Ghrelin: from discovery to cancer cachexia therapy

Psychological distress as a risk factor for the efficacy of chemotherapy in advanced gastric cancer patients

AIM

To assess the relationship between psychological distress and quality of life (QoL), cancer-related fatigue (CRF), and chemotherapy efficacy in advanced gastric cancer patients.

METHODS

Advanced gastric cancer patients (39 with psychological distress and 35 without psychological distress) completed the Distress Thermometer (DT), QoL, and CRF test before receiving chemotherapy and assessed the efficacy after completing 2 courses of chemotherapy.

RESULTS

Psychological distress was a significant factor in the efficacy of chemotherapy in advanced gastric cancer patients (χ2 = 6.324; p = 0.042). Compared to advanced gastric cancer patients with no psychological distress, advanced gastric cancer patients with psychological distress had a poorer QoL (50.41 ± 6.17 vs. 60.01 ± 7.94, t =  - 5.882, p < 0.01) and more pronounced CRF (5.75 ± 1.16 vs. 3.22 ± 0.75, t = 11.231, p < 0.01) while receiving chemotherapy. FACT-G (p = 0.0035, r =  - 0.4568), as well as PFS (p < 0.0001, r = 0.6599), correlated significantly with efficacy for patients in the psychological distress group. The FACT-G (p = 0.0134, r =  - 0.4139) of patients in the no psychological distress group correlated significantly with efficacy.

CONCLUSION

Psychological distress has a negative impact on QoL, CRF, and efficacy and may be a potential risk for the efficacy of palliative chemotherapy in advanced gastric cancer patients.

Fatigue Prevalence Among Palliative Care Cancer Patients in Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia: A Cross-Sectional Study

Objective: The aims of the current study are to assess the prevalence of cancer-related fatigue, to examine the difference in cancer-related fatigue severity in relation to patients' characteristics (age, gender, type of cancer, and palliative performance status), and to explore the correlation between cancer-related fatigue and pain, dyspnea, insomnia, and depression among palliative care patients. Methods: A cross-sectional descriptive observational study conducted at Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia. The study included cancer patients who received palliative care services from January 2016 to December 2021. Clinical data of study participants were retrospectively collected from Palliative Care department patient registry. Symptoms were assessed and scored using Edmonton Symptom Assessment Scale. Data analysis was performed using SPSS statistical software. Results: A total of 2616 patients were included in the study, 52.3% were females and 47.7% were males. The median age of study participants was 56 years (range: 2-101 years). Among all study population, the highest reported cancer type was gastrointestinal malignancy (33.5%), while the least was unknown primary malignancy (1.4%). With regards to Edmonton Symptom Assessment Scale, pain (86.4%) and fatigue (83%) were the highest reported symptom in comparison to constipation (17.3%) and insomnia (7.1%). Conclusion: Cancer-related fatigue is a prevalent and concerning issue among palliative care patients. It is essential that healthcare providers recognize the prevalence of fatigue among patients with life-limiting illnesses, assess patients for fatigue routinely, incorporate strategies for managing fatigue, work closely with affected individuals and their families in order to guide the establishment of a personalized care plan that addresses the patient's unique needs and preferences.

Modulation of Burn Hypermetabolism in Preclinical Models

Severe burns elicit a state of physiological stress and increased metabolism to help the body compensate for the changes associated with the traumatic injury. However, this hypermetabolic state is associated with increased insulin resistance, cardiovascular dysfunction, skeletal muscle catabolism, impaired wound healing, and delayed recovery. Several interventions were attempted to modulate burn hypermetabolism, including nutritional support, early excision and grafting, and growth hormone application. However, burn hypermetabolism still imposes significant morbidity and mortality in burn patients. Due to the limitations of in vitro models, animal models are indispensable in burn research. Animal models provide researchers with invaluable tools to test the safety and efficacy of novel treatments or advance our knowledge of previously utilized agents. Several animal studies evaluated novel therapies to modulate burn hypermetabolism in the last few years, including recombinant human growth hormone, erythropoietin, acipimox, apelin, anti-interleukin-6 monoclonal antibody, and ghrelin therapies. Results from these studies are promising and may be effectively translated into human studies. In addition, other studies revisited drugs previously used in clinical practice, such as insulin and metformin, to further investigate their underlying mechanisms as modulators of burn hypermetabolism. This review aims to update burn experts with the novel therapies under investigation in burn hypermetabolism with a focus on applicability and translation. Furthermore, we aim to guide researchers in selecting the correct animal model for their experiments by providing a summary of the methodology and the rationale of the latest studies.

