Association between genetic variants related to glutamatergic, dopaminergic and neurodevelopment pathways and white matter microstructure in child and adolescent patients with obsessive-compulsive disorder

Genetic and molecular correlates of cortical thickness alterations in adults with obsessive-compulsive disorder: a transcription-neuroimaging association analysis

BACKGROUND

Although numerous neuroimaging studies have depicted neural alterations in individuals with obsessive-compulsive disorder (OCD), a psychiatric disorder characterized by intrusive cognitions and repetitive behaviors, the molecular mechanisms connecting brain structural changes and gene expression remain poorly understood.

METHODS

This study combined the Allen Human Brain Atlas dataset with neuroimaging data from the Meta-Analysis (ENIGMA) consortium and independent cohorts. Later, partial least squares regression and enrichment analysis were performed to probe the correlation between transcription and cortical thickness variation among adults with OCD.

RESULTS

The cortical map of case-control differences in cortical thickness was spatially correlated with cortical expression of a weighted combination of genes enriched for neurobiologically relevant ontology terms preferentially expressed across different cell types and cortical layers. These genes were specifically expressed in brain tissue, spanning all cortical developmental stages. Protein-protein interaction analysis revealed that these genes coded a network of proteins encompassing various highly interactive hubs.

CONCLUSIONS

The study findings bridge the gap between neural structure and transcriptome data in OCD, fostering an integrative understanding of the potential biological mechanisms.

Shared molecular mechanisms and transdiagnostic potential of neurodevelopmental disorders and immune disorders

The co-occurrence and familial clustering of neurodevelopmental disorders and immune disorders suggest shared genetic risk factors. Based on genome-wide association summary statistics from five neurodevelopmental disorders and four immune disorders, we conducted genome-wide, local genetic correlation and polygenic overlap analysis. We further performed a cross-trait GWAS meta-analysis. Pleotropic loci shared between the two categories of diseases were mapped to candidate genes using multiple algorithms and approaches. Significant genetic correlations were observed between neurodevelopmental disorders and immune disorders, including both positive and negative correlations. Neurodevelopmental disorders exhibited higher polygenicity compared to immune disorders. Around 50%-90% of genetic variants of the immune disorders were shared with neurodevelopmental disorders. The cross-trait meta-analysis revealed 154 genome-wide significant loci, including 8 novel pleiotropic loci. Significant associations were observed for 30 loci with both types of diseases. Pathway analysis on the candidate genes at these loci revealed common pathways shared by the two types of diseases, including neural signaling, inflammatory response, and PI3K-Akt signaling pathway. In addition, 26 of the 30 lead SNPs were associated with blood cell traits. Neurodevelopmental disorders exhibit complex polygenic architecture, with a subset of individuals being at a heightened genetic risk for both neurodevelopmental and immune disorders. The identification of pleiotropic loci has important implications for exploring opportunities for drug repurposing, enabling more accurate patient stratification, and advancing genomics-informed precision in the medical field of neurodevelopmental disorders.

Morphogenetic theory of mental and cognitive disorders: the role of neurotrophic and guidance molecules

Mental illness and cognitive disorders represent a serious problem for the modern society. Many studies indicate that mental disorders are polygenic and that impaired brain development may lay the ground for their manifestation. Neural tissue development is a complex and multistage process that involves a large number of distant and contact molecules. In this review, we have considered the key steps of brain morphogenesis, and the major molecule families involved in these process. The review provides many indications of the important contribution of the brain development process and correct functioning of certain genes to human mental health. To our knowledge, this comprehensive review is one of the first in this field. We suppose that this review may be useful to novice researchers and clinicians wishing to navigate the field.

Cerebellar Microstructural Abnormalities in Obsessive-Compulsive Disorder (OCD): a Systematic Review of Diffusion Tensor Imaging Studies

Previous neuroimaging studies have suggested that obsessive-compulsive disorder (OCD) is associated with altered resting-state functional connectivity of the cerebellum. In this study, we aimed to describe the most significant and reproducible microstructural abnormalities and cerebellar changes associated with obsessive-compulsive disorder (OCD) using diffusion tensor imaging (DTI) investigations. PubMed and EMBASE were searched for relevant studies using the PRISMA 2020 protocol. A total of 17 publications were chosen for data synthesis after screening titles and abstracts, full-text examination, and executing the inclusion criteria. The patterns of cerebellar white matter (WM) integrity loss, determined by fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) metrics, varied across studies and symptoms. Changes in fractional anisotropy (FA) values were described in six publications, which were decreased in four and increased in two studies. An increase in diffusivity parameters of the cerebellum (i.e., MD, RD, and AD) in OCD patients was reported in four studies. Alterations of the cerebellar connectivity with other brain areas were also detected in three studies. Heterogenous results were found in studies that investigated cerebellar microstructural abnormalities in correlation with symptom dimension or severity. OCD's complex phenomenology may be characterized by changes in cerebellar WM connectivity across wide networks, as shown by DTI studies on OCD patients in both children and adults. Classification features in machine learning and clinical tools for diagnosing OCD and determining the prognosis of the disorder might both benefit from using cerebellar DTI data.

