Influence of the sample collection method on salivary interleukin–6 levels in resting and post-exercise conditions

Abstract

Previous studies demonstrated that no significant relationships exist between salivary and serum IL-6 in resting conditions and following exercise and that appropriate saliva collection procedures allow to avoid analytical drawbacks. This investigation aimed to: (a) compare the effects of two methods of saliva collection on IL-6 assay; (b) search for correlation between salivary and serum IL-6 in resting and post-exercise conditions; (c) evaluate the IL-6 response to isometric contractions. Seventeen sedentary subjects and fifteen athletes underwent one blood and two salivary draws: saliva was collected chewing on cotton salivettes and using a plastic straw (SA method and ST method, respectively). Afterwards, the athletes only completed a fatiguing isometric exercise of the knee extensors and blood and saliva were sampled after the exercise. In the entire group (n=32), ST method produced higher IL-6 levels than SA method and serum sampling. The exercise elicited significant responses of lactate, serum IL-6, salivary IL-6 (by ST method): salivary IL-6 values using the ST collection method were higher at each sampling point than with the SA method. The correlation analyses applied to both resting levels in the entire group and absolute changes above baseline in the athlete group showed that: (1) no significant relationships exist between serum and salivary IL-6 levels; (2) the greater the salivary IL-6 measurement, the higher the resultant inaccuracy of the SA method; (3) significant correlations exist between isometric force and mechanical fatigue during exercise and peaks of lactate and serum IL-6. These data provided demonstration of a cotton-interference effect for the results of salivary IL-6 assay and confirmed the lack of significant correlation between salivary and serum IL-6 in resting and post-exercise conditions.

Effects of the Menstrual Cycle and Acute Aerobic Exercise on Cytokine Levels

“…Previous studies agree with the current study as they reported that salivary IL-6 level was not related to circulating IL-6 at rest and post-exercise conditions in patients and mixed gender athletes [10,15,17,18]. Moreover, it has been discovered that IL-6 mRNA are up regulated in salivary glands of mouse models [28] and in humans [29].…”

“…Therefore, there is a lack of information regarding salivary IL-6 and IL-8 concentrations on resting healthy women during different phases of menstrual cycle. In addition, previous studies reported that salivary and circulating IL-6 levels do not relate to each other at rest [15,17,18] and at post-exercise [10]. Such findings need to be confirmed in healthy women at different timings of menstrual cycle to demonstrate whether salivary sampling can be employed as an alternative to blood sampling for an examination of inflammation status.…”

“…Recently, saliva sampling has received attention as an alternative to blood sampling to measure stress markers [8][9][10][11]. Saliva collection has the advantage over blood sampling in that it is a non-invasive method of sample collection which does not require any specialized training.…”

Resting plasma and salivary IL-6 concentrations are not correlated in distance runners

“…There are a number of investigations, in a range of clinical settings, reporting salivary IL-6 concentrations as a good correlate of disease severity in various immune-associated conditions (Nielsen et al 2005;Rhodus et al 2005a;Streckfus et al 2001). Despite these associations, we are aware of few investigations directly comparing plasma and salivary IL-6 concentrations (Minetto et al 2005;Minetto et al 2007). If salivary IL-6 concentrations provide a valid representation of plasma IL-6, in the same way that salivary cortisol is accepted as reXecting free (unbound) plasma cortisol concentrations (Stupnicki and Obminski 1992), then this would oVer an alternative to the invasive collection procedures currently required for monitoring IL-6 responses to exercise.…”

The detection and measurement of interleukin-6 in venous and capillary blood samples, and in sweat collected at rest and during exercise

“…Attempts have been made to detect cytokines in a variety of other body fluids using non-invasive methods including saliva (Cox et al 2008;Minetto et al 2005;Minetto et al 2007) and sweat (Cizza et al 2008;Marques-Deak et al 2006) with varying degrees of success. Saliva has been shown to be a poor medium for cytokine measurement, as there is no correlation between IL-6 concentrations in blood versus saliva either at rest (Cox et al 2008) or following strenuous exercise (Minetto et al 2005).…”