Ghrelin/Obestatin在草鱼摄食调控中的作用及机理研究

Ghrelin and obestatin are the two peptides isolated from the gastrointestinal tract and encoded by the same preproghrelin gene, the balance of ghrelin and obestatin is critical to the regulation of food intake and energy homeostasis. Until today, there are studies only for ghrelin providing well established and repeatedly validated insights on its regulatory effect on food intake. The effects of obestatin on feeding behavior still remain largely unknown and are being controversially discussed in the recent literatures. Grass carp are the important freshwater economic fish species in our country. The present study conducted to examine effect of ghrelin and obestatin proteins and feeding regime on the daily food intake, feeding rhythm, the key regulator and the proteins expression for grass carp in vivo and in vitro conditions; the interrelation of ghrelin, obestatin, and the receptor of ghrelin and obestatin of grass carp in different nutrition station using with the methods of fish nutrition and physiology research and the molecular biology techniques, exploring the function of ghrelin/obestatin in regulation of food intake for Grass carp, revealing the machanism of in regulation of food intake for Grass carp. To carry out the research would provide a theoretical basis for developing new products on orexigenic feed additive, the findings will enrich the information of the mechanism in regulation of food intake for fish, and could improve the utilization of aquatic animal feeds, providing a theoretial basis for reducing the water pollution in the process of aquaculture.

Ghrelin 和obestatin 来自于同一基因的多肽，是调控机体食欲和能量平衡的一对生理功能相反的调节因子，二者功能的协调发挥是机体维持自稳态调控摄食和能量平衡的重要机制。本项目拟以我国重要的淡水经济鱼类草鱼为研究对象，结合鱼类营养生理学研究方法和分子生物学技术，研究草鱼ghrelin 和obestatin 蛋白活体和离体条件下处理和投喂策略对草鱼日摄食率、摄食节律、摄食调控关键基因转录与蛋白表达的影响，以及不同营养状态草鱼ghrelin、obestatin及其受体表达的变化规律，探讨ghrelin和obestatin对草鱼摄食活动的可能调控作用，揭示ghrelin和obestatin 在鱼类摄食活动中的作用机理。本项目的开展将会为进一步优化草鱼的投饲策略提供一定的理论基础，研究结果将丰富鱼类摄食调控机理的研究资料，并有望提高鱼类饲料的利用率，为减轻养殖过程对水环境污染提供理论依据。

Ghrelin和Obestatin是来自于同一前体物质preproghrelin的脑肠肽，二者功能的协调发挥是机体维持自稳态调控摄食和能量平衡的重要机制。本项目运用鱼类营养生理学方法和分子生物学技术，以重要的淡水经济鱼类草鱼为研究对象，采用摄食生长实验与腹腔注射相结合的方式，较系统的解析了ghrelin和obestatin蛋白对草鱼摄食和摄食调控相关基因表达的调控机制，初步阐明了鱼类摄食调控的分子机制。本项目主要完成以下工作：①在利用同源克隆技术获得了草鱼ghrelin 及其受体基因GHS-R 1a的cDNA序列的基础上，采用生物信息学方法对ghrelin、obestain和GHS-R 1a的氨基酸序列进行了预测，并检测了草鱼ghrelin和GHS-R 1a 在各组织中mRNA的表达情况。②采用腹腔注射法研究了ghrelin和obestatin蛋白对草鱼摄食和摄食调控相关基因表达的影响，结果表明草鱼腹腔注射ghrelin（100 ng g-1 BW）后摄食量显著性增加，同时注射ghrelin（100 ng g-1 BW）与obestatin蛋白（25 ng g-1 BW）表现出抑制ghrelin引起的摄食量增加。在ghrelin蛋白高响应的草鱼个体中，相比注射生理盐水的对照组，注射ghrelin蛋白表现出NPY mRNA，Y8a和Y8b基因表达量显著性上升，草鱼腹腔同时注射ghrelin和obestatin蛋白后，以上基因表现出下调的趋势，预示着obestatin蛋白有抵消ghrelin蛋白诱导的食欲调控基因上调的现象。③研究了草鱼餐前和餐后、短期和长期饥饿处理其食欲相关基因的表达变化规律，结果表明饥饿处理会使草鱼脑垂体中GHS-R1a mRNA 表达水平和血浆中生长激素表达水平升高。④研究了不同投喂策略（投喂频率和月饱食度）对草鱼幼鱼摄食、生长、饲料利用和养殖水体水质的影响，结果表明草鱼幼鱼的摄食率和特定生长率随着投喂频率的增加而升高（P <0.05）。90%月饱食度组的饲料系数最低，饲料利用率最高。水体氨氮、硝态氮和磷酸盐含量随着月饱食度增加而显著性增加（P<0.05）。表明90%月饱食度为保持草鱼幼鱼最佳生长状态和水质污染最低的投喂策略。本项目的研究成果丰富了鱼类摄食调控机理的研究资料，同时也为提高鱼类饲料的利用率，为减轻养殖过程对水环境污染提供理论依据。