Humoral mediation for cachexia in tumour-bearing rats

Cancer Cachexia: Signaling and Transcriptional Regulation of Muscle Catabolic Genes

Simple Summary

An uncontrollable loss in the skeletal muscle of cancer patients which leads to a significant reduction in body weight is clinically referred to as cancer cachexia (CC). While factors derived from the tumor environment which trigger various signaling pathways have been identified, not much progress has been made clinically to effectively prevent muscle loss. Deeper insights into the transcriptional and epigenetic regulation of muscle catabolic genes may shed light on key regulators which can be targeted to develop new therapeutic avenues.

Abstract

Cancer cachexia (CC) is a multifactorial syndrome characterized by a significant reduction in body weight that is predominantly caused by the loss of skeletal muscle and adipose tissue. Although the ill effects of cachexia are well known, the condition has been largely overlooked, in part due to its complex etiology, heterogeneity in mediators, and the involvement of diverse signaling pathways. For a long time, inflammatory factors have been the focus when developing therapeutics for the treatment of CC. Despite promising pre-clinical results, they have not yet advanced to the clinic. Developing new therapies requires a comprehensive understanding of how deregulated signaling leads to catabolic gene expression that underlies muscle wasting. Here, we review CC-associated signaling pathways and the transcriptional cascade triggered by inflammatory cytokines. Further, we highlight epigenetic factors involved in the transcription of catabolic genes in muscle wasting. We conclude with reflections on the directions that might pave the way for new therapeutic approaches to treat CC.

Tumor cell anabolism and host tissue catabolism-energetic inefficiency during cancer cachexia

Cancer-associated cachexia (CC) is a pathological condition characterized by sarcopenia, adipose tissue depletion, and progressive weight loss. CC is driven by multiple factors such as anorexia, excessive catabolism, elevated energy expenditure by growing tumor mass, and inflammatory mediators released by cancer cells and surrounding tissues. In addition, endocrine system, systemic metabolism, and central nervous system (CNS) perturbations in combination with cachexia mediators elicit exponential elevation in catabolism and reduced anabolism in skeletal muscle, adipose tissue, and cardiac muscle. At the molecular level, mechanisms of CC include inflammation, reduced protein synthesis, and lipogenesis, elevated proteolysis and lipolysis along with aggravated toxicity and complications of chemotherapy. Furthermore, CC is remarkably associated with intolerance to anti-neoplastic therapy, poor prognosis, and increased mortality with no established standard therapy. In this context, we discuss the spatio-temporal changes occurring in the various stages of CC and highlight the imbalance of host metabolism. We provide how multiple factors such as proteasomal pathways, inflammatory mediators, lipid and protein catabolism, glucocorticoids, and in-depth mechanisms of interplay between inflammatory molecules and CNS can trigger and amplify the cachectic processes. Finally, we highlight current diagnostic approaches and promising therapeutic interventions for CC.

Biomarkers for Cancer Cachexia: A Mini Review

Cancer cachexia is a common condition in many cancer patients, particularly those with advanced disease. Cancer cachexia patients are generally less tolerant to chemotherapies and radiotherapies, largely limiting their treatment options. While the search for treatments of this condition are ongoing, standards for the efficacy of treatments have yet to be developed. Current diagnostic criteria for cancer cachexia are primarily based on loss of body mass and muscle function. However, these criteria are rather limiting, and in time, when weight loss is noticeable, it may be too late for treatment. Consequently, biomarkers for cancer cachexia would be valuable adjuncts to current diagnostic criteria, and for assessing potential treatments. Using high throughput methods such as "omics approaches", a plethora of potential biomarkers have been identified. This article reviews and summarizes current studies of biomarkers for cancer cachexia.

Insulin secretion decline in Walker-256 tumor-bearing rats is early, follows the course of cachexia, and is not improved by lixisenatide

Lixisenatide, a glucagon-like peptide-1 receptor agonist, is used to stimulate insulin secretion in patients with type 2 diabetes mellitus. However, its effect on insulin secretion in cancer patients, particularly during the cachexia course, has not yet been evaluated. The purpose of this study was to investigate the lixisenatide effect on INS secretion decline during the cachexia course (2, 6, and 12 days of tumor) in pancreatic islets isolated from Walker-256 tumor-bearing rats. Pancreatic islets of healthy and tumor-bearing rats were incubated in the presence or absence of lixisenatide (10 nM). Tumor-bearing rats showed reduction of body weight and fat and muscle mass, characterizing the development of cachexia, as well as reduction of insulinemia and INS secretion stimulated by glucose (5.6, 8.3, 11.1, 16.7, and 20 mM) on days 2, 6, and/or 12 of tumor. Lixisenatide increased the 16.7 mM glucose-stimulated insulin secretion, but not by 5.6 mM glucose, in the islets of healthy rats, without changing the insulin intracellular content. However, lixisenatide did not prevent the decreased 16.7 mM glucose-stimulated insulin secretion in the pancreatic islets of rats with 2, 6, and 12 days of tumor and neither the decreased insulin intracellular content of rats with 12 days of tumor. In consistency, in vivo treatment with lixisenatide (50 μg kg-1, SC, once daily, for 6 days) visually increased insulinemia of healthy fasted rats, but did not prevent hypoinsulinemia of tumor-bearing rats. In conclusion, Walker-256 tumor-bearing rats showed early decline (2 days of tumor) of insulin secretion, which followed the cachexia course (6 and 12 days of tumor) and was not improved by lixisenatide, evidencing that this insulin secretagogue, used to treat type 2 diabetes, does not have beneficial effect in cancer bearing-rats.

Evidence of Blood and Muscle Redox Status Imbalance in Experimentally Induced Renal Insufficiency in a Rabbit Model

Chronic kidney disease (CKD) is accompanied by a disturbed redox homeostasis, especially in end-stage patients, which is associated with pathological complications such as anemia, atherosclerosis, and muscle atrophy. However, limited evidence exists about redox disturbances before the end stage of CKD. Moreover, the available redox literature has not yet provided clear associations between circulating and tissue-specific (muscle) oxidative stress levels. The aim of the study was to evaluate commonly used redox status indices in the blood and in two different types of skeletal muscle (psoas, soleus) in the predialysis stages of CKD, using an animal model of renal insufficiency, and to investigate whether blood redox status indices could be reflecting the skeletal muscle redox status. Indices evaluated included reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione reductase (GR), catalase (CAT), total antioxidant capacity (TAC), protein carbonyls (PC), and thiobarbituric acid reactive substances (TBARS). Results showed that blood GSH was higher in the uremic group compared to the control (17.50 ± 1.73 vs. 12.43 ± 1.01, p = 0.033). In both muscle types, PC levels were higher in the uremic group compared to the control (psoas: 1.086 ± 0.294 vs. 0.596 ± 0.372, soleus: 2.52 ± 0.29 vs. 0.929 ± 0.41, p < 0.05). The soleus had higher levels of TBARS, PC, GSH, CAT, and GR and lower TAC compared to the psoas in both groups. No significant correlations in redox status indices between the blood and skeletal muscles were found. However, in the uremic group, significant correlations between the psoas and soleus muscles in PC, GSSG, and CAT levels emerged, not present in the control. Even in the early stages of CKD, a disturbance in redox homeostasis was observed, which seemed to be muscle type-specific, while blood levels of redox indices did not seem to reflect the intramuscular condition. The above results highlight the need for further research in order to identify the key mechanisms driving the onset and progression of oxidative stress and its detrimental effects on CKD patients.

