Is the 5-HTTLPR polymorphism associated with bipolar disorder or with suicidal behavior of bipolar disorder patients?

Zika virus-induced TNF-α signaling dysregulates expression of neurologic genes associated with psychiatric disorders

BACKGROUND

Zika virus (ZIKV) is an emerging flavivirus of global concern. ZIKV infection of the central nervous system has been linked to a variety of clinical syndromes, including microcephaly in fetuses and rare but serious neurologic disease in adults. However, the potential for ZIKV to influence brain physiology and host behavior following apparently mild or subclinical infection is less well understood. Furthermore, though deficits in cognitive function are well-documented after recovery from neuroinvasive viral infection, the potential impact of ZIKV on other host behavioral domains has not been thoroughly explored.

METHODS

We used transcriptomic profiling, including unbiased gene ontology enrichment analysis, to assess the impact of ZIKV infection on gene expression in primary cortical neuron cultures. These studies were extended with molecular biological analysis of gene expression and inflammatory cytokine signaling. In vitro observations were further confirmed using established in vivo models of ZIKV infection in immunocompetent hosts.

RESULTS

Transcriptomic profiling of primary neuron cultures following ZIKV infection revealed altered expression of key genes associated with major psychiatric disorders, such as bipolar disorder and schizophrenia. Gene ontology enrichment analysis also revealed significant changes in gene expression associated with fundamental neurobiological processes, including neuronal development, neurotransmission, and others. These alterations to neurologic gene expression were also observed in the brain in vivo using several immunocompetent mouse models of ZIKV infection. Mechanistic studies identified TNF-α signaling via TNFR1 as a major regulatory mechanism controlling ZIKV-induced changes to neurologic gene expression.

CONCLUSIONS

Our studies reveal that cell-intrinsic innate immune responses to ZIKV infection profoundly shape neuronal transcriptional profiles, highlighting the need to further explore associations between ZIKV infection and disordered host behavioral states.

The role of 5-HTTLPR in autism spectrum disorder: New evidence and a meta-analysis of this polymorphism in Latin American population with psychiatric disorders

The autism spectrum disorder (ASD) is a complex disorder encompassing a broad phenotypic and genotypic variability. The short (S)/long (L) 5-HTTLPR polymorphism has a functional role in the regulation of extracellular serotonin levels and both alleles have been associated to ASD. Most studies including European, American, and Asian populations have suggested an ethnical heterogeneity of this polymorphism; however, the short/long frequencies from Latin American population have been under-studied in recent meta-analysis. Here, we evaluated the 5-HTTLPR polymorphism in Colombian individuals with idiopathic ASD and reported a non-preferential S or L transmission and a non-association with ASD risk or symptom severity. Moreover, to recognize the allelic frequencies of an under-represented population we also recovered genetic studies from Latin American individuals and compared these frequencies with frequencies from other ethnicities. Results from meta-analysis suggest that short/long frequencies in Latin American are similar to those reported in Caucasian population but different to African and Asian regions.

The serotonin transporter gene polymorphism (5-HTTLPR) and affective symptoms among women diagnosed with borderline personality disorder

Gene variants of the serotonin transporter have been associated with vulnerability to affective disorders. In particular, the presence of one or two copies of the short (s) allele of the 5-HTTLPR polymorphism has been associated with reduced serotonin transporter expression and function, and vulnerability to affective disorders. To test for an association between variants of the serotonin transporter gene polymorphism (5-HTTLPR) and relevant clinical features of borderline personality disorder (BPD), a psychiatric disorder with symptoms characteristic for serotonin dysfunction, 77 women with BPD were genotyped in the 5-HTTLPR polymorphism. They rated their subjective experience of borderline-specific, depressive, anxious and obsessive-compulsive symptoms, and were interviewed about lifetime incidence of suicide attempts and self-harming acts. Carriers of two s alleles of the 5-HTTLPR reported more symptoms of borderline, depression, anxiety and obsessive-compulsive behaviours, but not of suicidal and self-injury behaviour, compared to carriers of a long (l) allele. This indicates that the 5-HTTLPR ss homozygous genotype might influence serotonin function affecting susceptibility to both borderline-specific, depressive, anxious and obsessive-compulsive symptoms in BPD, and leading to a more severe symptomatology related to these clinical features. Further, this suggests that 5-HTT gene variants may not be as influential on suicidal and self-injury behaviour in BPD.

Single nucleotide polymorphisms, variable number tandem repeats and allele influence on serotonergic enzyme modulators for aggressive and suicidal behaviors: A review

The serotonergic system plays key regulatory roles in cognition and emotion. Several lines of evidence suggest that genetic variation is associated with aggressive and suicidal behaviors. Genetic studies have largely focused on three types of variations: single nucleotide polymorphisms (SNPs), variable number tandem repeats (VNTRs), and alleles. 95 published papers (49 papers for aggression and 46 for suicide) were reviewed to summarize the impact of SNPs, VNTRs, and alleles of tryptophan hydroxylase (TPH, the rate-limiting enzyme in serotonin [5-HT] synthesis), 5-HT transporter (5-HTT), serotonergic receptors, monoamine oxidase (an enzyme that catalyzes 5-HT degradation) on aggression and suicidal behaviors. These study samples include healthy controls, psychiatric disease patients, and animal models. This article mainly reviews studies on the relationship between 5-HT transmissions and genetic variations involved in aggression (particularly impulsive aggression) or suicide in people with different ethnicities and psychiatric disorders. We found that most SNPs, VNTRs, and alleles exerted influences on aggression or suicide. Only A128C in TPH1, A138G in 5-HT2A, and L type in the VNTR of monoamine oxidase A (MAOA) affected both aggression and suicide. The associations between some genetic variations and aggression/suicide may be influenced by gender, age, ethnicity, psychiatric disease, and even parenting or prenatal stress. These findings may help clarify how genetic and environmental factors influence the development of aggressive and suicidal behaviors.

