Novel biochemical manipulation of brain serotonin reveals a role of serotonin in the circadian rhythm of sleep-wake cycles

Acupuncture in circadian rhythm sleep-wake disorders and its potential neurochemical mechanisms

Circadian rhythm sleep-wake disorders (CRSWDs) are becoming increasingly common in modern societies due to lifestyle changes. The detrimental effects of CRSWDs on sleep and psychological health have attracted considerable attention recently. Alternative remedies for the treatment of CRSWDs have also gained attention in recent years owing to the limitations of medications. Several in vivo and clinical investigations have shown that acupuncture, one of the most important components of traditional Chinese medicine (TCM), has been shown to modulate sleep-related circadian rhythms. Owing to the lack of research on the mechanism and effectiveness of acupuncture in treating CRSWDs, clinical applications of acupuncture have not gained popularity. This paper reviews the acupuncture methods, acupoint selection, and biochemical indicators supplied by in vivo and clinical studies to explore the effectiveness of acupuncture, and summarizes the circadian rhythm mechanisms and the acupuncture characteristics on circadian rhythm. The neurochemical mechanisms linked to acupuncture in treating CRSWDs are also outlined from the perspective of the central and peripheral biological clocks. Lastly, the inadequacy of previous studies on CRSWDs and conflicting results regarding acupuncture are explored and future research directions are envisioned.

Antibiotic exposure associated with nighttime sleep duration and daytime sleepiness in newlyweds

Few studies have explored the relationship between antibiotic exposure and sleep in newlyweds. We applied the actor-partner interdependence moderation model to estimate the relationships of antibiotic exposure with nighttime sleep duration (weekday, weekend, and average sleep durations) and daytime sleepiness in newlyweds. We found that 99.0% of the 2698 enrolled individuals were exposed to at least one antibiotic. Among the newlyweds, exposure to florfenicol (β, - 0.077; 95% confidence interval [CI], - 0.143, - 0.011), exposure to chloramphenicols (- 0.086 [- 0.160, - 0.011]), and exposure to veterinary antibiotics (VAs) (- 0.106 [- 0.201, - 0.010]) were negatively associated with weekday sleep duration. Florfenicol, chloramphenicols, and VAs were also inversely related to average sleep duration in the newlyweds. Ciprofloxacin and cyadox exposure was significantly associated with an increase of 0.264 (0.030, 0.497) and (0.375 [0.088, 0.663]) Epworth Sleepiness Scale (ESS) scores in the newlyweds, respectively. Gender moderated the actor-partner effects of erythromycin and tetracyclines on the newlyweds' weekday sleep duration and ESS scores. Overall, exposure to florfenicol, chloramphenicols, and VAs shortened weekday and average sleep durations of newlyweds. Exposure to ciprofloxacin and cyadox promoted daytime sleepiness. Gender moderated the actor-partner effects of specific antibiotics on the weekday sleep duration and ESS scores of the newlyweds.

Correlation Between Chronotypes and Depressive Symptoms Mediated by Sleep Quality Among Chinese College Students During the COVID-19 Pandemic

Purpose

The COVID-19 pandemic has adversely impacted the mental health of the population. The current study aimed to determine the prevalence of depressive symptoms and sleep disturbances among Chinese college students during the COVID-19 pandemic and investigate the correlations between chronotypes, sleep quality, and depressive symptoms.

Participants and Methods

In the current study, 2526 college students responded anonymously to an online questionnaire survey from 26 May 2020 to 20 July 2020. The participants' chronotypes, sleep quality, and depressive symptoms were evaluated using the Chinese version of the Morning and Evening Questionnaire-5 (MEQ-5), Pittsburgh Sleep Quality Index (PSQI), and Patient Health Questionnaire-9 (PHQ-9). Sociodemographic information of the participants was also acquired. Statistical analyses were performed using Statistical Package for Social Sciences (SPSS) 19.0 software, with the mediating effect assessed by Hayes' PROCESS Macro.

Results

During the COVID-19 pandemic, the prevalence of depressive symptoms and sleep disturbances among Chinese college students surveyed was 54.95% and 48.18%, respectively. From absolute evening chronotype to absolute morning chronotype, the surveyed college students' chronotypes were negatively correlated with their depressive symptoms. Moreover, the mediation analysis showed that the correlation between chronotypes and depressive symptoms was fully mediated by sleep quality. Eveningness college students with poorer sleep quality were more likely to report higher levels of depressive symptoms.

