How might circadian rhythms control mood? Let me count the ways

Circadian modulation of dopamine levels and dopaminergic neuron development contributes to attention deficiency and hyperactive behavior

Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent psychiatric disorders in children and adults. While ADHD patients often display circadian abnormalities, the underlying mechanisms are unclear. Here we found that the zebrafish mutant for the circadian gene period1b (per1b) displays hyperactive, impulsive-like, and attention deficit-like behaviors and low levels of dopamine, reminiscent of human ADHD patients. We found that the circadian clock directly regulates dopamine-related genes monoamine oxidase and dopamine β hydroxylase, and acts via genes important for the development or maintenance of dopaminergic neurons to regulate their number and organization in the ventral diencephalic posterior tuberculum. We then found that Per1 knock-out mice also display ADHD-like symptoms and reduced levels of dopamine, thereby showing highly conserved roles of the circadian clock in ADHD. Our studies demonstrate that disruption of a circadian clock gene elicits ADHD-like syndrome. The circadian model for attention deficiency and hyperactive behavior sheds light on ADHD pathogenesis and opens avenues for exploring novel targets for diagnosis and therapy for this common psychiatric disorder.

Graph theory reveals hyper-functionality in visual cortices of Seasonal Affective Disorder patients

OBJECTIVES

Seasonal affective disorder (SAD) is a subtype of recurrent unipolar or bipolar depressive disorder with a higher prevalence in winter than in summer. The biological underpinnings of SAD are so far poorly understood. Studies examining SAD have found disturbances between the molecular and connectivity scales. The aim of the study was to explore changes in functional connectivity typical for SAD.

METHODS

We investigated unmedicated, untreated SAD patients and healthy controls using resting-state functional magnetic resonance imaging (rs-fMRI) utilizing graph theory, a data driven and hypothesis free approach, to model functional networks of the brain.

RESULTS

Comparing whole brain network properties using graph theory we observed globally affected network topologies with increasing pathlength in SAD. Nodal changes, however, were highly restricted to bilateral inferior occipital cortex. Interestingly, we found a lateralization where hyper-connectedness was restricted to right inferior occipital cortex and hyper-efficiency was found in the left inferior occipital cortex. Furthermore, we found these nodes became more "hub like" in patients, suggesting a greater functional role.

CONCLUSIONS

Our work stresses the importance of abnormal intrinsic processing during rest, primarily affecting visual areas and subsequently changing whole brain networks, and thus providing an important hint towards potential future therapeutic approaches.

Locomotor Profiling from Rodents to the Clinic and Back Again

The quantification of unconditioned motoric activity is one of the oldest and most commonly utilized tools in behavioral studies. Although typically measured in reference to psychiatric disorders, e.g., amphetamine-induced hyperactivity used as a model of schizophrenia, bipolar disorder (BD), and Tourette's syndrome, the motoric behavior of psychiatric patients had not been quantified similarly to rodents until recently. The rodent behavioral pattern monitor (BPM) was reverse-translated for use in humans, providing the quantification of not only motoric activity but also the locomotor exploratory profile of various psychiatric populations. This measurement includes the quantification of specific exploration and locomotor patterns. As an example, patients with BD, schizophrenia, and those with history of methamphetamine dependence exhibited unique locomotor profiles. It was subsequently determined that reducing dopamine transporter function selectively recreated the locomotor profile of BD mania patients and not any other patient population. Hence, multivariate locomotor profiling offers a first-step approach toward understanding the neural mechanism(s) underlying abnormal behavior in patients with psychiatric disorders. Advances in wearable technology will undoubtedly enable similar multivariate assessments of exploratory and locomotor behavior in "real-world" contexts. Furthermore, trans-diagnostic studies of locomotor activity profiles will inform about essential brain-based functions that cut across diagnostic nosologies.

Major depressive disorder: mechanism-based prescribing for personalized medicine

Individual patients with depression present with unique symptom clusters - before, during, and even after treatment. The prevalence of persistent, unresolved symptoms and their contribution to patient functioning and disease progression emphasize the importance of finding the right treatment choice at the onset and the utility of switching medications based on suboptimal responses. Our primary goal as clinicians is to improve patient function and quality of life. In fact, feelings of well-being and the return to premorbid levels of functioning are frequently rated by patients as being more important than symptom relief. However, functional improvements often lag behind resolution of mood, attributed in large part to persistent and functionally impairing symptoms - namely, fatigue, sleep/wake disturbance, and cognitive dysfunction. Thus, patient outcomes can be optimized by deconstructing each patient's depressive profile to its component symptoms and specifically targeting those domains that differentially limit patient function. This article will provide an evidence-based framework within which clinicians may tailor pharmacotherapy to patient symptomatology for improved treatment outcomes.

