Exercise stimulates interleukin-6 secretion: inhibition by glucocorticoids and correlation with catecholamines

Endocrine responses of the stress system to different types of exercise

Physical activity is an important part of human lifestyle although a large percentage of the population remains sedentary. Exercise represents a stress paradigm in which many regulatory endocrine systems are involved to achieve homeostasis. These endocrine adaptive responses may be either beneficial or harmful in case they exceed a certain threshold. The aim of this review is to examine the adaptive endocrine responses of hypothalamic-pituitary-adrenal axis (HPA), catecholamines, cytokines, growth hormone (GH) and prolactin (PRL) to a single bout or regular exercise of three distinct types of exercise, namely endurance, high-intensity interval (HIIE) and resistance exercise. In summary, a single bout of endurance exercise induces cortisol increase, while regular endurance exercise-induced activation of the HPA axis results to relatively increased basal cortisolemia; single bout or regular exercise induce similar GH peak responses; regular HIIE training lowers basal cortisol concentrations, while catecholamine response is reduced in regular HIIE compared with a single bout of HIIE. HPA axis response to resistance exercise depends on the intensity and volume of the exercise. A single bout of resistance exercise is characterized by mild HPA axis stimulation while regular resistance training in elderly results in attenuated inflammatory response and decreased resting cytokine concentrations. In conclusion, it is important to consider which type of exercise and what threshold is suitable for different target groups of exercising people. This approach intends to suggest types of exercise appropriate for different target groups in health and disease and subsequently to introduce them as medical prescription models.

Higher Hospital Frailty Risk Score Is an Independent Predictor of In-Hospital Mortality in Hospitalized Older Adults with Obstructive Sleep Apnea

Background: Frailty predisposes individuals to stressors, increasing morbidity and mortality risk. Therefore, this study examined the impact of frailty defined by the Hospital Frailty Risk Score (HFRS) and other characteristics in older hospitalized patients with Obstructive Sleep Apnea (OSA). Methods: We conducted a retrospective study using the National Inpatient Sample 2016 in patients ≥65 years old with OSA. Logistic regression was used to evaluate the impact of frailty on inpatient mortality. A Kaplan-Meier curve with a log-rank test was used to estimate survival time between frailty groups. Results: 182,174 discharge records of elderly OSA were included in the study. 54% of the cohort were determined to be a medium/high frailty risk, according to HFRS. In multivariable analysis, frailty was associated with a fourfold (medium frailty, adjusted odd ratio (aOR): 4.12, 95% Confidence Interval (CI): 3.76−4.53, p-value < 0.001) and sixfold (high frailty, OR: 6.38, 95% CI: 5.60−7.27, p-value < 0.001) increased odds of mortality. Hospital survival time was significantly different between the three frailty groups (Log-rank test, p < 0.0001). Comorbidity burden defined by Charlson comorbidity Index (CCI) was associated with increased mortality (p < 0.001). Conclusion: More than half of the whole cohort was determined to be at medium and high frailty risk. Frailty was a significant predictor of in-hospital deaths in hospitalized OSA patients. Frailty assessment may be applicable for risk stratification of older hospitalized OSA patients.

Implications of Adipose Tissue Content for Changes in Serum Levels of Exercise-Induced Adipokines: A Quasi-Experimental Study

Human adipocytes release multiple adipokines into the bloodstream during physical activity. This affects many organs and might contribute to the induction of inflammation. In this study, we aimed to assess changes in circulating adipokine levels induced by intense aerobic and anaerobic exercise in individuals with different adipose tissue content. In the quasi-experimental study, 48 male volunteers (aged 21.78 ± 1.98 years) were assigned to groups depending on their body fat content (BF): LBF, low body fat (<8% BF, n = 16); MBF, moderate body fat (8−14% BF, n = 19); and HBF, high body fat (>14% BF, n = 13). The volunteers performed maximal aerobic effort (MAE) and maximal anaerobic effort (MAnE) exercises. Blood samples were collected at five timepoints: before exercise, immediately after, 2 h, 6 h, and 24 h after each exercise. The selected cytokines were analyzed: adiponectin, follistatin-like 1, interleukin 6, leptin, oncostatin M, and resistin. While the participants’ MAnE and MAE performance were similar regardless of BF, the cytokine response of the HBF group was different from that of the others. Six hours after exercise, leptin levels in the HBF group increased by 35%. Further, immediately after MAnE, resistin levels in the HBF group also increased, by approximately 55%. The effect of different BF was not apparent for other cytokines. We conclude that the adipokine exercise response is associated with the amount of adipose tissue and is related to exercise type.

The effects of local versus systemic passive heating on the acute inflammatory, vascular and glycaemic response

The aim of this study was to compare the acute cardiometabolic and perceptual responses between local and whole-body passive heating. Using a water-perfused suit, 10 recreationally active males underwent three 90 min conditions: heating of the legs with upper-body cooling (LBH), whole-body heating (WBH) and exposure to a thermoneutral temperature (CON). Blood samples were collected before and up to 3 h post-session to assess inflammatory markers, while a 2 h oral glucose tolerance test was initiated 1 h post-session. Femoral artery blood flow and perceptual responses were recorded at regular intervals. The interleukin (IL)-6 incremental area under the curve (iAUC) was higher for LBH (1096 ± 851 pg/mL × 270 min) and WBH (833 ± 476 pg/mL × 270 min) compared with CON (565 ± 325 pg/mL × 270 min; p < 0.047). Glucose concentrations were higher after WBH compared with LBH and CON (p < 0.046). Femoral artery blood flow was higher at the end of WBH (1713 ± 409 mL/min) compared with LBH (943 ± 349 mL/min; p < 0.001), and higher in LBH than CON (661 ± 222 mL/min; p = 0.002). Affect and thermal comfort were more negative during WBH compared with LBH and CON (p < 0.010). In conclusion, local passive heating elevated blood flow and the IL-6 iAUC. However, while resulting in more positive perceptual responses, the majority of the included cardiometabolic markers were attenuated compared with WBH.

Novelty: The increase in the IL-6 iAUC in response to passive heating is not reduced by upper-body cooling. Upper-body cooling attenuates the plasma nitrite, IL-1ra and femoral artery blood flow response to passive heating. Upper-body cooling leads to more positive perceptual responses to passive heating.

Impact of Acute and Chronic Stress on Thrombosis in Healthy Individuals and Cardiovascular Disease Patients

Psychological stress induces different alterations in the organism in order to maintain homeostasis, including changes in hematopoiesis and hemostasis. In particular, stress-induced hyper activation of the autonomic nervous system and hypothalamic–pituitary–adrenal axis can trigger cellular and molecular alterations in platelets, coagulation factors, endothelial function, redox balance, and sterile inflammatory response. For this reason, mental stress is reported to enhance the risk of cardiovascular disease (CVD). However, contrasting results are often found in the literature considering differences in the response to acute or chronic stress and the health condition of the population analyzed. Since thrombosis is the most common underlying pathology of CVDs, the comprehension of the mechanisms at the basis of the association between stress and this pathology is highly valuable. The aim of this work is to give a comprehensive review of the studies focused on the role of acute and chronic stress in both healthy individuals and CVD patients, focusing on the cellular and molecular mechanisms underlying the relationship between stress and thrombosis.

