The role of the brain-derived neurotrophic factor (BDNF) val66met variant in the phenotypic expression of 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.

Reduced Expression of the Htr2a, Grin1, and Bdnf Genes and Cognitive Inflexibility in a Model of High Compulsive Rats

Compulsivity is a core symptom in different psychopathological disorders, characterized by excessive behaviors and behavioral inflexibility. The selection of high drinker (HD) versus low drinker (LD) rats by schedule-induced polydipsia (SIP) is a valid model for studying the compulsive phenotype. The compulsive HD rats showed cognitive inflexibility and reduced serotonin 2A (5-HT2A) receptor binding levels in the frontal cortex (FC). According to that, we hypothesize that compulsive HD rats might have an alteration in the cognitive control domain regarding inflexibility, assessed by spatial memory on the Morris Water Maze (MWM), working and reference memory by the Radial Arm Maze, and behavioral deficits in stimulus processing by the Novel Object Recognition test. The possible underlying mechanisms might be linked to the brain gene expression of 5HT2A, 5HT2C, glutamate NMDA receptors, and brain-derived neurotrophic factor (BDNF) in FC, hippocampus, and amygdala. HD rats confirmed a cognitive inflexibility profile on the reversal condition in the MWM compared to LD rats, while no differences were observed on stimulus processing, spatial, and working memory. Moreover, HD rats showed a reduced expression of the Htr2a, Grin1, and Bdnf genes in FC. Furthermore, there was a negative correlation between the relative expression of the Htr2a, Grin1, and Bdnf genes in FC and the level of compulsive water intake in HD rats on SIP. These data reveal that cognitive inflexibility may not be associated with a memory or stimulus processing deficit in compulsive individuals but may result by a region-specific alteration of the Htr2a, Grin1, and Bdnf gene expression in FC.

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.

Impact of brain-derived neurotrophic factor Val66Met polymorphism and response to escitalopram or paroxetine in obsessive-compulsive disorder

OBJECTIVE

Obsessive-compulsive disorder (OCD) is a severe psychiatric disorder characterized by its heterogeneous nature and by different dimensions of obsessive-compulsive (OC) symptoms. Serotonin reuptake inhibitors (SRIs) are used to treat OCD, but up to 40% to 60% of patients do not show a significant improvement with these medications. In this study, we aimed to test the impact of brain-derived neurotrophic factor (BDNF) Val66Met polymorphism on the efficacy of antidepressants in OCD overall, and in relation to the different OC dimensions.

METHODS

In a 6-month prospective treatment study, 69 Caucasian OCD patients were treated with escitalopram for 24 weeks or with escitalopram for 12 weeks followed by paroxetine for an additional 12-week period. Patients were genotyped and assessed for treatment response. The main clinical outcomes were improvement of the Yale-Brown Obsessive-Compulsive Scale score and in different OC symptom dimension scores.

RESULTS

The Val/Val group comprised 43 (62%) patients, the Val/Met and Met/Met group comprised 26 (38%) patients. Forty-two patients were classified as responders at 12 weeks and 38 at 24 weeks; no significant association was found between BDNF Val66Met and SRIs response at 12 and 24 weeks. In analyses of the different OC symptom dimensions, the Met allele was associated with a slightly reduced score in the aggressive/checking dimension at 6 months (P = .048).

CONCLUSIONS

Our findings do not support the usefulness of BDNF Val66Met genotyping to predict overall response to treatment with SRIs in OCD; they did however suggest a better outcome at 6 months for the aggressive/checking symptom dimension for patients carrying the Met allele.

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.

