Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “COMT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed2004

COMT haplotypes suggest P2 promoter region relevance for schizophrenia.

A recent study found, in a large sample of Ashkenazi Jews, a highly significant association between schizophrenia and a particular haplotype of three polymorphic sites in the catechol-O-methyl transferase, COMT, gene: an IVS 1 SNP (dbSNP rs737865), the exon 4 functional SNP (Val158Met, dbSNP rs165688), and a downstream SNP (dbSNP rs165599). Subsequently, this haplotype was shown to be associated with lower levels of COMT cDNA derived from normal cortical brain tissue, most likely due to cis-acting element(s). As a first step toward evaluating whether this haplotype may be relevant to schizophrenia in populations other than Ashkenazi Jews, we have studied this haplotype in 38 populations representing all major regions of the world. Adding to our previous data on four polymorphic sites in the COMT gene, including the Val158Met polymorphism, we have typed the IVS 1 rs737865 and 3' rs615599 sites and also included a novel IVS 1 indel polymorphism, yielding seven-site haplotype frequencies for normal individuals in the 38 globally distributed populations, including a sample of Ashkenazi Jews. We report that the schizophrenia-associated haplotype is significantly heterogeneous in populations worldwide. The three-site, schizophrenia-associated haplotype frequencies range from 0% in South America to 37.1% in Southwest Asia, despite the fact that schizophrenia occurs at roughly equal frequency around the world. Assuming that the published associations found between the exon 4 Val158Met SNP and schizophrenia are due to linkage disequilibrium, these new haplotype data support the hypothesis of a relevant cis variant linked to the rs737865 site, possibly just upstream in the P2 promoter driving transcription of the predominant form of COMT in the brain. The previously described HindIII restriction site polymorphism, located within the P2 promoter, varies within all populations and may provide essential information in future studies of schizophrenia.

Catechol O-Methyltransferase↗
PubMed2004

Variants in the catechol-o-methyltransferase (COMT) gene are associated with schizophrenia in Irish high-density families.

The enzyme catechol-o-methyltransferase (COMT) transfers a methyl group from adenosylmethionine to catecholamines including the neurotransmitters dopamine, epinephrine and norepinephrine. This methylation results in the degradation of catecholamines. The involvement of the COMT gene in the metabolic pathway of these neurotransmitters has made it an attractive candidate gene for many psychiatric disorders. In this article, we reported our study of association of COMT with schizophrenia in Irish families with a high density of schizophrenia. Three single nucleotide polymorphisms (SNPs) were genotyped for the 274 such families and within-family transmission disequilibrium tests were performed. SNP rs4680, which is the functional Val/Met polymorphism, showed modest association with the disease by the TRANSMIT, FBAT and PDT programs, while the other two SNPs were negative. These SNPs showed lower level of LDs with each other in the Irish subjects than in Ashkenazi Jews. Haplotype analysis indicated that a haplotype, haplotype A-G-A for SNPs rs737865-rs4680-rs165599, was preferentially transmitted to the affected subjects. This was different from the reported G-G-G haplotype found in Ashkenazi Jews, but both haplotypes shared the Val allele. We concluded that COMT gene is associated with schizophrenia and carries a small but significant risk to the susceptibility in the Irish subjects.

Alleles↗
PubMed2005

Separate and interacting effects within the catechol-O-methyltransferase (COMT) are associated with schizophrenia.

