To investigate the role of glucose in regulating milk fatty acid synthesis, 6 lactating Guanzhong dairy goats were infused with 0, 60, or 100 g/d glucose via the external pubic artery in a 3 × 3 repeated Latin square experiment. A concomitant in vitro experiment was conducted to investigate possible mechanisms whereby glucose regulates milk fatty acid synthesis. RNA sequencing was used for cellular transcriptome analysis. Drugs, MK-2206, rapamycin, and dorsomorphin were used to block cellular mammalian AMP-activated protein kinase (AMPK), AKT serine/threonine kinase 1, and mechanistic target of rapamycin kinase signaling pathways, respectively. Carbohydrate response element binding protein (ChREBP) was knockdown and overexpressed to investigate its role in regulating milk fatty acid synthesis in mammary epithelial cells. Glucose infusion linearly elevated the concentration of C8:0 (P = 0.039) and C10:0 (P = 0.041) in milk fat while it linearly decreased (P = 0.049) that of C16:0. This result was in agreement with the upregulation of genes related to de novo synthesis of fatty acids and lipid droplet formation, including adipose differentiation-related protein, butyrophilin subfamily 1 member A1, fatty acid synthase (FASN) and ChREBP. Their expression increased (P < 0.05) linearly in the lactating goat mammary gland. In vitro, glucose linearly stimulated the expression of genes related to de novo synthesis of fatty acids and cellular triacylglycerol in cultured mammary epithelial cells. RNA sequencing and inhibition studies revealed that glucose induced transcriptomic changes increasing lipogenic pathways, with AMPK responding to glucose by controlling ChREBP and FASN. Knockdown and overexpression of ChREBP highlighted its essential role in lipogenesis. The knockdown and overexpression of ChREBP protein also revealed an essential role in regulating the de novo synthesis of fatty acids. Collectively, our data highlight that glucose supplementation promotes de novo fatty acid synthesis via the AMPK-ChREBP axis, hence increasing milk fat yield in the goat mammary gland. Results from the current study provide possible strategies to manipulate the fatty acid composition as well as improve ruminant milk quality.

为研究葡萄糖在调节乳脂肪酸合成中的作用，在 3 × 3 重复拉丁方实验中，通过耻骨外动脉向 6 只泌乳关中奶山羊输注 0、60 或 100 g/d 的葡萄糖。同时进行了一项体外实验，以研究葡萄糖调节乳脂肪酸合成的可能机制。RNA测序用于细胞转录组分析。药物 MK-2206、雷帕霉素和多索吗啡分别用于阻断细胞哺乳动物 AMP 活化蛋白激酶 (AMPK)、AKT 丝氨酸/苏氨酸激酶 1 和雷帕霉素激酶信号通路的机制靶点。碳水化合物反应元件结合蛋白（ChREBP) 被敲低并过表达以研究其在调节乳腺上皮细胞中乳脂肪酸合成中的作用。 葡萄糖输注使乳脂中C8：0（P  = 0.039）和C10：0（P = 0.041）的浓度线性升高，而C16：0的浓度线性降低（ P  = 0.049）。这一结果与脂肪酸从头合成和脂滴形成相关基因的上调一致，包括脂肪分化相关蛋白、嗜酪蛋白亚家族 1 成员 A1、脂肪酸合酶 ( FASN ) 和ChREBP。他们的表达增加（P < 0.05) 在泌乳山羊乳腺中呈线性关系。在体外，葡萄糖线性刺激培养的乳腺上皮细胞中与脂肪酸和细胞三酰基甘油从头合成相关的基因表达。RNA 测序和抑制研究表明，葡萄糖诱导的转录组变化增加了脂肪生成途径，AMPK 通过控制ChREBP和FASN对葡萄糖作出反应。ChREBP的敲低和过表达突出了其在脂肪生成中的重要作用。ChREBP的敲低和过表达蛋白质还揭示了在调节脂肪酸从头合成中的重要作用。总的来说，我们的数据强调葡萄糖补充通过 AMPK-ChREBP 轴促进从头脂肪酸合成，从而增加山羊乳腺中的乳脂产量。当前研究的结果提供了可能的策略来控制脂肪酸组成以及改善反刍动物奶的质量。