Investigating the role of the brain-derived neurotrophic factor (BDNF) val66met variant in obsessive-compulsive disorder (OCD)

Neurocognitive performance in the context of acute symptom reduction in OCD: Treatment effects and the impact of BDNF

BACKGROUND

Obsessive-compulsive disorder (OCD) has been associated with neurocognitive impairments. The present study examined the effect of treatment on neurocognitive performance in OCD and the relationship between neurocognitive change and symptom change. The present study also examined polymorphisms influencing brain derived neurotrophic factor (BDNF) as predictors of neurocognitive change.

METHOD

Treatment-seeking participants with OCD (N = 125) were assigned to cognitive behavioural therapy (CBT) alone, CBT combined with regular physical exercise, exercise alone, or a waitlist control group. Measures of OCD symptom severity and a neuropsychological battery were completed pre- and post-treatment. Blood or saliva samples were used to genotype the BDNF Val66Met polymorphism.

RESULTS

OCD symptom severity was not cross-sectionally associated with neurocognitive performance. Several neurocognitive measures improved over treatment. The BDNF Val66Met polymorphism was significantly associated with worse performance on the Stroop test but did not significantly predict change in neurocognitive performance over time.

LIMITATIONS

Limitations include lack of a healthy control group.

CONCLUSION

Improvement in neurocognitive performance corresponded to symptomatic improvement and was independent of the BDNF Val66Met genotype.

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.

Disclosing common biological signatures and predicting new therapeutic targets in schizophrenia and obsessive-compulsive disorder by integrated bioinformatics analysis

Schizophrenia (SCZ) is a severe mental illness mainly characterized by a number of psychiatric symptoms. Obsessive-compulsive disorder (OCD) is a long-lasting and devastating mental disorder. SCZ has high co-occurrence with OCD resulting in the emergence of a concept entitled "schizo-obsessive disorder" as a new specific clinical entity with more severe psychiatric symptoms. Many studies have been done on SCZ and OCD, but the common pathogenesis between them is not clear yet. Therefore, this study aimed to identify shared genetic basis, potential biomarkers and therapeutic targets between these two disorders. Gene sets were extracted from the Geneweaver and Harmonizome databases for each disorder. Interestingly, the combination of both sets revealed 89 common genes between SCZ and OCD, the most important of which were BDNF, SLC6A4, GAD1, HTR2A, GRIN2B, DRD2, SLC6A3, COMT, TH and DLG4. Then, we conducted a comprehensive bioinformatics analysis of the common genes. Receptor activity as the molecular functions, neuron projection and synapse as the cellular components as well as serotonergic synapse, dopaminergic synapse and alcoholism as the pathways were the most significant commonalities in enrichment analyses. In addition, transcription factor (TFs) analysis predicted significant TFs such as HMGA1, MAPK14, HINFP and TEAD2. Hsa-miR-3121-3p and hsa-miR-495-3p were the most important microRNAs (miRNAs) associated with both disorders. Finally, our study predicted 19 existing drugs (importantly, Haloperidol, Fluoxetine and Melatonin) that may have a potential influence on this co-occurrence. To summarize, this study may help us to better understand and handle the co-occurrence of SCZ and OCD by identifying potential biomarkers and therapeutic targets.

Anxiety Disorders and Prediction of Their Development in Patients with Hypothyroidism and Autoimmune Thyroiditis

Objective: Since the association between thyroid dysfunction and neuropsychiatric disorders has been known for many years, it is important to analyze the associations of the BDNF gene polymorphism (rs6265), the VDR gene polymorphism (rs2228570), and the NMDA gene polymorphism (rs4880213) with the anxiety in patients with autoimmune thyroiditis and hypothyroidism in the Western Ukrainian population and predict the development of anxiety disorders in these patients. Methods: The study involved a total of 153 patients with various forms of thyroid pathology. BDNF levels in the sera of the patients and healthy individuals were quantified using an enzyme-linked immunosorbent assay with a highly sensitive Human BDNF ELISA Kit (Elabscience®, United States, Catalog No: E-EL-H0010) on E.I.A. Reader Sirio S (Seac, Italy). Genotyping of the VDR (rs2228570), BDNF (rs6265), and NMDA (rs4880213) gene polymorphism using TaqMan probes and TaqMan Genotyping Master Mix (4371355) on CFX96™Real-Time PCR Detection System (Bio-Rad Laboratories, Inc., USA). Polymerase chain reaction (PCR) for TaqMan genotyping was carried out according to the kit instructions (Applied Biosystems, USA). Results: According to the data obtained when comparing the presence of anxiety on the Hamilton scale on SNP statistically significant differences were revealed depending on BDNF gene polymorphism (rs6265) (p < 0.001). When comparing the presence of anxiety on the Hamilton scale on SNP depending on VDR gene polymorphism (rs2228570), NMDA gene polymorphism (rs4880213) no statistically significant differences were revealed (p = 0.782, p = 0.677 respectively) We identified an inverse strong correlation between the presence of anxiety on Hamilton scale and BDNF, 25-OH Vitamin D levels, and fT4 in the blood (p <0.001) and a direct moderate correlation between the presence of anxiety on Hamilton scale and TSH, GRIN2B, and anti-TPO (p <0.001). Conclusion: Indicators such as BDNF, GRIN2B, fT4, anti-TG, and 25-OH levels of vitamin D are prognostically significant risk criteria for anxiety.

Brain-derived neurotrophic factor as a biomarker for obsessive-compulsive disorder: A meta-analysis

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a growth factor that plays many critical functions in the central nervous system (CNS) and may be involved in the development of a range of psychopathologies, including depression, dementia, and neurodegenerative disorders.

METHODS

In the present study, we performed the first systematic review with a meta-analysis to quantitatively compare the peripheral blood BDNF levels between patients with obsessive-compulsive disorder (OCD) and healthy controls (HCs). A systematic search was conducted using PubMed and Web of Science databases to identify the relevant articles.

RESULTS

Nine studies encompassing 474 adults with OCD and 436 HCs were included in this meta-analysis. A random-effects meta-analysis showed that patients with OCD had significantly decreased peripheral blood levels of Brain-derived neurotrophic factor (BDNF) when compared with the HCs (Hedges' g = -0.722, 95% confidence interval [CI] = -1.152 to -0.292, P = 0.001). Subgroup analyses revealed decreased BDNF levels in plasma of patients (Hedges' g = -1.137, 95% CI = -1.463 to -0.810, P = 0.000) and drug-free patients (Hedges' g = -1.269, 95% CI = -1.974 to -0.564, P = 0.000) as compared to patients on active drug therapy and HCs. Meta-regression analyses showed that age, sex, sample size, Y-BOS total score, and publication year had no moderating effects on the outcome.

CONCLUSION

Although the relationship between our findings and the pathophysiology of OCD and the role BDNF plays in the development of the disease remains to be determined, the outcomes suggest that BDNF may serve as a potential biomarker of OCD.

Genetic and epigenetic architecture of Obsessive-Compulsive Disorder: In search of possible diagnostic and prognostic biomarkers

Obsessive-Compulsive Disorder (OCD) is a prevalent and severe clinical condition whose hallmarks are excessive, unwanted thoughts (obsessions) and repetitive behaviors (compulsions). The onset of symptoms generally occurs during pre-adult life and typically affects subjects in different aspects of their life's, compromising social and professional relationships. Although robust evidence suggests a genetic component in the etiopathogenesis of OCD, the causes of the disorder are still not completely understood. It is thus of relevance to take into account how genes interact with environmental risk factors, thought to be mediated by epigenetic mechanisms. We here provide an overview of genetic and epigenetic mechanisms of OCD, focusing on the modulation of key central nervous system genes, in the attempt to suggest possible disease biomarkers.

