RNA结合蛋白HuR在肥胖发生中的作用研究

Although the mechanisms of obesity are not completely elucidated, the expressions of many genes are changed in obesity and have been considered to be associated with its pathogenesis. Recently the post-transcriptional regulation has been found to be important in gene expressions. The RNA-binding proteins, especially the HuR functions to stabilize the mRNA and is involved in the aging process and some chronic diseases such as cancers. Our preliminary data showed that expressions of the HuR mRNA and protein were significantly changed in the adipose tissue of the diet induced obese (DIO) mice, and that the HuR interacted with some gene related to fat metabolism. Thus, we hypothesize that abnormal expression of the HuR may interact with its target genes and result in changes in these genes' expression, finally lead to the occurrence of obesity. In this project, firstly we will investigate the mRNA expression of HuR and its distribution between nuclear and cytoplasm using the high fat diet induced obese mice. Then the casual relationship between the HuR and obesity will be determined by using adipose tissue-specific HuR gene knockout and knockin mice. Finally, the effects of the HuR on adipogenesis, lipolysis, and adipocyte proliferation and differentiation will be studied and the genes closely associated with the above processes will be focused to examine the mechanisms of the HuR regulating these genes' posttranscriptional regulation. This project will be helpful for elucidating the mechanisms, prevention and treatment of obesity.

肥胖的发生机制虽尚不完全清楚，然而已证实与多个基因表达异常均有关。转录后调控在基因表达过程中至关重要，其中RNA结合蛋白尤其是HuR通过对靶基因mRNA稳定性的调控参与衰老、肿瘤等慢病的发生。我们前期和他人的研究发现，肥胖小鼠脂肪组织中HuR的mRNA和蛋白表达发生了显著变化，同时体外实验显示HuR可与肪代谢过程中的一些基因作用。因此，我们假设HuR在肥胖状态下表达异常，进而引发下游相关靶基因表达变化，从而促使肥胖发生。本项目拟首先采用高脂诱导肥胖小鼠模型，观察肥胖状态下HuR表达和核浆分布的变化情况；然后通过脂肪组织特异性HuR敲除和敲入小鼠模型，探讨HuR对小鼠肥胖发生的影响；最后从脂肪生成与分解、脂肪酸氧化与产热、脂肪细胞增殖分化等环节，观察HuR对相关特异性关键基因表达的影响及调控机制。本项目研究有助于进一步揭示肥胖发生的分子机制，对于深入探讨肥胖防治的作用靶点具有十分重要的意义。

肥胖症及其相关代谢并发症（如非酒精性脂肪肝、血脂异常和II型糖尿病）的患病率迅速增加，已成为威胁人类健康的主要问题。关于肥胖的病因和发病机制，尽管人们进行了广泛的研究，但仍不十分清楚。本项目首先评估了肥胖发生过程中脂肪和肝脏等代谢相关组织中内参基因表达的稳定性，并进一步观察肥胖状态下脂肪组织中HuR表达和核浆分布的变化情况；然后通过脂肪组织特异性HuR敲除小鼠模型，探讨HuR缺失对小鼠肥胖发生的影响；最后通过动物和细胞实验研究HuR影响肥胖发生的机制。主要获取以下研究结果：首先，通过高脂饮食对小鼠内参基因表达稳定性影响的研究，发现在高脂饮食诱导的肥胖过程中，小鼠脂肪组织和肝脏中PPIA，RPLP0或YWHAZ比ACTB和GAPDH更适合用作内参基因。其次，通过高脂诱导的小鼠模型，以筛选出来的稳定性较好的RPLP0为内参，发现肥胖状态下脂肪组织中HuR mRNA和蛋白表达无明显变化，然而高脂饮食促进小鼠脂肪组织中HuR蛋白由细胞核转移至细胞质。第三，通过脂肪组织特异性HuR敲除小鼠模型，发现脂肪组织敲除HuR可抑制高脂饮食诱导小鼠体重的增加。第四，通过分析HuR敲除鼠脂肪组织中脂肪分解、脂肪酸氧化和产热等相关的基因的表达，发现敲除HuR导致产热基因包括 Pgc-1α、Ucp1 和 Dio2等表达增加。第五，通过体外和体内实验，发现HuR可与Ucp1 mRNA结合，进一步研究表明HuR可降低Ucp1 mRNA的稳定性。本项目研究有助于进一步揭示肥胖发生的分子机制，对于深入探讨肥胖防治的作用靶点，具有十分重要的意义。此外，我们筛选出了肥胖发生过程中脂肪和肝脏等代谢相关组织中稳定表达的内参基因，可肥胖研究过程中内参基因的选择提供参考。