Several lines of evidence have implicated the catechol-O-methyltransferase (COMT) gene as a candidate for schizophrenia (SZ) susceptibility, not only because it encodes a key dopamine catabolic enzyme but also because it maps to the velocardiofacial syndrome region of chromosome 22q11 which has long been associated with SZ predisposition. The interest in COMT as a candidate SZ risk factor has led to numerous case-control and family-based studies, with the majority placing emphasis on examining a functional Val/Met polymorphism within this enzyme. Unfortunately, these studies have continually produced conflicting results. To assess the genetic contribution of other COMT variants to SZ susceptibility, we investigated three single-nucleotide polymorphisms (SNPs) (rs737865, rs4633, rs165599) in addition to the Val/Met variant (rs4680) in a highly selected sample of Australian Caucasian families containing 107 patients with SZ. The Val/Met and rs4633 variants showed nominally significant associations with SZ (P<0.05), although neither of the individual SNPs remained significant after adjusting for multiple testing (most significant P=0.1174). However, haplotype analyses showed strong evidence of an association; the most significant being the three-marker haplotype rs737865-rs4680-rs165599 (global P=0.0022), which spans more than 26 kb. Importantly, conditional analyses indicated the presence of two separate and interacting effects within this haplotype, irrespective of gender. In addition, our results indicate the Val/Met polymorphism is not disease-causing and is simply in strong linkage disequilibrium with a causative effect, which interacts with another as yet unidentified variant approximately 20 kb away. These results may help explain the inconsistent results reported on the Val/Met polymorphism and have important implications for future investigations into the role of COMT in SZ susceptibility.

Amino Acid Substitution↗
PubMed2005

Lack of association of the COMT (Val158/108 Met) gene and schizophrenia: a meta-analysis of case-control studies.

There is strong evidence for a genetic contribution to schizophrenia, but the contribution of individual candidate genes remains uncertain. We attempted to replicate a recent meta-analysis that reported an association of the catechol O-methyltransferase (COMT) Val allele with schizophrenia, and suggested that this effect may be moderated by ancestry. We included reports published subsequent to the original meta-analysis, and included a formal test of the moderating effect of ancestry in order to test whether the association operates differently in populations of European ancestry compared to populations of Asian ancestry. A corrected P-value for the 5% significance threshold was employed where appropriate, using Bonferroni's method, and studies that demonstrated departure from Hardy-Weinberg equilibrium among controls were excluded. When all studies were included in a meta-regression, there was evidence for a significant association of COMT Val allele frequency with schizophrenia case status and a significant main effect of ancestry. The interaction of COMT Val allele frequency and ancestry was also significant. However, when only studies that reported allele frequencies that did not depart significantly from Hardy-Weinberg equilibrium among controls were included, these effects were no longer significant. The results of our meta-analysis do not support an association between the COMT Val allele and schizophrenia case status, and do not support recent claims that this association may be moderated by ancestry.

Amino Acid Substitution↗
PubMed2003

Bisubstrate inhibitors for the enzyme catechol-O-methyltransferase (COMT): influence of inhibitor preorganisation and linker length between the two substrate moieties on binding affinity.

Inhibition of the enzyme catechol-O-methyltransferase (COMT) is an important approach in the treatment of Parkinson's disease. A series of new potent bisubstrate inhibitors for COMT, resulting from X-ray structure-based design and featuring adenosine and catechol moieties have been synthesised. Biological results show a large dependence of binding affinity on inhibitor preorganisation and the length of the linker between nucleoside and catechol moieties. The most potent bisubstrate inhibitor for COMT has an IC50 value of 9 nM. It exhibits competitive kinetics for the SAM and mixed inhibition kinetics for the catechol binding site. Its bisubstrate binding mode was confirmed by X-ray structure analysis of the ternary complex formed by the inhibitor, COMT and a Mg2+ ion.

Binding Sites↗
PubMed2001

Catechol-O-Methyltransferase (COMT) gene polymorphism and breast cancer risk in young women.

Oestrogen exposure has long been considered to be a main risk factor of breast cancer. More recently, interest has also focused on the possible carcinogenic influence from oestrogen metabolites, such as catechol oestrogens. O-methylation, catalysed by Catechol-O-Methyltransferase (COMT), is one pathway by which the potentially carcinogenic catechol oestrogens can be inactivated. The gene coding for COMT protein contains a single-nucleotide polymorphism (SNP), resulting in an amino acid shift Val-->Met, which has been shown to determine high- and low-activity configuration of the enzyme. We hypothesized that the low-activity allele, COMT(Met), may be implicated in early onset breast cancer. In the present case-control study, including 126 young breast cancer patients (<or= 36 years) and 117 healthy female blood donors, we analysed the association between COMT(Met) genotype and risk of breast cancer. No significant difference in the frequency of low-/high-activity alleles was found between cases and controls, indicating that the polymorphism, as a single factor, may not contribute to breast carcinogenesis in young women.

