title: Adipokinetic hormones of insect: release, signal transduction, and responses.
abstract: Flight activity of insects provides an attractive yet relatively simple model system for regulation of processes involved in energy metabolism. This is particularly highlighted during long-distance flight, for which the locust constitutes a well-accepted model insect. Peptide adipokinetic hormones (AKHs) are synthesized and stored by neurosecretory cells of the corpus cardiacum, a neuroendocrine gland connected with the insect brain. The actions of these hormones on their fat body target cells trigger a number of coordinated signal transduction processes which culminate in the mobilization of both carbohydrate (trehalose) and lipid (diacylglycerol). These substrates fulfill differential roles in energy metabolism of the contracting flight muscles. The molecular mechanism of diacylglycerol transport in insect blood involving a reversible conversion of lipoproteins (lipophorins) has revealed a novel concept for lipid transport in the circulatory system. In an integrative approach, recent advances are reviewed on the consecutive topics of biosynthesis, storage, and release of insect AKHs, AKH signal transduction mechanisms and metabolic responses in fat body cells, and the dynamics of reversible lipophorin conversions in the insect blood.
authors.affiliation: Department of Biochemical Physiology, Faculty of Biology and Institute of Biomembranes, Utrecht University, The Netherlands.
authors.forename: D J
authors.initials: DJ
authors.lastname: Van der Horst
authors.forename: W J
authors.initials: WJ
authors.lastname: Van Marrewijk
authors.forename: J H
authors.initials: JH
authors.lastname: Diederen
mesh_terms: D000818:Animals; D001053:Apolipoproteins / Q000737:chemistry / Q000378:metabolism; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D005216:Fat Body / Q000166:cytology / Q000201:enzymology / Q000502:physiology; D005426:Flight, Animal / Q000502:physiology; D024981:Glycogen Phosphorylase / Q000378:metabolism; D007301:Insect Hormones / Q000378:metabolism*; D007313:Insecta / Q000502:physiology*; D050356:Lipid Metabolism; D008074:Lipoproteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism*; D009490:Neurosecretory Systems / Q000502:physiology / Q000648:ultrastructure; D009842:Oligopeptides / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D022142:Secretory Vesicles / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D001053:Apolipoproteins; D002352:Carrier Proteins; D007301:Insect Hormones; D008074:Lipoproteins; D009479:Neuropeptides; D009842:Oligopeptides; D011498:Protein Precursors; C044833:adipokinetic hormone; C042470:apolipophorin III; C032830:lipophorin; D024981:Glycogen Phosphorylase; D011761:Pyrrolidonecarboxylic Acid