Adropin调控罗非鱼摄食和糖脂代谢的作用机制研究

Adropin is a secreted protein which is encoded by energy homeostasis associated gene. Adropin plays important roles in food intake, glucose and lipid metabolism in mammals. However, the exact mechanisms by which adropin affects food intake, glucose and lipid metabolism remain unclear. Based on the successful identification of adropin in tilapia, our pilot studies further demonstrated that adropin could 1) promote food intake in tilapia, 2) stimulate glucose uptake in primary cultured tilapia hypothalamic cells, 3) control the expression of key hepatic metabolic enzymes and transcription factors, and 4) inhibit hepatic glucose output and triglyceride production. To further elucidate regulatory mechanisms of adropin on food intake, glucose and lipid metabolism in fish, using tilapia (Oreochromis niloticus) as an animal model, our research will employ in vivo and in vitro experimental methods to systematically study: 1) the expression and localization of adropin in different brain regions; 2) the stimulatory mechanisms of adropin on food intake in tilapia; 3) the molecular mechanisms of adropin regulating glucose sensing at the hypothalamic level; and 4) the molecular mechanisms of fish adropin on hepatic glucose and lipid metabolism. The proposed study will provide novel insights into the regulatory mechanisms of adropin on food intake, glucose and lipid metabolism in fish and its potential applications in aquaculture.

Adropin是由能量动态平衡相关基因编码的分泌性蛋白。在哺乳动物中adropin具有调节摄食和糖脂代谢的功能，但其作用机制仍待阐明。本项目在申请者成功鉴定罗非鱼adropin的基础上，进一步阐明adropin能促进罗非鱼摄食，促进下丘脑神经细胞对葡糖的摄取，并参与调控肝脏细胞糖脂代谢关键酶和转录因子表达，抑制肝糖输出和甘油三酯合成。为了深入解析adropin调控鱼类摄食和糖脂代谢的作用机制，本研究以尼罗罗非鱼为动物模型，采用在体和离体多种实验方法系统研究adropin：1)在不同脑区的表达定位；2)促进罗非鱼摄食的分子机制；3)在下丘脑葡萄糖感知中的调节机制；4)调控肝脏糖脂代谢的作用机制。项目成果对阐明adropin调控鱼类摄食和糖脂代谢的作用机制及其在水产养殖中潜在的应用提供理论基础。

神经肽通过下丘脑-垂体-靶腺轴调控脊椎动物摄食、生长和能量代谢等重要生理活动。Adropin是由能量动态平衡相关基因编码的内分泌因子。目前，针对adropin生物学功能和表达调控的研究只局限于哺乳类，在其他脊椎动物中的研究还是一片空白。我们研究发现罗非鱼餐后 1 小时，adropin mRNA表达水平在嗅球、下丘脑和视顶盖中下降，而禁食 7 天导致adropin mRNA 水平在嗅球、下丘脑和视顶盖中增加。腹腔注射adropin可以刺激罗非鱼摄食。进一步，在体和离体实验证实adropin通过上调食欲刺激因子（Npy，Orexin, 和Apelin）和下调食欲抑制因子（Pomc和Cart）进而刺激罗非鱼摄食。通过免疫组化检测adropin在罗非鱼垂体的远端 (PPD) 中表达。利用原代培养罗非鱼垂体细胞，罗非鱼 adropin 可有效刺激 GH mRNA 水平。然而，使用 adropin 抗血清会抑制 GH 基因表达。进一步发现adropin 处理增加GH 转录的半衰期，这表明 adropin 可以保护细胞质 GH mRNA 免受降解。此外通过高脂喂食，我们建立了稳定的营养型脂肪肝病罗非鱼模型。进一步，通过在体和离体实验研究发现adropin可以显著抑制肝脏糖异生关键酶PEPCK1和G6Pase表达和酶活性，最终抑制肝脏葡萄糖输出。同时，我们发现adropin可以通过抑制SREBP-1c、ACCα和CD36基因和蛋白表达，并阻碍成熟SREBP1向肝细胞核转运，进而下调甘油三酯合成。通过药理学和RNAi技术进一步证实AMPK等信号分子参与了adropin介导的罗非鱼糖脂代谢调控。这些研究结果丰富了内分泌因子对鱼类摄食、生长和能量代谢调控的分子机制和信号网络。