Endogenous and exogenous factors on sleep-wake cycle regulation

The relations of circulating agouti-related peptide and leptin with altered sleep architecture in patients with active Cushing's disease: a pilot study

AIM

To evaluate sleep architecture of patients with Cushing's disease (CD) and to explore whether agouti-related peptide (AgRP) and/or leptin play a permissive role in sleep alterations in patients with active CD.

METHODS

We performed polysomnography on 26 patients with active CD and age 26 age- and sex-matched control subjects. Blood samples were obtained from all participants for the analyzes of AgRP and leptin. The laboratory and sleep-related parameters were compared.

RESULTS

The groups were similar in age, gender, and body mass index. The CD group had reduced sleep efficiency (71.6 ± 12.1% vs. 78.8 ± 12.6%, p = 0.042) and increased wake after sleep onset (WASO%) (24.7 ± 13.1% vs. 17.4 ± 11.6%, p = 0.040) as compared to control group. Seventeen patients with CD (65.4%) and 18 control subjects (69.2%) had obstructive sleep apnea. Serum AgRP (13.2 ± 7.4 pg/ml vs. 9 ± 3.1, p = 0.029), leptin (59.5 mcg/l, [IQR] 32.6-94.6 vs. 25.3 mcg/l, [IQR] 12.9-57.5, p = 0.007) were higher in CD group. AgRP and leptin correlated negatively with total sleep time, sleep efficiency, stage N2 sleep (%), and positively with WASO%. In multiple regression analyses, serum cortisol (ß =  - 0.359, p = 0.042) and AgRP (ß =  - 0.481, p = 0.01) were significant predictor of sleep efficiency. AgRP was also significant predictor of WASO% (ß = 0.452 and p < 0.05).

CONCLUSIONS

Active CD carries an increased risk of impaired sleep efficiency and continuity which may worsen health-related quality of life. Elevated circulating AgRP and, to a lesser extent, leptin may be associated with decreased sleep efficiency and continuity in patients with CD. Patients with CD who have subjective sleep symptoms should be screened with polysomnography.

Determinants of natural adult sleep: An umbrella review

BACKGROUND

Sleep has a major impact on health, which makes it a relevant topic for research and health practitioners. Research on sleep determinants, i.e. factors that positively or negatively influence sleep, is fragmented.

OBJECTIVE

The purpose of this umbrella review is to provide an overview of the current evidence on determinants of natural adult sleep.

METHODS

A comprehensive literature search was performed on determinants of sleep. Reviews and meta-analyses on natural adult sleep were included. Six electronic databases (PubMed, WoS, Embase, CINAHL, PsycInfo and Cochrane) were used for the search, last accessed September 2021. The quality of the selected articles was assessed using the AMSTAR2 tool. Results were categorized in four main categories: biological, behavioral, environmental and personal/socio-economical determinants.

RESULTS

In total 93 reviews and meta-analyses resulted in a total of 30 identified determinants. The impact of each determinant differs per individual and per situation. Each determinant was found to affect different sleep parameters and the relationship with sleep is influenced by both generic and specific moderators.

DISCUSSION

A comprehensive overview on relevant sleep determinants provides a practical and scientifically based starting point to identify relevant intervention approaches to secure or improve individual sleep quality. The difference in aggregation level of the determinants and in measurement methods are the major limitations of this umbrella review. Extending existing generic sleep hygiene rules with an overview of all types of potential determinants will enhance the awareness of the complexity and can be used to improve the effect of sleep interventions in health promotion.

TRIAL REGISTRATION

The umbrella review was registered with PROSPERO (registration ID CRD42020149648) https://www.google.com/search?client=firefox-b-d&q=CRD42020149648.