Changes in γH2AX and H4K16ac levels are involved in the biochemical response to a competitive soccer match in adolescent players

The aim of this study was to examine novel putative markers of the response to the competitive soccer match in adolescent players, such as changes in global levels of γH2AX and H4K16ac in the chromatin of peripheral mononuclear blood cells (PMBCs) and a Fourier-transform infrared spectroscopy (FTIR)-based biochemical fingerprint of serum. These characteristics were examined with reference to the physiological and metabolic aspects of this response. Immediately post-match we noticed: (1) a systemic inflammatory response, manifesting as peaks in leukocyte count and changes in concentrations of IL-6, TNFα, and cortisol; (2) a peak in plasma lactate; (3) onset of oxidative stress, manifesting as a decline in GSH/GSSG; (4) onset of muscle injury, reflected in an increase in CK activity. Twenty-four hours post-match the decrease in GSH/GSSG was accompanied by accumulation of MDA and 8-OHdG, macromolecule oxidation end-products, and an increase in CK activity. No changes in SOD1 or GPX1 levels were found. Repeated measures correlation revealed several associations between the investigated biomarkers. The FTIR analysis revealed that the match had the greatest impact on serum lipid profile immediately post-game. In turn, increases in γH2AX and H4K16ac levels at 24 h post-match indicated activation of a DNA repair pathway.

The extended autonomic system, dyshomeostasis, and COVID-19

The pandemic viral illness COVID-19 is especially life-threatening in the elderly and in those with any of a variety of chronic medical conditions. This essay explores the possibility that the heightened risk may involve activation of the “extended autonomic system” (EAS). Traditionally, the autonomic nervous system has been viewed as consisting of the sympathetic nervous system, the parasympathetic nervous system, and the enteric nervous system. Over the past century, however, neuroendocrine and neuroimmune systems have come to the fore, justifying expansion of the meaning of “autonomic.” Additional facets include the sympathetic adrenergic system, for which adrenaline is the key effector; the hypothalamic-pituitary-adrenocortical axis; arginine vasopressin (synonymous with anti-diuretic hormone); the renin-angiotensin-aldosterone system, with angiotensin II and aldosterone the main effectors; and cholinergic anti-inflammatory and sympathetic inflammasomal pathways. A hierarchical brain network—the “central autonomic network”—regulates these systems; embedded within it are components of the Chrousos/Gold “stress system.” Acute, coordinated alterations in homeostatic settings (allostasis) can be crucial for surviving stressors such as traumatic hemorrhage, asphyxiation, and sepsis, which throughout human evolution have threatened homeostasis; however, intense or long-term EAS activation may cause harm. While required for appropriate responses in emergencies, EAS activation in the setting of chronically decreased homeostatic efficiencies (dyshomeostasis) may reduce thresholds for induction of destabilizing, lethal vicious cycles. Testable hypotheses derived from these concepts are that biomarkers of EAS activation correlate with clinical and pathophysiologic data and predict outcome in COVID-19 and that treatments targeting specific abnormalities identified in individual patients may be beneficial.

Role of Skeletal Muscle in Insulin Resistance and Glucose Uptake

The skeletal muscle is the largest organ in the body, by mass. It is also the regulator of glucose homeostasis, responsible for 80% of postprandial glucose uptake from the circulation. Skeletal muscle is essential for metabolism, both for its role in glucose uptake and its importance in exercise and metabolic disease. In this article, we give an overview of the importance of skeletal muscle in metabolism, describing its role in glucose uptake and the diseases that are associated with skeletal muscle metabolic dysregulation. We focus on the role of skeletal muscle in peripheral insulin resistance and the potential for skeletal muscle-targeted therapeutics to combat insulin resistance and diabetes, as well as other metabolic diseases like aging and obesity. In particular, we outline the possibilities and pitfalls of the quest for exercise mimetics, which are intended to target the molecular mechanisms underlying the beneficial effects of exercise on metabolic disease. We also provide a description of the molecular mechanisms that regulate skeletal muscle glucose uptake, including a focus on the SNARE proteins, which are essential regulators of glucose transport into the skeletal muscle. © 2020 American Physiological Society. Compr Physiol 10:785-809, 2020.

Extracellular Vesicles: Delivery Vehicles of Myokines

Movement and regular physical activity are two important factors that help the human body prevent, reduce and treat different chronic diseases such as obesity, type 2 diabetes, heart diseases, hypertension, sarcopenia, cachexia and cancer. During exercise, several tissues release molecules into the blood stream, and are able to mediate beneficial effects throughout the whole body. In particular, contracting skeletal muscle cells have the capacity to communicate with other organs through the release of humoral factors that play an important role in the mechanisms of adaptation to physical exercise. These muscle-derived factors, today recognized as myokines, act as endocrine and paracrine hormones. Moreover, exercise may stimulate the release of small membranous vesicles into circulation, whose composition is influenced by the same exercise. Combining the two hypotheses, these molecules related to exercise, named exer-kines, might be secreted from muscle cells inside small vesicles (nanovesicles). These could act as messengers in tissue cross talk during physical exercise. Thanks to their ability to deliver useful molecules (such as proteins and miRNA) in both physiological and pathological conditions, extracellular vesicles can be thought of as promising candidates for potential therapeutic and diagnostic applications for several diseases.

Sarilumab: patient-reported outcomes in rheumatoid arthritis

In the last few decades, strategies for the management of rheumatoid arthritis (RA) have been increasingly oriented toward more comprehensive control of the disease, taking into account even RA extra-articular manifestations, comorbidities, and the patient’s perception about the disease. The need for improving the shared decision-making process suggested by European League Against Rheumatism recommendations is leading to an increasing interest in the role of patient-reported outcomes (PROs) beside the usual more objective criteria for defining clinical response based on disease-activity composite indices. Measurement of such PROs as pain or fatigue may be significantly influenced by mood disorders often complicating RA, the pathogenesis of which is deeply interconnected with phlogistic processes mediated by proinflammatory cytokines. IL6 is a pleiotropic mediator involved in neuroendocrine and neuropsychological processes, besides its well known effects on immune, cardiovascular, and metabolic systems. Therefore, there is a growing body of evidence about the efficacy of IL6 blockade in PRO improvement in RA patients. Sarilumab is a monoclonal antibody binding both soluble and membrane-bound IL6Rα, inhibiting the IL6-mediated signaling pathway with favorable efficacy and safety profile. This review analyzes the importance of PROs in strategies for the management of RA and the pathogenic mechanisms linking IL6 with the patient’s perception of the disease. Moreover, the main findings from sarilumab randomized controlled trials are summarized in detail, emphasizing the potential role of this IL6 blocker in the holistic treatment of RA.

Early life socioeconomic status associates with interleukin-6 responses to acute laboratory stress in adulthood

It is proposed that environmental exposures in early life influence immune programming. Specifically, socioeconomic disadvantage is thought to program an immune phenotype that is prone to inflammation and associated with increased risk for inflammatory disease later in life. Existing literature shows an inverse association of early childhood socioeconomic status (SES) with adult levels of systemic inflammation. Here, we extend that literature to examine whether early childhood SES also relates to the magnitude of inflammatory response to acute psychological stress in adulthood. Healthy volunteers (N = 110; 40-58 years; 59% female; 90% white) performed a laboratory stress protocol, with blood samples drawn at the end of a 30-min baseline, a 5-min speech task, and a 30-min recovery to assess interleukin (IL)-6 stress responses. An early childhood SES index was derived from reports of parental home and vehicle ownership, and number of bedrooms per child in the home across ages 1-2, 3-4, and 5-6. Regressions adjusted for current age, sex, race, and BMI showed that lower SES at age 1-2 was associated with larger IL-6 stress responses in adulthood (ΔR² = 0.05, β = -0.24, p = .03). This association was independent of adult SES and task-evoked affective responses. No association was found between SES at ages 3-4 or 5-6 and IL-6 responses. These results provide initial evidence for a link between disadvantage in the first 2 years of life and heightened inflammatory response to stress in adulthood; this link may contribute to the increased disease risk that accompanies being raised in disadvantaged socioeconomic circumstances.

