Diaphragm and ventilatory dysfunction during cancer cachexia

Myofiber-specific FoxP1 knockout protects against pancreatic cancer-induced muscle wasting in male but not female mice

Cancer cachexia affects up to 80% of cancer patients and results in reduced quality of life and survival. We previously demonstrated that the transcriptional repressor Forkhead box P1 (FoxP1) is upregulated in skeletal muscle of cachectic mice and people with cancer, and when overexpressed in skeletal muscle is sufficient to induce pathological features characteristic of cachexia. However, the role of myofiber-derived FoxP1 in both normal muscle physiology and cancer-induced muscle wasting remains largely unexplored. To address this gap, we generated a conditional mouse line with myofiber-specific ablation of FoxP1 (FoxP1SkmKO) and found that in cancer-free mice, deletion of FoxP1 in skeletal myofibers resulted in increased myofiber size in both males and females, with a significant increase in muscle mass in males. In response to murine KPC pancreatic tumor burden, we found that myofiber-derived FoxP1 is required for cancer-induced muscle wasting and diaphragm muscle weakness in male mice. In summary, our findings identify myofiber-specific FoxP1 as a negative regulator of skeletal muscle with sex-specific differences in the context of cancer.

Cancer cachexia: biomarkers and the influence of age

Cancer cachexia (Ccx) is a complex metabolic condition characterized by pronounced muscle and fat wasting, systemic inflammation, weakness and fatigue. Up to 30% of cancer patients succumb directly to Ccx, yet therapies that effectively address this perturbed metabolic state are rare. In recent decades, several characteristics of Ccx have been established in mice and humans, of which we here highlight adipose tissue dysfunction, muscle wasting and systemic inflammation, as they are directly linked to biomarker discovery. To counteract cachexia pathogenesis as early as possible and mitigate its detrimental impact on anti-cancer treatments, identification and validation of clinically endorsed biomarkers assume paramount importance. Ageing was recently shown to affect both the validity of Ccx biomarkers and Ccx development, but the underlying mechanisms are still unknown. Thus, unravelling the intricate interplay between ageing and Ccx can help to counteract Ccx pathogenesis and tailor diagnostic and treatment strategies to individual needs.

Cancer-associated muscle weakness - From triggers to molecular mechanisms

Skeletal muscle weakness is a debilitating consequence of many malignancies. Muscle weakness has a negative impact on both patient wellbeing and outcome in a range of cancer types and can be the result of loss of muscle mass (i.e. muscle atrophy, cachexia) and occur independently of muscle atrophy or cachexia. There are multiple cancer specific triggers that can initiate the progression of muscle weakness, including the malignancy itself and the tumour environment, as well as chemotherapy, radiotherapy and malnutrition. This can induce weakness via different routes: 1) impaired intrinsic capacity (i.e., contractile dysfunction and intramuscular impairments in excitation-contraction coupling or crossbridge cycling), 2) neuromuscular disconnection and/or 3) muscle atrophy. The mechanisms that underlie these pathways are a complex interplay of inflammation, autophagy, disrupted protein synthesis/degradation, and mitochondrial dysfunction. The current lack of therapies to treat cancer-associated muscle weakness highlight the critical need for novel interventions (both pharmacological and non-pharmacological) and mechanistic insight. Moreover, most research in the field has placed emphasis on directly improving muscle mass to improve muscle strength. However, accumulating evidence suggests that loss of muscle function precedes atrophy. This review primarily focuses on cancer-associated muscle weakness, independent of cachexia, and provides a solid background on the underlying mechanisms, methodology, current interventions, gaps in knowledge, and limitations of research in the field. Moreover, we have performed a mini-systematic review of recent research into the mechanisms behind muscle weakness in specific cancer types, along with the main pathways implicated.

Cancer survivor inspiratory muscle training: systematic review and Bayesian meta-analysis

BACKGROUND

The long-term impact of cancer treatment is associated with respiratory dysfunction and physical fitness impairment. Although inspiratory muscle training (IMT) has been shown as an effective exercise therapy in cancer survivors, there is no evidence on the optimal dose, application moment nor specific population effects of this intervention. The main objective of this meta-analysis is to analyse the effects of IMT on pulmonary function, physical fitness and quality of life (QoL) in cancer survivors.

METHODS

This systematic review and meta-analysis was preregistered in the International Prospective Register of Systematic Reviews (PROSPERO) register and conducted according to the Preferred Reporting for Systematic Reviews and Meta-analysis statement. We used a Bayesian multilevel random-effects meta-analysis model to pool the data. Multilevel metaregression models were used to examine the conditional effects of our covariates. Convergence and model fit were evaluated through specific model parameters. Sensitivity analyses removing influential cases and using a frequentist approach were carried out.

RESULTS

Pooled data showed that IMT intervention is effective to improve pulmonary function (standardised mean difference=0.53, 95% credible interval 0.13 to 0.94, SE=0.19). However, IMT did not present statistically significant results on physical fitness and QoL. Metaregression analyses found that the type of cancer, the moment of application and the evaluation tool used had significant moderation effects on pulmonary function.

CONCLUSION

IMT could be an important part in the management of side effects suffered by cancer survivors. Considering the current evidence, this intervention is highly recommended in patients diagnosed with oesophageal and lung cancers. IMT may provide superior benefits before the biological treatment and after the surgery.

PROSPERO REGISTRATION NUMBER

304909.

The Relationship between Exercise Capacity and Muscle Strength, Physical Activity, Fatigue and Quality of Life in Patients with Cancer Cachexia

BACKGROUND

Exercise capacity is a significant determinant of mortality for cancer patients, so knowing the possible determinants of exercise capacity will produce physical and psychological benefits for individuals with cancer cachexia.

PURPOSE

To investigate the relationship between exercise capacity on peripheric and respiratory muscle strength, physical activity, fatigue and quality of life in subjects with cancer cachexia.

METHODS

The study included 31 patients diagnosed with cancer cachexia. Functional capacity was assessed by 6-Minute Walk Test, hand grip strength and proximal muscle mass by hand dynamometer, respiratory muscle strength by the Maximum Expiratory Pressure and Maximum Inspiratory Pressure measurements, physical activity by International Physical Activity Questionnaire Short Form, fatigue by Brief Fatigue Inventory, and quality of life by EORT-QLQ-C30. The relationship between functional capacity and continuous independent variables was determined using Spearman's or Pearson's tests.

RESULTS

A strong positive correlation was observed between exercise capacity and expiratory muscle strength (r = 0.75, p < 0.001), activity level (r = 0.68, p < 0.001), and quality of life global health status (r = 0.74, p < 0.001). Conversely, a strong negative correlation was found between exercise capacity and fatigue severity (r = -0.64, p < 0.001).

CONCLUSION

Higher exercise capacity in cancer cachexia patients is linked to reduced fatigue, improved respiratory muscle strength, increased physical activity levels, and enhanced quality of life. When designing rehabilitation programs or exercise interventions for individuals with cancer cachexia, it is crucial to assess their exercise capacity and tailor the programs accordingly.

Skeletal muscle atrophy, regeneration, and dysfunction in heart failure: Impact of exercise training

This review highlights some established and some more contemporary mechanisms responsible for heart failure (HF)-induced skeletal muscle wasting and weakness. We first describe the effects of HF on the relationship between protein synthesis and degradation rates, which determine muscle mass, the involvement of the satellite cells for continual muscle regeneration, and changes in myofiber calcium homeostasis linked to contractile dysfunction. We then highlight key mechanistic effects of both aerobic and resistance exercise training on skeletal muscle in HF and outline its application as a beneficial treatment. Overall, HF causes multiple impairments related to autophagy, anabolic-catabolic signaling, satellite cell proliferation, and calcium homeostasis, which together promote fiber atrophy, contractile dysfunction, and impaired regeneration. Although both wasting and weakness are partly rescued by aerobic and resistance exercise training in HF, the effects of satellite cell dynamics remain poorly explored.

The Incidence of Diaphragmatic Dysfunction in Patients Presenting With Dyspnea in the Emergency Department

OBJECTIVES

Diaphragmatic dysfunction has been reported as a cause of dyspnea, and its diagnosis can be made using ultrasound. Diaphragmatic ultrasound is mainly used to predict respiratory failure in chronic conditions. The use of diaphragmatic ultrasound has also risen in acute settings, such as emergency departments (EDs). However, the number of studies on its use still needs to be increased. The present study aimed to find the incidence of diaphragmatic dysfunction in the ED.

METHODS

This prospective cohort study was conducted in an ED. We enrolled patients aged greater than 18 years who presented with dyspnea. Diaphragmatic excursion and diaphragmatic thickness techniques were performed. The primary outcome was the incidence of diaphragmatic dysfunction. The secondary outcomes were the associations between diaphragmatic dysfunction and the composition of respiratory therapies within 24 hours, intubation within 24 hours, and 7-day mortality.

RESULTS

A total of 237 patients were analyzed. The incidences of diaphragmatic dysfunction assessed by diaphragmatic excursion and diaphragm thickness were 22.4 and 32.1%, respectively. Patients with sepsis and cancer had the highest incidences. Diaphragmatic dysfunction assessed by both techniques was not associated with the composition of respiratory support therapies within 24 hours, intubation within 24 hours, or 7-day mortality.