Variability and Discontinuity of the Pathognomonic Systemic Effects Caused by Walker 256 Tumor Progression in Rats

Cancer pathognomonic systemic effects (PSE) have high individual variability. For this reason present data were collected daily and synchronized considering four main points: inoculation day, onset of PSE, aggravation and death. The subclinical period free of PSE ranged between 15.7±2.2 days, the clinical period was less variable, 8.9±0.5 days, divided in a moderate and a grave phase of nearly the same length. PSE involved disturbances of fundamental homeostatic regulations: appetite, sodium, water, immune, etc. PSE triggering correlated highly with survival (r2=0.95, P<0.01), but poorly with primary tumor growth, and it was anticipated by metastases from 20.5±2.6 to 10.6±1.1 days (P<0.01). After multifocal simultaneous inoculations, PSE triggering was anticipated to 4.2±0.2 days (marked reduction of individual variability), in the presence of small total-tumor masses, absence of macroscopic metastases, and without changes in the following clinical period features. PSE triggering seems to be a major prognostic indicator probably related to multifocal tumor growth.

Biomarkers of cancer cachexia

Cachexia is a complex multifactorial syndrome, characterized by loss of skeletal muscle and fat mass, which affects the majority of advanced cancer patients and is associated with poor prognosis. Interestingly, reversing muscle loss in animal models of cancer cachexia leads to prolong survival. Therefore, detecting cachexia and maintaining muscle mass represent a major goal in the care of cancer patients. However, early diagnosis of cancer cachexia is currently limited for several reasons. Indeed, cachexia development is variable according to tumor and host characteristics. In addition, safe, accessible and non-invasive tools to detect skeletal muscle atrophy are desperately lacking in clinical practice. Finally, the precise molecular mechanisms and the key players involved in cancer cachexia remain poorly characterized. The need for an early diagnosis of cancer cachexia supports therefore the quest for a biomarker that might reflect skeletal muscle atrophy process. Current research offers different promising ways to identify such a biomarker. Initially, the quest for a biomarker of cancer cachexia has mostly focused on mediators of muscle atrophy, produced by both tumor and host, in an attempt to define new therapeutic approaches. In another hand, molecules released by the muscle into the circulation during the atrophy process have been also considered as potential biomarkers. More recently, several "omics" studies are emerging to identify new muscular or circulating markers of cancer cachexia. Some genetic markers could also contribute to identify patients more susceptible to develop cachexia. This article reviews our current knowledge regarding potential biomarkers of cancer cachexia.

TNF-α and cancer cachexia: Molecular insights and clinical implications

Cancer cachexia characterized by a chronic wasting syndrome, involves skeletal muscle loss and adipose tissue loss and resistance to conventional nutritional support. Cachexia is responsible for the reduction in quality and length of life of cancer patients. It also decreases the muscle strength of the patients. The pro-inflammatory and pro-cachectic factors produced by the tumor cells have important role in genesis of cachexia. A number of pro-inflammatory cytokines, like interleukin-1 (IL-1), IL-6, tumor necrosis factor- alpha (TNF-α) may have important role in the pathological mechanisms of cachexia in cancer. Particularly, TNF-α has a direct catabolic effect on skeletal muscle and causes wasting of muscle by the induction of the ubiquitin-proteasome system (UPS). In cancer cachexia condition, there is alteration in carbohydrate, protein and fat metabolism. TNF-α is responsible for the increase in gluconeogenesis, loss of adipose tissue and proteolysis, while causing decrease in protein, lipid and glycogen synthesis. It has been associated with the formation of IL-1 and increases the uncoupling protein-2 (UCP2) and UCP3 expression in skeletal muscle in cachectic state. The main aim of the present review is to evaluate and discuss the role of TNF-α in different metabolic alterations and muscle wasting in cancer cachexia.

Effects of neuromuscular electrical stimulation on cytokines in peripheral blood for healthy participants: a prospective, single-blinded Study

INTRODUCTION

The effect of exercise on cytokines may improve muscle strength. Neuromuscular electrical stimulation (NMES) is a muscle-preserving therapy that benefits patients unable to participate in active exercise. How NMES alters cytokines is unclear. The aim of this study was to study the effects of 1 NMES session on cytokines associated with protein metabolism during exercise.

METHODS

We evaluated the effects of NMES on IL-1, IL-6, IL-10 and TNF-α levels in peripheral blood. Participants received NMES to bilateral lower extremity muscles (quadriceps, tibialis anterior, gastrocnemius) for 30 min. Blood samples immediately pre- and post-NMES were drawn at 15-min intervals to 2-h follow-up, and the mean values of pre-NMES levels were compared to peak and trough post-NMES levels. For cytokines with significant changes, we conducted a repeated-measures linear regression analysis. We also measured post-NMES lactate and creatine kinase levels.

RESULTS

We enrolled nine eligible participants. There was a significant increase in peak IL-6 from the mean pre-NMES value [0·65 (0·89) to 1·04 (0·89) pg ml^-1 , P = 0·001] and a significant decrease in trough IL-1 [0·08 (0·07) to 0·02 (0·02) pg ml^-1 , P = 0·041] and TNF-α [2·42 (0·54) to 2·16 (0·59) pg ml^-1 , P = 0·021]. In repeated-measures regression analysis, we identified significantly higher mean IL-6 values throughout the full 120 min post-NMES period, and a significantly higher mean IL-1 value at 30 min post-NMES. There were no significant differences in peak IL-10, trough IL-6, lactate, or creatine kinase values.

CONCLUSIONS

In nine healthy humans, 30 min of NMES was temporally associated with changes in cytokines similar to the effects of active exercise and may mediate NMES' observed effects on reducing muscle weakness.

Rikkunshito Ameliorates Cancer Cachexia Partly through Elevation of Glucarate in Plasma

Cancer cachexia, which is characterized by decreased food intake, weight loss and systemic inflammation, increases patient's morbidity and mortality. We previously showed that rikkunshito (RKT), a Japanese traditional herbal medicine (Kampo), ameliorated the symptoms of cancer cachexia through ghrelin signaling-dependent and independent pathways. To investigate other mechanisms of RKT action in cancer cachexia, we performed metabolome analysis of plasma in a rat model bearing the Yoshida AH-130 hepatoma. A total of 110 metabolites were detected in plasma and RKT treatment significantly altered levels of 23 of those metabolites in cachexia model rats. Among them, glucarate, which is known to have anticarcinogenic activity through detoxification of carcinogens via inhibition of β-glucuronidase, was increased in plasma following administration of RKT. In our AH-130 ascites-induced cachexia rat model, administration of glucarate delayed onset of weight loss, improved muscle atrophy, and reduced ascites content. Additionally, glucarate reduced levels of plasma interferon-γ (IFN-γ) in tumor-bearing rats and was also found to suppress LPS-induced IFN-γ expression in splenocytes in vitro. These results suggest that glucarate has anti-inflammatory activity via a direct effect on immune host cells and suggest that RKT may also ameliorate inflammation partly through the elevation of glucarate in plasma.