Relation between serum myokines and phase II cardiac rehabilitation

Patients with coronary heart disease or acute myocardial infarction after cardiac catheterization with stenting referred for phase II cardiac rehabilitation (CR) were grouped according to their preference. Cardio-pulmonary exercise testing (CPET) was used to determine oxygen uptake ((Equation is included in full-text article.)) at peak exercise and anaerobic threshold (AT). The control patients received counseling only while the experiment group received 36 sessions of CR in 3 to 6 months. Exercise physiology parameters and serum myokines (myostatin, insulin-like growth factor-1 (IGF-1), and interleukin-6 (IL-6) were measured pre- and postrehabilitation.There were 29 patients in the experiment group and 10 in the control group, with no significant differences in baseline parameters. The experiment group had prominent progress in aerobic capacity and body composition after CR, but their serum myokine concentrations did not change significantly. Serum myostatin is positively correlated to peak (Equation is included in full-text article.)pre- and post-training, and pretraining AT (Equation is included in full-text article.), after adjusting for age, sex, and body composition. Serum IGF-1 is positively correlated with grip strength before training.Serum myostatin level is positively correlated to aerobic capacity, and IGF-1 level is positively correlated to grip strength in cardiac patients receiving CR.

Association of Plasma Heat Shock Protein 70, Interleukin 6, and Creatine Kinase Concentrations in a Healthy, Young Adult Population

Variations of baseline plasma concentrations of creatine kinase (CK), heat shock protein 70 (HSP70), and interleukin 6 (IL-6) have been reported. We report categorical associations which may influence these protein levels. Methods. Blood was harvested for DNA and plasma protein analysis from 567 adults. Mean protein levels of CK, HSP70, and IL-6 were compared by sex, ethnicity, genetic variants-CKMM Nco1 (rs1803285), HSPA1B +A1538G (rs1061581), and IL6 G-174C (rs1800795)-self-reported history of exercise, oral contraceptive use, and dietary supplement use. Results. SNP major allele frequencies for CKMM, HSPA1B, and IL6 were 70% A, 57% A, and 60%. Mean CK statistically differed by sex, ethnicity, oral contraceptives, and caffeine. Plasma HSP70 differed by caffeine and protein. Mean IL-6 concentration differed by sex, ethnicity, and genotype. Plasma IL-6 was significantly lower (29%) in males (1.92 ± 0.08 pg/mL) and higher (29%) among African Americans (2.85 ± 0.50 pg/mL) relative to the others. IL6 G-174C GG genotype (2.23 ± 0.14 pg/mL) was 19% greater than CG or CC genotypes. Conclusion. Differences in baseline CK and IL-6 plasma protein concentrations are associated with genetics, sex, ethnicity, and the use of oral contraceptives, caffeine, and protein supplements in this young and athletic population.

Effects of Acute Endurance Exercise Performed in the Morning and Evening on Inflammatory Cytokine and Metabolic Hormone Responses

Purpose

To compare the effects of endurance exercise performed in the morning and evening on inflammatory cytokine responses in young men.

Methods

Fourteen healthy male participants aged 24.3 ± 0.8 years (mean ± standard error) performed endurance exercise in the morning (0900–1000 h) on one day and then in the evening (1700–1800 h) on another day with an interval of at least 1 week between each trial. In both the morning and evening trials, the participants walked for 60 minutes at approximately 60% of the maximal oxygen uptake (V·O2max) on a treadmill. Blood samples were collected to determine hormones and inflammatory cytokines at pre-exercise, immediately post exercise, and 2 h post exercise.

Results

Plasma interleukin (IL)-6 and adrenaline concentrations were significantly higher immediately after exercise in the evening trial than in the morning trial (P < 0.01, both). Serum free fatty acids concentrations were significantly higher in the evening trial than in the morning trial at 2 h after exercise (P < 0.05). Furthermore, a significant correlation was observed between the levels of IL-6 immediately post-exercise and free fatty acids 2 h post-exercise in the evening (r = 0.68, P < 0.01).

Conclusions

These findings suggest that the effect of acute endurance exercise in the evening enhances the plasma IL-6 and adrenaline concentrations compared to that in the morning. In addition, IL-6 was involved in increasing free fatty acids, suggesting that the evening is more effective for exercise-induced lipolysis compared with the morning.

The organization of the stress system and its dysregulation in depressive illness

Stressors are imminent or perceived challenges to homeostasis. The stress response is an innate, stereotypic, adaptive response to stressors that has evolved in the service of restoring the nonstressed homeostatic set point. It is encoded in specific neuroanatomical sites that activate a specific repertoire of cognitive, behavioral and physiologic phenomena. Adaptive responses, though essential for survival, can become dysregulated and result in disease. A clear example is autoimmune disease. I postulate that depression, like autoimmunity, represents a dysregulated adaptive response: a stress response that has gone awry. The cardinal manifestation of the normal stress response is anxiety. Cognitive programs shift from complex associative operations to rapid retrieval of unconscious emotional memories acquired during prior threatening situations. These emerge automatically to promote survival. To prevent distraction during stressful situations, the capacity to seek and experience pleasure is reduced, food intake is diminished and sexual activity and sleep are held in abeyance. Monoamines, cytokines, glutamate, GABA and other central mediators have key roles in the normal stress response. Many central loci are involved. The subgenual prefrontal cortex restrains the amygdala, the corticotropin-releasing hormone/hypothalamic-pituitary-adrenal (CRH/HPA) axis and the sympathomedullary system. The function of the subgenual prefrontal cortex is moderately diminished during normal stress to disinhibit these loci. This disinhibition promotes anxiety and physiological hyperarousal, while diminishing appetite and sleep. The dorsolateral prefrontal cortex is downregulated, diminishing cognitive regulation of anxiety. The nucleus accumbens is also downregulated, to reduce the propensity for distraction by pleasurable stimuli or the capacity to experience pleasure. Insulin resistance, inflammation and a prothrombotic state acutely emerge. These provide increased glucose for the brain and establish premonitory, proinflammatory and prothrombotic states in anticipation of either injury or hemorrhage during a threatening situation. Essential adaptive intracellular changes include increased neurogenesis, enhancement of neuroplasticity and deployment of a successful endoplasmic reticulum stress response. In melancholic depression, the activities of the central glutamate, norepinephrine and central cytokine systems are significantly and persistently increased. The subgenual prefrontal cortex is functionally impaired, and its size is reduced by as much as 40%. This leads to sustained anxiety and activations of the amygdala, CRH/HPA axis, the sympathomedullary system and their sequella, including early morning awakening and loss of appetite. The sustained activation of the amygdala, in turn, further activates stress system neuroendocrine and autonomic functions. The activity of the nucleus accumbens is further decreased and anhedonia emerges. Concomitantly, neurogenesis and neuroplasticity fall significantly. Antidepressants ameliorate many of these processes. The processes that lead to the behavioral and physiological manifestations of depressive illness produce a significant decrease in lifespan, and a doubling of the incidence of premature coronary artery disease. The incidences of premature diabetes and osteoporosis are also substantially increased. Six physiological processes that occur during stress and that are markedly increased in melancholia set into motion six different mechanisms to produce inflammation, as well as sustained insulin resistance and a prothrombotic state. Clinically, melancholic and atypical depression seem to be antithesis of one another. In melancholia, depressive systems are at their worst in the morning when arousal systems, such as the CRH/HPA axis and the noradrenergic systems, are at their maxima. In atypical depression, depressive symptoms are at their worst in the evening, when these arousal systems are at their minima. Melancholic patients experience anorexia and insomnia, whereas atypical patients experience hyperphagia and hypersomnia. Melancholia seems like an activation and persistence of the normal stress response, whereas atypical depression resembles a stress response that has been excessively inhibited. It is important that we stratify clinical studies of depressed patients to compare melancholic and atypical subtypes and establish their differential pathophysiology. Overall, it is important to note that many of the major mediators of the stress response and melancholic depression, such as the subgenual prefrontal cortex, the amygdala, the noradrenergic system and the CRH/HPA axis participate in multiple reinforcing positive feedback loops. This organization permits the establishment of the markedly exaggerated, persistent elevation of the stress response seen in melancholia. Given their pronounced interrelatedness, it may not matter where in this cascade the first abnormality arises. It will spread to the other loci and initiate each of their activations in a pernicious vicious cycle.

