Mechanisms of host wasting induced by administration of cytokines in rats

Correlation Between Serum Tumor Necrosis Factor-Alpha (TNF-α) and Clinical Severity of Tuberculosis: A Hospital-Based Study

AIM

The main aim of this study was to assess the correlation between serum tumor necrosis factor-alpha (TNF-α) levels the and clinical severity of tuberculosis.

METHODS

This was a hospital-based case-control prospective study and was conducted at the Sher-i-Kashmir Institute of Medical Sciences, a tertiary care hospital in the northern part of India, from May 2016 to May 2018. The subjects were recruited in the study considering inclusion and exclusion criteria. All patients with pulmonary tuberculosis as well as patients with extrapulmonary tuberculosis were included as subjects and a clinical severity score based on anemia, weight loss, presence of hypoxia, and radiological features was calculated and compared with TNF-α levels. Age- and sex-matched healthy individuals were recruited as controls.

RESULTS

A total of 75 subjects comprising 50 cases and 25 controls were taken for the study. There were 34 (68.0%) patients with elevated TNF-α levels while only 16 (32.0%) patients had normal TNF-α levels. And, TNF-α levels were normal in 21 (84%) control subjects as compared to tuberculosis (TB) patients. Such difference in serum TNF-α levels between cases and controls was statistically significant (p<0.05). The mean serum TNF-α level in TB cases was 1265.63 pg/mL, while the mean serum TNF-α level in controls was 312.06 pg/mL. The difference in serum TNF-α levels between the two groups was statistically significant (p<0.01). We observed a significant increase in serum TNF-α levels with the increase in clinical severity score.

CONCLUSION

Serum TNF-α levels were significantly associated with increased severity of TB.

Myocardial Injury and Overload among Amateur Marathoners as Indicated by Changes in Concentrations of Cardiovascular Biomarkers

Marathons continue to grow in popularity among amateurs. However, the impact of intensive exercise on the amateur's cardiovascular system has not yet been studied. Analysis of the influence of the marathon on kinetics of biomarkers reflecting cardiac injury and overload may bring new insights into this issue. We investigated the effect of running a marathon on the concentrations of high sensitivity cardiac troponin I (hs-cTnI), heart-type fatty acid binding protein (H-FABP), N-terminal proatrial natriuretic peptide (NT-proANP), B-type natriuretic peptide (BNP), growth differentiation factor 15 (GDF-15) and galectin 3 (Gal-3) in the population of male amateur runners. The study included 35 amateur marathoners and followed 3 stages: S1-two weeks prior to the marathon, S2-at the finish line and S3-two weeks after. Blood samples were collected at each stage and analyzed for biomarkers and laboratory parameters. Concentrations of all studied biomarkers were significantly higher at S2, whereas at S3 did not differ significantly compared to S1. Running a marathon by an amateur causes an acute rise in biomarkers of cardiac injury and stress. Whether repetitive bouts of intensive exercise elicit long-term adverse cardiovascular effects in amateur marathoners needs further research.

Magnolol Attenuates Cisplatin-Induced Muscle Wasting by M2c Macrophage Activation

Cancer chemotherapy induces sarcopenia, which is a rapid loss of muscle mass that directly restricts daily activities and leads to poor quality of life and increased mortality. Although hormone-related therapies have been used to improve appetite and nutritional status, current treatments are considered palliative. Thus, the protection of skeletal muscle loss without adverse effects is essential to allow the maintenance of chemotherapy in cancer patients. Magnolol from Magnolia officinalis has several pharmacological effects including anti-cancer and anti-inflammatory activities, but the protection from muscle atrophy is not well-understood. In the present study, we investigated the effects of magnolol on muscle wasting and macrophage subtypes in a cisplatin-induced sarcopenia mouse model. We showed that magnolol significantly attenuated the body weight and the muscle loss induced by cisplatin injection. The diameter of the tibialis anterior muscle was markedly increased after magnolol treatment in cisplatin-treated mice. Importantly, magnolol increased macrophage infiltration into skeletal muscle while not affecting proliferation of macrophages. Magnolol attenuated the imbalance of M1/M2c macrophages by increasing CD206⁺CD163⁺ M2c tissue reparative macrophages. Further, magnolol increased insulin-like growth factor (IGF)-1 expression. This effect was also observed in bone marrow-derived macrophages upon magnolol treatment. Taken together, magnolol may be a promising chemoprotective agent for the prevention of muscle atrophy through the upregulating M2c macrophages, which are a major source of IGF-1.

Are Antioxidants a Potential Therapy for FSHD? A Review of the Literature

Facioscapulohumeral muscular dystrophy (FSHD) is an inherited myopathy affecting approximately 1 in 7500 individuals worldwide. It is a progressive disease characterised by skeletal muscle weakness and wasting. A genetic mutation on the 4q35 chromosome results in the expression of the double homeobox 4 gene (DUX4) which drives oxidative stress, inflammation, toxicity, and atrophy within the skeletal muscle. FSHD is characterised by oxidative stress, and there is currently no cure and a lack of therapies for the disease. Antioxidants have been researched for many years, with investigators aiming to use antioxidants therapeutically for oxidative stress-associated diseases. This has included both natural and synthetic antioxidants. The use of antioxidants in preclinical or clinical models has been largely successful with a plethora of research reporting positive results. However, when translated to clinical trials, the use of antioxidants as a therapeutic intervention for a variety of disease has been largely unsuccessful. Moreover, specifically focusing on FSHD, limited research has been conducted on the use of antioxidants as a therapy in either preclinical or clinical models. This review summarises the current state of antioxidant use in the treatment of FSHD and discusses their potential avenue for therapeutic use for FSHD patients.

