Restoration of brain energy metabolism as the function of sleep

Explainable vision transformer for automatic visual sleep staging on multimodal PSG signals

Polysomnography (PSG) is crucial for diagnosing sleep disorders, but manual scoring of PSG is time-consuming and subjective, leading to high variability. While machine-learning models have improved PSG scoring, their clinical use is hindered by the 'black-box' nature. In this study, we present SleepXViT, an automatic sleep staging system using Vision Transformer (ViT) that provides intuitive, consistent explanations by mimicking human 'visual scoring'. Tested on KISS-a PSG image dataset from 7745 patients across four hospitals-SleepXViT achieved a Macro F1 score of 81.94%, outperforming baseline models and showing robust performances on public datasets SHHS1 and SHHS2. Furthermore, SleepXViT offers well-calibrated confidence scores, enabling expert review for low-confidence predictions, alongside high-resolution heatmaps highlighting essential features and relevance scores for adjacent epochs' influence on sleep stage predictions. Together, these explanations reinforce the scoring consistency of SleepXViT, making it both reliable and interpretable, thereby facilitating the synergy between the AI model and human scorers in clinical settings.

Orthologs of Drosophila pointed and Arginine kinase 1 impact sleep in mice

Model organisms such as Drosophila are powerful tools to study the genetic basis of sleep. Previously, we identified the genes pointed and Arginine kinase 1 using selective breeding for long and short sleep duration in an outbred population of Drosophila. pointed is a transcription factor that is part of the epidermal growth factor receptor signaling pathway, while Arginine kinase 1 is involved in proline and arginine metabolism. Conserved orthologs of these genes exist in mice, leading us to hypothesize that they would also impact sleep in a murine model. We generated mutations in the murine orthologs Ets1 and Ckm using CRISPR in a C57BL/6N background and used video analysis to measure sleep in the mice. Both mutations affected sleep parameters, and the effects were observed predominantly in female mice, with males showing fewer differences from littermate controls. The study of natural populations in flies therefore leads to candidate genes with functional conservation on sleep in mammals.

Prospective associations between heterogeneous sleep profiles and depressive symptoms in adolescents: The mediating role of coping styles

INTRODUCTION

Extant literature has linked sleep disturbance to depressive symptoms. However, the coexistence of naturally occurring sleep profiles among adolescents and the prospective associations between sleep profiles and depressive symptoms remain poorly understood. This study aims to uncover sleep patterns in Chinese adolescents based on a comprehensive set of sleep features (e.g., latency, daytime dysfunction, etc.) derived from the Pittsburg Sleep Quality Index (PSQI) and investigate the relationship between these profiles and subsequent depressive symptoms mediated by positive and negative coping styles.

METHODS

Five thousand five hundred five adolescents from Shandong province, China, enrolled (Mage = 16.83 years; 49.9% girls) in a two-wave longitudinal study (T1 in August 2023; T2 in February 2024). Latent class analysis (LCA) was conducted to identify adolescent sleep patterns. Mediation and sensitivity analyses were used to examine prospective associations between sleep patterns, coping styles, and depressive symptoms.

RESULTS

Four qualitatively distinct sleep profiles emerged: Healthy Sleepers (18.9%), Latency but Functioning Sleepers (13.6%), Efficient but Dysfunctional Sleepers (57.5%), and Medicated Maladaptive Sleepers (10.0%). Using the Healthy Sleepers as a reference group, Latency but Functional Sleepers, Efficient but Dysfunctional Sleepers, and Medicated Maladaptive Sleepers all predicted subsequent depressive symptoms through positive coping styles rather than negative coping styles. The relative indirect effects were 0.19, 0.19, and 0.32, respectively.

CONCLUSIONS

The study underscored that adolescents exhibit distinct sleep patterns, and specific sleep profiles may be prospectively associated with depressive symptoms mediated by positive coping styles.

Enhanced homeostatic sleep response and decreased neurodegenerative proteins in cereblon knock-out mice

Energy homeostasis and sleep have a bidirectional relationship. Cereblon (CRBN) regulates energy levels by ubiquitinating the AMP-activated protein kinase(AMPK), an energy sensor. However, whether CRBN participates in sleep is unclear. Here, we examine sleep-wake patterns in Crbn+/+ and Crbn-/- mice during 24-h baseline, 6-h sleep deprivation (SD), and following 6-h recovery sleep (RS). At baseline, overall sleep patterns are similar between genotypes. However, SD decreases CRBN expression in Crbn+/+ mice and increases phospho-Tau, phospho-α-synuclein, DNAJA1 (DJ2), and DNAJB1 (DJ1) in both genotypes, with Crbn-/- mice showing a lesser extent of increase in p-Tau and p-α-synuclein and a higher level of heat shock protein 70 (HSP70), DJ2, and DJ1. During RS, Crbn-/- mice show increased slow-wave activity in the low-delta range (0.5-2.5 Hz), suggesting higher homeostatic sleep propensity associated with AMPK hyperactivation. By illuminating the role of CRBN in regulating sleep-wake behaviors through AMPK, we suggest CRBN as a potential therapeutic target for managing sleep disorders and preventing neurodegeneration.

An integrative analysis of cell-specific transcriptomics and nuclear proteomics of sleep-deprived mouse cerebral cortex

Sleep regulation follows a homeostatic pattern. The mammalian cerebral cortex is the repository of homeostatic sleep drive and neurons and astrocytes of the cortex are principal responders of sleep need. The molecular mechanisms by which these two cell types respond to sleep loss are not yet clearly understood. By combining cell-type specific transcriptomics and nuclear proteomics we investigated how sleep loss affects the cellular composition and molecular profiles of these two cell types in a focused approach. The results indicate that sleep deprivation regulates gene expression and nuclear protein abundance in a cell-type-specific manner. Our integrated multi-omics analysis suggests that this distinction arises because neurons and astrocytes employ different gene regulatory strategies under accumulated sleep pressure. These findings provide a comprehensive view of the effects of sleep deprivation on gene regulation in neurons and astrocytes.

Altered Metabolism during the Dark Period in Drosophila Short Sleep Mutants

Sleep is regulated via circadian mechanisms, but effects of sleep disruption on physiological rhythms, in particular metabolic cycling, remain unclear. To examine this question, we probed diurnal metabolic alterations of two Drosophila short sleep mutants, fumin and sleepless. Samples were collected with high temporal sampling (every 2 h) over 24 h under a 12:12 light:dark cycle, and profiling was done using an ion-switching LCMS/MS method. Fewer metabolites with 24 h oscillations were noted with short sleep (50 and 46 in fumin and sleepless, BH. Q < 0.2 by RAIN analysis) compared to a wild-type control (iso31, 63 with BH. Q < 0.2), and peak phases of the sleep mutants were consolidated into two major phase peaks at mid-day and middle of night. Overall, altered nicotinate/nicotinamide, alanine/aspartate/glutamate, acetylcholine, glyoxylate/dicarboxylate, and TCA cycle metabolism were observed in the short sleep mutants, indicative of increased energetic demand and oxidative stress compared to wild type. Both changes in cycling and discriminant models suggest unique alterations in the dark period indicative of constrained metabolic networks. Thus, we conclude that sleep loss alters metabolic function uniquely throughout the day, and further examination of specific mechanisms is warranted.

Signals of energy availability in sleep: consequences of a fat-based metabolism

Humans can flexibly switch between two primary metabolic modes, usually distinguished by whether substrate supply from glucose can meet energy demands or not. However, it is often overlooked that when glucose use is limited, the remainder of energy needs may still be met more or less effectively with fat and ketone bodies. Hence a fat-based metabolism marked by ketosis is often conflated with starvation and contexts of inadequate energy (including at the cellular level), even when energy itself is in ample supply. Sleep and satiation are regulated by common pathways reflecting energy metabolism. A conceptual analysis that distinguishes signals of inadequate energy in a glucose-dominant metabolism from signals of a fat-based metabolism that may well be energy sufficient allows a reexamination of experimental results in the study of sleep that may shed light on species differences and explain why ketogenic diets have beneficial effects simultaneously in the brain and the periphery. It may also help to distinguish clinically when a failure of a ketogenic diet to resolve symptoms is due to inadequate energy rather than the metabolic state itself.

