Dietary Modulation of Drosophila Sleep-Wake Behaviour

Background A complex relationship exists between diet and sleep but despite its impact on human health, this relationship remains uncharacterized and poorly understood. Drosophila melanogaster is an important model for the study of metabolism and behaviour, however the effect of diet upon Drosophila sleep remains largely unaddressed. Methodology/Principal Findings Using automated behavioural monitoring, a capillary feeding assay and pharmacological treatments, we examined the effect of dietary yeast and sucrose upon Drosophila sleep-wake behaviour for three consecutive days. We found that dietary yeast deconsolidated the sleep-wake behaviour of flies by promoting arousal from sleep in males and shortening periods of locomotor activity in females. We also demonstrate that arousal from nocturnal sleep exhibits a significant ultradian rhythmicity with a periodicity of 85 minutes. Increasing the dietary sucrose concentration from 5% to 35% had no effect on total sucrose ingestion per day nor any affect on arousal, however it did lengthen the time that males and females remained active. Higher dietary sucrose led to reduced total sleep by male but not female flies. Locomotor activity was reduced by feeding flies Metformin, a drug that inhibits oxidative phosphorylation, however Metformin did not affect any aspects of sleep. Conclusions We conclude that arousal from sleep is under ultradian control and regulated in a sex-dependent manner by dietary yeast and that dietary sucrose regulates the length of time that flies sustain periods of wakefulness. These findings highlight Drosophila as an important model with which to understand how diet impacts upon sleep and wakefulness in mammals and humans

Activation of Egf-r/ERK by rhomboid signaling regulates the consolidation and maintenance of sleep in Drosophila

The function of sleep remains a major mystery despite 200 years of research on the subject. Recently, the fruit fly Drosophila has been shown to display a behavior that has the essential characteristics of sleep and has thus become a model for the study of sleep's function. The EGFR/ErbB signaling pathway is well conserved in the central roles it plays in many signaling events during development in worms, flies, and mice. In mammals EGFR/ErbB signaling has also been shown to play a role in circadian regulation of activity. In the current study, its role in the regulation of sleep in Drosophila is examined. The findings reported here show a novel role for Egf-r/ERK signaling in sleep consolidation and maintenance in Drosophila melanogaster. In the adult fruit fly, Egf-r is expressed ubiquitously throughout the nervous system and the current analysis revealed that overexpression of Egf-r pathway signaling components Rho and Star causes an acute, reversible and dose-dependent increase in sleep that tightly parallels an increase in phosphorylated ERK in the head and brain. Inhibition of Egf-r with a dominant-negative form of the receptor was able to suppress the increase in sleep levels produced by Rho and Star, demonstrating that the signal is mediated by the Egf-r pathway. In contrast to the increase in sleep amount after Rho overexpression, inhibiting it lead to a significant decrease in sleep. Importantly, this decrease in sleep was due to a dramatic shortening of the duration of sleep episodes accompanied by an elevation of sleep bout number. This observation suggests a state of increased sleep need, but an inability to maintain the sleep state. Therefore, the function of Rho may be to keep a fly asleep once the state has been initiated. The inhibition of sleep depends on interfering with rhomboid expression in the pars intercerebralis, a part of the fly brain that is functionally analogous to the hypothalamus in vertebrates, which is a region of the mammalian brain well established to be a regulator of arousal. These studies suggest that sleep and its regulation by Egf-r signaling may be ancestral to insects and mammal