Effect of prolonged, submaximal exercise and carbohydrate ingestion on monocyte intracellular cytokine production in humans

1. The present study was undertaken to examine the effect of exercise and c arbohydrate (CHO) ingestion on intracellular monocyte cytokine production. Subjects performed 2 h of cycling at 70% peak pulmonary O-2 uptake ((V) ove r dot (O2,peak)) while ingesting either an 8% CHO beverage or a sweet place bo. Whole blood was incubated with (stimulated) or without (spontaneous) li popolysaccharide (LPS) and surface stained for monocyte surface antigens. T he cells were permeabilised, stained for intracellular cytokines and analys ed using flow cytometry. 2. Exercise had no effect on the number of monocytes spontaneously producin g cytokines, but the number of stimulated IL-1 alpha-, TNF-alpha- and IL-6- positive monocytes were elevated (P < 0.01) immediately post-exercise and 2 h post-exercise. These stimulated cells produced less (P < 0.05) TNF-alpha immediately post-exercise, and less (P < 0.05) TNF-<alpha> and IL-1 alpha 2 h post-exercise. There was a small, but significant increase (P < 0.05) i n the plasma IL-6 concentration immediately post-exercise. 3. Exercise resulted in an elevation (P < 0.01) in the plasma adrenaline co ncentration in the placebo trial, and ingestion of CHO attenuated this incr ease. CHO ingestion had no effect on monocyte cytokine production, plasma I L-B or circulating leukocyte numbers. 4. These data suggest that circulating monocytes are not the origin of incr eased levels of plasma IL-6 during exercise: prolonged cycling exercise inc reased the number of monocytes producing cytokines upon stimulation, but th ese cells produced less cytokines post-exercise. In addition, attenuation o f plasma adrenaline levels had no effect on plasma IL-6 or monocyte cytokin e production.