IL6 and endothelial dysfunction: Since it was shown that during a single bout of exercise AMPK activation correlates positively with eNOS phosphorylation in the mouse aorta [21] and that AMPK co-immunoprecipitates with eNOS [22], we hypothesized that impaired exercise capacity of IL-6−/− mice could be related to endothelial dysfunction and compromised NO-dependent peripheral vasodilation that is a limiting factor of tissue perfusion during exercise.