Endocrine Abstracts

Background: Low-serum concentrations of 25(OH)-vitamin D are associated with insulin resistance in adults. Recent in vitro studies have suggested that vitamin D may play a role in the regulation of adiponectin, leptin and resistin; since all these adipokines are related to insulin sensitivity modulation, they might represent a link between vitamin D status and insulin resistance.

Aim: To identify possible correlations between 25(OH)-vitamin D serum levels and adipokine’s profile in obese children and adolescents.

Material and method: Serum 25(OH)-vitamin D levels were assessed in 46 obese children and adolescents (age 14.3±2.2 years) compared to a control group of 30 age-matched healthy non-obese children (immunochemiluminiscence). We measured in both groups fasting insulinemia, HOMA-index, plasmatic levels of adiponectin, leptin and resistin.

Results: 85.5% of subjects were vitamin D deficient (serum vitamin D <30 ng/ml; 87% in the obese group, 83.3% in the control group). The plasmatic levels of 25(OH)-vitamin D were not different between groups. The adiponectin levels were significantly lower and the leptin and resistin levels were significantly higher in the obese group compared to the control group.

25(OH)-vitamin D was negatively correlated to fasting insulinemia (r=−0.324, P=0.036) and to plasmatic levels of leptin (r=−0.363, P=0.013); in multivariate regression analysis the only parameter that influenced vitamin D status in obese children was leptin.

We found no correlation between plasmatic levels of 25(OH)-vitamin D and the plasmatic levels of adiponectin or resistin.

Conclusion: We found a deficit of vitamin D in a large majority of selected Romanian children. Vitamin D deficit in obese children is related to hyperinsulinemia, their association being explained by a parallel variation with plasmatic levels of leptin.