CONCLUSIONS

The incidence of diaphragmatic dysfunction in dyspneic patients in the ED ranged from 22.4 to 32.1%, depending on the ultrasound technique. Diaphragmatic dysfunction was not associated with the composition of respiratory support therapies, intubation, or mortality.

SKELETAL MUSCLE SENSITIVITY TO WASTING INDUCED BY UROTHELIAL CARCINOMA

BACKGROUND

Skeletal muscle wasting is a common phenotypic feature of several types of cancer, and it is associated with functional impairment, respiratory complications, and fatigue. However, equivocal evidence remains regarding the impact of cancer-induced muscle wasting on the different fiber types.

AIM

The aim of this study was to investigate the impact of urothelial carcinoma induced in mice on the histomorphometric features and collagen deposition in different skeletal muscles.

MATERIALS AND METHODS

Thirteen ICR (CD1) male mice were randomly assigned into two groups: exposed to 0.05% N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in drinking water for 12 weeks, plus 8 weeks of tap water (BBN, n = 8) or with access to tap water for 20 weeks (CONT, n = 5). Tibialis anterior, soleus, and diaphragm muscles were collected from all animals. For cross-sectional area and myonuclear domain analysis, muscle sections were stained with hematoxylin and eosin, and for collagen deposition assessment, muscle sections were stained with picrosirius red.

RESULTS

All animals from the BBN group developed urothelial preneoplastic and neoplastic lesions, and the tibialis anterior from these animals presented a reduced cross-sectional area (p < 0.001), with a decreased proportion of fibers with a higher cross-sectional area, increased collagen deposition (p = 0.017), and higher myonuclear domain (p = 0.031). BBN mice also showed a higher myonuclear domain in the diaphragm (p = 0.015).

CONCLUSION

Urothelial carcinoma induced muscle wasting of the tibialis anterior, expressed by a decreased cross-sectional area, higher infiltration of fibrotic tissue, and increased myonuclear domain, which also increased in the diaphragm, suggesting that fast glycolytic muscle fibers are more susceptible to be affected by cancer development.

Exercise-based rehabilitation on functionality and quality of life in head and neck cancer survivors. A systematic review and meta-analysis

Head and Neck Cancer (HNC) is a globally rare cancer that includes a variety of tumors affecting the upper aerodigestive tract. It presents with difficulty breathing or swallowing and is mainly treated with radiation therapy, chemotherapy, or surgery for tumors that have spread locally or throughout the body. Alternatively, exercise can be used during cancer treatment to improve function, including pain relief, increase range of motion and muscle strength, and reduce cancer-related fatigue, thereby enhancing quality of life. Although existing evidence suggests the adjunctive use of exercise in other cancer types, no previous studies have examined the effects on HNC survivors. The aim of this meta-analysis was to quantify the effect of exercise-based rehabilitation on functionality and quality of life in HNC survivors who underwent surgery and/or chemoradiotherapy. A systematic review and meta-analysis were carried out following PRISMA statement and registered in PROSPERO (CRD42023390300). The search was performed in MEDLINE (PubMED), Cochrane Library, CINAHL and Web of Science (WOS) databases from inception to 31st December 2022 using the terms "cancer", "head and neck neoplasms", "exercise", "rehabilitation", "complications", "muscle contraction", "muscle stretching exercises" combining with booleans "AND"/"OR". PEDro scale, Cochrane Risk of Bias Tool and GRADE were used to assess methodological quality, risk of bias and grade of recommendation of included studies respectively. 18 studies (n = 1322) were finally included which 1039 (78.6%) were men and 283 (21.4%) were women. In patients who underwent radio-chemotherapy, overall pain [SMD = - 0.62 [- 4.07, 2.83] CI 95%, Z = 0.35, p = 0.72] and OP [SMD = - 0.07 [- 0.62, 0.48] CI 95%, Z = 0.25, p = 0.81] were slightly reduced with exercise in comparison to controls. Besides, lower limb muscle strength [SMD = - 0.10 [- 1.52, 1.32] CI 95%, Z = 0.14, p = 0.89] and fatigue [SMD = - 0.51 [- 0.97, - 0.057] CI 95%, Z = 2.15, p < 0.01] were also improved in those who receive radio-chemoradiation. In HNC survivors treated with neck dissection surgery, exercise was superior to controls in overall pain [SMD = - 1.04 [- 3.31, 1.23] CI 95%, Z = 0.90, p = 0.37] and, in mid-term, on shoulder pain SMD = - 2.81 [- 7.06, 1.43] CI 95%, Z = 1.76, p = 0.08]. No differences in quality of life were found at any of the follow-up periods. There is evidence of fair to good methodological quality, low to moderate risk of bias, and weak recommendations supporting the use of exercise-based rehabilitation to increase functionality. However, no evidence was found in favor of the use of this modality for improving the quality of life of HNC survivors who underwent chemoradiotherapy or surgery.

Low Muscle Mass and Radiodensity Associate with Impaired Pulmonary Function and Respiratory Complications in Patients with Esophageal Cancer

BACKGROUND

Sixty percent of patients with esophageal cancer display signs of cachexia at diagnosis. Changes in body composition are common, and muscle mass and quality are measurable through imaging studies. Cachexia leads to functional impairments that complicate treatments, including surgery. We hypothesize that low muscle mass and quality associate with pulmonary function testing parameters, highlighting ventilatory deficits, and postoperative complications in patients receiving esophagectomy.

STUDY DESIGN

We performed a retrospective review of patients receiving esophagectomy between 2012 and 2021 at our facility. PET/CT scans were used to quantify skeletal muscle at the L3 and T4 levels. Patient characteristics were recorded, including pulmonary function testing parameters. Regression models were created to characterize predictive associations.

RESULTS

One hundred eight patients were identified. All were included in the final analysis. In linear regression adjusted for sex, age, and COPD status, low L3 muscle mass independently associated with low forced vital capacity (p < 0.005, β 0.354) and forced expiratory volume in 1 second (p < 0.001, β 0.392). Similarly, T4 muscle mass independently predicted forced vital capacity (p < 0.005, β 0.524) and forced expiratory volume in 1 second (p < 0.01, β 0.480). L3 muscle quality correlated with total lung capacity ( R 0.2463, p < 0.05). Twenty-six patients had pleural effusions postoperatively, associated with low muscle quality on L3 images (p < 0.05). Similarly, patients with hospitalization more than 2 weeks presented with lower muscle quality (p < 0.005).

CONCLUSIONS

Cachexia and low muscle mass are common. Reduced muscle mass and quality independently associate with impaired forced vital capacity, forced expiratory volume in 1 second, and total lung capacity. We propose that respiratory muscle atrophy occurs with weight loss. Body composition analyses may aid in stratifying patients. Pulmonary function testing may also serve as a functional endpoint for clinical trials. These findings highlight the need to study mechanisms that lead to respiratory muscle pathology and dysfunction in tumor-bearing hosts.

Effects of Monoamino-Oxidase-A (MAO-A) Inhibition on Skeletal Muscle Inflammation and Wasting through Pancreatic Ductal Adenocarcinoma in Triple Transgenic Mice

Cancer cachexia describes a syndrome of muscle wasting and lipolysis that is still largely untreatable and negatively impacts prognosis, mobility, and healthcare costs. Since upregulation of skeletal muscle monoamine-oxidase-A (MAO-A), a source of reactive oxygen species, may contribute to cachexia, we investigated the effects of the MAO-inhibitor harmine-hydrochloride (HH, intraperitoneal, 8 weeks) on muscle wasting in a triple-transgenic mouse model of pancreatic ductal adenocarcinoma (PDAC) and wild type (WT) mice. Gastrocnemius and soleus muscle cryo-cross-sections were analyzed for fiber type-specific cross-sectional area (CSA), fraction and capillarization using ATPase- and lectin-stainings. Transcripts of pro-apoptotic, -atrophic, and -inflammatory signals were determined by RT-qPCR. Furthermore, we evaluated the integrity of neuromuscular junction (NMJ, pre-/post-synaptic co-staining) and mitochondrial ultrastructure (transmission electron microscopy). MAO-A expression in gastrocnemius muscle was increased with PDAC vs. WT (immunohistochemistry: p < 0.05; Western blot: by trend). PDAC expectedly reduced fiber CSA and upregulated IL-1β in both calf muscles, while MuRF1 expression increased in soleus muscle only. Although IL-1β decreased, HH caused an additional 38.65% (p < 0.001) decrease in gastrocnemius muscle (IIBX) fiber CSA. Moreover, soleus muscle CSA remained unchanged despite the downregulation of E3-ligases FBXO32 (p < 0.05) and MuRF1 (p < 0.01) through HH. Notably, HH significantly decreased the post-synaptic NMJ area (quadriceps muscle) and glutathione levels (gastrocnemius muscle), thereby increasing mitochondrial damage and centronucleation in soleus and gastrocnemius type IIBX fibers. Moreover, although pro-atrophic/-inflammatory signals are reversed, HH unfortunately fails to stop and rather promotes PDAC-related muscle wasting, possibly via denervation or mitochondrial damage. These differential adverse vs. therapeutic effects warrant studies regarding dose-dependent benefits and risks with consideration of other targets of HH, such as the dual-specificity tyrosine phosphorylation regulated kinases 1A and B (DYRK1A/B).

