The aim of study: to determine the involvement of folate cycle genes in the occurrence of hyperhomocysteinemia in children from Ivankivskyi district of Kyiv region of Ukraine 35 years after the accident at the Chornobyl nuclear power plant. Research methods. Immunochemical, mathematical and statistical. Results. Homocysteine levels were determined in 217 children aged 12-17 from Ivankivskyi district of Kyiv region, as well as genetic polymorphisms of the folate cycle. An excess of homocysteine in the blood over 10 µmol/l (a state of hyperhomocysteinemia) was detected in 65.44 % (142 out of 217) of those examined, among boys – 69.79 % (67 out of 96), among girls – 61.98 % (75 out of 121). The largest proportion of hyperhomocysteinemia cases was registered in the subgroup of children with the basic polymorphism MTHFR: 677TT – 94.44 % of cases. In most cases, hyperhomocysteinemia in children was associated with an environmental factor, including radioactive elements and their decay products. The system for the prevention of hyperhomocysteinemia and its consequences in children living in areas affected by the accident at the Chornobyl nuclear power plant should include regular monitoring of the content of radionuclides in the body of children and locally produced food, the content of homocysteine in the blood, and assessment of the state of folate cycle genes.

Objective We performed a comparative assessment of the blood levels of homocysteine, pituitary and thyroid hormones in children with different levels of physical development before and after forest fires in the Chornobyl exclusion zone (ChEZ) in 2015. Methods: We used immunochemical, instrumental, mathematical and statistical methods. Results: The analysis of variable dynamics was performed in 336 adolescents of the Polisskyi and the Ivankivskyi districts of Kyiv region. An association was found between homocysteine (Нсу), hormones of the pituitary-thyroid axis and physical development of children. A statistically significantly higher level of Нсу was observed in the adolescents from the Ivankivskyi district in comparison with the children from the Polisskyi district. Forest fires in the spring and summer of 2015 in the ChEZ should be considered the main cause for the increase in Нсу in the blood of the adolescents. The increased level of Т3 in the peripheral tissues induced by Нсy and TSH contributed to a decrease in the physical development index values. Due to a decrease in the intensity of the Т4 deiodination process, the insufficient formation of Т3 in the peripheral tissues was recorded in the group of children with a disharmonious high physical development.

The purpose of the study: to assess the impact of incorporated 137Cs radionuclides on the physical development of boys and girls living near the Chornobyl Exclusion Zone, taking into account the state of the folate cycle and the MTHFR:C677T genetic polymorphism. Research methods: іnstrumental, laboratory, mathematical and statistical. Results: Within the framework of international projects, an assessment of physical development was carried out according to the Rohrer index (IR), the levels and relationship of incorporated 137Cs, vitamins B6, B9, B12, homocysteine (Hcy), allelic variants of the MTHFR:C677T genetic polymorphism were determined in 260 children aged 13-17 years old from Ivankivskyi and Polisskyi districts of the Kyiv region, bordering the Chornobyl Exclusion Zone. It has been established that among the surveyed, the more proportion is the subgroup of adolescents with harmonious physical development (respectively, for boys - 70.40%, for girls - 65.93%). It was shown that boys and girls with disharmonious high physical development (respectively 15.20% and 25.19%) contained significantly less 137Cs radionuclides in their bodies, compared with children from the subgroups of harmonious and disharmonious low physical development. In the analyzed groups of boys and girls, an inverse correlation was recorded between the specific activity of 137Cs and the values of anthropometric indicators. The most pronounced inverse relationship between the specific activity of 137Cs and the values of mass, as well as body length and IR, was found in the subgroup of harmoniously developed girls. The subgroup of harmoniously developed boys differed from the subgroup of harmoniously developed girls by a higher specific activity of 137Cs in the body and a higher level of Hcy in the blood. The decrease in the level of Hcy in the blood of harmoniously developed girls, compared with harmoniously developed boys, may be associated with a higher level of vitamin B12 in the blood, as well as with a more intense functioning of the trans-sulfurization cycle. Comparative analysis showed that in the subgroup of girls with overweight, the proportion of cases of carriage of genotypes composed of neutral alleles of the C/C polymorphism MTHFR:677 is greater than in the subgroup of harmoniously developed girls. At the same time, a lower specific activity of 137Cs in their body was registered. It is concluded that incorporated 137Cs radionuclides cause a decrease in body weight in children living in the area affected by the accident at the Chоrnobyl nuclear power plant. At the same time, there is a metabolic disorder, in the form of an increase in the content of Hcy in the blood, more pronounced in boys. The process of incorporation of 137Cs radionuclides into the body of children may be associated with the T allele of the MTHFR:C677 polymorphism, which affects the activity of methylenetetrahydrofolate reductase.

