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Bilici ME, Savaş Erdeve Ş, Çetinkaya S, Aycan Z. The effect of 2000 ıu/day vitamin D supplementation on insulin resistance and cardiovascular risk parameters in vitamin D deficient obese adolescents. Turk J Pediatr 2019; 61: 723-732. The aim of this study was to determine the vitamin D deficiency prevalence in obese adolescents and to investigate the effect of vitamin D supplementation on insulin resistance and cardiovascular risk parameters in obese adolescents with vitamin D deficiency. Ninety-six obese adolescents aged 10-18 years were divided in 2 groups according to their vitamin D levels: Deficient group ( < 12ng/ ml) and sufficient group (≥12ng/ml). All patients in the vitamin D deficiency group were recommended 2000IU/day vitamin D supplementation. Fifty four (56.3%) patients had vitamin D deficiency. The only difference between the two groups was PTH level which was higher in the vitamin D deficiency group. Vitamin D reached sufficient levels in 22 (95.6%) out of the 23 patients with the 3 month supplementation of 2000 IU/day vitamin D. There was a significant decrease in weight Standard Deviation Score (SDS), Body Mass Index (BMI) SDS, hip circumference, total cholesterol, LDL, HbA1c, AST, PTH and interleukin-6 while no significant change was seen in measurements of glucose, insulin, HOMA-IR, C-peptide and the rate of metabolic syndrome. There were decreases in levels of total cholesterol and LDL with vitamin D treatment, while there was no significant change in insulin resistance. Vitamin D reduced interleukin-6 levels by its antiinflammatory effect.

Objective: Free hormones are biologically more active in target tissues. Thus, measurement of vitamin D taking into account bioavailability and free vitamin D may be preferable, especially when evidence is contradictory, as in obese children. In order to assess bioavailablity and free vitamin D, using a previously reported formula, vitamin D-binding protein (VDBP) level was measured and VDBP polymorphisms were also evaluated because of variations in binding affinity. Methods: Eighty-four obese and 78 healthy children were included. Anthropometry, calcium, phosphorus, alkaline-phosphatase, parathyroid hormone (PTH), 25 hydroxyvitamin D [25(OH)D], bioavailable-free vitamin D, and VDBP concentration and polymorphism were evaluated in the whole group. Results: Obese girls had significantly higher PTH than normal weight girls (p=0.001). Regardless of gender, obese children had significantly higher concentrations of VDBP (p=0.008) and PTH (p=0.002). When samples taken in winter were analyzed, PTH and VDBP were found to be higher and bioavailable and free vitamin D lower in the obese group. There was no difference in terms of total vitamin D between groups during the winter season. Conclusion: While total, free, and bioavailable vitamin D in the obese group was similar to the control group in autumn, free and bioavailable vitamin D in the winter was lower in the obese than the control group. In addition, PTH was higher in the obese group in both autumn and winter. Therefore, more research is needed to evaluate the variability of free and bioavailable vitamin D according to body habitus, season and the effect any differences may have. [ABSTRACT FROM AUTHOR]

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Copyright of Turkish Journal of Obstetrics & Gynecology is the property of Galenos Yayinevi Tic. LTD. STI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)