Sleep and metabolism: role of hypothalamic neuronal circuitry

Sleep quality in relation to perceived psychological stress in patients with type 2 diabetes and in age- and sex-matched control individuals

AIM

To assess sleep quality in relation to perceived stress in patients with type 2 diabetes (T2DM) and age- and sex-matched controls.

METHODS

Perceived stress level and sleep quality assessed in 154 patients with T2DM (58 men, 96 women, age 58.3 ± 11.9 years), 154 matched controls (58 men, 96 women, age 56.8 ± 12.2 years) using Perceived Stress Scale and Pittsburgh Sleep Quality Index.

RESULTS

Patients with T2DM had worse subjective sleep quality (p < 0.001), sleep latency (p = 0.047) than controls. Patients with high stress level had worse subjective sleep quality (p = 0.027), higher use of sleeping medication (p = 0.023), daytime dysfunction (p < 0.001) than those with low stress level. No significant differences in sleep quality between controls with high and low perceived stress level. Perceived stress level in patients with T2DM correlated with subjective sleep quality (r = 0.260, p = 0.002), sleep duration (r = 0.228, p = 0.005), use of sleep medication (r = 0.245, p = 0.004), daytime dysfunction (r = 0.326, p < 0.001), in age- and sex-matched controls-to daytime dysfunction (r = 0.191, p = 0.037).

CONCLUSION

Sleep quality (subjective sleep quality, sleep latency) is worse in patients with type 2 diabetes than in age- and sex-matched controls. Patients with high perceived stress level have worse subjective sleep quality, higher use of sleeping medication, daytime dysfunction than patients with low perceived stress level; no significant differences in sleep quality between controls with high and low stress level. Perceived stress level in patients with type 2 diabetes is related to subjective sleep quality, sleep duration, use of sleep medication, daytime dysfunction, in age- and sex-matched controls-to daytime dysfunction.

Orexin and MCH neurons: regulators of sleep and metabolism

Sleep-wake and fasting-feeding are tightly coupled behavioral states that require coordination between several brain regions. The mammalian lateral hypothalamus (LH) is a functionally and anatomically complex brain region harboring heterogeneous cell populations that regulate sleep, feeding, and energy metabolism. Significant attempts were made to understand the cellular and circuit bases of LH actions. Rapid advancements in genetic and electrophysiological manipulation help to understand the role of discrete LH cell populations. The opposing action of LH orexin/hypocretin and melanin-concentrating hormone (MCH) neurons on metabolic sensing and sleep-wake regulation make them the candidate to explore in detail. This review surveys the molecular, genetic, and neuronal components of orexin and MCH signaling in the regulation of sleep and metabolism.

Mental Health Conditions According to Stress and Sleep Disorders

The purpose of this study was to compare associations between stress and sleep disorders (insomnia, hypersomnia, and sleep apnea), identify potential modifying effects, and compare associations between stress and types of sleep disorders with selected mental health conditions. Analyses were based on 21,027 employees aged 18–64 years in 2020 who were insured by the Deseret Mutual Benefit Administrators (DMBA). The risk of stress (2.3%) was significantly greater in women, singles, and those with dependent children. The risk of a sleep disorder was 12.1% (2.1% for insomnia, 1.0% for hypersomnia, and 10.1% for sleep apnea). The risk of stress was significantly greater for those with a sleep disorder (136% overall, 179% for insomnia, and 102% for sleep apnea after adjusting for age, sex, marital status, dependent children, and sleep disorders). The risk of stress among those with sleep apnea was significantly greater for singles than for married individuals. Approximately 9.5% had anxiety, 8.5% had depression, 2.0% had ADHD, 0.6% had bipolar disorder, 0.4% had OCD, and 0.1% had schizophrenia. Each of these mental health conditions was significantly positively associated with stress and sleep disorders. Bipolar disorder and schizophrenia were more strongly associated with stress and sleep disorders than were the other mental health conditions. Insomnia was more strongly associated with anxiety, bipolar disorder, OCD, and schizophrenia than was sleep apnea.

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.

Sex-specific association of sleep duration with subclinical indicators of metabolic diseases among asymptomatic adults

Background

Accumulating evidence suggests sleep duration may be involved in metabolic regulation. However, studies regarding the association with the early stage of the metabolic disease are limited, and the findings were inconsistent.

