Association study of catechol-O-methyltransferase (COMT) gene Val158Met polymorphism with auditory P300 in Chinese Han patients with schizophrenia

COMT-Val158Met polymorphism modulates antipsychotic effects on auditory verbal hallucinations and temporal lobe gray matter volumes in healthy individuals-symptom relief accompanied by worrisome volume reductions

Investigation of auditory verbal hallucinations (AVHs) in schizophrenics is complicated by psychiatric symptoms. Investigating healthy individuals with AVHs (H-AVHs) can obviate such confounding factors. The objective of this study was to explore the effects of antipsychotic treatment on AVHs and gray matter volumes (GMVs) in H-AVH subjects and whether such are effects are influenced by COMT-Val158Met genotype. Magnetic resonance imaging (MRI) and genotyping studies were completed for 42 H-AVH subjects and 42 well-matched healthy controls (HCs). COMT-Met/Met homozygotes (158th codon) were identified as COMT-Met genotype; COMT-Met/Val heterozygotes and COMT-Val/Val homozygotes were identified as COMT-Val genotype. Data were compared across groups (H-AVH vs. HC, and between genotypes) with two-sample t-tests. The H-AVH COMT-Met group showed a stronger response to antipsychotic treatment than the H-AVH COMT-Val group (p < 0.001). Both H-AVH genotype groups exhibited temporal lobe GMV reductions after treatment, and relative to their respective genotype-matched HC groups. Antipsychotic treatment effects in H-AVH subjects were influenced by COMT-Val158Met genotype and associated with widespread GMV reductions. These findings provide clues for further exploration of treatment targets for AVHs. Treatment associated GMV reductions, however, raise concerns about use of antipsychotics in H-AVH subjects.

Effort-related decision making in humanized COMT mice: Effects of Val158Met polymorphisms and possible implications for negative symptoms in humans

Catechol-o-methyltransferase (COMT) is an enzyme that metabolizes catecholamines, and is crucial for clearance of dopamine (DA) in prefrontal cortex. Val¹⁵⁸Met polymorphism, which causes a valine (Val) to methionine (Met) substitution at codon 158, is reported to be associated with human psychopathologies in some studies. The Val/Val variant of the enzyme results in higher dopamine metabolism, which results in reduced dopamine transmission. Thus, it is important to investigate the relation between Val¹⁵⁸Met polymorphisms using rodent models of psychiatric symptoms, including negative symptoms such as motivational dysfunction. In the present study, humanized COMT transgenic mice with two genotype groups (Val/Val (Val) and Met/Met (Met) homozygotes) and wild-type (WT) mice from the S129 background were tested using a touchscreen effort-based choice paradigm. Mice were trained to choose between delivery of a preferred liquid diet that reinforced panel pressing on various fixed ratio (FR) schedules (high-effort alternative), vs. intake of pellets concurrently available in the chamber (low-effort alternative). Panel pressing requirements were controlled by varying the FR levels (FR1, 2, 4, 8, 16) in ascending and descending sequences across weeks of testing. All mice were able to acquire the initial touchscreen operant training, and there was an inverse relationship between the number of reinforcers delivered by panel pressing and pellet intake across different FR levels. There was a significant group x FR level interaction in the ascending limb, with panel presses in the Val group being significantly lower than the WT group in FR1-8, and lower than Met in FR4. These findings indicate that the humanized Val allele in mice modulates FR/pellet-choice performance, as marked by lower levels of panel pressing in the Val group when the ratio requirement was moderately high. These studies may contribute to the understanding of the role of COMT polymorphisms in negative symptoms such as motivational dysfunctions in schizophrenic patients.

The Effect of Dopamine Antagonist Treatment on Auditory Verbal Hallucinations in Healthy Individuals Is Clearly Influenced by COMT Genotype and Accompanied by Corresponding Brain Structural and Functional Alterations: An Artificially Controlled Pilot Study

Few studies have been conducted to explore the influence of the catechol-o-methyltransferase (COMT) genotype on the severity of and treatment efficacy on auditory verbal hallucination (AVH) symptoms in healthy individuals with AVHs (Hi-AVHs). We hypothesized that the efficacy of dopamine antagonist treatment on AVHs in Hi-AVHs may be influenced by their COMT genotype and may be accompanied by corresponding brain alterations. To preliminarily investigate and test our hypothesis in an artificially controlled pilot study, we enrolled 42 Hi-AVHs as subjects and used magnetic resonance imaging and genetic methods to explore the basis brain features to investigate whether the efficacy of dopamine antagonist treatment on AVHs in Hi-AVH subjects was influenced by their COMT genotype or not. We found that COMT-met genotype subjects’ treatment response was better than that of COMT-val subjects. Although COMT-met genotype subjects demonstrated an increase in global functional connectivity density (gFCD) but no difference on gray matter volume (GMV) compared to COMT-val genotype subjects at baseline, notably, we found that both groups demonstrated gFCD and GMV reduction after treatment, but the reduction was more widespread in COMT-met genotype subjects than in COMT-val genotype subjects. This is the first study to report that Hi-AVH subjects’ baseline brain functional features are influenced by their COMT genotypes and that the COMT-met genotype subjects exhibit better responses to dopamine antagonists but have more widespread GMV and gFCD reduction than subjects with the COMT-val genotype. Despite several limitations, these findings may provide auxiliary information to further explain the mechanisms of AVHs and provide a clue for scholars to further explore specific treatment targets for AVHs in Hi-AVH subjects or in schizophrenia patients.