Optimum polygenic profile to resist exertional rhabdomyolysis during a marathon

Purpose

Exertional rhabdomyolysis can occur in individuals performing various types of exercise but it is unclear why some individuals develop this condition while others do not. Previous investigations have determined the role of several single nucleotide polymorphisms (SNPs) to explain inter-individual variability of serum creatine kinase (CK) concentrations after exertional muscle damage. However, there has been no research about the interrelationship among these SNPs. The purpose of this investigation was to analyze seven SNPs that are candidates for explaining individual variations of CK response after a marathon competition (ACE = 287bp Ins/Del, ACTN3 = p.R577X, CKMM = NcoI, IGF2 = C13790G, IL6 = 174G>C, MLCK = C37885A, TNFα = 308G>A).

Methods

Using Williams and Folland’s model, we determined the total genotype score from the accumulated combination of these seven SNPs for marathoners with a low CK response (n = 36; serum CK <400 U·L^-1) vs. marathoners with a high CK response (n = 31; serum CK ≥400 U·L^-1).

Results

At the end of the race, low CK responders had lower serum CK (290±65 vs. 733±405 U·L^-1; P<0.01) and myoglobin concentrations (443±328 vs. 1009±971 ng·mL^-1, P<0.01) than high CK responders. Although the groups were similar in age, anthropometric characteristics, running experience and training habits, total genotype score was higher in low CK responders than in high CK responders (5.2±1.4 vs. 4.4±1.7 point, P = 0.02).

Conclusion

Marathoners with a lower CK response after the race had a more favorable polygenic profile than runners with high serum CK concentrations. This might suggest a significant role of genetic polymorphisms in the levels of exertional muscle damage and rhabdomyolysis. Yet other SNPs, in addition to exercise training, might also play a role in the values of CK after damaging exercise.

Genetic variation and exercise-induced muscle damage: implications for athletic performance, injury and ageing

Prolonged unaccustomed exercise involving muscle lengthening (eccentric) actions can result in ultrastructural muscle disruption, impaired excitation-contraction coupling, inflammation and muscle protein degradation. This process is associated with delayed onset muscle soreness and is referred to as exercise-induced muscle damage. Although a certain amount of muscle damage may be necessary for adaptation to occur, excessive damage or inadequate recovery from exercise-induced muscle damage can increase injury risk, particularly in older individuals, who experience more damage and require longer to recover from muscle damaging exercise than younger adults. Furthermore, it is apparent that inter-individual variation exists in the response to exercise-induced muscle damage, and there is evidence that genetic variability may play a key role. Although this area of research is in its infancy, certain gene variations, or polymorphisms have been associated with exercise-induced muscle damage (i.e. individuals with certain genotypes experience greater muscle damage, and require longer recovery, following strenuous exercise). These polymorphisms include ACTN3 (R577X, rs1815739), TNF (-308 G>A, rs1800629), IL6 (-174 G>C, rs1800795), and IGF2 (ApaI, 17200 G>A, rs680). Knowing how someone is likely to respond to a particular type of exercise could help coaches/practitioners individualise the exercise training of their athletes/patients, thus maximising recovery and adaptation, while reducing overload-associated injury risk. The purpose of this review is to provide a critical analysis of the literature concerning gene polymorphisms associated with exercise-induced muscle damage, both in young and older individuals, and to highlight the potential mechanisms underpinning these associations, thus providing a better understanding of exercise-induced muscle damage.

Leptin, IL-6, and suPAR reflect distinct inflammatory changes associated with adiposity, lipodystrophy and low muscle mass in HIV-infected patients and controls

Background

HIV-infected patients could exhibit accelerated ageing, since age-associated complications like sarcopenia; increased inflammation; lipodystrophy with loss of subcutaneous adipose tissue and/or gain of visceral adipose tissue (VAT); and cardiovascular disease occur at an earlier age. Inflammation is involved in age-associated complications. However, it is not understood whether it is the same inflammatory changes that are involved in the various ageing-associated complications. Our objective was to study whether leptin, interleukin 6 (IL-6), and soluble urokinase plasminogen activator receptor (suPAR) were associated distinctively with adiposity, lipodystrophy and sarcopenia, in HIV-infected patients and healthy Controls.

Results

Systemic leptin levels were significantly higher in patients with lipodystrophy than without, whereas there was no difference in IL-6 or suPAR levels. Leptin was significantly positively associated with fat mass index (FMI) and abdominal VAT, but not with lean mass index (LMI). IL-6 was significantly associated with both FMI and VAT, and low LMI. High suPAR was associated with low LMI, and weakly with high FMI and VAT.

Conclusions

Leptin reflected adiposity- and lipodystrophy-related inflammation, but not sarcopenia. IL-6 reflected both adiposity-, but also sarcopenia-related inflammation; and suPAR was a marker of sarcopenia-related inflammation. Our results indicate that different inflammatory processes can be active simultaneously contributing to the systemic low grade inflammatory state. Identifying major contributors to circulating leptin, IL-6, and suPAR levels could levels could therefore improve our understanding of which inflammatory processes are involved in the various age-related complications.

Toll-like receptor (TLR4) Asp299Gly and Thr399Ile polymorphisms in relation to clinical falciparum malaria among Nigerian children: a multisite cross-sectional immunogenetic study in Lagos

INTRODUCTION

This study determined the association of TLR4 Asp299Gly and Thr399Ile with uncomplicated and severe malaria among Nigerian children of similar ethnic background in Lagos. The association of these SNPs with high parasite density, malnutrition, hyperpyrexia and anaemia was also investigated.

METHODS

Genomic DNA of the study participants was screened for the genotypes of TLR4 Asp299Gly and Thr399Ile by PCR-RFLP. Anthropometric measurement was performed on the Pf infected children stratified into asymptomatic malaria (control), uncomplicated and severe malaria (case). Parasites were detected by light microscopy and Hardy Weinberg Equilibrium (HWE) of SNP genotypes was also determined.