Microbial Reprogramming in Obsessive-Compulsive Disorders: A Review of Gut-Brain Communication and Emerging Evidence

Obsessive-compulsive disorder (OCD) is a debilitating mental health disorder characterized by intrusive thoughts (obsessions) and repetitive behaviors (compulsions). Dysbiosis, an imbalance in the gut microbial composition, has been associated with various health conditions, including mental health disorders, autism, and inflammatory diseases. While the exact mechanisms underlying OCD remain unclear, this review presents a growing body of evidence suggesting a potential link between dysbiosis and the multifaceted etiology of OCD, interacting with genetic, neurobiological, immunological, and environmental factors. This review highlights the emerging evidence implicating the gut microbiota in the pathophysiology of OCD and its potential as a target for novel therapeutic approaches. We propose a model that positions dysbiosis as the central unifying element in the neurochemical, immunological, genetic, and environmental factors leading to OCD. The potential and challenges of microbial reprogramming strategies, such as probiotics and fecal transplants in OCD therapeutics, are discussed. This review raises awareness of the importance of adopting a holistic approach that considers the interplay between the gut and the brain to develop interventions that account for the multifaceted nature of OCD and contribute to the advancement of more personalized approaches.

Neuronal glutamate transporters control reciprocal inhibition and gain modulation in D1 medium spiny neurons

Understanding the function of glutamate transporters has broad implications for explaining how neurons integrate information and relay it through complex neuronal circuits. Most of what is currently known about glutamate transporters, specifically their ability to maintain glutamate homeostasis and limit glutamate diffusion away from the synaptic cleft, is based on studies of glial glutamate transporters. By contrast, little is known about the functional implications of neuronal glutamate transporters. The neuronal glutamate transporter EAAC1 is widely expressed throughout the brain, particularly in the striatum, the primary input nucleus of the basal ganglia, a region implicated with movement execution and reward. Here, we show that EAAC1 limits synaptic excitation onto a population of striatal medium spiny neurons identified for their expression of D1 dopamine receptors (D1-MSNs). In these cells, EAAC1 also contributes to strengthen lateral inhibition from other D1-MSNs. Together, these effects contribute to reduce the gain of the input-output relationship and increase the offset at increasing levels of synaptic inhibition in D1-MSNs. By reducing the sensitivity and dynamic range of action potential firing in D1-MSNs, EAAC1 limits the propensity of mice to rapidly switch between behaviors associated with different reward probabilities. Together, these findings shed light on some important molecular and cellular mechanisms implicated with behavior flexibility in mice.

HUMAN STUDY COMT and DRD3 haplotype-associated pain intensity and acute care utilization in adult sickle cell disease

A previous exploratory analysis of a COMT gene single-nucleotide polymorphism (SNP) and a DRD3 SNP by our group suggested possible contributions to pain-related acute care utilization in people with sickle cell disease (SCD). Our aim was to extend the analysis to gene-spanning haplotypes of COMT SNPs and DRD3 SNPs to investigate possible associations with pain intensity and pain-related acute care utilization in an SCD cohort. Genotyping was conducted, and clinical data were collected, including self-reported pain intensity using PAINReportIt^® (average of current pain and least and worst in past 24 hours, average pain intensity [API]) and medical record-extracted, pain-related acute care utilization data of 130 adults with SCD. Haplotype blocks were identified based on linkage disequilibria (COMT = 7 haploblocks; DRD3 = 8 haploblocks). Regression analyses were tested for association between haplotypes and API and utilization, yielding several significant findings. For COMT block 1 (rs2075507, rs4646310, rs737865), the A-G-G haplotype was associated with higher API compared to the reference A-G-A (p = 0.02), whereas the A-A-A haplotype was associated with higher utilization (p = 0.02). For DRD3 block 2 (rs9817063, rs2134655, rs963468, and rs3773679), relative to reference T-C-G-C, the T-T-G-C haplotype was associated with higher utilization (p = 0.01). For DRD3 block 4 (rs167770, rs324029, and rs324023), the A-G-T haplotype was associated with higher API (p = 0.04) and utilization (p < 0.001) relative to reference G-A-T, whereas the A-A-T haplotype was associated with higher utilization (p = 0.01). We found COMT and DRD3 haplotypes associated with pain-related SCD features, suggesting that in future studies more emphasis be placed on cis effects of SNP alleles in evaluating genetic contributions to SCD pain and acute care utilization for pain.

