Skeletal Muscle Cytokines following Repeated Bouts of Exercise and Orange Juice

Abstract

The primary aim of this study is to determine if orange juice (OJ) supplementation can attenuate cytokine (IL-6 and TNF-α) levels in human skeletal muscle following exercise in the heat. We hypothesized that exercise in a hot humid environment will increase IL-6 and TNF-α levels in skeletal muscle. Secondly we hypothesized that supplementation with 100% OJ will partially attenuate the cytokine response to exercise in a similar manner to carbohydrate-electrolyte beverage (CEB) but more so than just drinking water (W) following exercise. In a single blind fashion, twenty healthy males and six healthy females, consumed either 100% OJ, W, or a CEB for eleven days. Over five of those days they performed 80 minutes of intermittent cycling (4 sets of 15min at 70% max heart rate) in an environmental chamber set at a mild, thermal temperature (30°C, 50% humidity). Muscle biopsies were taken from vastus lateralis on days 1, 4, 8, and 11 of the study and analyzed for the cytokines IL-6 and TNF-α via Western Blot protein immunoblotting technique. There was no main effect for either time or group IL-6 in skeletal muscle. However, there was a group x time interaction (p=0.018), where the group that consumed W linearly increased from day 1 to day 11 while the OJ, and CEB groups did not change. Post-hoc independent T-tests found a significant difference between the OJ and W group on Day 8 (p=0.028). TNF-α skeletal muscle levels were below the detection level of the imaging system and were not analyzed statisctically. In conclusion, there was no significant difference in intramuscular IL-6 between groups that consumed OJ, CEB, or W after repeated bouts of aerobic exercise. However, our data does suggest that the carbohydrate content of OJ and CEB could plausibly attenuate IL-6 increase when compared to just W.