SREBP-2、RXRα和ApoA-2基因在高血糖长爪沙鼠胰岛素抵抗中的机制

SREBP-2, RXRα and ApoA-2 were separately correlated with diabetes mellitus or IR and the expression of ApoA-2 was regulated by SREBP-2 and RXRα. In our previous studies, hyperglycemia Mongolian gerbil inbred strain with the insulin resistance (IR) phenotype has been breeded. We found that the expression of ApoA-2 and RXRα were decreased in keletal muscle and adipose tissue of hyperglycemia Mongolian gerbil. But taget organ or tissue and pathogenesis of IR are unclear. Moveover, we also found that expression of SREBP-2 was not feedback inhibited result insusceptibility of non-alcoholic fatty liver disease in Mongolian gerbils. We hypothesize that SREBP-2 and RXRα induced IR by regulating ApoA-2 in some tissue of hyperglycemia Mongolian gerbil. To answer these questions, We will detect the expression of insulin receptor, insulin receptor substrate (IRS) and insulin signal transduction pathway in main organ of IR in hyperglycemia Mongolian gerbil, which will illuminate taget organ or tissue and pathogenesis of IR. Base on this, we explain SREBP-2, RXRα and ApoA-2 regulated insulin signal transduction pathway by over-expression and konwdown in target histocype. The RXRα and ApoA-2 will be knowout in Mongolian gerbil for dominstrste their effect. This results present study will illuminate the pathogenesis of IR in hyperglycemia Mongolian gerbil, and help the animal model standardization.

SREBP-2、RXRα和ApoA-2基因分别与胰岛素抵抗（IR）或糖尿病相关，其中SREBP-2和RXRα可直接调控ApoA-2表达。我们培育了具有IR表型的高血糖长爪沙鼠模型近交系，其肌肉和脂肪组织中ApoA-2和RXRα表达显著降低，但其受累器官和发生机制不清；我们还发现长爪沙鼠无法反馈抑制SREBP-2基因表达。推测高血糖长爪沙鼠IR组织器官中SREBP-2和（或）RXRα通过ApoA-2影响IR。为验证这一假说，本课题拟首先比较分析胰岛素受体表达及胰岛素信号通路变化，探明IR组织器官；采用组织细胞原代培养和基因表达调控技术，分析SREBP-2、RXRα和ApoA-2基因对胰岛素信号通路的影响及相互关系，阐明上述基因在长爪沙鼠IR中的调控关系；构建ApoA-2和RXRα基因敲除长爪沙鼠，进一步证实RXRα和ApoA-2对IR的影响，揭示长爪沙鼠IR发生机制，为该模型标准化奠定基础。

前期自行培育的自发糖尿病长爪沙鼠模型，但是其胰岛素耐受机制不清。本研究该模型为研究材料，首先通过血液学指标和组织学指标初步确认了肝脏和胰腺为受累器官。利用SHH技术和候选基因法筛选并验证了与糖代谢和脂代谢相关基因17个，初步阐释长爪沙鼠自发糖尿病的发病机制和信号通路。利用肝脏、肌肉和脂肪细胞以及基因抑制剂和激动剂证实了SREBP-2和RXRα基因可以通过调节ApoA-2基因表达进而调控胰岛素受体基因表达并影响胰岛素敏感性。本研究还在国内外首次利用CRSIPR技术成功建立长爪沙鼠基因敲除动物。分析发现基因敲除长爪沙鼠空腹血糖、体重、糖耐量等指标中仅RXRα基因敲除雄性长爪沙鼠OGTT有升高趋势，其他表型未见明显差异。在高脂饲料诱导下ApoA-2基因敲除长爪沙鼠血清中胰岛素、总胆固醇、高密度脂蛋白和游离脂肪酸变化不明显，但是胰岛素耐量和糖耐量明显升高，表明胰岛素敏感性降低，进一步将导致胰岛素耐受并发生2型糖尿病。本项目中初步明确了长爪沙鼠自发糖尿病模型靶器官，建立长爪沙鼠基因敲除技术体系，并在细胞和动物水平初步阐释了SREBP-2和RXRα可以通过ApoA-2基因影响对胰岛素敏感性的机制。