Emergence of ghrelin as a treatment for cachexia syndromes

Combating chronic kidney disease-associated cachexia: A literature review of recent therapeutic approaches

In 2008, the Society on Sarcopenia, Cachexia, and Wasting Disorders introduced a generic definition for all types of cachexia: "a complex metabolic syndrome associated with the underlying illness characterized by a loss of muscle, with or without fat loss". It is well-known that the presence of inflammatory burden in end-stage renal disease (ESRD) patients may lead to the evolution of cachexia. Since the etiology of cachexia in chronic kidney disease (CKD) is multifactorial, thus the successful treatment must involve several concomitant measures (nutritional interventions, appetite stimulants, and anti-inflammatory pharmacologic agents) to provide integrated effective therapeutic modalities to combat causative factors and alleviate the outcomes of patients. Given the high mortality rate associated with cachexia, developing new therapeutic modalities are prerequisite for ameliorating patients with CKD worldwide. The present review aims to discuss some therapeutic strategies and provide an update on advances in nutritional approaches to counteract cachexia.

Therapeutic potential of ghrelin/GOAT/GHSR system in gastrointestinal disorders

Ghrelin, a peptide primarily secreted in the stomach, acts via the growth hormone secretagogue receptor (GHSR). It regulates several physiological processes, such as feeding behavior, energy homeostasis, glucose and lipid metabolism, cardiovascular function, bone formation, stress response, and learning. GHSR exhibits significant expression within the central nervous system. However, numerous murine studies indicate that ghrelin is limited in its ability to enter the brain from the bloodstream and is primarily confined to specific regions, such as arcuate nucleus (ARC) and median eminence (ME). Nevertheless, the central ghrelin system plays an essential role in regulating feeding behavior. Furthermore, the role of vagal afferent fibers in regulating the functions of ghrelin remains a major topic of discussion among researchers. In recent times, numerous studies have elucidated the substantial therapeutic potential of ghrelin in most gastrointestinal (GI) diseases. This has led to the development of numerous pharmaceutical agents that target the ghrelin system, some of which are currently under examination in clinical trials. Furthermore, ghrelin is speculated to serve as a promising biomarker for GI tumors, which indicates its potential use in tumor grade and stage evaluation. This review presents a summary of recent findings in research conducted on both animals and humans, highlighting the therapeutic properties of ghrelin system in GI disorders.

Ghrelin and Cancer: Examining the Roles of the Ghrelin Axis in Tumor Growth and Progression

Ghrelin, a hormone produced and secreted from the stomach, is prim arily known as an appetite stimulant. Recently, it has emerged as a potential regulator/biomarker of cancer progression. Inconsistent results on this subject make this body of literature difficult to interpret. Here, we attempt to identify commonalities in the relationships between ghrelin and various cancers, and summarize important considerations for future research. The main players in the ghrelin family axis are unacylated ghrelin (UAG), acylated ghrelin (AG), the enzyme ghrelin O-acyltransferase (GOAT), and the growth hormone secretagogue receptor (GHSR). GOAT is responsible for the acylation of ghrelin, after which ghrelin can bind to the functional ghrelin receptor GHSR-1a to initiate the activation cascade. Splice variants of ghrelin also exist, with the most prominent being In1-ghrelin. In this review, we focus primarily on the potential of In1-ghrelin as a biomarker for cancer progression, the unique characteristics of UAG and AG, the importance of the two known receptor variants GHSR-1a and 1b, as well as the possible mechanisms through which the ghrelin axis acts. Further understanding of the role of the ghrelin axis in tumor cell proliferation could lead to the development of novel therapeutic approaches for various cancers.

Acylated and unacylated ghrelin relieve cancer cachexia in mice through multiple mechanisms

Cancer cachexia is a wasting syndrome resulting from decreased protein synthesis and increased protein degradation. Calpain-dependent cleavage of myofilament is the initial step of myofilament degradation and plays a critical role in muscle atrophy. Ghrelin is a multifunctional hormone known to improve protein synthesis and inhibit protein degradation. However, its mechanism of action is not fully understood. Here we investigated whether acylated ghrelin (AG) and unacylated ghrelin (UnAG) could protect against cancer cachexia in mice bearing CT26 colorectal adenocarcinoma. We found for the first time that both AG and UnAG could inhibit calpain activity in skeletal muscle of cancer cachectic mice. AG and UnAG also improved tumor-free body weight, grip strength, muscle mass, epididymal fat mass, and nutritional state in tumor-bearing (TB) mice. Moreover, AG and UnAG reduced serum tumor necrosis factor-± concentration, increased Akt activity, and downregulated atrogin-1 expression in TB mice. Our results may contribute to the development of an AG/UnAG-based therapy for cancer cachexia.