Pharmacological targeting of the mammalian clock regulates sleep architecture and emotional behaviour

Synthetic drug-like molecules that directly modulate the activity of key clock proteins offer the potential to directly modulate the endogenous circadian rhythm and treat diseases associated with clock dysfunction. Here we demonstrate that synthetic ligands targeting a key component of the mammalian clock, the nuclear receptors REV-ERBα and β, regulate sleep architecture and emotional behaviour in mice. REV-ERB agonists induce wakefulness and reduce REM and slow-wave sleep. Interestingly, REV-ERB agonists also reduce anxiety-like behaviour. These data are consistent with increased anxiety-like behaviour of REV-ERBβ-null mice, in which REV-ERB agonists have no effect. These results indicate that pharmacological targeting of REV-ERB may lead to the development of novel therapeutics to treat sleep disorders and anxiety.

Differential effects of theta/beta and SMR neurofeedback in ADHD on sleep onset latency

Recent studies suggest a role for sleep and sleep problems in the etiology of attention deficit hyperactivity disorder (ADHD) and a recent model about the working mechanism of sensori-motor rhythm (SMR) neurofeedback, proposed that this intervention normalizes sleep and thus improves ADHD symptoms such as inattention and hyperactivity/impulsivity. In this study we compared adult ADHD patients (N = 19) to a control group (N = 28) and investigated if differences existed in sleep parameters such as Sleep Onset Latency (SOL), Sleep Duration (DUR) and overall reported sleep problems (PSQI) and if there is an association between sleep-parameters and ADHD symptoms. Secondly, in 37 ADHD patients we investigated the effects of SMR and Theta/Beta (TBR) neurofeedback on ADHD symptoms and sleep parameters and if these sleep parameters may mediate treatment outcome to SMR and TBR neurofeedback. In this study we found a clear continuous relationship between self-reported sleep problems (PSQI) and inattention in adults with- and without-ADHD. TBR neurofeedback resulted in a small reduction of SOL, this change in SOL did not correlate with the change in ADHD symptoms and the reduction in SOL only happened in the last half of treatment, suggesting this is an effect of symptom improvement not specifically related to TBR neurofeedback. SMR neurofeedback specifically reduced the SOL and PSQI score, and the change in SOL and change in PSQI correlated strongly with the change in inattention, and the reduction in SOL was achieved in the first half of treatment, suggesting the reduction in SOL mediated treatment response to SMR neurofeedback. Clinically, TBR and SMR neurofeedback had similar effects on symptom reduction in ADHD (inattention and hyperactivity/impulsivity). These results suggest differential effects and different working mechanisms for TBR and SMR neurofeedback in the treatment of ADHD.

Lifestyle choices and mental health: a representative population survey

Background

Identifying healthy lifestyle behaviours that promote psychological wellbeing is crucial to preventing mental disorders. The aim of the current study was to evaluate the individual and combined associations between different aspects of everyday life and mental health within a representative community sample in Germany.

Method

The study was conducted in 2012/2013 and included 7,937 participants representative of the German population. Lifestyle factors were assessed via self-report and included frequency of physical and mental activity, alcohol consumption, smoking, body mass index as well as circadian and social regularity. Outcome variables were depression, anxiety, stress and satisfaction with life.

Results

All lifestyle factors were associated with the mental health outcomes. Better mental health was linked to higher frequency of physical and mental activity, moderate alcohol consumption (i.e. not increased or no alcohol consumption), non-smoking, a body mass index within the range of normal to overweight (i.e. not underweight or obese) and a regular life rhythm. The more healthy lifestyle choices an individual makes, the higher life satisfaction and lower psychological distress he or she tends to have.

Conclusions

The current study underlines the importance of healthy lifestyle choices in respect to psychological wellbeing.

