Association study of catechol-O-methyltransferase gene polymorphisms with schizophrenia and psychopathological symptoms in Han Chinese

Genotypic and Haplotypic Association of Catechol-O-Methyltransferase rs4680 and rs4818 Gene Polymorphisms with Particular Clinical Symptoms in Schizophrenia

Catechol-O-methyl transferase (COMT) gene variants are involved in different neuropsychiatric disorders and cognitive impairments, associated with altered dopamine function. This study investigated the genotypic and haplotypic association of COMT rs4680 and rs4618 polymorphisms with the severity of cognitive and other clinical symptoms in 544 male and 385 female subjects with schizophrenia. COMT rs4818 G carriers were more frequent in male patients with mild abstract thinking difficulties, compared to CC homozygotes or C allele carriers. Male carriers of COMT rs4680 A allele had worse abstract thinking (N5) scores than GG carriers, whereas AA homozygotes were more frequent in male subjects with lower scores on the intensity of the somatic concern (G1) item, compared to G carriers. Male carriers of COMT rs4818-rs4680 GA haplotype had the highest scores on the G1 item (somatic concern), whereas GG haplotype carriers had the lowest scores on G2 (anxiety) and G6 (depression) items. COMT GG haplotype was less frequent in female patients with severe disturbance of volition (G13 item) compared to the group with mild symptoms, while CG haplotype was more frequent in female patients with severe then mild symptoms. These findings suggest the sex-specific genotypic and haplotypic association of COMT variants with a severity of cognitive and other clinical symptoms of schizophrenia.

The effects of catechol-O-methyltransferase single nucleotide polymorphisms on positive and negative symptoms of schizophrenia: A systematic review and meta-analysis

The catechol-O-methyltransferase (COMT) gene is thought to have an important role in the etiopathogenesis of schizophrenia, but there are conflicting results regarding its role in clinical presentation. We aimed to elucidate the relationship between the single nucleotide polymorphisms (SNPs) in the COMT gene and the severity of positive and negative symptoms. In order to investigate the relationship, the PubMed, PubMed Central, Scopus, and Cochrane CENTRAL databases were screened for eligible articles. Thirty-eight studies, including 4443 adult patients with schizophrenia, were included in the quantitative analyses, and four studies were qualitatively assessed. Quantitative analyses were performed for acutely ill and clinically stable patient subgroups regarding the different genotypes of rs4680 SNP. Our results showed that the severity of negative symptoms was higher in patients who were rs4680 Met homozygous compared to Val/Met heterozygotes only in acutely ill samples. There was no other significant difference between genotypes. Meta-regression did not reveal any significant moderator effect on the difference in negative symptoms. General psychopathology, positive, negative, and total psychotic symptom levels also were similar between Val homozygotes and Met carriers. Nonetheless, there are some limitations in the study. First, SNPs except for rs4680 were under-researched because of the limited number of studies. Second, high heterogeneity across studies was the main concern. Our results suggested that the COMT rs4680 Met allele was associated with higher levels of negative symptoms within acutely ill patients. Future studies should focus on specific patient subgroups to reveal the moderating effects of SNPs.

Association of COMT Polymorphisms with Multiple Physical Activity-Related Injuries among University Students in China

The catechol-O-methyltransferase (COMT) is a candidate gene to provide promising evidence of psychiatric disorders, but there is a knowledge gap between the genetic factor and multiple physical activity-related injuries (PARIs). The aim of this study was to explore the contribution of COMT to the risk of PARIs among university students in the Chinese Han population. We can further search for the intrinsic risk factors for the occurrence of multiple physical activity injuries and provide a scientific basis for early screening and precise intervention for the high-risk group of college students with multiple PARIs. A 1:1 matched case-control study of 61 PARIs cases and 61 healthy controls were carried out. DNA samples of the participants were isolated from saliva and genotyped on eight SNPs of the COMT gene (rs9265, rs4680, rs6269, rs4818, rs4633, rs165655, rs165656, and rs165722) using the MALDI-TOF MS method. We found that rs6269 and rs4818 were significantly associated with PARIs, and rs6269-GG and rs4818-GG contributed to the reduced risk of PARIs. Further haplotype analysis showed a four-marker C-G-C-G haplotype (rs165722-rs6269-rs4633-rs4818) acted with a protective role in the development of PARIs (p = 0.037; OR: 0.474, 95% CI: 0.269 to 0.834). However, the interactions between club membership and rs6269 or rs4818 would significantly increase the risk of PARIs (both p < 0.001, OR: 5.121 and 4.977, respectively). This is the first study to find the contribution of COMT to PARIs occurrence, suggesting that the COMT polymorphisms and the gene-environment interactions may alter the risk of PARIs.

