Increased voluntary exercise in mice deficient for tumour necrosis factor-alpha and lymphotoxin-alpha

The effect of anti-TNF-α vs. DMARDs on fatigue in rheumatoid arthritis patients

OBJECTIVES

Fatigue is experienced frequently by patients with rheumatoid arthritis (RA). Fatigue may be caused by high levels of pain and disease activity in RA but can remain present while disease activity is moderate to low. It is not clear whether RA patients receiving anti-tumour necrosis factor (TNF) treatment reach lower levels of acute fatigue than RA patients receiving disease-modifying anti-rheumatic drug (DMARD) treatment. The aim of our study was to analyse whether, in patients with RA, the effect of anti-TNF on fatigue is greater than the effect of DMARD treatment.

METHOD

Sixty-seven RA patients receiving anti-TNF treatment and 104 RA patients receiving DMARDs were included. All patients were on stable treatment for at least 6 months prior to baseline measurement. Fatigue was measured monthly over 1 year with the fatigue severity subscale of the Checklist Individual Strength (CIS-fatigue). The association between persistent severe fatigue and medication group was analysed using multiple linear regression including confounders.

RESULTS

In the anti-TNF group the mean (SD) level of persistent fatigue was significantly higher than in the DMARD group [32.2 (11.4) vs. 28.3 (10.9), p = 0.025] and more patients experienced persistent severe (CIS-fatigue score ≥ 35) fatigue (42% and 27% respectively, p = 0.043). However, when correcting for age, disease activity, haemoglobin, treatment duration, pain, physical disability, and clinical depression, medication type seemed to influence neither the mean level of persistent fatigue (p = 0.251) nor the percentage of patients with persistent severe fatigue (p = 0.745).

CONCLUSIONS

When taking into account probable confounders including disease activity, medication type did not influence persistent fatigue in RA patients. It seems that, besides its anti-inflammatory effect, anti-TNF has no complementary effect on persistent fatigue.

Prospective association between C-reactive protein and fatigue in the coronary artery risk development in young adults study

BACKGROUND

Fatigue is highly prevalent and causes serious disruption in quality of life. Although the underlying biological mechanism is unknown, increases in inflammation have been implicated. This prospective study examined the association between C-reactive protein (CRP), a biomarker of systemic inflammation, and fatigue 5 years later.

METHODS

The Coronary Artery Risk Development in Young Adults (CARDIA) study is a population-based longitudinal study conducted in four U.S. cities. Highly sensitive CRP concentration and fatigue were measured in 2983 African American and white adults at both year 15 (2000-2001, ages 33-45 years) and year 20 (2005-2006) examinations. Fatigue was assessed using the vitality subscale of the 12-item Short Form Health Survey.

RESULTS

Plasma CRP concentration at baseline (i.e., CARDIA year 15) was a significant predictor of fatigue level 5 years later (unadjusted beta = .126, p < .001). After adjustment for potential confounders, this association remained significant (adjusted beta = .044, p = .033). Additionally, baseline CRP independently predicted fatigue in the subgroup of participants without medical comorbidity (adjusted beta = .051, p = .039). Fatigue was associated with a persistent elevation of CRP at both examinations but not with a transient elevation of CRP at only one of the examinations.

CONCLUSIONS

This is the first study to demonstrate a prospective association between an inflammatory marker and fatigue in a general population. Furthermore, the association between low-grade systemic inflammation and fatigue seems primarily driven by persistent immune activation and not explained by the presence or development of medical comorbidity.

A critical review of human endotoxin administration as an experimental paradigm of depression

The syndrome called depression may represent the common final pathway at which different aetiopathogenic processes converge. One such aetiopathogenic process is innate immune system activation. Some depressed patients have increased levels of inflammatory cytokines and other immunologic abnormalities. It is not known whether immune system activation contributes to the pathogenesis of depressive symptoms. Supporting this possibility is the observation that in both rodents and humans, exogenous immune stimuli such as endotoxin can produce symptoms that resemble depression. A new approach to depression research would be to use immune stimuli to elicit depressive symptoms in humans. Here we review each of the symptoms elicited in humans by endotoxin administration, and compare this model to two other immune depression paradigms: interferon-alpha treatment and typhoid vaccine administration, to assess to what degree endotoxin administration represents a valid model of immune depression. We also review corresponding behavioral changes in rodents and the potential molecular pathways through which immune system activation produces each symptom.

Exacerbated fatigue and motor deficits in interleukin-10-deficient mice after peripheral immune stimulation

The anti-inflammatory cytokine interleukin (IL)-10 is important for regulating inflammation in the periphery and brain, but whether it protects against infection- or age-related psychomotor disturbances and fatigue is unknown. Therefore, the present study evaluated motor coordination, time to fatigue, and several central and peripheral proinflammatory cytokines in male young adult (3-mo-old) and middle-aged (12-mo-old) wild-type (IL-10(+/+)) and IL-10-deficient (IL-10(-/-)) mice after intraperitoneal injection of lipopolysaccharide (LPS) or saline. No age-related differences were observed; therefore, data from the two ages were pooled and analyzed to determine effects of genotype and treatment. LPS treatment increased IL-1beta, IL-6, and TNFalpha mRNA in all brain areas examined in IL-10(+/+) and IL-10(-/-) mice, but to a greater extent and for a longer time in IL-10(-/-) mice. Plasma IL-1beta and IL-6 were increased similarly in IL-10(+/+) and IL-10(-/-) mice 4 h after LPS but remained elevated longer in IL-10(-/-) mice, whereas TNFalpha was higher in IL-10(-/-) mice throughout after LPS treatment. Motor performance and motor learning in IL-10(+/+) mice were not affected by LPS treatment; however, both were reduced in IL-10(-/-) mice treated with LPS compared with those treated with saline. Furthermore, although LPS reduced the time to fatigue in IL-10(+/+) and IL-10(-/-) mice, the effects were exacerbated in IL-10(-/-) mice. Thus the increased brain and peripheral inflammation induced by LPS in IL-10(-/-) mice was associated with increased coordination deficits and fatigue. These data suggest that IL-10 may inhibit motor deficits and fatigue associated with peripheral infections via its anti-inflammatory effects.