The effect of different temperatures on sugar metabolism in Galleria mellonella larvae

Abstract Background Galleria mellonella (Lepidoptera: Pyralidae), a destructive natural enemy of honeybees, is primarily found in beekeeping regions worldwide. By analyzing the carbohydrate content and trehalase activity in G. mellonella larvae, the mechanism of energy change during adaptation to different temperatures was investigated. Methods The changes in trehalose, glycogen, glucose, and sorbitol contents, as well as trehalase activity, were analyzed in the sixth-instar larvae of G. mellonella after treatment at different temperatures (0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, and 40℃) for 1, 2, and 4 h. Results In sixth-instar G. mellonella larvae, both temperature and treatment time were found to have a significant impact on carbohydrate metabolism and trehalase activity. Trehalose, glucose, sorbitol and soluble trehalase activity all first decreased and then increased. Conversely, glycogen content exhibited an opposite trend to membrane-bound trehalase activity. Specifically, the lowest trehalose content and the highest glycogen content corresponded to 30℃. At 0℃, glycogen content was lowest, while glucose content and membrane-bound trehalase activity were highest. After a 4 h exposure period, the levels of glycogen and glucose at 0℃ differed significantly from those in the other temperature groups. Sorbitol content and soluble trehalase activity reached maximum values at 40℃, and soluble trehalase activity differed significantly among all temperature treatments after 1 h exposure. Conclusion This indicates that G. mellonella larvae can accelerate the conversion of sugars such as trehalose into small molecules by regulating sugar metabolism levels to enhance resistance to extreme temperatures. This metabolic process is reversible, and trehalose is an important antifreeze substance found in insects. The levels of glycogen in G. mellonella larvae are significantly correlated with changes in concentrations of trehalose, glucose, and sorbitol, as well as soluble trehalase activity. The larvae respond to temperature changes through metabolic regulation mediated by trehalase.