Effects of Transcranial Alternating Current Stimulation and Neurofeedback on Alpha (EEG) Dynamics: A Review

Transcranial alternating current stimulation (tACS) and neurofeedback (NFB) are two different types of non-invasive neuromodulation techniques, which can modulate brain activity and improve brain functioning. In this review, we compared the current state of knowledge related to the mechanisms of tACS and NFB and their effects on electroencephalogram (EEG) activity (online period/stimulation period) and on aftereffects (offline period/post/stimulation period), including the duration of their persistence and potential behavioral benefits. Since alpha bandwidth has been broadly studied in NFB and in tACS research, the studies of NFB and tACS in modulating alpha bandwidth were selected for comparing the online and offline effects of these two neuromodulation techniques. The factors responsible for variability in the responsiveness of the modulated EEG activity by tACS and NFB were analyzed and compared too. Based on the current literature related to tACS and NFB, it can be concluded that tACS and NFB differ a lot in the mechanisms responsible for their effects on an online EEG activity but they possibly share the common universal mechanisms responsible for the induction of aftereffects in the targeted stimulated EEG band, namely Hebbian and homeostatic plasticity. Many studies of both neuromodulation techniques report the aftereffects connected to the behavioral benefits. The duration of persistence of aftereffects for NFB and tACS is comparable. In relation to the factors influencing responsiveness to tACS and NFB, significantly more types of factors were analyzed in the NFB studies compared to the tACS studies. Several common factors for both tACS and NFB have been already investigated. Based on these outcomes, we propose several new research directions regarding tACS and NFB.

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.

Factors affecting stability of plasma brain-derived neurotrophic factor

Circulating concentrations of brain-derived neurotrophic factor (BDNF) have been linked to cancer, neuropsychiatric, diabetes, and gynecological disorders. However, factors influencing plasma storage and subsequent BDNF quantification are incompletely understood. Therefore, the anticoagulant used in plasma separator tubes, storage-time, storage-temperature, and repeated freeze–thaw cycles on circulating BDNF concentrations was evaluated. Peripheral blood samples were collected from healthy women (n = 14) and men (n = 10) recruited prospectively from McMaster University (August 2014). Blood was collected from the cubital vein into plasma separator tubes containing five different anticoagulant systems [K2EDTA, Li-Hep, Li-Hep (gel), Na-Hep, Na-Hep (glass)], and placed on ice for transport to the lab for centrifugation. Plasma samples (n = 16) collected in K2EDTA tubes from women recruited to a previous study (April 2011 to December 2012) were used to determine the effect of multiple freeze–thaw cycles. Plasma BDNF was quantified using a commercially available ELISA kit. Plasma concentrations of BDNF were significantly affected by the type of plasma separator tube, storage-time, and number of freeze–thaw cycles. Storage temperature (− 20 vs. − 80 °C) did not significantly affect the quantity of BDNF measured as mean BDNF concentrations generally fell within our calculated acceptable change limit up to 6 months in the freezer. Our results suggest that for quantification of circulating BDNF blood collected in K2EDTA tubes and plasma stored up to 6 months at either − 20 or − 80 °C produces reproducible results that fall within an acceptable range. However, plasma samples stored beyond 6 months and repeated freeze–thaw cycles should be avoided.

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.

Looking into the genetic bases of OCD dimensions: a pilot genome-wide association study

The multidimensional nature of obsessive-compulsive disorder (OCD) has been consistently reported. Clinical and biological characteristics have been associated with OCD dimensions in different ways. Studies suggest the existence of specific genetic bases for the different OCD dimensions. In this study, we analyze the genomic markers, genes, gene ontology and biological pathways associated with the presence of aggressive/checking, symmetry/order, contamination/cleaning, hoarding, and sexual/religious symptoms, as assessed via the Dimensional Yale-Brown Obsessive Compulsive Scale (DY-BOCS) in 399 probands. Logistic regression analyses were performed at the single-nucleotide polymorphism (SNP) level. Gene-based and enrichment analyses were carried out for common (SNPs) and rare variants. No SNP was associated with any dimension at a genome-wide level (p < 5 × 10^-8). Gene-based analyses showed one gene to be associated with hoarding (SETD3, p = 1.89 × 10^-08); a gene highly expressed in the brain and which plays a role in apoptotic processes and transcriptomic changes, and another gene associated with aggressive symptoms (CPE; p = 4.42 × 10^-6), which is involved in neurotrophic functions and the synthesis of peptide hormones and neurotransmitters. Different pathways or biological processes were represented by genes associated with aggressive (zinc ion response and lipid metabolism), order (lipid metabolism), sexual/religious (G protein-mediated processes) and hoarding (metabolic processes and anion transport) symptoms after FDR correction; while no pathway was associated with contamination. Specific genomic bases were found for each dimension assessed, especially in the enrichment analyses. Further research with larger samples and different techniques, such as next-generation sequencing, are needed to better understand the differential genetics of OCD dimensions.

