Association between measures of insulin sensitivity and circulating levels of interleukin-8, interleukin-6 and tumor necrosis factor-alpha. Effect of weight loss in obese men

Abstract

OBJECTIVE: To study the association between anthropometric and metabolic parameters as well as the effect of weight loss on plasma levels of the adipose tissue-derived cytokines interleukin-8 (IL-8), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) in abdominal obese men. SUBJECTS: Nineteen obese (mean body mass index (BMI): 38.6+/-0.6 kg/m(2)) and ten lean men (mean BMI: 23.4+/-0.4 kg/m(2)) were included in the study. The obese subjects received a 4.2 MJ/day diet for 8 weeks, followed by 8 weeks on energy restriction (6.2 MJ/day) and 8 weeks on a weight-maintenance diet. MEASUREMENTS: A dual energy X-ray absorptiometry (DEXA)-scan was performed to estimate body composition. Plasma levels of IL-8, IL-6 and TNF-alpha were measured by a specific ELISA method. Insulin sensitivity was assessed by the homeostasis model assessment method (HOMA). RESULTS: Plasma levels of IL-8 and IL-6 were 30-40% higher in obese as compared with lean subjects (P<0.05), whereas no group difference in TNF-alpha was observed. During the intervention, obese subjects obtained a 30% reduction in fat mass (P<0.001), fasting insulin (P<0.05) and HOMA (P<0.05). Plasma levels of TNF-alpha and IL-6 were decreased by 25-30% (P<0.001) but IL-8 was increased by 30% (P<0.001) after weight loss. IL-8 and IL-6 were correlated with measures of insulin resistance, and changes in IL-6 but not IL-8 were correlated with the improvement in insulin sensitivity after weight loss. CONCLUSION: Plasma levels of IL-8 and IL-6 were found to be increased and were correlated with measures of insulin resistance in abdominal obese male subjects. Weight loss was associated with changes in the circulating levels of IL-8, IL-6 and TNF-alpha indicating that these cytokines are influenced by weight loss.