Dietary β-glucan modulates sucrose preference via gut–brain neuropeptide signaling in a sex-dependent manner in Drosophila

Abstract

This study investigated the role of soluble dietary fiber, specifically β-glucan, as a modulator of nutrient-specific food choice and metabolic function using Drosophila melanogaster as a model. Adult males and mated females were assigned to a blank group (B), a corn starch control group (C), or groups fed diets supplemented with β-glucan at 5% (LBG), 10% (MBG), or 20% (HBG), or arabinoxylan (AX; 10%) for 4 days. Short-term food preference was quantified using dye-based dual-choice assays, and long-term sucrose preference was assessed using the capillary feeder assay. Circulating glucose, whole-body triglycerides (TG), whole-body Drosulfakinin (DSK), and midgut Neuropeptide F (NPF) were measured by ELISA, complemented by immunofluorescence analyses in gut and brain tissues. Dietary β-glucan modulated sucrose-related feeding behavior in a sex- and dose-dependent manner. In females, neither short- nor long-term sucrose preference differed across interventions (p > 0.05). In males, β-glucan produced a non-linear response: in the sucrose-yeast assay, MBG reduced the preference index relative to C (0.50 ± 0.04 versus 0.63 ± 0.07, p = 0.014), whereas HBG increased it (0.77 ± 0.07 versus 0.63 ± 0.07, p = 0.006). In the high–low sucrose assay, HBG showed a nominal trend toward reduced short-term preference (p = 0.094). Long-term sucrose preference was significantly lower in males receiving β-glucan compared with the control (−0.09 ± 0.38 versus 0.45 ± 0.56, p = 0.022). AX did not significantly affect sucrose preference. TG levels increased in females at MBG and HBG but decreased in males at the same doses. DSK levels were higher in females (LBG and HBG, p < 0.001) and in males (LBG, MBG, HBG and AX, p < 0.001), while NPF concentrations increased in multiple intervention groups in both sexes (p < 0.001). Immunofluorescence analyses revealed broadly comparable neuropeptide distributions across groups. These findings demonstrate that dietary β-glucan modulates sucrose-related feeding behavior in a sex- and dose-dependent manner, with males exhibiting a non-linear response and reduced long-term sucrose preference. The metabolic and neuropeptide changes support a gut–brain-metabolic framework through which dietary fiber may shape sugar preference, highlighting a behavioral dimension of dietary fiber function.