The Skeletal Muscle as an Active Player Against Cancer Cachexia

The role of TGF-β signaling in muscle atrophy, sarcopenia and cancer cachexia

Skeletal muscle, comprising a significant proportion (40 to 50 percent) of total body weight in humans, plays a critical role in maintaining normal physiological conditions. Muscle atrophy occurs when the rate of protein degradation exceeds protein synthesis. Sarcopenia refers to age-related muscle atrophy, while cachexia represents a more complex form of muscle wasting associated with various diseases such as cancer, heart failure, and AIDS. Recent research has highlighted the involvement of signaling pathways, including IGF1-Akt-mTOR, MuRF1-MAFbx, and FOXO, in regulating the delicate balance between muscle protein synthesis and breakdown. Myostatin, a member of the TGF-β superfamily, negatively regulates muscle growth and promotes muscle atrophy by activating Smad2 and Smad3. It also interacts with other signaling pathways in cachexia and sarcopenia. Inhibition of myostatin has emerged as a promising therapeutic approach for sarcopenia and cachexia. Additionally, other TGF-β family members, such as TGF-β1, activin A, and GDF11, have been implicated in the regulation of skeletal muscle mass. Furthermore, myostatin cooperates with these family members to impair muscle differentiation and contribute to muscle loss. This review provides an overview of the significance of myostatin and other TGF-β signaling pathway members in muscular dystrophy, sarcopenia, and cachexia. It also discusses potential novel therapeutic strategies targeting myostatin and TGF-β signaling for the treatment of muscle atrophy.

Influence of Amino Acids and Exercise on Muscle Protein Turnover, Particularly in Cancer Cachexia

Cancer cachexia is a multifaceted syndrome that impacts individuals with advanced cancer. It causes numerous pathological changes in cancer patients, such as inflammation and metabolic dysfunction, which further diminish their quality of life. Unfortunately, cancer cachexia also increases the risk of mortality in affected individuals, making it an important area of focus for cancer research and treatment. Several potential nutritional therapies are being tested in preclinical and clinical models for their efficacy in improving muscle metabolism in cancer patients. Despite promising results, no special nutritional therapies have yet been validated in clinical practice. Multiple studies provide evidence of the benefits of increasing muscle protein synthesis through an increased intake of amino acids or protein. There is also increasing evidence that exercise can reduce muscle atrophy by modulating protein synthesis. Therefore, the combination of protein intake and exercise may be more effective in improving cancer cachexia. This review provides an overview of the preclinical and clinical approaches for the use of amino acids with and without exercise therapy to improve muscle metabolism in cachexia.

Hepatocellular carcinoma and musculoskeletal system: A narrative literature review

Musculoskeletal alterations in hepatocellular carcinoma (HCC) are less common than liver-related complications. However, they can significantly impact the quality of life and overall prognosis of patients with HCC. The main obstacle in the clinical assessment of HCC-induced musculoskeletal alterations is related to effective and timely diagnosis because these complications are often asymptomatic and unapparent during routine clinical evaluations. This narrative literature review aimed to provide a comprehensive overview of the contemporary literature related to the changes in the musculoskeletal system in patients with HCC, focusing on its clinical implications and underlying etiopathogenetic mechanisms. Osteolytic bone metastases are the most common skeletal alterations associated with HCC, which could be associated with an increased risk of low-trauma bone fracture. Moreover, previous studies reported that osteopenia, sarcopenia, and myosteatosis are associated with poor clinical outcomes in patients with HCC. Even though low bone mineral density and sarcopenia are consistently reported as reliable predictors of pretransplantation and post-transplantation mortality in HCC patients, these complications are frequently overlooked in the clinical management of patients with HCC. Taken together, contemporary literature suggests that a multidisciplinary approach is essential for early recognition and clinical management of HCC-associated musculoskeletal alterations to improve patient prognosis. Further research into the mechanisms and treatment options for musculoskeletal complications is warranted to enhance our understanding and clinical management of this aspect of HCC.

Restoration of epigenetic impairment in the skeletal muscle and chronic inflammation resolution as a therapeutic approach in sarcopenia

Sarcopenia is an age-associated loss of skeletal muscle mass, strength, and function, accompanied by severe adverse health outcomes, such as falls and fractures, functional decline, high health costs, and mortality. Hence, its prevention and treatment have become increasingly urgent. However, despite the wide prevalence and extensive research on sarcopenia, no FDA-approved disease-modifying drugs exist. This is probably due to a poor understanding of the mechanisms underlying its pathophysiology. Recent evidence demonstrate that sarcopenia development is characterized by two key elements: (i) epigenetic dysregulation of multiple molecular pathways associated with sarcopenia pathogenesis, such as protein remodeling, insulin resistance, mitochondria impairments, and (ii) the creation of a systemic, chronic, low-grade inflammation (SCLGI). In this review, we focus on the epigenetic regulators that have been implicated in skeletal muscle deterioration, their individual roles, and possible crosstalk. We also discuss epidrugs, which are the pharmaceuticals with the potential to restore the epigenetic mechanisms deregulated in sarcopenia. In addition, we discuss the mechanisms underlying failed SCLGI resolution in sarcopenia and the potential application of pro-resolving molecules, comprising specialized pro-resolving mediators (SPMs) and their stable mimetics and receptor agonists. These compounds, as well as epidrugs, reveal beneficial effects in preclinical studies related to sarcopenia. Based on these encouraging observations, we propose the combination of epidrugs with SCLI-resolving agents as a new therapeutic approach for sarcopenia that can effectively attenuate of its manifestations.

The Prognostic Impact of Preoperative Osteopenia in Patients With Colorectal Cancer

BACKGROUND

Osteopenia, a condition in which bone mineral density is lower than normal, is a noted risk factor that leads to a shortened healthy life expectancy.

OBJECTIVE

To investigate the prognostic impact of preoperative osteopenia in patients with colorectal cancer.

DESIGN

This was a retrospective study.

SETTING

This study was conducted at a university hospital.

PATIENTS

A total of 1086 patients with stage I to III colorectal cancer who underwent curative resection.

MAIN OUTCOME MEASURES

Osteopenia was evaluated with CT. Overall survival, disease-specific survival, and recurrence-free survival were the primary end points.

RESULTS

Osteopenia was identified in 300 patients (27.6%). Compared with the no osteopenia group, the 5-year overall survival (74.0% vs 93.4%, p < 0.001), disease-specific survival (81.6% vs 97.2%, p < 0.001), and recurrence-free survival rates (57.1% vs 88.3%, p < 0.001) were significantly lower in the osteopenia group. Multivariate analyses showed that preoperative osteopenia was significantly associated with worse overall survival (HR: 4.135; 95% CI, 2.963-5.770; p < 0.001), disease-specific survival (HR: 7.673; 95% CI, 4.646-12.675; p < 0.001), and recurrence-free survival (HR: 5.039; 95% CI, 3.811-6.662; p < 0.001). The prognosis of the osteopenia group was poorer than that of the no osteopenia group in every stage: 5-year overall survival (stage I: 89.4% vs 96.9%, p = 0.028; stage II: 76.5% vs 91.9%, p < 0.001; stage III: 56.4% vs 90.8%, p < 0.001) and 5-year recurrence-free survival (stage I: 85.4% vs 96.6%, p = 0.002; stage II: 62.0% vs 86.5%, p < 0.001; stage III: 26.4% vs 80.0%, p < 0.001).

LIMITATIONS

The main limitations are retrospective single-institutional features and races of the study population.

CONCLUSIONS

Preoperative osteopenia could be a strong predictive marker for long-term prognosis in colorectal cancer regardless of stage.

