CCHamide-2 Signaling Regulates Food Intake and Metabolism in Gryllus bimaculatus

SIMPLE SUMMARY: CCHamide-2 is a newly identified neuropeptide associated with the regulation of feeding behavior as a brain-gut peptide in insects. Data revealed CCHamide-2 signaling inhibited feeding along with increasing circulating carbohydrate and lipid levels in the two-spotted crickets, Gryllus bimaculatus. Consequently, we demonstrated that the signaling involving CCHamide-2 and its receptor contributes to the regulation of feeding and metabolism in the neuropeptide-mediated regulatory network of energy homeostasis in insects. ABSTRACT: Neuropeptides play vital roles in energy homeostasis in insects and other animals. Although the importance of the regulatory network of neuropeptides in feeding and metabolism has been illuminated, a complete understanding of the mechanisms has not been addressed as many factors are involved in the regulation. CCHamide-2 is a newly identified brain-gut neuropeptide that regulates feeding behavior in several insect species including Drosophila melanogaster. However, little is known about the mechanisms controlling the feeding-related behavior and metabolic functions modulated by CCHamide-2 in other insects. In this study, we addressed the functions of CCHamide-2 in the two-spotted cricket, Gryllus bimaculatus, which was used as the experimental material to research the mechanisms of feeding and metabolism in this omnivorous insect species. Knockdown crickets by RNA interference against GbCCHamide-2R increased the amount of food intake, while injection of chemically synthetic GbCCHamide-2 peptide reduced the amount of food intake. Further, knockdown and peptide injection experiments revealed that GbCCHamide-2 signaling increased the concentrations of circulating lipids and carbohydrates, and the carbohydrate-rich diet increased the transcript levels of GbCCHa-2R. Moreover, GbCCHa-2 injection decreased the transcript level of Gbilp. By contrast, GbCCHamide-2 signaling did not affect nymphal growth or the transcript level of GbAKH, as well as feeding preferences. Taken together, CCHamide-2 signaling in G. bimaculatus regulates food intake associated with alterations in lipid and carbohydrate levels in hemolymph.