Lack of IL-6 production during exercise in patients with mitochondrial myopathy

In the present study we investigated the possibility that exercise-induced increases in plasma levels of interleukin (IL)-6 are associated with plasma lactate levels. Patients with mitochondrial myopathy (MM) are characterised by high levels of plasma lactate. In this study, seven patients with MM underwent an ergometer cycle test for 25 min without treatment. They were then treated with dichloroacetate (DCA) for 15 days. DCA inhibits pyruvate-dehydrogenase-kinase, thereby increasing the activity of the pyruvate-dehydrogenase complex. The same exercise test was repeated on the last day of treatment. DCA lowered the plasma lactate and increased plasma IL-6 concentrations at rest. IL-6 increased in response to exercise only during DCA treatment. Furthermore, plasma IL-6 was negatively correlated to plasma lactate at rest (r = -0.786, P = 0.05). Given that IL-6 is a cytokine with growth-promoting potential, the results of this study suggest that high lactate production contributes to the decreased muscle function observed in MM patients by inhibiting the production of IL-6.