The Genetics of Obsessive-Compulsive Disorder

Glutamate dynamics and BOLD response during OCD symptom provocation in the lateral occipital cortex: A 7 Tesla fMRI-fMRS study

Obsessive-compulsive disorder (OCD) is linked with dysfunction in frontal-striatal, fronto-limbic, and visual brain regions. Research using proton magnetic resonance spectroscopy (1H-MRS) suggests that altered neurometabolite levels, like glutamate, may contribute to this dysfunction. However, static neurometabolite levels in OCD patients have shown inconsistent results, likely due to previous studies' limited focus on neurometabolite dynamics. We employ functional MRS (fMRS) and functional magnetic resonance imaging (fMRI) to explore these dynamics and brain activation during OCD symptom provocation. We utilized a combined 7-tesla fMRI-fMRS setup to examine task-related BOLD response and glutamate changes in the lateral occipital cortex (LOC) of 30 OCD participants and 34 matched controls during an OCD-specific symptom provocation task. The study examined main effects and between-group differences in brain activation and glutamate levels during the task. A whole sample task-effects analysis on data meeting predefined quality criteria showed significant glutamate increases (n = 41 (22 OCD, 19 controls), mean change: 3.2 %, z = 3.75, p < .001) and task activation (n = 54 (26 OCD, 28 controls), p < .001) in the LOC during OCD blocks compared to neutral blocks. However, no differences in task-induced glutamate dynamics or activation between groups were found, nor a correlation between glutamate levels and task activation. We were able to measure task-induced increases in glutamate and BOLD levels, emphasizing its feasibility for OCD research. The absence of group differences highlights the need for further exploration to discern to what extent neurometabolite dynamics differ between OCD patients and controls. Once established, future studies can use pre-post intervention fMRS-fMRI to probe the effects of therapies modulating glutamate pathways in OCD.

Disgust as a primary emotional system and its clinical relevance

This paper advocates for considering disgust as a primary emotional system within Panksepp's Affective Neuroscience framework, which has the potential to improve the efficacy of psychotherapy with obsessive-compulsive disorder, hypochondriasis, and emetophobia. In 2007, Toronchuk and Ellis provided comprehensive evidence that DISGUST system, as they defined it, matched all Panksepp's criteria for a primary emotional system. A debate ensued and was not unambiguously resolved. This paper is an attempt to resume this discussion and supplement it with the data that accumulated since then on DISGUST's relationship with the immune system and the role of DISGUST dysregulation in psychopathology. We hope that renewed research interest in DISGUST has the potential to improve clinical efficacy with hard-to-treat conditions.

Longitudinal changes in neurometabolite concentrations in the dorsal anterior cingulate cortex after concentrated exposure therapy for obsessive-compulsive disorder

BACKGROUND

The dorsal anterior cingulate cortex (dACC) plays an important role in the pathophysiology of obsessive-compulsive disorder (OCD) due to its role in error processing, cognitive control and emotion regulation. OCD patients have shown altered concentrations in neurometabolites in the dACC, particularly Glx (glutamate+glutamine) and tNAA (N-acetylaspartate+N-acetyl-aspartyl-glutamate). We investigated the immediate and prolonged effects of exposure and response prevention (ERP) on these neurometabolites.

METHODS

Glx and tNAA concentrations were measured using magnetic resonance spectroscopy (1H-MRS) in 24 OCD patients and 23 healthy controls at baseline. Patients received concentrated ERP over four days. A subset was re-scanned after one week and three months.

RESULTS

No Glx and tNAA abnormalities were observed in OCD patients compared to healthy controls before treatment or over time. Patients with childhood or adult onset differed in the change over time in tNAA (F(2,40) = 7.24, ɳ²_p= 0.27, p = 0.004): concentrations increased between one week after treatment and follow-up in the childhood onset group (t(39) = -2.43, d = -0.86, p = 0.020), whereas tNAA concentrations decreased between baseline and follow-up in patients with an adult onset (t(42) = 2.78, d = 1.07, p = 0.008). In OCD patients with versus without comorbid mood disorders, lower Glx concentrations were detected at baseline (t(38) = -2.28, d = -1.00, p = 0.028). Glx increased after one week of treatment within OCD patients with comorbid mood disorders (t(30) = -3.09, d = -1.21, p = 0.004).

LIMITATIONS

Our OCD sample size allowed the detection of moderate to large effect sizes only.

CONCLUSION

ERP induced changes in neurometabolites in OCD seem to be dependent on mood disorder comorbidity and disease stage rather than OCD itself.