RESULTS

A total of 279 children comprising 182 children (62.1 % male; mean ± SEM age, 57.3 ± 1.7 months) with clinical falciparum malaria and 97 children (55.7 % male; mean ± SEM age, 55.6 ± 2.5 years) with asymptomatic falciparum malaria were enrolled. All the genotypes of both TLR4 SNPs were found in the study population with their minor alleles: 299Gly and 399Ile, found to be 17.6 % and 14.7 % in severe malaria children. Unlike in asymptomatic population, the genotype distribution of TLR4 Asp299Gly SNP was not in HWE in the clinical malaria group but did not condition susceptibility. However, Asp299Gly and Thr399Ile polymorphisms were found to increase the risk of severe malaria 3-fold and 8-fold respectively (P < 0.05). They also increased the risk of severe anaemia, high parasite density and severe malnutrition 3.8 -5.3-fold, 3.3 - 4.4-fold and 4-fold respectively.

CONCLUSIONS

Based on the above findings, we conclude that TLR4 Asp299Gly and Thr399Ile polymorphisms may modulate susceptibility to severe malaria among Nigerian children of Yoruba ethnic background.

Immune Function and Muscle Adaptations to Resistance exercise in Older Adults: Study Protocol for a Randomized Controlled Trial of a Nutritional Supplement

BACKGROUND

Immune function may influence the ability of older adults to maintain or improve muscle mass, strength, and function during aging. Thus, nutritional supplementation that supports the immune system could complement resistance exercise as an intervention for age-associated muscle loss. The current study will determine the relationship between immune function and exercise training outcomes for older adults who consume a nutritional supplement or placebo during resistance training and post-training follow-up. The supplement was chosen due to evidence suggesting its ingredients [arginine (Arg), glutamine (Gln), and β-hydroxy β-methylbutyrate (HMB)] can improve immune function, promote muscle growth, and counteract muscle loss.

METHODS/DESIGN

Veterans (age 60 to 80 yrs, N = 50) of the United States military will participate in a randomized double-blind placebo-controlled trial of consumption of a nutritional supplement or placebo during completion of three study objectives: 1) determine if 2 weeks of supplementation improve immune function measured as the response to vaccination and systemic and cellular responses to acute resistance exercise; 2) determine if supplementation during 36 sessions of resistance training boosts gains in muscle size, strength, and function; and 3) determine if continued supplementation for 26 weeks post-training promotes retention of training-induced gains in muscle size, strength, and function. Analyses of the results for these objectives will determine the relationship between immune function and the training outcomes. Participants will undergo nine blood draws and five muscle (vastus lateralis) biopsies so that the effects of the supplement on immune function and the systemic and cellular responses to exercise can be measured.

DISCUSSION

Exercise has known effects on immune function. However, the study will attempt to modulate immune function using a nutritional supplement and determine the effects on training outcomes. The study will also examine post-training benefit retention, an important issue for older adults, usually omitted from exercise studies. The study will potentially advance our understanding of the mechanisms of muscle gain and loss in older adults, but more importantly, a nutritional intervention will be evaluated as a complement to exercise for supporting muscle health during aging.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02261961, registration date 10 June 2014, recruitment active.

Characterization and regulation of mechanical loading-induced compensatory muscle hypertrophy

In mammalian systems, skeletal muscle exists in a dynamic state that monitors and regulates the physiological investment in muscle size to meet the current level of functional demand. This review attempts to consolidate current knowledge concerning development of the compensatory hypertrophy that occurs in response to a sustained increase in the mechanical loading of skeletal muscle. Topics covered include: defining and measuring compensatory hypertrophy, experimental models, loading stimulus parameters, acute responses to increased loading, hyperplasia, myofiber-type adaptations, the involvement of satellite cells, mRNA translational control, mechanotransduction, and endocrinology. The authors conclude with their impressions of current knowledge gaps in the field that are ripe for future study.

Treatment of cachexia: melanocortin and ghrelin interventions

Cachexia is a condition typified by wasting of fat and LBM caused by anorexia and further endocrinological modulation of energy stores. Diseases known to cause cachectic symptoms include cancer, chronic kidney disease, and chronic heart failure; these conditions are associated with increased levels of proinflammatory cytokines and increased resting energy expenditure. Early studies have suggested the central melanocortin system as one of the main mediators of the symptoms of cachexia. Pharmacological and genetic antagonism of these pathways attenuates cachectic symptoms in laboratory models; effects have yet to be studied in humans. In addition, ghrelin, an endogenous orexigenic hormone with receptors on melanocortinergic neurons, has been shown to ameliorate symptoms of cachexia, at least in part, by an increase in appetite via melanocortin modulation, in addition to its anticatabolic and anti-inflammatory effects. These effects of ghrelin have been confirmed in multiple types of cachexia in both laboratory and human studies, suggesting a positive future for cachexia treatments.

TNF-Alpha in the Locomotor System beyond Joints: High Degree of Involvement in Myositis in a Rabbit Model

The importance of TNF-alpha in arthritis is well documented. It may be that TNF-alpha is also markedly involved in muscle inflammation (myositis). An animal model where this can be investigated is needed. A newly developed rabbit myositis model involving pronounced muscle overuse and local injections of substances having proinflammatory effects was therefore used in the present study. The aim was to investigate the patterns of TNF-alpha expression in the developing myositis and to evaluate the usefulness of this myositis model for further TNF-alpha research. Human rheumatoid arthritis (RA) synovial tissue was examined as a reference. TNF-alpha immunoexpression and TNF-alpha mRNA, visualized via in situ hybridization, were detected in cells in the inflammatory infiltrates of the affected muscle (soleus muscle). Coexistence of TNF-alpha and CD68 immunoreactions was noted, suggesting that the TNF-alpha reactive cells are macrophages. Expression of TNF-alpha mRNA was also noted in muscle fibers and blood vessel walls in areas with inflammation. These findings demonstrate that TNF-alpha is highly involved in the myositis process. The model can be used in further studies evaluating the importance of TNF-alpha in developing myositis.