EL IMPACTO PRONSTICO DE LA OSTEOPENIA PREOPERATORIA EN PACIENTES CON CNCER COLORRECTAL

ANTECEDENTES:La osteopenia, una afección en la que la densidad mineral ósea es más baja de lo normal, es un relevante factor de riesgo que conduce a una expectativa menor de vida saludable.OBJETIVO:Investigar el impacto pronóstico de la osteopenia preoperatoria en pacientes con cáncer colorrectal (CCR).DISEÑO:Un estudio retrospectivo.AJUSTE:Estudio realizado en un hospital universitario.PACIENTES:Un total de 1.086 pacientes con CCR en estadio I-III sometidos a una resección curativa.PRINCIPALES MEDIDAS DE RESULTADO:La osteopenia se evaluó con imágenes de tomografía computarizada. La supervivencia global la supervivencia específica de la enfermedad y la supervivencia libre de recurrencia fueron los criterios de valoración primaria.RESULTADOS:Se identificó osteopenia en 300 pacientes (27,6%). En comparación con el grupo sin osteopenia, las tasas de supervivencia global a 5 años (74,0% frente a 93,4%, p < 0,001), supervivencia especifica de la enfermedad (81,6 % frente a 97,2%, p < 0,001) tasas de supervivencia libre de recurrencia (57,1% frente a 88,3%, p < 0,001) fueron significativamente más bajas en el grupo de osteopenia. Los análisis multivariados mostraron que la osteopenia preoperatoria se asoció significativamente con una peor supervivencia global (HR 4,135; IC 95% 2,963-5,770; p < 0,001), supervivencia especifica de la enfermedad (HR 7,673; IC 95% 4,646-12,675; p < 0,001) y tasas de supervivencia libre de recurrencia (HR 5,039; IC 95% 3,811-6,662; p < 0,001). El pronóstico del grupo con osteopenia fue peor que el del grupo sin osteopenia en todos los estadios: supervivencia global a 5 años (estadio I: 89,4% frente a 96,9%, p = 0,028; estadio II: 76,5% frente a 91,9%, p < 0,001; estadio III: 56,4% frente a 90,8%, p < 0,001) y tasas de supervivencia libre de recurrencia a 5 años (estadio I: 85,4% frente a 96,6%, p < 0,002; estadio II: 62,0% frente a 86,5%, p < 0,001; estadio III: 26,4% frente a 80,0%, p < 0,001).LIMITACIONES:Las principales limitaciones son las características retrospectivas de una sola institución y las razas de la población de estudio.CONCLUSIONES:La osteopenia preoperatoria puede ser un fuerte marcador predictivo para el pronóstico a largo plazo en CCR independientemente de la etapa. (Traducción-Dr. Fidel Ruiz Healy ).

Astaxanthin Supplementation Assists Sorafenib in Slowing Skeletal Muscle Atrophy in H22 Tumor-Bearing Mice via Reversing Abnormal Glucose Metabolism

SCOPE

Cachexia, which is often marked by skeletal muscular atrophy, is one of the leading causes of death in cancer patients. Astaxanthin, a carotenoid obtained from marine organisms that can aid in the prevention and treatment of a variety of disorders. In this study, to assess whether astaxanthin ameliorates weight loss and skeletal muscle atrophy in sorafenib-treated hepatocellular carcinoma mice is aimed.

METHODS AND RESULTS

H22 mice are treated with 30 mg kg-1  day-1 of sorafenib and 60 mg kg-1  day-1 of astaxanthin by gavage lasted for 18 days. Sorafenib does not delay skeletal muscle atrophy and weight loss, although it does not reduce tumor burden. Astaxanthin dramatically delays weight loss and skeletal muscle atrophy in sorafenib-treating mice, without affecting the food intake. Astaxanthin inhibits the tumor glycolysis, slows down gluconeogenesis, and improves insulin resistance in tumor-bearing mice. Astaxanthin increases glucose competition in skeletal muscle by targeting the PI3K/Akt/GLUT4 signaling pathway, and enhances glucose utilization efficiency in skeletal muscle, thereby slowing skeletal muscle atrophy.

CONCLUSION

The findings show the significant potential of astaxanthin as nutritional supplements for cancer patients, as well as the notion that nutritional interventions should be implemented at the initiation of cancer treatment, as instead of waiting until cachexia sets in.

Exploring skeletal muscle tolerance and whole-body metabolic effects of FDA-approved drugs in a volumetric muscle loss model

Volumetric muscle loss (VML) is associated with persistent functional impairment due to a lack of de novo muscle regeneration. As mechanisms driving the lack of regeneration continue to be established, adjunctive pharmaceuticals to address the pathophysiology of the remaining muscle may offer partial remediation. Studies were designed to evaluate the tolerance and efficacy of two FDA-approved pharmaceutical modalities to address the pathophysiology of the remaining muscle tissue after VML injury: (1) nintedanib (an anti-fibrotic) and (2) combined formoterol and leucine (myogenic promoters). Tolerance was first established by testing low- and high-dosage effects on uninjured skeletal muscle mass and myofiber cross-sectional area in adult male C57BL/6J mice. Next, tolerated doses of the two pharmaceutical modalities were tested in VML-injured adult male C57BL/6J mice after an 8-week treatment period for their ability to modulate muscle strength and whole-body metabolism. The most salient findings indicate that formoterol plus leucine mitigated the loss in muscle mass, myofiber number, whole-body lipid oxidation, and muscle strength, and resulted in a higher whole-body metabolic rate (p ≤ 0.016); nintedanib did not exacerbate or correct aspects of the muscle pathophysiology after VML. This supports ongoing optimization efforts, including scale-up evaluations of formoterol treatment in large animal models of VML.

The Role of Natural Products in the Improvement of Cancer-Associated Cachexia

The enormous library of natural products and herbal medicine prescriptions presents endless research avenues. However, the lack of research evidence and trials on cancer-induced cachexia limit the therapeutic potential of natural products. Cancer-induced cachexia is a systemic wasting syndrome characterized by continuous body weight loss with skeletal muscle and adipose tissue atrophy. Cancer cachexia is a problem in itself and reduces the quality of life by lessening the treatment efficacy of anticancer drugs. This review summarizes single natural product extracts for cancer-induced cachexia, not compounds derived from natural products and herbal medicine prescriptions. This article also discusses the effect of natural products on cachexia induced by anticancer drugs and the role of AMPK in cancer-induced cachexia. The article included the mice model used in each experiment to encourage researchers to utilize animal models for research on cancer-induced cachexia in the future.

Chemotherapy-Induced Molecular Changes in Skeletal Muscle

Paraneoplastic conditions such as cancer cachexia are often exacerbated by chemotherapy, which affects the patient’s quality of life as well as the response to therapy. The aim of this narrative review was to overview the body-composition-related changes and molecular effects of different chemotherapy agents used in cancer treatment on skeletal-muscle remodeling. A literature search was performed using the Web of Science, Scopus, and Science Direct databases and a total of 77 papers was retrieved. In general, the literature survey showed that the molecular changes induced by chemotherapy in skeletal muscle have been studied mainly in animal models and mostly in non-tumor-bearing rodents, whereas clinical studies have essentially assessed changes in body composition by computerized tomography. Data from preclinical studies showed that chemotherapy modulates several molecular pathways in skeletal muscle, including the ubiquitin–proteasome pathway, autophagy, IGF-1/PI3K/Akt/mTOR, IL-6/JAK/STAT, and NF-κB pathway; however, the newest chemotherapy agents are underexplored. In conclusion, chemotherapy exacerbates skeletal-muscle wasting in cancer patients; however, the incomplete characterization of the chemotherapy-related molecular effects on skeletal muscle makes the development of new preventive anti-wasting strategies difficult. Therefore, further investigation on molecular mechanisms and clinical studies are necessary.