The Associations between COMT and MAO-B Genetic Variants with Negative Symptoms in Patients with Schizophrenia

Negative symptoms of schizophrenia, including anhedonia, represent a heavy burden on patients and their relatives. These symptoms are associated with cortical hypodopamynergia and impaired striatal dopamine release in response to reward stimuli. Catechol-O-methyltransferase (COMT) and monoamine oxidase type B (MAO-B) degrade dopamine and affect its neurotransmission. The study determined the association between COMT rs4680 and rs4818, MAO-B rs1799836 and rs6651806 polymorphisms, the severity of negative symptoms, and physical and social anhedonia in schizophrenia. Sex-dependent associations were detected in a research sample of 302 patients with schizophrenia. In female patients with schizophrenia, the presence of the G allele or GG genotype of COMT rs4680 and rs4818, as well as GG haplotype rs4818-rs4680, which were all related to higher COMT activity, was associated with an increase in several dimensions of negative symptoms and anhedonia. In male patients with schizophrenia, carriers of the MAO-B rs1799836 A allele, presumably associated with higher MAO-B activity, had a higher severity of alogia, while carriers of the A allele of the MAO-B rs6651806 had a higher severity of negative symptoms. These findings suggest that higher dopamine degradation, associated with COMT and MAO-B genetic variants, is associated with a sex-specific increase in the severity of negative symptoms in schizophrenia patients.

Association between COMT gene rs165599 SNP and schizophrenia: A meta-analysis of case-control studies

BACKGROUND

There are many studies with different results that examine the association between Catechol-O-MethylTransferase (COMT) gene single-nucleotide polymorphisms (SNPs) and schizophrenia. In this study, the aim was to conduct a meta-analysis to achieve a pooled effect size of the association between COMT gene rs165599 SNP and schizophrenia.

METHODS

Odds ratio (OR) was used as an effect size to determine the association between schizophrenia and the SNP. The pooled ORs were achieved under four different genetic models. When the heterogeneity among studies was high the DerSimonian-Laird random-effects model, otherwise the Mantel-Haenszel fixed-effects model was used. Publication bias was evaluated by Egger's test.

RESULTS

Under different genetic models no statistically significant association was found between rs165599 SNP and schizophrenia by meta-analyses consist of 20 independent studies. There was high heterogeneity among studies, for the possible reason the population differences, although the subgroup analyzes reduced the heterogeneity, no association was obtained. However, the sex-specific estimation of the females showed that to be a G allele carrier is a risk factor for schizophrenia (OR = 1.366 [95% confidence interval = 1.094-1.706]) compared to AA homozygous.

CONCLUSION

The COMT gene rs165599 SNP does not appear to be a single-risk factor for schizophrenia.

Haplotypic and Genotypic Association of Catechol-O-Methyltransferase rs4680 and rs4818 Polymorphisms and Treatment Resistance in Schizophrenia

Treatment-resistant schizophrenia (TRS) continues to be a challenge. It was related to different factors, including alterations in the activity of brain dopaminergic system, which could be influenced by the dopamine-degrading enzyme, catechol-O-methyltransferase (COMT). Variants of the COMT gene have been extensively studied as risk factors for schizophrenia; however, their association with TRS has been poorly investigated. The aim of the present study was to determine the haplotypic and genotypic association of COMT rs4680 and rs4818 polymorphisms with the presence of TRS. Overall, 931 Caucasian patients diagnosed with schizophrenia (386 females and 545 males) were included, while 270 participants met the criteria for TRS. In males, no significant haplotypic and genotypic associations between COMT rs4680 and rs4818 polymorphisms and TRS were detected. However, genotypic analyses demonstrated higher frequency of COMT rs4680 AA genotype carriers compared to G-allele carriers (p = 0.033) and higher frequency of COMT rs4818 CC genotype carriers than G-allele carriers (p = 0.014) in females with TRS. Haplotype analyses confirmed that the presence of the G allele in females was associated with lower risk of TRS. In women with TRS, the high activity G-G/G-G haplotype was rare, while carriers of other haplotypes were overrepresented (p = 0.009). Such associations of COMT rs4680 and rs4818 high-activity (G variants), as well as G-G/G-G haplotype, with the lower risk of TRS in females, but not in males, suggest significant, but sex-specific influence of COMT variants on the development of treatment-resistance in patients with schizophrenia. However, due to relatively low number of females, those findings require replication in a larger sample.

