Neural control of the anorexia-cachexia syndrome

Protective effects of an anti-melanocortin-4 receptor scFv derivative in lipopolysaccharide-induced cachexia in rats

BACKGROUND

Cachexia is a complex syndrome defined by weight loss due to an ongoing loss of skeletal muscle mass with or without loss of body fat. It is often associated with anorexia. Numerous results from experimental studies suggest that blockade of the melanocortin-4 receptor (MC4R) could be an effective treatment for anorexia and cachexia. In a previous study, we reported the basic pharmacological properties of a blocking anti-MC4R mAb 1E8a and its scFv derivative in vitro and in vivo.

METHODS

In the present study, we further characterized the mode of action of the 1E8a scFv, evaluated its pharmacokinetic properties in mice, and assessed its therapeutic potential in a lipopolysaccharide (LPS)-induced cachexia model in rats.

RESULTS

In vitro, scFv enhanced the efficacy of the endogenous inverse agonist Agouti-related protein. After intravenous (i.v.) administration in mice, the scFv penetrated the blood-brain barrier (BBB) and reached its central sites of action: the scFv brain-serum concentration ratios increased up to 15-fold which suggests an active uptake into brain tissue. In telemetry experiments, i.v. administration of the scFv in rats was well tolerated and only induced slight cardiovascular effects consistent with MC4R blockade, i.e., a small decrease in mean arterial pressure and heart rate. In the model of LPS-induced anorexia, i.v. administration of scFv 1E8a prevented anorexia and loss of body weight. Moreover, it stimulated a myogenic response which may contribute to the preservation of muscle mass in cachexia.

CONCLUSION

The pharmacological profile of scFv 1E8a suggests its potential value in the treatment of cachexia or anorexia.

Timing of antioxidant supplementation is critical in improving anorexia in an experimental model of cancer

Increased oxidative stress may contribute to cancer anorexia, which could be ameliorated by antioxidant supplementation. methylcholanthrene (MCA) sarcoma-bearing Fisher rats were studied. After tumour inoculation, rats were randomly assigned to standard diet (CTR group, n = 6), or to an antioxidant-enriched diet (AOX group, n = 8). Eight more rats (STD-AOX group) switched from standard to antioxidant diet when anorexia developed. At the end of the study, food intake (FI, g/d), body weight and tumour weight (g) were recorded, and plasma samples were obtained. On day 16, anorexia has appeared only in CTR and STD-AOX animals. At the end of the study, FI in AOX animals was still higher than in the other groups (p = 0.08). No differences in body and tumour weights were observed among groups. However, hydrogen peroxide and interleukin-1β levels were significantly reduced only in AOX rats. Data obtained suggest that early antioxidant supplementation improves cancer anorexia, ameliorates oxidative stress and reduces inflammation.

Disease specific substrates in cancer cachexia - Reality and anticipation

In recent years, the concept of nutrition in patients with tumour diseases has been changing very significantly. The article discusses the pathogenesis of tumour cachexia and sarcopenia, which have been intensively studied, particularly in the last ten years. The possibilities and modern approaches in nutritional support in oncology are reviewed with a special emphasis on the group of elderly patients. Also, a detailed list of the most frequently used pharmaconutrients in oncology is presented. The recommendations for nutritional care of elderly oncological patients are given and discussed.

Cancer cachexia: mediators, signaling, and metabolic pathways

Cancer cachexia is characterized by a significant reduction in body weight resulting predominantly from loss of adipose tissue and skeletal muscle. Cachexia causes reduced cancer treatment tolerance and reduced quality and length of life, and remains an unmet medical need. Therapeutic progress has been impeded, in part, by the marked heterogeneity of mediators, signaling, and metabolic pathways both within and between model systems and the clinical syndrome. Recent progress in understanding conserved, molecular mechanisms of skeletal muscle atrophy/hypertrophy has provided a downstream platform for circumventing the variations and redundancy in upstream mediators and may ultimately translate into new targeted therapies.

