Circadian genes, rhythms and the biology of mood disorders

An earlier time of scan is associated with greater threat-related amygdala reactivity

Time-dependent variability in mood and anxiety suggest that related neural phenotypes, such as threat-related amygdala reactivity, may also follow a diurnal pattern. Here, using data from 1,043 young adult volunteers, we found that threat-related amygdala reactivity was negatively coupled with time of day, an effect which was stronger in the left hemisphere (β = -0.1083, p-fdr = 0.0012). This effect was moderated by subjective sleep quality (β = -0.0715, p-fdr = 0.0387); participants who reported average and poor sleep quality had relatively increased left amygdala reactivity in the morning. Bootstrapped simulations suggest that similar cross-sectional samples with at least 300 participants would be able to detect associations between amygdala reactivity and time of scan. In control analyses, we found no associations between time and V1 activation. Our results provide initial evidence that threat-related amygdala reactivity may vary diurnally, and that this effect is potentiated among individuals with average to low sleep quality. More broadly, our results suggest that considering time of scan in study design or modeling time of scan in analyses, as well as collecting additional measures of circadian variation, may be useful for understanding threat-related neural phenotypes and their associations with behavior, such as fear conditioning, mood and anxiety symptoms, and related phenotypes.

Individual differences in circadian locomotor parameters correlate with anxiety- and depression-like behavior

Disrupted circadian rhythms are a core feature of mood and anxiety disorders. Circadian rhythms are coordinated by a light-entrainable master clock located in the suprachiasmatic nucleus. Animal models of mood and anxiety disorders often exhibit blunted rhythms in locomotor activity and clock gene expression. Interestingly, the changes in circadian rhythms correlate with mood-related behaviours. Although animal models of depression and anxiety exhibit aberrant circadian rhythms in physiology and behavior, it is possible that the methodology being used to induce the behavioral phenotype (e.g., brain lesions, chronic stress, global gene deletion) affect behavior independently of circadian system. This study investigates the relationship between individual differences in circadian locomotor parameters and mood-related behaviors in healthy rats. The circadian phenotype of male Lewis rats was characterized by analyzing wheel running behavior under standard 12h:12h LD conditions, constant dark, constant light, and rate of re-entrainment to a phase advance. Rats were then tested on a battery of behavioral tests: activity box, restricted feeding, elevated plus maze, forced swim test, and fear conditioning. Under 12h:12h LD conditions, percent of daily activity in the light phase and variability in activity onset were associated with longer latency to immobility in the forced swim test. Variability in onset also correlated positively with anxiety-like behavior in the elevated plus maze. Rate of re-entrainment correlated positively with measures of anxiety in the activity box and elevated plus maze. Lastly, we found that free running period under constant dark was associated with anxiety-like behaviors in the activity box and elevated plus maze. Our results provide a previously uncharacterized relationship between circadian locomotor parameters and mood-related behaviors in healthy rats and provide a basis for future examination into circadian clock functioning and mood.

Implications of Circadian Rhythm in Dopamine and Mood Regulation

Mammalian physiology and behavior are regulated by an internal time-keeping system, referred to as circadian rhythm. The circadian timing system has a hierarchical organization composed of the master clock in the suprachiasmatic nucleus (SCN) and local clocks in extra-SCN brain regions and peripheral organs. The circadian clock molecular mechanism involves a network of transcription-translation feedback loops. In addition to the clinical association between circadian rhythm disruption and mood disorders, recent studies have suggested a molecular link between mood regulation and circadian rhythm. Specifically, genetic deletion of the circadian nuclear receptor Rev-erbα induces mania-like behavior caused by increased midbrain dopaminergic (DAergic) tone at dusk. The association between circadian rhythm and emotion-related behaviors can be applied to pathological conditions, including neurodegenerative diseases. In Parkinson's disease (PD), DAergic neurons in the substantia nigra pars compacta progressively degenerate leading to motor dysfunction. Patients with PD also exhibit non-motor symptoms, including sleep disorder and neuropsychiatric disorders. Thus, it is important to understand the mechanisms that link the molecular circadian clock and brain machinery in the regulation of emotional behaviors and related midbrain DAergic neuronal circuits in healthy and pathological states. This review summarizes the current literature regarding the association between circadian rhythm and mood regulation from a chronobiological perspective, and may provide insight into therapeutic approaches to target psychiatric symptoms in neurodegenerative diseases involving circadian rhythm dysfunction.

ARNTL, CLOCK and PER3 polymorphisms - links with chronotype and affective dimensions

Recently, seven single nucleotide polymorphisms (SNPs) of ARNTL, TIM and PER3 genes were found associated with affective temperaments in bipolar disorder patients. This study aimed to test whether a) the same associations appear in a non-clinical sample; b) the SNPs are related to other affective dimensions; c) the SNPs underpin the associations between chronotype and affective temperaments/dimensions. Three hundred thirty-eight university students completed the Temperament Scale of Memphis, Pisa, Paris and San Diego Auto-questionnaire, the Centre for Epidemiological Studies Depression Scale, the Perceived Stress Scale, the General Health Questionnaire, the Seasonal Pattern Assessment Questionnaire and the Composite Scale of Morningness. Seven SNPs of the ARNTL, TIM and PER3 genes were genotyped. According to nominal significance, ARNTL rs7107287 was associated with a cyclothymic temperament, depressive and stress symptoms, general mental health and perceived negative impact of seasonality, while TIM rs10876890 was associated with a hyperthymic temperament, and the TIM rs2291738 was associated with chronotype. Different SNPs were related to chronotype and affective temperaments/dimensions, and therefore, they seem to not underpin relationships between chronotype and affective dysfunction, that is, in the present study, eveningness was related to dysthymic, cyclothymic and irritable temperaments, more symptoms of depression, stress, worse mental health and a negative impact of seasonality, while morningness was related to hyperthymic temperament. The SNPs associations need further replication given that they did not achieve Bonferroni criteria of significance accounting for the number of polymorphisms considered and tests conducted.