The underexplored links between cancer and the internal body climate: Implications for cancer prevention and treatment

In order to effectively manage and cure cancer we should move beyond the general view of cancer as a random process of genetic alterations leading to uncontrolled cell proliferation or simply a predictable evolutionary process involving selection for traits that increase cell fitness. In our view, cancer is a systemic disease that involves multiple interactions not only among cells within tumors or between tumors and surrounding tissues but also with the entire organism and its internal "milieu". We define the internal body climate as an emergent property resulting from spatial and temporal interactions among internal components themselves and with the external environment. The body climate itself can either prevent, promote or support cancer initiation and progression (top-down effect; i.e., body climate-induced effects on cancer), as well as be perturbed by cancer (bottom-up effect; i.e., cancer-induced body climate changes) to further favor cancer progression and spread. This positive feedback loop can move the system towards a "cancerized" organism and ultimately results in its demise. In our view, cancer not only affects the entire system; it is a reflection of an imbalance of the entire system. This model provides an integrated framework to study all aspects of cancer as a systemic disease, and also highlights unexplored links that can be altered to both prevent body climate changes that favor cancer initiation, progression and dissemination as well as manipulate or restore the body internal climate to hinder the success of cancer inception, progression and metastasis or improve therapy outcomes. To do so, we need to (i) identify cancer-relevant factors that affect specific climate components, (ii) develop 'body climate biomarkers', (iii) define 'body climate scores', and (iv) develop strategies to prevent climate changes, stop or slow the changes, or even revert the changes (climate restoration).

Pathological features of tissues and cell populations during cancer cachexia

Cancers remain among the most devastating diseases in the human population in spite of considerable advances in limiting their impact on lifespan and healthspan. The multifactorial nature of cancers, as well as the number of tissues and organs that are affected, have exposed a considerable diversity in mechanistic features that are reflected in the wide array of therapeutic strategies that have been adopted. Cachexia is manifested in a number of diseases ranging from cancers to diabetes and ageing. In the context of cancers, a majority of patients experience cachexia and succumb to death due to the indirect effects of tumorigenesis that drain the energy reserves of different organs. Considerable information is available on the pathophysiological features of cancer cachexia, however limited knowledge has been acquired on the resident stem cell populations, and their function in the context of these diseases. Here we review current knowledge on cancer cachexia and focus on how tissues and their resident stem and progenitor cell populations are individually affected.

Amino Acids in Cancer and Cachexia: An Integrated View

Rapid tumor growth requires elevated biosynthetic activity, supported by metabolic rewiring occurring both intrinsically in cancer cells and extrinsically in the cancer host. The Warburg effect is one such example, burning glucose to produce a continuous flux of biomass substrates in cancer cells at the cost of energy wasting metabolic cycles in the host to maintain stable glycemia. Amino acid (AA) metabolism is profoundly altered in cancer cells, which use AAs for energy production and for supporting cell proliferation. The peculiarities in cancer AA metabolism allow the identification of specific vulnerabilities as targets of anti-cancer treatments. In the current review, specific approaches targeting AAs in terms of either deprivation or supplementation are discussed. Although based on opposed strategies, both show, in vitro and in vivo, positive effects. Any AA-targeted intervention will inevitably impact the cancer host, who frequently already has cachexia. Cancer cachexia is a wasting syndrome, also due to malnutrition, that compromises the effectiveness of anti-cancer drugs and eventually causes the patient's death. AA deprivation may exacerbate malnutrition and cachexia, while AA supplementation may improve the nutritional status, counteract cachexia, and predispose the patient to a more effective anti-cancer treatment. Here is provided an attempt to describe the AA-based therapeutic approaches that integrate currently distant points of view on cancer-centered and host-centered research, providing a glimpse of several potential investigations that approach cachexia as a unique cancer disease.

Exosomal Plasminogen Activator Inhibitor-1 Induces Ionizing Radiation-Adaptive Glioblastoma Cachexia

Cancer cachexia is a muscle-wasting syndrome that leads to a severely compromised quality of life and increased mortality. A strong association between cachexia and poor prognosis has been demonstrated in intractable cancers, including glioblastoma (GBM). In the present study, it was demonstrated that ionizing radiation (IR), the first-line treatment for GBM, causes cancer cachexia by increasing the exosomal release of plasminogen activator inhibitor-1 (PAI-1) from glioblastoma cells. Exosomal PAI-1 delivered to the skeletal muscle is directly penetrated in the muscles and phosphorylates STAT3 to intensify muscle atrophy by activating muscle RING-finger protein-1 (MuRF1) and muscle atrophy F-box (Atrogin1); furthermore, it hampers muscle protein synthesis by inhibiting mTOR signaling. Additionally, pharmacological inhibition of PAI-1 by TM5441 inhibited muscle atrophy and rescued muscle protein synthesis, thereby providing survival benefits in a GBM orthotopic xenograft mouse model. In summary, our data delineated the role of PAI-1 in the induction of GBM cachexia associated with radiotherapy-treated GBM. Our data also indicated that targeting PAI-1 could serve as an attractive strategy for the management of GBM following radiotherapy, which would lead to a considerable improvement in the quality of life of GBM patients undergoing radiotherapy.

Muscle-to-tumor crosstalk: The effect of exercise-induced myokine on cancer progression

Physical exercise has gradually become a focus in cancer treatment due to its pronounced role in reducing cancer risk, enhancing therapeutic efficacy, and improving prognosis. In recent decades, skeletal muscles have been considered endocrine organs, exerting their biological functions via the endocrine, autocrine, and paracrine systems by secreting various types of myokines. The amount of myokines secreted varies depending on the intensity, type, and duration of exercise. Recent studies have shown that muscle-derived myokines are highly involved the effects of exercise on cancer. Multiple myokines, such as interleukin-6 (IL-6), oncostatin M (OSM), secreted protein acidic and rich in cysteine (SPARC), and irisin, directly mediate cancer progression by influencing the proliferation, apoptosis, stemness, drug resistance, metabolic reprogramming, and epithelial-mesenchymal transformation (EMT) of cancer cells. In addition, IL-6, interleukin-8 (IL-8), interleukin-15 (IL-15), brain-derived neurotrophic factor (BDNF), and irisin can improve obesity-induced inflammation by stimulating lipolysis of adipose tissues, promoting glucose uptake, and accelerating the browning of white fat. Furthermore, some myokines could regulate the tumor microenvironment, such as angiogenesis and the immune microenvironment. Cancer cachexia occurs in up to 80% of cancer patients and is responsible for 22%-30% of patient deaths. It is characterized by systemic inflammation and decreased muscle mass. Exercise-induced myokine production is important in regulating cancer cachexia. This review summarizes the roles and underlying mechanisms of myokines, such as IL-6, myostatin, IL-15, irisin, fibroblast growth factor 21 (FGF21) and musclin, in cancer cachexia. Through comprehensive analysis, we conclude that myokines are potential targets for inhibiting cancer progression and the associated cachexia.

Pectoralis major muscle atrophy is associated with mitochondrial energy wasting in cachectic patients with gastrointestinal cancer

BACKGROUND

Cancer cachexia is a multifactorial syndrome characterized by involuntary and pathological weight loss, mainly due to skeletal muscle wasting, resulting in a decrease in patients' quality of life, response to cancer treatments, and survival. Our objective was to investigate skeletal muscle alterations in cachectic cancer patients.

METHODS

This is a prospective study of patients managed for pancreatic or colorectal cancer with an indication for systemic chemotherapy (METERMUCADIG - NCT02573974). One lumbar CT image was used to determine body composition. Patients were divided into three groups [8 noncachectic (NC), 18 with mild cachexia (MC), and 19 with severe cachexia (SC)] based on the severity of weight loss and muscle mass. For each patient, a pectoralis major muscle biopsy was collected at the time of implantable chamber placement. We used high-resolution oxygraphy to measure mitochondrial muscle oxygen consumption on permeabilized muscle fibres. We also performed optical and electron microscopy analyses, as well as gene and protein expression analyses.