BDNF Val66Met Genetic Polymorphism Results in Poor Recovery Following Repeated Mild Traumatic Brain Injury in a Mouse Model and Treatment With AAV-BDNF Improves Outcomes

Clinicians have long noticed that some Traumatic Brain Injury (TBI) patients have worse symptoms and take a longer time to recover than others, for reasons unexplained by known factors. Identifying what makes some individuals more susceptible is critical to understanding the underlying mechanisms through which TBI causes deleterious effects. We have sought to determine the effect of a single nucleotide polymorphism (SNP) in Brain-derived neurotrophic factor (BDNF) at amino acid 66 (rs6265) on recovery after TBI. There is controversy from human studies as to whether the BDNF Val66Val or Val66Met allele is the risk factor for worse outcomes after brain trauma. We therefore investigated cellular and behavioral outcomes in genetically engineered mice following repeated mild TBI (rmTBI) using a lateral fluid percussion (LFP) injury model. We found that relative to injured Val66Val carriers, injured Val66Met carriers had a larger inflammation volume and increased levels of neurodegeneration, apoptosis, p-tau, activated microglia, and gliosis in the cortex and/or hippocampus at 1 and/or 21 days post-injury (DPI). We therefore concluded that the Val66Met genetic polymorphism is a risk factor for poor outcomes after rmTBI. In order to determine the mechanism for these differences, we investigated levels of the apoptotic-inducing pro BDNF and survival-inducing mature BDNF isoforms and found that Met carriers had less total BDNF in the cortex and a higher pro/mature ratio of BDNF in the hippocampus. We then developed a personalized approach to treating genetically susceptible individuals by overexpressing wildtype BDNF in injured Val66Met mice using an AAV-BDNF virus. This intervention improved cellular, motor, and cognitive behavior outcomes at 21 DPI and increased levels of mature BDNF and phosphorylation of mature BDNF's receptor trkB. This study lays the groundwork for further investigation into the genetics that play a role in the extent of injury after rmTBI and highlights how personalized therapeutics may be targeted for recovery in susceptible individuals.

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.

Association between miscellaneous symptoms and primary symptom dimensions among chinese adults with obsessive-compulsive disorder

Obsessive compulsive-disorder (OCD) is a common mental illness characterized by the presence of obsessions and/or compulsions. Symptom presence and severity is typically evaluated through the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS). However, miscellaneous symptoms embedded within the Y-BOCS Symptom Checklist have often been overlooked despite being associated with certain dimensions. In this study, we used exploratory factor analysis and logistic regression to explore the relationship between various miscellaneous symptoms and OCD symptom dimensions among 123 Chinese adults with OCD. A four-dimensional model was factorially derived: Obsessions, Symmetry/Ritual, Contamination/Cleaning and Contamination/Cleaning. In general, 11 out of 17 miscellaneous symptoms were associated with one or more of the symptom dimensions. Among them, the Obsessions dimension was significantly associated with seven miscellaneous symptoms: "Fear of not saying just the right thing," "Intrusive (non-violent) images," "Intrusive nonsense sounds, words", etc. The Symmetry/Ritual dimension was significantly associated with "Need to tell, ask, or confess." The Contamination/Cleaning dimension was related to "Need to know or remember". The Hoarding/Religion dimension was related to "Fear of losing things," and "Superstitious fears". Results contribute to the clinical assessment, diagnosis and treatment of Chinese patients with OCD by understanding the extent to which certain miscellaneous symptoms are associated with primary symptom dimensions.

