食物甜度通过肠道甜受体诱发饱腹感激素释放量值关系研究

Satiety refers to the processes that induce meal termination, thereby limiting energy intake. Intestine plays a crucial role in regulation of satiety, which mainly results from the release of intestinal satiety hormones (cholecystokinin, CCK; glucagons-like peptide 1, GLP-1; peptide tyrosine tyrosine, PYY). We all know that sweet substance is an important part of animal foodstuff and one of the critical sources of energy for animals. However, the details that sweet stimuli augment release of intestinal satiety hormones through sweet receptor on the endocrine cells remain unclear. Consequently, in this proposal, the endocrine cell lines STC-1, NCI-H716 and ICR mice will be used as cell and animal model system to investigate the correlation between the intestinal satiety hormones (CCK, GLP-1, PYY) release and the sweet stimuli, including single sweetener and blend sweeteners (binary or ternary mixtures of sweeteners, mixtures of sweeteners and sweet enhancers, mixtures sweeteners with and without sweet inhibitors). The satiety hormones levels will be determined using enzyme-linked immunosorbent assay (ELISA) which has been widely used. To determine the secretion of satiety hormones (CCK, GLP-1, PYY) from cell model, the supernatant is collected from the cultures of STC-1 or NCI-H716 incubated with kinds of sweeteners (including single sweetener and blend sweeteners ) in a sweetness and time dependent. Whereas, the intestinal hormones secretions from model mice and dissected alive intestine tissue mince are collected from the blood sample after different exposure mode of sweet stimuli (oral, gavage administration, specific intestinal) and the supernatant between minced specific intestinal minced tissue and sweet stimuli, respectively. Moreover, the qualitative and quantitative analysis of sweet receptor and taste signaling transduction protein (α-gustducin, PLCβ2) of cell and animal model (duodenum, jejunum and ileum) will detected by immunohistochemistry and real-time PCR. Through above experiments, we will try to reveal following scientific questions, which is also the core issue proposed in this study: Is there any difference between the effects of differnt sweet stimuli on satiety hormones release and what is the correlation between sweetness of sweetener and the level of satiety hormones release? Is there any synergism between sweeteners, or/and sweeteners and sweet enhancers on the satiety release just like their functions in the oral? and what is the relationship of the distribution and expression level of sweet receptor, sweet perception and the satiety hormones secretion rates. The elaboration of above mentioned scientific questions may be provide necessary evidentce for the comprehensive understanding of mechanism of intestinal sweet taste perception and the development of new sweeteners，which will have significant influence on the food science and food industry.

肠道也有味受体？也能感受味道？它们的功能是什么？新的科学视野聚焦于肠道味受体对营养物质吸收和饱腹感的调控上，热切需要新的发现。申请人在长期味觉分子细胞生物学研究积累基础上，从食品科学基础角度，提出了食物甜感强度经肠道甜味受体途径诱发饱腹感激素释放量值关系的科学问题和研究方案。基于食物甜味及甜度作用方式的复杂性，本研究以肠道味细胞系STC-1及NCI-H716、ICR小鼠离体肠道活组织和小鼠活体三个层次为研究对象，通过甜味物质的天然与人工、单一与复合、増强与抑制等方式，定量肠道饱腹感激素CCK、GLP-1、PYY释放。围绕甜感强度与肠道饱腹感激素释放之间的定量关系这个核心，从刺激甜感强度依赖性和刺激时间依赖性出发，试图了解不同甜味物质的甜感强度组合复配对肠道饱腹感激素释放是否有増效作用？了解天然甜味剂与人工甜味剂对肠道甜味受体作用方式效果是否一致？这对食品科学和产业具有最基础的科学意义。

随着社会经济及生活方式的快速发展，流行性慢性代谢综合症正严重威胁着人类健康，高甜度人工甜味剂广泛应用是否在其中也起着推波助澜的作用，引起科学界长期焦虑性困惑。甜味感受受体不仅存在于口腔，还广泛存在于胃肠道、胰腺等各种器官中，或许可能与能量摄入及慢性代谢综合症的发生发展息息相关，但一直都缺少完整的合理的科学实验证据，这是迫切需要去认知的一个科学问题。. 项目组基于对甜味生物学研究长期积累，围绕人工甜味剂正常甜度、肠道葡萄糖吸收及肠道甜味受体之间相关性这个核心问题，在多模型体系中建立了有特色的实验研究体系，获得了系列原创性成果，明确了人工甜味剂生物不安全性的表现形式及机制。结论是：（1）甜味剂短期暴露即可升高食物的固有属性——升糖指数GI（Glycemic Index），该指数的升高可能是导致餐后血糖异常的一个直接原因； （2）人工甜味剂短期暴露可实时导致实验大鼠可观察的血糖异常波动，在大鼠动态血糖波动实时监测实验模型中，其结果显著大于饮水对照组；（3）人工甜味剂短期暴露即可导致十二指肠葡萄糖吸收速率明显提升，其通过影响肠道内分泌细胞甜味受体显著上调，从而诱发肠道激素分泌增加，调控了十二指肠组织细胞中葡萄糖转运体表达量，但整个肠段葡萄糖吸收总量并不改变，这个过程在细胞及动物模型中都已被证实； （4）食物饮食结构调整（特别是碳水化合物含量降低），对甜味剂暴露诱发血糖异常波动发生的风险有积极的调控作用；（5）人工甜味剂长期暴露可独立直接诱发机体葡萄糖耐受能力降低，这可能与甜味受体介导的十二指肠葡萄糖吸收速率增强长期改变有关。. 在上述新的实验结果启示下，重新审视消化系统中胰十二指区系的结构与功能，特别是从胰头十二指肠、胰尾、肠系（空肠回肠等）三路独立的动静脉血流通路，导致胰头（新生血糖胰岛应激）与胰尾（体血管循环血糖胰岛应激）具独立功能区的事实出发，在食品科学的角度一个值得关注的更深入的科学问题是：餐后十二指肠葡萄糖吸收高速率驱动着一个胰头部通路中高风险性的高血糖应激动态区，导致经常性餐后血糖异常波动，这或许是现代慢性代谢综合症发生的一个主要驱动力，人工甜味剂可能在其中起着重要的强化作用。这些科学发现，或许将对餐后血糖的控制及餐后血糖异常波动衍生的系列慢性代谢综合症研究提供了一个新的科学观点与视野。