Associations of the serotonin transporter promoter polymorphism (5-HTTLPR) with bipolar disorder and treatment response: A systematic review and meta-analysis

BACKGROUND

Associations of the serotonin transporter promoter polymorphism (5-HTTLPR) with bipolar disorder (BPD) and treatment response in bipolar patients were not conclusive. This study not only assessed the association between the 5-HTTLPR and BPD with accumulating relevant studies, but also in the first time evaluated the effect of the 5-HTTLPR on both anti-depressive and anti-manic treatment responses in bipolar patients.

METHODS

PubMed, Embase, PsycINFO, Cochrane Library and Cochrane Control Trials databases were systematically searched before February 2017. This meta-analysis followed the PRISMA guidelines.

RESULTS

A total of 32 population-based studies (5567 cases and 6993 controls) and 9 family-based studies (837 trios) were finally screened out and statistically joined into a single meta-analysis that revealed an association between S allele and an increased risk of BPD (OR = 1.06, p = .038). Pooled analysis of the 32 population-based studies indicated an association of S-carrier genotypes with an increased risk of BPD (OR = 1.10, p = .029). Meanwhile, the association remained significant in Caucasians (OR = 1.15, p = .004), which could provide an enough power (88%) to detect a significant association. Regarding the treatment response studies, 6 studies reporting the relationship of the 5-HTTLPR in anti-depressive remission rate (1034 patients) and 7 studies reporting in response rate (1098 patients) were included for pooled analyses. We observed a significant association of S-carrier genotypes with a reduced anti-depressive remission rate (OR = 0.64, p = .006) but not with anti-depressive response rate. The association between the 5-HTTLPR with anti-manic response rate was not observed in the included 6 studies (676 patients).

CONCLUSIONS

The present study supported the presence of a marginal but detectable effect of the 5-HTTLPR on susceptibility to BPD. Moreover, the detected association in Caucasian was statistically reliable. Besides, the 5-HTTLPR was identified as a useful predictor for anti-depressive remission but not for anti-depressive or anti-manic response.

5-HTTLPR-brain-derived neurotrophic factor (BDNF) gene interactions and early adverse life events effect on impulsivity in suicide attempters

OBJECTIVES

An expanding body of research suggests that childhood adverse experiences can lead to different negative health outcomes, including attempted suicide. Serotonergic genes such as the promoter region of the serotonin transporter gene (5-HTTLPR) have been associated both with impulsivity in suicide attempts and reactivity to environmental stress exposure. BDNF gene may play an epigenetic role.

METHODS

We studied the influence of childhood stressful events and 5-HTTLPR genotype on impulsivity measured by Barratt Impulsivity Scale (BIS-10) in a multicentre sample of 1,655 suicide attempters (69.4% women, 30.6% men; mean age 40.13 years). A co-dominant additive genetic model was used for the statistical analyses. Interaction between 5-HTTLPR genotype and early trauma exposure was tested using moderated and multiple regression techniques. Interaction plots were used to explore BDNF genotype modulation.

RESULTS

Mildly higher impulsivity scores were found in men with SS compared with SL or LL genotypes, and men with childhood emotional and physical abuse. Interaction analyses showed that combination of 5-HTTLPR-SS genotype and early trauma exposure increase impulsivity scores independently. Impulsivity scores were not affected by the modulation of BDNF genes.

CONCLUSIONS

Childhood trauma and 5-HTTLPR genotype seem to be independently involved in suicide attempts, sharing a common pathway of increasing impulsivity.

Serotonin transporter gene polymorphism as a predictor of short-term risk of suicide reattempts

Objective:

The serotonin-transporter-linked polymorphic region (5-HTTLPR) polymorphisms are associated with suicidal behavior; however, prospective studies are scarce. Herein we aim to determine if 5-HTTLPR polymorphisms predict risk of short-term suicide reattempt in a high-risk suicidal sample. We also explore possible mediators or moderators of this relationship.

Methods:

A multicenter prospective cohort study was designed to compare data obtained form 136 patients admitted to the emergency department for current suicidal ideation or a recent suicide attempt. Subjects were clinically evaluated, genotyped, and monitored for a new suicide attempt for 6 months.

Results:

At 6 months of follow up, 21% of the subjects had a new suicide attempt. The frequency of L-allele and L-carrier was higher in reattempters when compared with non-reattempters (55.8% vs. 35.4%, p = 0.01 and 76.9% vs. 54.2%, p = 0.04, respectively). Reattempters also differ from non-reattempters patients with respect to age, history of previous suicide attempts, and age of onset of suicidal behavior. The logistic regression model showed that L-carriers had an odds ratio of 2.8 (95% CI: 1.0–7.6) for reattempts when compared to SS genotype. The adjusted model indicates that this association is not mediated or moderated by impulsivity.

