Is monoacylglycerol as an intermediate of triacylglycerol digestion absorbed by Aeshna cyanea larvae?
The isolated digestive juice of Aeshna cyanea larvae hydrolysed trioleoylglycerol preferentially at the terminal 1 and 3 positions, yielding 1, 2-dioleoylglycerol as first intermediate. Hydrolysis continued to 1- and 2-monooleoylglycerol as second intermediate. Separate incubation of monooleoylglycerol revealed that hydrolysis could proceed to completion. Inadequate inhibition of mono[1-14C]oleoylglycerol hydrolysis in the cold and in the presence of the lipase inhibitor tetrahydrolipstatin provided no information on whether monooleoylglycerol was absorbed in addition to free oleic acid. On the other hand, the analogue oleylglyceryl ethers were resistant towards hydrolysis by the digestive juice. Both monoethers and both diethers were esterified with [1-14C]palmitic acid by the homogenate of the midgut wall, whereas esterification in vivo occurred only with the monoethers. These were recovered from the haemolymph after saponification of the joint diacylglycerol and acyl-0-alkylglycerol fraction, indicating that the monoethers had been absorbed and transported into the haemolymph. Ingestion of mono-1-0-[3H]octadecylglycerol showed that the ether was absorbed unchanged by the midgut epithelium, where the major part of the alkyl moiety was oxidized to free fatty acid and incorporated into phospholipids, acylglycerols and acyl-0-alkylglycerols. It is concluded from the absorption of the analogous monoalkylglyceryl ethers that monoacylglyceryl esters are also absorbed by Aeshna larvae.
Komnick
H
H
Institute of Cell Biology, University of Bonn, Germany. komnick@uni-bonn.de
Weiher
B
B
Wachtmann
D
D
D000818:Animals; D002250:Carbon Radioisotopes; D004064:Digestive System / Q000033:anatomy & histology / Q000378:metabolism* / Q000648:ultrastructure; D004075:Diglycerides / Q000737:chemistry / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005989:Glycerides / Q000737:chemistry / Q000378:metabolism; D006458:Hemolymph / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis; D007313:Insecta / Q000378:metabolism*; D007408:Intestinal Absorption / Q000502:physiology; D007783:Lactones / Q000494:pharmacology; D007814:Larva / Q000502:physiology; D008049:Lipase / Q000037:antagonists & inhibitors; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D009829:Oleic Acids / Q000737:chemistry; D000077403:Orlistat; D014280:Triglycerides / Q000378:metabolism*; D014316:Tritium
D002250:Carbon Radioisotopes; D004075:Diglycerides; D004791:Enzyme Inhibitors; D005227:Fatty Acids; D005989:Glycerides; D007783:Lactones; D008055:Lipids; D009829:Oleic Acids; D014280:Triglycerides; D014316:Tritium; D000077403:Orlistat; C005953:monoolein; D008049:Lipase