Increased serum brain-derived neurotrophic factor and adrenocorticotropic hormone levels are associated with obsessive compulsive disorder in medication‑free children

This study aimed to investigate serum levels of neurotrophins, including brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), nerve growth factor (NGF) and neurotrophin-3 (NTF3), and hypothalamic-pituitary-adrenal axis (HPA) members including adrenocorticotropic hormone (ACTH) and cortisol in children with obsessive-compulsive disorder (OCD). The possible relationships between serum neurotrophins and HPA axis members were also addressed. A total of 60 medication-free children with OCD and 57 controls aged 8-18 years were enrolled in this study. The severity of OCD symptoms was determined by the Children's Yale-Brown Obsessive Compulsive Scale. The severity of anxiety and depression symptoms were assessed by self-report inventories. The serum levels of neurotrophins, ACTH, and cortisol were measured using enzyme-linked immunosorbent assay kits. Serum BDNF levels were significantly higher in the OCD group than in the control group for either sex and for the whole sample. Compared to controls, serum ACTH levels were significantly higher in the OCD group for the whole sample. An analysis of covariance was also conducted for the whole sample and indicated that, while controlling the potential confounders, including body-mass index percentile, age, sex, and the severity of depression and anxiety, the results did not change. Strong negative correlations between BDNF, NGF and NTF3, and HPA axis members were determined in the patient group for either sex and for the whole sample. These findings suggest that dysregulations of BDNF and ACTH may be associated with childhood OCD. Furthermore, there may be inverse relationships between certain neurotrophins and HPA axis members in these patients.

Changes in the stool and oropharyngeal microbiome in obsessive-compulsive disorder

Although the etiology of obsessive–compulsive disorder (OCD) is largely unknown, it is accepted that OCD is a complex disorder. There is a known bi-directional interaction between the gut microbiome and brain activity. Several authors have reported associations between changes in gut microbiota and neuropsychiatric disorders, including depression or autism. Furthermore, a pediatric-onset neuropsychiatric OCD-related syndrome occurs after streptococcal infection, which might indicate that exposure to certain microbes could be involved in OCD susceptibility. However, only one study has investigated the microbiome of OCD patients to date. We performed 16S ribosomal RNA gene-based metagenomic sequencing to analyze the stool and oropharyngeal microbiome composition of 32 OCD cases and 32 age and gender matched controls. We estimated different α- and β-diversity measures and performed LEfSe and Wilcoxon tests to assess differences in bacterial distribution. OCD stool samples showed a trend towards lower bacterial α-diversity, as well as an increase of the relative abundance of Rikenellaceae, particularly of the genus Alistipes, and lower relative abundance of Prevotellaceae, and two genera within the Lachnospiraceae: Agathobacer and Coprococcus. However, we did not observe a different Bacteroidetes to Firmicutes ratio between OCD cases and controls. Analysis of the oropharyngeal microbiome composition showed a lower Fusobacteria to Actinobacteria ratio in OCD cases. In conclusion, we observed an imbalance in the gut and oropharyngeal microbiomes of OCD cases, including, in stool, an increase of bacteria from the Rikenellaceae family, associated with gut inflammation, and a decrease of bacteria from the Coprococcus genus, associated with DOPAC synthesis.

Association of CDH11 with Autism Spectrum Disorder Revealed by Matched-gene Co-expression Analysis and Mouse Behavioral Studies

A large number of putative risk genes for autism spectrum disorder (ASD) have been reported. The functions of most of these susceptibility genes in developing brains remain unknown, and causal relationships between their variation and autism traits have not been established. The aim of this study was to predict putative risk genes at the whole-genome level based on the analysis of gene co-expression with a group of high-confidence ASD risk genes (hcASDs). The results showed that three gene features - gene size, mRNA abundance, and guanine-cytosine content - affect the genome-wide co-expression profiles of hcASDs. To circumvent the interference of these features in gene co-expression analysis, we developed a method to determine whether a gene is significantly co-expressed with hcASDs by statistically comparing the co-expression profile of this gene with hcASDs to that of this gene with permuted gene sets of feature-matched genes. This method is referred to as "matched-gene co-expression analysis" (MGCA). With MGCA, we demonstrated the convergence in developmental expression profiles of hcASDs and improved the efficacy of risk gene prediction. The results of analysis of two recently-reported ASD candidate genes, CDH11 and CDH9, suggested the involvement of CDH11, but not CDH9, in ASD. Consistent with this prediction, behavioral studies showed that Cdh11-null mice, but not Cdh9-null mice, have multiple autism-like behavioral alterations. This study highlights the power of MGCA in revealing ASD-associated genes and the potential role of CDH11 in ASD.

Microstructural white matter abnormalities in pediatric and adult obsessive-compulsive disorder: A systematic review and meta-analysis

OBJECTIVE

To identify the most prominent and replicable fractional anisotropy (FA) alterations of white matter associated with obsessive-compulsive disorder (OCD) in tract-based spatial statistics (TBSS) studies.

