Association study between genetic monoaminergic polymorphisms and OCD response to clomipramine treatment

Mechanisms of pathogenesis and environmental moderators in preclinical models of compulsive-like behaviours

Obsessive-compulsive and related disorders (OCRD) is an emergent class of psychiatric illnesses that contributes substantially to the global mental health disease burden. In particular, the prototypical illness, obsessive-compulsive disorder (OCD), has a profoundly deleterious effect on the quality of life of those with lived experience. Both clinical and preclinical studies have investigated the genetic and environmental influences contributing to the pathogenesis of obsessive-compulsive and related disorders. Significant progress has been made in recent years in our understanding of the genetics of OCD, along with the critical role of common environmental triggers (e.g., stress). Some of this progress can be attributed to the sophistication of rodent models used in the field, particularly genetic mutant models, which demonstrate promising construct, face, and predictive validity. However, there is a paucity of studies investigating how these genetic and environmental influences interact to precipitate the behavioural, cellular, and molecular changes that occur in OCD. In this review, we assert that preclinical studies offer a unique opportunity to carefully manipulate environmental and genetic factors, and in turn to interrogate gene-environment interactions and relevant downstream sequelae. Such studies may serve to provide a mechanistic framework to build our understanding of the pathogenesis of complex neuropsychiatric disorders such as OCD. Furthermore, understanding gene-environment interactions and pathogenic mechanisms will facilitate precision medicine and other future approaches to enhance treatment, reduce side-effects of therapeutic interventions, and improve the lives of those suffering from these devastating disorders.

Serotonin Transporter Genetic Variation and Antidepressant Response and Tolerability: A Systematic Review and Meta-Analysis

Antidepressants are used to treat several psychiatric disorders; however, a large proportion of patients do not respond to their first antidepressant therapy and often experience adverse drug reactions (ADR). A common insertion–deletion polymorphism in the promoter region (5-HTTLPR) of the serotonin transporter (SLC6A4) gene has been frequently investigated for its association with antidepressant outcomes. Here, we performed a systematic review and meta-analysis to assess 5-HTTLPR associations with antidepressants: (1) response in psychiatric disorders other than major depressive disorder (MDD) and (2) tolerability across all psychiatric disorders. Literature searches were performed up to January 2021, yielding 82 studies that met inclusion criteria, and 16 of these studies were included in the meta-analyses. Carriers of the 5-HTTLPR LL or LS genotypes were more likely to respond to antidepressant therapy, compared to the SS carriers in the total and European ancestry-only study populations. Long (L) allele carriers taking selective serotonin reuptake inhibitors (SSRIs) reported fewer ADRs relative to short/short (SS) carriers. European L carriers taking SSRIs had lower ADR rates than S carriers. These results suggest the 5-HTTLPR polymorphism may serve as a marker for antidepressant outcomes in psychiatric disorders and may be particularly relevant to SSRI treatment among individuals of European descent.

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.

Pharmacogenetics of Obsessive-Compulsive Disorder: An Evidence-Update

Pharmacogenetics has become increasingly important in the treatment of psychiatric disorders because approximately 50% of individuals who take psychotropic medications do not typically respond to them. Obsessive-compulsive disorder (OCD) is one such chronic and often debilitating mental illness with significant non-response to even the first-line medication, serotonin reuptake inhibitors. Precision medicine utilizing genetic testing panels has received significant attention based on the evidence that the variability of antidepressant response and adverse effects is partly due to the variability in an individual's genome. Thus, extensive research has investigated the role of genetic factors on antidepressant response in major depressive disorder (MDD) and their utility for guiding antidepressant treatment to significantly improving outcomes in individuals with MDD. However, limited progress remains in the pharmacogenetics of OCD. This chapter will provide an overview of the recent findings in the pharmacogenetics of OCD. Promising results with limited replications have been reported for the cytochrome P450 liver metabolism genes in addition to several serotonergic and glutamatergic system genes, which may play an important role in antidepressant response in the treatment of OCD.

Pharmacogenetics of anxiety disorders

Anxiety disorders are common and disabling conditions the treatment of which remains a challenge. While different groups of medication are available for their treatment, a substantial proportion of patients remain refractory to pharmacotherapy. The reason for this variation in the individual response to treatment has yet to be understood; however genetic factors have been shown to play an important role. Up to now there have been limited publications about pharmacogenetics of anxiety disorders, compared to studies in depression. Published studies are focused on pharmacogenetics of antidepressants rather than being disease specific. This review summarizes pharmacogenetic findings related to the anxiolytic treatment response and their possible functional mechanisms. This inevitably focuses on genes involved in the pharmacodynamics of the medications used, along with some genes implicated in the disease process, as well as briefly mentioning genetic factors associated with psychotherapeutic response.

Association of serotonin receptor 2a haplotypes with obsessive-compulsive disorder and its treatment response in Iranian patients: a genetic and pharmacogenetic study

INTRODUCTION

Obsessive-compulsive disorder (OCD) is a debilitating psychiatric disorder causing intrusive thoughts or repetitive behaviors. Serotonin reuptake inhibitors are used for OCD treatment, but 40%-60% of patients do not respond to them adequately. In this study, the associations of serotonin receptor 2a polymorphisms rs6311 and rs6313 with OCD, its familial form and fluvoxamine treatment response in Iranian population were investigated.

