Is the Golgi apparatus the obligatory final step for lipoprotein secretion by intestinal cells?

doi:10.1016/0040-8166(86)90064-9

Tissue and Cell

Volume 18, Issue 3, 1986, Pages 447-460

https://doi.org/10.1016/0040-8166(86)90064-9 Get rights and content

Abstract

It is currently admitted that the synthesis and excretion of triglyceride-rich lipoproteins (chylomicrons and ‘small chylomicrons’) by intestinal epithelial cells involves the Golgi apparatus as an obligatory final step before exocytosis. The cells of the proximal intestine of the trout are an excellent model for investigating functional compartmentalization in the course of lipid absorption. Using this model, our data invalidate morphological data which were the basis for considering the Golgi apparatus as the mandatory final stage for their secretion. In particular, we show that triglyceride-rich particles can be transported directly from the endoplasmic reticulum to the intercellular space. Two pathways of intestinal lipoprotein excretion appear to coexist. One follows the classical export route, the second functions in a manner that bypasses the Golgi apparatus. The arguments used to affirm the requirement for the Golgi apparatus as a final step (glycosylation of apoprotein B, membrane vehicle for exocytosis) are discussed.

References (40)

D.J. Alpers et al.
Distribution of apolipoproteins A I and B among intestinal lipoproteins
J. Lipid Res.
(1985)
C.M. Arbeeny et al.
The uptake of chylomicron remnants and very low density lipoprotein remnants by the perfused rat liver
J. Biol. Chem.
(1984)
E.G. Berger
Mini-review: How Golgi-associated glycosylation works
Cell Biol. Int. Rep.
(1985)
M.J. Chapman
Animal lipoproteins: chemistry, structure and comparative aspects
J. Lipid Res.
(1980)
N.J. Christensen et al.
Ultrastructural immunolocalization of apolipoprotein B within human jejunal absorptive cells
J Lipid Res.
(1983)
W.O. Dobbins
An ultrastructural study of the intestinal mucosa in congenital β-lipoprotein deficiency with particular emphasis upon the intestinal absorptive cell
Gastroenlerology
(1966)
H.I. Friedman et al.
Intestinal fat digestion, absorption, and transport. A review
Am. J. Clin. Nutr.
(1980)
R.M. Glickman et al.
Immunofluorescence studies of apolipoprotein B in intestinal mucosa
Gastroenterology
(1979)
R.M. Glickman et al.
Chylomicron apoproteins localization within rat intestinal epithelium: studies of normal and impaired lipid absorption
J. Lipid Res.
(1978)
H. Hönigsmann et al.
Continuity of intercellular space and endoloplasmic reticulum of keratinocytes
Expl Cell Res.
(1973)

D.Y. Hui et al.

Binding of chylomicron remnant and β-very low density lipoproteins to hepatic and extrahepatic lipoprotein receptors. A process independent of apolipoprotein B 48

J. biol. Chem.

(1984)

K. Imaizumi et al.

Composition of proteins of mesenteric lymph chylomicrons in rat and alteration produced upon exposure of chylomicrons to blood serum and serum proteins

J. Lipid Res.

(1978)

D.R. Janero et al.

S. Lauverjat et al.

Les voies génitales femelles (oviductes et glandes pseudocollétériques) de Locusta migratoria. I. Etude ultrastructurale du developement imaginai. Rôle des corps allatea

Gen comp. Endocrinol

(1974)

S.M. Sabesin et al.

M.A. Sheridan et al.

Chylomicra in the serum of postprandial steelhead trout (Salmo gairdnerii)

Comp. Biochem. Physiol.

(1985)

M.F. Sire et al.

New views on intestinal absorption of lipids in teleostean fishes: an ultrastructural and biochemical study in the rainbow trout

J. Lipid. Res.

(1981)

P. Siuta-Mangano et al.

A. Steinmetz et al.

Activation of lecithin: cholesterol acyltransferase by human apolipoprotein A-IV

J. biol. Chem.

(1985)

J. Bell-Quint et al.

Glycosylation of apolipoproteins by cultured rat hepatocytes

Biochem. J.