A Dairy-Derived Ghrelinergic Hydrolysate Modulates Food Intake In Vivo

Recent times have seen an increasing move towards harnessing the health-promoting benefits of food and dietary constituents while providing scientific evidence to substantiate their claims. In particular, the potential for bioactive protein hydrolysates and peptides to enhance health in conjunction with conventional pharmaceutical therapy is being investigated. Dairy-derived proteins have been shown to contain bioactive peptide sequences with various purported health benefits, with effects ranging from the digestive system to cardiovascular circulation, the immune system and the central nervous system. Interestingly, the ability of dairy proteins to modulate metabolism and appetite has recently been reported. The ghrelin receptor (GHSR-1a) is a G-protein coupled receptor which plays a key role in the regulation of food intake. Pharmacological manipulation of the growth hormone secretagogue receptor-type 1a (GHSR-1a) receptor has therefore received a lot of attention as a strategy to combat disorders of appetite and body weight, including age-related malnutrition and the progressive muscle wasting syndrome known as cachexia. In this study, a milk protein-derivative is shown to increase GHSR-1a-mediated intracellular calcium signalling in a concentration-dependent manner in vitro. Significant increases in calcium mobilisation were also observed in a cultured neuronal cell line heterologously expressing the GHS-R1a. In addition, both additive and synergistic effects were observed following co-exposure of GHSR-1a to both the hydrolysate and ghrelin. Subsequent in vivo studies monitored standard chow intake in healthy male and female Sprague-Dawley rats after dosing with the casein hydrolysate (CasHyd). Furthermore, the provision of gastro-protected oral delivery to the bioactive in vivo may aid in the progression of in vitro efficacy to in vivo functionality. In summary, this study reports a ghrelin-stimulating bioactive peptide mixture (CasHyd) with potent effects in vitro. It also provides novel and valuable translational data supporting the potential role of CasHyd as an appetite-enhancing bioactive. Further mechanistic studies are required in order to confirm efficacy as a ghrelinergic bioactive in susceptible population groups.

Chitosan-coated liposome dry-powder formulations loaded with ghrelin for nose-to-brain delivery

The nose-to-brain delivery of ghrelin loaded in liposomes is a promising approach for the management of cachexia. It could limit the plasmatic degradation of ghrelin and provide direct access to the brain, where ghrelin's specific receptors are located. Anionic liposomes coated with chitosan in either a liquid or a dry-powder formulation were compared. The powder formulation showed stronger adhesion to mucins (89 ± 4% vs 61 ± 4%), higher ghrelin entrapment efficiency (64 ± 2% vs 55 ± 4%), higher enzymatic protection against trypsin (26 ± 2% vs 20 ± 3%) and lower ghrelin storage degradation at 25 °C (2.67 ± 1.1% vs 95.64 ± 0.85% after 4 weeks). The powder formulation was also placed in unit-dose system devices that were able to generate an appropriate aerosol characterized by a Dv50 of 38 ± 6 µm, a limited percentage of particles smaller than 10 µm of 4 ± 1% and a reproducible mass delivery (CV: 1.49%). In addition, the device was able to deposit a large amount of powder (52.04% w/w) in the olfactory zone of a 3D-printed nasal cast. The evaluated combination of the powder formulation and the device could provide a promising treatment for cachexia.

Development of coated liposomes loaded with ghrelin for nose-to-brain delivery for the treatment of cachexia

The aim of the present study was to develop a ghrelin-containing formulation based on liposomes coated with chitosan intended for nose–brain delivery for the treatment of cachexia. Among the three types of liposomes developed, anionic liposomes provided the best results in terms of encapsulation efficiency (56%) and enzymatic protection against trypsin (20.6% vs 0% for ghrelin alone) and carboxylesterase (81.6% vs 17.2% for ghrelin alone). Ghrelin presented both electrostatic and hydrophobic interactions with the anionic lipid bilayer, as demonstrated by isothermal titration calorimetry. Then, anionic liposomes were coated with N-(2-hydroxy) propyl-3-trimethyl ammonium chitosan chloride. The coating involved a size increment from 146.9±2.7 to 194±6.1 nm, for uncoated and coated liposomes, respectively. The ζ-potential was similarly increased from -0.3±1.2 mV to 6±0.4 mV before and after coating, respectively. Chitosan provided mucoadhesion, with an increase in mucin adsorption of 22.9%. Enhancement of permeation through the Calu3 epithelial monolayer was also observed with 10.8% of ghrelin recovered in the basal compartment in comparison to 0% for ghrelin alone. Finally, aerosols generated from two nasal devices (VP3 and SP270) intended for aqueous dispersion were characterized with either coated or uncoated liposomes. Contrarily to the SP270 device, VP3 device showed minor changes between coated and uncoated liposome aerosols, as shown by their median volume diameters of 38.4±5.76 and 37.6±5.74 µm, respectively. Overall, the results obtained in this study show that the developed formulation delivered by the VP3 device can be considered as a potential candidate for nose–brain delivery of ghrelin.

Acylated and unacylated ghrelin inhibit atrophy in myotubes co-cultured with colon carcinoma cells

Cancer cachexia is a result of increased protein degradation and decreased protein synthesis. The multifunctional circulating hormone ghrelin promotes synthesis and inhibits degradation of muscle protein, but its mechanism of action is not fully understood. Here, we investigated whether co-culturing C2C12 myotubes with CT26 colon carcinoma cells induces myotube atrophy, and whether acylated ghrelin (AG) and unacylated ghrelin (UnAG) had anti-atrophic effects. We found that co-culture induced myotube atrophy and increased tumor necrosis factor-alpha (TNF-α) and myostatin concentrations in the culture medium. Moreover, co-culture down-regulated myogenin and MyoD expression, inhibited the Akt signaling, up-regulated ubiquitin E3 ligase expression, and activated the calpain system and autophagy in myotubes. Both AG and UnAG inhibited these changes. Our study describes a novel in vitro model that can be employed to investigate cancer cachexia, and our findings suggest a possible use for AG and UnAG in treating cancer cachexia.

From Belly to Brain: Targeting the Ghrelin Receptor in Appetite and Food Intake Regulation

Ghrelin is the only known peripherally-derived orexigenic hormone, increasing appetite and subsequent food intake. The ghrelinergic system has therefore received considerable attention as a therapeutic target to reduce appetite in obesity as well as to stimulate food intake in conditions of anorexia, malnutrition and cachexia. As the therapeutic potential of targeting this hormone becomes clearer, it is apparent that its pleiotropic actions span both the central nervous system and peripheral organs. Despite a wealth of research, a therapeutic compound specifically targeting the ghrelin system for appetite modulation remains elusive although some promising effects on metabolic function are emerging. This is due to many factors, ranging from the complexity of the ghrelin receptor (Growth Hormone Secretagogue Receptor, GHSR-1a) internalisation and heterodimerization, to biased ligand interactions and compensatory neuroendocrine outputs. Not least is the ubiquitous expression of the GHSR-1a, which makes it impossible to modulate centrally-mediated appetite regulation without encroaching on the various peripheral functions attributable to ghrelin. It is becoming clear that ghrelin’s central signalling is critical for its effects on appetite, body weight regulation and incentive salience of food. Improving the ability of ghrelin ligands to penetrate the blood brain barrier would enhance central delivery to GHSR-1a expressing brain regions, particularly within the mesolimbic reward circuitry.

