Acute effects of recombinant human interleukin-6 on endocrine and central nervous sleep functions in healthy men

Cortisol, cytokines, and hippocampal volume interactions in the elderly

Separate bodies of literature report that elevated pro-inflammatory cytokines and cortisol negatively affect hippocampal structure and cognitive functioning, particularly in older adults. Although interactions between cytokines and cortisol occur through a variety of known mechanisms, few studies consider how their interactions affect brain structure. In this preliminary study, we assess the impact of interactions between circulating levels of IL-1Beta, IL-6, IL-8, IL-10, IL-12, TNF-alpha, and waking cortisol on hippocampal volume. Twenty-eight community-dwelling older adults underwent blood draws for quantification of circulating cytokines and saliva collections to quantify the cortisol awakening response. Hippocampal volume measurements were made using structural magnetic resonance imaging. Elevated levels of waking cortisol in conjunction with higher concentrations of IL-6 and TNF-alpha were associated with smaller hippocampal volumes. In addition, independent of cortisol, higher levels of IL-1beta and TNF-alpha were also associated with smaller hippocampal volumes. These data provide preliminary evidence that higher cortisol, in conjunction with higher IL-6 and TNF-alpha, are associated with smaller hippocampal volume in older adults. We suggest that the dynamic balance between the hypothalamic-pituitary adrenal axis and inflammation processes may explain hippocampal volume reductions in older adults better than either set of measures do in isolation.

Sleep disordered breathing, fatigue, and sleepiness in HIV-infected and -uninfected men

Study Objectives

We investigated the association of HIV infection and highly active antiretroviral therapy (HAART) with sleep disordered breathing (SDB), fatigue, and sleepiness.

Methods

HIV-uninfected men (HIV−; n = 60), HIV-infected men using HAART (HIV+/HAART+; n = 58), and HIV-infected men not using HAART (HIV+/HAART−; n = 41) recruited from two sites of the Multicenter AIDS cohort study (MACS) underwent a nocturnal sleep study, anthropometric assessment, and questionnaires for fatigue and the Epworth Sleepiness Scale. The prevalence of SDB in HIV- men was compared to that in men matched from the Sleep Heart Health Study (SHHS).

Results

The prevalence of SDB was unexpectedly high in all groups: 86.7% for HIV−, 70.7% for HIV+/HAART+, and 73.2% for HIV+/HAART−, despite lower body-mass indices (BMI) in HIV+ groups. The higher prevalence in the HIV− men was significant in univariate analyses but not after adjustment for BMI and other variables. SDB was significantly more common in HIV− men in this study than those in SHHS, and was common in participants with BMIs <25 kg/m². HIV+ men reported fatigue more frequently than HIV− men (25.5% vs. 6.7%; p = 0.003), but self-reported sleepiness did not differ among the three groups. Sleepiness, but not fatigue, was significantly associated with SDB.

Conclusions

SDB was highly prevalent in HIV− and HIV+ men, despite a normal or slightly elevated BMI. The high rate of SDB in men who have sex with men deserves further investigation. Sleepiness, but not fatigue, was related to the presence of SDB. Clinicians caring for HIV-infected patients should distinguish between fatigue and sleepiness when considering those at risk for SDB, especially in non-obese men.

The detection and measurement of interleukin-6 in venous and capillary blood samples, and in sweat collected at rest and during exercise

PURPOSE

This study aimed to quantify the relationship between venous and capillary blood sampling methods for the measurement of plasma interleukin-6 (IL-6). A parallel study was conducted to determine the possibility of measuring IL-6 in sweat using an enzyme-linked immunosorbent assay (ELISA) and investigate the relationship between plasma- and sweat-derived measures of IL-6.

METHODS

Twelve male participants were recruited for the measurement of IL-6 at rest and during exercise (study 1). An additional group of five female participants was recruited for the measurement of IL-6 in venous blood versus sweat at rest and following exercise (study 2). In study 1, venous and capillary blood samples were collected at rest and in response to exercise. In study 2, venous and sweat samples were collected following exercise.

RESULTS

Mean plasma IL-6 concentration was not different between venous and capillary blood sampling methods either at rest (4.27 ± 5.40 vs. 4.14 ± 4.45 pg ml(-1)), during (5.40 ± 5.17 vs. 5.58 ± 6.34 pg ml(-1)), or in response to exercise (6.95 ± 6.37 vs. 6.99 ± 6.74 pg ml(-1)). There was no IL-6 detectable in sweat either at rest or following exercise.

CONCLUSION

There are no differences in the measurement of plasma IL-6 using either venous or capillary blood sampling methods. Capillary measurement represents a minimally invasive way of measuring IL-6 and detecting changes in IL-6, which are linked to fatigue and overtraining.

Endothelial function and sleep: associations of flow-mediated dilation with perceived sleep quality and rapid eye movement (REM) sleep

Endothelial function typically precedes clinical manifestations of cardiovascular disease and provides a potential mechanism for the associations observed between cardiovascular disease and sleep quality. This study examined how subjective and objective indicators of sleep quality relate to endothelial function, as measured by brachial artery flow-mediated dilation (FMD). In a clinical research centre, 100 non-shift working adults (mean age: 36 years) completed FMD testing and the Pittsburgh Sleep Quality Index, along with a polysomnography assessment to obtain the following measures: slow wave sleep, percentage rapid eye movement (REM) sleep, REM sleep latency, total arousal index, total sleep time, wake after sleep onset, sleep efficiency and apnea-hypopnea index. Bivariate correlations and follow-up multiple regressions examined how FMD related to subjective (i.e., Pittsburgh Sleep Quality Index scores) and objective (i.e., polysomnography-derived) indicators of sleep quality. After FMD showed bivariate correlations with Pittsburgh Sleep Quality Index scores, percentage REM sleep and REM latency, further examination with separate regression models indicated that these associations remained significant after adjustments for sex, age, race, hypertension, body mass index, apnea-hypopnea index, smoking and income (Ps < 0.05). Specifically, as FMD decreased, scores on the Pittsburgh Sleep Quality Index increased (indicating decreased subjective sleep quality) and percentage REM sleep decreased, while REM sleep latency increased (Ps < 0.05). Poorer subjective sleep quality and adverse changes in REM sleep were associated with diminished vasodilation, which could link sleep disturbances to cardiovascular disease.

Fatigue in adolescents and young adults with sickle cell disease: biological and behavioral correlates and health-related quality of life

This descriptive, correlational study examined fatigue and potential biological and behavioral correlates in adolescents and young adults with sickle cell disease. Sixty adolescents and young adults with sickle cell disease completed the Brief Fatigue Inventory, Multidimensional Fatigue Symptom Inventory-Short Form, Patient Reported Outcomes Measurement Information System (PROMIS) fatigue short form and measures of pain, sleep quality, anxiety, depressive mood, stress, disease severity, and quality of life. Blood samples were obtained for hemoglobin and cytokines. Fatigue scores were mostly moderate in severity. Fatigue interfered to a moderate degree with daily activities and correlated significantly with pain, sleep quality, state and trait anxiety, depressive mood, stress, and quality of life. Fatigue was correlated with hemoglobin on the PROMIS measure. Fatigue was not correlated with cytokines or age, nor differed by disease severity. Fatigue was common in these adolescents and young adults, interfered with daily activities such as school, work and exercise, and significantly correlated with several potentially modifiable factors. As life expectancy increases in sickle cell disease, research is needed to test interventions to reduce fatigue.

