Abstract
The high prevalence and socioeconomic burden of bronchial asthma (BA) encourage scientists to continue active study of both exogenous and genetic factors influencing the course of BA. The connection between vitamin D deficiency and asthma in children has been shown in many studies. Work on the analysis of vitamin D content in patients with asthma is often carried out without taking into account the geographical location and level of insolation, and is also often performed on small samples of patients, which makes it difficult to interpret the results obtained. Studies devoted to the connection between genetic polymorphisms of the VDR gene and AD with a comprehensive analysis of the influence of exogenous and endogenous factors are rare and provide contradictory results. That is why the present study compared the supply of vitamin D with clinical phenotypes of asthma, the response to cholecalciferol supplementation and genetic markers that influence 25(OH)D metabolism among children of three equidistant regions of the Russian Federation. Objective. Тo study the 25(OH)D content of children with bronchial asthma (BA) depending on exogenous factors (region of residence, volume of basic therapy, intake of vitamin D from food, dietary supplementation with cholecalciferol) and endogenous factors (gender, age, course characteristics AD, VDR gene polymorphism genotypes). Patients and methods. The study included 160 children with asthma (median age 8.55 years), the comparison group consisted of 333 children (median age 6.4 years). All subjects were assessed for calcidiol levels in different seasons of the year. Testing of polymorphic variants of the VDR gene (c.1206T>C, c.1175-9G>T, c.152T>C, c.1174+283G>A) was carried out using PCR and RFLP analysis. Results. The average level of 25(OH)D in patients with BA and healthy children was significantly different and was 21.3 ng/ml in patients with BA and 29.6 ng/ml in healthy children (p < 0.01). It was revealed that 89.62% of patients with asthma and 60.8% of healthy children had a low supply of vitamin D (p < 0.05). The frequency of severe deficiency in children with asthma was 23.7%; no pronounced deficiency was recorded among healthy children. A 25(OH)D concentration of 10–20 ng/ml was more often observed in asthma (46.66%) compared to healthy children (26.5%). It was found that 25(OH)D deficiency 21–29 ng/ml was more often recorded in healthy children (34.3%) compared to BA (19.25%, p < 0.05). Low 25(OH)D levels are observed among 92.6% of patients with BA from Krasnoyarsk, among all patients with BA from Stavropol and 70.6% of patients with BA from Moscow. There was no effect of vitamin D content in food on the concentration of 25(OH)D in the blood. Taking vitamin D in doses from 500 IU to 1500 IU per day does not significantly increase the level of 25(OH)D and achieve optimal vitamin D status. Patients with the minor genotype AA of the BsmlI VDR gene polymorphism do not respond by increasing the level of 25(OH)D in response for supplementation. Conclusion. The status of vitamin D in asthma in the Russian Federation does not depend on the climatic and geographical characteristics of the region of residence, the intake of vitamin D from food and PSS during prophylaxis with standard doses of cholecalciferol, but is determined by gender, age, season of the year, lack of intake or intake of a low preventive dose cholecalciferol (less than 1000 IU), as well as the influence of BsmlI polymorphism of the VDR gene. Key words: bronchial asthma, children, vitamin D, supplementation, VDR gene
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