Adolescent↗
PubMed2004

[No evidence for gender-specific sharing of COMT alleles in schizophrenia].

Catechol-o-methyltransferase (COMT) plays a major role in dopamine metabolism and has been the object of extensive investigations in subjects affected by schizophrenia. Interest in the enzyme has grown in recent years following positive linkage findings for schizophrenia in the chromosomal region surrounding the COMT gene locus on 22q. In several studies, a gender-specific association of COMT polymorphisms with schizophrenia has been reported and has given rise to speculations on transmission ratio distortions. The present investigation addressed allelic distributions in 307 men and women with respect to the rs165599 A > G polymorphism. No evidence was obtained for gender bias in allelic patterns, nor did we observe association with schizophrenia (p = 0.4). While studies involving same-sex siblings are lacking, gender-specific sharing of alleles does not appear to be a consistent feature of the COMT variant investigated.

Adult↗
PubMed2001

Effect of COMT Val108/158 Met genotype on frontal lobe function and risk for schizophrenia.

Abnormalities of prefrontal cortical function are prominent features of schizophrenia and have been associated with genetic risk, suggesting that susceptibility genes for schizophrenia may impact on the molecular mechanisms of prefrontal function. A potential susceptibility mechanism involves regulation of prefrontal dopamine, which modulates the response of prefrontal neurons during working memory. We examined the relationship of a common functional polymorphism (Val(108/158) Met) in the catechol-O-methyltransferase (COMT) gene, which accounts for a 4-fold variation in enzyme activity and dopamine catabolism, with both prefrontally mediated cognition and prefrontal cortical physiology. In 175 patients with schizophrenia, 219 unaffected siblings, and 55 controls, COMT genotype was related in allele dosage fashion to performance on the Wisconsin Card Sorting Test of executive cognition and explained 4% of variance (P = 0.001) in frequency of perseverative errors. Consistent with other evidence that dopamine enhances prefrontal neuronal function, the load of the low-activity Met allele predicted enhanced cognitive performance. We then examined the effect of COMT genotype on prefrontal physiology during a working memory task in three separate subgroups (n = 11-16) assayed with functional MRI. Met allele load consistently predicted a more efficient physiological response in prefrontal cortex. Finally, in a family-based association analysis of 104 trios, we found a significant increase in transmission of the Val allele to the schizophrenic offspring. These data suggest that the COMT Val allele, because it increases prefrontal dopamine catabolism, impairs prefrontal cognition and physiology, and by this mechanism slightly increases risk for schizophrenia.

Adult↗
PubMed1984

Brain irradiation: effects on regional MAO and COMT activity in the brain of the squirrel monkey and on the incorporation of [14C]tyrosine into catecholamines.

The effects of brain irradiation on the enzyme activity of monoamine oxidase (MAO) and catecholamine O-methyltransferase (COMT), as well as on the rate of incorporation of [14C]tyrosine into catecholamines (CAs), were examined in brain regions of the squirrel monkey (Saimiri sciureus). Results indicated that proton irradiation of the striate visual cortex at either 10,000 or 20,000 rad drastically affected the MAO activity, moderately affected the COMT activity, and significantly altered the incorporation of [14C]tyrosine into CAs in several brain regions. After 10,000 rad, MAO activity was increased in caudate nucleus (by 135%) and cerebellum (by 41%); significantly decreased in putamen (by 49%), gray matter (by 19%), and hippocampus (by 18%); and unchanged in brainstem. After 20,000 rad, MAO activity was markedly increased in caudate nucleus (by 114%), but decreased in cerebellum (by 24%), putamen (by 38%), gray matter (by 30%), and hippocampus (by 36%), and unchanged in brainstem. After 10,000 rad, COMT activity was significantly decreased in putamen (by 27%) and brainstem (28%). After 20,000 rad, COMT activity was significantly decreased in putamen (by 22%) and cortical gray matter (by 37%) but unchanged in the other brain regions examined. The 10,000 rad significantly increased the rate of incorporation of [14C]tyrosine into CAs in both the cerebellum (by 68%) and hypothalamus (by 26%), but 20,000 rad increased the rate only in hypothalamus (by 17%) and decreased the rate in hippocampus (by 24%). The whole-brain weights were significantly decreased after both 10,000 or 20,000 rad, by 17% and 11%, respectively. The only significant change in regional tissue weight was observed in putamen after 20,000 rad (a decrease by 17%). The protein concentration was significantly increased in hippocampus at both 10,000 (by 13%) and 20,000 (by 30%) but not affected in other brain regions examined. These data support our previous conclusion that a sustained chemical change occurs at the irradiated site and that the effect was transmitted to nonirradiated brain regions. Results also suggest that catecholaminergic pathways may exist between striate visual cortex and other cortical or subcortical brain areas where chemical changes were observed after visual cortical lesion by proton irradiation at various doses.