Ghrelin and its role in gastrointestinal tract tumors (Review)

Ghrelin, an orexigenic hormone, is a peptide that binds to the growth hormone secretagogue receptor; it is secreted mainly by enteroendocrine cells in the oxyntic glands of the stomach. Ghrelin serves a role in both local and systemic physiological processes, and is implicated in various pathologies, including neoplasia, with tissue expression in several types of malignancies in both in vitro and in vivo studies. However, the precise implications of the ghrelin axis in metastasis, invasion and cancer progression regulation has yet to be established. In the case of gastrointestinal (GI) tract malignancies, ghrelin has shown potential to become a prognostic factor or even a therapeutic target, although data in the literature are inconsistent and unsystematic, with reports untailored to a specific histological subtype of cancer or a particular localization. The evaluation of immunohistochemical expression shows a limited outlook owing to the low number of cases analyzed, and in vivo analyses have conflicting data regarding differences in ghrelin serum levels in patients with cancer. The aim of this review was to examine the relationship between ghrelin and GI tract malignancies to demonstrate the inconsistencies in current results and to highlight its clinical significance in the outcome of these patients.

Cancer cachexia: molecular mechanism and pharmacological management

Cancer cachexia often occurs in malignant tumors and is a multifactorial and complex symptom characterized by wasting of skeletal muscle and adipose tissue, resulting in weight loss, poor life quality and shorter survival. The pathogenic mechanism of cancer cachexia is complex, involving a variety of molecular substrates and signal pathways. Advancements in understanding the molecular mechanisms of cancer cachexia have provided a platform for the development of new targeted therapies. Although recent outcomes of early-phase trials have showed that several drugs presented an ideal curative effect, monotherapy cannot be entirely satisfactory in the treatment of cachexia-associated symptoms due to its complex and multifactorial pathogenesis. Therefore, the lack of definitive therapeutic strategies for cancer cachexia emphasizes the need to develop a better understanding of the underlying mechanisms. Increasing evidences show that the progression of cachexia is associated with metabolic alternations, which mainly include excessive energy expenditure, increased proteolysis and mitochondrial dysfunction. In this review, we provided an overview of the key mechanisms of cancer cachexia, with a major focus on muscle atrophy, adipose tissue wasting, anorexia and fatigue and updated the latest progress of pharmacological management of cancer cachexia, thereby further advancing the interventions that can counteract cancer cachexia.

Quality by Design Approach for the Development of Liposome Carrying Ghrelin for Intranasal Administration

The therapeutic use of peptides has increasingly recognized in the development of new therapies. However, the susceptible enzymatic cleavage is a barrier that needs to overcome. Nose-to-brain delivery associated with liposomes can protect peptides against biodegradation and improve the accessibility to brain targets. The aim was to develop a liposomal formulation as ghrelin carrier. The quality by design (QbD) approach was used as a strategy for method development. The initial risk assessments were carried out using a fishbone diagram. A screening design study was performed for the critical material attributes/critical process parameters (CMAs/CPPs) on critical quality attributes (CQAs). Liposomes were obtained by hydrating phospholipid films, followed by extrusion or homogenization, and coated with chitosan. The optimized liposome formulation was produced by high-pressure homogenization coated with chitosan, and the resulted were liposomes size 72.25 ± 1.46 nm, PDI of 0.300 ± 0.027, the zeta potential of 50.3 ± 1.46 mV, and encapsulation efficiency of 53.2%. Moreover, chitosan coating improved performance in ex vivo permeation and mucoadhesion analyzes when compared to the uncoated liposome. In this context, chitosan coating is essential for the performance of the formulations in the ex vivo permeation and mucoadhesion analyzes. The intranasal administration of ghrelin liposomes coated with chitosan offers an innovative opportunity to treat cachexia.

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.

Cachexia, muscle wasting, and frailty in cardiovascular disease

The last several years have seen increasing interest in understanding cachexia, muscle wasting, and physical frailty across the broad spectrum of patients with cardiovascular illnesses. This interest originally started in the field of heart failure, but has recently been extended to other areas such as atrial fibrillation, coronary artery disease, peripheral artery disease as well as to patients after cardiac surgery or transcatheter aortic valve implantation. Tissue wasting and frailty are prevalent among many of the affected patients. The ageing process itself and concomitant cardiovascular illness decrease lean mass while fat mass is relatively preserved, making elderly patients particularly prone to develop wasting syndromes and frailty. The aim of this review is to provide an overview of the available knowledge of body wasting and physical frailty in patients with cardiovascular illness, particularly focussing on patients with heart failure in whom most of the available data have been gathered. In addition, mechanisms of wasting and possible therapeutic targets are discussed.