Circulating ghrelin levels and obestatin/ghrelin ratio as a marker of activity in ulcerative colitis

Background/Aims

Ghrelin levels are known to increase in patients with ulcerative colitis (UC), but serum obestatin levels in UC patients are not well elucidated. The aim of this study was to examine the relationship between serum ghrelin and obestatin levels and disease activity in UC patients.

Methods

The serum ghrelin and obestatin levels were measured in 21 UC patients (12 with active disease and 9 in remission) using enzyme-linked immunosorbent assay. The relationship between the circulating levels of these 2 hormones and disease activity was analyzed. The colonic mucosal mRNA expression of ghrelin and obestatin was measured by quantitative reverse transcription polymerase chain reaction.

Results

The mean serum ghrelin values were significantly higher in patients with active disease than in patients with remission (1370.6±404.3 vs. 783.5±235.3 pg/mL, P=0.001). Colonic mucosal mRNA expression of ghrelin was also significantly higher in patients with active disease than in patients in remission (0.805±0.214 vs. 0.481±0.356, P=0.018). However, the mean serum obestatin levels and colonic mucosal mRNA expression of obestatin were not significantly different between both groups. The circulating obestatin/ghrelin ratio was significantly lower in patients with active UC than in patients in remission (0.32±0.08 vs. 0.58±0.20, P=0.001).

Conclusions

The serum ghrelin levels and the obestatin/ghrelin ratio were related to the activity of UC, but serum obestatin was not related to activity of UC. The ghrelin levels and the obestatin/ghrelin ratio could serve as activity markers in patients with UC.

Serum ghrelin and adiponectin levels are increased but serum leptin level is unchanged in low weight Chronic Obstructive Pulmonary Disease patients

BACKGROUND

Weight loss and muscle wasting are common features reported in COPD patients and they are all related with systemic inflammation. In this study, the relationship between pulmonary functions and inflammatory and metabolic parameters in low weight COPD patients were investigated.

METHODS

Fifty male COPD patients were grouped according to the Global Initiative for Chronic Obstructive Lung Disease criteria. Group 1: Mild-moderate COPD patients (n=18; with a mean age of 66.4 ± 9.2 yrs; body mass index (BMI):19.7 ± 1.5 kg/m(2)), group 2: Severe-very severe COPD patients (n=32; with a mean age of 65.9 ± 10.0 yrs; BMI:19.3 ± 1.6 kg/m(2)), group 3: Control group composed of healthy nonsmoking males (n=17; with a mean age of 50.2 ± 8.4 yrs; BMI:21.85 ± 1.5 kg/m(2)). Anthropometric parameters, serum levels of adiponectin (ApN), ghrelin, leptin, hsCRP, IL-6, IL-1β, IL-8, TNF-α and pulmonary functions were compared.

RESULTS

Adiponectin concentration was higher in group 1 (43.3 ± 28.6 ng/mL; p<0.05) and group 2 (59.9 ± 31.8 ng/mL; p<0.001) when compared with the control group (23.5 ± 13.6 ng/mL). Ghrelin concentrations were higher in COPD groups (1281.0 ± 1173.7 and 1840.0 ± 403.6 pg/mL; p<0.05) compared to the control subjects (554.0 ± 281.9 pg/mL). When the groups were compared, no significant difference was found for leptin, IL-1β, TNF-α, and IL-8. Interleukin-6 and hsCRP levels were higher in group 1 than in the control group. ApN was negatively correlated with BMI and FEV1. In all groups, FEV1 showed positive correlation with BMI, skinfold thicknesses, insulin and triglyceride; negative correlation with age, pack/years, HDL-Chol and ApN. Increased SHBG with decreased insulin level and HOMA-IR may indicate increased insulin sensitivity in COPD groups.

CONCLUSION

The anti-inflammatory effect of ApN and ghrelin is more evident in severe-very severe COPD patients.

Drugs in development for treatment of patients with cancer-related anorexia and cachexia syndrome

Cancer-related anorexia and cachexia syndrome (CACS) is a complex multifactorial condition, with loss of lean body mass, chronic inflammation, severe metabolic derangements, reduced food intake, reduced physical activity, and poor quality of life as key symptoms. Cachexia recognizes different phases or stages, moving from precachexia through overt cachexia to advanced or refractory cachexia. The purpose of this review is to describe currently effective approaches for the treatment of cachexia, moving forward to drugs and treatments already shown to be effective but needing further clinical trials to confirm their efficacy. We then introduce novel promising investigational drugs and approaches which, based on a strong rationale from the most recent data on the molecular targets/pathways driving the pathophysiology of cachexia, need to be tested either in currently ongoing or appropriate future clinical trials to confirm their clinical potential. Although different drugs and treatments have been tested, we can speculate that a single therapy may not be completely successful. Indeed, considering the complex clinical picture and the multifactorial pathogenesis of CACS, we believe that its clinical management requires a multidisciplinary and multitargeted approach. In our opinion, appropriate treatment for cachexia should target the following conditions: inflammatory status, oxidative stress, nutritional disorders, muscle catabolism, immunosuppression, quality of life, and above all, fatigue. A comprehensive list of the most interesting and effective multitargeted treatments is reported and discussed, with the aim of suggesting the most promising with regard to clinical outcome. A critical issue is that of testing therapies at the earliest stages of cachexia, possibly at the precachexia stage, with the aim of preventing or delaying the development of overt cachexia and thereby obtaining the best possible clinical outcome for patients.

