65 Exogenic and Endogenic Factors Affecting the Supply of Vitamin D in Healthy Children and Adolescents of the South of Russia in Winter-Spring Periods

Study objectives – to analyze the influence of exogenous and endogenous factors on the supply of vitamin D in children and adolescents living in southern Russia in the winter-spring period. The study included 27 healthy children and adolescents, aged 3 months to 16 years, living in Stavropol (45°02′ N 41°58′E). Children under 3 years old were 9 (33.3%), 4 to 7 years old – 5 (18.5%), 8 to 11 years old – 6 (22.3%), 12 to 16 years old – 7 (25.9%) people. Blood sampling was performed in February-March 2018. Vitamin D provision was assessed by the serum calcidiol level. Satisfactory supply was diagnosed at a level of 25 (OH) D 30-100 ng/ml, insufficiency – 20 to 30 ng/ml, deficiency – less than 20 ng/ml. The study of polymorphism of biotransformation genes was carried out by PCR and subsequent RFLP analysis. Polymorphisms selected for study included CYP2C9*2 (430C>T; R144C), CYP2C9*3 (1075A>C; I359L), CYP2D6*4 (1846G>A), CYP3A4*1B (-392C>T). Median vitamin D availability was 34.6 [23.5-44.6] ng/ml. Vitamin D deficiency was detected in 5 (18.5%) children, deficiency was also found in 5 (18.5%) children, satisfactory provision was revealed in 17 (63.0%) children. There is a negative correlation between the age of children and the level of 25(OH)D: r = -0.69, p = 0.0001, as well as between body weight and calcidiol level r = -0.64, p = 0.0004. Direct correlation was found between the dose of cholecalciferol products and serum 25(OH)D level, r = -0.60, p = 0.001. With CC polymorphism (CYP2C9*2) 25(OH) D < 30 ng/ml was detected in 8 (80.0%) children, and more than 30 ng/ml – in 2 (20.0%), with CT – in 2 (20.0%) and in 2 (11.8%) respectively. With polymorphism AA (CYP2C9*3) 25(OH) D < 30 ng/ml was in 9 (90.0%) children, more than 30 ng/ml – in 15 (88.2%), with CA – in 1 (10.0%) child and in 2 (11.8%) children respectively. With TT polymorphism (CYP3A4*1B) 25(OH) D < 30 ng/ml was detected in 9 (90.0%) children, and more than 30 ng/ml – in 16 (94.1%) children, with TC – in 1 (10.0%) and in 1 (5.9%) respectively. With polymorphism GG (CYP2D6*4) 25(OH)D < 30 ng/ml was detected in 7 (70.0%) children, and more than 30 ng/ml – in 13 (76.5%) children, with GA 25(OH)D <30 ng/ml was in 2 (20.0%), more than 30 ng/ml – in 4 (23.5%), AA was only in 1 (10.0%) child with vitamin D less than 30 ng/ml. Insufficient vitamin D levels were found in 37.0% of healthy children and adolescents living in the Southern Russia. The serum calcidiol level depends on age; the older is the child, the higher is the likelihood of hypovitaminosis D. Intake of cholecalciferol product is an effective way to prevent vitamin D deficiency and insufficiency, while hypovitaminosis D was not convincingly associated with any of the studied polymorphisms of biotransformation genes: CYP2C9*2, CYP2C9*3, CYP2D6*4, CYP3A4*1B.