Interleukin-6, soluble interleukin-6 receptor/interleukin-6 complex and insulin resistance in obese children and adolescents

Background/aim: To study the characteristics of interleukin 6 (IL6), soluble form of interleukin 6 receptor (sILR)/IL6 complex in obese children and adolescents and its relationship with insulin resistance (IR). Subjects and methods: 66 obese children and adolescents [34 boys, mean age 10.3 ± 2.9 years, z-score of body mass index (BMI) 4.76 ± 1.36] and 24 non-obese healthy sex- and age-matched controls. Fasting levels of glucose, insulin, IL6, sIL6, sgp130 were measured. IR was assessed by homeostasis model assessment of IR (HOMA-IR). Results: Obese subjects showed increased levels of insulin and IL-6 and higher HOMA-IR compared to controls (117.67 ± 50.9 vs. 62.42 ± 29.4 pmol/L, 2.73 ± 0.98 vs. 1.07 ± 0.41 pg/ml and 4.03 ± 2.16 vs. 1.83 ± 1.05 for insulin, IL-6 and HOMA-IR, respectively, p < 0.01 in all cases). sIL-6R levels were significantly lower in obese subjects (34.7 ± 14.2 vs. 55.6 ± 15.2 ng/ml in controls, p = 0.005), whereas sgp130 levels were not significantly different. In obese subjects, IL-6 directly correlated with z-score BMI (r = 0.481, p = 0.009) and with waist-to-height ratio (r = 0.494, p = 0.007), while sIL6-R was inversely related to HOMA-IR (r = -0.522, p = 0.002). Insulin resistant subjects showed higher levels of IL6 and lower levels of sIL6R (3.31 ± 0.72 vs. 2.25 ± 0.64 pg/ml, p = 0.020 and 25.3 ± 9.3 vs. 42.5 ± 10.4 ng/ml, p = 0.013, respectively). Conclusions: In obese children and adolescents, IR is associated with elevated levels of IL-6 and diminished values of sIL-6R.