Depressive symptoms in schizophrenia and dopamine and serotonin gene polymorphisms

Although depressive symptoms seem to be frequent in schizophrenia they have received significantly less attention than other symptom domains. As impaired serotonergic and dopaminergic neurotransmission is implicated in the pathogenesis of depression and schizophrenia this study sought to investigate the putative association between several functional gene polymorphisms (SERT 5-HTTLPR, MAO-A VNTR, COMT Val158Met and DAT VNTR) and schizophrenia. Other objectives of this study were to closely examine schizophrenia symptom domains by performing factor analysis of the two most used instruments in this setting (Positive and negative syndrome scale - PANSS and Calgary depression rating scale - CDSS) and to examine the influence of investigated gene polymorphisms on the schizophrenia symptom domains, focusing on depressive scores. A total of 591 participants were included in the study (300 schizophrenic patients and 291 healthy volunteers). 192 (64%) of schizophrenic patients had significant depressive symptoms. Genotype distribution revealed no significant differences regarding all investigated polymorphisms except the separate gender analysis for MAO-A gene polymorphism which revealed significantly more allele 3 carriers in schizophrenic males. Factor analysis of the PANSS scale revealed the existence of five separate factors (symptom domains), while the CDSS scale revealed two distinct factors. Several investigated gene polymorphisms (mostly SERT and MAO-A, but also COMT) significantly influenced two factors from the PANSS (aggressive/impulsive and negative symptoms) and one from the CDSS scale (suicidality), respectively. Depressive symptoms in schizophrenic patients may be influenced by functional gene polymorphisms, especially those implicated in serotonergic neurotransmission.

Association of catechol-O-methyltransferase Val(108/158) Met genetic polymorphism with schizophrenia, P50 sensory gating, and negative symptoms in a Chinese population

Catechol-O-methyltransferase (COMT), an enzyme involved in the degradation and inactivation of the neurotransmitter dopamine, is associated with the sensory gating phenomenon, protecting the cerebral cortex from information overload. The COMT Val(108/158)Met polymorphism is essential for prefrontal cortex processing capacity and efficiency. The current study was designed to investigate the role of COMT Val(108/158)Met polymorphism in development, sensory gating deficit, and symptoms of schizophrenia in Han Chinese population. P50 gating was determined in 139 schizophrenic patients and 165 healthy controls. Positive and Negative Syndrome Scale (PANSS) was used to assess the clinical symptomatology in 370 schizophrenic subjects. COMT Val(108/158)Met polymorphism was genotyped by PCR-restriction fragment length polymorphism (PCR-RFLP). No significant differences in COMT allele and genotype distributions were observed between schizophrenic patients and control groups. Although P50 deficits were present in patients, there was no evidence for an association between COMT Val(108/158)Met polymorphism and the P50 biomarker. Moreover, PANSS negative subscore was significantly higher in Val allele carriers than in Met/Met individuals. The present findings suggest that COMT Val(108/158)Met polymorphism may not contribute to the risk of schizophrenia and to the P50 deficits, but may contribute to the negative symptoms of schizophrenia among Han Chinese.

Catechol-O-methyltransferase gene variants may associate with negative symptom response and plasma concentrations of prolactin in schizophrenia after amisulpride treatment

Catechol-O-methyltransferase (COMT) enzyme is involved in the pathogenesis of psychotic symptoms and may be associated with a therapeutic response to antipsychotic drugs. The aim of this study was to examine the relationship between COMT variants, plasma prolactin level, and the therapeutic effectiveness of amisulpride treatment in patients with schizophrenia. A 12-week naturalistic study of amisulpride treatment was carried out in 185 Han Chinese patients with schizophrenia. The patients were screened for 14 single-nucleotide polymorphisms of the COMT gene. The Positive and Negative Syndrome Scale (PANSS) was used to assess the improvement of psychopathological symptoms from the baseline to the end point in each subject. For better presentation of time-course changes in response status, a mixed model for repeated-measures (MMRM) analysis of symptom improvement during the 12-week treatment period was conducted. The change in plasma prolactin level after amisulpride treatment was also examined (n=51). No significant differences in the genotype frequencies of the COMT variants investigated were observed between responders and non-responders. Moreover, an MMRM analysis of psychopathological symptom improvement during the 12-week treatment course showed that it depended significantly on COMT variants (rs4680, rs4633, and rs6267), particularly regarding changes in negative symptoms. The increase in plasma prolactin levels observed was influenced by the COMT rs4680 variant and was positively correlated with a reduction in PANSS negative scores. Our results suggest that variation of the COMT gene is associated with treatment response regarding negative symptoms and prolactin changes after amisulpride treatment in patients with schizophrenia.

