CCL2 and obstructive sleep apnea syndrome: Although some literature sources have demonstrated the increased circulating IL-8 levels in OSA patients [17,18,19], one study published by Kim et al. showed that the serum concentrations of IL-8 did not differ between the OSA patients and the normal controls while the plasma MCP-1 and adiponectin levels differed between the OSA patients and the normal controls [24].