Activin Receptor Ligand Blocking and Cancer Have Distinct Effects on Protein and Redox Homeostasis in Skeletal Muscle and Liver

The Role of Skeletal Muscle Mitochondria in Colorectal Cancer Related Cachexia: Friends or Foes?

Up to 60% of colorectal cancer (CRC) patients develop cachexia. The presence of CRC related cachexia is associated with more adverse events during systemic therapy, leading to a high mortality rate. The main manifestation in CRC related cachexia is the loss of skeletal muscle mass, resulting from an imbalance between skeletal muscle protein synthesis and protein degradation. In CRC related cachexia, systemic inflammation, oxidative stress, and proteolytic systems lead to mitochondrial dysfunction, resulting in an imbalanced skeletal muscle metabolism. Mitochondria fulfill an important function in muscle maintenance. Thus, preservation of the skeletal muscle mitochondrial homeostasis may contribute to prevent the loss of muscle mass. However, it remains elusive whether mitochondria play a benign or malignant role in the development of cancer cachexia. This review summarizes current (mostly preclinical) evidence about the role of skeletal muscle mitochondria in the development of CRC related cachexia. Future human research is necessary to determine the physiological role of skeletal muscle mitochondria in the development of human CRC related cachexia.

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.

Multi-compartment metabolomics and metagenomics reveal major hepatic and intestinal disturbances in cancer cachectic mice

BACKGROUND

Cancer cachexia is a multifactorial syndrome characterized by multiple metabolic dysfunctions. Besides the muscle, other organs such as the liver and the gut microbiota may also contribute to this syndrome. Indeed, the gut microbiota, an important regulator of the host metabolism, is altered in the C26 preclinical model of cancer cachexia. Interventions targeting the gut microbiota have shown benefits, but mechanisms underlying the host-microbiota crosstalk in this context are still poorly understood.

METHODS

To explore this crosstalk, we combined proton nuclear magnetic resonance (¹ H-NMR) metabolomics in multiple compartments with 16S rDNA sequencing. These analyses were complemented by molecular and biochemical analyses, as well as hepatic transcriptomics.

RESULTS

¹ H-NMR revealed major changes between control (CT) and cachectic (C26) mice in the four analysed compartments (i.e. caecal content, portal vein, liver, and vena cava). More specifically, glucose metabolism pathways in the C26 model were altered with a reduction in glycolysis and gluconeogenesis and an activation of the hexosamine pathway, arguing against the existence of a Cori cycle in this model. In parallel, amino acid uptake by the liver, with an up to four-fold accumulation of nine amino acids (q-value <0.05), was mainly used for acute phase response proteins synthesis rather than to fuel the tricarboxylic acid cycle and gluconeogenesis. We also identified a 35% reduction in hepatic carnitine levels (q-value <0.05) and a lower activation of the phosphatidylcholine pathway as potential contributors to the hepatic steatosis present in this model. Our work also reveals a reduction of different beneficial intestinal bacterial activities in cancer cachexia. We found decreased levels of two short-chain fatty acids, acetate and butyrate (72% and 88% reduction in C26 caecal content; q-value <0.001), and a reduction in aromatic amino acid metabolites, which may contribute to the altered intestinal homeostasis in these mice. A member of the Ruminococcaceae family (ASV 2) was identified as the main bacterium responsible for the drop in butyrate. Finally, we report a two-fold intestinal transit acceleration (P-value <0.001) as a key factor shaping the gut microbiota composition and activity in cancer cachexia, which together lead to a faecal loss of proteins and amino acids.

CONCLUSIONS

Our work highlights new metabolic pathways potentially involved in cancer cachexia and further supports the interest of exploring the gut microbiota composition and activity, as well as intestinal transit, in cancer patients with and without cachexia.

Proposal of a Panel of Genes Identified by miRNA Profiling as Candidate Prognostic Biomarkers in Lung Carcinoids

AIM

To validate the prognostic role of a panel of genes previously uncovered by our group to be specific targets of miRNAs differentially expressed in lung carcinoids with aggressive pathological features.

METHODS

Four genes, namely, cyclic AMP response element binding protein-1 (CREBP1), activin A receptor type 2B (ACVR2B), LIM homeobox 2 (LHX2), and Krüppel-like factor 12 (KLF12), were identified in a previous study by our group using in silico analysis to be regulated by 3 miRNAs (miR-409-3p, miR-409-5p, and miR-431-5p) that were shown to be downregulated in aggressive lung carcinoids. These genes were analyzed using real-time PCR in a cohort of 102 lung carcinoids. Fifty high-grade lung carcinomas served as control group. Their expression was correlated with the expression of miR-409-3p, miR-409-5p, and miR-431-5p and with clinical pathological parameters and disease-free survival.

RESULTS

The expression of all but CREBP1 gene was significantly different between lung carcinoids and high-grade neuroendocrine carcinomas. ACVR2B and LHX2 were significantly inversely correlated with miR-409-3p and miR-409-5p. High levels of ACVR2B and LHX2 were significantly associated with atypical histotype, high tumor grade, and higher proliferation Ki-67 index (all p < 0.05). Low levels of KLF12 were significantly associated with the presence of necrosis and positive nodal status (all p < 0.05). Finally, low KLF12 expression was associated with shorter disease-free survival in lung carcinoids as a whole and in atypical carcinoids, only (all p < 0.001).

CONCLUSIONS

ACVR2B, LHX2, and KFL12 are novel potential biomarkers associated with aggressive features in lung carcinoids.

