Genomic organization of the human catechol O-methyltransferase gene and its expression from two distinct promoters

The association of gene polymorphisms in catechol-O'methyltransferase (COMT) and β2-adrenergic receptor (ADRB2) with temporomandibular joint disorders

OBJECTIVE

Temporomandibular disorder (TMD) has a multifactorial etiology that includes environmental, psychological, and genetic factors. This study aimed to evaluate the possible relationship between polymorphisms in Catechol-O-methyltransferase (COMT) and β2-adrenergic receptor (ADRB2) genes with TMD.

DESIGN

This observational case-control study included 80 patients and 70 healthy controls. The diagnosis of TMD was made using the diagnostic criteria for TMD and the following TMD categories were used for the case group: muscular TMD and articular TMD (disc displacement and arthralgia). A genotyping study of gene polymorphisms in COMT (rs 9332377) and ADRB2 (rs20530449) was performed from genomic DNA isolated from blood. The chi-square test was used to analyze the relationships. P < 0.05 was accepted as a significant difference.

RESULTS

The polymorphic TT and CT genotype for COMT (rs rs9332377) was significantly higher in the articular TMD group while the non-polymorphic CC genotype was significantly lower in the articular TMD group (P < 0.05). Regarding ADRB2 (rs20530449), the polymorphic GG genotype was similarly considerably more common in the articular TMD group (p < 0.05). In addition, the T allele in the COMT (rs rs9332377) gene was found to be significantly higher in the articular TMD group (p < 0.05).

CONCLUSIONS

In the Turkish population, gene polymorphisms in COMT (rs9332377) and ADRB2 (rs2053044) were associated with articular TMD. This study supports the hypothesis that changes in COMT and ADRB2 genes may play a role in temporomandibular joint pain and predisposition to TMD.

Relationship between gene-environment interaction and obsessive-compulsive disorder: A systematic review

BACKGROUND

Gene-environment interaction (G × E) refers to the change of genetic effects under the participation of environmental factors resulting in differences in genetic expression. G × E has been studied in the occurrence and development of many neuropsychiatric disorders, including obsessive-compulsive disorder (OCD).

AIM

A systematic review was conducted to investigate the role of G × E plays in OCD. This review explored the relationship between G × E and the susceptibility to OCD occurrence, disease progression, and treatment response.

METHODS

This systematic literature search was performed using Web of Science, PubMed, Cochrane Library, and CNKI. Seven studies were selected, which included seven genes (BDNF, COMT, MAO, 5-HTT, SMAD4, PGRN, and SLC1A1) polymorphisms, polygenic risk score (PRS), and two environmental factors (childhood trauma and stressful life events).

RESULTS

Information from this systematic review indicated that G × E increased the susceptibility to OCD, played a crucial role in the clinical characteristics, and had an inconsistent impact on treatment response of OCD.

FUTURE DIRECTIONS

The multi-omics studies and the inclusion of G × E in future GWAS studies of OCD should be drawn more attention, which may contribute to a deeper understanding of the etiology of OCD as well as guide therapeutic interventions for the disease.

A comparative investigation of catalytic mechanism and domain between catechol-O-methyltransferase isoforms by isomeric shikonin and alkannin

The differences in catalytic mechanism and domain between the soluble (S-COMT) and membrane-bound catechol-O-methyltransferase (MB-COMT) are poorly documented due to the unavailable crystal structure of MB-COMT. Considering the enzymatic nature of S-COMT and MB-COMT, the challenge could be solvable by probing the interactions between the enzymes with the ligands with minor differences in structures. Herein, isomeric shikonin and alkannin bearing a R/S -OH group in side chain at the C2 position were used for domain profiling of COMTs. Human and rat liver-derived COMTs showed the differences in inhibitory response (human's IC₅₀ and K_i values for S-COMT < rat's, 5.80-19.56 vs. 19.56-37.47 μM; human's IC₅₀ and K_i values for MB-COMT > rat's) and mechanism (uncompetition vs. noncompetition) towards the two isomers. The inhibition of the two isomers against human and rat S-COMTs was stronger than those for MB-COMTs (S-COMT's IC₅₀ and K_i values < MB-COMT's, 5.80-37.47 vs. 40.01-111.8 μM). Additionally, the inhibition response of alkannin was higher than those of shikonin in no matter human and rat COMTs. Molecular docking stimulation was used for analysis. The inhibitory effects observed in in vitro and in silico tests were confirmed in vivo. These findings would facilitate further COMT-associated basic and applied research.

Are catechol-O-methyltransferase gene polymorphisms genetic markers for pain sensitivity after all? - A review and meta-analysis

The catechol-O-methyltransferase (COMT) gene has arguably been the designated pain sensitivity gene for nearly two decades. However, the literature provides inconsistent evidence. We performed several meta-analyses including k = 31 samples and n = 4631 participants thereby revealing small effects of rs4680 on pain thresholds in fibromyalgia, headache and across chronic pain conditions. Moreover, rs4680 effects were found across pain patients when affected, but not unaffected, body sites were assessed. No effect was detected for any other SNP investigated. Importantly, our results corroborate earlier findings in that we found a small effect of COMT haplotypes on pain sensitivity. Our review and meta-analysis contribute to the understanding of COMT-dependent effects on pain perception, provide insights into research issues and offer future directions. The results support the theory that rs4680 might only impact behavioural measures of pain when descending pain modulatory pathways are sufficiently challenged. After all, COMT polymorphisms are genetic markers of pain sensitivity, albeit with some limitations which are discussed with respect to their implications for research and clinical significance.

Unveiling the biopathway for the design of novel COMT inhibitors

Catechol-O-methyltransferase (COMT) is an enzyme responsible for the O-methylation of biologically active catechol-based molecules. It has been associated with several neurological disorders, especially Parkinson's disease (PD), because of its involvement in catecholamine metabolism, and has been considered an important therapeutic target for central nervous system disorders. In this review, we summarize the biophysical, structural, and therapeutical relevance of COMT; the medicinal chemistry behind the development of COMT inhibitors and the application of computer-aided design to support the design of novel molecules; current methodologies for the biosynthesis, isolation, and purification of COMT; and revise existing bioanalytical approaches for the assessment of enzymatic activity in several biological matrices.

