Orexitropic Signaling Proteins in Obese Children

Abstract

Adipose tissue is not only the main organ for energy storage, but it also has endocrine properties, producing “adipokines” responsible for energy homeostasis, insulin sensitivity, and inflammation. Leptin, produced by adipocytes, is the key hormone in appetite regulation and suppression of orexigenic, hypothalamic neuropeptide Y (NPY). We wanted to establish and compare levels of leptin and NPY in different obesity types in childhood, and to investigate their correlations with auxological parameters. Twenty-one obese children (seven girls and 14 boys), divided into two groups, were compared with 14 controls. The mean age of the study group was 10.81 ± 3.69 years and the mean puberty stage was 2.21. The mean body mass index (BMI) was 32.80 kg/m (range 23.30– 47.02) and the mean overweight 30.73 kg (range 8.00–74.00). The mean leptin level was higher in boys and in the group with central obesity, but was not significant. Leptin/NPY ratio and leptin/BMI ratio was also higher in the central obesity group and there was a more significant difference compared with controls. We found significant correlation of the leptin level with body mass (BM), body mass excess (BME), and BMI (p < 0.05). The mean leptin level in obese children was very high (36.39 ng/ml). Leptin and NPY levels showed inverse values in two different obesity types. Results are suggestive for leptin resistance rather than leptin deficiency in our group of obese children. Orexitropic signaling proteins correlated significantly with auxological parameters. Determination of the leptin and NPY concentrations provided evidence that obesity represents disease with neuroendocrine dysfunction and high leptin/NPY ratio, which could be a useful marker for central obesity.