Department of Nutrition & Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
Department of Nutrition & Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
J Nutr Biochem. 2022 Oct;108:109087. doi: 10.1016/j.jnutbio.2022.109087. Epub 2022 Jun 10.
Although the role of mechanistic target of rapamycin complex 1 (mTORC1) in lipid metabolism has been the subject of previous research, its function in chylomicron production is not known. In this study, we created three stable human colorectal adenocarcinoma Caco-2 cell lines exhibiting normal, low, or high mTORC1 kinase activity, and used these cells to investigate the consequences of manipulating mTORC1 activity on enterocyte differentiation and chylomicron-like particle production. Constitutively active mTORC1 induced Caco-2 cell proliferation and differentiation (as judged by alkaline phosphatase activity) but weakened transepithelial electrical resistance (TEER). Repressed mTORC1 activity due to the knockdown of RPTOR significantly decreased the expression of lipogenic genes FASN, DGAT1, and DGAT2, lipoprotein assembly genes APOB and MTTP, reduced protein expression of APOB, MTTP, and FASN, downregulated the gene expression of very long-chain fatty acyl-CoA ligase (FATP2), acyl-CoA binding protein (DBI), and prechylomicron transport vesicle-associated proteins VAMP7 (vesicle-associated membrane protein 7) and SAR1B (secretion associated Ras related GTPase 1B) resulting in the repression of apoB-containing triacylglycerol-rich lipoprotein secretion. Exposure of Caco-2 cells harboring a constitutively active mTORC1 to short-chain fatty acid derivatives, R-α-lipoic acid and 4-phenylbutyric acid, downregulated chylomicron-like particle secretion by interfering with the lipidation and assembly of the particles, and concomitantly repressed mTORC1 activity with no change to Raptor abundance or PRAS40 (Thr246) phosphorylation. R-α-lipoic acid and 4-phenylbutyric acid may be useful to mitigate intestinal lipoprotein overproduction and associated postprandial inflammation.
虽然雷帕霉素靶蛋白复合物 1（mTORC1）在脂质代谢中的作用是之前研究的主题，但它在乳糜微粒生成中的功能尚不清楚。在这项研究中，我们构建了三个具有正常、低或高 mTORC1 激酶活性的稳定人结肠直肠腺癌细胞系，并使用这些细胞研究操纵 mTORC1 活性对肠细胞分化和乳糜微粒样颗粒生成的影响。组成型激活的 mTORC1 诱导 Caco-2 细胞增殖和分化（根据碱性磷酸酶活性判断），但降低了跨上皮电阻（TEER）。由于 RPTOR 的敲低而抑制的 mTORC1 活性显著降低了脂肪生成基因 FASN、DGAT1 和 DGAT2、脂蛋白组装基因 APOB 和 MTTP 的表达，降低了 APOB、MTTP 和 FASN 的蛋白表达，下调了非常长链脂肪酸酰基辅酶 A 连接酶（FATP2）、酰基辅酶 A 结合蛋白（DBI）和前乳糜微粒转运囊泡相关蛋白 VAMP7（囊泡相关膜蛋白 7）和 SAR1B（分泌相关 Ras 相关 GTP 酶 1B）的基因表达，从而抑制载 apoB 的三酰甘油富含脂蛋白的分泌。用短链脂肪酸衍生物 R-α-硫辛酸和 4-苯基丁酸处理含有组成型激活的 mTORC1 的 Caco-2 细胞，通过干扰颗粒的脂质化和组装来下调乳糜微粒样颗粒的分泌，并同时抑制 mTORC1 活性，而不改变 Raptor 的丰度或 PRAS40（Thr246）磷酸化。R-α-硫辛酸和 4-苯基丁酸可能有助于减轻肠道脂蛋白过度产生和相关的餐后炎症。