Conclusion

Our findings suggest that during the COVID-19 pandemic, delayed circadian preference (ie, eveningness) may be linked to worse depressive symptoms among Chinese college students, and call for more attention to the sleep quality of Chinese college students as sleep quality fully mediated the correlation between chronotypes and depressive symptoms among them. Reasonable adjustment in bedtime/circadian preference and improvement in sleep quality may help to reduce the prevalence and severity of depressive symptoms among Chinese college students.

Simultaneous determination of serum tryptophan metabolites in an older Chinese population

Tryptophan (TRP) and its metabolites exhibit significant biological effects and are strongly associated with age-related disease and mortality. However, reports on quantitatively analyzing these metabolites in older individuals are not available. We used ultra-high-performance liquid chromatography-tandem mass spectrometry to optimize and validate a method for isotope dilution analysis of TRP metabolites in older individuals. The targeted analytes are TRP, serotonin or 5-hydroxytryptamine, kynurenine, kynurenic acid, xanthurenic acid, indole-3-acetic acid, indole-3-propionic acid, and tryptamine. The serum sample was purified using solid-phase extraction and was separated on a Waters HSS T3 column (100 mm × 2.1 mm, 1.8 μm). The analytes were detected in the multiple reaction monitoring mode under positive ionization. TRP was confirmed and measured after being diluted 100 times. This method exhibited satisfactory linearity (r > 0.99). The intrabatch and interbatch accuracies (85.7-114%) and precisions (<15%) were acceptable. The standard-normalized matrix effects ranged from 51.6 to 145%. This method was successfully applied to a cohort of 1021 older Chinese individuals, and this study may enable further understanding of the metabolic phenotypes associated with TRP in other populations.

Sleep Deficiency Is Associated With Exacerbation of Symptoms and Impairment of Anorectal and Autonomic Functions in Patients With Functional Constipation

Objective

Sleep deficiency (SD) is commonly seen in patients with functional constipation (FC). Our aim was to determine whether the presence of SD would influence symptoms, anorectal motility, sensation, and autonomic function in FC patients.

Materials and Methods

A total of 85 FC patients with SD and 193 FC patients without SD underwent high-resolution anorectal manometry. SD was assessed by using the Pittsburgh Sleep Quality Index (PSQI) score. Participants were required to fill in the entire questionnaires, including Patients' Constipation-symptoms, State-Trait Anxiety Inventory, and Hamilton Depression Scale. Autonomic dysfunction was studied by recording the heart rate variability. Multiple logistic regression was performed to explore the potential risk factors for anorectal function.

Results

Functional constipation patients with SD had a higher total score of constipation symptom (P < 0.001), in comparison with those without SD. FC patients with SD demonstrated significantly lower threshold volume for first sensation (P < 0.001) and urge (P < 0.001), as compared to those without SD. The PSQI score positively correlated with constipation symptom total score (P < 0.001), and negatively correlated with threshold volume for first sensation (P < 0.001) and urge (P < 0.001). FC patients with SD had a reduced vagal activity (P = 0.016) and a higher sympathetic activity as compared to those without SD (P = 0.003). Multivariate logistic regression revealed that SD, anxiety and depression were independent risk factors for anorectal function, with SD exhibiting the highest degree of association with first sensation (OR: 4.235).

Conclusion

Sleep deficiency is associated with worse constipation related symptoms, altered anorectal function and perception, and impaired autonomic function in FC patients.

The Circadian Molecular Machinery in CNS Cells: A Fine Tuner of Neuronal and Glial Activity With Space/Time Resolution

The circadian molecular machinery is a fine timekeeper with the capacity to harmonize physiological and behavioral processes with the external environment. This tight-knit regulation is coordinated by multiple cellular clocks across the body. In this review, we focus our attention on the molecular mechanisms regulated by the clock in different brain areas and within different cells of the central nervous system. Further, we discuss evidence regarding the role of circadian rhythms in the regulation of neuronal activity and neurotransmitter systems. Not only neurons, but also astrocytes and microglia actively participate in the maintenance of timekeeping within the brain, and the diffusion of circadian information among these cells is fine-tuned by neurotransmitters (e.g., dopamine, serotonin, and γ-aminobutyric acid), thus impacting on the core clock machinery. The bidirectional interplay between neurotransmitters and the circadian clockwork is fundamental in maintaining accuracy and precision in daily timekeeping throughout different brain areas. Deepening the knowledge of these correlations allows us to define the basis of drug interventions to restore circadian rhythms, as well as to predict the onset of drug treatment/side effects that might promote daily desynchronization. Furthermore, it may lead to a deeper understanding of the potential impacts of modulations in rhythmic activities on the pace of aging and provide an insight in to the pathogenesis of psychiatric diseases and neurodegenerative disorders.

