Modification of fluidity and lipid-protein relationships in pig intestinal brush-border membrane by dietary essential fatty acid deficiency.

The effect of dietary essential fatty acid (EFA) deficiency on the dynamic molecular organization of pig intestinal brush-border membrane (BBM) was studied using purified BBM vesicles. A 6 week dietary treatment of weaning piglets induced a typical EFA-deficient pattern in the lipid composition of both plasma and epithelial membranes. In pigs fed on the EFA-deficient diet, the plasma 20:3(n - 9)/20:4(n - 6) ratio progressively increased and reached a stable value after 3 weeks of experiment, whereas it remained low (less than 0.2) in controls. In the intestinal BBM, the cholesterol/protein, phospholipid/protein and consequently the cholesterol/phospholipid ratios, as well as the phospholipid class distribution, were unchanged. In particular, the sphingomyelin/phosphatidylcholine (SM/PC) molar ratio was not affected. However, the fatty acid composition of phospholipid main classes was markedly modified, leading to decreased lipid fluidity and to a large change in membrane protein behaviour with EFA deficiency. These findings could be interpreted in terms of reduced lipid-protein interactions. Moreover, the increasing gradient of fluidity which took place within the lipidic matrix from its surface was modified by the dietary treatment, as fluidity was lowered by EFA deficiency at different depths of the layer.