Drosophila insulin-like peptide 2mediates dietary regulation of sleep intensity

Abstract

18Sleep is a nearly universal behavior that is regulated by diverse environmental and physiological 19 stimuli. A defining feature of sleep is a homeostatic rebound following deprivation, where 20 animals compensate for lost sleep by increasing sleep duration and/or sleep depth. Fruit flies 21 exhibit robust recovery sleep following deprivation and represent a powerful model to study 22 neural circuits regulating sleep homeostasis. Numerous neuronal populations have been 23 identified in modulating sleep homeostasis as well as depth, raising the possibility that recovery 24 sleep is differentially regulated by environmental or physiological processes that induce sleep 25 deprivation. Here, we find that unlike most pharmacological and environmental manipulations 26 commonly used to restrict sleep, starvation potently induces sleep loss without a subsequent 27 rebound in sleep duration or depth. We find that both starvation and a sucrose-only diet result in 28 reduced metabolic rate and increased sleep depth, suggesting that dietary yeast protein is 29 essential for normal sleep depth and homeostasis. Finally, we find that Drosophila insulin like 30 peptide 2 (Dilp2) is required for starvation-induced changes in sleep depth without regulating the 31 duration of sleep. Remarkably, Dilp2 mutant flies require rebound sleep following sleep 32 deprivation, suggesting Dilp2 underlies resilience to sleep loss. Together, these findings reveal 33 innate resilience to starvation-induced sleep loss and identify distinct mechanisms that underlie 34 starvation-induced changes in sleep duration and depth.35 3 Author Summary 36 Sleep is nearly universal throughout the animal kingdom and homeostatic regulation represents 37 a defining feature of sleep, where animals compensate for lost sleep by increasing sleep over 38 subsequent time periods. Despite the robustness of this feature, surprisingly little is known 39 about how recovery-sleep is regulated in response to different types of sleep deprivation. Fruit 40 flies provide a powerful model for investigating the genetic regulation of sleep, and like 41 mammals, display robust recovery sleep following deprivation. Here, we find that unlike most 42 stimuli that suppress sleep, sleep deprivation by starvation does not require a homeostatic 43 rebound. These findings appear to be due to flies engaging in deeper sleep during the period of 44 partial deprivation, suggesting a natural resilience to starvation-induced sleep loss. This unique 45 resilience to starvation-induced sleep loss is dependent on Drosophila insulin-like peptide 2, 46 suggesting a critical role for insulin signaling in regulating interactions between diet and sleep 47 homeostasis. 48 4 Introduction 49Sleep is a near universal behavior that is modulated in accordance with internal and external 50 environments [1][2][3]. Numerous environmental factors can alter sleep including daily changes in 51 light and temperature, stress, social interactions, and nutrient availability [4,5]. A central factor 52 defining sleep i...

Drosophila insulin‐like peptides: from expression to functions – a review

“…It has been shown that a control group of starving flies was more active at night than dilp2 mutants. Consequently, DILP2 is necessary for the depth of sleep regulation (Brown et al, 2020).…”

Dietary fatty acids promote sleep through a taste‐independent mechanism

“…The finding that fatty acids, like sugars, promote sleep in wild‐type flies suggest many types of dietary macronutrients play a role in sleep regulation. Not all macronutrients are sleep promoting, as we have recently shown that the addition of yeast protein to sucrose does not increase sleep, although it does affect sleep architecture and depth at certain concentrations . Nevertheless, a systematic study of different dietary macronutrients may provide insight into whether sleep is simply regulated by energy availability or is differentially regulated by specific dietary macronutrients.…”

“…Evidence suggests that at least some of the neural mechanisms regulating sleep pressure as measured by rebound following deprivation differ from those that regulate sleep duration in undisturbed conditions . Further, arousal threshold to odors is reduced in starved flies, while starvation increases arousal threshold to mechanical stimuli, suggesting a complex interplay between diet and the sensory stimuli that mediate arousal. An investigation into the effects of different diets on measures of sleep intensity, sleep‐dependent reductions in metabolic rate, and sleep rebound, may identify additional mechanisms through which diet regulates sleep.…”