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The phase-shifting effect of bright light exposure on circadian rhythmicity in the human transcriptome

ABSTRACT: Eleven healthy human subjects were enrolled in a 6-day simulated shift work protocol. Blood samples were collected during the two 24-hour measurement periods. Blood samples were collected every 4 hours during both measurement periods. Subjects entered the lab on Day 1. At the start of Day 2, the first 24-hour measurement period was started. Subjects slept according to their habitual sleep/wake schedule, followed by a 16-hour constant posture procedure. On days 3-6, the sleep period was delayed by 10 hours. Participants in the control group were exposed to dim light throughout the waking periods; participants in the bright group were exposed to bright light (~6,000lux) for 8 hours during the waking period. Following the third night on this schedule, subjects underwent another 24-hour measurement period. During both measurement periods, blood samples were collected and PBMCs were isolated. mRNA was extracted, labelled, and hybridized to microarrays.

ORGANISM(S): Homo sapiens

PROVIDER: GSE122725 | GEO | 2019/02/14

REPOSITORIES: GEO

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Project description:Extended periods of waking result in physiological impairments in humans, rats, and flies. Sleep homeostasis, the increase in sleep observed following sleep loss, is believed to counter the negative effects of prolonged waking by restoring vital biological processes that are degraded during sleep deprivation. Sleep homeostasis, as with other behaviors, is influenced by both genes and environment. We report here that during periods of starvation, flies remain spontaneously awake but, in contrast to sleep deprivation, do not accrue any of the negative consequences of prolonged waking. Specifically, the homeostatic response and learning impairments that are a characteristic of sleep loss are not observed following prolonged waking induced by starvation. To identify the genes responsible for the protective effects of starvation we conducted transcription profiling of sleep deprived flies that accrue sleep debt compared to starved siblings that do not. Genes involved in lipid metabolism were highly enriched in our dataset of 84 differentially regulated transcripts. Follow up genetic studies established that 6 genes involved in lipid metabolism strongly influence sleep homeostasis. Two of these genes, brummer (bmm) and Lipid storage droplet 2 (Lsd2), are in the same lipolysis pathway but exert antagonistic effects on lipid storage. bmm mutant flies have excess fat stores and display a large homeostatic response following sleep deprivation. In contrast, Lsd2 mutant flies, which phenocopy aspects of starvation as measured by low triglyceride stores, do not exhibit a homeostatic response following sleep loss. Importantly, Lsd2 mutant flies are not learning impaired after sleep deprivation. These results provide the first genetic evidence, to our knowledge, that lipid metabolism plays an important role in regulating the homeostatic response and can protect against neuronal impairments induced by prolonged waking. Two-condition experiments: sleep deprived vs starved. RNA from 8 biological replicates for each condition was pooled in groups of 2 to create 4 samples. Each of the 4 samples is run in duplicate with untreated circadian matched controls.

Project description:Background: Age-related cognitive deficits negatively affect quality of life and can presage serious neurodegenerative disorders. Despite sleep disruption’s well-recognized negative influence on cognition, and its prevalence with age, surprisingly few studies have tested sleep’s relationship to cognitive aging. Methodology: We measured sleep stages in young adult and aged F344 rats during inactive (enhanced sleep) and active (enhanced wake) periods. Animals were behaviorally characterized on the Morris water maze and gene expression profiles of their parietal cortices were taken. Principal Findings: Water maze performance was impaired, and inactive period deep sleep was decreased with age. However, increased deep sleep during the active period was most strongly correlated to maze performance. Transcriptional profiles were strongly associated with behavior and age, and were validated against prior studies. Bioinformatic analysis revealed increased translation and decreased myelin/ neuronal pathways. Conclusions: The F344 rat appears to serve as a reasonable model for some common sleep architecture and cognitive changes seen with age in humans, including the cognitively disrupting influence of active period deep sleep. Microarray analysis suggests that the processes engaged by this sleep are consistent with its function. Thus, active period deep sleep appears temporally misaligned but mechanistically intact, leading to the following: first, aged brain tissue appears capable of generating the slow waves necessary for deep sleep, albeit at a weaker intensity than in young. Second, this activity, presented during the active period, seems disruptive rather than beneficial to cognition. Third, this active period deep sleep may be a cognitively pathologic attempt to recover age-related loss of inactive period deep sleep. Finally, therapeutic strategies aimed at reducing active period deep sleep (e.g., by promoting active period wakefulness and/or inactive period deep sleep) may be highly relevant to cognitive function in the aging community. KEYWORDS: frontal cortex, rat, young or aged

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The phase-shifting effect of bright light exposure on circadian rhythmicity in the human transcriptome

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