High-fat diet (HFD) often causes obesity and it has detrimental effects on the sensory system. In particular, sensory-mediated responses are crucial for maintaining energy balance, as they are involved in a metabolic regulation; however, there is still no clear explanation about the relationship between HFD-induced stress and sensory system. To gain insight on how HFD-induced stress affects olfactory sensitivity and behavioral responses, we have used a Drosophila melanogaster model for olfactory and nutrient-related signaling and accessed physiological, behavioral, and transcriptional changes. We demonstrated that lifespan and climbing ability in HFD-treated flies decreased and that olfactory sensitivity and behavioral responses to odorants were changed. Olfactory sensitivity to eight of ten odorants after 14 days on HFD treatment were reduced, while behavioral attraction was increased to benzaldehyde in flies that were treated with HFD. This behavioral and physiological modification in HFD-treated flies for 14 days was accompanied by a significant decrease in DmOrco gene expression in a peripheral olfactory organ, suggesting that is could be involved in the action of metabolic and sensory signal. Gene expression profiles of antennae showed significant differences on the olfactory receptors, odorant-binding proteins, and insulin signaling. Our results suggested that olfactory sensitivity and behavioral responses to HFD-induced stress are mediated through olfactory and nutrient-related signaling pathways.

Climate warming increasingly threatens honey bee health, yet diet-associated molecular patterns under thermal stress remain poorly understood. In this study, newly emerged honey bees were fed eight dietary treatments, including natural diets (honey and bee bread) and artificial diets (sugar syrup and pollen substitute diets), for 5 days before exposure to acute heat stress (45 °C for 4 h). Transcriptional responses were quantified by quantitative real-time PCR (qRT-PCR) using genes associated with nutrient sensing, metabolism, immunity, and stress responses, and the resulting expression profiles were analyzed using principal component analysis, hierarchical clustering, and univariate statistical analyses. Distinct diet-associated transcriptional patterns were observed under both baseline and heat-stress conditions. Under baseline conditions, transcriptional variation was primarily associated with nutrient-sensing and metabolic pathways, whereas under heat-stress conditions, metabolic and stress-response pathways contributed more strongly to transcriptional variation. Sugar syrup-fed honey bees exhibited elevated expression of several immune-related genes following heat stress, suggesting greater physiological disturbance. In contrast, honey- and bee bread-based diets exhibited more coordinated regulation of nutrient-sensing and metabolic pathways and comparatively lower expression of selected immune-related genes. These findings demonstrate that dietary quality is associated with distinct molecular profiles under thermal stress and provide mechanistic insights into the relationship between nutrition and gene expression under heat-stress conditions, supporting the development of nutrition-based strategies for promoting honey bee health under climate warming.

Heat events and nutritional stress threaten honey bee health, but how pollen substitute formulation shapes responses to acute heat remains unclear. Newly emerged Apis mellifera workers received three pollen substitute diets or two beebread-based reference diets for five days before exposure to 45 °C for 4 h. Expression of 12 genes related to nutrition, endocrine regulation, immunity, oxidative defense, and cellular stress was examined using mixed-effects and multivariate analyses. Immune-derived predicted biological age was estimated before and after heat exposure. Apparent consumption and survival were evaluated in an independent 18-day feeding assay without heat. Significant diet × heat interactions occurred for 10 genes, whereas tor and dome showed no significant interactions. At baseline, Diet2(M) exhibited a transcriptional profile similar to the control and a lower predicted biological age than Diet1(S) and Diet3(O). Diet2(M) also supported higher survival than Diet1(S), despite similar apparent consumption among substitute diets. These findings indicate that pollen substitute composition, rather than apparent consumption alone, can shape physiology and survival. Diet2(M) is therefore a priority candidate for colony-level evaluation, although improved heat tolerance was not demonstrated. These findings may guide the development of supplemental feeds supporting honey bee health under climate-related pollen scarcity and heat risk.