Rong Rong, Ramachandran Sumathi, Penumetcha Meera, Khan Nadya, Parthasarathy Sampath
Department of Gynecology and Obstetrics and Nutrition and Health Sciences Program, Emory University School of Medicine, Atlanta, GA 30322, USA.
J Lipid Res. 2002 Apr;43(4):557-64.
Apolipoprotein (apo)A-I, the major protein component of HDL, is synthesized principally in the small intestine and liver. Recently we observed an increase in plasma apoA-I level in humans who were on an oxidized fat diet. To test whether oxidized fatty acids could affect apoA-I synthesis, we incubated day 4 (undifferentiated) and day 14 (differentiated) Caco-2 cells with varying concentrations of oxidized linoleic acid (ox-linoleic acid) (5, 10, and 25 microM) and unoxidized linoleic acid for 24 h. Ox-linoleic acid caused a dose-dependent increase in the levels of apoA-I protein in both differentiated and undifferentiated Caco-2 cells as assessed by ELISA and Western blot analysis. Whereas apoB production was not increased by ox-linoleic acid in both day 4 and day 14 Caco-2 cells. The mRNA expression for apoA-I paralleled the protein expression when measured by RT-PCR. We also found that both day 4 and day 14 Caco-2 cells did express peroxisomal proliferator-activated receptor-gamma (PPAR-gamma). mRNA and PPAR-gamma ligand could increase apoA-I secretion in these cells. Therefore we propose that the mechanism for the induction of apoA-I might include PPAR-gamma for which oxidized fatty acid is a ligand.
载脂蛋白（apo）A-I是高密度脂蛋白（HDL）的主要蛋白质成分，主要在小肠和肝脏中合成。最近我们观察到，食用氧化脂肪饮食的人的血浆apoA-I水平有所升高。为了测试氧化脂肪酸是否会影响apoA-I的合成，我们将第4天（未分化）和第14天（已分化）的Caco-2细胞与不同浓度的氧化亚油酸（ox-亚油酸）（5、10和25微摩尔）以及未氧化的亚油酸一起孵育24小时。通过酶联免疫吸附测定（ELISA）和蛋白质印迹分析评估，ox-亚油酸导致已分化和未分化的Caco-2细胞中apoA-I蛋白水平呈剂量依赖性增加。而在第4天和第14天的Caco-2细胞中，ox-亚油酸均未增加apoB的产生。通过逆转录聚合酶链反应（RT-PCR）测量时，apoA-I的信使核糖核酸（mRNA）表达与蛋白质表达平行。我们还发现，第4天和第14天的Caco-2细胞均表达过氧化物酶体增殖物激活受体γ（PPAR-γ）。mRNA和PPAR-γ配体可增加这些细胞中apoA-I的分泌。因此我们提出，诱导apoA-I的机制可能包括以氧化脂肪酸为配体的PPAR-γ。
