A functional dopamine-beta-hydroxylase gene promoter polymorphism is associated with impulsive personality styles, but not with affective disorders

Association of dopamine β-hydroxylase polymorphism rs1611115 and serum levels with psychiatric disorders in Pakistani population

AIM

Dopamine β-hydroxylase (DBH) is a copper-containing enzyme that has an important role in maintaining the cellular homeostasis between the two neurotransmitters, dopamine (DA) and nor-adrenaline (NA). DBH functional polymorphisms are associated with multiple neuro-psychiatric conditions and are found to alter the DBH protein levels in serum affecting DBH enzymatic activity. The current study was conducted to determine the genetic and serum levels association of DBH rs1611115 functional polymorphism with major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SHZ) in the Pakistani population.

METHODS

In total n = 1097 subjects including MDD (n = 427), BD (n = 204), SHZ (n = 134) and healthy controls (n = 332), were screened for the functional polymorphism by polymerase chain reaction-restriction fragment length polymorphism. Univariate logistic regression analysis was applied and the results were adjusted for age and sex. The DBH levels in serum were determined through enzyme-linked immunosorbent assay (ELISA) and the Mann Whitney U test was applied.

RESULTS

The minor allele (-1021 C > T) was found to be significantly associated with a higher risk of developing BD and SHZ in both univariable and multivariable analyses. The overall total serum concentration of DBH was comparatively raised in MDD, however, in cross-comparison DBH serum levels were found markedly higher in CC homozygotes compared to TT homozygotes within the BD group.

CONCLUSION

The present study suggested a significant association of DBH rs1611115 with BD and SHZ and also the effect of rs1611115 on DBH serum levels in MDD and BD for the first time in the Pakistani population.

Cognitive impairment in 'non-user' first-degree relatives of persons with cannabis dependence syndrome: A pilot, endophenotype study

INTRODUCTION

Cannabis use disorders are global emerging problem nowadays, with high prevalence and morbidity. Cognitive impairments, and also corresponding genetic vulnerability, has been fairly replicated in individuals with cannabis dependence. However, there are few studies that assess cognitive functioning as an endophenotype or a trait marker for cannabis dependence. While the primary objective of this study was to assess the endophenotype pattern of cognitive dysfunction in cannabis dependence, assessing the association between the degree of cognitive functioning, and their socio-demographic and clinical variables in the cannabis dependence patients and their first-degree relatives was the secondary objective.

METHODOLOGY

We compared cognitive functioning across three groups- patients with cannabis dependence syndrome, their 'non-user' first-degree relatives and healthy controls, with 30 participants in each group. Five cognitive domains- attention and concentration, verbal fluency, memory, visuospatial ability and executive functions were assessed. We assessed for endophenotype pattern of statistical significance in pairwise analyses of Kruskal-Wallis test, which was corrected for multiple comparisons. Subsequently, correlation analysis to assess association of cognitive impairment with socio-demographic and clinical variables was conducted.

RESULTS

Although impairment in attention and executive functions also was seen in patients with cannabis dependence, endophenotype pattern of statistical significance in pairwise analyses, with impairment in first-degree relatives too, was seen in all sub-scores of verbal fluency and verbal memory. None of the correlations were significant.

CONCLUSION

'Non-user' first-degree relatives of patients with cannabis dependence too show significant cognitive impairment. Verbal fluency and verbal memory are possible endophenotypes or trait markers for cannabis dependence syndrome.

Potential biomarkers and therapeutic targets for obsessive compulsive disorder: Evidences from clinical studies

Obsessive compulsive disorder (OCD) is a prevalent behavioral disorder with a complex etiology. However, the underlying pathogenic molecular pathways and the associated risk factors are largely obscure. This has hindered both the identification of relevant prognostic biomarkers and the development of effective treatment strategies. Because of the diverse range of clinical manifestations, not all patients benefit from therapies currently practiced in the clinical setting. Nevertheless, several lines of evidence indicate that neurotrophic, neurotransmitter, and oxidative signaling are involved in the pathophysiology of OCD. Based upon evidences from clinical (and pre-clinical studies), the present review paper sets out to decipher the utilities of three parameters (i.e. brain-derived neurotrophic factor; BDNF, noradrenalin-synthesizing enzyme dopamine beta-hydroxylase; DBH; and oxidative damage marker malondialdehyde; MDA) as diagnostic peripheral biomarkers as well as bio-targets for therapeutic strategies. While the data indicates promising results, there is necessitation for future studies to further confirm and establish these. Further, based again on the available clinical data, we investigated the possibilities of exploiting the etiological links between disruptions in the sleep-wake cycle and insulin signaling, and OCD for the identification of potential anti-OCD ameliorative agents with the ability to elicit multimodal effects, including attenuation of the alterations in BDNF, noradrenergic and redox pathways. In this respect, agomelatine and metformin may represent particularly interesting candidates; however, further clinical studies are warranted to establish these as singular or complementary medications in OCD subjects.

Associations between Omega-3 Index, Dopaminergic Genetic Variants and Aggressive and Metacognitive Traits: A Study in Adult Male Prisoners

Omega-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) are critical for cell membrane structure and function. Human beings have a limited ability to synthesise docosahexaenoic acid (DHA), the main n-3 LCPUFA required for neurological development. Inadequate levels of n-3 LCPUFA can affect the dopaminergic system in the brain and, when combined with genetic and other factors, increase the risk of developing aggression, inattention and impulse-control disorders. In this study, male prisoners were administered questionnaires assessing aggressive behaviour and executive functions. Participants also produced blood sampling for the measurement of the Omega-3 Index and the genotyping of dopaminergic genetic variants. Significant associations were found between functional genetic polymorphism in DBH rs1611115 and verbal aggression and between DRD2 rs4274224 and executive functions. However, the Omega-3 Index was not significantly associated with the tested dopaminergic polymorphisms. Although previous interactions between specific genotypes and n-3 LCPUFA were previously reported, they remain limited and poorly understood. We did not find any association between n-3 LCPUFA and dopaminergic polymorphisms in adult male prisoners; however, we confirmed the importance of genetic predisposition for dopaminergic genes (DBH and DRD2) in aggressive behaviour, memory dysfunction and attention-deficit disorder.

Ambient ultraviolet B radiation induced valve behavioral acclimation of Pacific oyster which resulted from the different response strategies of smooth and striated adductor muscles

Light not only conveys image-forming vision but also has an impact on various physiological functions. In particular, ultraviolet B (UVB) radiation has the closest relationship with living organisms. For Pacific oysters (Crassostrea gigas), alteration of valve behavior is one of the most important ways responding to ambient UVB. In the present study, the response of adult C. gigas to sunlight (especially UVB) was evaluated by monitoring valve activity and further elucidated at the physiological and metabolomic levels. After exposure, the valve activity of C. gigas demonstrated flexible acclimation to the ambient conditions. The potential adjustment of osmoregulation and oxidative stress might be related to ambient UVB radiation. Mycosporine-like amino acids might contribute to the protection of C. gigas against UVB, while precursors of β-alanine and degradation products of 5-hydroxytryptamine might adjust the contraction of the adductor muscles. The different responses of the adductor muscles (smooth and striated) were manifested in signal transduction and metabolisms of energy and nucleotide. This study not only indicated the correlation between the valve behavioral changes in oysters and light radiation, especially UVB, but illustrated the acclimation strategies of oysters to ambient light (UVB) environment.