Seasonal affective disorder and alcohol abuse disorder in a population-based study

Seasonal affective disorder (SAD) is a recurrent major depressive disorder with a seasonal pattern, which is characterized by sad mood, low energy, longer sleep duration and carbohydrate craving. Furthermore, seasonal changes in mood and behavior may be closely related to alcohol use disorder (AUD). Nevertheless, there is scarce research on the study of cognitive impairments in SAD and AUD. We aimed to examine the relationship between the prevalence between SAD and AUD patients, and how cognitive functioning might be related to these variables. To do this, a sample of 8135 Finnish subjects was invited to take part in the population-based Health 2011 Survey, of whom 5903 did participate and 4554 were interviewed for mental health status with the Munich version of Composite International Diagnostic Interview. They also completed the modified Seasonal Pattern Assessment Questionnaire, the Mini-Mental State Examination, the category (animals) verbal fluency test, and the Rey Auditory Verbal Learning Test. Our results reveal the existence of a strong link between SAD and AUD in a large sample of Finnish population, as well as association between SAD and short-term memory problems.

mPer1 promotes morphine-induced locomotor sensitization and conditioned place preference via histone deacetylase activity

RATIONALE

Previous studies have shown that repeated exposure to drugs of abuse is associated with changes in clock genes expression and that mice strains with various mutations in clock genes show alterations in drug-induced behaviors.

OBJECTIVE

The objective of this study is to characterize the role of the clock gene mPer1 in the development of morphine-induced behaviors and a possible link to histone deacetylase (HDAC) activity.

METHODS

In Per1 ^Brdm1 null mutant mice and wild-type (WT) littermates, we examined whether there were any differences in the development of morphine antinociception, tolerance to antinociception, withdrawal, sensitization to locomotion, and conditioned place preference (CPP).

RESULTS

Per1 ^Brdm1 mutant mice did not show any difference in morphine antinociception, tolerance development, nor in physical withdrawal signs precipitated by naloxone administration compared to WT. However, morphine-induced locomotor sensitization and CPP were significantly impaired in Per1 ^Brdm1 mutant mice. Because a very similar dissociation between tolerance and dependence vs. sensitization and CPP was recently observed after the co-administration of morphine and the HDAC inhibitor sodium butyrate (NaBut), we studied a possible link between mPer1 and HDAC activity. As opposed to WT controls, Per1 ^Brdm1 mutant mice showed significantly enhanced striatal global HDAC activity within the striatum when exposed to a locomotor-sensitizing morphine administration regimen. Furthermore, the administration of the HDAC inhibitor NaBut restored the ability of morphine to promote locomotor sensitization and reward in Per1 ^Brdm1 mutant mice.

CONCLUSIONS

Our results reveal that although the mPer1 gene does not alter morphine-induced antinociception nor withdrawal, it plays a prominent role in the development of morphine-induced behavioral sensitization and reward via inhibitory modulation of striatal HDAC activity. These data suggest that PER1 inhibits deacetylation to promote drug-induced neuroplastic changes.

New targets for rapid antidepressant action

Current therapeutic options for major depressive disorder (MDD) and bipolar disorder (BD) are associated with a lag of onset that can prolong distress and impairment for patients, and their antidepressant efficacy is often limited. All currently approved antidepressant medications for MDD act primarily through monoaminergic mechanisms. Glutamate is the major excitatory neurotransmitter in the central nervous system, and glutamate and its cognate receptors are implicated in the pathophysiology of MDD, and in the development of novel therapeutics for this disorder. The rapid and robust antidepressant effects of the N-methyl-d-aspartate (NMDA) antagonist ketamine were first observed in 2000. Since then, other NMDA receptor antagonists have been studied in MDD. Most have demonstrated relatively modest antidepressant effects compared to ketamine, but some have shown more favorable characteristics. This article reviews the clinical evidence supporting the use of novel glutamate receptor modulators with direct affinity for cognate receptors: (1) non-competitive NMDA receptor antagonists (ketamine, memantine, dextromethorphan, AZD6765); (2) subunit (GluN2B)-specific NMDA receptor antagonists (CP-101,606/traxoprodil, MK-0657); (3) NMDA receptor glycine-site partial agonists (GLYX-13); and (4) metabotropic glutamate receptor (mGluR) modulators (AZD2066, RO4917523/basimglurant). We also briefly discuss several other theoretical glutamate receptor targets with preclinical antidepressant-like efficacy that have yet to be studied clinically; these include α-amino-3-hydroxyl-5-methyl-4-isoxazoleproprionic acid (AMPA) agonists and mGluR2/3 negative allosteric modulators. The review also discusses other promising, non-glutamatergic targets for potential rapid antidepressant effects, including the cholinergic system (scopolamine), the opioid system (ALKS-5461), corticotropin releasing factor (CRF) receptor antagonists (CP-316,311), and others.

Clock Genes and Altered Sleep-Wake Rhythms: Their Role in the Development of Psychiatric Disorders

In mammals, the circadian clocks network (central and peripheral oscillators) controls circadian rhythms and orchestrates the expression of a range of downstream genes, allowing the organism to anticipate and adapt to environmental changes. Beyond their role in circadian rhythms, several studies have highlighted that circadian clock genes may have a more widespread physiological effect on cognition, mood, and reward-related behaviors. Furthermore, single nucleotide polymorphisms in core circadian clock genes have been associated with psychiatric disorders (such as autism spectrum disorder, schizophrenia, anxiety disorders, major depressive disorder, bipolar disorder, and attention deficit hyperactivity disorder). However, the underlying mechanisms of these associations remain to be ascertained and the cause–effect relationships are not clearly established. The objective of this article is to clarify the role of clock genes and altered sleep–wake rhythms in the development of psychiatric disorders (sleep problems are often observed at early onset of psychiatric disorders). First, the molecular mechanisms of circadian rhythms are described. Then, the relationships between disrupted circadian rhythms, including sleep–wake rhythms, and psychiatric disorders are discussed. Further research may open interesting perspectives with promising avenues for early detection and therapeutic intervention in psychiatric disorders.

Circadian Rhythm Dysregulation in Bipolar Spectrum Disorders

PURPOSE OF REVIEW

We review recent evidence for circadian rhythm dysregulation in bipolar spectrum disorders (BSDs). We examine evidence for endogenous abnormalities in the biological clock and disruptions in the external entrainment of circadian rhythms in BSDs. We also address whether circadian dysregulation provides vulnerability to onset of BSD and evidence for a new integration of reward and circadian dysregulation in BSD.