Circadian biomarkers in patients with bipolar disorder: promising putative predictors of lithium response

Bipolar disorder (BD) is a common, severe mental disorder with a high recurrence rate. Lithium (Li) is the cornerstone of BD treatments to reduce recurrence, suicide, and mortality risks. However, only 30% of patients treated with Li achieve complete remission, and few markers of the response to treatment have yet been identified for application in routine practice. Circadian biomarkers may be relevant predictors of individual responses to Li because (1) Li has been shown to affect circadian rhythms, (2) disrupted circadian rhythms are a core expression of susceptibility to BD, and (3) circadian abnormalities during euthymia are associated with relapses.

Chronotype predicts positive affect rhythms measured by ecological momentary assessment

Evening chronotype, a correlate of delayed circadian rhythms, is associated with depression. Altered positive affect (PA) rhythms may mediate the association between evening chronotype and depression severity. Consequently, a better understanding of the relationship between chronotype and PA may aid in understanding the etiology of depression. Recent studies have found that individuals with evening chronotype show delayed and blunted PA rhythms, although these studies are relatively limited in sample size, representativeness and number of daily affect measures. Further, published studies have not included how sleep timing changes on workday and non-workdays, or social jet lag (SJL) may contribute to the chronotype-PA rhythm link. Healthy non-depressed adults (n = 408) completed self-report affect and chronotype questionnaires. Subsequently, positive and negative affects were measured hourly while awake for at least two workdays and one non-workday by ecological momentary assessment (EMA). Sleep variables were collected via actigraphy and compared across chronotype groups. A cosinor variant of multilevel modeling was used to model individual and chronotype group rhythms and to calculate two variables: (1) amplitude of PA, or the absolute amount of daily variation from peak to trough during one period of the rhythm and (2) acrophase, or the time at which the peak amplitude of affect rhythms occurred. On workdays, individuals with evening chronotype had significantly lower PA amplitudes and later workday acrophase times than their morning type counterparts. In contrast to predictions, SJL was not found to be a mediator in the relationship between chronotype and PA rhythms. The association of chronotype and PA rhythms in healthy adults may suggest the importance of daily measurement of PA in depressed individuals and would be consistent with the hypothesis that evening chronotype may create vulnerability to depression via delayed and blunted PA rhythms.

Adrenal Clocks and the Role of Adrenal Hormones in the Regulation of Circadian Physiology

The mammalian circadian timing system consists of a master pacemaker in the suprachiasmatic nucleus (SCN) and subordinate clocks that disseminate time information to various central and peripheral tissues. While the function of the SCN in circadian rhythm regulation has been extensively studied, we still have limited understanding of how peripheral tissue clock function contributes to the regulation of physiological processes. The adrenal gland plays a special role in this context as adrenal hormones show strong circadian secretion rhythms affecting downstream physiological processes. At the same time, they have been shown to affect clock gene expression in various other tissues, thus mediating systemic entrainment to external zeitgebers and promoting internal circadian alignment. In this review, we discuss the function of circadian clocks in the adrenal gland, how they are reset by the SCN and may further relay time-of-day information to other tissues. Focusing on glucocorticoids, we conclude by outlining the impact of adrenal rhythm disruption on neuropsychiatric, metabolic, immune, and malignant disorders.

New insights on the antidepressant discontinuation syndrome

OBJECTIVE

Antidepressants are at best 50–55% effective. Non-compliance and the antidepressant discontinuation syndrome (ADS) are causally related yet poorly appreciated. While ADS is associated with most antidepressants, agomelatine seems to be devoid of such risk. We review the neurobiology and clinical consequences of antidepressant non-compliance and the ADS. Agomelatine is presented as a counterpoint to learn more on how ADS risk is determined by pharmacokinetics and pharmacology.

DESIGN

The relevant literature is reviewed through a MEDLINE search via PubMed, focusing on agomelatine and clinical and preclinical research on ADS.

RESULTS

Altered serotonergic dysfunction appears central to ADS so that how an antidepressant targets serotonin will determine its relative risk for inducing ADS and thereby affect later treatment outcome. Low ADS risk with agomelatine versus other antidepressants can be ascribed to its unique pharmacokinetic characteristics as well as its distinctive actions on serotonin, including melatonergic, monoaminergic and glutamatergic-nitrergic systems.