PATIENTS AND METHODS

Association analyses were conducted in 293 OCD cases fulfilling the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV-TR and 245 controls. Pharmacotherapy was defined as 12 weeks of treatment with fluvoxamine (150-300 mg). Treatment response was considered as >25% reduction in Yale-Brown Obsessive Compulsive Scale score. Genotyping was performed by means of PCR-RFLP.

RESULTS

The results showed no association of rs6311 or rs6313 with OCD, but their haplotypes had different distribution patterns in cases and controls. Moreover, rs6313 was associated with the familial form of OCD in females significantly (P=0.005) under the recessive genetic model. Moreover, rs6311-rs6313 haplotypes were associated with fluvoxamine treatment response in OCD patients with more AC and less AT in responders.

CONCLUSION

HTR2A haplotypes are associated with OCD and its treatment response with a fluvoxamine in Iranian patients. Furthermore, the observed association of rs6313 with the familial form of OCD in females suggests different genetic background of OCD familial and non-familial forms, which needs further investigation.

A review of the role of serotonin system genes in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a debilitating neuropsychiatric disorder that causes the patient to experience intrusive thoughts and/or to carry out repetitive, ritualized behaviors that are time consuming and impairing. OCD is familial and heritable. The genetic factors responsible for pathogenesis, however, remain largely unknown despite the numerous candidate gene studies conducted. Based on efficacy of serotonin reuptake inhibitors (SRIs) in treating OCD, serotonin system genes have been a dominant focus in OCD candidate gene studies. We review the most commonly studied candidate serotonin system gene variants (specifically in SLC6A4, HTR2A, HTR1B, and HTR2C) and their association with OCD. Although findings to date are mixed, serotonin transporter polymorphism 5-HTTLPR and HTR2A polymorphism rs6311 (or rs6313) are most consistently associated with OCD. Mixed findings may be the result of genetic complexity and phenotypic heterogeneity that future studies should account for. Homogenous patient subgroups reflecting OCD symptom dimensions, OCD subtypes, and sex should be used for gene discovery.

No association between the COMT Val158Met polymorphism and the long-term clinical response in obsessive-compulsive disorder in the Japanese population

OBJECTIVE

Catechol-O-methyltransferase (COMT) is an enzyme that participates in the metabolic inactivation of dopamine and norepinephrine, and the Met allele of the COMT Val158Met polymorphism is associated with lower enzymatic activity. The purpose of the present study was to investigate whether this functional variant is associated with obsessive-compulsive disorder (OCD) and the clinical responses in OCD.

METHODS

We first performed a case-control association study between the COMT Val158Met polymorphism and OCD (171 cases and 944 controls). Then, we examined the association between this polymorphism and the clinical responses in 91 of the OCD patients.

RESULTS

Our study did not find a significant association between the Met allele and OCD risk or between the Met allele and clinical responses (p > 0.05).

CONCLUSION

The present case-control/pharmacogenetic study did not provide clear evidence that the COMT Val158Met polymorphism is a predictor of OCD or of OCD patients' clinical responses.

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.

Endophenotypes and serotonergic polymorphisms associated with treatment response in obsessive-compulsive disorder

OBJECTIVES

Approximately 40-60% of obsessive-compulsive disorder patients are nonresponsive to serotonin reuptake inhibitors. Genetic markers associated with treatment response remain largely unknown. We aimed (1) to investigate a possible association of serotonergic polymorphisms in obsessive-compulsive disorder patients and therapeutic response to selective serotonin reuptake inhibitors and (2) to examine the relationship between these polymorphisms and endocrine response to intravenous citalopram challenge in responders and non-responders to serotonin reuptake inhibitors and in healthy volunteers.

METHODS

Patients with obsessive-compulsive disorder were classified as either responders or non-responders after long-term treatment with serotonin reuptake inhibitors, and both groups were compared with a control group of healthy volunteers. The investigated genetic markers were the G861C polymorphism of the serotonin receptor 1Dβ gene and the T102C and C516T polymorphisms of the serotonin receptor subtype 2A gene.

RESULTS

The T allele of the serotonin receptor subtype 2A T102C polymorphism was more frequent among obsessive-compulsive disorder patients (responders and non-responders) than in the controls (p<0.01). The CC genotype of the serotonin receptor subtype 2A C516T polymorphism was more frequent among the non-responders than in the responders (p<0.01). The CC genotype of the serotonin receptor subtype 1Dβ G681C polymorphism was associated with higher cortisol and prolactin responses to citalopram (p<0.01 and p<0.001, respectively) and with a higher platelet-rich plasma serotonin concentration among the controls (p<0.05). However, this pattern was not observed in the non-responders with the same CC genotype after chronic treatment with serotonin reuptake inhibitors. This CC homozygosity was not observed in the responders.