Systematic review of co-occurring OCD and TD: Evidence for a tic-related OCD subtype?

OBJECTIVE

The aim of this review is to summarize the current knowledge of associated features of co-occurring obsessive-compulsive disorder (OCD) and tic disorders (TD) and to critically evaluate hypotheses regarding the nature of their comorbidity.

METHOD

We conducted a systematic review following PRISMA guidelines. To this aim, the PubMed, PsychInfo and ISI Web of Knowledge databases were searched up to August 30, 2018. For gender and age-of-onset we additionally conducted meta-analyses.

RESULTS

One hundred eighty-nine studies met inclusion criteria. We substantiate some acknowledged features and report evidence for differential biological mechanisms and treatment response. In general, studies were of limited methodological quality.

CONCLUSIONS

Several specific features are reliable associated with co-occurring OCD + TD. The field lacks methodological sound studies. The review found evidence against and in favor for different hypotheses regarding the nature of comorbidity of OCD and TD. This could indicate the existence of a stepwise model of co-morbidity, or could be an artefact of the low methodological quality of studies.

Do obsessive-compulsive disorder and Tourette syndrome share a common susceptibility gene? An association study of the BDNF Val66Met polymorphism in the Chinese Han population

OBJECTIVES

We explored the association between the BDNF Val66Met polymorphism and susceptibility to both obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) in the Chinese Han population.

METHODS

Genotyping for the BDNF Val66Met polymorphism was performed in 321 OCD patients and 426 healthy control subjects and case-control association study data were analysed. Additionally, we evaluated the genetic contribution of this variant in 331 TS patients (including 267 TS trios) and 519 controls using the transmission disequilibrium test (TDT) and case-control study.

RESULTS

A statistically significant difference was found in the genetic contribution of the BDNF Val66Met polymorphism between both the OCD (χ(2) = 7.50, P = 0.023 by genotype; χ(2) = 6.67, P = 0.01 by allele) and TS (χ(2) = 6.76, P = 0.03 by genotype; χ(2) = 4.27, P = 0.04 by allele), and control groups. TDT and GHRR analysis for TS trios also showed a significant transform disequilibrium of this polymorphism (TDT: χ(2) = 3.96, P = 0.05; HHRR: χ(2) = 4.33 P = 0.04; GHRR: χ(2) = 5.74, P = 0.02; χ(2) = 0.98, P = 0.37). There was also a significant gender trend between patients and controls in female cases for OCD and in male cases for TS.

CONCLUSIONS

Our study supports the involvement of the BDNF Val66Met polymorphism as a common genetic susceptibility for OCD and TS in the Chinese Han population, showing specific gender trends.

Decreased Plasma BDNF Levels of Patients with Somatization Disorder

OBJECTIVE

Brain-derived neurotrophic factor (BDNF), one of the most abundant and important neurotrophins, is known to be involved in the development, survival, maintenance, and plasticity of neurons in the nervous system. Some studies have suggested that BDNF may play a role in the pathophysiology of several psychiatric illnesses such as depression and schizophrenia. Similarly, it is likely that the alteration of BDNF may be associated with the neuro-modulation that contributes to the development of somatization disorder.

METHODS

The purpose of this study was to determine whether there is an abnormality of plasma BDNF levels in patients with somatization disorder, and to analyze the nature of the alteration after pharmacotherapy using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The plasma BDNF levels of the patients with a somatization disorder were significantly lower compared with those of the control volunteers (83.61±89.97 pg/mL vs. 771.36±562.14 pg/mL); moreover, the plasma BDNF levels of those patients who received an antidepressant were significantly increased after the treatment (118.13±91.45 pg/mL vs. 72.92±88.21 pg/mL).

CONCLUSION

These results suggest that BDNF may play a role in the pathophysiology of somatization disorder.

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.