RECENT FINDINGS

Relative circadian phase delay (e.g., later melatonin peak, evening chronotype) is associated with BSD, particularly in the depressive phase. More consistent evidence supports irregularity of social rhythms, sleep/wake and activity patterns, and disruptions of social rhythms by life events, as stable trait markers of BSD and potential vulnerabilities for BSD onset. Growing research supports an integrative reward/circadian model. Both endogenous abnormalities in the biological clock pacemaking function and disruptions in the external entrainment of circadian rhythms by physical and social cues are involved in BSDs. Circadian dysregulation may provide vulnerability to BSD onset.

Clock-Enhancing Small Molecules and Potential Applications in Chronic Diseases and Aging

Normal physiological functions require a robust biological timer called the circadian clock. When clocks are dysregulated, misaligned, or dampened, pathological consequences ensue, leading to chronic diseases and accelerated aging. An emerging research area is the development of clock-targeting compounds that may serve as drug candidates to correct dysregulated rhythms and hence mitigate disease symptoms and age-related decline. In this review, we first present a concise view of the circadian oscillator, physiological networks, and regulatory mechanisms of circadian amplitude. Given a close association of circadian amplitude dampening and disease progression, clock-enhancing small molecules (CEMs) are of particular interest as candidate chronotherapeutics. A recent proof-of-principle study illustrated that the natural polymethoxylated flavonoid nobiletin directly targets the circadian oscillator and elicits robust metabolic improvements in mice. We describe mood disorders and aging as potential therapeutic targets of CEMs. Future studies of CEMs will shed important insight into the regulation and disease relevance of circadian clocks.

Circadian Plasticity of Mammalian Inhibitory Interneurons

Inhibitory interneurons participate in all neuronal circuits in the mammalian brain, including the circadian clock system, and are indispensable for their effective function. Although the clock neurons have different molecular and electrical properties, their main function is the generation of circadian oscillations. Here we review the circadian plasticity of GABAergic interneurons in several areas of the mammalian brain, suprachiasmatic nucleus, neocortex, hippocampus, olfactory bulb, cerebellum, striatum, and in the retina.

Comparison of Wearable Activity Tracker with Actigraphy for Sleep Evaluation and Circadian Rest-Activity Rhythm Measurement in Healthy Young Adults

OBJECTIVE

The purpose of this study was to evaluate the applicability of data obtained from a wearable activity tracker (Fitbit Charge HR) to medical research. This was performed by comparing the wearable activity tracker (Fitbit Charge HR) with actigraphy (Actiwatch 2) for sleep evaluation and circadian rest-activity rhythm measurement.

METHODS

Sixteen healthy young adults (female participants, 62.5%; mean age, 22.8 years) wore the Fitbit Charge HR and the Actiwatch 2 on the same wrist; a sleep log was recorded over a 14-day period. We compared the sleep variables and circadian rest-activity rhythm measures with Wilcoxon signed-rank tests and Spearman's correlations.

RESULTS

The periods and acrophases of the circadian rest-activity rhythms and the sleep start times did not differ and correlated significantly between the Fitbit Charge HR and the Actiwatch 2. The Fitbit Charge HR tended to overestimate the sleep durations compared with the Actiwatch 2. However, the sleep durations showed high correlation between the two devices for all days.

CONCLUSION

We found that the Fitbit Charge HR showed high accuracy in sleep evaluation and circadian rest-activity rhythm measurement when compared with actigraphy for healthy young adults. The results suggest that the Fitbit Charge HR could be applicable on medical research as an alternative tool to actigraphy for sleep evaluation and measurement of the circadian rest-activity rhythm.

Molecular Mechanisms in Mood Regulation Involving the Circadian Clock

The circadian system coordinates activities and functions in cells and tissues in order to optimize body functions in anticipation to daily changes in the environment. Disruption of the circadian system, due to irregular lifestyle such as rotating shift work, frequent travel across time-zones, or chronic stress, is correlated with several diseases such as obesity, cancer, and neurological disorders. Molecular mechanisms linking the circadian clock with neurological functions have been uncovered suggesting that disruption of the clock may be critically involved in the development of mood disorders. In this mini-review, I will summarize molecular mechanisms in which clock components play a central role for mood regulation. Such mechanisms have been identified in the monoaminergic system, the HPA axis, and neurogenesis.

Is physiological glucocorticoid replacement important in children?

Cortisol has a distinct circadian rhythm with low concentrations at night, rising in the early hours of the morning, peaking on waking and declining over the day to low concentrations in the evening. Loss of this circadian rhythm, as seen in jetlag and shift work, is associated with fatigue in the short term and diabetes and obesity in the medium to long term. Patients with adrenal insufficiency on current glucocorticoid replacement with hydrocortisone have unphysiological cortisol concentrations being low on waking and high after each dose of hydrocortisone. Patients with adrenal insufficiency complain of fatigue, a poor quality of life and there is evidence of poor health outcomes including obesity potentially related to glucocorticoid replacement. New technologies are being developed that deliver more physiological glucocorticoid replacement including hydrocortisone by subcutaneous pump, Plenadren, a once-daily modified-release hydrocortisone and Chronocort, a delayed and sustained absorption hydrocortisone formulation that replicates the overnight profile of cortisol. In this review, we summarise the evidence regarding physiological glucocorticoid replacement with a focus on relevance to paediatrics.

Genetic Basis of Chronotype in Humans: Insights From Three Landmark GWAS

Study Objectives

Chronotype, or diurnal preference, refers to behavioral manifestations of the endogenous circadian system that governs preferred timing of sleep and wake. As variations in circadian timing and system perturbations are linked to disease development, the fundamental biology of chronotype has received attention for its role in the regulation and dysregulation of sleep and related illnesses. Family studies indicate that chronotype is a heritable trait, thus directing attention toward its genetic basis. Although discoveries from molecular studies of candidate genes have shed light onto its genetic architecture, the contribution of genetic variation to chronotype has remained unclear with few related variants identified. In the advent of large-scale genome-wide association studies (GWAS), scientists now have the ability to discover novel common genetic variants associated with complex phenotypes. Three recent large-scale GWASs of chronotype were conducted on subjects of European ancestry from the 23andMe cohort and the UK Biobank. This review discusses the findings of these landmark GWASs in the context of prior research.

