Targeting Mitochondria by SS-31 Ameliorates the Whole Body Energy Status in Cancer- and Chemotherapy-Induced Cachexia

Metabolomics-driven discovery of therapeutic targets for cancer cachexia

Cancer cachexia (CC) is a devastating metabolic syndrome characterized by skeletal muscle wasting and body weight loss, posing a significant burden on the health and survival of cancer patients. Despite ongoing efforts, effective treatments for CC are still lacking. Metabolomics, an advanced omics technique, offers a comprehensive analysis of small-molecule metabolites involved in cellular metabolism. In CC research, metabolomics has emerged as a valuable tool for identifying diagnostic biomarkers, unravelling molecular mechanisms and discovering potential therapeutic targets. A comprehensive search strategy was implemented to retrieve relevant articles from primary databases, including Web of Science, Google Scholar, Scopus and PubMed, for CC and metabolomics. Recent advancements in metabolomics have deepened our understanding of CC by uncovering key metabolic signatures and elucidating underlying mechanisms. By targeting crucial metabolic pathways including glucose metabolism, amino acid metabolism, fatty acid metabolism, bile acid metabolism, ketone body metabolism, steroid metabolism and mitochondrial energy metabolism, it becomes possible to restore metabolic balance and alleviate CC symptoms. This review provides a comprehensive summary of metabolomics studies in CC, focusing on the discovery of potential therapeutic targets and the evaluation of modulating specific metabolic pathways for CC treatment. By harnessing the insights derived from metabolomics, novel interventions for CC can be developed, leading to improved patient outcomes and enhanced quality of life.

The role of mitochondrial dynamics and mitophagy in skeletal muscle atrophy: from molecular mechanisms to therapeutic insights

Skeletal muscle is the largest metabolic organ of the human body. Maintaining the best quality control and functional integrity of mitochondria is essential for the health of skeletal muscle. However, mitochondrial dysfunction characterized by mitochondrial dynamic imbalance and mitophagy disruption can lead to varying degrees of muscle atrophy, but the underlying mechanism of action is still unclear. Although mitochondrial dynamics and mitophagy are two different mitochondrial quality control mechanisms, a large amount of evidence has indicated that they are interrelated and mutually regulated. The former maintains the balance of the mitochondrial network, eliminates damaged or aged mitochondria, and enables cells to survive normally. The latter degrades damaged or aged mitochondria through the lysosomal pathway, ensuring cellular functional health and metabolic homeostasis. Skeletal muscle atrophy is considered an urgent global health issue. Understanding and gaining knowledge about muscle atrophy caused by mitochondrial dysfunction, particularly focusing on mitochondrial dynamics and mitochondrial autophagy, can greatly contribute to the prevention and treatment of muscle atrophy. In this review, we critically summarize the recent research progress on mitochondrial dynamics and mitophagy in skeletal muscle atrophy, and expound on the intrinsic molecular mechanism of skeletal muscle atrophy caused by mitochondrial dynamics and mitophagy. Importantly, we emphasize the potential of targeting mitochondrial dynamics and mitophagy as therapeutic strategies for the prevention and treatment of muscle atrophy, including pharmacological treatment and exercise therapy, and summarize effective methods for the treatment of skeletal muscle atrophy.

Interactions and Transport of a Bioconjugated Peptide Targeting the Mitomembrane

The Szeto-Schiller (SS) peptides are a subclass of cell-penetrating peptides that can specifically target mitochondria and mediate conditions caused by mitochondrial dysfunction. In this work, we constructed an iron-chelating SS peptide and studied its interaction with a mitochondrial-mimicking membrane using atomistic molecular dynamics (MD) simulations. We report that the peptide/membrane interaction is thermodynamically favorable, and the localization of the peptide to the membrane is driven by electrostatic interactions between the cationic residues and the anionic phospholipid headgroups. The insertion of the peptide into the membrane is driven by hydrophobic interactions between the aromatic side chains in the peptide and the lipid acyl tails. We also probed the translocation of the peptide across the membrane by applying nonequilibrium steered MD simulations and resolved the translocation pathway, free energy profile, and metastable states. We explored four distinct orientations of the peptide along the translocation pathway and found that one orientation was energetically more favorable than the other orientations. We tested a significantly slower pulling velocity on the most thermodynamically favorable system and compared metastable states during peptide translocation. We found that the peptide can optimize hydrophobic interactions with the membrane by having aromatic side chains interacting with the lipid acyl tails instead of forming π-π interactions with each other. The mechanistic insights emerging from our work will potentially facilitate improved peptide design with enhanced activity.