RESULTS

Forty-five patients were included. Patients were 67% male, aged 67 years (interquartile range, 59-77). Twenty-three (51%) and 22 (49%) patients were managed for pancreatic and colorectal cancer, respectively. Our results show a positive correlation between median myofibres area and skeletal muscle index (P = 0.0007). Cancer cachexia was associated with a decrease in MAFbx protein expression (P < 0.01), a marker of proteolysis through the ubiquitin-proteasome pathway. Mitochondrial oxygen consumption related to energy wasting was significantly increased (SC vs. NC, P = 0.028) and mitochondrial area tended to increase (SC vs. MC, P = 0.056) in SC patients. On the contrary, mitochondria content and networks remain unaltered in cachectic cancer patients. Finally, our results show no dysfunction in lipid storage and endoplasmic reticulum homeostasis.

CONCLUSIONS

This clinical protocol brings unique data that provide new insight to mechanisms underlying muscle wasting in cancer cachexia. We report for the first time an increase in mitochondrial energy wasting in the skeletal muscle of severe cachectic cancer patients. Additional clinical studies are essential to further the exploring and understanding of these alterations.

Activin A Causes Muscle Atrophy through MEF2C-Dependent Impaired Myogenesis

Activin A (ActA) is considered to play a major role in cancer-induced cachexia (CC). Indeed, circulating ActA levels are elevated and predict survival in patients with CC. However, the mechanisms by which ActA mediates CC development and in particular skeletal muscle (SM) atrophy in humans are not yet fully understood. In this work, we aimed to investigate the effects of ActA on human SM and in mouse models of CC. We used a model of human muscle cells in culture to explore how ActA acts towards human SM. In this model, recombinant ActA induced myotube atrophy associated with the decline of MyHC-β/slow, the main myosin isoform in human muscle cells studied. Moreover, ActA inhibited the expression and activity of MEF2C, the transcription factor regulating MYH7, the gene which codes for MyHC-β/slow. This decrease in MEF2C was involved in the decline of MyHC-β/slow expression, since inhibition of MEF2C by a siRNA leads to the decrease in MyHC-β/slow expression. The relevance of this ActA/MEF2C pathway in vivo was supported by the parallel decline of MEF2C expression and SM mass, which are both blunted by ActA inhibition, in animal models of CC. In this work, we showed that ActA is a potent negative regulator of SM mass by inhibiting MyHC-β/slow synthesis through downregulation of MEF2C. This observation highlights a novel interaction between ActA signaling and MEF2C transcriptional activity which contributes to SM atrophy in CC models.

The clinical impact of malnutrition on the postoperative outcomes of patients undergoing gastrectomy for gastric cancer: Propensity score matched analysis of 2011-2017 hospital database

BACKGROUND & AIMS

Malnutrition is a prominent feature of gastric cancer patients who suffer from gastric outlet obstruction, impaired peristalsis, and cancer-mediated disruptions in metabolic hemostasis. In this study, we systematically evaluate the impact of malnutrition on the postoperative outcome of patients with gastric cancer undergoing gastrectomy.

METHODS

2011-2017 National Inpatient Sample was used to isolate patients with gastric cancer who underwent gastrectomy, who were stratified using malnutrition. The malnutrition-present cohort was matched to the malnutrition-absent controls using 1:1 propensity score-matching analysis, and compared to the following endpoints: mortality, length of stay (LOS), hospitalization costs, and postoperative complications.

RESULTS

5309 were identified to have undergone gastric resection procedure for gastric cancer, from which there were 1044 with malnutrition and 1044 matched controls. Malnourished patients had higher mortality (6.80 vs 3.83% p = 0.003, OR 1.83 95% CI 1.23-2.73), LOS (17.2 vs 11.4 d p < 0.001), costs ($197,702 vs $124,133 p < 0.001), and were more often discharged to rehabilitation facilities. Malnourished patients had higher rates of wound complications (3.64 vs 1.25% p < 0.001, OR 3.00 95% CI 1.59-5.66), infection (6.90 vs 3.26% p < 0.001, OR 2.20 95% CI 1.45-3.34), and respiratory failure (6.80 vs 3.64% p = 0.002, OR 1.93 95% CI 1.29-2.89). In multivariate analysis, malnourished patients had higher rates of mortality (p = 0.002, aOR 1.87 95% CI 1.25-2.80), length of stay (p < 0.001, aOR 1.52 95% CI 1.48-1.55), costs (p < 0.001, aOR 1.61 95% CI 1.61-1.61) despite controlling for non-matched hospital variables.

CONCLUSION

In this propensity score matched analysis, malnutrition is associated with increased postoperative mortality, LOS, and hospitalization costs in patients with gastric cancer undergoing gastric resection surgery.

Leucine-Rich Diet Improved Muscle Function in Cachectic Walker 256 Tumour-Bearing Wistar Rats

Skeletal muscle atrophy occurs in several pathological conditions, such as cancer, especially during cancer-induced cachexia. This condition is associated with increased morbidity and poor treatment response, decreased quality of life, and increased mortality in cancer patients. A leucine-rich diet could be used as a coadjutant therapy to prevent muscle atrophy in patients suffering from cancer cachexia. Besides muscle atrophy, muscle function loss is even more important to patient quality of life. Therefore, this study aimed to investigate the potential beneficial effects of leucine supplementation on whole-body functional/movement properties, as well as some markers of muscle breakdown and inflammatory status. Adult Wistar rats were randomly distributed into four experimental groups. Two groups were fed with a control diet (18% protein): Control (C) and Walker 256 tumour-bearing (W), and two other groups were fed with a leucine-rich diet (18% protein + 3% leucine): Leucine Control (L) and Leucine Walker 256 tumour-bearing (LW). A functional analysis (walking, behaviour, and strength tests) was performed before and after tumour inoculation. Cachexia parameters such as body weight loss, muscle and fat mass, pro-inflammatory cytokine profile, and molecular and morphological aspects of skeletal muscle were also determined. As expected, Walker 256 tumour growth led to muscle function decline, cachexia manifestation symptoms, muscle fibre cross-section area reduction, and classical muscle protein degradation pathway activation, with upregulation of FoxO1, MuRF-1, and 20S proteins. On the other hand, despite having no effect on the walking test, inflammation status or muscle oxidative capacity, the leucine-rich diet improved muscle strength and behaviour performance, maintained body weight, fat and muscle mass and decreased some protein degradation markers in Walker 256 tumour-bearing rats. Indeed, a leucine-rich diet alone could not completely revert cachexia but could potentially diminish muscle protein degradation, leading to better muscle functional performance in cancer cachexia.

Skeletal Muscle Deconditioning in Breast Cancer Patients Undergoing Chemotherapy: Current Knowledge and Insights From Other Cancers

Breast cancer represents the most commonly diagnosed cancer while neoadjuvant and adjuvant chemotherapies are extensively used in order to reduce tumor development and improve disease-free survival. However, chemotherapy also leads to severe off-target side-effects resulting, together with the tumor itself, in major skeletal muscle deconditioning. This review first focuses on recent advances in both macroscopic changes and cellular mechanisms implicated in skeletal muscle deconditioning of breast cancer patients, particularly as a consequence of the chemotherapy treatment. To date, only six clinical studies used muscle biopsies in breast cancer patients and highlighted several important aspects of muscle deconditioning such as a decrease in muscle fibers cross-sectional area, a dysregulation of protein turnover balance and mitochondrial alterations. However, in comparison with the knowledge accumulated through decades of intensive research with many different animal and human models of muscle atrophy, more studies are necessary to obtain a comprehensive understanding of the cellular processes implicated in breast cancer-mediated muscle deconditioning. This understanding is indeed essential to ultimately lead to the implementation of efficient preventive strategies such as exercise, nutrition or pharmacological treatments. We therefore also discuss potential mechanisms implicated in muscle deconditioning by drawing a parallel with other cancer cachexia models of muscle wasting, both at the pre-clinical and clinical levels.