5-Hydroxytryptophan as adjuvant therapy in treatment of moderate to severe obsessive-compulsive disorder: a double-blind randomized trial with placebo control

On the basis of numerous previous studies, the serotonergic system plays a role in the pathogenesis of obsessive-compulsive disorder (OCD) and effective agents in this pathway, such as 5-hydroxytryptophan, can potentially contribute to treatment of patients with this disorder. Evaluating the efficacy of 5-hydroxytryptophan in treating OCD was the aim of the present randomized, double-blind, placebo-controlled 12-week trial. In a 12-week, randomized double-blind study, 60 patients with a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition diagnosis of moderate to severe OCD and a Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score of >21 were randomly assigned to receive either fluoxetine plus placebo or fluoxetine plus 5-hydroxytryptophan (100 mg twice daily). All patients, regardless of their treatment group, received fluoxetine at 20 mg/day for the initial 4 weeks of the study followed by 60 mg/day of fluoxetine for the rest of the trial course. Symptoms were assessed using the Y-BOCS at baseline and weeks 4, 8 and 12. General linear model repeated measure showed significant effects for time × treatment interaction on total Y-BOCS (F = 12.07, df = 2.29, P-value <0.001), obsession (F = 8.25, df = 1.91, P-value = 0.001) and compulsion subscale scores (F = 6.64, df = 2.01, P-value = 0.002). 5-Hydroxytryptophan augmentation therapy demonstrated higher partial and complete treatment response rate (P = 0.032 and P = 0.001, respectively) according to the Y-BOCS total scores. The results of this study confirm that 5-hydroxytryptophan may be effective as an augmentative agent in treatment of moderate-to-severe 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.

Integrative analysis of shared genetic pathogenesis by obsessive‑compulsive and eating disorders

A number of common pathological features have been observed in obsessive‑compulsive disorder (OCD) and eating disorders (EDs). The present study examined the association between OCD and EDs at the genetic level in order to gain an improved understanding of the shared genetic basis of the diseases and identify novel potential risk genes for the two diseases. An integrated analysis using large‑scale disease‑gene association data and gene expression data was conducted. Disease‑gene association data were acquired from the Pathway Studio Mammalian database. Gene expression data were acquired from samples of 133 subjects, including 15 ED cases, 16 OCD cases and 102 normal controls. Genes associated with OCD and ED presented significant overlap (21 genes, P=6.70x10‑34), serving roles within multiple common genetic pathways (top 10 pathway enrichment P<4.30x10‑7) that were implicated in the two diseases. A genetic network of 17 genes was constructed, through which OCD and ED were observed to influence each other. Expression analysis revealed four novel common significant genes for OCD and ED (oxytocin receptor, glutamate decarboxylase 2, neuropeptide Y and glutamate ionotropic receptor kainate type subunit 3). These genes demonstrated a strong functional association with the two diseases. The results of the present study supported the presence of complex genetic associations between OCD and ED. Genes associated with one disease are worthy of further investigation as potential risk factors for the other. The findings of the present study may provide novel insights into the understanding of the pathogenesis of OCD and ED.

Cortico-striato-thalamo-cortical circuit abnormalities in obsessive-compulsive disorder: A voxel-based morphometric and fMRI study of the whole brain

The primary aim of this study was to identify structural and functional abnormalities in the brains of obsessive-compulsive disorder (OCD) patients. Another aim was to assess the effect of serotonin selective reuptake inhibitors (SSRIs) on brain structure of OCD patients. All subjects underwent brain magnetic resonance imaging (MRI) and resting functional MRI (fMRI). High-resolution three-dimensional images were processed using the voxel-based morphometry (VBM) method. The final analysis included 18 OCD patients and 16 healthy controls. In the OCD patients there was a decrease in gray matter volume in the bilateral cingulate cortex and bilateral striatum. In some cortical structures including the cerebellar anterior lobe, left orbital frontal gyrus, right middle frontal gyrus, left middle temporal gyrus, precentral gyrus, and postcentral gyrus, there was an increase in gray matter volume. On fMRI the OCD patients had overactivation of the right cerebellum and right parietal lobe and reduced activation of the left cingulate gyrus, putamen, and caudate nucleus. Eleven OCD patients who improved during 12 weeks of drug treatment with sertraline hydrochloride had a significant increase in gray matter volume in several brain structures but no significant differences were found on resting fMRI. The results indicated a consistent trend between structural and functional images. Higher cortical structures showed increased gray matter volume and increased activation as did the cerebellum whereas subcortical structures showed decreased gray matter volume and decreased activation. And brain structure improvement consisted with symptom improvement after SSRIs treatment in OCD patients.

ASSOCIATION STUDY BETWEEN OLIGODENDROCYTE TRANSCRIPTION FACTOR 2 GENE AND OBSESSIVE-COMPULSIVE DISORDER IN A CHINESE HAN POPULATION

BACKGROUND

Oligodendrocyte transcription factor 2 (OLIG2) is primarily concentrated in the brain and spinal cord ventricular zone, where this protein stimulates oligodendrocytes and specific neurons, determines motor neuron and oligodendrocyte differentiation, and sustains replication in early development. Recent studies have demonstrated that OLIG2 gene is associated with mental disorders, such as schizophrenia, mood disorder, and obsessive-compulsive disorder (OCD).

