Characterization and implications of estrogenic down-regulation of human catechol-O-methyltransferase gene transcription

Gonadectomy and hormone replacement exert region- and enzyme isoform-specific effects on monoamine oxidase and catechol-O-methyltransferase activity in prefrontal cortex and neostriatum of adult male rats

Sex differences and gonadal hormone influences are well known for diverse aspects of forebrain amine and indolamine neurotransmitter systems, the cognitive and affective functions they govern and their malfunction in mental illness. This study explored whether hormone regulation/dysregulation of these systems could be related to gonadal steroid effects on catechol-O-methyltransferase and monoamine oxidase which are principal enzymatic controllers of forebrain dopamine, serotonin and norepinephrine levels. Driven by male over female differences in cortical enzyme activities, by male-specific associations between monoamine oxidase and catechol-O-methyltransferase gene polymorphisms and cognitive and dysfunction in disease and by male-specific consequences of gene knockouts in mice, the question of hormone sensitivity was addressed here using a male rat model where prefrontal dopamine levels and related behaviors are also known to be affected. Specifically, quantitative O-methylation and oxidative deamination assays were used to compare the activities of catechol-O-methyltransferase's soluble and membrane-bound isoforms and of monoamine oxidase's A and B isoforms in the pregenual medial prefrontal cortex and dorsal striatum of male rats that were sham operated, gonadectomized or gonadectomized and supplemented with testosterone propionate or with estradiol for 28 days. These studies revealed significant effects of hormone replacement but not gonadectomy on the soluble but not the membrane-bound isorfom of catechol-O-methyltransferase in both striatum and cortex. A significant, cortex-specific testosterone-but not estradiol-attenuated effect (increase) of gonadectomy on monoamine oxidase's A but not B isoform was also observed. Although none of these actions suggest potential roles in the regulation/dysregulation of prefrontal dopamine, the suppressive effects of testosterone on cortical monoamine oxidase-A that were observed could have bearing on the increased incidence of cognitive deficits and symptoms of depression and anxiety that are repeatedly observed in males in conditions of hypogonadalism related to aging, other biological factors or in prostate cancer where androgen deprivation is used as a neoadjuvant treatment.

Effects of catechol-O-methyltransferase on normal variation in the cognitive function of children

OBJECTIVE

Genetic variants that contribute to the risk of psychiatric disorders may also affect normal variation in psychological function. Indeed, the behavioral effects of many genetic variants may be better understood as process-specific rather than disease-specific. A functional valine-to-methionine (Val(158)Met) polymorphism in the catechol-O-methyltransferase (COMT) gene has been associated with cognitive function and brain metabolic activity accompanying such tasks. Not all studies are consistent, and less is known about the effect of this polymorphism during development. The authors tested the hypothesis that a more informative COMT haplotype predicts normal cognitive development in a large population-based cohort of children enrolled in the Avon Longitudinal Study of Parents and Children.

METHOD

Effects on verbal and performance IQ as well as verbal inhibition were assessed at age 8, and effects on working memory were assessed at age 10. From the five COMT single nucleotide polymorphisms (SNPs) genotyped, the effect of a functional three-SNP haplotype consisting of Val(158)Met and two synonymous SNPs (rs6269 and rs4818), which together exert a major influence on the level of COMT expression and enzyme activity, was evaluated.

RESULTS

This three-SNP haplotype predicted both verbal inhibition and working memory, and there was a genotype-by-sex interaction on verbal IQ. The effect of COMT genotype (diplotype) on cognition was curvilinear, which is consistent with the "inverted U" model of dopamine effect on frontal cortical efficiency. In addition, the SNP rs2075507 (previously rs2097603) was independently associated with verbal inhibition, while rs165599 showed no main cognitive effects. However, rs165599 showed a genotype-by-sex interaction with working memory.

CONCLUSIONS

Genetic variation at several loci in the COMT gene affects normal cognitive function in children.

Influence of Catechol-O-Methyltransferase (COMT) Genotypes on the Prognosis of Canine Mammary Tumors

Catechol-O-methyltransferase (COMT) is an important enzyme involved in inactivation of catechol estrogens, which are metabolites with carcinogenic properties. Some investigations in human breast cancer associate a genetic polymorphism in the COMT gene (COMT val158met) with an increased risk and poor clinical progression of the disease. In dogs, there are 2 recognized single nucleotide polymorphisms in the COMT gene (COMTG216A and COMTG482A); however, their influence on the outcome of mammary neoplasms has never been investigated. The purpose of this study is to investigate the influence of COMT in the clinical progression of canine mammary tumors, namely in recurrence, metastasis and survival by testing 2 SNPs (G216A and G482A), and 2 genotypes of the COMT gene. A case series was conducted analyzing genomic DNA samples by polymerase chain reaction-restriction fragment length polymorphism from 80 bitches with mammary tumors. Animals were submitted to an active follow-up study for a period of 24 months after surgery. We observed that bitches carrying both genetic variations simultaneously are more likely to develop recurrence of mammary lesions. Our results demonstrate a possible role for COMT genotypes in the outcome of mammary neoplasms in the dog. Identifying a genetic factor predictive of recurrence may be useful in selecting the most effective surgical approach for canine mammary neoplasms.

Effect of estradiol on striatal dopamine activity of female hemiparkinsonian monkeys

A higher prevalence and incidence of Parkinson's disease is observed in men, and beneficial motor effects of estrogens are observed in parkinsonian women. In rodents, an effect of estradiol on dopamine systems is documented, whereas much less is known in monkeys. Enkephalin was shown to exert a compensatory modulatory effect on the denervated dopamine nigrostriatal pathway in monkeys and in humans. Moreover in rodents, striatal preproenkephalin mRNA is increased by estrogen treatment. Hence, we investigated the responsiveness of striatal dopamine to estradiol in long-term ovariectomized monkeys bearing a unilateral lesion with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to mimic parkinsonian postmenopausal women. Seven ovariectomized female monkeys received a unilateral MPTP lesion; 4 years after ovariectomy, three received 1-month treatment with 17beta-estradiol and the others received vehicle. The lesioned striata showed extensive denervation in all monkeys as measured with dopamine and metabolite concentrations assayed by high-performance liquid chromatography and by autoradiography of the dopamine transporter. The lesioned and intact striata of estradiol-treated monkeys had increased 3-methoxytyramine, and lesioned putamen increased dopamine concentrations compared with vehicle-treated monkeys. Estradiol treatment increased the dopamine transporter in subregions of the intact caudate and putamen compared with the intact striata of vehicle-treated monkeys, but not in the lesioned striata. Preproenkephalin mRNA levels measured by in situ hybridization were increased in the lesioned striata of vehicle treated monkeys and were not further enhanced in estradiol-treated monkeys. These results show that long after ovariectomy, modeling postmenopausal hormonal conditions, brain dopamine metabolism, and transporter are still responsive to estradiol.

Effects of age, genes, and pulse pressure on executive functions in healthy adults

Executive functions (EF) evidence significant age-related declines, but the mechanisms underpinning those changes are unclear. In this study, we focus on two potential sources of variation: a physiological indicator of vascular health, and genetic variants related to vascular functions. In a sample of healthy adults (n=158, ages 18-81), we examine the effects of age, pulse pressure, and two polymorphisms (comt val158met and ace insertion/deletion) on working memory and cognitive flexibility. Results indicate that in addition to often-replicated age differences, the alleles of two polymorphisms that promote vasoconstriction (comt val and ace D) and reduced availability of dopamine in neocortical synapses (comt val), negatively impact virtually all aspects of EF tasks that involve working memory. In some cases, suppression of cognitive performance is limited to men or necessitates a combination of both risk-associated alleles. After accounting for genetic and age-related variation, pulse pressure had no additional effect on EF. These findings suggest that in healthy adults, the effects of genetic risk factors significantly modulate the course of cognitive aging.