METHODS

We reviewed previous TBSS studies (n = 20) in OCD and performed a meta-analysis (n = 16) of FA differences.

RESULTS

No between-group differences in FA were detected in the pooled meta-analysis. However, reduced FA was identified in the genu and anterior body of corpus callosum (CC) in adult OCD. FA reductions in the anterior body of CC were associated with a later age of onset in adult patients with OCD. For pediatric OCD, decreased FA in earlier adolescence and increased FA in later adolescence were seemingly related to an altered trajectory of brain maturation.

CONCLUSIONS

Absent in the pooled sample but robust in adults, disrupted microstructural organization in the anterior part of CC indicates a bias of deficits toward connections in interhemispheric connections of rostral neocortical regions, which could lead to deficits of interhemispheric communication and thus contribute to cognitive and emotional deficits in adult OCD. The correlation between FA in the anterior body of CC and older illness onset suggests that patients with later adult onset of illness may represent a biologically distinct subgroup. For pediatric OCD, alterations in neurodevelopmental maturation may contribute to inconsistent patterns of FA alteration relative to controls during adolescence. While most studies of OCD have emphasized alterations of within hemisphere fronto-striatal circuits, these results indicate that between hemisphere connectivity of this circuitry may also represent important pathophysiology of the illness.

White matter microstructure and connectivity in patients with obsessive-compulsive disorder and their unaffected siblings

OBJECTIVE

We aimed to examine white matter microstructure and connectivity in individuals with obsessive-compulsive disorder (OCD) and their unaffected siblings, relative to healthy controls.

METHODS

Diffusion-weighted magnetic resonance imaging (dMRI) scans were acquired in 30 patients with OCD, 21 unaffected siblings, and 31 controls. We examined white matter microstructure using measures of fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). Structural networks were examined using network-based statistic (NBS).

RESULTS

Compared to controls, OCD patients showed significantly reduced FA and increased RD in clusters traversing the left forceps minor, inferior fronto-occipital fasciculus, anterior thalamic radiation, and cingulum. Furthermore, the OCD group displayed significantly weaker connectivity (quantified by the streamline count) compared to controls in the right hemisphere, most notably in edges connecting subcortical structures to temporo-occipital cortical regions. The sibling group showed intermediate streamline counts, FA and RD values between OCD and healthy control groups in connections found to be abnormal in patients with OCD. However, these reductions did not significantly differ compared to controls.

CONCLUSION

Therefore, siblings of OCD patients display intermediate levels in dMRI measures of microstructure and connectivity, suggesting white matter abnormalities might be related to the familial predisposition for OCD.

Psychopharmacological Treatment of Obsessive-Compulsive Disorder (OCD)

Background:

Obsessive-compulsive disorder (OCD) is associated with affective and cognitive symptoms causing personal distress and reduced global functioning. These have considerable societal costs due to healthcare service utilization.

Objective:

Our aim was to assess the efficacy of pharmacological interventions in OCD and clinical guidelines, providing a comprehensive overview of this field.

Methods:

We searched the PubMed database for papers dealing with drug treatment of OCD, with a specific focus on clinical guidelines, treatments with antidepressants, antipsychotics, mood stabilizers, off-label medications, and pharmacogenomics.

Results:

Prolonged administration of selective serotonin reuptake inhibitors (SSRIs) is most effective. Better results can be obtained with a SSRI combined with cognitive behavioral therapy (CBT) or the similarly oriented exposure and response prevention (ERP). Refractory OCD could be treated with different strategies, including a switch to another SSRI or clomipramine, or augmentation with an atypical antipsychotic. The addition of medications other than antipsychotics or intravenous antidepressant administration needs further investigation, as the evidence is inconsistent. Pharmacogenomics and personalization of therapy could reduce treatment resistance.

Conclusions:

SSRI/clomipramine in combination with CBT/ERP is associated with the optimal response compared to each treatment alone or to other treatments. New strategies for refractory OCD are needed. The role of pharmacogenomics could become preponderant in the coming years.

The Neuronal Glutamate Transporter EAAT3 in Obsessive-Compulsive Disorder

Obsessive compulsive disorder (OCD) is a heterogeneous psychiatric disorder affecting 1%–3% of the population worldwide. About half of OCD afflicted individuals do not respond to currently available pharmacotherapy, which is mainly based on serotonin reuptake inhibition. Therefore, there is a critical need to search novel and improved therapeutic targets to treat this devastating disorder. In recent years, accumulating evidence has supported the glutamatergic hypothesis of OCD, and particularly pointing a potential role for the neuronal glutamate transporter EAAT3. This mini-review summarizes recent findings regarding the neurobiological basis of OCD, with an emphasis on the glutamatergic neurotransmission and EAAT3 as a key player in OCD etiology.

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.