The aim of study: determination of the genetic factor’s involvement (MTHFR:C677T polymorphism), which affects the activity of the main enzyme of the folate cycle, methylenetetrahydrofolate reductase, and environmental exposure, including the radiation factor, in the occurrence of hyperhomocysteinemia in children which living near the Chornobyl Exclusion Zone (ChEZ). Research methods. Immunochemical, mathematical and statistical. Results. Within the framework of international projects, the levels of homocysteine (Hcy) and allelic variants of the genetic polymorphism MTHFR:C677T were determined in 624 children aged 13-17 years old from Ivankivskyi and Poliskyi districts of the Kyiv region. It has been established that an increase in the level of Hcy in the blood and an increase in the number of cases of hyperhomocysteinemia in the examined groups of children are associated with forest fires in the ChEZ in 2015 and 2020. Under conditions of pronounced exposure to radioactive agents and combustion products of forest trees, the proportion of cases of hyperhomocysteinemia in groups of children with and without the T allele of the MTHFR:677 polymorphism in the genome did not have statistical differences. An indicator of ecological trouble in the ChEZ and adjacent areas is an increase, above the physiological level, in the concentration of Hcy in the blood of adolescent children with the absence of the T allele of the MTHFR:677 polymorphism in the genome. Conclusion. In areas affected by the accident at the Chornobyl nuclear power plant, it is necessary to constantly conduct regular monitoring studies of the health of children, using tests for the content of Hcy in the blood and the state of the folate cycle genes.

Objective: The aim of the study was to identify interrelations between the state of folate cycle genetic apparatus and blood levels of homocysteine, thyroid and adenohypophysis hormones in the blood among the children from Ivankivskyi and Poliskyi districts, Kyiv region, bordering the Chornobyl exclusion zone (СhEZ). Methods: Immunochemical, genetic, statistical ones. Results: We measured blood levels of homocysteine (Hcy), pituitary thyroid-stimulating hormone (TSH), free triiodothyronine (T3), free thyroxine (T4) in 158 children from Poliskyi district and 178 children from Ivankivskyi district and assessed the state of a genetic system of the folate cycle (FC). The average age of the examined was (15.2 ± 0.9) years old (95% CI 15.0-15.4 years old). Taking into account the FC genotypes, genetic subgroups were formed, they were based on 100% representation of one specific genotype. The laboratory examination was carried out twice: in April and December 2015 (before and after the fires in the ChEZ). It was found out that in the total group of the children, as well as in most of analyzed genetic subgroups, the level of Hcy and thyroid hormones (TG) in the children from Ivankivskyi district was statistically significantly higher than in those from Poliskyi district. At the same time, a direct association between Hcy and TSH was observed in the total group, as well as in most of the genetic subgroups of children from Ivankivskyi district, and this ssociation was absent in the children from Poliskyi district. The blood level of Hcy both in the children from Poliskyi district and in the children from Ivankivskyi district was statistically significantly higher in the subgroup containing only homozygous variants of the T allele of the MTHFR:677 genetic polymorphism in comparison with the subgroups containing neutral C alleles of the same polymorphism. At the same time, there were no differences for TSH, T3 and T4. Сonclusions: The analysis enabled to establish a synchronous reaction of metabolic cycles ensuring the metabolism of Hcy and thyroid hormones in the adolescents, regardless of the FC genotypes. Correlation analysis, as well as the results of statistical analysis, indicate that an increase in the level of Hcy in the blood of children induced the synthesis of TSH and T3. The results show a close relationship between thyroid hormone genesis and the metabolism of methionine sulfur-containing amino acids and Hcy. A forest fire, containing long-lived radioactive elements, is the most likely reason for the increase of Hcy level and, as a result, the hormones of the pituitary-thyroid axis in the blood of the children living in the districts, bordering the ChEZ.