Ghrelin and cachexia in chronic kidney disease

Ghrelin is a growth hormone (GH) secretagogue and a potent orexigenic factor that stimulates feeding by interacting with hypothalamic feeding-regulatory nuclei. Its multifaceted effects are potentially beneficial as a treatment in human disease states. In both adult and pediatric chronic kidney disease (CKD) patients, decreased appetite plays a major role in wasting, which in turn is linked to morbidity and mortality; wasting has also been linked to high levels of leptin and proinflammatory cytokines. The beneficial effects of ghrelin treatment in CKD are potentially mediated by multiple concurrent actions, including the stimulation of appetite-regulating centers, anti-inflammatory effects, and direct kidney effects. Further evaluation of this appetite-regulating hormone in CKD is needed to confirm previous findings and to determine the underlying mechanisms.

Acylated and unacylated ghrelin impair skeletal muscle atrophy in mice

Cachexia is a wasting syndrome associated with cancer, AIDS, multiple sclerosis, and several other disease states. It is characterized by weight loss, fatigue, loss of appetite, and skeletal muscle atrophy and is associated with poor patient prognosis, making it an important treatment target. Ghrelin is a peptide hormone that stimulates growth hormone (GH) release and positive energy balance through binding to the receptor GHSR-1a. Only acylated ghrelin (AG), but not the unacylated form (UnAG), can bind GHSR-1a; however, UnAG and AG share several GHSR-1a-independent biological activities. Here we investigated whether UnAG and AG could protect against skeletal muscle atrophy in a GHSR-1a-independent manner. We found that both AG and UnAG inhibited dexamethasone-induced skeletal muscle atrophy and atrogene expression through PI3Kβ-, mTORC2-, and p38-mediated pathways in myotubes. Upregulation of circulating UnAG in mice impaired skeletal muscle atrophy induced by either fasting or denervation without stimulating muscle hypertrophy and GHSR-1a-mediated activation of the GH/IGF-1 axis. In Ghsr-deficient mice, both AG and UnAG induced phosphorylation of Akt in skeletal muscle and impaired fasting-induced atrophy. These results demonstrate that AG and UnAG act on a common, unidentified receptor to block skeletal muscle atrophy in a GH-independent manner.

Treatment of cachexia: melanocortin and ghrelin interventions

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

Current pharmacotherapy options for cancer anorexia and cachexia

INTRODUCTION

Anorexia and cachexia syndrome represents a complex clinical picture that occurs in the late stage of several chronic inflammatory diseases, including cancer. Unless counteracted cancer-related anorexia and cachexia syndrome affects quality of life (QL) and survival. However, to date a standard effective treatment is lacking.

AREAS COVERED

The aim of this review is to describe the current pharmacological approaches for anorexia and cachexia syndrome, focusing on cancer-related syndrome. The several pharmacological agents tested so far are discussed, distinguishing them in unproven drugs, effective drugs, and drugs under investigation. Moreover, a section is devoted to the promising use of nutritional supplements and nutraceuticals. The emerging role of a multitargeted combined treatment approach is exhaustively reviewed.

EXPERT OPINION

Considering the complex clinical picture and the multifactorial pathogenesis of anorexia and cachexia syndrome, we believe that its clinical management requires a multidisciplinary and multipharmacological approach. In our opinion the anorexia and cachexia syndrome treatment should include drugs that target the following conditions: inflammatory status, oxidative stress, nutritional disorders, muscle catabolism, anemia, immunosuppression, and fatigue. The multidimensional therapies for anorexia and cachexia syndrome should ideally be introduced within a context of the "best supportive care," which includes optimal symptom management and careful psychosocial counseling.

The ghrelin axis--does it have an appetite for cancer progression?

Ghrelin, the endogenous ligand for the GH secretagogue receptor (GHSR), is a peptide hormone with diverse physiological roles. Ghrelin regulates GH release, appetite and feeding, gut motility, and energy balance and also has roles in the cardiovascular, immune, and reproductive systems. Ghrelin and the GHSR are expressed in a wide range of normal and tumor tissues, and a fluorescein-labeled, truncated form of ghrelin is showing promise as a biomarker for prostate cancer. Plasma ghrelin levels are generally inversely related to body mass index and are unlikely to be useful as a biomarker for cancer, but may be useful as a marker for cancer cachexia. Some single nucleotide polymorphisms in the ghrelin and GHSR genes have shown associations with cancer risk; however, larger studies are required. Ghrelin regulates processes associated with cancer, including cell proliferation, apoptosis, cell migration, cell invasion, inflammation, and angiogenesis; however, the role of ghrelin in cancer is currently unclear. Ghrelin has predominantly antiinflammatory effects and may play a role in protecting against cancer-related inflammation. Ghrelin and its analogs show promise as treatments for cancer-related cachexia. Further studies using in vivo models are required to determine whether ghrelin has a role in cancer progression.

Plasma leptin levels increase to a greater extent following on-pump coronary artery surgery in type 2 diabetic patients than in nondiabetic patients

AIMS

We aimed to evaluate whether leptin and ghrelin responses to cardiopulmonary bypass (CPB) are dependent on type 2 diabetes and whether these responses are associated with interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP), cortisol and insulin.

METHODS

We examined stress-response patterns in plasma leptin, ghrelin, hsCRP, IL-6, cortisol and insulin levels before and up to 5 days after cardiopulmonary bypass in 20 patients with type 2 diabetes and 20 patients without diabetes.