Developmental vitamin D deficiency alters dopamine turnover in neonatal rat forebrain

There is growing evidence that low vitamin D impacts adversely on brain development. The current study investigated the impact of developmental vitamin D (DVD) deficiency on dopamine and serotonin metabolism in the neonatal rat brain. DVD-deficiency resulted in an altered dopaminergic metabolic profile in the forebrain, with a decrease in the conversion of dihydroxyphenylacetic acid (DOPAC) to homovanillic acid (HVA). Correspondingly, expression of the enzyme required for this conversion, catechol-O-methyl transferase (COMT), was decreased. These results suggest that DVD-deficiency influences dopamine turnover during development.

Recent adaptive selection at MAOB and ancestral susceptibility to schizophrenia

The ancestral susceptibility hypothesis has been proposed to explain the existence of susceptibility alleles to common diseases. Some ancestral alleles, reflecting ancient adaptations, may be poorly adapted to the more contemporary environmental conditions giving rise to an increased risk to suffer some common disorders. In order to test this hypothesis in schizophrenia, we focused on the monoamine oxidase B gene (MAOB). This gene is involved in deamination of several monoamines, including both xenobiotic amines present in several foods, as well as neurotransmitters such as dopamine. In addition, preliminary analysis based on phase I HapMap data suggested that recent natural selection has acted on this locus. We further explored the existence of this recent positive selection using a test based on extension of linkage disequilibrium (LD) to large distance at the specific selected haplotype taking data from HapMap phase II, and searched for association of the ancestral haplotypes with schizophrenia in a sample of 532 schizophrenic patients and 597 controls from Spain. Our analysis suggested the existence of a haplotype of MAOB subject to recent selection. In agreement with the ancestral susceptibility hypothesis, the ancestral haplotypes were significantly over-represented in patients (P = 0.047). These haplotypes conferred an increased risk to schizophrenia, restricted to males (P = 0.024, OR = 1.41, 95% CI 1.01-1.90). Thus, pending on replication studies, MAOB seems to fit the ancestral susceptibility model, validating a new strategy to search for common schizophrenia susceptibility genes by focusing in those functional candidate genes subject to recent positive selection.

The effects of gender and COMT Val158Met polymorphism on fearful facial affect recognition: a fMRI study

The functional catechol-O-methyltransferase (COMT Val108/158Met) polymorphism has been shown to have an impact on tasks of executive function, memory and attention and recently, tasks with an affective component. As oestrogen reduces COMT activity, we focused on the interaction between gender and COMT genotype on brain activations during an affective processing task. We used functional MRI (fMRI) to record brain activations from 74 healthy subjects who engaged in a facial affect recognition task; subjects viewed and identified fearful compared to neutral faces. There was no main effect of the COMT polymorphism, gender or genotypexgender interaction on task performance. We found a significant effect of gender on brain activations in the left amygdala and right temporal pole, where females demonstrated increased activations over males. Within these regions, Val/Val carriers showed greater signal magnitude compared to Met/Met carriers, particularly in females. The COMT Val108/158Met polymorphism impacts on gender-related patterns of activation in limbic and paralimbic regions but the functional significance of any oestrogen-related COMT inhibition appears modest.

Characterization of NF-kB-mediated inhibition of catechol-O-methyltransferase

BACKGROUND

Catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines, has recently been implicated in the modulation of pain. Specifically, low COMT activity is associated with heightened pain perception and development of musculoskeletal pain in humans as well as increased experimental pain sensitivity in rodents.

RESULTS

We report that the proinflammatory cytokine tumor necrosis factor alpha (TNFalpha) downregulates COMT mRNA and protein in astrocytes. Examination of the distal COMT promoter (P2-COMT) reveals a putative binding site for nuclear factor kappaB (NF-kappaB), the pivotal regulator of inflammation and the target of TNFalpha. Cell culture assays and functional deletion analyses of the cloned P2-COMT promoter demonstrate that TNFalpha inhibits P2-COMT activity in astrocytes by inducing NF-kappaB complex recruitment to the specific kappaB binding site.

CONCLUSION

Collectively, our findings provide the first evidence for NF-kappaB-mediated inhibition of COMT expression in the central nervous system, suggesting that COMT contributes to the pathogenesis of inflammatory pain states.

The effect of catechol-O-methyltransferase Met/Val functional polymorphism on smoking cessation: retrospective and prospective analyses in a cohort study

OBJECTIVE

The Met/Val functional polymorphism of the gene-encoding catechol-O-methyltransferase (COMT) is one of the most widely tested variants for association with different phenotypes of addictive behavior, but replication has been inconsistent for smoking status. We investigated the relationship of this COMT single nucleotide polymorphism with smoking cessation in elderly persons in retrospective and prospective analyses.

METHODS

The study is embedded in the population-based Rotterdam Study cohort and included 5,115 persons aged 55 years and more. In the retrospective analyses using logistic regression, current smokers who had smoked 10 or more cigarettes daily for 10 or more years were compared with former smokers. In the prospective analyses, we followed 1,195 current smokers up to 12 years and used Cox proportional hazard model to detect the effect of the COMT single nucleotide polymorphism on self-reported incidence of smoking cessation.

RESULTS

The Val/Val genotype of COMT had a consistent association with smoking cessation as compared with the Met/Met+Met/Val genotypes in retrospective [odds ratio=0.79, 95% confidence interval (CI): 0.66-0.96, P=0.02] and prospective analyses (hazard ratio=0.80, 95% CI: 0.63-1.01, P=0.06). In the pooled analyses of prevalent and incident cessation cases that we compared with persisting smokers, the odds ratio was 0.70 (95% CI: 0.55-0.88, P=0.003). No sex difference and no effect of the COMT polymorphism on smoking initiation were observed.

CONCLUSION

Our results suggest that COMT Met/Val polymorphism is strongly associated with smoking cessation. The Met allele is the risk allele that decreases the likelihood of smoking cessation in men and women.

Sexually dimorphic effect of catechol-O-methyltransferase val158met polymorphism on clinical response to fluoxetine in major depressive patients

BACKGROUND

Essential in dopamine degradation, it was suggested that catechol-O-methyltransferase (COMT) might be involved in the action of antidepressants and may therefore be a promising candidate for antidepressant pharmacogenetic studies.

METHODS

COMT Val158met polymorphism was genotyped in 334 Chinese major depressive disorder (MDD) patients who were treated with fluoxetine for at least 4 weeks. Clinical response was evaluated using the 21-item Hamilton Rating Scale for Depression (HAM-D(21)). In the analysis of association, response was defined as >or=50% decrease in HAM-D(21) score after treatment and then further clarified by intra-individual changes in HAM-D(21) score.

RESULTS

We found that the COMT val158met polymorphism was not associated with 4-week fluoxetine therapeutic response; however, association analysis showed that patients with the COMT(Val/Val) genotype had poorer responses in the eighth week (CLUMP T1 P=0.020) and consistently showed significantly smaller reductions in HAM-D(21) scores in the eighth week (P=0.027). Further stratification based on gender revealed an isolated effect of the COMT genotype in males (P=0.035) but not in females (P=0.650) in percent reduction in HAM-D(21) scores in the eighth week.

LIMITATIONS

There was a lack of placebo control and the serum fluoxetine concentration was not taken into account.

CONCLUSIONS

This identified association between the COMT genetic variation and antidepressant response may be useful either as a clinical predictor in the future.

Longitudinal study on poor sleep and life dissatisfaction in a nationwide cohort of twins

Life satisfaction and quality of sleep are important, related components of subjective well-being and general health. However, no earlier investigation is known to have tested the direction of the temporal relation between poor sleep and diminished life satisfaction, including simultaneous examination of shared genetic influences. These features were examined in the present study of a nationwide cohort of 18,631 same-sex Finnish twins with repeated measurements of life satisfaction, sleep quality, and several potential confounders within an interval of 6 years (1975 and 1981). Most individuals (59%) with new-onset life dissatisfaction had experienced suboptimal sleep at baseline. Poor sleep predicted a consistent pattern of life dissatisfaction (odds ratio = 2.1, 95% confidence interval: 1.7, 2.7 from logistic regression on individuals; odds ratio = 3.0, 95% confidence interval: 1.7, 5.3 from conditional logistic regression on twin pairs discordant for life dissatisfaction), whereas life dissatisfaction did not consistently predict poor sleep. There was substantial heritability for both traits, but their shared genetic component was relatively weak, as indicated by genetic correlations of 0.21 for men and 0.27 for women in a multivariate genetic model. This finding is consistent with the hypothesis that poor sleep may have direct effects on the brain, emotions, and mood.

