Genetic polymorphisms associated with circadian rhythm dysregulation provide new perspectives on bipolar disorder

Associations between chronotype, sleep quality, maternal mental health, and child development in mother-infant dyads

OBJECTIVE/BACKGROUND

Studies on circadian rhythms throughout development and their physiological and behavioral impacts at early stages are still scarce. Previous studies have shown that mother-infant interactions are important for both sleep and child development. In this cross-sectional study we investigated whether infants' chronotype, sleep and development were associated with their respective mothers' chronotype, sleep, mental health and socioeconomic status.

PATIENTS/METHODS

the following were used to evaluate mothers: the Morningness-Eveningness Questionnaire (MEQ), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS) and Self-Reporting Questionnaire 20 (SRQ-20). To assess the infants' characteristics, the following were used: the 19th question from the Morningness-Eveningness Questionnaire (MEQ), infant nocturnal midpoint of sleep (iMSF), Brief Infant Sleep Questionnaire (BISQ) and Ages and Stages Questionnaire-3 (ASQ3). Socioeconomic aspects were assessed using the Brazilian Economic Class Criterion of the Brazilian Association of Research Companies (ABEP).

RESULTS

A hundred and eight mother-infant dyads participated in the study. Sleep disorders were observed in 38 (35%) infants and atypical development (ASQ3) in 35 (32%). The infants' sleep phases were partially explained by the mother's chronotype. Infants' sleep duration was negatively correlated with sleep latency, which was higher in the group with atypical development. Mothers of infants with sleep disorders or discordant chronotypes (32%) had higher Pittsburgh scores (worse sleep quality) and higher SRQ-20 scores (screen for Common Mental Disorders).

CONCLUSIONS

We found evidence for the contribution of sleep quality and chronotypes to mothers' mental health and infant development. However, further studies are needed to confirm the influence of sleep and circadian phenotypes in the early stages.

The Mediation Effect of Peripheral Biomarkers of Calcium Metabolism and Chronotypes in Bipolar Disorder Psychopathology

Calcium (Ca++) metabolism may be impaired in several psychiatric diseases. We hypothesize that calcium imbalance might also correlate with a specific chronotype and could be recognized as a marker of illness severity in bipolar disorder (BD). We aimed to (1) identify the association between calcium imbalance and a specific chronotype in a cohort of BD patients, and (2) test the mediation role of high parathyroid hormone (PTH) levels towards a specific chronotype and illness severity in BD patients. Patients’ socio-demographic and clinical characteristics were collected with an ad-hoc schedule. We administered the Hamilton Depression Rating Scale (HAM-D), the Hamilton Rating Scale for Anxiety (HAM-A), the Young Mania Rating Scale (YMRS), and the Morningness Eveningness Questionnaire (MEQ). 100 patients affected by BD were recruited. The Kruskal-Wallis test showed a significant difference between the three MEQ groups in PTH levels (p < 0.001) and vitamin D levels (p = 0.048) but not in Ca++ levels (p = 0.426). Dwass-Steel-Critchlow-Fligner Pairwise analyses performed concerning three MEQ groups revealed significantly higher scores on PTH levels in MEQ-E subjects compared to MEQ-M and MEQ-I (in both cases, p < 0.001). No differences emerged between calcium levels among the three chronotypes. The mediation analysis has shown that elevated PTH levels are directly influenced by more severe HAM-A, HAM-D, and YMRS scores. MEQ-E could be a marker related to BD and predispose to various factors influencing mood symptoms. The combination of vitamin D therapy in MEQ-E may help to improve prognosis in this subtype of patients affected by BD.

