The Effects of Acute Aerobic Exercise on Inflammatory Markers and Mood in Individuals with Multiple Sclerosis and Spinal Cord Injury

Abstract

The purpose of this study was to determine if acute exercise-induced reductions in pro-inflammatory cytokines contribute to exercise-induced improvements in mood in individuals with spinal cord injury (SCI) and multiple sclerosis (MS). Thirteen participants completed a single 30-minute bout of moderate-intensity exercise at 60% of their pre-determined VO2 peak. Mood was assessed before, immediately after, and one- hour post-exercise, via the Profile of Mood States Questionnaire (POMS). Blood samples were taken before, immediately after, and one-hour post exercise, and subsequently analyzed for serum pro-inflammatory cytokines (IL-6, IFN-γ, and TNF-α), as well as the amino acids tryptophan (TRP) and kynurenine (KYN). Previous work from our lab has shown that chronic reductions in pro-inflammatory cytokines via diet improve mood via the kynurenine pathway, which is integral in serotonin production. Following the bout of exercise, there was a significant improvement in mood as shown by a reduction in the total POMS questionnaire score from pre to post-exercise (32.5±25.8 to 22.4±21.9; p=0.025), as well as pre to one hour post-exercise (32.5±25.8 to 21.6±25.0; p=0.008). Subscale analysis showed significant reductions in the Tension, Depression and Anger components of the POMS from pre to post-exercise and from pre to one-hour post- exercise. Regarding pro-inflammatory cytokines, there were no exercise-induced changes in IL-6, but there was a significant main effect for time for TNF-α (with post-hoc analyses showing significant reductions from pre to one-hour post-exercise) and a trend for a main effect for time for IFN-γ (p=0.06). There were no changes in TRP, KYN or KYN/TRP. There were no correlations between changes in mood and changes in cytokines when all participants were analyzed. However, when considering only the participants that responded to exercise with an improved mood (n=7), there were significant correlations between exercise-induced changes in depression and exercise- induced changes in IL-6 (r=0.853; p=0.031) and a trend for a correlation with exercise- induced changes in TNF-α (r=0.722; p=0.067). These results suggest that exercise- induced changes in mood may be partially accounted for by exercise-induced changes in pro-inflammatory cytokines in individuals with SCI and MS, but not through a kynurenine pathway-dependent manner.