Ghrelin–leptin network influences serum chitinase 3-like protein 1 (YKL-40) levels in obese prepubertal children

•Ghrelin but not leptin levels are associated with serum YKL-40 for the first time.•Ghrelin–leptin network influenced serum YKL-40 in obese prepubertal children.•Lower ghrelin levels may indicate more severe inflammation in childhood obesity.•Ghrelin–leptin network's interaction with immune system is mediated by YKL-40.

ObjectiveThis study aimed to investigate any possible interactions between hormonal regulators of weight gain and markers of subclinical inflammation in childhood obesity. Forty-one obese prepubertal children and 41 age- and gender-matched lean controls were included. Children were classified as obese or non-obese according to international age- and gender-specific body mass index (BMI) cutoff points defined by the International Obesity Task Force to define childhood obesity. Anthropometric measurements, serum insulin, chitinase 3-like protein (YKL-40), ghrelin and leptin levels as well as plasma glucose in the fasting state were determined.ResultsObese children as compared with controls had higher YKL-40 (50.7 ± 15.2 vs 41.0 ± 10.5 ng/ml, p = 0.003), higher leptin (33.8 ± 16.0 vs 9.7 ± 7.5 ng/ml, p < 0.001) and lower ghrelin serum levels (871.4 ± 368.0 vs 1417.6 ± 387.3 pg/ml, p < 0.001). The obese children with ghrelin levels above median (43.8 ± 10.2 ng/ml) as compared to those with ghrelin below median (57.2 ± 16.6 ng/ml) presented lower serum YKL-40 levels (p = 0.009), indicating more severe inflammation with lower levels of ghrelin. By contrast, although the obese children with leptin levels above median (49.7 ± 16.3 ng/ml) presented lower serum YKL-40 levels as compared to those with leptin levels below median (51.6 ± 14.6 ng/ml), this difference did not reach the level of statistical significance (p = 0.726). Moreover, serum YKL-40 levels were significantly correlated with ghrelin (r = − 0.359, p = 0.014) but not with leptin levels (r = 0.169, p = 0.261). A significant negative correlation between ghrelin and leptin levels was also found (r = − 0.276, p = 0.041). These findings remained unchanged for obese, when analyses were done separately, whereas the significance of correlations was lost for non-obese subjects.ConclusionsGhrelin–leptin network had an impact on serum YKL-40 levels in obese prepubertal children; upregulation of YKL-40 secretion seems to be a consequence of reduced ghrelin rather than elevated leptin concentrations.