Specific dopaminergic genetic variants influence impulsivity, cognitive deficit, and disease severity of Indian ADHD probands

BACKGROUND

Impulsivity (Imp), being one of the cardinal symptoms of Attention Deficit Hyperactivity Disorder (ADHD), often leads to inappropriate responses to stimuli. Since the dopaminergic system is the primary target for pharmaceutical intervention in ADHD, we investigated the association between ADHD-related Imp and functional gene variants of the dopamine transporter (SLC6A3) and catechol-O-methyltransferase involved in dopamine clearance.

METHODS AND RESULTS

Indo-Caucasoid families with ADHD probands (N = 217) were recruited based on the Diagnostic and Statistical Manual of Mental Disorders (DSM). Imp of the probands was assessed using the Domain Specific Imp Scale for Children and DSM. Peripheral blood was collected after obtaining informed written consent for participation, genomic DNA was isolated, and target sites were genotyped by DNA sequencing. The association of genetic variants with Imp was examined by the Quantitative trait analysis (QTA) and Analysis of variance (ANOVA). Post-Hoc analysis following QTA and ANOVA showed significant associations of rs2254408, rs2981359, and rs2239393 with different domains of Imp (P < 0.05). Various haplotypic combinations also showed statistically significant associations with Imp (P < 0.05). Multifactor dimensionality reduction models revealed strong effects of the variants on Imp. ADHD probands harboring the risk alleles exhibited a deficit in performance during cognitive assessment. Longitudinal follow-up revealed a significant association of rs2254408 with trait persistence.

CONCLUSION

The present study indicates the influence of the studied genetic variants on ADHD-associated imp, executive deficit, and disease persistence. Thus, these variants may be helpful as predictors for the success of individual therapeutic sessions during cognitive training.

Childhood trauma and genetic variation in the DAT 40-bp VNTR contribute to HIV-associated neurocognitive disorders

HIV/AIDS is a major public health burden in South Africa, currently affecting an estimated 13.5% of the population. Despite improved access to antiretroviral therapies, HIV-associated neurocognitive disorders (HAND), characterised by a spectrum of neurocognitive impairment, emotional disturbances and motor abnormalities, continue to persist. Gene-environment interactions contribute to HAND pathophysiology and previous research has identified childhood trauma as an environmental risk factor. Dopaminergic signalling in the prefrontal cortex plays a key role in cognitive function. Thus, variants in genes encoding the dopamine transporter (DAT) and catechol-O-methyltransferase (COMT), which are responsible for dopamine transport and metabolism, could represent genetic risk factors for HAND. This study investigated whether the DAT variable number of tandem repeats (VNTR) and COMT Val158Met (rs4680) polymorphisms are associated with longitudinal change in cognitive function in the context of childhood trauma and HIV. Participants (n = 49 HIV-negative and n = 64 HIV-positive women) completed the Childhood Trauma Questionnaire - Short Form (CTQ-SF) and provided blood for genetic analyses. Global cognitive scores were generated from baseline and one-year follow-up assessments. Following polymerase chain reaction, genotypes were determined using gel electrophoresis and confirmed by Sanger sequencing. Baseline global cognitive scores, genotype, HIV status and CTQ-SF scores were regressed on one-year global cognitive scores in regression models. Analysis of variance was used to examine the effect of including predictor variable interactions on model fit. HIV seropositivity was associated with poorer cognitive performance at one-year follow-up (p = 2.46 ×10-4). The combination of HIV and DAT 10-repeat homozygosity (DAT 10/10) was associated with reduced global cognitive scores in longitudinal models (p = 0.010). Including the interaction between DAT 10/10, childhood trauma, and HIV explained significantly more of the variance in longitudinal cognitive scores (p = 0.008). There were no significant associations with the COMT genotype. Our research indicates that childhood trauma and genetic variation in DAT contribute toward the aetiology of HAND. Future studies in larger cohorts are warranted to verify these results.

Prediction of COMT Inhibitors Using Machine Learning and Molecular Dynamics Methods

Catechol O-methyltransferase (COMT) plays a vital role in deactivating neurotransmitters like dopamine, norepinephrine, etc., by methylating those compounds. However, the deactivation of an excess amount of neurotransmitters leads to serious mental ailments such as Parkinson's disease. Molecules that bind inside the enzyme's active site inhibit this methylation mechanism by methylating themselves, termed COMT inhibitors. Our study is focused on designing these inhibitors by various machine learning methods. First, we have developed a classification model with experimentally available COMT inhibitors, which helped us generate a new data set of small inhibitor-like molecules. Then, to predict the activity of the new molecules, we have applied regression techniques such as Random Forest, AdaBoost, gradient boosting, and support vector machines. Each of the regression models yielded an R² value > 70% for both training and test data sets. Finally, to validate our models, 200 ns long molecular dynamics (MD) simulations of the two known inhibitors with known IC₅₀ values and the resultant inhibitors were performed inside the binding pockets to check their stability within. The free energy barrier of the methyl transfer from S-adenosyl-l-methionine (SAM) to each inhibitor was determined by combining steered molecular dynamics (SMD) and umbrella sampling using the quantum mechanics/molecular mechanics (QM/MM) method.

Epigenetic moderators of naltrexone efficacy in reducing heavy drinking in Alcohol Use Disorder: a randomized trial

Polymorphisms in genes associated with opioid signaling and dopamine reuptake and inactivation may moderate naltrexone efficacy in Alcohol Use Disorder (AUD), but the effects of epigenetic modification of these genes on naltrexone response are largely unexplored. This study tested interactions between methylation in the μ-opioid receptor (OPRM1), dopamine transporter (SLC6A3), and catechol-O-methyltransferase (COMT) genes as predictors of naltrexone effects on heavy drinking in a 16-week randomized, placebo-controlled trial among 145 treatment-seeking AUD patients. OPRM1 methylation interacted with both SLC6A3 and COMT methylation to moderate naltrexone efficacy, such that naltrexone-treated individuals with lower methylation of the OPRM1 promoter and the SLC6A3 promoter (p = 0.006), COMT promoter (p = 0.005), or SLC6A3 3' untranslated region (p = 0.004), relative to placebo and to those with higher OPRM1 and SLC6A3 or COMT methylation, had significantly fewer heavy drinking days. Epigenetic modification of opioid- and dopamine-related genes may represent a novel pharmacoepigenetic predictor of naltrexone efficacy in AUD.