Growth hormone secretagogue receptor-1a mediates ghrelin's effects on attenuating tumour-induced loss of muscle strength but not muscle mass

BACKGROUND

Ghrelin may ameliorate cancer cachexia (CC) by preventing anorexia, muscle, and fat loss. However, the mechanisms mediating these effects are not fully understood. This study characterizes the pathways involved in muscle mass and strength loss in the Lewis lung carcinoma (LLC)-induced cachexia model, and the effects of ghrelin in mice with or without its only known receptor: the growth hormone secretagogue receptor-1a ((GHSR-1a), Ghsr+/+ and Ghsr-/- ).

METHODS

Five to 7-month-old male C57BL/6J Ghsr+/+ and Ghsr-/- mice were inoculated with 1 × 106 heat-killed (HK) or live LLC cells (tumour implantation, TI). When tumours were palpable (7 days after TI), tumour-bearing mice were injected with vehicle (T + V) or ghrelin twice/day for 14 days (T + G, 0.8 mg/kg), while HK-treated mice were given vehicle (HK + V). Body weight and grip strength were evaluated before TI and at termination (21 days after TI). Hindlimb muscles were collected for analysis.

RESULTS

Less pronounced body weight (BW) loss (87.70 ± 0.98% vs. 83.92 ± 1.23%, percentage of baseline BW in tumour-bearing Ghsr+/+ vs. Ghsr-/- , P = 0.008), and lower upregulation of ubiquitin-proteasome system (UPS, MuRF1/Trim63, 5.71 ± 1.53-fold vs. 9.22 ± 1.94-fold-change from Ghsr+/+ HK + V in tumour-bearing Ghsr+/+ vs. Ghsr-/- , P = 0.036) and autophagy markers (Becn1, Atg5, Atg7, tumour-bearing Ghsr+/+  < Ghsr-/- , all P < 0.02) were found in T + V Ghsr+/+ vs. Ghsr-/- mice. Ghrelin attenuated LLC-induced UPS marker upregulation in both genotypes, [Trim63 was decreased from 5.71 ± 1.53-fold to 1.96 ± 0.47-fold in Ghsr+/+ (T + V vs. T + G: P = 0.032) and 9.22 ± 1.94-fold to 4.72 ± 1.06-fold in Ghsr-/- (T + V vs. T + G: P = 0.008)]. Only in Ghsr+/+ mice ghrelin ameliorated LLC-induced grip strength loss [improved from 89.24 ± 3.48% to 97.80 ± 2.31% of baseline (T + V vs. T + G: P = 0.042)], mitophagy markers [Bnip3 was decreased from 2.28 ± 0.56 to 1.38 ± 0.14-fold (T + V vs. T + G: P ≤ 0.05)], and impaired mitochondrial respiration [State 3u improved from 698.23 ± 73.96 to 934.37 ± 95.21 pmol/min (T + V vs. T + G: P ≤ 0.05)], whereas these markers were not improved by ghrelin Ghsr-/- . Compared with Ghsr+/+ , Ghsr-/- tumour-bearing mice also showed decreased response to ghrelin in BW [T + G-treated Ghsr+/+ vs. Ghsr -/- : 91.75 ± 1.05% vs. 86.18 ± 1.13% of baseline BW, P < 0.001)], gastrocnemius (T + G-treated Ghsr+/+ vs. Ghsr-/- : 96.9 ± 2.08% vs. 88.15 ± 1.78% of Ghsr+/+ HK + V, P < 0.001) and quadriceps muscle mass (T + G-treated Ghsr+/+ vs. Ghsr-/- : 96.12 ± 2.31% vs. 88.36 ± 1.94% of Ghsr+/+ HK + V, P = 0.01), and gastrocnemius type IIA (T + G-treated Ghsr+/+ vs. Ghsr-/- : 1250.49 ± 31.72 vs. 1017.62 ± 70.99 μm2 , P = 0.027) and IIB fibre cross-sectional area (T + G-treated Ghsr+/+ vs. Ghsr-/- : 2496.48 ± 116.88 vs. 2183.04 ± 103.43 μm2 , P = 0.024).

CONCLUSIONS

Growth hormone secretagogue receptor-1a mediates ghrelin's effects on attenuating LLC-induced weakness but not muscle mass loss by modulating the autophagy-lysosome pathway, mitophagy, and mitochondrial respiration.

Phosphorylation of Dynamin-Related Protein 1 (DRP1) Regulates Mitochondrial Dynamics and Skeletal Muscle Wasting in Cancer Cachexia

Background

Cancer-associated cachexia (CAC) is a syndrome characterized by skeletal muscle atrophy, and the underlying mechanisms are still unclear. Recent research studies have shed light on a noteworthy link between mitochondrial dynamics and muscle physiology. In the present study, we investigate the role of dynamin-related protein 1 (DRP1), a pivotal factor of mitochondrial dynamics, in myotube atrophy during cancer-associated cachexia.

Methods

Seventy-six surgical patients, including gastrointestinal tumor and benign disease, were enrolled in the study and divided to three groups: control, non-cachexia, and cancer-associated cachexia. Demographic data were collected. Their rectus abdominis samples were acquired intraoperatively. Muscle fiber size, markers of ubiquitin proteasome system (UPS), mitochondrial ultrastructure, and markers of mitochondrial function and dynamics were assayed. A cachexia model in vitro was established via coculturing a C2C12 myotube with media from C26 colon cancer cells. A specific DRP1 inhibitor, Mdivi-1, and a lentivirus of DRP1 knockdown/overexpression were used to regulate the expression of DRP1. Muscle diameter, mitochondrial morphology, mass, reactive oxygen species (ROS), membrane potential, and markers of UPS, mitochondrial function, and dynamics were determined.

Results

Patients of cachexia suffered from a conspicuous worsened nutrition status and muscle loss compared to patients of other groups. Severe mitochondrial swelling and enlarged area were observed, and partial alterations in mitochondrial function were found in muscle. Analysis of mitochondrial dynamics indicated an upregulation of phosphorylated DRP1 at the ser616 site. In vitro, cancer media resulted in the atrophy of myotube. This was accompanied with a prominent unbalance of mitochondrial dynamics, as well as enhanced mitochondrial ROS and decreased mitochondrial function and membrane potential. However, certain concentrations of Mdivi-1 and DRP1 knockdown rebalanced the mitochondrial dynamics, mitigating this negative phenotype caused by cachexia. Moreover, overexpression of DRP1 aggravated these phenomena.

Conclusion

In clinical patients, cachexia induces abnormal mitochondrial changes and possible fission activation for the atrophied muscle. Our cachexia model in vitro further demonstrates that unbalanced mitochondrial dynamics contributes to this atrophy and mitochondrial impairment, and rebuilding the balance by regulating of DRP1 could ameliorate these alterations.

Liquid Biopsy for Cancer Cachexia: Focus on Muscle-Derived microRNAs

Cancer cachexia displays a complex nature in which systemic inflammation, impaired energy metabolism, loss of muscle and adipose tissues result in unintentional body weight loss. Cachectic patients have a poor prognosis and the presence of cachexia reduces the tolerability of chemo/radio-therapy treatments and it is frequently the primary cause of death in advanced cancer patients. Early detection of this condition could make treatments more effective. However, early diagnostic biomarkers of cachexia are currently lacking. In recent years, although solid biopsy still remains the "gold standard" for diagnosis of cancer, liquid biopsy is gaining increasing interest as a source of easily accessible potential biomarkers. Moreover, the growing interest in circulating microRNAs (miRNAs), has made these molecules attractive for the diagnosis of several diseases, including cancer. Some muscle-derived circulating miRNA might play a pivotal role in the onset/progression of cancer cachexia. This topic is of great interest since circulating miRNAs might be easily detectable by means of liquid biopsies and might allow an early diagnosis of this syndrome. We here summarize the current knowledge on circulating muscular miRNAs involved in muscle atrophy, since they might represent easily accessible and promising biomarkers of cachexia.

