The genetic studies of obsessive-compulsive disorder and its future directions

Catechol-O-methyltransferase gene Val158Met polymorphism and obsessive compulsive disorder susceptibility: a meta-analysis

Obsessive-compulsive disorder (OCD) is a common psychiatric disorder that affects approximately 1-3% of the general population. It is characterized by disabling obsessions (intrusive unwanted thoughts) and/or compulsions (ritualized repetitive behaviors). Catechol-O-methyltransferase (COMT) enzyme has an important role in inactivation of dopamine and higher dopamine levels may be implicated in OCD, hence COMT gene is a suitable candidate for OCD. Several case-control studies have evaluated the role of COMT Val 158Met (rs4680;472G- > A) polymorphism as a risk factor for OCD but the results remained inconclusive, hence present meta-analysis was designed to find out correct assessment. All studies that investigated the association of COMT gene Val158Met polymorphism with OCD risk, were considered in the present meta-analysis. Statistical analysis was performed with the software program MetaAnalyst. In the current meta-analysis, 14 case-control studies with 1435 OCD cases and 2753 healthy controls were included. The results indicated significant association between COMT Val158Met polymorphism and OCD risk using allele contrast, homozygote and dominant models (OR_{A vs G} = 1.14; 95% CI = 1.02-1.27; p = 0.01; OR_AAvs.GG = 1.33; 95% CI = 1.09-1.62, p = 0.004; OR_{AA + AGvs.GG} = 1.14; 95% CI = 1.0-1.32; p = 0.04). In subgroup analysis based on case gender, meta-analysis of male cases showed significant association using all five genetic models (OR_AAvsGG = 1.99; 95%CI = 1.42-2.59; p = <0.001; OR_{AA + AGvs.GG} = 1.59; 95% CI = 1.20-2.10; p = 0.001), but did not show any association between COMT Val 158Met polymorphism and OCD risk in females. In conclusion, results of present meta-analysis supports that the COMT Val158Met polymorphism is a risk factor for OCD especially for males.

Changes of motor cortical excitability and response inhibition in patients with obsessive–compulsive disorder

BACKGROUND

Deficits in cortical inhibitory processes have been suggested as underlying pathophysiological mechanisms of obsessive–compulsive disorder (OCD). We examined whether patients with OCD have altered cortical excitability using paired-pulse transcranial magnetic stimulation (TMS). We also tested associations between TMS indices and OCD-related characteristics, including age of onset and response inhibition in the go/no-go paradigm, to examine whether altered cortical excitability contributes to symptom formation and behavioural inhibition deficit in patients with OCD.

METHODS

We assessed motor cortex excitability using paired-pulse TMS in 51 patients with OCD and 39 age-matched healthy controls. We also assessed clinical symptoms and response inhibition in the go/nogo task. All patients were undergoing treatment with serotonin reuptake inhibitors. We performed repeated-measures multivariate analysis of covariance to compare TMS indices between patients with OCD and controls.

RESULTS

Compared to controls, patients with OCD showed a shorter cortical silent period and decreased intracortical facilitation. However, we found no significant difference between groups for resting motor threshold or short-interval intracortical inhibition. In the OCD group, the shortened cortical silent period was associated with a prompt reaction time in the go/no-go task and with early onset of OCD.

LIMITATIONS

We could not exclude the influence of medications on motor cortex excitability.

CONCLUSION

These findings suggest abnormal cortical excitability in patients with OCD. The associations between cortical silent period and response inhibition and age of onset further indicate that altered cortical excitability may play an important role in the development of OCD.

Association between serotonin transporter gene polymorphisms and childhood asthma

BACKGROUND

Asthma is a common chronic inflammatory disease of the airways in which genetic factors play a major role in its pathogenesis. High serotonin serum levels in patients with asthma suggest that serotonin is involved in the pathophysiology of the disease. Serotonin clearance is mediated by the serotonin reuptake transporter, and functional polymorphisms in this gene lead to altered serotonin reuptake efficiency.

OBJECTIVE

The aim of this study was to investigate the relationship between serotonin transporter gene polymorphisms and asthma.

METHODS

Serotonin transporter gene polymorphisms (5-HTTLPR, rs35521 and STin2.VNTR) were assessed by PCR-based methods in 100 children with mild to moderate persistent asthma and compared with 100 healthy controls.

RESULTS

There were no significant differences in allele, genotype or haplotype frequencies between patients and controls. No association was observed between SERT gene polymorphisms after stratification of patients for sex, age, spirometry indices, family history, passive smoking behavior and concomitant allergic rhinitis. Significant differences were observed in the distribution of 5-HTTLPR alleles (p = 0.025) and genotypes (p = 0.021) between patients with and without atopic dermatitis.

CONCLUSIONS

Despite strong evidence suggesting the role of serotonin in the pathophysiology of asthma, we found no association between serotonin transporter gene polymorphisms and mild to moderate persistent asthma. Further serotonin transporter gene analyses in patients with severe asthma may open up new horizons in the utilization of common serotonin regulators to treat asthma, based on their pharmacogenetic effects. However, serotonin may also be indirectly influenced by emotional stress during asthma attacks.

Serotonin transporter gene polymorphisms in Southwestern Iranian patients with irritable bowel syndrome

BACKGROUND AND STUDY AIMS

Irritable bowel syndrome is a common chronic functional gastrointestinal disorder of unknown etiology. Serotonin is an important factor in sensory signaling in the brain-gut axis, which plays a key role in intestinal motility and secretion. Serotonin clearance is mediated by a specific protein called the serotonin reuptake transporter. Transcription activity of the serotonin transporter gene is affected by some polymorphisms in this gene. The aim of this study was to investigate the relationship between serotonin transporter gene polymorphisms and irritable bowel syndrome.

