Taste-Mediated Suppression of Sugar Intake in Drosophila melanogaster

Abstract

All organisms need to secure nutrients from the external environment for its survival. To do so, they must be able not only to identify a viable food source, but also to maintain the level of intake at an appropriate level. Costs associated with feeding (e.g. vulnerability to predator, metabolic cost) make it critical that an animal sometimes suppresses its feeding behavior, even when the available food is not potentially toxic. However, despite the progress in understanding the chemoreceptive mechanisms for detection of tastants, regulatory processes for the amount of nutrient intake remain elusive.

Despite differences in the specific receptors that sense taste qualities, flies display a striking resemblance with mammals in the overall coding logic and central processing of taste information. Unlike many mammals whose hedonic control of feeding often overrides homeostatic regulation, flies are remarkably adept at adjusting food intake to achieve a target level of nutrition. Our lab uses Drosophila melanogaster as a relatively simple model to understand how dietary composition and internal physiology translates to food intake when not occluded by the effects of hedonic feeding; and to investigate the genes and circuits that underlie the suppression of sugar intake, taking advantage of the genetic tractability of the model organism.

On rich diets, compensatory feeding allows animals to maintain consistent levels of nutrition. In contrast, on nutrient-poor diets, animals do not simply maximize food intake. Instead, nutritional needs are likely weighed against potential opportunities to find better food sources. Our preliminary data show there is a “sweet spot” of sugar concentration that elicits the peak consumption response and suggest that there are at least two distinct inhibitory mechanisms for food consumption, one for food that is not sweet enough and another for nutrient-rich food. Our proposed studies investigate the mechanisms underlying the sensing and evaluation of food, and how that contributes to the complex decision of how much to eat. Using behavioral and genetic tools available in Drosophila, we investigate the genes and circuits that underlie the suppression of sugar intake.