Role of peripheral inflammatory markers in postoperative cognitive dysfunction (POCD): a meta-analysis

Background

Postoperative cognitive dysfunction (POCD) is common following cardiac and non-cardiac surgery, but the pathogenic mechanisms remain unknown. Many studies suggest that an inflammatory response is a key contributor to POCD. The current meta-analysis shows that the levels of peripheral inflammatory markers are associated with POCD.

Methods

An online search was performed to identify peer-reviewed studies without language restriction that measured peripheral inflammatory markers of patients with and without POCD, using PubMed, ScienceDirect, SinoMed and the National Knowledge Infrastructure database. Extracted data were analyzed with STATA (version 12).The standardized mean difference (SMD) and the 95% confidence interval (95%CI) were calculated for each outcome using a random effect model. Tests of heterogeneity assessment of bias, and meta-regression were performed in the meta-analysis.

Results

A total of 13 studies that measured the concentrations of peripheral inflammatory markers were included. The current meta-analysis found significantly higher concentrations of S-100β(SMD[95%CI]) (1.377 [0.423, 2.331], p-value < 0.001, N [POCD/non-POCD] =178/391, 7 studies), and interleukin(IL)-6 (SMD[95%CI]) (1.614 [0.603,2.624], p-value < 0.001, N[POCD/non-POCD] = 91/99, 5 studies), but not of neuron specific enolase, interleukin-1β, or tumor necrosis factor-α , in POCD compared with patients without POCD. In meta-regression analyses, a significant positive association was found between the SMD and the preoperative interleukin-6 peripheral blood concentration in patients with POCD (Coef.= 0.0587, p-value=0.038, 5 studies).

Conclusions

This study shows that POCD is indeed correlated with the concentrations of peripheral inflammatory markers, particularly interleukin-6 and S-100β.

Association of C-reactive protein and interleukin-6 with new-onset fatigue in the Whitehall II prospective cohort study

BACKGROUND

Although basic research on neuroimmune interactions suggests that inflammatory processes may play a role in the development of fatigue, population-based evidence on this association is limited. This study examined whether plasma C-reactive protein (CRP) and interleukin-6 (IL-6), biomarkers of systemic inflammation, predict fatigue onset.

METHOD

The Whitehall II study is a large-scale cohort study conducted in 20 civil service departments in London. Plasma CRP and IL-6 were measured in 4847 non-fatigued participants at phase 3 (1991-1993, aged 39-63 years). Fatigue was assessed using the Vitality subscale of the 36-item Short Form Health Survey (SF-36) at phase 3 and phase 4 (1995-1996).

RESULTS

During a mean follow-up of 3.1 years, 957 new fatigue cases (19.7%) were identified using the pre-established cut-off score of ≤ 50 on the Vitality subscale. CRP values were dichotomized as low (<1.0 mg/l ) or high (≥ 1.0 mg/l) using the Centers for Disease Control/American Heart Association recommendations. Similarly, IL-6 values were also dichotomized as low (<1.5 pg/ml) or high (≥ 1.5 pg/ml). After full adjustment for sociodemographic and biobehavioral covariates, the odds ratios for new-onset fatigue were 1.28 [95% confidence interval (CI) 1.09-1.49, p = 0.003] for high CRP and 1.24 (95% CI 1.06-1.45, p = 0.008) for high IL-6. Similar results were found when CRP and IL-6 were treated as continuous variables.

CONCLUSIONS

Plasma CRP and IL-6 were prospectively associated with new-onset fatigue, supporting the hypothesis that low-grade inflammation has a role in the development of fatigue.

C-reactive protein is elevated in atypical but not nonatypical depression: data from the National Health and Nutrition Examination survey (NHANES) 1999-2004

Little is known about the association of depression subtypes with inflammatory markers predictive of coronary artery disease. In a sample of younger adults representative of the U.S. population, we examined differences in serum C-reactive protein (CRP) among individuals with atypical major depressive disorder (MDD; n = 16), nonatypical MDD (n = 93), and no MDD (n = 1,682). Adults with atypical MDD exhibited higher CRP levels than those with no MDD (mean difference = 1.56 mg/L) or nonatypical MDD (mean difference = 1.40 mg/L), even after adjustment for potential cofounders, anxiety disorders, body mass, and smoking. Nearly twice as many adults with atypical MDD had CRP levels in the high cardiovascular risk range than did those with no MDD or nonatypical MDD. CRP levels of adults with nonatypical MDD or no MDD did not differ. Individuals with atypical depression may be partially driving the overall depression-inflammation relationship and may be a subgroup at elevated risk for coronary artery disease.

Preliminary evidence of an association between an interleukin 6 promoter polymorphism and self-reported attentional function in oncology patients and their family caregivers

Subgroups of individuals may be at greater risk of cytokine-induced changes in attentional function. The purposes of this study were to identify subgroups of individuals with distinct trajectories of attentional function and evaluate for phenotypic and genotypic (i.e., cytokine gene polymorphisms) differences among these subgroups. Self-reported attentional function was evaluated in 252 participants (167 oncology patients and 85 family caregivers) using the Attentional Function Index before radiation therapy and at six additional assessments over 6 months. Three latent classes of attentional function were identified using growth mixture modeling: moderate (36.5%), moderate-to-high (48.0%), and high (15.5%) attentional function. Participants in the moderate class were significantly younger, with more comorbidities and lower functional status, than those in the other two classes. However, only functional status remained significant in multivariable models. Included in the genetic association analyses were 92 single nucleotide polymorphisms (SNPs) among 15 candidate genes. Additive, dominant, and recessive genetic models were assessed for each SNP. Controlling for functional status, only Interleukin 6 (IL6) rs1800795 remained a significant genotypic predictor of class membership in multivariable models. Each additional copy of the rare "G" allele was associated with a 4-fold increase in the odds of belonging to the lower attentional function class (95% confidence interval: [1.78, 8.92]; p = .001). Findings provide preliminary evidence of subgroups of individuals with distinct trajectories of attentional function and of a genetic association with an IL6 promoter polymorphism.

Sleep disturbance, cytokines, and fatigue in women with ovarian cancer

Pro-inflammatory cytokines, such as interleukin-6 (IL-6), have been implicated in the underlying processes contributing to sleep regulation and fatigue. Despite evidence for sleep difficulties, fatigue, and elevations in IL-6 among women with ovarian cancer, the association between these symptoms and IL-6 has not been investigated. To address this knowledge gap, we examined relationships between sleep disturbance, fatigue, and plasma IL-6 in 136 women with ovarian cancer prior to surgery. These relationships were also examined in 63 of these women who were disease-free and not receiving chemotherapy one year post-diagnosis. At both time-points, higher levels of IL-6 were significantly associated with sleep disturbances (p<0.05), controlling for potentially confounding biological and psychosocial covariates. Higher IL-6 was significantly associated with fatigue prior to surgery (p<0.05); however, when sleep disturbance was included in the model, the relationship was no longer significant. IL-6 was not significantly associated with fatigue at one year. Changes in sleep over time were significantly associated with percent change in IL-6 from pre-surgery to one year, adjusting for covariates (p<0.05). These findings support a direct association of IL-6 with sleep disturbances in this population, whereas the relationship between IL-6 and fatigue prior to surgery may be mediated by poor sleep. As this study is the first to examine cytokine contributions to sleep and fatigue in ovarian cancer, further research is warranted to clarify the role of biological correlates of sleep and fatigue in this population.

