Cytokines for evaluation of chronic inflammatory status in ageing research: reliability and phenotypic characterisation

Abstract

Background: There is a growing interest in the role of inflammageing for chronic disease development. Cytokines are potent soluble immune mediators that can be used as target biomarkers of inflammageing; however, their measurement in human samples has been challenging. This study aimed to assess the reliability of a pro- and anti-inflammatory cytokine panel in a sample of healthy people measured with a novel electrochemiluminescent multiplex immunoassay platform (Meso Scale Discovery, MSD), and to characterize their associations with metabolic and inflammatory phenotypes.

Results: Overall, the majority of cytokines were above the limit of detection (in at least 85.3% of the samples). Cytokines IL-6, IL-8, TNF-α, IL-10, IL-13, and IFN-γ showed overall good to fair reliability (ICC > 0.40), whereas IL-1β, IL-2, IL-4, and IL-12p70 showed poor reliability (ICC < 0.40). The reliability estimates were not substantially influenced by participants' age, sex, obesity and C-reactive protein (CRP) levels. As expected, cytokine concentrations were elevated with advanced age most pronouncedly for IL-6, IL-8, Il-2, IFN- γ, and TNF-α. No major associations with metabolic phenotypes were observed for most cytokines, with the exception of a positive association between IL-6 and TNF-α with body mass index and CRP (ρ: 0.36; ρ: 0.20; ρ: 0.53; ρ: 0.22, respectively), and IFN-γ and IL-10 with CRP (ρ: 0.23 and ρ: 0.19, respectively).

Conclusions: Single measurements of selected cytokines using MSD platform, including IL-6, IL-8, IL-10, IL-13, TNF-α, and IFN-γ have shown to be representative of an individual's average level over time and could be suitable for use in prospective epidemiological and clinical studies. Such studies are highly warranted to characterize associations of cytokines with phenotypes and diseases associated with ageing.

Keywords: Ageing; BMI; Biomarkers; Cytokines; Inflammaging; Multiplex platforms; Reliability.

Fig. 1

Bland-Altman plots showing the agreement between log-transformed cytokine concentrations at baseline and 4-months later in relation to average concentrations for each individual. Agreement of repeated measurements (y-axis) in relation to average concentrations (x-axis) for each individual. Horizontal lines show the mean difference and the 95% CI of limits of agreement, which are defined as the mean difference +/− 1.96 times the standard deviation of the differences

Fig. 2

Box plots visualizing the distributions of log transformed cytokine concentrations stratified by age tertiles. This figure represents distributions of interleukin 1-beta (IL-1β), interleukin 2 (IL-2), interleukin 4 (IL-4), interleukin 6 (IL-6), interleukin 8 (IL-8), interleukin 10 (IL-10), interleukin 12p70 (IL-12p70), interleukin 13 (IL-13), interferon gamma (IFN-γ), and tumor necrosis factor alpha (TNF-α) according to increasing age categories (red: 44.9–54.7 years, green: 54.8–58.8 years, and purple: 58.9–64.0 years). Concentrations are from plasma samples collected during the first measurement

Fig. 3

Flow diagram of the study design. A total of 207 participants (124 women and 83 men) from the EPIC-Potsdam Cohort completed this study. Single blood samples were collected on two occasions, 4 months apart