Hepcidin, soluble transferrin receptor and IL-6 levels in obese children and adolescents with and without type 2 diabetes mellitus/impaired glucose tolerance and their association with obstructive sleep apnea.

Abstract

Obesity, type 2 diabetes mellitus (T2DM), and obstructive sleep apnea (OSA) are associated with chronic low-grade inflammation. Iron metabolism is linked with insulin-resistant states and with OSA in adults. The association of body iron status with T2DM in children remains undefined. We aimed to evaluate plasma interleukin-6 (IL-6), hepcidin, and soluble transferrin receptor (sTfR) levels in obese patients with T2DM or impaired glucose tolerance (IGT) and in those without, and the contribution of OSA to their levels. In this cross-sectional study, obese children and adolescents with and without T2DM/IGT underwent overnight polysomnography. Fasting plasma concentrations of IL-6, hepcidin, and sTfR were measured and evaluated according to glycemic status (T2DM/IGT and normal glucose tolerance) and the presence of OSA. Ten patients with T2DM (age 15.9±3.6years), 8 with IGT (age 13.1±2.5years) and 20 subjects with normal glucose tolerance matched for body mass index standard deviation score (age 12.6±3.3years) were studied. Sleep measures or IL-6, hepcidin, and sTfR levels were not significantly different between the group with T2DM/IGT vs. the control group. No significant differences were found in hepcidin or sTfR levels between patients with OSA and those without. However, patients with OSA showed higher plasma IL-6 values compared with those without (4.56±2.92 vs. 2.83±1.54pg/ml, P=0.025), and the highest values were evident in patients affected by both T2DM/IGT and OSA. Higher IL-6 levels were associated with both glycemic status and OSA. No differences in body iron regulator levels were found in obese patients with T2DM/IGT compared to those without or in those with OSA compared to those without. Further longitudinal studies in larger population samples are warranted.