Effect of GAD1 genotype status on auditory attention and acute nicotine administration in healthy volunteers

OBJECTIVE

The effects of GABA modulating drugs and nicotine, the prototypical nicotinic cholinergic agonist, on attention have been investigated using subcomponents of the P300 event-related potentials (ERP), which index involuntary (P3a) and voluntary attention (P3b). However, investigations into how such pharmacologic effects interact with genetic features in the GABA system remain unclear. This study examined the moderating effects of a single nucleotide polymorphism (rs7557793) in the glutamic acid decarboxylase 67 (GAD1) gene, which is implicated in the conversion of glutamate to GABA, on P300-indices of auditory attentional processing; the influence of nicotine administration was also assessed.

METHODS

The effects of GAD1 genotype (TT/CC/CT) were examined on the P3a/b in response to an auditory selective attention task in healthy, nonsmoking male volunteers (N = 126; 18-40 years). Participants responded to rare target stimuli (P3b-eliciting) and ignored frequent nontarget stimuli as well as rare distractor stimuli (P3a-eliciting). In a subsample (N = 59), P3a/b profiles to acute nicotine (vs. placebo) administration were examined as a function of GAD1 genotype. As a secondary aim, earlier sensory processes were assessed with N200 ERP subcomponents elicited by novel (N2a) and target (N2b) auditory stimuli.

RESULTS

GAD1 allelic variation moderated early sensory processes, enhancing N2a amplitudes in CT versus TT carriers. Further, TT homozygotes exhibited larger P3b amplitudes than CC homozygotes in the placebo versus nicotine condition. Regardless of genotype, nicotine versus placebo moderated the N200 ERP.

CONCLUSION

These findings expand our knowledge regarding the attentional effects of GAD1 genetic variants in relation to nicotine.

Influence of Concussion History and Genetics on Event-Related Potentials in Athletes: Potential Use in Concussion Management

Sports-related concussions are an increasing public health issue with much concern about the possible long-term decrements in cognitive function and quality of life that may occur in athletes. The measurement of cognitive function is a common component of concussion management protocols due to cognitive impairments that occur after sustaining a concussion; however, the tools that are often used may not be sensitive enough to expose long term problems with cognitive function. The current paper is a brief review, which suggests that measuring cognitive processing through the use of event related potentials (ERPs) may provide a more sensitive assessment of cognitive function, as shown through recent research showing concussion history to influence ERPs components. The potential influence of genetics on cognitive function and ERPs components will also be discussed in relation to future concussion management.

Research in China on the molecular genetics of schizophrenia

Schizophrenia is a complex disease caused by genetic and environmental factors with a global heritability of more than 80%. By the end of the 1970s, Chinese scientists reported a heritability of schizophrenia of 82.9% in the Chinese Han population. Continuous improvements in research techniques and the recruitment of larger samples have made it possible for Chinese scientists to identify a number of candidate susceptibility genes for schizophrenia. This article reviews the results in genetic research of schizophrenia by Chinese scientists over the last five decades

Auditory event-related potentials (P3a, P3b) and genetic variants within the dopamine and serotonin system in healthy females

The late positive components of the human event-related brain potential comprise electrocortical reflections of stimulus-driven attentional capture (the anteriorly distributed P3a) and top-down control detection of relevant events (the posteriorly distributed P3b). As of yet, the neuropharmacologic and neurogenetic origin of the P3a and P3b is not fully understood. In this study, we address the contribution of dopaminergic and serotoninergic mechanisms. Sixty healthy females completed an active auditory novelty oddball paradigm while EEG was recorded. In all subjects, genetic polymorphisms within the dopamine system (dopamine transporter [DAT1], catecholamine-O-methyltransferase val158met [COMT val158met]) and the serotonin system (serotonin transporter [5HTTLPR]) were assessed. Across genotypes, novels (relative to standards) elicited a fronto-centrally distributed P3a, and targets (relative to standards) a parieto-centrally distributed P3b. Genotypes effects were observed for both P3a (COMT, 5HTTPLR) and P3b (DAT1, COMT, 5HTTLPR) only at prefrontal electrode location (Fz). Specifically, the frontal P3a was enhanced in COMT met/met homozygotes, but not in DAT1 9R. The target-related P3b was enhanced in COMT met/met and DAT1 9R relative to its genetic counterparts, but only at frontal electrodes. This 'anteriorized' enhancement may reflect either an additional frontal component in the target-related P3 dependent on dopamine, or a more subtle shift in the neural ensemble that generates the target-related P3. Results for 5HTTLPR short allele homozygotes mimicked those in COMT met/met homozygotes. In all, the present findings suggest involvement of frontal-cortical dopaminergic and serotoninergic mechanisms in bottom-up attentional capture (COMT val158met, 5HTTLPR), with an additional top-down component sensitive to striatal signals (DAT1).