Chronotype, circadian rhythm, and psychiatric disorders: Recent evidence and potential mechanisms

The circadian rhythm is crucial for physiological and behavioral functions. Chronotype, which represents individual preferences for activity and performance, is associated with human health issues, particularly psychiatric disorders. This narrative review, which focuses on the relationship between chronotype and mental disorders, provides an insight into the potential mechanism. Recent evidence indicates that (1) the evening chronotype is a risk factor for depressive disorders and substance use disorders, whereas the morning chronotype is a protective factor. (2) Evening chronotype individuals with bipolar disorder tend to have more severe symptoms and comorbidities. (3) The evening chronotype is only related to anxiety symptoms. (4) The relationship between chronotype and schizophrenia remains unclear, despite increasing evidence on their link. (5) The evening chronotype is significantly associated with eating disorders, with the majority of studies have focused on binge eating disorders. Furthermore, the underlying mechanisms or influence factors are described in detail, including clock genes, brain characteristics, neuroendocrinology, the light/dark cycle, social factors, psychological factors, and sleep disorders. These findings provide the latest evidence on chronotypes and psychiatric disorders and serve as a valuable reference for researchers.

Shared postulations between bipolar disorder and polycystic ovary syndrome pathologies

INTRODUCTION

Women with bipolar disorder (BD) present a high prevalence of polycystic ovary syndrome (PCOS) and other reproductive disorders even before diagnosis or treatment of the disease. Postulations on the potential molecular mechanisms of comorbid PCOS in women with BD remain limited to influence of medications and need further extension.

OBJECTIVES

This review focuses on evidence suggesting that common metabolic and immune disorders may play an important role in the development of BD and PCOS.

RESULTS

The literature covered in this review suggests that metabolic and immune disorders, including the dysfunction of the hypothalamic-pituitary-adrenal axis, chronic inflammatory state, gut microbial alterations, adipokine alterations and circadian rhythm disturbance, are observed in patients with BD and PCOS. Such disorders may be responsible for the increased prevalence of PCOS in the BD population and indicate a susceptibility gene overlap between the two diseases. Current evidence supports postulations of common metabolic and immune disorders as endophenotype in BD as well as in PCOS.

CONCLUSIONS

Metabolic and immune disorders may be responsible for the comorbid PCOS in the BD population. The identification of hallmark metabolic and immune features common to these two diseases will contribute to the clarification of the effect of BD on the reproductive endocrine function and development of symptomatic treatments targeting the biomarkers of the two diseases.

A Comparison of Different Approaches to Clinical Phenotyping of Lithium Response: A Proof of Principle Study Employing Genetic Variants of Three Candidate Circadian Genes

Optimal classification of the response to lithium (Li) is crucial in genetic and biomarker research. This proof of concept study aims at exploring whether different approaches to phenotyping the response to Li may influence the likelihood of detecting associations between the response and genetic markers. We operationalized Li response phenotypes using the Retrospective Assessment of Response to Lithium Scale (i.e., the Alda scale) in a sample of 164 cases with bipolar disorder (BD). Three phenotypes were defined using the established approaches, whilst two phenotypes were generated by machine learning algorithms. We examined whether these five different Li response phenotypes showed different levels of statistically significant associations with polymorphisms of three candidate circadian genes (RORA, TIMELESS and PPARGC1A), which were selected for this study because they were plausibly linked with the response to Li. The three original and two revised Alda ratings showed low levels of discordance (misclassification rates: 8–12%). However, the significance of associations with circadian genes differed when examining previously recommended categorical and continuous phenotypes versus machine-learning derived phenotypes. Findings using machine learning approaches identified more putative signals of the Li response. Established approaches to Li response phenotyping are easy to use but may lead to a significant loss of data (excluding partial responders) due to recent attempts to improve the reliability of the original rating system. While machine learning approaches require additional modeling to generate Li response phenotypes, they may offer a more nuanced approach, which, in turn, would enhance the probability of identifying significant signals in genetic studies.

Molecular Link between Circadian Rhythmicity and Mood Disorders

BACKGROUND

The internal clock is driven by circadian genes [e.g., Clock, Bmal1, Per1-3, Cry1-2], hormones [e.g., melatonin, cortisol], as well as zeitgeber ['synchronisers']. Chronic disturbances in the circadian rhythm in patients diagnosed with mood disorders have been recognised for more than 50 years.

OBJECTIVES

The aim of this review is to summarise the current knowledge and literature regarding circadian rhythms in the context of mood disorders, focussing on the role of circadian genes, hormones, and neurotransmitters.

METHOD

The review presents the current knowledge and literature regarding circadian rhythms in mood disorders using the Pubmed database. Articles with a focus on circadian rhythms and mood disorders [n=123], particularly from 1973 to 2020, were included.

