(21-03-08) Visceral obesity and plasma glucose-insulin homeostasis: contributions of IL-6 and TNF-{alpha} in men.

Cartier A, Lemieux I, Alm?ras N, Tremblay A, Bergeron J, Despr?s JP.
Qu?bec Heart Institute, H?pital Laval Research Centre, H?pital Laval, Qu?bec (Qc), Canada; Department of Anatomy and Physiology, Universit? Laval, Qu?bec (Qc), Canada; Lipid Research Centre, CHUL Research Centre, Qu?bec (Qc), Canada; Division of Kinesiology, Department of Social and Preventive Medicine, Universit? Laval, Qu?bec (Qc), Canada.
Objective: This study examined the relationships of two inflammatory cytokines, IL-6 and TNF-alpha, to visceral adiposity and indices of plasma glucose-insulin homeostasis. Research Design and Methods: Plasma levels of IL-6 and TNF-alpha were measured in 189 untreated asymptomatic men (age: 43.7+/-7.8 years; body mass index (BMI): 29.0+/-4.3 kg/m(2); waist girth: 98.6+/-10.3 cm). Results: Significant and positive associations were found between both cytokines with adiposity and adipose tissue distribution indices (0.15/=25 kg/m(2)) with similar BMI values (28.7 kg/m(2) in both groups) but with markedly different levels of visceral adipose tissue (< vs. >/=130 cm(2)) 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-alpha (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-alpha). Conclusions: As IL-6 appeared to be clearly associated with visceral adiposity, TNF-alpha rather showed associations with indices of total body fatness. Thus, TNF-alpha 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.

Source: J Clin Endocrinol Metab. 2008 Mar 4

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