Association between COMT, PTSD, and increased smoking following hurricane exposure in an epidemiologic sample

Tobacco smoking has been found to increase after the experience of a traumatic event and has been associated with posttraumatic stress disorder (PTSD). Initiation and persistence of cigarette smoking is moderately heritable; two recent investigations have implicated the COMT Val158Met (also known as rs4680) polymorphism in smoking age of initiation, dependence, as well as in quantity and frequency of smoking. To examine a possible association of COMT Val158Met and posttrauma increases in cigarette smoking, we studied 614 adults from the 2004 Florida Hurricane Study who returned saliva DNA samples via mail. PTSD was strongly associated with increased smoking. Moreover, each COMT Val158Met 'Met' allele predicted a 2.10-fold risk of smoking post-hurricane, independent of PTSD; follow-up analyses revealed that this finding was primarily driven by European-American males. This study represents the first genetic association study (to our knowledge) of smoking behavior following an acute stressor.

Urine levels of catecholamines in Greek children with obstructive sleep-disordered breathing

INTRODUCTION

Adults with obstructive sleep apnea have increased sympathetic activity. It was hypothesized that in children with symptoms of obstructive sleep-disordered breathing (SDB), morning urine levels of catecholamines correlate with severity of nocturnal hypoxemia.

METHODS

Children with snoring referred for polysomnography and controls without snoring were recruited. Morning urine norepinephrine, epinephrine, normetanephrine, and metanephrine levels were measured (ng/mg urine creatinine).

RESULTS

Twelve children (age 5.2 +/- 2.3 years) with severe hypoxemia (oxygen saturation of hemoglobin-SpO2 nadir < or =86%), 20 subjects (age 6.1 +/- 2.1 years) with moderate hypoxemia (SpO2 nadir < or =90% and >86%), 22 children (age 6.6 +/- 1.5 years) with mild nocturnal hypoxemia (SpO2 nadir >90%), and 10 controls (age 7.1 +/- 2.8 years) were studied. Children with severe hypoxemia had significantly higher log-transformed norepinephrine levels (1.63 +/- 0.29) compared to those with moderate hypoxemia (1.43 +/- 0.22; P < 0.05) or compared to controls (1.39 +/- 0.31; P < 0.05). In subjects with SDB, log-transformed oxygen desaturation of hemoglobin index or SpO2 nadir predicted log-transformed norepinephrine levels after adjustment by age, gender and body mass index (r2 = 0.24; and r2 = 0.24, respectively; P < 0.01).

CONCLUSIONS

Severity of nocturnal hypoxemia in children with intermittent upper airway obstruction during sleep correlates with morning urine levels of norepinephrine suggesting increased sympathetic tone.

Catechol-O-methyltransferase (COMT): a gene contributing to sex differences in brain function, and to sexual dimorphism in the predisposition to psychiatric disorders

Sex differences in the genetic epidemiology and clinical features of psychiatric disorders are well recognized, but the individual genes contributing to these effects have rarely been identified. Catechol-O-methyltransferase (COMT), which metabolizes catechol compounds, notably dopamine, is a leading candidate. COMT enzyme activity, and the neurochemistry and behavior of COMT null mice, are both markedly sexually dimorphic. Genetic associations between COMT and various psychiatric phenotypes frequently show differences between men and women. Many of these differences are unconfirmed or minor, but some appear to be of reasonable robustness and magnitude; eg the functional Val(158)Met polymorphism in COMT is associated with obsessive-compulsive disorder in men, with anxiety phenotypes in women, and has a greater impact on cognitive function in boys than girls. Sex-specific effects of COMT are usually attributed to transcriptional regulation by estrogens; however, additional mechanisms are likely to be at least as important. Here we review the evidence for a sexually dimorphic influence of COMT upon psychiatric phenotypes, and discuss its potential basis. We conclude that despite the evidence being incomplete, and lacking a unifying explanation, there are accumulating and in places compelling data showing that COMT differentially impacts on brain function and dysfunction in men and women. Since sex differences in the genetic architecture of quantitative traits are the rule not the exception, we anticipate that additional evidence will emerge for sexual dimorphisms, not only in COMT but also in many other autosomal genes.

Executive attention in schizophrenic males and the impact of COMT Val108/158Met genotype on performance on the attention network test

BACKGROUND

Executive control of attention in schizophrenia has recently been assessed by means of the Attention Network Test (ANT). In the past, for tasks assessing executive attention, findings in schizophrenia have been contradictory, among others suggesting a lack of increased stimulus interference effects. Attention and executive functioning are substantially influenced by candidate genes of schizophrenia, including the functional single-nucleotide polymorphism catechol-o-methyltransferase (COMT) Val108/158Met, with task-dependent, specific effects of Met allele load on cognitive function. Therefore, we aimed at investigating executive attention in schizophrenic patients (SZP) as compared with healthy controls (HC), and to assess the specific impact of COMT Val108/158Met on executive attention, using ANT.

METHODS

We applied ANT to 63 SZP and 40 HC. We calculated a general linear model to investigate the influence of affection status and the COMT Val108/158Met genotype on executive attention as assessed by the ANT.

RESULTS

Multivariate analysis of variance revealed a significant effect of group on executive attention. SZP exhibited smaller conflict effects in the ANT. Met allele load significantly modulated executive attention efficiency, with homozygous Met individuals showing low overall reaction time but increased effects conflicting stimulus information in executive attention.

CONCLUSIONS

Our data suggest a disease-related dissociation of executive attention with reduced conflict effects in SZP. Furthermore, they support the hypothesis of differential tonic-phasic dopamine activation and specific dopamine level effects in different cognitive tasks, which helps interpreting contradictory findings of Met allele load on cognitive performance. Disease status seems to modulate the impact of COMT Val108/158Met on cognitive performance.

Catechol-O-methyltransferase (COMT) gene variants: possible association of the Val158Met variant with opiate addiction in Hispanic women

Catechol-O-methyltransferase (COMT) catalyzes the breakdown of catechol neurotransmitters, including dopamine, which plays a prominent role in drug reward. A common single nucleotide polymorphism (SNP), G472A, codes for a Val158Met substitution and results in a fourfold down regulation of enzyme activity. We sequenced exon IV of COMT gene in search for novel polymorphisms and then genotyped four out of five identified by direct sequencing, using TaqMan assay on 266 opioid-dependent and 173 control subjects. Genotype frequencies of the G472A SNP varied significantly (P = 0.029) among the three main ethnic/cultural groups (Caucasians, Hispanics, and African Americans). Using a genotype test, we found a trend to point-wise association (P = 0.053) of the G472A SNP in Hispanic subjects with opiate addiction. Further analysis of G472A genotypes in Hispanic subjects with data stratified by gender identified a point-wise significant (P = 0.049) association of G/A and A/A genotypes with opiate addiction in women, but not men. These point-wise significant results are not significant experiment-wise (at P < 0.05) after correction for multiple testing. No significant association was found with haplotypes of the three most common SNPs. Linkage disequilibrium patterns were similar for the three ethnic/cultural groups.

Genetic polymorphisms in methyl-group metabolism and epigenetics: lessons from humans and mouse models

Choline is an essential nutrient that is critical during fetal brain development. Choline deficiency, through disturbing methyl metabolism, may alter DNA methylation and thereby influence neural precursor cell proliferation and apoptosis. This results in long term alterations in brain structure and function, specifically memory function. A recommended dietary intake for choline in humans was set in 1998, and a portion of the choline requirement can be met via endogenous de novo synthesis of phosphatidylcholine catalyzed by phosphatidylethanolamine N-methyltransferase (PEMT) in the liver. Though many foods contain choline, many humans do not get enough in their diets. When deprived of dietary choline, most adult men and postmenopausal women developed signs of organ dysfunction (fatty liver, liver or muscle cell damage). However, only a portion of premenopausal women developed such problems. The difference in requirement occurs because estrogen induces expression of the PEMT gene and allows premenopausal women to make more of their needed choline endogenously. In addition, there is significant variation in the dietary requirement for choline that can be explained by common genetic variants (single nucleotide polymorphisms; SNPs) in genes of choline and folate metabolism. Some of these increase the risk of choline deficiency many-fold. These variations in choline requirement could have important implications for brain development.

