Adipokinetic and hypertrehalosemic neurohormones

Definition

Peptide neurohormones released from the corpora cardiaca that coordinate energy mobilization during sustained activity or metabolic stress in insects. Adipokinetic hormones (AKHs) stimulate lipid release from the fat body and enhance fatty acid oxidation in flight muscle; hypertrehalosemic hormones (HTHs) promote trehalose (the main circulating sugar in insects) synthesis and release. These structurally related octapeptides or decapeptides belong to the AKH/RPCH family, act via G-protein-coupled receptors, and often show partial functional overlap in vivo despite their distinct names.

Etymology

Greek adipos (fat) + kinesis (movement) for lipid mobilization; Greek hyper (above, excessive) + trehalose (the disaccharide trehalose) + haima (blood) for elevated hemolymph sugar; neuro- (nerve) + hormone (chemical messenger)

Example

In the migratory locust Locusta migratoria, adipokinetic hormone I (Lom-AKH-I) is released within minutes of flight initiation, triggering the conversion of diacylglycerol transport lipoproteins and shuttling lipids to power hours of continuous wingbeat; concomitant hypertrehalosemic activity ensures trehalose remains available for neural tissue when flight muscles switch to lipid oxidation.

Synonyms

• AKH/HTH hormones
• AKH/RPCH family peptides
• adipokinetic hormones
• hypertrehalosemic hormones

Related Terms

• Corpus cardiacum
• fat body
• trehalose
• Diacylglycerol
• Metabolic flight syndrome
• juvenile hormone
• ecdysteroids
• Neurosecretory cells
• hemolymph

Usage Notes

The combined term reflects historical nomenclature where distinct bioassays (lipid vs. sugar mobilization) yielded separate names, though modern sequencing often reveals the same peptide has both activities. Specialists now frequently use 'AKH' as the family name for all members, with functional qualifiers (adipokinetic, hypertrehalosemic, or hyperprolinemic) describing observed activity in a given species. The related peptide RPCH (red pigment-concentrating hormone) in crustaceans is the ancestral family member. Do not confuse with vertebrate glucagon, which convergently regulates glucose but differs in structure and receptor mechanism.