Fatigue in systemic lupus erythematosus

Systemic lupus erythematosus is a chronic inflammatory autoimmune disease often characterized by fatigue, with significant effects on physical functioning and wellbeing. The definition, prevalence and factors associated with fatigue, including physical activity, obesity, sleep, depression, anxiety, mood, cognitive dysfunction, vitamin D deficiency/insufficiency, pain, effects of medications and comorbidities, as well as potential therapeutic options of fatigue in the systemic lupus erythematosus population are reviewed. Due to variability in the reliability and validity of various fatigue measures used in clinical studies, clinical trial data have been challenging to interpret. Further investigation into the relationships between these risk factors and fatigue, and improved measures of fatigue, may lead to an improvement in the management of this chronic inflammatory disease.

Neuroimmune endocrine effects of antidepressants

Antidepressant pharmacotherapy is to date the most often used treatment for depression, but the exact mechanism of action underlying its therapeutic effect is still unclear. Many theories have been put forward to account for depression, as well as antidepressant activity, but none of them is exhaustive. Neuroimmune endocrine impairment is found in depressed patients; high levels of circulating corticosteroids along with hyperactivation of the immune system, high levels of proinflammatory cytokines, low levels of melatonin in plasma and urine, and disentrainment of circadian rhythms have been demonstrated. Moreover, antidepressant treatment seems to correct or at least to interfere with these alterations. In this review, we summarize the complex neuroimmune endocrine and chronobiological alterations found in patients with depression and how these systems interact with each other. We also explain how antidepressant therapy can modify these systems, along with some possible mechanisms of action shown in animal and human models.

Sleep and immune function

Sleep and the circadian system exert a strong regulatory influence on immune functions. Investigations of the normal sleep–wake cycle showed that immune parameters like numbers of undifferentiated naïve T cells and the production of pro-inflammatory cytokines exhibit peaks during early nocturnal sleep whereas circulating numbers of immune cells with immediate effector functions, like cytotoxic natural killer cells, as well as anti-inflammatory cytokine activity peak during daytime wakefulness. Although it is difficult to entirely dissect the influence of sleep from that of the circadian rhythm, comparisons of the effects of nocturnal sleep with those of 24-h periods of wakefulness suggest that sleep facilitates the extravasation of T cells and their possible redistribution to lymph nodes. Moreover, such studies revealed a selectively enhancing influence of sleep on cytokines promoting the interaction between antigen presenting cells and T helper cells, like interleukin-12. Sleep on the night after experimental vaccinations against hepatitis A produced a strong and persistent increase in the number of antigen-specific Th cells and antibody titres. Together these findings indicate a specific role of sleep in the formation of immunological memory. This role appears to be associated in particular with the stage of slow wave sleep and the accompanying pro-inflammatory endocrine milieu that is hallmarked by high growth hormone and prolactin levels and low cortisol and catecholamine concentrations.

Inflammation and behavioral symptoms after breast cancer treatment: do fatigue, depression, and sleep disturbance share a common underlying mechanism?

PURPOSE

Fatigue, depression, and sleep disturbance are common adverse effects of cancer treatment and frequently co-occur. However, the possibility that inflammatory processes may underlie this constellation of symptoms has not been examined.

PATIENTS AND METHODS

Women (N = 103) who had recently finished primary treatment (ie, surgery, radiation, chemotherapy) for early-stage breast cancer completed self-report scales and provided blood samples for determination of plasma levels of inflammatory markers: soluble tumor necrosis factor (TNF) receptor II (sTNF-RII), interleukin-1 receptor antagonist, and C-reactive protein.

RESULTS

Symptoms were elevated at the end of treatment; greater than 60% of participants reported clinically significant problems with fatigue and sleep, and 25% reported elevated depressive symptoms. Women treated with chemotherapy endorsed higher levels of all symptoms and also had higher plasma levels of sTNF-RII than women who did not receive chemotherapy (all P < .05). Fatigue was positively associated with sTNF-RII, particularly in the chemotherapy-treated group (P < .05). Depressive symptoms and sleep problems were correlated with fatigue but not with inflammatory markers.

CONCLUSION

This study confirms high rates of behavioral symptoms in breast cancer survivors, particularly those treated with chemotherapy, and indicates a role for TNF-α signaling as a contributor to postchemotherapy fatigue. Results also suggest that fatigue, sleep disturbance, and depression may stem from distinct biologic processes in post-treatment survivors, with inflammatory signaling contributing relatively specifically to fatigue.

Role of nuclear factor κB-mediated inflammatory pathways in cancer-related symptoms and their regulation by nutritional agents

Cancer is a disease characterized by dysregulation of multiple genes and is associated with symptoms such as cachexia, anorexia, fatigue, depression, neuropathic pain, anxiety, cognitive impairment, sleep disorders and delirium (acute confusion state) in medically ill patients. These symptoms are caused by either the cancer itself or the cancer treatment. During the past decade, increasing evidence has shown that the dysregulation of inflammatory pathways contributes to the expression of these symptoms. Cancer patients have been found to have higher levels of proinflammatory cytokines such as interleukin-6. The nuclear factor (NF)-κB is a major mediator of inflammatory pathways. Therefore, anti-inflammatory agents that can modulate the NF-κB activation and inflammatory pathways may have potential in improving cancer-related symptoms in patients. Because of their multitargeting properties, low cost, low toxicity and immediate availability, natural agents have gained considerable attention for prevention and treatment of cancer-related symptoms. How NF-κB and inflammatory pathways contribute to cancer-related symptoms is the focus of this review. We will also discuss how nutritional agents such as curcumin, genistein, resveratrol, epigallocatechin gallate and lycopene can modulate inflammatory pathways and thereby reduce cancer-related symptoms in patients.

Inflammatory pathways in children with insufficient or disordered sleep

Sleep is not only an essential physiological function, but also serves important roles in promoting growth, maturation, and overall health of children and adolescents. There is increasing interest regarding the impact of sleep and its disorders on the regulation of inflammatory processes and end-organ morbidities, particularly in the context of metabolic and cardiovascular diseases (CVD) and their complications. Obstructive sleep apnea syndrome (OSAS) is an increasingly common health problem in children, and in the last decade, the emergence of increasing obesity rates has further led to remarkable increases in the prevalence of OSAS, along with more prominent neurocognitive, behavioral, cardiovascular and metabolic morbidities. Although the underlying mechanisms leading to OSAS-induced morbidities are likely multi-factorial, and remain to be fully elucidated, activation of inflammatory pathways by OSAS has emerged as an important pathophysiological component of the end-organ injury associated with this disorder. To this effect, it would appear that OSAS could be viewed as a chronic, low-grade inflammatory disorder. Furthermore, the concurrent presence of obesity and OSAS poses a theoretically increased risk of OSAS-related complications. In this review, we will critically review the current state of research regarding the impact of insufficient and disrupted sleep and OSAS on the immune processes and inflammatory pathways that underlie childhood OSAS as a distinctive systemic inflammatory condition in children, and will explore potential interactions between OSAS and obesity.