Mazzola P, Souto EB, Chaud MV. Cachexia: Pathophysiology and Ghrelin Liposomes for Nose-to-Brain Delivery

Cachexia, a severe multifactorial condition that is underestimated and unrecognized in patients, is characterized by continuous muscle mass loss that leads to progressive functional impairment, while nutritional support cannot completely reverse this clinical condition. There is a strong need for more effective and targeted therapies for cachexia patients. There is a need for drugs that act on cachexia as a distinct and treatable condition to prevent or reverse excess catabolism and inflammation. Due to ghrelin properties, it has been studied in the cachexia and other treatments in a growing number of works. However, in the body, exogenous ghrelin is subject to very rapid degradation. In this context, the intranasal release of ghrelin-loaded liposomes to cross the blood-brain barrier and the release of the drug into the central nervous system may be a promising alternative to improve its bioavailability. The administration of nose-to-brain liposomes for the management of cachexia was addressed only in a limited number of published works. This review focuses on the discussion of the pathophysiology of cachexia, synthesis and physiological effects of ghrelin and the potential treatment of the diseased using ghrelin-loaded liposomes through the nose-to-brain route.

Physiological Effect of Ghrelin on Body Systems

Ghrelin is a relatively novel multifaceted hormone that has been found to exert a plethora of physiological effects. In this review, we found/confirmed that ghrelin has effect on all body systems. It induces appetite; promotes the use of carbohydrates as a source of fuel while sparing fat; inhibits lipid oxidation and promotes lipogenesis; stimulates the gastric acid secretion and motility; improves cardiac performance; decreases blood pressure; and protects the kidneys, heart, and brain. Ghrelin is important for learning, memory, cognition, reward, sleep, taste sensation, olfaction, and sniffing. It has sympatholytic, analgesic, antimicrobial, antifibrotic, and osteogenic effects. Moreover, ghrelin makes the skeletal muscle more excitable and stimulates its regeneration following injury; delays puberty; promotes fetal lung development; decreases thyroid hormone and testosterone; stimulates release of growth hormone, prolactin, glucagon, adrenocorticotropic hormone, cortisol, vasopressin, and oxytocin; inhibits insulin release; and promotes wound healing. Ghrelin protects the body by different mechanisms including inhibition of unwanted inflammation and induction of autophagy. Having a clear understanding of the ghrelin effect in each system has therapeutic implications. Future studies are necessary to elucidate the molecular mechanisms of ghrelin actions as well as its application as a GHSR agonist to treat most common diseases in each system without any paradoxical outcomes on the other systems.

Tumour-derived transforming growth factor-β signalling contributes to fibrosis in patients with cancer cachexia

BACKGROUND

Cachexia is a paraneoplastic syndrome related with poor prognosis. The tumour micro-environment contributes to systemic inflammation and increased oxidative stress as well as to fibrosis. The aim of the present study was to characterise the inflammatory circulating factors and tumour micro-environment profile, as potentially contributing to tumour fibrosis in cachectic cancer patients.

METHODS

74 patients (weight stable cancer n = 31; cachectic cancer n = 43) diagnosed with colorectal cancer were recruited, and tumour biopsies were collected during surgery. Multiplex assay was performed to study inflammatory cytokines and growth factors. Immunohistochemistry analysis was carried out to study extracellular matrix components.

RESULTS

Higher protein expression of inflammatory cytokines and growth factors such as epidermal growth factor, granulocyte-macrophage colony-stimulating factor, interferon-α, and interleukin (IL)-8 was observed in the tumour and serum of cachectic cancer patients in comparison with weight-stable counterparts. Also, IL-8 was positively correlated with weight loss in cachectic patients (P = 0.04; r = 0.627). Immunohistochemistry staining showed intense collagen deposition (P = 0.0006) and increased presence of α-smooth muscle actin (P < 0.0001) in tumours of cachectic cancer patients, characterizing fibrosis. In addition, higher transforming growth factor (TGF)-β1, TGF-β2, and TGF-β3 expression (P = 0.003, P = 0.05, and P = 0.047, respectively) was found in the tumour of cachectic patients, parallel to p38 mitogen-activated protein kinase alteration. Hypoxia-inducible factor-1α mRNA content was significantly increased in the tumour of cachectic patients, when compared with weight-stable group (P = 0.005).

CONCLUSIONS

Our results demonstrate TGF-β pathway activation in the tumour in cachexia, through the (non-canonical) mitogen-activated protein kinase pathway. The results show that during cachexia, intratumoural inflammatory response contributes to the onset of fibrosis. Tumour remodelling, probably by TGF-β-induced transdifferentiation of fibroblasts to myofibroblasts, induces unbalanced inflammatory cytokine profile, angiogenesis, and elevation of extracellular matrix components (EMC). We speculate that these changes may affect tumour aggressiveness and present consequences in peripheral organs.

