Soayfane Zeina, Tercé François, Cantiello Michela, Robenek Horst, Nauze Michel, Bézirard Valérie, Allart Sophie, Payré Bruno, Capilla Florence, Cartier Christel, Peres Christine, Al Saati Talal, Théodorou Vassilia, Nelson David W, Yen Chi-Liang Eric, Collet Xavier, Coméra Christine
Institut des Maladies Métaboliques et Cardiovasculaires - I2MC, UMR 1048, Institut National de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, Toulouse, F-31000 France.
Leibniz-Institut für Arterioskleroseforschung, Universität Münster, Münster, Germany.
Nutr Metab (Lond). 2016 Jul 28;13:48. doi: 10.1186/s12986-016-0107-9. eCollection 2016.
Intestinal absorption of dietary lipids involves their hydrolysis in the lumen of proximal intestine as well as uptake, intracellular transport and re-assembly of hydrolyzed lipids in enterocytes, leading to the formation and secretion of the lipoproteins chylomicrons and HDL. In this study, we examined the potential involvement of cytosolic lipid droplets (CLD) whose function in the process of lipid absorption is poorly understood.
Intestinal lipid absorption was studied in mouse after gavage. Three populations of CLD were purified by density ultracentrifugations, as well as the brush border membranes, which were analyzed by western-blots. Immunofluorescent localization of membranes transporters or metabolic enzymes, as well as kinetics of CLD production, were also studied in intestine or Caco-2 cells.
We isolated three populations of CLD (ranging from 15 to 1000 nm) which showed differential expression of the major lipid transporters scavenger receptor BI (SR-BI), cluster of differentiation 36 (CD-36), Niemann Pick C-like 1 (NPC1L1), and the ATP-binding cassette transporters ABCG5/G8 but also caveolin 2 and fatty acid binding proteins. The enzyme monoacylglycerol acyltransferase 2 (MGAT2) was identified in the brush border membrane (BBM) in addition to the endoplasmic reticulum, suggesting local synthesis of triglycerides and CLD at both places.
We show a very fast production of CLD by enterocytes associated with a transfer of apical constituents as lipid transporters. Our findings suggest that following their uptake by enterocytes, lipids can be partially metabolized at the BBM and packaged into CLD for their transportation to the ER.
膳食脂质的肠道吸收涉及它们在近端肠腔中的水解，以及水解脂质在肠细胞中的摄取、细胞内运输和重新组装，从而导致乳糜微粒和高密度脂蛋白等脂蛋白的形成和分泌。在本研究中，我们研究了胞质脂滴（CLD）的潜在作用，其在脂质吸收过程中的功能尚不清楚。
通过灌胃研究小鼠的肠道脂质吸收。通过密度超速离心纯化了三种脂滴群体，以及刷状缘膜，并通过蛋白质免疫印迹法进行分析。还在肠道或Caco-2细胞中研究了膜转运蛋白或代谢酶的免疫荧光定位以及脂滴产生的动力学。
我们分离出三种脂滴群体（大小范围为15至1000纳米），它们显示出主要脂质转运蛋白清道夫受体BI（SR-BI）、分化簇36（CD-36）、尼曼-匹克C样1（NPC1L1）以及ATP结合盒转运蛋白ABCG5/G8的差异表达，还有小窝蛋白2和脂肪酸结合蛋白。除内质网外，在刷状缘膜（BBM）中还鉴定出单酰甘油酰基转移酶2（MGAT2），这表明甘油三酯和脂滴在这两个部位均可进行局部合成。
我们发现肠细胞能非常快速地产生脂滴，并伴随着顶端成分作为脂质转运蛋白的转移。我们的研究结果表明，脂质被肠细胞摄取后，可在刷状缘膜进行部分代谢，并包装成脂滴运输至内质网。