Emerging biobehavioral factors of fatigue in sickle cell disease

PURPOSE

The symptom most frequently associated with sickle cell disease (SCD) is pain, but recent research is beginning to indicate that fatigue as an increasingly important symptom of this disease upon which to focus research efforts. This article explores biological and behavioral factors that can potentially contribute to fatigue in SCD.

ORGANIZING FRAMEWORK

A biobehavioral framework guides this discussion of factors that may contribute to SCD fatigue.

FINDINGS

The pathophysiology of the disease process, such as the profound hemolytic anemia and unpredictable vasoocclusive crises, suggests that individuals with SCD are at risk for both acute and chronic fatigue. For example, hypoxemia can cause muscle weakness and produce oxidative stress, which, in turn, increases fatigue. Sickled erythrocytes disrupt the vascular endothelium and stimulate proinflammatory cytokines, which are linked to sleep disruptions. Pain, the most notorious symptom of SCD, has a complex and mechanistically poorly understood relationship with fatigue.

CONCLUSIONS

Little is known about the symptom of fatigue in SCD. Considering the biological and behavioral factors of SCD that could potentially contribute to fatigue, there is a great need for research on the nature and potential mechanisms of fatigue in SCD.

CLINICAL RELEVANCE

Fatigue in SCD may negatively affect quality of life. Understanding factors that may contribute to fatigue aids the clinician in identifying causes and determining treatment.

A biological pathway linking inflammation and depression: activation of indoleamine 2,3-dioxygenase

This article highlights the evidence linking depression to increased inflammatory drive and explores putative mechanisms for the association by reviewing both preclinical and clinical literature. The enzyme indoleamine 2,3-dioxygenase is induced by proinflammatory cytokines and may form a link between immune functioning and altered neurotransmission, which results in depression. Increased indoleamine 2,3-dioxygenase activity may cause both tryptophan depletion and increased neurotoxic metabolites of the kynurenine pathway, two alterations which have been hypothesized to cause depression. The tryptophan-kynurenine pathway is comprehensively described with a focus on the evidence linking metabolite alterations to depression. The use of immune-activated groups at high risk of depression have been used to explore these hypotheses; we focus on the studies involving chronic hepatitis C patients receiving interferon-alpha, an immune activating cytokine. Findings from this work have led to novel strategies for the future development of antidepressants including inhibition of indoleamine 2,3-dioxygenase, moderating the cytokines which activate it, or addressing other targets in the kynurenine pathway.

Chronic interferon-alpha administration disrupts sleep continuity and depth in patients with hepatitis C: association with fatigue, motor slowing, and increased evening cortisol

BACKGROUND

Consequences of chronic exposure to cytokines of the innate immune system on sleep in humans and the association of cytokine-induced sleep alterations with behavior, motor performance, and cortisol secretion are unknown.

METHODS

Thirty-one patients with hepatitis C without pre-existing sleep disorders underwent nighttime polysomnography, daytime multiple sleep latency testing, behavioral assessments, neuropsychological testing, and serial blood sampling at baseline and after ∼12 weeks of either treatment with the innate immune cytokine interferon (IFN)-alpha (n = 19) or no treatment (n = 12). Fatigue and sleepiness were assessed using the Multidimensional Fatigue Inventory and Epworth Sleepiness Scale.

RESULTS

Interferon-alpha administration led to significant increases in wake after sleep onset and significant decreases in stage 3/4 sleep and sleep efficiency. Rapid eye movement latency and stage 2 sleep were significantly increased during IFN-alpha treatment. Decreases in stage 3/4 sleep and increases in rapid eye movement latency were associated with increases in fatigue, whereas decreases in sleep efficiency were associated with reduced motor speed. Increased wake after sleep onset was associated with increased evening plasma cortisol. Despite IFN-alpha-induced increases in fatigue, daytime sleepiness did not increase. In fact, IFN-alpha-treated patients exhibited decreased propensity to fall asleep during daytime nap opportunities.

CONCLUSIONS

Chronic exposure to an innate immune cytokine reduced sleep continuity and depth and induced a sleep pattern consistent with insomnia and hyperarousal. These data suggest that innate immune cytokines may provide a mechanistic link between disorders associated with chronic inflammation, including medical and/or psychiatric illnesses and insomnia, which, in turn, is associated with fatigue, motor slowing, and altered cortisol.

Sleep loss and inflammation

Controlled, experimental studies on the effects of acute sleep loss in humans have shown that mediators of inflammation are altered by sleep loss. Elevations in these mediators have been found to occur in healthy, rigorously screened individuals undergoing experimental vigils of more than 24h, and have also been seen in response to various durations of sleep restricted to between 25 and 50% of a normal 8h sleep amount. While these altered profiles represent small changes, such sub-clinical shifts in basal inflammatory cytokines are known to be associated with the future development of metabolic syndrome disease in healthy, asymptomatic individuals. Although the mechanism of this altered inflammatory status in humans undergoing experimental sleep loss is unknown, it is likely that autonomic activation and metabolic changes play key roles.

The role of interleukin 6 in the pathophysiology of rheumatoid arthritis

Interleukin 6 (IL-6) is a pleiotropic cytokine with a pivotal role in the pathophysiology of rheumatoid arthritis (RA). It is found in abundance in the synovial fluid and serum of patients with RA and the level correlates with the disease activity and joint destruction. IL-6 can promote synovitis and joint destruction by stimulating neutrophil migration, osteoclast maturation and vascular endothelial growth factor (VEGF)-stimulated pannus proliferation. IL-6 may also be mediating many of the systematic manifestations of RA including inducing the acute-phase reaction [including C-reactive protein (CRP)], anaemia through hecipidin production, fatigue via the hypothalamic-pituitary-adrenal (HPA) axis) and osteoporosis from its effect on osteoclasts. In addition, IL-6 may contribute to the induction and maintenance of the autoimmune process through B-cell maturation and TH-17 differentiation. All of the above makes IL-6 blockade a desirable therapeutic option in the treatment of RA. Following successful animal studies, a humanized anti-interleukin-6 receptor (anti-IL-6R) monoclonal antibody, tocilizumab (TCZ), entered into clinical trials and it has been shown to be an effective treatment in several large phase III clinical trials in RA with rapid and sustained improvement in disease activity, reducing radiographic joint damage and improving physical function.