Long-term Musculoskeletal Consequences of Chemotherapy in Pediatric Mice

Thanks to recent progress in cancer research, most children treated for cancer survive into adulthood. Nevertheless, the long-term consequences of anticancer agents are understudied, especially in the pediatric population. We and others have shown that routinely administered chemotherapeutics drive musculoskeletal alterations, which contribute to increased treatment-related toxicity and long-term morbidity. Yet, the nature and scope of these enduring musculoskeletal defects following anticancer treatments and whether they can potentially impact growth and quality of life in young individuals remain to be elucidated. Here, we aimed at investigating the persistent musculoskeletal consequences of chemotherapy in young (pediatric) mice. Four-week-old male mice were administered a combination of 5-FU, leucovorin, irinotecan (a.k.a., Folfiri) or the vehicle for up to 5 wk. At time of sacrifice, skeletal muscle, bones, and other tissues were collected, processed, and stored for further analyses. In another set of experiments, chemotherapy-treated mice were monitored for up to 4 wk after cessation of treatment. Overall, the growth rate was significantly slower in the chemotherapy-treated animals, resulting in diminished lean and fat mass, as well as significantly smaller skeletal muscles. Interestingly, 4 wk after cessation of the treatment, the animals exposed to chemotherapy showed persistent musculoskeletal defects, including muscle innervation deficits and abnormal mitochondrial homeostasis. Altogether, our data support that anticancer treatments may lead to long-lasting musculoskeletal complications in actively growing pediatric mice and support the need for further studies to determine the mechanisms responsible for these complications, so that new therapies to prevent or diminish chemotherapy-related toxicities can be identified.

Application research of novel peptide mitochondrial-targeted antioxidant SS-31 in mitigating mitochondrial dysfunction

Due to the pivotal role of mitochondria in the generation of adenosine triphosphate (ATP) and the regulation of cellular homeostasis, mitochondrial dysfunction may exert a profound impact on various physiological systems, potentially precipitating a spectrum of distinct diseases. Consequently, research pertaining to mitochondrial therapeutics has assumed increasing significance, warranting heightened scrutiny. In recent years, the field of mitochondrial therapy has witnessed noteworthy advancements, with active exploration into diverse pharmacological agents aimed at ameliorating mitochondrial function. Elamipretide (SS-31), a novel synthetic mitochondrial-targeted antioxidant, has emerged as a promising candidate with extensive therapeutic potential. Its notable attributes encompass the mitigation of oxidative stress, the suppression of inflammatory processes, the maintenance of mitochondrial dynamics, and the prevention of cellular apoptosis. As such, SS-31 may emerge as a viable choice for the treatment of mitochondrial dysfunction-related ailments in the foreseeable future. This article extensively expounds upon the superiority of SS-31 over natural antioxidants and traditional mitochondrial-targeted antioxidants, delves into its mechanisms of modulating mitochondrial function, and comprehensively summarizes its applications in alleviating mitochondrial dysfunction-associated disorders. Furthermore, we offer a comprehensive outlook on the expansive prospects of SS-31's future development and application.

Antioxidant peptides, the guardian of life from oxidative stress

Reactive oxygen species (ROS) are produced during oxidative metabolism in aerobic organisms. Under normal conditions, ROS production and elimination are in a relatively balanced state. However, under internal or external environmental stress, such as high glucose levels or UV radiation, ROS production can increase significantly, leading to oxidative stress. Excess ROS production not only damages biomolecules but is also closely associated with the pathogenesis of many diseases, such as skin photoaging, diabetes, and cancer. Antioxidant peptides (AOPs) are naturally occurring or artificially designed peptides that can reduce the levels of ROS and other pro-oxidants, thus showing great potential in the treatment of oxidative stress-related diseases. In this review, we discussed ROS production and its role in inducing oxidative stress-related diseases in humans. Additionally, we discussed the sources, mechanism of action, and evaluation methods of AOPs and provided directions for future studies on AOPs.

FK506 bypasses the effect of erythroferrone in cancer cachexia skeletal muscle atrophy

Skeletal muscle atrophy is a hallmark of cachexia, a wasting condition typical of chronic pathologies, that still represents an unmet medical need. Bone morphogenetic protein (BMP)-Smad1/5/8 signaling alterations are emerging drivers of muscle catabolism, hence, characterizing these perturbations is pivotal to develop therapeutic approaches. We identified two promoters of "BMP resistance" in cancer cachexia, specifically the BMP scavenger erythroferrone (ERFE) and the intracellular inhibitor FKBP12. ERFE is upregulated in cachectic cancer patients' muscle biopsies and in murine cachexia models, where its expression is driven by STAT3. Moreover, the knock down of Erfe or Fkbp12 reduces muscle wasting in cachectic mice. To bypass the BMP resistance mediated by ERFE and release the brake on the signaling, we targeted FKBP12 with low-dose FK506. FK506 restores BMP-Smad1/5/8 signaling, rescuing myotube atrophy by inducing protein synthesis. In cachectic tumor-bearing mice, FK506 prevents muscle and body weight loss and protects from neuromuscular junction alteration, suggesting therapeutic potential for targeting the ERFE-FKBP12 axis.

Females display relatively preserved muscle quality compared with males during the onset and early stages of C26-induced cancer cachexia

