Dietary lipids influence the activity of delta 5-desaturase and phospholipid fatty acids in rat enterocyte microsomal membranes.

Previous studies have shown that isocaloric modifications in the type of lipids in the diet alter the nutrient uptake and lipid composition of the intestinal brush border membrane. In this study adult rats were fed for 2 weeks isocaloric semisynthetic diets with triglycerides enriched with either saturated (S) or polyunsaturated (P) fatty acids. Enterocyte microsomal membranes (EMMs) were isolated from along the jejunal villus. The activity of delta 5-desaturase was higher in the upper than in the lower portions of the villus, and was greater in P than in S. The activity of delta 9- and delta 6-desaturases did not vary along the villus or with changes in dietary S or P. The two predominant EMM phospholipids were phosphatidylcholine and phosphatidylethanolamine, and these did not vary along the villus or with changes in diet. The major EMM fatty acids in phosphatidylcholine and phosphatidylethanolamine were 16:0, 18:0, 18:2 omega 6, and 20:4 omega 6; none of the individual fatty acids varied along the villus or with diet, although minor changes in fatty acid classes were observed. Thus, alterations in dietary lipids modify the activity of delta 5-desaturase in the EMMs collected from the upper portion of the villus, but this does not result in the expected changes in fatty acids in the EMM phospholipids.