Features of the Neonatal Period Course in Children with Different Allelic Variants of Glutathione S-Transferase T1 and M1 Polymorphism

The dissertation is devoted to the study of allelic polymorphism of glutathione S-transferase GSTM1 and GSTT1 genes in newborns and its association with the features of the neonatal period course. The frequency of various allelic variants of the specified genes was determined both in healthy full-term newborns and in children who experienced perinatal pathology. The research is aimed at identifying associations between the presence of "null" genotypes of GSTT1 and GSTM1 and the severity of neonatal complications, including hypoxic damage, hyperbilirubinemia, intraventricular hemorrhages, and bronchopulmonary dysplasia.

The work was carried out at the Saint Petersburg State Pediatric Medical Academy and contains an original clinical-genetic study employing polymerase chain reaction and electrophoresis methods for genotype determination. The obtained data indicate a reliably higher frequency of "null" genotypes among children with a complicated neonatal period, which points to the potential significance of genetic polymorphism of detoxification systems in the formation of outcomes of perinatal pathology.

RELEVANCE OF THE PROBLEM

Perinatal pathology is a socially significant problem of modern pediatrics. Despite the undeniable successes achieved in understanding the features of perinatal pathology, the improvement of instrumental and pharmacological capabilities of modern resuscitation, the remote consequences of severe perinatal pathology leave a wide range for research.

The relevance of studying the polymorphism of glutathione S-transferase M1 and T1 genes in newborns is due to the fact that the products encoded by them, synthesized in lymphocytes, leukocytes, and liver cells, are among the important phase II enzymes of the xenobiotic detoxification system. At the phenotype level, "null" genotypes of these genes manifest as the absence of protein products — glutathione S-transferases (GST). Presumably, in this case, the absence of the corresponding enzymes in lymphocytes and leukocytes may be accompanied by a violation of their function, i.e., immunological insufficiency (specific and nonspecific).

According to literature data, the presence of null alleles of these genes in the homozygous state is accompanied by a high risk of developing malignant neoplasms of epithelial, connective, and hematopoietic tissues, pituitary adenomas, chronic bronchitis, and bronchial asthma (Baranov B.C. et al., 2000). Usually these diseases arise against the background of impaired immunological control. In the perinatal period, this may manifest as developmental defects, fetal hypoxia, complicated course of labor, neonatal infections, hemorrhagic disorders. According to L.V. Ermana, V.I. Kalinichenko (1970), glutathione reductase ensures a stable level of glutathione in erythrocytes, and when its concentration decreases, there is a risk of developing hemolytic anemia. The first reports on normative values of glutathione reductase activity in human serum belong to Horn N. and Bruns F. (1958, cited after Ermana L.V., 1970).

Data on the frequency of polymorphic alleles GSTM1 0/0 and GSTT1 0/0 among children who have experienced severe neonatal pathology are absent from the available literature.

RESEARCH OBJECTIVE

To study the features of allelic polymorphism of GSTM1 and GSTT1 genes responsible for the synthesis of glutathione S-transferase M1 and T1, and their possible contribution to the features of the course of diseases in children with perinatal pathology.

RESEARCH TASKS

1. To determine the frequency of allelic variants of GSTM1 and GSTT1 genes among healthy full-term newborns.

2. To determine the frequency of allelic variants of GSTM1 and GSTT1 genes in children who have experienced perinatal pathology.

3. To determine the correlation between the degree of severity of hypoxic damage in newborns and allelic variants of GSTM1 and GSTT1 genes.

4. To determine the correlation between the presence of allelic polymorphism of GSTM1 and GSTT1 genes and the degree of hyperbilirubinemia in newborns.

5. To evaluate the role of determining GSTT1 and GSTM1 gene polymorphism in the diagnosis and prognosis of perinatal pathology.

SCIENTIFIC NOVELTY

1. For the first time, the frequency of various allelic variants of glutathione S-transferase M1 and T1 genes in healthy full-term newborns born from mothers without severe somatic pathology against the background of a favorable pregnancy was determined.

