乳腺对氨基酸的摄取及其调控机制研究进展

乳蛋白是乳中重要的营养成分之一，超过90%的乳蛋白是乳腺利用从血液中摄取的氨基酸从头合成，因此在保证氨基酸充足供给的前提下，乳腺对氨基酸摄取率的高低是影响乳蛋白产量的关键因素。血液中的氨基酸不能自由扩散进出乳腺，需要由乳腺上皮细胞膜上特异的氨基酸转运载体(AAT)协助完成。而乳腺AAT活性受到营养物质和激素水平的调节，当乳腺感知到营养物质和激素水平变化的信号，能够通过激活或抑制以哺乳动物雷帕霉素靶蛋白复合物1(mTORC1)和一般性调控阻遏蛋白激酶2(GCN2)为核心的2条信号通路的活性，进而影响AAT活性，调节乳腺对氨基酸的摄取。本文主要从乳腺AAT的分类和功能、影响乳腺摄取氨基酸的主要因素以及调控乳腺氨基酸摄取的信号通路机制3个方面作一综述，旨在从氨基酸摄取的角度为提高乳蛋白的合成提供参考。

Advances in Amino Acids Uptake and Its Regulatory Mechanism in Mammary Gland

Milk protein is one of the most important nutrients of milk,over 90% of milk protein is de novo synthesized in the mammary gland by using the amino acids extracted from the blood. Therefore,under the premise of ensuring adequate supply of amino acids,the efficiency of amino acids extraction by the mammary gland is crucial for milk protein synthesis. Amino acids in the blood cannot freely diffused into and out of the mammary gland,this sort of transmembrane transport need to be assisted by specific amino acid transporters(AAT)on the mammary epithelial cells membrane. The mammary gland AAT activity is regulated by the nutrients and hormone level,when the mammary gland perceives changes of nutrients and hormone level,it can activate or inhibit the activities of two signal pathways as the core of mechanistic target of rapamycin complex 1(mTORC1)and general control nonderepressible 2 kinase(GCN2),and to affects the AAT activity,regulates the uptake of amino acids mammary gland. This review summarized three aspects of AAT classification and function,main factors affecting amino acids uptake by the mammary gland and signal pathway mechanism regulating mammary gland amino acid uptake,and it is aiming to provide reference for improving milk protein synthesis from the perspective of amino acids uptake.[Chinese Journal of Animal Nutrition,2022,34(2):720-726]