Subtle gene-environment interactions driving paranoia in daily life

It has been suggested that genes impact on the degree to which minor daily stressors cause variation in the intensity of subtle paranoid experiences. The objective of the present study was to test the hypothesis that catechol-O-methyltransferase (COMT) Val(158)Met and brain-derived neurotrophic factor (BDNF) Val(66)Met in part mediate genetic effects on paranoid reactivity to minor stressors. In a general population sample of 579 young adult female twins, on the one hand, appraisals of (1) event-related stress and (2) social stress and, on the other hand, feelings of paranoia in the flow of daily life were assessed using momentary assessment technology for five consecutive days. Multilevel regression analyses were used to examine moderation of daily life stress-induced paranoia by COMT Val(158)Met and BDNF Val(66)Met genotypes. Catechol-O-methyltransferase Val carriers displayed more feelings of paranoia in response to event stress compared with Met carriers. Brain-derived neurotrophic factor Met carriers showed more social-stress-induced paranoia than individuals with the Val/Val genotype. Thus, paranoia in the flow of daily life may be the result of gene-environment interactions that can be traced to different types of stress being moderated by different types of genetic variation.

Phenotypic characterization of cognition and social behavior in mice with heterozygous versus homozygous deletion of catechol-O-methyltransferase

Catechol-O-methyltransferase is an important enzyme in the metabolism of dopamine and an important regulator of aspects of dopamine-dependent working memory in prefrontal cortex that are disturbed in schizophrenia. This study investigated the phenotype of mice with heterozygous deletion vs. homozygous knockout of the catechol-O-methyltransferase gene across paradigms that access processes relevant for psychotic illness. Homozygotes evidenced improved performance in spontaneous alternation, an index of immediate spatial working memory; this effect appeared more substantive in males and was reflected in performance in aspects of the Barnes maze, an index of spatial learning/memory. Heterozygotes evidenced impaired performance in object recognition, an index of recognition memory; this effect was evident for both sexes at a retention interval of 5 min but appeared more enduring in males. There were no material effects for either genotype in relation to sociability or social novelty preference. While homozygous catechol-O-methyltransferase deletion results in improvement in spatial learning/working memory with little effect on social behavior, heterozygous deletion results in impairment of recognition memory. We have reported recently, using similar methods, that mice with deletion of the schizophrenia risk gene neuregulin-1 evidence disruption to social behavior, with little effect on spatial learning/working memory. The data suggest that catechol-O-methyltransferase and neuregulin-1 may influence, respectively, primarily cognitive and social endophenotypes of the overall schizophrenia syndrome.

Catechol-O-methyltransferase Val158Met polymorphism and clinical characteristics in first episode non-affective psychosis

Catechol-O-methyltransferase (COMT) Val158Met polymorphism has been identified as a potential etiologic factor in schizophrenia. It has been proposed that this polymorphism could be associated with specific clinical markers. The aim of the study was to evaluate the influence of COMT Val158Met polymorphism genotype in the phenotypic expression of first episode psychosis at onset. Age of onset, DUP, SANS, and SAPS (positive, disorganized, and negative dimensions) were studied in 169 Caucasian drug-naïve patients with a first-episode of non-affective psychosis. The COMT Val158Met polymorphism was typed using PCR amplification of the relevant region followed by digestion with NlaIII and electrophoresis. A multivariate ANCOVA was performed with COMT and gender as independent variables. Patients with Val/Val genotype had significantly higher levels of SANS negative dimension scores (F: 3.539; P = 0.031) and had a younger age of onset (F: 4.649; P = 0.011) than Met carriers. Our findings suggest that the Val allele is associated with onset phenotypic features related to a poor prognosis of the illness. These data would indicate that COMT genotype may have a role in the etiological model for schizophrenia and other psychotic disorders.

Obesity is Associated with Genetic Variants That Alter Dopamine Availability

Human and animal studies have implicated dopamine in appetite regulation, and family studies have shown that BMI has a strong genetic component. Dopamine availability is controlled largely by three enzymes: COMT, MAOA and MAOB, and by the dopamine transporter SLC6A3, and each gene has a well-characterized functional variant. Here we look at these four functional polymorphisms together, to investigate how heritable variation in dopamine levels influences the risk of obesity in a cohort of 1150, including 240 defined as obese (BMI > or = 30). The COMT and SLC6A3 polymorphisms showed no association with either weight, BMI or obesity risk. We found, however, that both MAOA and MAOB show an excess of the low-activity genotypes in obese individuals (MAOA:chi2= 15.45, p = 0.004; MAOB:chi2= 8.05, p = 0.018). Additionally, the MAOA genotype was significantly associated with both weight (p = 0.0005) and BMI (p = 0.001). When considered together, the 'at risk genotype'--low activity genotypes at both the MAOA and MAOB loci--shows a relative risk for obesity of 5.01. These results have not been replicated and, given the experience of complex trait genetics, warrant caution in interpretation. In implicating both the MAOA and MOAB variants, however, this study provides the first indication that dopamine availability (as opposed to other effects of MAOA) is involved in human obesity. It is therefore a priority to assess the associations in replication datasets.

Differential effects of COMT on gait and executive control in aging

Walking speed is associated with attention and executive control processes subserved by the prefrontal cortex. Because polymorphisms in catechol-O-methyltransferase (COMT) influence these cognitive processes we hypothesized that the same polymorphisms may influence gait velocity. We examined the associations between the Val(158)Met polymorphism in COMT and gait velocity as well as attention and executive function. Participants were 278 non-demented older adults. The results revealed that methionine (Met)/valine (Val) was associated with faster gait velocity. This association can be explained by the putative role of the Val allele in regulating tonic dopamine release in the striatum. In contrast, Met/Met was associated with better attention and executive function. Stratification by gender revealed that the association between COMT genotype and gait was significant only in men. Conversely, the association between COMT genotype and attention and executive function was significant only in women. These findings suggest a differential effect in relating the Val(158)Met polymorphism to gait and to cognitive function while supporting the previously described sexual dimorphism in the phenotypic expressions of COMT.

Association of COMT Val108/158Met genotype with smoking cessation

OBJECTIVES

We attempted to extend a previous finding of an association of COMT genotype with response to nicotine-replacement therapy (NRT), in a larger cohort of treatment-seeking smokers, with greater statistical power to detect possible moderating effects of sex. We also investigated the association of the COMT genotype with withdrawal and mood symptoms, to identify possible mediating mechanisms by which the COMT genotype might influence response to NRT.

METHODS

Participants were eligible if they were aged 18 years or older, and if they smoked 10 cigarettes per day or more; they were recruited from 26 general practice clinics in Buckinghamshire and Oxfordshire in the United Kingdom. All participants received 8 weeks of 15-mg NRT transdermal patch. Confirmation of abstinence was defined as an exhaled CO of less than 10 parts per million (ppm), or salivary cotinine concentration of less than 15 ng/ml.

RESULTS

Cox regression analysis indicated a significant effect of the COMT genotype on relapse into smoking (P=0.001), with shorter times to relapse being observed among the AG (Val/Met) and GG (Val/Val) genotype groups. These effects were observed both during active treatment and as soon as active treatment had ended. The effect, however, was greater, once active treatment had ended, in the subgroup of smokers who had abstained up to this point. We did not observe any evidence of a sex difference in the effect of the COMT genotype. These effects did not seem to be mediated by self-reported withdrawal or mood symptoms.

