The aim is to study the features of the antioxidant system (AOS), lipid peroxidation and to evaluate the functional significance of the CAT-262G/A catalase gene polymorphism in the severity of ulcerative colitis (UC) in patients in the Perm region.
Material and methods. 50 patients with UC in the active phase of the disease and 50 healthy donors were examined. The serum levels of catalase, glutathione peroxidase (HLP) and malondialdehyde (MDA) and the catalase gene polymorphism in the-262G/A region were determined.
Results. The study revealed a significant decrease in the levels of antioxidant enzymes in the group of patients with UC in comparison with healthy individuals. The level of catalase was on average 2,74 times lower, and HLP – 2,02 times as compared with the control group (p = 0,0000). The average MDA was 2,82 times higher in UC patients than in the group of healthy individuals (p=0,0007). When the genotypes and alleles of the-262G/A region of the CAT gene were not distributed, there were no statistically significant differences between the compared groups of patients with UC and healthy individuals in the Perm region. However, the minor A allele and the heterozygote GA were significantly more common in UC patients with a high degree of endoscopic activity and severe often relapsing course of UC (χ2=9,53; p=0,002 and χ2=5,59; p=0,01, respectively).
Conclusions. The concentration of MDA increases and the level of catalase and HLP decreases in the active phase of UC. The risk of developing a severe course of UC, prone to frequent relapses and progression, is associated with the carrier of the minor allele A gene CAT-262G/A, which can be taken into account when predicting the nature of the disease and choosing a treatment tactics.

Keywords: severe course, catalase gene polymorphism, glutathion peroxidase, malonic dialdehyde, catalase, ulcerative colitis