Excessive body weight and obesity in childhood and adolescence are becoming more and more important unfavorable factors that entail extremely adverse consequences and require close attention of physicians of any specialty. Along with the high prevalence of obesity and metabolic syndrome in pediatric patients, children and adolescents in the majority of countries are diagnosed with vitamin D deficiency. Among the non-calcaemic effects of vitamin D, a significant role is played by its impact on the hormonal regulation of glucose metabolism and the synthesis of adipokines by fat tissue. The review presents literature data indicative of a close pathogenic relationship between vitamin D insufficiency and impaired tissue insulin sensitivity. It demonstrates the role of vitamin D insufficiency in immune reactions resulting in development of subclinical inflammation in fat tissue infiltrated with macrophages and lymphocytes. It also shows the role of adipokines, immune system cells and pro-inflammatory cytokines produced by them in the pathogenesis of obesity, as well as the function of vitamin D as an endocrine and paracrine regulator of the process of inflammation in adipose tissue. The relationships between the principal adipokines (leptin, adiponectin, resistin) are revealed in the presence of normal vitamin D content and in vitamin D deficiency. The carbohydrate and lipid metabolism parameters in overweight children and adolescents with vitamin D insufficiency are analyzed. A high prevalence of vitamin D insufficiency in overweight and obese children and adolescents (increasing along with the severity of obesity) is demonstrated. The review also presents the current recommendations for the correction of vitamin D insufficiency and underlines the need for higher cholecalciferol doses to achieve serum calcifediol targets in overweight and obese children and adolescents.

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Ставропольский государственный медицинский университет, Российская Федерация 2 медико-генетический научный центр им. академика Н. п. Бочкова, москва, Российская Федерация feaTures of ViTamin D proVision of chilDren WiTh cYsTic fiBrosis resiDing in The souTh of russia in summer Dolbnya s. V. 1 , Dyatlova a. a. 1 , Klimov l. Ya. 1 , Kondratyeva e. i. 2 , Kuryaninova V. a. 1 , Tsutsaeva a. n. 1 , enina e. a. 1 , Zodbinova a. e. 2 1 stavropol state medical university, russian federation 2 research center for medical genetic, moskow, russian federation В исследование включено 30 пациентов с муковисцидозом (МВ) (средний возраст 8,3±5,1 лет) и 30 здоровых детей (средний возраст 7,1±5,3 лет), проживающих в Ставропольском крае в летнее время года. Оценка обеспеченности витамином D проводилась по содержанию кальцидиола -25(ОН)D в плазме крови.Недостаточность витамина D менее 30 нг/мл обнаружена у 15 (50,0 %) больных муковисцидозом и у 4 (13,3 %) здоровых детей. Уровень 25(ОН)D пациентов с МВ, не получающих препараты витамина D, составлял 15,9 [12,6-17,1] нг/ мл, у здоровых детей -24,6 [19,8-29,9] нг/мл (р=0,001). Средняя саплементационная доза холекальциферола у пациентов с МВ составляла 3080,0±257,7 МЕ/сутки, у здоровых детей -1468,8±132,8 МЕ/сутки (р=0,0007), при этом обеспеченность витамином D больных с МВ была 32,3 [25,7] нг/мл, а здоровых детей -36,7 [34,9] (p=0,03). Уровень витамина D в сыворотке коррелирует с возрастом (в группе детей с МВ r=-0,47, р=0,009, в контрольной группе -r=-0,44, p=0,016).Исключительно естественная инсоляция не позволяет поддерживать оптимальный уровень 25(OH)D сыворотки ни у здоровых детей, ни у больных МВ. Препараты холекальциферола эффективно восстанавливают обеспеченность витамином D, однако доза должна подбираться индивидуально. Обеспеченность витамином D пациентов с МВ зависит от возраста, вероятность дефицита витамина D возрастает по мере взросления ребенка.

Kondratyeva et al. Exogenous Factors in Vitamin D Results: We found that the blood level of 25(OH)D depended on the geographical location and the number of sunny days per year. The average blood level of 25(OH)D in adolescent boys was statistically significantly lower than in girls of this age group. The level of 25(OH)D also significantly depended on the prophylactic dose of cholecalciferol administered to the subjects. In the study, it was shown that a dose of cholecalciferol ≥1,000 IU per day can achieve a normal level of 25(OH)D in healthy children. We found no statistically significant association between single-nucleotide polymorphic variants of cytochrome P450 genes (CYP2C9 * 3, CYP3A4 * 3, CYP2C9 * 2, CYP2D6 * 4, and CYP3A4 * 1B) and blood level of 25(OH)D in the subjects. We also did not find a relationship between the TaqI, FokI, and BsmI polymorphisms of the VDR gene and serum 25(OH)D concentration. Conclusion: Exogenous factors (time of year, place of residence, and prophylactic administration of cholecalciferol), as well as endogenous factors (age and sex), play a determining role in the development of vitamin D deficiency and insufficiency; in contrast to genetic factors-polymorphic variants of the genes of xenobiotic phase 1 enzymes (CYP2C9, CYP2C19, CYP2D6, and CYP3A4) and the VDR gene-which do not play such role. This study shows the need to create a diagnostic algorithm for Vitamin D deficiency based on the age, season of the year, and prophylactic dose of cholecalciferol.

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