Methods

We systematically reviewed and compared methodological and analytical approaches and results across the three GWASs of chronotype.

Results

A good deal of consistency was observed across studies with 9 genes identified in 2 of the 3 GWASs. Several genes previously unknown to influence chronotype were identified.

Conclusions

GWAS is an important tool in identifying common variants associated with the complex chronotype phenotype, the findings of which can supplement and guide molecular science. Future directions in model systems and discovery of rare variants are discussed.

A multicenter randomized controlled trial for bright light therapy in adults with intellectual disabilities and depression: Study protocol and obstacle management

Due to the limited cognitive and communicative abilities of adults with intellectual disabilities (ID), current treatment options for depression are often limited to lifestyle changes and pharmacological treatment. Bright light therapy (BLT) is an effective intervention for both seasonal and non-seasonal depression in the general population. BLT is an inexpensive, easy to carry out intervention with minimal side effects. However, knowledge on its anti-depressant effect in adults with ID is lacking. Obstacles in realizing a controlled intervention study in this particular study population may have contributed to this lack. To study the effect of BLT on depression in this population, it is necessary to successfully execute a multicenter randomized controlled trial (RCT). Therefore, the study protocol and the management of anticipated obstacles regarding this trial are presented.

Low social rhythm regularity predicts first onset of bipolar spectrum disorders among at-risk individuals with reward hypersensitivity

The social zeitgeber model (Ehlers, Frank, & Kupfer, 1988) suggests that irregular daily schedules or social rhythms provide vulnerability to bipolar spectrum disorders. This study tested whether social rhythm regularity prospectively predicted first lifetime onset of bipolar spectrum disorders in adolescents already at risk for bipolar disorder based on exhibiting reward hypersensitivity. Adolescents (ages 14-19 years) previously screened to have high (n = 138) or moderate (n = 95) reward sensitivity, but no lifetime history of bipolar spectrum disorder, completed measures of depressive and manic symptoms, family history of bipolar disorder, and the Social Rhythm Metric. They were followed prospectively with semistructured diagnostic interviews every 6 months for an average of 31.7 (SD = 20.1) months. Hierarchical logistic regression indicated that low social rhythm regularity at baseline predicted greater likelihood of first onset of bipolar spectrum disorder over follow-up among high-reward-sensitivity adolescents but not moderate-reward-sensitivity adolescents, controlling for follow-up time, gender, age, family history of bipolar disorder, and initial manic and depressive symptoms (β = -.150, Wald = 4.365, p = .037, odds ratio = .861, 95% confidence interval [.748, .991]). Consistent with the social zeitgeber theory, low social rhythm regularity provides vulnerability to first onset of bipolar spectrum disorder among at-risk adolescents. It may be possible to identify adolescents at risk for developing a bipolar spectrum disorder based on exhibiting both reward hypersensitivity and social rhythm irregularity before onset occurs.

Genetic Disruption of Circadian Rhythms in the Suprachiasmatic Nucleus Causes Helplessness, Behavioral Despair, and Anxiety-like Behavior in Mice

BACKGROUND

Major depressive disorder is associated with disturbed circadian rhythms. To investigate the causal relationship between mood disorders and circadian clock disruption, previous studies in animal models have employed light/dark manipulations, global mutations of clock genes, or brain area lesions. However, light can impact mood by noncircadian mechanisms; clock genes have pleiotropic, clock-independent functions; and brain lesions not only disrupt cellular circadian rhythms but also destroy cells and eliminate important neuronal connections, including light reception pathways. Thus, a definitive causal role for functioning circadian clocks in mood regulation has not been established.

METHODS

We stereotactically injected viral vectors encoding short hairpin RNA to knock down expression of the essential clock gene Bmal1 into the brain's master circadian pacemaker, the suprachiasmatic nucleus (SCN).

RESULTS

In these SCN-specific Bmal1-knockdown (SCN-Bmal1-KD) mice, circadian rhythms were greatly attenuated in the SCN, while the mice were maintained in a standard light/dark cycle, SCN neurons remained intact, and neuronal connections were undisturbed, including photic inputs. In the learned helplessness paradigm, the SCN-Bmal1-KD mice were slower to escape, even before exposure to inescapable stress. They also spent more time immobile in the tail suspension test and less time in the lighted section of a light/dark box. The SCN-Bmal1-KD mice also showed greater weight gain, an abnormal circadian pattern of corticosterone, and an attenuated increase of corticosterone in response to stress.

CONCLUSIONS

Disrupting SCN circadian rhythms is sufficient to cause helplessness, behavioral despair, and anxiety-like behavior in mice, establishing SCN-Bmal1-KD mice as a new animal model of depression.

Treatment of depression with low-strength transcranial pulsed electromagnetic fields: A mechanistic point of view

BACKGROUND

Mood disorders constitute a high burden for both patients and society. Notwithstanding the large arsenal of available treatment options, a considerable group of patients does not remit on current antidepressant treatment. There is an urgent need to develop alternative treatment strategies. Recently, low-strength transcranial pulsed electromagnetic field (tPEMF) stimulation has been purported as a promising strategy for such treatment-resistant depression (TRD). The mode of action of this new technique is however largely unknown.

METHODS

We searched PubMed for literature reports on the effects of tPEMF and for information regarding its working mechanism and biological substrate.

RESULTS

Most studies more or less connect with the major hypotheses of depression and concern the effects of tPEMF on brain metabolism, neuronal connectivity, brain plasticity, and the immune system. Relatively few studies paid attention to the possible chronobiologic effects of electromagnetic fields.

LIMITATIONS

We reviewed the literature of a new and still developing field. Some of the reports involved translational studies, which inevitably limits the reach of the conclusions.

CONCLUSION

Weak magnetic fields influence divergent neurobiological processes. The antidepressant effect of tPEMF may be specifically attributable to its effects on local brain activity and connectivity.

Influence of lithium on sleep and chronotypes in remitted patients with bipolar disorder

BACKGROUND

Lithium (Li) is the first-line treatment for bipolar disorder (BD), but its mechanisms of action remain unknown. Although the chronobiological action of Li is well documented in animals, its effects on sleep and chronotypes in remitted BD patients have never been investigated.