From Alpha Diversity to Zzz: Interactions among sleep, the brain, and gut microbiota in the first year of life

Sleep disorders have been linked to alterations of gut microbiota composition in adult humans and animal models, but it is unclear how this link develops. With longitudinal assessments in 162 healthy infants, we present a so far unrecognized sleep-brain-gut interrelationship. First, we report a link between sleep habits and gut microbiota: daytime sleep is associated with bacterial diversity, and nighttime sleep fragmentation and variability link with bacterial maturity and enterotype. Second, we demonstrate a sleep-brain-gut link: bacterial diversity and enterotype are associated with sleep neurophysiology. Third, we show that the sleep-brain-gut link is relevant in development: sleep habits and bacterial markers predict behavioral-developmental outcomes. Our results demonstrate the dynamic interplay between sleep, gut microbiota, and the maturation of brain and behavior during infancy, which aligns with the lately emerging concept of a sleep-brain-gut axis. Importantly, sleep and gut microbiota represent promising health targets since both can be modified non-invasively. As many adult diseases root in early childhood, leveraging protective factors of adequate sleep and age-appropriate gut microbiota in infancy could constitute a health promoting factor across the entire human lifespan.

The association between dietary patterns and quality and duration of sleep in children and adolescents: A systematic review

BACKGROUND

Dietary pattern has been represented as a contributor to the duration and quality of sleep. This study aimed to review the evidence on this relation among children and adolescents.

STUDY DESIGN

This was a systematic review on the association of dietary pattern and sleep.

METHODS

A literature search was conducted for all articles published between 1980 and August 2020 using the terms "diet" AND "sleep" in PubMed/Medline, Scopus, Web of Science, Cochrane, and Embase databases. Screening and selection of eligible studies were performed by two separate investigators. Studies reporting the impact of different dietary patterns and indices on sleep duration or quality were included.

RESULTS

Fourteen publications (12 cross-sectional, 1 cohort, and 1 clinical trial) were identified. Findings from most studies suggested that long sleep duration was consistently associated with healthy dietary patterns, such as "Vegetables & Healthy Proteins", "Traditional", "Fruit & Vegetables", etc. Results were more mixed and inconclusive regarding the quality of sleep, with 2 studies supporting, 2 studies disapproving, and one study neutral about the association between better sleep quality and healthier dietary patterns. The association between diet and sleep seemed to be affected by confounders and covariates, including sex, physical activity, screen time, etc. CONCLUSIONS: Longer sleep duration appears to be associated with healthier dietary pattern. However, various results in regard to the relation between dietary patterns and sleep quality preclude definitive conclusions. Further research with standard measures of sleep quality and experimental study designs are needed to better define the causal relationship between sleep and diet.

Aberrant Lighting Causes Anxiety-like Behavior in Mice but Curcumin Ameliorates the Symptoms

Simple Summary

In the present study, we exposed mice to aberrant lighting system and noticed anxiety-like behavior. These symptoms were ameliorated by oral administration of curcumin. The study was carried out on the animals for three weeks in dim light at night (dLAN) and complete darkness (DD), monitoring the body weight, daily food intake, anxiety-like behavior, and expression of the period (PER1) gene. The exposure to dim light at night was found to significantly enhance the anxiety-like behavior and increased the body weight possibly through altered metabolism in mice. In contrast, exposure to DD caused increased anxiety but no significant difference in the body weight. Moreover, the expression of the PER1 gene involved in sleep was also found to be decreased in the aberrant light conditions (dLAN and DD). Although the treatment of curcumin had no effect on the body weight, it had ameliorated the anxiety-like behavior possibly by modulating the expression of the PER1 gene. Thus, the alteration in the light/dark cycle has negative influences on body weight, affecting even the emotional quotient. This study identifies the risk factors associated with aberrant lighting conditions in laboratory animal and ameliorative effects of curcumin.

