CARBOHYDRATE INGESTION INFLUENCES SKELETAL MUSCLE CYTOKINE mRNA AND PLASMA CYTOKINE LEVELS AFTER A 3-H RUN

Abstract

PURPOSE To determine the influence of carbohydrate ingestion on skeletal muscle cytokine mRNA content and plasma cytokine levels after a 3-h run. METHODS Sixteen experienced marathoners ran on treadmills for 3 h at ∼70% VO2max on two occasions while receiving 1 l/h carbohydrate (CHO) or placebo (PLA) beverages. Blood and vastus lateralis muscle biopsy samples were collected before and after exercise. Plasma was analyzed for IL-6, IL-10, IL-1ra, IL-8, cortisol, glucose, and insulin. Muscle was analyzed for glycogen content and relative gene expression of 13 cytokines (IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p35, IL-12p40, IL-15, IFN-γ, TNF-α) using real-time quantitative RT-PCR and the ΔΔCt method that monitors the degradation of a dual-labeled fluorescent probe (TaqMan) in real time concomitant with PCR amplification. The data were analyzed using a 2 × 2 repeated measures ANOVA. RESULTS Plasma glucose and insulin were higher and cortisol, IL-6, IL-10, and IL-1ra, but not IL-8, were significantly lower post-exercise in CHO vs PLA. Change in muscle glycogen content did not differ between CHO and PLA (P=0.246). Muscle cytokine mRNA was detected for IL-1β, IL-2, IL-6, IL-8, IL-10, IL-12p35, IL-15, IFN-γ, and TNF-α, but only IL-1β, IL-6, and IL-8 were significantly increased with exercise (P < 0.05). The increase in mRNA (fold difference from pre-exercise) was attenuated in CHO (15.9-fold) compared to PLA (35.2-fold) for IL-6 (P = 0.071) and IL-8 (CHO, 7.8-fold; PLA, 23.3-fold; P = 0.063). CONCLUSION CHO compared to PLA beverage ingestion attenuates the increase in plasma IL-6, IL-10, and IL-1ra, and gene expression for IL-6 and IL-8 in athletes running 3 h at 70% VO2max despite no differences in muscle glycogen content. Supported by a grant from the Gatorade Sports Science Institute.