CONCLUSIONS

Our results indicate that the COMT genotype is associated with the likelihood of smoking cessation in smokers treated with the NRT transdermal patch. Future large-scale studies will be required to afford sufficient power to simultaneously investigate the role of multiple genetic variants in treatment responses, and the effects of potential moderating variables on these associations.

Analyses of variants located in estrogen metabolism genes (ESR1, ESR2, COMT and APOE) and schizophrenia

Relationships between gender, age-of-onset of schizophrenia and reproductive age strongly suggest a key role for gonadal hormones, and more specifically for estrogens, in the etiology of the illness. Also, estrogens act as neural growth and trophic factors influencing neuron and glial cells in many areas of the central nervous system. Therefore, we investigated the association between schizophrenia and 4 genes related to estrogen metabolism. These genes are ESR1 (estrogen receptor 1), ESR2 (estrogen receptor 2), APOE (apolipoprotein E) and COMT (catechol-O-methyltransferase). The expression of APOE and COMT, which contain estrogen response elements, have been demonstrated to be regulated by the estrogen receptors. In this current association study, we examined 59 single nucleotide polymorphisms (SNPs) located in the ESR1 (26), ESR2 (14), APOE (7) and COMT (12) loci. Allele frequencies were evaluated in the schizophrenia (n=585)-control (n=615) sample and no association was found with any of the four genes. In conclusion, our data suggest that the four analyzed genes do not play an important role in susceptibility to schizophrenia.

Association of the COMT val158met variant with antidepressant treatment response in major depression

In several previous biochemical, pharmacological, and genetic studies, the catechol-O-methyltransferase (COMT) has been suggested to be involved in the pathogenesis as well as the pharmacological treatment of affective disorders. In the present study, 256 patients with major depression (DSM-IV) of Caucasian descent were genotyped for the functional COMT val158met polymorphism and characterized for clinical response to antidepressive pharmacological treatment as measured by intra-individual changes of Hamilton Depression (HAM-D-21) scores over 6 weeks. The COMT 158val/val genotype conferred a significant risk of worse response after 4-6 weeks of antidepressant treatment in patients with major depression (week 4: p=0.003; week 5: p<0.0001; week 6: p<0.0001) after Bonferroni correction for multiple comparisons. The present results strongly point toward a negative influence of the higher activity COMT 158val/val genotype on antidepressant treatment response during the first 6 weeks of pharmacological treatment in major depression, possibly conferred by consecutively decreased dopamine availability. This finding suggests a potentially beneficial effect of an antidepressive add-on therapy with substances increasing dopamine availability individually tailored according to COMT val158met genotype.

Polymorphisms in catechol-O-methyltransferase and methylenetetrahydrofolate reductase in relation to the risk of schizophrenia

BACKGROUND

Evidence is emerging for the association of aberrant homocysteine-methylation cycle and increased risk of schizophrenia.

METHODS

We examined the prevalence of the catechol-O-methyltransferase (COMT) 324G>A (Val108/158Met) and methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphisms in 252 patients with schizophrenia and 405 control subjects. All subjects were of Dutch ancestry.

RESULTS

The COMT 324AA genotype was not associated with an increased risk of schizophrenia (odds ratio (OR)=1.38 [95% CI: 0.88-2.16], P=0.162), and the MTHFR 677TT genotype showed a nearly significant increased risk for schizophrenia (OR=1.65 [95% CI: 0.97-2.82], P=0.067). The odds ratio for schizophrenia associated with joint occurrence of the COMT 324AA and MTHFR 677TT genotype was 3.08 (95% CI: 1.08-8.76) (P=0.035). Increasing number of low enzyme activity alleles in the COMT and MTHFR genotype combinations were associated with an increased risk of schizophrenia (test for trend, P=0.017).

CONCLUSIONS

Our findings do not support a major role for the COMT 324AA and MTHFR 677TT genotype alone, but the combination of both genotypes might increase schizophrenia susceptibility.

Soy isoflavones decrease the catechol-O-methyltransferase-mediated inactivation of 4-hydroxyestradiol in cultured MCF-7 cells

The tissue concentrations of the female sex hormone 17beta-estradiol (E2) and its reactive catechol metabolites such as 4-hydroxyestradiol (4-HO-E2) play important roles in hormonal carcinogenesis. They are influenced by the activity of local enzymes involved in the metabolic activation and inactivation of E2. In the mammary gland, catechol estrogens are predominately inactivated by catechol-O-methyltransferase (COMT). Food supplements containing the soy isoflavones genistein and daidzein are consumed because they are believed to protect from breast cancer; however, this proposed benefit is controversial. The aim of the present study was to investigate the influence of soy isoflavones on the gene expression and activity of COMT in cultured human mammary adenocarcinoma MCF-7 cells. Levels of COMT messenger RNA (mRNA) were determined by reverse transcription/competitive polymerase chain reaction and COMT activity was determined by high-performance liquid chromatography analysis of the methylation products of both the model substrate quercetin and the physiological relevant substrate 4-HO-E2. Our study demonstrates for the first time that soy isoflavones at hormonally active concentrations cause a significant reduction of both COMT mRNA levels and COMT activity as well as of the methylation of 4-HO-E2. Experiments using the estrogen receptor (ER) antagonist ICI 182,780 support a role of the ER in the isoflavone-induced down-regulation of COMT expression. Thus, this study not only demonstrates that hormonally active concentrations of soy isoflavones inhibit the detoxification of catechols in this human breast cancer cell line but also implies that diet might influence COMT activity to a greater extent than heretofore recognized.

FKBP5, SERT and COMT mRNA expressions in the peripheral leukocytes during menstruation cycle in healthy reproductive females

There have been several evidences that the mRNA expressions in the peripheral leukocytes may indicate not only physical but also psychological states. The purpose of this study is whether the mRNA expressional changes in the leukocytes are related to the mental states across the menstrual cycle in reproductive healthy female subjects. Thirty-eight female subjects (22.4+/-1.4 year-old) were participated in this study at three menstruation cycle periods (menstrual, follicular and luteal phase). The FKBP5 (FK506-binding protein gene), SERT (serotonin transporter gene) and COMT (catechol-o-methyltransferase gene) mRNA expressions in the leukocytes were determined with hormonal data. The psychological changes were assessed with self-rating hospital anxiety and depression scale (HADS). Only one thirds of subjects (n=12) had regular menstrual cycles during the experiment. So we analyzed the data from these 12 subjects. The anxiety score of each subject was changed across the menstrual cycle (Friedman test: P<0.05). The FKBP5 mRNA expression was significantly lower in the follicular phase than in the other phases but no changes were seen in either SERT or COMT mRNA expressions among the phases. In conclusion, there are differences of HADS anxiety score and FKBP5 mRNA expression in the leukocytes across the menstrual cycle but there is no correlation between anxiety scores and FKBP5 mRNA.

Gene response elements, genetic polymorphisms and epigenetics influence the human dietary requirement for choline

Recent progress in the understanding of the human dietary requirement for choline highlights the importance of genetic variation and epigenetics in human nutrient requirements. Choline is a major dietary source of methyl-groups (one of choline's metabolites, betaine, participates in the methylation of homocysteine to form methionine); also choline is needed for the biosynthesis of cell membranes, bioactive phospholipids and the neurotransmitter acetylcholine. A recommended dietary intake for choline in humans was set in 1998, and a portion of the choline requirement can be met via endogenous de novo synthesis of phosphatidylcholine catalyzed by phosphatidylethanolamine N-methyltransferase (PEMT) in the liver. Though many foods contain choline, many humans do not get enough in their diets. When deprived of dietary choline, most adult men and postmenopausal women developed signs of organ dysfunction (fatty liver, liver or muscle cell damage, and reduces the capacity to handle a methionine load, resulting in elevated homocysteine). However, only a portion of premenopausal women developed such problems. The difference in requirement occurs because estrogen induces expression of the PEMT gene and allows premenopausal women to make more of their needed choline endogenously. In addition, there is significant variation in the dietary requirement for choline that can be explained by common polymorphisms in genes of choline and folate metabolism. Choline is critical during fetal development, when it alters DNA methylation and thereby influences neural precursor cell proliferation and apoptosis. This results in long term alterations in brain structure and function, specifically memory function.

