The Key Laboratory of Dairy Science of Education Ministry , Northeast Agricultural University , Harbin 150030 , P. R. China.
J Agric Food Chem. 2019 Aug 14;67(32):8884-8895. doi: 10.1021/acs.jafc.9b03574. Epub 2019 Aug 1.
Leucine is an essential amino acid in the milk production of bovine mammary glands, but the regulatory roles and molecular mechanisms of leucine are still not known well. This study investigated the roles of leucine on milk synthesis and explored the corresponding mechanism in bovine mammary epithelial cells (BMECs). Leucine (0, 0.25, 0.5, 0.75, 1.0, and 1.25 mM) was added to BMECs that were cultured in FBS-free OPTI-MEM medium. Leucine significantly promoted milk protein and milk fat synthesis and also increased phosphorylation of mTOR signaling protein and the protein expression levels of SREBP-1c, with the most significant effects at 0.75 mM concentration. Leucine increased the expression and nuclear localization of DDX59, and loss and gain of gene function experiments further reveal that DDX59 mediates the stimulation of leucine on the mRNA expression variation of and genes. PI3K inhibition experiment further detected that leucine upregulated expression of DDX59 and its downstream signaling via PI3K activation. ChIP-qPCR analysis further proved the binding of DDX59 to the promoter regions of and . In summary, these data prove that DDX59 positively regulates the mTOR and SREBP-1c signaling pathways leading to synthesis of milk, and leucine regulates these two signaling pathways through the PI3K-DDX59 signaling.
亮氨酸是乳牛乳腺中牛奶合成的必需氨基酸，但亮氨酸的调节作用和分子机制仍不清楚。本研究探讨了亮氨酸对牛奶合成的作用，并在奶牛乳腺上皮细胞（BMECs）中探索了相应的机制。在无 FBS 的 OPTI-MEM 培养基中培养 BMECs 时，添加亮氨酸（0、0.25、0.5、0.75、1.0 和 1.25 mM）。亮氨酸显著促进乳蛋白和乳脂的合成，同时增加 mTOR 信号蛋白的磷酸化和 SREBP-1c 的蛋白表达水平，在 0.75 mM 浓度下效果最显著。亮氨酸增加了 DDX59 的表达和核定位，基因功能缺失和获得实验进一步表明，DDX59 介导了亮氨酸对 和 基因 mRNA 表达变化的刺激。PI3K 抑制实验进一步检测到亮氨酸通过激活 PI3K 上调 DDX59 及其下游信号的表达。ChIP-qPCR 分析进一步证明了 DDX59 与 和 的启动子区域结合。综上所述，这些数据证明 DDX59 正向调节 mTOR 和 SREBP-1c 信号通路，从而促进牛奶的合成，亮氨酸通过 PI3K-DDX59 信号通路调节这两条信号通路。