Gene variations in PBX1, LMX1A and SLITRK1 are associated with obsessive-compulsive disorder and its clinical features

Genetic factors probably influence OCD development and a current hypothesis proposes that genes involved in the development of the central nervous system (CNS) are related to OCD. The aim of this study was to analyze six Single Nucleotide Polymorphisms (SNPs) in five genes with functions related to neurodevelopment in OCD. A total of 203 patient and 203 control samples were genotyped using the TaqMan® methodology. Statistically significant associations between OCD and PBX1 (rs2275558) in total sample (P = 0.002) and in males (P = 0.0003) were observed. Concerning symptom dimensions, the expression of neutralization showed a statistical significant association with LMX1A (rs4657411, P = 0.004) in total sample. We also observed significant association between LMX1A (rs4657411) and washing dimension in females (P = 0.01). Additionally, SLITRK1 (rs9593835) was significantly associated with checking dimension in male patients (P = 0.04). Our results indicate an important influence of neurodevelopment genes in the OCD susceptibility. Additional studies with larger samples are needed to confirm these results.

Do polygenic risk and stressful life events predict pharmacological treatment response in obsessive compulsive disorder? A gene-environment interaction approach

The rate of response to pharmacological treatment in Obsessive-compulsive disorder (OCD) oscillates between 40 and 70%. Genetic and environmental factors have been associated with treatment response in OCD. This study analyzes the predictive ability of a polygenic risk score (PRS) built from OCD-risk variants, for treatment response in OCD, and the modulation role of stressful life events (SLEs) at the onset of the disorder. PRSs were calculated for a sample of 103 patients. Yale-Brown Obsessive Compulsive Scale (YBOCS) scores were obtained before and after a 12-week treatment. Regression analyses were performed to analyze the influence of the PRS and SLEs at onset on treatment response. PRS did not predict treatment response. The best predictive model for post-treatment YBOCS (post YBOCS) included basal YBOCS and age. PRS appeared as a predictor for basal and post YBOCS. SLEs at onset were not a predictor for treatment response when included in the regression model. No evidence for PRS predictive ability for treatment response was found. The best predictor for treatment response was age, agreeing with previous literature specific for SRI treatment. Suggestions are made on the possible role of neuroplasticity as a mediator on this association. PRS significantly predicted OCD severity independent on pharmacological treatment. SLE at onset modulation role was not evidenced. Further research is needed to elucidate the genetic and environmental bases of treatment response in OCD.

Glutamate transporter gene polymorphisms and obsessive-compulsive disorder: A case-control association study

The etiology of obsessive-compulsive disorder (OCD) is largely unknown, but family, twin, neuroimaging, and pharmacological studies suggest that glutamatergic system plays a significant role on its underlying pathophysiology. We performed an association analysis of six Single Nucleotide Polymorphisms (SNPs) within SLC1A1 gene (rs12682807, rs2075627, rs3780412, rs301443, rs301430, rs301434) in a group of 199 patients and 200 healthy controls. Symptom profiles were evaluated using the Florida Obsessive-Compulsive Inventory (FOCI) and the Obsessive-Compulsive Inventory-Revised (OCI-R). SNPs were analyzed by Taqman® methodology (Thermo Fisher, Brazil). The genotype distributions were in Hardy-Weinberg equilibrium. The A-A-G (rs301434-rs3780412-rs301443) haplotype was twice as common in OCD as in controls (P = 0.02). We also found significant differences between male patients and controls for rs301443 in a dominant model (P = 0.04) and a protective effect of GG genotype of rs2072657 in women (P = 0.02). Regarding clinical characteristics, the G-A (rs301434-rs3780412) haplotype was almost twice more common in patients with vs. without hoarding (P = 0.04). Further analyses showed significant associations between hoarding and rs301434 (P = 0.04) and rs3780412 (P = 0.04) in women, both in a dominant model. A dominant effect was also observed on ordering dimension for rs301434 (P = 0.01, in women) and rs301443 (P = 0.04). Finally, the rs2072657 showed a recessive effect on neutralization (P = 0.04) and checking (P = 0.03, in men). These preliminary results demonstrated that the SLC1A1 may contribute to some extent the susceptibility to OCD and its symptoms. However, additional studies are still needed.

Genetics of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) has been seen to run in families and genetics help to understand its heritability. In this review, we summarize older studies which focused on establishing the familial nature of OCD, including its various dimensions of symptoms, and we focus on recent findings from studies using both the candidate gene approach and genome-wide association study (GWAS) approach. The family studies and twin studies establish the heritability of OCD. Candidate gene approaches have implicated genes in the serotonergic, glutamatergic, and dopaminergic pathways. GWAS has not produced significant results possibly due to the small sample size. Newer techniques such as gene expression studies in brain tissue, stem cell technology, and epigenetic studies may shed more light on the complex genetic basis of OCD.

