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Carbohydrate intake during endurance exercise increases natural killer cell responsiveness to IL-2

Wastl Human Performance Laboratory, Department of Health and Kinesiology, Purdue University, West Lafayette, Indiana 47905

Submitted 6 June 2003 ; accepted in final form 5 September 2003

The purpose of this study was to evaluate the effect of high-intensity endurance exercise and carbohydrate consumption on in vitro responsiveness of natural killer (NK) to IL-2 (2.5 U/ml for 24 h). Thirteen male subjects (18-26 yr old; peak O₂ consumption = 59.79 ± 5.13 ml·kg^-1·ml^-1) were recruited to complete two 1-h (75-80% peak O₂ consumption) cycling trials in a random counterbalanced order: carbohydrate (CHO) and placebo (Pla). Venous blood samples were collected before (Pre), immediately (Post), 2 h (2H), and 4 h (4H) after exercise. All resting samples were taken after 15 min of seated rest. NK (CD3^-/56⁺), activated NK (CD3^-/56⁺/69⁺), helper T cell (Th; CD3⁺/4⁺), and cytotoxic T cell (Tc; CD3⁺/8⁺) number were measured by using flow cytometry. NK cell activity (NKCA) was determined by using both a ⁵¹Cr release assay (NKCA-51) and activated NK cell number (NKCA-69). Immune system variables were not different between CHO and Pla, with the exception of NK cell responsiveness to IL-2, where Post (116.2%) and 4H (48.4%) was significantly greater in CHO (P < 0.05). NK, Th, and Tc were significantly higher Post (40.7, 102.7, and 82.0%, respectively) and lower at 2H (-51.9, -53.3, and -53.2%, respectively) than Pre (time effect). 4H was not different from Pre for NK, Th, and Tc. NKCA was significantly lower 2H (NKCA-51, NKCA-69) and 4H (NKCA-69) than Pre. CHO consumption during exercise did not prevent disruptions in unstimulated immune system function, but it did enhance NK responsiveness to IL-2.

natural killer cell activity; flow cytometry; CD69; cyclists; whole blood natural killer assay; interleukin-2

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