Body weight loss after myocardial infarction in rats as a marker of early heart failure development

BACKGROUND AND AIMS

We evaluated the use of body weight (BW) loss soon after acute myocardial infarction (MI) in rats as a marker of acute heart failure (HF).

METHODS

Female Wistar rats (200-240 g) were submitted either to sham operation or to coronary artery occlusion. In individual cages, daily BW and food and water intake were measured. Seven days later, cardiac function was evaluated by left ventricular catheterization. HF was defined by a left ventricular end-diastolic pressure greater than the upper limit of the 95% confidence interval. MI group was then divided into those that developed HF (n = 27; MI-HF) and those that did not (n = 47; MI).

RESULTS

The MI-HF group experienced increased BW loss (sham: 4.2 ± 0.6% MI: 0.4 ± 0.8%, MI-HF: -4.9 ± 1.2%; p <0.05) and reduced water and food intake compared with other groups. HF animals showed greater lung weight (sham: 1.460 ± 0.076 g, MI: 1.748 ± 0.086 g, MI-HF: 2.033 ± 0.13 g; p <0.05). Infarct area was significantly different between the groups (MI: 35.9 ± 0.9%, MI-HF: 39.7 ± 1.3%; p <0.05). ROC curve showed that BW loss over 7 days has 100% sensitivity and 72.3% specificity for identifying acute HF. Moreover, excluding the effect of infarct area on these results, a sample of animals with the same infarct area displayed similar morphometric and hemodynamic patterns as the entire sample. Multivariate linear regression analysis confirmed that BW loss is a HF marker independent of infarct area.

CONCLUSIONS

BW is an easy and reliable noninvasive method to detect HF early after MI in rats.

Decreased limb muscle and increased central adiposity are associated with 5-year all-cause mortality in HIV infection

BACKGROUND

Unintentional loss of weight and muscle due to aging and disease has been associated with increased mortality. Wasting and weight loss occur in HIV infection even in the modern era of effective antiretroviral therapy.

METHODS

We determined the association of MRI-measured regional and total skeletal muscle and adipose tissue with 5-year, all-cause mortality in 922 HIV-infected persons in the study of Fat Redistribution and Metabolic Change in HIV Infection (FRAM).

RESULTS

After 5 years of follow-up, HIV-infected participants with arm skeletal muscle in the lowest tertile had a mortality rate of 23%, compared with 11 and 8% for those in the middle and highest tertiles. After multivariable adjustment for demographics, cardiovascular risk factors, HIV-related factors, inflammatory markers, and renal disease, we found that lower arm skeletal muscle, lower leg skeletal muscle and higher visceral adipose tissue (VAT) were each independently associated with increased mortality. Those in the lowest tertile of arm or leg skeletal muscle had higher odds of death [arm: odds ratio (OR) = 2.0, 95% confidence interval (CI) 0.96-4.0; leg: OR = 2.4, 95% CI 1.2-4.8] compared with the highest respective tertiles. Those in the highest tertile of VAT had 2.1-fold higher odds of death (95% CI 1.1-4.0) compared with the lowest VAT tertile.

CONCLUSION

Lower muscle mass and central adiposity appear to be important risk factors for mortality in HIV-infected individuals. A substantial proportion of this risk may be unrecognized because of the current reliance on body mass index in clinical practice.

Does Vitamin E and C Supplementation Improve the Recovery From Anterior Cruciate Ligament Surgery?

Muscular (quadriceps) weakness is a predominant impairment that follows anterior cruciate ligament injury and surgery. This continued weakness impairs activities of daily living and could predispose patients to adverse conditions later in life, such as knee osteoarthritis. Vitamins E and C have potent antioxidant and anti-inflammatory activity. Herein, the authors summarize the state-of-the science and suggest directions for future research endeavors regarding the therapeutic influence of vitamins E and C, or other antioxidants, on the recovery from anterior cruciate ligament injury and surgery.

The muscle fiber type-fiber size paradox: hypertrophy or oxidative metabolism?

An inverse relationship exists between striated muscle fiber size and its oxidative capacity. This relationship implies that muscle fibers, which are triggered to simultaneously increase their mass/strength (hypertrophy) and fatigue resistance (oxidative capacity), increase these properties (strength or fatigue resistance) to a lesser extent compared to fibers increasing either of these alone. Muscle fiber size and oxidative capacity are determined by the balance between myofibrillar protein synthesis, mitochondrial biosynthesis and degradation. New experimental data and an inventory of critical stimuli and state of activation of the signaling pathways involved in regulating contractile and metabolic protein turnover reveal: (1) higher capacity for protein synthesis in high compared to low oxidative fibers; (2) competition between signaling pathways for synthesis of myofibrillar proteins and proteins associated with oxidative metabolism; i.e., increased mitochondrial biogenesis via AMP-activated protein kinase attenuates the rate of protein synthesis; (3) relatively higher expression levels of E3-ligases and proteasome-mediated protein degradation in high oxidative fibers. These observations could explain the fiber type-fiber size paradox that despite the high capacity for protein synthesis in high oxidative fibers, these fibers remain relatively small. However, it remains challenging to understand the mechanisms by which contractile activity, mechanical loading, cellular energy status and cellular oxygen tension affect regulation of fiber size. Therefore, one needs to know the relative contribution of the signaling pathways to protein turnover in high and low oxidative fibers. The outcome and ideas presented are relevant to optimizing treatment and training in the fields of sports, cardiology, oncology, pulmonology and rehabilitation medicine.

Are tumoral factors responsible for host tissue wasting in cancer cachexia?

