Intestinal lipid absorption (original) (raw)
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Intestinal lipid absorption and transport
Frontiers in Bioscience, 2001
Introduction 3. Dietary lipids 4. Structured lipids 5. Digestion of dietary lipids and structured lipids 5.1. Gastric lumen 5.2. Intestinal lumen 5.3. Digestion of phospholipid 5.4. Digestion of cholesteryl ester 6. Uptake of dietary lipids by enterocytes 6.1. Importance of micellar solubilization 6.2. Importance of unilamellar vesicles 6.3. Uptake of fat digestion products by enterocytes 7. Resynthesis of triglycerides and formation of chylomicrons 7.1. Monoglycerides and fatty acid 7.2. Phospholipids 7.3. Cholesterol 8. Assembly of intestinal lipoproteins 9. Clinical disorders of intestinal lipid transport 10. Acknowledgements 11. References
The absorption and transport of lipids by the small intestine
Brain Research Bulletin, 1991
TSO, P. AND K. FUJIMOTO. The absorption and transport of lipids by the small infestine. BRAIN RES BULL 27(3/4) 477-482, 1991.-Dietary lipid provides as much as 40% of the caloric intake in the Western diet. Triacylgiycerol is the main dietary fat. The human small intestine is also presented daily with II-12 g of phosphol~pid, predominantly phosphatidyicholine. The predominant sterol in the Western diet is cholesterol, which is derived from animal fat. Plant sterols account for up to 20-25% of total dietary sterol. This paper reviews our current unde~t~ding of the process and the factors that regulate the absorption and transport of different dietary lipids by the human small intestine.
Lipid Absorption and Metabolism
Environmental Health Perspectives, 1979
Metabolic processes occurring within the mucosal cell are critical in determining results of interactions between environmental agents and the alimentary tract. The absorption, metaboUsm, and transport of lAds affects most those agents which are lipid soluble. The understanding of the process involved in lipid absorption and transport is therefore important for both appreciation of the mechanism of uptake of these twdns and for an effective interference with it. Most of the detailed mechanisms of lipid absorption and trnport have been proposed from in vitro studies with soluble cell-free systems. The present review integrates these results with recent in vivo and in vitro findings with intact animal tissues and isolated mucesal cells. While there is much general agreement occasional startling differences are also observed, which may have a bearing on the mechanism of normal fat absorption and on the understanding of the transport of the fat-soluble toxins across the mucosal villus cell.
Mechanisms involved in vitamin E transport by primary enterocytes and in vivo absorption
Journal of Lipid Research, 2007
It is generally believed that vitamin E is absorbed along with chylomicrons. However, we previously reported that human colon carcinoma Caco-2 cells use dual pathways, apolipoprotein B (apoB)-lipoproteins and HDLs, to transport vitamin E. Here, we used primary enterocytes and rodents to identify in vivo vitamin E absorption pathways. Uptake of [ 3 H]a-tocopherol by primary rat and mouse enterocytes increased with time and reached a maximum at 1 h. In the absence of exogenous lipid supply, these cells secreted vitamin E with HDL. Lipids induced the secretion of vitamin E with intermediate density lipoproteins, and enterocytes supplemented with lipids and oleic acid secreted vitamin E with chylomicrons. The secretion of vitamin E with HDL was not affected by lipid supply but was enhanced when incubated with HDL. Microsomal triglyceride transfer protein inhibition reduced vitamin E secretion with chylomicrons without affecting its secretion with HDL. Enterocytes from Mttpdeficient mice also secreted less vitamin E with chylomicrons. In vivo absorption of [ 3 H]a-tocopherol by mice after poloxamer 407 injection to inhibit lipoprotein lipase revealed that vitamin E was associated with triglyceride-rich lipoproteins and small HDLs containing apoB-48 and apoA-I. These studies indicate that enterocytes use two pathways for vitamin E absorption. Absorption with chylomicrons is the major pathway of vitamin E absorption. The HDL pathway may be important when chylomicron assembly is defective and can be exploited to deliver vitamin E without increasing fat consumption.-Anwar, K., J. Iqbal, and M. M. Hussain. Mechanisms involved in vitamin E transport by primary enterocytes and in vivo absorption. J. Lipid Res.