Effects of celecoxib and ibuprofen on metabolic disorders induced by Walker-256 tumor in rats

The contribution of anti-inflammatory property of celecoxib in the improvement of metabolic disorders in cancer is unknown. The purpose of this study was to compare the effects of celecoxib and ibuprofen, non-steroidal anti-inflammatory drugs (NSAIDs), on several metabolic changes observed in Walker-256 tumor-bearing rats. The effects of these NSAIDs on the tumor growth were also assessed. Celecoxib or ibuprofen (both at 25 mg/Kg) was administered orally for 12 days, beginning on the day the rats were inoculated with Walker-256 tumor cells. Celecoxib treatment prevented the losses in body mass and mass of retroperitoneal adipose tissue, gastrocnemius, and extensor digitorum longus muscles in tumor-bearing rats. Celecoxib also prevented the rise in blood levels of triacylglycerol, urea, and lactate, the inhibition of peripheral response to insulin and hepatic glycolysis, and tended to attenuate the decrease in the food intake, but had no effect on the reduction of glycemia induced by the tumor. In addition, celecoxib treatment increased the number of Walker-256 cells with signs of apoptosis and the tumor necrosis area and prevented the tumor growth. In contrast, ibuprofen treatment had no effect on metabolic parameters affected by the Walker-256 tumor or tumor growth. It can be concluded that celecoxib, unlike ibuprofen, ameliorated several metabolic changes in rats with Walker-256 tumor due to its anti-tumor effect and not its anti-inflammatory property.

Muscle wasting in cancer

Skeletal muscle loss appears to be the most significant clinical event in cancer cachexia and is associated with a poor outcome. With regard to such muscle loss, despite extensive study in a range of models, there is ongoing debate as to whether a reduction in protein synthesis, an increase in degradation or a combination of both is the more relevant. Each model differs in terms of key mediators and the pathways activated in skeletal muscle. Certain models do suggest that decreased synthesis accompanied by enhanced protein degradation via the ubiquitin proteasome pathway (UPP) is important. Murine models tend to involve rapid development of cachexia and may represent more acute muscle atrophy rather than the chronic wasting observed in humans. There is a paucity of human data both at a basic descriptive level and at a molecular/mechanism level. Progress in treating the human form of cancer cachexia can only move forwards through carefully designed large randomised controlled clinical trials of specific therapies with validated biomarkers of relevance to underlying mechanisms. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.

A phase I trial assessing the safety, tolerability, pharmacokinetic and pharmacodynamic characteristics of single-dose Auron Misheil therapy in healthy male subjects

BACKGROUND AND OBJECTIVE

Auron Misheil therapy (AMT) is a combination of widely used pharmaceuticals and herbal components that has been used since the 1980s as a supportive therapy, mainly in end-stage cancer patients on a compassionate basis. This phase I study was conducted to assess the safety, tolerability, and pharmacokinetic (PK) and pharmacodynamic (PD) properties of AMT in a controlled trial environment.

METHODS

The study was conducted in a single rising dose, double-blind, placebo-controlled design. Three groups of eight healthy male volunteers received one of three doses of AMT (0·011, 0·033 or 0·066 mL AMT/kg body weight intramuscularly; n = 6 per group) or placebo (n = 2 per group).

RESULTS AND DISCUSSION

Auron Misheil therapy was shown to be well tolerated, revealing no severe or serious adverse events. There were no unexpected PK or PD results for any of the three components of AMT.

CONCLUSIONS

These data provide important PK, PD and safety data for AMT, and support further controlled clinical investigation in patients with different types of cancer as an option for supportive care.

Decreased response to cAMP in the glucose and glycogen catabolism in perfused livers of Walker-256 tumor-bearing rats

The hepatic response to cyclic adenosine monophosphate (cAMP) and N6-monobutyryl-cAMP (N6-MB-cAMP) in the glucose and glycogen catabolism and hepatic glycogen levels were evaluated in Walker-256 tumor-bearing rats, on days 5 (WK5), 8 (WK8), and 11 (WK11) after the implantation of tumor. Rats without tumor fed ad libitum (fed control rats) or that received the same daily amount of food ingested by anorexics tumor-bearing rats (pair-fed control rats) or 24 h fasted (fasted control rats) were used as controls. Glucose and glycogen catabolism were measured in perfused liver. Hepatic glycogen levels were lower (p < 0.05) in WK5, WK8, and WK11 rats in comparison with fed control rats, but not in relation to the pair-fed control rats. However, the stimulatory effect of cAMP (3 and 9 μM) in the glycogen catabolism was lower (p < 0.05), respectively, in WK5 and WK8 rats compared to the pair-fed and fed control rats. Accordingly, the suppressive effect of cAMP (6 μM) in the glucose catabolism, under condition of depletion of hepatic glycogen (24 h fast), was lower (p < 0.05) in WK5 and WK11 rats than in fasted control rats. Similarly, the suppressive effect of N6-MB-cAMP (1 μM), a synthetic analogue of cAMP that it is not degraded by phosphodiesterase 3B (PDE3B), in the glucose catabolism was lower (p < 0.05) in WK5 rats compared to fasted control rats. In conclusion, livers of Walker-256 tumor-bearing rats showed lower response to cAMP in the glucose and glycogen catabolism in various stages of tumor development (days 5, 8 and 11), which was probably not due to the lower hepatic glycogen levels nor due to the increased activity of PDE3B.

Muscle wasting in animal models of severe illness

Muscle wasting is a serious complication of various clinical conditions that significantly worsens the prognosis of the illnesses. Clinically relevant models of muscle wasting are essential for understanding its pathogenesis and for selective preclinical testing of potential therapeutic agents. The data presented here indicate that muscle wasting has been well characterized in rat models of sepsis (endotoxaemia, and caecal ligation and puncture), in rat models of chronic renal failure (partial nephrectomy), in animal models of intensive care unit patients (corticosteroid treatment combined with peripheral denervation or with administration of neuromuscular blocking drugs) and in murine and rat models of cancer (tumour cell transplantation). There is a need to explore genetically engineered mouse models of cancer. The degree of protein degradation in skeletal muscle is not well characterized in animal models of liver cirrhosis, chronic heart failure and chronic obstructive pulmonary disease. The major difficulties with all models are standardization and high variation in disease progression and a lack of reflection of clinical reality in some of the models. The translation of the information obtained by using these models to clinical practice may be problematic.

Foetal proglucagon processing in relation to adult appetite control: lessons from a transplantable rat glucagonoma with severe anorexia

We have previously reported severe anorexia abruptly induced in rats 2-3 weeks after they have been transplanted subcutaneously with the glucagonoma MSL-G-AN. Vagotomy did not affect the time of onset and severity of anorexia, and the anorectic state resembles hunger with strongly elevated neuropeptide Y (NPY) mRNA levels in the nucleus arcuatus. We now show that circulating levels of bioactive glucagon-like peptide-1 (GLP-1) (7-36amide) start to increase above control levels exactly at the time of onset of anorexia. At this time-point, bioactive glucagon as well as total glucagon precursors and GLP-1 metabolites are already vastly elevated compared to controls. We further show that intravenous administration of very high concentrations of GLP-1 to hungry schedule-fed rats causes anorexia in a dose-dependent manner, which is blocked by the GLP-1 receptor antagonist exendin (9-39). GLP-1 (7-36amide) has a well-characterized anorectic effect but also causes taste aversion when administered centrally. The anorectic effect is blocked in rats treated neonatally by monosodium glutamate (MSG). We show that MSG treatment does not prevent the MSL-G-AN-induced anorexia, thereby suggesting a different type of anorectic function. We show a very strong component of taste aversion as anorectic rats, when presented to novel or known alternative food items, will resume normal feeding for 1 day, and then redevelop anorexia. We hypothetize that the anorexia in MSL-G-AN tumour-bearing rats correlates with a foetal processing pattern of proglucagon to both glucagon and GLP-1 (7-36amide), and is due to taste aversion. The sudden onset is characterized by a dramatic increase in circulating levels of biologically active GLP-1 (7-36amide), suggesting eventual saturation of proteolytic inactivation of its N-terminus.