Biomathematical modeling of fatigue due to sleep inertia

Biomathematical models of fatigue capture the physiology of sleep/wake regulation and circadian rhythmicity to predict changes in neurobehavioral functioning over time. We used a biomathematical model of fatigue linked to the adenosinergic neuromodulator/receptor system in the brain as a framework to predict sleep inertia, that is, the transient neurobehavioral impairment experienced immediately after awakening. Based on evidence of an adenosinergic basis for sleep inertia, we expanded the biomathematical model with novel differential equations to predict the propensity for sleep inertia during sleep and its manifestation after awakening. Using datasets from large laboratory studies of sleep loss and circadian misalignment, we calibrated the model by fitting just two new parameters and then validated the model's predictions against independent data. The expanded model was found to predict the magnitude and time course of sleep inertia with generally high accuracy. Analysis of the model's dynamics revealed a bifurcation in the predicted manifestation of sleep inertia in sustained sleep restriction paradigms, which reflects the observed escalation of the magnitude of sleep inertia in scenarios with sleep restriction to less than ∼ 4 h per day. Another emergent property of the model involves a rapid increase in the predicted propensity for sleep inertia in the early part of sleep followed by a gradual decline in the later part of the sleep period, which matches what would be expected based on the adenosinergic regulation of non-rapid eye movement (NREM) sleep and its known influence on sleep inertia. These dynamic behaviors provide confidence in the validity of our approach and underscore the predictive potential of the model. The expanded model provides a useful tool for predicting sleep inertia and managing impairment in 24/7 settings where people may need to perform critical tasks immediately after awakening, such as on-demand operations in safety and security, emergency response, and health care.

The role of ATP in sleep-wake regulation: In adenosine-dependent and -independent manner

ATP plays a crucial role as an energy currency in the body's various physiological functions, including the regulation of the sleep-wake cycle. Evidence from genetics and pharmacology demonstrates a strong association between ATP metabolism and sleep. With the advent of new technologies such as optogenetics, genetically encoded biosensors, and novel ATP detection methods, the dynamic changes in ATP levels between different sleep states have been further uncovered. The classic mechanism for regulating sleep by ATP involves its conversion to adenosine, which increases sleep pressure when accumulated extracellularly. However, emerging evidence suggests that ATP can directly bind to P2 receptors and influence sleep-wake regulation through both adenosine-dependent and independent pathways. The outcome depends on the brain region where ATP acts and the expression type of P2 receptors. This review summarizes the experimental evidence on the relationship between ATP levels and changes in sleep states and outlines the mechanisms by which ATP is involved in regulating the sleep-wake cycle through both adenosine-dependent and independent pathways. Hopefully, this review will provide a comprehensive understanding of the current research basis and progress in this field and promote further investigations into the specific mechanisms of ATP in regulating sleep.

Considerations towards a neurobiologically-informed EEG measurement of sleepiness

Sleep is a daily experience across humans and other species, yet our understanding of how and why we sleep is presently incomplete. This is particularly prevalent in research examining the neurophysiological measurement of sleepiness in humans, where several electroencephalogram (EEG) phenomena have been linked with prolonged wakefulness. This leaves researchers without a solid basis for the measurement of homeostatic sleep need and complicates our understanding of the nature of sleep. Recent theoretical and technical advances may allow for a greater understanding of the neurobiological basis of homeostatic sleep need: this may result from increases in neuronal excitability and shifts in excitation/inhibition balance in neuronal circuits and can potentially be directly measured via the aperiodic component of the EEG. Here, we review the literature on EEG-derived markers of sleepiness in humans and argue that changes in these electrophysiological markers may actually result from neuronal activity represented by changes in aperiodic markers. We argue for the use of aperiodic markers derived from the EEG in predicting sleepiness and suggest areas for future research based on these.

A metabolic perspective to sleep genetics

The metabolic signals that regulate sleep and the metabolic functions that occur during sleep are active areas of research. Prior studies have focused on sugars and nucleotides but new genetic evidence suggests novel functions of lipid and amino acid metabolites in sleep. Additional genetic studies of energetic signaling pathways and the circadian clock transcription factor network have increased our understanding of how sleep responds to changes in the metabolic state. This review focuses on key recent insights from genetic experiments in humans and model organisms to improve our understanding of the interrelationship between metabolism and sleep.

Noradrenergic tone is not required for neuronal activity-induced rebound sleep in zebrafish

Sleep pressure builds during wakefulness, but the mechanisms underlying this homeostatic process are poorly understood. One zebrafish model suggests that sleep pressure increases as a function of global neuronal activity, such as during sleep deprivation or acute exposure to drugs that induce widespread brain activation. Given that the arousal-promoting noradrenergic system is important for maintaining heightened neuronal activity during wakefulness, we hypothesised that genetic and pharmacological reduction of noradrenergic tone during drug-induced neuronal activation would dampen subsequent rebound sleep in zebrafish larvae. During stimulant drug treatment, dampening noradrenergic tone with the α2-adrenoceptor agonist clonidine unexpectedly enhanced subsequent rebound sleep, whereas enhancing noradrenergic signalling with a cocktail of α1- and β-adrenoceptor agonists did not enhance rebound sleep. Similarly, CRISPR/Cas9-mediated elimination of the dopamine β-hydroxylase (dbh) gene, which encodes an enzyme required for noradrenalin synthesis, enhanced baseline sleep in larvae but did not prevent additional rebound sleep following acute induction of neuronal activity. Across all drug conditions, c-fos expression immediately after drug exposure correlated strongly with the amount of induced rebound sleep, but was inversely related to the strength of noradrenergic modulatory tone. These results are consistent with a model in which increases in neuronal activity, as reflected by brain-wide levels of c-fos induction, drive a sleep pressure signal that promotes rebound sleep independently of noradrenergic tone.

Restless nights when sick: ectoparasite infections alter rest-activity cycles of diurnal fish hosts

Circadian rhythms are timekeeping mechanisms responsible for an array of biological processes. Disruption of such cycles can detrimentally affect animal health. Circadian rhythms are critical in the co-evolution of host–parasite systems, as synchronization of parasite rhythms to the host can influence infection dynamics and transmission potential. This study examines the circadian rhythms in behaviour and activity of a model fish species (Poecilia reticulata) in isolation and in shoals, both when uninfected and infected with an ectoparasite (Gyrodactylus turnbulli). Additionally, the rhythmical variance of parasite activity under different light conditions as well as rhythmical variance in parasite transmissibility was explored. Overall, infection alters the circadian rhythm of fish, causing nocturnal restlessness. Increased activity of gyrodactylids on the host's skin at night could potentially contribute to this elevated host activity. Whilst migration of gyrodactylids across the host's skin may have caused irritation to the host resulting in nocturnal restlessness, the disruption in guppy activity rhythm caused by the expression of host innate immunity cannot be excluded. We discuss the wider repercussions such behavioural responses to infection have for host health, the implications for animal behaviour studies of diurnal species as well as the application of chronotherapeutic approaches to aquaculture.

Glymphatic and lymphatic communication with systemic responses during physiological and pathological conditions in the central nervous system

Crosstalk between central nervous system (CNS) and systemic responses is important in many pathological conditions, including stroke, neurodegeneration, schizophrenia, epilepsy, etc. Accumulating evidence suggest that signals for central-systemic crosstalk may utilize glymphatic and lymphatic pathways. The glymphatic system is functionally connected to the meningeal lymphatic system, and together these pathways may be involved in the distribution of soluble proteins and clearance of metabolites and waste products from the CNS. Lymphatic vessels in the dura and meninges transport cerebrospinal fluid, in part collected from the glymphatic system, to the cervical lymph nodes, where solutes coming from the brain (i.e., VEGFC, oligomeric α-syn, β-amyloid) might activate a systemic inflammatory response. There is also an element of time since the immune system is strongly regulated by circadian rhythms, and both glymphatic and lymphatic dynamics have been shown to change during the day and night. Understanding the mechanisms regulating the brain-cervical lymph node (CLN) signaling and how it might be affected by diurnal or circadian rhythms is fundamental to find specific targets and timing for therapeutic interventions.