CONCLUSIONS

This review raises awareness of the long-term negative aspects of non-compliance and inappropriate antidepressant discontinuation, and suggests possible approaches to “design-out” a risk for ADS. It reveals intuitive and rational ideas for antidepressant drug design, and provides new thoughts on antidepressant pharmacology, ADS risk and how these affect long-term outcome.

[Travel and psychotic disorders: clinical aspects and practical recommendations]

Psychotic disorders are frequent among travelers (10 to 20 % of medical evacuations). The travel is a concentrate of stressors. Psychotic disorders are not a contraindication to travel. Special precautions should be taken for patients with psychotic disorders wishing to travel. These precautions could apply to patients at risk of transition to a psychotic disorder.

Faster, better, stronger: towards new antidepressant therapeutic strategies

Major depression is a highly prevalent disorder and is predicted to be the second leading cause of disease burden by 2020. Although many antidepressant drugs are currently available, they are far from optimal. Approximately 50% of patients do not respond to initial first line antidepressant treatment, while approximately one third fail to achieve remission following several pharmacological interventions. Furthermore, several weeks or months of treatment are often required before clinical improvement, if any, is reported. Moreover, most of the commonly used antidepressants have been primarily designed to increase synaptic availability of serotonin and/or noradrenaline and although they are of therapeutic benefit to many patients, it is clear that other therapeutic targets are required if we are going to improve the response and remission rates. It is clear that more effective, rapid-acting antidepressants with novel mechanisms of action are required. The purpose of this review is to outline the current strategies that are being taken in both preclinical and clinical settings for identifying superior antidepressant drugs. The realisation that ketamine has rapid antidepressant-like effects in treatment resistant patients has reenergised the field. Further, developing an understanding of the mechanisms underlying the rapid antidepressant effects in treatment-resistant patients by drugs such as ketamine may uncover novel therapeutic targets that can be exploited to meet the Olympian challenge of developing faster, better and stronger antidepressant drugs.

Impact of circadian nuclear receptor REV-ERBα on midbrain dopamine production and mood regulation

The circadian nature of mood and its dysfunction in affective disorders is well recognized, but the underlying molecular mechanisms are still unclear. Here, we show that the circadian nuclear receptor REV-ERBα, which is associated with bipolar disorder, impacts midbrain dopamine production and mood-related behavior in mice. Genetic deletion of the Rev-erbα gene or pharmacological inhibition of REV-ERBα activity in the ventral midbrain induced mania-like behavior in association with a central hyperdopaminergic state. Also, REV-ERBα repressed tyrosine hydroxylase (TH) gene transcription via competition with nuclear receptor-related 1 protein (NURR1), another nuclear receptor crucial for dopaminergic neuronal function, thereby driving circadian TH expression through a target-dependent antagonistic mechanism. In conclusion, we identified a molecular connection between the circadian timing system and mood regulation, suggesting that REV-ERBα could be targeting in the treatment of circadian rhythm-related affective disorders.

Analysis of genetic association and epistasis interactions between circadian clock genes and symptom dimensions of bipolar affective disorder

Bipolar affective disorder (BD) is a severe psychiatric disorder characterized by periodic changes in mood from depression to mania. Disruptions of biological rhythms increase risk of mood disorders. Because clinical representation of disease is heterogeneous, homogenous sets of patients are suggested to use in the association analyses. In our study, we aimed to apply previously computed structure of bipolar disorder symptom dimension for analyses of genetic association. We based quantitative trait on: main depression, sleep disturbances, appetite disturbances, excitement and psychotic dimensions consisted of OPCRIT checklist items. We genotyped 42 polymorphisms from circadian clock genes: PER3, ARNTL, CLOCK and TIMELSSS from 511 patients BD (n = 292 women and n = 219 men). As quantitative trait we used clinical dimensions, described above. Genetic associations between alleles and quantitative trait were performed using applied regression models applied in PLINK. In addition, we used the Kruskal-Wallis test to look for associations between genotypes and quantitative trait. During second stage of our analyses, we used multidimensional scaling (multifactor dimensionality reduction) for quantitative trait to compute pairwise epistatic interactions between circadian gene variants. We found association between ARNTL variant rs11022778 main depression (p = 0.00047) and appetite disturbances (p = 0.004). In epistatic interaction analyses, we observed two locus interactions between sleep disturbances (p = 0.007; rs11824092 of ARNTL and rs11932595 of CLOCK) as well as interactions of subdimension in main depression and ARNTL variants (p = 0.0011; rs3789327, rs10766075) and appetite disturbances in depression and ARNTL polymorphism (p = 7 × 10(-4); rs11022778, rs156243).