A Narrative Review of Cancer-Related Fatigue (CRF) and Its Possible Pathogenesis

Many cancer patients suffer from severe fatigue when treated with chemotherapy or radiotherapy; however, the etiology and pathogenesis of this kind of fatigue remains unknown. Fatigue is associated with cancer itself, as well as adjuvant therapies and can persist for a long time. Cancer patients present a high degree of fatigue, which dramatically affects the quality of their everyday life. There are various clinical research studies and reviews that aimed to explore the mechanisms of cancer-related fatigue (CRF). However, there are certain limitations in these studies: For example, some studies have only blood biochemical texts without histopathological examination, and there has been insufficient systemic evaluation of the dynamic changes in relevant indexes. Thus, we present this narrative review to summarize previous studies on CRF and explore promising research directions. Plenty of evidence suggests a possible association between CRF and physiological dysfunction, including skeletal muscular and mitochondrial dysfunction, peripheral immune activation and inflammation dysfunction, as well as central nervous system (CNS) disorder. Mitochondrial DNA (mtDNA), mitochondrial structure, oxidative pressure, and some active factors such as ATP play significant roles that lead to the induction of CRF. Meanwhile, several pro-inflammatory and anti-inflammatory cytokines in the peripheral system, even in the CNS, significantly contribute to the occurrence of CRF. Moreover, CNS function disorders, such as neuropeptide, neurotransmitter, and hypothalamic-pituitary-adrenal (HPA) axis dysfunction, tend to amplify the sense of fatigue in cancer patients through various signaling pathways. There have been few accurate animal models established to further explore the molecular mechanisms of CRF due to different types of cancer, adjuvant therapy schedules, living environments, and physical status. It is imperative to develop appropriate animal models that can mimic human CRF and to explore additional mechanisms using histopathological and biochemical methods. Therefore, the main purpose of this review is to analyze the possible pathogenesis of CRF and recommend future research that will clarify CRF pathogenesis and facilitate the formulation of new treatment options.

The role of adiponectin, LEPTIN, and ghrelin in the progress and prognosis of childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy. Dysregulation of adipokine pathways is implicated in the carcinogenesis and ALL. The aim of this study is to present the most recent data available regarding the role of leptin, adiponectin and ghrelin in the pathogenesis and prognosis of ALL. The PubMed database was searched using 'Leptin', 'Adiponectin', 'Ghrelin', 'Cancer', 'Children' and 'Acute Lymphoblastic Leukemia' as keywords. The majority of the studies indicated that leptin levels are increased and adiponectin levels are decreased in ALL children at diagnosis, as well as in ALL survivors. Ghrelin levels were found to be lower at diagnosis and progressively increased during treatment. Further research is warranted, as the heterogeneity of the current studies, various treatment protocols and differences in sample sizes make it difficult to deduce solid conclusions regarding the role of adipokines in ALL.

In Vitro and In Vivo Characterization of Novel Stable Peptidic Ghrelin Analogs: Beneficial Effects in the Settings of Lipopolysaccharide-Induced Anorexia in Mice

Ghrelin, the only known orexigenic gut hormone produced primarily in the stomach, has lately gained attention as a potential treatment of anorexia and cachexia. However, its biologic stability is highly limited; therefore, a number of both peptide and nonpeptide ghrelin analogs have been synthesized. In this study, we provide in vitro and in vivo characterization of a series of novel peptide growth hormone secretagogue receptor (GHS-R1a) agonists, both under nonpathologic conditions and in the context of lipopolysaccharide (LPS)-induced anorexia. These analogs were based on our previous series modified by replacing the Ser³ with diaminopropionic acid (Dpr), the N-terminal Gly with sarcosine, and Phe⁴ with various noncoded amino acids. New analogs were further modified by replacing the n-octanoyl bound to Dpr³ with longer or unsaturated fatty acid residues, by incorporation of the second fatty acid residue into the molecule, or by shortening the peptide chain. These modifications preserved the ability of ghrelin analogs to bind to the membranes of cells transfected with GHS-R1a, as well as the GHS-R1a signaling activation. The selected analogs exhibited long-lasting and potent orexigenic effects after a single s.c. administration in mice. The stability of new ghrelin analogs in mice after s.c. administration was significantly higher when compared with ghrelin and [Dpr³]ghrelin, with half-lives of approximately 2 hours. A single s.c. injection of the selected ghrelin analogs in mice with LPS-induced anorexia significantly increased food intake via the activation of orexigenic pathways and normalized blood levels of proinflammatory cytokines, demonstrating the anti-inflammatory potential of the analogs.

