van Greevenbroek M M, Robertus-Teunissen M G, Erkelens D W, de Bruin T W
Department of Medicine and Endocrinology, Maastricht University, The Netherlands.
J Lipid Res. 1998 Jan;39(1):173-85.
This study was designed to gain insight into the role of microsomal triglyceride transfer protein (MTP) in the association of apolipoprotein (apo) B with lipid during intestinal lipoprotein assembly. The MTP-inhibiting compound BMS-200150 (Jamil et al. 1996. Proc. Natl. Acad. Sci. USA 93: 11991-11995) was used to inhibit the lipid transfer activity of MTP in Caco-2 cells. MTP inhibition reduced the number of apoB-containing lipoproteins that were secreted from the cells. Secretion of apoB-100 appeared to be more sensitive to BMS-200150 than apoB-48 secretion, which appeared to be relatively insensitive. BMS-200150 caused a decrease in the triglyceride content of the secreted lipoproteins, compared with control incubations without MTP inhibition. This indicated that, in Caco-2 cells, MTP is not only involved in the first step of lipoprotein synthesis, i.e., the rescue of apoB from intracellular degradation through early lipidation of the protein, but also in further steps involving the association of lipoproteins with triglycerides. When 0.5 mM oleic acid (18:1) was used to stimulate cellular lipid synthesis, secreted lipoproteins were predominantly of chylomicron/VLDL density and their secretion could be efficiently inhibited with BMS-200150. With 0.5 mm palmitic acid (16:0), lipoproteins of distinct densities (i.e., chylomicron/VLDL and IDL/LDL) were secreted by Caco-2 cells, as reported before (van Greevenbroek et al. 1995. J. Lipid Res. 36: 13-24). Secretion of the lipoproteins at chylomicron/VLDL density was strongly reduced by inhibition of MTP activity by BMS-200150, whereas the IDL/LDL density lipoproteins were relatively insensitive. In conclusion, specific inhibition of MTP activity in Caco-2 cells with BMS-200150 resulted in reduced secretion of apoB-containing lipoproteins (predominantly apoB-100) by Caco-2 cells and furthermore reduced the triglyceride content of these lipoproteins. MTP inhibition preferentially reduced the secretion of triglyceride-rich lipoproteins (d < 1.006 g/ml).
本研究旨在深入了解微粒体甘油三酯转运蛋白（MTP）在肠道脂蛋白组装过程中载脂蛋白（apo）B与脂质结合中的作用。使用MTP抑制化合物BMS - 200150（Jamil等人，1996年。美国国家科学院院刊93: 11991 - 11995）抑制Caco - 2细胞中MTP的脂质转运活性。MTP抑制减少了细胞分泌的含apoB脂蛋白的数量。apoB - 100的分泌似乎比apoB - 48的分泌对BMS - 200150更敏感，而apoB - 48的分泌似乎相对不敏感。与未抑制MTP的对照孵育相比，BMS - 200150导致分泌的脂蛋白中甘油三酯含量降低。这表明，在Caco - 2细胞中，MTP不仅参与脂蛋白合成的第一步，即通过蛋白质的早期脂化将apoB从细胞内降解中拯救出来，还参与涉及脂蛋白与甘油三酯结合的后续步骤。当使用0.5 mM油酸（18:1）刺激细胞脂质合成时，分泌的脂蛋白主要是乳糜微粒/极低密度脂蛋白密度，并且它们的分泌可以被BMS - 200150有效抑制。如之前报道（van Greevenbroek等人，1995年。脂质研究杂志36: 13 - 24），使用0.5 mM棕榈酸（16:0）时，Caco - 2细胞分泌不同密度的脂蛋白（即乳糜微粒/极低密度脂蛋白和中间密度脂蛋白/低密度脂蛋白）。BMS - 200150抑制MTP活性可强烈降低乳糜微粒/极低密度脂蛋白密度脂蛋白的分泌，而中间密度脂蛋白/低密度脂蛋白密度脂蛋白相对不敏感。总之，用BMS - 200150特异性抑制Caco - 2细胞中的MTP活性导致Caco - 2细胞分泌的含apoB脂蛋白（主要是apoB - 100）减少，并且进一步降低了这些脂蛋白的甘油三酯含量。MTP抑制优先减少富含甘油三酯脂蛋白（d < 1.006 g/ml）的分泌。