Diurnal cortisol rhythms in youth from risky families: effects of cumulative risk exposure and variation in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) [corrected]

Building on research on cumulative risk and psychopathology, this study examines how cumulative risk exposure is associated with altered diurnal cortisol rhythms in an ethnically diverse, low-income sample of youth. In addition, consistent with a diathesis-stress perspective, this study explores whether the effect of environmental risk is moderated by allelic variation in the promoter region of the serotonin transporter gene-linked polymorphic region (5-HTTLPR). Results show that youth with greater cumulative risk exposure had flatter diurnal cortisol slopes, regardless of 5-HTTLPR genotype. However, the association of cumulative risk with average cortisol output (area under the curve [AUC]) was moderated by the 5-HTTLPR genotype. Among youth homozygous for the long allele, greater cumulative risk exposure was associated with lower cortisol AUC, driven by significant reductions in cortisol levels at waking. In contrast, there was a trend-level association between greater cumulative risk and higher cortisol AUC among youth carrying the short allele, driven by a trend-level increase in bedtime cortisol levels. Findings are discussed with regard to the relevance of dysregulated diurnal cortisol rhythms for the development of psychopathology and the implications of genetically mediated differences in psychophysiological adaptations to stress.

Links between Circadian Rhythms and Psychiatric Disease

Determining the cause of psychiatric disorders is a goal of modern neuroscience, and will hopefully lead to the discovery of treatments to either prevent or alleviate the suffering caused by these diseases. One roadblock to attaining this goal is the realization that neuropsychiatric diseases are rarely due to a single gene polymorphism, environmental exposure, or developmental insult. Rather, it is a complex interaction between these various influences that likely leads to the development of clinically relevant syndromes. Our lab is exploring the links between environmental exposures and neurobehavioral function by investigating how disruption of the circadian (daily) clock alters the structure and function of neural circuits, with the hypothesis that disrupting this crucial homeostatic system can directly contribute to altered vulnerability of the organism to other factors that interact to produce psychiatric illness. This review explores some historical and more recent findings that link disrupted circadian clocks to neuropsychiatric disorders, particularly depression, mania, and schizophrenia. We take a comparative approach by exploring the effects observed in human populations, as well as some experimental models used in the laboratory to unravel mechanistic and causal relationships between disruption of the circadian clock and behavioral abnormalities. This is a rich area of research that we predict will contribute greatly to our understanding of how genes, environment, and development interact to modulate an individual’s vulnerability to psychiatric disorders.

Circadian rhythms and addiction: mechanistic insights and future directions

Circadian rhythms are prominent in many physiological and behavioral functions. Circadian disruptions either by environmental or molecular perturbation can have profound health consequences, including the development and progression of addiction. Both animal and humans studies indicate extensive bidirectional relationships between the circadian system and drugs of abuse. Addicted individuals display disrupted rhythms, and chronic disruption or particular chronotypes may increase the risk for substance abuse and relapse. Moreover, polymorphisms in circadian genes and an evening chronotype have been linked to mood and addiction disorders, and recent efforts suggest an association with the function of reward neurocircuitry. Animal studies are beginning to determine how altered circadian gene function results in drug-induced neuroplasticity and behaviors. Many studies suggest a critical role for circadian rhythms in reward-related pathways in the brain and indicate that drugs of abuse directly affect the central circadian pacemaker. In this review, we highlight key findings demonstrating the importance of circadian rhythms in addiction and how future studies will reveal important mechanistic insights into the involvement of circadian rhythms in drug addiction.

Sleep in remitted bipolar disorder: a naturalistic case-control study using actigraphy

INTRODUCTION

Findings from actigraphic studies suggesting that sleep and circadian rhythms are disrupted in bipolar disorder (BD) patients have been undermined by methodological heterogeneity and the failure to adequately address potential confounders.