Dynamic DNA Methylation Changes in the COMT Gene Promoter Region in Response to Mental Stress and Its Modulation by Transcranial Direct Current Stimulation

Changes in epigenetic modifications present a mechanism how environmental factors, such as the experience of stress, can alter gene regulation. While stress-related disorders have consistently been associated with differential DNA methylation, little is known about the time scale in which these alterations emerge. We investigated dynamic DNA methylation changes in whole blood of 42 healthy male individuals in response to a stressful cognitive task, its association with concentration changes in cortisol, and its modulation by transcranial direct current stimulation (tDCS). We observed a continuous increase in COMT promotor DNA methylation which correlated with higher saliva cortisol levels and was still detectable one week later. However, this lasting effect was suppressed by concurrent activity-enhancing anodal tDCS to the dorsolateral prefrontal cortex. Our findings support the significance of gene-specific DNA methylation in whole blood as potential biomarkers for stress-related effects. Moreover, they suggest alternative molecular mechanisms possibly involved in lasting behavioral effects of tDCS.

Effect of Catechol-O-Methyltransferase Genotype Polymorphism on Neurological and Psychiatric Disorders: Progressing Towards Personalized Medicine

Different polymorphisms of the catechol-O-methyltransferase (COMT) gene affect the COMT enzyme activity. The COMT enzyme plays a major role in the pathophysiology of various neurological and psychiatric disorders. This review article aims to discuss what recent research has discovered about the association of COMT genotype polymorphism with neurological and psychiatric disorders and the scope for the knowledge to be applied for advancement in therapeutics. We searched PubMed and Google Scholar databases and found 1656 articles. We included observational studies, clinical trials, and meta-analyses in the English language published between 2019 and 2021. We screened the articles based on the title and the abstract and found 26 relevant articles. Diseases or conditions studied primarily were schizophrenia, Parkinson’s disease, Alzheimer’s disease, substance use, and depression. This article highlights how genetics influences the susceptibility of an individual to neurological and psychiatric diseases and the variations in the specific symptoms of those diseases. The review showed that the variability in individual response to therapeutic interventions stems from the gene level. This knowledge can contribute towards the dawn of a new era of personalized medicine.

Polymorphisms of Nav1.6 sodium channel, Brain-derived Neurotrophic Factor, Catechol-O-methyltransferase and Guanosine Triphosphate Cyclohydrolase 1 genes in trigeminal neuralgia

SUBJECTS

Trigeminal neuralgia is a neuropathic pain characterized by episodes of severe shock-like pain within the distribution of one or more divisions of the trigeminal nerve. Pain can be influenced by ethnicity, environment, gender, psychological traits, and genetics. Molecules Nav1.6 sodium channel, Brain-derived Neurotrophic Factor, Catechol-O-methyltransferase and Guanosine Triphosphate Cyclohydrolase 1 have been involved in mechanisms that underlie pain and neurological conditions.

OBJECTIVE

The aim of this case-control study was to investigate the occurrence of genetic polymorphisms in Nav1.6 sodium channel (SCN8A/rs303810), Brain-derived Neurotrophic Factor (BDNF/rs6265/Val66Met), Catechol-O-methyltransferase (COMT/rs4680/Val158Met), and Guanosine Triphosphate Cyclohydrolase 1 (GCH1/rs8007267) genes in trigeminal neuralgia patients.

METHODS

Ninety-six subjects were divided into two groups: 48 with trigeminal neuralgia diagnosis and 48 controls. Pain was evaluated by visual analog scale and genomic DNA was obtained from oral swabs and analyzed by real-time polymerase chain reaction.

RESULTS

No association was observed among SCN8A, BDNF, COMT or GCH1 polymorphisms and the presence of trigeminal neuralgia. Genotype distribution and allele frequencies did not correlate to pain severity.

CONCLUSIONS

Although no association of evaluated polymorphisms and trigeminal neuralgia or pain was observed, our data contributes to the knowledge of genetic susceptibility to trigeminal neuralgia, which is very scarce. Further studies may focus on other polymorphisms and mutations, as well as on epigenetics and transcriptional regulation of these genes, in order to clarify or definitively exclude the role of Nav1.6, BDNF, COMT or GCH1 in trigeminal neuralgia susceptibility and pathophysiology.

Insight into the Therapeutic Potential of a Bicyclic Hydroxypyridone Compound 2-[(2,4-Dichlorophenyl)methyl]-7-hydroxy-1,2,3,4-tetrahydro-8H-pyrido[1,2-a]pyrazin-8-one as COMT Inhibitor in the Treatment of Parkinson's Disease: A Molecular Dynamic Simulation Approach

Parkinson's disease (PD) is one of the most targeted neurodegenerative diseases in clinical research. Awareness of research is due to its increasing number of affected people worldwide. The pathology of PD has been linked to several key proteins upregulation such as the catechol O-Methyltransferase (COMT). Hence, the synthesis of compounds possessing inhibitory capacity has been the frontline of research in recent years. Several compounds have been synthesized among which is the nitrocatechol. However, major limitations associated with the nitrocatechol scaffold include the inability to possess adequate CNS penetration properties and hepatic toxicity associated with the compounds. However, a series of bicyclic hydroxypyridones compounds were synthesized to evaluate their inhibitory potentials on COMT protein with compound 38 (c38) 2-[(2,4-dichlorophenyl)methyl]-7-hydroxy-1,2,3,4-tetrahydro-8H-pyrido[1,2-a]pyrazin-8-one shown to have a 40 fold increase level coverage in its IC₅₀ over brain exposure when compared to the other synthesized compound. The molecular dynamics method was employed to understand the nature of interaction exhibited by c38. Molecular mechanics of c38 revealed a disruptive effect on the secondary structure of COMT protein. Per residue decomposition analysis revealed similar crucial residues involved in the favorable binding of c38 and tolcapone implicated its increased inhibitory capacity on COMT in preventing PD. Free binding energy (ΔG_bind ) of c38 further revealed the inhibitory capacity towards COMT protein in comparison to the FDA approved tolcapone. Ligand mobility analysis of both compounds showed a timewise different mobility pattern across the simulation time frame at the active site pocket of the protein connoting the different inhibitory potency exhibited by c38 and tolcapone. Findings from this study revealed optimization of c38 could facilitate the discovery of new compounds with enhanced inhibitory properties towards COMT in treating PD.