Methods

A study among 4922 asymptomatic adults was conducted based on a Chinese national survey in 2009. The early stage of metabolic diseases was evaluated using three proxies: triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C), the product of triglyceride and fasting glucose (TyG), and lipid accumulation product (LAP). Multivariable linear and logistic regression models were used to explore the associations of sleep duration with the three indicators.

Results

The linear regression models revealed that, among females, sleep duration <7 h per day, compared with 7-9 h, was associated with an increased value of LAP and TyG by 25.232% (95%CI: 10.738%, 41.623%) and 0.104 (95%CI: 0.024, 0.185), respectively, in the crude model. The effects were attenuated but remained significant for LAP (11.405%; 95%CI: 1.613%, 22.262%). Similarly, the logistic regression models further found that sleep duration <7 h per day could increase the risk of elevated LAP (OR: 1.725, 95CI%:1.042, 2.856) after adjusting for multiple covariates. By contrast, no associations were found among males.

Conclusions

Short sleep duration was associated with subclinical indicators of metabolic diseases, and females were more susceptible to the association.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-022-01626-w.

Was it something I ate? Understanding the bidirectional interaction of migraine and appetite neural circuits

Migraine attacks can involve changes of appetite: while fasting or skipping meals are often reported triggers in susceptible individuals, hunger or food craving are reported in the premonitory phase. Over the last decade, there has been a growing interest and recognition of the importance of studying these overlapping fields of neuroscience, which has led to novel findings. The data suggest additional studies are needed to unravel key neurobiological mechanisms underlying the bidirectional interaction between migraine and appetite. Herein, we review information about the metabolic migraine phenotype and explore migraine therapeutic targets that have a strong input on appetite neuronal circuits, including the calcitonin gene-related peptide (CGRP), the pituitary adenylate cyclase-activating polypeptide (PACAP) and the orexins. Furthermore, we focus on potential therapeutic peptide targets that are involved in regulation of feeding and play a role in migraine pathophysiology, such as neuropeptide Y, insulin, glucagon and leptin. We then examine the orexigenic - anorexigenic circuit feedback loop and explore glucose metabolism disturbances. Additionally, it is proposed a different perspective on the most reported feeding-related trigger - skipping meals - as well as a link between contrasting feeding behaviors (skipping meals vs food craving). Our review aims to increase awareness of migraine through the lens of appetite neurobiology in order to improve our understanding of the earlier phase of migraine, encourage better studies and cross-disciplinary collaborations, and provide novel migraine-specific therapeutic opportunities.

A Novel Insight of Effects of a 3-Hz Binaural Beat on Sleep Stages During Sleep

The dichotic presentation of two almost equivalent pure tones with slightly different frequencies leads to virtual beat perception by the brain. In this phenomenon, the so-called binaural beat has a frequency equaling the difference of the frequencies of the two pure tones. The binaural beat can entrain neural activities to synchronize with the beat frequency and induce behavioral states related to the neural activities. This study aimed to investigate the effect of a 3-Hz binaural beat on sleep stages, which is considered a behavioral state. Twenty-four participants were allocated to experimental and control groups. The experimental period was three consecutive nights consisting of an adaptation night, a baseline night, and an experimental night. Participants in both groups underwent the same procedures, but only the experimental group was exposed to the 3-Hz binaural beat on the experimental night. The stimulus was initiated when the first epoch of the N2 sleep stage was detected and stopped when the first epoch of the N3 sleep stage detected. For the control group, a silent sham stimulus was used. However, the participants were blinded to their stimulus group. The results showed that the N3 duration of the experimental group was longer than that of the control group, and the N2 duration of the experimental group was shorter than that of the control group. Moreover, the N3 latency of the experimental group was shorter.