Acute effects of bright light exposure on cortisol levels

Multisynaptic neural and endocrine pathways from the suprachiasmatic nucleus of the hypothalamus have been hypothesized to communicate circadian and photic information to the adrenal glands. In humans, light exposure has been reported to have no effect, increase, or decrease cortisol levels. These inconsistent findings in humans may be related to differences among studies including the intensity (approximately 500 to 5500 lux), duration (15 min to 4 h), and circadian phase of light exposure. The authors assessed the influence of exposure to bright light on cortisol levels in humans during the rising and descending phases of the circadian rhythm of cortisol, that is, when cortisol levels are high. Twenty healthy men and women were studied using a within-subject research design. Subjects were studied in an environment free of time cues for 9 to 10 days. Subjects received a 6.7-h exposure of bright light (approximately 10,000 lux; equivalent to ambient light intensity just after sunrise or just before sunset) or dim light (approximately 3 lux; equivalent to candle light) during the biological night and morning. Bright light exposure significantly reduced plasma cortisol levels at both circadian phases studied, whereas dim light exposure had little effect on cortisol levels. The finding of an acute suppressive effect of bright light exposure on cortisol levels supports the existence of a mechanism by which photic information can acutely influence the human adrenal glands.

Interferon-alpha effects on diurnal hypothalamic-pituitary-adrenal axis activity: relationship with proinflammatory cytokines and behavior

Interferon (IFN)-alpha has been used to investigate pathways by which innate immune cytokines influence the brain and behavior. Accordingly, the impact of IFN-alpha on diurnal secretion of hypothalamic-pituitary-adrenal (HPA) axis hormones was assessed in 33 patients eligible for treatment with IFN-alpha plus ribavirin for hepatitis C. In addition, the relationship between IFN-alpha-induced HPA axis changes and proinflammatory cytokines and behavior was examined. Plasma ACTH and cortisol as well as tumor necrosis factor (TNF)-alpha, interleukin-6 and their soluble receptors, were measured hourly between 0900 and 2100 hours at baseline and following approximately 12 weeks of either no treatment (n=13) or treatment with IFN-alpha/ribavirin (n=20). Plasma IFN-alpha was also measured at each visit. Depression and fatigue were assessed using the Montgomery-Asberg depression rating scale and the multidimensional fatigue inventory. Compared to no treatment, IFN-alpha/ribavirin administration was associated with significant flattening of the diurnal ACTH and cortisol slope and increased evening plasma ACTH and cortisol concentrations. Flattening of the cortisol slope and increases in evening cortisol were correlated with increases in depression (r=0.38, P<0.05 and r=0.36, P<0.05, respectively) and fatigue (r=0.43, P<0.05 and r=0.49, P<0.01, respectively). No relationship was found between immune and HPA axis measures, although increases in plasma IFN-alpha, TNF-alpha and soluble TNF-alpha receptor2 were independently correlated with behavioral endpoints. These data indicate that chronic exposure to innate immune cytokines may contribute to the altered diurnal HPA axis activity and behavior found in medically ill individuals. However, given the lack of correlation between HPA axis and immune measures, the mechanism by which chronic cytokine exposure influences HPA axis function remains to be determined.

Sleep quality, cortisol levels, and behavioral regulation in toddlers

This study examines the association between nighttime sleep characteristics and cortisol levels and how these variables relate to aspects of children's temperament and behavior. Twenty-seven healthy children, aged 12-36 months, attending group childcare settings, participated in the study. Each child's sleep was measured at home with actigraphy over three nights. Saliva samples were collected by the mothers at bedtime and within 30 min of awakening. In addition, both the mother and the daycare teacher rated the child's behavioral difficulties and negative emotionality. It was found that children with more fragmented sleep displayed higher awakening cortisol levels compared to children with more efficient sleep. Moreover, elevated awakening cortisol levels were correlated with teachers' ratings of internalizing behavior and negative emotionality. These preliminary findings suggest that awakening cortisol may serve as a useful index of adrenocortical reactivity in young children, signaling a disturbance in physiological regulation, and underscore the need for more research pertaining to the dynamic associations between sleep and HPA-axis across the 24-hr period.

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.

Cytokine-induced depression during IFN-alpha treatment: the role of IL-6 and sleep quality

Depressive symptoms, poor sleep quality, and systemic markers of inflammation (e.g., interleukin (IL)-6) are frequently associated. Interferon-alpha (IFN-alpha) therapy results in Major Depressive Disorder (MDD) in some people, offering the possibility to elucidate the relationship of MDD to sleep and inflammation during treatment. In particular, delineating the temporal relations among these factors could help inform their causal relationships. To this end, a cohort of 95 non-depressed hepatitis C patients was followed prospectively for four consecutive months during IFN-alpha therapy. We found that higher pre-treatment levels of circulating IL-6 predicted incidence of MDD (X(2)(1)=7.7; p<0.05). Time-lagged mixed-effect analyses supported uni-directional associations in which IL-6 predicted next month's PSQI scores (F(47,11.6)=78.4; p<0.0005), and PSQI scores predicted next month's depressive Beck Depression Inventory-II (BDI) scores (F(16,22.6)=3.4; p<0.005). In addition, on any given month of treatment, IL-6 levels predicted BDI symptoms the following month (F(16,97.5)=7.3; p<0.0005), and conversely BDI predicted next month's IL-6 (F(14,7.4)=5.2; p<0.05) - providing evidence for a positive feedback relationship between depressive symptoms and systemic inflammation. These data provide further evidence that high levels of inflammation and poor sleep quality may be risk factors for IFN-alpha induced depression. Furthermore, these findings highlight the complex temporal relationships that exist among sleep, depression, and inflammation, and support the need for further prospective investigations to elucidate the dynamics that underlie depression during IFN-alpha treatment.

Therapeutic targets in rheumatoid arthritis: the interleukin-6 receptor

RA is a chronic, debilitating disease in which articular inflammation and joint destruction are accompanied by systemic manifestations including anaemia, fatigue and osteoporosis. IL-6 is expressed abundantly in the SF of RA patients and is thought to mediate many of the local and systemic effects of this disease. Unlike a number of other cytokines, IL-6 can activate cells through both membrane-bound (IL-6R) and soluble receptors (sIL-6R), thus widening the number of cell types responsive to this cytokine. Indeed, trans-signalling, where IL-6 binds to the sIL-6R, homodimerizes with glycoprotein 130 subunits and induces signal transduction, has been found to play a key role in acute and chronic inflammation. Elevated levels of IL-6 and sIL-6R in the SF of RA patients can increase the risk of joint destruction and, at the joint level, IL-6/sIL-6R can stimulate pannus development through increased VEGF expression and increase bone resorption as a result of osteoclastogenesis. Systemic effects of IL-6, albeit through conventional or trans-signalling, include regulation of acute-phase protein synthesis, as well as hepcidin production and stimulation of the hypothalamo-pituitary-adrenal axis, the latter two actions potentially leading to anaemia and fatigue, respectively. This review aims to provide an insight into the biological effects of IL-6 in RA, examining how IL-6 can induce the articular and systemic effects of this disease.

Evaluation of psychological and physiological predictors of fatigue in patients with COPD

BACKGROUND

Fatigue in COPD impairs functional status; however there are few studies examining mechanistic pathways of this symptom. The aims of this study are to compare fatigue between COPD patients and healthy age-matched subjects, and to identify predictors of fatigue in COPD.