Biological mechanisms underlying the role of physical fitness in health and resilience

Physical fitness, achieved through regular exercise and/or spontaneous physical activity, confers resilience by inducing positive psychological and physiological benefits, blunting stress reactivity, protecting against potentially adverse behavioural and metabolic consequences of stressful events and preventing many chronic diseases. In this review, we discuss the biological mechanisms underlying the beneficial effects of physical fitness on mental and physical health. Physical fitness appears to buffer against stress-related disease owing to its blunting/optimizing effects on hormonal stress responsive systems, such as the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. This blunting appears to contribute to reduced emotional, physiological and metabolic reactivity as well as increased positive mood and well-being. Another mechanism whereby regular exercise and/or physical fitness may confer resilience is through minimizing excessive inflammation. Chronic psychological stress, physical inactivity and abdominal adiposity have been associated with persistent, systemic, low-grade inflammation and exert adverse effects on mental and physical health. The anti-inflammatory effects of regular exercise/activity can promote behavioural and metabolic resilience, and protect against various chronic diseases associated with systemic inflammation. Moreover, exercise may benefit the brain by enhancing growth factor expression and neural plasticity, thereby contributing to improved mood and cognition. In summary, the mechanisms whereby physical fitness promotes increased resilience and well-being and positive psychological and physical health are diverse and complex.

Blunted IL-6 and IL-10 response to maximal aerobic exercise in patients with traumatic brain injury

INTRODUCTION

In healthy individuals, strenuous exercise typically results in a transient increase in the inflammatory cytokine, interleukin-6 (IL-6). This increase in IL-6 is reported to have pleiotropic effects including increased glucose uptake, increased fat oxidation, and anti-inflammatory actions.

PURPOSE

The purpose of this study was to determine if patients with a traumatic brain injury (TBI) have a differential cytokine response to exercise compared to healthy control subjects (CON).

METHODS

Eight patients with a TBI and eight age- and sex-matched controls completed an exercise test to volitional exhaustion. Metabolic data were collected continuously, and blood was collected at baseline, immediately post-exercise, and every 10 min for an hour post-exercise. Serum was analyzed for IL-6, tumor necrosis factor-alpha, interleukin-10 (IL-10), and cortisol.

RESULTS

Peak oxygen consumption (CON 33 ± 2 ml kg(-1) min(-1); TBI 29 ± 2 ml kg(-1) min(-1)) and respiratory exchange ratio during exercise were equivalent between groups. There were no baseline differences between groups for cytokine or cortisol concentrations. Exercise did not increase IL-6 in TBI, whereas IL-6 was elevated from baseline in CON at 0, 40, and 50 min post-exercise (p < 0.05). IL-10 and cortisol increased from baseline in CON at 40 min post-exercise (p < 0.05).

CONCLUSIONS

These data indicate that patients recovering from TBI have blunted IL-6, IL-10, and cortisol responses following a peak exercise test compared to non-TBI controls. This lack of an exercise response may represent impaired hypothalamic-pituitary-adrenal axis function.

β3-Adrenergic receptor antagonist improves exercise performance in pacing-induced heart failure

In heart failure (HF), the impaired left ventricular (LV) arterial coupling and diastolic dysfunction present at rest are exacerbated during exercise. We have previously shown that in HF at rest stimulation of β3-adrenergic receptors by endogenous catecholamine depresses LV contraction and relaxation. β3-Adrenergic receptors are activated at higher concentrations of catecholamine. Thus exercise may cause increased stimulation of cardiac β3-adrenergic receptors and contribute to this abnormal response. We assessed the effect of L-748,337 (50 μg/kg iv), a selective β3-adrenergic receptor antagonist (β3-ANT), on LV dynamics during exercise in 12 chronically instrumented dogs with pacing-induced HF. Compared with HF at rest, exercise increased LV end-systolic pressure (PES), minimum LV pressure (LVPmin), and the time constant of LV relaxation (τ) with an upward shift of early diastolic portion of LV pressure-volume loop. LV contractility decreased and arterial elastance (EA) increased. LV arterial coupling (EES/EA) (0.40 vs. 0.51) was impaired. Compared with exercise in HF preparation, exercise after β3-ANT caused similar increases in heart rate and PES but significantly decreased τ (34.9 vs. 38.3 ms) and LVPmin with a downward shift of the early diastolic portion of LV pressure-volume loop and further augmented dV/dtmax. Both EES and EES/EA (0.68 vs. 0.40) were increased. LV mechanical efficiency improved from 0.39 to 0.53. In conclusion, after HF, β3-ANT improves LV diastolic filling; increases LV contractility, LV arterial coupling, and mechanical efficiency; and improves exercise performance.

Adipo-myokines: two sides of the same coin--mediators of inflammation and mediators of exercise

This review summarizes the current literature regarding the most discussed contraction-regulated moykines like IL-6, IL-15, irisin, BDNF, ANGPTL4, FGF21, myonectin and MCP-1. It is suggested that the term myokine is restricted to proteins secreted from skeletal muscle cells, excluding proteins that are secreted by other cell types in skeletal muscle tissue and excluding proteins which are only described on the mRNA level. Interestingly, many of the contraction-regulated myokines described in the literature are additionally known to be secreted by adipocytes. We termed these proteins adipo-myokines. Within this review, we try to elaborate on the question why pro-inflammatory adipokines on the one hand are upregulated in the obese state, and have beneficial effects after exercise on the other hand. Both, adipokines and myokines do have autocrine effects within their corresponding tissues. In addition, they are involved in an endocrine crosstalk with other tissues. Depending on the extent and the kinetics of adipo-myokines in serum, these molecules seem to have a beneficial or an adverse effect on the target tissue.

Identification and validation of novel contraction-regulated myokines released from primary human skeletal muscle cells

Proteins secreted by skeletal muscle, so called myokines, have been shown to affect muscle physiology and additionally exert systemic effects on other tissues and organs. Although recent profiling studies have identified numerous myokines, the amount of overlap from these studies indicates that the secretome of skeletal muscle is still incompletely characterized. One limitation of the models used is the lack of contraction, a central characteristic of muscle cells. Here we aimed to characterize the secretome of primary human myotubes by cytokine antibody arrays and to identify myokines regulated by contraction, which was induced by electrical pulse stimulation (EPS). In this study, we validated the regulation and release of two selected myokines, namely pigment epithelium derived factor (PEDF) and dipeptidyl peptidase 4 (DPP4), which were recently described as adipokines. This study reveals that both factors, DPP4 and PEDF, are secreted by primary human myotubes. PEDF is a contraction-regulated myokine, although PEDF serum levels from healthy young men decrease after 60 min cycling at VO2max of 70%. Most interestingly, we identified 52 novel myokines which have not been described before to be secreted by skeletal muscle cells. For 48 myokines we show that their release is regulated by contractile activity. This profiling study of the human skeletal muscle secretome expands the number of myokines, identifies novel contraction-regulated myokines and underlines the overlap between proteins which are adipokines as well as myokines.