RESULTS

The article suggests a molecular link between disruptions in the circadian rhythm and mood disorders. Circadian disturbances, caused by the dysregulation of circadian genes, hormones, and neurotransmitters, often result in a clinical picture resembling depression.

CONCLUSION

Circadian rhythms are intrinsically linked to affective disorders, such as unipolar depression and bipolar disorder.

For whom the circadian clock ticks? Investigation of PERIOD and CLOCK gene variants in bipolar disorder

Clock genes play significant roles in the regulation of circadian rhythms, which are thought to be involved in the pathophysiology of neurodegenerative and psychiatric diseases. We aimed to investigate the association of five gene polymorphisms (PER3 VNTR (rs57875989), PER2 rs2304672, CLOCK rs1801260, CLOCK rs10462028, CLOCK rs11932595) with PCR-based methods as potential risk factors in bipolar disorder (BD). We used a multiple testing methodology in BD patients (n = 121) and healthy control individuals (n = 121) of Turkish descent to analyze the effects of these gene variants both as risk factors for the disorder and for the evaluation of these variants in the patient group with multiple subscales. We evaluated the circadian rhythm disturbances and seasonal variations in mood and behavior in BD patients using the Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN) and Seasonal Pattern Assessment Questionnaire (SPAQ) to enlighten the possible links between these scores and the studied circadian gene variants. The results of our study revealed significant associations: PER3 VNTR (rs57875989) 5/5 repeat genotype displayed a protective effect against BD when compared with 4/4 repeat genotype. Moreover, patients with PER3 VNTR 5/5 repeat genotype displayed a higher ratio of hypomania. PER2 rs2304672 G allele frequency increased the risk for BD. There was no association in terms of genotype/allele frequency comparisons between patients and controls for CLOCK gene variants. However, significant associations were found in patients in terms of clinical and behavioral patterns such as mean age at disease onset and BRIAN total scores enabling some risk stratifications for patients. Our results indicate the significance of circadian gene variants in BD, which need to be confirmed in different studies with larger samples. Thus, the possible endophenotypes of BD can be enlightened and advanced chronotherapeutics approaches can be manipulated in the future for clinical benefit.

Ziprasidone, a second-generation antipsychotic, affects core clock gene mRNA expression in mice

Some psychiatric diseases are associated with disruptions in the circadian clock system. Ziprasidone (ZIP), a second-generation antipsychotic, is widely used for psychiatry-related pharmacotherapy but its mechanism has not been clearly elucidated. We measured clock gene fluctuation patterns in the hippocampus and the amygdala in ZIP-treated mice. ZIP significantly increased Per1, Per2, and Bmal1 mRNA 2 h after the lights were turned off (ZT14) in the hippocampus, but not in the amygdala. These results suggest that ZIP might affect clock gene regulation, which could represent the pathway underlying symptom amelioration.

Clinical, genetic, and brain imaging predictors of risk for bipolar disorder in high-risk individuals

Introduction: Early detection and intervention in bipolar disorder (BD) might reduce illness severity, slow its progression, and, in specific cases, even ward off the full-blown disorder. Therefore, identifying at-risk individuals and targeting them promptly before the illness onset is of the utmost importance. In the last decades, there has been a significant effort aimed at identifying genetic and molecular factors able to modulate risk and pharmacological outcomes.Areas covered: We performed a narrative review of articles aimed at identifying clinical, genetics, molecular, and brain imaging markers of BD specifically focusing on samples of individuals at high-risk for BD. Special emphasis was put on studies applying an integrative design, e.g. studies combining different markers such as genetic and brain imaging.Expert opinion: Findings from studies in risk individuals are still too sparse to allow drawing definite conclusions. However, the high potentiality of longitudinal studies in individuals considered at risk to develop BD supports the need for more efforts. Future investigations should focus on more homogeneous subpopulations and evaluate the cross-linking between clinical, genetic, and brain morphostructural/functional neuroimaging characteristics as predictors of risk for BD.