Molecular Insights into Transcranial Direct Current Stimulation Effects: Metabolomics and Transcriptomics Analyses

INTRODUCTION

Transcranial direct current stimulation (tDCS) is an evolving non-invasive neurostimulation technique. Despite multiple studies, its underlying molecular mechanisms are still unclear. Several previous human studies of the effect of tDCS suggest that it generates metabolic effects. The induction of metabolic effects by tDCS could provide an explanation for how it generates its long-term beneficial clinical outcome.

AIM

Given these hints of tDCS metabolic effects, we aimed to delineate the metabolic pathways involved in its mode of action.

METHODS

To accomplish this, we utilized a broad analytical approach of co-analyzing metabolomics and transcriptomic data generated from anodal tDCS in rat models. Since no metabolomic dataset was available, we performed a tDCS experiment of bilateral anodal stimulation of 200 µA for 20 min and for 5 consecutive days, followed by harvesting the brain tissue below the stimulating electrode and generating a metabolomics dataset using LC-MS/MS. The analysis of the transcriptomic dataset was based on a publicly available dataset.

RESULTS

Our analyses revealed that tDCS alters the metabolic profile of brain tissue, affecting bioenergetic-related pathways, such as glycolysis and mitochondrial functioning. In addition, we found changes in calcium-related signaling.

CONCLUSIONS

We conclude that tDCS affects metabolism by modulating energy production-related processes. Given our findings concerning calcium-related signaling, we suggest that the immediate effects of tDCS on calcium dynamics drive modifications in distinct metabolic pathways. A thorough understanding of the underlying molecular mechanisms of tDCS has the potential to revolutionize its applicability, enabling the generation of personalized medicine in the field of neurostimulation and thus contributing to its optimization.

Sleep and circadian rhythmicity as entangled processes serving homeostasis

Sleep is considered essential for the brain and body. A predominant concept is that sleep is regulated by circadian rhythmicity and sleep homeostasis, processes that were posited to be functionally and mechanistically separate. Here we review and re-evaluate this concept and its assumptions using findings from recent human and rodent studies. Alterations in genes that are central to circadian rhythmicity affect not only sleep timing but also putative markers of sleep homeostasis such as electroencephalogram slow-wave activity (SWA). Perturbations of sleep change the rhythmicity in the expression of core clock genes in tissues outside the central clock. The dynamics of recovery from sleep loss vary across sleep variables: SWA and immediate early genes show an early response, but the recovery of non-rapid eye movement and rapid eye movement sleep follows slower time courses. Changes in the expression of many genes in response to sleep perturbations outlast the effects on SWA and time spent asleep. These findings are difficult to reconcile with the notion that circadian- and sleep-wake-driven processes are mutually independent and that the dynamics of sleep homeostasis are reflected in a single variable. Further understanding of how both sleep and circadian rhythmicity contribute to the homeostasis of essential physiological variables may benefit from the assessment of multiple sleep and molecular variables over longer time scales.

Insomnia and related mental health conditions: Essential neurobiological underpinnings towards reduced polypharmacy utilization rates

Insomnia represents a significant public health burden, with a 10% prevalence in the general population. Reduced sleep affects social and working functioning, productivity, and patient's quality of life, leading to a total of $100 billion per year in direct and indirect healthcare costs. Primary insomnia is unrelated to any other mental or medical illness; secondary insomnia co-occurs with other underlying medical, iatrogenic, or mental conditions. Epidemiological studies found a 40-50% comorbidity prevalence between insomnia and psychiatric disorders, suggesting a high relevance of mental health in insomniacs. Sleep disturbances also worsen the outcomes of several psychiatric disorders, leading to more severe psychopathology and incomplete remission, plausibly contributing to treatment-resistant conditions. Insomnia and psychiatric disorder coexistence can lead to polypharmacy, namely, the concurrent use of two or more medications in the same patient, regardless of their purpose or rationale. Polypharmacy increases the risk of using unnecessary drugs, the likelihood of drug interactions and adverse events, and reduces the patient's compliance due to regimen complexity. The workup of insomnia must consider the patient's sleep habits and inquire about any medical and mental concurrent conditions that must be handled to allow insomnia to be remitted adequately. Monotherapy or limited polypharmacy should be preferred, especially in case of multiple comorbidities, promoting multipurpose molecules with sedative properties and with bedtime administration. Also, non-pharmacological interventions for insomnia, such as sleep hygiene, relaxation training and Cognitive Behavioral Therapy may be useful in secondary insomnia to confront behaviors and thoughts contributing to insomnia and help optimizing the pharmacotherapy. However, insomnia therapy should always be patient-tailored, considering drug indications, contraindications, and pharmacokinetics, besides insomnia phenotype, clinical picture, patient preferences, and side effect profile.

Prolonged sleep deprivation induces a cytokine-storm-like syndrome in mammals

Most animals require sleep, and sleep loss induces serious pathophysiological consequences, including death. Previous experimental approaches for investigating sleep impacts in mice have been unable to persistently deprive animals of both rapid eye movement sleep (REMS) and non-rapid eye movement sleep (NREMS). Here, we report a "curling prevention by water" paradigm wherein mice remain awake 96% of the time. After 4 days of exposure, mice exhibit severe inflammation, and approximately 80% die. Sleep deprivation increases levels of prostaglandin D2 (PGD2) in the brain, and we found that elevated PGD2 efflux across the blood-brain-barrier-mediated by ATP-binding cassette subfamily C4 transporter-induces both accumulation of circulating neutrophils and a cytokine-storm-like syndrome. Experimental disruption of the PGD2/DP1 axis dramatically reduced sleep-deprivation-induced inflammation. Thus, our study reveals that sleep-related changes in PGD2 in the central nervous system drive profound pathological consequences in the peripheral immune system.

Reduced left hippocampal perfusion is associated with insomnia in patients with cerebral small vessel disease

OBJECTIVES

Insomnia was associated with cerebral structural changes and Alzheimer's disease. However, associations among cerebral perfusion, insomnia with cerebral small vessel disease (CSVD), and cognitive performance were little investigated.

METHODS

This cross-sectional study included 89 patients with CSVDs and white matter hyperintensities (WMHs). They were dichotomized into the normal sleep and poor sleep group, according to Pittsburgh sleep quality index (PSQI). Baseline characteristics, cognitive performance, and cerebral blood flow (CBF) were measured and compared between the two groups. The association or correlation between cerebral perfusion, cognition, and insomnia was analyzed using binary logistic regression.

RESULTS

Our study found that declined MoCA score (P = .0317) was more prevalent in those with poor sleep. There was a statistical difference in the recall (P = .0342) of MMSE, the delayed recall (P = .0289) of MoCA between the two groups. Logistic regression analysis showed educational background (P < .001) and insomnia severity index (ISI) score (P = .039) were independently correlated with MoCA scores. Arterial spin labeling demonstrated that left hippocampal gray matter perfusion was significantly reduced (P = .0384) in the group with poor sleep. And, negative correlation was found between left hippocampal perfusion and PSQI scores.

CONCLUSIONS

In the patients with CSVDs, insomnia severity was associated with cognitive decline. Left hippocampal gray matter perfusion was correlated with PSQI scores in CSVDs.

