Retinol-binding protein 4 and lipocalin-2 in childhood and adolescent obesity: when children are not just "small adults".
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.
Kanaka-Gantenbein
Christina
C
First Department of Pediatrics, Division of Endocrinology, Metabolism and Diabetes, Athens University Medical School, Athens, Greece.
Margeli
Alexandra
A
Pervanidou
Panagiota
P
Sakka
Sophia
S
Mastorakos
George
G
Chrousos
George P
GP
Papassotiriou
Ioannis
I
D000209:Acute-Phase Proteins; D052242:Adiponectin / Q000097:blood; D000293:Adolescent; D001786:Blood Glucose / Q000032:analysis; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000032:analysis; D002648:Child; D005260:Female; D006706:Homeostasis; D006801:Humans; D007333:Insulin Resistance; D020738:Leptin / Q000097:blood; D000071068:Lipocalin-2; D054834:Lipocalins / Q000097:blood*; D009767:Obesity, Morbid / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000097:blood*; D054839:Retinol-Binding Proteins, Plasma / Q000032:analysis*
D000209:Acute-Phase Proteins; D052242:Adiponectin; D001786:Blood Glucose; C489506:LCN2 protein, human; D020738:Leptin; D000071068:Lipocalin-2; D054834:Lipocalins; D011518:Proto-Oncogene Proteins; C101326:RBP4 protein, human; D054839:Retinol-Binding Proteins, Plasma; D002097:C-Reactive Protein