Syndecan-3调节猪采食的作用机制及其营养调控

Limited feed intake is a crucial obstacle for pig growth and development.The key determinant of voluntary feed take of pig is the appetite. Recent evidences demonstrated that syndecan-3,an important extra-cellular matrix, plays important role in modulating the appetite of animals. However, the exact mechanism of syndecan-3 to effect animal's appetite remains unclear. Based on our previous research, the transwell co-culture system will adopted to reveal the potential role of syndecan-3 in facilitating the fatty acids across the blood-brain barrier in this project. Meanwhile, we also investigate the function of syndecan-3 to modulate the expression and secretion of several nueropeptides, such as AgRP, NPY and α-MSH, as well as the signaling pathway and the transcript control using porcine primary hypothalamic neurons and brain slices. Moreover, the Cre-LoxP strategy will also applied to generate the syndecan-3 knockout mouse specifically in AgRP or POMC neurons to find out how the syndecan-3 in different hypothalamic neurons modulate animal appetite. Finally, the effect of substrates to synthesis syndecan-3 and the nutritional regulators for heparinase on pig feed intake and growth performance were also investigated by the in vivo experiments of pig. The main purpose of this project is to reveal the potential mechanisms underlines the effect of syndecan-3 on pig appetite, and the results will also provide the fundamental data for the development of novel nutritional and efficient feed additives to promote pig appetite.

采食量不足是限制猪生产性能的重要障碍，影响采食量的核心因素是食欲。近年来有研究表明，细胞外基质的一种重要成分Syndecan-3能够影响动物的食欲，但其作用机制尚不清楚。本项目拟在前期基础上，采用Transwell共培养模型，研究猪Syndecan-3参与血脑屏障对脂肪酸转运的机制；同时，以猪下丘脑原代细胞和脑片为模型，研究Syndecan-3调控AgRP、NPY和α-MSH的表达和分泌的信号通路及其转录调控机制。在此基础上，采用Cre-LoxP转基因小鼠模型，研究AgRP和POMC神经元特异性敲除Syndecan-3对小鼠采食的影响机制，最后通过猪的饲养试验和营养调控手段，在日粮中添加Syndecan-3合成底物和肝素酶营养性调控物，验证其对猪采食量的影响，并揭示其调控机制。研究结果不仅可从理论上阐明Syndecan-3调控猪采食的作用机制，还可为研发安全、高效的新型诱食剂提供试验依据。

采食量不足是限制猪生产性能的重要障碍，影响采食量的核心因素是食欲。近年来有研究表明，细胞外基质的一种重要成分 Syndecan-3 能够影响动物的食欲，但其作用机制尚不清楚。本项目首先通过检测不同能量状态下弓状核Syndecan-3表达以及利用转基因小鼠特异性过表达AgRP神经元Syndecan-3发现AgRP神经元中Syndecan-3核心蛋白对动物食欲并没有影响。但是Syndecan-3 发挥其共受体功能主要由核心蛋白和与之相连的糖胺聚糖共同完成，因此本项目随即检测不同能量状态下下丘脑糖胺聚糖含量变化发现饥饿可显著提高弓状核糖胺聚糖的含量。随后通过尾静脉注射不同糖胺聚糖揭示肝素可显著提高小鼠采食量和体增重，而进一步研究发现肝素主要通过降低AgRP神经元胰岛素通路促进下丘脑AgRP神经元兴奋性从而提高AgRP表达和分泌，进而提高小鼠采食量和体增重，此外，猪下丘脑原代细胞试验同样发现肝素可显著提高猪下丘脑AgRP的表达。同时，本项目还通过灌服海带多糖发现显著促进小鼠肠道GLP-1的分泌，抑制下丘脑AgRP神经元兴奋性进而降低小鼠的采食量，而且海带多糖还可以抑制动物体内白色脂肪组织的合成途径和缓解胰岛素抵抗从而抵抗高脂诱导的肥胖。最后，为验证肝素在养猪生产中的实际应用效果，我们初步探究了肝素对保育猪生长性能的影响，结果发现肝素可显著提高保育猪体增重。总体来说，本项目的研究结果初步阐明了Syndecan-3在动物食欲调控中作用，揭示了Syndecan-3侧链糖胺聚糖，特别是肝素以及海带多糖在调节动物采食以及能量稳态方面的作用及分子机制，为开发新型高效的生理诱食剂以及降低饲料原料中的厌食成分提供了一定的理论与试验依据。