METHODS

Seventy four COPD patients, mean age 69.9 (49-87) yrs, mean (SD) % predicted FEV1 46.5 (20.0) % and FEV1/FVC ratio 0.45 (0.13) and 35 healthy subjects, mean age 67.1 (50-84) yrs completed the Multidimensional Fatigue Inventory (MFI 20). Patients' assessment included Depression (HADS), lung function, BMI, muscle strength, incremental shuttle walk test (ISWT), exercise oxygen saturation (SpO2), Borg breathlessness (CR-10) and exertion (RPE). Serum level of Interleukin 6 (IL-6) was recorded. Differences in MFI 20 between groups were examined and predictors of fatigue identified using logistic regression.

RESULTS

Significant differences (p < 0.01) were found between the COPD and healthy subjects for all MFI 20 dimensions. There were significant differences when classified according to GOLD and dyspnoea stages for selected dimensions only. Predictors of General Fatigue were depression, muscle strength and end SpO2 (R2 = .62); of Physical Fatigue: depression, % predicted FEV1, ISWT and age (R2 = .57); Reduced Activity: % predicted FEV1, BMI and depression (R2 = .36); Reduced Motivation: RPE, depression and end SpO2 (R2 = .37) and Mental Fatigue: depression and end SpO2 (R2 = .38).

CONCLUSION

All dimensions of fatigue were higher in COPD than healthy aged subjects. Predictive factors differ according to the dimension of fatigue under investigation. COPD-RF is a multi component symptom requiring further consideration.

A prospective evaluation of the directionality of the depression-inflammation relationship

Cross-sectional studies have found that individuals with depressive disorders or symptoms have elevated levels of inflammatory markers predictive of coronary artery disease, including interleukin-6 (IL-6) and C-reactive protein (CRP). Due to the paucity of prospective studies, however, the directionality of the depression-inflammation relationship is unclear. We evaluated the longitudinal associations between depressive symptoms and both IL-6 and CRP among 263 healthy, older men and women enrolled in the Pittsburgh Healthy Heart Project, a 6-year prospective cohort study. During the baseline and follow-up visits, participants completed the Beck Depression Inventory-II (BDI-II) to assess depressive symptoms and underwent blood draws to quantify serum IL-6 and CRP. Path analyses revealed that baseline BDI-II (beta=0.18, p=0.01, DeltaR(2)=0.02) was a predictor of 6-year change in IL-6, even after adjustment for demographic, biomedical, and behavioral factors as well as other negative emotions. Of all the factors examined, only body-mass index was a stronger predictor of IL-6 change than depressive symptoms. In contrast to these results, baseline IL-6 did not predict 6-year change in BDI-II. Evidence of a weak bidirectional relationship between BDI-II and CRP was also observed; however, neither of these longitudinal associations was significant. The present findings indicate that depressive symptoms may precede and augment some inflammatory processes relevant to coronary artery disease among healthy, older adults. Therefore, our results imply that depression may lead to inflammation and that inflammation may be one of the mechanisms through which depression contributes to cardiovascular risk.

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.

IL-6-trans-signalling increases rapid-eye-movement sleep in rats

Interleukin 6 (IL-6), a cytokine of the gp130-signalling-family, plays an important role in immediate immunological functions, in metabolism and in the central nervous system. IL-6-signalling is mediated by classic-signalling via the membrane bound IL-6 receptor or by IL-6-trans-signalling via the soluble IL-6 receptor. Whereas the receptor subunit gp130 is ubiquitously expressed within the body, IL-6 receptor expression is restricted to distinct cell populations. Within the brain parenchyma the IL-6 receptor is sparsely expressed, and therefore the brain is mostly dependent on IL-6-trans-signalling in its response to IL-6. Recently we have shown that IL-6-trans-signalling but not classic-signalling plays a pivotal role in the establishment and maintenance of chronic inflammation and cancer, whereas its role in sleep regulation has not been studied so far. We reasoned that the IL-6-trans-signalling mimetic Hyper-IL-6 which in contrast to IL-6 alone can activate almost all cells of the brain might have a profound effect on sleep regulation and performed sleep recordings with rats injected with recombinant Hyper-IL-6. In the present study, the i.c.v. administration of the designer cytokine Hyper-IL-6 into rats at dark onset increased the amount of rapid-eye-movement sleep (REM sleep) but did not affect non-rapid-eye-movement sleep (non-REM sleep). Our data define a new role of IL-6-trans-signalling in sleep regulation.

Cardiovascular, inflammatory, and metabolic consequences of sleep deprivation

That insufficient sleep is associated with poor attention and performance deficits is becoming widely recognized. Fewer people are aware that chronic sleep complaints in epidemiologic studies have also been associated with an increase in overall mortality and morbidity. This article summarizes findings of known effects of insufficient sleep on cardiovascular risk factors including blood pressure, glucose metabolism, hormonal regulation, and inflammation with particular emphasis on experimental sleep loss, using models of total and partial sleep deprivation, in healthy individuals who normally sleep in the range of 7 to 8 hours and have no sleep disorders. These studies show that insufficient sleep alters established cardiovascular risk factors in a direction that is known to increase the risk of cardiac morbidity.

Sleep is increased by weight gain and decreased by weight loss in mice

OBJECTIVE

To determine whether weight loss could reverse excessive sleep in high-fat diet-induced obesity.

DESIGN

Three groups of mice participated in the study. A weight gain/loss group was fed with high-fat food for 6 weeks (weight gain), and regular food again for 4 weeks (weight loss). A control group and a weight gain only group were fed with regular food and high-fat food, respectively, for 10 weeks after the baseline.

PARTICIPANTS

Adult male C57BL/6 mice.

MEASUREMENTS

The amounts of wake, rapid eye movement sleep (REMS) and non-REM sleep (NREMS) were determined at week 0 (baseline), week 6, and week 10.

RESULTS

The weight gain/loss group displayed a significant decrease in wakefulness and increases in NREMS and episodes of NREMS during 6 weeks of weight gain, which were reversed during subsequent 4 weeks of weight loss. The weight gain only group displayed significant decrease in wakefulness and increase of NREMS and REMS at both week 6 and week 10. The control group did not show significant sleep alterations during the experiment.

CONCLUSION

These observations indicate that sleep alterations induced by weight gain are reversed by weight loss in obese animals. These data may shed light on the mechanisms underlying the well-established association between obesity and sleepiness in humans and may lead to new therapeutic strategies for these 2 increasingly prevalent problems in the modern societies.