Control of food intake by MC4-R signaling in the lateral hypothalamus, nucleus accumbens shell and ventral tegmental area: interactions with ethanol

The melanocortin system is involved in animal models of obesity and anorexia-cachexia and MC4 receptors (MC4-R) are currently a target system for the development of drugs aimed to treat obesity and eating disorders in humans. Previous evidence suggest that feeding peptides might lack their orexigenic activity while stimulate ethanol intake. The present study comparatively evaluated food intake (4-h interval) in Sprague-Dawley (SD) rats drinking ethanol (6% w/v, 2 bottle choice paradigm) (EE group) and ethanol-naïve (EN) rats in response to bilateral infusion of the selective MC4-R antagonist HS014 (0, 0.02 or 0.05 μg/0.5 μl/site) or the selective MC4-R agonist cyclo(NH-CH(2)-CH(2)-CO-His-d-Phe-Arg-Trp-Glu)-NH(2) (0, 0.75 or 1.5 μg/0.5 μl/site), into the lateral hypothalamus (LH), the nucleus accumbens (NAc), or the ventral tegmental area (VTA). The main findings in the study are: (1) LH-infusions of the MC4-R antagonist increased and the agonist reduced feeding and total calories consumed, while ethanol intake remained unaltered. (2) NAc- and VTA-infusions of the selective agonist reduced food, ethanol and total calories intake. (3) NAc- and VTA-infusions of the MC4-R antagonist increased feeding in EN rats, but not in EE animals which showed a mild increase in ethanol intake, while total calories consumed remained unaltered. Present data show that having ethanol available reduces feeding elicited by NAc and VTA-MC4-R blockade. Additionally, while MC4-R signaling in the LH appears to modulate homeostatic aspects of feeding, it may contribute to non-homeostatic aspects of ingestive behaviors in the VTA and the NAc.

A role of active brown adipose tissue in cancer cachexia?

Until a few years ago, adult humans were not thought to have brown adipose tissue (BAT). Now, this is a rapidly evolving field of research with perspectives in metabolic syndromes such as obesity and new therapies targeting its bio-energetic pathways. White, brown and so-called brite adipose fat seem to be able to trans-differentiate into each other, emphasizing the dynamic nature of fat tissue for metabolism. Human and animal data in cancer cachexia to date provide some evidence for BAT activation, but its quantitative impact on energy expenditure and weight loss is controversial. Prospective clinical studies can address the potential role of BAT in cancer cachexia using ¹⁸F-fluoro- deoxyglucose positron emission tomography-computed tomography scanning, with careful consideration of co-factors such as diet, exposure to the cold, physical activity and body mass index, that all seem to act on BAT recruitment and activity.

Exploring metabolic dysfunction in chronic kidney disease

Impaired kidney function and chronic kidney disease (CKD) leading to kidney failure and end-stage renal disease (ESRD) is a serious medical condition associated with increased morbidity, mortality, and in particular cardiovascular disease (CVD) risk. CKD is associated with multiple physiological and metabolic disturbances, including hypertension, dyslipidemia and the anorexia-cachexia syndrome which are linked to poor outcomes. Specific hormonal, inflammatory, and nutritional-metabolic factors may play key roles in CKD development and pathogenesis. These include raised proinflammatory cytokines, such as interleukin-1 and −6, tumor necrosis factor, altered hepatic acute phase proteins, including reduced albumin, increased C-reactive protein, and perturbations in normal anabolic hormone responses with reduced growth hormone-insulin-like growth factor-1 axis activity. Others include hyperactivation of the renin-angiotensin aldosterone system (RAAS), with angiotensin II and aldosterone implicated in hypertension and the promotion of insulin resistance, and subsequent pharmacological blockade shown to improve blood pressure, metabolic control and offer reno-protective effects. Abnormal adipocytokine levels including leptin and adiponectin may further promote the insulin resistant, and proinflammatory state in CKD. Ghrelin may be also implicated and controversial studies suggest activities may be reduced in human CKD, and may provide a rationale for administration of acyl-ghrelin. Poor vitamin D status has also been associated with patient outcome and CVD risk and may indicate a role for supplementation. Glucocorticoid activities traditionally known for their involvement in the pathogenesis of a number of disease states are increased and may be implicated in CKD-associated hypertension, insulin resistance, diabetes risk and cachexia, both directly and indirectly through effects on other systems including activation of the mineralcorticoid receptor. Insight into the multiple factors altered in CKD may provide useful information on disease pathogenesis, clinical assessment and treatment rationale such as potential pharmacological, nutritional and exercise therapies.

