Five functional adipokinetic peptides expressed in the corpus cardiacum of the moth genus Hippotion (Lepidoptera, Sphingidae)

This is the first study that finds five adipokinetic hormones (AKHs) in the corpus cardiacum of an insect. From two species of the sphingid moth genus Hippotion, eson and celerio, three novel and two known AKHs were isolated and sequenced by deduction from multiple MS electrospray mass data: two octapeptides are pGlu-Leu-Thr-Phe-Thr-Ser-Ser-Trp amide (denoted Hipes-AKH-I) and its Thr(7) analogue (Hipes-AKH-II); two nonapeptides are pGlu-Leu-Thr-Phe-Thr-Ser-Ser-Trp-Gly amide (Manse-AKH) and its Thr(7) analogue (Hipes-AKH-III), as well as a decapeptide pGlu-Leu-Thr-Phe-Ser-Ser-Gly-Trp-Gly-Gln amide (Manse-AKH-II). All sequences were confirmed by identical behaviour of natural and synthetic peptides in reversed-phase HPLC and liquid chromatography coupled to electrospray mass spectrometry, resulting in identical retention times and tandem mass spectral data. High resolution mass spectrometry and retention time data also confirmed that the amino acid at position 10 in Manse-AKH-II is Gin and not the isobaric Lys. Conspecific injections of all five peptides in synthetic form and low doses caused hyperlipaemia in H. eson. Our results and pertaining literature suggest that five genes code for the mature peptides, which are very likely released during flight to provide energy for long distance migration in this genus via lipid oxidation; as all five peptides are active at low doses in a conspecific bioassay, it may be speculated, but not proven, that there is only one AKH receptor present in Hippotion that can bind all five peptides with high affinity. (C) 2013 Elsevier B.V. All rights reserved.