Dietary tryptophan depletion alters the faecal bacterial community structure of compulsive drinker rats in schedule-induced polydipsia

RATIONALE

Compulsive behaviour, present in different psychiatric disorders such as obsessive-compulsive disorder, schizophrenia and drug abuse, is associated with altered levels of serotonin (5-hydroxytryptamine, 5-HT). The gut microbiota regulates tryptophan (TRP) metabolism and may affect global 5-H synthesis in the enteric and central nervous systems, suggesting a possible involvement of gut microbiota in compulsive spectrum disorders.

OBJECTIVES

The present study investigated whether chronic TRP depletion by diet alters the faecal bacterial community profiles of compulsive versus non-compulsive rats in schedule-induced polydipsia (SIP). Peripheral plasma 5-HT and brain-derived neurotrophic factor (BDNF) levels were evaluated.

METHODS

Wistar rats were selected as High Drinkers (HD) or Low Drinkers (LD) according to their SIP behaviour and were fed for 14 days with either a TRP-free diet (T-) or a TRP-supplemented diet (T+). The faecal bacterial community structure was investigated with 16S rRNA gene-targeted denaturing gradient gel electrophoresis (DGGE) fingerprinting analysis.

RESULTS

Compulsive HD rats showed a lower bacterial diversity than LD rats, irrespectively of the diet. The TRP-depleted HD rats, the only group increasing compulsive licking in SIP, showed a reduction of bacterial evenness and a highly functionally organized community compared with the other groups, indicating that this bacterial community is more fragile to external changes due to the dominance of a low number of species. The chronic TRP depletion by diet effectively reduced peripheral plasma 5-HT levels in both HD and LD rats, while plasma BDNF levels were not altered.

CONCLUSIONS

These results highlight the possible implication of reduced microbial diversity in compulsive behaviour and the involvement of the serotonergic system in modulating the gut brain-axis in compulsive spectrum disorders.

The Brain-Derived Neurotrophic Factor Val66Met Polymorphism Is Associated With Female Obsessive-Compulsive Disorder: An Updated Meta-Analysis of 2765 Obsessive-Compulsive Disorder Cases and 5558 Controls

Objective: Accumulated evidence has implicated that brain-derived neurotrophic factor (BDNF) gene polymorphisms play a role in the etiology of obsessive-compulsive disorder (OCD). A single nucleotide polymorphism in the coding exon of the BDNF gene at position 66, Val66Met (rs6265), is found to be associated with OCD in different populations, but results linking Val66Met with OCD have been inconsistent and inconclusive. In our study we performed a meta-analysis to further examine whether rs6265 genetic variants are involved in the etiology of OCD. Methods: By searching databases, relevant case-control studies were retrieved; using established inclusion criteria, we selected eligible studies for analysis. Results: Thirteen studies were identified that examined the association between the rs6265 polymorphism and OCD. After statistical analyses, no significant association was found between the rs6265 polymorphism and OCD (OR = 1.07, 95% CI = 1.00-1.15, P = 0.06 for genotype; OR = 1.06, 95% CI = 0.98-1.15, P = 0.15 for allele). However, in gender-specific analysis, female Val carriers might be a risk factor for OCD (OR = 1.36, 95% CI = 1.03-1.80, P = 0.03 for genotype; OR = 1.15, 95% CI = 1.01-1.32, P = 0.04 for allele). Conclusion: Our updated meta-analysis suggests that female carriers of the Val66Met BDNF polymorphism might be more suspectable to develop OCD.

Animal Models for OCD Research

OCD has lagged behind other psychiatric illnesses in the identification of molecular treatment targets, due in part to a lack of significant findings in genome-wide association studies. However, while progress in this area is being made, OCD's symptoms of obsessions, compulsions, and anxiety can be deconstructed into distinct neural functions that can be dissected in animal models. Studies in rodents and non-human primates have highlighted the importance of cortico-basal ganglia-thalamic circuits in OCD pathophysiology, and emerging studies in human post-mortem brain tissue point to glutamatergic synapse abnormalities as a potential cellular substrate for observed dysfunctional behaviors. In addition, accumulated evidence points to a potential role for neuromodulators including serotonin and dopamine in both OCD pathology and treatment. Here, we review current efforts to use animal models for the identification of molecules, cell types, and circuits relevant to OCD pathophysiology. We start by describing features of OCD that can be modeled in animals, including circuit abnormalities and genetic findings. We then review different strategies that have been used to study OCD using animal model systems, including transgenic models, circuit manipulations, and dissection of OCD-relevant neural constructs. Finally, we discuss how these findings may ultimately help to develop new treatment strategies for OCD and other related disorders.

The Psychopharmacology of Obsessive-Compulsive Disorder: A Preclinical Roadmap

This review evaluates current knowledge about obsessive-compulsive disorder (OCD), with the goal of providing a roadmap for future directions in research on the psychopharmacology of the disorder. It first addresses issues in the description and diagnosis of OCD, including the structure, measurement, and appropriate description of the disorder and issues of differential diagnosis. Current pharmacotherapies for OCD are then reviewed, including monotherapy with serotonin reuptake inhibitors and augmentation with antipsychotic medication and with psychologic treatment. Neuromodulatory therapies for OCD are also described, including psychosurgery, deep brain stimulation, and noninvasive brain stimulation. Psychotherapies for OCD are then reviewed, focusing on behavior therapy, including exposure and response prevention and cognitive therapy, and the efficacy of these interventions is discussed, touching on issues such as the timing of sessions, the adjunctive role of pharmacotherapy, and the underlying mechanisms. Next, current research on the neurobiology of OCD is examined, including work probing the role of various neurotransmitters and other endogenous processes and etiology as clues to the neurobiological fault that may underlie OCD. A new perspective on preclinical research is advanced, using the Research Domain Criteria to propose an adaptationist viewpoint that regards OCD as the dysfunction of a normal motivational system. A systems-design approach introduces the security motivation system (SMS) theory of OCD as a framework for research. Finally, a new perspective on psychopharmacological research for OCD is advanced, exploring three approaches: boosting infrastructure facilities of the brain, facilitating psychotherapeutic relearning, and targeting specific pathways of the SMS network to fix deficient SMS shut-down processes. SIGNIFICANCE STATEMENT: A significant proportion of patients with obsessive-compulsive disorder (OCD) do not achieve remission with current treatments, indicating the need for innovations in psychopharmacology for the disorder. OCD may be conceptualized as the dysfunction of a normal, special motivation system that evolved to manage the prospect of potential danger. This perspective, together with a wide-ranging review of the literature, suggests novel directions for psychopharmacological research, including boosting support systems of the brain, facilitating relearning that occurs in psychotherapy, and targeting specific pathways in the brain that provide deficient stopping processes in OCD.

Neurotrophin mediated HPA axis dysregulation in stress induced genesis of psychiatric disorders: Orchestration by epigenetic modifications

Apart from their established role in embryonic development, neurotrophins (NTs) have diverse functions in the nervous system. Their role in the integration of physiological and biochemical aspects of the nervous system is currently attracting much attention. Based on a systematic analysis of the literature, we here propose a new paradigm that, by exploiting a novel role of NTs, may help explain the genesis of stress-related psychiatric disorders, opening new avenues for better management of the same. We hypothesize that NTs as an integrated network play a crucial role in maintaining an indivdual's psychological wellbeing. Given the evidence that stress can induce chronic disruption of the hypothalamic-pituitary-adrenal (HPA) axis which, in turn, is causally linked to several psychiatric disorders, this function may be mediated through the homeostatic mechanisms governing regulation of this axis. In fact, NTs, such as nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) are known to participate in neuroendocrine regulation. Recent studies suggest epigenetic modification of NT-HPA axis interplay in the precipitation of psychiatric disorders. Our article highlights why this new knowledge regarding NTs should be considered in the etiogenesis and treatment of stress-induced psychopathology.

