Changes in fatty acid composition during cell differentiation in the small intestine of suckling piglets.

Alterations of phospholipid fatty acid composition in the renewing intestine were studied in the infant piglet. Newborn piglets were fed from birth to 2 weeks of age a concentrated cow's milk which defined a standard supply of dietary fatty acids. Phospholipids were isolated from the whole mucosa, isolated intestinal cells and purified brush border membranes. Intestinal cells were isolated according to their position along the crypt-villus axis and cell phospholipids were extracted at each step of differentiation. Changes in fatty acid composition of cell phospholipids were related to those of lactase activity in the corresponding cell homogenates. In cell phospholipids, the relative content of linoleic and linoleic acids increased about 2-fold from crypt base to villus tip. Substantial contents of alkenylacyl glycerophospholipids (plasmalogens) were found in crypt cell phospholipids and in purified brush border membrane phosphatidylethanolamine (11 and 14% of alkenyl groups by weight of total fatty acids, respectively). The proportion of alkenylacyl glycerophospholipids decreased as cells ascended the villus column and became more differentiated. The results show that fatty acid compositional changes in differentiating cell phospholipids occurred in the immature intestine (before weaning) and suggest that these alterations might be related to the appearance of specific functions.

Diet-induced alterations of lipids during cell differentiation in the small intestine of growing rats: effect of an essential fatty acid deficiency.

The lipid components of columnar cells harvested from rat small intestine were analyzed at each step of cell maturation. The effect of dietary lipids on the evolution of lipids in differentiating cells was studied using two diets representative either of a control or of an essential polyunsaturated fatty acid deficient lipid supply. Two groups of weanling rats were fed a semisynthetic diet composed of corn oil (control diet) or hydrogenated coconut oil (deficient diet) for 11 weeks. Intestinal cells were extracted according to their position along the villus column. Linoleic and arachidonic acids constitutive of cell phospholipids increased as cells migrated from the lower to the mid-part of the crypt-villus axis only with the control diet. This gradient disappeared after a 3-week feeding period with hydrogenated coconut oil diet so that columnar cells of essential fatty acid deficient rats exhibited the same overall fatty acid composition all along the crypt-villus axis. Essential fatty acid deficiency resulted in an increase of both the triene to tetraene and arachidonic acid to linoleic acid weight ratios regardless of the maturational step of cells. As compared to the control diet, the essential fatty acid deficient diet induced a decrease of both the cholesterol and free fatty acid to phospholipid molar ratios only in lower villus cells. We conclude that (a) progressive compositional modifications of lipids occur while ascending the crypt-villus axis and (b) essential fatty acid deficiency induces substantial alterations of the lipid evolution normally linked to cell differentiation.

[The mucosa of the small intestine: development of the cellular lipid composition during enterocyte differentiation and postnatal maturation]. / La muqueuse de l'intestin grêle: évolution de la composition en lipides cellulaires au cours de la différenciation entérocytaire et de la maturation postnatale.

Alterations in lipids linked to intestinal maturation and enterocyte differentiation were reviewed. The 3 main lipid components of cell membranes, ie cholesterol, phospholipids and glycolipids, were examined. Cell phospholipid content increases from the crypts to the mid-villus, which accounts for membrane development and organelle growth in differentiating cells. Changes in the proportion of phospholipid polar head groups occur in brush border membrane during postnatal maturation of the small intestine. The possibility that phospholipid fatty acid composition in differentiating cells might be altered by dietary lipids is discussed. Cholesterol biosynthesis mainly occurs in crypt and lower villus cells whereas its absorption from luminal content and esterification into lipoproteins occur in upper villus mature cells. Cholesterol cell content increases in mature cells in comparison to immature cells on the one hand, and in the distal by comparison with proximal parts of the intestine on the other. Increasing cholesterol content is generally correlated with decreasing membrane fluidity, which in turn could modulate functional properties of the mucosa. Glycosphingolipids are mainly found in the brush border membrane, which contains 20-30% glycolipids by weight of total lipids. These components tend to reinforce the membrane stability and significantly contribute to the surface properties of epithelial cells. The latter undergo noticeable changes during cell differentiation and postnatal maturation. Significant changes in both the glycosidic and lipophilic parts of glycosphingolipid molecules occur in differentiating cells and are of possible importance in the process of mucosal maturation. It is possible that the addition of a terminal sialic acid (sialyltransferase activity) instead of a terminal galactose (galactosyltransferase) to an endogenous acceptor (lactosylceramide) could constitute an important event in the differentiation process, and may account for the increasing content of hematosides along the intestinal villus of rat. Alterations in lipid counterpart mainly consist of hydroxylation of fatty acids in hematosides during postnatal maturation or in glucosylceramides during cell differentiation. Collectively these intestinal lipid changes may contribute in part to the development of mucosal barrier, selective permeability and functional properties of the mature intestinal mucosa.

Comparative chromatographic study of modifications of brush-border membrane vesicles induced by an essential fatty acid-deficient diet.

The surface properties of small intestine brush-border membranes (BBMs) were examined by frontal affinity chromatography using three types of unsolubilized ligands: phlorizin polymer, immobilized lectins and linolenic acid bound to agarose gel. BBM vesicles were purified from piglets fed a corn oil diet (control diet) or a hydrogenated coconut oil diet. The second diet was representative of a deficient supply of essential polyunsaturated fatty acid (EPUFA). It induced a marked decrease in 18:2n-6 content in membrane choline phosphoglycerides and ethanolamine phosphoglycerides, whereas 20:3n-9 appeared in each class of phospholipids. Control and EPUFA-deprived BBM vesicles bound to phlorizin polymer, linolenic acid-agarose and wheat germ agglutinin (WGA) gel. In contrast, concanavalin A gel and Lens culinaris A gel exhibited a low binding capacity towards the two types of vesicles. EPUFA deficiency induced a slight decrease in binding on phlorizin polymer and a marked increase in binding on WGA gel, whereas the two types of vesicles similarly bound to linolenic acid-agarose. Desorption of phlorizin polymer-bound membranes was performed using several detergents with special regard to sodium deoxycholate (NaDOC) micelles. Sucrase activity recovery showed that the efficiency of NaDOC desorption was diminished in the case of EPUFA-deprived vesicles. EPUFA-deprived membrane domains involved in the binding would be less sensitive to the detergent attack. This assumption agrees with the putative decrease in membrane fluidity induced by the deficient diet. The possibility that fatty acid compositional changes induced by dietary lipids are extensive enough to alter some chromatographic properties of BBM vesicles is discussed.