Candidate mechanisms underlying effects of contractile activity on muscle morphology and energetics in cancer cachexia

Skeletal muscle wasting is a prominent pathophysiological feature of cancer cachexia. Recent evidence suggests the manifestation of mitochondrial dysfunction along with a diminished oxidative capacity. These abnormalities have been concurrently observed with impaired muscle force production and the accelerated onset of fatigue in both tumour-bearing animals and cancer patients exhibiting wasting. To address the burden imposed by cachexia, nutritional and pharmacological interventions have been investigated extensively; in contrast, contractile activity-based countermeasures (i.e. exercise training) have been less frequently explored. Although limited, several preclinical studies that implemented contractile activity have reported favourable outcomes such as the retention of muscle mass and the restoration of energetic homeostasis. Even fewer investigations have examined the mechanisms accounting for these protective effects. An experimental approach addressing contractile activity-dependent expression of muscle mass and energy metabolism regulators may yield information that provides mechanistic support for exercise countermeasures. In this review, we present several candidate mechanisms underlying the protective effects of contractile activity as support for exercise countermeasure strategies. Given the limited quantity of data in this area, insights will be derived from studies on contractile activity-dependent modulation of common cellular and molecular events regulating muscle morphology and energetics during other muscle wasting conditions (e.g. sarcopenia).

l-carnitine and cancer cachexia: Clinical and experimental aspects

Cancer cachexia is a multifaceted syndrome characterized, among many symptoms, by extensive muscle wasting. Chronic systemic inflammation, partly triggered and sustained by cytokines, as well as increased oxidative stress contributes to the pathogenesis of this complex metabolic disorder. l-carnitine plays a central role in the metabolism of fatty acids and shows important antioxidant and anti-inflammatory properties. Systemic carnitine depletion has been described in several diseases, and it is characterized by fatigue, muscle weakness, and decreased tolerance to metabolic stress. In cachectic cancer patients, low serum carnitine levels have been reported, and this change has been suggested to play an important contributory role in the development of cachexia. Based on these data, carnitine supplementation has been tested in preliminary studies concerning human cachexia, resulting in improved fatigue and quality of life. We present here a review of clinical and experimental evidence regarding the use of carnitine supplementation in the management of cancer cachexia.

Muscle atrophy in experimental cancer cachexia: is the IGF-1 signaling pathway involved?

Skeletal muscle wasting, one of the main features of cancer cachexia, is associated with marked protein hypercatabolism, and has suggested to depend also on impaired IGF-1 signal transduction pathway. To investigate this point, the state of activation of the IGF-1 system has been evaluated both in rats bearing the AH-130 hepatoma and in mice transplanted with the C26 colon adenocarcinoma. In the skeletal muscle of tumor hosts, the levels of phosphorylated (active) Akt, one of the most relevant kinases involved in the IGF-1 signaling pathway, were comparable to controls, or even increased. Accordingly, downstream targets such as GSK3beta, p70(S6K) and FoxO1 were hyperphosphorylated, while the levels of phosphorylated eIF2alpha were markedly reduced with respect to controls. In the attempt to force the metabolic balance toward anabolism, IGF-1 was hyperexpressed by gene transfer in the tibialis muscle of the C26 hosts. In healthy animals, IGF-1 overexpression markedly increased both fiber and muscle size. As a positive control, IGF-1 was also overexpressed in the muscle of aged mice. In IGF-1 hyperexpressing muscles the fiber cross-sectional area definitely increased in both young and aged animals, while, by contrast, loss of muscle mass or reduction of fiber size in mice bearing the C26 tumor were not modified. These results demonstrate that muscle wasting in tumor-bearing animals is not associated with downregulation of molecules involved in the anabolic response, and appears inconsistent, at least, with reduced activity of the IGF-1 signaling pathway.

Muscle myostatin signalling is enhanced in experimental cancer cachexia

BACKGROUND/AIMS

Myostatin belongs to the transforming growth factor-beta superfamily and negatively regulates skeletal muscle mass. Its deletion induces muscle overgrowth, while, on the contrary, its overexpression or systemic administration cause muscle atrophy. The present study was aimed at investigating whether muscle depletion as occurring in an experimental model of cancer cachexia, the rat bearing the Yoshida AH-130 hepatoma, is associated with modulations of myostatin signalling and whether the cytokine tumour necrosis factor-alpha may be relevant in this regard.

MATERIALS AND METHODS

Protein levels of myostatin, follistatin (myostatin endogenous inhibitor) and the activin receptor type IIB have been evaluated in the gastrocnemius of tumour-bearing rats by Western blotting. Circulating myostatin and follistatin in tumour hosts were evaluated by immunoprecipitation, while the DNA-binding activity of the SMAD transcription factors was determined by electrophoretic-mobility shift assay.

RESULTS

In day 4 tumour hosts muscle myostatin levels were comparable to controls, yet follistatin was reduced, and SMAD DNA-binding activity was enhanced. At day 7, both myostatin and follistatin increased in tumour bearers, while SMAD DNA-binding activity was unchanged. To investigate whether tumour necrosis factor-alpha contributed to induce such changes, rats were administered pentoxifylline, an inhibitor of tumour necrosis factor-alpha synthesis that partially corrects muscle depletion in tumour-bearing rats. The drug reduced both myostatin expression and SMAD DNA-binding activity in day 4 tumour hosts and up-regulated follistatin at day 7.

CONCLUSIONS

These observations suggest that myostatin pathway should be regarded as a potential therapeutic target in cancer cachexia.

Muscle wasting in diabetic and in tumor-bearing rats: role of oxidative stress

Cachexia is a debilitating syndrome characterized by body weight loss, muscle wasting, and anemia. Muscle wasting results from an altered balance between protein synthesis and degradation rates. Reactive oxygen species are indicated as crucial players in the onset of muscle protein hypercatabolism by upregulating elements of the ubiquitin-proteasome pathway. The present study has been aimed at evaluating comparatively the involvement of oxidative stress in the pathogenesis of skeletal muscle wasting in two different experimental models: rats rendered hyperglycemic by treatment with streptozotocin and rats bearing the Yoshida AH-130 ascites hepatoma. For this purpose, both tumor bearers and diabetic animals have been treated with dehydroepiandrosterone (DHEA), a multifunctional steroid endowed with multitargeted antioxidant properties. We show that diabetic rats and AH-130 rats share several features, hypoinsulinemia, occurrence of oxidative stress, and positive response to DHEA administration, although the extent of the effects of DHEA largely differs between diabetic animals and tumor-bearing rats. The hypercatabolism, evaluated in terms of proteasome activity and expression of atrogin-1 and MuRF1, is activated in AH-130 rats, whereas it is lacking in streptozotocin-treated rats. Moreover, we demonstrate that the role of oxidative stress can interfere with muscle wasting through different mechanisms, not necessarily involving NF-kappaB activation. In conclusion, the present results show that, although skeletal muscle wasting occurs in both diabetic rats and tumor-host rats, the underlying mechanisms are different. Moreover, despite oxidative stress being detectable in both experimental models, its contribution to muscle wasting is not comparable.

Emerging drugs for cancer cachexia

Cachexia is a complex syndrome. The main components of this pathological state are anorexia and metabolic abnormalities such as glucose intolerance, fat depletion and muscle protein catabolism among others. The altered metabolic status generates a high degree of energetic inefficiency that results in weight loss, fatigue and a considerable loss of muscle and, therefore, asthenia. The aim of the present article is to review the different therapeutic approaches and emerging drugs that have been designed to fight and counteract cachexia associated with cancer.

