Studying the activity of matrix metalloproteinases and antibodies to DNA in patients with autoimmune thyroiditis

Background. In autoimmune thyroiditis, in addition to impaired immunological tolerance, a significant role is played by biochemical markers such as matrix metalloproteinases and antibodies to deoxyribonucleic acid (DNA), which can contribute to the pathogenesis of the disease.

Aim. Studying the activity of metalloproteinases-3, -7 and the level of antibodies to DNA in patients with autoimmune thyroiditis.

Material and methods. In 2019–2021 a non-randomized study in the research laboratory at the Department of Biochemistry of the Azerbaijan Medical University, during which the blood serum of 170 patients with autoimmune thyroiditis, 64 (37.6%) men, average age 39.4±11.2 years and 106 (62.4%) women, average age 37.8±9.05 years, was conducted. Inclusion criteria: men and women aged 18 years and older with a primary diagnosis of “autoimmune thyroiditis” without concomitant allergic or other autoimmune diseases and severe somatic disorders. The control group consisted of 65 people (average age 38.7±10.8 years) without any thyroid disease or autoimmune pathology. Analysis of clinical and laboratory studies with determination of the level of thyroid-stimulating hormone, free thyroxine and free triiodothyronine made it possible to divide patients into two groups: the first group — 74 patients with a subclinical form of the disease; the second group — 96 patients with a manifest form of the disease. In all patients, the activity of metalloproteinases-3 and -7 in the blood serum was determined by enzyme-linked immunosorbent assay, and the content of antibodies to native and denatured DNA was determined by enzyme-linked immunosorbent assay. Intergroup comparisons on quantitative indicators were carried out using the nonparametric Mann–Whitney rank test, taking into account the difference in the distribution of the analyzed indicators from the normal one. Qualitative characteristics were assessed as percentages.

Results. The median activity of metalloproteinases-3 and -7 in the total group of patients was 56 (51.0; 59.0) and 4.6 (4.3; 5.2) ng/ml, respectively, which was significantly higher than the control values — 23.0 (16.0; 26.0) and 3.6 (3.4; 4.1) ng/ml, respectively (p=0.0001252 and p=0.00054). There were no statistically significant differences in the level of metalloproteinase-7 in patients with subclinical and manifest thyroiditis (p=0.097), while the median activity of metalloproteinase-3 in the manifest group was 59.0 (56.0; 65.0) ng/ml and it was higher than in patients of the subclinical group by 13.2%. The content of antibodies to native DNA in patients was 4.4 (2.3; 9.9) units/ml, which was statistically significantly higher compared to the control group — 2.6 (1.5; 3.6) units/ml (p <0.001), while no significant differences were found in the levels of antibodies to denatured DNA in patients compared to control values.

Conclusion. The worsening of the autoimmune process is accompanied by an increase in the activity of metalloproteinases and antinuclear antibodies.