Metabolic signals in sleep regulation: recent insights

Role of Thymoquinone on sleep restriction and its mitigating effect on leptin-mediated signaling pathway in rat brain

BACKGROUND

Sleep and stress interact bidirectionally by acting on brain circuits that affect metabolism. Sleep and its alterations have impact on blood leptin levels, metabolic hormone that regulates appetite. Brain expresses the receptors for the peptide hormone leptin produced from adipocytes. The hypothalamic orexin neurons are low during sleep and active when awake, influenced by a complex interaction with leptin. Thymoquinone was found to be the major bioactive component of Nigella sativa. The aim of this study was to study the role of thymoquinone on sleep restriction and its mitigating effect on leptin-mediated signaling pathway in rat brain.

METHODS AND RESULTS

30 adult male Wistar rats were divided into 5 groups with 6 animals in each group: Control; Thymoquinone (TQ); Corn oil; Chronic Sleep restriction (CSR); and CSR + TQ. After 30 days, behavioral analysis, antioxidant, lipid profile, glucose level, liver and kidney function test, neurotransmitters, neuropeptides, and mRNA expression in in vivo studies were also assessed and pharmacokinetic and docking were done for thymoquinone. Thymoquinone has also shown good binding affinity to the target proteins. CSR has induced oxidative stress in the discrete brain regions and plasma. Current study has shown many evidences that sleep restriction has altered the neurobehavioral, antioxidant status, lipid profile, neurotransmitters, neuropeptide levels, and feeding behavior which damage the Orexin-leptin system which regulates the sleep and feeding that leads to metabolic dysfunction.

CONCLUSION

The potentiality of Thymoquinone was revealed in in silico studies, and its action in in vivo studies has proved its effectiveness. The study concludes that Thymoquinone has exhibited its effect by diminishing the metabolic dysfunction by its neuroprotective, antioxidant, and hypolipidemic properties.

Carbohydrate and sleep: An evaluation of putative mechanisms

Sleep problems are extremely common in industrialized countries and the possibility that diet might be used to improve sleep has been considered. The topic has been reviewed many times, resulting in the frequent suggestion that carbohydrate increases the uptake of tryptophan by the brain, where it is metabolized into serotonin and melatonin, with the suggestion that this improves sleep. An alternative mechanism was proposed based on animal literature that has been largely ignored by those considering diet and sleep. The hypothesis was that, as in the hypothalamus there are glucose-sensing neurons associated with the sleep-wake cycle, we should consider the impact of carbohydrate-induced changes in the level of blood glucose. A meta-analysis found that after consuming a lower amount of carbohydrate, more time was spent in slow-wave sleep (SWS) and less in rapid-eye-movement sleep. As the credibility of alternative mechanisms has tended not to have been critically evaluated, they were considered by examining their biochemical, nutritional, and pharmacological plausibility. Although high carbohydrate consumption can increase the uptake of tryptophan by the brain, it only occurs with such low levels of protein that the mechanism is not relevant to a normal diet. After entering the brain tryptophan is converted to serotonin, a neurotransmitter known to influence so many different aspects of sleep and wakefulness, that it is not reasonable to expect a uniform improvement in sleep. Some serotonin is converted to melatonin, although the exogenous dose of melatonin needed to influence sleep cannot be credibly provided by the diet. This review was registered in the International Prospective Register of Systematic Reviews (CRD42020223560).

Short-term effect of physical activity on sleep health: A population-based study using accelerometry

BACKGROUND

Regular physical activity (PA) is an important behavior in improving sleep health. However, the short-term effects of PA on sleep are still controversial. This study aimed to verify the effect of different intensities of PA practiced in different periods of the day on the subsequent sleep night in a population-based cohort of young adults.

METHODS

Prospective analyses were conducted for PA performed during the day and its effect on the following sleep night using data from the 22-year follow-up of the 1993 Pelotas Birth Cohort in Brazil (mean age of participants = 22.6 years). Wrist-worn accelerometry was used to measure both PA and sleep parameters. Regarding intensity, we analyzed the sleep effect of light PA (LPA), moderate PA, and vigorous PA, stratified by sex. Sleep variables were sleep time window (STW; the difference between sleep onset and sleep end), total sleep time (TST; the sum of minutes classified as sleep in STW), and sleep percent (SP; SP = (TST/STW); expressed in percentage). We performed generalized estimating equations using Stata software.

RESULTS

The means of STW, TST, and SP were 443.6 min/day, 371.1 min/day, and 84%, respectively. Time spent in moderate PA and vigorous PA in the morning and afternoon was not associated with sleep variables. Among men, 10 min/day of morning LPA increased TST by 2.56 min/day. Among women, 10 min/day of morning LPA increased SP by 0.15 percentage points. Afternoon LPA also increased SP by 0.09 percentage points for women. Night PA seems to have an inverse effect on sleep variables for any intensity and both sexes.

CONCLUSION

The effect of PA on sleep health is intrinsically related to the period of the day in which it is performed. The effect magnitude is different between sexes. For better sleep health, it is preferable that PA be performed during the day.

