Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Xianyang 712100, China.
Int J Mol Sci. 2024 Sep 14;25(18):9923. doi: 10.3390/ijms25189923.
Sirtuin 1 (SIRT1) is a key upstream regulator of lipid metabolism; however, the molecular mechanisms by which SIRT1 regulates milk fat synthesis in dairy goats remain unclear. This study aimed to investigate the regulatory roles of SIRT1 in modulating lipid metabolism in goat mammary epithelial cells (GMECs) and its impact on the adipose triglyceride lipase (ATGL) promoter activity using RNA interference (RNAi) and gene overexpression techniques. The results showed that SIRT1 is significantly upregulated during lactation compared to the dry period. Additionally, SIRT1 knockdown notably increased the expressions of genes related to fatty acid synthesis (SREBP1, SCD1, FASN, ELOVL6), triacylglycerol (TAG) production (DGAT2, AGPAT6), and lipid droplet formation (PLIN2). Consistent with the transcriptional changes, SIRT1 knockdown significantly increased the intracellular contents of TAG and cholesterol and the lipid droplet abundance in the GMECs, while SIRT1 overexpression had the opposite effects. Furthermore, the co-overexpression of SIRT1 and Forkhead box protein O1 (FOXO1) led to a more pronounced increase in ATGL promoter activity, and the ability of SIRT1 to enhance ATGL promoter activity was nearly abolished when the FOXO1 binding sites (FKH1 and FKH2) were mutated, indicating that SIRT1 enhances the transcriptional activity of ATGL via the FKH element in the ATGL promoter. Collectively, our data reveal that SIRT1 enhances the transcriptional activity of ATGL through the FOXO1 binding sites located in the ATGL promoter, thereby regulating lipid metabolism. These findings provide novel insights into the role of SIRT1 in fatty acid metabolism in dairy goats.
Sirtuin 1（SIRT1）是脂质代谢的关键上游调节剂；然而，SIRT1 调节奶山羊乳脂合成的分子机制尚不清楚。本研究旨在使用 RNA 干扰（RNAi）和基因过表达技术研究 SIRT1 在调节山羊乳腺上皮细胞（GMEC）中脂质代谢及其对脂肪甘油三酯脂肪酶（ATGL）启动子活性的调控作用。结果表明，与干奶期相比，泌乳期 SIRT1 显著上调。此外，SIRT1 敲低显著增加了脂肪酸合成相关基因（SREBP1、SCD1、FASN、ELOVL6）、三酰基甘油（TAG）生成（DGAT2、AGPAT6）和脂滴形成（PLIN2）的表达。与转录变化一致，SIRT1 敲低显著增加了 GMEC 内 TAG 和胆固醇的细胞内含量以及脂滴丰度，而 SIRT1 过表达则产生相反的效果。此外，SIRT1 和 Forkhead box 蛋白 O1（FOXO1）的共过表达导致 ATGL 启动子活性显著增加，并且当 FOXO1 结合位点（FKH1 和 FKH2）发生突变时，SIRT1 增强 ATGL 启动子活性的能力几乎被消除，表明 SIRT1 通过 ATGL 启动子中的 FKH 元件增强 ATGL 的转录活性。总之，我们的数据表明，SIRT1 通过位于 ATGL 启动子中的 FOXO1 结合位点增强 ATGL 的转录活性，从而调节脂质代谢。这些发现为 SIRT1 在奶山羊脂肪酸代谢中的作用提供了新的见解。