Inflammation in cancer cachexia: to resolve or not to resolve (is that the question?)

BACKGROUND & AIMS

Cachexia is associated with poor prognosis and shortened survival in cancer patients. Growing evidence points out to the importance of chronic systemic inflammation in the aetiology of this syndrome. In the recent past, chronic inflammation was considered to result from overexpression and release of pro-inflammatory factors. However, this conception is now the focus of debate, since the importance of a crescent number of pro-resolving agents in the dissolution of inflammation is now recognised--leading to the hypothesis that chronic inflammation occurs rather due to failure in the resolution process. We intend to put forward the possibility that this may also be occurring in cancer cachexia.

METHODS

Recent reviews on inflammation and cachexia, and on the factors involved in the resolution of inflammation are discussed.

RESULTS

The available information suggests that indeed, inflammation resolution failure may be present in cachexia and therefore we speculate on possible mechanisms.

CONCLUSIONS

We emphasise the importance of studying resolution-related mechanisms in cancer cachexia and propose the opening of a new venue for cachexia treatment.

A Phase II dose titration study of thalidomide for cancer-associated anorexia

CONTEXT

Sixty-five percent of people with advanced cancer suffers from loss of appetite. Several inflammatory cytokines appear to cause appetite loss in animal models. Thalidomide is an immunomodulatory drug that has been associated with improved appetite in those with HIV infections and cancer.

OBJECTIVES

We completed a two-stage Phase II dose titration study of thalidomide, the primary purpose of which was to assess appetite response to thalidomide in cancer-associated anorexia.

METHODS

Individuals older than 18 years of age with active cancer, loss of appetite by numerical rating scale (NRS), life expectancy of at least four weeks, and Eastern Cooperative Oncology Group performance status of 0-3 were entered into the study. Pretreatment screening included medical history, neurologic examination, and symptoms by NRS and categorical scale (CAT). Patients received 50mg of thalidomide by mouth at bedtime for two weeks. Individuals who did not respond were dose escalated to 100mg at night for two weeks. Assessment of appetite, early satiety, fatigue, insomnia, night sweats, pain, and quality of life (QOL) occurred at two-week intervals. Toxicity also was assessed. The primary outcome was appetite response defined as a two-point reduction in the NRS or a one-point improvement in the CAT.

RESULTS

Thirty-five patients entered the study; 33 completed 14 days of therapy and were analyzed for efficacy and toxicity. Sixty-four percent who completed at least two weeks of thalidomide had improved appetite. The CAT scores for appetite, insomnia, and QOL improved significantly. The 95% confidence intervals did not overlap. Five participants dropped out because of toxicity: two before two weeks and three later.

CONCLUSION

Thalidomide reduced multiple symptoms commonly associated with cancer-related anorexia and improved QOL. Our findings confirmed and validated a previously published single-arm trial. A recent randomized trial demonstrated greater benefits when thalidomide is used combined with other agents to treat cancer-associated anorexia and cachexia. Thalidomide helped cancer-associated anorexia in most patients. It also improved insomnia and QOL in advanced cancer.

