胆汁酸肠肝循环介导日粮瘤胃可降解淀粉调控奶山羊乳脂合成的微生物学机制

乳脂含量及其组成是反映生鲜乳品质的重要指标。本团队研究发现，日粮瘤胃可降解淀粉（RDS）水平调控瘤胃和小肠微生物代谢过程，影响乳脂合成；而改变的肝脏和乳腺胆汁酸代谢可能参与此过程。基于此，本项目假设日粮RDS通过改变胃肠道微生物区系及其代谢产物，调节胆汁酸肠肝循环，影响空肠长链脂肪酸转运和吸收、乳腺脂肪酸从头合成过程，进而调节乳脂合成。本项目通过调整奶山羊日粮RDS水平，结合多组学关联和功能验证分析，在体试验分析乳脂合成过程与胃肠道微生物参与的胆汁酸代谢过程的相关性，离体验证胆汁酸调节乳脂合成的潜在信号通路；进而通过在体试验探究RDS调控胆汁酸生成过程对乳脂合成的调节作用，阐明RDS-胃肠道微生物-胆汁酸循环-乳脂合成间的互作关系，揭示胆汁酸肠肝循环介导日粮RDS调控奶山羊乳脂合成的宿主-微生物互作机制，为通过常规日粮成分调控乳脂肪酸合成提供理论依据和更为现实的途径。

Milk fat content and composition have been widely serve as the key index of milk quality, and the suitable way to improve milk quality and meanwhile increase milk production has been acted as a major issue for the development of the dairy industry. Our previous study has proved that the dietary rumen degradable starch（RDS）levels could influence ruminal and intestinal microbiota and microbial metabolism, which could further affect the hepatic and mammary bile acid metabolism, and then result in the change of milk lipid synthesis. Based on these results, we hypothesized that the microbiological hepato-intestinal circulation of bile acids process regulated by dietary RDS could take part in the regulation of milk fat synthesis metabolism. In the present study, by feeding the dairy goat with different RDS levels of feeds, the correlation between the milk fat synthesis and microbially regulated bile acid metabolism will be identified using microbiome and metabolome analysis. Then, the key pathways that bile acid regulate the mammary fatty acids synthesis will be further screened out and tested by using primary cell which was cultured with the selected bile acid. Finally, duodenal perfusion of selected bile acid in dairy goats will be used to verify the effect of related microbes and bile acid to regulate mammary fatty acids synthesis. Overall, the objectives of this project are to explore the roles of ruminal and intestinal microbiota in regulating the hepato-intestinal circulation of bile acids process and the consequent milk fat synthesis. Our results can illuminate the relationship among RDS, microbes, bile acid, and host during the regulation of milk fat synthesis, and further provide the available feeding strategy for regulation of mammary fatty acids synthesis.