Conclusion:

The 5-HTTLPR polymorphisms predicted short-term risk of suicidal reattempt independently of age and sex. L-carriers have almost three times more risk of relapse when compared with SS carriers.

Evaluation of psychiatric and genetic risk factors among primary relatives of suicide completers in Delhi NCR region, India

Suicide as a public health problem is studied worldwide and association of psychiatric and genetic risk factors for suicidal behavior are the point of discussion in studies across different ethnic groups. The present study is aimed at evaluating psychiatric and genetic traits among primary relatives of suicide completer families in an urban Indian population. Bi-variate analysis shows significant increase in major depression (PHQ and Hamilton), stress, panic disorder, somatoform disorder and suicide attemptamong primary compared to other relatives. Sib pair correlations also reveal significant results for major depression (Hamilton), stress, suicide attempt, intensity of suicide ideation and other anxiety syndrome. 5-HTTLPR, 5-HTT (Stin2) and COMT risk alleles are higher among primary relatives, though statistically insignificant. Backward conditional logistic regression analysis show only independent variable, Depression (Hamilton) made a unique statistically significant contribution to the model in primary relatives.

Epidemiology, neurobiology and pharmacological interventions related to suicide deaths and suicide attempts in bipolar disorder: Part I of a report of the International Society for Bipolar Disorders Task Force on Suicide in Bipolar Disorder

OBJECTIVES

Bipolar disorder is associated with elevated risk of suicide attempts and deaths. Key aims of the International Society for Bipolar Disorders Task Force on Suicide included examining the extant literature on epidemiology, neurobiology and pharmacotherapy related to suicide attempts and deaths in bipolar disorder.

METHODS

Systematic review of studies from 1 January 1980 to 30 May 2014 examining suicide attempts or deaths in bipolar disorder, with a specific focus on the incidence and characterization of suicide attempts and deaths, genetic and non-genetic biological studies and pharmacotherapy studies specific to bipolar disorder. We conducted pooled, weighted analyses of suicide rates.

RESULTS

The pooled suicide rate in bipolar disorder is 164 per 100,000 person-years (95% confidence interval = [5, 324]). Sex-specific data on suicide rates identified a 1.7:1 ratio in men compared to women. People with bipolar disorder account for 3.4-14% of all suicide deaths, with self-poisoning and hanging being the most common methods. Epidemiological studies report that 23-26% of people with bipolar disorder attempt suicide, with higher rates in clinical samples. There are numerous genetic associations with suicide attempts and deaths in bipolar disorder, but few replication studies. Data on treatment with lithium or anticonvulsants are strongly suggestive for prevention of suicide attempts and deaths, but additional data are required before relative anti-suicide effects can be confirmed. There were limited data on potential anti-suicide effects of treatment with antipsychotics or antidepressants.

CONCLUSION

This analysis identified a lower estimated suicide rate in bipolar disorder than what was previously published. Understanding the overall risk of suicide deaths and attempts, and the most common methods, are important building blocks to greater awareness and improved interventions for suicide prevention in bipolar disorder. Replication of genetic findings and stronger prospective data on treatment options are required before more decisive conclusions can be made regarding the neurobiology and specific treatment of suicide risk in bipolar disorder.

Seasonality and its distinct clinical correlates in bipolar II disorder

Seasonality is one of the key features in subjects with mood disorders and is involved in the multi-faceted nature of the clinical course. However, few studies have explored the clinical implications of seasonality in bipolar disorders. We examined the differential effects of seasonality on clinical variables between bipolar I and II disorder (BD I and II). Seasonality was assessed using the Seasonal Pattern Assessment Questionnaire (SPAQ) in 204 subjects with BD I and 308 with BD II. Following the comparisons between BD I and II groups, clinical characteristics related to seasonality were explored. Next, to predict the presence of seasonality, a logistic regression model was applied. The global seasonality score on the SPAQ was significantly higher in the BD II group than in the BD I group. In the BD I group, seasonality was associated with suicide attempt history. In the BD II group, on the other hand, seasonality was associated with female gender, depressive predominance, and premenstrual dysphoric disorder (PMDD). In the regression models, the presence of PMDD and female gender was significantly associated with seasonality in the BD II group. Our findings suggest that high seasonality tendency, a vulnerability maker for cyclic worsening, may contribute to a differential pattern of clinical characteristics in BD II.

Integrated neurobiology of bipolar disorder

From a neurobiological perspective there is no such thing as bipolar disorder. Rather, it is almost certainly the case that many somewhat similar, but subtly different, pathological conditions produce a disease state that we currently diagnose as bipolarity. This heterogeneity - reflected in the lack of synergy between our current diagnostic schema and our rapidly advancing scientific understanding of the condition - limits attempts to articulate an integrated perspective on bipolar disorder. However, despite these challenges, scientific findings in recent years are beginning to offer a provisional "unified field theory" of the disease. This theory sees bipolar disorder as a suite of related neurodevelopmental conditions with interconnected functional abnormalities that often appear early in life and worsen over time. In addition to accelerated loss of volume in brain areas known to be essential for mood regulation and cognitive function, consistent findings have emerged at a cellular level, providing evidence that bipolar disorder is reliably associated with dysregulation of glial-neuronal interactions. Among these glial elements are microglia - the brain's primary immune elements, which appear to be overactive in the context of bipolarity. Multiple studies now indicate that inflammation is also increased in the periphery of the body in both the depressive and manic phases of the illness, with at least some return to normality in the euthymic state. These findings are consistent with changes in the hypothalamic-pituitary-adrenal axis, which are known to drive inflammatory activation. In summary, the very fact that no single gene, pathway, or brain abnormality is likely to ever account for the condition is itself an extremely important first step in better articulating an integrated perspective on both its ontological status and pathogenesis. Whether this perspective will translate into the discovery of innumerable more homogeneous forms of bipolarity is one of the great questions facing the field and one that is likely to have profound treatment implications, given that fact that such a discovery would greatly increase our ability to individualize - and by extension, enhance - treatment.