Obsessive-compulsive disorder and growth factors: A comparative review

The goal of this article is to clarify the role of various growth factors in the establishment and progression of obsessive-compulsive disorder (OCD). OCD is a chronic mental disorder with recurrent intrusive thoughts and/or repetitive compulsive behaviors that increase during stressful periods. Growth and neurotrophic factors may be contributing factors in the pathophysiology of OCD. Many of them are synthesized and released within the central nervous system and act as trophic agents in neurons; some of them are involved in brain growth, development, neurogenesis, myelination and plasticity, while others take part in the protection of the nervous system following brain injuries. This paper attempts to identify all articles investigating the relationship between OCD and neurotrophic and growth factors, in both animal and human studies, with a focus on adult brain studies. Based on the PubMed and Scopus and Science Direct search tools, the available articles and studies are reviewed. Out of 230 records in total, the ones related to our review topic were taken into account to further understand the pathophysiological mechanism(s) of OCD, providing methods to improve its symptoms via the modification of neurotrophins and growth factor imbalances.

OCD-like behavior is caused by dysfunction of thalamo-amygdala circuits and upregulated TrkB/ERK-MAPK signaling as a result of SPRED2 deficiency

Obsessive-compulsive disorder (OCD) is a common neuropsychiatric disease affecting about 2% of the general population. It is characterized by persistent intrusive thoughts and repetitive ritualized behaviors. While gene variations, malfunction of cortico-striato-thalamo-cortical (CSTC) circuits, and dysregulated synaptic transmission have been implicated in the pathogenesis of OCD, the underlying mechanisms remain largely unknown. Here we show that OCD-like behavior in mice is caused by deficiency of SPRED2, a protein expressed in various brain regions and a potent inhibitor of Ras/ERK-MAPK signaling. Excessive self-grooming, reflecting OCD-like behavior in rodents, resulted in facial skin lesions in SPRED2 knockout (KO) mice. This was alleviated by treatment with the selective serotonin reuptake inhibitor fluoxetine. In addition to the previously suggested involvement of cortico-striatal circuits, electrophysiological measurements revealed altered transmission at thalamo-amygdala synapses and morphological differences in lateral amygdala neurons of SPRED2 KO mice. Changes in synaptic function were accompanied by dysregulated expression of various pre- and postsynaptic proteins in the amygdala. This was a result of altered gene transcription and triggered upstream by upregulated tropomyosin receptor kinase B (TrkB)/ERK-MAPK signaling in the amygdala of SPRED2 KO mice. Pathway overactivation was mediated by increased activity of TrkB, Ras, and ERK as a specific result of SPRED2 deficiency and not elicited by elevated brain-derived neurotrophic factor levels. Using the MEK inhibitor selumetinib, we suppressed TrkB/ERK-MAPK pathway activity in vivo and reduced OCD-like grooming in SPRED2 KO mice. Altogether, this study identifies SPRED2 as a promising new regulator, TrkB/ERK-MAPK signaling as a novel mediating mechanism, and thalamo-amygdala synapses as critical circuitry involved in the pathogenesis of OCD.

No gene-by-environment interaction of BDNF Val66Met polymorphism and childhood maltreatment on anxiety sensitivity in a mixed race adolescent sample

Background: Anxiety disorders in youth are attributable to multiple causal mechanisms, comprising biological vulnerabilities, such as genetics and temperament, and unfavourable environmental influences, such as childhood maltreatment (CM). Objective: A gene-environment (G x E) interaction study was conducted to determine the interactive effect of the BDNF Val66Met polymorphism and CM to increase susceptibility to anxiety sensitivity (AS) in a sample of mixed race adolescents. Method: Participants (n = 308, mean age = 15.8 years) who were all secondary school students and who completed measures for AS and CM were genotyped for the BDNF Val66Met polymorphism. Hierarchical multiple regression analysis was conducted to assess G x E influences on AS. Age and gender were included in the models as covariates as age was significantly associated with AS total score (p < .05), and females had significantly higher AS scores than males (p < .05). Results: A main effect of CM on AS was evident (p < .05), however, no main effect of BDNF genotype on AS was observed (p > .05). A non-significant G x E effect on AS was revealed (p < .05). Conclusions: Our results suggest that CM does not have a moderating role in the relationship between the BDNF Val66Met genotype and the increased risk of anxiety-related phenotypes, such as AS. Given the exploratory nature of this study, findings require replication in larger samples and adjustment for population stratification to further explore the role of BDNF Val66Met and CM on AS in mixed race adolescents.

A translational approach to the genetics of anxiety disorders

There have been important advances in our understanding of the genetic architecture of anxiety disorders. At the same time, relatively few genes have reached genome wide significance in anxiety disorders, and there is relatively little work on how exposure to an adverse environment impacts on gene expression in either animal models or human clinical populations. Here we assessed differential expression of genes of the dorsal striatum involved in synaptic transmission in an animal models of early adversity (maternal separation followed by restraint stress), and investigated whether variants in these genes were associated with risk for anxiety disorders, particularly in the presence of environmental stressors. Fifty-two male Sprague Dawley rats underwent maternal separation, and gene expression was studied using array technology. The human homologues of the differentially expressed genes were screened and analysed in a DSM-IV anxiety disorders cohort, and healthy controls (patients, n = 92; controls, n = 194), using blood. Two candidate genes (Mmp9 and Bdnf) were aberrantly expressed in the experimental rodent group relative to controls. Four single nucleotide polymorphisms (SNPs) in the human homologues of these genes were significantly associated with susceptibility for anxiety disorders (MMP9: rs3918242 and BDNF: rs6265, rs10835210 and rs11030107). Three of these (BDNF: rs6265, rs10835210, rs11030107) were found to interact significantly with childhood trauma severity resulting in increased likelihood of an anxiety disorder diagnosis. This study provides insights into the utility of rat models for identifying molecular candidates for anxiety disorders in humans.

BDNF and LTP-/LTD-like plasticity of the primary motor cortex in Gilles de la Tourette syndrome

Gilles de la Tourette syndrome (GTS) is characterized by motor and vocal tics and often associated with obsessive-compulsive disorder (OCD). Responses to intermittent/continuous theta-burst stimulation (iTBS/cTBS), which probe long-term potentiation (LTP)-/depression (LTD)-like plasticity in the primary motor cortex (M1), are reduced in GTS. ITBS-/cTBS-induced M1 plasticity can be affected by brain-derived neurotrophic factor (BDNF) polymorphism. We investigated whether the BDNF polymorphism influences iTBS-/cTBS-induced LTP-/LTD-like M1 plasticity in 50 GTS patients and in 50 age- and sex-matched healthy subjects. In GTS patients, motor and psychiatric (OCD) symptom severity was rated using the Yale Global Tic Severity Scale (YGTSS) and the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS). We compared M1 iTBS-/cTBS-induced plasticity in healthy subjects and in patients with GTS. We also compared responses to TBS according to BDNF polymorphism (Val/Val vs Met carriers) in patients and controls. Fourteen healthy subjects and 13 GTS patients were Met carriers. When considering the whole group of controls, as expected, iTBS increased whereas cTBS decreased MEPs. Differently, iTBS/cTBS failed to induce LTP-/LTD-like plasticity in patients with GTS. When comparing responses to TBS according to BDNF polymorphism, in healthy subjects, Met carriers showed reduced MEP changes compared with Val/Val individuals. Conversely, in patients with GTS, responses to iTBS/cTBS were comparable in Val/Val individuals and Met carriers. YGTSS and Y-BOCS scores were comparable in Met carriers and in Val/Val subjects. We conclude that iTBS and cTBS failed to induce LTP-/LTD-like plasticity in patients with GTS, and this was not affected by BDNF genotype.