Angiotensin-converting enzyme inhibition intervention in elderly persons: effects on body composition and physical performance

The disablement process is often accompanied by sarcopenia or muscle loss, which is associated with virtually all identified disability risk factors. Clinically, the association between body composition and physical performance has been documented by several studies. However, loss of strength is greater than loss of muscle mass with age implying that the quality of remaining muscle may be reduced. Although there are limited data explaining potential physiological mechanisms that contribute to muscle quality, sarcopenia is frequently associated with fat accumulation, and the percentage of body fat increases with age even if weight does not. However, the relationship between fat and muscle function may not be linear, suggesting that there may be an optimal ratio of lean to fat mass for physical function. There are no definitive pharmacological interventions proven to prevent decline in physical function either by modulating body composition or by other means. One exception may be angiotensin-converting enzyme inhibitors (ACEIs). ACE is an important component of the renin-angiotensin system, the central hormonal regulator of blood pressure. Recent evidence suggests that ACEIs may improve physical function by means of direct effects on body composition in older persons, rather than through its blood-pressure-lowering effects. Clinical and genetic studies in humans and experimental evidence in animals suggest that modulation of the renin-angiotensin system is associated with metabolic and biochemical changes in skeletal muscle and fat, changes that are associated with declining physical function. ACEIs may modulate this process through a variety of molecular mechanisms including their influence on oxidative stress and on metabolic and inflammation pathways. This review describes potential biological mechanisms of ACE inhibition and its contribution to declining physical performance and changing body composition. Promising pharmacoepidemiological studies and experimental evidence in animals suggest that there are appropriate models in which to study this effect.

TNF-alpha acts via p38 MAPK to stimulate expression of the ubiquitin ligase atrogin1/MAFbx in skeletal muscle

Atrogin1/MAFbx is an ubiquitin ligase that mediates muscle atrophy in a variety of catabolic states. We recently found that H2O2 stimulates atrogin1/MAFbx gene expression. Since the cytokine tumor necrosis factor-alpha (TNF-alpha) stimulates both reactive oxygen production and general activity of the ubiquitin conjugating pathway, we hypothesized that TNF-alpha would also increase atrogin1/MAFbx gene expression. As with H2O2, we found that TNF-alpha exposure up-regulates atrogin1/MAFbx mRNA within 2 h in C2C12 myotubes. Intraperitoneal injection of TNF-alpha increased atrogin1/MAFbx mRNA in skeletal muscle of adult mice within 4 h. Exposing myotubes to either TNF-alpha or H2O2 also produced general activation of the mitogen-activated protein kinases (MAPKs): p38, ERK1/2, and JNK. The increase in atrogin1/MAFbx gene expression induced by TNF-alpha was not altered significantly by ERK inhibitor PD98059 or the JNK inhibitor SP600125. In contrast, atrogin1/MAFbx up-regulation and the associated increase in ubiquitin conjugating activity were both blunted by p38 inhibitors, either SB203580 or curcumin. These data suggest that TNF-alpha acts via p38 to increase atrogin1/MAFbx gene expression in skeletal muscle.

A proinflammatory tumor that activates protein degradation sensitizes rats to catabolic effects of endotoxin

Chronic or acute inflammation may participate in the etiology of cancer cachexia. To investigate the interaction between tumor and a secondary inflammatory stimulus on muscle wasting, rats with and without tumors (Yoshida ascites hepatoma) received low doses of endotoxin (LPS, 400 microg/kg sc) or saline. Nitrogen balance was measured 24 h before and after LPS/saline. Epitrochlearis muscle was used to measure in vitro protein metabolism, and gastrocnemius muscle was used for quantification of the mRNA for components of the ubiquitin proteolytic pathway. The YAH reduced muscle mass (P = 0.002), increased muscle protein degradation (P = 0.042), and elevated mRNA expression of components of the ubiquitin proteolytic pathway (P < 0.01) including ubiquitin, ubiquitin-conjugating enzyme E2(14k), and ubiquitin ligases muscle RING Finger 1 and atrogin-1. Although the selected low dose of LPS had no impact on protein metabolism in control rats, LPS in rats bearing YAH caused weight loss (P = 0.0007), lowered nitrogen balance (P = <0.0001), and increased muscle protein degradation (P = 0.0336). In conclusion, the presence of a tumor can potentiate whole body and muscle-specific catabolic losses of protein in response to a stimulus that is not catabolic in healthy animals. This effect might be dependent on the inflammatory nature of the tumor.

Both oxidative and nitrosative stress are associated with muscle wasting in tumour-bearing rats

Reactive oxygen and nitrogen species (ROS and RNS) have been proposed as mechanisms of cancer-induced cachexia. In this study, we assessed using Western blot analysis the levels of total protein carbonylation (2,4-dinitrophenylhydrazine assay), both malondialdehyde- (MDA-) and 2-hydroxy-4-nonenal- (HNE-) protein adducts, Mn-superoxide dismutase (Mn-SOD), catalase, heme oxygenase-1 (HO-1) and 3-nitrotyrosine formation in gastrocnemius muscles of rats bearing the Yoshida AH-130 hepatoma. In the muscles of the tumour-bearing animals, protein carbonylation as measured by total levels of carbonyl group formation and both HNE and MDA-protein adducts, and protein tyrosine nitration were significantly greater than in control muscles. Protein levels of the antioxidant enzymes Mn-SOD, catalase, and HO-1 were not significantly modified in the rat cachectic muscles compared to controls. The inefficiency of the antioxidant enzymes in neutralizing excessive ROS production may account for elevated markers of protein oxidation and be responsible for the development of both oxidative and nitrosative stress in cancer-induced cachexia.

Mechanism for the increased skeletal muscle protein degradation in the obese Zucker rat

Obese (fa/fa) Zucker rats showed a decreased protein content in skeletal muscle compared with their lean counterparts. This was associated with both a decrease in the fractional rate of protein synthesis and an enhanced fractional rate of protein degradation in skeletal muscle, as studied by pre-loading body proteins with (14)C-bicarbonate. The increased protein degradation could be the result of the clearly enhanced expression for several transcripts of the ubiquitin genes in skeletal muscle. The results suggest that the increased protein degradation in the skeletal muscle of the obese animals may be due to increased activity of the ubiquitin-dependent proteolytic system.

Interleukin-15 is able to suppress the increased DNA fragmentation associated with muscle wasting in tumour-bearing rats

Administration of interleukin-15 (IL-15) to rats bearing the Yoshida AH-130 ascites hepatoma (a tumour that induces an important cachectic response) resulted in a significant reduction of muscle wasting, both measured as muscle weight and as protein content of different types of skeletal muscle. In addition, the administration of the cytokine completely reversed the increased DNA fragmentation observed in skeletal muscle of tumour-bearing animals. Concerning the mechanism(s) involved in the anti-apoptotic effects of IL-15 on skeletal muscle, the administration of the cytokine resulted in a considerable decrease in both R1 (43%) and R2 (64%) TNF-alpha receptors (TNFRs), and therefore it may be suggested that IL-15 decreases apoptosis by affecting TNF-alpha signalling. Formation of NO could be the signalling event associated with the activation of apoptosis in muscle of tumour-bearing rats; indeed, administration of IL-15 decreased the inducible nitric oxide synthase protein levels by 73%, suggesting that NO formation and muscle apoptosis during tumour growth are related. In conclusion, IL-15 seems to be able to reduce/suppress protein loss and apoptosis related to muscle wasting during cancer cachexia in experimental animals.

Effects of simvastatin administration in an experimental model of cancer cachexia

OBJECTIVE

We evaluated whether statins, in view of their anti-inflammatory properties, may effectively prevent the onset or modulate the severity of muscle wasting during cancer cachexia.