What is the role of meteorological variables on involuntary admission in psychiatric ward? An Italian cross-sectional study

Weather affects physical and mental health through several modalities which are not fully elucidated. The aim of the present study was to investigate the impact of meteorological variables and other indexes in a large sample of hospitalized patients, focusing on subjects who were involuntarily admitted. We hypothesized a direct relation between the amount of involuntary admissions and mean sunshine hours. Furthermore, we supposed that specific meteorological factors may significantly influence hospitalizations of patients affected by severe psychiatric conditions. All subjects were consecutively recruited from the Psychiatric Inpatient Unit of San Luigi Gonzaga Hospital, Orbassano (Turin, Italy) from September 2013 to August 2015. Socio-demographic and clinical characteristics were carefully collected. Meteorological data were derived by the Italian Meteorology's Climate Data Service of Physics Department of the University of Turin (Latitude: 45°03'07,15″ Nord, Longitude: 007°40'53,30″ Est, Altitude: 254 m above the sea level) (http://www.meteo.dfg.unito.it/). Our data indicate significant differences regarding temperature (minimum, maximum, and medium), solar radiation, humidex and windchill index, and hours of sunshine in psychiatric patients who were involuntarily hospitalized. After logistic regression analyses, only maximum and medium temperature, and humidex index remained significantly associated with involuntary admission in an emergency psychiatric ward. The limitations of this study include the cross-sectional study design and the single hospital for patients' recruitment. Furthermore, results and seasonal patterns obtained by patients requiring hospitalization might significantly differ from those who were not hospitalized. Exploring in a more detailed manner those environmental factors associated with involuntary admissions could lead to early intervention and prevention strategies for such distressing hospitalizations.

Sex differences in stress-related disorders: Major depressive disorder, bipolar disorder, and posttraumatic stress disorder

Stress-related disorders, such as mood disorders and posttraumatic stress disorder (PTSD), are more common in women than in men. This sex difference is at least partly due to the organizing effect of sex steroids during intrauterine development, while activating or inhibiting effects of circulating sex hormones in the postnatal period and adulthood also play a role. Such effects result in structural and functional changes in neuronal networks, neurotransmitters, and neuropeptides, which make the arousal- and stress-related brain systems more vulnerable to environmental stressful events in women. Certain brainstem nuclei, the amygdala, habenula, prefrontal cortex, and hypothalamus are important hubs in the stress-related neuronal network. Various hypothalamic nuclei play a central role in this sexually dimorphic network. This concerns not only the hypothalamus-pituitary-adrenal axis (HPA-axis), which integrates the neuro-endocrine-immune responses to stress, but also other hypothalamic nuclei and systems that play a key role in the symptoms of mood disorders, such as disordered day-night rhythm, lack of reward feelings, disturbed eating and sex, and disturbed cognitive functions. The present chapter focuses on the structural and functional sex differences that are present in the stress-related brain systems in mood disorders and PTSD, placing the HPA-axis in the center. The individual differences in the vulnerability of the discussed systems, caused by genetic and epigenetic developmental factors warrant further research to develop tailor-made therapeutic strategies.

Whole Genome Expression Analyses of miRNAs and mRNAs Suggest the Involvement of miR-320a and miR-155-3p and their Targeted Genes in Lithium Response in Bipolar Disorder

Lithium is the mainstay in the maintenance of bipolar disorder (BD) and the most efficacious pharmacological treatment in suicide prevention. Nevertheless, its use is hampered by a high interindividual variability and important side effects. Genetic and epigenetic factors have been suggested to modulate lithium response, but findings so far have not allowed identifying molecular targets with predictive value. In this study we used next generation sequencing to measure genome-wide miRNA expression in lymphoblastoid cell lines from BD patients excellent responders (ER, n = 12) and non-responders (NR, n = 12) to lithium. These data were integrated with microarray genome-wide expression data to identify pairs of miRNA/mRNA inversely and significantly correlated. Significant pairs were prioritized based on strength of association and in-silico miRNA target prediction analyses to select candidates for validation with qRT-PCR. Thirty-one miRNAs were differentially expressed in ER vs. NR and inversely correlated with 418 genes differentially expressed between the two groups. A total of 331 of these correlations were also predicted by in-silico algorithms. miR-320a and miR-155-3p, as well as three of their targeted genes (CAPNS1 (Calpain Small Subunit 1) and RGS16 (Regulator of G Protein Signaling 16) for miR-320, SP4 (Sp4 Transcription Factor) for miR-155-3p) were validated. These miRNAs and mRNAs were previously implicated in psychiatric disorders (miR-320a and SP4), key processes of the central nervous system (CAPNS1, RGS16, SP4) or pathways involved in mental illnesses (miR-155-3p). Using an integrated approach, we identified miRNAs and their targeted genes potentially involved in lithium response in BD.