Progressive development of melanoma-induced cachexia differentially impacts organ systems in mice

Cachexia is a systemic wasting syndrome that increases cancer-associated mortality. How cachexia progressively and differentially impacts distinct tissues is largely unknown. Here, we find that the heart and skeletal muscle undergo wasting at early stages and are the tissues transcriptionally most impacted by cachexia. We also identify general and organ-specific transcriptional changes that indicate functional derangement by cachexia even in tissues that do not undergo wasting, such as the brain. Secreted factors constitute a top category of cancer-regulated genes in host tissues, and these changes include upregulation of the angiotensin-converting enzyme (ACE). ACE inhibition with the drug lisinopril improves muscle force and partially impedes cachexia-induced transcriptional changes, although wasting is not prevented, suggesting that cancer-induced host-secreted factors can regulate tissue function during cachexia. Altogether, by defining prevalent and temporal and tissue-specific responses to cachexia, this resource highlights biomarkers and possible targets for general and tissue-tailored anti-cachexia therapies.

Impact of cancer cachexia on respiratory muscle function and the therapeutic potential of exercise

Cancer cachexia is defined as a multi-factorial syndrome characterised by an ongoing loss of skeletal muscle mass and progressive functional impairment, estimated to affect 50-80% of patients and responsible for 20% of cancer deaths. Elevations in the morbidity and mortality rates of cachectic cancer patients has been linked to respiratory failure due to atrophy and dysfunction of the ventilatory muscles. Despite this, there is a distinct scarcity of research investigating the structural and functional condition of the respiratory musculature in cancer, with the majority of studies exclusively focusing on limb muscle. Treatment strategies are largely ineffective in mitigating the cachectic state. It is now widely accepted that an efficacious intervention will likely combine elements of pharmacology, nutrition and exercise. However, of these approaches, exercise has received comparatively little attention. Therefore, it is unlikely to be implemented optimally, whether in isolation or combination. In consideration of these limitations, the current review describes the mechanistic basis of cancer cachexia and subsequently explores the available respiratory- and exercise-focused literature within this context. The molecular basis of cachexia is thoroughly reviewed. The pivotal role of inflammatory mediators is described. Unravelling the mechanisms of exercise-induced support of muscle via antioxidant and anti-inflammatory effects in addition to promoting efficient energy metabolism via increased mitochondrial biogenesis, mitochondrial function and muscle glucose uptake provide avenues for interventional studies. Currently available pre-clinical mouse models including novel transgenic animals provide a platform for the development of multi-modal therapeutic strategies to protect respiratory muscles in people with cancer.

Depleting Ly6G Positive Myeloid Cells Reduces Pancreatic Cancer-Induced Skeletal Muscle Atrophy

Immune cells can mount desirable anti-cancer immunity. However, some immune cells can support cancer disease progression. The presence of cancer can lead to production of immature myeloid cells from the bone marrow known as myeloid-derived suppressor cells (MDSCs). The immunosuppressive and pro-tumorigenic effects of MDSCs are well understood. Whether MDSCs are involved in promoting cancer cachexia is not well understood. We orthotopically injected the pancreas of mice with KPC cells or PBS. One group of tumor-bearing mice was treated with an anti-Ly6G antibody that depletes granulocytic MDSCs and neutrophils; the other received a control antibody. Anti-Ly6G treatment delayed body mass loss, reduced tibialis anterior (TA) muscle wasting, abolished TA muscle fiber atrophy, reduced diaphragm muscle fiber atrophy of type IIb and IIx fibers, and reduced atrophic gene expression in the TA muscles. Anti-ly6G treatment resulted in greater than 50% Ly6G+ cell depletion efficiency in the tumors and TA muscles. These data show that, in the orthotopic KPC model, anti-Ly6G treatment reduces the number of Ly6G+ cells in the tumor and skeletal muscle and reduces skeletal muscle atrophy. These data implicate Ly6G+ cells, including granulocytic MDSCs and neutrophils, as possible contributors to the development of pancreatic cancer-induced skeletal muscle wasting.

The myokine Fibcd1 is an endogenous determinant of myofiber size and mitigates cancer-induced myofiber atrophy

Decline in skeletal muscle cell size (myofiber atrophy) is a key feature of cancer-induced wasting (cachexia). In particular, atrophy of the diaphragm, the major muscle responsible for breathing, is an important determinant of cancer-associated mortality. However, therapeutic options are limited. Here, we have used Drosophila transgenic screening to identify muscle-secreted factors (myokines) that act as paracrine regulators of myofiber growth. Subsequent testing in mouse myotubes revealed that mouse Fibcd1 is an evolutionary-conserved myokine that preserves myofiber size via ERK signaling. Local administration of recombinant Fibcd1 (rFibcd1) ameliorates cachexia-induced myofiber atrophy in the diaphragm of mice bearing patient-derived melanoma xenografts and LLC carcinomas. Moreover, rFibcd1 impedes cachexia-associated transcriptional changes in the diaphragm. Fibcd1-induced signaling appears to be muscle selective because rFibcd1 increases ERK activity in myotubes but not in several cancer cell lines tested. We propose that rFibcd1 may help reinstate myofiber size in the diaphragm of patients with cancer cachexia.

Weight Loss in Cancer Patients Correlates With p38β MAPK Activation in Skeletal Muscle

Unintentional weight loss, a first clinical sign of muscle wasting, is a major threat to cancer survival without a defined etiology. We previously identified in mice that p38β MAPK mediates cancer-induced muscle wasting by stimulating protein catabolism. However, whether this mechanism is relevant to humans is unknown. In this study, we recruited men with cancer and weight loss (CWL) or weight stable (CWS), and non-cancer controls (NCC), who were consented to rectus abdominis (RA) biopsy and blood sampling (n = 20/group). In the RA of both CWS and CWL, levels of activated p38β MAPK and its effectors in the catabolic pathways were higher than in NCC, with progressively higher active p38β MAPK detected in CWL. Remarkably, levels of active p38β MAPK correlated with weight loss. Plasma analysis for factors that activate p38β MAPK revealed higher levels in some cytokines as well as Hsp70 and Hsp90 in CWS and/or CWL. Thus, p38β MAPK appears a biomarker of weight loss in cancer patients.

Aerobic Exercise Training and In Vivo Akt Activation Counteract Cancer Cachexia by Inducing a Hypertrophic Profile through eIF-2α Modulation

Simple Summary

Chronic disease-related muscle atrophy is a serious public health problem since it reduces mobility and contributes to increases in hospitalization costs. Unfortunately, there is no approved treatment for muscle wasting at present. Thus, an understanding of the mechanisms underlying the control of muscle mass and function under chronic diseases can pave the way for the discovery of innovative therapeutic strategies to counteract muscle wasting. Since numerous types of cancer induce cachexia, which has no cure nor an effective treatment, the main proposal here was to study the effects of AET in cancer cachexia, and to investigate, through in vivo manipulation of the Akt/mTORC1 pathway, whether the cachectic muscle still presents conditions to respond adaptively to hypertrophic stimuli. Our results could provide a basis for innovative research lines to better understand muscle plasticity and to investigate potential therapeutic approaches necessary to prevent muscle loss.

Abstract

Cancer cachexia is a multifactorial and devastating syndrome characterized by severe skeletal muscle mass loss and dysfunction. As cachexia still has neither a cure nor an effective treatment, better understanding of skeletal muscle plasticity in the context of cancer is of great importance. Although aerobic exercise training (AET) has been shown as an important complementary therapy for chronic diseases and associated comorbidities, the impact of AET on skeletal muscle mass maintenance during cancer progression has not been well documented yet. Here, we show that previous AET induced a protective mechanism against tumor-induced muscle wasting by modulating the Akt/mTORC1 signaling and eukaryotic initiation factors, specifically eIF2-α. Thereafter, it was determined whether the in vivo Akt activation would induce a hypertrophic profile in cachectic muscles. As observed for the first time, Akt-induced hypertrophy was able and sufficient to either prevent or revert cancer cachexia by modulating both Akt/mTORC1 pathway and the eIF-2α activation, and induced a better muscle functionality. These findings provide evidence that skeletal muscle tissue still preserves hypertrophic potential to be stimulated by either AET or gene therapy to counteract cancer cachexia.

Feasibility and Efficacy of Inspiratory Muscle Training in Patients with Head and Neck Cancer receiving Concurrent Chemoradiotherapy

OBJECTIVES

Patients with head and neck cancer (HNC) undergoing concurrent chemoradiotherapy (CCRT) often experience pulmonary symptoms. This study evaluated if a 7-week inspiratory muscle training (IMT) program during CCRT is feasible, adherent, and safe in patients with HNC. This study also evaluated the effect of IMT on diaphragm thickness, mobility, and cardiorespiratory parameters in patients with HNC receiving CCRT.

METHODS

Ten participants with advanced stage HNC receiving CCRT were recruited for the study. Feasibility, adherence, and safety of the intervention were the primary outcomes. Changes in diaphragm thickness and mobility, maximal inspiratory pressure, maximal expiratory pressure, forced vital capacity, forced expiratory volume in first second and functional capacity using 6-MWT were measured at baseline and post 7 weeks of CCRT. IMT was performed at one session per day for 5 days a week for 7 weeks. Eight sets of two minutes of inspiratory manoeuvres with one minute rest period between them with intensity of 40% MIP were given.