The neurobiology of human aggressive behavior: Neuroimaging, genetic, and neurochemical aspects

In modern societies, there is a strive to improve the quality of life related to risk of crimes which inevitably requires a better understanding of brain determinants and mediators of aggression. Neurobiology provides powerful tools to achieve this end. Pre-clinical and clinical studies show that changes in regional volumes, metabolism-function and connectivity within specific neural networks are related to aggression. Subregions of prefrontal cortex, insula, amygdala, basal ganglia and hippocampus play a major role within these circuits and have been consistently implicated in biology of aggression. Genetic variations in proteins regulating the synthesis, degradation, and transport of serotonin and dopamine as well as their signal transduction have been found to mediate behavioral variability observed in aggression. Gene-gene and gene-environment interactions represent additional important risk factors for aggressiveness. Considering the social burden of pathological forms of aggression, more basic and translational studies should be conducted to accelerate applications to clinical practice, justice courts, and policy making.

Membrane bound catechol-O-methytransferase is the dominant isoform for dopamine metabolism in PC12 cells and rat brain

Impaired dopamine activity in the dorsolateral prefrontal cortex (DLPFC) is thought to contribute to cognitive deficits in diseases such as schizophrenia, attention deficit hyperactivity disorder (ADHD) and traumatic brain injury. Catechol-O-methyltransfease (COMT) metabolizes dopamine and is an important regulator of dopamine signaling in the DLPFC. In mammalian species, two isoforms of COMT protein, membrane-bound COMT (MB-COMT) and soluble COMT (S-COMT), are encoded by one COMT gene and expressed widely. While S-COMT is thought to play a dominant role in the peripheral tissues, MB-COMT is suggested to have a greater role in dopamine metabolism in the brain. However, whether a selective inhibitor for MB-COMT may effectively block dopamine metabolism remains unknown. We generated a knockout of MB-COMT in PC12 cells using CRISPR-cas9 technology to evaluate the effect of both MB and S-COMT on dopamine metabolism. Deletion of MB-COMT in PC12 cells significantly decreased homovanillic acid (HVA), completely depleted 3-methyoxytyramine (3-MT), and significantly increased 3,4-dihydroxyphenylacetic acid (DOPAC) levels. Comparison of the effect of a MB-COMT selective inhibitor LI-1141 on dopamine metabolism in wild type and MB-COMT knockout PC12 cells allowed us to confirm the selectivity of LI-1141 with respect to MB-COMT in cells. Under conditions in which LI-1141 was shown to inhibit only MB-COMT but not S-COMT, it effectively changed dopamine metabolites similar to the effect induced by tolcapone, a non-selective COMT inhibitor, suggesting that selective inhibition of MB-COMT will be effective in blocking dopamine metabolism, providing an attractive therapeutic approach in improving cognition for patients.

Tissue and interspecies comparison of catechol-O-methyltransferase mediated catalysis of 6-O-methylation of esculetin to scopoletin and its inhibition by entacapone and tolcapone

Catechol-O-methyltransferase (COMT) methylates both endogenous and exogenous catechol compounds to inactive and safe metabolites. We first optimised conditions for a convenient and sensitive continuous fluorescence-based 6-O-methylation assay of esculetin, which we used for investigating the COMT activity in human, mouse, rat, dog, rabbit, and sheep liver cytosols and microsomes and in ten different rat tissues. Furthermore, we compared the inhibition potencies and mechanisms of two clinically used COMT inhibitors, entacapone and tolcapone, in these species. In most tissues, the COMT activity was at least three times higher in cytosol than in microsomes. In the rat, the highest COMT activity was found in the liver, followed by kidney, ileum, thymus, spleen, lung, pancreas, heart, brain, and finally, skeletal muscle. Entacapone and tolcapone were characterised as highly potent mixed type tight-binding inhibitors. The competitive inhibition type dominated over the uncompetitive inhibition with entacapone, whereas uncompetitive inhibition dominated with tolcapone. Rats, dogs, pigs, and sheep are high COMT activity species, in contrast to humans, mice, and rabbits; COMT activity is highest in the liver. Both entacapone and tolcapone are potent COMT inhibitors, but their inhibition mechanisms differ.

Novel, non-nitrocatechol catechol-O-methyltransferase inhibitors modulate dopamine neurotransmission in the frontal cortex and improve cognitive flexibility

RATIONALE

Cognitive impairment is a primary feature of many neuropsychiatric disorders and there is a need for new therapeutic options. Catechol-O-methyltransferase (COMT) inhibitors modulate cortical dopaminergic function and have been proposed as potential cognitive enhancers. Unfortunately, currently available COMT inhibitors are not good candidates due to either poor blood-brain barrier penetration or severe toxicity.

OBJECTIVES

To address the need for safe, brain-penetrant COMT inhibitors, we tested multiple novel compounds in a set of preclinical in vivo efficacy assays in rats to determine their ability to inhibit COMT function and viability as potential clinical candidates.

METHODS

We measured the change in concentration of dopamine (DA) metabolites in cerebrospinal fluid (CSF) from the cisterna magna and extracellular fluid (ECF) from the frontal cortex produced by our novel compounds. Additionally, we tested the effects of our brain-penetrant COMT inhibitors in an attentional set-shifting assay (ASST). We benchmarked the performance of the novel COMT inhibitors to the effects produced by the known COMT inhibitor tolcapone.

RESULTS

We found that multiple COMT inhibitors, exemplified by LIBD-1 and LIBD-3, significantly modulated dopaminergic function measured as decreases in homovanillic acid (HVA) and increases in 3,4-Dihydroxyphenylacetic acid (DOPAC), two DA metabolites, in CSF and the frontal cortex. Additionally, we found that LIBD-1 significantly improved cognitive flexibility in the ASST, an effect previously reported following tolcapone administration.