Neurobiological background of negative symptoms

Studies investigating neurobiological bases of negative symptoms of schizophrenia failed to provide consistent findings, possibly due to the heterogeneity of this psychopathological construct. We tried to review the findings published to date investigating neurobiological abnormalities after reducing the heterogeneity of the negative symptoms construct. The literature in electronic databases as well as citations and major articles are reviewed with respect to the phenomenology, pathology, genetics and neurobiology of schizophrenia. We searched PubMed with the keywords "negative symptoms," "deficit schizophrenia," "persistent negative symptoms," "neurotransmissions," "neuroimaging" and "genetic." Additional articles were identified by manually checking the reference lists of the relevant publications. Publications in English were considered, and unpublished studies, conference abstracts and poster presentations were not included. Structural and functional imaging studies addressed the issue of neurobiological background of negative symptoms from several perspectives (considering them as a unitary construct, focusing on primary and/or persistent negative symptoms and, more recently, clustering them into factors), but produced discrepant findings. The examined studies provided evidence suggesting that even primary and persistent negative symptoms include different psychopathological constructs, probably reflecting the dysfunction of different neurobiological substrates. Furthermore, they suggest that complex alterations in multiple neurotransmitter systems and genetic variants might influence the expression of negative symptoms in schizophrenia. On the whole, the reviewed findings, representing the distillation of a large body of disparate data, suggest that further deconstruction of negative symptomatology into more elementary components is needed to gain insight into underlying neurobiological mechanisms.

Generation and characterization of humanized mice carrying COMT158 Met/Val alleles

The Val158Met polymorphism of human catechol-o-methyltransferase (COMT) is one of the most well-studied single-nucleotide polymorphisms in neuropsychiatry; however, findings are inconsistent due to human genetic heterogeneity. We created the first 'humanized' COMTVal158Met mouse lines, which carry either human COMT Val or Met alleles via gene targeting. The 'humanized' mouse model enables strict comparison of the physiological functions of the two alleles. Consistent with human observation, Met/Met mice exhibited a 30% reduction in enzymatic activity compared with Val/Val mice. On the basis of the reported differences in human Met and Val carriers across working memory, fear processes and sensorimotor gating, we examined these functions between sibling Met/Met and Val/Val mice. Val/Val mice exhibited robust reductions in spatial working memory compared with Met/Met mice in both sexes, with tolcapone treatment significantly reversing the Val/Val alternation deficits. Sex effects were observed in other behaviors, with male Val/Val mice exhibited lower prepulse inhibition compared with Met/Met mice, whereas female mice exhibited the opposite phenotype. Female but not male Met/Met mice exhibited reduced contextual fear, increased cued fear, and reduced extinction recall. Thus, these mice (1) support the argument that human COMT Val158Met polymorphism modulates behavioral functions and most importantly (2) exhibit the expected treatment effects supporting the 'inverted U shaped' dose response of catecholamine signaling on cognitive function. This model will be invaluable for understanding the effects of human COMT Val158Met polymorphism on cortical development and behavioral functions, and how this polymorphism modulates treatment response.

Association of BDNF gene polymorphisms with schizophrenia and clinical symptoms in a Chinese population

The neurodevelopmental hypothesis is well established in schizophrenia. Accumulating evidence has shown that BDNF may be involved in the pathogenesis of schizophrenia. This study aimed to investigate the potential association of BDNF gene polymorphisms with susceptibility to schizophrenia and with the psychopathological symptoms in patients with schizophrenia in a Han Chinese population. Three polymorphisms (rs6265, rs12273539, and rs10835210) of the BDNF gene were analyzed in a case-control study of 709 Han Chinese individuals (375 patients and 334 controls). The patients' psychopathology was assessed using the positive and negative syndrome scale (PANSS). We found no significant differences in the genotype and allele distributions of all three polymorphisms between the patient and control groups; however, we found a trend toward to significant overall difference in the estimated haplotype frequencies, with more frequent haplotype ATC of rs6265-rs12273539-rs10835210 in the schizophrenic patients than in controls (P = 0.027). The quantitative trait analysis by the UNPHASED program showed significant associations between the rs6265 (A)-rs12273539 (C)-rs10835210 (A) haplotype and negative symptom scores from the PANSS (x(2)  = 5.79, P = 0.016). Our findings suggest that the BDNF gene polymorphisms may play a small effect on susceptibility to schizophrenia, but may contribute to the negative symptoms of the disease.