RESULTS

Ten participants  were included in this study out of the 13 patients screened, indicating the feasibility to be 76.9%. Participants completed a total of 260 training sessions out of the 350 planned sessions denoting the adherence level as 74%. Diaphragm thickness and MEP remained significantly unchanged while significant decline was seen in diaphragm mobility, MIP,FVC, FEV1 and 6-MWD at the end of 7 weeks. No adverse events were reported following the intervention.

CONCLUSION

Inspiratory muscle training did not show significant effect on the diaphragm thickness, mobility, and cardiorespiratory parameters; however, it was feasible, adherent, and safe in patients with HNC receiving CCRT.

Is sarcopenia a risk factor for reduced diaphragm function following hepatic resection? A study protocol for a prospective observational study

INTRODUCTION

Sarcopenia is associated with reduced pulmonary function in healthy adults, as well as with increased risk of pneumonia following abdominal surgery. Consequentially, postoperative pneumonia prolongs hospital admission, and increases in-hospital mortality following a range of surgical interventions. Little is known about the function of the diaphragm in the context of sarcopenia and wasting disorders or how its function is influenced by abdominal surgery. Liver surgery induces reactive pleural effusion in most patients, compromising postoperative pulmonary function. We hypothesise that both major hepatic resection and sarcopenia have a measurable impact on diaphragm function. Furthermore, we hypothesise that sarcopenia is associated with reduced preoperative diaphragm function, and that patients with reduced preoperative diaphragm function show a greater decline and reduced recovery of diaphragm function following major hepatic resection. The primary goal of this study is to evaluate whether sarcopenic patients have a reduced diaphragm function prior to major liver resection compared with non-sarcopenic patients, and to evaluate whether sarcopenic patients show a greater reduction in respiratory muscle function following major liver resection when compared with non-sarcopenic patients.

METHODS AND ANALYSIS

Transcostal B-mode, M-mode ultrasound and speckle tracking imaging will be used to assess diaphragm function perioperatively in 33 sarcopenic and 33 non-sarcopenic patients undergoing right-sided hemihepatectomy starting 1 day prior to surgery and up to 30 days after surgery. In addition, rectus abdominis and quadriceps femoris muscles thickness will be measured using ultrasound to measure sarcopenia, and pulmonary function will be measured using a hand-held bedside spirometer. Muscle mass will be determined preoperatively using CT-muscle volumetry of abdominal muscle and adipose tissue at the third lumbar vertebra level (L3). Muscle function will be assessed using handgrip strength and physical condition will be measured with a short physical performance battery . A rectus abdominis muscle biopsy will be taken intraoperatively to measure proteolytic and mitochondrial activity as well as inflammation and redox status. Systemic inflammation and sarcopenia biomarkers will be assessed in serum acquired perioperatively.

ETHICS AND DISSEMINATION

This trial is open for recruitment. The protocol was approved by the official Independent Medical Ethical Committee at Uniklinik (Rheinish Westphälische Technische Hochschule (RWTH) Aachen (reference EK309-18) in July 2019. Results will be published via international peer-reviewed journals and the findings of the study will be communicated using a comprehensive dissemination strategy aimed at healthcare professionals and patients.

TRIAL REGISTRATION NUMBER

ClinicalTrials. gov (EK309-18); Pre-results.

Skeletal muscle-specific calpastatin overexpression mitigates muscle weakness in aging and extends life span

Calpain activation has been postulated as a potential contributor to the loss of muscle mass and function associated with both aging and disease, but limitations of previous experimental approaches have failed to completely examine this issue. We hypothesized that mice overexpressing calpastatin (CalpOX), an endogenous inhibitor of calpain, solely in skeletal muscle would show an amelioration of the aging muscle phenotype. We assessed four groups of mice (age in months): 1) young wild type (WT; 5.71 ± 0.43), 2) young CalpOX (5.6 ± 0.5), 3) old WT (25.81 ± 0.56), and 4) old CalpOX (25.91 ± 0.60) for diaphragm and limb muscle (extensor digitorum longus, EDL) force frequency relations. Aging significantly reduced diaphragm and EDL peak force in old WT mice, and decreased the force-time integral during a fatiguing protocol by 48% and 23% in aged WT diaphragm and EDL, respectively. In contrast, we found that CalpOX mice had significantly increased diaphragm and EDL peak force in old mice, similar to that observed in young mice. The impact of aging on the force-time integral during a fatiguing protocol was abolished in the diaphragm and EDL of old CalpOX animals. Surprisingly, we found that CalpOX had a significant impact on longevity, increasing median survival from 20.55 mo in WT mice to 24 mo in CalpOX mice (P = 0.0006).NEW & NOTEWORTHY This is the first study to investigate the role of calpastatin overexpression on skeletal muscle specific force in aging rodents. Muscle-specific overexpression of calpastatin, the endogenous calpain inhibitor, prevented aging-induced reductions in both EDL and diaphragm specific force and, remarkably, increased life span. These data suggest that diaphragm dysfunction in aging may be a major factor in determining longevity. Targeting the calpain/calpastatin pathway may elucidate novel therapies to combat skeletal muscle weakness in aging.

Muscle-specific deletion of the vitamin D receptor in mice is associated with diaphragm muscle weakness

Diseases or conditions where diaphragm muscle (DIAm) function is impaired, including chronic obstructive pulmonary disease, cachexia, asthma, and aging, are associated with an increased risk of pulmonary symptoms, longer duration of hospitalizations, and increasing requirements for mechanical ventilation. Vitamin D deficiency is associated with proximal muscle weakness that resolves following therapy with vitamin D3. Skeletal muscle expresses the vitamin D receptor (VDR), which responds to the active form of vitamin D, 1,25-dihydroxyvitamin D3 by altering gene expression in target cells. In knockout mice without skeletal muscle VDRs, there is marked atrophy of muscle fibers and a change in skeletal muscle biochemistry. We used a tamoxifen-inducible skeletal muscle Cre recombinase in Vdrfl/fl mice (Vdrfl/fl actin.iCre+) to assess the role of muscle-specific VDR signaling on DIAm-specific force, fatigability, and fiber type-dependent morphology. Vdrfl/fl actin.iCre+ mice treated with vehicle and Vdrfl/fl mice treated with tamoxifen served as controls. Seven days following the final treatment, mice were euthanized, the DIAm was removed, and isometric force and fatigue were assessed in DIAm strips using direct muscle stimulation. The proportion and cross-sectional areas of DIAm fiber types were evaluated by immunolabeling with myosin heavy chain antibodies differentiating type I, IIa and IIx, and/or IIb fibers. We show that in mice with skeletal muscle-specific VDR deletion, maximum specific force and residual force following fatigue are impaired, along with a selective atrophy of type IIx and/or IIb fibers. These results show that the VDR has a significant biological effect on DIAm function independent of systemic effects on mineral metabolism.NEW & NOTEWORTHY Vitamin D deficiency and vitamin D receptor (VDR) polymorphisms are associated with adverse pulmonary and diaphragm muscle (DIAm)-associated respiratory outcomes. We used a skeletal muscle-specific tamoxifen-inducible VDR knockout to investigate DIAm dysfunction following reduced VDR signaling. Marked DIAm weakness and atrophy of type IIx and/or IIb fibers are present in muscle-specific tamoxifen-induced VDR knockout mice compared with controls. These results show that the VDR has a significant biological effect on DIAm function independent of systemic effects on mineral metabolism.

Phenotypic features of cancer cachexia-related loss of skeletal muscle mass and function: lessons from human and animal studies

Cancer cachexia is a complex multi-organ catabolic syndrome that reduces mobility, increases fatigue, decreases the efficiency of therapeutic strategies, diminishes the quality of life, and increases the mortality of cancer patients. This review provides an exhaustive and comprehensive analysis of cancer cachexia-related phenotypic changes in skeletal muscle at both the cellular and subcellular levels in human cancer patients, as well as in animal models of cancer cachexia. Cancer cachexia is characterized by a major decrease in skeletal muscle mass in human and animals that depends on the severity of the disease/model and the localization of the tumour. It affects both type 1 and type 2 muscle fibres, even if some animal studies suggest that type 2 muscle fibres would be more prone to atrophy. Animal studies indicate an impairment in mitochondrial oxidative metabolism resulting from a decrease in mitochondrial content, an alteration in mitochondria morphology, and a reduction in mitochondrial metabolic fluxes. Immuno-histological analyses in human and animal models also suggest that a faulty mechanism of skeletal muscle repair would contribute to muscle mass loss. An increase in collagen deposit, an accumulation of fat depot outside and inside the muscle fibre, and a disrupted contractile machinery structure are also phenotypic features that have been consistently reported in cachectic skeletal muscle. Muscle function is also profoundly altered during cancer cachexia with a strong reduction in skeletal muscle force. Even though the loss of skeletal muscle mass largely contributes to the loss of muscle function, other factors such as muscle-nerve interaction and calcium handling are probably involved in the decrease in muscle force. Longitudinal analyses of skeletal muscle mass by imaging technics and skeletal muscle force in cancer patients, but also in animal models of cancer cachexia, are necessary to determine the respective kinetics and functional involvements of these factors. Our analysis also emphasizes that measuring skeletal muscle force through standardized tests could provide a simple and robust mean to early diagnose cachexia in cancer patients. That would be of great benefit to cancer patient's quality of life and health care systems.