METHOD

Twenty-six euthymic BD cases and 29 healthy controls (HC), recruited from University Paris-Est and matched for age and gender, were compared on subjective (Pittsburgh Sleep Questionnaire Inventory; PQSI) and objective (mean scores and variability in actigraphy) measures of sleep as recorded by over 21 consecutive days.

RESULTS

Multivariate generalized linear modelling (GLM) revealed significant differences between BD cases and HC for five PSQI items (total score and four subscales), four actigraphy variables (mean scores) and five actigraphy variability measures. Backward stepwise linear regression (BSLR) indicated that a combination of four variables (mean sleep duration, mean sleep latency, variability of the fragmentation index over 21 days, and mean score on PSQI daytime dysfunction sub-scale) correctly classified 89% of study participants as cases or controls (Chi-square=39.81; df=6; p=0.001).

LIMITATIONS

The sample size (although larger than most actigraphy studies) and incomplete matching of cases and controls may have influenced our findings. It was not possible to control for potential effects of psychotropic medication or differences in employment status between groups.

CONCLUSIONS

When potential confounders of sleep and circadian profiles are adequately taken into account (particularly age, gender, daytime sleepiness, mood symptoms, body mass index, and risk of sleep apnoea), a selected subset of quantitative (mean scores) and qualitative (variability) features differentiated euthymic BD cases from HC.

Risk behaviors and negative health outcomes for adolescents with late bedtimes

Late bedtimes in adolescence may be a serious risk factor for later poor health and functional outcomes. The current study sought to extend existing cross sectional data by examining whether late bedtimes in adolescence predicts poor outcomes in young adulthood. Data from wave 2 (1996) and wave 3 (2001-2002) of the nationally representative sample of US youth (National Longitudinal Study of Adolescent Health) was used to examine the longitudinal relationship between late bedtime, and several risk behaviors and negative health outcomes following 3,843 adolescents into young adulthood. At wave 2 the mean age was 16 with 52.1% female. At wave 3 the mean age was 21.8. In cross sectional analyses, late bedtime was associated with 1.5 to over 3 times greater odds of involvement in risk behaviors and negative health outcomes, including emotional distress, suicidality, criminal and violent activity, and use of cigarettes, alcohol and illicit drugs. In longitudinal analyses, late bedtime assessed at wave 2 predicted a number of serious health outcomes at wave 3, with late bedtime in adolescence associated with around 1.5 greater odds of involvement in health jeopardizing behaviors such as criminal activity, alcohol abuse, cigarette use, illicit drug use and emotional distress in young adulthood. There was also a dose effect, such that the later the bedtime in adolescence, the greater the risk of involvement in risk behaviors in young adulthood. This research suggests that late bedtime in adolescence predicts multiple serious risk behaviors and health outcomes in young adulthood.

Calcium signalling and psychiatric disease: bipolar disorder and schizophrenia

Neurons have highly developed Ca(2+) signalling systems responsible for regulating many neural functions such as the generation of brain rhythms, information processing and the changes in synaptic plasticity that underpins learning and memory. The signalling mechanisms that regulate neuronal excitability are particularly important for processes such as sensory perception, cognition and consciousness. The Ca(2+) signalling pathway is a key component of the mechanisms responsible for regulating neuronal excitability, information processing and cognition. Alterations in gene transcription are particularly important as they result in subtle alterations in the neuronal signalling mechanisms that have been implicated in many neural diseases. In particular, dysregulation of the Ca(2+) signalling pathway has been implicated in the development of some of the major psychiatric diseases such as bipolar disorder (BPD) and schizophrenia.

Defective craniofacial development and brain function in a mouse model for depletion of intracellular inositol synthesis

myo-Inositol is an essential biomolecule that is synthesized by myo-inositol monophosphatase (IMPase) from inositol monophosphate species. The enzymatic activity of IMPase is inhibited by lithium, a drug used for the treatment of mood swings seen in bipolar disorder. Therefore, myo-inositol is thought to have an important role in the mechanism of bipolar disorder, although the details remain elusive. We screened an ethyl nitrosourea mutant mouse library for IMPase gene (Impa) mutations and identified an Impa1 T95K missense mutation. The mutant protein possessed undetectable enzymatic activity. Homozygotes died perinatally, and E18.5 embryos exhibited striking developmental defects, including hypoplasia of the mandible and asymmetric fusion of ribs to the sternum. Perinatal lethality and morphological defects in homozygotes were rescued by dietary myo-inositol. Rescued homozygotes raised on normal drinking water after weaning exhibited a hyper-locomotive trait and prolonged circadian periods, as reported in rodents treated with lithium. Our mice should be advantageous, compared with those generated by the conventional gene knock-out strategy, because they carry minimal genomic damage, e.g. a point mutation. In conclusion, our results reveal critical roles for intracellular myo-inositol synthesis in craniofacial development and the maintenance of proper brain function. Furthermore, this mouse model for cellular inositol depletion could be beneficial for understanding the molecular mechanisms underlying the clinical effect of lithium and myo-inositol-mediated skeletal development.