Molecular mechanisms of cachexia in chronic disease

Cachexia is a metabolic syndrome that manifests with excessive weight loss and disproportionate muscle wasting. It is related to many different chronic diseases, such as cancer, infections, liver disease, inflammatory bowel disease, cardiac disease, chronic obstructive pulmonary disease, chronic renal failure and rheumatoid arthritis. Cachexia is linked with poor outcome for the patients. In this article, we explore the role of the hypothalamus, liver, muscle tissue and adipose tissue in the pathogenesis of this syndrome, particularly concentrating on the role of cytokines, hormones and cell energy-controlling pathways (such as AMPK, PI3K/Akt and mTOR). We also look at possible future directions for therapeutic strategies.

Brain-immune interactions and the neural basis of disease-avoidant ingestive behaviour

Neuro-immune interactions are widely manifested in animal physiology. Since immunity competes for energy with other physiological functions, it is subject to a circadian trade-off between other energy-demanding processes, such as neural activity, locomotion and thermoregulation. When immunity is challenged, this trade-off is tilted to an adaptive energy protecting and reallocation strategy that is identified as 'sickness behaviour'. We review diverse disease-avoidant behaviours in the context of ingestion, indicating that several adaptive advantages have been acquired by animals (including humans) during phylogenetic evolution and by ontogenetic experiences: (i) preventing waste of energy by reducing appetite and consequently foraging/hunting (illness anorexia), (ii) avoiding unnecessary danger by promoting safe environments (preventing disease encounter by olfactory cues and illness potentiation neophobia), (iii) help fighting against pathogenic threats (hyperthermia/somnolence), and (iv) by associative learning evading specific foods or environments signalling danger (conditioned taste avoidance/aversion) and/or at the same time preparing the body to counteract by anticipatory immune responses (conditioning immunomodulation). The neurobiology behind disease-avoidant ingestive behaviours is reviewed with special emphasis on the body energy balance (intake versus expenditure) and an evolutionary psychology perspective.

Cachexia and sarcopenia: emerging syndromes of importance in dogs and cats

Cachexia is the loss of lean body mass (LBM) that affects a large proportion of dogs and cats with congestive heart failure (CHF), chronic kidney disease (CKD), cancer, and a variety of other chronic diseases. Sarcopenia, the loss of LBM that occurs with aging, is a related syndrome, although sarcopenia occurs in the absence of disease. As many of the diseases associated with muscle loss are more common in aging, cachexia and sarcopenia often are concurrent problems. Both cachexia and sarcopenia have important clinical implications because they are associated with increased morbidity and mortality. The pathophysiology of these 2 syndromes is complex and multifactorial, but recent studies have provided new information that has helped to clarify mechanisms and identify potential new targets for treatment. Newly identified mechanisms and pathways that mediate cachexia appear to act by increasing energy requirements, decreasing energy intake, impairing nutrient absorption, and causing metabolic alterations. Whereas cachexia and sarcopenia are important areas of research for drug development in people, they are only beginning to be recognized in veterinary medicine. Greater awareness and earlier diagnosis will help provide practical approaches to managing body weight and lean tissue in dogs and cats, as well as more directed targets for treatment.

Pathophysiology and treatment options for cardiac anorexia

The anorexia-cachexia syndrome (ACS) occurs in many chronic illnesses, such as cancer, AIDS, and chronic obstructive pulmonary disease in addition to chronic congestive heart failure (CHF). Comparable to other chronic states, the ACS complicates CHF and impacts its prognosis; however, the available treatment options for this syndrome remain unsatisfactory. This review article focuses on the complex pathophysiology of cardiac anorexia. We focus on the recent data demonstrating the relationships between central appetite-regulating structures, inflammatory processes, and neurohormonal activation, and their respective roles in the development of anorexia. We then describe the different treatment options and discuss some future prospects for the management for cardiac anorexia.

Hypothalamic inflammation is reversed by endurance training in anorectic-cachectic rats

Aim

We tested the effects of a cancer cachexia-anorexia sydrome upon the balance of anti and pro-inflammatory cytokines in the hypothalamus of sedentary or trained tumour-bearing (Walker-256 carcinosarcoma) rats.