Both cytokines and tumor factors have been implicated in tissue loss in cancer cachexia. Loss of adipose tissue is most likely due to the tumor (and host) factor zinc-alpha2-glycoprotein because of its direct lipolytic effect, ability to sensitize adipocytes to lipolytic stimuli and increased expression in cachexia. TNF-alpha and the tumor factor proteolysis-inducing factor are the major contenders for skeletal muscle atrophy; both increase protein degradation through the ubiquitin-proteasome pathway and depress protein synthesis through phosphorylation of eukaryotic initiation factor 2 alpha. However, while most studies report proteolysis-inducing factor levels to correlate with the appearance of cachexia, there is some disagreement regarding a correlation between serum levels of TNF-alpha and weight loss. Furthermore, only antagonists to proteolysis inducing factor prevent muscle loss in cancer patients, suggesting that tumor factors are the most important.

Aging and its effects on inflammation in skeletal muscle at rest and following exercise-induced muscle injury

The world's elderly population is expanding rapidly, and we are now faced with the significant challenge of maintaining or improving physical activity, independence, and quality of life in the elderly. Counteracting the progressive loss of muscle mass that occurs in the elderly, known as sarcopenia, represents a major hurdle in achieving these goals. Indirect evidence for a role of inflammation in sarcopenia is that markers of systemic inflammation correlate with the loss of muscle mass and strength in the elderly. More direct evidence is that compared with skeletal muscle of young people, the number of macrophages is lower, the gene expression of several cytokines is higher, and stress signaling proteins are activated in skeletal muscle of elderly people at rest. Sarcopenia may also result from inadequate repair and chronic maladaptation following muscle injury in the elderly. Macrophage infiltration and the gene expression of certain cytokines are reduced in skeletal muscle of elderly people compared with young people following exercise-induced muscle injury. Further research is required to identify the cause(s) of inflammation in skeletal muscle of elderly people. Additional work is also needed to expand our understanding of the cells, proteins, and transcription factors that regulate inflammation in the skeletal muscle of elderly people at rest and after exercise. This knowledge is critical for devising strategies to restrict sarcopenia, and improve the health of today's elderly population.

The role of systemic inflammation in age-related muscle weakness and wasting

Ageing is associated with a slow, but progressive muscle weakness, which is largely attributable to muscle wasting. A diminished function of satellite cells at old age may hamper preservation and repair from (contraction)-induced injury and contribute to the age-related muscle wasting. Satellite cell function may be affected by circulating factors, as muscle regeneration in old mice sharing the circulation of young mice is not impaired. Chronic low-grade systemic inflammation in old organisms may be that environmental factor. Indeed, the inflammatory cytokine tumor necrosis factor-alpha (TNFalpha) negatively affects the muscle regenerating capacity. TNFalpha destabilizes MyoD, a muscle-specific transcription factor involved in satellite cell proliferation and differentiation, and induces apoptosis of satellite cells, particularly at old age. Here it is proposed that some of these effects are mediated by TNFalpha-induced expression of inhibitors of differentiation proteins. Yet, the increase in TNFalpha during the normal inflammatory response helps, rather than impairs, the repair process. This apparent contradiction may be resolved by the fact that the effects of TNFalpha are concentration and time dependent. Thus, the negative effect of systemic inflammation on muscle strength at old age may only become apparent when it exceeds a certain threshold and persists for a prolonged period.

Skeletal muscle growth in young rats is inhibited by chronic exposure to IL-6 but preserved by concurrent voluntary endurance exercise

Childhood diseases are often accompanied by chronic inflammation, which is thought to negatively impact growth. Interleukin-6 (IL-6) is typically cited as an indicator of inflammation and is linked to impaired growth. This study was designed to isolate and identify potential effects of chronic IL-6 exposure on skeletal muscle growth during development. A second aim was to determine if endurance exercise, thought to antagonize chronic inflammation, would interact with any effects of IL-6. The muscles of one leg of rapidly growing rats were exposed to IL-6 or vehicle for 14 days. Subgroups of IL-6-infused rats were provided access to running wheels. Local IL-6 infusion resulted in approximately 13% muscle growth deficit (myofibrillar protein levels). Exercise (>4,000 m/day) prevented this deficit. IL-6 infusion increased mRNA for suppressor of cytokine signaling-3 (SOCS3) and tumor necrosis factor-alpha (TNF-alpha), and this was not prevented by exercise. IL-6 infusion increased the mRNAs for atrogin, insulin-like growth factor-I (IGF-I), and IGF binding protein-4 (IGFBP4), and these effects were mitigated by exercise. Exercise stimulated an increase in total RNA ( approximately 19%) only in the IL-6-infused muscle, suggesting that a compensatory increase in translational capacity was required to maintain muscle growth. This study indicates that IL-6 exposure during periods of rapid growth in young animals can retard growth possibly via interactions with key growth factors. Relatively high volumes of endurance-type exercise do not exacerbate the negative effects of IL-6 and in fact were found to be beneficial in protecting muscle growth.

IL6 (-174) and TNFA (-308) promoter polymorphisms are associated with systemic creatine kinase response to eccentric exercise

Exertional rhabdomyolysis is a complex and poorly understood entity. The inflammatory system has an important role in muscle injury and repair. Serum creatine kinase (CK) is often used as systemic biomarker representing muscle damage. Considerable variation exists in CK response between different subjects. Genetic elements may act as predisposition factors for exertional rhabdomyolysis. Based on their biological activity, we hypothesized that in healthy subjects IL6 G-174C and TNFA G-308A promoter polymorphisms would be associated with CK response to exercise. We determined serum CK activity pre- and post-maximal eccentric contractions of the elbow flexor muscles. IL6 G-174C and TNFA G-308A genotypes were analyzed for possible relationship with changes in serum CK activity. IL6 G-174C genotype was associated with CK activity in a dose-dependent fashion. Subjects with one or more of the -174C allele had a greater increase and higher peak CK values than subjects homozygous for the G allele (mean +/- SE U/L: GG, 2,604 +/- 821; GC, 7,592 +/- 1,111; CC, 8,403 +/- 3,849, ANOVA P = 0.0003 for GG + GC genotypes versus CC genotype, P = 0.0005 for linear trend). IL6-174CC genotype was associated with a greater than threefold increased risk of massive CK response (adjusted odds ratio 3.29, 95% confidence interval 1.27-7.85, P = 0.009). A milder association (P = 0.06) was noted between TNFA G-308A genotype and CK activity. In conclusion, we found a strong association of the IL6 G-174C genotype with systemic CK response to strenuous exercise. Data suggest that homozygosity for the IL6-174C allele is a clinically important risk factor for exercise-induced muscle injury, further supporting the central role of cytokines in the reactive inflammatory process of muscle damage and repair.

