Association between Val158Met polymorphism in the COMT gene with anxiety and heart rate variability in children with irritable bowel syndrome

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The aim of this study was to examine the peculiarities of trait anxiety and heart rate variability parameters as well as their relationship depending on the catechol O-methyltransferase (COMT) gene Val158Met polymorphism in children with irritable bowel syndrome. Materials and methods. A total of 26 children aged 6–12 years with a verified diagnosis of irritable bowel syndrome according to the Rome IV criteria were examined. Beforehand, all the patients underwent molecular genetic testing for the COMT Val158met single nucleotide polymorphism by using the polymerase chain reaction-restriction fragment length polymorphism method. Heart rate variability was analyzed via cardiointervalography (Neurosoft) based on short five-minute resting-state ECG recordings. The CMAS (Children’s Manifest Anxiety Scale) test was used to measure trait anxiety levels. The Pearson’s test was used to assess correlations between heart rate variability parameters and anxiety levels. Data were processed using Microsoft Excel 2016 and analyzed with GraphPad (Prism 5.0). Results. Depending on the functional COMT Val158met polymorphism, all the patients were allocated to 3 groups: 8 children with 472 GA (Val/Met) COMT genotype; 10 children with 472 AA (Met/Met) genotype; 8 children with 472 GG (Val/Val) genotype. Time and frequency domain parameters of heart rate variability were significantly different in each group. The highest level of anxiety and the largest percentage of LF component (mainly sympathetic activity) in the structure of heart rate variability was noted among Met/Met carriers. Val/Val carriers had a significantly lower anxiety level and an autonomic imbalance with a higher percentage of HF component (parasympathetic activity). Positive correlations between trait anxiety and heart rate variability parameters were found only in Val/Val and Val/Met groups. Conclusions. Our study has revealed the influence of the COMT Val158met polymorphism on the level of trait anxiety and heart rate variability parameters. It is important for a better understanding of the gut-brain axis dysregulation and impaired stress resilience in children with irritable bowel syndrome. Also, these data could be used to improve current schemes for the treatment of irritable bowel syndrome, supplementing them with activation therapy, psychotherapy, psychopharmacotherapy.