名为MODY7基因,但是KLF11突变导致糖尿病发生的分子机理不清。我们前期工作表明：在db/db糖尿病小鼠或高脂饮食诱导的肥胖小鼠肝脏中通过腺病毒诱导转录因子KLF11表达能激活脂肪酸氧化途径，从而改善脂肪肝表型，降低血脂水平,该项工作已经发表在Journal of Hepatology (2013)。后续工作表明：在原代小鼠肝脏细胞通过腺病毒介导过量表达KLF11能抑制糖异生关键基因PGC-1α及其靶基因PEPCK,G6Pase等基因的表达，减少原代肝脏细胞葡萄糖分泌。但是KLF11抑制这些糖异生基因表达的分子机理不清，KLF11基因是否在体内抑制肝脏糖异生基因表达，是否影响机体血糖水平及葡萄糖耐受，是否影响胰岛细胞的胰岛素分泌，是否影响脂肪组织的分化及发育等还不清楚。本申请拟从分子水平，细胞水平及动物整体水平全面深入研究KLF11对机体糖脂代谢的影响。

现有的研究表明，KLF11也参与了机体糖脂代谢。KLF11已经被命名为MODY7基因。 KLF11基因突变将抑制其转录活性，患者表现为糖尿病症状。我们前期工作表明KLF11能调节肝脏脂代谢 (Mouse KLF11 regulates hepatic lipid metabolism. Huabing Zhang, et al; Journal of Hepatology, 2013，58(4):763-770)。在此基础上，我们进一步发现在原代小鼠肝脏细胞激活KLF11表达能抑制糖异生关键基因PGC-1α及其靶基因PEPCK,G6Pase等基因的表达，减少肝脏细胞葡萄糖分泌。在db/db小鼠肝脏中激活KLF11抑制肝脏糖异生，降低血糖水平，改善葡萄糖耐受。相反，在正常小鼠肝脏中敲低KLF11表达，能促进肝脏糖异生，升高血糖，伤害葡萄糖耐受。这些结果表明KLF11可能是通过抑制肝脏糖异生而影响机体血糖水平。这些结果发表在Plos One (Huabing Zhang,et al. Involvement of KLF11 in hepatic glucose metabolism in mice via suppressing of PEPCK-C expression. 2014, 9(2): e89552)。在此基础上，我们发现KLF11能调控其他基因的表达，包括FOXP1和FOXQ1等基因，我们进一步拓展这些研究，发现这些被KLF11调控的基因也能调控机体糖脂代谢，从而形成一个复杂的调控网络。FOXP1和FOXQ1均能抑制肝脏糖异生。在糖尿病小鼠肝脏中激活FOXP1降低血糖，改善葡萄糖耐受；分子机制研究表明，FOXP1一方面同FOXO1形成复合物，另一方面直接结合到糖异生基因G6pc和PEPCK基因启动子区IRE原件，从而阻止了FOXO1对糖异生的激活。尽管FOXQ1也具有抑制糖异生的功能，但FOXQ1只能同FOXO1直接相互作用，并不能直接结合到IRE原件，从而阻断FOXO1功能，抑制糖异生，降低血糖。这些研究分别发表在JBC和Diabetologia。