Mice Lacking Alternatively Activated (M2) Macrophages Show Impairments in Restorative Sleep after Sleep Loss and in Cold Environment

The relationship between sleep, metabolism and immune functions has been described, but the cellular components of the interaction are incompletely identified. We previously reported that systemic macrophage depletion results in sleep impairment after sleep loss and in cold environment. These findings point to the role of macrophage-derived signals in maintaining normal sleep. Macrophages exist either in resting form, classically activated, pro-inflammatory (M1) or alternatively activated, anti-inflammatory (M2) phenotypes. In the present study we determined the contribution of M2 macrophages to sleep signaling by using IL-4 receptor α-chain-deficient [IL-4Rα knockout (KO)] mice, which are unable to produce M2 macrophages. Sleep deprivation induced robust increases in non-rapid-eye-movement sleep (NREMS) and slow-wave activity in wild-type (WT) animals. NREMS rebound after sleep deprivation was ~50% less in IL-4Rα KO mice. Cold exposure induced reductions in rapid-eye-movement sleep (REMS) and NREMS in both WT and KO mice. These differences were augmented in IL-4Rα KO mice, which lost ~100% more NREMS and ~25% more REMS compared to WTs. Our finding that M2 macrophage-deficient mice have the same sleep phenotype as mice with global macrophage depletion reconfirms the significance of macrophages in sleep regulation and suggests that the main contributors are the alternatively activated M2 cells.

Pathophysiology of Migraine: A Disorder of Sensory Processing

Plaguing humans for more than two millennia, manifest on every continent studied, and with more than one billion patients having an attack in any year, migraine stands as the sixth most common cause of disability on the planet. The pathophysiology of migraine has emerged from a historical consideration of the "humors" through mid-20th century distraction of the now defunct Vascular Theory to a clear place as a neurological disorder. It could be said there are three questions: why, how, and when? Why: migraine is largely accepted to be an inherited tendency for the brain to lose control of its inputs. How: the now classical trigeminal durovascular afferent pathway has been explored in laboratory and clinic; interrogated with immunohistochemistry to functional brain imaging to offer a roadmap of the attack. When: migraine attacks emerge due to a disorder of brain sensory processing that itself likely cycles, influenced by genetics and the environment. In the first, premonitory, phase that precedes headache, brain stem and diencephalic systems modulating afferent signals, light-photophobia or sound-phonophobia, begin to dysfunction and eventually to evolve to the pain phase and with time the resolution or postdromal phase. Understanding the biology of migraine through careful bench-based research has led to major classes of therapeutics being identified: triptans, serotonin 5-HT1B/1D receptor agonists; gepants, calcitonin gene-related peptide (CGRP) receptor antagonists; ditans, 5-HT1F receptor agonists, CGRP mechanisms monoclonal antibodies; and glurants, mGlu5 modulators; with the promise of more to come. Investment in understanding migraine has been very successful and leaves us at a new dawn, able to transform its impact on a global scale, as well as understand fundamental aspects of human biology.

Sleep-Dependent Structural Synaptic Plasticity of Inhibitory Synapses in the Dendrites of Hypocretin/Orexin Neurons

Sleep is tightly regulated by the circadian clock and homeostatic mechanisms. Although the sleep/wake cycle is known to be associated with structural and physiological synaptic changes that benefit the brain, the function of sleep is still debated. The hypothalamic hypocretin/orexin (Hcrt) neurons regulate various functions including feeding, reward, sleep, and wake. Continuous imaging of single neuronal circuits in live animals is vital to understanding the role of sleep in regulating synaptic dynamics, and the transparency of the zebrafish model enables time-lapse imaging of single synapses during both day and night. Here, we use the gephyrin (Gphnb) protein, a central inhibitory synapse organizer, as a fluorescent post-synaptic marker of inhibitory synapses. Double labeling showed that Gphnb-tagRFP and collybistin-EGFP clusters co-localized in dendritic inhibitory synapses. Using a transgenic hcrt:Gphnb-EGFP zebrafish, we showed that the number of inhibitory synapses in the dendrites of Hcrt neurons was increased during development. To determine the effect of sleep on the inhibitory synapses, we performed two-photon live imaging of Gphnb-EGFP in Hcrt neurons during day and night, under light/dark and constant light and dark conditions, and following sleep deprivation (SD). We found that synapse number increased during the night under light/dark conditions but that these changes were eliminated under constant light or dark conditions. SD reduced synapse number during the night, and the number increased during post-deprivation daytime sleep rebound. These results suggest that rhythmic structural plasticity of inhibitory synapses in Hcrt dendrites is independent of the circadian clock and is modulated by consolidated wake and sleep.