High levels of inflammation and insulin resistance in obstructive sleep apnea patients with hypertension

Hypertension induced by obstructive sleep apnea (OSA) may be multifactorial in origin, and systemic inflammation is one of the major factors. However, OSA patients do not always have the identical probability with hypertension even in patients with the same history and degree of OSA. The aim of this study was to compare the levels of inflammation and insulin resistance in two groups of patients who had the same degree as well as the same long history of OSA, but with/without hypertension. OSA patients (Apnea Hyponea Index, AHI ≥ 40/h, n = 70) were examined by polysomnography and blood analysis for the measurements of fasting plasma glucose, serum insulin (FINS), high-sensitivity C-reactive protein (CRP), peptide C,TNF-α, IL-6, and IL-10. Patients with hypertension (n = 40) had higher level of LDL-C and lower HDL-C levels than patients without hypertension. Almost half (16/40) of OSA patients with hypertension had family history of hypertension. Moreover in OSA patients with hypertension, the levels of TNF-α, IL-6, and CRP were higher, but IL-10 was lower than those without hypertension. FINS, peptide C, HOMA-IR, and HOMA-islet were also higher in OSA patients with hypertension. OSA patients with hypertension have higher level of inflammation and insulin resistance. Systemic inflammation and insulin resistance are both important factors for the development of hypertension in OSA patients.

Role of the immune system in hypertension: modulation by dietary antioxidants

Hypertension is a major health problem worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease, and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Insulin resistance is a common feature of hypertension in both humans and animal models affecting glucose and lipid metabolism producing excess aldehydes including methylglyoxal. These aldehydes react with proteins to form conjugates called advanced glycation end products (AGEs). This alters protein structure and function and can affect vascular and immune cells leading to their activation and secretion of inflammatory cytokines. AGEs also act via receptors for advanced glycation end products on these cells altering the function of antioxidant and metabolic enzymes, and ion channels. This results in an increase in cytosolic free calcium, decrease in nitric oxide, endothelial dysfunction, oxidative stress, peripheral vascular resistance, and infiltration of vascular and kidney tissue with inflammatory cells leading to hypertension. Supplementation with dietary antioxidants including vitamins C, E, or B(6), thiols such as cysteine and lipoic acid, have been shown to lower blood pressure and plasma inflammatory cytokines in animal models and humans with essential hypertension. A well-balanced diet rich in antioxidants that includes vegetables, fruits, low fat dairy products, low salt, and includes whole grains, poultry, fish and nuts, lowers blood pressure and vascular inflammation. These antioxidants may achieve their antihypertensive and anti-inflammatory/immunomodulatory effects by reducing AGEs and improving insulin resistance and associated alterations. Dietary supplementation with antioxidants may be a beneficial, inexpensive, front-line alterative treatment modality for hypertension.

Maternal and cord serum cytokine changes with continuous and intermittent labor epidural analgesia: a randomized study

Background. Maternal fever during labor epidural analgesia (LEA) may cause increased maternal and cord serum inflammatory cytokines. We report the effects of intermittent and continuous LEA on these cytokines. Methods. Ninety-two women were randomly assigned to continuous (CLEA) or intermittent (ILEA) groups, 46 in each. Maternal temperature was checked and blood drawn at epidural insertion (baseline) and four-hourly until 4 h postpartum (4 PP). Cord blood was drawn after placental delivery. Interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), granulocyte macrophage-colony stimulating factor (GM-CSF), and tumor necrosis factor-α (TNF-α) were measured and analyzed according to group randomization, and then combined and reanalyzed as febrile (temperature ≥38°C) or afebrile groups. Results. Significant intragroup changes from baseline were noted in some groups. Data are pg/mL, median (Q1/Q3). IL-6 rose at all time points in all groups. CLEA: baseline: 18.5 (12.5/31.1), 4 h: 80.0 (46.3/110.8), 8 h: 171.9 (145.3/234.3), and 4 PP: 81 (55.7/137.4). ILEA: baseline: 15.7 (10.2/27.1), 4 h: 68.2 (33.3/95.0), 8 h: 125.0 (86.3/195.0), and 4 PP: 70.2 (54.8/103.6). Febrile group: baseline: 21.6 (13.8/40.9), 4 h: 83.9 (47.5/120.8), 8 h: 186.7 (149.6/349.9), and 4 PP: 105.8 (65.7/158.8). Afebrile group: baseline: 10.9 (2.1/17.4), 4 h: 38.2 (15.0/68.2), 8 h: 93.8 (57.1/135.7), and 4 PP: 52.9 (25.1/78). IL-8 rose at all time points in CLEA: baseline: 2.68 (0.0/4.3), 4 h: 3.7 (0.0/6.5), 8 h: 6.0 (3.3/9.6), 4 PP: 5.6 (0.8/8.0), and afebrile group baseline: 2.5 (0.0/4.7), 4 h: 3.3 (0.0/6.2), 8 h: 5.3 (1.9/9.8), and 4 PP: 4.7 (0.0/7.6). It fell at 4 PP in febrile group: baseline: 4.1 (0.0/6.4), 4 h: 3.8 (0.0/6.5), 8 h: 5.2 (2.5/8.0), and 4 PP: 2.9 (0.0/4.0). GM-CSF increased at 8 h and decreased at 4 PP in ILEA baseline: 2.73 (0.0/7.2), 4 h: 2.73 (0.0/7.9), 8 h: 3.9 (2.7/11.5), and 4 PP: 2.0 (0.0/7.2). It increased at 4 h and 8 h and decreased at 4 PP in febrile group: baseline: 2.6 (0.0/4.2), 4 h: 3.2 (2.1/7.0), 8 h: 4.0 (3.2/12.3), and 4 PP: 2.4 (1.7/12.6). There were no intergroup cytokine changes in maternal or cord serum in CLEA versus ILEA or febrile versus afebrile groups. Conclusions. Some cytokines, especially IL-6, rise physiologically during labor epidural analgesia.

A closer look at the role of urotensin II in the metabolic syndrome

Urotensin II (UII) is a vasoactive peptide that was first discovered in the teleost fish, and later in mammals and humans. UII binds to the G protein coupled receptor GPR14 (now known as UT). UII mediates important physiological and pathological actions by interacting with its receptor. The metabolic syndrome (MetS) is described as cluster of factors such as obesity, dyslipidemia, hypertension, and insulin resistance (IR), further leading to development of type 2 diabetes mellitus and cardiovascular diseases. UII levels are upregulated in patients with the MetS. Evidence directly implicating UII in every risk factor of the MetS has been accumulated. The mechanism that links the different aspects of the MetS relies primarily on IR and inflammation. By directly modulating both of these factors, UII is thought to play a central role in the pathogenesis of the MetS. Moreover, UII also plays an important role in hypertension and hyperlipidemia thereby contributing to cardiovascular complications associated with the MetS.

Biobehavioral influences on cancer progression

This review focuses on the contributions of stress-related behavioral factors to cancer growth and metastasis and the biobehavioral mechanisms underlying these relationships. Behavioral factors that are important in modulation of the stress response and the pivotal role of neuroendocrine regulation in the downstream alteration of physiologic pathways relevant to cancer control, including the cellular immune response, inflammation, and tumor angiogenesis, invasion, and cell signaling pathways are described. Consequences for cancer progression and metastasis, as well as quality of life, are delineated. Behavioral and pharmacologic interventions with the potential to alter these biobehavioral pathways for patients with cancer are discussed.

Influence of interleukin-6 and G174C polymorphism in IL-6 gene on obesity and energy balance

Obesity is a multifactor disease with a very complicated etiology. Genetic factors play an important role in the development of primary obesity. They may be responsible for up to 40% of causes leading to obesity. There are a great number of genes affecting food intake and energy expenditure. Serious consequences accompanying obesity, e.g., type 2 diabetes and lipid abnormalities may be caused by increased level of proinflammatory cytokines, such as IL-1, IL-6, and TNF. It is possible that polymorphisms located in cytokine genes affect the level of protein expression. It is known that IL-6 plays a role in lipid metabolism and energy expenditure. The polymorphism found in point 174 (G174C) of a promoter region of IL-6 gene affects the level of interleukin-6 expression and, consequently, may lead to obesity and correlated conditions.