Methods

Animals were randomly assigned to a sedentary control (SC), sedentary tumour-bearing (ST), and sedentary pair-fed (SPF) groups or, exercised control (EC), exercised tumour-bearing (ET) and exercised pair-fed (EPF) groups. Trained rats ran on a treadmill (60%VO_2max) for 60 min/d, 5 days/wk, for 8 wks. We evaluated food intake, leptin and cytokine (TNF-α, IL1β) levels in the hypothalamus.

Results

The cumulative food intake and serum leptin concentration were reduced in ST compared to SC. Leptin gene expression in the retroperitoneal adipose tissue (RPAT) was increased in SPF in comparison with SC and ST, and in the mesenteric adipose tissue (MEAT) the same parameter was decreased in ST in relation to SC. Leptin levels in RPAT and MEAT were decreased in ST, when compared with SC. Exercise training was also able to reduce tumour weight when compared to ST group. In the hypothalamus, IL-1β and IL-10 gene expression was higher in ST than in SC and SPF. Cytokine concentration in hypothalamus was higher in ST (TNF-α and IL-1β, p < 0.05), compared with SC and SPF. These pro-inflammatory cytokines concentrations were restored to control values (p < 0.05), when the animals were submitted to endurance training.

Conclusion

Cancer-induced anorexia leads towards a pro-inflammatory state in the hypothalamus, which is prevented by endurance training which induces an anti-inflammatory state, with concomitant decrease of tumour weight.

Melanocortin control of energy balance: evidence from rodent models

Regulation of energy balance is extremely complex, and involves multiple systems of hormones, neurotransmitters, receptors, and intracellular signals. As data have accumulated over the last two decades, the CNS melanocortin system is now identified as a prominent integrative network of energy balance controls in the mammalian brain. Here, we will review findings from rat and mouse models, which have provided an important framework in which to study melanocortin function. Perhaps most importantly, this review attempts for the first time to summarize recent advances in our understanding of the intracellular signaling pathways thought to mediate the action of melanocortin neurons and peptides in control of longterm energy balance. Special attention will be paid to the roles of MC4R/MC3R, as well as downstream neurotransmitters within forebrain and hindbrain structures that illustrate the distributed control of melanocortin signaling in energy balance. In addition, distinctions and controversy between rodent species will be discussed.

Beyond anorexia -cachexia. Nutrition and modulation of cancer patients' metabolism: supplementary, complementary or alternative anti-neoplastic therapy?

Anorexia and muscle wasting are frequently observed in cancer patients and influence their clinical outcome. The better understanding of the mechanisms underlying behavioral changes and altered metabolism yielded to the development of specialized nutritional support, which enhances utilization of provided calories and proteins by counteracting some of the metabolic derangements occurring during tumor growth. Inflammation appears to be a key factor determining the cancer-associated biochemical abnormalities eventually leading to anorexia and cachexia. Interestingly, inflammation is also involved in carcinogenesis, cancer progression and metastasis by impairing immune surveillance, among other mechanisms. Therefore, nutritional interventions aiming at modulating inflammation to restore nutritional status may also result in improved response to pharmacological anti-cancer therapies. Recent clinical data show that supplementation with nutrients targeting inflammation and immune system increases response rate and survival in cancer patients. This suggests that nutrition therapy should be considered as an important adjuvant strategy in the multidimensional approach to cancer patients.

Ghrelin and cachexia: will treatment with GHSR-1a agonists make a difference for patients suffering from chronic wasting syndromes?

