| Markers of inflammation and antioxidant status were used to partially characterize physiological responses to a single bout of intense, exhaustive exercise in healthy Standardbreds, and to evaluate anti-inflammatory and antioxidant properties of an antioxidant enzyme supplement, with a particular focus on joint health. Main objectives were to (1) identify a model of exercise-induced inflammation by comparing inflammatory responses to different modes of exercise, (2) evaluate effects of supplemental superoxide dismutase (SOD) on exercise-induced inflammatory response and antioxidant status, and (3) evaluate effects of repeated arthrocentesis, exercise, and SOD supplementation on markers of inflammation and cartilage metabolism, in horses. For the first study, a repeated sprint exercise test was identified as the most strenuous compared to interval- and graded exercise tests. This was based upon post-exercise systemic increases in pro-inflammatory cytokine transcripts, decreases in circulating nitric oxide (NO), and peak heart rate response. The second study showed increases in interferon-gamma, interleukin-1 beta, and interleukin-10 cytokine transcripts, upregulated antioxidant defenses (SOD, total glutathione, glutathione peroxidase), and a decline in plasma NO, following intense exercise. Supplemental SOD (3000 IU/d for 6 wks) had no detectable influence on markers of performance, inflammatory response, or antioxidant status relative to intense exercise, and compared to the placebo control. The third study showed that repeated arthrocentesis in the same joint did not alter synovial fluid concentrations of prostaglandin E2 (PGE2), although anabolic cartilage metabolism, measured by chondroitin sulfate-846 (CS), was elevated at the last sample, indicating sensitivity to repeated synovial fluid aspiration. Following exercise, increases in PGE2 relative to pre-exercise concentrations, and transient increases in CS, indicated healthy adaptive responses to exercise. Similar to the second study, supplemental SOD had no influence on PGE2 or CS, suggesting it was not an effective solution for reducing exercise-induced inflammation or improving antioxidant status in horses. These studies contribute to a limited working knowledge of inflammatory and antioxidant responses to intense exercise, and may be useful when differentiating between adaptive responses and early pathological changes resulting from exercise-induced stress in horses. |
