外周5-羟色胺系统在糖皮质激素及高脂饮食诱导胰岛素抵抗时的作用研究

It has been reported that 5-HT can induce insulin resistance (IR) in the hepatocytes, adipocytes and myotubes, and exacerbate hepatic steatosis in the mouse model of non-alcoholic fatty liver disease (NAFLD). We have found originally that chronic stress, dexamethasone (Dex) or high-fat diet (HFD) feeding-induced IR are closely associated with increased 5-HT synthesis and 5-HT 2 receptors (5-HT2Rs) in the hepatic tissue and visceral adipose tissue, and increased 5-HT2Rs in the skeletal muscle. The purposes of this study are to elucidate whether the alteration of peripheral 5-HT system is a crucial reason for aforementioned factors-induced IR, and to clarify the mechanism and key signaling pathways when 5-HT mediates glucocorticoids or HFD-induced IR. The research would chiefly focus on hepatic tissue IR, and also on visceral adipose tissue and skeletal muscle IR secondarily; We would make animals and cells IR models with SD rats, wild-type and gene knock-out mice, primary hepatocytes and adipocytes, and gene silencing cell lines. The research findings would have theoretical and clinical value for us to assess the role of peripheral 5-HT system in mediating IR generation and to understand whether has a common mechanism for various factor-inducing IR, this would also provide a new idea and target for the treatment of metobolism syndrome and type 2 diabetes mellitus.

5-羟色胺(5-HT)已被证明可诱导肝细胞、脂肪细胞、肌管细胞产生胰岛素抵抗(IR)并加重非酒精性脂肪肝小鼠模型脂肪变性。我们首次发现，慢性应激、地塞米松或高脂饲料喂养诱导的IR与肝组织、内脏脂肪组织5-HT合成及5-HT2受体(5-HT2Rs)增加、骨骼肌5-HT2Rs增加密切相关。本项目旨在阐明这种外周5-HT系统改变是否为这些因素诱导IR的重要原因，阐明机制并弄清牵涉的关键的能量代谢调节信号通路。研究拟主要针对肝脏IR，次要涉及内脏脂肪组织及骨骼肌IR；应用“SD大鼠、野生型及基因敲除小鼠、原代肝细胞及脂肪细胞、基因沉默的细胞株”建立动物及细胞IR模型。研究成果对于“评价外周5-HT系统在IR发生时的作用、了解多种因素诱导IR是否存在普遍规律”有理论和临床意义，可能为代谢综合征、2型糖尿病的临床治疗提供新思路和新靶点。

背景 5-HT涉及肝脏及脂肪组织代谢已有研究报导。研究认为，来自于胃肠道的5-HT通过作用于5-HT2A受体(5-HT2AR)介导代谢异常。本项目研究了器官本身合成的5-HT及5-HT2AR在诱导代谢异常及器官损伤时的作用。.主要研究内容 研究了5-HT合成及5-HT2AR与“糖皮质激素(GC)、慢性应激(CS)诱导胰岛素抵抗(IR)及糖脂代谢异常，高脂饲料诱导肝脂肪变性，2型糖尿病(T2DM)小鼠的骨骼肌能量代谢异常，四氯化碳(CCl4)诱导急性肝损伤，顺铂诱导急性肾损伤，及动脉粥样硬化(AS)发生”的相关性。.重要结果 研究表明，器官本身的5-HT系统激活在其能量代谢异常、器官损伤时起关键性作用。综合研究结果，有害刺激(高脂、高糖、毒性化学物质)通过诱导细胞的5-HT2AR上调、5-HT合成增加及5-HT在线粒体经单胺氧酶A(MAO-A)催化的降解增加调控细胞功能。5-HT2AR介导PKCε激活及其下游的Akt、mTOR、ERK1/2磷酸化，促进细胞的脂质合成、糖异生等糖脂代谢异常，导致脂肪变性、IR。同时，5-HT2AR也调控MAO-A表达；激活的5-HT降解，诱导线粒体产生ROS并抑制抗氧化酶(SOD，过氧化氢酶等)活性，激活MAPKs、STAT3激酶及NF-κB，从而促进炎症、细胞凋亡。.关键数据 有关细胞5-HT系统调控细胞功能，经动物及细胞实验，获得了以下研究的实验数据：GC、CS诱导肝细胞糖脂代谢异常、脂肪组织脂解及骨骼肌IR；高脂饲料诱导NAFLD；T2DM小鼠的疲劳，骨骼肌氧化应激、糖原及ATP合成减少；CCl4诱导急性肝损伤，导致肝细胞氧化应激、炎症信号通路激活、炎症；顺铂诱导急性肾损伤，导致肾小管上皮细胞氧化应激、炎症、细胞凋亡；高脂饲料喂养ApoE基因敲除小鼠引起的AS，脂质诱导THP-1源性巨噬细胞泡沫细胞化、炎症因子分泌及诱导人脐静脉内皮细胞炎症因子、单核细胞趋化因子分泌。.科学意义 有害刺激通过诱导细胞的5-HT2AR表达、5-HT合成及降解增加，使其发生代谢紊乱、氧化应激、炎症、细胞凋亡等异常。这是普遍规则，可见于肝细胞、骨骼肌细胞、肾小管上皮细胞、巨噬细胞、血管内皮细胞。本研究对于弄清肝、肾、动脉相关疾病的发病机制，细胞5-HT系统的生物学作用，及相关疾病的治疗方法有明确的理论及实践意义。