Abstract

In the modern research field, laboratory animals are constantly kept under artificial lighting conditions. However, recent studies have shown the effect of artificial light on animal behavior and metabolism. In the present study on mice, following three weeks of housing in dim light at night (dLAN; 5lux) and complete darkness (DD; 0lux), we monitored the effect on body weight, daily food intake, anxiety-like behavior by employing the open field test, and expression of the period (PER1) gene. We also studied the effect of oral administration of different concentrations of curcumin (50, 100, and 150 mg/kg) for three weeks in the same mice and monitored these parameters. The exposure to dLAN had significantly increased the anxiety-like behavior and body weight possibly through the altered metabolism in mice, whereas exposure to DD caused increased anxiety but no significant difference in weight gain. Moreover, the expression of the PER1 gene involved in sleep was also found to be decreased in the aberrant light conditions (dLAN and DD). Although the treatment of curcumin had no effect on body weight, it ameliorated the anxiety-like behavior possibly by modulating the expression of the PER1 gene. Thus, alteration in the light/dark cycle had a negative effect on laboratory animals on the body weight and emotions of animals. The present study identifies the risk factors associated with artificial lighting systems on the behavior of laboratory animals and the ameliorative effects of curcumin, with a focus on anxiety-like behavior.

Microbiota and sleep: awakening the gut feeling

Various lifestyle and environmental factors are known to influence sleep. Increasingly, evidence points to a role for the microbiota in regulating brain and behaviour. This article explores how the microbiota-gut-brain axis affects sleep directly and indirectly. We summarize the possible molecular mechanisms underlying sleep-microbiome interactions and discuss how various factors interact with the gut microbiota to influence sleep. Furthermore, we present the current evidence of alterations of the microbiota-gut-brain axis in various sleep disorders and pathologies where comorbid sleep disturbances are common. Since manipulating the gut microbiota could potentially improve sleep, we outline ways in which this can be achieved.

Healthy lifestyle behaviors are major predictors of mental wellbeing during COVID-19 pandemic confinement: A study on adult Arabs in higher educational institutions

BACKGROUND

In the past infectious diseases affected the quality of lifestyle during home confinement. The study conducted examines the influence of home confinement during the COVID-19 pandemic outbreak on lifestyle, mental wellbeing, nutritional status, and sleeping pattern.

METHOD

An online multicategorical questionnaire was distributed to collect demographic information combined with the following tools: Food Frequency Questionnaire (FFQ), International Physical Activity Questionnaire (IPAQ), WHO-5 wellbeing score, and Pittsburgh Sleep Quality Index (PSQI). A snowball non-discriminate sampling procedure was conducted to collect data from people attending or working at higher institutions from March 1, 2020 to April 24, 2020. A total of 1723 completed responses (917 males, 37.4 ±13.4 years old and 806 females 32.2 ± 11.5 years old) were collected.

RESULTS

The female participants had significantly lower mental health scores than males (53.9% vs. 46.1%). The mental wellbeing scores were higher among participants with medium and high physical activity (PA) levels (p < 0.00). Additionally, the mental wellbeing scores were significantly improved by dietary quality and it's sleeping score (p < 0.001). However, PA was by far the major determinant of the mental health scores.

CONCLUSION

Factors such as PA, diet, and sleeping patterns were associated with mental wellbeing during the COVID-19 confinement among Arab participants.

Gut microbiota depletion by chronic antibiotic treatment alters the sleep/wake architecture and sleep EEG power spectra in mice

Dysbiosis of the gut microbiota affects physiological processes, including brain functions, by altering the intestinal metabolism. Here we examined the effects of the gut microbiota on sleep/wake regulation. C57BL/6 male mice were treated with broad-spectrum antibiotics for 4 weeks to deplete their gut microbiota. Metabolome profiling of cecal contents in antibiotic-induced microbiota-depleted (AIMD) and control mice showed significant variations in the metabolism of amino acids and vitamins related to neurotransmission, including depletion of serotonin and vitamin B6, in the AIMD mice. Sleep analysis based on electroencephalogram and electromyogram recordings revealed that AIMD mice spent significantly less time in non-rapid eye movement sleep (NREMS) during the light phase while spending more time in NREMS and rapid eye movement sleep (REMS) during the dark phase. The number of REMS episodes seen in AIMD mice increased during both light and dark phases, and this was accompanied by frequent transitions from NREMS to REMS. In addition, the theta power density during REMS was lower in AIMD mice during the light phase compared with that in the controls. Consequently, the gut microbiota is suggested to affect the sleep/wake architecture by altering the intestinal balance of neurotransmitters.