Role of myokines and osteokines in cancer cachexia

Cancer-induced muscle wasting, i.e. cachexia, is associated with different types of cancer such as pancreatic, colorectal, lung, liver, gastric and esophageal. Cachexia affects prognosis and survival in cancer, and it is estimated that it will be the ultimate cause of death for up to 30% of cancer patients. Musculoskeletal alterations are known hallmarks of cancer cachexia, with skeletal muscle atrophy and weakness as the most studied. Recent evidence has shed light on the presence of bone loss in cachectic patients, even in the absence of bone-metastatic disease. In particular, we and others have shown that muscle and bone communicate by exchanging paracrine and endocrine factors, known as myokines and osteokines. This review will focus on describing the role of the most studied myokines, such as myostatin, irisin, the muscle metabolite β-aminoisobutyric acid, BAIBA, and IL-6, and osteokines, including TGF-β, osteocalcin, sclerostin, RANKL, PTHrP, FGF23, and the lipid mediator, PGE₂ during cancer-induced cachexia. The interplay of muscle and bone factors, together with tumor-derived soluble factors, characterizes a complex clinical scenario in which musculoskeletal alterations are amongst the most debilitating features. Understanding and targeting the "secretome" of cachectic patients will likely represent a promising strategy to preserve bone and muscle during cancer cachexia thereby enhancing recovery.

Skeletal Muscle-Adipose Tissue-Tumor Axis: Molecular Mechanisms Linking Exercise Training in Prostate Cancer

Increased visceral adiposity may influence the development of prostate cancer (PCa) aggressive tumors and cancer mortality. White adipose tissue (WAT), usually referred to as periprostatic adipose tissue (PPAT), surrounds the prostatic gland and has emerged as a potential mediator of the tumor microenvironment. Exercise training (ET) induces several adaptations in both skeletal muscle and WAT. Some of these effects are mediated by ET-induced synthesis and secretion of several proteins, known as myo- and adipokines. Together, myokines and adipokines may act in an endocrine-like manner to favor communication between skeletal muscle and WAT, as they may work together to improve whole-body metabolic health. This crosstalk may constitute a potential mechanism by which ET exerts its beneficial role in the prevention and treatment of PCa-related disorders; however, this has not yet been explored. Therefore, we reviewed the current evidence on the effects of skeletal muscle–WAT–tumor crosstalk in PCa, and the potential mediators of this process to provide a better understanding of underlying ET-related mechanisms in cancer.

α-Syntrophin alleviates ER stress to maintain protein homeostasis during myoblast differentiation

We have previously shown evidence that α-syntrophin plays an important role in myoblast differentiation. In this study, we focused on abnormal myotube formation of the α-syntrophin knockdown C2 cell line (SNKD). The overall amount of intracellular protein and muscle-specific proteins in SNKD cells were significantly lower than those in the control. Akt-mTOR signaling, an important pathway for protein synthesis and muscle hypertrophy, was downregulated. In addition, the levels of endoplasmic reticulum (ER) stress markers increased in SNKD cells. The decrease in intracellular protein synthesis and reduction in the myotube diameter in SNKD cells were restored by 4-phenylbutyric acid, a chemical chaperone, or overexpression of α-syntrophin. These results suggest a novel role for α-syntrophin in protein homeostasis during myoblast differentiation.

Targeting the Activin Receptor Signaling to Counteract the Multi-Systemic Complications of Cancer and Its Treatments

Muscle wasting, i.e., cachexia, frequently occurs in cancer and associates with poor prognosis and increased morbidity and mortality. Anticancer treatments have also been shown to contribute to sustainment or exacerbation of cachexia, thus affecting quality of life and overall survival in cancer patients. Pre-clinical studies have shown that blocking activin receptor type 2 (ACVR2) or its ligands and their downstream signaling can preserve muscle mass in rodents bearing experimental cancers, as well as in chemotherapy-treated animals. In tumor-bearing mice, the prevention of skeletal and respiratory muscle wasting was also associated with improved survival. However, the definitive proof that improved survival directly results from muscle preservation following blockade of ACVR2 signaling is still lacking, especially considering that concurrent beneficial effects in organs other than skeletal muscle have also been described in the presence of cancer or following chemotherapy treatments paired with counteraction of ACVR2 signaling. Hence, here, we aim to provide an up-to-date literature review on the multifaceted anti-cachectic effects of ACVR2 blockade in preclinical models of cancer, as well as in combination with anticancer treatments.

Body Composition and Response and Outcome of Neoadjuvant Treatment for Pancreatic Cancer

To assess the correlation of body composition with the response and outcome of neoadjuvant treatment (NAT) in patients with pancreatic ductal adenocarcinoma (PDAC). One hundred and nineteen PDAC patients underwent curative resection after NAT. Computed tomography scans of the third lumbar vertebra were used to assess the body composition of these patients before and after NAT. Three distinct wasting phenotypes were identified during NAT, with 51 patients (42.9%) developing muscle and fat wasting (MFW), 17 patients (14.3%) developing fat-only wasting (FW), and 51 patients (42.9%) having no wasting (NW). The response rate was higher in the NW phenotype than in the MFW and FW phenotypes (P = 0.007). In univariate and multivariate analyses, histological grade, sarcopenia before NAT, and MFW during NAT were associated with decreased overall survival (OS). Sarcopenia before NAT and MFW during NAT were associated with decreased disease-free survival (DFS). Body composition was associated with the response and outcome of patients undergoing NAT for PDAC. The response rate was higher in patients having NW during NAT. Sarcopenia before NAT and MFW during NAT were associated with decreased OS and DFS.

Ubiquitin Ligases at the Heart of Skeletal Muscle Atrophy Control

Skeletal muscle loss is a detrimental side-effect of numerous chronic diseases that dramatically increases mortality and morbidity. The alteration of protein homeostasis is generally due to increased protein breakdown while, protein synthesis may also be down-regulated. The ubiquitin proteasome system (UPS) is a master regulator of skeletal muscle that impacts muscle contractile properties and metabolism through multiple levers like signaling pathways, contractile apparatus degradation, etc. Among the different actors of the UPS, the E3 ubiquitin ligases specifically target key proteins for either degradation or activity modulation, thus controlling both pro-anabolic or pro-catabolic factors. The atrogenes MuRF1/TRIM63 and MAFbx/Atrogin-1 encode for key E3 ligases that target contractile proteins and key actors of protein synthesis respectively. However, several other E3 ligases are involved upstream in the atrophy program, from signal transduction control to modulation of energy balance. Controlling E3 ligases activity is thus a tempting approach for preserving muscle mass. While indirect modulation of E3 ligases may prove beneficial in some situations of muscle atrophy, some drugs directly inhibiting their activity have started to appear. This review summarizes the main signaling pathways involved in muscle atrophy and the E3 ligases implicated, but also the molecules potentially usable for future therapies.

Prognostic relevance of temporal muscle thickness as a marker of sarcopenia in patients with glioblastoma at diagnosis

OBJECTIVES

Temporal muscle thickness (TMT) is a surrogate marker of sarcopenia, correlated with survival expectancy in patients suffering from brain metastases and recurrent or treated glioblastoma. We evaluated the prognostic relevance of TMT measured on brain MRIs acquired at diagnosis in patients affected by glioblastoma.

METHODS

We retrospectively enrolled 51 patients in our Institution affected by methylated MGMT promoter, IDH1-2 wild-type glioblastoma, who underwent complete surgical resection and subsequent radiotherapy with concomitant and maintenance temozolomide, from January 1, 2015, to April 30, 2017. The last clinical/radiological follow-up date was set to September 3, 2019. TMT was measured bilaterally on reformatted post-contrast 3D MPRAGE images, acquired on our 3-T scanner no more than 2 days before surgery. The median, 25th, and 75th percentile TMT values were identified and population was subdivided accordingly; afterwards, statistical analyses were performed to verify the association among overall survival (OS) and TMT, sex, age, and ECOG performance status.