Genetic and pharmacogenetic study of glutamate transporter (SLC1A1) in Iranian patients with obsessive-compulsive disorder

WHAT IS KNOWN AND OBJECTIVE

Obsessive-compulsive disorder (OCD) is a chronic neuropsychiatric disorder. Selective serotonin reuptake inhibitors (SSRIs) are the first line of medication for OCD treatment; however, 40%-60% of patients with OCD do not respond to SSRIs adequately. There are growing pieces of evidence which suggest a significant role for the glutamatergic system in the genesis of OCD and its consequent treatment. In the present study, we aimed to assess the association of SLC1A1 polymorphisms (rs301430, rs2228622 and rs3780413) with OCD and its clinical characteristics, as well as the importance of these SNPs in the response of OCD patients to SSRI pharmacotherapy.

METHODS

Sample study consisted of 243 OCD cases and 221 control subjects. Patients were treated 12 weeks with fluvoxamine (daily dose: 150-300 mg). Based on the reduction in obsessive and compulsive severity scores using Y-BOCS severity scale, patients were classified as responders, non-responders and refractory. A total of 239, 228 and 215 patients were genotyped for rs301430, rs2228622 and rs3780413, respectively, by the means of PCR-RFLP.

RESULTS AND DISCUSSION

No association was detected between SLC1A1 SNPs and OCD, except an association between the familial form of the disease in males with rs2228622 (P = 0.033). The results of pharmacogenetic studies revealed the associations of two SLC1A1 SNPs, rs2228622 (P = 0.031) and rs3780413 (P = 0.008), with treatment response.

WHAT IS NEW AND CONCLUSION

Results of the current study suggest a role for the glutamate transporter in OCD treatment response with SSRIs which should encourage researchers to further investigate the importance of glutamate transporter in OCD pharmacogenetics.

Gender differences in obsessive-compulsive disorder: Findings from a multicentric study from India

Obsessive-compulsive disorder (OCD) is phenotypically heterogeneous. Gender is an important factor mediating this heterogeneity. We examined gender differences in a large sample (n = 945) of OCD patients under a multi-centric study in India. Cross-sectional assessments were done on consecutive adult (>18 years) treatment-seeking patients with a DSM-5 diagnosis of OCD. Subjects were assessed on Structured Clinical Interview for DSM-5-Research Version for comorbid psychiatric illnesses, Yale Brown Obsessive Compulsive Scale for OCD phenomenology and symptom severity, Brown Assessment of Beliefs Scale for insight, Beck's Depression Inventory for severity of depressive symptoms, and the Obsessive Beliefs Questionnaire. On multivariate backward Wald logistic regression analysis, males (59.7%) had more years of education, had a higher rate of checking compulsions and comorbid substance use disorders. Women were more likely to be married, more commonly reported precipitating factors, had a higher rate of hoarding compulsions and comorbid agoraphobia. Findings from this large study validate gender as an important mediator of phenotypic heterogeneity in OCD. The mechanistic basis for these differences might involve complex interactions between biological, cultural and environmental factors.

Could dietary glutamate be contributing to the symptoms of obsessive-compulsive disorder?

A 50-year-old man who had suffered from daily obsessive-compulsive disorder (OCD) symptoms for 39 years, in addition to fibromyalgia and irritable bowel syndrome symptoms, was enrolled in a randomized double-blind placebo-controlled clinical trial to test the effects of a low-glutamate diet on fibromyalgia/irritable bowel syndrome symptoms. After 1 month on the low-glutamate diet all of his symptoms remitted, including his OCD, which had previously been nonresponsive to pharmacological treatment. This case study is limited by self-report of symptoms; however, glutamatergic neurotransmission appears to be dysregulated in OCD, suggesting biological plausibility for this observation. Future research is needed.

Involvement of polymorphisms of the nerve growth factor and its receptor encoding genes in the etiopathogenesis of ischemic stroke

Background

Despite the important role of the nerve growth factor in the survival and maintenance of neurons in ischemic stroke, data regarding the relationships between variations in the encoding gene and stroke are lacking. In the present study, we evaluated the association of the functional polymorphisms in NGF (rs6330) and NGFR (rs2072446 and rs734194) genes with ischemic stroke in an Armenian population.

Methods

In total, 370 unrelated individuals of Armenian nationality were enrolled in this study. Genomic DNA samples of patients and healthy controls were genotyped using polymerase chain reaction with sequence-specific primers.

Results

The results obtained indicate that the minor allele of rs6330 (P_corr = 2.4E-10) and rs2072446 (P_corr = 0.02) are significantly overrepresented in stroke group, while the minor allele of rs734194 (P_corr = 8.5E-10) was underrepresented in diseased subjects. Single nucleotide polymorphisms in NGF gene (rs6330) and NGFR gene (rs2072446 and rs734194) are associated with the disease. Furthermore, it was shown that the carriage of the NGF rs6330*T minor allele is associated with increased infarct volume and higher risk of recurrent stroke.