Genetic variability at IMPA2, INPP1 and GSK3β increases the risk of suicidal behavior in bipolar patients

Bipolar patients (BP) are at high risk of suicide. Causal factors underlying suicidal behavior are still unclear. However, it has been shown that lithium has antisuicidal properties. Genes involved in its putative mechanism of action such as the phosphoinositol and the Wnt/β-catenine pathways could be considered candidates for suicidal behavior (SB). Our aim was to investigate the association of the IMPA1 and 2, INPP1, GSK3α and β genes with suicidal behavior in BP. 199 BP were recruited. Polymorphisms at the IMPA1 (rs915, rs1058401 and rs2268432) and IMPA2 (rs66938, rs1020294, rs1250171 and rs630110), INPP1 (rs3791809, rs4853694 and 909270), GSK3α (rs3745233) and GSK3β (rs334558, rs1732170 and rs11921360) genes were genotyped. All patients were grouped and compared according to the presence or not of history of SB (defined as the presence of at least one previous suicidal attempt). Single SNP analyses showed that suicide attempters had higher frequencies of AA genotype of the rs669838-IMPA2 and GG genotype of the rs4853694-INPP1gene compared to non-attempters. Results also revealed that T-allele carriers of the rs1732170-GSK3β gene and A-allele carriers of the rs11921360-GSK3β gene had a higher risk for attempting suicide. Haplotype analysis showed that attempters had lower frequencies of A:A haplotype (rs4853694:rs909270) at the INPP1 gene. Higher frequencies of the C:A haplotype and lower frequencies of the A:C haplotype at the GSK-3β gene (rs1732170:rs11921360) were also found to be associated to SB in BP. Therefore, our results suggest that genetic variability at IMPA2, INPP1 and GSK3β genes is associated with the emergence of SB in BP.

Serotonergic genes and suicide: a systematic review

Suicide is one of the leading causes of death in the world. Its aetiology is complex and diverse, however, epidemiological studies show that suicidal behavior is partly heritable. Neurobiological evidence implicates serotonergic dysfunction in suicidality, stimulating genetic research to focus on genes related to the serotonergic system. In this paper, we review evidence from studies examining the association between various serotonergic genes (Tryptophan Hydroxylase genes: TPH1; TPH2, Serotonin Transporter gene: 5-HTTLPR in SLC6A4, Serotonin Receptor genes: HTR1A, HTR2A, HTR1B, HTR2C and Monoamine Oxidase A gene: MAOA) and suicidal behavior. The data show associations between variation on the TPH1 gene and 5-HTTLPR gene and violent suicidal behavior in Caucasian populations, with the least inconsistencies. Results are mixed for the TPH2 gene and serotonin receptor genes, but for some genes, studies that include haplotypic analyses or that examine a larger coding region of the genes tend to provide more reliable results. Findings on endophenotypes of suicidality, such as aggression and impulsivity traits, show positive associations for the TPH1, HTR2A, and MAOA genes, but need further replication, since negative associations are also occasionally reported. Since genes can only partially explain suicidal risk, several studies during the past decade have tried to incorporate environmental factors in the susceptibility model. Studies to date show that variation on the 5-HTTLPR, MAOA and HTR2A gene can interact with stressful life events to increase risk for suicidal behavior. Limitations of case-control studies are discussed and future considerations are put forward with regard to endophenotypic measurements and gene-environment interactions.

Meta-analysis confirms a functional polymorphism (5-HTTLPR) in the serotonin transporter gene conferring risk of bipolar disorder in European populations

The serotonin transporter (5-HTT) is a candidate risk gene for bipolar disorder, and a functional polymorphism of 44-bp insertion/deletion (5-HTTLPR) located in the promoter region of this gene has been investigated for the association with the illness extensively among worldwide populations, but overall results were inconsistent and its role in the disorder remains unclear. The present study attempts to find its potential association with bipolar disorder using meta-analyzes that maximize the statistical power. We applied meta-analysis techniques by combining all available case-control studies of 5-HTTLPR and bipolar disorder in samples of European ancestry (with a total of 3778 cases and 4997 controls), and we assessed the evidence for allelic associations, heterogeneity among different studies, influence of each single study, and potential publication bias. The short allele (S allele) of 5-HTTLPR showed a significant association with bipolar disorder in our meta-analysis (odds ratio=1.10, p-value=0.005), suggesting it is likely a risk polymorphism for the illness, and the observed OR is consistent with other susceptibility loci identified through recent large-scale genetic association studies on bipolar disorder, which could be regarded simply as a small but detectable effects.