RESULTS

Plasma leptin levels increased significantly in both groups (p<0.05) and rose significantly higher in diabetics when compared with nondiabetic patients (p=0.004). Plasma ghrelin levels increased significantly only in diabetics (p=0.033). Patients with and without diabetes showed significantly elevated serum concentrations of IL-6, hsCRP, cortisol and insulin (p<0.005 for IL-6, hsCRP; p<0.05 for cortisol, insulin) but the difference between the two groups was nonsignificant. Leptin was independently predicted by hsCRP (p<0.05, F=2.9), gender (women p<0.001, F=4.7), body mass index (BMI p<0.0001, F=6.1) whereas ghrelin levels were not associated with any variables in the total patient population. (critical F=2.26, p≤0.05).

CONCLUSIONS

Acute phase response in diabetics differs by higher leptin levels independent of BMI, gender and IL-6, hsCRP, insulin and cortisol levels.

Hypothalamic inflammation: a double-edged sword to nutritional diseases

The hypothalamus is one of the master regulators of various physiological processes, including energy balance and nutrient metabolism. These regulatory functions are mediated by discrete hypothalamic regions that integrate metabolic sensing with neuroendocrine and neural controls of systemic physiology. Neurons and nonneuronal cells in these hypothalamic regions act supportively to execute metabolic regulations. Under conditions of brain and hypothalamic inflammation, which may result from overnutrition-induced intracellular stresses or disease-associated systemic inflammatory factors, extracellular and intracellular environments of hypothalamic cells are disrupted, leading to central metabolic dysregulations and various diseases. Recent research has begun to elucidate the effects of hypothalamic inflammation in causing diverse components of metabolic syndrome leading to diabetes and cardiovascular disease. These new understandings have provocatively expanded previous knowledge on the cachectic roles of brain inflammatory response in diseases, such as infections and cancers. This review describes the molecular and cellular characteristics of hypothalamic inflammation in metabolic syndrome and related diseases as opposed to cachectic diseases, and also discusses concepts and potential applications of inhibiting central/hypothalamic inflammation to treat nutritional diseases.

Ghrelin modulates baroreflex-regulation of sympathetic vasomotor tone in healthy humans

Ghrelin, a neuropeptide originally known for its growth hormone-releasing and orexigenic properties, exerts important pleiotropic effects on the cardiovascular system. Growing evidence suggests that these effects are mediated by the sympathetic nervous system. The present study aimed at elucidating the acute effect of ghrelin on sympathetic outflow to the muscle vascular bed (muscle sympathetic nerve activity, MSNA) and on baroreflex-mediated arterial blood pressure (BP) regulation in healthy humans. In a randomized double-blind cross-over design, 12 lean young men were treated with a single dose of either ghrelin 2 μg/kg iv or placebo (isotonic saline). MSNA, heart rate (HR), and BP were recorded continuously from 30 min before until 90 min after substance administration. Sensitivity of arterial baroreflex was repeatedly tested by injection of vasoactive substances based on the modified Oxford protocol. Early, i.e., during the initial 30 min after ghrelin injection, BP significantly decreased together with a transient increase of MSNA and HR. In the course of the experiment (>30 min), BP approached placebo level, while MSNA and HR were significantly lower compared with placebo. The sensitivity of vascular arterial baroreflex significantly increased at 30-60 min after intravenous ghrelin compared with placebo, while HR response to vasoactive drugs was unaltered. Our findings suggest two distinct phases of ghrelin action: In the immediate phase, BP is decreased presumably due to its vasodilating effects, which trigger baroreflex-mediated counter-regulation with increases of HR and MSNA. In the delayed phase, central nervous sympathetic activity is suppressed, accompanied by an increase of baroreflex sensitivity.

Characterization of new stable ghrelin analogs with prolonged orexigenic potency

Ghrelin, the only known peripherally produced and centrally acting peptide that stimulates food intake, is synthesized primarily in the stomach and acts through the growth hormone secretagogue receptor (GHS-R1a). In addition to its orexigenic effect, ghrelin stimulates the release of growth hormone (GH). In this study, we investigated the biological properties of full-length and shortened ghrelin analogs in which octanoylated Ser(3) is replaced with an octanoic acid moiety coupled to diaminopropionic acid (Dpr). Ghrelin analogs stabilized with Dpr(N-octanoyl) in position 3 and noncoded amino acids in position 1 (sarcosine) and/or position 4 (naphthylalanine or cyclohexylalanine) were found to possess affinities similar to those of ghrelin for cell membranes with transfected GHS-R1a. In vivo, the prolonged orexigenic effects of analogs containing Dpr(N-octanoyl)(3) compared with that of ghrelin in adult mice and a similar impact on GH secretion in young mice were found. Full-length [Dpr(N-octanoyl)(3)]ghrelin and its analogs with a noncoded amino acid in position 1 and/or 4 showed significantly prolonged stability in blood plasma compared with that of ghrelin. Ghrelin analogs with a prolonged orexigenic effect are potential treatments for GH deficiency or cachexia that accompanies chronic diseases. Desoctanoylated ghrelin analogs and N-terminal penta- and octapeptides of ghrelin did not show any biological activity.