METHODS

OPTHYMUM is a multicenter, cross-sectional, observational study conducted in France. We compared the sleep (Pittsburgh Sleep Quality Index, PSQI) and chronotypes (Composite Scale of Morningness, CSM) of 525 euthymic adult bipolar outpatients with (n=149) and without (n=376) current Li treatment. We used a general linear mixed-effects Poisson model to correct for age, gender, BD subtype, and mood symptoms.

RESULTS

In patients with BD type I, women taking Li had significantly lower PSQI (-23% [-37; -7]), but men did not (-4% [-20; +16]). Patients with BD I taking Li had better sleep efficiency (-40% [-61; -7]) and tended to better sleep duration scores (-42% [-68; +3]). A Li effect exists in women for both sleep duration and the use of night sedation (resp. -70% [-90; -10] and -37% [-60; +0.01]) but not in men (resp. -12% [-63;+113] and +9% [-31;+72]). No such associations were observed for BD II. No lithium effect was detected in the CSM score.

LIMITATIONS

No controls for other medications but no between-group differences for sedative or antidepressant intakes.

CONCLUSIONS

Euthymic BD I patients with Li have better sleep efficiency and longer sleep duration than those without Li. Women with Li have better sleep quality, longer sleep duration and less frequent use of night sedation.

A double-blind randomized controlled trial to assess the effect of bright light therapy on depression in patients with Parkinson's disease

BACKGROUND

A disturbed circadian rhythm seems to be a causal factor in the occurrence of depressive disorders in patients with Parkinson's disease (PD). The circadian rhythm can be restored with light. Therefore, Bright Light Therapy (BLT) might be a new treatment option for depression in PD patients.

METHODS/DESIGN

In this double-blind controlled trial, 84 subjects with idiopathic PD are randomized to either BLT or a control light condition. The BLT condition emits white light with an intensity of 10,000 Lux, while the control device emits dim white light of 200 Lux, which is presumed to be too low to influence the circadian rhythm. Subjects receive 30 min of home treatment twice daily for three months. Timing of treatment is based on the individual chronotype. After finishing treatment, subjects enter a follow-up period of six months. The primary outcome of the study is the severity of depressive symptoms, as measured with the Hamilton Depression Rating Scale. Secondary outcomes are alternative depression measures, objective and subjective sleep measures, and salivary melatonin and cortisol concentrations. For exploratory purposes, we also assess the effects on motor symptoms, global cognitive function, comorbid psychiatric disorders, quality of life and caregiver burden. Data will be analyzed using a linear mixed models analysis.

DISCUSSION

Performing a placebo-controlled trial on the effects of BLT in PD patients is challenging, as the appearance of the light may provide clues on the treatment condition. Moreover, fixed treatment times lead to an improved sleep-wake rhythm, which also influences the circadian system. With our study design, we do not compare BLT to placebo treatment, i.e. an ineffective control treatment. Rather, we compare structuring of the sleep-wake cycle in both conditions with additional BLT in the experimental condition, and additional dim light in the control condition. Participants are not informed about the exact details of the two light devices and the expected therapeutic effect, and expectancies are rated prior to the start of treatment. Ideally, the design of a future study on BLT should include two extra treatment arms where BLT and control light are administered at random times.

TRIAL REGISTRATION

This trial was registered on ClinicalTrials.gov on May 17th 2012 (ClinicalTrials.gov Identifier: NCT01604876 ).

Schizophrenia: the role of sleep and circadian rhythms in regulating dopamine and psychosis

Schizophrenia has long been associated with abnormalities in circadian rhythms and sleep. Up until now, there have been no thorough reviews of the potential mechanisms behind the myriad of circadian and sleep abnormalities observed in schizophrenia and psychosis. We present evidence of sleep playing an important role in psychosis predominantly mediated by dopaminergic pathways. A synthesis of both human and animal experimental work suggests that the interplay between sleep and dopamine is important in the generation and maintenance of psychosis. In particular, both animal and human data point to sleep disruption increasing dopamine release and sensitivity. Furthermore, elevated dopamine levels disrupt sleep and circadian rhythms. The synthesis of knowledge suggests that circadian rhythms, dopamine dysregulation, and psychosis are intricately linked. This suggests that treatment of circadian disturbance may be a useful target in improving the lives and symptoms of patients with schizophrenia.

Utilization of Diurnal Rodents in the Research of Depression

Preclinical Research Most neuropsychiatric research, including that related to the circadian system, is performed using nocturnal animals, mainly laboratory mice and rats. Mood disorders are known to be associated with circadian rhythm abnormalities, but the mechanisms by which circadian rhythm disruptions interact with depression remain unclear. As the circadian system of diurnal and nocturnal mammals differs, we previously suggested that the utilization of diurnal animal models may be advantageous for understanding these relations. During the last 10 years, we and others established the validity of several diurnal rodent species as a model for the interactions between circadian rhythms and depression. Diurnal rodents respond to photoperiod manipulation in a similar way to humans, the behavioral outcome is directly related to the circadian system, and treatment that is effective in patients is also effective in the model. Moreover, less effective treatments in patients are also less effective in the model. We, therefore, suggest that using diurnal animal models to study circadian rhythms-related affective disorders, such as depression, will provide new insights that will hopefully lead to the development of more effective treatments. Drug Dev Res 77 : 347-356, 2016. © 2016 Wiley Periodicals, Inc.

SCOP/PHLPP1β in the basolateral amygdala regulates circadian expression of mouse anxiety-like behavior

While disruption of the circadian clock triggers a spectrum of affective abnormalities, how the clock regulates mammalian emotionality remains unclear. Here, we characterized the time-of-day-dependent regulation of mouse anxiety-like behaviors. We show that anxiety-like behaviors are expressed in a circadian manner in mice and demonstrate that the clock machineries in the dorsal telencephalon (dTel) are required for the time-of-day-dependent regulation of anxiety-like behaviors. We identify suprachiasmatic nucleus circadian oscillatory protein (SCOP/PHLPP1β) as an essential intracellular signaling molecule mediating this temporal regulation downstream of the clock. Using viral-mediated, basolateral amygdala (BLA)-specific knockout of Scop, we demonstrate that deletion of SCOP in the BLA exerts anxiolytic effects on the elevated plus maze at early subjective night, thereby blunting the circadian variation in the anxiety-like behavior. We conclude that the circadian expression of SCOP in the BLA plays a key role in generating circadian rhythmicity in the anxiety-like behavior. Our results demonstrate SCOP as a regulator of anxiety-like behaviors and reveal its key roles in the anxiogenic functions of the BLA.