CONCLUSIONS

These results demonstrate that LIBD-1 is a novel COMT inhibitor with promising in vivo activity and the potential to serve as a new therapy for cognitive impairment.

In Silico Prediction of the Effects of Nonsynonymous Single Nucleotide Polymorphisms in the Human Catechol-O-Methyltransferase (COMT) Gene

Catechol-O-methyltransferase (COMT) enzyme performs transfer of methyl group to endogenous and exogenous catechol substrates. The COMT enzyme draws interest because of its association with psychiatric, neurological and cardiovascular diseases, and several cancers. Moreover, many prescribed drugs, supplements, and their metabolites are used as substrates of COMT enzyme. The human COMT gene has 226 nonsynonymous single nucleotide polymorphisms (nsSNPs) according to public databases. Uncovering of the molecular impacts of nsSNPs on COMT enzyme function and structure may provide standpoint on how COMT nsSNPs affect enzyme activity and contribute to disease development. Therefore, we aimed in this study to predict possible structural and functional damaging effects of all knowns nsSNPs in COMT gene by applying various bioinformatics tools. Two hundred and twenty-six nsSNPs were obtained from Ensembl, HGMD, ClinVar, and dbSNP databases. Twenty-eight nsSNPs were found to be high-risk changes for protein structure. Some of them were detected in extremely conserved sequences have functional and structural properties. Besides, high-risk nsSNPs were also uncovered to change properties of native COMT protein. Our findings demonstrated the significance of COMT high-risk nsSNPs on protein structure and function. We expect that our results will be helpful in future studies concerning experimental evaluation of the COMT gene polymorphisms and/or the association between COMT polymorphisms and disease development.

Human steroid biosynthesis, metabolism and excretion are differentially reflected by serum and urine steroid metabolomes: A comprehensive review

Advances in technology have allowed for the sensitive, specific, and simultaneous quantitative profiling of steroid precursors, bioactive steroids and inactive metabolites, facilitating comprehensive characterization of the serum and urine steroid metabolomes. The quantification of steroid panels is therefore gaining favor over quantification of single marker metabolites in the clinical and research laboratories. However, although the biochemical pathways for the biosynthesis and metabolism of steroid hormones are now well defined, a gulf still exists between this knowledge and its application to the measured steroid profiles. In this review, we present an overview of steroid hormone biosynthesis and metabolism by the liver and peripheral tissues, specifically highlighting the pathways linking and differentiating the serum and urine steroid metabolomes. A brief overview of the methodology used in steroid profiling is also provided.

Differential COMT DNA methylation in patients with Borderline Personality Disorder: Genotype matters

Differential DNA methylation in peripheral tissues has been associated with Borderline Personality Disorder (BPD). Alterations have been found in several genes, among them the Catechol-O-methyltransferase (COMT) gene. COMT is a known neuropsychiatric candidate gene, which contains a genotype variant (Val^108/158Met) that affects protein function and has been found associated with several psychiatric disorders. In addition, this variant also affects COMT DNA methylation. However, in previous epigenetic studies, the DNA methylation results have not always been controlled for genotype, even though overrepresentation of the Met allele has been frequently reported in cohorts of BPD patients. Therefore, in the present study, we investigated whether alteration of COMT DNA methylation in BPD patients is indeed associated with mental health status or merely influenced by a differential distribution of the COMT genotype between BPD patients and healthy control individuals. We found significant group differences, as well as a strong effect of genotype on COMT DNA methylation. While the direction of effect was different compared to a previous study, our study supports the finding of altered COMT DNA methylation in patients with BPD and reinforces the need to include genotype information in future DNA methylation studies of COMT.

Transcriptional effects in the estuarine guppy Poecilia vivipara exposed to sanitary sewage in laboratory and in situ

The urban growth has increased sanitary sewage discharges in coastal ecosystems, negatively affecting the aquatic biota. Mangroves, one of the most human-affected coastal biomes, are areas for reproduction and nursing of several species. In order to evaluate the effects of sanitary sewage effluents in mangrove species, this study assessed the hepatic transcriptional responses of guppy fish Poecilia vivipara exposed to sanitary sewage 33% (v:v), using suppressive subtraction hybridization (SSH), high throughput sequencing of RNA (Ion-proton) and quantification of transcript levels by qPCR of some identified genes in fish kept in a sewage-contaminated environment. Genes identified are related predominantly to xenobiotic biotransformation, immune system and sexual differentiation. The qPCR results confirmed the induction of cytochrome P450 1A (CYP1A), glutathione S transferase A-like (GST A-like) methyltransferase (MET) and UDP glycosyltransferase 1A (UDPGT1A), and repression of complement component C3 (C3), doublesex and mab-3 related transcription factor 1 (DMRT1), and transferrin (TF) in the laboratory experiment. In the field exposure, the transcript levels of CYP1A, DMRT1, MET, GST A-like and UDPGT1A were higher in fishes exposed at the contaminated sites compared to the reference site. Chemical analysis in fish from the laboratory and in situ experiments, and surface sediment from the sewage-contaminated sites revealed relevant levels of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCBs) and linear alkylbenzenes (LABs). These data reinforce the use of P. vivipara as a sentinel for monitoring environmental contamination in coastal regions.

Catechol-O-methyltransferase gene expression in stress-induced and non-stress induced schizophrenia

INTRODUCTION

As schizophrenia is a complex mental disorder and the outcome of gene-gene-environmental interactions, there are different possible pathophysiological mechanisms in different schizophrenia subtypes corresponding to various risk factors. This study was aimed at examining the impact of one of the most likely interactions, that is, 'dopamine and stress', in schizophrenia pathogenesis.

METHODS

Here, we investigated the interaction between 'war-related psychological trauma' without brain trauma and catechol-O-methyltransferase gene. Using real-time PCR analysis we measured catechol-O-methyltransferase gene expression level in the blood cells of 66 male subjects in four groups, namely veteran schizophrenia patients as 'stress-exposed schizophrenia' (S-schizophrenia), their healthy brothers as 'their genetically closest relatives' (S-siblings), schizophrenia patients without any history of significant stress as 'non-stress-exposed schizophrenia' (NoS-schizophrenia), and the control group. The results were analyzed by Relative Expression Software Tool 2009 software.