Circadian clock proteins in mood regulation

Mood regulation is known to be affected by the change of seasons. Recent research findings have suggested that mood regulation may be influenced by the function of circadian clocks. In addition, the activity of brown adipocytes has been hypothesized to contribute to mood regulation. Here, the overarching link to mood disorders might be the circadian clock protein nuclear receptor subfamily 1, group D, member 1.

Circadian rhythms and mood: opportunities for multi-level analyses in genomics and neuroscience: circadian rhythm dysregulation in mood disorders provides clues to the brain's organizing principles, and a touchstone for genomics and neuroscience

In the healthy state, both circadian rhythm and mood are stable against perturbations, yet they are capable of adjusting to altered internal cues or ongoing changes in external conditions. The dual demands of stability and flexibility are met by the collective properties of complex neural networks. Disruption of this balance underlies both circadian rhythm abnormality and mood disorders. However, we do not fully understand the network properties that govern the crosstalk between the circadian system and mood regulation. This puzzle reflects a challenge at the center of neurobiology, and its solution requires the successful integration of existing data across all levels of neural organization, from molecules, cells, circuits, network dynamics, to integrated mental function. This essay discusses several open questions confronting the cross-level synthesis, and proposes that circadian regulation, and its role in mood, stands as a uniquely tractable system to study the causal mechanisms of neural adaptation.

Does prior sepsis alter subsequent circadian and sickness behaviour response to lipopolysaccharide treatment in mice?

Previous data has shown that prior history of immune challenge may affect central and behavioural responses to subsequent immune challenge, either leading to exaggerated responses via priming mechanisms or lessened responses via endotoxin tolerance. In this set of experiments we have examined how previously lipopolysaccharide (LPS)-induced sepsis shapes the response to subsequent treatment with lower dose LPS. After treatment with LPS (5 mg/kg) or saline mice were allowed to recover for 3-4 months before being challenged with a lower dose of LPS (100 μg/kg) for assessment of sickness behaviours. Performance on the open field test and the tail suspension test was assessed, and no evidence was found that prior sepsis altered sickness or depressive-like behaviour following LPS treatment. We then examined the responsiveness of the circadian system of mice to LPS. We found that in control animals, LPS induced a significant phase delay of the behavioural rhythm and that this was not the case in post-septic animals (4-6 weeks after sepsis), indicating that prior sepsis alters the responsivity of the circadian system to subsequent immune challenge. We further assessed the induction of the immediate early genes c-Fos and EGR1 in the hippocampus and the suprachiasmatic nucleus (SCN; the master circadian pacemaker) by LPS in control or post-septic animals, and found that post-septic animals show elevated expression in the hippocampus but not the SCN. These data suggest that previous sepsis has some effect on behavioural and molecular responses to subsequent immune challenge in mice.

Circadian rhythms and psychiatric illness

PURPOSE OF REVIEW

The present review provides a conceptual introduction to sleep and circadian research in psychiatric illness, and discusses recent experimental and intervention findings in this area.

RECENT FINDINGS

In this review, studies published since January 2011 on circadian disturbance and psychiatric illness have been summarized.

SUMMARY

Exciting new results have increasingly utilized objective and validated instruments to measure the circadian system in experimental studies. Since 2011, treatment research has still predominantly utilized self-report measures as outcome variables. However, research in the treatment domain for sleep/circadian disturbances comorbid with psychiatric illness has advanced the field in its work to broaden the validation of existing sleep treatments to additional patient populations with comorbid sleep/circadian disruptions and address how to increase access to and affordability of treatment for sleep and circadian dysfunction for patients with psychiatric disorders, and how to combine psychosocial treatments with psychopharmacology to optimize treatment outcomes.