Differences in the Course of Physiological Functions and in Subjective Evaluations in Connection With Listening to the Sound of a Chainsaw and to the Sounds of a Forest

We explored differences in the course of physiological functions and in the subjective evaluations in response to listening to a 7-min recording of the sound of a chainsaw and to the sounds of a forest. A Biofeedback 2000x-pert apparatus was used for continual recording of the following physiological functions in 50 examined persons: abdominal and thoracic respiration and their amplitude and frequency, electrodermal activity (skin conductance level), finger skin temperature, heart rate (pulse, blood volume pulse and blood volume pulse amplitude) and heart rate variability (HRV). The group of 25 subjects listening to the sound of a chainsaw exhibited significantly lower values of blood volume pulse amplitude, lower values in peak alpha frequency HRV and higher values in peak high-frequency HRV. In the time interval from 80 s to 209 s, in which the two groups showed the greatest differences, lower values of blood volume pulse were also recorded while listening to the sound of a chainsaw. Listening to the sound of a chainsaw is associated with a greater feeling of fatigue and higher tension, while listening to the sounds of a forest is even considered to elicit feelings of improved learning abilities. The assumption that listening to the sound of a chainsaw results in higher defense arousal was confirmed. The greater variability which is exhibited by a majority of physiological functions while listening to the forest sounds may also be an innovative finding. It seems that there are two types of arousal (sympathetic and parasympathetic) following from correlations between physiological functions and subjective assessment. Low values of blood volume pulse amplitude are especially important from the health perspective. They correspond to the amount of vasoconstriction which occurs in the endothelial dysfunction related to increased mortality, incidence of myocardial infarction, leg atherosclerosis and topically to COVID-19.

Sleep Duration and Quality and Sensory Reactivity in School-Aged Children: The Spanish Cross-Sectional InProS Study

Background: The relationship between children's sleep and health has been widely examined; however, research focused on the link between sleep and sensory reactivity in children without medical conditions is relatively new and based on studies with small samples. Hence, we aimed at exploring the association between sleep duration and quality and prevalence of sensory reactivity in a population-based sample of children aged 3-7. Methods: We examined data on 579 school-age children from the InProS project, a cross-sectional population-based study. Children's sleep duration was classified as <10 vs. ≥10 h/day, and sleep quality was measured using the Pediatric Sleep Questionnaire, defining poor quality sleep as a score of ≥0.33. The Short Sensory Profile (SSP) was used to classify children with or without sensory reactivity using the cut-off points proposed by W. Dunn for SSP total score and each SSP subscale. Prevalence ratios (PR) using Poisson multiple regression models with robust variance were estimated to examine main associations. Results: Around a third (32.6%; n = 189) slept <10 h/day and 10.4% presented poor sleep quality. The prevalence of sensory reactivity was 29.5% for total SSP (<155), 11.4% for tactile sensitivity (<30), 15% for taste/smell sensitivity (<15), 22.5% for movement sensitivity (<13), 49.1% for under-responsive/seeks sensation (<27), 44.4% for auditory filtering (<23), 12.4% for low energy/weak (<26), and 25.4% for visual/auditory sensitivity (<19). Main findings indicated that poor sleep quality was significantly associated with a greater prevalence of sensory reactivity for SSP total score (PR = 1.27; IC 95%: 1.18; 1.38), tactile sensitivity (PR = 1.09, IC95%: 1.00-1.19), taste/smell sensitivity (PR = 1.18, IC95%: 1.08-1.30), under-responsive/seeks sensation (PR = 1.28, IC95%: 1.20-1.37), auditory filtering (PR = 1.31, IC95%: 1.23-1.39), low energy/weak (PR = 1.14, IC95%: 1.04-1.25) and audiovisual sensitivity (PR = 1.15, IC95%: 1.05-1.26) scores after adjusting for potential confounders. Conclusions: In this study, we observed that poor sleep quality was statistically significantly associated with a higher prevalence of sensory reactivity as measured by the total SSP and almost all SSP subscales. To our knowledge, this is the first time that this association has been explored and reported. Further research from prospective studies is required to confirm these findings.

An exploratory study examining the associations between sunlight exposure, sleep behaviours and sleep outcomes during an Arctic summer

