葡萄糖和泌乳相关激素对奶牛乳腺上皮细胞乳蛋白合成的影响及其作用机制研究

Increasing milk protein content can promote the overall development level of dairy industry. As energy substrate glucose play an important role in energy balance and milk protein synthesis in mammary cells. Hormones involved in milk secretion affect glucose uptake and metabolism. In addition, signaling pathways of milk protein synthesis can be regulated by hormones. However previous studies about regulation of milk protein synthesis by energy substrate and neuroendocrine show inconsistent results, and the regulation mechanisms are still not clear. Previous studies about milk components synthesis in bovine mammary epithelial cell are almost conducted by two-dimensional cultivation model, whereas due to loss of acinar-like structures, results obtained from two-dimensional cultivation model can’t really reflect mammary gland metabolism in vivo. In this research subject, three-dimensional cultivation model will be applied to study the effect of glucose and hormones on glucose uptake, metabolism and milk protein synthesis in bovine mammary epithelial cells. Meanwhile, the molecular mechanisms of glucose and hormones regulation of milk protein synthesis will be clarified through genes expression, translation and phosphorylation levels of protein in mTOR signaling pathways. Results of this subject can provide theory basis for regulation of milk protein synthesis.

提高乳蛋白含量，对于提升我国奶业整体发展水平，促进奶业持续发展具有重要意义。葡萄糖作为能量底物对乳腺细胞能量平衡和乳蛋白合成有重要影响。泌乳相关激素影响乳腺细胞对葡萄糖的摄取和代谢，同时对乳蛋白合成信号通路具有调控作用。然而，前人关于能量底物和神经内分泌调控奶牛乳蛋白合成的研究结果不尽一致，葡萄糖和激素调控乳蛋白合成的机制仍不明确。国内外学者关于乳成分合成的体外研究大多是以二维培养的细胞模型开展的，研究结果不能真实反映体内乳腺组织的代谢情况。为此，本项目以三维培养的奶牛乳腺上皮细胞为模型，研究葡萄糖和激素对乳腺细胞葡萄糖摄取、代谢以及乳蛋白合成的影响，并从mTOR信号通路上下游基因转录、翻译和表观遗传修饰等方面揭示葡萄糖和激素调控奶牛乳蛋白合成的分子机理，旨在为调控乳蛋白合成提供理论依据。

葡萄糖作为能量底物对泌乳乳腺乳腺的能量平衡和乳蛋白合成有重要影响。泌乳相关激素影响乳腺细胞对葡萄糖的摄取和代谢，同时对乳蛋白合成相关信号通路具有调控作用。本项目以奶牛乳腺上皮细胞（BMECs）为模型，研究了葡萄糖和泌乳相关激素对乳腺细胞葡萄糖摄取、代谢以及乳蛋白合成的影响。并从AMPK/mTOR和JAK/STAT信号通路上下游基因转录、翻译和磷酸化修饰等方面初步揭示了葡萄糖和激素调控奶牛乳蛋白合成的分子机理。研究表明，14 mmol/L~17.5 mmol/L的葡萄糖对BMECs葡萄糖的摄取、代谢和能量生成具有较好的促进效果，同时促进了BMECs酪蛋白及mTOR信号通路蛋白的表达。雌激素和催乳素添加总量为300ng/mL，比例为1:2时，BMECs中酪蛋白表达量最高；葡萄糖、雌激素和催乳素的添加量分别为14 mmol/L、100 ng/mL和200ng/mL时，是促进BMECs酪蛋白合成的最佳组合模式。葡萄糖和泌乳激素的协同作用进一步加强了BMECs对葡萄糖的转运、摄取和利用能力，为乳蛋白的合成提供更多的能量，同时最大程度的激活了AMPK/mTOR和JAK/STAT信号通路，进而促进了酪蛋白的转录和翻译过程。项目的完成对营养素和激素协同调控乳蛋白合成具有重要的理论与实际意义。