Cancer cachexia is clinically defined by involuntary weight loss >5% in <6 mo, primarily affecting skeletal muscle. Here, we aimed to identify sex differences in the onset of colorectal cancer cachexia with specific consideration to skeletal muscle contractile and metabolic functions. Eight-weeks old BALB/c mice (69 males, 59 females) received subcutaneous C26 allografts or PBS vehicle. Tumors were developed for 10-, 15-, 20-, or 25 days. Muscles and organs were collected, in vivo muscle contractility, protein synthesis rate, mitochondrial function, and protein turnover markers were assessed. One-way ANOVA within sex and trend analysis between sexes were performed, P < 0.05. Gastrocnemius and tibialis anterior (TA) muscles became atrophic in male mice at 25 days, whereas female mice exhibited no significant differences in muscle weights at endpoints despite presenting hallmarks of cancer cachexia (fat loss, hepatosplenomegaly). We observed lowered muscle contractility and protein synthesis concomitantly to muscle mass decay in males, with higher proteolytic markers in muscles of both sexes. mRNA of Opa1 was lower in TA, whereas Bnip3 was higher in gastrocnemius after 25 days in male mice, with no significant effect in female mice. Our data suggest relative protections to skeletal muscle in females compared with males despite other canonical signs of cancer cachexia and increased protein degradation markers; suggesting we should place onus upon nonmuscle tissues during early stages of cancer cachexia in females. We noted potential protective mechanisms relating to skeletal muscle contractile and mitochondrial functions. Our findings underline possible heterogeneity in onset of cancer cachexia between biological sexes, suggesting the need for sex-specific approaches to treat cancer cachexia.NEW & NOTEWORTHY Our study demonstrates biological-sex differences in phenotypic characteristics of cancer cachexia between male and female mice, whereby females display many common characteristics of cachexia (gonadal fat loss and hepatosplenomegaly), protein synthesis markers alterations, and common catabolic markers in skeletal muscle despite relatively preserved muscle mass in early-stage cachexia compared with males. Mechanisms of cancer cachexia appear to differ between sexes. Data suggest need to place onus of early cancer cachexia detection and treatment on nonmuscle tissues in females.

Inflammation o'clock: interactions of circadian rhythms with inflammation-induced skeletal muscle atrophy

Circadian rhythms are ∼24 h cycles evident in behaviour, physiology and metabolism. The molecular mechanism directing circadian rhythms is the circadian clock, which is composed of an interactive network of transcription-translation feedback loops. The core clock genes include Bmal1, Clock, Rev-erbα/β, Per and Cry. In addition to keeping time, the core clock regulates a daily programme of gene expression that is important for overall cell homeostasis. The circadian clock mechanism is present in all cells, including skeletal muscle fibres, and disruption of the muscle clock is associated with changes in muscle phenotype and function. Skeletal muscle atrophy is largely associated with a lower quality of life, frailty and reduced lifespan. Physiological and genetic modification of the core clock mechanism yields immune dysfunction, alters inflammatory factor expression and secretion and is associated with skeletal muscle atrophy in multiple conditions, such as ageing and cancer cachexia. Here, we summarize the possible interplay between the circadian clock modulation of immune cells, systemic inflammatory status and skeletal muscle atrophy in chronic inflammatory conditions. Although there is a clear disruption of circadian clocks in various models of atrophy, the mechanism behind such alterations remains unknown. Understanding the modulatory potential of muscle and immune circadian clocks in inflammation and skeletal muscle health is essential for the development of therapeutic strategies to protect skeletal muscle mass and function of patients with chronic inflammation.

The time-course of cancer cachexia onset reveals biphasic transcriptional disruptions in female skeletal muscle distinct from males

BACKGROUND

Cancer-cachexia (CC) is a debilitating condition affecting up to 80% of cancer patients and contributing to 40% of cancer-related deaths. While evidence suggests biological sex differences in the development of CC, assessments of the female transcriptome in CC are lacking, and direct comparisons between sexes are scarce. This study aimed to define the time course of Lewis lung carcinoma (LLC)-induced CC in females using transcriptomics, while directly comparing biological sex differences.

RESULTS

We found the global gene expression of the gastrocnemius muscle of female mice revealed biphasic transcriptomic alterations, with one at 1 week following tumor allograft and another during the later stages of cachexia development. The early phase was associated with the upregulation of extracellular-matrix pathways, while the later phase was characterized by the downregulation of oxidative phosphorylation, electron transport chain, and TCA cycle. When DEGs were compared to a known list of mitochondrial genes (MitoCarta), ~ 47% of these genes were differently expressed in females exhibiting global cachexia, suggesting transcriptional changes to mitochondrial gene expression happens concomitantly to functional impairments previously published. In contrast, the JAK-STAT pathway was upregulated in both the early and late stages of CC. Additionally, we observed a consistent downregulation of Type-II Interferon signaling genes in females, which was associated with protection in skeletal muscle atrophy despite systemic cachexia. Upregulation of Interferon signaling was noted in the gastrocnemius muscle of cachectic and atrophic male mice. Comparison of female tumor-bearing mice with males revealed ~ 70% of DEGs were distinct between sexes in cachectic animals, demonstrating dimorphic mechanisms of CC.

CONCLUSION

Our findings suggest biphasic disruptions in the transcriptome of female LLC tumor-bearing mice: an early phase associated with ECM remodeling and a late phase, accompanied by the onset of systemic cachexia, affecting overall muscle energy metabolism. Notably, ~ 2/3 of DEGs in CC are biologically sex-specific, providing evidence of dimorphic mechanisms of cachexia between sexes. Downregulation of Type-II Interferon signaling genes appears specific to CC development in females, suggesting a new biological sex-specific marker of CC not reliant on the loss of muscle mass, that might represent a protective mechanism against muscle loss in CC in female mice.