Animals↗
PubMed2002

A highly significant association between a COMT haplotype and schizophrenia.

Several lines of evidence have placed the catechol-O-methyltransferase (COMT) gene in the limelight as a candidate gene for schizophrenia. One of these is its biochemical function in metabolism of catecholamine neurotransmitters; another is the microdeletion, on chromosome 22q11, that includes the COMT gene and causes velocardiofacial syndrome, a syndrome associated with a high rate of psychosis, particularly schizophrenia. The interest in the COMT gene as a candidate risk factor for schizophrenia has led to numerous linkage and association analyses. These, however, have failed to produce any conclusive result. Here we report an efficient approach to gene discovery. The approach consists of (i) a large sample size-to our knowledge, the present study is the largest case-control study performed to date in schizophrenia; (ii) the use of Ashkenazi Jews, a well defined homogeneous population; and (iii) a stepwise procedure in which several single nucleotide polymorphisms (SNPs) are scanned in DNA pools, followed by individual genotyping and haplotype analysis of the relevant SNPs. We found a highly significant association between schizophrenia and a COMT haplotype (P=9.5x10-8). The approach presented can be widely implemented for the genetic dissection of other common diseases.

Case-Control Studies↗
PubMed2002

Combined COMT and GST genotypes and hormone replacement therapy associated breast cancer risk.

Our previous studies suggested that both COMT and GST genotypes might modify individual breast cancer risk. Here, we extended the studies to examine the potential combined effect of these genotypes in susceptibility to breast cancer. Our study population consisted of 483 Finnish breast cancer cases and 482 population control subjects. The odds ratios (ORs) and (95%) confidence intervals (CIs) were calculated by unconditional logistic regression adjusting for known or suspected confounding factors. No significant increase in the overall breast cancer risk was seen for any combinations of the studied genotypes. However, a substantially increased risk of breast cancer was seen for women who had used hormone replacement therapy (HRT) and simultaneously carried the COMT-L allele containing genotypes and either the GSTP1 Ile/Ile genotype (OR 4.10, 95% CI 1.24-13.6) or the GSTT1 null genotype (OR 4.19, 95% CI 1.30-13.5). These associations appeared to be mainly attributable to long-term users of HRT; the respective ORs were 7.00 (95% CI 1.21-40.6) and 8.36 (95% CI 1.44-49.0) among the users of HRT of more than 30 months. In addition, the combination of COMT-L allele containing genotypes with the GSTM1 null genotype posed a remarkably increased risk (OR 9.10, 95% CI 1.84-45.0) of breast cancer in this study group. These results suggest that the use of HRT could substantially increase the risk of breast cancer among women with specific combinations of the at-risk genotypes of COMT and GST genes.

Adult↗
PubMed1996

Preferential transmission of the high activity allele of COMT in schizophrenia.

