Vaccination, a human model of inflammation, activates systemic inflammation but does not trigger proinflammatory gene expression in adipose tissue

Acute Systemic Inflammation is Unlikely to Affect Adiponectin and Leptin Synthesis in Humans

Adipose tissue (AT), classically thought to be merely an energy store, has been shown to produce inflammatory and metabolically active cytokines. Recently, adiponectin and leptin, adipokines primarily synthesized by adipocytes, have attracted considerable attention because inflammation has been suggested to modulate adipokine levels. However, the regulation of adiponectin and leptin is complex and the knowledge about their synthesis within the early onset of inflammation is poorly understood. The aim of this study was to investigate if the synthesis of adiponectin and leptin is affected during the early phase of an acute systemic inflammation. Eighteen healthy subjects were allocated to vaccination against Salmonella typhi or to a control group, and adiponectin and leptin concentrations measured in plasma during 24 h. Nine patients, without markers of inflammation, undergoing open heart surgery were investigated before and after the operation by analysis of plasma levels and AT gene expression of adiponectin and leptin. Plasma interleukin (IL)-6 concentrations were measured in both cohorts. Plasma levels of IL-6 were doubled after vaccination and increased 30-fold after open heart surgery. Plasma levels of adiponectin and leptin were unchanged after vaccination whereas adiponectin and leptin tended to decrease after surgery. The gene expression of adiponectin and leptin was unaltered in omental and subcutaneous AT after surgery. Despite the use of two models of stimulated in vivo systemic inflammation, we found no evidence of an early regulation of adiponectin and leptin synthesis, indicating that these two adipokines are not key elements in an acute systemic inflammation in humans.

Induced mild systemic inflammation is associated with impaired ability to improve cognitive task performance by practice

Elevated inflammatory levels are linked to poorer cognition, but experimental confirmation is lacking. This report examined associations between cognitive performance and inflammation induced by exercise and vaccination. Thirty-six (exercise N = 18, vaccination N = 18) healthy males completed a paced auditory serial addition test (PASAT), which is a multifaceted measure of cognitive function. The task was completed in placebo and elevated inflammation states. Improvements in PASAT performance were related to inflammation. In the exercise study, IL-6 during the first PASAT negatively correlated with PASAT improvement (p = .022). In the vaccination study, increases in C-reactive protein between PASATs correlated with reduced PASAT improvement (p < .001). Inflammation was linked to reduced improvements in cognitive performance. Further research should identify the specific cognitive functions affects and the underlying mechanisms.

Eccentric-exercise induced inflammation attenuates the vascular responses to mental stress

Mental stress has been identified as a trigger of myocardial infarction (MI), with inflammation and vascular responses to mental stress independently implicated as contributing factors. This study examined whether inflammation moderates the vascular responses to mental stress. Eighteen healthy male participants completed a stress task under two counter balanced conditions. In the exercise condition, a morning bout of eccentric exercise (12×5 repetitions of unilateral eccentric knee extension at 120% intensity of concentric one repetition maximum) was used to increase levels of inflammatory-responsive cytokines during an afternoon stress session scheduled 6h later. In the control condition, participants sat and relaxed for 45min, 6h prior to the afternoon stress session. Forearm blood flow, calf blood flow (measured in the leg which completed the exercise task), blood pressure, heart rate and cardiac output were assessed at rest and in response to mental stress. As expected, interleukin-6 was higher (p=.02) 6h post exercise, i.e., at the start of the stress session, as compared to the no-exercise control condition. Mental stress increased forearm blood flow, calf blood flow, blood pressure, heart rate, and cardiac output in both conditions (p's<.001). Stress-induced calf blood flow was attenuated in the exercise condition compared to the control condition (p<.05) which was not the case for forearm blood flow. This study found that the inflammatory response to eccentric exercise attenuated the vascular responses to mental stress locally at the site of eccentric exercise-induced inflammation. The observed impairment in vascular responses to stress associated with increased levels of inflammation suggests a mechanism through which inflammation might increase the risk for MI.

The time course of the inflammatory response to the Salmonella typhi vaccination

The Salmonella typhi vaccination induces transient increases in inflammatory-responsive cytokines and molecules. For instance, it causes small, mild increases in interleukin-6 (IL-6) within a few hours and C-reactive protein (CRP) within 24h. No study has charted either the time course of the inflammatory response to this vaccine or any associated changes in mood, physical symptoms, and cardiac function. In a blinded crossover experimental design, eight participants received the S. typhi vaccine (vaccination condition) and a saline (control condition) injection on two separate days, at least one week apart. Blood samples and mood ratings were collected at 0, 4, 5, 6, 7, 8 and 24h post-injection, physical symptoms and pain were assessed at 4-8 and 24h post-injection, and cardiovascular function was recorded until 8h post-injection. Repeated measures analyses of variance and polynomial trend analyses compared the timecourse of the response patterns between the two conditions. Whereas there were no temporal changes in the control condition, the vaccination increased granulocytes, IL-6, TNF-α, and CRP (all p's<.05). Specifically, the granulocytes, IL-6 and TNF-α peaked after 6-8h while CRP peaked after 24h. This vaccine-induced mild inflammatory response was not accompanied by any changes in mood or cardiovascular activity. We also found that participants tended to report more pain in the injected limb in the vaccination condition (p<.07). In sum, our study charted the timecourse of key inflammatory-responsive markers following S. typhi vaccination and identified the timing of their modest peaks. It is worth noting that changes in these markers were not accompanied by any notable changes in mood or cardiovascular activity, and thus the S. typhi vaccination is a suitable method to induce increases in inflammatory-responsive markers, without altering mood or cardiovascular parameters.