The role of the serotonergic system at the interface of aggression and suicide

Alterations in serotonin (5-HT) neurochemistry have been implicated in the aetiology of all major neuropsychiatric disorders, ranging from schizophrenia to mood and anxiety-spectrum disorders. This review will focus on the multifaceted implications of 5-HT-ergic dysfunctions in the pathophysiology of aggressive and suicidal behaviours. After a brief overview of the anatomical distribution of the 5-HT-ergic system in the key brain areas that govern aggression and suicidal behaviours, the implication of 5-HT markers (5-HT receptors, transporter as well as synthetic and metabolic enzymes) in these conditions is discussed. In this regard, particular emphasis is placed on the integration of pharmacological and genetic evidence from animal studies with the findings of human experimental and genetic association studies. Traditional views postulated an inverse relationship between 5-HT and aggression and suicidal behaviours; however, ample evidence has shown that this perspective may be overly simplistic, and that such pathological manifestations may reflect alterations in 5-HT homoeostasis due to the interaction of genetic, environmental and gender-related factors, particularly during early critical developmental stages. The development of animal models that may capture the complexity of such interactions promises to afford a powerful tool to elucidate the pathophysiology of impulsive aggression and suicidability, and identify new effective therapies for these conditions.

Molecular medicine: a path towards a personalized medicine

Psychiatric disorders are among the most common human illnesses; still, the molecular and cellular mechanisms underlying their complex pathophysiology remain to be fully elucidated. Over the past 10 years, our group has been investigating the molecular abnormalities in major signaling pathways involved in psychiatric disorders. Recent evidences obtained by the Instituto Nacional de Ciência e Tecnologia de Medicina Molecular (National Institute of Science and Technology - Molecular Medicine, INCT-MM) and others using behavioral analysis of animal models provided valuable insights into the underlying molecular alterations responsible for many complex neuropsychiatric disorders, suggesting that "defects" in critical intracellular signaling pathways have an important role in regulating neurodevelopment, as well as in pathophysiology and treatment efficacy. Resources from the INCT have allowed us to start doing research in the field of molecular imaging. Molecular imaging is a research discipline that visualizes, characterizes, and quantifies the biologic processes taking place at cellular and molecular levels in humans and other living systems through the results of image within the reality of the physiological environment. In order to recognize targets, molecular imaging applies specific instruments (e.g., PET) that enable visualization and quantification in space and in real-time of signals from molecular imaging agents. The objective of molecular medicine is to individualize treatment and improve patient care. Thus, molecular imaging is an additional tool to achieve our ultimate goal.

Clinical implications of genetic variation in the serotonin transporter promoter region: a review

OBJECTIVE

To determine the state of the art in understanding the role of genetic variation in the serotonin transporter (5-HTT) promoter region (5-HTTLPR) in the development of a depressive episode and in its response to treatment.

DATA SOURCES

PubMed and Ovid were used to search for articles published prior to December 2007 utilizing the key words serotonin transporter, 5-HTT, 5-HTTLPR, serotonin transporter gene, and SLC6A4.

STUDY SELECTION

All studies were reviewed, but case reports and small case series were excluded.

DATA EXTRACTION

All relevant articles were read by at least 2 of the coauthors and notes regarding study design, measures, data analysis, and findings were later used to construct the review.

DATA SYNTHESIS

A common genetic variant, the short allele, in which 44 base pairs are missing from the promoter of SLC6A4, is associated with a greater risk for developing a major depressive disorder in patients following exposure to adversity. This association appears to be most important in the early stages of the depressive disorder. Additionally, the likelihood of a positive response to antidepressant treatment may be reduced in these patients in terms of delayed response, greater adverse event load, or, in bipolar patients, mania induction and rapid cycling.

CONCLUSIONS

Selected genetic testing of patients with a recent history of significant adversity may be a reasonable tool that can enlighten treatment options and the course of illness. Ongoing work with the short allele of 5-HTT may also inform clinical guidelines of long-term treatment with antidepressants.

Clinical and pathogenic aspects of candidate genes for lithium prophylactic efficacy

A number of candidate genes for lithium prophylactic efficacy have been proposed, some of them being also associated with a predisposition to bipolar illness. The aim of the present study was to investigate a possible association between polymorphisms of 14 common genes with the quality of prophylactic lithium response in patients with bipolar mood disorder, in relation to the putative role of these genes in the pathogenesis of this disorder. Some association with lithium prophylactic efficacy was found for the polymorphisms of 5HTT, DRD1, COMT, BDNF and FYN genes, but not for 5HT2A, 5HT2C, DRD2, DRD3, DRD4, GSK-3, NTRK2, GRIN2B and MMP-9. Possible aspects of these genes with regard to the mechanism of lithium activity and pathogenesis of bipolar mood disorder are discussed.

Pharmacogenetics of lithium response in bipolar disorder

Bipolar disorder (BD) is a serious mental illness with well-established, but poorly characterized genetic risk. Lithium is among the best proven mood stabilizer therapies for BD, but treatment responses vary considerably. Based upon these and other findings, it has been suggested that lithium-responsive BD may be a genetically distinct phenotype within the mood disorder spectrum. This assertion has practical implications both for the treatment of BD and for understanding the neurobiological basis of the illness: genetic variation within lithium-sensitive signaling pathways may confer preferential treatment response, and the involved genes may underlie BD in some individuals. Presently, the mechanism of lithium is reviewed with an emphasis on gene-expression changes in response to lithium. Within this context, findings from genetic-association studies designed to identify lithium response genes in BD patients are evaluated. Finally, a framework is proposed by which future pharmacogenetic studies can incorporate advances in genetics, molecular biology and bioinformatics in a pathway-based approach to predicting lithium treatment response.