Blood concentrations of the cytokines IL-1beta, IL-6, IL-10, TNF-alpha and IFN-gamma during experimentally induced swine dysentery

Background

Knowledge of the cytokine response at infection with Brachyspira hyodysenteriae can help understanding disease mechanisme involved during swine dysentery. Since this knowledge is still limited the aim of the present study was to induce dysentery experimentally in pigs and to monitor the development of important immunoregulatory cytokines in blood collected at various stages of the disease.

Methods

Ten conventional pigs (~23 kg) were orally inoculated with Brachyspira hyodysenteriae B204^T. Eight animals developed muco-haemorrhagic diarrhoea with impaired general body condition. Blood was sampled before inoculation and repeatedly during acute dysentery and recovery periods and cytokine levels of IL-1β, IL-6, Il-10, TNF-α and IFN-γ were measured by ELISA.

Results

IL-1β was increased at the beginning of the dysentery period and coincided with the appearance of Serum amyloid A and clinical signs of disease. TNF-α increased in all animals after inoculation, with a peak during dysentery, and IL-6 was found in 3 animals during dysentery and in the 2 animals that did not develop clinical signs of disease. IL-10 was found in all sick animals during the recovery period. IFN-γ was not detected on any occasion.

Conclusion

B. hyodysenteriae inoculation induced production of systemic levels of IL-1β during the dysentery period and increased levels of IL-10 coincided with recovery from dysentery.

Central blockade of melanocortin receptors attenuates the metabolic and locomotor responses to peripheral interleukin-1beta administration

Loss of appetite and cachexia is an obstacle in the treatment of chronic infection and cancer. Proinflammatory cytokines released from activated immune cells and acting in the central nervous system (CNS) are prime candidates for mediating these metabolic changes, potentially affecting both energy intake as well as energy expenditure. The effect of intravenous administration of two proinflammatory cytokines, interleukin (IL)-1beta (15 microg/kg) and tumor necrosis factor (TNF)-alpha (10 microg/kg), on food and water intake, locomotor activity, oxygen consumption (VO2), and respiratory exchange ratio (RER) was evaluated. The two cytokines elicited a comparable decrease in food intake and activated similar numbers of cells in the paraventricular nucleus of the hypothalamus (PVH), a region that plays a critical role in the regulation of appetite and metabolism (determined via expression of the immediate early gene, c-fos). However, only IL-1beta reduced locomotion and RER, and increased VO2, while TNF-alpha was without effect. To examine the role of the melanocortins in mediating IL-1beta- induced metabolic changes, animals were pretreated centrally with a melanocortin receptor antagonist, HS014. Pretreatment with HS014 blocked the effect of IL-1beta on food intake and RER at later time points (beyond 8 h post injection), as well as the hypoactivity and increased metabolic rate. Further, HS014 blocked the induction of Fos-ir in the PVH. These data highlight the importance of the melanocortin system, particularly within the PVH, in mediating a broad range of metabolic responses to IL-1beta.

Tumor necrosis factor-α promotes the accumulation of neutrophils and macrophages in skeletal muscle

Tumor necrosis factor-α (TNF-α) has been associated with cachexia and is known to regulate multiple inflammatory cell (neutrophil and macrophage) responses. We tested the hypothesis that neutrophils and macrophages accumulate in the extensor digitorum longus (EDL) and soleus muscles of mice after chronic TNF-α administration. Murine recombinant TNF-α (∼100 μg·kg−1·day−1) in vehicle solution or vehicle solution alone (sham) was administered to C57BL/6 mice for 7 days via osmotic minipumps. In EDL muscles from TNF-α-treated mice, neutrophil and macrophage concentrations were elevated seven- and threefold, respectively, compared with sham mice. Neutrophil and macrophage concentrations were also elevated five- and twofold, respectively, in solei of TNF-α- relative to sham-treated mice. Treatment with TNF-α elevated ubiquitin content by ∼25% relative to sham values for both the EDL and soleus muscles; however, these elevations were not statistically significant. No differences were observed between TNF-α- and sham-treated mice in body weight, food consumption, muscle mass, myofiber cross-sectional area, carbonyl groups, total protein content, or relative abundance of myosin heavy chain protein. Furthermore, no overt signs of muscle injury or regeneration were observed in muscles from TNF-α-treated mice in either the EDL or soleus muscles. These observations suggest that 7 days of TNF-α administration promote muscle inflammation as indicated by the accumulation of neutrophils and macrophages without overt signs of atrophy, injury, or regeneration.

IL-6-induced skeletal muscle atrophy

Chronic, low-level elevation of circulating interleukin (IL)-6 is observed in disease states as well as in many outwardly healthy elderly individuals. Increased plasma IL-6 is also observed after intense, prolonged exercise. In the context of skeletal muscle, IL-6 has variously been reported to regulate carbohydrate and lipid metabolism, increase satellite cell proliferation, or cause muscle wasting. In the present study, we used a rodent local infusion model to deliver modest levels of IL-6, comparable to that present after exercise or with chronic low-level inflammation in the elderly, directly into a single target muscle in vivo. The aim of this study was to examine the direct effects of IL-6 on skeletal muscle in the absence of systemic changes in this cytokine. Data included cellular and molecular markers of cytokine and growth factor signaling (phosphorylation and mRNA content) as well as measurements to detect muscle atrophy. IL-6 infusion resulted in muscle atrophy characterized by a preferential loss of myofibrillar protein (-17%). IL-6 induced a decrease in the phosphorylation of ribosomal S6 kinase (-60%) and STAT5 (-33%), whereas that of STAT3 was increased approximately twofold. The changes seen in the IL-6-infused muscles suggest alterations in the balance of growth factor-related signaling in favor of a more catabolic profile. This suggests that downregulation of growth factor-mediated intracellular signaling may be a mechanism contributing to the development of muscle atrophy induced by elevated IL-6.