The association of C789A polymorphism in the dopamine beta-hydroxylase gene (DBH) and aggressive behaviour in dogs

The genetic basis of aggressive behaviour has been examined extensively, including analysis of genes encoding neurotransmitters, signalling molecules and regulatory enzymes, as well as their synthesis and degradation. Dopamine beta-hydroxylase, an enzyme catalysing the conversion of dopamine into norepinephrine in synaptic endings, significantly affects the modulation of emotional states and behaviour. The aim of this study was to determine the association of C789A polymorphism in the canine dopamine beta-hydroxylase gene (DBH) and aggressive behaviour in dogs. A total of 110 dogs of different breeds were analysed. All animals were classified according to their individual behavioural characteristics, defined by a veterinary interview and observation. Polymorphism was analysed using ACRS-PCR (amplification created restriction site-polymerase chain reaction) method. Significant differences in DBH genotypes and allele frequency between aggressive and non-aggressive dogs were observed (χ2 = 16,232, P = 0.0003). In aggressive dogs, the CC genotype (0.788) and C allele (0.815) were most frequent while in non-aggressive dogs, their frequencies were significantly lower (0.361 and 0.404, respectively). The obtained results indicate that DBH is a promising candidate gene for canine behavioural study.

An electrophysiological model of major depression: Relevance to clinical subtyping and pharmacological management

We present a neurochemical model of unipolar major depressive disorder that makes predictions for optimizing pharmacological treatment of this debilitating neuropsychiatric disorder. We suggest that there are two principal electrophysiological subtypes of depression, with the more common one involving a high excitatory/inhibitory (E/I) electrophysiological ratio, and a less common low E/I subtype. The high E/I subtype is paradoxically a variant of previous conceptions of atypical depression, whereas the low E/I subtype is a variant of melancholic depression. We focus on the ratio of norepinephrine (NE) to serotonin (5HT) as primary determinants of E/I ratio, which have opposing effects on mood regulation. We suggest that high NE/5HT (or E/I) ratio depressions should be treated with pharmacological agents that boost 5HT (such as SSRIs) and/or drugs that reduce noradrenergic transmission (such as clonidine, guanfacine, propranolol, prazosin). In contrast, low NE/5HT (or E/I) depressions should be treated with agents that boost NE (such as most tricyclics) and/or drugs that reduce serotonergic transmission. Our model predicts that the rapidly acting antidepressant ketamine (and possibly scopolamine), which has an acutely excitatory electrophysiological profile that may be followed by sustained increased inhibition, should improve the high NE/5HT subtype and worsen the low subtype.

The why behind the high: determinants of neurocognition during acute cannabis exposure

Acute cannabis intoxication may induce neurocognitive impairment and is a possible cause of human error, injury and psychological distress. One of the major concerns raised about increasing cannabis legalization and the therapeutic use of cannabis is that it will increase cannabis-related harm. However, the impairing effect of cannabis during intoxication varies among individuals and may not occur in all users. There is evidence that the neurocognitive response to acute cannabis exposure is driven by changes in the activity of the mesocorticolimbic and salience networks, can be exacerbated or mitigated by biological and pharmacological factors, varies with product formulations and frequency of use and can differ between recreational and therapeutic use. It is argued that these determinants of the cannabis-induced neurocognitive state should be taken into account when defining and evaluating levels of cannabis impairment in the legal arena, when prescribing cannabis in therapeutic settings and when informing society about the safe and responsible use of cannabis.

Functional Polymorphisms in Oxytocin and Dopamine Pathway Genes and the Development of Dispositional Compassion Over Time: The Young Finns Study

Background: We define compassion as an enduring disposition that centers upon empathetic concern for another person's suffering and the motivation to act to alleviate it. The contribution of specific candidate genes to the development of dispositional compassion for others is currently unknown. We examine candidate genes in the oxytocin and dopamine signaling pathways.

Methods: In a 32-year follow-up of the Young Finns Study (N = 2,130, 44.0% men), we examined with multiple indicators latent growth curve modeling the molecular genetic underpinnings of dispositional compassion for others across the life span. We selected five single nucleotide polymorphisms (SNPs) whose functions are known in humans: rs2268498 (OXTR), rs3796863 (CD38) (related to lower oxytocin levels), rs1800497 (ANKK1/DRD2), rs4680 (COMT), and rs1611115 (DBH) (related to higher dopamine levels). Compassion was measured with Cloninger's Temperament and Character Inventory on three repeated observations spanning 15 years (1997–2012). Differences between gender were tested.

Results: We did not find an effect of the five SNPs in oxytocin and dopamine pathway genes on the initial levels of dispositional compassion for others. Individuals who carry one or two copies of the T-allele of DBH rs1611115, however, tend to increase faster in compassion over time than those homozygotes for the C-allele, b = 0.063 (SE = 0.027; p = 0.018). This effect was largely driven by male participants, 0.206 (SE = 0.046; p < 0.001), and was not significant in female participants when analyzed separately.

Conclusions: Men who are known to have, on average, lower compassion than women seem to reduce this difference over time if they carry the T-allele of DBH rs1611115. The direction of the association indicates that dopamine signaling activity rather than overall dopamine levels might drive the development of compassion.

Post-weaning Social Isolated Flinders Sensitive Line Rats Display Bio-Behavioural Manifestations Resistant to Fluoxetine: A Model of Treatment-Resistant Depression

Treatment-resistant depression (TRD) complicates the management of major depression (MD). The underlying biology of TRD involves interplay between genetic propensity and chronic and/or early life adversity. By combining a genetic animal model of MD and post-weaning social isolation rearing (SIR), we sought to produce an animal that displays more severe depressive- and social anxiety-like manifestations resistant to standard antidepressant treatment. Flinders Sensitive Line (FSL) pups were social or isolation reared from weaning [postnatal day (PND) 21], receiving fluoxetine (FLX) from PND 63 (10 mg/kg × 14 days), and compared to Sprague Dawley (SD) controls. Depressive-, anxiety-like, and social behaviour were assessed from PND 72 in the forced swim test (FST) and social interaction test (SIT). Post-mortem cortico-hippocampal norepinephrine (NE), serotonin (5-HT), and dopamine (DA), as well as plasma interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-α), corticosterone (CORT), and dopamine-beta-hydroxylase (DBH) levels were assayed. FSL rats displayed significant cortico-hippocampal monoamine disturbances, and depressive- and social anxiety-like behaviour, the latter two reversed by FLX. SIR-exposed FSL rats exhibited significant immobility in the FST and social impairment which were, respectively, worsened by or resistant to FLX. In SIR-exposed FSL rats, FLX significantly raised depleted NE and 5-HT, significantly decreased DBH and caused a large effect size increase in DA and decrease in CORT and TNF-α. Concluding, SIR-exposed FSL rats display depressive- and social anxiety-like symptoms that are resistant to, or worsened by, FLX, with reduced plasma DBH and suppressed cortico-hippocampal 5-HT, NE and DA, all variably altered by FLX. Exposure of a genetic animal model of MD to post-weaning SIR results in a more intractable depressive-like phenotype as well as changes in TRD-related biomarkers, that are resistant to traditional antidepressant treatment. Given the relative absence of validated animal models of TRD, these findings are especially promising and warrant study, especially further predictive validation.

