Nutritional geometry framework on sleep in Drosophila

Sleep is a fundamental physiological function and is essential for all animals, including humans. Sleep has been reported to be affected by diet compositions including protein (P) and carbohydrates (C), but there has not been a systematic investigation of the effect of dietary macronutrient balance on sleep. Here, we used the nutritional geometry framework (NGF) to explore the interactive effects on sleep of protein (P) and carbohydrate (C) in the model organism Drosophila. Our results showed that the combination of low protein and moderate carbohydrate prolonged sleep time and sleep quality, with fewer sleep episodes and longer sleep duration. We further found that the effects of macronutrients on sleep mirrored levels of haemolymph glucose and whole-body glycogen. Moreover, transcriptome analyses revealed that high protein, low carbohydrate diet elevated the gene expression of amino acid metabolic pathways when compared to a diet lacking protein, with the glycine, serine, threonine metabolism pathway being most strongly regulated. However, sleep was not decreased in flies fed on a protein-deficient diet with added glycine, serine and threonine. In summary, our results demonstrate that sleep is affected by the balance of protein and carbohydrates in the diet and that reduced protein coupled with moderate carbohydrate promote sleep duration and quality. Brain mRNA profiles of 4-7-day old flies treated with low protein and high carbohydrates diet（P:C=0:1,180g/L) that caused longest sleep time and high protein and low carbohydrates diet（P:C=1:1,180g/L) that induced shortest sleep time.