Clinical Relevance of Sleep Duration: Results from a Cross-Sectional Analysis Using NHANES

STUDY OBJECTIVES

To assess the clinical relevance of sleep duration, hours slept were compared by health status, presence of insomnia, and presence of depression, and the association of sleep duration with BMI and cardiovascular risk was quantified.

METHODS

Cross-sectional analysis of subjects in the US National Health and Nutrition Examination Surveys using adjusted linear and logistic regressions.

RESULTS

A total of 22,281 adults were included, 37% slept ≤ 6 hours, 36% were obese, and 45% reported cardiovascular conditions. Mean sleep duration was 6.87 hours. Better health was associated with more hours of sleep. Subjects with poor health reported sleeping 46 min, (95% CI -56.85 to -35.67) less than subjects with excellent health. Individuals with depression (vs. not depressed) reported 40 min less sleep, (95% CI -47.14 to -32.85). Individuals with insomnia (vs. without insomnia) reported 39 min less sleep, (95% CI -56.24 to -22.45). Duration of sleep was inversely related to BMI; for every additional hour of sleep, there was a decrease of 0.18 kg/m(2) in BMI, (95% CI -0.30 to -0.06). The odds of reporting cardiovascular problems were 6.0% lower for every hour of sleep (odds ratio = 0.94, 95% CI [0.91 to 0.97]). Compared with subjects who slept ≤ 6 h, subjects who slept more had lower odds of reporting cardiovascular problems, with the exception of subjects ≥ 55 years old who slept ≥ 9 hours.

CONCLUSIONS

Long sleep duration is associated with better health. The fewer the hours of sleep, the greater the BMI and reported cardiovascular disease. A difference of 30 minutes of sleep is associated with substantive impact on clinical well-being.

Hypocretin neuron-specific transcriptome profiling identifies the sleep modulator Kcnh4a

Sleep has been conserved throughout evolution; however, the molecular and neuronal mechanisms of sleep are largely unknown. The hypothalamic hypocretin/orexin (Hcrt) neurons regulate sleep\wake states, feeding, stress, and reward. To elucidate the mechanism that enables these various functions and to identify sleep regulators, we combined fluorescence cell sorting and RNA-seq in hcrt:EGFP zebrafish. Dozens of Hcrt-neuron–specific transcripts were identified and comprehensive high-resolution imaging revealed gene-specific localization in all or subsets of Hcrt neurons. Clusters of Hcrt-neuron–specific genes are predicted to be regulated by shared transcription factors. These findings show that Hcrt neurons are heterogeneous and that integrative molecular mechanisms orchestrate their diverse functions. The voltage-gated potassium channel Kcnh4a, which is expressed in all Hcrt neurons, was silenced by the CRISPR-mediated gene inactivation system. The mutant kcnh4a (kcnh4a^-/-) larvae showed reduced sleep time and consolidation, specifically during the night, suggesting that Kcnh4a regulates sleep.

DOI:http://dx.doi.org/10.7554/eLife.08638.001

Sleep appears to be essential for all animals. The loss of a type of brain cell called the Hypocretin/Orexin (Hcrt) neurons causes the sleep disorder narcolepsy, which disturbs sleep patterns. These neurons also control several other fundamental behaviors and activities, including eating and processing rewards, but it is not clear how Hcrt neurons are able to influence multiple behaviors.

The development and activity of a cell depends to a large extent on the genes it expresses. Yelin-Bekerman et al. have now used genetic techniques to identify a set of genes that are specifically expressed in the Hcrt neurons of zebrafish. Some of these genes are expressed in all of the Hcrt neurons, and some are only expressed in certain subsets of them. Computational methods also revealed a set of “transcription factor” proteins that regulate the expression of clusters of these genes.

Yelin-Bekerman et al. focused on a gene called kcnh4a, and found that this encodes an ion channel protein that allows potassium ions to exit the neurons and stop neuronal activity (this activity is also known as an “action potential”). This gene is expressed in all Hcrt neurons. Further experiments showed that zebrafish that lack the potassium channel sleep less during the night. This therefore suggests that the potassium channel is important for regulating sleep.