Cachexia is a syndrome of wasting and anorexia that worsens the prognosis of many chronic diseases including cancer, chronic kidney disease, chronic heart disease and chronic obstructive pulmonary disease. Properties of the orexigenic hormone ghrelin-including appetite-stimulation, weight-gain production and increased cardiac output make it a logical treatment for cachexia. While endogenous ghrelin levels are increased in the setting of cachexia, treatment with ghrelin and other GHSR-1a agonists in animal models of cachexia and in humans with cachexia has demonstrated consistent effects of increased appetite and improved weight gain. These positive effects occur in multiple underlying diseases associated with cachexia and appear to be sustained over treatment duration of up to 12 weeks. The mechanism of action in producing these effects is likely related to stimulation of central appetite centers such as the central melanocortin system and to increased growth hormone release, though ghrelin's effects may also relate to decreased systemic inflammation and other direct and indirect actions. Questions regarding the long-term safety of ghrelin treatment are still unanswered, as is the important question of whether successful treatment of cachexia will improve the prognosis of the underlying disease itself.

Contribution of anorexia to tissue wasting in cachexia

PURPOSE OF REVIEW

Anorexia is a severe debilitating symptom characterizing the clinical course of several chronic diseases. It negatively impacts on patient outcome by contributing to weight loss, lean body mass catabolism and adipose tissue wasting. Although disease-associated anorexia may stand alone as a clinically relevant symptom, it is now considered as a component of the cachexia syndrome. The present review discusses experimental and clinical data indicating that the pathogenic mechanisms of anorexia may also suggest a neural control of tissue wasting in cachexia.

RECENT FINDINGS

Consistent data show that selective melanocortin receptor antagonism modulates food intake and reduces wasting in experimental models of chronic disease. Consequently, ghrelin administration, whose prophagic effects are related to melanocortin antagonism, has been tested both in animal studies and human trials, with promising effects, although restoration of lean body mass has been not achieved. More interest is driven by the use of small molecules selectively antagonising hypothalamic melanocortin receptors.

SUMMARY

The 'brain-muscle axis' coordinated by the hypothalamus seems to mediate the onset of not only anorexia but also tissue wasting in cachexia, by centrally influencing energy homeostasis and the balance between anabolism and catabolism.

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.

Visfatin induces sickness responses in the brain

Background/Objective

Visfatin, also known as nicotiamide phosphoribosyltransferase or pre-B cell colony enhancing factor, is a pro-inflammatory cytokine whose serum level is increased in sepsis and cancer as well as in obesity. Here we report a pro-inflammatory role of visfatin in the brain, to mediate sickness responses including anorexia, hyperthermia and hypoactivity.

Methodology

Rats were intracerebroventricularly (ICV) injected with visfatin, and changes in food intake, body weight, body temperature and locomotor activity were monitored. Real-time PCR was applied to determine the expressions of pro-inflammatory cytokines, proopiomelanocortin (POMC) and prostaglandin-synthesizing enzymes in their brain. To determine the roles of cyclooxygenase (COX) and melanocortin in the visfatin action, rats were ICV-injected with visfatin with or without SHU9119, a melanocortin receptor antagonist, or indomethacin, a COX inhibitor, and their sickness behaviors were evaluated.

Principal Findings

Administration of visfatin decreased food intake, body weight and locomotor activity and increased body temperature. Visfatin evoked significant increases in the levels of pro-inflammatory cytokines, prostaglandin-synthesizing enzymes and POMC, an anorexigenic neuropeptide. Indomethacin attenuated the effects of visfatin on hyperthermia and hypoactivity, but not anorexia. Further, SHU9119 blocked visfatin-induced anorexia but did not affect hyperthermia or hypoactivity.

Conclusions

Visfatin induced sickness responses via regulation of COX and the melanocortin pathway in the brain.