2. For the first time, a reliably increased frequency of "null" genotypes of glutathione S-transferase T1 and M1 genes was identified in children whose neonatal period proceeded with complications and required emergency hospitalization to the resuscitation and intensive care department for newborns.

3. For the first time, the frequencies of polymorphic variants of glutathione transferase M1 and T1 genes were compared with the nature of neonatal pathology.

4. For the first time, an associative association between the presence of a null genotype of the GSTT1 and GSTM1 detoxification gene system and the severity of hypoxic damage in newborns was identified.

5. For the first time, a correlation between the presence of pathological hyperbilirubinemia in newborns and the null genotype of GSTT1 and GSTM1 was identified.

6. An association was identified between the presence in premature infants of less than 30 weeks of gestational development of intraventricular hemorrhages, bronchopulmonary dysplasia, disseminated intravascular coagulation syndrome, and a combination of functionally weakened genotypes of GSTT1 and GSTM1 genes.

PRACTICAL SIGNIFICANCE OF THE WORK

The feasibility of determining polymorphic variants of GSTT1 and GSTM1 genes for identifying children at risk of developing severe hyperbilirubinemias, bronchopulmonary dysplasia, and intraventricular hemorrhages has been demonstrated. Prospects are opened for the development of new methods of treatment and prognosis of the consequences of transferred perinatal pathology.

FORM OF IMPLEMENTATION

The results of the work were used for teaching physicians in cycles of the pediatrics department of Advanced Training and Postgraduate Education with courses in perinatology and endocrinology at SPbGPMU.

The main materials of the dissertation work can be introduced into the practice of genetic centers of Russia as a screening method. The following publications have been issued:

1. Bulletin of the Russian Military-Medical Academy. Supplement, 2005.-No. 1 (13). Pp. 218-219.

Features of the neonatal period course in children with different variants of glutathione transferase M1 and T1 polymorphism.

2. Abstracts of the jubilee conference "100 Years of the Clinical Hospital of SPbGPMU. 80th Anniversary of the Saint Petersburg Pediatric Medical Academy" — Saint Petersburg. 2005. Pp. 30-32.

Frequency of null alleles GSTM1 and GSTT1 among healthy children.

3. Russian Scientific Conference "Pediatrics from the 19th to the 21st Century". Saint Petersburg, 2005 — p. 214.

Features of the neonatal period course in children with different variants of glutathione transferase M1 and T1 polymorphism.

PERSONAL CONTRIBUTION OF THE AUTHOR

The author compiled the research program, the program of mathematical-statistical processing. Collection of research material, DNA extraction, and analysis of the polymorphism of the studied genes were carried out in the Laboratory of Prenatal Diagnosis of NIIAG by the author personally.

BASIC PROVISIONS SUBMITTED FOR DEFENSE

1. The "null" genotype of GSTT1 and GSTM1 genes and their combination are reliably more frequently encountered among children whose condition in the early neonatal period required their emergency transfer from the maternity hospital to a specialized hospital.

2. The risk of forming severe hypoxic damage is reliably higher among children with a "null" genotype of the studied genes.

3. The frequency of forming pathological hyperbilirubinemia is reliably higher among children with a "null" genotype of GSTT1 and GSTM1 genes.

4. The formation in premature infants with a gestational age of less than 30 weeks of intraventricular hemorrhages, bronchopulmonary dysplasia, disseminated intravascular coagulation syndrome occurs reliably more frequently among children with a "null" genotype of GSTT1 and GSTM1.

5. The frequency of miscarriages in the anamnesis is reliably higher among mothers whose children had a combination of two functionally weakened genotypes of GSTT1 and GSTM1 genes (GSTT1 0/0 / GSTM1 0/0).

STRUCTURE AND SCOPE OF THE DISSERTATION

The dissertation is presented on 143 pages of typed text and consists of an introduction, a literature review, a description of the volumes and methods of research, results of original research, conclusions, and practical recommendations. The bibliographic index includes 28 sources of domestic literature and 114 sources of foreign literature. The dissertation is illustrated by 44 tables and 3 figures.