Modification of the association between early adversity and obsessive-compulsive disorder by polymorphisms in the MAOA, MAOB and COMT genes

The monoamine oxidases (MAOA/B) and catechol-O-methyltransferase (COMT) enzymes break down regulatory components within serotonin and dopamine pathways, and polymorphisms within these genes are candidates for OCD susceptibility. Childhood trauma has been linked OCD psychopathology, but little attention has been paid to the interactions between genes and environment in OCD aetiology. This pilot study investigated gene-by-environment interactions between childhood trauma and polymorphisms in the MAOA, MAOB and COMT genes in OCD. Ten polymorphisms (MAOA: 3 variants, MAOB: 4 variants, COMT: 3 variants) were genotyped in a cohort of OCD patients and controls. Early-life trauma was assessed using the Childhood Trauma Questionnaire (CTQ). Gene-by-gene (GxG) and gene-by-environment interactions (GxE) of the variants and childhood trauma were assessed using logistic regression models. Significant GxG interactions were found between rs362204 (COMT) and two independent polymorphisms in the MAOB gene (rs1799836 and rs6651806). Haplotype associations for OCD susceptibility were found for MAOB. Investigation of GxE interactions indicated that the sexual abuse sub-category was significantly associated with all three genes in haplotype x environment interaction analyses. Preliminary findings indicate that polymorphisms within the MAOB and COMT genes interact resulting in risk for OCD. Childhood trauma interacts with haplotypes in COMT, MAOA and MAOB, increasing risk for OCD.

The human BDNF gene: peripheral gene expression and protein levels as biomarkers for psychiatric disorders

Brain-derived neurotrophic factor (BDNF) regulates the survival and growth of neurons, and influences synaptic efficiency and plasticity. The human BDNF gene consists of 11 exons, and distinct BDNF transcripts are produced through the use of alternative promoters and splicing events. The majority of the BDNF transcripts can be detected not only in the brain but also in the blood cells, although no study has yet investigated the differential expression of BDNF transcripts at the peripheral level. This review provides a description of the human BDNF gene structure as well as a summary of clinical and preclinical evidence supporting the role of BDNF in the pathogenesis of psychiatric disorders. We will discuss several mechanisms as possibly underlying BDNF modulation, including epigenetic mechanisms. We will also discuss the potential use of peripheral BDNF as a biomarker for psychiatric disorders, focusing on the factors that can influence BDNF gene expression and protein levels. Within this context, we have also characterized, for we believe the first time, the expression of BDNF transcripts in the blood, with the aim to provide novel insights into the molecular mechanisms and signaling that may regulate peripheral BDNF gene expression levels.

Influence of interactions between genes and childhood trauma on refractoriness in psychiatric disorders

Psychiatric disorders are excellent disease models in which gene-environmental interaction play a significant role in the pathogenesis. Childhood trauma has been known as a significant environmental factor in the progress of, and prognosis for psychiatric illness. Patients with refractory illness usually have more severe symptoms, greater disability, lower quality of life and are at greater risk of suicide than other psychiatric patients. Our literature review uncovered some important clinical factors which modulate response to treatment in psychiatric patients who have experienced childhood trauma. Childhood trauma seems to be a critical determinant of treatment refractoriness in psychotic disorder, bipolar disorder, major depressive disorder, and post-traumatic stress disorder. In patients with psychotic disorders, the relationship between childhood trauma and treatment-refractoriness appears to be mediated by cognitive impairment. In the case of bipolar disorder, the relationship appears to be mediated by greater affective disturbance and earlier onset, while in major depressive disorder the mediating factors are persistent, severe symptoms and frequent recurrence. In suicidal individuals, childhood maltreatment was associated with violent suicidal attempts. In the case of PTSD patients, it appears that childhood trauma makes the brain more vulnerable to subsequent trauma, thus resulting in more severe, refractory symptoms. Given that several studies have suggested that there are distinct subtypes of genetic vulnerability to childhood trauma, it is important to understand how gene-environment interactions influence the course of psychiatric illnesses in order to improve therapeutic strategies.

DNA Methylation at the Neonatal State and at the Time of Diagnosis: Preliminary Support for an Association with the Estrogen Receptor 1, Gamma-Aminobutyric Acid B Receptor 1, and Myelin Oligodendrocyte Glycoprotein in Female Adolescent Patients with OCD

Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder. Non-genetic factors and their interaction with genes have attracted increasing attention. Epigenetics is regarded an important interface between environmental signals and activation/repression of genomic responses. Epigenetic mechanisms have not previously been examined in OCD in children and adolescents. The aim of the present study was to examine the DNA methylation profile of selected genes in blood spots from neonates later diagnosed with OCD and in the same children/adolescents at the time of diagnosis compared with age- and sex-matched controls. Furthermore, we wanted to characterize the association of the differential methylation profiles with the severity of OCD and treatment outcome. Dried and new blood spot samples were obtained from 21 female children/adolescents with verified OCD and 12 female controls. The differential methylation was analyzed using a linear model and the correlation with the severity of OCD and treatment outcome was analyzed using the Pearson correlation. We evaluated selected Illumina Infinium HumanMethylation450 BeadChip probes within and up to 100,000 bp up- and downstream of 14 genes previously associated with OCD (SLC1A1, SLC25A12, GABBR1, GAD1, DLGAP1, MOG, BDNF, OLIG2, NTRK2 and 3, ESR1, SL6A4, TPH2, and COMT). The study found no significantly differential methylation. However, preliminary support for a difference was found for the gamma-aminobutyric acid (GABA) B receptor 1 (cg10234998, cg17099072) in blood samples at birth and for the estrogen receptor 1 (ESR1) (cg10939667), the myelin oligodendrocyte glycoprotein (MOG) (cg16650906), and the brain-derived neurotrophic factor (BDNF) (cg14080521) in blood samples at the time of diagnosis. Preliminary support for an association was observed between the methylation profiles of GABBR1 and MOG and baseline severity, treatment effect, and responder status; and between the methylation profile of ESR1 and baseline severity. To our knowledge, this is the first study to examine the DNA methylation profiles in OCD. The study points towards possible differences in the methylation profiles and suggests a correlation with the severity of OCD. However, the results warrant further studies in larger sample sets.

No association between BDNF Val66Met polymorphism and treatment response in obsessive-compulsive disorder in the Japanese population

AIM

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family, and it promotes the development and function of dopaminergic and serotonergic neurons. The Met allele of the BDNF Val66Met polymorphism is associated with a decrease in activity-dependent secretion of BDNF compared with the Val allele, and a number of studies have provided evidence for the association between this polymorphism and obsessive-compulsive disorder (OCD). The purpose of this study was to investigate whether this functional variant of the BDNF gene is associated with OCD and treatment response in patients with OCD in the Japanese population.

METHODS

We first performed a case-control association study between the BDNF Val66Met polymorphism and OCD (175 cases and 2,027 controls). Then, we examined an association between this polymorphism and treatment response in 96 patients with OCD.

RESULTS

We found no significant association between the Met allele and OCD risk or between the Met allele and treatment responses to selective serotonin reuptake inhibitors or serotonin reuptake inhibitor with an atypical antipsychotic (P>0.05).

CONCLUSION

Our results suggest that the BDNF Val66Met polymorphism may not be associated as a risk factor for developing OCD or with therapeutic response in patients with OCD in the Japanese population.

Meta-analysis of the association of brain-derived neurotrophic factor Val66Met polymorphism with obsessive-compulsive disorder

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) plays an important role in neural survival and was proposed to be related to psychiatric disorders. Val66Met (also known as rs6265 or G196A), the only known functional polymorphism of the BDNF gene, has been widely studied and considered to be associated with risk of some psychiatric disorders such as bipolar disorder and schizophrenia. However, studies evaluating its association with obsessive-compulsive disorder (OCD) obtained inconsistent results. The purpose of this study was to derive a more precise estimation of the association between BDNF Val66Met polymorphism and OCD susceptibility by a meta-analysis.

