Cucurbitacin B Suppresses Hyperglycemia Associated with a High Sugar Diet and Promotes Sleep in Drosophila melanogaster

Abstract

Secondary metabolites enable plants to protect themselves from herbivorous insects. Among these, cucurbitacin B (cuc-B) is a bitter-tasting compound with promising pharmacological potential. Dietary exposure to cuc-B lowered the hemolymph glucose levels of Drosophila melanogaster fed with a high carbohydrate diet, which is homologous to high blood glucose in humans, and its effect was comparable to that of metformin, a well-known glucose-lowering drug. Furthermore, cuc-B reduced tissue sugar levels and glycogen levels, as well as triacylglycerol levels. Our results thus highlight the potential applicability of this compound to treat chronic metabolic diseases such as diabetes and obesity. Additionally, we analyzed sleep quality and taste-associative memory enhancement after cuc-B and metformin treatment. Both supplements increased nighttime bout length and metformin increased memory consolidation. Therefore, discarded shell of Cucurbitaceae could be processed into health supplements.

A single pair of pharyngeal neurons functions as a commander to reject high salt inDrosophila melanogaster

“…However, this assay did not discern whether or not the volume of the high salt-containing food consumed by the Ir60b mutant flies was reduced relative to control flies. Therefore, to assess the volume of food ingested, we used the DrosoX system, which we recently developed ( Figure 3—figure supplement 1A ) 44 . This system consists of a set of five separately housed flies, each of which is exposed to two capillary tubes with different liquid food options.…”

“…We conducted Droso-X assays following the methods outlined in a previous study 47 . The amount of ingestion was measured using a Droso-X system (Scitech Korea, Korea) located in a controlled incubator (25°C, 60% humidity).…”

“…To assess the ingestion of different food types, we employed the binary food choice assay, a qualitative method that utilizes blue, red, or purple dye colors in the abdomen 46 . However, for a more precise quantification of food ingestion, we recently developed the DrosoX system (Figure S5A) 47 . This system allowed us to directly measure the actual amount of food ingested over a period of 6 hours.…”

“…Introduction of the rat capsaicin receptor, TRPV1 43 , into Ir60b GRNs induces aversion towards capsaicin, supporting the conclusion that Ir60b -positive GRNs are sufficient for instinctive avoidance. To validate these findings further, we used a two-way choice DrosoX assay 44 to measure actual ingestion levels. We found that the three Ir mutants consumed high salt at levels similar to sucrose over an extended period, emphasizing the critical role of this single pair of pharyngeal GRNs in controlling harmful ingestion of high salt.…”

Protocol for binary food choice assays using Drosophila melanogaster

“…For analysis of feeding behavior, different approaches have been employed for qualitative and quantitative analyses of food consumption. These include binary-choice feeding assays ( Charroux and Royet, 2020 ; Tanimura et al., 1982 ; Zhang et al., 2013 ), the capillary feeder (CAFE) assay ( Ja et al., 2007 ), Fly Liquid-Food Interaction Counter (FLIC) assay ( Ro et al., 2014 ), radiolabel-based feeding ( Deshpande et al., 2014 ; Thompson and Reeder, 1987 ), electronic-based feeding assays ( Itskov et al., 2014 ; Ro et al., 2014 ), and Droso-X assay ( Aryal and Lee, 2021 ; Sang et al., 2021 ). Binary-choice feeding assays are the most widely used behavioral approaches to monitor feeding, since they are simple to perform, safe, relatively inexpensive, can be used in a classroom setting and can be applied to large-scale genetic screening.…”