Assessment of Serum Myokines and Markers of Inflammation Associated with Exercise in Endurance Racing Sled Dogs

Abstract

The endurance sled dog is the ultimate endurance athlete in which to examine the exercise-associated acute phase and myokine responses that might be related to changes in muscle metabolism and damage. An inciting cause for increased C-reactive protein has yet to be elucidated, which might involve interleukin-6 and other myokines. To examine concentrations of interleukin-6 (IL-6), interleukin-15 (IL-15), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α), and markers of the inflammatory response of exercise; monocyte chemoattractant protein-1(MCP-1) and C-reactive protein (CRP) before, during, and after an endurance racing event. 26 sled dogs completing a 1650-km race. In a prospective study, cephalic venipuncture was performed before racing, at the midpoint, and after racing. Body weight and serum CRP, MCP-1, IL-15, IL-8, IL-6, and TNF-α concentrations were evaluated using enzyme-linked immunoabsorbance-based assays or a luminex multiplex assay. There were no significant differences in concentrations of IL-6, IL-15, IL-8, or TNF-α at the 3 time points, whereas there were significant increases in MCP-1 (median and range-start: 86pg/mL [30-1845]; midpoint: 179pg/mL [53-730]; finish: 180pg/mL [21-1294]; P<.01) and CRP (median and range-start: 18μg/mL [11-58]; midpoint: 76μg/mL [12-198]; finish: 60μg/mL [12-170]; P<.01) at the midpoint and race finish. There was a significant linear relationship between MCP-1 and IL-6 (R=0.68; P<.01). The inflammatory response to exercise increases as measured by MCP-1 during and after endurance exercise in sled dogs. IL-6 appears to be associated with MCP-1; however, the reasons for increases in the acute phase response (CRP) cannot be attributed to IL-6 or other myokines. IL-6 and MCP-1 concentrations might be useful in future investigations of exertional rhabdomyolysis.