Sleep, circadian rhythm, and gut microbiota

From asthma and heart disease to diabetes and obesity, the human microbiome plays a role in the pathogenesis of each chronic health condition plaguing today's society. Recent work has shown that the gut microbiota and its metabolites exhibit diurnal rhythmicity which predominantly respond to the feeding/fasting cycle. Persistent jet lag, an obesogenic diet, and clock gene deficiency can dampen the oscillatory nature of gut bacterial composition, which can subsequently be rescued by time restricted feeding. Contrastingly, gut microbial metabolites influence central and hepatic clock gene expression and sleep duration in the host and regulate body composition through circadian transcription factors. Both sleep fragmentation and short sleep duration are associated with gut dysbiosis which may be due to activation of the HPA-axis. Metabolic disturbances associated with sleep loss may in fact be mediated through the overgrowth of specific gut bacteria. Reciprocally, the end products of bacterial species which grow in response to sleep loss are able to induce fatigue. Furthermore, probiotic supplementation has been found to improve subjective sleep quality. Sleep quality and duration may be an important target for supporting healthy gut microbiota composition, but the cyclic nature of this relationship should not be overlooked.

Early weaning disrupts feeding patterns in female juvenile rats through 5HT-system modulations

Convergent evidence in literature shows that rapid disruption of maternal care and breastfeeding due to an early weaning protocol changes the development of several neurobehavioral patterns in rodents, including the circadian pattern of feeding. The serotoninergic system has been associated with the control of feeding patterns. Therefore, we aim to evaluate the patterns of feeding, the mRNA expression of 5 H T-1b, 5 H T-2c, and SERT on the hypothalamus, brainstem, and the body weight of female juvenile Wistar rats, submitted to early (PND15) or regular (PND30) weaning. The results demonstrate that early weaning promotes an increase in food intake in a 24 -h period, in the dark phase of the circadian cycle and in the four-hour time intervals at the beginning of the dark and light phases. Also, early weaning decreases the mRNA expression of 5 H T-1b, 5 H T-2c, and SERT on the hypothalamus, but increases it on the brainstem. Additionally, early weaning promotes an increase in body weight. Therefore, the present data demonstrate that early weaning changes the patterns of feeding in juvenile female rats and suggests that this behavioral modification is due to the modulations promoted in the 5 H T-system.

Impaired cortico-striatal excitatory transmission triggers epilepsy

STXBP1 and SCN2A gene mutations are observed in patients with epilepsies, although the circuit basis remains elusive. Here, we show that mice with haplodeficiency for these genes exhibit absence seizures with spike-and-wave discharges (SWDs) initiated by reduced cortical excitatory transmission into the striatum. Mice deficient for Stxbp1 or Scn2a in cortico-striatal but not cortico-thalamic neurons reproduce SWDs. In Stxbp1 haplodeficient mice, there is a reduction in excitatory transmission from the neocortex to striatal fast-spiking interneurons (FSIs). FSI activity transiently decreases at SWD onset, and pharmacological potentiation of AMPA receptors in the striatum but not in the thalamus suppresses SWDs. Furthermore, in wild-type mice, pharmacological inhibition of cortico-striatal FSI excitatory transmission triggers absence and convulsive seizures in a dose-dependent manner. These findings suggest that impaired cortico-striatal excitatory transmission is a plausible mechanism that triggers epilepsy in Stxbp1 and Scn2a haplodeficient mice.

Spike and wave discharge (SWD) activity is seen during absence seizures and is thought to be thalamocortical in origin. Here, the authors show that SWDs are initiated through the impaired corticostriatal excitatory transmissions onto striatal fast spiking interneurons.