The effect of interactions between genetics and cannabis use on neurocognition. A review

BACKGROUND

Cannabis is one of the most widely-used drugs in industrialized countries. It is now well established that cannabis use impacts neurocognition. In the intoxication period time episodic memory, working memory and attention are impacted and impulsivity is increased. The long-term effects of cannabis use tend to be similar. Various internal factors, such as sex differences, modulate this impact. It is unclear whether genetic variations can also influence the impact of cannabis on neurocognition. We set out to examine the impact of genetic variations on neurocognition in cannabis users.

METHOD

We conducted a search via the PubMed, Web of Science, and ScienceDirect databases to identify studies measuring neurocognition and assessing genotypes in the context of cannabis use.

RESULTS

We included 13 articles. We found that working memory, verbal and visual memory and sustained attention are more impacted during intoxication in subjects with the Val COMT allele. COMT gene could also modulate sustained attention in regular use. The CNR1, AKT1, DBH and 5-HTT/SLC6A4 genes may also modulate effects.

CONCLUSION

Most of these genes are linked to schizophrenia. A fuller understanding of their impact on the effects of cannabis on neurocognition would thus help elucidate the mechanisms linking cannabis and psychosis. However, evidence is still scant, and more research is needed.

Psychiatric (Axis I) and personality (Axis II) disorders and subjective psychiatric symptoms in chronic tinnitus

OBJECTIVE

Chronic tinnitus has been associated with several psychiatric disorders. Only few studies have investigated these disorders using validated diagnostic interviews. The aims were to diagnose psychiatric and personality disorders with structured interviews, to assess self-rated psychiatric symptoms and elucidate temporal relations between psychiatric disorders and tinnitus.

DESIGN

Current and lifetime DSM-IV diagnoses of axis-I (psychiatric disorders) and axis-II (personality disorders) were assessed using structured clinical interviews (SCID-I and -II). Current subjective psychiatric symptoms were evaluated via self-rating instruments: the Symptom Check List-90 (SCL-90), the Beck Depression Inventory, and the Dissociative Experiences Scale (DES).

STUDY SAMPLE

83 patients (mean age 51.7, 59% men) with chronic, disturbing tinnitus and a median Tinnitus Handicap Inventory score of 32.

RESULTS

The rates of lifetime and current major depression were 26.5% and 2.4%. The lifetime rate of obsessive-compulsive personality disorder (type C) was 8.4%. None of the patients had cluster B personality disorder or psychotic symptoms. The SCL-90 subscales did not differ from the general population, and median DES score was low, 2.4.

CONCLUSIONS

Tinnitus patients are prone to episodes of major depression and often also have obsessive-compulsive personality features. Psychiatric disorders seem to be comorbid or predisposing conditions rather than consequences of tinnitus. Clinical trial reference: ClinicalTrials.gov (ID NCT 01929837).

Cannabis and cocaine decrease cognitive impulse control and functional corticostriatal connectivity in drug users with low activity DBH genotypes

The dopamine β-hydroxylase (DβH) enzyme transforms dopamine into noradrenaline. We hypothesized that individuals with low activity DBH genotypes (rs1611115 CT/TT) are more sensitive to the influence of cannabis and cocaine on cognitive impulse control and functional connectivity in the limbic ‘reward’ circuit because they experience a drug induced hyperdopaminergic state compared to individuals with high activity DBH genotypes (rs1611115 CC). Regular drug users (N = 122) received acute doses of cannabis (450 μg/kg THC), cocaine HCl 300 mg and placebo. Cognitive impulse control was assessed by means of the Matching Familiar Figures Test (MFFT). Resting state fMRI was measured in a subset of participants to determine functional connectivity between the nucleus accumbens (NAc) and (sub)cortical areas. The influence of cannabis and cocaine on impulsivity and functional connectivity significantly interacted with DBH genotype. Both drugs increased cognitive impulsivity in participants with CT/TT genotypes but not in CC participants. Both drugs also reduced functional connectivity between the NAc and the limbic lobe, prefrontal cortex, striatum and thalamus and primarily in individuals with CT/TT genotypes. Correlational analysis indicated a significant negative association between cognitive impulsivity and functional connectivity in subcortical areas of the brain. It is concluded that interference of cannabis and cocaine with cognitive impulse control and functional corticostriatal connectivity depends on DBH genotype. The present data provide a neural substrate and behavioral mechanism by which drug users can progress to drug seeking and may also offer a rationale for targeted pharmacotherapy in chronic drug users with high risk DBH genotypes.

A biopsychosocial model of violence when sleepwalking: review and reconceptualisation

SUMMARY

Violence towards others during sleepwalking is relatively uncommon, but can result in serious injury or even death. Much of the research in this field has focused on the forensic consequences of violence during sleepwalking without sufficient attention to an understanding of the risk factors for violence during sleepwalking and the development of prevention and interventions based on these risk factors. This paper reviews the characteristics of impulsive violence in general and reconceptualises violence during sleepwalking as an extension of this prior vulnerability. We propose a biopsychosocial model of the risk for violence during sleepwalking that is supported through a review of empirical literature both within sleepwalking and violent behaviour more generally. Biological, psychological and social risk factors are hypothesised to mediate the relationship between sleepwalking and violence. Implications for prevention and treatment of this potentially fatal problem are discussed.

DECLARATION OF INTEREST

None.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2017. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) license.

[Combination of DAT and DBH gene polymorphisms with a family history of alcohol use disorders increases the risk of withdrawal seizures and delirium tremens during alcohol withdrawal in alcohol-dependent men]

AIM

To explore the genetic influence of a family history of alcohol use disorders and the dopamine transporter SLC6A3 (DAT1) and dopamine beta-hydroxylase (DBH) gene polymorphisms on the risk of severe complications (withdrawal seizures (AWS) and delirium tremens (DT)) during alcohol withdrawal in alcohol-dependent men.

MATERIAL AND METHODS

We investigated the effects of 3 previously reported candidate genetic variations: 40-bp variable number tandem repeat (VNTR) polymorphism and C/T exon 15 (rs27072) in the 3' untranslated region (3' UTR) of the SLC6A3(DAT1) gene, and -1021 C/T (rs1611115) of DBH gene in 266 alcohol-dependent Russian male inpatients in two groups by presence (SC group: AWS, DT, AWS+DT, n=130) or absence (n=136) of severe complications diagnosed by ICD-10 during current alcohol withdrawal. Clinically important information and a family history of alcohol use disorders (FH) were obtained by semi-structured interview.

