Objective: This study examined the relationships of two inflammatory cytokines, IL-6 and TNF-, to visceral adiposity and indices of plasma glucose-insulin homeostasis.

Research Design and Methods: Plasma levels of IL-6 and TNF- were measured in 189 untreated asymptomatic men (age: 43.7±7.8 years; body mass index (BMI): 29.0±4.3 kg/m²; waist girth: 98.6±10.3 cm).

Results: Significant and positive associations were found between both cytokines with adiposity and adipose tissue distribution indices (0.15r<0.32; p<0.05) as well as with plasma glucose-insulin homeostasis variables (0.22r<0.28; p<0.05). Comparison of two subgroups each composed of 32 overweight men (25 kg/m²) with similar BMI values (28.7 kg/m² in both groups) but with markedly different levels of visceral adipose tissue (< vs. 130 cm²) revealed significant differences only for IL-6 levels (1.42±1.15 vs. 0.86±0.52 pg/mL; p<0.02 for men with high vs. low visceral adipose tissue, respectively). Finally, when subjects were stratified on the basis of their respective concentrations of IL-6 and TNF- (using the 50^th percentile of their overall distribution), an analysis of variance revealed an independent contribution of IL-6 to the variation of fasting insulin (p<0.01) and of each of these two cytokines to the variation of insulin levels measured following a 75g oral glucose challenge (p<0.01 for IL-6 and p<0.05 for TNF-).

Conclusions: As IL-6 appeared to be clearly associated with visceral adiposity, TNF- rather showed associations with indices of total body fatness. Thus, TNF- may contribute to the insulin resistance of overall obesity whereas IL-6 may be one of the mediators of the hyperinsulinemic state specifically related to excess visceral adiposity.