Exposure to dietary lipid leads to rapid production of cytosolic lipid droplets near the brush border membrane.

Zeina Soayfane,Horst Robenek,Michela Cantiello,Sophie Allart,Florence Capilla,François Tercé,Christine Peres,Christine Coméra,Bruno Payré,Chi-Liang Eric Yen,Valérie Bézirard,Christel Cartier,David W Nelson,Vassilia Théodorou,Talal Al Saati,Michel Nauze,Xavier Collet

doi:10.1186/s12986-016-0107-9

Abstract

BackgroundIntestinal 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.MethodsIntestinal 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.ResultsWe 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.ConclusionsWe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-016-0107-9) contains supplementary material, which is available to authorized users.

Highlights

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
1 h, as shown using either isolated mouse intestine, stained with red oil O (Fig. 1b) or differentiated Caco-2 cells colored with the fluorescent Bodipy 493/503 or LD540 (Fig. 1c) where the cell outline were indicated by immunodetection of Zonula occludens-1 (ZO-1) and the nucleus by DAPI staining
When mixed micelles were added to the apical milieu, cytosolic lipid droplets (CLD) accumulated which progressively settled in the cell basement as shown at T = 10 min after lipid addition

Summary

Introduction

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. We examined the potential involvement of cytosolic lipid droplets (CLD) whose function in the process of lipid absorption is poorly understood. The process of intestinal lipid absorption from lumen to blood [1,2,3] can be divided into four major steps. The first one concerns the emulsification and hydrolysis of dietary triglycerides, phospholipids and cholesteryl esters in the intestinal lumen through the combined actions of bile acids and digestive enzymes. The exact function of CLD in enterocytes, between lipid storage, transport and metabolism still remains to be clarified [1,2,3, 19, 28]

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Results

Conclusion