RESULTS

Patients in SC group more often have positive FH (54.6% vs. 33%, p=0.001) and their age at first alcohol use (FAU) was lower (16±3.53y.o vs. 17±1.66 y.o, p=0.001). Logistic regression revealed that FH predicts severe complications in total (р=0.001) and DT (р=0.003), FAU independently predicts severe complications in total (р=0.008), AWS (р=0.04), DT (р=0.032), AWS+DT (р=0.048) and every year of delay alcohol use decreases the risk by 18-30%. The gene polymorphisms interact with FAU to decrease the FAU influence on the risk of AWS (T variant of DAT (rs27072), р=0.04), (AWS+DT) and DT (T variant of DBH (rs1611115), р=0.023 and р=0.06). The T variant of DAT (rs27072) is associated with FAU (p=0.007) and increases the risk of (AWS+DT) (р=0.036), but decreases the risk of AWS (р=0.038) and of DT (р=0.021) too, but only in interaction with positive FH. The 9 repeat variant (9R) of DAT VNTR is associated with AWS (p=0.009), but the risk of AWS (р=0.004) and of SC in total (р=0.001) are elevated only in 9R carriers with positive FH. The 9R independently increases the risk of DT (р=0.048) and the effect become more robust in 9R carriers with high density of FH (р=0.014). The gene x gene interaction decreases the risk of DT (р=0.055). According to an analysis of total cohort of patients, the T variant of DBH (rs1611115) is associated with any kind of manifestation of delirium in alcohol-dependent men (p=0.039).

CONCLUSION

This study demonstrate the genetic influence of a family history of alcohol use disorders and DAT and DBH gene polymorphisms on the risk of withdrawal seizures and delirium tremens. The interaction of genetic variations with positive family history provides the most robust effect, the interaction of genetic variations with the age at first alcohol use may «protect» their carriers from negative influence of this «behavioral» risk factor. Replication in large cohorts of patients is necessary to verify these findings for subsequent use in prevention programs.

Exploring possible association between DβH genotype (C1021T), early onset of conduct disorder and psychopathic traits in juvenile delinquents

Early onset of conduct disorder (CD) with callous-unemotional traits has been linked to low levels of dopamine β-hydroxylase (DβH), an enzyme involved in dopamine turnover. The C1021T polymorphism in the DβH gene is a major quantitative-trait locus, regulating the level of DβH. In this study of juvenile delinquents from Northern Russia (n = 180), the polymorphism at -1021 was associated neither with early-onset CD nor with psychopathic traits. Association was found between psychopathic traits and early-onset CD, ADHD and mania.

Identification and functional characterisation of a novel dopamine beta hydroxylase gene variant associated with attention deficit hyperactivity disorder

OBJECTIVES

Dysregulation in neurotransmitter signalling has been implicated in the aetiology of attention deficit hyperactivity disorder (ADHD). Polymorphisms of the gene encoding dopamine beta hydroxylase (DBH) have been reported to be associated with ADHD; however, small sample sizes have led to inconsistency.

METHODS

We conducted transmission disequilibrium test analysis in 794 nuclear families to examine the relationship between DBH and ADHD. The effects of the ADHD-associated polymorphisms on gene expression were assessed by luciferase reporter assays in a human neuroblastoma cell line, SH-SY5Y.

RESULTS

A SNP within the 3' untranslated region of DBH rs129882 showed a significant association with ADHD (χ(2) = 9.71, p = 0.0018, OR = 1.37). This association remained significant after Bonferroni correction for multiple testing (p = 0.02). Further, allelic variation in rs129882 significantly impacted luciferase expression. Specifically, the C allele of the ADHD-associated rs129882 SNP produced a 2-fold decrease (p < 0.001) in luciferase activity.

CONCLUSIONS

These data demonstrate for the first time that a DBH gene variant, rs129882, which confers risk to ADHD is also associated with reduced in vitro gene expression. Reduced DBH expression would be consistent with decreased conversion of dopamine to noradrenaline and thus with a relative hypo-noradrenergic state in ADHD.

The neurobiological basis of human aggression: A review on genetic and epigenetic mechanisms

Aggression is an evolutionary conserved behavior present in most species including humans. Inadequate aggression can lead to long-term detrimental personal and societal effects. Here, we differentiate between proactive and reactive forms of aggression and review the genetic determinants of it. Heritability estimates of aggression in general vary between studies due to differing assessment instruments for aggressive behavior (AB) as well as age and gender of study participants. In addition, especially non-shared environmental factors shape AB. Current hypotheses suggest that environmental effects such as early life stress or chronic psychosocial risk factors (e.g., maltreatment) and variation in genes related to neuroendocrine, dopaminergic as well as serotonergic systems increase the risk to develop AB. In this review, we summarize the current knowledge of the genetics of human aggression based on twin studies, genetic association studies, animal models, and epigenetic analyses with the aim to differentiate between mechanisms associated with proactive or reactive aggression. We hypothesize that from a genetic perspective, the aminergic systems are likely to regulate both reactive and proactive aggression, whereas the endocrine pathways seem to be more involved in regulation of reactive aggression through modulation of impulsivity. Epigenetic studies on aggression have associated non-genetic risk factors with modifications of the stress response and the immune system. Finally, we point to the urgent need for further genome-wide analyses and the integration of genetic and epigenetic information to understand individual differences in reactive and proactive AB. © 2015 Wiley Periodicals, Inc.

Attention-deficit hyperactivity disorder in adults: A systematic review and meta-analysis of genetic, pharmacogenetic and biochemical studies

The adult form of attention-deficit/hyperactivity disorder has a prevalence of up to 5% and is the most severe long-term outcome of this common disorder. Family studies in clinical samples as well as twin studies suggest a familial liability and consequently different genes were investigated in association studies. Pharmacotherapy with methylphenidate (MPH) seems to be the first-line treatment of choice in adults with attention-deficit hyperactive disorder (ADHD) and some studies were conducted on the genes influencing the response to this drug. Finally some peripheral biomarkers were identified in ADHD adult patients. We believe this work is the first systematic review and meta-analysis of candidate gene association studies, pharmacogenetic and biochemical (metabolomics) studies performed in adults with ADHD to identify potential genetic, predictive and peripheral markers linked specifically to ADHD in adults. After screening 5129 records, we selected 87 studies of which 61 were available for candidate gene association studies, 5 for pharmacogenetics and 21 for biochemical studies. Of these, 15 genetic, 2 pharmacogenetic and 6 biochemical studies were included in the meta-analyses. We obtained an association between adult ADHD and the gene BAIAP2 (brain-specific angiogenesis inhibitor 1-associated protein 2), even after Bonferroni correction, with any heterogeneity in effect size and no publication bias. If we did not apply the Bonferroni correction, a trend was found for the carriers allele 9R of dopamine transporter SLC6A3 40 bp variable tandem repeat polymorphism (VNTR) and for 6/6 homozygotes of SLC6A3 30 bp VNTR. Negative results were obtained for the 9-6 haplotype, the dopamine receptor DRD4 48 bp VNTR, and the enzyme COMT SNP rs4680. Concerning pharmacogenetic studies, no association was found for the SLC6A3 40 bp and response to MPH with only two studies selected. For the metabolomics studies, no differences between ADHD adults and controls were found for salivary cortisol, whereas lower serum docosahexaenoic acid (DHA) levels were found in ADHD adults. This last association was significant even after Bonferroni correction and in absence of heterogeneity. Other polyunsaturated fatty acids (PUFAs) such as AA (arachidonic acid), EPA (eicosapentaenoic acid) and DyLA (dihomogammalinolenic acid) levels were not different between patients and controls. No publication biases were observed for these markers. Genes linked to dopaminergic, serotoninergic and noradrenergic signaling, metabolism (DBH, TPH1, TPH2, DDC, MAOA, MAOB, BCHE and TH), neurodevelopment (BDNF and others), the SNARE system and other forty genes/proteins related to different pathways were not meta-analyzed due to insufficient data. In conclusion, we found that there were not enough genetic, pharmacogenetic and biochemical studies of ADHD in adults and that more investigations are needed. Moreover we confirmed a significant role of BAIAP2 and DHA in the etiology of ADHD exclusively in adults. Future research should be focused on the replication of these findings and to assess their specificity for ADHD.