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.

Synergistic effects of COMT and TPH2 on social cognition

Whether genetic factors affect social cognition, particularly emotion management, requires elucidation. This study investigates whether social cognition varies with genetic variations of COMT and tryptophan hydroxylase-2 (TPH2), which modulate dopamine and serotonin neurotransmissions respectively, and thereby emotion regulation. NIMH-recommended "managing emotions branch and 2 subtasks" of MSCEIT and six neurocognition domains, and genotypes of COMT Val158Met and TPH2 G703T were measured in 150 Han-Chinese healthy adults. Subjects carrying the M allele (M group) of COMT exceeded Val/Val homozygotes (V group) in managing emotions branch (p = 0.032) and emotional relation subtask (p = 0.037). TPH2 T/T homozygotes (T group) excelled those with the G allele (G group) in emotional management subtask (p = 0.025). Subjects with M+T variation surpassed the other 3 groups (M+G, V+T and V+G) in managing emotion branch (p = 0.002), emotional relation subtask (p = 0.023), and emotional management subtask (p = 0.002). The findings remained after control for gender, age, education, and neurocognitive functions. Synergistically, the effect size of COMT-TPH2 combination surmounted the sum of separate effect sizes of COMT and TPH2. The findings suggest that genetic variations of COMT and TPH2 have synergistic effects on social cognition in the general population.

No association between catechol-o-methyltransferase Val108/158Met polymorphism and schizophrenia or its clinical symptomatology in a Mexican population

The gene coding for catecol-o-methyltransferase (COMT), participant in the metabolism of catecholamines, has long been implicated as a candidate gene for schizophrenia. We determined the relation of the COMT Val108/158Met polymorphism with schizophrenia or its symptomatology (negative, disorganized and psychotic dimension). We conducted a case–control study comprising 186 patients with schizophrenia and 247 controls. The diagnosis of schizophrenia was established using the DSM-IV criteria for this illness. The clinical symptomatology was assessed through the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms. No significant differences were found in the distribution of alleles (χ2 = 0.01, df = 1, p = 0.90) or genotypes (χ2 = 1.66, df = 2, p = 0.43) between schizophrenic patients and the control group. Multivariate analysis showed that the COMT Val108/158Met polymorphism has no influence in the clinical symptomatology of schizophrenia. Our results showed no association between COMT Val108/158Met and schizophrenia or evidence for an association between COMT and the clinical symptomatology of this illness. This suggests that the COMT gene may not contribute to the risk for schizophrenia among the Mexican population.

Association of catechol-O-methyltransferase gene polymorphisms with schizophrenia and negative symptoms in a Chinese population

The gene encoding Catechol-O-methyltransferase (COMT), a dopamine catabolic enzyme, has been associated inconsistently with schizophrenia in spite of consistent evidence for dopaminergic dysfunction in the prefrontal cortex (PFC) of schizophrenia. Since one contribution to this inconsistency might be genetic heterogeneity, this study investigated whether the COMT gene was associated with the development and symptoms of schizophrenia in relatively genetically homogeneous Chinese schizophrenic patients. We analyzed two polymorphisms (rs740603 and rs4818) of the COMT gene in a case-control study of 604 Han Chinese (284 patients and 320 controls). The patients' psychopathology was assessed using the Positive and Negative Syndrome Scale (PANSS). We found no significant differences in the rs740603 and rs4818 genotype and allele distributions between the patient and control groups. Quantitative trait analysis by the UNPHASED program showed that the rs740603 and rs740603(G)-rs4818(G) haplotypes were associated with negative symptoms in the schizophrenic patients, particularly among female patients. Thus, the COMT gene polymorphisms may not contribute to the susceptibility to schizophrenia, but may contribute to the negative symptoms of schizophrenia among Han Chinese.