The 5-HTTLPR polymorphism, impulsivity and suicide behavior in euthymic bipolar patients

BACKGROUND

Suicide behavior is very frequent in Bipolar Disorder (BD) and they are both closely associated with impulsivity. Furthermore they are, impulsivity, BD and suicide behavior, associated with serotonergic function, at least partially, under genetic determinism and somewhat associated with the serotonin transporter gene polymorphism, the 5-HTTLPR. We aimed to assess different impulsivity components in BD sub-grouped by suicidal attempt and healthy controls. We hypothesized that the non-planning/cognitive impulsivity, could be more closely associated with suicidal behavior. We further associated 5-HTTLPR genotypes with neuropsychological results to test the hypothesis that this polymorphism is associated with cognitive impulsivity.

METHOD

We assessed 95 euthymic bipolar patients sub-grouped by suicidal attempt history in comparison with 94 healthy controls. All subjects underwent a laboratory assessment of impulsivity (Continuous Performance Test and Iowa Gambling Test). Furthermore the genotyping of 5-HTTLPR was performed in all subjects.

RESULTS

We found that bipolar patients are more impulsive than healthy controls in all impulsivity dimensions we studied. Furthermore bipolar patients with a suicide attempt history have a greater cognitive impulsivity when compared to both bipolar patients without such a history as well when compared to healthy controls. No association was found between 5-HTTLPR genotypes and neuropsychological measures of impulsive behavior.

LIMITATIONS

The sample studied can be considered small and a potentially confounding variable - medication status - was not controlled.

CONCLUSION

A lifetime suicide attempt seems associated with cognitive impulsivity independently of the socio-demographic and clinical variables studied as well with 5-HTTLPR genotype. Further studies in larger samples are necessary.

P2RX7 gene is associated consistently with mood disorders and predicts clinical outcome in three clinical cohorts

We investigated the effect of nine candidate genes on risk for mood disorders, hypothesizing that predisposing gene variants not only elevate the risk for mood disorders but also result in clinically significant differences in the clinical course of mood disorders. We genotyped 178 DSM-IV bipolar I and II and 272 major depressive disorder patients from three independent clinical cohorts carefully diagnosed with semistructured interviews and prospectively followed up with life charts for a median of 60 (range 6-83) months. Healthy control subjects (n = 1322) were obtained from the population-based national Health 2000 Study. We analyzed 62 genotyped variants within the selected genes (BDNF, NTRK2, SLC6A4, TPH2, P2RX7, DAOA, COMT, DISC1, and MAOA) against the presence of mood disorder, and in post-hoc analyses, specifically against bipolar disorder or major depressive disorder. Estimates for time ill were based on life charts. The P2RX7 gene variants rs208294 and rs2230912 significantly elevated the risk for a familial mood disorder (OR = 1.35, P = 0.0013, permuted P = 0.06, and OR = 1.44, P = 0.0031, permuted P = 0.17, respectively). The results were consistent in all three cohorts. The same risk alleles predicted more time ill in all cohorts (OR 1.3, 95% CI 1.1-1.6, P = 0.0069 and OR 1.7, 95% CI 1.3-2.3, P = 0.0002 with rs208294 and rs2230912, respectively), so that homozygous carriers spent 12 and 24% more time ill. P2RX7 and its risk alleles predisposed to mood disorders consistently in three independent clinical cohorts. The same risk alleles resulted in clinically significant differences in outcome of patients with major depressive and bipolar disorder.

Genome-wide association study of suicide attempts in mood disorder patients

OBJECTIVE

Family and twin studies suggest that liability for suicide attempts is heritable and distinct from mood disorder susceptibility. The authors therefore examined the association between common genomewide variation and lifetime suicide attempts.

METHOD

The authors analyzed data on lifetime suicide attempts from genomewide association studies of bipolar I and II disorder as well as major depressive disorder. Bipolar disorder subjects were drawn from the Systematic Treatment Enhancement Program for Bipolar Disorder cohort, the Wellcome Trust Case Control Consortium bipolar cohort, and the University College London cohort. Replication was pursued in the NIMH Genetic Association Information Network bipolar disorder project and a German clinical cohort. Depression subjects were drawn from the Sequential Treatment Alternatives to Relieve Depression cohort, with replication in the Netherlands Study of Depression and Anxiety/Netherlands Twin Register depression cohort.

RESULTS

Strongest evidence of association for suicide attempt in bipolar disorder was observed in a region without identified genes (rs1466846); five loci also showed suggestive evidence of association. In major depression, strongest evidence of association was observed for a single nucleotide polymorphism in ABI3BP, with six loci also showing suggestive association. Replication cohorts did not provide further support for these loci. However, meta-analysis incorporating approximately 8,700 mood disorder subjects identified four additional regions that met the threshold for suggestive association, including the locus containing the gene coding for protein kinase C-epsilon, previously implicated in models of mood and anxiety.

