Exercise Improves Insulin Sensitivity in the Absence of Changes in Cytokines.

PURPOSE: The benefits of aerobic exercise training on insulin sensitivity in subjects with the metabolic syndrome (MetS) are, at least in part, associated with changes in cytokines. Recent studies identified novel cytokines (e.g. fractalkine, omentin and osteopontin) that are strongly involved in glucose homeostasis and therefore potentially contribute in the exercise-induced changes in insulin sensitivity. Therefore, we aim to examine changes in skeletal muscle RNA expression and plasma levels of novel cytokines after exercise training, and correlate these changes to the exercise-induced changes in insulin sensitivity. METHODS: Women with the metabolic syndrome (MetS, n=11) and healthy women (n=10) participated in a 6-month aerobic exercise training intervention (3/week, 45min per session at 65%-85% of individual heart rate reserve). Before and after training, we examined insulin sensitivity (M-value during hyperinsulinemic euglycaemic clamp), circulating blood levels of cytokines (venous blood sample; leptin, adiponectin, omentin, fraktalkin, osteopontin). Skeletal muscle RNA-expression of these cytokines (muscle biopsy) was examined in two subgroups (MetS n=6; healthy women n=6). RESULTS: At baseline, plasma levels of omentin (85.8±26.2ng/ml) and adiponectin (5.0±1.7μg/ml) levels were significantly higher in controls compared to MetS (51.1±27.1; 3.6±1.1 respectively), and leptin levels were lower in controls (18.7±11.5ng/ml vs 53.0±23.5). M-value was significantly higher in controls (8.1±1.9mg/kg/min) than in MetS (4.0±1.7). Exercise training significantly improved M-values in both groups (P0.05). CONCLUSION: Whilst exercise training successfully improves insulin sensitivity in MetS and healthy women, we found no change in plasma and mRNA expression levels of novel cytokines