Cancer-associated cachexia - understanding the tumour macroenvironment and microenvironment to improve management

Cachexia is a devastating, multifactorial and often irreversible systemic syndrome characterized by substantial weight loss (mainly of skeletal muscle and adipose tissue) that occurs in around 50-80% of patients with cancer. Although this condition mainly affects skeletal muscle (which accounts for approximately 40% of total body weight), cachexia is a multi-organ syndrome that also involves white and brown adipose tissue, and organs including the bones, brain, liver, gut and heart. Notably, cachexia accounts for up to 20% of cancer-related deaths. Cancer-associated cachexia is invariably associated with systemic inflammation, anorexia and increased energy expenditure. Understanding these mechanisms is essential, and the progress achieved in this area over the past decade could help to develop new therapeutic approaches. In this Review, we examine the currently available evidence on the roles of both the tumour macroenvironment and microenvironment in cancer-associated cachexia, and provide an overview of the novel therapeutic strategies developed to manage this syndrome.

Current perspectives of mitochondria-targeted antioxidants in cancer prevention and treatment

Oxidative stress nearly always accompanies all stages of cancer development. At the early stages, antioxidants may help to reduce reactive oxygen species (ROS) production and exhibit anticarcinogenic effects. In the later stages, ROS involvement becomes more complex. On the one hand, ROS are necessary for cancer progression and epithelial-mesenchymal transition. On the other hand, antioxidants may promote cancer cell survival and may increase metastatic frequency. The role of mitochondrial ROS in cancer development remains largely unknown. This paper reviews experimental data on the effects of both endogenous and exogenous antioxidants on cancerogenesis focusing on the development and application of mitochondria-targeted antioxidants. We also discuss the prospects for antioxidant cancer therapy, focusing on the use of mitochondria-targeted antioxidants.

Muscle weakness precedes atrophy during cancer cachexia and is linked to muscle-specific mitochondrial stress

Muscle weakness and wasting are defining features of cancer-induced cachexia. Mitochondrial stress occurs before atrophy in certain muscles, but the possibility of heterogeneous responses between muscles and across time remains unclear. Using mice inoculated with Colon-26 cancer, we demonstrate that specific force production was reduced in quadriceps and diaphragm at 2 weeks in the absence of atrophy. At this time, pyruvate-supported mitochondrial respiration was lower in quadriceps while mitochondrial H2O2 emission was elevated in diaphragm. By 4 weeks, atrophy occurred in both muscles, but specific force production increased to control levels in quadriceps such that reductions in absolute force were due entirely to atrophy. Specific force production remained reduced in diaphragm. Mitochondrial respiration increased and H2O2 emission was unchanged in both muscles versus control while mitochondrial creatine sensitivity was reduced in quadriceps. These findings indicate muscle weakness precedes atrophy and is linked to heterogeneous mitochondrial alterations that could involve adaptive responses to metabolic stress. Eventual muscle-specific restorations in specific force and bioenergetics highlight how the effects of cancer on one muscle do not predict the response in another muscle. Exploring heterogeneous responses of muscle to cancer may reveal new mechanisms underlying distinct sensitivities, or resistance, to cancer cachexia.

Bone-Muscle Crosstalk: Musculoskeletal Complications of Chemotherapy

PURPOSE OF REVIEW

Chemotherapy drugs combat tumor cells and reduce metastasis. However, a significant side effect of some chemotherapy strategies is loss of skeletal muscle and bone. In cancer patients, maintenance of lean tissue is a positive prognostic indicator of outcomes and helps to minimize the toxicity associated with chemotherapy. Bone-muscle crosstalk plays an important role in the function of the musculoskeletal system and this review will focus on recent findings in preclinical and clinical studies that shed light on chemotherapy-induced bone-muscle crosstalk.

RECENT FINDINGS

Chemotherapy-induced loss of bone and skeletal muscle are important clinical problems. Bone antiresorptive drugs prevent skeletal muscle weakness in preclinical models. Chemotherapy-induced loss of bone can cause muscle weakness through both changes in endocrine signaling and mechanical loading between muscle and bone. Chemotherapy-induced changes to bone-muscle crosstalk have implications for treatment strategies and patient quality of life. Recent findings have begun to determine the role of chemotherapy in bone-muscle crosstalk and this review summarizes the most relevant clinical and preclinical studies.

Mitochondrial Dysfunction as an Underlying Cause of Skeletal Muscle Disorders

Mitochondria are an important energy source in skeletal muscle. A main function of mitochondria is the generation of ATP for energy through oxidative phosphorylation (OXPHOS). Mitochondrial defects or abnormalities can lead to muscle disease or multisystem disease. Mitochondrial dysfunction can be caused by defective mitochondrial OXPHOS, mtDNA mutations, Ca2+ imbalances, mitochondrial-related proteins, mitochondrial chaperone proteins, and ultrastructural defects. In addition, an imbalance between mitochondrial fusion and fission, lysosomal dysfunction due to insufficient biosynthesis, and/or defects in mitophagy can result in mitochondrial damage. In this review, we explore the association between impaired mitochondrial function and skeletal muscle disorders. Furthermore, we emphasize the need for more research to determine the specific clinical benefits of mitochondrial therapy in the treatment of skeletal muscle disorders.

