The Effect of Exercise on Serum Levels of Interleukin-18 and Components of the Metabolic Syndrome

Background: There is increasing evidence that the metabolic syndrome is associated with a proinflammatory state. Interleukin-18 (IL-18) has been shown to be associated with multiple components of the syndrome and to predict the development of diabetes and cardiovascular events. The aim of the present work was to investigate if exercise could reduce serum levels of IL-18 in subjects with the metabolic syndrome, and if potential changes would be associated with changes in body composition and components of the syndrome. Pravastatin was used for comparison. Methods: We investigated the effect of 12 weeks of intervention with exercise, pravastatin, or both on serum levels of IL-18 in 34 subjects with the metabolic syndrome. Results: Levels of IL-18 were reduced by exercise (P = 0.036), pravastatin (P = 0.036), and the combination (P = 0.017) versus baseline, however without intergroup differences. Still, the reduction in the exercise group was not negligible (17.5%). Furthermore, reduced levels of IL-18 were significantly associated with improvement of an increasing number of components of the metabolic syndrome (P = 0.034). This effect is likely to be caused by exercise, because this intervention had a beneficial effect on components of the syndrome compared to the control group (P = 0.029). Conclusions: Our findings suggest that the protective effect of exercise might be due in part to reduced inflammation associated with improvement of the metabolic syndrome and its components. Studies with larger sample sizes are warranted to confirm this hypothesis.