Ghrelin for the management of cachexia associated with cancer

BACKGROUND

Cancer sufferers are amongst the most malnourished of all the patient groups. Studies have shown that ghrelin, a gut hormone can be a potential therapeutic agent for cachexia (wasting syndrome) associated with cancer. A variety of mechanisms of action of ghrelin in people with cancer cachexia have been proposed. However, safety and efficacy of ghrelin for cancer-associated cachexia have not been systematically reviewed. The aim of this review was to assess whether ghrelin is associated with better food intake, body composition and survival than other options for adults with cancer cachexia.

OBJECTIVES

To assess the efficacy and safety of ghrelin in improving food intake, body composition and survival in people with cachexia associated with cancer.

SEARCH METHODS

We searched CENTRAL, MEDLINE and Embase without language restrictions up to July 2017. We also searched for ongoing studies in trials registers, performed handsearching, checked bibliographic references of relevant articles and contacted authors and experts in the field to seek potentially relevant research. We applied no restrictions on language, date, or publication status.

SELECTION CRITERIA

We included randomised controlled (parallel-group or cross-over) trials comparing ghrelin (any formulation or route of administration) with placebo or an active comparator in adults (aged 18 years and over) who met any of the international criteria for cancer cachexia.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility. Two review authors then extracted data and assessed the risk of bias for individual studies using standard Cochrane methodology. For dichotomous variables, we planned to calculate risk ratio with 95% confidence intervals (CI) and for continuous data, we planned to calculate mean differences (MD) with 95% CI. We assessed the evidence using GRADE and created 'Summary of findings' tables.

MAIN RESULTS

We screened 926 individual references and identified three studies that satisfied the inclusion criteria. Fifty-nine participants (37 men and 22 women) aged between 54 and 78 years were randomised initially, 47 participants completed the treatment. One study had a parallel design and two had a cross-over design. The studies included people with a variety of cancers and also differed in the dosage, route of administration, frequency and duration of treatment.One trial, which compared ghrelin with placebo, found that ghrelin improved food intake (very low-quality evidence) and had no adverse events (very low-quality evidence). Due to unavailability of data we were unable to report on comparisons for ghrelin versus no treatment or alternative experimental treatment modalities, or ghrelin in combination with other treatments or ghrelin analogues/ghrelin mimetics/ghrelin potentiators. Two studies compared a higher dose of ghrelin with a lower dose of ghrelin, however due to differences in study designs and great diversity in the treatment provided we did not pool the results. In both trials, food intake did not differ between participants on higher-dose and lower-dose ghrelin. None of the included studies assessed data on body weight. One study reported higher adverse events with a higher dose as compared to a lower dose of ghrelin.All studies were at high risk of attrition bias and bias for size of the study. Risk of bias in other domains was unclear or low.We rated the overall quality of the evidence for primary outcomes (food intake, body weight, adverse events) as very low. We downgraded the quality of the evidence due to lack of data, high or unclear risk of bias of the studies and small study size.

AUTHORS' CONCLUSIONS

There is insufficient evidence to be able to support or refute the use of ghrelin in people with cancer cachexia. Adequately powered randomised controlled trials focusing on evaluation of safety and efficacy of ghrelin in people with cancer cachexia is warranted.

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.

Cancer-induced muscle wasting: latest findings in prevention and treatment

Cancer cachexia is a severe and disabling clinical condition that frequently accompanies the development of many types of cancer. Muscle wasting is the hallmark of cancer cachexia and is associated with serious clinical consequences such as physical impairment, poor quality of life, reduced tolerance to treatments and shorter survival. Cancer cachexia may evolve through different stages of clinical relevance, namely pre-cachexia, cachexia and refractory cachexia. Given its detrimental clinical consequences, it appears mandatory to prevent and/or delay the progression of cancer cachexia to its refractory stage by implementing the early recognition and treatment of the nutritional and metabolic alterations occurring during cancer. Research on the molecular mechanisms underlying muscle wasting during cancer cachexia has expanded in the last few years, allowing the identification of several potential therapeutic targets and the development of many promising drugs. Several of these agents have already reached the clinical evaluation, but it is becoming increasingly evident that a single therapy may not be completely successful in the treatment of cancer-related muscle wasting, given its multifactorial and complex pathogenesis. This suggests that early and structured multimodal interventions (including targeted nutritional supplementation, physical exercise and pharmacological interventions) are necessary to prevent and/or treat the devastating consequences of this cancer comorbidity, and future research should focus on this approach.