Translational findings on brain-derived neurotrophic factor and anxiety: contributions from basic research to clinical practice

BACKGROUND/AIMS

Anxious responses are evolutionarily adaptive, but excessive fear can become disabling and lead to anxiety disorders. Translational models of anxiety might be useful sources for understanding the neurobiology of fear and anxiety and can contribute to future proposals of therapeutic intervention for the disorders studied. Brain-derived neurotrophic factor (BDNF), which is known for its importance on neuroplasticity and contextual memory, has emerged as a relevant element for emotional memory. Recent studies show that the Val(66)Met BDNF polymorphism correlates with various psychiatric disorders, including anxiety, but there are several differences between experimental and clinical studies.

METHODS

In this work, we review the literature focused on the BDNF Val(66)Met polymorphism and anxiety, and discuss biological findings from animal models to clinical studies.

RESULTS

As occurs with other psychiatric disorders, anxiety correlates with anatomical, behavioral and physiological changes related to the BDNF polymorphism. In animal studies, it has been shown that a significant decrease in regulated secretion from both BDNFVal/Met and BDNFMet/Met neurons represented a significant decrease in available BDNF.

CONCLUSION

These studies suggest that developing pharmacological strategies facilitating the release of BDNF from synapses or prolongation of the half-life of secreted BDNF may improve the therapeutic responses of humans expressing the BDNF polymorphism.

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.

The interaction between Comt and Bdnf variants influences obsessive-compulsive-related dysfunctional beliefs

Cognitive models emphasize the importance of dysfunctional beliefs as overimportance/need to control thoughts, perfectionism, intolerance of uncertainty, responsibility, and overestimation of threat in obsessive-compulsive disorder (OCD). Twin studies suggest that these beliefs are significantly heritable, but candidate genes associated with them have not been analyzed. We genotyped the Val158Met in the COMT gene and Val66Met variant in the BDNF gene in 141 OCD patients and analyzed their single and interactive effects on the obsessive beliefs questionnaire (OBQ-44). Variability in dysfunctional beliefs was not affected by the COMT or BDNF genotype in isolation, but we detected a significant COMT×BDNF interaction effect on responsibility/overestimation of threat and overimportance/need to control thoughts scores. Subjects with the BDNF Met-present and the COMT Met-present genotype showed higher scores on responsibility/overestimation of threat. An interaction between dopaminergic and neurotrophic functional gene variants may influence dysfunctional beliefs hypothesized to contribute to the development of OCD.

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.

Gender differences in obsessive-compulsive disorder: a literature review

INTRODUCTION

Obsessive-compulsive disorder (OCD) is a heterogeneous condition, in which subtypes have been proposed. Previous studies suggested that gender plays a relevant role in OCD phenotypic expression. This study aimed to review the literature on gender differences in clinical, genetic or familial aspects of OCD.

METHOD

A conventional review was conducted, including all papers that investigated demographic, clinical, and genetic aspects of OCD according to gender. The search was based on data available in Medline and PsycINFO databases in the last 20 years, using as keywords: obsessive-compulsive disorder; and: gender, sex, male, female, demographic characteristics, clinical features, clinical characteristics, genetic, genes, genetics gender OCD, genes OCD, genes OCD males, genes OCD females.

RESULTS

Sixty three of 487 phenotypical and genetics studies were selected. Most studies indicate that male patients are more likely than females to be single, present early onset of symptoms and chronic course of the disorder, greater social impairment, more sexual-religious and aggressive symptoms, and greater comorbidity with tic and substance use disorders. Female patients present more contamination/cleaning symptoms and greater comorbidity with eating and impulse-control disorders. Genetic and family studies are inconclusive, but suggest that gender may play a role in the disease expression.

CONCLUSIONS

Gender is a relevant factor that should be taken into account when evaluating OCD patients. More studies are necessary to determine whether in fact it defines a homogeneous and particular group in OCD.

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.

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.

