Retinol-binding protein 4 and lipocalin-2 in childhood and adolescent obesity: when children are not just "small adults".

Abstract

BACKGROUND:

although there is much evidence regarding the physiologic and pathogenic roles of the newly described adipokines retinol-binding protein 4 (RBP4) and lipocalin-2 as potential promoters of insulin resistance in obese adults, relatively little information exists regarding their roles in obese children.

METHODS:

we investigated the circulating concentrations of RBP4 and lipocalin-2 in 80 obese girls (ages 9- 15 years) and their relationships with high-sensitivity C-reactive protein (hs-CRP) and the adipokines leptin and adiponectin. We divided participants by their body mass index standard deviation scores (BMI SDSs) into 4 groups of 20 girls each: overweight [mean BMI SDS (SD), 1.8 (0.4)], obese [2.2 (0.4)], morbidly obese [3.6 (0.4)], and lean controls [-0.11 (0.4)]. We measured plasma-soluble RBP4, the RBP4-binding protein transthyretin, lipocalin-2, hs-CRP, leptin, and adiponectin and calculated the homeostatic assessment model (HOMA) index from fasting glucose and insulin concentrations.

RESULTS:

unexpectedly, plasma RBP4 and lipocalin-2 concentrations were correlated negatively with BMI SDS values (P = 0.005, and P < 0.03, respectively). These results were different from those of adults and were not correlated with the HOMA index. In contrast, hs-CRP and leptin concentrations were positively correlated with BMI SDS values (P < 0.0001, and P < 0.00001, respectively), as expected, whereas the adiponectin concentration was negatively correlated (P = 0.008).

CONCLUSIONS:

although the correlations of leptin, adiponectin, and hs-CRP concentrations with BMI in children are similar to those of adults, the correlations of RBP4 and lipocalin-2 with BMI in children are the inverse of those observed in adults. Thus, although systemic inflammation and mild insulin resistance are present in childhood obesity, RBP4 and lipocalin-2 concentrations are not increased in children as they are in obese adults with long-standing severe insulin resistance and type 2 diabetes.

• Authors: Christina Kanaka-Gantenbein, Alexandra Margeli, Panagiota Pervanidou, Sophia Sakka, George Mastorakos, George P Chrousos, Ioannis Papassotiriou
• Journal: Clinical chemistry (Clin Chem) Vol. 54 Issue 7 Pg. 1176-82 (Jul 2008) ISSN: 0009-9147 [Print] England
• PMID: 18487287 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Acute-Phase Proteins
• Adiponectin
• Blood Glucose
• LCN2 protein, human
• Leptin
• Lipocalin-2
• Lipocalins
• Proto-Oncogene Proteins
• RBP4 protein, human
• Retinol-Binding Proteins, Plasma
• C-Reactive Protein

Topics

• Acute-Phase Proteins
• Adiponectin (blood)
• Adolescent
• Blood Glucose (analysis)
• Body Mass Index
• C-Reactive Protein (analysis)
• Child
• Female
• Homeostasis
• Humans
• Insulin Resistance
• Leptin (blood)
• Lipocalin-2
• Lipocalins (blood)
• Obesity, Morbid (metabolism)
• Proto-Oncogene Proteins (blood)
• Retinol-Binding Proteins, Plasma (analysis)