CONCLUSIONS

The results suggest that inherited risk for suicide among mood disorder patients is unlikely to be the result of individual common variants of large effect. They nonetheless provide suggestive evidence for multiple loci, which merit further investigation.

Is the serotonin transporter polymorphism (5-HTTLPR) a potential marker for suicidal behavior in bipolar disorder patients?

BACKGROUND

Suicide prediction is a huge challenge for mental health workers. Structured interviews based on epidemiological and clinical factors don't show effectiveness for suicide prevention. Biological markers, such as 5-HTTLPR, could help for identification of potential suicide attempters.

METHODS

We evaluated 198 bipolar patients and 103 health controls, using a structured interview according to DSM-IV criteria. Genotyping, blind of clinical assessment for identification of S carriers and structured interviews were performed in order to describe clinical and epidemiological factors which could be associated with suicide behavior. Statistical analyses were calculated by the x(2) test and logistic regression model.

RESULTS

We found that 26.77% and 16.67% had a lifetime history of non violent suicide attempt and violent suicide attempt, respectively. The clinical factors associated with violent and non violent suicide attempt had several differences. Violent suicide attempters had an earlier illness onset and had a higher number of psychiatric comorbidities (borderline personality disorder, panic disorder and alcoholism). The frequency of S allele carriers was higher only in those patients who had made a violent suicide attempt in their lifetime (x(2)=16.969; p=0.0001). In a logistic regression model including these factors, S allele carrier (5-HTTLPR) was the only factor associated with violent suicide attempt.

LIMITATIONS

Sample size and retrospective assessment of suicide behavior history are the limitations of this study.

CONCLUSIONS

Our study showed that serotonin polymorphism (5-HTTLPR) is strongly associated with violent suicidal behavior in BD patients. If confirmed, our results could be an important step to create a genetic tool for long-term suicide prediction.

Differences and similarities in the serotonergic diathesis for suicide attempts and mood disorders: a 22-year longitudinal gene-environment study

To investigate similarities and differences in the serotonergic diathesis for mood disorders and suicide attempts, we conducted a study in a cohort followed longitudinally for 22 years. A total of 1255 members of this cohort, which is representative of the French-speaking population of Quebec, were investigated. Main outcome measures included (1) mood disorders (bipolar disorder and major depression) and suicide attempts by early adulthood; (2) odds ratios and probabilities associated with 143 single nucleotide polymorphisms in 11 serotonergic genes, acting directly or as moderators in gene-environment interactions with childhood sexual or childhood physical abuse (CPA), and in gene-gene interactions; (3) regression coefficients for putative endophenotypes for mood disorders (childhood anxiousness) and suicide attempts (childhood disruptiveness). Five genes showed significant adjusted effects (HTR2A, TPH1, HTR5A, SLC6A4 and HTR1A). Of these, HTR2A variation influenced both suicide attempts and mood disorders, although through different mechanisms. In suicide attempts, HTR2A variants (rs6561333, rs7997012 and rs1885884) were involved through interactions with histories of sexual and physical abuse whereas in mood disorders through one main effect (rs9316235). In terms of phenotype-specific contributions, TPH1 variation (rs10488683) was relevant only in the diathesis for suicide attempts. Three genes contributed exclusively to mood disorders, one through a main effect (HTR5A (rs1657268)) and two through gene-environment interactions with CPA (HTR1A (rs878567) and SLC6A4 (rs3794808)). Childhood anxiousness did not mediate the effects of HTR2A and HTR5A on mood disorders, nor did childhood disruptiveness mediate the effects of TPH1 on suicide attempts. Of the serotonergic genes implicated in mood disorders and suicidal behaviors, four exhibited phenotype-specific effects, suggesting that despite their high concordance and common genetic determinants, suicide attempts and mood disorders may also have partially independent etiological pathways. To identify where these pathways diverge, we need to understand the differential, phenotype-specific gene-environment interactions such as the ones observed in the present study, using suitably powered samples.

Bipolar disorder first episode and suicidal behavior: are there differences according to type of suicide attempt?

OBJECTIVE: The objective of this study was to test the hypothesis that the polarity of the first mood episode may be a marker for suicidal behavior, particularly the violent subtype. METHOD: One hundred and sixty-eight patients diagnosed with bipolar disorder (DSM-IV) were grouped according to type of first episode: depression or manic/hypomanic. Groups were compared for demographic and clinical variables. We performed logistic regression in order to test the association between first episode polarity and suicidal behavior. RESULTS: We found that depressed patients have a lifetime history of more suicide attempts. However, univariate analysis of number of suicide attempts showed that the best model fits the bipolar II subtype (mean square = 15.022; p = 0.010) and lifetime history of psychotic episodes (mean square = 17.359; p = 0.021). Subgrouping the suicide attempts by subtype (violent or non-violent) revealed that manic/hypomanic patients had a greater tendency toward attempting violent suicide (21.2 vs. 14.7%, X² = 7.028, p = 0.03). Multiple logistic regression analysis confirmed this result. CONCLUSION: Depressed patients had more suicide attempts over time, which could be explained by the higher prevalence of bipolar II subtype in this group, whereas manic/hypomanic patients had a lifelong history of more frequent violent suicide attempts, not explained by any of the variables studied. Our results support the evidence that non-violent suicide attempters and violent suicide attempters tend to belong to different phenotypic groups.

