S100A8/A9经NF-κB信号通路调控肥胖儿童糖代谢异常的中枢机制研究

Abnormal glucose metabolism contributes to the pathogenesis of childhood obesity and type 2 diabetes mellitus (T2DM), but the detailed mechanism is still largely unknown. In our preliminary study, we found that serum S100A8/A9 protein levels were higher in obese than in healthy children using a proteomics method. S100A8/A9 proteins were highly expressed in the hypothalamus of the high fat diet (HFD)-induced obese mouse. Intracerebroventricular injection of S100A8/A9 increased plasma glucose concentration in young control mice. Furthermore, the firing frequencies of glucose sensing neurons in the hypothalamus were significantly reduced after treating with exogenous S100A8/A9 proteins in both control and obese mice. In addition, S100A8/A9 significantly up-regulated NF-κB expression in hypothalamic GT1-7 cells. These preliminary results suggest that S100A8/A9 may regulate glucose metabolism and energy balance via NF-κB pathway. In this project we propose to apply overexpressing and silencing strategy to explore the central mechanism of S100A8/A9. We will further investigate the roles of S100A8/A9 using neuronal tissue-specific S100A8/A9 transgenic and conditional knockout mice. We also plan to investigate the function of S100A8/A9 in T2DM by looking at the NF-κB signal pathway. This study is important to childhood obesity and T2DM research and will provide a new avenue for the prevention and treatment of obesity and T2DM in the future.

糖代谢异常是儿童青少年肥胖和2型糖尿病（T2DM）的重要病理学改变，但其机制尚未完全阐明。前期研究中，我们通过蛋白质组学技术发现S100A8/A9蛋白差异高表达于肥胖儿童血清中；小鼠脑室内注射S100A8/A9蛋白能显著升高血糖；S100A8/A9能显著降低肥胖小鼠的葡萄糖耐受性，显著抑制下丘脑葡萄糖敏感神经元的放电频率；下丘脑来源的GT1-7细胞过表达S100A8/A9后，上调NF-κB，提示S100A8/A9可能通过调节NF-κB信号通路导致糖代谢异常。本研究拟应用过表达、沉默策略评价S100A8/A9对中枢能量平衡、胰岛素途径信号通路的影响；应用转基因、基因敲除小鼠开展S100A8/A9在肥胖糖代谢异常中的功能与机制研究；并以NF-κB信号通路为切入点，分析S100A8/A9影响肥胖儿童糖代谢异常的分子机制。本课题研究具有源头创新性，若获成功可为肥胖及T2DM的防治提供新的理论依据。

S100A8/A9在肥胖、糖代谢异常以及胰岛素抵抗中发挥重要作用。本项目采用高脂饮食诱导构建幼鼠肥胖模型，利用免疫组化、分子生化、神经电生理等技术手段，对S100A8/A9参与肥胖以及糖代谢异常的中枢调控机制进行了初步研究。首先采用iTRAQ蛋白质组学技术检测肥胖患者外周血中S100A8/A9表达特点,发现S100A8/A9在肥胖儿童外周血中高表达。构建幼鼠肥胖模型，观察小鼠肥胖表型、摄食行为及能量代谢情况，发现肥胖小鼠存在阴门开放时间提前。到成年期，检测外周血中相关因子变化，发现其瘦素水平下降，血糖水平明显升高，胰岛素水平未见明显差异性改变。检测肥胖小鼠S100A8/A9在中枢的表达特点,发现S100A8/A9蛋白在肥胖小鼠下丘脑高表达, 进一步明确S100A8/A9 在下丘脑神经元和星形胶质细胞中表达。同时，采用膜片钳电生理，检测到S100A8/A9高表达后下丘脑神经元兴奋性下降，神经元葡萄糖代谢水平下降。S100A8/A9可通过改变POMC神经元抑制性突触后电流的幅度及decay时间，参与下丘脑代谢调控。构建干扰病毒构建S100A8/A9下丘脑条件敲除小鼠，可挽救高脂饮食导致的幼年肥胖发生。最后，通过检测 NF-κB 信号通路关键因子TLR4，p65以及ERK，发现S100A8/A9可上调pP65与pERK蛋白表达。综合上述结果，本研究为探讨S100A8/A9通过NF-κB信号通路调控肥胖儿童胰岛素抵抗的中枢机制奠定了坚实的工作基础，同时我们还发现了肥胖幼鼠存在性早熟的现象，对肥胖儿童发生性早熟研究提供了重要的启示性线索。