D. О. Labudzynskyi, І. О. Shymanskyy, V. М. Riasnyi, М. М. Veliky

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: konsument3@gmail.com

The study was devoted to identifying the relation between vitamin D₃ availability (assessed by the level of circulatory 25OHD₃), content of vitamin D₃ 25-hydroxylase isozymes CYP27A1 and CYP2R1 in hepatic tissue and functional activity of peripheral blood phagocytes in mice with experimental type 1 diabetes. It has been shown that diabetes is accompanied by the development of vitamin D₃-deficiency which is characterized by decreased 25OHD₃ content in blood serum and determined by changes in tissue expression of the major isoforms of vitamin D₃ 25-hydroxylase. The level of hepatic CYP27A1 was revealed to be markedly reduced with a concurrent significant augmentation of CYP2R1. Cholecalciferol administration resulted in normalization of tissue levels of both isoforms of vitamin D₃ 25-hydroxylase and blood serum 25OHD₃ content. Diabetes-associated vitamin D3 deficiency correlated with a decrease in phagocytic activity of granulocytes and monocytes, and their ability to produce antibacterial biooxidants such as reactive oxygen and nitrogen forms. Vitamin D₃ efficacy to attenuate these abnormalities of immune function was established, indicating an important immunoregulatory role of cholecalciferol in the phagocytic mechanism of antigens elimination implemented by granulocytes and monocytes.