Aquilaria sinensis leaf tea affects the immune system and increases sleep in zebrafish

The importance of adequate sleep for good health cannot be overstated. Excessive light exposure at night disrupts sleep, therefore, it is important to find more healthy drinks that can promote sleep under sleep-disturbed conditions. The present study investigated the use of A. sinensis (Lour.) Spreng leaf tea, a natural product, to reduce the adverse effects of nighttime light on sleep. Here, Aquilaria sinensis leaf tea at 1.0 and 1.5 g/L significantly increased sleep time in zebrafish larvae (5-7 dpf) with light-induced sleep disturbance. Transcriptome sequencing and qRT-PCR analysis revealed a decrease in the immune-related genes, such as nfkbiab, tnfrsf1a, nfkbiaa, il1b, traf3, and cd40 in the 1.5 g/L Aquilaria sinensis leaf tea treatment group. In addition, a gene associated with sleep, bhlhe41, showed a significant decrease. Moreover, Aquilaria sinensis leaf tea suppressed the increase in neutrophils of Tg(mpo:GFP) zebrafish under sleep-disturbed conditions, indicating its ability to improve the immune response. Widely targeted metabolic profiling of the Aquilaria sinensis tea using ultra-performance liquid chromatography coupled with electrospray tandem mass spectrometry (UPLC-ESI-MS/MS) revealed flavonoids as the predominant component. Network pharmacological and molecular docking analyses suggested that the flavonoids quercetin and eupatilin in Aquilaria sinensis leaf tea improved the sleep of zebrafish by interacting with il1b and cd40 genes under light exposure at night. Therefore, the results of the study provide evidence supporting the notion that Aquilaria sinensis leaf tea has a positive impact on sleep patterns in zebrafish subjected to disrupted sleep due to nighttime light exposure. This suggests that the utilization of Aquilaria sinensis leaf tea as a potential therapeutic intervention for sleep disturbances induced by light may yield advantageous outcomes.

Altered Metabolism During the Dark Period in Drosophila Short Sleep Mutants

Sleep is an almost universally required state in biology. Disrupted sleep has been associated with adverse health risks including metabolic perturbations. Sleep is in part regulated via circadian mechanisms, however, metabolic dysfunction at different times of day arising from sleep disruption is unclear. We used targeted liquid chromatography-mass spectrometry to probe metabolic alterations using high-resolution temporal sampling of two Drosophila short sleep mutants, fumin and sleepless, across a circadian day. Discriminant analyses revealed overall distinct metabolic profiles for mutants when compared to a wild type dataset. Altered levels of metabolites involved in nicotinate/nicotinamide, alanine, aspartate, and glutamate, glyoxylate and dicarboxylate metabolism, and the TCA cycle were observed in mutants suggesting increased energetic demands. Furthermore, rhythmicity analyses revealed fewer 24 hr rhythmic metabolites in both mutants. Interestingly, mutants displayed two major peaks in phases while wild type displayed phases that were less concerted. In contrast to 24 hr rhythmic metabolites, an increase in the number of 12 hr rhythmic metabolites was observed in fumin while sleepless displayed a decrease. These results support that decreased sleep alters the overall metabolic profile with short sleep mutants displaying altered metabolite levels associated with a number of pathways in addition to altered neurotransmitter levels.

Sleep disturbance induces a modulation of clock gene expression and alters metabolism regulation in drosophila

Sleep disorders are catching attention worldwide as they can induce dyshomeostasis and health issues in all animals, including humans. Circadian rhythms are biological 24-hour cycles that influence physiology and behavior in all living organisms. Sleep is a crucial resting state for survival and is under the control of circadian rhythms. Studies have shown the influence of sleep on various pathological conditions, including metabolic diseases; however, the biological mechanisms involving the circadian clock, sleep, and metabolism regulation are not well understood. In previous work, we standardized a sleep disturbance protocol and, observed that short-time sleep deprivation and sleep-pattern alteration induce homeostatic sleep regulation, locomotor deficits, and increase oxidative stress. Now, we investigated the relationship between these alterations with the circadian clock and energetic metabolism. In this study, we evaluated the expression of the circadian clock and drosophila insulin-like peptides (DILPs) genes and metabolic markers glucose, triglycerides, and glycogen in fruit flies subjected to short-term sleep disruption protocols. The sleep disturbance altered the expression of clock genes and DILPs genes expression, and modulated glucose, triglycerides, and glycogen levels. Moreover, we demonstrated changes in mTor/dFoxo genes, AKT phosphorylation, and dopamine levels in nocturnal light-exposed flies. Thus, our results suggest a connection between clock genes and metabolism disruption as a consequence of sleep disruption, demonstrating the importance of sleep quality in health maintenance.

The Effects of Commercially-Relevant Disturbances on Sleep Behaviour in Laying Hens

Ensuring the welfare of commercially kept animals is a legal and ethical responsibility. Sleep behaviour can be sensitive to environmental perturbations and may be useful in assessing welfare state. The objective of this study was to use behavioural and electrophysiological (EEG) measures to observe the effects of 24 h stressors followed by periods of no stressors on laying hen sleep behaviour, and to investigate the use of sleep behaviour as a means of welfare assessment in commercial poultry. Ten laying hens surgically implanted with EEG devices to record their brain activity over four batches were used. Hens were subjected to undisturbed, disturbed and recovery periods for 24 h. Disturbed periods consisted of either feed deprivation, increased ambient temperature (28 °C) or simulated footpad pain via injection of Freund's adjuvant into the footpad. Sleep state was scored using behaviour data from infrared cameras and EEG data. Over all periods, hens engaged in both SWS (average 60%) and REM sleep (average 12%) during the lights-off period. Feed deprivation and footpad pain had little to no effect on sleep states, while increased ambient temperature significantly reduced REM sleep (to near elimination, p < 0.001) and SWS (p = 0.017). During the lights-on period, footpad pain increased the proportion of time spent resting (p = 0.008) and in SWS (p < 0.001), with feed deprivation or increased ambient temperature (p > 0.05) having no effect. Increasing ambient temperatures are likely to affect sleep and welfare in commercially-kept laying hens in the face of global climate change.

The Relationship Between Slow Wave Sleep and Blood Oxygen Saturation Among Patients With Apnea: Retrospective Study

Background and Objective Prior research suggests that slow wave sleep (SWS) is disrupted in people with obstructive sleep apnea (OSA). However, it was not clear whether the reduction in SWS is related to abnormal breathing or the extent of OSA as determined by the minimum oxygen saturation. Further, there is limited research on the relationship between oxygen saturation and SWS. The present study examined the relationship between SWS and minimum oxygen saturation levels in patients with OSA.Methods The sample consisted of 589 patients with OSA (mean age: 48.54 years) who completed full-night polysomnography.Results Results showed that there was a significant difference in SWS scores across three apnea-hypopnea index (AHI) groups (AHI score 5–15 for mild apnea, 16–30 for moderate apnea, and >30 for severe apnea). Lower SWS scores were observed in the severe apnea group. Additionally, results indicated that as oxygen saturation decreased, the SWS scores decreased.Conclusions Results from this study indicate that oxygen saturation significantly predicts SWS amounts. These findings suggest that interventions for low oxygen saturation could enhance the amounts of SWS. The clinical ramifications of these findings are worthy of consideration.

Effects of chronic caffeine on patterns of brain blood flow and behavior throughout the sleep-wake cycle in freely behaving mice

Caffeine has significant effects on neurovascular activity and behavior throughout the sleep-wake cycle. We used a minimally invasive microchip/video system to continuously record effects of caffeine in the drinking water of freely behaving mice. Chronic caffeine shifted both rest and active phases by up to 2 h relative to the light-dark cycle in a dose-dependent fashion. There was a particular delay in the onset of rapid eye movement (REM) sleep as compared with non-REM sleep during the rest phase. Chronic caffeine increased wakefulness during the active phase and consolidated sleep during the rest phase; overall, there was no net change in the amount of time spent in the wake, sleep, or REM sleep states during caffeine administration. Despite these effects on wakefulness and sleep, chronic caffeine decreased mean cerebral blood volume (CBV) during the active phase and increased mean CBV during the rest phase. Chronic caffeine also increased heart rate variability in both the sleep and wake states. These results provide new insight into the effects of caffeine on the biology of the sleep-wake cycle. Increased blood flow during sleep caused by chronic caffeine may have implications for its potential neuroprotective effects through vascular mechanisms of brain waste clearance.