Catechol-O-methyl transferase (COMT) metabolizes a variety of catecholamines such as dopamine, adrenaline and noradrenaline. It exists in common high and low activity forms. The low activity form is the result of an amino acid substitution (val-108-met) which reduces the thermostability of the enzyme [Lotta et al. (1994) Biochemistry, 34, 4202-4210]. We have genotyped this polymorphism in 178 trios consisting of Han Chinese schizophrenic subjects and their parents in order to test the hypothesis that the high activity allele is transmitted more often to affected subjects. The data were analysed using the transmission disequilibrium test (TDT), a robust method of detecting linkage in the presence of allelic associations. Of the 131 parents heterozygous at this locus, 80 transmitted the high activity allele (val-108) to affected offspring, while the remaining 51 transmitted the low activity allele (p = 0.005, one-tailed). Combining this result with that of a previous TDT study of the same polymorphism in familial schizophrenia [Kunugi et al. (1996) submitted] gives significant evidence for linkage disequilibrium (p = 0.0015). However, val-108 is frequent in the Han Chinese population, and in the present sample, 239 of the 350 non-transmitted parental alleles were val-108 (68%). It is therefore unlikely that val-108 allele of COMT has a major effect on susceptibility to schizophrenia. Our results suggest that either val-108 is a minor risk factor for schizophrenia, that the COMT gene has additional polymorphisms with greater effect on risk, or that this region of chromosome 22 contains a susceptibility gene which is in linkage disequilibrium with the COMT gene.

Adolescent↗
PubMed1997

Lack of association of catechol-O-methyltransferase (COMT) functional polymorphism in bipolar affective disorder.

Abnormal catecholamine transmission has been implicated in the pathogenesis of mood disorders. Consequently, alterations in genes that are involved in catecholamine metabolism could be potential candidates for bipolar affective disorder (BPD) vulnerability. One such candidate is catechol-O-methyltransferase (COMT). A functional polymorphism has recently been characterized that is responsible for substantial variability in COMT enzymatic activity. A relatively low activity allele is associated with a methionine residue at amino acid 158 of membrane bound COMT whereas a high activity variant has a valine at this site. We have now screened 63 unrelated patients with BPD for this functional polymorphism. However, no significant association was detected. This suggests that the codon 158 COMT polymorphism is not a susceptibility gene in BPD.

Alleles↗
PubMed1999

Lack of evidence for association between the COMT locus and schizophrenia.

Family-based studies have been conducted with restriction fragment length polymorphism (RFLP) analysis for testing association between polymorphisms for the catechol-O-methyltransferase (COMT) locus and schizophrenia in 49 Caucasian nuclear families consisting of fathers, mothers and offspring affected with schizophrenia. The present results did not support the hypothesis that the COMT gene might play an important role in predisposing an individual to a genetic risk for schizophrenia. Neither did we find a significant association of the COMT locus with violent behaviour in schizophrenia. Nevertheless, there may be a susceptibility gene for schizophrenia in a distinct region from the COMT locus on chromosome 22q, as a genome scan has suggested recently.

Catechol O-Methyltransferase↗
PubMed1995

Pharmacokinetic-pharmacodynamic interaction between the COMT inhibitor tolcapone and single-dose levodopa.

1. Single oral doses of the catechol-O-methyltransferase (COMT) inhibitor tolcapone (10-800 mg) or placebo were administered simultaneously with a dose of levodopa/benserazide 100/25 mg to seven sequential groups of six healthy male subjects in a two-way crossover study. 2. Plasma concentrations of tolcapone, its metabolite 3-O-methyltolcapone, levodopa and 3-O-methyldopa (3-OMD) were determined in conjunction with COMT activity in erythrocytes. 3. The drug combination was well tolerated at all dose levels and there were no signs indicative of an increase in dopaminergic stimulation. 4. Tolcapone caused a rapid and reversible inhibition of COMT activity in erythrocytes in parallel with a dose-dependent decrease in the formation of 3-OMD. Tolcapone increased the area under the concentration-time curve and elimination half-life of levodopa. The maximum effects were obtained at a dose of about 200 mg when both parameters increased approximately twofold. The drug had no influence on the maximum concentration of levodopa. 5. Tolcapone was rapidly absorbed and eliminated with, on average, a tmax of 1.5 h and a t1/2 of 2.3 h. The drug showed dose-proportional pharmacokinetics, in contrast to 3-O-methyltolcapone whose formation was relatively decreased at higher doses. 6. Plasma concentrations of tolcapone correlated with inhibition of COMT activity in erythrocytes and suppression of 3-OMD levels, but not with changes in levodopa pharmacokinetics.