Current understanding of fear learning and memory in humans and animal models and the value of a linguistic approach for analyzing fear learning and memory in humans

Fear is an emotion that serves as a driving factor in how organisms move through the world. In this review, we discuss the current understandings of the subjective experience of fear and the related biological processes involved in fear learning and memory. We first provide an overview of fear learning and memory in humans and animal models, encompassing the neurocircuitry and molecular mechanisms, the influence of genetic and environmental factors, and how fear learning paradigms have contributed to treatments for fear-related disorders, such as posttraumatic stress disorder. Current treatments as well as novel strategies, such as targeting the perisynaptic environment and use of virtual reality, are addressed. We review research on the subjective experience of fear and the role of autobiographical memory in fear-related disorders. We also discuss the gaps in our understanding of fear learning and memory, and the degree of consensus in the field. Lastly, the development of linguistic tools for assessments and treatment of fear learning and memory disorders is discussed.

L-tryptophan administration and increase in cerebral serotonin levels: Systematic review

The amino acid tryptophan (2-Amino-3-(lH-indol-3-yl)-propanoic acid; Trp) is a precursor of the neurotransmitter serotonin (5-hydroxytryptamine; 5-HT) that performs various brain functions. The administration of Trp is used in experimental studies to manipulate the serotonergic system, however the dose of Trp required to raise brain 5-HT levels is controversial. The aim of this study was to systemically review the effect of the administration of different doses of Trp on cerebral 5-HT levels. Two independent authors conducted a systematic review in the electronic databases. Twenty-five studies were included in the present review. Trp was administered orally, intraperitoneally or subcutaneous in adult animals. The brain 5-HT levels elevated after Trp administration in different intensities, dependent of the brain region evaluated and the time of administration. Further studies are needed to assess the dose-response of Trp administration to brain 5-HT levels.

Effect of aripiprazole on non-24-hour sleep-wake rhythm disorder comorbid with major depressive disorder: a case report

BACKGROUND

Patients with non-24-hour sleep-wake rhythm disorder (N24SWD) exhibit a sleep pattern that is asynchronous with the external light-dark cycle, typically involving a cycling, relapsing-remitting pattern of sleep disturbances, including nighttime insomnia and daytime sleepiness. Here, we report the case of a patient with N24SWD comorbid with major depressive disorder, who was successfully treated with a low dose of aripiprazole.

CASE PRESENTATION

A 47-year-old female presented with an 8-year complaint of difficulty falling asleep and waking up in the morning. The patient was diagnosed with major depressive disorder at the age of 35 years and was treated with various antidepressants since that time. At the age of 40 years, the patient's sleep-wake cycle began to extend without exacerbation of depressive symptoms. The patient was diagnosed with N24SWD at the age of 43 years. Ramelteon 8 mg/d and then melatonin 1 mg/d were administered, but these did not provide effective treatment. In January 2016, after treatment with aripiprazole 3 mg/d in the morning for 4 weeks, the patient's sleep-wake cycle became markedly synchronized to the environmental light-dark cycle. Her sleep-wake cycle remained synchronized when the same dose of aripiprazole was administered for at least 6 months.

CONCLUSION

Treatment-refractory asynchrony of the sleep-wake cycle in an N24SWD patient with depression was successfully treated with aripiprazole. Although the detailed mechanism of action is unclear, aripiprazole may be an appropriate treatment for patients with circadian rhythm sleep-wake disorders.

Correlation study of basic Chinese medicine syndromes and neurotransmitter levels in patients with primary insomnia

OBJECTIVE

To investigate the correlation between basic Chinese medicine (CM) syndromes (deficiency and excess syndromes) and intracranial neurotransmitter levels in primary insomnia (PI), to provide objective indicators and syndrome-based medical evidence for the differentiation of PI.

METHODS

A total of 158 patients with PI were recruited for CM syndrome differentiation. Another 30 healthy people without sleep disorders were selected as control group. An encephalofluctuograph analyzer was used to test the levels of intracranial neurotransmitters, including γ- aminobutyric acid (GABA), glutamate (Glu), 5-hydroxytryptamine (5-HT), dopamine (DA), etc., and their relevance were analyzed.

RESULTS

The neurotransmitter levels in the basic-deficiency group were lower than those in the healthy-control group, while the basic-excess group had higher levels than the healthy-control and basic-deficiency groups. Among the neurotransmitters, the 5-HT level was higher in the basic-excess group than in the basic-deficiency group (24.20±4.07 vs. 21.13±3.23; P<0.05); for the intermingled deficiency-excess group, the level of GABA was higher than that in the basic-deficiency group (9.48±3.07 vs. 7.23±3.67; P<0.05), Glu level was higher than that in the healthy-control group (7.53±4.10 vs. 5.83±0.99, P<0.05), and 5-HT and DA levels were lower than those in the healthy-control group (19.80±5.68 vs. 22.63±3.31, 5.27±3.79 vs. 6.83±1.58, respectively; P<0.05).