RESULTS

The catechol-O-methyltransferase gene expression was not significantly different between the S-schizophrenia and NoS-schizophrenia groups. However, compared to the control group, the catechol-O-methyltransferase expression was significantly decreased in three groups of S-schizophrenia, their healthy siblings, and NoS-schizophrenia patients.

CONCLUSION

This data supports that reduced blood catechol-O-methyltransferase expression, which may be associated with higher dopamine level, is involved both in stress-induced and non-stress-induced schizophrenia.

No association of COMT with insight problem solving in Chinese college students

Genes involved in dopamine (DA) neurotransmission, such as the catechol-O-methyltransferase gene (COMT), have been suggested as key genetic candidates that might underlie the genetic basis of insight. In a sample of Chinese college students, this study examined whether COMT was associated with individual differences in the ability to solve classic insight problems. The results demonstrated that COMT was not associated with insight problem solving and there was no gender-dependent effect. This study, together with previous studies, raises the possibility of a complex relationship between COMT and insight problem solving.

A gender-specific COMT haplotype contributes to risk modulation rather than disease severity of major depressive disorder in a Chinese population

BACKGROUND

COMT rs4680 Val158 allele is associated with high MB-COMT protein expression and elevated activity compared to the Met158 allele in post-mortem brains. A meta-analysis study suggested the link between COMT SNPs and MDD risk; in addition, MB membrane-bound (MB-COMT) specific genetic variation was reported that influences predisposition to depression amongst females.

METHODS

Four tagSNPs, including rs4680, were genotyped. 268 MDD subjects and 223 controls were enrolled. MDD severity was rated by HDRS. Total-COMT and MB-COMT mRNA were detected by quantitative PCR. COMT protein and activity were assayed by western blot and methyltransferase assay, respectively.

RESULTS

Haplotype TG of rs4633-rs4680, rs4646312 C, and rs4633 T allele might be linked to MDD vulnerability. Haplotype TG may interact with gender and affect MDD risk, since female haplotype TG carriers were estimated for a 9.17-fold higher risk than counterparts. COMT SNPs were not associated with HDRS scores. Haplotype TG female controls had higher MB-COMT protein, whereas non-TG female controls had higher soluble cytoplasmic (S-COMT) protein than other groups. COMT activity was much higher in controls than in MDD subjects.

LIMITATIONS

Restricted numbers of homozygous TG carriers were recruited and analyzed for COMT mRNA, protein and activity. Only peripheral blood samples were used.

CONCLUSIONS

A female-specific haplotype (haplotype TG)-MDD vulnerability association was found. TG female controls had higher MB-COMT protein and S-COMT. Altogether, high COMT protein and activity in female TG controls may be predisposing factors for enhanced MDD risk, though not correlated to MDD severity as rated by HDRS.

Delayed O-methylation of l-DOPA in MB-COMT-deficient mice after oral administration of l-DOPA and carbidopa

1. Catechol-O-methyltransferase (COMT) is involved in the O-methylation of l-DOPA, dopamine, and other catechols. The enzyme is expressed in two isoforms: soluble (S-COMT), which resides in the cytoplasm, and membrane-bound (MB-COMT), which is anchored to intracellular membranes. 2. To obtain specific information on the functions of COMT isoforms, we studied how a complete MB-COMT deficiency affects the total COMT activity in the body, peripheral l-DOPA levels, and metabolism after l-DOPA (10 mg kg^-1) plus carbidopa (30 mg kg^-1) administration by gastric tube in wild-type (WT) and MB-COMT-deficient mice. l-DOPA and 3-O-methyl-l-DOPA (3-OMD) levels were assayed in plasma, duodenum, and liver. 3. We showed that the selective lack of MB-COMT did not alter the total COMT activity, COMT enzyme kinetics, l-DOPA levels, or the total O-methylation of l-DOPA but delayed production of 3-OMD in plasma and peripheral tissues.

Identification and characterization of a catechol-o-methyltransferase cDNA in the catfish Heteropneustes fossilis: Tissue, sex and seasonal variations, and effects of gonadotropin and 2-hydroxyestradiol-17β on mRNA expression

Catechol-O-methyltransferase (COMT) is involved in the methylation and inactivation of endogenous and xenobiotic catechol compounds, and serves as a common biochemical link in the catecholamine and catecholestrogen metabolism. Studies on cloning, sequencing and function characterization comt gene in lower vertebrates like fish are fewer. In the present study, a full-length comt cDNA of 1442bp with an open-reading frame (ORF) of 792bp, and start codon (ATG) at nucleotide 162 and stop codon (TAG) at nucleotide 953 was isolated and characterized in the stinging catfish Heteropneustes fossilis (accession No. KT597925). The ORF codes for a protein of 263 amino acid residues, which is also validated by the catfish transcriptome data analysis. The catfish Comt shared conserved putative structural regions important for S-adenosyl methionine (AdoMet)- and catechol-binding, transmembrane regions, two glycosylation sites (N-65 and N-91) at the N-terminus and two phosphorylation sites (Ser-235 and Thr-240) at the C-terminus. The gene was expressed in all tissues examined and the expression showed significant sex dimorphic distribution with high levels in females. The transcript was abundant in the liver, brain and gonads and low in muscles. The transcripts showed significant seasonal variations in the brain and ovary, increased progressively to the peak levels in spawning phase and then declined. The brain and ovarian comt mRNA levels showed periovulatory changes after in vivo and in vitro human chorionic gonadotropin (hCG) treatments with high fold increases at 16 and 24h in the brain and at 16h in the ovary. The catecholestrogen 2-hydroxyE₂ up regulated ovarian comt expression in vitro with the highest fold increase at 16h. The mRNA and protein was localized in the follicular layer of the vitellogenic follicles and in the cytoplasm of primary follicles. The data were discussed in relation to catecholamine and catecholestrogen-mediated functions in the brain and ovary of the stinging catfish.