RESULTS

In our cohort, the median OS was 20 months (range 3-51). Patients with a TMT ≥ 8.4 mm (median value) did not show a statistically significant increase in OS (Cox regression model: HR 1.34, 95% CI 0.68-2.63, p = 0.403). Similarly, patients with a TMT ≥ 9.85 mm (fourth quartile) did not differ in OS compared to those with TMT ≤ 7 mm (first quartile). The statistical analyses confirmed a significant association among TMT and sex (p = 0.0186), but none for age (p = 0.642) and performance status (p = 0.3982).

CONCLUSIONS

In our homogeneous cohort of patients with glioblastoma at diagnosis, TMT was not associated with prognosis, age, or ECOG performance status.

KEY POINTS

• Temporal muscle thickness (TMT) is a surrogate marker of sarcopenia and has been correlated with survival expectancy in patients suffering from brain metastases and recurrent or treated glioblastoma. • We appraised the correlation among TMT and survival, sex, age at surgery, and performance status, measured on brain MRIs of patients affected by glioblastoma at diagnosis. • TMT did not show any significant correlation with prognosis, age at surgery, or performance status, and its usefulness might be restricted only to patients with brain metastases and recurrent or treated glioblastoma.

Altered glucose metabolism and insulin resistance in cancer-induced cachexia: a sweet poison

Cancer cachexia is a wasting disorder characterised by specific skeletal muscle and adipose tissue loss. Cancer cachexia is also driven by inflammation, altered metabolic changes such as increased energy expenditure, elevated plasma glucose, insulin resistance and excess catabolism. In cachexia, host-tumor interaction causes release of the lactate and inflammatory cytokines. Lactate released by tumor cells takes part in hepatic glucose production with the help of gluconeogenic enzymes. Thus, Cori cycle between organs and cancerous cells contributes to increased glucose production and energy expenditure. A high amount of blood glucose leads to increased production of insulin. Overproduction of insulin causes inactivation of PI3K/Akt/m-TOR pathway and finally results in insulin resistance. Insulin is involved in maintaining the vitality of organs and regulate the metabolism of glucose, protein and lipids. Insulin insensitivity decreases the uptake of glucose in the organs and results in loss of skeletal muscles and adipose tissues. However, looking into the complexity of this metabolic syndrome, it is impossible to rely on a single variable to treat patients having cancer cachexia. Hence, it becomes greater a challenge to produce a clinically effective treatment for this metabolic syndrome. Thus, the present paper aims to provide an understanding of pathogenesis and mechanism underlining the altered glucose metabolism and insulin resistance and its contribution to the progression of skeletal muscle wasting and lipolysis, providing future direction of research to develop new pharmacological treatment in cancer cachexia.

Sarcopenia: looking to muscle mass to better manage pancreatic cancer patients

PURPOSE OF REVIEW

Overall survival of patients with pancreatic cancer is strongly conditioned by tumor biology and the incidence of malnutrition and metabolic disorders. In this landscape, the assessment of body composition is crucial to properly manage the clinical implications of muscle wasting. The pathogenesis of this condition is the result of a complex interplay between cancer and the host. In particular, sarcopenia is induced by an inadequate nutritional intake, hormonal abnormalities, inflammation and imbalance between anabolic and catabolic pathways.

RECENT FINDINGS

Recent evidences have highlighted the role of sarcopenia in cancer patients, revealing a prognostic impact on morbidity, mortality and survival.

SUMMARY

The occurrence of sarcopenia could amplify chemotherapy-induced toxicities, prolong hospitalizations and reduce adherence to anticancer treatment, worsening quality of life and survival. Although considerable efforts have been made to develop treatment strategies, no effective interventions have been identified so far. Nevertheless, if promptly and adequately supported, pancreatic cancer might benefit from adopted dietary intervention to avoid further loss of lean mass.

The ubiquitin-proteasome system in regulation of the skeletal muscle homeostasis and atrophy: from basic science to disorders

Skeletal muscle is one of the most abundant and highly plastic tissues. The ubiquitin-proteasome system (UPS) is recognised as a major intracellular protein degradation system, and its function is important for muscle homeostasis and health. Although UPS plays an essential role in protein degradation during muscle atrophy, leading to the loss of muscle mass and strength, its deficit negatively impacts muscle homeostasis and leads to the occurrence of several pathological phenotypes. A growing number of studies have linked UPS impairment not only to matured muscle fibre degeneration and weakness, but also to muscle stem cells and deficiency in regeneration. Emerging evidence suggests possible links between abnormal UPS regulation and several types of muscle diseases. Therefore, understanding of the role of UPS in skeletal muscle may provide novel therapeutic insights to counteract muscle wasting, and various muscle diseases. In this review, we focussed on the role of proteasomes in skeletal muscle and its regeneration, including a brief explanation of the structure of proteasomes. In addition, we summarised the recent findings on several diseases and elaborated on how the UPS is related to their pathological states.

Short-chain fatty acids as potential regulators of skeletal muscle metabolism and function

A key metabolic activity of the gut microbiota is the fermentation of non-digestible carbohydrate, which generates short-chain fatty acids (SCFAs) as the principal end products. SCFAs are absorbed from the gut lumen and modulate host metabolic responses at different organ sites. Evidence suggests that these organ sites include skeletal muscle, the largest organ in humans, which plays a pivotal role in whole-body energy metabolism. In this Review, we evaluate the evidence indicating that SCFAs mediate metabolic cross-talk between the gut microbiota and skeletal muscle. We discuss the effects of three primary SCFAs (acetate, propionate and butyrate) on lipid, carbohydrate and protein metabolism in skeletal muscle, and we consider the potential mechanisms involved. Furthermore, we highlight the emerging roles of these gut-derived metabolites in skeletal muscle function and exercise capacity, present limitations in current knowledge and provide suggestions for future work.

Withaferin A attenuates ovarian cancer-induced cardiac cachexia

Cachexia is a common multifactorial syndrome in the advanced stages of cancer and accounts for approximately 20–30% of all cancer-related fatalities. In addition to the progressive loss of skeletal muscle mass, cancer results in impairments in cardiac function. We recently demonstrated that WFA attenuates the cachectic skeletal muscle phenotype induced by ovarian cancer. The purpose of this study was to investigate whether ovarian cancer induces cardiac cachexia, the possible pathway involved, and whether WFA attenuates cardiac cachexia. Xenografting of ovarian cancer induced cardiac cachexia, leading to the loss of normal heart functions. Treatment with WFA rescued the heart weight. Further, ovarian cancer induced systolic dysfunction and diastolic dysfunction Treatment with WFA preserved systolic function in tumor-bearing mice, but diastolic dysfunction was partially improved. In addition, WFA abrogated the ovarian cancer-induced reduction in cardiomyocyte cross-sectional area. Finally, treatment with WFA ameliorated fibrotic deposition in the hearts of tumor-bearing animals. We observed a tumor-induced MHC isoform switching from the adult MHCα to the embryonic MHCβ isoform, which was prevented by WFA treatment. Circulating Ang II level was increased significantly in the tumor-bearing, which was lowered by WFA treatment. Our results clearly demonstrated the induction of cardiac cachexia in response to ovarian tumors in female NSG mice. Further, we observed induction of proinflammatory markers through the AT₁R pathway, which was ameliorated by WFA, in addition to amelioration of the cachectic phenotype, suggesting WFA as a potential therapeutic agent for cardiac cachexia in oncological paradigms.