PGC1α overexpression preserves muscle mass and function in cisplatin-induced cachexia

BACKGROUND

Chemotherapy induces a cachectic-like phenotype, accompanied by skeletal muscle wasting, weakness and mitochondrial dysfunction. Peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC1α), a regulator of mitochondrial biogenesis, is often reduced in cachectic skeletal muscle. Overexpression of PGC1α has yielded mixed beneficial results in cancer cachexia, yet investigations using such approach in a chemotherapy setting are limited. Utilizing transgenic mice, we assessed whether overexpression of PGC1α could combat the skeletal muscle consequences of cisplatin.

METHODS

Young (2 month) and old (18 month) wild-type (WT) and PGC1α transgenic male and female mice (Tg) were injected with cisplatin (C; 2.5 mg/kg) for 2 weeks, while control animals received saline (n = 5-9/group). Animals were assessed for muscle mass and force, motor unit connectivity, and expression of mitochondrial proteins.

RESULTS

Young WT + C mice displayed reduced gastrocnemius mass (male: -16%, P < 0.0001; female: -11%, P < 0.001), muscle force (-6%, P < 0.05, both sexes), and motor unit number estimation (MUNE; male: -53%, P < 0.01; female: -51%, P < 0.01). Old WT + C male and female mice exhibited gastrocnemius wasting (male: -22%, P < 0.05; female: -27%, P < 0.05), muscle weakness (male: -20%, P < 0.0001; female: -17%, P < 0.01), and loss of MUNE (male: -82%, P < 0.01; female: -62%, P < 0.05), suggesting exacerbated cachexia compared with younger animals. Overexpression of PGC1α had mild protective effects on muscle mass in young Tg + C male only (gastrocnemius: +10%, P < 0.05); however, force and MUNE were unchanged in both young Tg + C male and female, suggesting preservation of neuromuscular function. In older male, protective effects associated with PGC1α overexpression were heighted with Tg + C demonstrating preserved muscle mass (gastrocnemius: +34%, P < 0.001), muscle force (+13%, P < 0.01), and MUNE (+3-fold, P < 0.05). Similarly, old female Tg + C did not exhibit muscle wasting or reductions in MUNE, and had preserved muscle force (+11%, P < 0.05) compared with female WT + C. Follow-up molecular analysis demonstrated that aged WT animals were more susceptible to cisplatin-induced loss of mitochondrial proteins, including PGC1α, OPA1, cytochrome-C, and Cox IV.

CONCLUSIONS

In our study, the negative effects of cisplatin were heighted in aged animals, whereas overexpression of PGC1α was sufficient to combat the neuromuscular dysfunction caused by cisplatin, especially in older animals. Hence, our observations indicate that aged animals may be more susceptible to develop chemotherapy side toxicities and that mitochondria-targeted strategies may serve as a tool to prevent chemotherapy-induced muscle wasting and weakness.

Muscle and Bone Defects in Metastatic Disease

PURPOSE OF REVIEW

The present review addresses most recently identified mechanisms implicated in metastasis-induced bone resorption and muscle-wasting syndrome, known as cachexia.

RECENT FINDINGS

Metastatic disease in bone and soft tissues is often associated with skeletal muscle defects. Recent studies have identified a number of secreted molecules and extracellular vesicles that contribute to cancer cell growth and metastasis leading to bone destruction and muscle atrophy. In addition, alterations in muscle microenvironment including dysfunctions in hepatic and mitochondrial metabolism have been implicated in cancer-induced regeneration defect and muscle loss. Moreover, we review novel in vitro and animal models including promising new drug candidates for bone metastases and cancer cachexia. Preservation of bone health could be highly beneficial for maintaining muscle mass and function. Therefore, a better understanding of molecular pathways implicated in bone and muscle crosstalk in metastatic disease may provide new insights and identify new strategies to improve current anticancer therapeutics.

Short duration treadmill exercise improves physical function and skeletal muscle mitochondria protein expression after recovery from FOLFOX chemotherapy in male mice

FOLFOX (5-FU, leucovorin, oxaliplatin) is a chemotherapy treatment for colorectal cancer which induces toxic side effects involving fatigue, weakness, and skeletal muscle dysfunction. There is a limited understanding of the recovery from these toxicities after treatment cessation. Exercise training can improve chemotherapy-related toxicities. However, how exercise accelerates recovery and the dose required for these benefits are not well examined. The purpose of this study was to examine the effect of exercise duration on physical function, muscle mass, and mitochondria protein expression during the recovery from FOLFOX chemotherapy. 12-week-old male mice were administered four cycles of either PBS or FOLFOX over 8-weeks. Outcomes were assessed after the fourth cycle and after either 4 (short-term; STR) or 10 weeks (long-term; LTR) recovery. Subsets of mice performed 14 sessions (6 d/wk, 18 m/min, 5% grade) of 60 min/d (long) or 15 min/d (short duration) treadmill exercise during STR. Red and white gastrocnemius mRNA and protein expression were examined. FOLFOX treatment decreased run time (RT) (-53%) and grip strength (GS) (-9%) compared to PBS. FOLFOX also reduced muscle OXPHOS complexes, COXIV, and VDAC protein expression. At LTR, FOLFOX RT (-36%) and GS (-16%) remained reduced. Long- and short-duration treadmill exercise improved RT (+58% and +56%) without restoring GS in FOLFOX mice. Both exercise durations increased muscle VDAC and COXIV expression in FOLFOX mice. These data provide evidence that FOLFOX chemotherapy induces persistent deficits in physical function that can be partially reversed by short-duration aerobic exercise.