C-terminus of a hexapeptidic ghrelin receptor inverse agonist can switch peptide behavior from inverse agonism to agonism

Subtle changes in the sequence at the N-terminus and in the aromatic core of hexapeptidic ghrelin receptor inverse agonists can switch behavior from inverse agonism to agonism, but the C-terminal role of the sequence is unclear. Thus, analogs of the ghrelin receptor inverse agonist KbFwLL-NH2 (b = β-(3-benzothienyl)-d-alanine) were synthesized by solid phase peptide synthesis in order to identify the influence of aromaticity, charge, and hydrophobicity. Potency and efficacy of the hexapeptides were evaluated in inositol triphosphate turnover assays. Notably, modifications directly at the C-terminal Leu(6) could influence peptide efficacy leading to decreased constitutive activity. High hydrophobicity at the C-terminal position was of importance for elevated inverse agonist activity, the introduction of charged amino acids led to decreased potency. In contrast, structure-activity relationship studies of Leu(5) located closer to the aromatic core revealed an agonism-inducing position. These findings imply that amino acids with possible cation-π or π-π interactions and a suitable orientation at the C-terminus of the aromatic core induce agonism. Receptor binding studies showed that most peptides bind to the receptor at a concentration of 1 µM and modification directly at the C-terminus is generally more accepted than Leu(5) substitution. Interestingly, this observation is not dependent on the type of modification. These studies reveal another switch region of the short ghrelin receptor ligand pointing out the sensitivity of the ghrelin receptor binding pocket.

Cachexia in cancer: what is in the definition?

OBJECTIVE

This study aimed to provide evidence-based results on differences in overall survival (OS) rate to guide the diagnosis of cancer cachexia.

DESIGN

Data collection and clinical assessment was performed every 3 months (5 visits): baseline data, muscle strength, nutritional and psychosocial status. 2 definitions on cachexia using different diagnostic criteria were applied for the same patient population. Fearon et al's definition is based on weight loss, body mass index (BMI) and sarcopenia. Evans et al nuances the contribution of sarcopenia and attaches additional attention to abnormal biochemistry parameters, fatigue and anorexia. The mean OS rates were compared between patients with and without cachexia for both definitions.

RESULTS

Based on the population of 167 patients who enrolled, 70% developed cachexia according to Fearon et al's definition and 40% according to Evans et al's definition. The OS in the cachectic population is 0.97 and 0.55 years, respectively. The difference in OS between patients with and without cachexia is more significant using the diagnostic criteria of Evans et al. The focus of Fearon et al on weight loss and sarcopenia over-rates the assignment of patients to the cachectic group and OS rates have less prognostic value.

CONCLUSION

This study presents a correlation with prognosis in favour of Evans et al' definition as a tool for cachexia diagnosis. This means that weight loss and BMI decline are both key factors in patients with cancer leading to cachexia but less decisive as stated by Fearon et al. Instead, extra factors gain importance in order to predict survival, such as chronic inflammation, anaemia, protein depletion, reduced food intake, fatigue, decreased muscle strength and lean tissue depletion.

TRIAL REGISTRATION NUMBER

B300201112334.

Bariatric Embolization: Pilot Study on the Impact of Gastroprotective Agents and Arterial Distribution on Ulceration Risk and Efficacy in a Porcine Model

PURPOSE

To assess whether the number of fundal arteries embolized and use of gastroprotective agents have an impact on ghrelin suppression and gastric ulceration rates.

MATERIALS AND METHODS

Twenty-two healthy, growing swine (mean, 38.4 kg; range, 30.3-47.0 kg) were evaluated. Six control swine underwent a sham procedure. Gastric embolization was performed by the infusion of 40-µm microspheres selectively into some or all gastric arteries supplying the gastric fundus. In group 1, 6 swine underwent embolization of all 4 arteries to the gastric fundus. In group 2, 5 swine underwent embolization of 2 gastric fundal arteries. In group 3, 5 swine underwent embolization of 1 gastric fundal artery. Animals in groups 2 and 3 were treated with gastroprotective agents (sucralfate and omeprazole). Weight and fasting plasma ghrelin levels were analyzed at baseline and at week 4. Upon animal euthanasia, gross analysis was performed for identification of ulcers.

RESULTS

Only group 1 animals exhibited changes in serum ghrelin levels that rendered them significantly lower than those in control animals (P = .049). Group 3 animals exhibited marked elevations in serum ghrelin levels compared with control animals (P = .001). Gross pathologic evaluation revealed 0 ulcers in the control animals, 3 ulcers (50%) in group 1, 2 ulcers (40%) in group 2, and 2 ulcers (40%) in group 3.

