Decreased circulating 25-(OH) Vitamin D concentrations in obese female children and adolescents: Positive associations with Retinol Binding Protein-4 and Neutrophil Gelatinase-associated Lipocalin

OBJECTIVE Hypovitaminosis D has been associated with adult as well as childhood obesity. Retinol-binding-protein-4 (RBP-4) and Neutrophil Gelatinase-associated Lipocalin (NGAL) are altered in obese individuals. The aim of this study was to examine circulating 25-(OH) Vitamin D (25-(OH) D) concentrations according to BMI and its associations with RBP-4 and NGAL in female children and adolescents. DESIGN Seventy-nine (79) children, aged 8–16 years, were studied and divided into four groups: 19 control (BMI z-score range-2.15 — 1.24), 20 overweight (1.34 — 2.49), 20 obese (2.50 — 2.87) and 20 ultra-obese (3 — 4.37). Patients were derived from a Pediatric Obesity Clinic. Plasma 25-(OH) D, RBP-4 and NGAL concentrations were measured with specific assays. RESULTS Plasma 25-(OH) D concentrations were decreased significantly in the ultra-obese (p = 0.005) and marginally in the obese group (p = 0.05) compared to the control group. In the entire BMI range, Spearman correlations revealed strong positive associations between 25-(OH) D and RBP-4 (r=0.349, p = 0.002) and between 25-(OH) D and NGAL (r=0.338, p=0.003). CONCLUSIONS 25-(OH) D is deficient in a clinical population of obese female children and adolescents, whereas in the entire BMI range 25-(OH) D is associated with RBP4 and NGAL concentrations. Longitudinal studies are needed to reveal the role of these associations in metabolic alterations related to childhood and adolescent obesity and associated metabolic morbidities.