METHODS

Simvastatin was administered to rats bearing the Yoshida AH-130 ascites hepatoma, a well-studied cytokine-dependent experimental model of cancer cachexia.

RESULTS

Quite surprisingly, the drug negatively affected the wasting pattern induced by the AH-130 hepatoma. In fact, the administration of simvastatin to tumor hosts induced a further weight reduction of all the tissues examined except for the soleus, in the absence of significant effects of simvastatin on tumor growth or on food intake. No effects were observed after simvastatin administration in control animals, with the exception of a significant (P < 0.05) reduction in heart weight.

CONCLUSIONS

Simvastatin administration, although capable of negatively modulating the inflammatory response, did not prevent muscle wasting in this experimental model of cancer cachexia. Moreover, the further muscle loss observed in simvastatin-treated tumor-bearing animals suggests that a note of caution should be introduced in treating cancer patients with statins in view of the possible occurrence of harmful side effects.

A leucine-supplemented diet improved protein content of skeletal muscle in young tumor-bearing rats

Cancer cachexia induces host protein wastage but the mechanisms are poorly understood. Branched-chain amino acids play a regulatory role in the modulation of both protein synthesis and degradation in host tissues. Leucine, an important amino acid in skeletal muscle, is higher oxidized in tumor-bearing animals. A leucine-supplemented diet was used to analyze the effects of Walker 256 tumor growth on body composition in young weanling Wistar rats divided into two main dietary groups: normal diet (N, 18% protein) and leucine-rich diet (L, 15% protein plus 3% leucine), which were further subdivided into control (N or L) or tumor-bearing (W or LW) subgroups. After 12 days, the animals were sacrificed and their carcass analyzed. The tumor-bearing groups showed a decrease in body weight and fat content. Lean carcass mass was lower in the W and LW groups (W = 19.9 0.6, LW = 23.1 1.0 g vs N = 29.4 1.3, L = 28.1 1.9 g, P < 0.05). Tumor weight was similar in both tumor-bearing groups fed either diet. Western blot analysis showed that myosin protein content in gastrocnemius muscle was reduced in tumor-bearing animals (W = 0.234 0.033 vs LW = 0.598 0.036, N = 0.623 0.062, L = 0.697 0.065 arbitrary intensity, P < 0.05). Despite accelerated tumor growth, LW animals exhibited a smaller reduction in lean carcass mass and muscle myosin maintenance, suggesting that excess leucine in the diet could counteract, at least in part, the high host protein wasting in weanling tumor-bearing rats.

Skeletal muscle metabolism in physiology and in cancer disease

Skeletal muscle is a tissue of high demand and it accounts for most of daily energy consumption. The classical concept of energy metabolism in skeletal muscle has been profoundly modified on the basis of studies showing the influence of additional factors (i.e., uncoupling proteins (UCPs) and peroxisome proliferator activated receptors (PPARs)) controlling parameters, such as substrate availability, cellular enzymes, carrier proteins, and proton leak, able to affect glycolysis, nutrient oxidation, and protein degradation. This extremely balanced system is greatly altered by cancer disease that can induce muscle cachexia with significant deleterious consequences and results in muscle wasting and weakness, delaying or preventing ambulation, and rehabilitation in catabolic patients.

TNF-alpha increases ubiquitin-conjugating activity in skeletal muscle by up-regulating UbcH2/E220k

In some inflammatory diseases, TNF-alpha is thought to stimulate muscle catabolism via an NF-kappaB-dependent process that increases ubiquitin conjugation to muscle proteins. The transcriptional mechanism of this response has not been determined. Here we studied the potential role of UbcH2, a ubiquitin carrier protein and homologue of murine E220k. We find that UbcH2 is constitutively expressed by human skeletal and cardiac muscles, murine limb muscle, and cultured myotubes. TNF-alpha stimulates UbcH2 expression in mouse limb muscles in vivo and in cultured myotubes. The UbcH2 promoter region contains a functional NF-kappaB binding site; NF-kappaB binding to this sequence is increased by TNF-alpha stimulation. A dominant negative inhibitor of NF-kappaB activation blocks both UbcH2 up-regulation and the increase in ubiquitin-conjugating activity stimulated by TNF-alpha. In extracts from TNF-alpha-treated myotubes, ubiquitin-conjugating activity is limited by UbcH2 availability; activity is inhibited by an antiserum to UbcH2 or a dominant negative mutant of UbcH2 and is enhanced by wild-type UbcH2. Thus, UbcH2 up-regulation is a novel response to TNF-alpha/NF-kappaB signaling in skeletal muscle that appears to be essential for the increased ubiquitin conjugation induced by this cytokine.

Increased muscle proteasome activity correlates with disease severity in gastric cancer patients

OBJECTIVE

To investigate the state of activation of the ATP-ubiquitin-dependent proteolytic system in the skeletal muscle of gastric cancer patients.

SUMMARY BACKGROUND DATA

Muscle wasting in experimental cancer cachexia is frequently associated with hyperactivation of the ATP-dependent ubiquitin-proteasome proteolytic system. Increased muscle ubiquitin mRNA levels have been previously shown in gastric cancer patients, suggesting that this proteolytic system might be modulated also in human cancer.

METHODS

Biopsies of the rectus abdominis muscle were obtained intraoperatively from 23 gastric cancer patients and 14 subjects undergoing surgery for benign abdominal diseases, and muscle ubiquitin mRNA expression and proteasome proteolytic activities were assessed.

RESULTS

Muscle ubiquitin mRNA was hyperexpressed in gastric cancer patients compared to controls. In parallel, three proteasome proteolytic activities (CTL, chymotrypsin-like; TL, trypsin-like; PGP, peptidyl-glutamyl-peptidase) significantly increased in gastric cancer patients with respect to controls. Advanced tumor stage, poor nutritional status, and age more than 50 years were associated with significantly higher CTL activity but had no influence on TL and PGP activity.

CONCLUSIONS

These results confirm the involvement of the ubiquitin-proteasome proteolytic system in the pathogenesis of muscle protein hypercatabolism in cancer cachexia. The observation that perturbations of this pathway in gastric cancer patients occur even before clinical evidence of body wasting supports the thinking that specific pharmacologic and metabolic approaches aimed at counteracting the upregulation of this pathway should be undertaken as early as cancer is diagnosed.

Increased muscle proteasome activity correlates with disease severity in gastric cancer patients

OBJECTIVE

To investigate the state of activation of the ATP-ubiquitin-dependent proteolytic system in the skeletal muscle of gastric cancer patients.

SUMMARY BACKGROUND DATA

Muscle wasting in experimental cancer cachexia is frequently associated with hyperactivation of the ATP-dependent ubiquitin-proteasome proteolytic system. Increased muscle ubiquitin mRNA levels have been previously shown in gastric cancer patients, suggesting that this proteolytic system might be modulated also in human cancer.

METHODS

Biopsies of the rectus abdominis muscle were obtained intraoperatively from 23 gastric cancer patients and 14 subjects undergoing surgery for benign abdominal diseases, and muscle ubiquitin mRNA expression and proteasome proteolytic activities were assessed.

RESULTS

Muscle ubiquitin mRNA was hyperexpressed in gastric cancer patients compared to controls. In parallel, three proteasome proteolytic activities (CTL, chymotrypsin-like; TL, trypsin-like; PGP, peptidyl-glutamyl-peptidase) significantly increased in gastric cancer patients with respect to controls. Advanced tumor stage, poor nutritional status, and age more than 50 years were associated with significantly higher CTL activity but had no influence on TL and PGP activity.