No association of catechol-O-methyltransferase polymorphisms with schizophrenia in the Han Chinese population

AIMS

Genetics play a major role in the etiology of schizophrenia (SZ). Catechol-O-methyltransferase (COMT) is one of the promising candidate genes for SZ. A nonsynonymous single-nucleotide polymorphism (SNP), rs4680, causing a Valine (Val) to Methionine (Met) substitution, has been widely studied in relation to psychiatric phenotypes, including SZ, but with conflicting results. We conducted a two-stage study to examine the association of COMT polymorphisms with SZ in the Han Chinese population.

RESULTS

Association analysis of nine SNPs in 768 patients and 1348 controls failed to detect any positive markers or haplotypes. Then, we tested rs4680 in a validation sample of 963 patients and 992 controls, and no significant association was observed, but the cases significantly deviated from Hardy-Weinberg equilibrium (p=5.7e-4). There was no association of rs4680 with SZ in the combined sample (n=4071, p=0.110, odds ratio=1.08).

CONCLUSIONS

Our results do not support the association of COMT with SZ in the Han Chinese population.

DBH -1021C>T and COMT Val108/158Met genotype are not associated with the P300 ERP in an auditory oddball task

OBJECTIVE

The amplitude and latency of the P300 may be associated by variations in dopaminergic genes. The current study was conducted to determine whether functional variants of the catechol-O-methyltransferase (COMT) and dopamine beta-hydroxylase (DBH) gene were associated with P300 amplitude and latency in an auditory oddball task.

METHODS

The P300 ERP was assessed by a two-tone auditory oddball paradigm in a large sample of 320 healthy volunteers. The Val108/158Met polymorphism (rs4680) of the COMT gene and the -1021C>T polymorphism (rs1611115) of the DBH gene were genotyped. P300 amplitude and latency were compared across genotype groups using analysis of variance.

RESULTS

There were no differences in demographic characteristics in subjects for genotypic subgroups. No genotype associations were observed for the P300 amplitude and latency on frontal, central and parietal electrode positions.

CONCLUSIONS

COMT Val108/158Met and DBH -1021C>T polymorphisms do not show evidence of association with characteristics of the P300 ERP in an auditory oddball paradigm in healthy volunteers.

SIGNIFICANCE

We failed to find evidence for the association between dopaminergic enzymatic polymorphisms and the P300 ERP in healthy volunteers, in the largest study undertaken to date.

Association study of neuregulin 1 gene polymorphisms with auditory P300 in schizophrenia

Neuregulin 1 (NRG1), a gene involved with myelin production has been shown to have a positive correlation with schizophrenia. Event-related potentials (ERPs) studies provide the evidence of disturbed electrophysiologic marker in schizophrenia. The present study investigated the association of NRG1 genotypes with P300 in schizophrenia. Three polymorphisms in NRG1 gene were detected in 287 Chinese Han schizophrenics and 120 healthy control subjects. Among the total sample, 140 patients and 96 controls underwent P300. There were no significant differences for genotype distributions and allele frequencies between schizophrenic group and the control. A significant difference was observed between the schizophrenic patients and controls in the AT haplotype, with Odds Ratio 0.304 (P = 0.000882, 95% CI = 0.145-0.636). P300 amplitude in the schizophrenic group was significantly lower than that of the controls at Fz, Cz, Pz. P300 latency in the schizophrenic group was also significantly longer than that of the controls at Cz, Pz, Fz. Significant differences of P300 latency between three genotypes of rs3924999 were found at Cz and Pz both in schizophrenic group and the controls. The G/G carriers of rs3924999 tended to perform worse in the P300 latency as compared to A/A or A/G carriers both in the schizophrenia and controls. There were no significant differences for P300 latency and amplitude between schizophrenic group and controls for AT haplotype. NRG1 gene is a susceptible gene for Chinese Han schizophrenia and AT haplotype might have the protective role in the schizophrenia. Rs3924999 in NRG1 gene might functionally impact cognitive processing.

Impact of catechol-o-methyltransferase polymorphisms on risperidone treatment for schizophrenia and its potential clinical significance

OBJECTIVES

The main aim was to study the effects of COMT polymorphisms on response of risperidone treatment for schizophrenia and investigate the correlation between memory function of schizophrenia patients and COMT polymorphisms.

DESIGN AND METHODS

Subjects were 83 schizophrenic patients who were antipsychotic drug free at the initiation of this study. Peripheral blood samples were obtained to identify COMT polymorphisms by using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Clinical Global Impressions (CGI), Positive and Negative Syndrome Scale (PANSS) and Wechsler Memory Scale (WMS) test were used to assess the effect of risperidone treatment.

RESULTS

The Val/Met carriers showed a significant increase in change of P300 during treatment (P=0.032). Association of Val/Met carriers performed better than other genotypes (P=0.028). The mean plasma concentration of prolactin of Val/Val carriers was significantly lower (P=0.017).

CONCLUSIONS

The COMT polymorphisms may be a potential biomarker for clinical risperidone treatment in schizophrenia.