The challenge of appropriate identification and treatment of starvation, sarcopenia, and cachexia: a survey of Australian dietitians

Malnutrition is an umbrella term that includes starvation, sarcopenia, and cachexia; however, differentiating between these terms is infrequent in clinical practice. Given that the effectiveness of treatment depends on the aetiology of unintentional weight loss, it is important that clinicians are aware of the defining characteristics. The aim of this study was to determine whether Australian dietitians understand and use the terms starvation, sarcopenia, and cachexia and provide targeted treatment strategies accordingly. Members of the Dietitians Association of Australia were surveyed to gain information on practices and attitudes to diagnosis and treatment of adult malnutrition. In addition, three case studies were provided to examine understanding of starvation, sarcopenia, and cachexia. 221 dietitians accessed the survey. 81 respondents (43%) indicated the use of at least one alternate term (starvation, sarcopenia, and/or cachexia). Muscle wasting was the most commonly used diagnostic criterion. High-energy high-protein diet was the most common therapy prescribed. Correct diagnoses for case studies were recorded by 6% of respondents for starvation, 46% for sarcopenia, and 21% for cachexia. There is a need for increased awareness of the existence of starvation, sarcopenia, and cachexia amongst Australian dietitians and research into appropriate methods of identification and treatment for each condition.

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.

Ghrelin, appetite and gastric electrical stimulation

Ghrelin is a peptide hormone produced mainly by the stomach and has widespread physiological functions including increase in appetite. The stimulation of the ghrelin system represents a potential therapeutic approach in various disorders characterized by deficient ghrelin signaling or by low appetite. This stimulation may be achieved via pharmacological targeting of the ghrelin receptor with synthetic ghrelin or ghrelin mimetics or via increased endogenous ghrelin production. Recently, it was demonstrated that gastric electrical stimulation (GES) with Enterra parameters results in increased ghrelin production in rats. Furthermore, recent data revealed putative role of ghrelin-reactive immunoglobulins in the modulation of the ghrelin signaling which can be also stimulated by GES. Here, we review the links between GES and ghrelin in existing GES experimental and clinical applications for treatment of gastroparesis, functional dyspepsia or obesity and discuss if GES can be proposed as a non-pharmacological approach to improve ghrelin secretion in several pathological conditions characterized by low appetite, such as anorexia nervosa or anorexia-cachexia syndrome.

Use of ghrelin as a treatment for inflammatory bowel disease: mechanistic considerations

Inflammatory bowel diseases (IBD)-and in particular Crohn's disease-are immune-mediated processes that result in denuded intestinal mucosa and can produce decreased appetite, weight loss, and systemic inflammation. Current treatments include anti-inflammatory medications, immunomodulators, and feeding interventions. Ghrelin is an endogenous orexigenic hormone that directly stimulates growth hormone release, increases gut motility, and has cardiovascular and anti-inflammatory properties. Although ghrelin levels are elevated in active IBD, administration of ghrelin in most (but not all) animal models of colitis has produced improvements in disease activity and systemic inflammation. The mechanism for these effects is not known but may relate to decreased inflammation, increased motility, increased appetite, and increased colonic blood flow. Human trials have not been performed, however, and more research is clearly needed.

Treatment of cachexia in oncology

Cachexia is a complex metabolic syndrome associated with many chronic or end-stage diseases, especially cancer, and is characterized by loss of muscle with or without loss of fat mass. The management of cachexia is a complex challenge that should address the different causes underlying this clinical event with an integrated or multimodal treatment approach targeting the different factors involved in its pathophysiology. The purpose of this article was to review the current medical treatment of cancer-related cachexia, in particular focusing on combination therapy and ongoing research. Among the treatments proposed in the literature for cancer-related cachexia, some proved to be ineffective, namely, cyproheptadine, hydrazine, metoclopramide, and pentoxifylline. Among effective treatments, progestagens are currently considered the best available treatment option for cancer-related cachexia, and they are the only drugs approved in Europe. Drugs with a strong rationale that have failed or have not shown univocal results in clinical trials so far include eicosapentaenoic acid, cannabinoids, bortezomib, and anti-TNF-alpha MoAb. Several emerging drugs have shown promising results but are still under clinical investigation (thalidomide, selective cox-2 inhibitors, ghrelin mimetics, insulin, oxandrolone, and olanzapine). To date, despite several years of coordinated efforts in basic and clinical research, practice guidelines for the prevention and treatment of cancer-related muscle wasting are lacking, mainly because of the multifactorial pathogenesis of the syndrome. From all the data presented, one can speculate that one single therapy may not be completely successful in the treatment of cachexia. From this point of view, treatments involving different combinations are more likely to be successful.

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.

Combined approach to counteract experimental cancer cachexia: eicosapentaenoic acid and training exercise

BACKGROUND: Cancer cachexia is a syndrome characterized by loss of skeletal muscle protein, depletion of lipid stores, anorexia, weakness, and perturbations of the hormonal homeostasis. Despite several therapeutic approaches described in the past, effective interventions countering cancer cachexia are still lacking. METHODS: The present work was aimed to verify the ability of eicosapentaenoic acid (EPA) to prevent the muscle depletion in Lewis lung carcinoma-bearing mice and to test the ability of endurance exercise training to increase the EPA effect. RESULTS: EPA alone did not prevent the muscle loss induced by tumor growth while the combination with exercise induced a partial rescue of muscle strength and mass. Moreover, the association of EPA and exercise reduced the dramatic PAX-7 accumulation and stimulated the increase of PCG-1 protein. CONCLUSIONS: Overall, the present data suggest that exercise is an effective tool that should be added for combined therapeutic approaches against cancer cachexia. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s13539-011-0028-4) contains supplementary material, which is available to authorized users.

Cancer cachexia therapy: a key weapon in the fight against cancer

PURPOSE OF REVIEW

Cachexia affects millions of cancer patients around the world. Though its causes are poorly understood, its devastating impact on the patient and their loved ones underscore the urgency of this unmet medical need. Recent research efforts suggest multiple body systems are dysregulated in cachexia, not only increasing the challenge in effectively treating the disease but also expanding the opportunities for intervention.

RECENT FINDINGS

Agents as diverse as anti-inflammatory monoclonal antibodies and novel anabolic small molecules are under clinical evaluation for their ability to prevent and treat wasting. The therapies evaluated to date range in their ability to improve appetite, mitigate weight loss and reverse undesirable changes in body composition and physical function.