Conclusions

In conclusion, our findings suggest that the NGF rs6330*T and NGFR rs2072446*T minor alleles might be nominated as a risk factor for developing ischemic stroke and NGFR rs734194*G minor allele as a protective against this disease at least in Armenian population.

Neuroanatomic, epigenetic and genetic differences in monozygotic twins discordant for attention deficit hyperactivity disorder

The study of monozygotic twins discordant for attention deficit hyperactivity disorder can elucidate mechanisms that contribute to the disorder, which affects ~7% of children. First, using in vivo neuroanatomic imaging on 14 pairs of monozygotic twins (mean age 9.7, s.d. 1.9 years), we found that discordance for the disorder is mirrored by differing dimensions of deep brain structures (the striatum and cerebellum), but not the cerebral cortex. Next, using whole-blood DNA from the same twins, we found a significant enrichment of epigenetic differences in genes expressed in these 'discordant' brain structures. Specifically, there is differential methylation of probes lying in the shore and shelf and enhancer regions of striatal and cerebellar genes. Notably, gene sets pertaining to the cerebral cortex (which did not differ in volume between affected and unaffected twins) were not enriched by differentially methylated probes. Genotypic differences between the twin pairs-such as copy number and rare, single-nucleotide variants-did not contribute to phenotypic discordance. Pathway analyses of the genes implicated by the most differentially methylated probes implicated γ-aminobutyric acid (GABA), dopamine and serotonin neurotransmitter systems. The study illustrates how neuroimaging can help guide the search for epigenomic mechanisms in neurodevelopmental disorders.

Association between glutamate transporter gene polymorphisms and obsessive-compulsive disorder/trait empathy in a Korean population

Accumulating evidence suggests that the glutamatergic system plays a major role in the pathophysiology of obsessive compulsive disorder (OCD) and empathic processing. Particularly, genetic influence of glutamate transporter gene (SLC1A1) on OCD has been frequently replicated in previous studies, but several studies did not replicate the result. Therefore, we aimed to replicate the associations between the SLC1A1 and OCD in a Korean population. In addition, we investigated the influence of SLC1A1 on trait empathy, impairments in which are characteristic of OCD. Six single-nucleotide polymorphisms (SNP) of SLC1A1 were genotyped in 615 patients with OCD and 508 healthy controls. The interpersonal reactivity index (IRI)—which consists of four subscales (perspective taking, PT; fantasy seeking, FS; empathic concern, EC; personal distress, PD)—was assessed from 277 patients with OCD and 395 controls. There were no significant associations between OCD and SNPs or haplotypes of SLC1A1. Patients with OCD exhibited significantly lower PT and higher PD scores than controls. The C-T-G haplotype at rs301430-rs301434-rs3087879 of SLC1A1 was significantly associated with higher PD scores after adjusted for age, sex, and OCD status. Our results suggest that six common SNPs of SLC1A1 may not contribute to the development of OCD, but may contribute to certain aspect of trait empathy such as personal distress. However, insufficient sample size and limited number of SLC1A1 SNPs may have reduced the likelihood of detecting significant associations. Therefore, further studies with larger sample size and more tag SNPs of the SLC1A1 gene were warranted.

Dynamic interaction between fetal adversity and a genetic score reflecting dopamine function on developmental outcomes at 36 months

Background

Fetal adversity, evidenced by poor fetal growth for instance, is associated with increased risk for several diseases later in life. Classical cut-offs to characterize small (SGA) and large for gestational age (LGA) newborns are used to define long term vulnerability. We aimed at exploring the possible dynamism of different birth weight cut-offs in defining vulnerability in developmental outcomes (through the Bayley Scales of Infant and Toddler Development), using the example of a gene vs. fetal adversity interaction considering gene choices based on functional relevance to the studied outcome.

Methods

36-month-old children from an established prospective birth cohort (Maternal Adversity, Vulnerability, and Neurodevelopment) were classified according to birth weight ratio (BWR) (SGA ≤0.85, LGA >1.15, exploring a wide range of other cut-offs) and genotyped for polymorphisms associated with dopamine signaling (TaqIA-A1 allele, DRD2-141C Ins/Ins, DRD4 7-repeat, DAT1-10- repeat, Met/Met-COMT), composing a score based on the described function, in which hypofunctional variants received lower scores.

Results

There were 251 children (123 girls and 128 boys). Using the classic cut-offs (0.85 and 1.15), there were no statistically significant interactions between the neonatal groups and the dopamine genetic score. However, when changing the cut-offs, it is possible to see ranges of BWR that could be associated with vulnerability to poorer development according to the variation in the dopamine function.

Conclusion

The classic birth weight cut-offs to define SGA and LGA newborns should be seen with caution, as depending on the outcome in question, the protocols for long-term follow up could be either too inclusive—therefore most costly, or unable to screen true vulnerabilities—and therefore ineffective to establish early interventions and primary prevention.

