Abstract
BackgroundThe functional polymorphism Val158Met in the catechol-O-methyltransferase (COMT) gene has been associated with differences in prefrontal cognitive functions in patients with schizophrenia and healthy individuals. Several studies have indicated that the Met allele is associated with better performance on measures of cognitive function. We investigated whether the COMT Val158Met genotype was associated with cognitive function in 149 healthy controls and 118 patients with schizophrenia.MethodsCognitive function, including verbal memory, working memory, motor speed, attention, executive function and verbal fluency, was assessed by the Brief Assessment of Cognition in Schizophrenia (BACS-J). We employed a one-way analysis of variance (ANOVA) and a multiple regression analysis to determine the associations between the COMT Val158Met genotype and the BACS-J measurements. ResultsThe one-way ANOVA revealed a significant difference in the scores on the Tower of London, a measure of executive function, between the different Val158Met genotypes in the healthy controls (p = 0.023), and a post-hoc analysis showed significant differences between the scores on the Tower of London in the val/val genotype group (18.6 ± 2.4) compared to the other two groups (17.6 ± 2.7 for val/met and 17.1 ± 3.2 for met/met; p = 0.027 and p = 0.024, respectively). Multiple regression analyses revealed that executive function was significantly correlated with the Val158Met genotype (p = 0.003). However, no evidence was found for an effect of the COMT on any cognitive domains of the BACS-J in the patients with schizophrenia.ConclusionThese data support the hypothesis that the COMT Val158Met genotype maintains an optimal level of dopamine activity. Further studies should be performed that include a larger sample size and include patients on and off medication, as these patients would help to confirm our findings.
Highlights
The enzyme catechol-O-methyltransferase (COMT) metabolizes the neurotransmitters dopamine, adrenalin and noradrenalin, and COMT is the main component in the dopamine metabolic pathway [1,2]
We investigated whether the COMT Val158Met polymorphism affected cognitive function assessed by the BACS-J in healthy controls and in patients with schizophrenia
Our results showed a relatively weak association between executive function within the six cognitive domains and COMT Val158Met polymorphism in the healthy controls but not in the patients with schizophrenia
Summary
The enzyme catechol-O-methyltransferase (COMT) metabolizes the neurotransmitters dopamine, adrenalin and noradrenalin, and COMT is the main component in the dopamine metabolic pathway [1,2]. The activity of COMT in the prefrontal cortex (PFC) affects dopamine-mediated cognitive function in schizophrenic patients and healthy individuals [6]. This high level of activity has been hypothesized to result in the poorer performance of frontally mediated cognitive tasks because of the lower dopamine levels [7]. The functional polymorphism Val158Met in the catechol-O-methyltransferase (COMT) gene has been associated with differences in prefrontal cognitive functions in patients with schizophrenia and healthy individuals. We investigated whether the COMT Val158Met genotype was associated with cognitive function in 149 healthy controls and 118 patients with schizophrenia. Further studies should be performed that include a larger sample size and include patients on and off medication, as these patients would help to confirm our findings
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