Peptide-2 from mouse myostatin precursor protein alleviates muscle wasting in cancer-associated cachexia

Cancer cachexia, characterized by continuous muscle wasting, is a key determinant of cancer‐related death; however, there are few medical treatments to combat it. Myostatin (MSTN)/growth differentiation factor 8 (GDF‐8), which is a member of the transforming growth factor‐β family, is secreted in an inactivated form noncovalently bound to the prodomain, negatively regulating the skeletal muscle mass. Therefore, inhibition of MSTN signaling is expected to serve as a therapeutic target for intractable muscle wasting diseases. Here, we evaluated the inhibitory effect of peptide‐2, an inhibitory core of mouse MSTN prodomain, on MSTN signaling. Peptide‐2 selectively suppressed the MSTN signal, although it had no effect on the activin signal. In contrast, peptide‐2 slightly inhibited the GDF‐11 signaling pathway, which is strongly related to the MSTN signaling pathway. Furthermore, we found that the i.m. injection of peptide‐2 to tumor‐implanted C57BL/6 mice alleviated muscle wasting in cancer cachexia. Although peptide‐2 was unable to improve the loss of heart weight and fat mass when cancer cachexia model mice were injected with it, peptide‐2 increased the gastrocnemius muscle weight and muscle cross‐sectional area resulted in the enhanced grip strength in cancer cachexia mice. Consequently, the model mice treated with peptide‐2 could survive longer than those that did not undergo this treatment. Our results suggest that peptide‐2 might be a novel therapeutic candidate to suppress muscle wasting in cancer cachexia.

MEF2c-Dependent Downregulation of Myocilin Mediates Cancer-Induced Muscle Wasting and Associates with Cachexia in Patients with Cancer

Skeletal muscle wasting is a devastating consequence of cancer that contributes to increased complications and poor survival, but is not well understood at the molecular level. Herein, we investigated the role of Myocilin (Myoc), a skeletal muscle hypertrophy-promoting protein that we showed is downregulated in multiple mouse models of cancer cachexia. Loss of Myoc alone was sufficient to induce phenotypes identified in mouse models of cancer cachexia, including muscle fiber atrophy, sarcolemmal fragility, and impaired muscle regeneration. By 18 months of age, mice deficient in Myoc showed significant skeletal muscle remodeling, characterized by increased fat and collagen deposition compared with wild-type mice, thus also supporting Myoc as a regulator of muscle quality. In cancer cachexia models, maintaining skeletal muscle expression of Myoc significantly attenuated muscle loss, while mice lacking Myoc showed enhanced muscle wasting. Furthermore, we identified the myocyte enhancer factor 2 C (MEF2C) transcription factor as a key upstream activator of Myoc whose gain of function significantly deterred cancer-induced muscle wasting and dysfunction in a preclinical model of pancreatic ductal adenocarcinoma (PDAC). Finally, compared with noncancer control patients, MYOC was significantly reduced in skeletal muscle of patients with PDAC defined as cachectic and correlated with MEF2c. These data therefore identify disruptions in MEF2c-dependent transcription of Myoc as a novel mechanism of cancer-associated muscle wasting that is similarly disrupted in muscle of patients with cachectic cancer. SIGNIFICANCE: This work identifies a novel transcriptional mechanism that mediates skeletal muscle wasting in murine models of cancer cachexia that is disrupted in skeletal muscle of patients with cancer exhibiting cachexia.

Systemic Actions of Breast Cancer Facilitate Functional Limitations

Breast cancer is a disease of a specific organ, but its effects are felt throughout the body. The systemic effects of breast cancer can lead to functional limitations in patients who suffer from muscle weakness, fatigue, pain, fibromyalgia, or many other dysfunctions, which hasten cancer-associated death. Mechanistic studies have identified quite a few molecular defects in skeletal muscles that are associated with functional limitations in breast cancer. These include circulating cytokines such as TNF-α, IL-1, IL-6, and TGF-β altering the levels or function of myogenic molecules including PAX7, MyoD, and microRNAs through transcriptional regulators such as NF-κB, STAT3, and SMADs. Molecular defects in breast cancer may also include reduced muscle mitochondrial content and increased extracellular matrix deposition leading to energy imbalance and skeletal muscle fibrosis. This review highlights recent evidence that breast cancer-associated molecular defects mechanistically contribute to functional limitations and further provides insights into therapeutic interventions in managing functional limitations, which in turn may help to improve quality of life in breast cancer patients.

Proposal of predictive model on survival in unresectable pancreatic cancer receiving systemic chemotherapy

Aims: To construct a predictive model for overall survival (OS) in unresectable pancreatic cancer (PaC) undergoing systemic chemotherapy and to confirm its accuracy in an independent cohort. Patients and methods: The training set (Ts) and the validation set (Vs) included 93 patients (median age=71 years) and 75 patients (median age=76 years). In the Ts, we examined variables linked to OS by uni- and multivariate analyses and constructed a predictive model for OS. Next, we evaluated the reproducibility of the proposed model in the Vs. Results: In the multivariate analysis for the Ts, PaC stage IV (P=0.0020) and carbohydrate antigen (CA) 19-9 ≥437.5 IU/l (P=0.0237) were identified to be significant factors associated with OS. Patients with PaC stage IV or not were given a score of 1 or 0, whereas patients with CA19-9 ≥437.5 IU/l or <437.5 IU/l were given a score of 1 or 0. Sum of the point of PaC stage (0 or 1) and CA19-9 (0 or 1) was defined as "PaC-CA score". In the Ts, there were 16 patients with score 0, 40 with score 1 and 37 with score 2, while in the Vs, there were 9 patients with score 0, 32 with score 1 and 34 with score 2. Overall P values reached significance in the Ts (P=0.0002), the Vs (P=0.0029) and the combined Ts and Vs (P<0.0001) among patients with PaC score 0, 1 and 2. Conclusion: PaC-CA score can be helpful for risk stratification in PaC patients undergoing systemic chemotherapy.

ER Stress and Unfolded Protein Response in Cancer Cachexia

Cancer cachexia is a devastating syndrome characterized by unintentional weight loss attributed to extensive skeletal muscle wasting. The pathogenesis of cachexia is multifactorial because of complex interactions of tumor and host factors. The irreversible wasting syndrome has been ascribed to systemic inflammation, insulin resistance, dysfunctional mitochondria, oxidative stress, and heightened activation of ubiquitin-proteasome system and macroautophagy. Accumulating evidence suggests that deviant regulation of an array of signaling pathways engenders cancer cachexia where the human body is sustained in an incessant self-consuming catabolic state. Recent studies have further suggested that several components of endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) are activated in skeletal muscle of animal models and muscle biopsies of cachectic cancer patients. However, the exact role of ER stress and the individual arms of the UPR in the regulation of skeletal muscle mass in various catabolic states including cancer has just begun to be elucidated. This review provides a succinct overview of emerging roles of ER stress and the UPR in cancer-induced skeletal muscle wasting.

Anabolic and Pro-metabolic Functions of CREB-CRTC in Skeletal Muscle: Advantages and Obstacles for Type 2 Diabetes and Cancer Cachexia

cAMP is one of the earliest described mediators of hormone action in response to physiologic stress that allows acute stress responses and adaptation in every tissue. The classic role of cAMP signaling in metabolic tissues is to regulate nutrient partitioning. In response to acute stress, such as epinephrine released during strenuous exercise or fasting, intramuscular cAMP liberates glucose from glycogen and fatty acids from triglycerides. In the long-term, activation of Gs-coupled GPCRs stimulates muscle growth (hypertrophy) and metabolic adaptation through multiple pathways that culminate in a net increase of protein synthesis, mitochondrial biogenesis, and improved metabolic efficiency. This review focuses on regulation, function, and transcriptional targets of CREB (cAMP response element binding protein) and CRTCs (CREB regulated transcriptional coactivators) in skeletal muscle and the potential for targeting this pathway to sustain muscle mass and metabolic function in type 2 diabetes and cancer. Although the muscle-autonomous roles of these proteins might render them excellent targets for both conditions, pharmacologic targeting must be approached with caution. Gain of CREB-CRTC function is associated with excess liver glucose output in type 2 diabetes, and growing evidence implicates CREB-CRTC activation in proliferation and invasion of different types of cancer cells. We conclude that deeper investigation to identify skeletal muscle specific regulatory mechanisms that govern CREB-CRTC transcriptional activity is needed to safely take advantage of their potent effects to invigorate skeletal muscle to potentially improve health in people with type 2 diabetes and cancer.