Effects of i.c.v. administration of interleukin-1 on sleep and body temperature of interleukin-6-deficient mice

Cytokines in brain contribute to the regulation of physiological processes and complex behavior, including sleep. The cytokines that have been most extensively studied with respect to sleep are interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and IL-6. Administration of these cytokines into laboratory animals, or in some cases into healthy human volunteers, increases the amount of time spent in non-rapid eye movement (NREM) sleep. Although antagonizing the IL-1 or TNF systems reduces the amount of time laboratory animals spend in NREM sleep, interactions among these three cytokine systems as they pertain to the regulation of physiological NREM sleep are not well understood. To further elucidate mechanisms in brain by which IL-1beta, TNFalpha, and/or IL-6 contribute to NREM sleep regulation, we injected recombinant murine interleukin-1beta (muIL-1beta) into C57BL/6J mice and into IL-6-deficient mice (IL-6 knockout, KO). IL-6 KO (B6.129S6-Il6(tm1Kopf); n=13) and C57BL/6J mice (n=14) were implanted with telemeters to record the electroencephalogram (EEG) and core body temperature, as well as with indwelling guide cannulae targeted to one of the lateral ventricles. After recovery and habituation, mice were injected intracerebroventricularly just prior to dark onset on different days with either 0.5 microl vehicle (pyrogen-free saline; PFS) or with 0.5 microl PFS containing one of four doses of muIL-1beta (2.5 ng, 5 ng, 10 ng, 50 ng). No mouse received more than two doses of muIL-1beta, and administration of muIL-1beta doses was counter-balanced to eliminate potential order effects. Sleep-wake behavior was determined for 24 h after injections. i.c.v. administration of muIL-1beta increased in NREM sleep of both mouse strains in a dose-related fashion, but the maximal increase was of greater magnitude in C57Bl/6J mice. muIL-1beta induced fever in C57Bl/6J mice but not in IL-6 KO mice. Collectively, these data demonstrate IL-6 is necessary for IL-1 to induce fever, but IL-6 is not necessary for IL-1 to alter NREM sleep.

Effects of serotonergic activation by 5-hydroxytryptophan on sleep and body temperature of C57BL/6J and interleukin-6-deficient mice are dose and time related

STUDY OBJECTIVES

Extensive data implicate serotonin (5-hydroxytryptamine [5-HT]) in the regulation of sleep. Jouvet has hypothesized that 5-HT promotes wakefulness, yet is necessary for subsequent non-rapid eye movement (NREM) sleep, actions he proposes to be mediated by sleep factors. Studies in rat support this dual role for 5-HT. The objectives of this study were to (1) determine effects of serotonergic activation on sleep of mice and (2) elucidate a potential role for the cytokine interleukin-6 as a sleep factor mediating serotonergic effects on sleep.

DESIGN

C57BL/6J and B6.129S6-II6(tm1Kopf)(interleukin-6 knockout [IL-6 KO]) mice were purchased from the Jackson Laboratory and instrumented for recording the electroencephalogram and body temperature. After recovery, separate groups of mice were injected intraperitoneally at either light or dark onset with vehicle or with the 5-HT precursor 5-hydroxytryptophan (5-HTP). Sleep-wake behavior was determined and body temperature recorded for 24 hours after injections.

RESULTS

5-HTP induced hypothermia in both mouse strains. When injected at dark onset, the highest dose of 5-HTP (200 mg/kg) increased NREM sleep. Light onset administration initially increased wakefulness, with increases in NREM sleep apparent only during the subsequent dark period. For most parameters, there were no differences in responses between strains. However IL-6 KO mice at some doses exhibited a greater increase in NREM sleep.

CONCLUSIONS

5-HTP alters sleep-wake behavior and body temperature of mice in a manner similar to that of rats. Increases in NREM sleep after 5-HTP are apparent only during the dark period, which may represent a fundamental property of the serotonergic system. These results suggest that 5-HT should not be considered either wake promoting or NREM sleep promoting. Rather, the role of 5-HT in the regulation of sleep-wake behavior must be considered within the context of the degree to which the system is activated and the time at which the activation occurs.

Response of plasma IL-6 and its soluble receptors during submaximal exercise to fatigue in sedentary middle-aged men

The pleiotropic cytokine interleukin-6 (IL-6) has been demonstrated to increase during exercise. Little is known regarding the response of the soluble IL-6 receptors (sIL-6R and sgp130) during such exercise. The aim of the current study was to investigate the response of plasma IL-6, sIL-6R and sgp130 during fatiguing submaximal exercise in humans. Twelve participants underwent an incremental exercise test to exhaustion and one week later performed a submaximal exercise bout (96 +/- 6% lactate threshold) to volitional exhaustion. Blood samples taken at rest and immediately post exercise were analyzed for IL-6, sIL-6R and sgp130. IL-6 increased (P < 0.01) by 8.4 +/- 8.9 pg ml(-1) (75.7%) during the exercise period. sIL-6R and sgp130 also increased (P < 0.05) by 2.7 +/- 3.9 ng ml(-1) (9.6%) and 37.7 +/- 55.6 ng ml(-1) (9.6%), respectively. The current study is the first investigation to demonstrate that alongside IL-6, acute exercise stress results in an increase in both sIL-6R and sgp130.

Neuroendocrine-immune mechanisms of behavioral comorbidities in patients with cancer

Patients with cancer experience a host of behavioral alterations that include depression, fatigue, sleep disturbances, and cognitive dysfunction. These behavioral comorbidities are apparent throughout the process of diagnosis and treatment for cancer and can persist well into the survivorship period. There is a rich literature describing potential consequences of behavioral comorbidities in patients with cancer including impaired quality of life, reduced treatment adherence, and increased disease-related morbidity and mortality. Medical complications of cancer and its treatment such as anemia, thyroid dysfunction, and the neurotoxicity of cancer chemotherapeutic agents account in part for these behavioral changes. Nevertheless, recent advances in the neurosciences and immunology/oncology have revealed novel insights into additional pathophysiologic mechanisms that may significantly contribute to the development of cancer-related behavioral changes. Special attention has been focused on immunologic processes, specifically activation of innate immune inflammatory responses and their regulation by neuroendocrine pathways, which, in turn, influence CNS functions including neurotransmitter metabolism, neuropeptide function, sleep-wake cycles, regional brain activity, and, ultimately, behavior. Further understanding of these immunologic influences on the brain provides a novel conceptual framework for integrating the wide spectrum of behavioral alterations that occur in cancer patients and may reveal a more focused array of translational targets for therapeutic interventions and future research. Such developments warrant complementary advances in identification of cancer patients at risk as well as those currently suffering, including an increased emphasis on the status of behavior as a "sixth vital sign" to be assessed in all cancer patients throughout their disease encounter.

Cancer-related fatigue: links with inflammation in cancer patients and survivors

Fatigue is one of the most common and distressing side effects of cancer and its treatment and may persist long after successful treatment completion. Emerging evidence suggests that inflammatory processes may be involved in cancer-related fatigue both during and after treatment. In this review, we consider the evidence for an association between inflammation and fatigue in cancer patients and survivors. Further, we identify potential mechanisms for persistent inflammation, focusing on the HPA axis. Risk factors and treatments for cancer-related fatigue are also discussed.