Association between the NMDA glutamate receptor GRIN2B gene and obsessive-compulsive disorder

BACKGROUND

Recent data from neuroimaging, genetic and clinical trials and animal models suggest a role for altered glutamatergic neuro transmission in the pathogenesis of obsessive-compulsive disorder (OCD). The aim of this study was to investigate whether variants in the GRIN2B gene, the gene encoding the NR2 subunit of the N-methyl-D-aspartate (NMDA) glutamate receptor, may contribute to genetic susceptibility to OCD or to different OCD subphenotypes.

METHODS

Between 2003 and 2008, we performed a case-control association study in which we genotyped 10 tag single-nucleotide polymorphisms (SNPs) in the 3' untranslated region (3' UTR) of GRIN2B. We performed SNP association and haplotype analysis considering the OCD diagnosis and different OCD subphenotypes: early-onset OCD, comorbid tic disorders and OCD clinical symptom dimensions.

RESULTS

We enrolled 225 patients with OCD and 279 controls recruited from the OCD Clinic at Bellvitge Hospital (Barcelona, Spain). No significant difference in the distribution of alleles or genotypes was detected between patients with OCD and controls. Nonetheless, on analyzing OCD subphenotypes, the rs1805476 SNP in male patients (95% confidence interval [CI] 1.37-4.22, p = 0.002) and a 4-SNP haplotype in the whole sample (rs1805476, rs1805501, rs1805502 and rs1805477; odds ratio 1.92, 95% CI 1.22-3.01; permutation p = 0.023) were significantly associated with the presence of contamination obsessions and cleaning compulsions.

LIMITATIONS

Study limitations included the risk of population stratification associated with the case-control design, use of psychiatrically unscreened blood donors as the control group, reduced sample size of participants with certain OCD subphenotypes and tested polymorphisms limited to 3' UTR and exon 13 of GRIN2B.

CONCLUSION

Our results converge with recent data suggesting a possible contribution of glutamatergic variants to the genetic vulnerability to OCD or at least to certain OCD manifestations. The dissection of OCD into more homogeneous subphenotypes may constitute a useful tool to disentangle the complex genetic basis of the disorder.

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.

Ameliorative effect of BDNF on prenatal ethanol and stress exposure-induced behavioral disorders

Brain-derived neurotrophic factor (BDNF) plays critical role in neuronal development, function, survival and plasticity of mature neurons. The present experiments investigated whether BDNF ameliorates the damaging effect of prenatal ethanol and stress exposure on behavior in offspring. Prenatal exposure of ethanol and stress combined during gestation inverted sexual partner preference of male offspring, increased social contacts with juvenile male mouse and stereotypic burying activity in the marble-burying test suggesting predisposition to homosexuality and to obsessive-compulsive disorder. Centrally administered BDNF (300ng i.c.v.) restored sexual female preference of male adult offspring and decreased marble-burying activity. Ameliorative effect was shown in 7-10 days after BDNF administration. The results provide the first evidence that BDNF improves epigenetic impairment of behavior and may have profound implications in the treatment of neurologic disorders induced by early environmental challenges.

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.

Brain-derived neurotrophic factor in patients with Huntington's disease

Reduced Brain-Derived Neurotrophic Factor (BDNF) levels have been described in a number of patho-physiological conditions, most notably, in Huntington's disease (HD), a progressive neurodegenerative disorder. Since BDNF is also produced in blood, we have undertaken the measurement of its peripheral levels in the attempt to identify a possible link with HD prognosis and/or its progression. Here we evaluated BDNF level in 398 blood samples including 138 controls, 56 preHD, and 204 HD subjects. We found that BDNF protein levels were not reliably different between groups, whether measured in plasma (52 controls, 26 preHD, 105 HD) or serum (39 controls, 5 preHD, 29 HD). Our experience, and a re-analysis of the literature highlighted that intra-group variability and methodological aspects affect this measurement, especially in serum. We also assessed BDNF mRNA levels in blood samples from 47 controls, 25 preHD, and 70 HD subjects, and found no differences among the groups. We concluded that levels of BDNF in human blood were not informative (mRNA levels or plasma protein level) nor reliable (serum protein levels) as HD biomarkers. We also wish to warn the scientific community in interpreting the significance of changes measured in BDNF protein levels in serum from patients suffering from different conditions.

