Adipokinetic hormone-induced lipolysis in the fat body of an insect, Manduca sexta: synthesis of sn-1,2-diacylglycerols.

E L Arrese,M A Wells

doi:10.1016/s0022-2275(20)37276-x

Abstract

The pathway for the adipokinetic hormone-stimulated synthesis of sn-1,2-diacylglycerols in the adult Manduca sexta fat body was studied. Adult fat body lipids were labeled by feeding 5th instar larvae either with [9,10(n)-3H]oleic acid or [1(3)-3H] glycerol and after 32 days insects at the adult stage were used. This long-term prelabeling led to labeled fat body acylglycerols in which triacylglycerols comprised the main radioactive lipid component (95.5%), regardless of the radiolabeled compound used. Because the distribution of radioactivity among the lipid classes was very close to the mass distribution of the fat body lipid subspecies, it was concluded that homogeneous labeling of fat body lipids was obtained. After adipokinetic hormone treatment, an accumulation of radioactivity in the sn-1,2-diacylglycerol fraction was the only significant change found in the distribution of radioactivity among fat body lipids. The size of diacylglycerol pool increased 280% 60 min after adipokinetic hormone stimulation, whereas the fatty acid, monoacylglycerol and phosphatidic acid pool sizes remained constant. These results support the hypothesis that adipokinetic hormone-stimulated synthesis of sn-1,2-diacylglycerol in the fat body involves stereospecific hydrolysis of the triacylglycerol stores.

Highlights

The pathway for the adipokinetic hormone-stiniulated synthesis of sn-1,2-diacylglyceroIsin the adult Manducu sexta fat body was studied
adipokinetic hormone (AKH), a peptide that is released from the corpora cardiaca into the hemolymph during flight in many insects, greatly stimulates the secretion of sn-1,2-diacylglycerolfrom the fat body ( 6 ) .Octopamine, a monohydroxyphenolic analogue of noradrenaline, whose secretion is stimulated by stress, was shown to induce lipid mobilization in Locusta migralom'a [7] and Acheta domesticus [8]
We have studied the pathway for the synthesis of sn-l,2-DG from stored TG in the adult M. sexta fat body when lipid mobilization is stimulated by AKH

Summary

Introduction

The pathway for the adipokinetic hormone-stiniulated synthesis of sn-1,2-diacylglyceroIsin the adult Manducu sexta fat body was studied. Adult fat body lipids were labeled by feeding 5th instar larvae either with [9,10(n)-3H]oleicacid or [1(3)-3H]glyceroland after 32 days insects at the adult stage were used. This long-term prelabeling led to labeled fat body acylglycerols in which triacylglycerols comprised the main radioactive lipid component (95.5%),regardless of the radiolabeled compound used. AKH, a peptide that is released from the corpora cardiaca into the hemolymph during flight in many insects, greatly stimulates the secretion of sn-1,2-diacylglycerolfrom the fat body ( 6 ) .Octopamine, a monohydroxyphenolic analogue of noradrenaline, whose secretion is stimulated by stress, was shown to induce lipid mobilization in Locusta migralom'a [7] and Acheta domesticus [8]. Three different pathways for the formation of DG have been proposed: 1) the hydrolysis of TG into sn-2-monoacylglycerol

Methods

Results

Discussion

Conclusion