Few evidence-based recommendations exist for maintaining healthy sleep during Arctic summers. Our study aimed to examine associations between sleep hygiene, sunlight exposure and sleep outcomes in workers living in and/or near the Arctic Circle during a 24-h light period. A survey was administered July 2017 to 19 workers at 3 Arctic base camps in Northeastern Alaska. Participants with poorer sleep hygiene reported increased sleepiness (r=.62, p=0.01); this correlation remained moderately strong, albeit not statistically significant (NS), after controlling for shift work (r=.46, p=0.06). No other statistically significant correlations between sleep hygiene and sleep outcomes were found. Weekly daytime (<8pm) and evening (>8pm) sunlight exposures, estimated from daily self-reported sunlight exposures for a typical workday and day off, were dichotomised, based on means, into: longer (>45 h/week) versus shorter (<45 h/week) daytime exposures, and longer (>16 h/week) versus shorter (<16 h/week) evening exposures. Participants reporting longer, versus shorter, weekly daytime sunlight exposure had statistically significantly (Mann-Whitney U=18.00, Z=-1.98, p≤0.05) decreased median sleep duration (6 h, 18 min versus 8 h, respectively) during the past month. Correlations of r≥.3 for longer, vis-à-vis shorter, daylight sunlight exposure suggest it could be related to poorer sleep outcomes, such as insufficient sleep and sleep quality, yet, as these correlations were NS, future work is needed to determine this. Weak or no correlations (and NS differences) were found for longer, versus shorter, weekly evening sunlight exposure and sleep outcomes. Findings support previous research suggesting self-regulation behaviours alone are not protective against poor sleep in Arctic environments. Sleep outcomes did not differ statistically significantly by evening sunlight exposure length. Longer weekly daytime sunlight exposure, versus shorter, was significantly associated with decreased sleep duration. Results from this exploratory study should be confirmed in studies using larger sample sizes.

Role of the L-PGDS-PGD2-DP1 receptor axis in sleep regulation and neurologic outcomes

To meet the new challenges of modern lifestyles, we often compromise a good night's sleep. In preclinical models as well as in humans, a chronic lack of sleep is reported to be among the leading causes of various physiologic, psychologic, and neurocognitive deficits. Thus far, various endogenous mediators have been implicated in inter-regulatory networks that collectively influence the sleep-wake cycle. One such mediator is the lipocalin-type prostaglandin D2 synthase (L-PGDS)-Prostaglandin D2 (PGD2)-DP1 receptor (L-PGDS-PGD2-DP1R) axis. Findings in preclinical models confirm that DP1R are predominantly expressed in the sleep-regulating centers. This finding led to the discovery that the L-PGDS-PGD2-DP1R axis is involved in sleep regulation. Furthermore, we showed that the L-PGDS-PGD2-DP1R axis is beneficial in protecting the brain from ischemic stroke. Protein sequence homology was also performed, and it was found that L-PGDS and DP1R share a high degree of homology between humans and rodents. Based on the preclinical and clinical data thus far pertaining to the role of the L-PGDS-PGD2-DP1R axis in sleep regulation and neurologic conditions, there is optimism that this axis may have a high translational potential in human therapeutics. Therefore, here the focus is to review the regulation of the homeostatic component of the sleep process with a special focus on the L-PGDS-PGD2-DP1R axis and the consequences of sleep deprivation on health outcomes. Furthermore, we discuss whether the pharmacological regulation of this axis could represent a tool to prevent sleep disturbances and potentially improve outcomes, especially in patients with acute brain injuries.

Neuroscience: To Eat or to Sleep?

Energy and sleep homeostasis are entwined, each capable of exerting priority based on need. The identification of central nodes involved in the appropriate orchestration of these systems is critical to our understanding of how the brain regulates behavior.

Hypothalamic Neurons that Regulate Feeding Can Influence Sleep/Wake States Based on Homeostatic Need

Eating and sleeping represent two mutually exclusive behaviors that satisfy distinct homeostatic needs. Because an animal cannot eat and sleep at the same time, brain systems that regulate energy homeostasis are likely to influence sleep/wake behavior. Indeed, previous studies indicate that animals adjust sleep cycles around periods of food need and availability. Furthermore, hormones that affect energy homeostasis also affect sleep/wake states: the orexigenic hormone ghrelin promotes wakefulness, and the anorexigenic hormones leptin and insulin increase the duration of slow-wave sleep. However, whether neural populations that regulate feeding can influence sleep/wake states is unknown. The hypothalamic arcuate nucleus contains two neuronal populations that exert opposing effects on energy homeostasis: agouti-related protein (AgRP)-expressing neurons detect caloric need and orchestrate food-seeking behavior, whereas activity in pro-opiomelanocortin (POMC)-expressing neurons induces satiety. We tested the hypotheses that AgRP neurons affect sleep homeostasis by promoting states of wakefulness, whereas POMC neurons promote states of sleep. Indeed, optogenetic or chemogenetic stimulation of AgRP neurons in mice promoted wakefulness while decreasing the quantity and integrity of sleep. Inhibition of AgRP neurons rescued sleep integrity in food-deprived mice, highlighting the physiological importance of AgRP neuron activity for the suppression of sleep by hunger. Conversely, stimulation of POMC neurons promoted sleep states and decreased sleep fragmentation in food-deprived mice. Interestingly, we also found that sleep deprivation attenuated the effects of AgRP neuron activity on food intake and wakefulness. These results indicate that homeostatic feeding neurons can hierarchically affect behavioral outcomes, depending on homeostatic need.

