山羊消化道内甜味受体及信号转导通路对甜菊苷和甜菊苷A的感应机理

Animal food intake regulation has always been the key scientific problems in the field of animal nutrition and feed research. Research shows that feeding behavior of ruminant and selection of feeding forage are obviously affected by attractant, such as sweeteners. Furthermore, sweet receptors in mammalian oral-cavity can affect food intake by recognizing the sweet tastant. In recent years, the research areas about sweet receptor, widely existed in the gastrointestinal mucosal epithelial cells, recognizing sweet tastant and regulating the feed intake by means of G protein coupled receptor and sodium/glucose cotransporter 1 (SGLT1) has gradually aroused the attention in the scientific world. However, the effects of sweet taste receptor recognition and the related signal transduction pathways in digestive tract of ruminants on the induction of sweet tastant and feed intake regulation are rarely reported. In this research, goats were selected as test animal. Stevioside and stevioside A, two natural sweeteners with similar chemical structure isolated from Stevia rebaudiana, were used as sweeteners. The aim of this project intends to investigate the effect of the two sweeteners on the regulation of goat feeding, digestion and metabolism; the distribution of the sweet recognition receptor in the digestive tract; the effect of the two sweet substances on the expression of sweet taste receptors and related signaling pathway protein in different parts of the digestive tract mucosal epithelial cells. Thereafter, scientific basis for the development of new green natural sweeteners and food intake regulation of ruminants can be provided.

动物摄食调节一直是动物营养和饲料科学研究领域关注的热点科学问题。相关研究表明，反刍动物的采食行为和对饲料饲草的选择性采食受诱食剂(如甜味剂)的影响较为明显；而且哺乳动物口腔的甜味受体可通过识别甜味物质对采食产生影响。近年来，广泛存在于胃肠道粘膜上皮细胞中的甜味受体通过G蛋白偶联受体和钠离子/葡萄糖共转运载体1（SGLT1）识别甜味进而调节采食的研究业已逐步引起重视，但反刍动物消化道内甜味受体识别和相关信号转导通路对甜味物质的感应与摄食调节的影响鲜见报道。本项目拟以山羊作为试验动物，研究来源于甜叶菊的两种结构相似的天然甜味素甜菊苷和甜菊苷A对山羊摄食调节、消化代谢的影响，并深入研究甜味识别受体在消化道内的分布，以及两种甜味物质影响消化道不同部位粘膜上皮细胞中甜味受体及相关信号通路蛋白表达的差异化机制，为开发新型绿色天然甜味剂和对反刍动物进行摄食调控提供科学依据。

动物摄食调节是动物营养和饲料科学研究领域关注的一个热点科学问题，反刍动物的采食行为和对饲料饲草的采食会受到诱食剂(如甜味剂)的影响。目前天然甜味剂对反刍动物采食的影响以及反刍动物消化道内甜味受体对甜味物质的感应鲜见报道。本项目研究了甜叶菊中提取天然甜味剂甜菊苷和甜菊苷A的加热提取工艺方法，并以成年羊和羔羊作为试验动物，研究来源于甜叶菊的天然甜味素甜菊苷和甜菊苷A对山羊摄食调节、消化代谢的影响，并研究了甜菊苷A对羔羊消化道甜味剂受体基因表达的影响。筛选出甜叶菊中甜菊苷和甜菊苷A加热回流提取的最佳提取工艺，即以水为提取溶剂进行加热提取，提取温度80℃及提取时间60 min，提取3次。重复性试验验证结果表明，该提取工艺稳定可行。项目研究显示，甜菊苷倾向于增加山羊的日粮干物质采食量（P = 0.077），并且山羊粗饲料和日粮的日均干物质采食量均随着甜菊苷添加浓度的增加呈线性增加（P < 0.05），同时，甜菊苷显著影响了NDF和ADF的消化率（P < 0.05）。添加甜菊苷A组山羊的日粮日均采食量略高于对照组，但各处理组间的粗料和日粮日均采食量以及养分消化率没有显著差异。羔羊试验表明，在第1至10 d，甜菊苷A组日平均采食量明显高于对照组，两组间差异接近极显著水平（P = 0. 016），而在第11至20 d，两组日平均采食量没有显著差异（P = 0. 248），从试验全期（1-20 d）来看，饲喂甜菊苷A开食料有显著提高采食量的趋势（P=0. 068）。甜菊苷A组羔羊的平均日增重显著高于对照组羔羊（P=0. 049）。项目通过对甜菊苷或甜菊苷A对成年山羊和羔羊采食量的研究，为甜菊苷和甜菊苷A在山羊乃至反刍动物生产中的应用提供了科学依据。通过以上甜菊苷或甜菊苷A对成年山羊和羔羊采食影响的研究，为甜菊苷和甜菊苷A在山羊乃至反刍动物生产中的合理应用提供了科学依据。