Participation of homocysteine in the regulation of mineral metabolism in children living near the Chornobyl Exclusion Zone

Abstract

The aim of the study is to determine the participation of homocysteine (Hcy) in the regulation of calcium-phosphorus metabolism in children living near the Chornobyl Exclusion Zone (ChEZ). Materials and methods. Using the statistical processing program IBM SPSS Statistics 22 (USA), the results of laboratory, instrumental and genetic examination of 956 children aged 12-18 years who permanently reside near the ChEZ were assessed. The parameters reflecting the specific activity of 137Cs radionuclides in the body, the content of Hcy, calcium (Ca), inorganic phosphorus (P), ionized calcium (Ca2+), and parathyroid hormone (PTH) in the blood were analyzed. To determine the degree of physical development of adolescents, the Rohrer mass-height index (IR) was calculated - the quotient of dividing body weight in kilograms by body length in meters cubed. Results. 137Cs was registered in the body of all examined children, in the group of boys its values were from 0.78 to 95.11 Bq/kg, in the group of girls - from 1.06 to 26.96 Bq/kg. In the analyzed groups of children, an inverse correlation was established between the specific activity of 137Cs radionuclides in the body and the content of Ca in the blood, as well as the IR values, reflecting the ratio of body weight to its length. Hyperhomocysteinemia was registered in most genetic subgroups of the folate cycle. The highest statistically significant proportion of hyperhomocysteinemia cases was found in subgroups with the main genotypes G/G MTR:2756 and T/TMTHFR:677. Based on a comprehensive study of the results of the correlation analysis of the parameters under study, the mechanism of participation of Hcy, folate cycle genes and environmental factors in the regulation of Ca-P metabolism in children is presented. Conclusions. Incorporation of 137Cs into the body of people living in areas affected by the Chornobyl accident causes energy deficiency in the cells of vital organs, leading to a decrease in the intensity of anabolic processes, impaired methylation of Hcy and changes in Ca-P metabolism. Impaired physical development of the examined children is directly related to the content of Ca in their blood, as evidenced by the direct correlation between Ca and IR. Energy deficiency associated with the incorporation of 137Cs into the body, as well as mutations of the FC genes, are the causes of hyperhomocysteinemia - an increased content of the sulfur-containing amino acid Hcy in the blood of children living in settlements located near the ChEZ. Hcy, by affecting the skeletal system, compensates for the deficiency of Ca in the blood induced by 137Cs. An increase in the Ca content in the blood with hyperhomocysteinemia has a negative effect on the processes of PTH formation and, therefore, creates conditions for the disruption of P excretion from the body through the kidneys. However, in most genetic subgroups, a direct correlation between P and PTH was recorded, illustrating the ability of the child's body to stimulate the excretion of P with urine when its concentration in the blood increases. Thus, transient hyperhomocysteinemia is an element of the body's adaptation system to environmental radiation exposure. In subgroups of children with risk alleles of genetic polymorphisms MTHFR:C677T and MTR:A2756G in the genome, there was no direct correlation between P and PTH, which indicates the possibility of formation of calcium-phosphorus complexes in the blood and their deposition in soft tissues and vessel walls.