Mood and motor activity in euthymic bipolar disorder with sleep disturbance

BACKGROUND

The aims of this observational study of patients with euthymic bipolar disorder and sleep disturbance were to 1) compare characteristics related to mood and sleep between two groups with stable and unstable rest-activity cycles and 2) detect between-group differences in motor activity patterns.

METHODS

43 patients wore an actigraph for 6-8 days while reporting daily mood and sleep. Patients were defined as having an unstable rest-activity cycle if their diurnal active period duration presented variation above 2h from the mean during one week: 22 patients had stable and 21 unstable rest-activity cycles. Mood variability was defined as at least moderate symptoms and a change across two levels on a 7-point mood scale during one week.

RESULTS

Patients with unstable rest-activity cycles were younger (37 vs. 48 years, p=0.01) and displayed more mood variability (p=0.02). Ten of 11 patients diagnosed with delayed sleep phase disorder were in the unstable group (p<0.01), and the unstable group had later and more variable get-up-times and bedtimes. In actigraphy recordings, the mean activity counts per minute did not differ between groups, but the minute-to-minute variability was elevated (p=0.04) and increased relative to the overall variability (p=0.03).

LIMITATIONS

A relatively small study sample and a 1-week study period prevent exploration of long-term clinical implications of results.

CONCLUSIONS

A subgroup of euthymic patients with bipolar disorder displayed unstable rest-activity cycles combined with mood variability and motor activity patterns that resemble findings in affective episodes.

Dim light at night prior to adolescence increases adult anxiety-like behaviors

Dim light at night (dLAN) disrupts circadian organization and influences adult behavior. We examined early dLAN exposure on adult affective responses. Beginning 3 (juvenile) or 5 weeks (adolescent) of age, mice were maintained in standard light-dark cycles or exposed to nightly dLAN (5 lx) for 5 weeks, then anxiety-like and fear responses were assessed. Hypothalami were collected around the clock to assess core clock genes. Exposure to dLAN at either age increased anxiety-like responses in adults. Clock and Rev-ERB expression were altered by exposure to dLAN. In contrast to adults, dLAN exposure during early life increases anxiety and fear behavior.

Circadian influences on dopamine circuits of the brain: regulation of striatal rhythms of clock gene expression and implications for psychopathology and disease

Circadian clock proteins form an autoregulatory feedback loop that is central to the endogenous generation and transmission of daily rhythms in behavior and physiology. Increasingly, circadian rhythms in clock gene expression are being reported in diverse tissues and brain regions that lie outside of the suprachiasmatic nucleus (SCN), the master circadian clock in mammals. For many of these extra-SCN rhythms, however, the region-specific implications are still emerging. In order to gain important insights into the potential behavioral, physiological, and psychological relevance of these daily oscillations, researchers have begun to focus on describing the neurochemical, hormonal, metabolic, and epigenetic contributions to the regulation of these rhythms. This review will highlight important sites and sources of circadian control within dopaminergic and striatal circuitries of the brain and will discuss potential implications for psychopathology and disease . For example, rhythms in clock gene expression in the dorsal striatum are sensitive to changes in dopamine release, which has potential implications for Parkinson’s disease and drug addiction. Rhythms in the ventral striatum and limbic forebrain are sensitive to psychological and physical stressors, which may have implications for major depressive disorder. Collectively, a rich circadian tapestry has emerged that forces us to expand traditional views and to reconsider the psychopathological, behavioral, and physiological importance of these region-specific rhythms in brain areas that are not immediately linked with the regulation of circadian rhythms.

Advanced Circadian Phase in Mania and Delayed Circadian Phase in Mixed Mania and Depression Returned to Normal after Treatment of Bipolar Disorder

Disturbances in circadian rhythms have been suggested as a possible cause of bipolar disorder (BD). Included in this study were 31 mood episodes of 26 BD patients, and 18 controls. Circadian rhythms of BD were evaluated at admission, at 2-week intervals during hospitalization, and at discharge. All participants wore wrist actigraphs during the studies. Saliva and buccal cells were obtained at 8:00, 11:00, 15:00, 19:00, and 23:00 for two consecutive days. Collected saliva and buccal cells were used for analysis of the cortisol and gene circadian rhythm, respectively. Circadian rhythms had different phases during acute mood episodes of BD compared to recovered states. In 23 acute manic episodes, circadian phases were ~ 7 hour advanced (equivalent to ~ 17 hour delayed). Phases of 21 out of these 23 cases returned to normal by ~ 7 hour delay along with treatment, but two out of 23 cases returned to normal by ~ 17 hour advance. In three cases of mixed manic episodes, the phases were ~ 6–7 hour delayed. For five cases of depressive episodes, circadian rhythms phases were ~ 4–5 hour delayed. After treatment, circadian phases resembled those of healthy controls. Circadian misalignment due to circadian rhythm phase shifts might be a pathophysiological mechanism of BD.

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Bipolar disorder in acute mood episodes showed circadian dysregulation due to phase shifts which returned to normal after treatment.

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Acute manias were ~ 7 h circadian phase advanced, mixed manias were > 6 h delayed, whereas depressions were 4-5 h delayed compared to the controls.

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Circadian dysregulation due circadian rhythm phase shifts might be a pathophysiological mechanism of bipolar disorder.

Bipolar disorder is a common mental disorder characterized by mood disturbances with alternating episodes of mania and depression. Circadian rhythms are rhythms of about 24 h found in many body functions. We repeatedly measured circadian rhythms in bipolar disorder patients during hospitalization. Acute manic episodes were associated with circadian dysregulation of ~ 7 hour phase advances, mixed manias were > 6 hour delayed, whereas bipolar depression was associated with 4–5 hour phase delays compared to the controls. After treatment, the shifted rhythms recovered to the normal range. This study suggests that novel chronotherapy approaches based on our findings might be found useful for the prevention and treatment of bipolar disorder.