Aggressive behavior in humans: Genes and pathways identified through association studies

Aggressive behavior has both genetic and environmental components. Many association studies have been performed to identify genetic factors underlying aggressive behaviors in humans. In this review we summarize the previous work performed in this field, considering both candidate gene (CGAS) and genome-wide association studies (GWAS), excluding those performed in samples where the primary diagnosis is a psychiatric or neurological disorder other than an aggression-related phenotype. Subsequently, we have studied the enrichment of pathways and functions in GWAS data. The results of our searches show that most CGAS have identified associations with genes involved in dopaminergic and serotonergic neurotransmission and in hormone regulation. On the other hand, GWAS have not yet identified genome-wide significant associations, but top nominal findings are related to several signaling pathways, such as axon guidance or estrogen receptor signaling, and also to neurodevelopmental processes and synaptic plasticity. Future studies should use larger samples, homogeneous phenotypes and standardized measurements to identify genes that underlie aggressive behaviors in humans. © 2016 Wiley Periodicals, Inc.

Catecholamines and cognition after traumatic brain injury

Cognitive problems are one of the main causes of ongoing disability after traumatic brain injury. The heterogeneity of the injuries sustained and the variability of the resulting cognitive deficits makes treating these problems difficult. Identifying the underlying pathology allows a targeted treatment approach aimed at cognitive enhancement. For example, damage to neuromodulatory neurotransmitter systems is common after traumatic brain injury and is an important cause of cognitive impairment. Here, we discuss the evidence implicating disruption of the catecholamines (dopamine and noradrenaline) and review the efficacy of catecholaminergic drugs in treating post-traumatic brain injury cognitive impairments. The response to these therapies is often variable, a likely consequence of the heterogeneous patterns of injury as well as a non-linear relationship between catecholamine levels and cognitive functions. This individual variability means that measuring the structure and function of a person’s catecholaminergic systems is likely to allow more refined therapy. Advanced structural and molecular imaging techniques offer the potential to identify disruption to the catecholaminergic systems and to provide a direct measure of catecholamine levels. In addition, measures of structural and functional connectivity can be used to identify common patterns of injury and to measure the functioning of brain ‘networks’ that are important for normal cognitive functioning. As the catecholamine systems modulate these cognitive networks, these measures could potentially be used to stratify treatment selection and monitor response to treatment in a more sophisticated manner.

A Preliminary Study of DBH (Encoding Dopamine Beta-Hydroxylase) Genetic Variation and Neural Correlates of Emotional and Motivational Processing in Individuals With and Without Pathological Gambling

Background and aims Corticostriatal-limbic neurocircuitry, emotional and motivational processing, dopaminergic and noradrenergic systems and genetic factors have all been implicated in pathological gambling (PG). However, allelic variants of genes influencing dopaminergic and noradrenergic neurotransmitters have not been investigated with respect to the neural correlates of emotional and motivational states in PG. Dopamine beta-hydroxylase (DBH) converts dopamine to norepinephrine; the T allele of a functional single-nucleotide polymorphism rs1611115 (C-1021T) in the DBH gene is associated with less DBH activity and has been linked to emotional processes and addiction. Here, we investigate the influence of rs1611115 on the neural correlates of emotional and motivational processing in PG and healthy comparison (HC) participants. Methods While undergoing functional magnetic resonance imaging, 18 PG and 25 HC participants, all European Americans, viewed gambling-, sad-, and cocaine-related videotapes. Analyses focused on brain activation differences related to DBH genotype (CC/T-carrier [i.e., CT and TT]) and condition (sad/gambling/cocaine). Results CC participants demonstrated greater recruitment of corticostriatal-limbic regions, relative to T-carriers. DBH variants were also associated with altered corticostriatal-limbic activations across the different videotape conditions, and this association appeared to be driven by greater activation in CC participants relative to T-carriers during the sad condition. CC relative to T-carrier subjects also reported greater subjective sadness to the sad videotapes. Conclusions Individual differences in genetic composition linked to aminergic function contribute significantly to emotional regulation across diagnostic groups and warrant further investigation in PG.

Analysis of dopamine beta hydroxylase gene polymorphisms in migraine

BACKGROUND

Migraine is a complex neurological disorder characterized by severe recurrent headache, nausea, vomiting, photophobia, and phonophobia. The frequency and duration of these symptoms varies among individuals. Dopaminergic systems are believed to be involved in migraine pathophysiology. We aimed to look for association of polymorphisms in dopaminergic genes in genetic susceptibility to migraine in Turkey population.

METHODS

The present study was designed to explore possible association of three polymorphisms, (1021C>T (Rs1611115), +1603C>T (Rs6271; C535R) and +444G>A (rs1108580), of Dopamin Beta Hydroxylase gene in migraine patients. 200 migraine patients and 267 healthy controls were included in the study. Genomic DNA was extracted from blood and genotypes were analyzed using polymerase chain reaction-restriction fragment length polymorphism methods (PCR-RFLP).

RESULTS

Statistical evaluation of data results showed a significant association for allelic and genotypic frequency distribution between the Dopamin Beta Hydroxylase gene +1603C>T polymorphism and migraine (p=0.000, OR: 4.36, 95% CI: 2.73-7.16). There was no association observed between the -1021C>T and +444 G>A polymorphisms of the Dopamin Beta Hydroxylase gene and migraine (p=0.8731 and p=0.7584).

CONCLUSIONS

This study reflects that Dopamin Beta Hydroxylase gene +1603C>T polymorphism may be one of the many genetic factors for migraine susceptibility in the Turkish population.

Genetics of aggressive behavior: An overview

The Research Domain Criteria (RDoC) address three types of aggression: frustrative non-reward, defensive aggression and offensive/proactive aggression. This review sought to present the evidence for genetic underpinnings of aggression and to determine to what degree prior studies have examined phenotypes that fit into the RDoC framework. Although the constructs of defensive and offensive aggression have been widely used in the animal genetics literature, the human literature is mostly agnostic with regard to all the RDoC constructs. We know from twin studies that about half the variance in behavior may be explained by genetic risk factors. This is true for both dimensional, trait-like, measures of aggression and categorical definitions of psychopathology. The non-shared environment seems to have a moderate influence with the effects of shared environment being unclear. Human molecular genetic studies of aggression are in an early stage. The most promising candidates are in the dopaminergic and serotonergic systems along with hormonal regulators. Genome-wide association studies have not yet achieved genome-wide significance, but current samples are too small to detect variants having the small effects one would expect for a complex disorder. The strongest molecular evidence for a genetic basis for aggression comes from animal models comparing aggressive and non-aggressive strains or documenting the effects of gene knockouts. Although we have learned much from these prior studies, future studies should improve the measurement of aggression by using a systematic method of measurement such as that proposed by the RDoC initiative.