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.

A clinically relevant decrease in contractile force differentially regulates control of glucocorticoid receptor translocation in mouse skeletal muscle

Muscle atrophy decreases physical function and overall health. Increased glucocorticoid production and/or use of prescription glucocorticoids can significantly induce muscle atrophy by activating the glucocorticoid receptor, thereby transcribing genes that shift protein balance in favor of net protein degradation. Although mechanical overload can blunt glucocorticoid-induced atrophy in young muscle, those affected by glucocorticoids generally have impaired force generation. It is unknown whether contractile force alters the ability of resistance exercise to mitigate glucocorticoid receptor translocation and induce a desirable shift in protein balance when glucocorticoids are elevated. In the present study, mice were subjected to a single bout of unilateral, electrically induced muscle contractions by stimulating the sciatic nerve at 100 Hz or 50 Hz frequencies to elicit high or moderate force contractions of the tibialis anterior, respectively. Dexamethasone was used to activate the glucocorticoid receptor. Dexamethasone increased glucocorticoid signaling, including nuclear translocation of the receptor, but this was mitigated only by high force contractions. The ability of high force contractions to mitigate glucocorticoid receptor translocation coincided with a contraction-mediated increase in muscle protein synthesis, which did not occur in the dexamethasone-treated mice subjected to moderate force contractions. Though moderate force contractions failed to increase protein synthesis following dexamethasone treatment, both high and moderate force contractions blunted the glucocorticoid-mediated increase in LC3 II:I marker of autophagy. Thus, these data show that force generation is important for the ability of resistance exercise to mitigate glucocorticoid receptor translocation and promote a desirable shift in protein balance when glucocorticoids are elevated.NEW & NOTEWORTHY Glucocorticoids induce significant skeletal muscle atrophy by activating the glucocorticoid receptor. Our work shows that muscle contractile force dictates glucocorticoid receptor nuclear translocation. We also show that blunting nuclear translocation by high force contractions coincides with the ability of muscle to mount an anabolic response characterized by increased muscle protein synthesis. This work further defines the therapeutic parameters of skeletal muscle contractions to blunt glucocorticoid-induced atrophy.

Multiomics analysis of the mdx/mTR mouse model of Duchenne muscular dystrophy

PURPOSE/AIM

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease characterized by extensive muscle weakness. Patients with DMD lack a functional dystrophin protein, which transmits force and organizes the cytoskeleton of skeletal muscle. Multiomic studies have been proposed as a way to obtain novel insight about disease processes from preclinical models, and we used this approach to study pathological changes in dystrophic muscles.

MATERIALS AND METHODS

We evaluated hindlimb muscles of male mdx/mTR mice, which lack a functional dystrophin protein and have deficits in satellite cell abundance and proliferative capacity. Wild type (WT) C57BL/6 J mice served as controls. Muscle fiber contractility was measured, along with changes in the transcriptome using RNA sequencing, and in the proteome, metabolome, and lipidome using mass spectrometry.

RESULTS

While mdx/mTR mice displayed gross pathological changes and continued cycles of degeneration and regeneration, we found no differences in permeabilized fiber contractility between strains. However, there were numerous changes in the transcriptome and proteome related to protein balance, contractile elements, extracellular matrix, and metabolism. There was only a 53% agreement in fold-change data between the proteome and transcriptome. Numerous changes in markers of skeletal muscle metabolism were observed, with dystrophic muscles exhibiting elevated glycolytic metabolites such as 6-phosphoglycerate, fructose-6-phosphate and glucose-6-phosphate, fructose bisphosphate, phosphorylated hexoses, and phosphoenolpyruvate.

CONCLUSIONS

These findings highlight the utility of multiomics in studying muscle disease, and provide additional insight into the pathological changes in dystrophic muscles that might help to indirectly guide evidence-based nutritional or exercise prescription in DMD patients.

Pathophysiological mechanisms explaining poor clinical outcome of older cancer patients with low skeletal muscle mass

Low skeletal muscle mass is highly prevalent in older cancer patients and affects 5% to 89% depending on the type and stage of cancer. Low skeletal muscle mass is associated with poor clinical outcomes such as post-operative complications, chemotherapy toxicity and mortality in older cancer patients. Little is known about the mediating pathophysiological mechanisms. In this review, we summarize proposed pathophysiological mechanisms underlying the association between low skeletal muscle mass and poor clinical outcomes in older cancer patients including a) systemic inflammation; b) insulin-dependent glucose handling; c) mitochondrial function; d) protein status and; e) pharmacokinetics of anticancer drugs. The mechanisms of altered myokine balance negatively affecting the innate and adaptive immune system, and altered pharmacokinetics of anticancer drugs leading to a relative overdosage of anticancer drugs are best-substantiated. The effects of glucose intolerance and circulating mitochondrial DNA as a consequence of low skeletal muscle mass are topics of interest for future research. Restoring myokine balance through physical exercise, exercise mimetics, neuro-muscular activation and adapting anticancer drug dosing on skeletal muscle mass could be targeted approaches to improve clinical outcomes in older cancer patients with low skeletal muscle mass.

Respiratory Sarcopenia and Sarcopenic Respiratory Disability: Concepts, Diagnosis, and Treatment

The condition of muscle fiber atrophy and weakness that occurs in respiratory muscles along with systemic skeletal muscle with age is known as respiratory sarcopenia. The Japanese Working Group of Respiratory Sarcopenia of the Japanese Association of Rehabilitation Nutrition narratively reviews these areas, and proposes the concept and diagnostic criteria. We have defined respiratory sarcopenia as "whole-body sarcopenia and low respiratory muscle mass followed by low respiratory muscle strength and/or low respiratory function." Respiratory sarcopenia can be caused by various factors such as aging, decreased activity, undernutrition, disease, cachexia, and iatrogenic causes. We have also created an algorithm for diagnosing respiratory sarcopenia. Respiratory function decreases with age in healthy older people, along with low respiratory muscle mass and strength. We have created a new term, "Presbypnea," meaning a decline in respiratory function with aging. Minor functional respiratory disability due to aging, such as that indicated by a modified Medical Research Council level 1 (troubled by shortness of breath when hurrying or walking straight up hill), is an indicator of presbypnea. We also define sarcopenic respiratory disability as "a disability with deteriorated respiratory function that results from respiratory sarcopenia." Sarcopenic respiratory disability is diagnosed if respiratory sarcopenia is present with functional disability. Cases of respiratory sarcopenia without functional disability are diagnosed as "at risk of sarcopenic respiratory disability." Functional disability is defined as a modified Medical Research Council grade of 2 or more. Rehabilitation nutrition, treatment that combines rehabilitation and nutritional management, may be adequate to prevent and treat respiratory sarcopenia and sarcopenic respiratory disability.

Nutraceuticals and Exercise against Muscle Wasting during Cancer Cachexia

Cancer cachexia (CC) is a debilitating multifactorial syndrome, involving progressive deterioration and functional impairment of skeletal muscles. It affects about 80% of patients with advanced cancer and causes premature death. No causal therapy is available against CC. In the last few decades, our understanding of the mechanisms contributing to muscle wasting during cancer has markedly increased. Both inflammation and oxidative stress (OS) alter anabolic and catabolic signaling pathways mostly culminating with muscle depletion. Several preclinical studies have emphasized the beneficial roles of several classes of nutraceuticals and modes of physical exercise, but their efficacy in CC patients remains scant. The route of nutraceutical administration is critical to increase its bioavailability and achieve the desired anti-cachexia effects. Accumulating evidence suggests that a single therapy may not be enough, and a bimodal intervention (nutraceuticals plus exercise) may be a more effective treatment for CC. This review focuses on the current state of the field on the role of inflammation and OS in the pathogenesis of muscle atrophy during CC, and how nutraceuticals and physical activity may act synergistically to limit muscle wasting and dysfunction.

Cachexia, a Systemic Disease beyond Muscle Atrophy

Cachexia is a complication of dismal prognosis, which often represents the last step of several chronic diseases. For this reason, the comprehension of the molecular drivers of such a condition is crucial for the development of management approaches. Importantly, cachexia is a syndrome affecting various organs, which often results in systemic complications. To date, the majority of the research on cachexia has been focused on skeletal muscle, muscle atrophy being a pivotal cause of weight loss and the major feature associated with the steep reduction in quality of life. Nevertheless, defining the impact of cachexia on other organs is essential to properly comprehend the complexity of such a condition and potentially develop novel therapeutic approaches.

Mitochondrial Function and Protein Turnover in the Diaphragm are Altered in LLC Tumor Model of Cancer Cachexia

It is established that cancer cachexia causes limb muscle atrophy and is strongly associated with morbidity and mortality; less is known about how the development of cachexia impacts the diaphragm. The purpose of this study was to investigate cellular signaling mechanisms related to mitochondrial function, reactive oxygen species (ROS) production, and protein synthesis during the development of cancer cachexia. C57BL/J6 mice developed Lewis Lung Carcinoma for either 0 weeks (Control), 1 week, 2 weeks, 3 weeks, or 4 weeks. At designated time points, diaphragms were harvested and analyzed. Mitochondrial respiratory control ratio was ~50% lower in experimental groups, which was significant by 2 weeks of cancer development, with no difference in mitochondrial content markers COXIV or VDAC. Compared to the controls, ROS was 4-fold elevated in 2-week animals but then was not different at later time points. Only one antioxidant protein, GPX3, was altered by cancer development (~70% lower in experimental groups). Protein synthesis, measured by a fractional synthesis rate, appeared to become progressively lower with the cancer duration, but the mean difference was not significant. The development and progression of cancer cachexia induces marked alterations to mitochondrial function and ROS production in the diaphragm and may contribute to increased cachexia-associated morbidity and mortality.