Progesterone-mediated regulation of catechol-O-methyl transferase expression in endometrial cancer cells

The effects of estrogen and progesterone on the expression of estrogen-metabolizing enzymes such as catechol-O-methyl transferase (COMT) are not known. COMT converts genotoxic catecholestrogens to anticarcinogenic methoxyestrogens in the endometrium. The aim of this study is to investigate the effect of progesterone on COMT expression in well-differentiated endometrial cancer cells. The wild-type Ishikawa cell line as well as progesterone receptor A- or progesterone receptor B-transfected Ishikawa cells were used for in vitro studies. The regulation of COMT expression by progesterone was studied using Western blots, Hoechst dye DNA proliferation studies, and wild-type and/or site-directed mutagenesis of COMT promoter 1-luciferase reporter gene. Progesterone upregulated COMT protein expression in Ishikawa cells through progesterone receptor A isoform. COMT promoter activity was differentially regulated by the 3 half-site progesterone response elements in the COMT promoter. High doses of 2-ME2 inhibited Ishikawa cell proliferation. These data suggest that COMT expression is hormonally regulated in well-differentiated human endometrial cancer cells. COMT regulation and 2-ME2 production in the endometrium may affect endometrial carcinogenesis.

Progesterone regulates catechol-O-methyl transferase gene expression in breast cancer cells: distinct effect of progesterone receptor isoforms

There is strong evidence that catechol-O-methyl transferase (COMT) protects breast cells against estrogen-induced cancer by detoxifying catecholestrogens, the carcinogenic estrogen metabolites. COMT gene expression is controlled by two promoters - a proximal promoter (COMTP1) and a distal promoter (COMTP2) - that regulate the expression of soluble (S-COMT) and membrane-bound (MB-COMT) isoforms, respectively. We investigated the transcriptional regulation of the COMT gene by progesterone/progesterone receptors in breast cancer cells. Our results indicated that progesterone (P4) downregulates COMT gene expression in breast cancer cell lines. In addition, the COMTP1 and COMTP2 harbor several progesterone response elements (PREs). Electrophoretic mobility shift assay (EMSA) indicated that nuclear extracts of T47D cells bind to the identified PREs in COMTP1. Site-directed mutagenesis of PREs in COMTP1 not only reversed the P4-induced inhibition of COMTP1, but also increased its basal activity. The two progesterone receptor isoforms, PR-A and PR-B, were found to have opposite effects on the regulation of P4 in COMT expression; PR-A is associated with P4-induced upregulation of COMT, while PR-B is associated with P4-induced downregulation of COMT. In summary, our data demonstrated that P4 downregulates the COMT gene expression through multiple PREs in the COMT promoters and that different progesterone receptor isoforms have distinctive effects on COMT gene expression.

Risk for premenstrual dysphoric disorder is associated with genetic variation in ESR1, the estrogen receptor alpha gene

BACKGROUND

Premenstrual dysphoric disorder (PMDD) is a heritable mood disorder that is triggered by gonadal steroids during the luteal phase in susceptible women.

METHODS

We performed haplotype analyses of estrogen receptors alpha and beta (ESR1 and ESR2) in 91 women with prospectively confirmed PMDD and 56 control subjects to investigate possible sources of the genetic susceptibility to affective dysregulation induced by normal levels of gonadal steroids. We also examined associations with the valine (Val)158methionine (Met) single nucleotide polymorphism (SNP) of the gene for catechol-O-methyltransferase (COMT), an enzyme involved in estrogen metabolism and prefrontal cortical activation.

RESULTS

Four SNPs in intron 4 of ESR1 showed significantly different genotype and allele distributions between patients and control subjects. Significant case-control differences were seen in sliding-window analyses of two-, three-, and four-marker haplotypes but only in those haplotypes containing SNPs in intron 4 that were positive in the single-locus analysis. No significant associations were observed with ESR2 or with the COMT Val158Met polymorphism, although the significant associations with ESR1 were observed only in those with the Val/Val genotype.

CONCLUSIONS

These are the first positive (albeit preliminary) genetic findings in this reproductive endocrine-related mood disorder and involve the receptor for a hormone that is pathogenically relevant.

Phosphatidylethanolamine N-methyltransferase (PEMT) gene expression is induced by estrogen in human and mouse primary hepatocytes

Choline is an essential nutrient for humans, though some of the requirement can be met by endogenous synthesis catalyzed by phosphatidylethanolamine N-methyltransferase (PEMT). Premenopausal women are relatively resistant to choline deficiency compared with postmenopausal women and men. Studies in animals suggest that estrogen treatment can increase PEMT activity. In this study we investigated whether the PEMT gene is regulated by estrogen. PEMT transcription was increased in a dose-dependent manner when primary mouse and human hepatocytes were treated with 17-beta-estradiol for 24 h. This increased message was associated with an increase in protein expression and enzyme activity. In addition, we report a region that contains a perfect estrogen response element (ERE) approximately 7.5 kb from the transcription start site corresponding to transcript variants NM_007169 and NM-008819 of the human and murine PEMT genes, respectively, three imperfect EREs in evolutionarily conserved regions and multiple imperfect EREs in nonconserved regions in the putative promoter regions. We predict that both the mouse and human PEMT genes have three unique transcription start sites, which are indicative of either multiple promoters and/or alternative splicing. This study is the first to explore the underlying mechanism of why dietary requirements for choline vary with estrogen status in humans.

Meta-analysis of COMT val158met in panic disorder: ethnic heterogeneity and gender specificity

There is strong evidence for a genetic contribution to the pathogenesis of panic disorder, with the functional catechol-O-methyltransferase (COMT) val158met polymorphism having been suggested as a potential susceptibility factor. In the present study, a meta-analysis of six available case-control studies (557 patients with panic disorder and 763 healthy controls in total) on the role of the COMT val158met polymorphism in panic disorder was conducted in an attempt to reconcile previous conflicting results and to facilitate evaluation of the role of COMT gene variation in panic disorder. Overall, no significant association, but strong between-study heterogeneity, was discerned. Analysis of studies pooled by ancestry yielded a significant association of the COMT 158val allele with panic disorder in Caucasian samples and, conversely, a trend towards association of the COMT 158met allele with the disorder in Asian samples. Interestingly, stratification for gender as well as ethnicity revealed that association of the 158val allele in Caucasians and, reciprocally, the 158met allele in Asian samples was restricted to females. The present meta-analysis provides tentative support for the COMT val158met polymorphism as a possible risk factor for panic disorder, with differential effects in Caucasian and Asian populations, and suggests a female-specific effect. However, given the relatively small number of case-control studies presently available, several more association studies, preferably including a larger number of family-based studies, are warranted for conclusive evaluation of the COMT val158met polymorphism as a vulnerability factor in panic disorder.

Association of COMT Val108/158Met genotype with smoking cessation in a nicotine replacement therapy randomized trial

We investigated the association of catechol O-methyltransferase (COMT) genotype with abstinence following a smoking cessation attempt among a large cohort of smokers who attempted to quit using either the nicotine transdermal patch or placebo and were followed up over an 8-year period following their initial cessation attempt. In addition, we examined the possible moderating influence of sex on any association. The genotype x treatment interaction effect at 12-week follow-up indicated a greater benefit of active nicotine replacement treatment compared with placebo on likelihood of abstinence in the COMT Met/Met genotype group (33% versus 12%), in comparison to the Met/Val + Val/Val group (22% versus 16%). Our results indicate that COMT genotype may moderate the effect of active transdermal nicotine patch compared with placebo, with reduced relative benefit of nicotine replacement therapy in individuals with Met/Val or Val/Val genotype. Our data follow an emerging pattern of results suggesting that genetic variation in the dopamine pathway may provide a future basis for tailored smoking cessation therapies, but indicate that different genes influencing various components of this pathway may have different effects on response to smoking cessation pharmacotherapy.

