Effects of a low dietary linoleic acid level on intestinal morphology and enterocyte brush border membrane lipid composition.

The influence of low dietary linoleic acid level (an essential fatty acid deficiency) on the intestine mucosal morphology and the purified brush border membrane (BBM) lipid composition was investigated in the rat. Electron micrographs and morphometric measurements showed that villi and crypt sizes as well as the ultrastructure of epithelial cells were altered. Cholesterol (CHOL) and phospholipid (PL) levels, CHOL/PL ratio and PL class distribution were not changed by the low linoleate diet. However, the fatty acid composition of phospholipids was markedly modified in the enterocyte BBM, showing elevated amounts of palmitoleic (16:1n-7), oleic (18:1n-9) and 5,8,11-eicosatrienoic (20:3n-9) acids and, by contrast, depressed linoleic (18:2n-6) and arachidonic (20:4n-6) acid levels. Although the underlying mechanisms remain unknown the results obtained suggest that essential fatty acids (EFA) could be directly involved in the trigger action of the observed alterations, as regards both their dynamic (metabolic) and structural roles.

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.