GABAergic signaling by AgRP neurons prevents anorexia via a melanocortin-independent mechanism

The hypothalamic arcuate nucleus contains two anatomically and functionally distinct populations of neurons-the agouti-related peptide (AgRP)- and pro-opiomelanocortin (POMC)-expressing neurons that integrate various nutritional, hormonal, and neuronal signals to regulate food intake and energy expenditure, and thereby help achieve energy homeostasis. AgRP neurons, also co-release neuropeptide Y (NPY) and γ-aminobutyric acid (GABA) to promote feeding and inhibit metabolism through at least three possible mechanisms: (1) suppression of the melanocortin signaling system through competitive binding of AgRP with the melanocortin 4 receptors; (2) NPY-mediated inhibition of post-synaptic neurons that reside in hypothalamic nuclei; (3) GABAergic inhibition of POMC neurons in their post-synaptic targets including the parabrachial nucleus (PBN), a brainstem structure that relays gustatory and visceral sensory information. Acute ablation of AgRP neurons in adult mice by the action of diphtheria toxin (DT) results in precipitous reduction of food intake, and eventually leads to starvation within 6days of DT treatment. Chronic delivery of bretazenil, a GABA(A) receptor partial agonist, into the PBN is sufficient to restore feeding and body weight when AgRP neurons are ablated, whereas chronic blockade of melanocortin 4 receptor signaling is inadequate. This review summarizes the physiological roles of a neural circuitry regulated by AgRP neurons in control of feeding behavior with particular emphasis of the GABA output to the parabrachial nucleus. We also describe a compensatory mechanism that is gradually engaged after ablation of AgRP neurons that allows mice to continue eating without them.

The pathophysiology of cardiac cachexia

PURPOSE OF REVIEW

Cardiac cachexia, the loss of lean body mass that affects a large proportion of patients with chronic heart failure, is associated with increased morbidity and mortality. The pathophysiology of cardiac cachexia is complex and multifactorial, but recent studies are providing new information that is helping to clarify the pathophysiology and new targets for treatment.

RECENT FINDINGS

New attention is being paid to developing a definition as well as a clinically relevant way to diagnose this syndrome. The adverse clinical effects of cachexia are being emphasized by new research on the obesity paradox, suggesting that cardiac cachexia is such a detrimental process that obesity actually confers a survival benefit. This information is useful in developing practical approaches to managing body weight and lean tissue in chronic heart failure patients and may provide therapeutic targets. New mechanisms and pathways that mediate cardiac cachexia are being identified and appear to act by increasing energy requirements, reducing energy intake, impairing nutrient absorption, and causing metabolic alterations.

SUMMARY

Recent studies have helped to better delineate multifactorial mechanisms in the pathophysiology of cardiac cachexia that may lead to more effective treatments to address this common and important syndrome in patients with chronic heart failure.

Chronic renal failure, cachexia, and ghrelin

Protein energy wasting is frequently observed in patients with advanced chronic renal failure and end-stage renal disease. Anorexia and reduced food intake are critical contributing factors and negatively impact on patients' survival. Ghrelin is a prophagic peptide produced by the stomach and acting at the hypothalamic level to increase the activity of orexigenic neurons. In patients with chronic renal disease, plasma levels are increased as a likely effect of reduced renal clearance. Nevertheless, patients' food intake is significantly reduced, suggesting inflammation-mediated resistance of hypothalamic nuclei to peripheral signals. A number of forms of evidence show that ghrelin resistance could be overcome by the administration of exogenous ghrelin. Therefore, ghrelin has been proposed as a potential strategy to improve food intake in chronic renal failure patients with protein energy wasting. Preliminary data are encouraging although larger prospective clinical trials are needed to confirm the results and to identify those patients who are likely to benefit most from the administration of exogenous ghrelin.

Hypothalamic actions of tumor necrosis factor alpha provide the thermogenic core for the wastage syndrome in cachexia