METHOD

We carried a structured literature search in PubMed, Embase, PsycINFO and Chinese Biomedical Database up to December 2014; and retrieved all eligible case-control studies according to the including criteria. Meta-analysis was performed for four genetic models: allelic model: Met versus Val; additive model: Met/Met versus Val/Val; recessive model: Met/Met versus Val/Val+Val/Met; and dominant model: Val/Met+Met/Met versus Val/Val. Stratified analyses were performed by ethnicity and gender where appropriate.

RESULTS

A total of eight articles with nine studies including 1632 OCD cases and 2417 controls were identified. No significant association was detected in any comparison when the whole data were pooled together or stratified by ethnicity or gender in all four genetic models (p>0.05 for each comparison).

CONCLUSION

Despite some limitations, our meta-analysis suggests that no significant association exists between the BDNF Val66Met polymorphism and OCD susceptibility.

BDNF Val66Met polymorphism and plasma levels in Chinese Han population with obsessive-compulsive disorder and generalized anxiety disorder

BACKGROUND

Anxiety disorders are a category of mental disorders characterized by feelings of anxiety and fear, which include generalized anxiety disorder (GAD). Obsessive-Compulsive Disorder (OCD) used to be categorized as anxiety disorder in DSM-IV. However OCD was no longer included in anxiety disorders and came into its own category titled as Obsessive-Compulsive and Related Disorders (OCRD) in DSM-5. It will be interesting to explore is there any different biological characteristics between OCD and anxiety disorders. Brain-derived neurotrophic factor (BDNF) was a potential candidate gene in both OCD and GAD. The results of genetic association studies between BDNF and OCD have been inconsistent. BDNF plasma/serum levels in OCD have been found lower than those in healthy controls. However the heritable reason of the lowered BDNF levels was not well elucidated. The amount of studies about BDNF and GAD were relatively small. The aims of this study were to determine whether single nucleotide polymorphism Val66Met of BDNF was associated with OCD and GAD, to examine BDNF plasma levels in OCD and GAD, and to explore whether Val66Met variation influences BDNF plasma levels.

METHODS

We genotyped Val66Met variation in 148 OCD patients, 108 GAD patients and 99 healthy controls. Within the same sample, BDNF plasma levels were determined in 113 OCD patients, 102 GAD patients and 63 healthy controls.

RESULTS

Val66Met variation was not associated with OCD or GAD. BDNF plasma levels in OCD and GAD patients were significant lower than those in healthy controls. Val66Met variation had no influence on BDNF plasma levels. No difference was found between OCD and GAD. Results do not change no matter taking OCD and GAD as one group or separated two.

LIMITATIONS

First, the sample size for genotyping was relatively small, which leaded to a low statistical power of the genetic part in this study. Second, we genotyped just one SNP in BDNF gene. Third, parts of the participants did not be assayed for BDNF plasma levels.

CONCLUSIONS

Our findings support the hypothesis that BDNF is involved in the pathophysiology of mental disorders, not only OCD but also GAD. OCD and GAD patients both show lower BDNF plasma levels compared to healthy controls. The BDNF plasma levels are not associated with Val66Met variation.

The BDNF gene Val66Met polymorphism as a modifier of psychiatric disorder susceptibility: progress and controversy

Brain-derived neurotrophic factor (BDNF) has a primary role in neuronal development, differentiation and plasticity in both the developing and adult brain. A single-nucleotide polymorphism in the proregion of BDNF, termed the Val66Met polymorphism, results in deficient subcellular translocation and activity-dependent secretion of BDNF, and has been associated with impaired neurocognitive function in healthy adults and in the incidence and clinical features of several psychiatric disorders. Research investigating the Val66Met polymorphism has increased markedly in the past decade, and a gap in integration exists between and within academic subfields interested in the effects of this variant. Here we comprehensively review the role and relevance of the Val66Met polymorphism in psychiatric disorders, with emphasis on suicidal behavior and anxiety, eating, mood and psychotic disorders. The cognitive and molecular neuroscience of the Val66Met polymorphism is also concisely reviewed to illustrate the effects of this genetic variant in healthy controls, and is complemented by a commentary on the behavioral neuroscience of BDNF and the Val66Met polymorphism where relevant to specific disorders. Lastly, a number of controversies and unresolved issues, including small effect sizes, sampling of allele inheritance but not genotype and putative ethnicity-specific effects of the Val66Met polymorphism, are also discussed to direct future research.

BDNF Val66Met modifies the risk of childhood trauma on obsessive-compulsive disorder

Childhood trauma has been linked to the development of later psychopathology, including obsessive-compulsive disorder (OCD). Although evidence exists to suggest that genetic and environmental factors are involved in the aetiology of OCD, little attention has been paid to the interactions that exist between genes and environment. The aim of this study was to investigate gene-by-environment interactions between childhood trauma and the BDNF Val66Met variant in patients with OCD. Childhood trauma was assessed in 134 OCD patients and 188 controls using the Childhood Trauma Questionnaire (CTQ). Linear regression models were used for statistical analyses. Gene-environment interactions were estimated by including a combined genotype and CTQ score in the models as interaction terms. All analyses were adjusted for age, gender, CTQ minimisation-denial score and home language by including them in the logistic regression models as covariates. Childhood trauma, specifically emotional abuse and neglect, increased the odds of having OCD significantly (p < 0.001). Although no significant association was observed between BDNF Val66Met and the development of OCD, interaction analysis indicated that the BDNF Met-allele interacted with childhood emotional abuse to increase the risk of OCD significantly in a dose-dependent manner (p = 0.024). To our knowledge, this is one of the first studies to investigate gene-environment interactions in OCD, and the findings indicate the importance of collating genetic and environmental variables in future studies.

Association study between BDNF gene variants and Mexican patients with obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a psychiatric disorder whose etiology is not yet known. We investigate the role of three variants of the BDNF gene (rs6265, rs1519480 and rs7124442) by single SNP and haplotype analysis in OCD Mexican patients using a case-control and family-based association design. BDNF gene variants were genotyped in 283 control subjects, 232 OCD patients and first degree relatives of 111 OCD subjects. Single SNP analysis in case-control study showed an association between rs6265 and OCD with a high frequency of Val/Val genotype and Val allele (p=0.0001 and p=0.0001, respectively). Also, genotype and allele analysis of rs1519480 showed significant differences (p=0.0001, p=0.0001; respectively) between OCD and control groups. Haplotype analysis showed a high frequency of A-T (rs6265-rs1519480) in OCD patients compared with the control group (OR=2.06 [1.18-3.59], p=0.0093) and a low frequency of haplotype A-C in the OCD patients (OR=0.04 [0.01-0.16], p=0.000002). The family-based association study showed no significant differences in the transmission of any variant. Our study replicated the association between BDNF Val66Met gene polymorphism and OCD. Also, we found a significant association of rs1519480 in OCD patients compared with a control group, region that has never been analyzed in OCD. In conclusion, our findings suggest that BDNF gene could be related to the development of OCD.

The role of the brain-derived neurotrophic factor SNP rs2883187 in the phenotypic expression of obsessive-compulsive disorder

We investigated the association between a brain-derived neurotrophic factor (BDNF) gene polymorphism and clinical features in a sample of patients with obsessive-compulsive disorder (OCD). A total of 100 patients diagnosed with OCD according to the Diagnostic and Statistical Manual IV criteria and 110 control subjects were included in this study. The distribution of a single nucleotide polymorphism rs2883187 was compared in OCD patients and normal controls. Clinical features were compared between the subgroups of OCD patients with different genotypes. There was no significant difference for the allele frequencies and genotype distributions between the OCD and control groups. The Hamilton Anxiety Rating Scale, Yale-Brown Obsessive Compulsive Scale obsession and total scores were found to be higher in patients with the CC genotype than in the patients who are homozygous for the T allele. The rates of OCD in first-degree relatives of OCD patients who were homozygous for the C allele were significantly higher, compared to those with CT and TT genotypes. Our results indicate that the CC genotype may be associated with the severity and increased familial loading of OCD. Further investigation based on larger populations is needed to reveal the full association of the BDNF polymorphism with OCD.

