This experiment was conducted to study the effects of insulin on mRNA expression of genes related to milk protein and fat synthesis in bovine mammary cells cultured in vitro.Mammary epithelial cells were cultured for 24 h with the following hormone treatments:no hormones (NH,control),50 ng · mL-1 hydrocortisone + 200 ng · mL-1 prolactin (FP) or 100 ng · mL-1 insulin + 50 ng · mL-1 hydrocortisone + 200 ng · mL-1 prolactin (IFP).The relative expression of the related genes of milk protein and fat synthesis were measured by real-time PCR.The results showed that the mRNA relative abundance of β-casein (CSN2),κ-casein (CSN3),Acetyl-CoA carboxylase (ACACA),fatty acid synthase (FASN) and sterol regulatory element pinding protein1 (SREBP1) in IFP group were significantly up-regulated(P＜0.05).In addition,signal transducers and activators of transduction 5 (STAT5B) and ETS-related transcription factor Elf-5 (ELF5) in JAK2-STAT5 signal pathway,as well as Phosphoinositide-3-kinase (PI3K),protein kinase B(AKT1) and eukaryotic translation initiation factor 4E(EIF4E) in PI3K/Akt/mTOR siganal pathway in IFP group were significantly up-regulated (P＜0.05),while the IFP hormone combinations had no effect on TSC1,TSC2 or RHEB transcription in AMPK singal pathway.The data demonstrated that insulin induced the mRNA expression of genes related to milk protein synthesis through JAK2-STAT5 and PI3K/Akt/mTOR signal pathway and the mRNA expression of genes related to milk fat synthesis through PI3K/Akt/mTOR and SREBP signal pathway in bovine mammary epithelial cells cultured in vitro,which indicated insulin,hydrocortisone and prolactin regulate the mRNA expression of genes related to milk protein and fat synthes together.%旨在研究胰岛素对体外培养奶牛乳腺上皮细胞乳蛋白、乳脂肪合成相关基因mRNA表达的影响.采用无激素处理组(NH,对照组)、氢化可的松(50 ng·mL-1)+催乳素(200 ng·mL-1)处理组(FP)和胰岛素(100ng·mL-1)+氢化可的松(50 ng·mL-1)+催乳素(200 ng· mL-1)处理组(IFP)处理体外培养奶牛乳腺上皮细胞24 h,利用re-al-time PCR方法检测乳腺上皮细胞中乳蛋白、乳脂肪合成相关基因mRNA的相对表达丰度.结果表明,IFP激素处理组显著上调β-酪蛋白基因(CSN2)、κ-酪蛋白基因(CSN3)、乙酰辅酶A羧化酶基因(ACACA)、脂肪酸合成酶基因(FASN)和固醇调节元件结合蛋白-1基因(SREBP1) mRNA的相对表达丰度(P＜0.05);显著上调JAK2-STAT5信号通路中信号转导和转录激活因子5B基因(STAT5B)和E74样因子5基因(ELF5) mRNA的相对表达丰度(P＜0.05);显著上调PI3K/Akt/mTOR信号通路中磷脂酰肌醇-3激酶基因(PI3K)、蛋白激酶B基因(AKT1)及真核细胞翻译起始因子4E基因(EIF4E) mRNA的相对表达丰度(P＜0.05),但对AMPK信号通路中结节性硬化复合物基因(TSC1、TSC2)和RHEB(Ras homolog enriched in brain)mRNA的相对表达丰度无显著影响(P＞0.05).结果提示,胰岛素通过JAK2-STAT5和PI3K/Akt/mTOR信号通路诱导体外培养奶牛乳腺上皮细胞乳蛋白合成相关基因mRNA的表达,通过PI3K/Akt/mTOR和SREBP信号通路诱导体外培养奶牛乳腺上皮细胞脂合成相关基因mRNA的表达,表明胰岛素作为一种重要的催乳激素,与氢化可的松和催乳素共同调节乳蛋白和乳脂肪合成相关基因mRNA的表达.
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