METHODS

The aim of the present study was to explore whether OLIG2 gene is associated with OCD in a Chinese Han population through the assessment and analysis of three single nucleotide polymorphisms (SNPs), namely, rs762178, rs1059004, and rs9653711, selected from OLIG2 gene sequences from 400 OCD samples and 459 healthy controls in a case-controlled association study.

RESULTS

We demonstrated three principal results. First, SNP rs762178 was associated with OCD, female OCD, and early-onset OCD; rs1059004 was associated with OCD and early-onset OCD; and rs9653711 was also associated with OCD and early-onset OCD. Second, the pairs of loci rs762178 and rs1059004, rs1059004 and rs9653711, and rs762178 and rs9653711 exhibited linkage disequilibrium. Third, the three-locus A-C-G haplotype was associated with early-onset OCD.

CONCLUSIONS

The present study is the first to verify the associations of SNPs rs762178, rs1059004, and rs9653711 of the OLIG2 gene with OCD in a Chinese Han population. Thus, OLIG2 might serve as a potential target for OCD treatment in future studies. Further studies should verify the current findings.

OCDB: a database collecting genes, miRNAs and drugs for obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a psychiatric condition characterized by intrusive and unwilling thoughts (obsessions) giving rise to anxiety. The patients feel obliged to perform a behavior (compulsions) induced by the obsessions. The World Health Organization ranks OCD as one of the 10 most disabling medical conditions. In the class of Anxiety Disorders, OCD is a pathology that shows an hereditary component. Consequently, an online resource collecting and integrating scientific discoveries and genetic evidence about OCD would be helpful to improve the current knowledge on this disorder. We have developed a manually curated database, OCD Database (OCDB), collecting the relations between candidate genes in OCD, microRNAs (miRNAs) involved in the pathophysiology of OCD and drugs used in its treatments. We have screened articles from PubMed and MEDLINE. For each gene, the bibliographic references with a brief description of the gene and the experimental conditions are shown. The database also lists the polymorphisms within genes and its chromosomal regions. OCDB data is enriched with both validated and predicted miRNA-target and drug-target information. The transcription factors regulations, which are also included, are taken from David and TransmiR. Moreover, a scoring function ranks the relevance of data in the OCDB context. The database is also integrated with the main online resources (PubMed, Entrez-gene, HGNC, dbSNP, DrugBank, miRBase, PubChem, Kegg, Disease-ontology and ChEBI). The web interface has been developed using phpMyAdmin and Bootstrap software. This allows (i) to browse data by category and (ii) to navigate in the database by searching genes, miRNAs, drugs, SNPs, regions, drug targets and articles. The data can be exported in textual format as well as the whole database in.sql or tabular format. OCDB is an essential resource to support genome-wide analysis, genetic and pharmacological studies. It also facilitates the evaluation of genetic data in OCD and the detection of alternative treatments.

Obsessions appear after the removal a brain tumor in the right frontal lobe

A series of case reports and neuroimaging research points to the underlying neuropathological substrate for obsessive-compulsive disorder (OCD) and the underlying associations between OCD and areas of the frontal lobe. We report a patient wherein the onset of OCD occurred after resection of meningioma of the right frontal lobe and who was treated successfully with paroxetine hydrochloride. We suggest that the onset of secondary (organic) OCD is associated with the frontal lobe, and we propose that the origin of obsessions is located in the right frontal lobe.

Glutamate abnormalities in obsessive compulsive disorder: neurobiology, pathophysiology, and treatment

Obsessive compulsive disorder is prevalent, disabling, incompletely understood, and often resistant to current therapies. Established treatments consist of specialized cognitive-behavioral psychotherapy and pharmacotherapy with medications targeting serotonergic and dopaminergic neurotransmission. However, remission is rare, and more than a quarter of OCD sufferers receive little or no benefit from these approaches, even when they are optimally delivered. New insights into the disorder, and new treatment strategies, are urgently needed. Recent evidence suggests that the ubiquitous excitatory neurotransmitter glutamate is dysregulated in OCD, and that this dysregulation may contribute to the pathophysiology of the disorder. Here we review the current state of this evidence, including neuroimaging studies, genetics, neurochemical investigations, and insights from animal models. Finally, we review recent findings from small clinical trials of glutamate-modulating medications in treatment-refractory OCD. The precise role of glutamate dysregulation in OCD remains unclear, and we lack blinded, well-controlled studies demonstrating therapeutic benefit from glutamate-modulating agents. Nevertheless, the evidence supporting some important perturbation of glutamate in the disorder is increasingly strong. This new perspective on the pathophysiology of OCD, which complements the older focus on monoaminergic neurotransmission, constitutes an important focus of current research and a promising area for the ongoing development of new therapeutics.