Brain-Derived Neurotrophic Factor (BDNF) protein levels in anxiety disorders: systematic review and meta-regression analysis

Background: Brain-Derived Neurotrophic Factor (BDNF) is a neurotrophin that is involved in the synaptic plasticity and survival of neurons. BDNF is believed to be involved in the pathogenesis of several neuropsychiatric disorders. As findings of BDNF levels in anxiety disorders have been inconsistent, we undertook to conduct a systematic review and meta-analysis of studies that assessed BDNF protein levels in these disorders.

Methods: We conducted the review using electronic databases and searched reference lists of relevant articles for any further studies. Studies that measured BDNF protein levels in any anxiety disorder and compared these to a control group were included. Effect sizes of the differences in BDNF levels between anxiety disorder and control groups were calculated.

Results: Eight studies with a total of 1179 participants were included. Initial findings suggested that BDNF levels were lower in individuals with any anxiety disorder compared to those without [Standard Mean Difference (SMD) = −0.94 (−1.75, −0.12), p ≤ 0.05]. This was, however, dependent on source of BDNF protein [plasma: SMD = −1.31 (−1.69, −0.92), p ≤ 0.01; serum: SMD = −1.06 (−2.27, 0.16), p ≥ 0.01] and type of anxiety disorder [PTSD: SMD = −0.05 (−1.66, 1.75), p ≥ 0.01; OCD: SMD = −2.33 (−4.21, −0.45), p ≤ 0.01].

Conclusion: Although BDNF levels appear to be reduced in individuals with an anxiety disorder, this is not consistent across the various anxiety disorders and may largely be explained by the significantly lowered BDNF levels found in OCD. Results further appear to be mediated by differences in sampling methods. Findings are, however, limited by the lack of research in this area, and given the potential for BDNF as a biomarker of anxiety disorders, it would be useful to clarify the relationship further.

Neurotrophic factors in obsessive-compulsive disorder

In this cross-sectional study, we assessed the levels of neurotrophins (NF) of patients with obsessive-compulsive disorder (OCD) in different stages of treatment and their relationship with OCD clinical features. Forty patients with OCD and 40 healthy controls had Brain-Derived Neurotrophic Factor (BDNF), Nerve Growth Factor (NGF), and Glial Cell-Derived Neurotrophic Factor (GNDF) plasma levels measured by enzyme-linked immunosorbent assay (ELISA). Patients with OCD were further examined with the Obsessive-Compulsive Inventory-Revised, the Beck Depression Inventory, the Beck Anxiety Inventory, and the Sheehan Disability Scale (SDS). Patients with OCD exhibited significantly lower levels of BDNF and significantly increased levels of NGF as compared to healthy controls. In OCD, statistically significant negative correlations between BDNF levels and number of working days lost per week were found. Additional analyses revealed a statistically significant positive correlation between both NGF and GDNF and severity of washing symptoms. Plasma levels of NF were not affected by age, age at OCD onset, gender, major depressive disorder, the relative dose of serotonin-reuptake inhibitors being prescribed, or the use of antipsychotics. Our findings suggest that patients with OCD may exhibit a particular NF profile, with functional impairment correlating with BDNF levels and severity of washing symptoms correlating with NGF and GDNF levels.

Brain-derived neurotrophic factor gene Val66Met polymorphism and cognitive function in obsessive-compulsive disorder

In the present study, we have tested the hypothesis that brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism is associated with obsessive-compulsive disorder (OCD) and also investigated the association between the BDNF Val66Met polymorphism and the performance on tests measuring executive functions in a sample of patients with OCD. A total of 100 patients diagnosed with OCD according to DSM-IV criteria and 110 control subjects were included in this study. Single nucleotide polymorphism (G/A) leading to Val to Met substitution at codon 66 in BDNF was screened in the DNA samples of all participants. The genotype frequencies of BDNF Val66Met polymorphism were compared in OCD patients and healthy controls. The four subgroups of OCD and healthy control subjects, determined according to being Val homozygous or carrying a Met allele, were also compared according to their performance in a battery of neuropsychological tests of executive functions and verbal memory. There was no significant difference for the allele and genotype distributions of BDNF Val66Met polymorphism between the OCD and healthy control groups. Compared to the other three subgroups, OCD-Met carriers were slower on Trail-Making Test part A (TMT A), part B (TMT B) score and its speed-corrected score (TMT B-A). OCD-Met carriers had also poor performance on verbal fluency tasks and several CVLT measures compared only to the healthy control-Met carriers. These results demonstrate that the BDNF Val66Met polymorphism does not appear to be a risk factor for OCD. However, the presence of a BDNF Met allele, which is a known attenuator of BDNF activity, may be associated with a poorer executive functioning in OCD.

Influence of brain-derived neurotrophic factor genetic polymorphisms on the ages of onset for heroin dependence in a Chinese population

AIM

The study aims at evaluating the association between brain-derived neurotrophic factor (BDNF) gene polymorphisms and heroin-dependent patients in the Chinese population. Three polymorphisms of the BDNF-gene (rs10835210, rs16917234, and rs6265) in 486 heroin-dependent patients and in 226 healthy controls were genotyped for analyzing the association of these polymorphisms with age of onset of heroin dependence. We defined the healthy cases as "unknown phenotype" and used the endophenotype (behavior traits) to stratify the heroin dependents group on the basis of self-reporting traits for examining the association between BDNF polymorphisms (rs10835210, rs16917234, and rs6265) and heroin dependence.

RESULTS

Allelic distributions of BDNF gene polymorphisms did not differ significantly between heroin-dependent patients and controls. However, we found that the AA carriers of BDNF rs6265 had an earlier onset of heroin dependence and a clearer tendency of family history of heroin-dependent than GG carriers after controlling behavior characteristics across rs6265 genotypes.

CONCLUSIONS

Our findings suggested that the BDNF genetic polymorphism (rs6265) may have effects on the age of onset of heroin dependence among the Chinese population. The BDNF gene could contribute to vulnerabilities to heroin dependence.

Reprint of: Effects of BDNF polymorphisms on brain function and behavior in health and disease

Brain-derived neurotrophic factor (BDNF), the most abundant neurotrophin in the brain, serves an important role during brain development and in synaptic plasticity. Given its pleiotropic effects in the central nervous system, BDNF has been implicated in cognitive function and personality development as well as the pathogenesis of various psychiatric disorders. Thus, BDNF is considered an attractive candidate gene for the study of healthy and diseased brain function and behaviors. Over the past decade, many studies have tested BDNF genetic association, particularly its functional Val66Met polymorphism, with psychiatric diseases, personality disorders, and cognitive function. Although many reports indicated a possible role for BDNF genetic effects in mental problems or brain function, other reports were unable to replicate the findings. The conflicting results in BDNF genetic studies may result from confounding factors such as age, gender, other environmental factors, sample size, ethnicity and phenotype assessment. Future studies with more homogenous populations, well-controlled confounding factors, and well-defined phenotypes are needed to clarify the BDNF genetic effects on mental diseases and human behaviors.

