There is scant information regarding the role of interleukin (IL)-6 in obesity-related metabolic dysfunction in humans. Thus, we studied the serum levels of IL-6 in normal weight, overweight, and obese subjects, and examined associations of IL-6 with hyperglycemia, insulin resistance, dyslipidemia, and systemic inflammation. One hundred three women and men were included in the study. Anthropometric parameters, blood glucose, insulin, total cholesterol, and triglycerides were measured. Serum levels of tumor necrosis factor-alpha (TNF-alpha), IL-10, and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA). One-way analysis of variance (ANOVA) showed a 2.5-fold significant decrease in serum IL-6 in overweight and obese individuals when compared with normal weight controls. Serum IL-6 exhibited significant inverse correlations with body mass index (r = -0.39/P < 0.0001), waist circumference (r = -0.42/P < 0.001), blood glucose (r = -0.40/P < 0.0001), triglycerides (r = -0.34/P < 0.0001), and TNF-alpha (r = -0.48/P < 0.0001), whereas a strongly positive correlation was found with IL-10 (r = 0.77/P < 0.0001). Multiple linear regression analysis revealed that behavior of IL-6 was mainly influenced by IL-10 (beta = 0.28/P = 1.95 × 10-6), TNF-alpha (beta = -0.67/P = 0.0017), and body fat percentage (beta = -5.95/P = 7.67 × 10-5) in women. In contrast, IL-10 (beta = 0.37/P = 1.34 × 10-9), TNF-alpha (beta = -0.85/P = 0.0005), and triglycerides (beta = 1.07/P = 0.0007) were major influencing factors of IL-6 in men. This study demonstrates that IL-6 is a marker of metabolic dysfunction that is differentially regulated in obese women and men. [Figure: see text].
Keywords: TNF-alpha; glucose; interleukin-10; interleukin-6; triglycerides.