The interplay between macronutrients and sleep: focus on circadian and homeostatic processes

Sleep disturbances are an emerging risk factor for metabolic diseases, for which the burden is particularly worrying worldwide. The importance of sleep for metabolic health is being increasingly recognized, and not only the amount of sleep plays an important role, but also its quality. In this review, we studied the evidence in the literature on macronutrients and their influence on sleep, focusing on the mechanisms that may lay behind this interaction. In particular, we focused on the effects of macronutrients on circadian and homeostatic processes of sleep in preclinical models, and reviewed the evidence of clinical studies in humans. Given the importance of sleep for health, and the role of circadian biology in healthy sleep, it is important to understand how macronutrients regulate circadian clocks and sleep homeostasis.

The Metabotropic Glutamate 5 Receptor in Sleep and Wakefulness: Focus on the Cortico-Thalamo-Cortical Oscillations

Sleep is an essential innate but complex behaviour which is ubiquitous in the animal kingdom. Our knowledge of the distinct neural circuit mechanisms that regulate sleep and wake states in the brain are, however, still limited. It is therefore important to understand how these circuits operate during health and disease. This review will highlight the function of mGlu5 receptors within the thalamocortical circuitry in physiological and pathological sleep states. We will also evaluate the potential of targeting mGlu5 receptors as a therapeutic strategy for sleep disorders that often co-occur with epileptic seizures.

Role of astrocytes in sleep deprivation: accomplices, resisters, or bystanders?

Sleep plays an essential role in all studied animals with a nervous system. However, sleep deprivation leads to various pathological changes and neurobehavioral problems. Astrocytes are the most abundant cells in the brain and are involved in various important functions, including neurotransmitter and ion homeostasis, synaptic and neuronal modulation, and blood-brain barrier maintenance; furthermore, they are associated with numerous neurodegenerative diseases, pain, and mood disorders. Moreover, astrocytes are increasingly being recognized as vital contributors to the regulation of sleep-wake cycles, both locally and in specific neural circuits. In this review, we begin by describing the role of astrocytes in regulating sleep and circadian rhythms, focusing on: (i) neuronal activity; (ii) metabolism; (iii) the glymphatic system; (iv) neuroinflammation; and (v) astrocyte-microglia cross-talk. Moreover, we review the role of astrocytes in sleep deprivation comorbidities and sleep deprivation-related brain disorders. Finally, we discuss potential interventions targeting astrocytes to prevent or treat sleep deprivation-related brain disorders. Pursuing these questions would pave the way for a deeper understanding of the cellular and neural mechanisms underlying sleep deprivation-comorbid brain disorders.

FABP7: a glial integrator of sleep, circadian rhythms, plasticity, and metabolic function

Sleep and circadian rhythms are observed broadly throughout animal phyla and influence neural plasticity and cognitive function. However, the few phylogenetically conserved cellular and molecular pathways that are implicated in these processes are largely focused on neuronal cells. Research on these topics has traditionally segregated sleep homeostatic behavior from circadian rest-activity rhythms. Here we posit an alternative perspective, whereby mechanisms underlying the integration of sleep and circadian rhythms that affect behavioral state, plasticity, and cognition reside within glial cells. The brain-type fatty acid binding protein, FABP7, is part of a larger family of lipid chaperone proteins that regulate the subcellular trafficking of fatty acids for a wide range of cellular functions, including gene expression, growth, survival, inflammation, and metabolism. FABP7 is enriched in glial cells of the central nervous system and has been shown to be a clock-controlled gene implicated in sleep/wake regulation and cognitive processing. FABP7 is known to affect gene transcription, cellular outgrowth, and its subcellular localization in the fine perisynaptic astrocytic processes (PAPs) varies based on time-of-day. Future studies determining the effects of FABP7 on behavioral state- and circadian-dependent plasticity and cognitive processes, in addition to functional consequences on cellular and molecular mechanisms related to neural-glial interactions, lipid storage, and blood brain barrier integrity will be important for our knowledge of basic sleep function. Given the comorbidity of sleep disturbance with neurological disorders, these studies will also be important for our understanding of the etiology and pathophysiology of how these diseases affect or are affected by sleep.

AI-Driven sleep staging from actigraphy and heart rate

Sleep is an important indicator of a person's health, and its accurate and cost-effective quantification is of great value in healthcare. The gold standard for sleep assessment and the clinical diagnosis of sleep disorders is polysomnography (PSG). However, PSG requires an overnight clinic visit and trained technicians to score the obtained multimodality data. Wrist-worn consumer devices, such as smartwatches, are a promising alternative to PSG because of their small form factor, continuous monitoring capability, and popularity. Unlike PSG, however, wearables-derived data are noisier and far less information-rich because of the fewer number of modalities and less accurate measurements due to their small form factor. Given these challenges, most consumer devices perform two-stage (i.e., sleep-wake) classification, which is inadequate for deep insights into a person's sleep health. The challenging multi-class (three, four, or five-class) staging of sleep using data from wrist-worn wearables remains unresolved. The difference in the data quality between consumer-grade wearables and lab-grade clinical equipment is the motivation behind this study. In this paper, we present an artificial intelligence (AI) technique termed sequence-to-sequence LSTM for automated mobile sleep staging (SLAMSS), which can perform three-class (wake, NREM, REM) and four-class (wake, light, deep, REM) sleep classification from activity (i.e., wrist-accelerometry-derived locomotion) and two coarse heart rate measures-both of which can be reliably obtained from a consumer-grade wrist-wearable device. Our method relies on raw time-series datasets and obviates the need for manual feature selection. We validated our model using actigraphy and coarse heart rate data from two independent study populations: the Multi-Ethnic Study of Atherosclerosis (MESA; N = 808) cohort and the Osteoporotic Fractures in Men (MrOS; N = 817) cohort. SLAMSS achieves an overall accuracy of 79%, weighted F1 score of 0.80, 77% sensitivity, and 89% specificity for three-class sleep staging and an overall accuracy of 70-72%, weighted F1 score of 0.72-0.73, 64-66% sensitivity, and 89-90% specificity for four-class sleep staging in the MESA cohort. It yielded an overall accuracy of 77%, weighted F1 score of 0.77, 74% sensitivity, and 88% specificity for three-class sleep staging and an overall accuracy of 68-69%, weighted F1 score of 0.68-0.69, 60-63% sensitivity, and 88-89% specificity for four-class sleep staging in the MrOS cohort. These results were achieved with feature-poor inputs with a low temporal resolution. In addition, we extended our three-class staging model to an unrelated Apple Watch dataset. Importantly, SLAMSS predicts the duration of each sleep stage with high accuracy. This is especially significant for four-class sleep staging, where deep sleep is severely underrepresented. We show that, by appropriately choosing the loss function to address the inherent class imbalance, our method can accurately estimate deep sleep time (SLAMSS/MESA: 0.61±0.69 hours, PSG/MESA ground truth: 0.60±0.60 hours; SLAMSS/MrOS: 0.53±0.66 hours, PSG/MrOS ground truth: 0.55±0.57 hours;). Deep sleep quality and quantity are vital metrics and early indicators for a number of diseases. Our method, which enables accurate deep sleep estimation from wearables-derived data, is therefore promising for a variety of clinical applications requiring long-term deep sleep monitoring.