Ghrelin and its interactions with growth hormone, leptin and orexins: implications for the sleep-wake cycle and metabolism

Several studies have shown that ghrelin administration promotes wakefulness in rodents, while in human males it induces sleep but has no effect in women. Ghrelin also plays an important role in metabolism and appetite regulation, and as described in this review may participate in the energy balance during sleep. In this review, we summarize some of the effects induced by ghrelin administration on the sleep-wake cycle in relation to the effects of other hormones, such as growth hormone, leptin, and orexin. Finally we discuss the relationship between sleep deprivation, obesity and ghrelin secretion pattern.

Sodium oxybate for the treatment of fibromyalgia

INTRODUCTION

Gamma-hydroxybutyrate (GHB) is a short-chain fatty acid that is synthesized within the CNS, mostly from its parent compound gamma amino butyric acid (GABA). GHB acts as a neuromodulator/neurotransmitter to affect neuronal activity of other neurotransmitters and so, stimulate the release of growth hormone. Its sodium salt (sodium oxybate: SXB) was approved by the Food and Drug Administration (FDA) for the treatment of narcolepsy. SXB has shown to improve disrupted sleep and increase NR3 (slow-wave restorative) sleep in patients with narcolepsy. It is rapidly absorbed and has a plasma half-life of 30 - 60 min, necessitating twice-nightly dosing. Most of the observed effects of SXB result from binding to GABA-B receptors.

AREAS COVERED

Several randomized, controlled trials demonstrated significantly improved fibromyalgia (FM) symptoms with SXB. As seen in narcolepsy trials, SXB improved sleep of FM patients, increased slow-wave sleep duration as well as delta power, and reduced frequent night-time awakenings. Furthermore, FM pain and fatigue was consistently reduced with nightly SXB over time. Commonly reported adverse events included headache, nausea, dizziness and somnolence. Despite its proven efficacy, SXB did not receive FDA approval for the management of FM in 2010, mostly because of concerns about abuse.

EXPERT OPINION

Insomnia, fatigue and pain are important clinical FM symptoms that showed moderate improvements with SXB in several large, well-designed clinical trials. Because of the limited efficacy of currently available FM drugs additional treatment options are needed. In particular, drugs like SXB - which belong to a different drug class than other Food and Drug Administration (FDA)-approved FM medications such as pregabalin, duloxetine and milnacipran - would provide a much-needed addition to presently available treatment options. However, the FDA has set the bar high for future SXB re-submissions, with requirements of superior efficacy and improved risk mitigation strategies. At this time, no future FDA submission of SXB for the fibromyalgia indication is planned.

THE RELATIONSHIP OF HRV TO SLEEP EEG AND SLEEP RHYTHM

Previous studies have shown that there exists a cycle of NREM (non-rapid eye movement)-REM (rapid eye movement) during normal human sleep, and heart rate variability (HRV) has a close relationship to sleep stages and sleep cycle. This article reports the relationship between the electroencephalographic activity and the HRV spectral power in several specific frequency bands. The authors discovered that relationships do exist between HRV and electroencephalogram (EEG) during sleep. In particular, it was found that, prior to the changes of EEG, the changes of HRV usually indicate the shift of sleep stages. HRV frequency analysis indicates that the very-low-frequency components of HRV are closely related to sleep EEG. Results show that the rhythm of the spectral power oscillations in some specific frequency bands of HRV is almost the same as the sleep cycle, which reflects the rhythm of sleep to a certain extent.

