Pronounced inflammatory response to endotoxaemia during nighttime: a randomised cross-over trial

Abstract

Background: Circadian variation in bodily functions has been shown to impact health in acute and chronic medical conditions. Little is known about the relationship between circadian rhythm and sepsis in humans. We aimed to investigate circadian variations in the host response in a human endotoxaemia model.

Design and methods: A cross-over study, where 12 healthy young men received E. coli endotoxin (lipopolysaccharide, LPS) 0.3 ng/kg at 12 noon and, on another day, at 12 midnight. Blood samples were analysed for pro- and anti-inflammatory cytokines: tumour-necrosis factor (TNF)-alpha, soluble TNF receptors (sTNF-R)-1 and -2, interleukin (IL)-1beta, IL-1 receptor antagonist (IL-1Ra), IL-6, and IL-10 as well as YKL-40 and the oxidative stress markers malondialdehyde (MDA), ascorbic acid (AA) and dehydroascorbic acid (DHA) before and at 2, 4, 6 and 8 hours after LPS administration.

Results: The levels of MDA and IL-10 where significantly higher during the day time (P<0.05) whereas levels of TNF-alpha, sTNF-RI, sTNF-RII, IL-1Ra, IL-6, and YKL-40 were higher (P<0.01 for all comparisons) during the night time. No significant differences were seen in the levels of AA and DHA.

Conclusion: A day-night difference in the acute phase response to endotoxaemia exists in healthy volunteers with a more pronounced inflammatory response during the night time. This circadian difference in the response to endotoxaemia may play an important role in the clinical setting and should be investigated further.

Figure 1. Plasma levels of three pro-inflammatory markers and YKL-40.

The time point 0 indicates the administration of E. coli endotoxin (LPS). The endotoxaemia was induced at day time (blue curve) and night time (red curve). Results from the two-way ANOVA: (1) interaction term (time*day) were not significant for any of the markers. (2) between groups analyses were significant for IL-6 (P<0.0001) and YKL-40 (P<0.001). *) P-value<0.05 calculated by Wilcoxon-Rank test. **) P-value<0.01 calculated by Wilcoxon-Rank test. ***) P-value<0.001 calculated by Wilcoxon-Rank test.

Figure 2. Plasma levels of four anti-inflammatory cytokines and soluble cytokine receptors.

The time point 0 indicates the administration of LPS endotoxin 0.3/kg in 12 healthy men. The endotoxaemia was induced at day time (blue curve) and night time (red curve). Results from the two-way ANOVA: (1) interaction term (time*day) were significant for only IL-10 (P<0.001). (2) between groups analyses were significant for IL-1Ra (P<0.05), sTNF-RI (P<0.000000001) and sTNF-RII (P<0.000001). *) P-value<0.05 calculated by Wilcoxon-Rank test. **) P-value<0.01 calculated by Wilcoxon-Rank test. ***) P-value<0.001 calculated by Wilcoxon-Rank test.

Figure 3. Plasma levels of the analysed oxidative markers.

The time point 0 indicates the administration of LPS endotoxin 0.3/kg on 12 healthy men. The endotoxaemia was induced at day time (blue curve) and night time (red curve). Results from the two-way ANOVA: (1) interaction term (time*day) were significant for MDA (P<0.05). (2) between groups analyses were significant for MDA (P<0.05). *) P-value<0.05 calculated by Wilcoxon-Rank test.

Figure 4. Body temperature (A), heart rate (B) and mean blood pressure (C) during endotoxaemia.

The time point 0 indicates the time of LPS administration. Endotoxaemia was induced at day time (blue curve) and night time (red curve). Results from the two-way ANOVA: (1) interaction term (time*day) were not significant, (2) between groups analyses were significant for temperature (P<0.0001) and mean blood pressure (P<0.001).