Lack of relationship between interleukin-6 and CRP levels in healthy male athletes.

Interleukin-6 (IL-6) is the main cytokine involved in the induction of acute phase response, which includes synthesis of certain proteins in the liver, one of which is C-reactive protein (CRP). The aim of this study was to assess the impact of IL-6 released during physical exercise on CRP generation in healthy male athletes. Fourteen young cyclists were enrolled in the study, which involves the performance of strenuous physical exercise. Serum levels of IL-6 and CRP were measured at rest before exercise, and immediately after and 2h after cessation of exercise. IL-6 level was increased 2.42-fold immediately after, and 21.67-fold 2h after exercise. Serum CRP level did not change significantly over the course of observation: it was 3.25 mg/dl before, 2.36 mg/dl immediately after and 2.71 mg/dl 2h after exercise and unrelated to IL-6 level. No correlation between serum levels of IL-6 and CRP was observed during the period of observation. We conclude that under certain circumstances, acute, pulsatile release of IL-6 does not stimulate synthesis of CRP.