Expression and cyclic variations of catechol-O-methyl transferase in human endometrial stroma

OBJECTIVE

To investigate the role of catechol-O-methyl transferase (COMT) in the regulation of estrogen metabolism in human endometrium.

DESIGN

Laboratory study.

SETTING

Academic research laboratory.

INTERVENTION(S)

Immunohistochemistry was used to localize COMT protein in human endometrial tissues. Catechol-O-methyl transferase promoter-luciferace reporter gene transactivation assay was used to assess COMT promoter activity in response to estrogen and progesterone treatment in primary human endometrial stroma (pHES) cells. Catechol-O-methyl transferase protein and mRNA expression were determined by Western blot and/or real-time polymerase chain reaction. The effect of 2-methoxy estrogen treatment on DNA proliferation, B-cell lymphoma 2, and vascular epithelial growth factor protein expression were assessed by Hoechst and Western blot analyses, respectively.

MAIN OUTCOME MEASURE(S)

Catechol-O-methyl transferase protein and mRNA subcellular localization and expression in human endometrial tissues and pHES cells.

RESULT(S)

Catechol-O-methyl transferase protein expression in human endometrial tissues was up-regulated in the proliferative phase and down-regulated in the midsecretory phase of the menstrual cycle. Estrogen induced a dose-dependent increase in COMT proximal promotor-luciferace transactivation in pHES cells whereas progesterone inhibited it. Estrogen up-regulated soluble COMT protein isoform expression whereas the addition of progesterone down-regulated it in pHES cells. High doses of 2-methoxy estrogen inhibited endometrial stroma cell proliferation, and down-regulated B-cell lymphoma 2 and vascular epithelial growth factor protein expression.

CONCLUSION(S)

Catechol-O-methyl transferase expression is hormonally regulated in human endometrial stroma. Catechol-O-methyl transferase product, 2-methoxy estrogen, inhibited endometrial stroma cell proliferation and decreased vascular epithelial growth factor and B-cell lymphoma 2 protein expression.

Sex and genetic associations with cerebrospinal fluid dopamine and metabolite production after severe traumatic brain injury

Object

Dopamine (DA) pathways have been implicated in cognitive deficits after traumatic brain injury (TBI). Both sex and the dopamine transporter (DAT) 3′ variable number of tandem repeat polymorphism have been associated with differences in DAT protein density, and DAT protein affects both presynaptic DA release, through reverse transport, and DA reuptake. Catecholamines and associated metabolites are subject to autooxidation, resulting in the formation of reactive oxygen species that may contribute to subsequent oxidative injury. The purpose of this study was to determine associations between factors that affect DAT expression and cerebrospinal fluid (CSF) DA and metabolite levels after severe TBI.

Methods

Sixty-three patients with severe TBI (Glasgow Coma Scale score ≤ 8) were evaluated. The patients' genotypes were obtained using previously banked samples of CSF, and serial CSF samples (416 samples) were used to evaluate DA and metabolite levels. High-performance liquid chromatography was used to determine CSF levels of DA, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) during the first 5 days after injury.

Mixed-effects multivariate regression modeling revealed that patients with the DAT 10/10 genotype had higher CSF DA levels than patients with either the DAT 9/9 or DAT 9/10 genotypes (p = 0.009). Females with the DAT 10/10 genotype had higher CSF DA levels than females with the DAT 9/9 or DAT 9/10 genotypes, and sex was associated with higher DOPAC levels (p = 0.004). Inotrope administration also contributed to higher DA levels (p = 0.002).

Conclusions

In addition to systemic administration of DA, inherent factors such as sex and DAT genotype affect post-TBI CSF DA and DA metabolite levels, a phenomenon that may modulate susceptibility to DA-mediated oxidative injury.

Implications for estrogens in Parkinson's disease: an epidemiological approach

Evidence from experimental and epidemiological studies suggests a role of sex hormones in the pathogenic process leading to neurodegenerative diseases, (i.e., Alzheimer's and Parkinson's disease). The effects of sexual steroid hormones are complex and vary with the events of women's fertile life. Estrogens are supposed to influence dopamine synthesis, metabolism, and transport; however, there is no consensus regarding the direction, locus, and mechanism of the effect of estrogens on the dopaminergic system. A neuroprotective effect of estrogens has been demonstrated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-animal models of Parkinson's disease (PD). Epidemiological studies indicate gender differences regarding the onset and the prognosis of PD. Most of the analytical studies explored the relationship between PD and exogenous estrogens. Only three studies investigated the role of endogenous estrogens in the risk of developing PD. These studies reported an increased risk of PD in conditions causing an early reduction in endogenous estrogens (early menopause, reduced fertile life length). Longer cumulative length of pregnancies has also been associated with an increased PD risk. A lack of consensus still exists on the effect of the type of menopause (surgical vs. natural) on PD risk. Finally, the effect of postmenopausal estrogen replacement therapy is still debated. Inconsistencies across studies are in part explained by the complexity of the mechanisms of action of sexual hormones and by the paucity of analytical studies.

Estrogen deficient male mice develop compulsive behavior

BACKGROUND

Aromatase converts androgen to estrogen. Thus, the aromatase knockout (ArKO) mouse is estrogen deficient. We investigated the compulsive behaviors of these animals and the protein levels of catechol-O-methyltransferase (COMT) in frontal cortex, hypothalamus and liver.

METHODS

Grooming was analyzed during the 20-min period immediately following a water-mist spray. Running wheel activity over two consecutive nights and barbering were analyzed. COMT protein levels were measured by Western analysis.

RESULTS

Six-month old male but not female ArKO mice develop compulsive behaviors such as excessive barbering, grooming and wheel-running. Excessive activities were reversed by 3 weeks of 17beta-estradiol replacement. Interestingly, the presentation of compulsive behaviors is accompanied by concomitant decreases (p < .05) in hypothalamic COMT protein levels in male ArKO mice. These values returned to normal upon 17beta-estradiol treatment. In contrast, hepatic and frontal cortex COMT levels were not affected by the estrogen status, indicating region- and tissue-specific regulation of COMT levels by estrogen. No differences in COMT levels were detectable between female animals of both genotypes.

CONCLUSIONS

This study describes the novel observation of a possible link between estrogen, COMT and development of compulsive behaviors in male animals which may have therapeutic implications in obsessive compulsive disorder (OCD) patients.

Regulation of catechol-O-methyltransferase expression in human myometrial cells

OBJECTIVE

The catechol-O-methyltransferase enzyme catalyzes the methylation of the catechol estrogens, 2- or 4-hydroxyestrogen, to 2- or 4-methoxyestrogen. Both the hydroxy estrogens and methoxy estrogens were shown to modulate the effects of estrogen. Because catechol-O-methyltransferase activity controls levels of these metabolites, it may help regulate the cellular estrogenic milieu. In this study, we examined the regulation of catechol-O-methyltransferase expression in human myometrial cells.

METHODS

Catechol-O-methyltransferase expression was assessed by reverse transcription-polymerase chain reaction, Western blot, and luciferase assays in human myometrial cells after treatment with estrogen or progesterone. Catechol-O-methyltransferase expression was measured in cells after treatment with tumor necrosis factor alpha (TNFalpha) alone or with lactacystin, a proteasome inhibitor. Luciferase assays were also conducted using human myometrial cells containing an estrogen response element-luciferase reporter gene to measure levels of estrogen-mediated transactivation after treatment with estrogen and increasing concentrations of 2-hydroxestrogen.

RESULTS

Catechol-O-methyltransferase expression was down-regulated by progesterone or estrogen. Tumor necrosis factor alpha upregulated catechol-O-methyltransferase expression, whereas cotreatment with lactacystin attenuated this response, suggesting that TNFalpha activated nuclear factor kappa B to induce catechol-O-methyltransferase expression. Increased concentrations of 2-hydroxyestrogen attenuated estrogen-mediated transcription in the myometrial cells.

CONCLUSION

Catechol-O-methyltransferase expression may be regulated in the myometrium to control the local action of estrogen. Low levels of catechol-O-methyltransferase in the myometrium would result in an accumulation of 2-hydroxyestrogen and may antagonize the local effect of estrogen. High levels of catechol-O-methyltransferase in the myometrium would result in lower levels of 2-hydroxyestrogen and may increase sensitivity to estrogen.