Impact of Catechol-O-Methyltransferase Val 158Met (rs4680) Polymorphism on Breast Cancer Susceptibility in Asian Population

Background:

Catechol-O-methyltransferase (COMT) is an important estrogen-metabolizing enzyme. Numerous case-control studies have evaluated the role COMT Val 158Met (rs4680;472G->A) polymorphism in the risk of breast cancer and provided inconclusive results, hence present meta-analysis was designed to get a more reliable assessment in Asian population.

Methods:

A total of 26 articles were identified through a search of four electronic databases-PubMed, Google Scholar, Science Direct and Springer link, up to March, 2016. Pooled odds ratios (ORs) with 95% con¬fidence intervals (CIs) were used as association measure to find out relationship between COMT Val158Metpolymorphism and the risk of breast cancer. We also assessed between study heterogeneity and publication bias. All statistical analyses were done by Open Meta-Analyst.

Results:

Twenty six case-control studies involving 5,971 breast cancer patients and 7,253 controls were included in the present meta-analysis. The results showed that the COMT Val158Met polymorphism was significantly associated with breast cancer risk except heterozygote model(allele contrast odds ratio (ORAvsG)= 1.13, 95%CI=1.02-1.24,p=0.01; heterozygote/co-dominant ORGAvsGG= 1.03, 95%CI=0.96-1.11,p=0.34; homozygote ORAAvsGG= 1.38, 95%CI= 1.08-1.76,p=0.009; dominant model ORAA+GAvsGG= 1.08, 95%CI=1.01-1.16,p=0.02; and recessive model ORAAvsGA+GG= 1.35, 95%CI=1.07-1.71,p=0.01). In addition, we also performed subgroup analysis based on source of controls and menopausal state of patients.

Conclusions:

In conclusion, the COMT Val158Met polymorphism was related to increased breast cancer susceptibility in the Asian population.

Manic symptom severity correlates with COMT activity in the striatum: A post-mortem study

OBJECTIVES

The enzyme catechol-O-methyltransferase (COMT), which catalyses the degradation of dopamine and norepinephrine, is posited to participate in the pathophysiology of bipolar disorder (BD) and schizophrenia. In support of this notion, rich evidence has documented that the severity of various BD and schizophrenia symptoms is moderated by rs4680, a single nucleotide polymorphism of the COMT gene featuring a valine (Val)-to-methionine (Met) substitution that results in lower catalytic activity. Nevertheless, the specific relevance of COMT enzymatic activity in the pathophysiology of BD and schizophrenia dimensions remains elusive.

METHODS

We measured COMT catalytic activity in post-mortem prefrontal cortices, striata and cerebella of schizophrenia and BD patients, as well as non-affected controls. These values were then correlated with rs4680 genotypes and psychopathology scores in the last week of life.

RESULTS

No direct correlation between COMT activity and rs4680 genotypes was found; however, the severity of manic symptoms was highly correlated with COMT activity in the striatum, irrespective of the diagnostic group.

CONCLUSIONS

These results suggest that COMT striatal activity, but not rs4680 genotype, may serve as a biomarker for manic symptoms. Future studies are warranted to confirm these findings and assess the neurobiological links between COMT striatal activity and manic symptoms.

1H, 15N, 13C backbone resonance assignments of human soluble catechol O-methyltransferase in complex with S-adenosyl-L-methionine and 3,5-dinitrocatechol

Catechol O-methyltransferase (COMT) is an enzyme that plays a major role in catechol neurotransmitter deactivation. Inhibition of COMT can increase neurotransmitter levels, which provides a means of treatment for Parkinson's disease, schizophrenia and depression. COMT exists as two isozymes: a soluble cytoplasmic form (S-COMT), expressed in the liver and kidneys and a membrane-bound form (MB-COMT), found mostly in the brain. Here we report the backbone ¹H, ¹⁵N and ¹³C chemical shift assignments of S-COMT in complex with S-adenosyl-L-methionine, 3,5-dinitrocatechol and Mg²⁺. Assignments were obtained by heteronuclear multidimensional NMR spectroscopy. In total, 97 % of all backbone resonances were assigned in the complex, with 205 out of a possible 215 residues assigned in the ¹H-¹⁵N TROSY spectrum. Prediction of solution secondary structure from a chemical shift analysis using the TALOS+ webserver is in good agreement with published X-ray crystal structures.

Cloning and expression of a novel catechol-O-methyltransferase in common marmosets

Catechol-O-methyltransferase (COMT) catalyzes the O-methylation of endogenous catechol amines and estrogens and exogenous catechol-type of drugs. A Parkinson's disease model of common marmoset (Callithrix jacchus) has been widely used in preclinical studies to evaluate inhibitory potential of new drug candidates on marmoset COMT. Despite COMT inhibitors could potentiate the pharmacological action of levodopa on Parkinson's disease in animal models, marmoset COMT cDNA has not yet been identified and characterized. In this study, a cDNA highly homologous to human COMT was cloned from marmoset livers. This cDNA encoded 268 amino acids containing a transmembrane region and critical amino acid residues for catalytic function. The amino acid sequences of marmoset COMT shared high sequence identity (90%) with human COMT. COMT mRNA was expressed in all five tissues tested, including brain, lung, liver, kidney and small intestine, and was more abundant in marmoset liver and kidney. Membrane-bound COMT was immunochemically detected in livers and kidneys, whereas soluble COMT was detected in livers, similar to humans. These results indicated that the molecular characteristics of marmoset COMT were generally similar to the human ortholog.

Meta-analysis of the COMT Val158Met polymorphism in major depressive disorder: the role of gender

OBJECTIVES

Many studies have reported an association of the COMT Val158Met polymorphism and major depressive disorder (MDD), although with conflicting results. The role of gender is a possible modulator. To overcome the problem of poor sample size detecting genes of small effect, we perform a meta-analysis of the current literature, investigating the influence of the COMT Val158Met polymorphism on the pathogenesis of MDD, with a major focus on the effect of gender.

METHODS

Out of 977 retrieved articles, 21 included case-control studies allowed the analysis of 9005 patients with MDD and 12,095 controls. Allelic and genotypic pooled odds ratios (OR) were calculated for the total sample and gender-subgroups.

RESULTS

In the absence of publication bias, allelic and genotypic analyses showed no significant association in the total sample, as well as in gender-specific subgroups. Sensitivity analysis did not alter the ORs.