Future studies of the genes that are enriched in Hcrt neurons could uncover the mechanisms that enable the neurons to play a role in such a diverse range of processes, including feeding and sleep-wake cycles. These studies should enhance our understanding of the role of sleep and may help to develop treatments for metabolic and sleep disorders.

DOI:http://dx.doi.org/10.7554/eLife.08638.002

Interactions between sleep, stress, and metabolism: From physiological to pathological conditions

Poor sleep quality due to sleep disorders and sleep loss is highly prevalent in the modern society. Underlying mechanisms show that stress is involved in the relationship between sleep and metabolism through hypothalamic–pituitary–adrenal (HPA) axis activation. Sleep deprivation and sleep disorders are associated with maladaptive changes in the HPA axis, leading to neuroendocrine dysregulation. Excess of glucocorticoids increase glucose and insulin and decrease adiponectin levels. Thus, this review provides overall view of the relationship between sleep, stress, and metabolism from basic physiology to pathological conditions, highlighting effective treatments for metabolic disturbances.

Hypothalamic leptin-neurotensin-hypocretin neuronal networks in zebrafish

Neurotensin (NTS) is a 13 amino acid neuropeptide that is expressed in the hypothalamus. In mammals, NTS-producing neurons that express leptin receptor (LepRb) regulate the function of hypocretin/orexin (HCRT) and dopamine neurons. Thus, the hypothalamic leptin-NTS-HCRT neuronal network orchestrates key homeostatic output, including sleep, feeding, and reward. However, the intricate mechanisms of the circuitry and the unique role of NTS-expressing neurons remain unclear. We studied the NTS neuronal networks in zebrafish and cloned the genes encoding the NTS neuropeptide and receptor (NTSR). Similar to mammals, the ligand is expressed primarily in the hypothalamus, while the receptor is expressed widely throughout the brain in zebrafish. A portion of hypothalamic nts-expressing neurons are inhibitory and some coexpress leptin receptor (lepR1). As in mammals, NTS and HCRT neurons are localized adjacently in the hypothalamus. To track the development and axonal projection of NTS neurons, the NTS promoter was isolated. Transgenesis and double labeling of NTS and HCRT neurons showed that NTS axons project toward HCRT neurons, some of which express ntsr. Moreover, another target of NTS neurons is ntsr-expressing dopaminergeric neurons. These findings suggest structural circuitry between leptin, NTS, and hypocretinergic or dopaminergic neurons and establish the zebrafish as a model to study the role of these neuronal circuits in the regulation of feeding, sleep, and reward.

History of narcolepsy at Stanford University

Although narcolepsy was first described in the late nineteenth century in Germany and France, much of the research on this disorder has been conducted at Stanford University, starting with Drs. William C. Dement and Christian Guilleminault in the 1970s. The prevalence of narcolepsy was established, and a canine model discovered. Following the finding in Japan that almost all patients with narcolepsy carry a specific HLA subtype, HLA-DR2, Hugh Mac Devitt, F. Carl Grumet, and Larry Steinman initiated immunological studies, but results were generally negative. Using the narcoleptic canines, Dr. Nishino and I established that stimulants increased wakefulness by stimulating dopaminergic transmission while antidepressants suppress cataplexy via adrenergic reuptake inhibition. A linkage study was initiated with Dr. Grumet in 1988, and after 10 years of work, the canine narcolepsy gene was cloned by in 1999 and identified as the hypocretin (orexin) receptor 2. In 1992, studying African Americans, we also found that DQ0602 rather than DR2 was a better marker for narcolepsy across all ethnic groups. In 2000, Dr. Nishino and I, in collaboration with Dr. Lammers in the Netherlands, found that hypocretin 1 levels in the cerebrospinal fluid (CSF) were undetectable in most cases, establishing hypocretin deficiency as the cause of narcolepsy. Pursuing this research, our and Dr. Siegel's group, examining postmortem brains, found that the decreased CSF hypocretin 1 was secondary to the loss the 70,000 neurons producing hypocretin in the hypothalamus. This finding revived the autoimmune hypothesis but attempts at demonstrating immune targeting of hypocretin cells failed until 2013. At this date, Dr. Elisabeth Mellins and I discovered that narcolepsy is characterized by the presence of autoreactive CD4(+) T cells to hypocretin fragments when presented by DQ0602. Following reports that narcolepsy cases were triggered by vaccinations and infections against influenza A 2009 pH1N1, a new pandemic strain that erupted in 2009, our groups also established that a small epitope of pH1N1 resembles hypocretin and is likely involved in molecular mimicry. Although much remains to be done, these achievements, establishing hypocretin deficiency as the cause of narcolepsy, demonstrating its autoimmune basis, and showing molecular mimicry between hypocretin and sequences derived from a pandemic strain of influenza, are likely to remain classics in human immunology.

