利用代谢组学方法研究牛磺酸调控鱼类生长的机制

The sulfur-containing β-amino acid, taurine, is a conditionally essential amino acid for fish growth and plays a vital role in several important biological functions such as bile salt conjugation, osmoregulation, membrane stabilization, antioxidation, and early development of visual and neural systems. A comprehensive understanding of taurine in fish biosynthesis, metabolism and its regulation mechanisms will provide a theoretical basis for the efficient use of animal and plant protein ingredients and the development of feed formulations, thus improving the economic efficiency of fish farming. Using high resolution 1H nuclear magnetic resonance (NMR) spectroscopic profiling of biological fluids combined with multivariate analysis, the metabolites that correlate with changes of physiological conditions are identified. In this study, the economically important aquaculture species of grouper and tilapia are selected as the target animal. NMR-based metabolomic techniques are used to assess the effects of dietary taurine on the growth of the two fishes rearing in various research conditions. One dimensional 1H-NMR measurements of the tissue supernatants of plasma, liver and bile are recorded on a NMR spectrometer. The spectra were manually phased and the baseline was automatically corrected. The acquired spectrum for each sample is processed and subsequent data is reduced using unsupervised principal component analysis and supervised partial least squares discriminant analysis to detect the different spots corresponding low-molecular weight metabolites and identify the metabolites causing significant differences,thus constructing metabolic network of taurine related to fish growth. Based upon the above results, the metabolic characteristics of taurine and its biological mechanisms in fish will be elucidated.

牛磺酸是鱼类的条件性必需氨基酸，在渗透压调节、营养物质代谢、免疫调节、抗氧化等方面具广泛的生物学功能。全面了解牛磺酸在鱼体内的生物合成、代谢及其调控机制可为高效地利用动植物蛋白原料、合理地制定饲料配方、提高养殖效果提供理论依据。本项目选取具有重要经济意义的水产养殖种类石斑鱼和罗非鱼为研究对象，采用核磁共振（1H-NMR）技术，获得这些养殖鱼类在不同外在因素（牛磺酸丰缺和生长进程）下的血浆和肝脏中的代谢物指纹图谱，利用非监督的主成分分析方法和监督的偏最小二乘法辨别分析方法分析血浆和肝脏中的代谢物差异，鉴定和筛查其中有重要代谢差异的特征代谢物，揭示与牛磺酸营养和生长发育密切相关的代谢变化规律，构建鱼体牛磺酸代谢网络，阐明牛磺酸调节鱼类生长的生物学机制。

牛磺酸是鱼类的条件性必需氨基酸，且具有广泛的生物学功能。为了探明牛磺酸对鱼类营养代谢调控的生理学机制，本项目首先研究了饲料牛磺酸水平对养殖鱼类石斑鱼和罗非鱼生长和生化指标的影响，结果发现，饲料中维持一定水平的牛磺酸有利于鱼类生长，但饲料牛磺酸不足或过多均不利于其生长，饲料牛磺酸的需要随鱼龄的增长而降低。饲料中添加牛磺酸对鱼类具有明显的促生长和降脂作用，并能够显著影响其糖脂代谢。在此基础上，我们利用核磁共振（1H-NMR）技术进一步研究了不同生长阶段和饲料中不同牛磺酸水平下罗非鱼的血清代谢组学以及饲料不同牛磺酸和脂肪水平下石斑鱼肝、肠道组织代谢组学。结果表明，牛磺酸引起罗非鱼血清13种特征差异代谢物变化，且在后期生长阶段血清特征差异代谢物变化较前期也有明显不同；饲料牛磺酸引起石斑鱼肠道组织25种特征差异代谢物变化，这些代谢变化主要涉及糖代谢、氨基酸代谢、蛋白质代谢、甘油磷脂代谢、ATP结合转运蛋白（ABC转运蛋白）、三羧酸循环、尿素循环，胆碱代谢和嘌呤代谢等，但饲料脂肪水平引起肠道组织特征差异代谢物的差异较小。上述结果进一步揭示了牛磺酸和脂肪营养与石斑鱼生长之间的关系及其代谢变化规律，并由此构建了牛磺酸、脂肪影响下的石斑鱼代谢网络，从代谢组学层面探索了牛磺酸对斜带石斑鱼脂肪代谢影响的调控机制，客观评价了牛磺酸在斜带石斑鱼饲料中的应用效果，研究结果将为牛磺酸在水产饲料中的应用提供科学依据，同时对于防控脂肪肝综合征有积极现实意义。