Hyperbaric Oxygen Treatment Following Mid-Cervical Spinal Cord Injury Preserves Diaphragm Muscle Function

Oxidative damage to the diaphragm as a result of cervical spinal cord injury (SCI) promotes muscle atrophy and weakness. Respiratory insufficiency is the leading cause of morbidity and mortality in cervical spinal cord injury (SCI) patients, emphasizing the need for strategies to maintain diaphragm function. Hyperbaric oxygen (HBO) increases the amount of oxygen dissolved into the blood, elevating the delivery of oxygen to skeletal muscle and reactive oxygen species (ROS) generation. It is proposed that enhanced ROS production due to HBO treatment stimulates adaptations to diaphragm oxidative capacity, resulting in overall reductions in oxidative stress and inflammation. Therefore, we tested the hypothesis that exposure to HBO therapy acutely following SCI would reduce oxidative damage to the diaphragm muscle, preserving muscle fiber size and contractility. Our results demonstrated that lateral contusion injury at C3/4 results in a significant reduction in diaphragm muscle-specific force production and fiber cross-sectional area, which was associated with augmented mitochondrial hydrogen peroxide emission and a reduced mitochondrial respiratory control ratio. In contrast, rats that underwent SCI followed by HBO exposure consisting of 1 h of 100% oxygen at 3 atmospheres absolute (ATA) delivered for 10 consecutive days demonstrated an improvement in diaphragm-specific force production, and an attenuation of fiber atrophy, mitochondrial dysfunction and ROS production. These beneficial adaptations in the diaphragm were related to HBO-induced increases in antioxidant capacity and a reduction in atrogene expression. These findings suggest that HBO therapy may be an effective adjunctive therapy to promote respiratory health following cervical SCI.

Pharmacological targeting of mitochondrial function and reactive oxygen species production prevents colon 26 cancer-induced cardiorespiratory muscle weakness

Cancer cachexia is a syndrome characterized by profound cardiac and diaphragm muscle wasting, which increase the risk of morbidity in cancer patients due to failure of the cardiorespiratory system. In this regard, muscle relies greatly on mitochondria to meet energy requirements for contraction and mitochondrial dysfunction can result in muscle weakness and fatigue. In addition, mitochondria are a major source of reactive oxygen species (ROS) production, which can stimulate increased rates of muscle protein degradation. Therefore, it has been suggested that mitochondrial dysfunction may be an underlying factor that contributes to the pathology of cancer cachexia. To determine if pharmacologically targeting mitochondrial dysfunction via treatment with the mitochondria-targeting peptide SS-31 would prevent cardiorespiratory muscle dysfunction, colon 26 (C26) adenocarcinoma tumor-bearing mice were administered either saline or SS-31 daily (3 mg/kg/day) following inoculation. C26 mice treated with saline demonstrated greater ROS production and mitochondrial uncoupling compared to C26 mice receiving SS-31 in both the heart and diaphragm muscle. In addition, saline-treated C26 mice exhibited a decline in left ventricular function which was significantly rescued in C26 mice treated with SS-31. In the diaphragm, muscle fiber cross-sectional area of C26 mice treated with saline was significantly reduced and force production was impaired compared to C26, SS-31-treated animals. Finally, ventilatory deficits were also attenuated in C26 mice treated with SS-31, compared to saline treatment. These data demonstrate that C26 tumors promote severe cardiac and respiratory myopathy, and that prevention of mitochondrial dysfunction is sufficient to preclude cancer cachexia-induced cardiorespiratory dysfunction.

Trabectedin and Lurbinectedin Extend Survival of Mice Bearing C26 Colon Adenocarcinoma, without Affecting Tumor Growth or Cachexia

Trabectedin (ET743) and lurbinectedin (PM01183) limit the production of inflammatory cytokines that are elevated during cancer cachexia. Mice carrying C26 colon adenocarcinoma display cachexia (i.e., premature death and body wasting with muscle, fat and cardiac tissue depletion), high levels of inflammatory cytokines and subsequent splenomegaly. We tested whether such drugs protected these mice from cachexia. Ten-week-old mice were inoculated with C26 cells and three days later randomized to receive intravenously vehicle or 0.05 mg/kg ET743 or 0.07 mg/kg PM01183, three times a week for three weeks. ET743 or PM01183 extended the lifespan of C26-mice by 30% or 85%, respectively, without affecting tumor growth or food intake. Within 13 days from C26 implant, both drugs did not protect fat, muscle and heart from cachexia. Since PM01183 extended the animal survival more than ET743, we analyzed PM01183 further. In tibialis anterior of C26-mice, but not in atrophying myotubes, PM01183 restrained the NF-κB/PAX7/myogenin axis, possibly reducing the pro-inflammatory milieu, and failed to limit the C/EBPβ/atrogin-1 axis. Inflammation-mediated splenomegaly of C26-mice was inhibited by PM01183 for as long as the treatment lasted, without reducing IL-6, M-CSF or IL-1β in plasma. ET743 and PM01183 extend the survival of C26-bearing mice unchanging tumor growth or cachexia but possibly restrain muscle-related inflammation and C26-induced splenomegaly.

Increased tumour burden alters skeletal muscle properties in the KPC mouse model of pancreatic cancer

BACKGROUND

Cancer cachexia is a multifactorial wasting syndrome that is characterized by the loss of skeletal muscle mass and weakness, which compromises physical function, reduces quality of life, and ultimately can lead to mortality. Experimental models of cancer cachexia have recapitulated this skeletal muscle atrophy and consequent decline in muscle force generating capacity. We address these issues in a novel transgenic mouse model Kras, Trp53 and Pdx-1-Cre (KPC) of pancreatic ductal adenocarcinoma (PDA) using multi-parametric magnetic resonance (mp-MR) measures.

METHODS

KPC mice (n = 10) were divided equally into two groups (n = 5/group) depending on the size of the tumor i.e. tumor size <250 mm³ and >250 mm³. Using mp-MR measures, we demonstrated the changes in the gastrocnemius muscle at the microstructural level. In addition, we evaluated skeletal muscle contractile function in KPC mice using an in vivo approach.

RESULTS

Increase in tumor size resulted in decrease in gastrocnemius maximum cross sectional area, decrease in T₂ relaxation time, increase in magnetization transfer ratio, decrease in mean diffusivity, and decrease in radial diffusivity of water across the muscle fibers. Finally, we detected significant decrease in absolute and specific force production of gastrocnemius muscle with increase in tumor size.

CONCLUSIONS

Our findings indicate that increase in tumor size may cause alterations in structural and functional parameters of skeletal muscles and that MR parameters may be used as sensitive biomarkers to noninvasively detect structural changes in cachectic muscles.

Distinct cachexia profiles in response to human pancreatic tumours in mouse limb and respiratory muscle

BACKGROUND

Cancer cachexia is a life-threatening metabolic syndrome that causes significant loss of skeletal muscle mass and significantly increases mortality in cancer patients. Currently, there is an urgent need for better understanding of the molecular pathophysiology of this disease so that effective therapies can be developed. The majority of pre-clinical studies evaluating skeletal muscle's response to cancer have focused on one or two pre-clinical models, and almost all have focused specifically on limb muscles. In the current study, we reveal key differences in the histology and transcriptomic signatures of a limb muscle and a respiratory muscle in orthotopic pancreatic cancer patient-derived xenograft (PDX) mice.

METHODS

To create four cohorts of PDX mice evaluated in this study, tumours resected from four pancreatic ductal adenocarcinoma patients were portioned and attached to the pancreas of immunodeficient NSG mice.

RESULTS

Body weight, muscle mass, and fat mass were significantly decreased in each PDX line. Histological assessment of cryosections taken from the tibialis anterior (TA) and diaphragm (DIA) revealed differential effects of tumour burden on their morphology. Subsequent genome-wide microarray analysis on TA and DIA also revealed key differences between their transcriptomes in response to cancer. Genes up-regulated in the DIA were enriched for extracellular matrix protein-encoding genes and genes related to the inflammatory response, while down-regulated genes were enriched for mitochondria related protein-encoding genes. Conversely, the TA showed up-regulation of canonical atrophy-associated pathways such as ubiquitin-mediated protein degradation and apoptosis, and down-regulation of genes encoding extracellular matrix proteins.

CONCLUSIONS

These data suggest that distinct biological processes may account for wasting in different skeletal muscles in response to the same tumour burden. Further investigation into these differences will be critical for the future development of effective clinical strategies to counter cancer cachexia.

Exercise training reverses cancer-induced oxidative stress and decrease in muscle COPS2/TRIP15/ALIEN

OBJECTIVE

We tested the hypothesis that exercise training would attenuate metabolic impairment in a model of severe cancer cachexia.