Impact of obesity in children with narcolepsy

AIMS

To evaluate the impact of obesity on clinical and sleep characteristics in a population of narcoleptic children.

METHODS

Data from the children diagnosed with idiopathic narcolepsy in the National Reference Centers for Narcolepsy were collected between 2008 and 2011. Clinical and electrophysiological characteristics were compared between obese (body mass index [BMI] greater than P97) and nonobese children.

RESULTS

The 117 children (65 boys, 59 de novo patients) had a mean age of 11.6 ± 3.1 years on diagnosis. Cataplexy was present in 81%, DQB1*0602 in 91%. Mean BMI was 23.2 ± 5.2 kg/m(2) and BMI z-score was 2.9 ± 2.6. Obesity was found in 60% with a similar prevalence in treated versus de novo patients and in patients with and without cataplexy. Sleepiness and cataplexy started earlier in obese children. Obese narcoleptic children had lower sleep efficiency, higher apnea hypopnea index and respiratory arousals index (RAI) than nonobese children. BMI z-score was positively correlated with RAI. Obese children were more tired and missed more often school than nonobese children.

CONCLUSION

Obesity affects more than 50% of narcoleptic children, mostly younger at disease onset, and has a deleterious impact on sleep quality as well as on school attendance.

International Union of Basic and Clinical Pharmacology. LXXXVI. Orexin receptor function, nomenclature and pharmacology

Orexin signaling is essential for normal regulation of arousal and behavioral state control and represents an attractive target for therapeutics combating insomnia. Alternatively termed hypocretins, these neuropeptides were named to reflect sequence similarity to incretins and their potential to promote feeding. Current nomenclature reflects these molecular and biochemical discovery approaches in which HCRT, HCRTR1, and HCRTR2 genes encode prepro-orexin, the orexin 1 receptor (OX(1)) and the orexin 2 receptor (OX(2))-gene names designated by the Human Genome Organization and receptor names designated by the International Union of Basic and Clinical Pharmacology. Orexinergic neurons are most active during wakefulness and fall silent during inactive periods, a prolonged disruption in signaling most profoundly resulting in hypersomnia and narcolepsy. Hcrtr2 mutations underlie the etiology of canine narcolepsy, deficiencies in orexin-producing neurons are observed in the human disorder, and ablation of mouse orexin neurons or the Hcrt gene results in a narcolepsy-cataplexy phenotype. The development of orexin receptor antagonists and genetic models targeting components of the orexin pathway have elucidated the OX(2) receptor-specific role in histamine-mediated arousal and the contribution of both receptors in brainstem pathways involved in vigilance state gating. Orexin receptor antagonists of varying specificity uncovered additional roles beyond sleep and feeding that include addiction, depression, anxiety, and potential influences on peripheral physiology. Combined genetic and pharmacological approaches indicate that orexin signaling may represent a confluence of sleep, feeding, and reward pathways. Selective orexin receptor antagonism takes advantage of these properties toward the development of novel insomnia therapeutics.