SUMMARY

An increased understanding of cancer cachexia, both mechanistically and its impact on cancer patients' struggle with their disease, has resulted in diverse therapeutic concepts. Recent clinical efforts demonstrate progress with novel therapies but fall short of effectively treating most cachectic patients and highlight a clear need for further research. Given the inherent heterogeneity of cancer patients and the significant impact of muscle wasting on morbidity and mortality, continued research efforts are critical in developing effective therapies to prevent and treat cancer cachexia.

Mutational analysis of predicted extracellular domains of human growth hormone secretagogue receptor 1a

The Class A family of guanine nucleotide-binding protein (G protein)-coupled receptors that includes receptors for motilin, ghrelin, and growth hormone secretagogue (GHS) has substantial potential importance as drug targets. Understanding of the molecular basis of hormone binding and receptor activation should provide insights helpful in the development of such drugs. We previously reported that Cys residues and the perimembranous residues in the extracellular loops and amino-terminal tail of the motilin receptor are critical for peptide ligand, motilin, binding and biological activity. In the current work, we focused on the predicted extracellular domains of the human GHS receptor 1a, and identified functionally important residues by using sequential deletions ranging from one to twelve amino acid residues and site-directed replacement mutagenesis approach. Each construct was transiently expressed in COS cells, and characterized for ghrelin- and growth hormone releasing peptide (GHRP)-6-stimulated intracellular calcium responses and ghrelin radioligand binding. Cys residues in positions 116 and 198 in the first and second extracellular loops and the perimembranous Glu¹⁸⁷ residue in the second extracellular loop were critical for ghrelin and GHRP-6 biological activity. These results suggest that Cys residues in the extracellular domains in this family of Class A G protein-coupled receptor is likely involved in the highly conserved and functionally important disulfide bond, and that the perimembranous residues contribute peptide ligand binding and signaling.

Update on clinical trials of growth factors and anabolic steroids in cachexia and wasting

This article and others that focused on the clinical features, mechanisms, and epidemiology of skeletal muscle loss and wasting in chronic diseases, which include chronic kidney disease, cancer, and AIDS, were presented at a symposium entitled "Cachexia and Wasting: Recent Breakthroughs in Understanding and Opportunities for Intervention," held at Experimental Biology 2009. The clinical and anabolic efficacy of specific growth factors and anabolic steroids (eg, growth hormone, testosterone, megestrol acetate) in malnutrition and other catabolic states has been the subject of considerable research during the past several decades. Research on the effects of these agents in cachexia or wasting conditions, characterized by progressive loss of skeletal muscle and adipose tissue, focused on patients with AIDS in the early 1990s, when the devastating effects of the loss of body weight, lean body mass, and adipose tissue were recognized as contributors to these patients' mortality. These same agents have also been studied as methods to attenuate the catabolic responses observed in cancer-induced cachexia and in wasting induced by chronic obstructive pulmonary disease, congestive heart failure, renal failure, and other conditions. This article provides an updated review of recent clinical trials that specifically examined the potential therapeutic roles of growth hormone, testosterone, oxandrolone, and megestrol acetate and emerging data on the orexigenic peptide ghrelin, in human cachexia and wasting.

An update on promising agents for the treatment of cancer cachexia

PURPOSE OF REVIEW

There are no published conclusive phase III controlled clinical trials nor general consensus about treatment approaches despite several years of coordinated efforts in basic and clinical research. Consequently, practice guidelines for the prevention and treatment of cancer-related muscle wasting are lacking. The purpose of this review is to supply an update on the promising agents and/or combined approaches for the treatment of cancer cachexia.

RECENT FINDINGS

The choice for cancer cachexia treatment in clinical practice is very limited: the only approved drugs in Europe are progestagens. Several drugs with a strong rationale have failed or have not shown univocal results in clinical trials: they include eicosapentaenoic acid, cannabinoids, bortezomib and anti-tumor necrosis factor (TNF)-alpha monoclonal antibody. Several emerging drugs have shown promising results but are still under clinical investigation [thalidomide, selective cyclooxygenase (COX)-2 inhibitors, ghrelin mimetics, oxandrolone, olanzapine]. Moreover, increasing knowledge of cachexia pathophysiology and preliminary clinical findings seem to suggest that a combined treatment approach may be the most effective option.

SUMMARY

A number of promising new agents are currently being developed but are not as yet regarded as standard of care. They include: selective COX-2 inhibitors, ghrelin mimetics, oxandrolone, selective androgen receptor modulators (ostarine), olanzapine, anti-IL-6 antibody and an innovative approach of multitargeted combined treatment. The data reported seem to suggest that the most effective treatment for cancer cachexia may be a combination regimen rather than single-agent treatments. This is in keeping with the general consensus that cancer cachexia is a multifactorial process and, hence, a potentially effective approach should be multimodal.

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.

Update on melanocortin interventions for cachexia: progress toward clinical application

Cachexia is a devastating syndrome of body wasting that is associated with multiple common chronic diseases including cancer, chronic kidney disease, and chronic heart failure. These underlying diseases are associated with increased levels of inflammatory cytokines and result in anorexia, increased resting energy expenditure, and loss of fat and lean body mass. Prior experiments have implicated the central melanocortin system in the hypothalamus with the propagation of these symptoms of cachexia. Pharmacologic blockade of this system using melanocortin antagonists causes attenuation of the signs of cachexia in laboratory models. Recent advances in our knowledge of this disease process have involved further elucidation of the pathophysiology of melanocortin activation and demonstration of the efficacy of melanocortin antagonists in new models of cachexia, including cardiac cachexia. In addition, small molecule antagonists of the melanocortin-4 receptor continue to be introduced, including ones with oral bioavailability. These developments generate optimism that melanocortin antagonism will be used to treat humans with disease-associated cachexia. However, to date, human application has remained elusive and it is unclear when we will know whether humans with cachexia would benefit from treatment with these compounds.