Self-efficacy buffers the relationship between dementia caregiving stress and circulating concentrations of the proinflammatory cytokine interleukin-6

OBJECTIVE

the proinflammatory cytokine interleukin (IL)-6 has been linked with health morbidity, particularly risk for cardiovascular disease (CVD). The purpose of this study was to investigate the potential protective role of coping self-efficacy on the relationship between caregiving stress and circulating concentrations of IL-6.

METHODS

a total of 62 elderly caregivers of patients with Alzheimer's disease (mean age: 74 years) were assessed for plasma concentrations of IL-6, caregiving-related overload, and coping self-efficacy. Multiple regression was used to examine the main effects of stress and self-efficacy, as well as the interaction between stress and self-efficacy, in predicting plasma IL-6 after controlling for age, gender, resting blood pressure, and obesity.

RESULTS

there was a significant interaction between stress and self-efficacy in predicting IL-6. Post-hoc examination indicated that when self-efficacy was low, stress was significantly related to IL-6 (β = 0.43). However, when self-efficacy was high, stress was not significantly related to IL-6 (β = -0.10).

CONCLUSION

caregiving stress in combination with low coping self-efficacy is significantly related to IL-6, a known risk marker for health morbidity, particularly CVD. However, stress was not associated with IL-6 with high self-efficacy. Although limited and preliminary, these results point to a potential protective effect of self-efficacy on caregiver health that can be tested in longitudinal studies.

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.

Influence of proinflammatory cytokine gene polymorphism on childhood obesity

BACKGROUND

Obesity development is a complex process which can be influenced by genetic predisposition modified by environmental factors. Nowadays, the problem of overweight and obesity, including related complications, occurs in increasingly younger children. Thus, there is a need for new genetic markers of increased risk of excessive body mass.

OBJECTIVE

The aim of the present study was to examine the relation between polymorphisms located in promoter regions of IL-1beta, IL-6, and TNF-alpha genes and obesity development in children. Fifty obese and 55 normal weighing children were enrolled into the study. Genetic examination was performed using PCR-RFLP technique.

RESULTS

We found a relation between G174C polymorphism in IL-6 gene and G308A in TNF-alpha gene with the occurrence of obesity. Allele A in G308A was more frequent in the obese group than in the control one (P=0.04). The presence of allele C in promoter region of IL-6 gene was more frequent in obese children and connected with a statistically significant increase in the sum of 10 skin fold thickness measurements (P=0.03).

CONCLUSIONS

The polymorphism C3954T in IL-1beta gene showed no such relation. The examined polymorphisms of proinflammatory cytokines play a role in the regulation of body mass through their influence on metabolism and energetic homeostasis.

Effect of acute sleep deprivation on vascular function in healthy subjects

Sleep disorders are associated with inflammation and sympathetic activation, which are suspected to induce endothelial dysfunction, a key factor in the increased risk of cardiovascular disease. Less is known about the early effects of acute sleep deprivation on vascular function. We evaluated microvascular reactivity and biological markers of endothelial activation during continuous 40 h of total sleep deprivation (TSD) in 12 healthy men (29 ± 3 yr). The days before [ day 1 (D1)] and during TSD (D3), at 1200 and 1800, endothelium-dependent and -independent cutaneous vascular conductance was assessed by iontophoresis of acetylcholine and sodium nitroprusside, respectively, coupled to laser-Doppler flowmetry. At 0900, 1200, 1500, and 1800, heart rate (HR) and instantaneous blood pressure (BP) were recorded in the supine position. At D1, D3, and the day after one night of sleep recovery (D4), markers of vascular endothelial cell activation, including soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, and interleukin-6 were measured from blood samples at 0800. Compared with D1, plasma levels of E-selectin were raised at D3, whereas intercellular adhesion molecule-1 and interleukin-6 were raised at D4 ( P < 0.05). The endothelium-dependent and -independent CVC were significantly decreased after 29 h of TSD ( P < 0.05). By contrast, HR, systolic BP, and the normalized low-frequency component of HR variability (0.04–0.15 Hz), a marker of the sympathetic activity, increased significantly within 32 h of TSD ( P < 0.05). In conclusion, acute exposure to 40 h of TSD appears to cause vascular dysfunction before the increase in sympathetic activity and systolic BP.

Signaling pathways mediating beta3-adrenergic receptor-induced production of interleukin-6 in adipocytes

The beta(3)-adrenergic receptor (beta(3)AR) is an essential regulator of metabolic and endocrine functions. A major cellular and clinically significant consequence of beta(3)AR activation is the substantial elevation in interleukin-6 (IL-6) levels. Although the beta(3)AR-dependent regulation of IL-6 expression is well established, the cellular pathways underlying this regulation have not been characterized. Using a novel method of homogenous reporters, we assessed the pattern of activation of 43 transcription factors in response to the specific beta(3)AR agonist CL316243 in adipocytes, cells that exhibit the highest expression of beta(3)ARs. We observed a unique and robust activation of the CRE-response element, suggesting that IL-6 transcription is regulated via the G(s)-protein/cAMP/protein kinase A (PKA) but not nuclear factor kappa B (NF-kappaB) pathway. However, pretreatment of adipocytes with pharmacologic inhibitors of PKA pathway failed to block beta(3)AR-mediated IL-6 up-regulation. Additionally, stimulation of adipocytes with the exchange protein directly activated by cAMP (Epac) agonist did not induce IL-6 expression. Instead, the beta(3)AR-mediated transcription of IL-6 required activation of both the p38 and PKC pathways. Western blot analysis further showed that transcription factors CREB and ATF-2 but not ATF-1 were activated in a p38- and PKC-dependent manner. Collectively, our results suggest that while stimulation of the beta(3)AR leads to a specific activation of CRE-dependent transcription, there are several independent cellular pathways that converge at the level of CRE-response element activation, and in the case of IL-6 this activation is mediated by p38 and PKC but not PKA pathways.

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.

The underlying mechanisms for development of hypertension in the metabolic syndrome

High blood pressure is an important constituent of the metabolic syndrome. However, the underlying mechanisms for development of hypertension in the metabolic syndrome are very complicated and remain still obscure. Visceral/central obesity, insulin resistance, sympathetic overactivity, oxidative stress, endothelial dysfunction, activated renin-angiotensin system, increased inflammatory mediators, and obstructive sleep apnea have been suggested to be possible factors to develop hypertension in the metabolic syndrome. Here, we will discuss how these factors influence on development of hypertension in the metabolic syndrome.

C-reactive protein and vulnerability to mental stress-induced myocardial ischemia

Myocardial ischemia provoked in the laboratory during mental stress (MSI) in patients with stable coronary artery disease (CAD) predicts subsequent clinical events. The pathophysiology of MSI differs from that of exercise ischemia, and the mechanisms tying MSI to poor prognosis are not known. C-reactive protein (CRP) is a risk marker for cardiovascular events in patients with CAD, but little is known regarding the relationship of CRP to MSI. The purpose of this study was to examine the association of CRP to risk of MSI in CAD patients. Eighty-three patients with stable CAD underwent simultaneous single-photon emission computed tomography (SPECT) imaging with technetium-99m tetrofosmin myocardial perfusion imaging (MPI) and transthoracic echocardiography (TTE), at rest and during MS induced by laboratory mental stress. Serum CRP levels were measured 24 h after MS. MSI was defined by the presence of a new perfusion defect on SPECT and/or new regional wall motion abnormality on TTE during MS. Of the 83 patients, 30 (36%) developed MSI. There was no difference in gender, sex, BMI, histories of diabetes, hypertension, smoking, lipid profile, medications used (including statins, beta-blockers, ACE inhibitors, and aspirin), or hemodynamic response during MS between those with and without MSI. In univariate logistic regression analysis, each unit (1 mg/L) increase in CRP level was associated with 20% higher risk of MSI (OR 1.2, 95% CI 1.01-1.39, P=.04). This relationship remained in multivariate models. These data suggest that levels of CRP may be a risk marker for MSI in patients with CAD.