Rapid eye movement sleep behavior disorder and subtypes of Parkinson's disease

Numerous studies have explored the potential relationship between rapid eye movement sleep behavior disorder (RBD) and manifestations of PD. Our aim was to perform an expanded extensive assessment of motor and nonmotor manifestations in PD to identify whether RBD was associated with differences in the nature and severity of these manifestations. PD patients underwent polysomnography (PSG) to diagnose the presence of RBD. Participants then underwent an extensive evaluation by a movement disorders specialist blinded to PSG results. Measures of disease severity, quantitative motor indices, motor subtypes, therapy complications, and autonomic, psychiatric, visual, and olfactory dysfunction were assessed and compared using regression analysis, adjusting for disease duration, age, and sex. Of 98 included patients, 54 had RBD and 44 did not. PD patients with RBD were older (P = 0.034) and were more likely to be male (P < 0.001). On regression analysis, the most consistent links between RBD and PD were a higher systolic blood pressure (BP) change while standing (-23.9 ± 13.9 versus -3.5 ± 10.9; P < 0.001), a higher orthostatic symptom score (0.89 ± 0.82 versus 0.44 ± 0.66; P = 0.003), and a higher frequency of freezing (43% versus 14%; P = 0.011). A systolic BP drop >10 could identify PD patients with RBD with 81% sensitivity and 86% specificity. In addition, there was a probable relationship between RBD and nontremor predominant subtype of PD (P = 0.04), increased frequency of falls (P = 0.009), and depression (P = 0.009). Our results support previous findings that RBD is a multifaceted phenomenon in PD. Patients with PD who have RBD tend to have specific motor and nonmotor manifestations, especially orthostatic hypotension.

Olanzapine causes a leptin-dependent increase in acetylcholine release in mouse prefrontal cortex

STUDY OBJECTIVES

The atypical antipsychotic olanzapine is used effectively for treating symptoms of schizophrenia and bipolar disorder. Unwanted effects of olanzapine include slowing of the electroencephalogram (EEG) during wakefulness and increased circulating levels of leptin. The mechanisms underlying the desired and undesired effects of olanzapine are poorly understood. Sleep and wakefulness are modulated by acetylcholine (ACh) in the prefrontal cortex, and leptin alters cholinergic transmission. This study tested the hypothesis that olanzapine interacts with leptin to regulate ACh release in the prefrontal cortex.

DESIGN

Within/between subjects.

SETTING

University of Michigan.

PATIENTS OR PARTICIPANTS

Adult male C57BL/6J (B6) mice (n = 33) and B6.V-Lep(ob) (leptin-deficient) mice (n = 31).

INTERVENTIONS

Olanzapine was delivered to the prefrontal cortex by microdialysis. Leptin-replacement in leptin-deficient mice was achieved using subcutaneous micro-osmotic pumps.

MEASUREMENTS AND RESULTS

Olanzapine caused a concentration-dependent increase in ACh release in B6 and leptin-deficient mice. Olanzapine was 230-fold more potent in leptin-deficient than in B6 mice for increasing ACh release, yet olanzapine caused a 51% greater ACh increase in B6 than in leptin-deficient mice. Olanzapine had no effect on recovery time from general anesthesia. Olanzapine increased EEG power in the delta (0.5-4 Hz) range. Thus, olanzapine dissociated the normal coupling between increased cortical ACh release, increased behavioral arousal, and EEG activation. Leptin replacement significantly enhanced (75%) the olanzapine-induced increase in ACh release.

CONCLUSION

Replacing leptin by systemic administration restored the olanzapine-induced enhancement of ACh release in the prefrontal cortex of leptin-deficient mouse.

Sleep and metabolic function

Evidence for the role of sleep on metabolic and endocrine function has been reported more than four decades ago. In the past 30 years, the prevalence of obesity and diabetes has greatly increased in industrialized countries, and self-imposed sleep curtailment, now very common, is starting to be recognized as a contributing factor, alongside with increased caloric intake and decreased physical activity. Furthermore, obstructive sleep apnea, a chronic condition characterized by recurrent upper airway obstruction leading to intermittent hypoxemia and sleep fragmentation, has also become highly prevalent as a consequence of the epidemic of obesity and has been shown to contribute, in a vicious circle, to the metabolic disturbances observed in obese patients. In this article, we summarize the current data supporting the role of sleep in the regulation of glucose homeostasis and the hormones involved in the regulation of appetite. We also review the results of the epidemiologic and laboratory studies that investigated the impact of sleep duration and quality on the risk of developing diabetes and obesity, as well as the mechanisms underlying this increased risk. Finally, we discuss how obstructive sleep apnea affects glucose metabolism and the beneficial impact of its treatment, the continuous positive airway pressure. In conclusion, the data available in the literature highlight the importance of getting enough good sleep for metabolic health.