Induced Obsessive Compulsive Symptoms (OCS) in schizophrenia patients under Atypical 2 Antipsychotics (AAPs): review and hypotheses

The prevalence of OCS and OCD is higher in schizophrenic patients than in the general population. These disorders are sometimes induced by AAPs. There is higher frequency of OCS and greater severity in patients treated with antipsychotics with predominant anti-serotoninergic profiles opposed to those with predominant dopaminergic blockade. Induced OCS may be due to complex neuromodulation involving many serotonin, dopamine and glutamate receptors and several subtypes. Concerning connectivity, AAPs differentially influence the BOLD signal, depending on the intensity of D2 receptor blockade. The OFC could play a significant role, on account of its involvement in inhibitory control. There is a paradox: AAPs are efficient as augmentation to SSRI in treatment resistant OCD, some of them such as risperidone or aripiprazole have favourable effects in schizoptypic OCD, but AAPs cause induced OCS in schizophrenic patients. When prescribing AAPs, we should inform patients about this potential side effect and assess systematically OCS with Y-BOCS assessment after 1 month of treatment. Afterwards there are different strategies: Aripiprazole in combination can reduce OCS induced by clozapine, SSRI are slightly effective and CBT shows a few encouraging results. OCS are sometimes dose-dependent, so we also recommend prescribing the minimum effective dose and gradual introduction.

Can Neuroimaging Provide Reliable Biomarkers for Obsessive-Compulsive Disorder? A Narrative Review

In this integrative review, we discuss findings supporting the use neuroimaging biomarkers in the diagnosis and treatment of obsessive-compulsive disorder (OCD). To do so, we have selected the most recent studies that attempted to identify the underlying pathogenic process associated with OCD and whether they provide useful information to predict clinical features, natural history or treatment responses. Studies using functional magnetic resonance (fMRI), voxel-based morphometry (VBM), diffusion tensor imaging (DTI) and proton magnetic resonance spectroscopy (1H MRS) in OCD patients are generally supportive of an expanded version of the earlier cortico-striatal-thalamus-cortical (CSTC) model of OCD. Although it is still unclear whether this information will be incorporated into the daily clinical practice (due to current conceptual approaches to mental illness), statistical techniques, such as pattern recognition methods, appear promising in identifying OCD patients and predicting their outcomes.

The importance of the excitatory amino acid transporter 3 (EAAT3)

The neuronal excitatory amino acid transporter 3 (EAAT3) is fairly ubiquitously expressed in the brain, though it does not necessarily maintain the same function everywhere. It is important in maintaining low local concentrations of glutamate, where its predominant post-synaptic localization can buffer nearby glutamate receptors and modulate excitatory neurotransmission and synaptic plasticity. It is also the main neuronal cysteine uptake system acting as the rate-limiting factor for the synthesis of glutathione, a potent antioxidant, in EAAT3 expressing neurons, while on GABAergic neurons, it is important in supplying glutamate as a precursor for GABA synthesis. Several diseases implicate EAAT3, and modulation of this transporter could prove a useful therapeutic approach. Regulation of EAAT3 could be targeted at several points for functional modulation, including the level of transcription, trafficking and direct pharmacological modulation, and indeed, compounds and experimental treatments have been identified that regulate EAAT3 function at different stages, which together with observations of EAAT3 regulation in patients is giving us insight into the endogenous function of this transporter, as well as the consequences of altered function. This review summarizes work done on elucidating the role and regulation of EAAT3.

Integrating Genetic, Neuropsychological and Neuroimaging Data to Model Early-Onset Obsessive Compulsive Disorder Severity

We propose an integrative approach that combines structural magnetic resonance imaging data (MRI), diffusion tensor imaging data (DTI), neuropsychological data, and genetic data to predict early-onset obsessive compulsive disorder (OCD) severity. From a cohort of 87 patients, 56 with complete information were used in the present analysis. First, we performed a multivariate genetic association analysis of OCD severity with 266 genetic polymorphisms. This association analysis was used to select and prioritize the SNPs that would be included in the model. Second, we split the sample into a training set (N = 38) and a validation set (N = 18). Third, entropy-based measures of information gain were used for feature selection with the training subset. Fourth, the selected features were fed into two supervised methods of class prediction based on machine learning, using the leave-one-out procedure with the training set. Finally, the resulting model was validated with the validation set. Nine variables were used for the creation of the OCD severity predictor, including six genetic polymorphisms and three variables from the neuropsychological data. The developed model classified child and adolescent patients with OCD by disease severity with an accuracy of 0.90 in the testing set and 0.70 in the validation sample. Above its clinical applicability, the combination of particular neuropsychological, neuroimaging, and genetic characteristics could enhance our understanding of the neurobiological basis of the disorder.