SUMMARY Simultaneous portal blood absorption and intestinal mucosal catabolism of labelled fatty acids were investigated. Anaesthetized adult Wistar rats were infused intraduodenally either with 90 ,umol of capric (ClO:0), oleic (Cl8: 1), linoleic (Cl8:2) or arachidonic (C20:4) 1-14C acids or with 30 ,umol of each labelled fatty acid in addition to 30 ,umol of oleic acid and 30 ,umol of monopalmitin. For mixed infusates, experiments were carried out with two additional long-chain fatty acids: palmitic (C16:0) and erucic (C22: 1) 1-14C acids. Radioactivity was quantified in the lipids and in the catabolic products in portal blood recovered at 5 min intervals for 1 h after infusion. At the end of the experiment, the disappearance of radioactivity from the mucosa was quantified. When labelled fatty acids were infused alone, 49 % of the radiolabelled lipid disappearing from the mucosa was recovered in the blood for CIO :0, but only 7-8% for C18: 1, 64% for C18:2 and 10-6% for C20:4. With mixed infusates, 41 % of the radiolabelled lipid disappearing from the mucosa was recovered in the blood for C1O:0 compared with 12% for C18:1, 10 2% for C18:2, 10-5% for C20:4 and 2-7% for C16:0 and 2 % for C22: 1. Labelled catabolites appear with the same profiles as those of the respective fatty acids in blood. These studies confirm a minor absorption into blood of long-chain fatty acids compared to the medium-chain fatty acids and highlight differences in the catabolism of the fatty acids according to their chain length and their degree of unsaturation. The differences might be related to the differences in the fatty acid hydrosolubility and to their different affinities for the I-and L-cytosolic fatty acid binding proteins. These phenomena may be important in nutrition in relation to the availability of essential fatty acids.
The pathophysiology of intestinal lipoprotein production
Frontiers in Physiology, 2015
Intestinal lipoprotein production is a multistep process, essential for the absorption of dietary fats and fat-soluble vitamins. Chylomicron assembly begins in the endoplasmic reticulum with the formation of primordial, phospholipids-rich particles that are then transported to the Golgi for secretion. Several classes of transporters play a role in the selective uptake and/or export of lipids through the villus enterocytes. Once secreted in the lymph stream, triglyceride-rich lipoproteins (TRLs) are metabolized by Lipoprotein lipase (LPL), which catalyzes the hydrolysis of triacylglycerols of very low density lipoproteins (VLDLs) and chylomicrons, thereby delivering free fatty acids to various tissues. Genetic mutations in the genes codifying for these proteins are responsible of different inherited disorders affecting chylomicron metabolism. This review focuses on the molecular pathways that modulate the uptake and the transport of lipoproteins of intestinal origin and it will highlight recent findings on TRLs assembly.
Intestinal absorption of long-chain fatty acids: Evidence and uncertainties
Progress in Lipid Research, 2009
Over the two last decades, cloning of proteins responsible for trafficking and metabolic fate of long-chain fatty acids (LCFA) in gut has provided new insights on cellular and molecular mechanisms involved in fat absorption. To this systematic cloning period, functional genomics has succeeded in providing a new set of surprises. Disruption of several genes, thought to play a crucial role in LCFA absorption, did not lead to clear phenotypes. This observation raises the question of the real physiological role of lipid-binding proteins and lipid-metabolizing enzymes expressed in enterocytes. The goal of this review is to analyze present knowledge concerning the main steps of intestinal fat absorption from LCFA uptake to lipoprotein release and to assess their impact on health.
Characteristics and functions of lipid droplets and associated proteins in enterocytes
Experimental Cell Research, 2015
Cytosolic lipid droplets (LDs) are observed in enterocytes of jejunum during lipid absorption. One important function of the intestine is to secrete chylomicrons, which provide dietary lipids throughout the body, from digested lipids in meals. The current hypothesis is that cytosolic LDs in enterocytes constitute a transient pool of stored lipids that provides lipids during interprandial period while lowering chylomicron production during the post-prandial phase. This smoothens the magnitude of peaks of hypertriglyceridemia. Here, we review the composition and functions of lipids and associated proteins of enterocyte LDs, the known physiological functions of LDs as well as the role of LDs in pathological processes in the context of the intestine.