Exercise as a therapy for cancer-induced muscle wasting

Cancer cachexia is a progressive disorder characterized by body weight, fat, and muscle loss. Cachexia induces metabolic disruptions that can be analogous and distinct from those observed in cancer, obscuring both diagnosis and treatment options. Inflammation, hypogonadism, and physical inactivity are widely investigated as systemic mediators of cancer-induced muscle wasting. At the cellular level, dysregulation of protein turnover and energy metabolism can negatively impact muscle mass and function. Exercise is well known for its anti-inflammatory effects and potent stimulation of anabolic signaling. Emerging evidence suggests the potential for exercise to rescue muscle's sensitivity to anabolic stimuli, reduce wasting through protein synthesis modulation, myokine release, and subsequent downregulation of proteolytic factors. To date, there is no recommendation for exercise in the management of cachexia. Given its complex nature, a multimodal approach incorporating exercise offers promising potential for cancer cachexia treatment. This review's primary objective is to summarize the growing body of research examining exercise regulation of cancer cachexia. Furthermore, we will provide evidence for exercise interactions with established systemic and cellular regulators of cancer-induced muscle wasting.

Muscle NAD+ depletion and Serpina3n as molecular determinants of murine cancer cachexia-the effects of blocking myostatin and activins

Objective

Cancer cachexia and muscle loss are associated with increased morbidity and mortality. In preclinical animal models, blocking activin receptor (ACVR) ligands has improved survival and prevented muscle wasting in cancer cachexia without an effect on tumour growth. However, the underlying mechanisms are poorly understood. This study aimed to identify cancer cachexia and soluble ACVR (sACVR) administration-evoked changes in muscle proteome.

Methods

Healthy and C26 tumour-bearing (TB) mice were treated with recombinant sACVR. The sACVR or PBS control were administered either prior to the tumour formation or by continued administration before and after tumour formation. Muscles were analysed by quantitative proteomics with further examination of mitochondria and nicotinamide adenine dinucleotide (NAD⁺) metabolism. To complement the first prophylactic experiment, sACVR (or PBS) was injected as a treatment after tumour cell inoculation.

Results

Muscle proteomics in TB cachectic mice revealed downregulated signatures for mitochondrial oxidative phosphorylation (OXPHOS) and increased acute phase response (APR). These were accompanied by muscle NAD⁺ deficiency, alterations in NAD⁺ biosynthesis including downregulation of nicotinamide riboside kinase 2 (Nrk2), and decreased muscle protein synthesis. The disturbances in NAD⁺ metabolism and protein synthesis were rescued by treatment with sACVR. Across the whole proteome and APR, in particular, Serpina3n represented the most upregulated protein and the strongest predictor of cachexia. However, the increase in Serpina3n expression was associated with increased inflammation rather than decreased muscle mass and/or protein synthesis.

Conclusions

We present evidence implicating disturbed muscle mitochondrial OXPHOS proteome and NAD⁺ homeostasis in experimental cancer cachexia. Treatment of TB mice with a blocker of activin receptor ligands restores depleted muscle NAD⁺ and Nrk2, as well as decreased muscle protein synthesis. These results indicate putative new treatment therapies for cachexia and that although acute phase protein Serpina3n may serve as a predictor of cachexia, it more likely reflects a condition of elevated inflammation.

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Cachectic muscle proteome shows decreased OXPHOS and increased acute phase response.

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Cancer cachexia is characterized by lowered muscle Nrk2 expression and NAD⁺ levels.

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Blocking activin receptor 2B ligands rescues muscle NAD⁺ homeostasis in cachexia.

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Blocking activin receptor 2B ligands prevents affected protein synthesis in cachexia.

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Serpina3n predicts cachexia and cancer-induced APR independently from muscle atrophy.

ER Stress and Unfolded Protein Response in Cancer Cachexia

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

Muscle and serum metabolomes are dysregulated in colon-26 tumor-bearing mice despite amelioration of cachexia with activin receptor type 2B ligand blockade

Cancer-associated cachexia reduces survival, which has been attenuated by blocking the activin receptor type 2B (ACVR2B) ligands in mice. The purpose of this study was to unravel the underlying physiology and novel cachexia biomarkers by use of the colon-26 (C26) carcinoma model of cancer cachexia. Male BALB/c mice were subcutaneously inoculated with C26 cancer cells or vehicle control. Tumor-bearing mice were treated with vehicle (C26+PBS) or soluble ACVR2B either before (C26+sACVR/b) or before and after (C26+sACVR/c) tumor formation. Skeletal muscle and serum metabolomics analysis was conducted by gas chromatography-mass spectrometry. Cancer altered various biologically functional groups representing 1) amino acids, 2) energy sources, and 3) nucleotide-related intermediates. Muscle metabolomics revealed increased content of free phenylalanine in cancer that strongly correlated with the loss of body mass within the last 2 days of the experiment. This correlation was also detected in serum. Decreased ribosomal RNA content and phosphorylation of a marker of pyrimidine synthesis revealed changes in nucleotide metabolism in cancer. Overall, the effect of the experimental C26 cancer predominated over blocking ACVR2B ligands in both muscle and serum. However, the level of methyl phosphate, which was decreased in muscle in cancer, was restored by sACVR2B-Fc treatment. In conclusion, experimental cancer affected muscle and blood metabolomes mostly independently of blocking ACVR2B ligands. Of the affected metabolites, we have identified free phenylalanine as a promising biomarker of muscle atrophy or cachexia. Finally, the decreased capacity for pyrimidine nucleotide and protein synthesis in tumor-bearing mice opens up new avenues in cachexia research.