Does Marriage Moderate Genetic Effects on Delinquency and Violence?

Using data from the National Longitudinal Study of Adolescent to Adult Health (N = 1,254), the authors investigated whether marriage can foster desistance from delinquency and violence by moderating genetic effects. In contrast to existing gene-environment research that typically focuses on one or a few genetic polymorphisms, they extended a recently developed mixed linear model to consider the collective influence of 580 single nucleotide polymorphisms in 64 genes related to aggression and risky behavior. The mixed linear model estimates the proportion of variance in the phenotype that is explained by the single nucleotide polymorphisms. The authors found that the proportion of variance in delinquency/violence explained was smaller among married individuals than unmarried individuals. Because selection, confounding, and heterogeneity may bias the estimate of the Gene × Marriage interaction, they conducted a series of analyses to address these issues. The findings suggest that the Gene × Marriage interaction results were not seriously affected by these issues.

[The 444G/A and -1021 C/T polymorphisms of the dopamine-beta-hydroxylase gene modulate the trajectory of alcohol dependence development]

AIM

To study the influence of 444 G/A (rs 1108580) and -1021 C/T (rs 1611115) polymorphisms of the dopamine beta-hydroxylase (DBH) gene on clinical parameters of the trajectory of alcohol dependence.

MATERIAL AND METHODS

Authors studied 548 male inpatients, of Slavic ethnicity, with ICD-10 diagnosis of «alcohol dependence» (F-10.2).

RESULTS

The effects of DBH * 444 G/A on the rate of formation of alcohol withdrawal syndrome (AWS), and DBH *-1021C/T on the age of onset of alcohol abuse with significant role of the age of first alcohol use were identified. In 444 G/A GG carriers, the development of AWS was accelerated since the beginning of alcohol abuse compared with AA carriers (p=0.026), AG carriers occupied an intermediate position. In 22.5% of GG carriers, AWS developed within 2 years (AA: 8.11%, p=0.005; AG: 17.67%, p=0.04). According to the results of linear regression analysis, in AG carriers the alcohol abuse (p=0.037) and the AWS (p=0.049) developed earlier than in AA carriers if the first alcohol use occured at the age of about 15 years. Among -1021C/T genotype carriers who began to abuse alcohol at an early age (before 20 years), there were 23.45% patients with CC genotype and only 11.97% with a T allele (genotypes CT+TT) (p=0.03), but T carriers began to abuse alcohol earlier than others (p=0.05) if the first alcohol use occurred at the age of about 16 years.

CONCLUSION

The results can be used to search for genetic markers for prognosis of alcohol dependence development.

ABO Blood Type and Personality Traits in Healthy Japanese Subjects

There is no scientific consensus that a relationship exists between the ABO blood group and personality traits. However, a recent study hypothesized that the dopamine beta-hydroxylase (DBH) gene is in linkage with the ABO gene. The sample population consisted of 1,427 healthy Japanese subjects who completed the Temperament and Character Inventory (TCI). Each subject's ABO blood type was determined by genotyping the rs8176719 and rs8176746 ABO gene single-nucleotide polymorphisms (SNPs) using a TaqMan genotyping assay. The relationships between the six ABO genotypes or four ABO phenotypes and personality traits were examined using a multivariate analysis of covariance (MANCOVA), controlling for age and sex. The MANCOVA data showed a significant difference in TCI scores among the ABO genotype groups (F [7, 1393] = 3.354, p = 0.001). A subsequent univariate analysis showed a significant difference in the mean scores for Persistence among the genotype groups (F = 2.680, partial η2 = 0.010, p = 0.020). Similarly, dividing the ABO blood type into four phenotypes revealed a significant difference among the phenotype groups (F [7, 1397] = 2.529, p = 0.014). A subsequent univariate analysis showed a significant difference among the phenotype groups in the mean scores for Persistence (F = 2.952, partial η2= 0.006, p = 0.032). We observed a significant association between ABO blood group genotypes and personality traits in a large number of healthy Japanese subjects. However, these results should be regarded as preliminary and should be interpreted with caution because it is possible that the association between ABO blood group genotype and the Persistence trait is relatively weak.

Polymorphisms in genes implicated in dopamine, serotonin and noradrenalin metabolism suggest association with cerebrospinal fluid monoamine metabolite concentrations in psychosis

BACKGROUND

Homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) are the major monoamine metabolites in the central nervous system (CNS). Their cerebrospinal fluid (CSF) concentrations, reflecting the monoamine turnover rates in CNS, are partially under genetic influence and have been associated with schizophrenia. We have hypothesized that CSF monoamine metabolite concentrations represent intermediate steps between single nucleotide polymorphisms (SNPs) in genes implicated in monoaminergic pathways and psychosis.

METHODS

We have searched for association between 119 SNPs in genes implicated in monoaminergic pathways [tryptophan hydroxylase 1 (TPH1), TPH2, tyrosine hydroxylase (TH), DOPA decarboxylase (DDC), dopamine beta-hydroxylase (DBH), catechol-O-methyltransferase (COMT), monoamine oxidase A (MAOA) and MAOB] and monoamine metabolite concentrations in CSF in 74 patients with psychotic disorder.

RESULTS

There were 42 nominally significant associations between SNPs and CSF monoamine metabolite concentrations, which exceeded the expected number (20) of nominal associations given the total number of tests performed. The strongest association (p = 0.0004) was found between MAOB rs5905512, a SNP previously reported to be associated with schizophrenia in men, and MHPG concentrations in men with psychotic disorder. Further analyses in 111 healthy individuals revealed that 41 of the 42 nominal associations were restricted to patients with psychosis and were absent in healthy controls.

CONCLUSIONS

The present study suggests that altered monoamine turnover rates in CNS reflect intermediate steps in the associations between SNPs and psychosis.

Serum brain-derived neurotrophic factor levels and cocaine-induced transient psychotic symptoms

BACKGROUND

Cocaine-induced psychosis (CIP) is among the most serious adverse effects of cocaine. Reduced serum brain-derived neurotrophic factor (BDNF) levels have been reported in schizophrenia and psychosis; however, studies assessing the involvement of BDNF in CIP are lacking.

METHODS

A total of 22 cocaine-dependent patients (aged 33.65 ± 6.85) who had never experienced psychotic symptoms under the influence of cocaine (non-CIP) and 18 patients (aged 34.18 ± 8.54) with a history of CIP completed a 2-week detoxification program in an inpatient facility. Two serum samples were collected from each patient at baseline and at the end of the protocol. Demographic, consumption and clinical data were recorded for all patients. A paired group of healthy controls was also included.