PGC-1α overexpression is not sufficient to mitigate cancer cachexia in either male or female mice

Cancer-cachexia accounts for 20-40% of cancer-related deaths. Mitochondrial aberrations have been shown to precede muscle atrophy in different atrophy models, including cancer. Therefore, this study investigated potential protection from the cachectic phenotype through overexpression of PGC-1α. First, to establish potential of mitochondria-based approaches we showed that the mitochondrial antioxidant mitoTEMPO attenuates myotube atrophy induced by Lewis Lung Carcinoma (LLC) cell conditioned media. Next, cachexia was induced in muscle specific PGC-1α overexpressing (MCK-PCG1α) or wildtype (WT) littermate mice by LLC implantation. MCK-PCG1α did not protect LLC-induced muscle mass loss. In plantaris, Atrogin mRNA content was 6.2-fold and ~11-fold greater in WT-LLC vs. WT-PBS for males and females, respectively (p<0.05). MitoTimer red:green ratio for male PGC was ~65% higher than WT groups (p<0.05), with ~3-fold more red puncta in LLC than PBS (p<0.05). Red:green ratio was ~56% lower in females WT-LLC vs. PGC-LLC (p<0.05). In females, no change in red puncta was noted across conditions. Lc3 mRNA content was ~ 73% and 2-fold higher in male and female LLC mice respectively vs. PBS (p<0.05). While MitoTEMPO could mitigate cancer-induced atrophy in vitro, PGC1α overexpression was insufficient to protect muscle mass and mitochondrial health in vivo despite mitigation of cachexia-associated signaling pathways.

Tumor cell anabolism and host tissue catabolism-energetic inefficiency during cancer cachexia

Cancer-associated cachexia (CC) is a pathological condition characterized by sarcopenia, adipose tissue depletion, and progressive weight loss. CC is driven by multiple factors such as anorexia, excessive catabolism, elevated energy expenditure by growing tumor mass, and inflammatory mediators released by cancer cells and surrounding tissues. In addition, endocrine system, systemic metabolism, and central nervous system (CNS) perturbations in combination with cachexia mediators elicit exponential elevation in catabolism and reduced anabolism in skeletal muscle, adipose tissue, and cardiac muscle. At the molecular level, mechanisms of CC include inflammation, reduced protein synthesis, and lipogenesis, elevated proteolysis and lipolysis along with aggravated toxicity and complications of chemotherapy. Furthermore, CC is remarkably associated with intolerance to anti-neoplastic therapy, poor prognosis, and increased mortality with no established standard therapy. In this context, we discuss the spatio-temporal changes occurring in the various stages of CC and highlight the imbalance of host metabolism. We provide how multiple factors such as proteasomal pathways, inflammatory mediators, lipid and protein catabolism, glucocorticoids, and in-depth mechanisms of interplay between inflammatory molecules and CNS can trigger and amplify the cachectic processes. Finally, we highlight current diagnostic approaches and promising therapeutic interventions for CC.

The Mitochondria-Targeting Agent MitoQ Improves Muscle Atrophy, Weakness and Oxidative Metabolism in C26 Tumor-Bearing Mice

Cancer cachexia is a debilitating syndrome characterized by skeletal muscle wasting, weakness and fatigue. Several pathogenetic mechanisms can contribute to these muscle derangements. Mitochondrial alterations, altered metabolism and increased oxidative stress are known to promote muscle weakness and muscle catabolism. To the extent of improving cachexia, several drugs have been tested to stimulate mitochondrial function and normalize the redox balance. The aim of this study was to test the potential beneficial anti-cachectic effects of Mitoquinone Q (MitoQ), one of the most widely-used mitochondria-targeting antioxidant. Here we show that MitoQ administration (25 mg/kg in drinking water, daily) in vivo was able to improve body weight loss in Colon-26 (C26) bearers, without affecting tumor size. Consistently, the C26 hosts displayed ameliorated skeletal muscle and strength upon treatment with MitoQ. In line with improved skeletal muscle mass, the treatment with MitoQ was able to partially correct the expression of the E3 ubiquitin ligases Atrogin-1 and Murf1. Contrarily, the anabolic signaling was not improved by the treatment, as showed by unchanged AKT, mTOR and 4EBP1 phosphorylation. Assessment of gene expression showed altered levels of markers of mitochondrial biogenesis and homeostasis in the tumor hosts, although only Mitofusin-2 levels were significantly affected by the treatment. Interestingly, the levels of Pdk4 and CytB, genes involved in the regulation of mitochondrial function and metabolism, were also partially increased by MitoQ, in line with the modulation of hexokinase (HK), pyruvate dehydrogenase (PDH) and succinate dehydrogenase (SDH) enzymatic activities. The improvement of the oxidative metabolism was associated with reduced myosteatosis (i.e., intramuscular fat infiltration) in the C26 bearers receiving MitoQ, despite unchanged muscle LDL receptor expression, therefore suggesting that MitoQ could boost β-oxidation in the muscle tissue and promote a glycolytic-to-oxidative shift in muscle metabolism and fiber composition. Overall, our data identify MitoQ as an effective treatment to improve skeletal muscle mass and function in tumor hosts and further support studies aimed at testing the anti-cachectic properties of mitochondria-targeting antioxidants also in combination with routinely administered chemotherapy agents.