C-reactive protein and vulnerability to mental stress-induced myocardial ischemia

Myocardial ischemia provoked in the laboratory during mental stress (MSI) in patients with stable coronary artery disease (CAD) predicts subsequent clinical events. The pathophysiology of MSI differs from that of exercise ischemia, and the mechanisms tying MSI to poor prognosis are not known. C-reactive protein (CRP) is a risk marker for cardiovascular events in patients with CAD, but little is known regarding the relationship of CRP to MSI. The purpose of this study was to examine the association of CRP to risk of MSI in CAD patients. Eighty-three patients with stable CAD underwent simultaneous single-photon emission computed tomography (SPECT) imaging with technetium-99m tetrofosmin myocardial perfusion imaging (MPI) and transthoracic echocardiography (TTE), at rest and during MS induced by laboratory mental stress. Serum CRP levels were measured 24 h after MS. MSI was defined by the presence of a new perfusion defect on SPECT and/or new regional wall motion abnormality on TTE during MS. Of the 83 patients, 30 (36%) developed MSI. There was no difference in gender, sex, BMI, histories of diabetes, hypertension, smoking, lipid profile, medications used (including statins, beta-blockers, ACE inhibitors, and aspirin), or hemodynamic response during MS between those with and without MSI. In univariate logistic regression analysis, each unit (1 mg/L) increase in CRP level was associated with 20% higher risk of MSI (OR 1.2, 95% CI 1.01-1.39, P=.04). This relationship remained in multivariate models. These data suggest that levels of CRP may be a risk marker for MSI in patients with CAD.

High dexamethasone concentration prevents stimulatory effects of TNF-alpha and LPS on IL-6 secretion from the precursors of human muscle regeneration

A frequent finding in patients surviving critical illness myopathy is chronic muscle dysfunction. Its pathogenesis is mostly unknown; one explanation could be that muscle regeneration, which normally follows myopathy, is insufficient in these patients because of a high glucocorticoid level in their blood. Glucocorticoids can prevent stimulatory effects of proinflammatory factors on the interleukin (IL)-6 secretion, diminishing in this way the autocrine and paracrine IL-6 actions known to stimulate proliferation at the earliest, myoblast stage of muscle formation. To test this hypothesis, we compared the effects of major proinflammatory agents [tumor necrosis factor (TNF)-alpha and endotoxin lipopolysaccharide (LPS)] on the IL-6 secretion from the muscle precursors and then studied the influence of dexamethasone (Dex) on these effects. Mononuclear myoblasts, which still proliferate, were compared with myotubes in which this capacity is already lost. For correct interpretation of results, cultures were examined for putative apoptosis and necrosis. We found that constitutive secretion of IL-6 did not differ significantly between myoblasts and myotubes; however, the TNF-alpha- and LPS-stimulated IL-6 release was more pronounced (P < 0.001) in myoblasts. Dex, applied at the 0.1-100 nM concentration range, prevented constitutive and TNF-alpha- and LPS-stimulated IL-6 release at both developmental stages but only at high concentration (P < 0.01). Although there are still missing links to it, our results support the concept that high concentrations of glucocorticoids, met in critically ill patients, prevent TNF-alpha- and LPS-stimulated IL-6 secretion. This results in reduced IL-6-mediated myoblast proliferation, leading to the reduced final mass of the regenerated muscle.

Cytokine Responses at High Altitude

PURPOSE

This study tested the hypothesis that antioxidant supplementation would attenuate plasma cytokine (IL-6, tumor necrosis factor (TNF)-alpha), and C-reactive protein (CRP) concentrations at rest and in response to exercise at 4300-m elevation.

METHODS

A total of 17 recreationally trained men were matched and assigned to an antioxidant (N = 9) or placebo (N = 8) group in a double-blinded fashion. At sea level (SL), energy expenditure was controlled and subjects were weight stable. Then, 3 wk before and throughout high altitude (HA), an antioxidant supplement (10,000 IU beta-carotene, 200 IU alpha-tocopherol acetate, 250 mg ascorbic acid, 50 microg selenium, 15 mg zinc) or placebo was given twice daily. At HA, energy expenditure increased approximately 750 kcal.d(-1) and energy intake decreased approximately 550 kcal.d, resulting in a caloric deficit of approximately 1200-1500 kcal.d(-1). At SL and HA day 1 (HA1) and day HA13, subjects exercised at 55% of VO2peak until they expended approximately 1500 kcal. Blood samples were taken at rest, end of exercise, and 2, 4, and 20 h after exercise.

RESULTS

No differences were seen between groups in plasma IL-6, CRP, or TNF-alpha at rest or in response to exercise. For both groups, plasma IL-6 concentration was significantly higher at the end of exercise, 2, 4, and 20 h after exercise at HA1 compared with SL and HA13. Plasma CRP concentration was significantly elevated 20 h postexercise for both groups on HA1 compared to SL and HA13. TNF-alpha did not differ at rest or in response to exercise.

CONCLUSION

Plasma IL-6 and CRP concentrations were elevated following exercise at high altitude on day 1, and antioxidant supplementation did not attenuate the rise in plasma IL-6 and CRP concentrations associated with hypoxia, exercise, and caloric deficit.

Physical Activity and High-Sensitivity C-Reactive Protein

Cardiovascular disease (CVD) remains one of the leading causes of death and disability in developed countries around the world despite the documented success of lifestyle and pharmacological interventions. This illustrates the multifactorial nature of atherosclerosis and the use of novel inflammatory markers as an adjunct to risk factor reduction strategies. As evidence continues to accumulate that inflammation is involved in all stages of the development and progression of atherosclerosis, markers of inflammation such as high-sensitivity C-reactive protein (CRP) may provide additional information regarding the biological status of the atherosclerotic lesion. Recent investigations suggest that physical activity reduces CRP levels. Higher levels of physical activity and cardiorespiratory fitness are consistently associated with 6-35% lower CRP levels. Longitudinal training studies that have demonstrated reductions in CRP concentrations range from 16% to 41%, an effect that may be independent of baseline levels of CRP, body composition or weight loss. The average change in CRP associated with physical activity appears to be at least as good, if not better, than currently prescribed pharmacological interventions in similar populations. The primary purpose of this review will be to present evidence from both cross-sectional and longitudinal investigations that physical activity lowers CRP levels in a dose-response manner. Finally, this review will examine factors such as body composition, sex, blood sample timing, diet and smoking, which may influence the CRP response to physical activity.

Stress-induced increases in interleukin-6 and fibrinogen predict ambulatory blood pressure at 3-year follow-up

BACKGROUND

The biological mechanisms underlying the association between psychological stress and hypertension are poorly understood. Increased plasma concentrations of the inflammatory proteins interleukin-6 and fibrinogen are commonly reported both in hypertensive patients and in people subject to chronic psychological stress. Recent laboratory studies have also shown that acute psychological stress increases plasma interleukin-6 and fibrinogen concentrations in healthy individuals.

OBJECTIVE

To investigate the relationship between stress-induced inflammatory responses and blood pressure using a longitudinal design.

METHODS

Participants were 153 individuals from the Whitehall II cohort. Blood pressure, plasma interleukin-6 and fibrinogen were assessed in response to an acute laboratory stressor, and ambulatory blood pressure was monitored on a separate day. Three years later, a follow-up day of ambulatory blood pressure monitoring was carried out.

RESULTS

Individual differences in systolic pressure, fibrinogen and interleukin-6 stress responses predicted ambulatory blood pressure at the 3-year follow-up. Larger increases in ambulatory systolic pressure over the 3-year period were predicted by larger acute fibrinogen and interleukin-6 stress responses, independently of previous ambulatory blood pressure, acute blood pressure stress responses, age, sex, body mass and smoking.