Significant role of gene-gene interactions of clock genes in mood disorder

BACKGROUND

The genetic interactions in the circadian rhythm biological system are promising as a source of pathophysiology in mood disorder. We examined the role of the gene-gene interactions of clock genes in mood disorder.

METHODS

We included 413 patients with mood disorder and 1294 controls. The clock genes investigated were BHLHB2, CLOCK, CSNK1E, NR1D1, PER2, PER3, and TIMELESS. Allele, genotype, and haplotype associations were tested. Gene--gene interactions were analyzed using the non-parametric model-free multifactor-dimensionality reduction (MDR) method.

RESULTS

TIMELESS rs4630333 and CSNK1E rs135745 were significantly associated with both major depressive disorder and bipolar disorder. The CLOCK haplotype was also strongly associated. The genetic roles of these SNPs were consistent from the allele and genotypic associations to the MDR interaction results. In MDR analysis, the combination of TIMELESS rs4630333 and CSNK1E rs135745 exhibited the most significant association with mood disorders in the two-locus model. BHLHB2 rs2137947 for major depressive disorder and CLOCK rs12649507 for bipolar disorder were the most significant third loci in the three-locus combination model. The four-locus SNP combination model showed the best balanced accuracy (BA), but its cross-validation consistency (CVC) was unsatisfactory.

LIMITATIONS

We included only 17 SNPs for seven circadian genes due to our limited resources; all subjects were ethnically Korean.

CONCLUSIONS

Our results suggest significant single-gene associations and gene-gene interactions of circadian genes with mood disorder. Gene-gene interactions play a crucial role in mood disorder, even when individual clock genes do not have significant roles.

Chromatin Remodeling Complex NuRD in Neurodevelopment and Neurodevelopmental Disorders

The nucleosome remodeling and deacetylase (NuRD) complex presents one of the major chromatin remodeling complexes in mammalian cells. Here, we discuss current evidence for NuRD's role as an important epigenetic regulator of gene expression in neural stem cell (NSC) and neural progenitor cell (NPC) fate decisions in brain development. With the formation of the cerebellar and cerebral cortex, NuRD facilitates experience-dependent cerebellar plasticity and regulates additionally cerebral subtype specification and connectivity in postmitotic neurons. Consistent with these properties, genetic variation in NuRD's subunits emerges as important risk factor in common polygenic forms of neurodevelopmental disorders (NDDs) and neurodevelopment-related psychiatric disorders such as schizophrenia (SCZ) and bipolar disorder (BD). Overall, these findings highlight the critical role of NuRD in chromatin regulation in brain development and in mental health and disease.

Sleep Disturbance in Bipolar Disorder: Neuroglia and Circadian Rhythms

The worldwide prevalence of sleep disorders is approximately 50%, with an even higher occurrence in a psychiatric population. Bipolar disorder (BD) is a severe mental illness characterized by shifts in mood and activity. The BD syndrome also involves heterogeneous symptomatology, including cognitive dysfunctions and impairments of the autonomic nervous system. Sleep abnormalities are frequently associated with BD and are often a good predictor of a mood swing. Preservation of stable sleep-wake cycles is therefore a key to the maintenance of stability in BD, indicating the crucial role of circadian rhythms in this syndrome. The symptom most widespread in BD is insomnia, followed by excessive daytime sleepiness, nightmares, difficulty falling asleep or maintaining sleep, poor sleep quality, sleep talking, sleep walking, and obstructive sleep apnea. Alterations in the structure or duration of sleep are reported in all phases of BD. Understanding the role of neuroglia in BD and in various aspects of sleep is in nascent state. Contributions of the different types of glial cells to BD and sleep abnormalities are discussed in this paper.

