Long-term supplementation of culture medium with essential fatty acids alters alpha-linolenic acid uptake in Caco-2 clone TC7

We investigated the influence of four different culture media: 20% fetal bo vine serum (FBS), 5% FBS, 5% FBS supplemented with 10 mg.L-1 linoleic acid (18:2(n-6)) or alpha-linolenic acid (18:3(n-3)) on alpha-linolenic acid api cal uptake in clone TC7 of human intestinal Caco-2 cell line. Neither cellu lar viability nor cell monolayer integrity and permeability were altered by the four culture conditions. Our results show that the different culture m edia led to changes in alpha-linolenic acid maximal rate of uptake (V-max) but did not alter the apparent transport constant (K-m). Reducing FBS conce ntration from 20% to 5% increased significantly the rate of alpha-linolenic acid uptake, which was further increased by supplementation of the medium with 18:2(n-6) or 18:3(n-3). Supplementation with essential fatty acids led to a marked enrichment of brush-border membrane phospholipids in polyunsat urated fatty acids of the corresponding series and decreased significantly the levels of monounsaturated fatty acids. Saturated fatty acids, unsaturat ion index, and cholesterol / fatty acid ratios were unchanged. No clear rel ation could be established between the changes in membrane lipid compositio n and the alterations of alpha-linolenic acid uptake. These results indicat e a weak influence of membrane lipid composition in the modulation of the u ptake. Therefore, the increase of uptake following long-term supplementatio n of TC7 cells with essential fatty acids could be attributed to an increas e of the expression of membrane protein(s) involved in the apical uptake of long-chain fatty acids. This remains to be established.