METHODS

We used multiple in vivo and in vitro methods to explore the mechanisms underlying the beneficial effects induced by exercise training in tumor-bearing rats.

RESULTS

Exercise training improved running capacity, prolonged lifespan, reduced oxidative stress, and normalized muscle mass and contractile function in tumor-bearing rats. An unbiased proteomic screening revealed COP9 signalosome complex subunit 2 (COPS2) as one of the most downregulated proteins in skeletal muscle at the early stage of cancer cachexia. Exercise training normalized muscle COPS2 protein expression in tumor-bearing rats and mice. Lung cancer patients with low endurance capacity had low muscle COPS2 protein expression as compared to age-matched control subjects. To test whether decrease in COPS2 protein levels could aggravate or be an intrinsic compensatory mechanism to protect myotubes from cancer effects, we performed experiments in vitro using primary myotubes. COPS2 knockdown in human myotubes affected multiple cellular pathways, including regulation of actin cytoskeleton. Incubation of cancer-conditioned media in mouse myotubes decreased F-actin expression, which was partially restored by COPS2 knockdown. Direct repeat 4 (DR4) response elements have been shown to positively regulate gene expression. COPS2 overexpression decreased the DR4 activity in mouse myoblasts, and COPS2 knockdown inhibited the effects of cancer-conditioned media on DR4 activity.

CONCLUSIONS

These studies demonstrated that exercise training may be an important adjuvant therapy to counteract cancer cachexia and uncovered novel mechanisms involving COPS2 to regulate myotube homeostasis in cancer cachexia.

Is Mitochondrial Oxidative Stress the Key Contributor to Diaphragm Atrophy and Dysfunction in Critically Ill Patients?

Diaphragm dysfunction is prevalent in the progress of respiratory dysfunction in various critical illnesses. Respiratory muscle weakness may result in insufficient ventilation, coughing reflection suppression, pulmonary infection, and difficulty in weaning off respirators. All of these further induce respiratory dysfunction and even threaten the patients' survival. The potential mechanisms of diaphragm atrophy and dysfunction include impairment of myofiber protein anabolism, enhancement of myofiber protein degradation, release of inflammatory mediators, imbalance of metabolic hormones, myonuclear apoptosis, autophagy, and oxidative stress. Among these contributors, mitochondrial oxidative stress is strongly implicated to play a key role in the process as it modulates diaphragm protein synthesis and degradation, induces protein oxidation and functional alteration, enhances apoptosis and autophagy, reduces mitochondrial energy supply, and is regulated by inflammatory cytokines via related signaling molecules. This review aims to provide a concise overview of pathological mechanisms of diaphragmatic dysfunction in critically ill patients, with special emphasis on the role and modulating mechanisms of mitochondrial oxidative stress.

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.

Diaphragm weakness and proteomics (global and redox) modifications in heart failure with reduced ejection fraction in rats

Inspiratory dysfunction occurs in patients with heart failure with reduced ejection fraction (HFrEF) in a manner that depends on disease severity and by mechanisms that are not fully understood. In the current study, we tested whether HFrEF effects on diaphragm (inspiratory muscle) depend on disease severity and examined putative mechanisms for diaphragm abnormalities via global and redox proteomics. We allocated male rats into Sham, moderate (mHFrEF), or severe HFrEF (sHFrEF) induced by myocardial infarction and examined the diaphragm muscle. Both mHFrEF and sHFrEF caused atrophy in type IIa and IIb/x fibers. Maximal and twitch specific forces (N/cm²) were decreased by 19 ± 10% and 28 ± 13%, respectively, in sHFrEF (p < .05), but not in mHFrEF. Global proteomics revealed upregulation of sarcomeric proteins and downregulation of ribosomal and glucose metabolism proteins in sHFrEF. Redox proteomics showed that sHFrEF increased reversibly oxidized cysteine in cytoskeletal and thin filament proteins and methionine in skeletal muscle α-actin (range 0.5 to 3.3-fold; p < .05). In conclusion, fiber atrophy plus contractile dysfunction caused diaphragm weakness in HFrEF. Decreased ribosomal proteins and heighted reversible oxidation of protein thiols are candidate mechanisms for atrophy or anabolic resistance as well as loss of specific force in sHFrEF.

Irreversible metabolic abnormalities following chronic upper airway loading

STUDY OBJECTIVES

Treatment of obstructive sleep apnea increases obesity risk by an unclear mechanism. Here, we explored the effects of upper airway obstruction and its removal on respiratory homeostasis, energy expenditure, and feeding hormones during the sleep/wake cycle from weaning to adulthood.

METHODS

The tracheas of 22-day-old rats were narrowed, and obstruction removal was performed on post-surgery day 14. Energy expenditure, ventilation, and hormone-regulated feeding were analyzed during 49 days before and after obstruction.

RESULTS

Energy expenditure increased and body temperature decreased in upper airway obstruction and was only partially recovered in obstruction removal despite normalization of airway resistance. Increased energy expenditure was associated with upregulation of ventilation. Decreased body temperature was associated with decreased brown adipose tissue uncoupling protein 1 level, suppressed energy expenditure response to norepinephrine, and decreased leptin level. Upper airway obstructed animals added less body weight, in spite of an increase in food intake, due to elevated hypothalamic orexin and neuropeptide Y and plasma ghrelin. Animals who underwent obstruction removal fed more due to an increase in hypothalamic neuropeptide Y and plasma ghrelin.

CONCLUSIONS

The need to maintain respiratory homeostasis is associated with persistent abnormal energy metabolism and hormonal regulation of feeding. Surgical treatment per se may not be sufficient to correct energy homeostasis, and endocrine regulation of feeding may have a larger effect on weight change.

Upregulation of ZIP14 and Altered Zinc Homeostasis in Muscles in Pancreatic Cancer Cachexia

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer type in which the mortality rate approaches the incidence rate. More than 85% of PDAC patients experience a profound loss of muscle mass and function, known as cachexia. PDAC patients with this condition suffer from decreased tolerance to anti-cancer therapies and often succumb to premature death due to respiratory and cardiac muscle wasting. Yet, there are no approved therapies available to alleviate cachexia. We previously found that upregulation of the metal ion transporter, Zip14, and altered zinc homeostasis are critical mediators of cachexia in metastatic colon, lung, and breast cancer models. Here, we show that a similar mechanism is likely driving the development of cachexia in PDAC. In two independent experimental metastasis models generated from the murine PDAC cell lines, Pan02 and FC1242, we observed aberrant Zip14 expression and increased zinc ion levels in cachectic muscles. Moreover, in advanced PDAC patients, high levels of ZIP14 in muscles correlated with the presence of cachexia. These studies underscore the importance of altered ZIP14 function in PDAC-associated cachexia development and highlight a potential therapeutic opportunity for improving the quality of life and prolonging survival in PDAC patients.

Diaphragm Muscle Adaptations in Health and Disease

Breathing is achieved without thought despite being controlled by a complex neural network. The diaphragm is the predominant muscle responsible for force/pressure generation during breathing, but it is also involved in other non-ventilatory expulsive behaviors. This review considers alterations in diaphragm muscle fiber types and the neural control of the diaphragm across our lifespan and in various disease conditions.

IL-8 Released from Human Pancreatic Cancer and Tumor-Associated Stromal Cells Signals through a CXCR2-ERK1/2 Axis to Induce Muscle Atrophy

Tumor-derived cytokines are known to drive the catabolism of host tissues, including skeletal muscle. However, our understanding of the specific cytokines that initiate this process remains incomplete. In the current study, we conducted multiplex analyte profiling of cytokines in conditioned medium (CM) collected from human pancreatic cancer (PC) cells, human tumor-associated stromal (TAS) cells, and their co-culture. Of the factors identified, interleukin-8 (IL-8) is released at high levels from PC cells and PC/TAS co-culture and has previously been associated with low muscle mass in cancer patients. We, therefore, treated C2C12 myotubes with IL-8 which led to the activation of ERK1/2, STAT, and Smad signaling, and induced myotube atrophy. Moreover, the treatment of mice with IL-8 also induced significant muscle wasting, confirming the in vivo relevance of IL-8 on muscle. Mechanistically, IL-8-induced myotube atrophy is inhibited by treatment with the CXCR2 antagonist, SB225002, or by treatment with the ERK1/2 inhibitor, U0126. We further demonstrate that this axis mediates muscle atrophy induced by pancreatic cancer cell CM, as neutralization of IL-8 or treatment with SB225002 or U0126 significantly inhibit CM-induced myotube atrophy. Thus, these data support a key role of IL-8 released from human PC cells in initiating atrophy of muscle cells via CXCR2-ERK1/2.

Muscle alterations in the development and progression of cancer-induced muscle atrophy: a review

Cancer cachexia-cancer-associated body weight and muscle loss-is a significant predictor of mortality and morbidity in cancer patients across a variety of cancer types. However, despite the negative prognosis associated with cachexia onset, there are no clinical therapies approved to treat or prevent cachexia. This lack of treatment may be partially due to the relative dearth of literature on mechanisms occurring within the muscle before the onset of muscle wasting. Therefore, the purpose of this review is to compile the current scientific literature on mechanisms contributing to the development and progression of cancer cachexia, including protein turnover, inflammatory signaling, and mitochondrial dysfunction. We define "development" as changes in cell function occurring before the onset of cachexia and "progression" as alterations to cell function that coincide with the exacerbation of muscle wasting. Overall, the current literature suggests that multiple aspects of cellular function, such as protein turnover, inflammatory signaling, and mitochondrial quality, are altered before the onset of muscle loss during cancer cachexia and clearly highlights the need to study more thoroughly the developmental stages of cachexia. The studying of these early aberrations will allow for the development of effective therapeutics to prevent the onset of cachexia and improve health outcomes in cancer patients.

