Systemic inflammation and ex vivo inflammatory responses in first semester university students.

backgroundInflammation contributes to cardiovascular and metabolic disease development. Reducing disease risk by targeting inflammation is therefore desirable in prevention research. However, circulating markers of inflammation are often difficult to detect in younger individuals. Ex vivo stimulated cytokine production offers a promising alternative measure of immune function. Yet, few studies among younger adults have used this measure to date or have assessed its reliability over time.

methodsFirst-year university students (N = 110, age 18-19 years) completed two study visits, one each at the beginning and end of their first semester. Circulating cytokines and lipopolysaccharide-stimulated cytokine production were assayed at each visit; composites for each were created using IL-1β, IL-6, and IFN-γ. Analyses excluded participants with CRP ≥ 10 mg/L. Pearson's correlations were used to examine unadjusted associations between circulating and stimulated cytokine composites, within and across visits. Multiple linear regression was then used to test concurrent associations between the circulating and stimulated cytokine composites, and the within-person stability of each measure across visits, adjusting for sex, body mass index, perceived stress, physical activity, diet quality, and sleep quality.

resultsStudy visits occurred 13 weeks ± 8 days apart. The circulating and stimulated cytokine composites were significantly correlated at visit 1 (r= 0.374, p<0.01) and at visit 2 (r=0.246, p = 0.02). This association remained significant in regression analyses at both visit 1 (B [95 % CI] = 0.407 [0.196, 0.617], p < 0.01) and visit 2 (B [95 % CI] = 0.312 [0.041, 0.584], p=0.03). The circulating cytokine composite at visit 1 was not significantly associated with the circulating cytokine composite at visit 2 in either correlation (r=-0.009, p=0.94) or regression (B [95 % CI] = -0.007 [-0.192, 0.179], p = 0.94) analyses. Stimulated cytokine production at visit 1 was significantly associated with stimulated cytokine production at visit 2 in both correlation (r=0.515, p<0.01) and regression analyses (B [95 % CI] = 0.497 [0.293 0.701], p<0.01).

conclusionsContrasting with some past research, circulating cytokines were significantly associated with stimulated cytokine production in the present sample concurrently at both visits. Stimulated cytokine production was more stable within-person across visits (∼13 weeks apart) compared to circulating cytokines in these students. Measurement of stimulated cytokines may be informative for understanding between-person differences in inflammation-related disease risk in younger adults, in part because they appear more stable compared to circulating cytokines.