Pharmacogenetics of obsessive-compulsive disorders

Genetic factors have been shown to influence occurrence and severity of several psychiatric disorders and also to modulate outcome to drug treatment. Obsessive-compulsive disorder (OCD) is a severe psychiatric condition with clear genetic roots; there is also some evidence to suggest that genetic factors may impact on response to drug treatment. Typically between 40 and 60% of patients are deemed nonresponders to antidepressant medication and clinical factors have only been modestly correlated with treatment response. Thus, identification of biological factors which may relate to treatment response could be extremely valuable in improving clinical outcome. In this article, we briefly review previous work regarding clinical and demographical factors associated with drug response in OCD, then focus on recent findings regarding candidate genes which may influence drug response, including those in the serotonin system, brain-derived neurotrophic factor and the glutamate transporter gene. The cytochrome system may also be highly relevant to drug response. Thus far, relatively few studies regarding the pharmacogenetics of OCD have been published, and therefore further investigation with functional analyses and consideration of environmental factors are warranted to facilitate clinical use of pharmacogenetic findings in the future.

Brain-derived neurotrophic factor Val66Met polymorphism and obsessive-compulsive symptoms in Egyptian schizophrenia patients

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has been advanced as a candidate gene for schizophrenia. BDNF promote the function and growth of 5-HT neurons in the brain and modulate the synaptic plasticity of DRD3-secreting neurons in the striatum, suggesting involvement of BDNF in the mediation of obsessive-compulsive disorder.

OBJECTIVES

To test the hypothesis that the BDNF Val66Met polymorphism influence obsessive-compulsive symptoms (OCS) in schizophrenia, we examined the association between the BDNF Val66Met genotypes and OCS in a group of patients with schizophrenia.

METHODS

320 schizophrenia patients were assessed using the Yale-Brown Obsessive-Compulsive Scale (YBOCS). BDNF Val66Met polymorphism was genotyped using PCR-RFLP method, and severity of OCS were compared between the genotype groups.

RESULTS

Out of the 320 schizophrenia patients, 120 patients (37.5%) had significant OCS. There was a significant excess of valine allele in the schizophrenia with-OCS group compared to the without-OCS group. The mean YBOCS scores were significantly different among the three genotype groups. Val/Val homozygote patients had higher mean YBOCS scores compared to Val/Met genotype (p = 0.0001) as well as to the Met/Met homozygote group (p = 0.003).

CONCLUSION

Our data suggested an association between BDNF Val66Met polymorphism and OCS in Egyptian schizophrenia patients.

Hippocampal volume and the brain-derived neurotrophic factor Val66Met polymorphism in first episode psychosis

INTRODUCTION

Small hippocampi and impaired memory are common in patients with psychosis and brain-derived neurotrophic factor (BDNF) plays a critical role in hippocampal neuroplasticity and memory. A common BDNF allele (Val66Met) has been the focus of numerous studies but results from the few BDNF-imaging studies are complex and contradictory. The objective of this study was to determine the association between Val66Met and hippocampal volume in patients with first episode psychosis. Secondary analyses explored age-related associations and the relationship between Val66Met and memory.

METHOD

Hippocampal volume and BDNF genotyping were obtained for 58 patients with first-episode psychosis and 39 healthy volunteers. Patients were recruited from an early psychosis program serving a catchment-area population.

RESULTS

Hippocampal volume was significantly smaller in patients than controls (F(1,92)=4.03, p<0.05) and there was a significant group-by-allele interaction (F(1,92)=3.99, p<0.05). Hippocampal volume was significantly smaller in patients than controls who were Val-homozygotes but no group differences were found for Met carriers. Findings were not affected by diagnosis, antipsychotic medication, or age, and there was no change in hippocampal volume during a one-year follow-up. Val-homozygous patients had worse immediate and delayed memory than their Met counterparts.

CONCLUSIONS

Results suggest the effects of the BDNF Val66Met allele may be different in patients with psychosis than in healthy adults. Hippocampal volume in patient and control Met allele carriers was very similar suggesting that illness-related factors have minimal influence in this group. In contrast, Val homozygosity was related to smaller hippocampi and poorer memory functioning only in patients with psychosis.

Effects of BDNF polymorphisms on brain function and behavior in health and disease

Brain-derived neurotrophic factor (BDNF), the most abundant neurotrophin in the brain, serves an important role during brain development and in synaptic plasticity. Given its pleiotropic effects in the central nervous system, BDNF has been implicated in cognitive function and personality development as well as the pathogenesis of various psychiatric disorders. Thus, BDNF is considered an attractive candidate gene for the study of healthy and diseased brain function and behaviors. Over the past decade, many studies have tested BDNF genetic association, particularly its functional Val66Met polymorphism, with psychiatric diseases, personality disorders, and cognitive function. Although many reports indicated a possible role for BDNF genetic effects in mental problems or brain function, other reports were unable to replicate the findings. The conflicting results in BDNF genetic studies may result from confounding factors such as age, gender, other environmental factors, sample size, ethnicity and phenotype assessment. Future studies with more homogenous populations, well-controlled confounding factors, and well-defined phenotypes are needed to clarify the BDNF genetic effects on mental diseases and human behaviors.

Brain-derived neurotrophic factor (BDNF) plasma levels in drug-naïve OCD patients are lower than those in healthy people, but are not lower than those in drug-treated OCD patients

BACKGROUND

Brain-derived neurotrophic factor (BDNF) plays an important role in neural development, and has been implicated in the development of depressive and anxiety disorders. Obsessive-compulsive disorder (OCD) is a chronic anxiety disorder with an unclear pathophysiology. Although genetic studies have suggested an association between BDNF and OCD, the results have been inconsistent. The aims of this study were to determine whether BDNF plasma levels in OCD patients are lower than those in healthy controls and whether BDNF plasma levels differ between drug-naïve and drug-treated OCD patients.

METHODS

We examined BDNF plasma levels in 22 drug-naïve OCD patients, 52 drug-treated OCD patients, and 63 healthy controls. Individuals in all groups with a current or lifetime history of depression were excluded.

RESULTS

BDNF plasma levels in both drug-naïve OCD patients (1.97 ± 1.80 ng/ml, p=0.00) and drug-treated OCD patients (1.98 ± 1.54 ng/ml, p=0.00) were lower than those in normal controls (4.09 ± 2.00 ng/ml). However BDNF plasma levels in those two OCD patients groups were not different from each other significantly (p=0.99). Length of drug treatment was positively associated with BDNF plasma levels in the drug-treated patients (r=0.34, p=0.03).

LIMITATIONS

We used treatment length of two weeks and above as the criterion to recruit drug-treated patients. Probably this treatment length is not sufficient to identify drug-associated changes in BDNF levels.

CONCLUSIONS

Our findings support the hypothesis that BDNF is involved in the pathophysiology of OCD, and may be a peripheral marker indicating neurotrophic impairment in OCD.

Early versus late onset obsessive-compulsive disorder: evidence for distinct subtypes

The distinction between early versus late onset is important for understanding many different kinds of disorders. In an effort to identify etiologically homogeneous subtypes of obsessive-compulsive disorder (OCD), numerous studies have investigated whether early onset OCD (EO) can be reliably distinguished from a comparatively later onset form of the disorder (LO). The present article presents a systematic review and evaluation of this subtyping scheme, including meta-analyses and re-analyses of raw data. Regarding the latter, latent class analyses of nine datasets, including clinical and community samples, consistently indicated that age-of-onset is not a unimodal phenomena. Evidence suggests that there are two distinguishable groups; EO (mean onset 11 years) and LO (mean onset 23 years). Approximately three-quarters of cases of OCD (76%) were classified as EO. Meta-analyses indicated that EO, compared to LO, is (a) more likely to occur in males, (b) associated with greater OCD global severity and higher prevalence of most types of OC symptoms, (c) more likely to be comorbid with tics and possibly with other putative obsessive-compulsive spectrum disorders, and (d) associated with a greater prevalence of OCD in first-degree relatives. EO and LO were also distinguishable on other psychosocial and biological variables. Overall, results support the view that EO and LO are distinct subtypes of OCD. Comparisons with other, potentially overlapping OCD subtyping schemes are discussed, implications for DSM-V are considered, and important directions for future investigation are proposed.