PATIENTS/MATERIAL AND METHODS

The 5-HTTLPR, rs25531 and STin2VNTR polymorphisms of the serotonin transporter gene were analyzed by PCR-based methods in 50 patients with irritable bowel syndrome and 100 healthy controls.

RESULTS

Serotonin transporter polymorphisms were similar in patients and healthy controls. There were no significant differences in allele or genotype frequencies between the two groups.

CONCLUSION

Our findings suggest that polymorphisms in the gene encoding for the serotonin transporter are not associated with irritable bowel syndrome. Interactions between environmental factors and predisposing genetic factors are important in the pathophysiology of irritable bowel syndrome, and further genetic and epigenetic research may provide novel insights into the mechanisms contributing to this disease.

Reliability and validity of the Korean version of Obsessive-Compulsive Inventory-Revised in a non-clinical sample

PURPOSE

The reliability and validity of a Korean version of the Obsessive-Compulsive-Inventory-Revised (OCI-R) was examined in non-clinical student samples.

MATERIALS AND METHODS

The Korean version of OCI-R was administered to a total of 228 Korean college students. The Maudsley Obsessive Compulsive Inventory (MOCI), Beck's Depression Inventory (BDI), and Beck's Anxiety Inventory (BAI) were administered to 228 students.

RESULTS

The total and each of subscale of the Korean OCI-R demonstrated excellent internal consistency, good test-retest reliability, moderate convergent validity and good divergent validity.

CONCLUSION

It was concluded that the Korean version of the OCI-R has strong psychometric properties as the original version.

High ceruloplasmin levels are associated with obsessive compulsive disorder: a case control study

Background

Alterations in ceruloplasmin are currently assumed as one of the mechanisms underlying the development of a number of neurodegenerative disorders. Several studies indicate that elevated serum ceruloplasmin levels may play a role in schizophrenia by exacerbating or perpetuating dopaminergic dysregulation. No study investigating the relationship between ceruloplasmin and obsessive-compulsive disorder (OCD) has been published to date. Nowadays OCD is increasingly speculated to be a different disorder than other anxiety disorders, and rather is considered to be more similar to psychotic disorders. The objective of this study to explore whether there is an association of ceruloplasmin with OCD as in schizophrenia.

Method

26 pure OCD and 9 co-morbid OCD patients from Gaziantep University Sahinbey Research Hospital, Psychiatry Clinics, diagnosed according to the DSM IV and 40 healthy controls were included in the study. Blood samples were collected; ceruloplasmin levels were measured.

Results

The mean ceruloplasmin level in pure OCD patients, co-morbid OCD patients, and control group persons were 544.46 ± 26.53, 424.43 ± 31.50 and 222.35 ± 8.88 U/L respectively. Results of all 3 groups differ significantly. Positive predictive value of ceruloplasmin for that cut-off point is 31/31 (100%) and negative predictive value is 40/44 (91%) in our group.

Conclusion

Although the nature of relationship is not clear there was an association between ceruloplasmin levels and OCD in our study.

Strain differences in ‘compulsive’ lever-pressing

In the signal attenuation rat model of obsessive-compulsive disorder, 'compulsive' behavior is induced by attenuating a signal indicating that a lever-press response was effective in producing food. In recent years several studies have reported that Lewis rats, an inbred strain derived from the Sprague Dawley strain, exhibit addictive and/or compulsive tendencies. The aim of the present study was thus to test whether Lewis rats will also show increased compulsivity in the signal attenuation model. Because the model has been developed and validated using Wistar rats only, the present study compared the behavioral response to signal attenuation of Lewis, Sprague Dawley and Wistar rats, and assessed the effects of the anti-compulsive drug paroxetine on compulsive behavior in Lewis and Sprague Dawley rats. The results show that Lewis rats are more 'compulsive' than Sprague Dawley and Wistar rats in terms of both higher levels of compulsive lever-pressing and higher resistance to the anti-compulsive effect of paroxetine. The possibility that these strain differences are related to strain differences in the serotonergic and dopaminergic systems are discussed in light of current knowledge of the pathophysiology and pharmacotherapy of OCD.

Association between obsessive-compulsive disorder and a variable number of tandem repeats polymorphism in intron 2 of the serotonin transporter gene

BACKGROUND

Pharmacological studies indicate a dysregulation of the serotonergic system in obsessive-compulsive disorder (OCD). A variable number tandem repeats (VNTR) polymorphism with three alleles (Stin2.9, Stin2.10, Stin2.12) has been described in intron 2 of the serotonin transporter (5-HTT) gene. This polymorphism has been associated with unipolar depression, bipolar disorder, schizophrenia, and anxiety disorders including OCD.

METHODS

The association between OCD and the polymorphism is examined in 97 OCD patients, 578 psychiatric controls and 406 healthy controls, all Spanish Caucasians.

RESULTS

Genotype frequencies for the polymorphism were significantly different in OCD patients, psychiatric patients and controls. There was a significant excess of 12/12 and 12/10 genotypes in OCD patients compared to psychiatric patients and controls.

CONCLUSIONS

Our results indicate a possible association between the Stin2.12 allele of the VNTR polymorphism and OCD.