CONCLUSIONS

There was a correlation between the basic syndromes and intracranial neurotransmitter levels in patients with PI, which could objectively reflect the CM differentiation in PI. This information could be important for improving CM diagnosis and treatment in PI.

Influence of Tryptophan and Serotonin on Mood and Cognition with a Possible Role of the Gut-Brain Axis

The serotonergic system forms a diffuse network within the central nervous system and plays a significant role in the regulation of mood and cognition. Manipulation of tryptophan levels, acutely or chronically, by depletion or supplementation, is an experimental procedure for modifying peripheral and central serotonin levels. These studies have allowed us to establish the role of serotonin in higher order brain function in both preclinical and clinical situations and have precipitated the finding that low brain serotonin levels are associated with poor memory and depressed mood. The gut-brain axis is a bi-directional system between the brain and gastrointestinal tract, linking emotional and cognitive centres of the brain with peripheral functioning of the digestive tract. An influence of gut microbiota on behaviour is becoming increasingly evident, as is the extension to tryptophan and serotonin, producing a possibility that alterations in the gut may be important in the pathophysiology of human central nervous system disorders. In this review we will discuss the effect of manipulating tryptophan on mood and cognition, and discuss a possible influence of the gut-brain axis.

Effects of Genotype and Sleep on Temperament

BACKGROUND AND OBJECTIVES

Sleep problems are frequent in young children; however, children vary in the degree to which they are affected by poor sleep quality. We investigated whether a polymorphism in the serotonin transporter gene, which is linked to emotional function, is a potential moderator of the influences of sleep duration on infant temperament using longitudinal data.

METHODS

We examined the interactive effects of average sleep duration between 6 and 36 months of age and the 5-HTTLPR genotype on negative emotionality/behavioral dysregulation at 36 months in 209 children recruited into a longitudinal birth cohort study. Triallelic genotyping of 5-HTTLPR was performed by looking at SLC6A4 genotype, focusing on the serotonin transporter-linked polymorphic region (5-HTTLPR) including the SNP polymorphism (rs23351). Child sleep habits were assessed with a maternal self-report questionnaire.

RESULTS

After controlling for demographics and both previous and concurrent maternal depression, multiple linear regression analyses revealed a significant interaction effect of average sleep duration for the first 3 years of life and 5-HTTLPR genotype on child negative emotionality/behavioral dysregulation such that the effects were exclusive to those with low-expressing 5-HTTLPR genotypes.

CONCLUSIONS

The results suggest differential susceptibility to the effect of sleep duration early in life, which reiterates that the short allele of the 5-HTTLPR represents a marker of increased environmental sensitivity regarding emotional development. Differential susceptibility theory posits that certain factors may increase an individual's susceptibility to the environment, in either a positive or negative fashion.

The sleep-wake cycle and motor activity, but not temperature, are disrupted over the light-dark cycle in mice genetically depleted of serotonin

We examined the role that serotonin has in the modulation of sleep and wakefulness across a 12-h:12-h light-dark cycle and determined whether temperature and motor activity are directly responsible for potential disruptions to arousal state. Telemetry transmitters were implanted in 24 wild-type mice (Tph2(+/+)) and 24 mice with a null mutation for tryptophan hydroxylase 2 (Tph2(-/-)). After surgery, electroencephalography, core body temperature, and motor activity were recorded for 24 h. Temperature for a given arousal state (quiet and active wake, non-rapid eye movement, and paradoxical sleep) was similar in the Tph2(+/+) and Tph2(-/-) mice across the light-dark cycle. The percentage of time spent in active wakefulness, along with motor activity, was decreased in the Tph2(+/+) compared with the Tph2(-/-) mice at the start and end of the dark cycle. This difference persisted into the light cycle. In contrast, the time spent in a given arousal state was similar at the remaining time points. Despite this similarity, periods of non-rapid-eye-movement sleep and wakefulness were less consolidated in the Tph2(+/+) compared with the Tph2(-/-) mice throughout the light-dark cycle. We conclude that the depletion of serotonin does not disrupt the diurnal variation in the sleep-wake cycle, motor activity, and temperature. However, serotonin may suppress photic and nonphotic inputs that manifest at light-dark transitions and serve to shorten the ultraradian duration of wakefulness and non-rapid-eye-movement sleep. Finally, alterations in the sleep-wake cycle following depletion of serotonin are unrelated to disruptions in the modulation of temperature.