Sleep duration and quality are not associated with brown adipose tissue volume or activity-as determined by 18F-FDG uptake, in young, sedentary adults

Study Objectives

Short sleep duration and sleep disturbances have been related to obesity and metabolic disruption. However, the behavioral and physiological mechanisms linking sleep and alterations in energy balance and metabolism are incompletely understood. In rodents, sleep regulation is closely related to appropriate brown adipose tissue (BAT) thermogenic activity, but whether the same is true in humans has remained unknown. The present work examines whether sleep duration and quality are related to BAT volume and activity (measured by ¹⁸F-FDG) and BAT radiodensity in humans.

Methods

A total of 118 healthy adults (69% women, 21.9 ± 2.2 years, body mass index: 24.9 ± 4.7 kg/m²) participated in this cross-sectional study. Sleep duration and other sleep variables were measured using a wrist-worn accelerometer for seven consecutive days for 24 hours per day. The Pittsburgh Sleep Quality Index was used to assess sleep quality. All participants then underwent a personalized cold exposure to determine their BAT volume, activity, and radiodensity (a proxy of the intracellular triglyceride content), using static positron emission tomography combined with computed tomography (PET/CI) scan.

Results

Neither sleep duration nor quality was associated with BAT volume or activity (the latter represented by the mean and peak standardized ¹⁸F-FDG uptake values) or radiodensity (all p > .1). The lack of association remained after adjusting the analyses for sex, date of PET/CT, and body composition.

Conclusions

Although experiments in rodent models indicate a strong relationship to exist between sleep regulation and BAT function, it seems that sleep duration and quality may not be directly related to the BAT variables examined in the present work.

Clinical Trial Registration

NCT02365129 (ClinicalTrials.gov).

Sleep, Diet, and Cardiometabolic Health Investigations: a Systematic Review of Analytic Strategies

PURPOSE OF REVIEW

Poor sleep is a risk factor for cardiometabolic morbidity. The relationship of sleep and cardiometabolic health could be confounded, mediated, or modified by diet, yet the incorporation of diet in sleep-cardiometabolic health studies is inconsistent. This rapid systematic literature review evaluates the conceptualization of diet as a confounder, mediator, or effect modifier within sleep-cardiometabolic health investigations, and the statistical approaches utilized.

RECENT FINDINGS

Of 4692 studies identified, 60 were retained (28 adult, 32 pediatric). Most studies included diet patterns, quality, or energy intake as confounders, while a few examined these dietary variables as mediators or effect modifiers. There was some evidence, mostly in pediatric studies, that inclusion of diet altered sleep-cardiometabolic health associations. Diet plays a diverse role within sleep-cardiometabolic health associations. Investigators should carefully consider the conceptualization of diet variables in these relationships and utilize contemporary statistical approaches when applicable.

Food-Dependent Plasticity in Caenorhabditis elegans Stress-Induced Sleep Is Mediated by TOR-FOXA and TGF-β Signaling

Behavioral plasticity allows for context-dependent prioritization of competing drives, such as sleep and foraging. Despite the identification of neuropeptides and hormones implicated in dual control of sleep drive and appetite, our understanding of the mechanism underlying the conserved sleep-suppressing effect of food deprivation is limited. Caenorhabditis elegans provides an intriguing model for the dissection of sleep function and regulation as these nematodes engage a quiescence program following exposure to noxious conditions, a phenomenon known as stress-induced sleep (SIS). Here we show that food deprivation potently suppresses SIS, an effect enhanced at high population density. We present evidence that food deprivation reduces the need to sleep, protecting against the lethality associated with defective SIS. Additionally, we find that SIS is regulated by both target of rapamycin and transforming growth factor-β nutrient signaling pathways, thus identifying mechanisms coordinating sleep drive with internal and external indicators of food availability.

Brown adipose tissue plays a central role in systemic inflammation-induced sleep responses

We previously identified brown adipose tissue (BAT) as a source of sleep-inducing signals. Pharmacological activation of BAT enhances sleep while sleep loss leads to increased BAT thermogenesis. Recovery sleep after sleep loss is diminished in mice that lack uncoupling protein 1 (UCP-1), and also in wild-type (WT) mice after sensory denervation of the BAT. Systemic inflammation greatly affects metabolism and the function of adipose tissue, and also induces characteristic sleep responses. We hypothesized that sleep responses to acute inflammation are mediated by BAT-derived signals. To test this, we determined the effects of systemic inflammation on sleep and body temperature in UCP-1 knockout (KO) and WT mice. Intraperitoneal injections of lipopolysaccharide, tumor necrosis factor-α, interleukin-1 beta and clodronate containing liposomes were used to induce systemic inflammation. In WT animals, non-rapid-eye movement sleep (NREMS) was elevated in all four inflammatory models. All NREMS responses were completely abolished in UCP-1 KO animals. Systemic inflammation elicited an initial hypothermia followed by fever in WT mice. The hypothermic phase, but not the fever, was abolished in UCP-1 KO mice. The only recognized function of UCP-1 is to promote thermogenesis in brown adipocytes. Present results indicate that the presence of UCP-1 is necessary for increased NREMS but does not contribute to the development of fever in systemic inflammation.

