Uptake of dietary lipids: A novel pathway in Pieris brassicae

Abstract

In larvae of the cabbage butterfly, Pieris brassicae, a substantial proportion of lipids present in the midgut lumen, or added to the diet, are incorporated into polar lipids prior to lipid absorption. Four major luminal lipid fractions, not found in the diet, and identified as glycolipids, incorporated radiolabeled precursor lipids present in the diet, suggesting synthesis of these lipids prior to lipid absorption. Studies of the time course of incorporation showed that following ingestion of (1- 14C)linolenic acid 40 to 50% of luminal radioactivity was present in the major luminal glycolipid fraction within 24 h. These lipids are absent from midgut cells and are not significantly excreted in feces, suggesting that they are hydrolyzed before entry of lipids into mucosal cells. The data indicate that triacylglycerols and phosphatidylcholines are important intermediates in the absorption process in mucosal cells, before release of lipid into the hemolymph.