May genetic factors in fibromyalgia help to identify patients with differentially altered frequencies of immune cells?

There is common agreement that fibromyalgia (FM) is an extremely heterogeneous entity. Patients differ in their clinical symptoms, endocrine and immune parameters. In this study we evaluated endocrine and immunological features of distinct subsets of FM patients. In contrast to previous attempts to identify subsets of FM patients, based solely on their psychological and cognitive features, herein we propose to separate FM patients by genetic features. Allelic expression of the polymorphic promoter region of the serotonin transporter (5-HTTLPR) was analysed as a relevant genetic factor for FM. Seventy-five patients meeting the American College of Rheumatology criteria and 27 healthy age-matched controls participated in this study. All controls and FM patients were submitted to genotyping of 5-HTTLPR. Twenty-seven FM patients, who were able to discontinue hypnotic, sedative or psychotropic prescription medications for at least 2 weeks, were then subdivided into L (homozygote LL) or S groups (genotypes LS and SS). They were evaluated for salivary cortisol levels, absolute number of leucocyte subpopulations, including natural killer (NK) cells and activated T and B lymphocytes. Both groups presented decreased cortisol levels, more intense in the L group, increased all B lymphocytes subsets and reduced CD4+CD25high T lymphocytes. The L group had increased CD4+CD25low activated T lymphocytes, while the S group displayed elevated CD4+ human leucocyte antigen D-related (HLA-DR)+ activated T lymphocytes and decreased NK cells. We demonstrate that genetic factors may help to identify FM individuals with differentially altered frequencies of immune cells.

Suicide behavior and neuropsychological assessment of type I bipolar patients

BACKGROUND

Neuropsychological deficits are often described in patients with bipolar disorder (BD). Some symptoms and/or associated characteristics of BD can be more closely associated to those cognitive impairments. We aimed to explore cognitive neuropsychological characteristics of type I bipolar patients (BPI) in terms of lifetime suicide attempt history.

METHOD

We studied 39 BPI outpatients compared with 53 healthy controls (HC) matched by age, educational and intellectual level. All subjects were submitted to a neuropsychological assessment of executive functions, decision-making and declarative episodic memory.

RESULTS

When comparing BDI patients, regardless of suicide attempt history or HC, we observed that bipolar patients performed worse than controls on measures of memory, attention, executive functions and decision-making. Patients with a history of suicide attempt performed worse than non-attempters on measures of decision-making and there were a significant negative correlation between the number of suicide attempts and decision-making results (block 3 and net score). We also found significant positive correlation between the number of suicide attempts and amount of errors in Stroop Color Word Test (part 3).

LIMITATIONS

The sample studied can be considered small and a potentially confounding variable - medication status - were not controlled.

CONCLUSION

Our results show the presence of neuropsychological deficits in memory, executive functions, attention and decision-making in BPI patients. Suicide attempts BPI scored worse than non-suicide attempt BPI on measures of decision-making. More suicide attempts were associated with a worse decision-making process. Future research should explore the relationship between the association between this specific cognitive deficits in BPIs, serotonergic function and suicide behavior in bipolar patients as well other diagnostic groups.

Genetics of bipolar disorder

Bipolar disorder, especially the most severe type (type I), has a strong genetic component. Family studies suggest that a small number of genes of modest effect are involved in this disorder. Family-based studies have identified a number of chromosomal regions linked to bipolar disorder, and progress is currently being made in identifying positional candidate genes within those regions, À number of candidate genes have also shown evidence of association with bipolar disorder, and genome-wide association studies are now under way, using dense genetic maps. Replication studies in larger or combined datasets are needed to definitively assign a role for specific genes in this disorder. This review covers our current knowledge of the genetics of bipolar disorder, and provides a commentary on current approaches used to identify the genes involved in this complex behavioral disorder.

The genetics of bipolar disorder: genome 'hot regions,' genes, new potential candidates and future directions

Bipolar disorder (BP) is a complex disorder caused by a number of liability genes interacting with the environment. In recent years, a large number of linkage and association studies have been conducted producing an extremely large number of findings often not replicated or partially replicated. Further, results from linkage and association studies are not always easily comparable. Unfortunately, at present a comprehensive coverage of available evidence is still lacking. In the present paper, we summarized results obtained from both linkage and association studies in BP. Further, we indicated new potential interesting genes, located in genome 'hot regions' for BP and being expressed in the brain. We reviewed published studies on the subject till December 2007. We precisely localized regions where positive linkage has been found, by the NCBI Map viewer (http://www.ncbi.nlm.nih.gov/mapview/); further, we identified genes located in interesting areas and expressed in the brain, by the Entrez gene, Unigene databases (http://www.ncbi.nlm.nih.gov/entrez/) and Human Protein Reference Database (http://www.hprd.org); these genes could be of interest in future investigations. The review of association studies gave interesting results, as a number of genes seem to be definitively involved in BP, such as SLC6A4, TPH2, DRD4, SLC6A3, DAOA, DTNBP1, NRG1, DISC1 and BDNF. A number of promising genes, which received independent confirmations, and genes that have to be further investigated in BP, have been also systematically listed. In conclusion, the combination of linkage and association approaches provided a number of liability genes. Nevertheless, other approaches are required to disentangle conflicting findings, such as gene interaction analyses, interaction with psychosocial and environmental factors and, finally, endophenotype investigations.