Skin, reactive oxygen species, and circadian clocks

SIGNIFICANCE

Skin, a complex organ and the body's first line of defense against environmental insults, plays a critical role in maintaining homeostasis in an organism. This balance is maintained through a complex network of cellular machinery and signaling events, including those regulating oxidative stress and circadian rhythms. These regulatory mechanisms have developed integral systems to protect skin cells and to signal to the rest of the body in the event of internal and environmental stresses.

RECENT ADVANCES

Interestingly, several signaling pathways and many bioactive molecules have been found to be involved and even important in the regulation of oxidative stress and circadian rhythms, especially in the skin. It is becoming increasingly evident that these two regulatory systems may, in fact, be interconnected in the regulation of homeostasis. Important examples of molecules that connect the two systems include serotonin, melatonin, vitamin D, and vitamin A.

CRITICAL ISSUES

Excessive reactive oxygen species and/or dysregulation of antioxidant system and circadian rhythms can cause critical errors in maintaining proper barrier function and skin health, as well as overall homeostasis. Unfortunately, the modern lifestyle seems to contribute to increasing alterations in redox balance and circadian rhythms, thereby posing a critical problem for normal functioning of the living system.

FUTURE DIRECTIONS

Since the oxidative stress and circadian rhythm systems seem to have areas of overlap, future research needs to be focused on defining the interactions between these two important systems. This may be especially important in the skin where both systems play critical roles in protecting the whole body.

Food-derived serotonergic modulators: effects on mood and cognition

The most frequently described drugs in the treatment of mood disorders are selective serotonin reuptake and monoamine oxidase (MAO) inhibitors, enhancing serotonin levels in the brain. However, side-effects have been reported for these drugs. Because serotonin levels in the brain are dependent on the availability of the food-derived precursor tryptophan, foods such as chicken, soyabeans, cereals, tuna, nuts and bananas may serve as an alternative to improve mood and cognition. Here we discuss the effects of high- or low-tryptophan-containing food, as well as plant extracts with a modest monoamine reuptake and MAO-A inhibition functional profile, on mood and cognition in healthy and vulnerable human subjects and rodents. Together the studies suggest that there is an inverted U-shaped curve for plasma tryptophan levels, with low and too high tryptophan levels impairing cognition, and moderate to high tryptophan levels improving cognition. This relationship is found for both healthy and vulnerable subjects. Whereas this relationship may also exist for mood, the inverted U-shaped curve for plasma tryptophan levels and mood may be based on different tryptophan concentrations in healthyv.vulnerable individuals. Animal studies are emerging and allow further understanding of effects and the mode of action of food-derived serotonergic components on mood, cognition and mechanisms. Ultimately, insight into the concentrations of tryptophan and other serotonergic components in food having beneficial effects on mood and cognition in healthy, but particularly vulnerable, subjects may support well-being in our highly demanding society.

Serotonergic integration of circadian clock and ultradian sleep-wake cycles

In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus generates a 24 h rhythm of sleep and arousal. While neuronal spiking activity in the SCN provides a functional circadian oscillator that propagates throughout the brain, the ultradian sleep-wake state is regulated by the basal forebrain/preoptic area (BF/POA). How this SCN circadian oscillation is integrated into the shorter sleep-wake cycles remains unclear. We examined the temporal patterns of neuronal activity in these key brain regions in freely behaving rats. Neuronal activity in various brain regions presented diurnal rhythmicity and/or sleep-wake state dependence. We identified a diurnal rhythm in the BF/POA that was selectively degraded when diurnal arousal patterns were disrupted by acute brain serotonin depletion despite robust circadian spiking activity in the SCN. Local blockade of serotonergic transmission in the BF/POA was sufficient to disrupt the diurnal sleep-wake rhythm of mice. These results suggest that the serotonergic system enables the BF/POA to couple the SCN circadian signal to ultradian sleep-wake cycles, thereby providing a potential link between circadian rhythms and psychiatric disorders.