Interleukin-1 polymorphisms are associated with the inflammatory response in human muscle to acute resistance exercise

Inflammation appears to play an important role in the repair and regeneration of skeletal muscle after damage. We tested the hypothesis that the severity of the inflammatory response in muscle after an acute bout of resistance exercise is associated with single nucleotide polymorphisms (SNPs) previously shown to alter interleukin-1 (IL-1) activity. Using a double-blind prospective design, sedentary young men were screened (n = 100) for enrolment (n = 24) based upon having 1 of 4 haplotype patterns composed of five polymorphic sites in the IL-1 gene cluster: IL-1A (+4845), IL-1B (+3954), IL-1B (-511), IL-1B (-3737) and IL-1RN (+2018). Subjects performed a standard bout of resistance leg exercise and vastus lateralis biopsies were obtained pre-, and at 24, and 72 h post-exercise. Inflammatory marker mRNAs (IL-1beta, IL-6 and tumor necrosis factor-alpha (TNF-alpha)) and the number of CD68(+) macrophages were quantified. Considerable variation was observed in the expression of these gene products between subjects. At 72 h post-exercise, IL-1beta had increased in a number of subjects (n = 10) and decreased (n = 4) or did not change (n = 10) in others. Inflammatory responses were significantly associated with specific haplotype patterns and were also influenced by individual SNPs. Subjects with genotypes 1.1 at IL-1B (+3954) or 2.2 at IL-1B (-3737) had approximately a 2-fold higher median induction of several markers, but no increase in macrophages, suggesting that cytokine gene expression is elevated per macrophage. The IL-1RN (+2018) SNP maximized the response specifically within these groups and was associated with increased macrophage recruitment. This is the first report that IL-1 genotype is associated with the inflammation of skeletal muscle following acute resistance exercise that may potentially affect the adaptations to chronic resistance exercise.

Invited Review: Autocrine/paracrine IGF-I and skeletal muscle adaptation

This brief review presents the basic premises suggesting that insulin-like growth factor I (IGF-I), functioning in an autocrine/paracrine mode, is an important mediator of skeletal muscle adaptation. Key intracellular signaling mechanisms associated with ligation of the primary IGF-I receptor are highlighted to illustrate the mechanisms by which IGF-I may promote muscle hypertrophy. In addition, a number of recent findings are presented that highlight the potential for interactions between IGF-I-related signaling pathways and intracellular signaling mechanisms activated by cytokines or hormonal systems.

Central mechanisms involved with catabolism

PURPOSE OF REVIEW

Catabolism conjures up an end-metabolic process in which muscle and fat tissue are broken down into their constituent parts to provide nutrients for the body, secondary to a noxious stimulus that prevents the organism from adequately nourishing itself. However, catabolism is a primary event, initiated in the brain in response to perceived or real stresses or noxious stimuli, which has a secondary effect of inhibiting food intake and consequently the break down of skeletal muscle and adipose tissues to provide nutrients for the body to survive.

RECENT FINDINGS

This is achieved via a cascade of neurohormonal monoaminergic and peptidergic mediators in the central nervous system, invoking the cortex, the limbic system and the hypothalamus. Among the most detailed mediators studied are corticotropin-releasing factor and serotonin which, via the hypothalamic-pituitary-adrenal axis and the sympathetic and parasympathetic nervous system, stimulate catecholamines and cortisol and inhibit anabolic hormones, insulin, leptin, ghrelin, including neuropeptide Y and other neuropeptides, among them the paracrine-acting cytokines. Simultaneously, there occurs stimulation of the counter-regulatory hormones cortisol, glucagon and the melanocortin family of neuropeptides.

SUMMARY

The net effect is anorexia, with the inhibition of food intake, body weight loss, delayed gastric emptying and functions, the stimulation of gluconeogenesis, glycogenolysis and ketogenesis as sources of metabolic fuel, which if unabated leads ultimately to cachexia. The use of antagonists and the removal of stress or noxious stimuli experimentally test different pathways of this dynamic metabolic picture. Several studies have demonstrated important progress towards our understanding of the central mechanisms involved in anorexia and weight loss, which we summarize in this review.

Peripheral mechanisms involved with catabolism

PURPOSE OF REVIEW

This review summarizes recent developments concerning the mechanisms of skeletal muscle and adipose tissue breakdown, which are a hallmark of cachexia during many diseases. Current knowledge on the hypermetabolism which often contributes to cachexia is also considered.

RECENT FINDINGS

Recent studies have identified interactions between Ca2+, proinflammatory cytokines (in particular tumor necrosis factor-alpha) and the activation of transcription factors (e.g. nuclear factor-kappaB) in the stimulation of major proteolytic pathways in cachexia. Progress has also been made in explaining the inhibiting effects of several drugs on protein breakdown. Advances in our understanding of the mechanisms of adipose tissue catabolism in cachexia include demonstrations that (1) tumor necrosis factor-alpha, in addition to its direct lipolytic effect, promotes adipose tissue breakdown by inhibiting adipocyte differentiation and increasing adipocyte apoptosis, (2) interleukin-6 has a lipolytic effect, and (3) chemokines are expressed by adipocytes and interact with tumor necrosis factor-alpha to cause lipolysis. Concerning the hypermetabolism in cachexia, new evidence supports previous theories that uncoupling protein-2 and 3 are primarily involved in the generation of reactive oxygen species and in the control of fatty acid flux across the mitochondrial membrane, respectively. Furthermore, the cytokine-induced transcriptional coactivator-1 for the peroxysome proliferator-activated receptor-gamma was recently identified as a contributor to hypermetabolism.