Association of genetic polymorphisms of ACADSB and COMT with human hypertension

OBJECTIVES

Genetically hypertensive rats provide an excellent model to investigate the genetic mechanisms of hypertension. We previously identified three differentially expressed genes, Acadsb (short/branched chain acyl-CoA dehydrogenase), Comt (catecholamine-O-methyltransferase), and Pnpo (pyridoxine 5'-phosphate oxidase), in hypertensive and normotensive rat kidneys as potential susceptibility genes for rat hypertension. We examined the association of human homologues of these genes with human hypertension.

METHODS

We sequenced three genes using samples from 48 or 96 hypertensive patients, identified single nucleotide polymorphisms, and genotyped them in a population-based sample of 1818 Japanese individuals (771 hypertensive individuals and 1047 controls).

RESULTS

After adjustments for age, body mass index, present illness (hyperlipidaemia, diabetes mellitus), and lifestyle (smoking, alcohol consumption), multivariate logistic regression analysis revealed that -512A>G in ACADSB was associated with hypertension in women (AA vs AG + GG: odds ratio = 0.70, 95% confidence interval = 0.53-0.94). This single nucleotide polymorphism was in tight linkage disequilibrium with -254G>A. Furthermore, -1187G>C in COMT was associated with hypertension in men (GG vs CG + CC: odds ratio = 0.69, 95% confidence interval = 0.52-0.93) and was in tight linkage disequilibrium with 186C>T. After adjustments described above, -512 A>G and -254G>A in ACADSB were associated with variations in systolic blood pressure. ACADSB was in tight linkage disequilibrium with MGC35392 across a distance of 18.3 kb. COMT was not in linkage disequilibrium with any adjacent genes. Analysis indicated that two haplotypes of COMT were significantly associated with hypertension in men.

CONCLUSION

Our study suggests the possible involvement of genetic polymorphisms in ACADSB and COMT in essential hypertension in the Japanese population.

Sex difference in norepinephrine surge in response to psychological stress through nitric oxide in rats

Psychological stress elevates blood pressure through sympathetic nerve activation. This pressor response is supposedly associated with cardiovascular events. We investigated a sex difference in the pressor response and norepinephrine surge to cage-switch stress in rats. Wistar male and female rats were catheterized for blood pressure monitoring and blood sampling. Six days post-surgery, the rats were exposed to the cage-switch stress and blood samples were collected at rest and 30 min after the start of the stress. The stress-induced pressor response was greater in the male than in the female rats. The stress significantly increased the norepinephrine level in the male, but not in the female rats. Pre-treatment with N(G)-nitro-l-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, attenuated the norepinephrine response significantly in the male rats. There was no sex difference in the endothelial NO synthase expression in the gastrocnemius muscle. However the phosphorylation at serine 1177, a marker for eNOS activation, was higher in the male than in the female rats. These results suggest that NO is involved in the norepinephrine surge to psychological stress in the male rats, but not in the female rats. This is the first report on a sex difference in the norepinephrine surge in response to psychological stress through NO, in association with pressor response.

The COMT val158met polymorphism and brain morphometry in healthy young adults

Catechol-O-methyltransferase (COMT) is the most important mechanism for dopamine degradation in the prefrontal cortex and contains a functional polymorphism (val(158)met) influencing enzyme activity. The low-activity met allele has been associated with better performance on cognitive tasks relying on the prefrontal cortex. Whether COMT also affects brain structure, is still unclear. This study investigated the relationship between the COMT val(158)met polymorphism and brain anatomy in healthy young adults. In a cross-sectional study, structural MRI data and DNA for COMT genotyping were obtained from 154 healthy young adults. Statistical Parametric Mapping software (SPM2) and optimized voxel-based morphometry were used to determine total and regional gray and white matter density differences between genotype groups, as well as age-related gray and white matter density differences within the genotype groups. We found a significant effect of COMT genotype on age-related differences in gray and white matter density in females but not in males. In female val carriers increased gray matter in the temporal and parietal lobe and the cerebellum and increased white matter in the frontal lobes were positively correlated with age; in female met homozygotes decreased gray matter density in the parietal lobe and decreased white matter density in the frontal lobes, the parahippocampal gyrus and the corpus callosum were positively correlated with age. These results suggest that the COMT val(158)met polymorphism may affect age-related differences in gray and white matter density in females.

Catechol-o-methyltransferase, cognition, and psychosis: Val158Met and beyond

This review summarizes our current understanding of catechol-o-methyltransferase (COMT) and how it relates to brain function and schizophrenia. We begin by considering the COMT gene, its transcripts and proteins, and its relevance for central catecholamine function. We then describe how variation in COMT activity affects the function of the prefrontal cortex (PFC) and associated areas, reviewing evidence that COMT modulates executive function and working memory and highlighting recent data that also implicate it in emotional processing. Finally, we discuss briefly the genetic association between COMT and schizophrenia, focusing in particular on the complex interaction of functional loci within the gene that may underlie the mixed results of studies to date. We conclude by outlining preliminary data indicating that COMT is a promising therapeutic target for ameliorating the cognitive deficits associated with schizophrenia.

Gender disparities in Parkinson's disease

Parkinson's disease is a chronic neurodegenerative disorder of unknown etiology. There are sparse data on gender differences in this disorder, but it is clear that there are gender discrepancies in incidence, symptoms, medication effects and treatments. There also appear to be lifecycle fluctuations in the disease course of female Parkinson's disease patients. The effect of estrogen in this disorder is multifold and its role in the development and treatment of PD will be discussed.

Sex differences in the influence of COMT Val158Met on alcoholism and smoking in plains American Indians

BACKGROUND

Alcoholism and heavy smoking are highly comorbid and are cotransmitted in the general U.S. population; however little is known about comorbidity in American Indians. The catechol-O-methyltransferase (COMT) functional polymorphism, Val158Met, has been associated with alcoholism in Caucasians. The aims of our study were firstly to investigate patterns of alcohol and tobacco consumption and comorbidity between alcoholism and smoking in Plains American Indians and secondly to determine the influence, including sexual dimorphic effects, of COMT Val158Met and COMT haplotypes, on these behaviors.

METHODS

Diagnostic and Statistical Manual-III-R lifetime diagnoses were assigned to 342 community-ascertained Plains American Indians (201 women, 141 men). Lifetime drinking and smoking histories were obtained. Five COMT loci, including Val158Met, were genotyped. Haplotype-based analyses identified 1 block with 3 common haplotypes; 2 included Val158, and 1 had the Met158 allele.

RESULTS

The alcoholics drank heavily (12+/-8 drinks/drinking day) but episodically (max 10+/-8 d/mo). Although 62% of male alcoholics and 40% of female alcoholics were smokers (> or =10 cigarettes/d), only 12% of alcoholic men and 8% of alcoholic women smoked heavily (>20/d). In women, the COMT Val158 allele frequency was maximal in alcoholic smokers (0.85), decreasing to 0.74 in nonalcoholic smokers, 0.67 in alcoholic nonsmokers, and 0.64 in nonalcoholic nonsmokers (chi2 = 11.1, 3 df, p = 0.011). Women showed a main effect of Val158 on smoking (p=0.003). Both male and female alcoholics were more likely to have at least 1 Val158 allele compared with nonalcoholics (0.95 vs 0.88, p < 0.05). Approximately 30% of all participants were long-term, nonaddicted light, social smokers (3.6+/-1.7 cigarettes/d); they had the same Val158Met frequencies as nonsmokers. Haplotype analyses supported the Val158Met findings; however, only 1 of the 2 Val158 haplotypes was implicated.

CONCLUSIONS

Plains Indians have different smoking and drinking patterns and considerably less comorbidity between alcoholism and heavy smoking compared with the general U.S. population. Our COMT Val158Met results suggest that there may be both sex differences in the genetic origins of alcoholism and smoking in this population and overlap in genetic vulnerability to both addictions in women.