CONCLUSIONS

These results confirm the involvement of the ubiquitin-proteasome proteolytic system in the pathogenesis of muscle protein hypercatabolism in cancer cachexia. The observation that perturbations of this pathway in gastric cancer patients occur even before clinical evidence of body wasting supports the thinking that specific pharmacologic and metabolic approaches aimed at counteracting the upregulation of this pathway should be undertaken as early as cancer is diagnosed.

Respiratory and limb muscle weakness induced by tumor necrosis factor-alpha: involvement of muscle myofilaments

The respiratory and limb skeletal muscles become weakened in sepsis, congestive heart failure, and other inflammatory diseases. A potential mediator of muscle weakness is tumor necrosis factor (TNF)-alpha, a cytokine that can stimulate muscle wasting and also can induce contractile dysfunction without overt catabolism. This study addressed the latter process. Murine diaphragm and limb muscle (flexor digitorum brevis [FDB]) preparations were used to determine the relative sensitivities of these muscles to TNF-alpha. Intact muscle fibers were isolated from FDB and microinjected with indo-1 to measure changes in sarcoplasmic calcium regulation. We found that TNF-alpha depressed tetanic force of the diaphragm and FDB to comparable degrees across a range of stimulus frequencies. In isolated muscle fibers, TNF-alpha decreased tetanic force without altering tetanic calcium transients or resting calcium levels. We conclude that (1) TNF-alpha compromises contractile function of diaphragm and limb muscle similarly, and (2) TNF-alpha decreases force by blunting the response of muscle myofilaments to calcium activation.

What is the role of the insulin-like growth factor system in the pathophysiology of cancer cachexia, and how is it regulated?

OBJECTIVE AND BACKGROUND

The cancer cachexia syndrome is characterized by anorexia, weight loss with muscle wasting and increased energy expenditure. It is associated with increased morbidity and mortality, but its aetiology is poorly understood and no effective therapeutic intervention is available. It may result from an imbalance between the activity or effect of anabolic and catabolic hormones, mediated by the inflammatory cytokines. IGF-I is a potent anabolic agent, with therapeutic potential. Our objective was to investigate the role and regulation of the IGF system in cancer cachexia.

DESIGN AND PATIENTS

We set up a prospective study of 30 patients with newly diagnosed unresectable non-small cell lung cancer, together with a cross-sectional comparison group of healthy volunteers.

MEASUREMENTS

We examined the relationship between aspects of the IGF system, including IGFBP-3 proteolysis (using Western ligand and immunoblotting and an in vitro IGFBP-3 protease assay); the inflammatory cytokines and their soluble receptors; and food intake and nutritional status (including biochemical and anthropometric assessments).

RESULTS

Although we did not observe a marked reduction in food intake in the cancer patients, the majority lost weight and functionally important lean body mass. We observed GH resistance in the cancer patients, and intermittent proteolysis of IGFBP-3, which correlated with the circulating interleukin-6 (IL-6) concentration. The pattern of IGFBP-3 proteolysis was unusual, with a prominent 17-kDa fragment. Less IGFBP-3 proteolysis was associated with more weight loss, suggesting that this could be a protective counter-regulatory mechanism, increasing IGF-I bioavailability to the tissues.

CONCLUSIONS

Cancer cachexia in humans is a complex condition. Patients tend to be GH resistant. The significance of the intermittent increases in IGFBP-3 proteolysis, which may be regulated by IL-6, remains uncertain. A better understanding of the pathophysiology should enable the development of novel therapeutic approaches.

Eicosanoid-dependent cancer cachexia and wasting

The reversal of catabolic processes remains a significant challenge related, in part, to their complexity and our incomplete understanding of the mechanisms involved. The eicosanoids are key players in the inflammatory process and have been implicated in the process of cancer cachexia. They are unsaturated C20 fatty acids which can be separated into two main groups: the lipoxygenase products including leukotrienes and lipoxins, and the prostanoids including prostaglandins, prostacyclin and thromboxane. This review examines the biology of the eicosanoids and the evidence of a role for the eicosanoids in cancer cachexia and wasting.

Heterogeneous response of adipose tissue to cancer cachexia

Cancer cachexia causes disruption of lipid metabolism. Since it has been well established that the various adipose tissue depots demonstrate different responses to stimuli, we assessed the effect of cachexia on some biochemical and morphological parameters of adipocytes obtained from the mesenteric (MES), retroperitoneal (RPAT), and epididymal (EAT) adipose tissues of rats bearing Walker 256 carcinosarcoma, compared with controls. Relative weight and total fat content of tissues did not differ between tumor-bearing rats and controls, but fatty acid composition was modified by cachexia. Adipocyte dimensions were increased in MES and RPAT from tumor-bearing rats, but not in EAT, in relation to control. Ultrastructural alterations were observed in the adipocytes of tumor-bearing rat RPAT (membrane projections) and EAT (nuclear bodies).

Curcumin, a natural product present in turmeric, decreases tumor growth but does not behave as an anticachectic compound in a rat model

Systemic administration of curcumin [1,7-bis(4-hydroxy-3-methoxyphenil)1,6-heptadiene-3,5-dione] (20 microg/kg body weight) for 6 consecutive days to rats bearing the highly cachectic Yoshida AH-130 ascites hepatoma resulted in an important inhibition of tumor growth (31% of total cell number). Interestingly, curcumin was also able to reduce (24%) in vitro tumor cell content at concentrations as low as 0.5 microM without promoting any apoptotic events. Although systemic administration of curcumin has previously been shown to facilitate muscle regeneration, administration of the compound to tumor-bearing rats did not result in any changes in muscle wasting, when compared with the non-treated tumor-bearing animals. Indeed, both the weight and protein content of the gastrocnemius muscle significantly decreased as a result of tumor growth and curcumin was unable to reverse this tendency. It is concluded that curcumin, in spite of having clear antitumoral effects, has little potential as an anticachectic drug in the tumor model used in the present study.

Increased muscle ubiquitin mRNA levels in gastric cancer patients

The intramuscular ATP-dependent ubiquitin (Ub)-proteasome proteolytic system is hyperactivated in experimental cancer cachexia. The present study aimed at verifying whether the expression of the muscle Ub mRNA is altered in patients with cancer. Total muscle RNA was extracted using the guanidinium isothiocyanate/phenol/chloroform method from rectus abdominis biopsies obtained intraoperatively from 20 gastric cancer (GC) patients and 10 subjects with benign abdominal diseases (CON) undergoing surgery. Ub mRNA levels were measured by northern blot analysis. Serum soluble tumor necrosis factor receptor (sTNFR) was measured by ELISA. Ub mRNA levels (arbitrary units, means +/- SD) were 2,345 +/- 195 in GC and 1,162 +/- 132 in CON (P = 0.0005). Ub mRNA levels directly correlated with disease stage (r = 0.608, P = 0.005), being 1,945 +/- 786 in stages I and II, 2,480 +/- 650 in stage III, and 3,799 +/- 66 in stage IV. Ub mRNA and sTNFR did not correlate with age and nutritional parameters. This study confirms experimental data indicating an overexpression of muscle Ub mRNA in cancer cachexia. Lack of correlation with nutritional status suggests that Ub activation in human cancer is an early feature that precedes any clinical sign of cachexia.