SUMMARY

These new insights into major catabolic pathways during cachexia provide a focus for future studies in this area and may help to develop promising therapeutic approaches.

IL-6-like cytokines and cancer cachexia: consequences of chronic inflammation

An estimated 30% of cancer deaths are attributed to cachexia and its consequences. Cachexia (wasting syndrome) is the hypercatabolism of the body's carbon sources, proteins and lipids, for conversion into energy. It is induced by a variety of pathological conditions, including cancer. Among the inflammatory responses to cancer is the synthesis of cytokines, including IL-6 and related cytokines. These cytokines have been found to induce cachexia by altering metabolism of lipids and proteins. IL-6-like cytokines have been found to inhibit lipid biosynthesis by adipocytes, which increased the rate of lipid catabolism. Others have described the atrophy and increased catabolism of muscle protein due to IL-6. A cytokine closely-related to IL-6 is leptin, which plays a major role in lipid metabolism under normal conditions. The role of leptin in pathological conditions such as cancer cachexia has not yet been fully elucidated. Detailed mechanistic information about the induction of cancer cachexia by IL-6-like cytokines requires more research.

Hemodialysis stimulates muscle and whole body protein loss and alters substrate oxidation

The hemodialysis (HD) procedure has been implicated as a potential catabolic factor predisposing the chronic HD (CHD) patients to protein calorie malnutrition. To assess the potential effects of HD on protein and energy metabolism, we studied 11 CHD patients 2 h before, during, and 2 h after HD by use of primed constant infusion of L-[1-13C]leucine and L-[ring-2H5]phenylalanine. Our results showed that HD led to increased whole body (10%) and muscle protein (133%) proteolysis. Simultaneously, whole body protein synthesis did not change, and forearm synthesis increased (120%). The net result was increased net whole body protein loss (96%) and net forearm protein loss (164%). During the 2-h post-HD period, the muscle protein breakdown trended toward baseline, whereas whole body protein breakdown increased further. Substrate oxidation during the post-HD was significantly altered, with diminished carbohydrate and accelerated lipid and amino acid oxidation. These data demonstrate that hemodialysis is an overall catabolic event, decreasing the circulating amino acids, accelerating rates of whole body and muscle proteolysis, stimulating muscle release of amino acids, and elevating net whole body and muscle protein loss.

High blood soluble receptor p80 for tumour necrosis factor-alpha is associated with erythropoietin resistance in haemodialysis patients

BACKGROUND

Inflammation is one of the major causes of resistance to erythropoietin (rHuEpo) treatment. Tumour necrosis factor-alpha (TNF-alpha), one of the most potent proinflammatory cytokines, is known to inhibit human erythropoiesis directly in vitro. Although blood levels of soluble receptors for TNF-alpha (sTNFRs) are elevated in haemodialysis (HD) patients, the role of sTNFR for rHuEpo responsiveness in HD patients remains to be clarified.

METHODS

We measured serum sTNFR (p55 and p80) levels in 83 stable outpatients undergoing regular HD (age 62+/-1, HD duration 15+/-1 years). After dividing the patients into three groups according to rHuEpo dose: (low (L) <60, n=31; moderate (M) > or =60 to <120, n=31; high (H) > or =120 U/kg/week rHuEpo, n=21), we examined the relationship between serum sTNFR levels and the degree of renal anaemia and rHuEpo dosage.

RESULTS

Haemoglobin was significantly higher in patients receiving low rHuEpo dosage (L, 10.5+/-0.2; M, 9.7+/-0.1; H, 9.5+/-0.2 g/dl, P<0.01 vs M and H groups). There were no differences in blood TNF-alpha, sTNFR p55, C-reactive protein, albumin, ferritin, or intact parathyroid hormone levels among the three groups. Body mass index and creatinine generation rate, a marker of whole-body muscle volume, were significantly reduced in group H (P<0.01). Serum sTNFR p80 levels were significantly higher in group H (4.88+/-0.45 ng/ml) than in L (3.73+/-0.14 ng/ml) and M (3.67+/-0.21 ng/ml) groups (P<0.05). The blood interleukin (IL)-6 level was also increased in patients requiring high rHuEpo doses (L, 5.5+/-0.5; M, 6.4+/-0.5; H, 10.2+/-2.0 pg/ml, P<0.05 vs L and H groups). A stepwise regression analysis revealed that gender and sTNFR p80 were significant predictors of rHuEpo dosage. A significant direct relationship was found between rHuEpo dose and sTNFR p80 (r=0.499) and IL-6 (r=0.439) values in women (P<0.01) but not in men.

CONCLUSIONS

These findings suggest that high blood sTNFR p80 may contribute to the development of rHuEpo resistance in female patients undergoing long-term HD.

Role of cytokines in AIDS wasting

There is now a large literature implicating cytokines in the development of wasting and cachexia commonly observed in a variety of pathophysiologic conditions. In the acquired immunodeficiency syndrome (AIDS), cytokines elicited by primary and secondary infections seem to exert subtle and sustained effects on behavioral, hormonal, and metabolic axes, and their combined effects on appetite and metabolism have been postulated to drive wasting. However, correlations of increased blood levels of a particular cytokine with wasting in AIDS have not been consistent observations, perhaps because cytokines act principally as paracrine and autocrine hormones, as well as indirectly by activating other systems. A better understanding of the mechanisms underlying the catabolic effects of cytokines in clearly needed if more efficacious strategies are to be developed for the prevention and treatment of wasting in AIDS. In this review we first examine the interacting factors contributing to the AIDS wasting syndrome. We then analyze the complex and overlapping role of cytokines in the pathophysiology of this condition, and put forward a number of hypotheses to explain some of the most important features of this syndrome.