Metabolomics and its Applications in Cancer Cachexia

Cancer cachexia (CC) is a complicated metabolic derangement and muscle wasting syndrome, affecting 50–80% cancer patients. So far, molecular mechanisms underlying CC remain elusive. Metabolomics techniques have been used to study metabolic shifts including changes of metabolite concentrations and disturbed metabolic pathways in the progression of CC, and expand further fundamental understanding of muscle loss. In this article, we aim to review the research progress and applications of metabolomics on CC in the past decade, and provide a theoretical basis for the study of prediction, early diagnosis, and therapy of CC.

Silibinin Alleviates Muscle Atrophy Caused by Oxidative Stress Induced by Cisplatin through ERK/FoxO and JNK/FoxO Pathways

Cisplatin (DDP), a widely used chemotherapeutic drug in cancer treatment, causes oxidative stress, resulting in cancer cachexia and skeletal muscle atrophy. This study investigated the effects and activity of silibinin (SLI) in reducing DDP-induced oxidative stress and skeletal muscle atrophy in vivo and in vitro. SLI alleviated weight loss, food intake, muscle wasting, adipose tissue depletion, and organ weight reduction induced by DDP and improved the reduction of grip force caused by DDP. SLI can attenuated the increase in reactive oxygen species (ROS) levels, the decrease in Nrf2 expression, the decrease in the fiber cross-sectional area, and changes in fiber type induced by DDP. SLI regulated the ERK/FoxO and JNK/FoxO pathways by downregulating the abnormal increase in ROS and Nrf2 expression in DDP-treated skeletal muscle and C2C12 myotube cells. Further, SLI inhibited the upregulation of MAFbx and Mstn, the downregulation of MyHC and MyoG, the increase in protein degradation, and the decrease of protein synthesis. The protective effects of SLI were reversed by cotreatment with JNK agonists and ERK inhibitors. These results suggest that SLI can reduce DDP-induced skeletal muscle atrophy by reducing oxidative stress and regulating ERK/FoxO and JNK/FoxO pathways.

Development of metabolic and contractile alterations in development of cancer cachexia in female tumor-bearing mice

Cancer cachexia (CC) results in impaired muscle function and quality of life and is the primary cause of death for ∼20%-30% of patients with cancer. We demonstrated mitochondrial degeneration as a precursor to CC in male mice; however, whether such alterations occur in females is currently unknown. The purpose of this study was to elucidate muscle alterations in CC development in female tumor-bearing mice. Sixty female C57BL/6J mice were injected with PBS or Lewis lung carcinoma at 8 wk of age, and tumors developed for 1, 2, 3, or 4 wk to assess the time course of cachectic development. In vivo muscle contractile function, protein fractional synthetic rate (FSR), protein turnover, and mitochondrial health were assessed. Three- and four-week tumor-bearing mice displayed a dichotomy in tumor growth and were reassigned to high tumor (HT) and low tumor (LT) groups. HT mice exhibited lower soleus, tibialis anterior, and fat weights than PBS mice. HT mice showed lower peak isometric torque and slower one-half relaxation time than PBS mice. HT mice had lower FSR than PBS mice, whereas E3 ubiquitin ligases were greater in HT than in other groups. Bnip3 (mitophagy) and pMitoTimer red puncta (mitochondrial degeneration) were greater in HT mice, whereas Pgc1α1 and Tfam (mitochondrial biogenesis) were lower in HT mice than in PBS mice. We demonstrate alterations in female tumor-bearing mice where HT exhibited greater protein degradation, impaired muscle contractility, and mitochondrial degeneration compared with other groups. Our data provide novel evidence for a distinct cachectic development in tumor-bearing female mice compared with previous male studies.NEW & NOTEWORTHY Our study demonstrates divergent tumor development and tissue wasting within 3- and 4-wk mice, where approximately half the mice developed large tumors and subsequent cachexia. Unlike previous male studies, where metabolic perturbations precede the onset of cachexia, females appear to exhibit protections from the metabolic perturbations and cachexia development. Our data provide novel evidence for divergent cachectic development in tumor-bearing female mice compared with previous male CC studies, suggesting different mechanisms of CC between sexes.

Bile Acid Dysregulation Is Intrinsically Related to Cachexia in Tumor-Bearing Mice

Simple Summary

Cancer cachexia is considered a multi-organ syndrome. An improved understanding of how circulating molecules can affect tissues and mediate their crosstalk in the pathogenesis of cancer cachexia is emerging. Considering the various actions of bile acids on host metabolism and immunity, they could represent innovative targets in cancer cachexia. In this study, we investigated how bile acids could contribute to this syndrome by assessing the bile flow, by comparing the impact on bile acid pathways of cachexia-inducing and non-cachexia-inducing cell sublines, and by investigating the effects of ursodeoxycholic acid, a choleretic compound, in cachectic mice. Altogether, our analyses strengthen the importance of bile acids and their receptors as key players in the metabolic disorders associated with cancer, thereby laying the foundation for new therapeutic opportunities.

