Serum retinol-binding protein 4 concentration and its ratio to serum retinol are associated with obesity and metabolic syndrome components in children

Context: Although retinol-binding protein ( RBP)-4 concentrations are elevated in animal models of obesity and insulin resistance ( IR), the link between RBP4 and IR in humans is less clear. There are few published data on RBP4 levels in overweight children, and most previous studies did not control for vitamin A ( VA) status and/or subclinical inflammation. Objective: The objective of the study was to measure serum RBP4, serum retinol ( SR), the RBP4-to-SR molar ratio, and dietary VA intakes in normal-weight and overweight children and investigate the relationship of these variables to IR, subclinical inflammation, and the metabolic syndrome in this age group. Design: This was a cross-sectional study. Setting: The study was conducted in Northern Switzerland. Patients: Patients included 6- to 14-yr-old normal-weight, overweight, and obese children ( n = 79). Main Outcome Measures: Body mass index, body fat percentage, waist-to-hip ratio, dietary VA intakes, serum RBP4, and SR were determined. IR was assessed using fasting insulin and the quantitative insulin sensitivity check index, and components of the metabolic syndrome and indices of subclinical inflammation were measured. Results: Only 3% of children had low VA status. Independent of age, VA intakes, and C-reactive protein, body mass index, body fat percentage, and waist-to-hip ratio were significant predictors of RBP4, SR, and RBP4/SR. Independent of adiposity, RBP4 and RBP4/SR were significantly correlated with serum triglycerides, and RBP4/SR was correlated with fasting insulin. The RBP4-to-SR ratio more strongly correlated with components of the metabolic syndrome than serum RBP4. Conclusion: Independent of subclinical inflammation and vitamin A intakes, serum RBP4 and the RBP4-to-SR ratio are correlated with obesity, central obesity, and components of the metabolic syndrome in prepubertal and early pubertal children.