Laboratory of Functional Foods, Madrid Institute for Advanced Studies (IMDEA)-Food, CEI UAM + CSIC, Madrid, Spain.
Division of Nutritional Sciences, Cornell University, Ithaca NY, USA.
J Nutr Biochem. 2015 Feb;26(2):165-72. doi: 10.1016/j.jnutbio.2014.10.002. Epub 2014 Nov 12.
High-density lipoproteins (HDLs) are atheroprotective because of their role in reverse cholesterol transport. The intestine is involved in this process because it synthesizes HDL, removes cholesterol from plasma and excretes it into the lumen. We investigated the role of selected dietary fatty acids on intestinal cholesterol uptake and HDL functionality. Caco-2 monolayers grown on Transwells were supplemented with either palmitic, palmitoleic, oleic, linoleic, docosahexaenoic, eicosapentaenoic, arachidonic or conjugated linoleic acids (CLAs): c9,t11-CLA; t9,t11-CLA; c10,t12-CLA. Cells synthesized HDL in the basolateral compartment for 24 h in the absence or presence of an antibody to SR-BI (aSR-BI), which inhibits its interaction with HDL. Free cholesterol (FC) accumulated to a greater extent in the presence than in the absence of aSR-BI, indicating net uptake of FC by SR-BI. Uptake's efficiency was significantly decreased when cells were treated with c9,t11-CLA relative to the other fatty acids. These differences were associated with lower HDL functionality, since neither SR-BI protein expression nor expression and alternative splicing of other genes involved lipid metabolism were affected. Only INSIG2 expression was decreased, with no increase of its target genes. Increasing pre-β-HDL synthesis, by inducing ABCA1 and adding APOA1, resulted in reduced uptake of FC by SR-BI after c9,t11-CLA treatment, indicating reduced functionality of pre-β-HDL. Conversely, treatment with c9,t11-CLA resulted in a greater uptake of FC and esterified cholesterol from mature HDL. Therefore, Caco-2 monolayers administered c9,t11-CLA produced a nonfunctional pre-β-HDL but took up cholesterol more efficiently via SR-BI from mature HDL.
高密度脂蛋白（HDL）具有抗动脉粥样硬化作用，因为它在胆固醇逆转运中发挥作用。肠道参与了这个过程，因为它合成 HDL，从血浆中去除胆固醇并将其排泄到腔中。我们研究了选定的膳食脂肪酸对肠道胆固醇摄取和 HDL 功能的作用。在 Transwell 上生长的 Caco-2 单层被补充了棕榈酸、棕榈油酸、油酸、亚油酸、二十二碳六烯酸、二十碳五烯酸、花生四烯酸或共轭亚油酸（CLA）：c9,t11-CLA；t9,t11-CLA；c10,t12-CLA。细胞在不存在或存在抗 SR-BI（aSR-BI）抗体的情况下在基底外侧隔室中合成 HDL24 小时，该抗体抑制其与 HDL 的相互作用。游离胆固醇（FC）在存在 aSR-BI 的情况下比不存在 aSR-BI 的情况下积累得更多，这表明 FC 通过 SR-BI 的净摄取。当用 c9,t11-CLA 处理细胞时，摄取效率显着降低。这些差异与较低的 HDL 功能相关，因为 SR-BI 蛋白表达以及涉及脂质代谢的其他基因的表达和选择性剪接均不受影响。只有 INSIG2 的表达减少，而其靶基因没有增加。通过诱导 ABCA1 和添加 APOA1 增加前-β-HDL 的合成，导致 c9,t11-CLA 处理后 SR-BI 摄取的 FC 减少，表明前-β-HDL 的功能降低。相反，用 c9,t11-CLA 处理会导致从成熟 HDL 摄取更多的 FC 和酯化胆固醇。因此，用 c9,t11-CLA 处理的 Caco-2 单层产生了无功能的前-β-HDL，但通过 SR-BI 从成熟的 HDL 更有效地摄取胆固醇。