CONCLUSIONS

Administration of gastroprotective agents and embolization of fewer arteries to the gastric fundus did not prevent gastric ulceration in treated animals. Only animals that underwent embolization of all gastric arteries exhibited significant decreases in serum ghrelin levels.

Cardiac cachexia: hic et nunc

Cardiac cachexia (CC) is the clinical entity at the end of the chronic natural course of heart failure (HF). Despite the efforts, even the most recent definition of cardiac cachexia has been challenged, more precisely, the addition of new criteria on top of obligatory weight loss. The pathophysiology of CC is complex and multifactorial. A better understanding of pathophysiological pathways in body wasting will contribute to establish potentially novel treatment strategies. The complex biochemical network related with CC and HF pathophysiology underlines that a single biomarker cannot reflect all of the features of the disease. Biomarkers that could pick up the changes in body composition before they convey into clinical manifestations of CC would be of great importance. The development of preventive and therapeutic strategies against cachexia, sarcopenia, and wasting disorders is perceived as an urgent need by healthcare professionals. The treatment of body wasting remains an unresolved challenge to this day. As CC is a multifactorial disorder, it is unlikely that any single agent will be completely effective in treating this condition. Among all investigated therapeutic strategies, aerobic exercise training in HF patients is the most proved to counteract skeletal muscle wasting and is recommended by treatment guidelines for HF.

Cancer cachexia, recent advances, and future directions

Cancer cachexia is defined as a multifactorial syndrome characterized by an ongoing loss of skeletal muscle mass with or without loss of fat mass. The syndrome cannot be fully reversed by conventional nutritional support, and despite an increased number of studies related to cancer cachexia, the underlying mechanisms are still poorly defined, and therapeutic options are limited. This review focuses on recent studies investigating mechanisms and pathways in cancer cachexia. The role of molecular and functional imaging in identifying cachexia at an earlier stage, in identifying potential metabolic targets and pathways, and in assessing treatment efficacy is also reviewed.

Cardiac cachexia: hic et nunc: "hic et nunc" - here and now

Cardiac cachexia (CC) is the clinical entity at the end of chronic natural course of heart failure (HF). Despite the efforts, even the most recent definition of cardiac cachexia has been challenged, more precisely the addition of new criteria on top of obligatory weight loss. The pathophysiology of CC is complex and multifactorial. Better understanding of pathophysiological pathways in body wasting will contribute to establish potentially novel treatment strategies. The complex biochemical network related with CC and HF pathophysiology underlines that a single biomarker cannot reflect all of the features of the disease. Biomarkers that could pick-up the changes in body composition before they convey into clinical manifestations of CC would be of great importance. The development of preventive and therapeutic strategies against cachexia, sarcopenia and wasting disorders is perceived as an urgent need by healthcare professionals. The treatment of body wasting remains an unresolved challenge to this day. As CC is a multifactorial disorder, it is unlikely that any single agent will be completely effective in treating this condition. Among all investigated therapeutic strategies, aerobic exercise training in HF patients is the most proved to counteract skeletal muscle wasting and is recommended by treatment guidelines for HF.

Mitochondrial plasticity in cancer-related muscle wasting: potential approaches for its management

PURPOSE OF REVIEW

Cancer cachexia represents a critical problem in clinical oncology due to its negative impact on patients' quality of life, therapeutic tolerance and survival. This paraneoplasic condition is characterized by significant weight loss mainly from skeletal muscle wasting. Understanding the molecular mechanisms underlying cancer cachexia is urgent in order to develop and apply efficient therapeutic strategies.

RECENT FINDINGS

Mitochondrial dysfunction is an early event in cancer-induced muscle wasting. Decreased ability for ATP synthesis, impaired mitochondrial biogenesis, increased oxidative stress, impairment of protein quality control systems, increased susceptibility to mitophagy and to apoptosis were all shown to mediate contractile dysfunction and wasting in cancer cachexia. Anti-inflammatory therapies as well as exercise training seem to counteract muscle mass loss in part by improving mitochondrial functionality.

SUMMARY

Given its central role in muscle wasting, mitochondrial plasticity should be viewed as a key therapeutic target for the preservation of muscle mass in cancer cachexia. Few studies have addressed the mitochondrial events modulated by cancer cachexia and contradictory data were reported. Scarcer studies have focused on the mitochondrial adaptation to anticancer cachexia strategies.

