仔猪肠道微生物对冷应激的响应规律及其介导机制

Cold stress is an important cause of death in piglets through reducing immunity. Intestinal microbiota can relieve cold stress by providing energy to the host and regulating the body's energy intake, absorption and metabolism through metabolite. Studies in mice have found that gut microbiota under cold stress increased energy expenditure through the regulation of body brown fat metabolism by bile acids. However, the response mechanism of gut microbiota in weaned piglets lacking brown fat under cold stress needs to be explored further. Therefore, in this project, the weaned piglets were fed under normal temperature and cold stress via aseptic chamber with comparison of "aseptic piglets" constructed by combined antibiotic removal of gut microbiota. The following scientific questions are studied using 16S rRNA sequencing, metagenomics, metabolomics, and real-time PCR. The characteristics of energy metabolism in weaned piglet are investigated. The response model of gut microbial composition and function in weaned piglet under cold stress is studied. The interaction mechanism between intestinal microbial and host energy metabolism in weaned piglet under cold stress is investigated mainly focusing on the metabolism of the short-chain fatty acids and bile acids. The response mechanism of intestinal microbiota in weaned piglet under cold stress would be addressed through this project, providing technical support for relieving cold stress and maintaining intestinal health in piglets by regulating intestinal microbiota.

冷应激是导致仔猪抵抗力下降、诱发死亡的重要原因之一。肠道微生物能够增强机体对能量的摄取、吸收与代谢，对于缓解宿主冷应激有重要潜力。研究表明，冷应激下小鼠肠道微生物通过胆汁酸介导宿主褐色脂肪分解来增加适应性产热，但仔猪缺乏褐色脂肪，而且冷应激下其肠道微生物的响应规律和介导机制鲜见报道。基于此，本课题通过温湿可控的代谢箱模拟冷应激环境，以保育猪为模型，利用联合抗生素去除肠道微生物技术构建的“无菌”仔猪为对照，通过饲养试验，利用16S rRNA测序、宏基因组学、代谢组学以及定量PCR等生物学技术手段，研究：①冷应激下仔猪的能量平衡特征；②肠道微生物的响应规律及参与冷应激的关键微生物菌株；③肠道微生物通过胆汁酸和短链脂肪酸等信号分子介导宿主能量代谢的机制。通过上述研究，揭示冷应激下仔猪肠道微生物的响应规律及其介导机制，为减缓仔猪冷应激和维护其肠道健康提供理论依据。

在冷刺激下，肠道微生物群通过激活UCP1，促进白色脂肪组织（WAT）的褐变过程在宿主代谢产热中发挥关键作用。然而，对于缺乏UCP1基因的仔猪，在冷应激时，肠道微生物群和宿主之间如何互作还鲜见报道。本研究以公仔猪作为模型，评估肠道微生物在冷应激时对宿主能量代谢的介导机制（试验分为四组：室温组；冷应激组；冷应激+抗生素组；室温+抗生素组）。结果发现：在冷应激刺激下，仔猪胰岛素抵抗能力增强，血清中的代谢物如甘胆酸（GCA）和甘鹅去氧胆酸（GCDCA）的水平升高，并改变了盲肠微生物群的组成和功能。冷应激下瘤胃球菌科、普雷沃菌科和鼠杆菌科的丰度增加。肝脏中与胆汁酸和短链脂肪酸（SCFA）代谢相关的基因表达增加，脂肪中的脂肪分解基因表达增加。如冷应激下仔猪脂肪中的脂肪分解基因CLPS、PNLIPRP1、CPT1B和UCP3显著增加。然而，抗生素扰动仔猪肠道微生物后，减弱或增强了部分耐寒表型，表明肠道微生物在宿主能量代谢中起着重要作用。综上，肠道微生物可通过血液-肝和脂肪轴在仔猪适应冷应激时调节宿主能量平衡。