Abstract

Bile acids exert diverse actions on host metabolism and immunity through bile acid-activated receptors, including Takeda G protein-coupled receptor 5 (TGR5). We have recently evidenced an alteration in bile acids in cancer cachexia, an inflammatory and metabolic syndrome contributing to cancer death. This current study aims to further explore the links emerging between bile acids and cancer cachexia. First, we showed that bile flow is reduced in cachectic mice. Next, comparing mice inoculated with cachexia-inducing and with non-cachexia-inducing C26 colon carcinoma cells, we demonstrated that alterations in the bile acid pathways and profile are directly associated with cachexia. Finally, we performed an interventional study using ursodeoxycholic acid (UDCA), a compound commonly used in hepatobiliary disorders, to induce bile acid secretion and decrease inflammation. We found that UDCA does not improve hepatic inflammation and worsens muscle atrophy in cachectic mice. This exacerbation of the cachectic phenotype upon UDCA was accompanied by a decreased TGR5 activity, suggesting that TGR5 agonists, known to reduce inflammation in several pathological conditions, could potentially counteract cachectic features. This work brings to light major evidence sustaining the emerging links between bile acids and cancer cachexia and reinforces the interest in studying bile acid-activated receptors in this context.

Mitochondrial Dysfunction in Cancer Cachexia: Impact on Muscle Health and Regeneration

Cancer cachexia is a frequently neglected debilitating syndrome that, beyond representing a primary cause of death and cancer therapy failure, negatively impacts on patients' quality of life. Given the complexity of its multisystemic pathogenesis, affecting several organs beyond the skeletal muscle, defining an effective therapeutic approach has failed so far. Revamped attention of the scientific community working on cancer cachexia has focused on mitochondrial alterations occurring in the skeletal muscle as potential triggers of the complex metabolic derangements, eventually leading to hypercatabolism and tissue wasting. Mitochondrial dysfunction may be simplistically viewed as a cause of energy failure, thus inducing protein catabolism as a compensatory mechanism; however, other peculiar cachexia features may depend on mitochondria. On the one side, chemotherapy also impacts on muscle mitochondrial function while, on the other side, muscle-impaired regeneration may result from insufficient energy production from damaged mitochondria. Boosting mitochondrial function could thus improve the energetic status and chemotherapy tolerance, and relieve the myogenic process in cancer cachexia. In the present work, a focused review of the available literature on mitochondrial dysfunction in cancer cachexia is presented along with preliminary data dissecting the potential role of stimulating mitochondrial biogenesis via PGC-1α overexpression in distinct aspects of cancer-induced muscle wasting.

The Role of Autophagy Modulated by Exercise in Cancer Cachexia

Cancer cachexia is a syndrome experienced by many patients with cancer. Exercise can act as an autophagy modulator, and thus holds the potential to be used to treat cancer cachexia. Autophagy imbalance plays an important role in cancer cachexia, and is correlated to skeletal and cardiac muscle atrophy and energy-wasting in the liver. The molecular mechanism of autophagy modulation in different types of exercise has not yet been clearly defined. This review aims to elaborate on the role of exercise in modulating autophagy in cancer cachexia. We evaluated nine studies in the literature and found a potential correlation between the type of exercise and autophagy modulation. Combined exercise or aerobic exercise alone seems more beneficial than resistance exercise alone in cancer cachexia. Looking ahead, determining the physiological role of autophagy modulated by exercise will support the development of a new medical approach for treating cancer cachexia. In addition, the harmonization of the exercise type, intensity, and duration might play a key role in optimizing the autophagy levels to preserve muscle function and regulate energy utilization in the liver.

Chemotherapy-Induced Myopathy: The Dark Side of the Cachexia Sphere

Simple Summary

In addition to cancer-related factors, anti-cancer chemotherapy treatment can drive life-threatening body wasting in a syndrome known as cachexia. Emerging evidence has described the impact of several key chemotherapeutic agents on skeletal muscle in particular, and the mechanisms are gradually being unravelled. Despite this evidence, there remains very little research regarding therapeutic strategies to protect muscle during anti-cancer treatment and current global grand challenges focused on deciphering the cachexia conundrum fail to consider this aspect—chemotherapy-induced myopathy remains very much on the dark side of the cachexia sphere. This review explores the impact and mechanisms of, and current investigative strategies to protect against, chemotherapy-induced myopathy to illuminate this serious issue.

Abstract

Cancer cachexia is a debilitating multi-factorial wasting syndrome characterised by severe skeletal muscle wasting and dysfunction (i.e., myopathy). In the oncology setting, cachexia arises from synergistic insults from both cancer–host interactions and chemotherapy-related toxicity. The majority of studies have surrounded the cancer–host interaction side of cancer cachexia, often overlooking the capability of chemotherapy to induce cachectic myopathy. Accumulating evidence in experimental models of cachexia suggests that some chemotherapeutic agents rapidly induce cachectic myopathy, although the underlying mechanisms responsible vary between agents. Importantly, we highlight the capacity of specific chemotherapeutic agents to induce cachectic myopathy, as not all chemotherapies have been evaluated for cachexia-inducing properties—alone or in clinically compatible regimens. Furthermore, we discuss the experimental evidence surrounding therapeutic strategies that have been evaluated in chemotherapy-induced cachexia models, with particular focus on exercise interventions and adjuvant therapeutic candidates targeted at the mitochondria.

Cancer cachexia: molecular mechanism and pharmacological management

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