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Quercetin's influence on exercise-induced changes in plasma cytokines and muscle and leukocyte cytokine mRNA

¹Departments of Health, Leisure, and Exercise Science, and Biology, Appalachian State University, Boone, North Carolina; and ²Department of Exercise Science, University of South Carolina, Columbia, South Carolina

Submitted 30 June 2007 ; accepted in final form 21 August 2007

Trained male cyclists (n = 40) ingested quercetin (Q; n = 20) (1,000 mg/day) or placebo (P; n = 20) supplements under randomized, double-blinded methods for 3 wk before and during a 3-day period in which subjects cycled for 3 h/day at 57% maximal work rate. Blood samples were collected before and after each exercise session and assayed for plasma IL-6, IL-10, IL-1ra, IL-8, TNF-, and monocyte chemoattractant protein 1, and leukocyte IL-10, IL-8, and IL-1ra mRNA. Muscle biopsies were obtained before and after the first and third exercise sessions and assayed for NF-B and cyclooxygenase-2 (COX-2), IL-6, IL-8, IL-1β, and TNF- mRNA. Postexercise increases in plasma cytokines did not differ between groups, but the pattern of change over the 3-day exercise period tended to be lower in Q vs. P for IL-8 and TNF- (P = 0.094 for both). mRNA increased significantly postexercise for each cytokine measured in blood leukocyte and muscle samples. Leukocyte IL-8 and IL-10 mRNA were significantly reduced in Q vs. P (interaction effects, P = 0.019 and 0.012, respectively) with no other leukocyte or muscle mRNA group differences. Muscle NF-B did not increase postexercise and did not differ between Q and P. Muscle COX-2 mRNA increased significantly postexercise but did not differ between Q and P. In summary, 1 g/day quercetin supplementation by trained cyclists over a 24-day period diminished postexercise expression of leukocyte IL-8 and IL-10 mRNA, indicating that elevated plasma quercetin levels exerted some effects within the blood compartment. Quercetin did not, however, influence any of the muscle measures, including NF-B content, cytokine mRNA, or COX-2 mRNA expression across a 3-day intensified exercise period.

nuclear factor kappa B; cyclooxygenase-2; immune; inflammation; flavonoids