Administration of the protein synthesis inhibitor, anisomycin, has distinct sleep-promoting effects in lateral preoptic and perifornical hypothalamic sites in rats

Although a robust relationship between sleep and increased brain protein synthesis is well-documented, there have been few reports of the effects of local application of a protein synthesis inhibitor (PSI) on sleep. In this study, we compared the effects of local microdialytic administration of the protein synthesis inhibitor, anisomycin (ANI) into the lateral preoptic area (LPOA), a sleep promoting area vs. the perifornical/lateral hypothalamus (PF/LH), a wake and rapid eye movement (REM) sleep-promoting area. ANI administered to the LPOA at night resulted in an increase in stage 2 of rat non-REM sleep, whereas ANI delivered into the PF/LH during the daytime increased REM sleep. ANI microdialysis into hippocampus did not affect sleep or waking. These differential effects of local protein synthesis inhibition on sleep support a hypothesis that mechanisms controlling protein synthesis are critically involved in the regulation of both NREM sleep and REM sleep.

Potential participation of cystatin C in rapid eye movement sleep (REMS) modulation

It has been hypothesized that proteins modulate rapid eye movement sleep (REMS). Studies have shown an increase in the liberation of proteins in the mesencephalic reticular formation of cats during REMS. It has also been determined that protein-synthesis inhibitors diminish REMS and that protease-inhibitors increase this sleep phase. These and other studies support the importance of "di novo" protein molecules in sleep, and in particular, in REMS regulation. In this context, it is important to determine the role of endogenous proteases and their endogenous inhibitors in sleep regulation. In this study, we found that Cystatin C (CC), an endogenous protease inhibitor, diminishes wakefulness and increases REMS. We have also found an increase in CC expression after REMS deprivation and a tendency to decrease after a 2 h period of REMS rebound. We further showed that REMS deprivation increases the expression of Cathepsin H (CH), a protease inhibited by CC. These results suggest that naturally occurring protease-inhibitors enhance REMS, perhaps by facilitating the availability of proteins.

Sleep in captive chimpanzee (Pan troglodytes): the effects of individual and environmental factors on sleep duration and quality

Various abiotic and social factors are hypothesized to influence sleep in primates. Chimpanzee sleeping behavior has been examined only in a limited fashion, both in the wild and in captivity. Previous research, however limited, has suggested that chimpanzee sleep is non-dynamic. This study used an objective behavioral model of sleep as a framework in which to test the hypothesis that changes in individual (age and sex) and environmental (temperature and humidity) factors influence sleep patterns in 20 captive chimpanzees. The nocturnal behavior of the subjects was recorded continuously using video cameras equipped with enhanced nighttime visibility connected to time-lapse videocassette recorders. Chimpanzees in this study slept 8.81 h per night, close to the averages reported for both industrialized and traditional human societies (7-9h), as opposed to that of previous chimpanzee studies (11-12h). Also, the idea that chimpanzees sleep in one continuous period with little to no nocturnal awakenings was also refuted. Captive chimpanzee sleep behavior was, in fact, dynamic and complex with frequent awakenings. Older chimpanzees slept longer, had higher sleep quality, and shorter nighttime disturbances than prime adult chimpanzees. Finally, ambient temperature and humidity affected sleep duration and quality. The results of this study reveal that chimpanzee sleep behaviors are complicated interactions between both intrinsic and extrinsic factors.

Toward an integrative theory of sleep and dreaming

Non-rapid-eye-movement sleep (NREMS) is triggered by the accumulation of adenosine, as a result of the perceptual overload of the brain cortex. NREMS starts in the most burdened regions of the cortex first and then eventually, after the released adenosine has reached the ventrolateral pre-optic nucleus area of the hypothalamus, triggers the "general NREMS pattern". This is accompanied by the usual familiar changes in the thalamocortical system. When NREMS reaches the slow-wave sleep (SWS) phase, with its predominant delta activity, brain metabolism drops significantly with the brain temperature, and this is recognized by the alarm system in the pre-optic anterior hypothalamus and/or the other thermostat circuit in the brainstem as a life-threatening situation. This alarm system triggers a reaction similar to abortive or partial awakening called rapid-eye-movement sleep (REMS), which is aimed at restoring the optimal body-core temperature. As soon as this restoration is accomplished by the activation of the brainstem-to-cortex ascending pathways, NREMS may continue, as may the interchange of the two sleep phases during the entire sleep period. During both NREMS and REMS, the same essential pattern occurs in the cortex: the loops "used" during the previous waking period, now deprived of external input, replay their waking activity at a lower frequency, one which enables them to restore the membrane's potential (possibly by means of LTD). During REMS, however, the cholinergic flood originating in the LTD/PPT nuclei of the pons tegmentum, increases in the basal forebrain and, provoking theta activity in the medial septum is extended to the hippocampus, causing the circuits that are active at that particular moment in the cortex, to store the information they carry as memory. This is the explanation of both the memory improvement known to be related to REMS and of dreams. Both phenomena are clearly side effects of REMS.