RESULTS

At the beginning of the detoxification treatment, serum BDNF levels were similar in both the non-CIP and the CIP groups. During early abstinence, the non-CIP group exhibited a significant increase in serum BDNF levels (p = 0.030), whereas the CIP group exhibited a decrease. Improvements in depression (Beck Depression Inventory, BDI, p = 0.003) and withdrawal symptoms (Cocaine Selective Severity Assessment, CSSA, p = 0.013) show a significant positive correlation with serum BDNF levels in the non-CIP group, whereas no correlation between the same variables was found in the CIP group.

CONCLUSIONS

This study suggests that BDNF plays a role in the transient psychotic symptoms associated with cocaine consumption. In the non-CIP group, the increase in serum BDNF appears to be driven by the effects of chronic cocaine consumption and withdrawal. In contrast, patients with CIP share some of the neurotrophic deficiencies that characterize schizophrenia and psychosis.

Clinical features of methamphetamine-induced paranoia and preliminary genetic association with DBH-1021C→T in a Thai treatment cohort

AIMS

To explore the clinical features of methamphetamine-induced paranoia (MIP) and associations between MIP and a genetic polymorphism in dopamine β-hydroxylase (DBH-1021C→T).

DESIGN

Retrospective analysis of clinical presentation and genetic association by χ(2) test and logistic regression analysis.

SETTING

A Thai substance abuse treatment center.

PARTICIPANTS

A total of 727 methamphetamine-dependent (MD) individuals.

MEASUREMENTS

Clinical: Semi-Structured Assessment for Drug Dependence and Alcoholism (SSADDA) and the Methamphetamine Experience Questionnaire (MEQ). Genetic: DBH-1021C→T.

FINDINGS

Forty per cent of individuals (289 of 727; 39.8%) with MD had MIP. Within-binge latency to MIP onset occurred more rapidly in the most recent compared with initial MIP episode (P = 0.02), despite unchanging intake (P = 0.89). Individuals with MIP were significantly less likely to carry lower (TT/CT) compared with higher (CC) activity genotypes (34.3 versus 43.3%; χ(2) 1  = 5, P = 0.03). DBH effects were confirmed [odds ratio (OR) = 0.7, P = 0.04] after controlling for associated clinical variables (MD severity, OR = 3.4, P < 0.001; antisocial personality disorder, OR = 2.2, P < 0.001; alcohol dependence, OR = 1.4, P = 0.05; and nicotine dependence, OR = 1.4, P = 0.06). TT/CT carriers were more likely to initiate cigarette smoking (OR = 3.9, P = 0.003) and probably less likely to be dependent on alcohol (OR = 0.6, P = 0.05).

CONCLUSIONS

Among methamphetamine-dependent individuals, paranoia appears to occur increasingly rapidly in the course of a session of methamphetamine use. Severity of methamphetamine dependence and antisocial personality disorder predicts methamphetamine-induced paranoia. The genetic polymorphism in dopamine β-hydroxylase is associated with methamphetamine-induced paranoia and influences smoking initiation.

Pharmacogenetics of naltrexone and disulfiram in alcohol dependent, dually diagnosed veterans

BACKGROUND

Disulfiram and naltrexone were evaluated in treatment of individuals with co-occurring alcohol dependence and other Axis I disorders (e.g., Major Depression). We explored pharmacogenetic interactions in genotyped subjects.

METHODS

Alcohol dependent (AD) subjects received naltrexone alone, placebo alone, disulfiram with placebo or disulfiram with naltrexone. They were genotyped for OPRM1 rs1799971 (Asn40Asp), and DBH rs1611115 (C-1021T). N = 107 male European-American subjects were included.

RESULTS

There were no significant interactions with OPRM1. DBH interacted with naltrexone on the primary outcome of abstinence from heavy drinking (χ(2) (1) = 5.23, p = .02). "T" allele carriers on naltrexone had more abstinence compared to "CC" subjects on naltrexone (FET, p = .01). "T" allele carriers on naltrexone had the highest overall rates of abstinence from heavy drinking (>90%). Also, DBH genotype interacted with disulfram (F(1,17) = 7.52, p = .01) on drinks per drinking day with less drinking for subjects with the "CC" genotype than for T allele carriers on disulfiram.

CONCLUSIONS

DBH*rs1611115*T associated with better response to naltrexone, while for those on disulfiram that drank, "CC" subjects drank less than T carriers. For rs1799971*G, we did not replicate findings from previous studies showing a more favorable response to NTX, possibly due to the small available sample.

SCIENTIFIC SIGNIFICANCE

Genotyping rs1611115 may be useful in understanding inter-individual differences in AD treatment response.

FUTURE DIRECTIONS

Further study of rs1611115 pharmacogenetics is warranted.

Low dopamine function in attention deficit/hyperactivity disorder: should genotyping signify early diagnosis in children?

Attention deficit/hyperactivity disorder (ADHD) is present in 8% to 12% of children, and 4% of adults worldwide. Children with ADHD can have learning impairments, poor selfesteem, social dysfunction, and an increased risk of substance abuse, including cigarette smoking. Overall, the rate of treatment with medication for patients with ADHD has been increasing since 2008, with ≥ 2 million children now being treated with stimulants. The rise of adolescent prescription ADHD medication abuse has occurred along with a concomitant increase of stimulant medication availability. Of adults presenting with a substance use disorder (SUD), 20% to 30% have concurrent ADHD, and 20% to 40% of adults with ADHD have a history of SUD. Following a brief review of the etiology of ADHD, its diagnosis and treatment, we focus on the benefits of early and appropriate testing for a predisposition to ADHD. We suggest that by genotyping patients for a number of known, associated dopaminergic polymorphisms, especially at an early age, misdiagnoses and/or over-diagnosis can be reduced. Ethical and legal issues of early genotyping are considered. As many as 30% of individuals with ADHD are estimated to either have secondary side-effects or are not responsive to stimulant medication. We also consider the benefits of non-stimulant medication and alternative treatment modalities, which include diet, herbal medications, iron supplementation, and neurofeedback. With the goals of improving treatment of patients with ADHD and SUD prevention, we encourage further work in both genetic diagnosis and novel treatment approaches.

Association of functional DBH genetic variants with alcohol dependence risk and related depression and suicide attempt phenotypes: results from a large multicenter association study

OBJECTIVE

Dopamine-beta-hydroxylase (DBH) metabolizes the conversion of dopamine to noradrenaline. DBH, located on chromosome 9q34.2 has variants with potential functional consequences which may be related to alterations of neurotransmitter function and several psychiatric phenotypes, including alcohol dependence (AD), depression (MD) and suicidal behavior (SA). The aim of this association study in a large multicenter sample of alcohol-dependent individuals and controls is to investigate the role of DBH SNPs and haplotypes in AD risk and associated phenotypes (AD with MD or SA).

METHOD

1606 inpatient subjects with DSM-IV AD from four addiction treatment centers and 1866 control subjects were included. Characteristics of AD, MD and SA were obtained using standardized structured interviews. After subjects were genotyped for 4 DBH polymorphisms, single SNP case-control and haplotype analyses were conducted.

