IL‐6 Gene Expression in Human Adipose Tissue in Response to Exercise – Effect of Carbohydrate Ingestion

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Abstract
Interleukin‐6 (IL‐6) is a cytokine involved in a number of immunological processes, but it is also linked to exercise and possibly energy status. During exercise, muscle IL‐6 mRNA levels and plasma IL‐6 levels are increased and further augmented when intramuscular glycogen levels are low. In contrast, the increase in plasma IL‐6 is blunted if carbohydrate is administered, indicating a substrate‐regulated induction of IL‐6 in human skeletal muscle. Recent studies have demonstrated that IL‐6 is also released from adipose tissue in response to an exercise bout. Furthermore, IL‐6 has been demonstrated to have a lipolytic effect, thus possibly playing a role in mobilisation of energy as free fatty acids (FFA) in response to exercise. The purpose of the present study was to investigate the gene expression pattern of IL‐6 in adipose tissue in response to exercise, and to determine whether gene expression was affected by the ingestion of carbohydrate. Eight male subjects performed 3 h of bicycling with ingestion of a carbohydrate drink or placebo. Fat biopsy samples and blood samples were obtained before, during and in the recovery phase of exercise. Both plasma IL‐6 and adipose IL‐6 mRNA levels increased in response to exercise. IL‐6 gene expression was lower (P < 0.05) in the CHO trial (1.98‐fold increase, confidence interval (CI) 1.16–3.83) compared with the control (6.49‐fold increase, CI 3.57–13.91) at end of exercise. Furthermore, CHO ingestion blunted the increase in plasma IL‐6 levels (P < 0.05) at end of exercise (26.0 ± 3.7 pg ml−1 in the control vs. 15.6 ± 2.4 pg ml−1 in the CHO trial). In conclusion, exercise results in an increase in IL‐6 gene expression in adipose tissue in response to exercise, an effect that is significantly blunted by ingestion of carbohydrate.