Multi-target therapeutics for neuropsychiatric and neurodegenerative disorders

Historically, neuropsychiatric and neurodegenerative disease treatments focused on the 'magic bullet' concept; however multi-targeted strategies are increasingly attractive gauging from the escalating research in this area. Because these diseases are typically co-morbid, multi-targeted drugs capable of interacting with multiple targets will expand treatment to the co-morbid disease condition. Despite their theoretical efficacy, there are significant impediments to clinical success (e.g., difficulty titrating individual aspects of the drug and inconclusive pathophysiological mechanisms). The new and revised diagnostic frameworks along with studies detailing the endophenotypic characteristics of the diseases promise to provide the foundation for the circumvention of these impediments. This review serves to evaluate the various marketed and nonmarketed multi-targeted drugs with particular emphasis on their design strategy.

Altered Expression Pattern of Clock Genes in a Rat Model of Depression

BACKGROUND

Abnormalities in circadian rhythms may be causal factors in development of major depressive disorder. The biology underlying a causal relationship between circadian rhythm disturbances and depression is slowly being unraveled. Although there is no direct evidence of dysregulation of clock gene expression in depressive patients, many studies have reported single-nucleotide polymorphisms in clock genes in these patients.

METHODS

In the present study we investigated whether a depression-like state in rats is associated with alternations of the diurnal expression of clock genes. The validated chronic mild stress (CMS) animal model of depression was used to investigate rhythmic expression of three clock genes: period genes 1 and 2 (Per1 and Per2) and Bmal1. Brain and liver tissue was collected from 96 animals after 3.5 weeks of CMS (48 control and 48 depression-like rats) at a 4h sampling interval within 24h. We quantified expression of clock genes on brain sections in the prefrontal cortex, nucleus accumbens, pineal gland, suprachiasmatic nucleus, substantia nigra, amygdala, ventral tegmental area, subfields of the hippocampus, and the lateral habenula using in situ hybridization histochemistry. Expression of clock genes in the liver was monitored by real-time quantitative polymerase chain reaction (PCR).

RESULTS

We found that the effect of CMS on clock gene expression was selective and region specific. Per1 exhibits a robust diurnal rhythm in most regions of interest, whereas Bmal1 and in particular Per2 were susceptible to CMS.

CONCLUSION

The present results suggest that altered expression of investigated clock genes is likely associated with the induction of a depression-like state in the CMS model.

Light therapy in the treatment of patients with bipolar depression: A meta-analytic study

Light therapy (LT) has been widely used in the treatment of seasonal affective disorder. Recently some evidence indicated that LT may play a role in bipolar depression, either as monotherapy or in combination with total sleep deprivation (TSD). However, the studies examining the treatment effect of LT in bipolar depression resulted in inconsistent findings. To clarify the role of LT in the disorder, we conducted a meta-analysis to compare the efficacy of LT in the treatment of bipolar depression. The results of individual studies were synthesized by a random effects model. Nine studies including 489 patients with bipolar depression were included in this current meta-analysis. We found that disease severity was significantly decreased after LT, in both with and without TSD, and with concomitant medication (p<0.001). Augmentation treatment with LT significantly decreased disease severity compared to treatment without LT (p=0.024). Our results highlight the significant efficacy of LT, either as monotherapy or in combination with TSD, in the treatment of bipolar depression. However, the detailed mechanism of LT still remains elusive. Further well-designed controlled trials are required to investigate the optimal intensity and frequency of LT in the treatment of bipolar depression.

Impact of chronobiology on neuropathic pain treatment

Inflammatory pain exhibits circadian rhythmicity. Recently, a distinct diurnal pattern has been described for peripheral neuropathic conditions. This diurnal variation has several implications: advancing understanding of chronobiology may facilitate identification of new and improved treatments; developing pain-contingent strategies that maximize treatment at times of the day associated with highest pain intensity may provide optimal pain relief as well as minimize treatment-related adverse effects (e.g., daytime cognitive dysfunction); and consideration of the impact of chronobiology on pain measurement may lead to improvements in analgesic study design that will maximize assay sensitivity of clinical trials. Recent and ongoing chronobiology studies are thus expected to advance knowledge and treatment of neuropathic pain.

I Believe I Can Fly!: Use of Drosophila as a Model Organism in Neuropsychopharmacology Research

Neuropsychiatric disorders are of complex etiology, often including a large genetic component. In order to help identify and study the molecular and physiological mechanisms that such genes participate in, numerous animal models have been established in a variety of species. Over the past decade, this has increasingly included the vinegar fly, Drosophila melanogaster. Here, we outline why we study an invertebrate organism in the context of neuropsychiatric disorders, and we discuss how we can gain insight from studies in Drosophila. We focus on a few disorders and findings to make the larger point that modeling these diseases in flies can have both mechanistic and predictive validity. Highlighting some translational examples, we underline the fact that their brains works more like ours than one would have anticipated.

Pushing the threshold: How NMDAR antagonists induce homeostasis through protein synthesis to remedy depression

Healthy neurons have an optimal operating range, coded globally by the frequency of action potentials or locally by calcium. The maintenance of this range is governed by homeostatic plasticity. Here, we discuss how new approaches to treat depression alter synaptic activity. These approaches induce the neuron to recruit homeostatic mechanisms to relieve depression. Homeostasis generally implies that the direction of activity necessary to restore the neuron's critical operating range is opposite in direction to its current activity pattern. Unconventional antidepressant therapies-deep brain stimulation and NMDAR antagonists-alter the neuron's "depressed" state by pushing the neuron's current activity in the same direction but to the extreme edge. These therapies rally the intrinsic drive of neurons in the opposite direction, thereby allowing the cell to return to baseline activity, form new synapses, and restore proper communication. In this review, we discuss seminal studies on protein synthesis dependent homeostatic plasticity and their contribution to our understanding of molecular mechanisms underlying the effectiveness of NMDAR antagonists as rapid antidepressants. Rapid antidepressant efficacy is likely to require a cascade of mRNA translational regulation. Emerging evidence suggests that changes in synaptic strength or intrinsic excitability converge on the same protein synthesis pathways, relieving depressive symptoms. Thus, we address the question: Are there multiple homeostatic mechanisms that induce the neuron and neuronal circuits to self-correct to regulate mood in vivo? Targeting alternative ways to induce homeostatic protein synthesis may provide, faster, safer, and longer lasting antidepressants. This article is part of a Special Issue entitled SI:RNA Metabolism in Disease.