CONCLUSIONS

The results imply a complex nature of the genotype × phenotype interaction. Further studies of the COMT gene or the locus remain to be justified given the important positional and functional relevance and the plethora of gender-specific findings. A possible way to further dissect this topic is shifting the focus to gene-based or genome-wide analyses of intermediate phenotypes.

The Role of the Catechol-o-Methyltransferase (COMT) GeneVal158Met in Aggressive Behavior, a Review of Genetic Studies

Aggressive behaviors have become a major public health problem, and early-onset aggression can lead to outcomes such as substance abuse, antisocial personality disorder among other issues. In recent years, there has been an increase in research in the molecular and genetic underpinnings of aggressive behavior, and one of the candidate genes codes for the catechol-O-methyltransferase (COMT). COMT is involved in catabolizing catecholamines such as dopamine. These neurotransmitters appear to be involved in regulating mood which can contribute to aggression. The most common gene variant studied in the COMT gene is the Valine (Val) to Methionine (Met) substitution at codon 158. We will be reviewing the current literature on this gene variant in aggressive behavior.

Evaluation of the Bioavailability and Metabolism of Nitroderivatives of Hydroxytyrosol Using Caco-2 and HepG2 Human Cell Models

Considering that nitrocatechols present putative effects against Parkinson's disease, the absorption and metabolism of nitroderivatives of hydroxytyrosol (HT) were assessed using human cell model systems. The test compounds nitrohydroxytyrosol (NO2HT), nitrohydroxytyrosyl acetate (NO2HT-A), and ethyl nitrohydroxytyrosyl ether (NO2HT-E) were efficiently transferred across human Caco-2 cell monolayers as an intestinal barrier model, NO2HT-A and NO2HT-E being better (p < 0.05) absorbed (absorption rate (AR) = 1.4 ± 0.1 and 1.5 ± 0.2, respectively) than their precursor, NO2HT (AR = 1.1 ± 0.1). A significant amount of the absorbed compounds remained unconjugated (81, 70, and 33% for NO2HT, NO2HT-A, and NO2HT-E, respectively) after incubation in Caco-2 cells, being available for hepatic metabolism. Nitrocatechols were extensively taken up and metabolized by human hepatoma HepG2 cells as a model of the human liver. Both studies revealed extensive hydrolysis of NO2HT-A into NO2HT, whereas NO2HT-E was not hydrolyzed. Glucuronide (75-55%), methylglucuronide (25-33%), and methyl derivatives (0-12%) were the main nitrocatechol metabolites detected after metabolism in Caco-2 and HepG2 cells. In conclusion, NO2HT, NO2HT-A, and NO2HT-E show high in vitro bioavailability and are extensively metabolized by hepatic cells.

Meta-Analysis of the COMT Val158Met Polymorphism in Major Depressive Disorder: Effect of Ethnicity

The COMT (catechol-O-methyltransferase) Val158Met polymorphism (rs4680) is a potential susceptibility variant for major depressive disorder (MDD). Although many genetic studies have examined the association between MDD and this polymorphism, the results were inconclusive. In the present study, we conducted a series of meta-analyses of samples consisting of 2905 MDD cases and 2403 controls with the goal of determining whether this variant indeed has any effect on MDD. We revealed a significant association in the comparison of Val/Val + Val/Met vs. Met/Met (OR =1.180; 95 % CI = 1.019, 1.367; P = 0.027), Val/Met vs. Val/Val (OR =1.18; 95 % CI = 1.038, 1.361; P = 0.013), and Val/Met vs. Met/Met (OR =1.229; 95 % CI = 1.053, 1.435; P = 0.009). Further meta-analyses of samples with European ancestry demonstrated a significant association of this SNP with MDD susceptibility in Val/Val + Val/Met vs. Met/Met (OR =1.231, 95 % CI = 1.046, 1.449; P = 0.013) and Val/Met vs. Met/Met (OR =1.284, 95 % CI = 1.050, 1.484; P = 0.012). For the samples with East Asian ancestry, we found a significant association in both allelic (Val vs. Met: OR =0.835; 95 % CI = 0.714, 0.975; P = 0.023) and genotypic (Met/Met + Val/Met vs. Val/Val: OR =1.431, 95 % CI = 1.143, 1.791; P = 0.002; Val/Met vs. Val/Val: OR =1.482, 95 % CI = 1.171, 1.871; P = 0.001) analyses. No evidence of heterogeneity among studies or publication bias was observed. Together, our results indicate that the COMT Val158Met polymorphism is a vulnerability factor for MDD with distinct effects in different ethnic populations.

Methylation, Glucuronidation, and Sulfonation of Daphnetin in Human Hepatic Preparations In Vitro: Metabolic Profiling, Pathway Comparison, and Bioactivity Analysis

Our previous study demonstrated that daphnetin is subject to glucuronidation in vitro. However, daphnetin metabolism is still poorly documented. This study aimed to investigate daphnetin metabolism and its consequent effect on the bioactivity. Metabolic profiles obtained by human liver S9 fractions and human hepatocytes showed that daphnetin was metabolized by glucuronidation, sulfonation, and methylation to form 6 conjugates which were synthesized and identified as 7-O-glucuronide, 8-O-glucuronide, 7-O-sulfate and 8-O-sulfate, 8-O-methylate, and 7-O-suflo-8-O-methylate. Regioselective 8-O-methylation of daphnetin was investigated using in silico docking calculations, and the results suggested that a close proximity (2.03 Å) of 8-OH to the critical residue Lysine 144 might be the responsible mechanism. Compared with glucuronidation and sulfonation pathways, the methylation of daphnetin had a high clearance rate (470 μL/min/mg) in human liver S9 fractions and contributed to a large amount (37.3%) of the methyl-derived metabolites in human hepatocyte. Reaction phenotyping studies showed the major role of SULT1A1, -1A2, and -1A3 in daphnetin sulfonation, and soluble COMT in daphnetin 8-O-methylation. Of the metabolites, only 8-O-methyldaphnetin exhibited an inhibitory activity on lymphocyte proliferation comparable to that of daphnetin. In conclusion, methylation is a crucial pathway for daphnetin clearance and might be involved in pharmacologic actions of daphnetin in humans.