Interleukin-15 mediates reciprocal regulation of adipose and muscle mass: a potential role in body weight control

Interleukin (IL)-15 is a cytokine which is highly expressed in skeletal muscle. Cell culture studies have indicated that IL-15 may have an important role in muscle fiber growth and anabolism. However, data concerning the metabolic effects of this cytokine in vivo are lacking. In the present study, IL-15 was administered to adult rats for 7 days. While IL-15 did not cause changes in either muscle mass or muscle protein content, it induced significant changes in the fractional rates of both muscle protein synthesis and degradation, with no net changes in protein accumulation. Additionally, IL-15 administration resulted in a 33% decrease in white adipose tissue mass and a 20% decrease in circulating triacylglycerols; this was associated with a 47% lower hepatic lipogenic rate and a 36% lower plasma VLDL triacylglycerol content. The decrease in white fat induced by IL-15 was in adipose tissue. No changes were observed in the rate of lipolysis as a result of cytokine administration. These findings indicate that IL-15 has significant effects on both protein and lipid metabolism, and suggest that this cytokine may participate in reciprocal regulation of muscle and adipose tissue mass.

Activation of Ca(2+)-dependent proteolysis in skeletal muscle and heart in cancer cachexia

Cachexia is a syndrome characterized by profound tissue wasting that frequently complicates malignancies. In a cancer cachexia model we have shown that protein depletion in the skeletal muscle, which is a prominent feature of the syndrome, is mostly due to enhanced proteolysis. There is consensus on the views that the ubiquitin/proteasome pathway plays an important role in such metabolic response and that cytotoxic cytokines such as TNFalpha are involved in its triggering (Costelli and Baccino, 2000), yet the mechanisms by which the relevant extracellular signals are transduced into protein hypercatabolism are largely unknown. Moreover, little information is presently available as to the possible involvement in muscle protein waste of the Ca(2+)-dependent proteolysis, which may provide a rapidly activated system in response to the extracellular signals. In the present work we have evaluated the status of the Ca(2+)-dependent proteolytic system in the gastrocnemius muscle of AH-130 tumour-bearing rats by assaying the activity of calpain as well as the levels of calpastatin, the natural calpain inhibitor, and of the 130 kDa Ca(2+)-ATPase, both of which are known calpain substrates. After tumour transplantation, total calpastatin activity progressively declined, while total calpain activity remained unchanged, resulting in a progressively increasing unbalance in the calpain/calpastatin ratio. A decrease was also observed for the 130 kDa plasma membrane form of Ca(2+)-ATPase, while there was no change in the level of the 90 kDa sarcoplasmic Ca(2+)-ATPase, which is resistant to the action of calpain. Decreased levels of both calpastatin and 130 kDa Ca(2+)-ATPase have been also detected in the heart of the tumour-bearers. These observations strongly suggest that Ca(2+)-dependent proteolysis was activated in the skeletal muscle and heart of tumour-bearing animals and raise the possibility that such activation may play a role in sparking off the muscle protein hypercatabolic response that characterizes cancer cachexia.

Cytokines and oxidative signalling in skeletal muscle

A growing body of literature indicates that cytokines regulate skeletal muscle function, including gene expression and adaptive responses. Tumour necrosis factor-alpha (TNF-alpha) is the cytokine most prominently linked to muscle pathophysiology and, therefore, has been studied most extensively in muscle-based systems. TNF-alpha is associated with muscle catabolism and loss of muscle function in human diseases that range from cancer to heart failure, from arthritis to AIDS. Recent advances have established that TNF-alpha causes muscle weakness via at least two mechanisms, accelerated protein loss and contractile dysfunction. Protein loss is a chronic response that occurs over days to weeks. Changes in gene expression required for TNF-alpha induced catabolism are regulated by the transcription factor nuclear factor-kappaB which is essential for the net loss of muscle protein caused by chronic TNF-alpha exposure. Contractile dysfunction is an acute response to TNF-alpha stimulation, developing over hours and resulting in decreased force production. Both actions of TNF-alpha involve a rapid rise in endogenous oxidants as an essential step in post-receptor signal transduction. These oxidants appear to include reactive oxygen species derived from mitochondrial electron transport. Such information provides insight into the cellular and molecular mechanisms of TNF-alpha action in skeletal muscle and establishes a scientific basis for continued research into cytokine signalling.

Cancer cachexia: a therapeutic approach

Cancer cachexia is a complex syndrome which occurs in more than two-thirds of patients who die with advanced cancer. The main components of this pathological state are anorexia and metabolic abnormalities such as glucose intolerance, fat depletion, and muscle protein catabolism among others. The aim of the present study is to review the different therapeutic approaches that have been designed to fight and counteract cancer cachexia.

Re-assessment of the renal hydrosaline dysfunction in rats bearing the Walker-256 tumor

Sodium retention is a frequent effect of cancer in humans and animals, but the mechanism involved is not yet understood. In the Walker-256 tumor, sodium retention has been considered to be a late effect, secondary to retention in the tumor mass, and/or to adrenal hypertrophy. Normally, (in rats receiving single tumor implants), the development of different tumor systemic effects (TSE) such as anorexia, sodium and fluid retention, anemia and immune depression in rats is synchronous within each individual but random among individuals of a given group in which they appear 6-47 days, or more, after inoculation. In present study, multifocal simultaneous inoculations of tumor cells resulted in a rapid and synchronous initiation of TSE (in 3-4 days) in all rats when no local effects of metastases could mask the results. Sodium retention is a special tumor effect on Na+ balance and a very sensitive indicator of TSE initiation. The results from multifocally inoculated rats were averaged in each (sub-clinical (SubC), moderate (mCP) and grave (gCP)) clinical phase and compared to food-restricted (FR) rats. There was a significant, early decrease in urinary Na+ excretion during mCP when compared to SubC and FR. The renal sites involved were studied in awake, unrestrained animals by measuring of sodium, creatinine and lithium clearances. There was an initial increase in the absolute proximal (mCP: 21.4 +/- 1.7 vs FR: 16.0 +/- 1.1 mmol/min/100 g b.w., p < 0.05) and post-proximal (mCP: 11.1 +/- 0.4 vs FR: 6.6 +/- 0.4 mmol/min/100 g b.w., p < 0.001) Na+ reabsorption, which were partially compensated for by a rise in glomerular filtration rate (mCP: 213 +/- 11.4 vs FR: 162 +/- 10.2 microL/min/100 g b.w., p < 0.01) and by a fall in fractional proximal Na+ reabsorption (mCP: 62.8 +/- 2.2% vs FR: 70.1 +/- 1.7%, p < 0.05), despite significant Na+ and fluid retention. The terminal phase of illness (gCP) culminated with a marked decrease in creatinine clearance, suggesting a significant fall in renal function. The multifocal model proved useful for studying the initial TSE, since the sites of action would, in principle, be easy to identify. These observations may be of physiological interest since TSE may result from the abnormal production of physiological modulators.

Day-night pattern of energy expenditure and body temperature in cachectic tumour-bearing rats

The implication of an increase in energy expenditure in cancer cachexia, which seems to be related to the type of tumour, remains unclear. We therefore investigated the energy metabolism and body temperature in anorectic and cachectic rats bearing the Yoshida sarcoma (TB), in comparison with pair-fed (PF) and ad-libitum fed (AL) control rats. The resting energy expenditure was higher in the TB than in the two control groups when corrected for the modifications of body composition. However, the total energy expenditure did not differ between the TB and the AL, presumably because of the drop of activity in TB. There was a temporal distribution of differences in energy expenditure with higher energy expenditure in TB than in AL during the diurnal phase and a lack of difference during the nocturnal phase. The TB presented a fever, which was limited to the diurnal period. Moreover, the acrophase of the body temperature rhythm was delayed in the TB. These results highlight the circadian effects of tumour development on the energy metabolism of the host and hint to the possible implication of cytokines.