Disturbed diurnal rhythm of three classical phase markers in the chronic mild stress rat model of depression

Disturbances of circadian rhythms have been suggested to be a causal factor in the development of major depressive disorder. However, the mechanisms underlying the association between circadian rhythm abnormalities and mood disorders are still unknown. In the current study the association between diurnal pattern of key phase markers (melatonin, corticosterone, and core body temperature) and anhedonic-like behavior was investigated using the highly validated rat chronic mild stress (CMS) model of depression. Phase marker measurements were done after 3.5 weeks of CMS in 48 control rats and 48 anhedonic-like rats at 6 time points within 24h. The results showed that anhedonic-like behavior associates with changes in all three phase markers: an increased dark phase melatonin secretion, an additional peak in corticosterone level in the beginning of the light phase, and hypothermia in the dark phase. The result adds to the validity of the CMS model in general and in particular to be adequate as a model for studying the chronobiology of depressive disorder.

A PERIOD3 variant causes a circadian phenotype and is associated with a seasonal mood trait

In humans, the connection between sleep and mood has long been recognized, although direct molecular evidence is lacking. We identified two rare variants in the circadian clock gene PERIOD3 (PER3-P415A/H417R) in humans with familial advanced sleep phase accompanied by higher Beck Depression Inventory and seasonality scores. hPER3-P415A/H417R transgenic mice showed an altered circadian period under constant light and exhibited phase shifts of the sleep-wake cycle in a short light period (photoperiod) paradigm. Molecular characterization revealed that the rare variants destabilized PER3 and failed to stabilize PERIOD1/2 proteins, which play critical roles in circadian timing. Although hPER3-P415A/H417R-Tg mice showed a mild depression-like phenotype, Per3 knockout mice demonstrated consistent depression-like behavior, particularly when studied under a short photoperiod, supporting a possible role for PER3 in mood regulation. These findings suggest that PER3 may be a nexus for sleep and mood regulation while fine-tuning these processes to adapt to seasonal changes.

Molecular analyses of circadian gene variants reveal sex-dependent links between depression and clocks

An extensive literature links circadian irregularities and/or sleep abnormalities to mood disorders. Despite the strong genetic component underlying many mood disorders, however, previous genetic associations between circadian clock gene variants and major depressive disorder (MDD) have been weak. We applied a combined molecular/functional and genetic association approach to circadian gene polymorphisms in sex-stratified populations of control subjects and case subjects suffering from MDD. This approach identified significant sex-dependent associations of common variants of the circadian clock genes hClock, hPer3 and hNpas2 with major depression and demonstrated functional effects of these polymorphisms on the expression or activity of the hCLOCK and hPER3 proteins, respectively. In addition, hCLOCK expression is affected by glucocorticoids, consistent with the sex-dependency of the genetic associations and the modulation of glucocorticoid-mediated stress response, providing a mechanism by which the circadian clock controls outputs that may affect psychiatric disorders. We conclude that genetic polymorphisms in circadian genes (especially hClock and hPer3, where functional assays could be tested) influence risk of developing depression in a sex- and stress-dependent manner. These studies support a genetic connection between circadian disruption and mood disorders, and confirm a key connection between circadian gene variation and major depression.

Altered Sleep Homeostasis in Rev-erbα Knockout Mice

STUDY OBJECTIVES

The nuclear receptor REV-ERBα is a potent, constitutive transcriptional repressor critical for the regulation of key circadian and metabolic genes. Recently, REV-ERBα's involvement in learning, neurogenesis, mood, and dopamine turnover was demonstrated suggesting a specific role in central nervous system functioning. We have previously shown that the brain expression of several core clock genes, including Rev-erbα, is modulated by sleep loss. We here test the consequences of a loss of REV-ERBα on the homeostatic regulation of sleep.

METHODS

EEG/EMG signals were recorded in Rev-erbα knockout (KO) mice and their wild type (WT) littermates during baseline, sleep deprivation, and recovery. Cortical gene expression measurements after sleep deprivation were contrasted to baseline.

RESULTS

Although baseline sleep/wake duration was remarkably similar, KO mice showed an advance of the sleep/wake distribution relative to the light-dark cycle. After sleep onset in baseline and after sleep deprivation, both EEG delta power (1-4 Hz) and sleep consolidation were reduced in KO mice indicating a slower increase of homeostatic sleep need during wakefulness. This slower increase might relate to the smaller increase in theta and gamma power observed in the waking EEG prior to sleep onset under both conditions. Indeed, the increased theta activity during wakefulness predicted delta power in subsequent NREM sleep. Lack of Rev-erbα increased Bmal1, Npas2, Clock, and Fabp7 expression, confirming the direct regulation of these genes by REV-ERBα also in the brain.

CONCLUSIONS

Our results add further proof to the notion that clock genes are involved in sleep homeostasis. Because accumulating evidence directly links REV-ERBα to dopamine signaling the altered homeostatic regulation of sleep reported here are discussed in that context.

Molecular neurobiological clues to the pathogenesis of bipolar disorder

Bipolar disorder is a serious psychiatric disorder, with a high heritability and unknown pathogenesis. Recent genome-wide association studies have identified the first loci, implicating genes such as CACNA1C and ANK3. The genes highlight several pathways, notably calcium signalling, as being of importance. Molecular studies suggest that the risk variants impact on gene regulation and expression. Preliminary studies using reprogrammed patient-derived cells report alterations in the transcriptome and in cellular adhesion and differentiation. Mouse models show that genes involved in circadian biology, acting via dopaminergic effects, reproduce aspects of the bipolar phenotype. These findings together represent significant advances in identification of the genetic and molecular basis of bipolar disorder, yet we are still far from an integrated, evidence-based understanding of its aetiopathogenesis.