Vitamin D Deficiency in Obese Children and Its Relationship to Insulin Resistance and Adipokines

Low-serum concentrations of 25-hydroxyvitamin D [25(OH)D] are associated with insulin resistance in adults. Less data are available in pediatric populations. Serum 25(OH) D serum concentrations were assessed in 125 obese and 31 nonobese children (age 11.9 +/- 2.7 y, range 6-16 y, 49% male) living in Bonn, Germany. The relationship between 25(OH) D, measured by liquid chromatography-tandem mass spectrometry, and measures of insulin sensitivity and adipokines adiponectin and resistin were analyzed. Seventy-six % of subjects were 25(OH) D deficient (<20 ng/mL). Higher insulin, homeostasis model assessment-insulin resistance (HOMA-IR r = -0.269, P = 0.023), and hemoglobin A1c (HbA(1c)) as well as lower quantitative insulin-sensitivity check index (QUICKI r = 0.264, P = 0.030) values were found in obese children with lower 25(OH) D concentrations even after adjustment for gender, age, and body mass index. Furthermore, 25(OH) D correlated significantly with adiponectin, but not with resistin. Our results suggest that hypovitaminosis D is a risk factor for developing insulin resistance independent of adiposity.