Arginine depletion by arginine deiminase does not affect whole protein metabolism or muscle fractional protein synthesis rate in mice

Due to the absolute need for arginine that certain cancer cells have, arginine depletion is a therapy in clinical trials to treat several types of cancers. Arginine is an amino acids utilized not only as a precursor for other important molecules, but also for protein synthesis. Because arginine depletion can potentially exacerbate the progressive loss of body weight, and especially lean body mass, in cancer patients we determined the effect of arginine depletion by pegylated arginine deiminase (ADI-PEG 20) on whole body protein synthesis and fractional protein synthesis rate in multiple tissues of mice. ADI-PEG 20 successfully depleted circulating arginine (<1 μmol/L), and increased citrulline concentration more than tenfold. Body weight and body composition, however, were not affected by ADI-PEG 20. Despite the depletion of arginine, whole body protein synthesis and breakdown were maintained in the ADI-PEG 20 treated mice. The fractional protein synthesis rate of muscle was also not affected by arginine depletion. Most tissues (liver, kidney, spleen, heart, lungs, stomach, small and large intestine, pancreas) were able to maintain their fractional protein synthesis rate; however, the fractional protein synthesis rate of brain, thymus and testicles was reduced due to the ADI-PEG 20 treatment. Furthermore, these results were confirmed by the incorporation of ureido [14C]citrulline, which indicate the local conversion into arginine, into protein. In conclusion, the intracellular recycling pathway of citrulline is able to provide enough arginine to maintain protein synthesis rate and prevent the loss of lean body mass and body weight.

Emerging treatments in Neurogastroenterology: relamorelin: a novel gastrocolokinetic synthetic ghrelin agonist

BACKGROUND

Synthetic ghrelin agonists, predominantly small molecules, are being developed as prokinetic agents that may prove useful in the treatment of gastrointestinal motility disorders. Relamorelin (RM-131) is a pentapeptide synthetic ghrelin analog that activates the growth hormone secretagogue (GHS)-1a (also called the ghrelin) receptor with approximately sixfold greater potency than natural ghrelin. The ability of relamorelin to stimulate growth hormone (GH) release is comparable to that of native ghrelin. Relamorelin has enhanced efficacy and plasma stability compared to native ghrelin.

PURPOSE

In this review, we discuss the pharmacokinetics, pharmacodynamics and potential indications for relamorelin. Relamorelin is administered subcutaneously, dosed daily or twice daily. Relamorelin is being studied for the treatment of patients with gastrointestinal motility disorders. Phase IIA pharmacodynamic studies have demonstrated acceleration of gastric emptying in patients with type 1 diabetes mellitus (T1DM) and type 2 DM (T2DM) and upper gastrointestinal symptoms. In a phase IIA study in patients with diabetic gastroparesis, relamorelin accelerated gastric emptying and significantly improved vomiting frequency compared to placebo and improved other symptoms of gastroparesis in a prespecified subgroup of patients with vomiting at baseline. In patients with chronic idiopathic constipation with defined transit profile at baseline, relamorelin relieved constipation and accelerated colonic transit compared to placebo. These characteristics suggest that this new ghrelin analog shows great promise to relieve patients with upper or lower gastrointestinal motility disorders.

Rikkunshito, a ghrelin potentiator, ameliorates anorexia-cachexia syndrome

Anorexia–cachexia syndrome develops during the advanced stages of various chronic diseases in which patients exhibit a decreased food intake, weight loss, and muscle tissue wasting. For these patients, this syndrome is a critical problem leading to an increased rate of morbidity and mortality. The present pharmacological therapies for treating anorexia–cachexia have limited effectiveness. The Japanese herbal medicine rikkunshito is often prescribed for the treatment of anorexia and upper gastrointestinal (GI) disorders. Thus, rikkunshito is expected to be beneficial for the treatment of patients with anorexia–cachexia syndrome. In this review, we summarize the effects of rikkunshito and its mechanisms of action on anorexia–cachexia. Persistent loss of appetite leads to a progressive depletion of body energy stores, which is frequently associated with cachexia. Consequently, regulating appetite and energy homeostasis is critically important for treating cachexia. Ghrelin is mainly secreted from the stomach, and it plays an important role in initiating feeding, controlling GI motility, and regulating energy expenditure. Recent clinical and basic science studies have demonstrated that the critical mechanism of rikkunshito underlies endogenous ghrelin activity. Interestingly, several components of rikkunshito target multiple gastric and central sites, and regulate the secretion, receptor sensitization, and degradation of ghrelin. Rikkunshito is effective for the treatment of anorexia, body weight loss, muscle wasting, and anxiety-related behavior. Furthermore, treatment with rikkunshito was observed to prolong survival in an animal model of cachexia. The use of a potentiator of ghrelin signaling, such as rikkunshito, may represent a novel approach for the treatment of anorexia–cachexia syndrome.