CONCLUSION

Given the important roles of interleukin-6 and fibrinogen in hypertensive pathophysiology, these results indicate that psychological stress could promote hypertension through stimulating these inflammatory proteins.

Effect of exercise, training, and glycogen availability on IL-6 receptor expression in human skeletal muscle

The cytokine interleukin-6 (IL-6) exerts it actions via the IL-6 receptor (IL-6R) in conjunction with the ubiquitously expressed gp130 receptor. IL-6 is tightly regulated in response to exercise, being affected by factors such as exercise intensity and duration, as well as energy availability. Although the IL-6 response to exercise has been extensively studied, little is known about the regulation of the IL-6R response. In the present study, we aimed to investigate the effect of exercise, training, and glycogen availability, factors known to affect IL-6, on the regulation of gene expression of the IL-6R in human skeletal muscle. Human subjects performed either 10 wk of training with an acute exercise bout before and after the training period, or a low-glycogen vs. normal-glycogen acute exercise trial. The IL-6R mRNA response was evaluated in both trials. In response to acute exercise, an increase in IL-6R mRNA levels was observed. Neither training nor intramuscular glycogen levels had an effect on the IL-6R mRNA response to exercise. However, after 10 wk of training, the skeletal muscle expressed a higher mRNA level of IL-6R compared with before training. The present study demonstrated that the IL-6R gene expression levels in skeletal muscle are increased in response to acute exercise, a response that is very well conserved, being affected by neither training status nor intramuscular glycogen levels, as opposed to IL-6. However, after the training period, IL-6R mRNA production was increased in skeletal muscle, suggesting a sensitization of skeletal muscle to IL-6 at rest.

Differential responses of serum and salivary interleukin-6 to acute strenuous exercise

Physical exercise is associated with elevation of serum levels of interleukin-6 (IL-6) because of its production in the muscles. The use of IL-6 measurements in saliva has been proposed in the field of immunopathology, mainly involving salivary gland disease. We evaluated the responses of serum and salivary IL-6 in two different groups of athletes submitted to different types of controlled strenuous exercise (spinning activity and maximal isokinetic test). Serum and salivary samples for IL-6 measurements, and serum samples for lactate and myoglobin determination before and after exercise, were obtained. Salivary IL-6 was measured by ELISA after dilution experiments and compared with results obtained by immunoradiometric assay. Spinning activity elicited significant increases in all the variables, and no correlation was found among the respective variations. A significant response to the isokinetic exercise was observed for serum IL-6, lactate and myoglobin only; no correlation was found between serum and salivary IL-6. Our study demonstrated that serum and salivary IL-6 responses to exercise are dissociated, possibly in relation to the lack of relationships between the systemic/muscular and the salivary routes of IL-6 production. Analytical issues that concern IL-6 measurement in saliva deserve attention, notably regarding the collection method used to absorb saliva. Concomitant monitoring of serum markers of inflammation, muscle metabolism and damage can provide information about muscle function properties and adaptations to physical effort in different types of athletes.

Epinephrine stimulates IL-6 expression in skeletal muscle and C2C12 myoblasts: role of c-Jun NH2-terminal kinase and histone deacetylase activity

Although an individual's genetic makeup is a major determinant of muscle mass, other influences, such as hormones, cytokines, nutrition, and exercise can also modulate muscle size. IL-6 is an important inflammatory cytokine. Mice that overexpress IL-6 fail to thrive and/or have reduced skeletal muscle mass. The purpose of the present study was to determine whether the stress hormone epinephrine increases inflammatory cytokine expression in skeletal muscle and muscle cells. Infusion of epinephrine in vivo for 2 h increased IL-6 protein (15-fold) and mRNA (40-fold) in skeletal muscle but not in liver. Epinephrine had a similar effect in C2C12 muscle cells, where the hormone increased IL-6 protein and mRNA in a dose- and time-dependent manner. Epinephrine-stimulated IL-6 expression was attenuated by the alpha-adrenergic receptor antagonist phentolamine and completely blocked by either the beta1/2-adrenergic receptor antagonist propranalol or the beta2-antagonist ICI-118551. The transcriptional inhibitor DRB and the synthetic glucocorticoid dexamethasone also blocked epinephrine-induced IL-6. SP-600125 (a JNK inhibitor) and SB-202190 (a p38 MAP kinase inhibitor) completely blocked epinephrine-induced IL-6 synthesis. Endotoxin and epinephrine given together had a synergistic affect on IL-6 mRNA and protein expression. Trichostatin A (a histone deacetylase inhibitor) blocked both endotoxin- and epinephrine-induced IL-6 expression. These data suggest that epinephrine induces IL-6 synthesis in skeletal muscle in vivo and myocytes in vitro. Epinephrine utilizes predominantly the beta1/2-adrenergic receptors to stimulate IL-6 synthesis. Endotoxin and epinephrine synergize to increase IL-6 mRNA expression. Optimal IL-6 synthesis may require both stress kinase and histone deacetylase activity.

Regulation of adipocytokines and insulin resistance

It has long been known that obesity and insulin resistance are linked. Recently, it has been shown that adipocytes secrete several proteins including tumour necrosis factor-alpha, interleukin-6, resistin, and adiponectin. Since several of these so-called adipocytokines influence insulin sensitivity and glucose metabolism profoundly, they might provide a molecular link between increased adiposity and impaired insulin sensitivity. Thiazolidinediones which decrease insulin resistance and are used in the treatment of Type 2 diabetes seem to mediate part of their insulin-sensitising effects via modulation of adipocytokine expression. Furthermore, hormones such as beta-adrenergic agonists, insulin, glucocorticoids, and growth hormone might impair insulin sensitivity at least in part via up-regulation or down-regulation of adipocytokine synthesis. We summarise the current knowledge on how major adipocyte-secreted proteins are regulated by hormones and drugs influencing insulin sensitivity and discuss its implications for insulin resistance and obesity.

In vivo stimulation of sympathetic nervous system modulates osteoblastic activity in mouse calvaria

Previously, we demonstrated that epinephrine induced the expression of interleukin (IL)-6 mRNA via beta-adrenoceptors in cultured human osteoblastic cells. IL-6 is well known to modulate bone metabolism by regulating the development and function of osteoclasts and osteoblasts. Recently, restraint stress and intracerebroventricular injection of lipopolysaccharide (LPS) have been reported to induce the expression of IL-6 mRNA in peripheral organs in mice in which expression is mediated by the activation of the sympathetic nervous system. To prove the physiological role of sympathetic nerves in bone metabolism in vivo, we examined by RT-PCR analysis the effects of restraint stress and intracerebroventricular injection of LPS on IL-6 mRNA expression in mouse calvaria. The expression of IL-6 mRNA in mouse calvaria was stimulated by either restraint stress (30 min) or intracerebroventricular injection of LPS (50 ng/mouse, 60 min). The treatment of mice with the neurotoxin 6-hydroxydopamine (6-OHDA, 100 mg x kg-1 x day-1 ip for 3 days) inhibited LPS (icv)-induced expression of IL-6 mRNA in their calvaria. The expression of IL-6 mRNA induced by the restraint stress was not influenced by 6-OHDA, which destroys noradrenergic nerve terminals. Furthermore, pretreatment with a beta-blocker, propranolol (15 or 25 mg/kg ip), inhibited both stress- and LPS-induced increases in the level of IL-6 mRNA, but pretreatment with an alpha-blocker, phentolamine (5 mg/kg sc), did not inhibit them in mouse calvaria. In addition, treatment of calvaria with isoprenaline or norepinephrine increased IL-6 synthesis in the organ culture system. These results indicate that in vivo adrenergic stimulation modulates the osteoblastic activity in mouse calvaria via noradrenergic nerve terminals.