The genetics of obsessive-compulsive disorder and Tourette syndrome: an epidemiological and pathway-based approach for gene discovery

OBJECTIVE

To provide a contemporary perspective on genetic discovery methods applied to obsessive-compulsive disorder (OCD) and Tourette syndrome (TS).

METHOD

A review of research trends in genetics research in OCD and TS is conducted, with emphasis on novel approaches.

RESULTS

Genome-wide association studies (GWAS) are now in progress in OCD and TS and will provide a platform for future discovery of common gene variants. Optimally, newer next-generation genome sequencing methods can also be used to detect larger effect genes (rare gene variants), taking advantage of pedigrees. Studies of gene networks or sets rather than individual genes will be required to elucidate biological etiology, as neural systems appear to act redundantly. Newer phenotyping strategies, such as symptom-based subtypes, cross-disorder latent class types, and intermediate phenotypes (endophenotypes) will need to be developed and tested to better align clinical and physiological measures with genetic architecture.

CONCLUSION

Although genetics research has made significant advances based on computational strength and bioinformatics advances, newer approaches to phenotyping and judicious study of gene etiological networks will be needed to uncover the genetic etiology of OCD and TS.

Population genetic study of the brain-derived neurotrophic factor (BDNF) gene

Genetic variants in the brain-derived neurotrophic factor (BDNF) gene, predominantly the functional Val66Met polymorphism, have been associated with risk of bipolar disorder and other psychiatric disorders. However, not all studies support these findings, and overall the evidence for the association of BDNF with disease risk is weak. As differences in population genetic structure between patient samples could cause discrepant or spurious association results, we investigated this possibility by carrying out population genetic analyses of the BDNF genomic region. Substantial variation was detected in BDNF coding region single-nucleotide polymorphism (SNP) allele and haplotype frequencies between 58 global populations, with the derived Met allele of Val66Met ranging in frequency from 0 to 72% across populations. F(ST) analyses to assess diversity in the HapMap populations determined that the Val66Met F(ST) value was at the 99.8th percentile among all SNPs in the genome. As the BDNF population genetic differences may be due to local selection, we performed the long-range haplotype test for selection using 68 SNPs spanning the BDNF genomic region in 12 European-derived pedigrees. Evidence for positive selection was found for a high-frequency Val-carrying haplotype, with a relative extended haplotype homozygosity value above the 99 th percentile compared with HapMap data (P=4.6 x 10(-4)). In conclusion, we observed considerable BDNF allele and haplotype diversity among global populations and evidence for positive selection at the BDNF locus. These phenomena can have a profound impact on the detection of disease susceptibility genes and must be considered in gene association studies of BDNF.

Should OCD be classified as an anxiety disorder in DSM-V?

In DSM-III, DSM-III-R, and DSM-IV, obsessive-compulsive disorder (OCD) was classified as an anxiety disorder. In ICD-10, OCD is classified separately from the anxiety disorders, although within the same larger category as anxiety disorders (as one of the "neurotic, stress-related, and somatoform disorders"). Ongoing advances in our understanding of OCD and other anxiety disorders have raised the question of whether OCD should continue to be classified with the anxiety disorders in DSM-V. This review presents a number of options and preliminary recommendations to be considered for DSM-V. Evidence is reviewed for retaining OCD in the category of anxiety disorders, and for moving OCD to a separate category of obsessive-compulsive (OC)-spectrum disorders, if such a category is included in DSM-V. Our preliminary recommendation is that OCD be retained in the category of anxiety disorders but that this category also includes OC-spectrum disorders along with OCD. If this change is made, the name of this category should be changed to reflect this proposed change.

The Genetics of Obsessive-Compulsive Disorder

OCD is a psychiatric disorder with a lifetime prevalence of 1-3% and is a significant cause of disability worldwide. Family studies indicate that OCD has a significant hereditable component, with relatives of OCD cases being 4 times more likely to develop the disorder than the general population. Linkage studies in OCD have generally been underpowered and have failed to reach the statistical threshold for genome-wide significance, but they have nevertheless been useful for revealing potential regions of interest for future candidate gene studies. Candidate gene studies in OCD have thus far focused on genes involved in the serotonergic, dopaminergic, and glutamatergic pathways. These studies have been for the most part inconclusive, and failures to replicate have been the norm until very recently. The only genetic association replicated by multiple groups was with a glutamate transporter gene (SLC1A1). Genome-wide association studies in OCD are in progress, but final results have not yet been reported. As with the study of many other psychiatric disorders, an improved understanding of OCD will only be achieved (1) with larger collaborative efforts involving more probands, (2) the use of probands and controls drawn from epidemiologically-based populations rather than clinical samples, (3) developing a more precise phenotypic description of OCD and (4) measuring important environmental influences that affect OCD pathogenesis and severity.

Symptom dimensions in OCD: item-level factor analysis and heritability estimates

To reduce the phenotypic heterogeneity of obsessive-compulsive disorder (OCD) for genetic, clinical and translational studies, numerous factor analyses of the Yale-Brown Obsessive Compulsive Scale checklist (YBOCS-CL) have been conducted. Results of these analyses have been inconsistent, likely as a consequence of small sample sizes and variable methodologies. Furthermore, data concerning the heritability of the factors are limited. Item and category-level factor analyses of YBOCS-CL items from 1224 OCD subjects were followed by heritability analyses in 52 OCD-affected multigenerational families. Item-level analyses indicated that a five factor model: (1) taboo, (2) contamination/cleaning, (3) doubts, (4) superstitions/rituals, and (5) symmetry/hoarding provided the best fit, followed by a one-factor solution. All 5 factors as well as the one-factor solution were found to be heritable. Bivariate analyses indicated that the taboo and doubts factor, and the contamination and symmetry/hoarding factor share genetic influences. Contamination and symmetry/hoarding show shared genetic variance with symptom severity. Nearly all factors showed shared environmental variance with each other and with symptom severity. These results support the utility of both OCD diagnosis and symptom dimensions in genetic research and clinical contexts. Both shared and unique genetic influences underlie susceptibility to OCD and its symptom dimensions.

The role of the brain-derived neurotrophic factor (BDNF) val66met variant in the phenotypic expression of obsessive-compulsive disorder (OCD)

Evidence suggests that the Val66Met variant of the brain-derived neurotrophic factor (BDNF) gene may play a role in the etiology of Obsessive-Compulsive Disorder (OCD). In this study, the role of the BDNF Val66Met variant in the etiology and the phenotypic expression of OCD is investigated. Associations between the BDNF Val66Met variant and OCD, obsessive-compulsive symptom dimensions, Yale-Brown Obsessive Compulsive Scale (YBOCS) severity scores, age of onset and family history of obsessive-compulsive symptoms were assessed. The BDNF Val66Met variant was genotyped in 419 patients with sub-/clinical OCD and 650 controls. No differences in allele or genotype frequency were observed between cases and controls. In females with OCD, the Met66Met genotype was associated with later age of onset and a trend for a negative family history, whereas the Val66Val genotype was associated with a trend for lower YBOCS severity scores. Item-level factor analysis revealed six factors: 1) Contamination/cleaning; 2) Aggressive obsessions/checking; 3) Symmetry obsessions, counting, ordering and repeating; 4) Sexual/religious obsessions; 5) Hoarding and 6) Somatic obsessions/checking. A trend was found for a positive association between Factor 4 (Sexual/religious obsessions) and the BDNF Val66Val genotype. The results suggest that BDNF function may be implicated in the mediation of OCD. We found that for the BDNF Met66Met genotype may be associated with a milder phenotype in females and a possible role for the BDNF Val66Val genotype and the BDNF Val66 allele in the sexual/religious obsessions.