The association of the COMT rs4818 G allele and COMT CpG51.52 methylation with the motor impulsivity symptom in MAUD patients.
The relationships of the 8 SNPs in the DRD4 and COMT genes with the motor impulsive symptoms in MAUD patients were also investigated. The Mann-Whitney U nonparametric test revealed that there were statistically significant differences in motor impulsivity scores between COMT rs4818 genotypes (Table 3). Patients carrying the minor alleles had significantly higher motor impulsivity scores (GG and CG, 42.61) than patients with the major allele (CC, 36.89) (z=-2.271, p=0.023, Figure 2A), indicating that the G allele carriers were more impulsive in this study. As shown in Figure 2B, there was a significant difference in the methylation level in the promoter region of COMT gene between MAUD patients carrying the minor allele (CG and GG) and the major allele (CC), and this difference was identified to the methylation degree of the CpG51.52 unit (Figure 2B, C, p=0.035 & p=0.023, respectively). Neither the methylation level of COMT nor the methylation degrees at the CpG 51.52 unit of the COMT gene had a correlation with motor impulsivity score among MAUD patients (Figure 2D, E). Depending on the COMT rs4818 CC polymorphism, there were negative correlations between COMT methylation status and motor impulsivity scores in MAUD patients (r= -0.315, p=0.011) (Figure 2F). However, as shown in Figure 2G showed that, depending on COMT polymorphism, there was a weak correlation between the degree of methylation of the CpG51.52 unit at the promoter region of the COMT gene and the motor impulsivity score (r= -0.268, p=0.042). The results indicated that the interaction of the COMT rs4818 G allele and COMT methylation status was associated with motor impulsivity symptom prevalence in MAUD patients.