The stress of losing sleep: Sex-specific neurobiological outcomes

Sleep is a vital and evolutionarily conserved process, critical to daily functioning and homeostatic balance. Losing sleep is inherently stressful and leads to numerous detrimental physiological outcomes. Despite sleep disturbances affecting everyone, women and female rodents are often excluded or underrepresented in clinical and pre-clinical studies. Advancing our understanding of the role of biological sex in the responses to sleep loss stands to greatly improve our ability to understand and treat health consequences of insufficient sleep. As such, this review discusses sex differences in response to sleep deprivation, with a focus on the sympathetic nervous system stress response and activation of the hypothalamic-pituitary-adrenal (HPA) axis. We review sex differences in several stress-related consequences of sleep loss, including inflammation, learning and memory deficits, and mood related changes. Focusing on women's health, we discuss the effects of sleep deprivation during the peripartum period. In closing, we present neurobiological mechanisms, including the contribution of sex hormones, orexins, circadian timing systems, and astrocytic neuromodulation, that may underlie potential sex differences in sleep deprivation responses.

Goodnight, astrocyte: waking up to astroglial mechanisms in sleep

Astrocytes mediate many important aspects of neural homeostasis, but until recently, their role in sleep was largely unknown. The situation has dramatically changed in the last decade. The use of transgenic animals, optogenetics, chemogenetics, brain imaging and sophisticated molecular assays has led to exciting discoveries. Astrocytes dynamically change their activity across the sleep-wake cycle and may encode sleep need via changes in intracellular signalling pathways. Astrocytes also exocytose/secrete sleep-inducing molecules which modulate brain activity, sleep architecture and sleep regulation. Many of these observations have been made in mice and Drosophila melanogaster, indicating that astroglial sleep mechanisms are evolutionarily conserved. We review recent findings and discuss future directions.

Ontogenesis of the molecular response to sleep loss

Sleep deprivation (SD) results in profound cellular and molecular changes in the adult mammalian brain. Some of these changes may result in, or aggravate, brain disease. However, little is known about how SD impacts gene expression in developing animals. We examined the transcriptional response in the prefrontal cortex (PFC) to SD across postnatal development in male mice. We used RNA sequencing to identify functional gene categories that were specifically impacted by SD. We find that SD has dramatically different effects on PFC genes depending on developmental age. Gene expression differences after SD fall into 3 categories: present at all ages (conserved), present when mature sleep homeostasis is first emerging, and those unique to certain ages. Developmentally conserved gene expression was limited to a few functional categories, including Wnt-signaling which suggests that this pathway is a core mechanism regulated by sleep. In younger ages, genes primarily related to growth and development are affected while changes in genes related to metabolism are specific to the effect of SD in adults.

Sleep and dreaming in the light of reactive and predictive homeostasis

Dreams are often viewed as fascinating but irrelevant mental epihenomena of the sleeping mind with questionable functional relevance. Despite long hours of oneiric activity, and high individual differences in dream recall, dreams are lost into oblivion. Here, we conceptualize dreaming and dream amnesia as inherent aspects of the reactive and predictive homeostatic functions of sleep. Mental activity during sleep conforms to the interplay of restorative processes and future anticipation, and particularly during the second half of the night, it unfolds as a special form of non-constrained, self-referent, and future-oriented cognitive process. Awakening facilitates constrained, goal-directed prospection that competes for shared neural resources with dream production and dream recall, and contributes to dream amnesia. We present the neurophysiological aspects of reactive and predictive homeostasis during sleep, highlighting the putative role of cortisol in predictive homeostasis and forgetting dreams. The theoretical and methodological aspects of our proposal are discussed in relation to the study of dreaming, dream recall, and sleep-related cognitive processes.

Nutritional geometry framework of sleep

AIMS

Sleep is a fundamental physiological function and is essential for all animals. Sleep is affected by diet compositions including protein (P) and carbohydrates (C), but there has not been a systematic investigation on the effect of dietary macronutrient balance on sleep.

MAIN METHODS

We used the nutritional geometry framework (NGF) to explore the interactive effects on sleep of protein (P) and carbohydrates (C) in the model organism Drosophila. Both female and male flies were fed various diets containing seven ratios of protein-to-carbohydrates at different energetic levels for 5 days and sleep was monitored by the Drosophila Activity Monitor (DAM) system.

KEY FINDINGS

Our results showed that the combination of low protein and high carbohydrates (LPHC) 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 hemolymph glucose and whole-body glycogen. Moreover, transcriptomic analyses revealed that a high-protein, low-carbohydrate (HPLC) diet significantly elevated the gene expression of metabolic pathways when compared to the LPHC diet, with the glycine, serine, and threonine metabolism pathway being most strongly elevated. Further studies confirmed that the contents of glycine, serine, and threonine affected sleep.

SIGNIFICANCE

Our results demonstrate that sleep is affected by the dietary balance of protein and carbohydrates possibly mediated by the change in glucose, glycogen, glycine, serine, and threonine.

Low Levels of Adenosine and GDNF Are Potential Risk Factors for Parkinson's Disease with Sleep Disorders

Sleep disturbances are the most prevalent non-motor symptoms in the preclinical stage of Parkinson's disease (PD). Adenosine, glial-derived neurotrophic factor (GDNF), and associated neurotransmitters are crucial in the control of sleep arousal. This study aimed to detect the serum levels of adenosine, GDNF, and associated neurotransmitters and explored their correlations with PD with sleep disorders. Demographic characteristics and clinical information of PD patients and healthy participants were assessed. Serum concentrations of adenosine, GDNF, and related neurotransmitters were detected by ELISA and LC-MS. The correlation between serum levels of adenosine, GDNF, and associated neurotransmitters and sleep disorders was explored using logistic regression. PD patients with sleep disorders had higher scores of HAMA, HAMD, ESS, UPDRS-III, and H-Y stage. Lower levels of adenosine, GDNF, and γ-GABA were observed in PD patients who had sleep problems. Logistic regression analysis showed adenosine and GDNF were protective factors for preventing sleep disorders. Adenosine combined with GDNF had a higher diagnostic efficiency in predicting PD with sleep disorders by ROC analysis. This study revealed low adenosine and GDNF levels may be risk factors for sleep disorders in PD. The decrease of serum adenosine and GDNF levels may contribute to the diagnosis of PD with sleep disturbances.

Ontogenesis of the molecular response to sleep loss

Sleep deprivation (SD) results in profound cellular and molecular changes in the adult mammalian brain. Some of these changes may result in, or aggravate, brain disease. However, little is known about how SD impacts gene expression in developing animals. We examined the transcriptional response in the prefrontal cortex (PFC) to SD across postnatal development in male mice. We used RNA sequencing to identify functional gene categories that were specifically impacted by SD. We find that SD has dramatically different effects on PFC genes depending on developmental age. Gene expression differences after SD fall into 3 categories: present at all ages (conserved), present when mature sleep homeostasis is first emerging, and those unique to certain ages in adults. Developmentally conserved gene expression was limited to a few functional categories, including Wnt-signaling which suggests that this pathway is a core mechanism regulated by sleep. In younger ages, genes primarily related to growth and development are affected while changes in genes related to metabolism are specific to the effect of SD in adults.

Increased interaction between endoplasmic reticulum and mitochondria following sleep deprivation

BACKGROUND

Prolonged cellular activity may overload cell function, leading to high rates of protein synthesis and accumulation of misfolded or unassembled proteins, which cause endoplasmic reticulum (ER) stress and activate the unfolded protein response (UPR) to re-establish normal protein homeostasis. Previous molecular work has demonstrated that sleep deprivation (SD) leads to ER stress in neurons, with a number of ER-specific proteins being upregulated to maintain optimal cellular proteostasis. It is still not clear which cellular processes activated by sleep deprivation lead to ER- stress, but increased cellular metabolism, higher request for protein synthesis, and over production of oxygen radicals have been proposed as potential contributing factors. Here, we investigate the transcriptional and ultrastructural ER and mitochondrial modifications induced by sleep loss.