Association between solar insolation and a history of suicide attempts in bipolar I disorder

In many international studies, rates of completed suicide and suicide attempts have a seasonal pattern that peaks in spring or summer. This exploratory study investigated the association between solar insolation and a history of suicide attempt in patients with bipolar I disorder. Solar insolation is the amount of electromagnetic energy from the Sun striking a surface area on Earth. Data were collected previously from 5536 patients with bipolar I disorder at 50 collection sites in 32 countries at a wide range of latitudes in both hemispheres. Suicide related data were available for 3365 patients from 310 onset locations in 51 countries. 1047 (31.1%) had a history of suicide attempt. There was a significant inverse association between a history of suicide attempt and the ratio of mean winter solar insolation/mean summer solar insolation. This ratio is smallest near the poles where the winter insolation is very small compared to the summer insolation. This ratio is largest near the equator where there is relatively little variation in the insolation over the year. Other variables in the model that were positively associated with suicide attempt were being female, a history of alcohol or substance abuse, and being in a younger birth cohort. Living in a country with a state-sponsored religion decreased the association. (All estimated coefficients p < 0.01). In summary, living in locations with large changes in solar insolation between winter and summer may be associated with increased suicide attempts in patients with bipolar disorder. Further investigation of the impacts of solar insolation on the course of bipolar disorder is needed.

The human hypothalamus in mood disorders: The HPA axis in the center

There are no specific structural neuropathological hallmarks found in the brain of mood disorders. Instead, there are molecular, functional and structural alterations reported in many brain areas. The neurodevelopmental underpinning indicated the presence of various genetic and developmental risk factors. The effect of genetic polymorphisms and developmental sequalae, some of which may start in the womb, result in functional changes in a network mediated by neurotransmitters and neuropeptides, which make the emotion- and stress-related brain systems more vulnerable to stressful events. This network of stress-related neurocircuits consists of, for instance, brainstem nuclei, the amygdala, habenula, prefrontal cortex and hypothalamus. Various nuclei of the hypothalamus form indeed one of the crucial hubs in this network. This structure concerns not only the hypothalamo-pituitary-adrenal (HPA) axis that integrate the neuro-endocrine-immune responses to stress, but also other hypothalamic nuclei and systems that play a key role in the symptoms of depression, such as disordered day-night rhythm, lack of reward feelings, disturbed eating, sex, and disturbed cognitive functions. The present review will focus on the changes in the human hypothalamus in depression, with the HPA axis in the center. We will discuss the inordinate network of neurotransmitters and neuropeptides involved, with the hope to find the most vulnerable neurobiological systems and the possible development of tailor-made treatments for mood disorders in the future.

Clock genes polymorphisms in male bipolar patients with comorbid alcohol abuse

BACKGROUND

Psychiatric comorbidity affects 24-65% patients with bipolar disorder (BD), 45% of which have alcohol abuse/dependence (AAD). Despite the fact that BD has an equal incidence in both genders, AAD more often occurs in men. We hypothesized that the presence of BD and AAD, reported as a secondary diagnosis, may result from a common genetic background. However, specific genetic factors predispose to gender differences.

METHODS

Based on the relationship between circadian clock genes pathway and BD/AAD we decided to test the connection of four core clock genes with common genetic background of both diseases. We analyzed 436 patients with BD, among which 17% were diagnosed with AAD. The control group consisted of 417 healthy subjects. We analyzed 44 SNPs of the previously described core molecular clock genes: CLOCK, ARNTL, TIMELESS and PER3.

RESULT

We found association of ARNTL gene (rs11600996) and PER3 gene (rs228642) polymorphisms with an increased risk of BD/AAD in a group of male patients. We also found that two other polymorphisms of PER3 gene, rs228682 and rs2640909, were associated with both AAD and family history of affective disorders.

LIMITATIONS

Possible factors that could have influenced the results are: relatively small sample size, gender disproportion and unverifiable data form the patient interview.

CONCLUSIONS

Our study confirms the existence of a link between clock genes and increased risk of alcohol abuse/dependence in male patients and the accumulation of risk genes in patients with a positive family history.