Brainstem prolactin mRNA is enhanced in mice with suppressed neuronal nitric oxide synthase activity

Prolactin (PRL) and vasoactive intestinal polypeptide (VIP) mRNA levels were elevated in the brainstem of neuronal nitric oxide synthase (nNOS) gene knockout (KO) mice compared to the levels in nNOS control mice. In addition, PRL mRNA levels increased in the hypothalamus and the brainstem of nNOS control mice after administration of 7-nitro-indazole (7-NI), a relatively selective nNOS inhibitor. The results suggest that NO inhibits PRL. No differences in the genes measured were observed in inducible NOS KO mice.

Sleep disturbance and nonmalignant chronic pain: a comprehensive review of the literature

Sleep disturbance is an important clinical complaint for individuals with nonmalignant pain conditions. This review is a broad introduction to the literature on sleep disturbance and chronic pain conditions. The article critically reviews studies of sleep disturbance in musculoskeletal pain, arthritis, headache, and fibromyalgia. Current neurobiological hypotheses regarding the pathogenesis of sleep disturbance and chronic pain, common comorbid disorders, and pharmacologic and non-pharmacologic treatments for sleep disturbance are reviewed.

Potential role of the cannabinoid receptor CB1 in rapid eye movement sleep rebound

Sleep is an unavoidable activity of the brain. The delay of the time to sleep (sleep deprivation), induces an increase of slow-wave sleep and rapid-eye-movement (REM) sleep (rebound) once the subject is allowed to sleep. This drive to sleep has been hypothesized to be dependent on the accumulation of sleep-inducing molecules and on the high expression of these molecule receptors. In this study we selectively deprived rats of REM sleep for 24 h by using the flowerpot technique. One group deprived of REM sleep was treated with SR141716A, a cannabinoid receptor 1 (CB1) receptor antagonist and then allowed to sleep for the next 4 h. Two other groups were killed, one immediately after the REM sleep deprivation period and the other after 2 h of REM sleep rebound (REM sleep deprivation plus 2 h of rebound). In both groups we determined the expression of the CB1 receptor and its mRNA. Results indicated that SR141716A prevents REM sleep rebound and REM sleep deprivation does not modify the expression of the CB1 protein or mRNA. However, REM sleep deprivation plus 2 h of sleep rebound increased the CB1 receptor protein and, slightly but significantly, decreased mRNA expression. These results suggest that endocannabinoids may be participating in the expression of REM sleep rebound.

Systemic injection of a nitric oxide synthase inhibitor suppresses sleep responses to sleep deprivation in rats

We hypothesized that nitric oxide (NO) may play a role in homeostatic sleep regulation. To test this hypothesis, we studied the sleep deprivation (SD)-induced homeostatic sleep responses after intraperitoneal administration of an NO synthase inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME, a cumulative dose of 100 mg/kg). Amounts and intensity of sleep were increased in response to 8 h of SD in control rats (n = 8). Sleep amounts remained above baseline for 16 h after SD followed by a negative rebound. Rapid eye movement sleep (REMS) and non-REMS (NREMS) intensities were elevated for 16 and 4 h, respectively. L-NAME treatment (n = 8) suppressed the rebound increases in NREMS amount and intensity. REMS rebound was attenuated by L-NAME in the first dark period after SD; however, a second rebound appeared in the subsequent dark period. REMS intensity did not increase after SD in L-NAME-injected rats. The finding that the NO synthase inhibitor suppressed rebound increases in NREMS suggests that NO may play a role as a signaling molecule in homeostatic regulation of NREMS.