Skeletal myofiber VEGF deficiency leads to mitochondrial, structural, and contractile alterations in mouse diaphragm

Diaphragm dysfunction accompanies cardiopulmonary disease and impaired oxygen delivery. Vascular endothelial growth factor (VEGF) regulates oxygen delivery through angiogenesis, capillary maintenance, and contraction-induced perfusion. We hypothesized that myofiber-specific VEGF deficiency contributes to diaphragm weakness and fatigability. Diaphragm protein expression, capillarity and fiber morphology, mitochondrial respiration and hydrogen peroxide (H₂O₂) generation, and contractile function were compared between adult mice with conditional gene ablation of skeletal myofiber VEGF (SkmVEGF^-/-; n = 12) and littermate controls (n = 13). Diaphragm VEGF protein was ~50% lower in SkmVEGF^-/- than littermate controls (1.45 ± 0.65 vs. 3.04 ± 1.41 pg/total protein; P = 0.001). This was accompanied by an ~15% impairment in maximal isometric specific force (F[1,23] = 15.01, P = 0.001) and a trend for improved fatigue resistance (P = 0.053). Mean fiber cross-sectional area and type I fiber cross-sectional area were lower in SkmVEGF^-/- by ~40% and ~25% (P < 0.05). Capillary-to-fiber ratio was also lower in SkmVEGF^-/- by ~40% (P < 0.05), and thus capillary density was not different. Sarcomeric actin expression was ~30% lower in SkmVEGF^-/- (P < 0.05), whereas myosin heavy chain and MAFbx were similar (measured via immunoblot). Mitochondrial respiration, citrate synthase activity, PGC-1α, and hypoxia-inducible factor 1α were not different in SkmVEGF^-/- (P > 0.05). However, mitochondrial-derived reactive oxygen species (ROS) flux was lower in SkmVEGF^-/- (P = 0.0003). In conclusion, myofiber-specific VEGF gene deletion resulted in a lower capillary-to-fiber ratio, type I fiber atrophy, actin loss, and contractile dysfunction in the diaphragm. In contrast, mitochondrial respiratory function was preserved alongside lower ROS generation, which may play a compensatory role to preserve fatigue resistance in the diaphragm.NEW & NOTEWORTHY Diaphragm weakness is a hallmark of diseases in which oxygen delivery is compromised. Vascular endothelial growth factor (VEGF) modulates muscle perfusion; however, it remains unclear whether VEGF deficiency contributes to the onset of diaphragm dysfunction. Conditional skeletal myofiber VEGF gene ablation impaired diaphragm contractile function and resulted in type I fiber atrophy, a lower number of capillaries per fiber, and contractile protein content. Mitochondrial function was similar and reactive oxygen species flux was lower. Diaphragm VEGF deficiency may contribute to the onset of respiratory muscle weakness.

Chronic Systemic Symptoms in Head and Neck Cancer Patients

The systemic effects and manifestations of disease and treatment have been of interest for millennium. Until recently, basic and clinical research is just now reaching a watershed. Systemic symptoms usually do not occur in isolation but rather in clusters; however, much of the cutting-edge research pertaining to the etiology, mechanism, manifestations, and moderators of systemic symptoms in humans has been directed at individual symptoms, thus creating silos of knowledge. Breaching these silos and bridging the knowledge from disparate arenas of investigation to build a comprehensive depiction of acute and chronic systemic symptoms has been a challenge. In addition, much of the recent work in systemic symptoms has been conducted in the setting of nonmalignant disease. The degree to which the findings from other chronic disease processes can be translated into the oncologic realm is unknown. This article will explore inflammation as a major contributing factor to systemic symptoms and sickness behavior, discuss the most common manifestations in cancer survivors, and, where available, discuss specific data pertaining to head and neck cancer survivors.

Mitochondrial respiration and H2O2 emission in saponin-permeabilized murine diaphragm fibers: optimization of fiber separation and comparison to limb muscle

Diaphragm abnormalities in aging or chronic diseases include impaired mitochondrial respiration and H₂O₂ emission, which can be measured using saponin-permeabilized muscle fibers. Mouse diaphragm presents a challenge for isolation of fibers due to relatively high abundance of connective tissue in healthy muscle that is exacerbated in disease states. We tested a new approach to process mouse diaphragm for assessment of intact mitochondria respiration and ROS emission in saponin-permeabilized fibers. We used the red gastrocnemius (RG) as "standard" limb muscle. Markers of mitochondrial content were two- to fourfold higher in diaphragm (Dia) than in RG (P < 0.05). Maximal O₂ consumption (JO₂: pmol·s^-1·mg^-1) in Dia was higher with glutamate, malate, and succinate (Dia 399 ± 127, RG 148 ± 60; P < 0.05) and palmitoyl-CoA + carnitine (Dia 15 ± 5, RG 7 ± 1; P < 0.05) than in RG, but not different between muscles when JO₂ was normalized to citrate synthase activity. Absolute JO₂ for Dia was two- to fourfold higher than reported in previous studies. Mitochondrial JH₂O₂ was higher in Dia than in RG (P < 0.05), but lower in Dia than in RG when JH₂O₂ was normalized to citrate synthase activity. Our findings are consistent with an optimized diaphragm preparation for assessment of intact mitochondria in permeabilized fiber bundles. The data also suggest that higher mitochondrial content potentially makes the diaphragm more susceptible to "mitochondrial onset" myopathy. Overall, the new approach will facilitate testing and understanding of diaphragm mitochondrial function in mouse models that are used to advance biomedical research and human health.

Impact of sarcopenia on diaphragm muscle fatigue

NEW FINDINGS

What is the central question of this study? Is the residual force generated by the diaphragm muscle after repeated activation reduced with sarcopenia, and is the residual force generated after fatiguing activation sufficient to sustain ventilatory behaviours of diaphragm muscle in young and old rats? What is the main finding and its importance? After diaphragm muscle fatigue, the residual specific force after 120 s of repeated stimulation was unaffected by ageing and was sufficient to accomplish ventilatory behaviours, but not expulsive manoeuvres (e.g. coughing). The inability to perform expulsive behaviours might underlie the increased susceptibility of older individuals to respiratory tract infections.

ABSTRACT

Type IIx and/or IIb diaphragm muscle (DIAm) fibres make up more fatigable motor units that are more vulnerable to sarcopenia, i.e. age-associated reductions of specific force and cross-sectional area. In contrast, type I and IIa DIAm fibres form fatigue-resistant motor units that are relatively unchanged with age. The fatigue resistance of the DIAm is assessed by normalizing the residual force generated after a period of repeated supramaximal stimulation (e.g. 120 s) to the initial maximal force. Given that sarcopenia primarily affects more fatigable DIAm motor units, apparent fatigue resistance improves with ageing. However, the central question is whether there is an ageing-related difference in the residual force generated by the DIAm after repeated stimulation and whether this force is sufficient to sustain ventilatory behaviours of DIAm. In 6- and 24-month-old Fischer 344 rats, we assessed the loss of ex vivo DIAm force throughout 120 s of repeated supramaximal stimulation at 10, 40 and 75 Hz. We found that relative fatigue resistance improved in older rats at 40 and 75 Hz stimulation. Across all stimulation frequencies, DIAm residual force was unchanged with age (∼5 N cm^-2 ). We conclude that ageing increases the relative contribution of type I and IIa fibres to DIAm force, with decreased contributions of type IIx and/or IIb fibres. The residual force generated by the DIAm after repeated stimulation is sufficient to accomplish ventilatory behaviours, regardless of age.

Colon 26 adenocarcinoma (C26)-induced cancer cachexia impairs skeletal muscle mitochondrial function and content

The present study aimed to determine the impact of colon 26 adenocarcinoma (C26)-induced cancer cachexia on skeletal muscle mitochondrial respiration and content. Twelve male CD2F1 mice were injected with C26-cells (tumor bearing (TB) group), whereas 12 age-matched mice received PBS vehicle injection (non-tumor bearing (N-TB) group). Mitochondrial respiration was studied in saponin-permeabilized soleus myofibers. TB mice showed lower body weight (~ 20%) as well as lower soleus, gastrocnemius-plantaris complex and tibialis anterior masses versus N-TB mice (p < 0.05). Soleus maximal state III mitochondrial respiration was 20% lower (10 mM glutamate, 5 mM malate, 5 mM adenosine diphosphate; p < 0.05) and acceptor control ratio (state III/state II) was 15% lower in the TB vs. N-TB (p < 0.05), with the latter suggesting uncoupling. Lower VDAC protein content suggested reduced mitochondrial content in TB versus N-TB (p < 0.05). Skeletal muscle in C26-induced cancer cachexia exhibits reductions in: maximal mitochondrial respiration capacity, mitochondrial coupling and mitochondrial content.