Animal models of anorexia and cachexia

BACKGROUND: Cachexia is a devastating syndrome of body wasting that worsens quality of life and survival for patients suffering from diseases such as cancer, chronic kidney disease and chronic heart failure. Successful treatments have been elusive in humans, leaving a clear need for the development of new treatment compounds. Animal models of cachexia are able to recapitulate the clinical findings from human disease and have provided a much-needed means of testing the efficacy of prospective therapies. OBJECTIVE: This review focuses on animal models of cachexia caused by cancer, chronic heart failure and chronic kidney disease, including the features of these models, their implementation, and commonly-followed outcome measures. CONCLUSION: Given a dire clinical need for effective treatments of cachexia, animal models will continue a vital role in assessing the efficacy and safety of potential treatments prior to testing in humans. Also important in the future will be the use of animal models to assess the durability of effect from anti-cachexia treatments and their effect on prognosis of the underlying disease states.

Cancer cachexia: medical management

BACKGROUND

Cachexia is a complex metabolic syndrome associated with many chronic or end-stage diseases, especially cancer, and is characterized by loss of muscle with or without loss of fat mass. The management of cachexia is a complex challenge that should address the different causes underlying this clinical event with an integrated or multimodal treatment approach targeting the different factors involved in its pathophysiology.

MATERIALS AND METHODS

The purpose of this article was to review the current medical treatment of cancer-related cachexia, in particular focusing on combination therapy and ongoing research.

RESULTS

Among the treatments proposed in the literature for cancer-related cachexia, some proved to be ineffective, namely, cyproheptadine, hydrazine, metoclopramide, and pentoxifylline. Among effective treatments, progestagens are currently considered the best available treatment option for cancer-related cachexia, and they are the only drugs approved in Europe. Drugs with a strong rationale that have failed or have not shown univocal results in clinical trials so far include eicosapentaenoic acid, cannabinoids, bortezomib, and anti-TNF-alpha MoAb. Several emerging drugs have shown promising results but are still under clinical investigation (thalidomide, selective cox-2 inhibitors, ghrelin mimetics, insulin, oxandrolone, and olanzapine).

CONCLUSIONS

To date, despite several years of co-ordinated efforts in basic and clinical research, practice guidelines for the prevention and treatment of cancer-related muscle wasting are lacking, mainly because of the multifactorial pathogenesis of the syndrome. From all the data presented, one can speculate that one single therapy may not be completely successful in the treatment of cachexia. From this point of view, treatments involving different combinations are more likely to be successful.

Recent insights on chronic heart failure, cachexia and nutrition

PURPOSE OF REVIEW

To provide recent observations on the interrelation between chronic heart failure (CHF), cachexia and human nutrition and updating epidemiological issues in CHF.

RECENT FINDINGS

Present evidence suggests that impairment in cardiac muscle energetics plays an important role in the pathogenesis of heart failure. New concepts such as microRNA expression are emerging as potential agents in heart failure. Recent research suggests mechanisms by which inflammatory catabolic states may persist in the presence of adequate growth factors and nutrition. A consensus panel has recently designed a definition for general cachexia and its stratification. Together with classicals, new nutrients and substrates are showing efficacies in the malnutrition associated with CHF. Although still promising, ghrelin, growth factors and other biological compounds maintain emergent therapeutical positions for heart failure or associated catabolic states or both.

SUMMARY

Altered intestinal function as an agent for CHF is rising in evidence. New techniques to well diagnose and stratify malnutrition and cardiac cachexia in CHF are needed. Treatment of cachexia in CHF appears to be a combination of different approaches, in which metabolic, nutritional, immunological and hormonal strategies may play an important role. Although the current experimental research is of great help, well designed randomized controlled trials are needed to test these hypothesis and generate clinical evidence.

Weight regain after Roux-en-Y: a significant 20% complication related to PYY

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) produces rapid and dramatic weight loss in very heavy obese patients. Up to 20% cannot sustain their weight loss beyond 2 to 3 y after surgery.

METHODS

To identify putative etiologic factors producing post-RYGB weight regain, a literature survey of metabolic changes in very obese and a review of our diet-induced obese RYGB rat model data was done.

RESULTS

Weight regain suggests an imbalance in physiologic mechanisms regulating appetite and metabolic rate. Weight regain occurred in 25% of our rats, produced by return to presurgical energy intake levels. The 75% of rats that sustained weight loss secreted a significantly larger amount of peptide YY (PYY) while suppressing leptin secretion; those that failed were unable to develop or sustain a sufficiently large plasma PYY:leptin ratio. Metabolic consequences of this failure included reversal of initial postsurgical increases in peripheral fatty acid oxidation, anorexigenic activity in the hypothalamic arcuate nucleus and paraventricular nucleus, and the expression of uncoupling protein-2 in adipose tissues, and decreases in hepatic lipogenesis, free tri-iodothyronine secretion, expression of orexigenic activity in the arcuate nucleus and paraventricular nucleus, expression of adenosine monophosphate kinase in adipose tissues, skeletal muscle mitochondrial mass, and endocannabinoid content and appetite.

CONCLUSION

Weight regain after RYGB occurs in approximately 20% of patients and constitutes a serious complication. Weight regain-promoting consequences are attributed to a failure to sustain elevated plasma PYY concentrations, indicating that combining RYGB with pharmacologic stimulation of PYY secretion in patients after RYGB who exhibit inadequate PYY concentration may increase long-term success of surgical weight reduction in morbidly obese adults.