GLP-LEU-ASN-PHE-THR-PRO-ASN-TRP-GLY-THR-NH2

Description

Adipokinetic hormone (AKH) mobilizes carbohydrates and lipids from storage into the hemolymph for energy demands such as a long flight. Thus, AKH is a functional counterpart of vertebrate glucagon. The red pigment concentrating hormone (RPCH), structurally related to AKH, controls the granule of the crustacean chromatophore, eventually changing the body color.

Structure

AKH has been identified in more than 40 insect species so far.In most insect species, several AKH subtypes are present. In L. migratoria, two structurally related subtypes (AKH-II and -III) have been identified.Some AKH subtypes are exceptionally nonapeptides and decapeptides. The number of subtypes differs according to species. No subtypes of crustacean RPCH are known.

Biological functions

AKH stimulates the fat body, where lipids and carbohydrates are stored, eventually resulting in lipid and carbohydrate mobilization into the hemolymph. The increase in hemolymph lipids is accompanied by the activation of the lipid transfer system. According to the effects of the increase in hemolymph carbohydrates and lipids, locomotor and flight muscles are concomitantly activated.AKH is also required for proper food digestion, enhancing the protease and amylase activities in the midgut of Sarcophaga crassipalpis and Periplaneta americana, respectively.RPCH, however, influences the concentration of the pigment chromatophore, causing drastic body color changes in the crustacean species.

Regulation of synthesis and release

AKH is released from the secretary granule in the CC. AKH secretion is modulated by nutritional status, including the need for extra loading of lipids and carbohydrates for long migratory flights.In a recent study, a glucosesensing neuron pair was identified as regulating AKH release in Drosophila.AKH is released from the CC by a high concentration of potassium in vitro.