(1981)

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It has been known for almost 25 years now that inclusion of intact phospholipids in the diet could improve culture performance of various freshwater and marine fish species. The primary beneficial effect was improved growth in both larvae and early juveniles, but also increased survival rates and decreased incidence of malformation in larvae, and perhaps increased stress resistance. Determination of absolute dietary requirements has been hampered by the use, in different dietary trials, of a wide range of phospholipid preparations that can vary greatly both in phospholipid content and class composition. Larval studies have been compromised further by the need on many occasions to supply phospholipid through enrichment of live feeds with subsequent re-modelling of the phospholipid and fatty acid compositions. Generally, the levels of phospholipid requirement are around 2–4% of diet for juvenile fish and probably higher in larval fish. The effects were restricted to young fish, as a requirement for dietary phospholipids has not been established for adult fish, although this has been virtually unstudied. As the majority of studies have used crude mixed phospholipid preparations, particularly soybean lecithin, but also other plant phospholipids and egg yolk lecithin, that are enriched in several phospholipids, it has been difficult to elucidate which specific phospholipid classes impart beneficial effects. Based on the few studies where single pure phospholipid species have been used, the rank order for efficacy appears to be phosphatidylcholine > phosphatidylinositol > phosphatidylethanolamine > phosphatidylserine. The efficacy of other phospholipid classes or sphingolipids is not known. The mechanism underpinning the role of the phospholipids in larval and early juvenile fish must also explain their lack of effect in adult fish. The role of phospholipids appears to be independent of fatty acid requirements although the presence of an unsaturated fatty acid at the sn-2 position may be important. Similarly, the phospholipid requirement is not related to the delivery of other essential dietary components such as the bases choline and inositol. Studies also suggested that the phospholipid effect was not due to generally enhanced emulsification and digestion of lipids. Rather the evidence led to the hypothesis that early developing stages of fish had impaired ability to transport dietary lipids away from the intestine possibly through limitations in lipoprotein synthesis. The current hypothesis is that the enzymic location of the limitation is actually in phospholipid biosynthesis, perhaps the production of the glycerophosphobase backbone and that dietary supplementation with intact phospholipids in larvae and juvenile fish compensated for this. Thus, dietary phospholipids increase the efficiency of transport of dietary fatty acids and lipids from the gut to the rest of the body possibly through enhanced lipoprotein synthesis.
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In the trout, dietary fat is absorbed by enterocytes in the anterior segment of the intestine and the pyloric caeca. Ultrastructural analyses showed lipoprotein particles resynthesized by the endoplasmic reticulum, appearing inside this structure, as well as inside membranes of the Golgi apparatus and lamellar structures. The lamellar structures are involved in the transport of these particles to the lateral and basal intercellular spaces. In animals fed a carbohydrate-rich, low-protein diet, electron microscopic images showed a distinct arrangement of the endoplasmic reticulum, forming spiral structures in which the cisternae of the endoplasmic reticulum were tightly wound about themselves, and their membranes were fused. We interpret these results to illustrate a mode of phospholipid and glycolipid storage in the form of lipid bilayers.
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Is the Golgi apparatus the obligatory final step for lipoprotein secretion by intestinal cells?

Abstract

J. Lipid Res.

J. Biol. Chem.

Cell Biol. Int. Rep.

J. Lipid Res.

J Lipid Res.

Gastroenlerology

Am. J. Clin. Nutr.

Gastroenterology

J. Lipid Res.

Expl Cell Res.

J. biol. Chem.

J. Lipid Res.

Gen comp. Endocrinol

Comp. Biochem. Physiol.

J. Lipid. Res.

J. biol. Chem.

Glycosylation of apolipoproteins by cultured rat hepatocytes

Biochem. J.