Summary: Diet influences dopamine and insulin signaling in the brain, which in turn directly affects the peripheral sensory response in fruit flies. This response influences what the fly decides to eat next.
What you eat influences your taste for what you might want to eat next. So claims a University of California, Riverside, study performed on fruit flies.
The study, published in the Journal of Neuroscience, offers a better understanding of neurophysiological plasticity of the taste system in flies.
To maintain ideal health, animals require a balanced diet with optimum amounts of different nutrients. Macronutrients like carbohydrates and proteins are essential; indeed, an unbalanced intake of these nutrients can be detrimental to health. Flies require macronutrients such as sugars and amino acids for survival. They use the gustatory system, the sensory system responsible for the perception of taste, to sense these nutrients and begin feeding.
In their experiments in the lab, the researchers Anindya Ganguly and Manali Dey, led by Anupama Dahanukar, fed adult flies different diets: A balanced diet, a sugar-reduced and protein-enriched diet, and a sugar-enriched and protein-depleted diet. They ensured that all three diets were similar in total calorie content and tested the flies daily for a week to examine modifications in their food choice and taste sensitivity.
The researchers report that diet affects dopamine and insulin signaling in the brain, which, in turn, affects the flies’ peripheral sensory response, which is comprised of neurons directly involved in detecting external stimuli. This response then influences what the flies eat next.
“We found diet changed the flies’ taste preference,” said Dahanukar, an associate professor of molecular, cell and systems biology. “For a diet with excess protein at the expense of carbohydrates, the flies’ taste sensitivity changed so that they mounted a compensatory behavioral response in the short term to eat more carbohydrates and less protein in order to regain a balanced diet.”
What this may mean for other animals, including humans, is that conserved signaling pathways could play a role in mounting similar diet-induced changes in taste. Individuals on a high sugar diet could see a dampening of sugar taste, making sugars less palatable at least for the short term. Similarly, a low protein diet would enhance umami taste, increasing the value of protein-rich foods to be consumed next.
“Changes in gene expression appear to be involved,” said Ganguly, a former graduate student at UC Riverside and now a postdoctoral researcher at UC Santa Barbara. “We see these changes in flies based on dietary exposure for just a day or two.”
Interestingly, when the flies that were fed unbalanced diets were returned to a balanced diet, their taste sensitivity returned to baseline levels, suggesting that changes in taste preference are reversible.
“Our work shows that imbalances in diet affect your taste preferences in a way that help you in the short term at least,” said Dey, a graduate student in Dahanukar’s lab. “They help you change your taste so that you prefer foods that benefit you, foods that would help you achieve metabolic homeostasis again.”
Dahanukar cautioned, however, that long term effects on consumption may be more complex. For example, research by other scientists has shown that while flies raised on a high sugar diet saw their sugar response decrease in the short term, flies maintained on that diet consumed more of that food in the long term.
Dahanukar, Ganguly, and Dey were joined in the study by Christi Scott and Vi-Khoi Duong. Scott is a former graduate student and postdoctoral researcher at UCR. She helped analyze transcriptome data. Duong is a former undergraduate student who did his honors thesis in Dahanukar’s lab. He is now in dental school.
About this diet and taste research news
Author: Iqbal Pittalwala Source: UCR Contact: Iqbal Pittalwala – UCR Image: The image is in the public domain
Food choice, in animals, has been known to change with internal nutritional state and also with variable dietary conditions. To better characterize mechanisms of diet-induced plasticity of food preference in Drosophila melanogaster, we synthesized diets with macronutrient imbalances and examined how food choice and taste sensitivity were modified in flies that fed on these diets.
We found that dietary macronutrient imbalances caused compensatory behavioral shifts in both sexes to increase preference for the macronutrient that was scant in the food source, and simultaneously reduce preference for the macronutrient that was enriched.
Further analysis with females revealed analogous changes in sweet taste responses in labellar neurons, with increased sensitivity on sugar-reduced diet and decreased sensitivity on sugar-enriched diet. Interestingly, we found differences in the onset of changes in taste sensitivity and behavior, which occur over 1–4 d, in response to dietary sugar reduction or enrichment. To investigate molecular mechanisms responsible for diet-induced taste modulation, we used candidate gene and transcriptome analyses.
Our results indicate that signaling via Dop2R is involved in increasing cellular and behavioral sensitivity to sugar as well as in decreasing behavioral sensitivity to amino acids on dietary sugar reduction. On the other hand, cellular and behavioral sensitivity to sugar relies on dilp5 and a decrease in sugar preference following dietary sugar abundance was correlated with downregulation of dilp5.
Together, our results suggest that feeding preference for sugar and amino acid can be modulated independently to facilitate food choice that accounts for prior dietary experience.
Animals adjust their feeding preferences based on prior dietary experiences.
Here, we find that upon dietary macronutrient deprivation, flies undergo compensatory changes in food preference. The altered preference correlates with changes in peripheral taste sensitivity. While Dop2R mediates changes following dietary sugar reduction, downregulation of dilp5 is associated with changes caused by a sugar-enriched diet.
This study contributes to a better understanding of neurophysiological plasticity of the taste system in flies, and its role in facilitating adjustment of foraging behavior based on nutritional requirements.