Adult↗
PubMed2001

Effect of inhibition of MAO and COMT on intrarenal dopamine and serotonin and on renal function.

The purpose of the present investigation was to study the effects of inhibition of monoamine oxidase (MAO) and/or catechol-O-methyltransferase (COMT), enzymes involved in the degradation of dopamine (DA) and serotonin (5-HT), on intrarenal DA and 5-HT, as reflected in the renal interstitial fluid (RIF) microdialysate and urine, and on renal function. Inhibition of MAO selectively increased RIF 5-HT from 3.16 +/- 0.38 to 8.03 +/- 1.83 pg/min (n = 7, P < 0.05), concomitant with decreases in mean arterial blood pressure and glomerular filtration rate (2.09 +/- 0. 18 to 1.57 +/- 0.22 ml/min, n = 7, P < 0.05). Inhibition of COMT significantly increased RIF DA (3.47 +/- 0.70 to 8.68 +/- 1.96 pg/min, n = 9, P < 0.05), urinary DA (2.00 +/- 0.16 to 2.76 +/- 0.26 ng/min, n = 9, P < 0.05), and absolute excretion of sodium (6.42 +/- 2.00 to 9.82 +/- 1.62 micromol/min, n = 10, P < 0.05). Combined inhibition of MAO and COMT significantly increased RIF DA, urinary DA, and urinary 5-HT, which was accompanied with increases in urine flow rate, and absolute (3.03 +/- 0.59 to 8.40 +/- 1.61 micromol/min, n = 9, P < 0.01) and fractional excretion of sodium. We conclude that inhibition of MAO selectively increases RIF 5-HT. COMT appears to be more important than MAO in the metabolism of intrarenal DA. Physiological increases in intrarenal DA/5-HT induced by inhibition of their degrading enzymes are accompanied with significant alterations of renal function.

Animals↗
PubMed1976

In vivo and in vitro studies on the effect of tetrahydropapaveroline and salsolinol on COMT and MAO activity in rat brain.

Studies were made on COMT and MAO activity in rats 2, 4, 6, 12 and 24 h after intraperitoneal treatment with 8 and 60 mg/kg doses of tetrahydropapaveroline (THP), and 10 and 20 days after treatment with 8 mg/kg/day. Results suggested COMT activity inhibition only after 2 h of treatment. Experiments were also performed on THP and salsolinol methylation capacity in vitro. Results showed that both alkaloids use COMT enzymes for methylation and can also act as competitive inhibitors of COMT and MAO activity.

Alkaloids↗
PubMed2004

Interaction of COMT (Val(108/158)Met) genotype and olanzapine treatment on prefrontal cortical function in patients with schizophrenia.

OBJECTIVE: Deficits in working memory and in prefrontal cortical physiology are important outcome measures in schizophrenia, and both have been associated with dopamine dysregulation and with a functional polymorphism (Val(108/158)Met) in the catechol O-methyltransferase (COMT) gene that affects dopamine inactivation in the prefrontal cortex. The purpose of the present study was to evaluate in patients with schizophrenia the effect of COMT genotype on symptom variation, working memory performance, and prefrontal cortical physiology in response to treatment with an atypical antipsychotic drug. METHOD: Thirty patients with acute untreated schizophrenia were clinically evaluated with the Positive and Negative Syndrome Scale, underwent COMT Val/Met genotyping, and entered an 8-week prospective study of olanzapine treatment. Twenty patients completed two 3-T functional magnetic resonance imaging scans at 4 and 8 weeks during performance of N-back working memory tasks. RESULTS: There was a significant interaction of COMT genotype and the effects of olanzapine on prefrontal cortical function. Met allele load predicted improvement in working memory performance and prefrontal physiology after 8 weeks of treatment. A similar effect was found also for negative symptoms assessed with the Positive and Negative Syndrome Scale. CONCLUSIONS: These results suggest that a genetically determined variation in prefrontal dopamine catabolism impacts the therapeutic profile of olanzapine.

Adult↗