Psychobiological mechanisms of exercise dependence

Exercise dependence (ED) is characterised by an obsessive and unhealthy preoccupation with exercise. Previous research has focused largely on identifying behavioural aspects of ED, although the biological mechanisms remain unknown and are under researched. We review various ED hypotheses including affect regulation, anorexia analogue, sympathetic arousal and beta-endorphin. We also present a novel hypothesis pertaining to ED and interleukin (IL)-6, which combines previous hypotheses with literature from the field of psycho-neuroimmunology. We explore the notion that IL-6 provides a link from the periphery to the brain, which may mediate the underlying features of ED. We propose a conceptual model indicating that, in individuals prone to ED, exercise results in a transient reduction in negative affect, but concurrently results in excessive production of IL-6 and the activation of neuroendocrine pathways, which are associated with behavioural and psychological disturbances of exercise withdrawal. Our intention is for this model to serve as a basis for further research in the area of ED, which may eventually lead to the development of successful treatment strategies. Recent developments in methods to reliably assess these biological markers from blood and saliva samples should encourage such research to be undertaken in exercise settings.

Mild acute inflammatory stimulation induces transient negative mood

OBJECTIVE

This study aims to assess the mood changes induced by mild acute inflammatory stimulation (typhoid vaccination).

METHODS

Using a double blind study design, 26 healthy volunteers underwent baseline assessments of mood, financial strain and work stress and were randomised to injection of Salmonella typhi vaccine or placebo injection. Mood, symptoms and body temperature was assessed by a modified version of the Profile of Mood States at 1, 2, 3, 4, 6 and 8 h post injection.

RESULTS

Typhoid vaccination induces no increases in physical symptoms or temperature. Mood improved over the day in the placebo but not in the vaccine condition. Negative changes in mood following injection were correlated with chronic stress (financial strain) in the vaccination condition (r=-.65, P<.025).

CONCLUSION

A mild acute inflammatory stimulus induces transient negative mood, and responses were modulated by chronic stress. Implications for depressed mood in physical illness are discussed.

Preoperative dexamethasone improves surgical outcome after laparoscopic cholecystectomy: a randomized double-blind placebo-controlled trial

OBJECTIVE

To determine the effects of preoperative dexamethasone on surgical outcome after laparoscopic cholecystectomy (LC).

SUMMARY BACKGROUND DATA

Pain and fatigue are dominating symptoms after LC and may prolong convalescence.

METHODS

In a double-blind, placebo-controlled study, 88 patients were randomized to intravenous dexamethasone (8 mg) or placebo 90 minutes before LC. Patients received a similar standardized anesthetic, surgical, and multimodal analgesic treatment. All patients were recommended 2 days postoperative duration of convalescence. The primary endpoints were fatigue and pain. Preoperatively and at several times during the first 24 postoperative hours, we measured C-reactive protein (CRP) and pulmonary function, pain scores, nausea, and number of vomiting episodes were registered. Analgesic and antiemetic requirements were recorded. Also, on a daily basis, patients reported scores of fatigue and pain before and during the first postoperative week and the dates for resumption of work and recreational activities.

RESULTS

Eight patients were excluded from the study, leaving 40 patients in each study group for analysis. There were no apparent side effects of the study drug. Dexamethasone significantly reduced postoperative levels of CRP (P = 0.01), fatigue (P = 0.01), overall pain, and incisional pain during the first 24 postoperative hours (P < 0.05) and total requirements of opioids (P < 0.05). In addition, cumulated overall and visceral pain scores during the first postoperative week were significantly reduced (P < 0.05). Dexamethasone also reduced nausea and vomiting on the day of operation (P < 0.05). Resumption of recreational activities was significantly faster in the dexamethasone group versus placebo group (median 1 day versus 2 days) (P < 0.05).

CONCLUSION

Preoperative dexamethasone (8 mg) reduced pain, fatigue, nausea and vomiting, and duration of convalescence in patients undergoing noncomplicated LC, when compared with placebo, and is recommended for routine use.

Fibromyalgia, hepatitis C infection, and the cytokine connection

Fibromyalgia and chronic hepatitis C infection share many clinical features including prominent somatic complaints such as musculoskeletal pain and fatigue. There is a growing body of evidence supporting a link between cytokines and somatic complaints. This review discusses alterations of cytokines in fibromyalgia, including increased serum levels of interleukin (IL)-2, IL-2 receptor, IL-8, IL-1 receptor antagonist; increased IL-1 and IL-6 produced by stimulated peripheral blood mononuclear cell in patients with FM for longer than 2 years; increased gp130, which is a neutrophil cytokine transducing protein; increased soluble IL-6 receptor and soluble IL-1 receptor antagonist only in patients with fibromyalgia who are depressed; and IL-1 beta, IL-6, and TNF-a by reverse transcriptase-polymerase chain reaction in skin biopsies of some patients with fibromyalgia. In addition, this review describes the mechanism by which alterations in cytokines in fibromyalgia and chronic hepatitis C infection can produce hyperalgesia and other neurally mediated symptoms through the presence of cytokine receptors on glial cells and opiate receptors on lymphocytes and the influence of cytokines on the hypothalamus-pituitary-adrenal axis such as IL-1, IL-6, and TNF-a activating and IL-2 and IFN-a down-regulating the HPA axis, respectively. The association between chronic hepatitis C infection and fibromyalgia is discussed, including a description of key cytokine changes in chronic hepatitis C infection. Future studies are encouraged to further characterize these immunologic alterations with potential pathophysiologic and therapeutic implications.

Acute phase responses and cytokine secretion in chronic fatigue syndrome

This study addresses the hypothesis that clinical manifestations of chronic fatigue syndrome (CFS) are due in part to abnormal production of or sensitivity to cytokines such as interleukin-1beta (IL-1beta) and IL-6 under basal conditions or in response to a particular physical stress: 15 min of exercise consisting of stepping up and down on a platform adjusted to the height of the patella. The study involved 10 CFS patients and 11 age-, sex-, and activity-matched controls: of these, 6 patients and 4 controls were tested in both the follicular and the luteal phases of the menstrual cycle, and the remainder were tested in only one phase, for a total of 31 experimental sessions. Prior to exercise, plasma concentrations of the acute phase reactant alpha2-macroglobulin were 29% higher in CFS patients (P < 0.008) compared to controls. Secretion of IL-6 was generally higher for CFS patients (approximately 38%), however, this difference was statistically significant only if all values over a 3-day period were analyzed by repeated-measures ANOVA (P = 0.035). IL-6 secretion correlated with plasma alpha2-macroglobulin in control subjects at rest (R = 0.767, P = 0.001). Immediately after exercise, the CFS patients reported greater ratings of perceived exertion (P=0.027) compared to the healthy control subjects. Ratings of perceived exertion correlated with IL-1beta secretion by cells from healthy control subjects (R = 0.603, P = 0.022), but not from CFS patients, and IL-1beta secretion was not different between groups. Exercise induced a slight (< 12%) but significant (P = 0.006) increase in IL-6 secretion, but the responses of the CFS patients were not different than controls. Furthermore, no significant exercise-induced changes in body temperature or plasma alpha2-macroglobulin were observed. These data indicate that under basal conditions, CFS is associated with increased IL-6 secretion which is manifested by chronically elevated plasma alpha2-macroglobulin concentrations. These modest differences suggest that cytokine dysregulation is not a singular or dominant factor in the pathogenesis of CFS.