RESULTS

We used gene expression analysis in mouse forebrains to show that SD was associated with significant transcriptional modifications of genes involved in ER stress but also in ER-mitochondria interaction, calcium homeostasis, and mitochondrial respiratory activity. Using electron microscopy, we also showed that SD was associated with a general increase in the density of ER cisternae in pyramidal neurons of the motor cortex. Moreover, ER cisternae established new contact sites with mitochondria, the so-called mitochondria associated membranes (MAMs), important hubs for molecule shuttling, such as calcium and lipids, and for the modulation of ATP production and redox state. Finally, we demonstrated that Drosophila male mutant flies (elav > linker), in which the number of MAMs had been genetically increased, showed a reduction in the amount and consolidation of sleep without alterations in the homeostatic sleep response to SD.

CONCLUSIONS

We provide evidence that sleep loss induces ER stress characterized by increased crosstalk between ER and mitochondria. MAMs formation associated with SD could represent a key phenomenon for the modulation of multiple cellular processes that ensure appropriate responses to increased cell metabolism. In addition, MAMs establishment may play a role in the regulation of sleep under baseline conditions.

[Molecular and cellular mechanisms of restorative effects of sleep]

The review article enlightens contemporary concept about a role of sleep in cellular energy metabolism, neuroplasticity and glymphatic clearance of waste products. Many researches have demonstrated that prolonged wakefulness is an energetic and a neurophysiologic issue for the brain. The article provides description of biochemical processes that are responsive for energy restoration in sleep, particularly the role of ATP, adenosine and glycogen. Energy metabolism substrates depletion leads to endoplasmic reticulum stress and unfolded protein response. At the same time the conductance of synapses increases that worsens energetic problems. Level of the glymphatic clearance during wakefulness is substantially lower in comparison with sleep, and waste products are not removed fast enough.

Sleep-mediated regulation of reward circuits: implications in substance use disorders

Our modern society suffers from both pervasive sleep loss and substance abuse-what may be the indications for sleep on substance use disorders (SUDs), and could sleep contribute to the individual variations in SUDs? Decades of research in sleep as well as in motivated behaviors have laid the foundation for us to begin to answer these questions. This review is intended to critically summarize the circuit, cellular, and molecular mechanisms by which sleep influences reward function, and to reveal critical challenges for future studies. The review also suggests that improving sleep quality may serve as complementary therapeutics for treating SUDs, and that formulating sleep metrics may be useful for predicting individual susceptibility to SUDs and other reward-associated psychiatric diseases.

Validity of Two Consumer Multisport Activity Tracker and One Accelerometer against Polysomnography for Measuring Sleep Parameters and Vital Data in a Laboratory Setting in Sleep Patients

Two commercial multisport activity trackers (Garmin Forerunner 945 and Polar Ignite) and the accelerometer ActiGraph GT9X were evaluated in measuring vital data, sleep stages and sleep/wake patterns against polysomnography (PSG). Forty-nine adult patients with suspected sleep disorders (30 males/19 females) completed a one-night PSG sleep examination followed by a multiple sleep latency test (MSLT). Sleep parameters, time in bed (TIB), total sleep time (TST), wake after sleep onset (WASO), sleep onset latency (SOL), awake time (WASO + SOL), sleep stages (light, deep, REM sleep) and the number of sleep cycles were compared. Both commercial trackers showed high accuracy in measuring vital data (HR, HRV, SpO2, respiratory rate), r > 0.92. For TIB and TST, all three trackers showed medium to high correlation, r > 0.42. Garmin had significant overestimation of TST, with MAE of 84.63 min and MAPE of 25.32%. Polar also had an overestimation of TST, with MAE of 45.08 min and MAPE of 13.80%. ActiGraph GT9X results were inconspicuous. The trackers significantly underestimated awake times (WASO + SOL) with weak correlation, r = 0.11−0.57. The highest MAE was 50.35 min and the highest MAPE was 83.02% for WASO for Garmin and ActiGraph GT9X; Polar had the highest MAE of 21.17 min and the highest MAPE of 141.61% for SOL. Garmin showed significant deviations for sleep stages (p < 0.045), while Polar only showed significant deviations for sleep cycle (p = 0.000), r < 0.50. Garmin and Polar overestimated light sleep and underestimated deep sleep, Garmin significantly, with MAE up to 64.94 min and MAPE up to 116.50%. Both commercial trackers Garmin and Polar did not detect any daytime sleep at all during the MSLT test. The use of the multisport activity trackers for sleep analysis can only be recommended for general daily use and for research purposes. If precise data on sleep stages and parameters are required, their use is limited. The accuracy of the vital data measurement was adequate. Further studies are needed to evaluate their use for medical purposes, inside and outside of the sleep laboratory. The accelerometer ActiGraph GT9X showed overall suitable accuracy in detecting sleep/wake patterns.

The Relationship Between Thiamine Intake and Long Sleep Duration: Results From the Korea National Health and Nutrition Examination Survey

OBJECTIVES

Thiamine is thought to modify sleeping patterns, while alcohol use diminishes internal thiamine levels. We investigated the association between thiamine intake and sleep duration and explored possible heterogeneity in the effect according to alcohol use.

METHODS

In total, 15 384 participants aged 19-64 were obtained from the Korea National Health and Nutrition Examination Survey 2012-2016. Nutrient intake, including thiamine, was measured using a food frequency questionnaire. Sleep duration was measured by a self-reported questionnaire. The highest thiamine intake quartile was set as the reference group. Participants were divided into 3 groups, with 7-8 hours of daily sleep as a reference group and those who slept more or less than that as "oversleeping" and "insufficient sleeping," respectively. Multivariate logistic regression was used, adjusting for socioeconomic, medical, and nutritional factors. Additionally, participants were stratified according to high-risk alcohol use defined by the World Health Organization standards on alcohol use.

RESULTS

Low thiamine intake was associated with oversleeping (Q3: odds ratio [OR], 1.06; 95% confidence interval [CI], 0.86 to 1.32; Q2: OR, 1.24; 95% CI, 0.99 to 1.55; Q1: OR, 1.49; 95% CI, 1.16 to 1.91) and showed a significant trend for higher ORs at lower intake levels (p-trend&lt;0.001). The effect was stronger in the high-risk alcohol use group (Q1: OR, 1.78; 95% CI, 1.28 to 2.49).

CONCLUSIONS

Low thiamine intake was associated with oversleeping, and alcohol use intensified that association. These results were found in a context where overt clinical symptoms due to thiamine deficiency are considered rare. More awareness of the potential relationship of thiamine intake with oversleeping and its related risks should be considered.

Progressive muscle relaxation increases slow-wave sleep during a daytime nap

Sleep is critical for health, cognition, and restorative processes, and yet, many experience chronic sleep restriction. Sleep interventions have been designed to enhance overnight sleep quality and physiology. Components of these interventions, like relaxation-based progressive muscle relaxation (PMR), have been studied in isolation and have shown direct effects on sleep architecture, including increasing time in restorative, slow-wave sleep (SWS). These relaxation methods have been understudied in naps, which are effective fatigue countermeasures that reduce deleterious effects of chronic sleep restriction. We hypothesised that PMR should boost SWS in a nap, as compared to an active control. We used a between-subject design in which healthy young adults underwent PMR training or listened to Mozart music (control) prior to a 90-min nap opportunity. We assessed changes in the amount and lateralisation of SWS, as evidence suggests left hemispheric lateralisation may be a proxy for recuperative sleep needs, and changes to state-dependent anxiety and fatigue before and after the nap to assess intervention success. We found PMR participants spent ~10 min more in SWS, equivalent to 125% more time, than the control group, and concomitantly, significantly less time in rapid eye movement sleep. PMR participants also had greater right lateralised slow-wave activity and delta activity compared to the control suggesting a more well-rested brain profile during sleep. Further, pre-sleep anxiety levels predicted nap architecture in the intervention group, suggesting benefits may be impacted by anxiety. The feasibility and accessibility of PMR prior to a nap make this an interesting research avenue to pursue with strong translational application.

