Geometric Framework for nutrition on Sucrose Taste Sensitization in Drosophila

Numerous studies show dietary carbohydrates (C) affect the sensation of sweetness. However, protein (P) is one of the most critical macronutrients in the diet as well. It is still unclear how carbohydrates and proteins interact to influence sweet taste sensitivity. Here, we use the nutritional geometry framework (NGF) to tackle this problem in Drosophila melanogaster. Our results showed that the combination of high protein and low carbohydrates caused higher taste responses to sucrose stimuli in both sexes. Additionally, transcriptome analysis revealed that the gene expression of glycine, serine, and threonine pathway in the high-protein, low-carbohydrate diet was significantly upregulated, compared to a diet with low protein, and high carbohydrate. We confirmed that serine and threonine supplementation in the high-carbohydrate, low-protein diet enhanced the sucrose sensitivity of flies. Our results demonstrate that sucrose taste sensitivity is affected by the dietary balance of protein and carbohydrates possibly mediated by the change in serine, and threonine. The high protein, low carbohydrate diets enhanced sucrose taste sensitivity. Brain mRNA profiles of 4-7-day old flies treated with low protein and high carbohydrates diet（P:C=0:1,360g/L) that caused lower taste responses to sucrose stimuli and high protein and low carbohydrates diet（P:C=1:2,360g/L) that induced higher taste responses to sucrose stimuli.