RESULTS

rs1611115 (near 5') C-allele and related haplotypes were significantly associated with alcohol dependence in females. This association with female alcohol dependence also accounts for the significant relationship between this variant and comorbid conditions and traits.

CONCLUSIONS

This study presents evidence for a potentially functional DBH variant influencing the risk for alcohol dependence while other comorbid conditions are not independently influenced by this SNP. However, the study also supports the possible role of the dopamine system in the etiology of female alcohol dependence.

Association between dopamine Beta-hydroxylase gene polymorphisms and attention-deficit hyperactivity disorder in korean children

Attention-deficit hyperactivity disorder (ADHD) is a common disorder of the school-age population. ADHD is familial, and genetic studies estimate heritability at 80%-90%. The aim of the present study was to investigate the association between the genetic type and alleles for the dopamine beta-hydroxylase (DBH) gene in Korean children with ADHD. The sample consisted of 142 ADHD children and 139 control children. We diagnosed ADHD according to DSM-IV. ADHD symptoms were evaluated with the Conners' Parent Rating Scales and Dupaul Parent ADHD Rating Scales. Blood samples were taken from the 281 subjects; DNA was extracted from blood lymphocytes, and polymerase chain reaction was performed for the DBH polymorphism. The alleles and genotype frequencies were compared using the chi-square test. We compared the allele and genotype frequencies of the DBH gene polymorphism in the ADHD and control groups. This study showed that there was a significant correlation among the frequencies of rs1611115 (odds ratio=0.64, 95% confidence interval=0.42-0.97, p=0.034) of the alleles of DBH, but the final conclusions are not definite. Follow-up studies with larger patient or pure subgroups are expected. These results suggested that DBH might be related to ADHD symptoms.

Positive association between--1021TT genotype of dopamine beta hydroxylase gene and progressive behavior of injection heroin users

By balancing the ratios of dopamine and norepinephrine, dopamine beta hydroxylase (DBH) plays an important role in brain reward circuit that is involved with behavioral effects of heroin addiction. DBH -1021C/T (rs1611115) is a functional variant with strong correlation with plasma DBH activity and several nerval and psychic disorders. In the present study, we have collected 333 male cases with heroin addiction and 200 male healthy controls to explore the role of -1021C/T in heroin addiction. There is no evidence of association between -1021C/T and heroin addiction on both genotype and allele levels (P>0.05). In the injection subgroup of cases, -1021TT carriers have longer heroin addiction time (P<0.001) and higher dosage of self-administered heroin (P=0.045) than carriers with -1021CC or -1021CT, suggesting that patients with TT genotype are likely to have more progressive style of heroin users with injection route. In conclusion, our results support -1021TT genotype may be implicated with a more progressive nature of heroin addiction, although DBH -1021C/T is unlikely to be involved in the risk of heroin addiction.

Noradrenergic versus dopaminergic modulation of impulsivity, attention and monitoring behaviour in rats performing the stop-signal task: possible relevance to ADHD

RATIONALE

Deficient response inhibition is a prominent feature of many pathological conditions characterised by impulsive and compulsive behaviour. Clinically effective doses of catecholamine reuptake inhibitors are able to improve such inhibitory deficits as measured by the stop-signal task (SST) in humans and other animals. However, the precise therapeutic mode of action of these compounds in terms of their relative effects on dopamine (DA) and noradrenaline (NA) systems in prefrontal cortical and striatal regions mediating attention and cognitive control remains unclear.

OBJECTIVES

We sought to fractionate the effects of global catecholaminergic manipulations on SST performance by using receptor-specific compounds for NA or DA. The results are described in terms of the effects of modulating specific receptor subtypes on various behavioural measures such as response inhibition, perseveration, sustained attention, error monitoring and motivation.

RESULTS

Blockade of α2-adrenoceptors improved sustained attention and response inhibition, whereas α1 and β1/2 adrenergic receptor antagonists disrupted go performance and sustained attention, respectively. No relevant effects were obtained after targeting DA D1, D2 or D4 receptors, while both a D3 receptor agonist and antagonist improved post-error slowing and compulsive nose-poke behaviour, though generally impairing other task measures.

CONCLUSIONS

Our results suggest that the use of specific pharmacological agents targeting α2 and β noradrenergic receptors may improve existing treatments for attentional deficits and impulsivity, whereas DA D3 receptors may modulate error monitoring and perseverative behaviour.

Toward a definition of affective instability

Affective instability is a psychophysiological symptom observed in some psychopathologies. It is a complex construct that encompasses (1) primary emotions, or affects, and secondary emotions, with each category having its own characteristics, amplitude, and duration, (2) rapid shifting from neutral or valenced affect to intense affect, and (3) dysfunctional modulation of emotions. Affective instability is often confused with mood lability, as in bipolar disorders, as well as with other terms. To clarify the concept, we searched databases for the term affective instability and read related articles on the topic. In this article we situate the term within the current affective nomenclature and human emotional experience, explore its psychophysiological features, and place it within the context of psychopathology. We explain why the term can potentially be confused with mood pathology and then define affective instability as an inherited temperamental trait modulated by developmental experience.

Limbic system pathologies associated with deficiencies and excesses of the trace elements iron, zinc, copper, and selenium

Deficiencies of nutrients such as amino acids, vitamins, lipids, and trace elements during gestation and early infanthood have strong deleterious effects on the development of the limbic system; these effects may be irreversible, even when adequate supplementation is provided at later developmental stages. Recent advances in the neurochemistry of biometals are increasingly establishing the roles of the trace elements iron, copper, zinc, and selenium in a variety of cell functions and are providing insight into the repercussions of deficiencies and excesses of these elements on the development of the central nervous system, especially the limbic system. The limbic system comprises diverse areas with high metabolic demands and differential storage of iron, copper, zinc, and selenium. This review summarizes available evidence suggesting the involvement of these trace elements in pathological disorders of the limbic system.

The genetics of attention deficit/hyperactivity disorder in adults, a review

The adult form of attention deficit/hyperactivity disorder (aADHD) has a prevalence of up to 5% and is the most severe long-term outcome of this common neurodevelopmental disorder. Family studies in clinical samples suggest an increased familial liability for aADHD compared with childhood ADHD (cADHD), whereas twin studies based on self-rated symptoms in adult population samples show moderate heritability estimates of 30-40%. However, using multiple sources of information, the heritability of clinically diagnosed aADHD and cADHD is very similar. Results of candidate gene as well as genome-wide molecular genetic studies in aADHD samples implicate some of the same genes involved in ADHD in children, although in some cases different alleles and different genes may be responsible for adult versus childhood ADHD. Linkage studies have been successful in identifying loci for aADHD and led to the identification of LPHN3 and CDH13 as novel genes associated with ADHD across the lifespan. In addition, studies of rare genetic variants have identified probable causative mutations for aADHD. Use of endophenotypes based on neuropsychology and neuroimaging, as well as next-generation genome analysis and improved statistical and bioinformatic analysis methods hold the promise of identifying additional genetic variants involved in disease etiology. Large, international collaborations have paved the way for well-powered studies. Progress in identifying aADHD risk genes may provide us with tools for the prediction of disease progression in the clinic and better treatment, and ultimately may help to prevent persistence of ADHD into adulthood.