Single-cell transcriptomics and cell-specific proteomics reveals molecular signatures of sleep

Every day, we sleep for a third of the day. Sleep is important for cognition, brain waste clearance, metabolism, and immune responses. The molecular mechanisms governing sleep are largely unknown. Here, we used a combination of single-cell RNA sequencing and cell-type-specific proteomics to interrogate the molecular underpinnings of sleep. Different cell types in three important brain regions for sleep (brainstem, cortex, and hypothalamus) exhibited diverse transcriptional responses to sleep need. Sleep restriction modulates astrocyte-neuron crosstalk and sleep need enhances expression of specific sets of transcription factors in different brain regions. In cortex, we also interrogated the proteome of two major cell types: astrocytes and neurons. Sleep deprivation differentially alters the expression of proteins in astrocytes and neurons. Similarly, phosphoproteomics revealed large shifts in cell-type-specific protein phosphorylation. Our results indicate that sleep need regulates transcriptional, translational, and post-translational responses in a cell-specific manner.

Noradrenergic Signaling in Astrocytes Influences Mammalian Sleep Homeostasis

Astrocytes influence sleep expression and regulation, but the cellular signaling pathways involved in these processes are poorly defined. We proposed that astrocytes detect and integrate a neuronal signal that accumulates during wakefulness, thereby leading to increased sleep drive. Noradrenaline (NA) satisfies several criteria for a waking signal integrated by astrocytes. We therefore investigated the role of NA signaling in astrocytes in mammalian sleep. We conditionally knocked out (cKO) β2-adrenergic receptors (β2-AR) selectively in astrocytes in mice and recorded electroencephalographic and electromyographic activity under baseline conditions and in response to sleep deprivation (SDep). cKO of astroglial β2-ARs increased active phase siesta duration under baseline conditions and reduced homeostatic compensatory changes in sleep consolidation and non-rapid eye movement slow-wave activity (SWA) after SDep. Overall, astroglial NA β2-ARs influence mammalian sleep homeostasis in a manner consistent with our proposed model of neuronal-astroglial interactions.

Astrocyte-derived adenosine excites sleep-promoting neurons in the ventrolateral preoptic nucleus: Astrocyte-neuron interactions in the regulation of sleep

Although ATP and/or adenosine derived from astrocytes are known to regulate sleep, the precise mechanisms underlying the somnogenic effects of ATP and adenosine remain unclear. We selectively expressed channelrhodopsin-2 (ChR2), a light-sensitive ion channel, in astrocytes within the ventrolateral preoptic nucleus (VLPO), which is an essential brain nucleus involved in sleep promotion. We then examined the effects of photostimulation of astrocytic ChR2 on neuronal excitability using whole-cell patch-clamp recordings in two functionally distinct types of VLPO neurons: sleep-promoting GABAergic projection neurons and non-sleep-promoting local GABAergic neurons. Optogenetic stimulation of VLPO astrocytes demonstrated opposite outcomes in the two types of VLPO neurons. It led to the inhibition of non-sleep-promoting neurons and excitation of sleep-promoting neurons. These responses were attenuated by blocking of either adenosine A₁ receptors or tissue-nonspecific alkaline phosphatase (TNAP). In contrast, exogenous adenosine decreased the excitability of both VLPO neuron populations. Moreover, TNAP was expressed in galanin-negative VLPO neurons, but not in galanin-positive sleep-promoting projection neurons. Taken together, these results suggest that astrocyte-derived ATP is converted into adenosine by TNAP in non-sleep-promoting neurons. In turn, adenosine decreases the excitability of local GABAergic neurons, thereby increasing the excitability of sleep-promoting GABAergic projection neurons. We propose a novel mechanism involving astrocyte-neuron interactions in sleep regulation, wherein endogenous adenosine derived from astrocytes excites sleep-promoting VLPO neurons, and thus decreases neuronal excitability in arousal-related areas of the brain.

Sleep Disruption and Cancer: Chicken or the Egg?

Sleep is a nearly ubiquitous phenomenon across the phylogenetic tree, highlighting its essential role in ensuring fitness across evolutionary time. Consequently, chronic disruption of the duration, timing, or structure of sleep can cause widespread problems in multiple physiological systems, including those that regulate energy balance, immune function, and cognitive capacity, among others. Many, if not all these systems, become altered throughout the course of cancer initiation, growth, metastatic spread, treatment, and recurrence. Recent work has demonstrated how changes in sleep influence the development of chronic diseases, including cancer, in both humans and animal models. A common finding is that for some cancers (e.g., breast), chronic disruption of sleep/wake states prior to disease onset is associated with an increased risk for cancer development. Additionally, sleep disruption after cancer initiation is often associated with worse outcomes. Recently, evidence suggesting that cancer itself can affect neuronal circuits controlling sleep and wakefulness has accumulated. Patients with cancer often report difficulty falling asleep, difficulty staying asleep, and severe fatigue, during and even years after treatment. In addition to the psychological stress associated with cancer, cancer itself may alter sleep homeostasis through changes to host physiology and via currently undefined mechanisms. Moreover, cancer treatments (e.g., chemotherapy, radiation, hormonal, and surgical) may further worsen sleep problems through complex biological processes yet to be fully understood. This results in a "chicken or the egg" phenomenon, where it is unclear whether sleep disruption promotes cancer or cancer reciprocally disrupts sleep. This review will discuss existing evidence for both hypotheses and present a framework through which the interactions between sleep and cancer can be dissociated and causally investigated.

Adenosine, caffeine, and sleep-wake regulation: state of the science and perspectives

For hundreds of years, mankind has been influencing its sleep and waking state through the adenosinergic system. For ~100 years now, systematic research has been performed, first started by testing the effects of different dosages of caffeine on sleep and waking behaviour. About 70 years ago, adenosine itself entered the picture as a possible ligand of the receptors where caffeine hooks on as an antagonist to reduce sleepiness. Since the scientific demonstration that this is indeed the case, progress has been fast. Today, adenosine is widely accepted as an endogenous sleep‐regulatory substance. In this review, we discuss the current state of the science in model organisms and humans on the working mechanisms of adenosine and caffeine on sleep. We critically investigate the evidence for a direct involvement in sleep homeostatic mechanisms and whether the effects of caffeine on sleep differ between acute intake and chronic consumption. In addition, we review the more recent evidence that adenosine levels may also influence the functioning of the circadian clock and address the question of whether sleep homeostasis and the circadian clock may interact through adenosinergic signalling. In the final section, we discuss the perspectives of possible clinical applications of the accumulated knowledge over the last century that may improve sleep‐related disorders. We conclude our review by highlighting some open questions that need to be answered, to better understand how adenosine and caffeine exactly regulate and influence sleep.

Detecting sleep outside the clinic using wearable heart rate devices

The adoption of multisensor wearables presents the opportunity of longitudinal monitoring of sleep in large populations. Personalized yet device-agnostic algorithms can sidestep laborious human annotations and objectify cross-cohort comparisons. We developed and tested a heart rate-based algorithm that captures inter- and intra-individual sleep differences in free-living conditions and does not require human input. We evaluated it on four study cohorts using different research- and consumer-grade devices for over 2000 nights. Recording periods included both 24 h free-living and conventional lab-based night-only data. We compared our optimized method against polysomnography, sleep diaries and sleep periods produced through a state-of-the-art acceleration based method. Against sleep diaries, the algorithm yielded a mean squared error of 0.04-0.06 and a total sleep time (TST) deviation of [Formula: see text]2.70 (± 5.74) and 12.80 (± 3.89) minutes, respectively. When evaluated with PSG lab studies, the MSE ranged between 0.06 and 0.11 yielding a time deviation between [Formula: see text]29.07 and [Formula: see text]55.04 minutes. These results showcase the value of this open-source, device-agnostic algorithm for the reliable inference of sleep in free-living conditions and in the absence of annotations.