Adipokinetic hormones

Adipokinetic hormones control metabolism of insects during long-distance flight.359 363 In the migratory locust these hormones consist of a pair of related octapeptides and a decapeptide (Table 30-5). The hormones stimulate triacylglycerol lipase in the insects fat bodies, induce release of carbohydrates from body stores, and affect many other aspects of metabolism.363 Insects also have hormones of the insulin family, proteins consisting of disulfide-linked A and B chains as in insulin. The silkworm Bombyx mori has 38 genes for the insulinlike bombyxins, which are synthesized in the brain.364... 

The invertebrate peptides PCH (pigment-concentrating hormone 46) and AKH I (adipokinetic hormone 47) were the first neuropeptides from invertebrates to have their structure and synthesis described by L. Josefsson in 1983 94). 

Adipokinetic hormone Pigment-concentrating hormone Adipokinetic hormone Hypertrehalosaemic hormone... 

Insects use camouflage coloration as a means of avoiding predation. The green color of the tobacco hornworm larvae, (Manduca sexta) can be separated into constituent blue and yellow components. The water soluble blue component is the biliprotein, insecticyanin. The yellow color is derived from lipoprotein bound carotenes. This lipoprotein, lipophorin, is the major lipid transport vehicle in insect hemolymph. In addition to transporting dietary lipid, lipophorin is also involved in the transport of lipophilic insecticides. Nearly all the recovered radioactivity in hemolymph from topically applied [14c] ddt is associated with lipophorin. Lipophorin of adult M. sexta is larger, less dense and is associated with small amounts of a third, adult specific, apoprotein. Alterations in adult lipophorin density, lipid content and apoprotein stoichiometry can be caused by injection of the decapeptide, adipokinetic hormone. 

Above, saline injected control animals below, adipokinetic hormone (200 pmoles/animal) injected. Reproduced with permission from Ref. 23. Copyright 1983 Academic Press. 

Both of these peptides exhibited considerable sequence identity with the locust adipokinetic hormone (Lom-AKH-I) and the crustacean red pigment-concentrating hormone (RPCH), as had been suggested by chromatographic behavior, N-terminal analysis, and amino acid analysis (3,4). Indeed, both peptides were shown to be far more potent as stimulators of hyperglycaemia than as myotropins (3). 

Since these initial reports, numerous peptides have been described for what is now recognized as the insect adipokinetic/red pigment-concentrating hormone (AKH/RPCH) family. The first representative of this family isolated and characterized from insects was the L, migratoria adipokinetic hormone (I m-AKH-I)... 

The similarity of the crustacean blanching substance (Factor A) found in crustacean sinus glands and insect corpora cardiaca has been confirmed by the structural identification of a family of neuropeptides common to arthropods. The first identified member of this family is RPCH (red pigment concentrating hormone), an octapeptide (pGlu-Leu-Asn-Phe-Ser-Pro-Gly-Trp-amide) isolated from eyestalks of the shrimp Pandalus borealis (28). Shortly thereafter, a related peptide--designated as adipokinetic hormone (AKH)--was purified from locust... 

The analysis of neuropeptides in insects may lead to the development of both specific insect control strategies and model systems that clarify the role of neuropeptides in all animals. Therefore it is important to vigorously pursue neuropeptide studies and to exploit the available technologies to the fullest. This paper will review the importance of current recombinant DNA techniques to the study of neuropeptide biology. Studies of the adipokinetic hormone (AKH) family will be emphasized as examples, but other peptides will be mentioned to present a broader picture of the advantages and problems associated with the techniques. 

SCHAFFER AND NOYES Adipokinetic Hormone Neuropeptide Family 229... 

Fig. 8. Role of lipophorin in DG delivery to flight muscle. Adipokinetic hormone (AKH) is released from the corpus cardiacum and binds to the fat body, where it cause production of cAMP and entry of Ca . These second messengers activate lipolysis of triacylglycerol (TG) and production of diacylglycerol (DG). The DG leaves the fat body with the assistance of a lipid transfer particle (LTP) and is taken up by HDLp. The capacity of HDLp to carry DG is increased by binding of apoLp-HI to the surface. Ultimately, LDLp is formed and moves to the flight muscle, where a lipoprotein lipase hydrolyzes the DG to produce fatty acid (FA) and regenerate HDLp and apoLp-IIl. The FA enters the flight muscle, where it is oxidized to produce the ATP required to power flight. HDLp and apoLp-HI circulate back to the fat body to complete the cycle.

Locusta Glandular lobe Release of adipokinetic hormone Brain 30-32... 

Examination of the titres of the three adipokinetic hormones, octopamine, AKHI and AKHII (see 52) reveals a model as shown in Figure 3. Flight induces an elevation in haemolymph octopamine which acts on the fat body to result in the initial elevation in haemolymph lipid. After some minutes, the release of the peptidergic AKHs is stimulated by octopaminergic synapses within the glandular lobe. 

Insects adipokinetic hormone Locmi-AKH-I Locusta migratoria pELNFTPNWGT-NH2 [30]... 

The detailed pathways of the biosynthesis of the two adipokinetic hormones from S. gregaria, including the characterization of the... 

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