应用转基因、基因敲除小鼠研究新基因NYGGF4在肥胖发生发展中的功能与机制

In the previous report, we isolated and characterized a novel human gene NYGGF4 (GenBank accession No. AY317148), which was expressed at a higher level in adipose tissue from obese versus normal weight subjects. Our further studies revealed that NYGGF4 stimulates preadipocytes proliferation and is involved in obesity-associated insulin resistance through the mitochondrial dysfunction and blocking the PI3K/Akt pathway in adipocytes. All of these results provided evidence that NYGGF4 might play an important role in the development of obesity. Furthermore, we generated adipose tissue-specific NYGGF4 expression transgenic mice (F5) and NYGGF4(flox/+) mice (F4) for adipose tissue-specific conditional knockout, and found that the transgenic mice fed with high fat diet have increasing weights, dyslipidemia, insulin resistance and inhibition of the PI3K/Akt pathway. Based on these data, we will further investigate the roles of NYGGF4 using adipose tissue-specific NYGGF4 expression transgenic mice and adipose tissue-specific NYGGF4 conditional knockout mice in this study. We will dissect the functions and mechanisms of NYGGF4 on the development of obesity by analyzing the obesity phenotype, the function of adipose tissue and adipocytes, and the underlying mechanisms in NYGGF4 transgenic and knockout mice. This study is of certain creativity and will provide a new avenue for the prevention and treatment of obesity and its complications in the future.

NYGGF4基因是本研究小组2003年克隆到的、一条差异高表达于肥胖者脂肪组织中的人类全长新基因（GenBank登录号AY317148）。前期研究发现，该基因能显著影响脂肪细胞增殖，并以线粒体功能障碍、PI3K/Akt通路抑制等机制影响脂肪细胞的胰岛素敏感性，提示NYGGF4基因参与肥胖发生发展。本研究在已获得NYGGF4脂肪组织特异性转基因小鼠F5代、有良好预实验结果（高脂饮食下转基因小鼠体重显著增高、血脂异常、胰岛素抵抗、PI3K/Akt通路明显受抑）、脂肪组织特异性敲除小鼠的制备已获NYGGF4(flox/+)小鼠F4代等基础上，拟应用转基因、基因敲除小鼠开展NYGGF4基因的整体功能研究，通过肥胖表型分析、脂肪组织与细胞功能评估、机制论证等，阐明NYGGF4基因在肥胖发生发展中的功能与机制。本课题研究具有源头创新性，若获成功可为肥胖及并发症的防治提供新靶标。

NYGGF4是我们克隆到的、一条差异高表达于肥胖者脂肪组织中的人类全长新基因，本项目在前期发现其显著影响脂肪细胞增殖，以线粒体功能障碍、PI3K/Akt 通路抑制等机制影响脂肪细胞胰岛素敏感性基础上，应用转基因、基因敲除小鼠，阐明NYGGF4基因的整体功能。研究发现：①正常饮食下NYGGF4脂肪组织特异性转基因小鼠无异常表型，但高脂饮食诱导12周后即陆续呈现体重显著下降、胰岛素敏感性与糖耐量降低、高血糖伴肝功能受损、甘油三酯清除率降低等表型，且体脂减少、脂肪细胞炎症反应、线粒体功能受损、胰岛素信号通路受抑等；②NFGGF4脂肪组织特异性敲除小鼠虽无明显异常表型，但其全身敲除小鼠的糖代谢却显著增强，其机制与多组织（肝、骨骼肌、脂肪等）AKT磷酸化活性增强有关，部分指标（如：胰岛素敏感性等）则存在雌雄差异；③NYGGF4基因过表达能促进人脂肪细胞的增殖、明显抑制人脂肪细胞糖摄取能力；④NYGGF4可能存在于GLUT4转运囊泡，并通过与LRP1直接结合，降低GLUT4蛋白总量，致NYGGF4转基因小鼠出现胰岛素抵抗的表型，从而为理解NYGGF4基因的功能及在肥胖、2型糖尿病中的作用与机制提供了新的实验证据。