The neurobiological basis of sleep: Insights from Drosophila

Sleep is a biological enigma that has raised numerous questions about the inner workings of the brain. The fundamental question of why our nervous systems have evolved to require sleep remains a topic of ongoing scientific deliberation. This question is largely being addressed by research using animal models of sleep. Drosophila melanogaster, also known as the common fruit fly, exhibits a sleep state that shares common features with many other species. Drosophila sleep studies have unearthed an immense wealth of knowledge about the neuroscience of sleep. Given the breadth of findings published on Drosophila sleep, it is important to consider how all of this information might come together to generate a more holistic understanding of sleep. This review provides a comprehensive summary of the neurobiology of Drosophila sleep and explores the broader insights and implications of how sleep is regulated across species and why it is necessary for the brain.

Restoring Serotonergic Homeostasis in the Lateral Hypothalamus Rescues Sleep Disturbances Induced by Early-Life Obesity

Early-life obesity predisposes to obesity in adulthood, a condition with broad medical implications including sleep disorders, which can exacerbate metabolic disturbances and disrupt cognitive and affective behaviors. In this study, we examined the long-term impact of transient peripubertal diet-induced obesity (ppDIO, induced between 4 and 10 weeks of age) on sleep-wake behavior in male mice. EEG and EMG recordings revealed that ppDIO increases sleep during the active phase but reduces resting-phase sleep quality. This impaired sleep phenotype persisted for up to 1 year, although animals were returned to a non-obesiogenic diet from postnatal week 11 onwards. To better understand the mechanisms responsible for the ppDIO-induced alterations in sleep, we focused on the lateral hypothalamus (LH). Mice exposed to ppDIO did not show altered mRNA expression levels of orexin and melanin-concentrating hormone, two peptides that are important for sleep-wake behavior and food intake. Conversely, the LH of ppDIO-exposed mice had reduced contents of serotonin (5-hydroxytryptamine, 5-HT), a neurotransmitter involved in both sleep-wake and satiety regulation. Interestingly, an acute peripheral injection of the satiety-signaling peptide YY 3-36 increased 5-HT turnover in the LH and ameliorated the ppDIO-induced sleep disturbances, suggesting the therapeutic potential of this peptide. These findings provide new insights into how sleep-wake behavior is programmed during early life and how peripheral and central signals are integrated to coordinate sleep.SIGNIFICANCE STATEMENT Adult physiology and behavior are strongly influenced by dynamic reorganization of the brain during puberty. The present work shows that obesity during puberty leads to persistently dysregulated patterns of sleep and wakefulness by blunting serotonergic signaling in the lateral hypothalamus. It also shows that pharmacological mimicry of satiety with peptide YY_3-36 can reverse this neurochemical imbalance and acutely restore sleep composition. These findings add insight into how innate behaviors such as feeding and sleep are integrated and suggest a novel mechanism through which diet-induced obesity during puberty imposes its long-lasting effects on sleep-wake behavior.

Dopamine D2 receptors and the circadian clock reciprocally mediate antipsychotic drug-induced metabolic disturbances

Antipsychotic drugs are widely prescribed medications, used for numerous psychiatric illnesses. However, antipsychotic drugs cause serious metabolic side effects that can lead to substantial weight gain and increased risk for type 2 diabetes. While individual drugs differ, all antipsychotic drugs may cause these important side effects to varying degrees. Given that the single unifying property shared by these medications is blockade of dopamine D₂ and D₃ receptors, these receptors likely play a role in antipsychotic drug-induced metabolic side effects. Dopamine D₂ and dopamine D₃ receptors are expressed in brain regions critical for metabolic regulation and appetite. Surprisingly, these receptors are also expressed peripherally in insulin-secreting pancreatic beta cells. By inhibiting glucose-stimulated insulin secretion, dopamine D₂ and dopamine D₃ receptors are important mediators of pancreatic insulin release. Crucially, antipsychotic drugs disrupt this peripheral metabolic regulatory mechanism. At the same time, disruptions to circadian timing have been increasingly recognized as a risk factor for metabolic disturbance. Reciprocal dopamine and circadian signaling is important for the timing of appetitive/feeding behaviors and insulin release, thereby coordinating cell metabolism with caloric intake. In particular, circadian regulation of dopamine D₂ receptor/dopamine D₃ receptor signaling may play a critical role in metabolism. Therefore, we propose that antipsychotic drugs’ blockade of dopamine D₂ receptor and dopamine D₃ receptors in pancreatic beta cells, hypothalamus, and striatum disrupts the cellular timing mechanisms that regulate metabolism. Ultimately, understanding the relationships between the dopamine system and circadian clocks may yield critical new biological insights into mechanisms of antipsychotic drug action, which can then be applied into clinical practice.