Inflammatory Cytokine Concentrations in Saliva versus Plasma at Rest and in Response to Intense Exercise in Adolescent Athletes

Salivary and plasma concentrations of inflammatory cytokines at rest and following high-intensity interval exercise were compared in adolescent swimmers (21 male and 22 female, aged 13-17 years) to validate a non-invasive method of assessing inflammation in youth. Following provision of morning, fasted, resting blood and saliva samples, swimmers performed an intense swimming trial consisting of a maximal 200m swim, plus a high intensity interval swimming protocol (5x100m, 5x50m and 5x25m; 1:1 work-to-rest ratio), followed by post-exercise blood and saliva samples (~15 min). Salivary and plasma concentrations of interleukin-6 (IL-6), interleukin 10 (IL-10), and tumor necrosis factor alpha (TNF-α) were similar in males and females across time. Resting concentrations of IL-10 were significantly lower while IL-6 and TNF-α were significantly higher in saliva compared with plasma. IL-6 did not show a significant time effect or interaction, so although its relative decrease from pre- to post-swimming was higher in saliva than in plasma this difference was not significant (-21% vs. -3%, respectively; p = 0.06). There was a significant time-by-media interaction for IL-10, which increased from pre- to post-swimming in plasma, but this response was attenuated in saliva (51% vs. 29%; p = 0.02). TNF-α showed a significant time-by-media interaction, reflecting a decrease from pre- to post-swimming only in saliva (-27%, p = 0.01). Intraclass correlation coefficients revealed no agreement between salivary and plasma cytokine levels, and low Pearson correlations revealed no association between these measures either at rest or in response to intense swimming. In conclusion, although the overall direction of the post-exercise response was similar between saliva and plasma, the magnitude of the response was consistently different in saliva compared with plasma, which combined with the different resting concentrations and the absence of correlation between measures, suggest that salivary cytokine measures are not representative of blood levels in young athletes

Cytokine concentrations in saliva vs. plasma at rest and in response to intense exercise in adolescent athletes

Background Salivary measures are advantageous in conducting large paediatric studies involving repeated measures. However, research measuring salivary cytokines in youth is limited. Aim Compare salivary with plasma concentrations of inflammatory cytokines at rest and following exercise in adolescent swimmers (21 male, 22 female). Methods Following collection of resting saliva and blood samples, participants performed a bout of high-intensity interval swimming, with samples taken again ∼15 min post-swimming and analysed for interleukin-6 (IL-6), interleukin 10 (IL-10), and tumour necrosis factor-alpha (TNF-α). Results Resting IL-10 was significantly lower, while IL-6 and TNF-α were significantly higher in saliva compared with plasma. IL-10 increased from pre- to post-swimming in plasma, but less so in saliva (51% vs. 29%; p = 0.02). TNF-α decreased post-swimming in saliva, but not in plasma (–27% vs −1%; p = 0.01). IL-6 decreased post-swimming in saliva compared with plasma (–21% vs. −3%; p = 0.06). Intraclass correlation coefficients (ICC) revealed no association between salivary and plasma IL-6 and TNF-α, while IL-10 showed a weak correlation only at rest (ICC = 0.39; p = 0.05). Conclusions Differences in concentrations and exercise responses, along with weak correlations, suggest that salivary cytokine levels are not an accurate representation of blood cytokine levels, and should not be used as a surrogate measure in paediatric studies