基于斑马鱼仔鱼活体模型探究双酚S的致肥胖效应及作用机制

In recent years, increasing exposure to environmental chemicals is one of the great causes of the dramatic increase in obese children. Bisphenol S, an important plastic additive widely used in infants products and food cans, has been described as a potential obesogen, but the underlying mechanism remains unclear. In this study, a zebrafish larvae model was used for in vivo assessment of the obesogenic effect of bisphenol S regarding the cause of obesity through adipocyte cellular biology. First, we evaluated the obesogenic effects of bisphenol S by examining the white adipocyte amount and lipid droplet size, and then explored whether this adiposity was mediated by transcription activation of retinoid X receptor alpha (RXRα) in vivo and in vitro. Furthermore, from the point of lipid metabolism disruption, the obesogenic mechanism of bisphenol S was also revealed by evaluating changes of expression of the triglyceride synthesis and decomposition enzymes (molecular level), lipoprotein levels and expression of the fatty acid binding protein (cellular level), absorption and metabolism of fatty acids in intestine and liver (tissue level), as well as the fatty acids composition and concentration (metabolite level). This research will provide a new thought for understanding the role of chemicals play in the development of obesity, and establish more theoretical basis for the molecular toxicology and health effect evaluation of bisphenol S in the field of food safety.

环境化学物质暴露是近年来儿童肥胖率急剧升高的重要原因之一，双酚S是目前广泛应用于婴幼儿制品及食品包装中的一种重要塑料添加剂，具有潜在的致肥胖效应，但作用机制尚不清楚。本研究利用斑马鱼仔鱼活体模型，基于肥胖发生的细胞生物学成因，首先从脂肪细胞分化、数量与体积的变化，阐明双酚S的致肥胖效应；并从视黄酸X受体(RXRα)的转录激活调控入手，联合体内和体外实验探究双酚S促进斑马鱼仔鱼脂肪细胞分化的分子机制；进一步检测甘油三酯合成和分解相关酶的分子水平、脂蛋白含量及脂肪酸结合蛋白表达量、肠和肝脏中脂肪酸吸收与代谢水平的变化，以及脂肪酸组成与含量(代谢物层次)，从干扰脂质代谢造成过量甘油三脂积累的角度，揭示双酚S的致肥胖作用机制。以期为外源化学物质的致肥胖效应及机制研究提供新的思路与研究体系，为食品安全领域双酚S的分子毒理效应与健康效应评价奠定更多的理论基础。

为探明新型有机污染物双酚S(BPS)在动物体内的致肥胖机制，本项目首先利用环境相关浓度(1、10和100μg/L) BPS暴露斑马鱼自2hpf胚胎到15dpf幼鱼，观察脂肪蓄积部位并定量，检测体内甘油三酯(TAG)等脂质的含量，从不同水平证实BPS可导致15dpf斑马鱼仔鱼脂质蓄积进而引起肥胖；基于斑马鱼仔鱼活体模型，采用相关核受体激动剂或抑制剂与BPS联合处理方法并结合分子对接及离体细胞实验，研究BPS促进斑马鱼仔鱼体内脂肪细胞分化的核受体介导的分子机制；继而从脂肪合成、分解、运输和储存角度检测相关基因表达量及酶活水平变化，并延长暴露至120天，从脂代谢干扰角度进一步阐明BPS的致肥胖机制。.研究结果表明，在BPS的暴露下，15dpf斑马鱼仔鱼肝脏合成TAG显著增加(促进肝脏中催化TAG从头合成相关酶基因acc1、fsan和agpat4表达)，脂质运输受到抑制(下调载脂蛋白apoEa、apoBb.1和apoA-IVb.1基因表达)，使得过量合成的TAG不能被代谢，造成肝脏内TAG蓄积；而过量饮食诱导是通过引起15dpf斑马鱼仔鱼肠内TAG合成增加造成脂质积累引起斑马鱼肥胖。导致斑马鱼仔鱼肥胖的一方面因素是过量脂质蓄积，另一方面则是脂肪细胞数目的增多，本研究还发现，BPS可通过RXRα信号通路促进脂肪细胞分化，由于RXRα可与很多核受体形成“被动”型异源二聚体，继而调控下游靶基因表达，因此结合分子对接和离体细胞实验进一步推断BPS可激活LXRα/RXRα通路，从转录水平影响脂肪酸合成关键基因表达。当延长BPS暴露至斑马鱼成年后，研究结果表明雄鱼肝脏脂肪合成增加但分解代谢能力降低，血浆中脂肪运输受阻，造成肝脏脂肪蓄积，这些脂质得不到充分的转运、消化，导致内质网发生非折叠蛋白反应，加剧肝细胞炎症的发生甚至造成肝细胞凋亡，进而促进了斑马鱼脂代谢紊乱相关疾病的发展。.本研究所建立的斑马鱼仔鱼脂代谢干扰研究体系为解决离体细胞难以模拟体内过程、环境真相难以在体内重现的瓶颈问题提供了有效手段，研究成果对污染性疾病的认识、预防及环境健康与生态安全具有重要的现实意义。