Mice exposed to dim light at night exaggerate inflammatory responses to lipopolysaccharide

The mammalian circadian system regulates many physiological functions including inflammatory responses. Appropriately timed light information is essential for maintaining circadian organization. Over the past ∼120 years, urbanization and the widespread adoption of electric lights have dramatically altered lighting environments. Exposure to light at night (LAN) is pervasive in modern society and disrupts core circadian clock mechanisms. Because microglia are the resident macrophages in the brain and macrophages contain intrinsic circadian clocks, we hypothesized that chronic exposure to LAN would alter microglia cytokine expression and sickness behavior following LPS administration. Exposure to 4 weeks of dim LAN elevated inflammatory responses in mice. Mice exposed to dimly lit, as compared to dark, nights exaggerated changes in body temperature and elevated microglia pro-inflammatory cytokine expression following LPS administration. Furthermore, dLAN mice had a prolonged sickness response following the LPS challenge. Mice exposed to dark or dimly lit nights had comparable sickness behavior directly following the LPS injection; however, dLAN mice showed greater reductions in locomotor activity, increased anorectic behavior, and increased weight loss than mice maintained in dark nights 24h post-LPS injection. Overall, these data suggest that chronic exposure to even very low levels of light pollution may alter inflammatory responses. These results may have important implications for humans and other urban dwelling species that commonly experience nighttime light exposure.

Exposure to light at night and risk of depression in the elderly

BACKGROUND

Recent advances in understanding the fundamental links between chronobiology and depressive disorders have enabled exploring novel risk factors for depression in the field of biological rhythms. Increased exposure to light at night (LAN) is common in modern life, and LAN exposure is associated with circadian misalignment. However, whether LAN exposure in home settings is associated with depression remains unclear.

METHODS

We measured the intensities of nighttime bedroom light and ambulatory daytime light along with overnight urinary melatonin excretion (UME) in 516 elderly individuals (mean age, 72.8). Depressive symptoms were assessed using the Geriatric Depression Scale.

RESULTS

The median nighttime light intensity was 0.8lx (interquartile range, 0.2-3.3). The depressed group (n=101) revealed significantly higher prevalence of LAN exposure (average intensity, ≥ 5 lx) compared with that of the nondepressed group (n=415) using a multivariate logistic regression model adjusted for daytime light exposure, insomnia, hypertension, sleep duration, and physical activity [adjusted odds ratio (OR): 1.89; 95% confidence interval (CI), 1.10-3.25; P=0.02]. Consistently, another parameter of LAN exposure (duration of intensity ≥ 10 lx, ≥ 30 min) was significantly more prevalent in the depressed than in the nondepressed group (adjusted OR: 1.71; 95% CI, 1.01-2.89; P=0.046). In contrast, UME was not significantly associated with depressive symptoms.

LIMITATION

Cross-sectional analysis.

CONCLUSION

These results suggested that LAN exposure in home settings is significantly associated with depressive symptoms in the general elderly population. The risk of depression may be reduced by keeping nighttime bedroom dark.

Circadian rhythm hypotheses of mixed features, antidepressant treatment resistance, and manic switching in bipolar disorder

Numerous hypotheses have been put forth over the years to explain the development of bipolar disorder. Of these, circadian rhythm hypotheses have gained much importance of late. While the hypothalamus-pituitary-adrenal (HPA) axis hyperactivation hypothesis and the monoamine hypothesis somewhat explain the pathogenic mechanism of depression, they do not provide an explanation for the development of mania/hypomania. Interestingly, all patients with bipolar disorder display significant disruption of circadian rhythms and sleep/wake cycles throughout their mood cycles. Indeed, mice carrying the Clock gene mutation exhibit an overall behavioral profile that is similar to human mania, including hyperactivity, decreased sleep, lowered depression-like behavior, and lower anxiety. It was recently reported that monoamine signaling is in fact regulated by the circadian system. Thus, circadian rhythm instability, imposed on the dysregulation of HPA axis and monoamine system, may in turn increase individual susceptibility for switching from depression to mania/hypomania. In addition to addressing the pathophysiologic mechanism underlying the manic switch, circadian rhythm hypotheses can explain other bipolar disorder-related phenomena such as treatment resistant depression and mixed features.