Consideration of the BDNF gene in relation to two phenotypes: hoarding and obesity

The gene coding for the brain derived neurotrophic factor (BDNF) has emerged as an interesting candidate for multiple brain and brain disorder-related phenomena. The primary aim of the present investigation was to consider the relationship between the BDNF Val66Met variant and two phenotypes: compulsive hoarding as a symptom dimension of obsessive-compulsive disorder (OCD), and body mass index (BMI). We examined the BDNF gene in a large (N=301) clinical sample of probands with OCD. Participants were classified as hoarding or nonhoarding using a strict, multimeasure grouping approach. Results revealed that the Val/Val genotype was linked with hoarding classification and more severe hoarding behaviors, as well as greater BMI levels. Hoarding status was also associated with greater BMI scores, with individuals in the hoarding group being far more likely to be classified as obese compared with the nonhoarding group. Our findings may provide a distinct avenue through which hoarding and BMI could be linked. These findings are suggestive of a complex gene, body weight, and psychopathology relationship wherein a primitive, survival "thrifty gene" strategy may be conserved and represented in a subgroup of humans manifesting severe hoarding symptoms.

Genetic association between BDNF gene polymorphisms and phobic disorders: a case-control study among mainland Han Chinese

INTRODUCTION

Phobic disorders are a common group of syndromes comprising persistently recurring, irrational severe anxiety of specific objects, activities, or situations with avoidance behavior of the phobic stimulus. The present study investigated the association between whole region polymorphisms, (including the Val66Met variant), in the BDNF gene and phobic disorders among Han Chinese young adults.

METHODS

We conducted a case-control study to investigate the genetic association between BDNF polymorphisms and phobic disorders among mainland Chinese. One hundred and twenty young adults with phobic disorders and 267 matched controls were recruited. Three tag SNPs of BDNF were successfully genotyped by using PCR-based ligase detection reaction (PCR-LDR).

RESULTS

We found significant differences in allele distributions of SNP rs10835210 (P<0.001) between the experimental and the control groups. In the haplotype analysis based on linkage-disequilibrium across this gene locus, we demonstrated significant association between phobic disorders and BDNF haplotype CAC (P=0.004). Association was significant after 10(4) permutation tests (P<0.001).

CONCLUSION

To the best of our knowledge, this is the first study showing that the BDNF gene may play a significant role in the etiology of phobic disorders in the Han Chinese population.

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.

Variants in estrogen receptor alpha gene are associated with phenotypical expression of obsessive-compulsive disorder

Compelling data from animal and clinical studies suggest that sex steroids may play a role in the etiopathology of obsessive-compulsive disorder (OCD). The aim of this study was to investigate whether variants in estrogen receptor genes ESR1 and ESR2 may contribute to the genetic susceptibility to OCD, through a case-control association study using an extensive linkage disequilibrium-mapping approach. Twenty tag single-nucleotide polymorphisms (tagSNPs) covering the ESR2 region and nine tagSNPS from regions of ESR1 reported to be related to transcriptional control were genotyped in 229 OCD patients and 279 controls. SNP association and haplotype analysis were performed. The association of these genes and OCD subphenotypes was tested, considering early-onset OCD, comorbid tic and affective disorders, and OCD symptom dimensions. No significant difference in the distribution of alleles or genotypes was detected between controls and OCD subjects. Nevertheless, on analyzing OCD subphenotypes, SNP rs34535804 in ESR1 and a five SNPs haplotype, located at the 5' end of intron 1 of ESR1, were associated with the presence of contamination obsessions and cleaning compulsions. Specifically, carriers of the ACCCG haplotype, a combination of functional alleles related to higher ER alpha expression, showed a reduced risk of suffering from these symptoms. Our results suggest that the ESR1 gene may contribute to the genetic vulnerability to certain OCD manifestations. The dissection of OCD into more homogeneous subphenotypes may well help to identify susceptibility genes for the disorder.