20-Hydroxyecdysone and Receptor Interplay in the Regulation of Hemolymph Glucose Level in Honeybee (Apis mellifera) Larvae

Abstract

The hormone 20-hydroxyecdysone (20E) and the ecdysone receptors (ECR and USP) play critical roles in the growth and metabolism of insects, including honeybees. In this study, we investigated the effect of 20E on the growth and development of honeybee larvae by rearing them in vitro and found reduced food consumption and small-sized pupae with increasing levels of 20E. A liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based analysis of widely targeted metabolomics was used to examine the changes in the metabolites after an exogenous 20E application to honeybee larvae and the underlying mechanisms. A total of 374 different metabolites were detected between the control group and the 20E treatment group, covering 12 subclasses. The most significant changes occurred in 7-day-old larvae, where some monosaccharides, such as D-Glucose and UDP-galactose, were significantly upregulated. In addition, some metabolic pathways, such as glycolysis/gluconeogenesis and galactose metabolism, were affected by the 20E treatment, suggesting that the 20E treatment disrupts the metabolic homeostasis of honeybee larvae hemolymph and that the response of honeybee larvae to the 20E treatment is dynamic and contains many complex pathways. Many genes involved in carbohydrate metabolism, including genes of the glycolysis and glycogen synthesis pathways, were downregulated during molting and pupation after the 20E treatment. In contrast, the expression levels of the genes related to gluconeogenesis and glycogenolysis were significantly increased, which directly or indirectly upregulated glucose levels in the hemolymph, whereas RNA interference with the 20E receptor EcR-USP had an opposite effect to that of the 20E treatment. Taken together, 20E plays a critical role in the changes in carbohydrate metabolism during metamorphosis.

LC-MS Profiling Reveals Metabolic Dynamics in <em>Apis mellifera</em> Worker Bee Larvae–Pupae Transition

“…The wings of honey bees consist of a double body wall, each containing multiple layers of chitin [26]. Chitin synthesis is essential for the growth and development of insects, including honey bee pupal stage larvae, which need to shed their old epidermal bonds before significant cuticle growth [27]. Chitin synthase is responsible for synthesizing chitin using uridine diphosphate-N-acetylglucosamine [28].…”

Mechanisms of Neuroendocrine Stress Response in Drosophila and Its Effect on Carbohydrate and Lipid Metabolism

“…OA likely plays the role of an additional regulator in insects when it is released into the hemolymph as a neurohormone and further transported to a target tissue, where it mobilizes lipids and carbohydrates [ 78 , 79 ]; other stress-related hormones, such as JH, 20E and DA, also play this part [ 74 , 76 ]. The largest amount of data on this have been obtained for 20E on different insect species: it stimulates glycolysis increasing the glucose level in hemolymph in the honeybee, Apis mellifera , larvae [ 80 ], as well as in pupae of the cotton bollworm, Helicoverpa armigera, [ 81 ] and the Chinese oak silk moth, Antheraea pernyi , [ 82 ]; it also increases lipolysis and inhibits lipid synthesis in the fall webworm, Hyphantria cunea , larvae [ 83 ].…”