TNFalpha is an important mediator of catabolism in cachexia. Most of its effects have been characterized in peripheral tissues, such as skeletal muscle and fat. However, by acting directly in the hypothalamus, TNFalpha can activate thermogenesis and modulate food intake. Here we show that high concentration TNFalpha in the hypothalamus leads to increased O(2) consumption/CO(2) production, increased body temperature, and reduced caloric intake, resulting in loss of body mass. Most of the thermogenic response is produced by beta 3-adrenergic signaling to the brown adipose tissue (BAT), leading to increased BAT relative mass, reduction in BAT lipid quantity, and increased BAT mitochondria density. The expression of proteins involved in BAT thermogenesis, such as beta 3-adrenergic receptor, peroxisomal proliferator-activated receptor-gamma coactivator-1 alpha, and uncoupling protein-1, are increased. In the hypothalamus, TNFalpha produces reductions in neuropeptide Y, agouti gene-related peptide, proopiomelanocortin, and melanin-concentrating hormone, and increases CRH and TRH. The activity of the AMP-activated protein kinase signaling pathway is also decreased in the hypothalamus of TNFalpha-treated rats. Upon intracerebroventricular infliximab treatment, tumor-bearing and septic rats present a significantly increased survival. In addition, the systemic inhibition of beta 3-adrenergic signaling results in a reduced body mass loss and increased survival in septic rats. These data suggest hypothalamic TNFalpha action to be important mediator of the wastage syndrome in cachexia.

Energy intake and expenditure profile in chronic peritoneal dialysis patients complicated with circulatory congestion

BACKGROUND

Circulatory congestion is an adverse predictor of mortality in peritoneal dialysis (PD) patients.

OBJECTIVE

This study evaluated the nutritional status, energy intake, and expenditure profile of PD patients with and without previous circulatory congestion.

DESIGN

We conducted a cross-sectional study in 244 PD patients, of whom 92 had previous circulatory congestion. We estimated dietary energy intake by using a locally validated 7-d food-frequency questionnaire and by assessing resting energy expenditure (REE) and total energy expenditure (TEE) with indirect calorimetry and a locally validated physical activity questionnaire, respectively.

RESULTS

In comparison with those without circulatory congestion, patients with previous circulatory congestion were more malnourished by subjective global assessment (59% compared with 36%; P < 0.001), had lower handgrip strength, had lower midarm muscle circumference, had lower dietary protein (0.98 +/- 0.45 compared with 1.19 +/- 0.44 g x kg(-1) x d(-1); P < 0.001), and had lower energy intake (92.5 +/- 37.0 compared with 110.9 +/- 35.7 kJ x kg(-1) x d(-1); P < 0.001) but had higher C-reactive protein (P = 0.025) and higher REE (P < 0.001). However, no difference in TEE was noted between the 2 groups, which indicated lower activity energy expenditure among patients with previous circulatory congestion. The resulting energy balance was significantly more negative for patients with previous circulatory congestion than for those without previous circulatory congestion (P = 0.050). Furthermore, the prevalence of malnutrition increased with increasing episodes of circulatory congestion (P = 0.017).

CONCLUSIONS

Patients with previous circulatory congestion had significantly more inflammation, more muscle wasting, and higher REE but lower activity energy expenditure and energy and protein intakes in keeping with an anorexia-cachexia syndrome. The mechanisms of increased REE and reduced energy intake among patients with previous circulatory congestion warrant further investigation.

Tryptophan in wasting diseases: at the crossing between immune function and behaviour

PURPOSE OF REVIEW

Wasting diseases are characterized by progressive deterioration of nutritional status that negatively influences patients' outcome. The better understanding of the pathogenic mechanisms of wasting may lead to effective therapies. Tryptophan metabolism has unique features suggesting a critical role in influencing human metabolism under normal and pathological conditions.

RECENT FINDINGS

During disease, inflammatory response favours the local depletion of the essential amino acid tryptophan, thereby inhibiting cellular proliferation. Tryptophan depletion may also mediate immunotolerance to foreign antigens. In contrast, brain accumulation of tryptophan contributes to wasting by increasing oxidative stress and hypothalamic serotonin neurotransmission, and thereby triggering the onset of sickness behaviour followed by depressive-like behaviour.

SUMMARY

Tryptophan metabolism is critical in mediating a number of important biological responses. Restoring tryptophan metabolism may well result in enhanced recovery from disease.