Gut barrier dysfunction in the Apc(Min/+) mouse model of colon cancer cachexia

A comprehensive review of animal models for cancer cachexia: Implications for translational research

Cancer cachexia is a multifactorial syndrome characterized by progressive weight loss and a disease process that nutritional support cannot reverse. Although progress has been made in preclinical research, there is still a long way to go in translating research findings into clinical practice. One of the main reasons for this is that existing preclinical models do not fully replicate the conditions seen in clinical patients. Therefore, it is important to understand the characteristics of existing preclinical models of cancer cachexia and pay close attention to the latest developments in preclinical models. The main models of cancer cachexia used in current research are allogeneic and xenograft models, genetically engineered mouse models, chemotherapy drug-induced models, Chinese medicine spleen deficiency models, zebrafish and Drosophila models, and cellular models. This review aims to revisit and summarize the commonly used animal models of cancer cachexia by evaluating existing preclinical models, to provide tools and support for translational medicine research.

Role of the intestinal microbiota in contributing to weight disorders and associated comorbidities

SUMMARYThe gut microbiota is a major factor contributing to the regulation of energy homeostasis and has been linked to both excessive body weight and accumulation of fat mass (i.e., overweight, obesity) or body weight loss, weakness, muscle atrophy, and fat depletion (i.e., cachexia). These syndromes are characterized by multiple metabolic dysfunctions including abnormal regulation of food reward and intake, energy storage, and low-grade inflammation. Given the increasing worldwide prevalence of obesity, cachexia, and associated metabolic disorders, novel therapeutic strategies are needed. Among the different mechanisms explaining how the gut microbiota is capable of influencing host metabolism and energy balance, numerous studies have investigated the complex interactions existing between nutrition, gut microbes, and their metabolites. In this review, we discuss how gut microbes and different microbiota-derived metabolites regulate host metabolism. We describe the role of the gut barrier function in the onset of inflammation in this context. We explore the importance of the gut-to-brain axis in the regulation of energy homeostasis and glucose metabolism but also the key role played by the liver. Finally, we present specific key examples of how using targeted approaches such as prebiotics and probiotics might affect specific metabolites, their signaling pathways, and their interactions with the host and reflect on the challenges to move from bench to bedside.

Involvement of the gut microbiota in cancer cachexia

Cancer cachexia, or the unintentional loss of body weight in patients with cancer, is a multiorgan and multifactorial syndrome with a complex and largely unknown etiology; however, metabolic dysfunction and inflammation remain hallmarks of cancer-associated wasting. Although cachexia manifests with muscle and adipose tissue loss, perturbations to the gastrointestinal tract may serve as the frontline for both impaired nutrient absorption and immune-activating gut dysbiosis. Investigations into the gut microbiota have exploded within the past two decades, demonstrating multiple gut-tissue axes; however, the link between adipose and skeletal muscle wasting and the gut microbiota with cancer is only beginning to be understood. Furthermore, the most used anticancer drugs (e.g. chemotherapy and immune checkpoint inhibitors) negatively impact gut homeostasis, potentially exacerbating wasting and contributing to poor patient outcomes and survival. In this review, we 1) highlight our current understanding of the microbial changes that occur with cachexia, 2) discuss how microbial changes may contribute to adipose and skeletal muscle wasting, and 3) outline study design considerations needed when examining the role of the microbiota in cancer-induced cachexia.

Exploring heterogeneity: a dive into preclinical models of cancer cachexia

Cancer cachexia (CC) is a multifactorial and complex syndrome experienced by up to 80% of patients with cancer and implicated in ∼40% of cancer-related deaths. Given its significant impact on patients' quality of life and prognosis, there has been a growing emphasis on elucidating the underlying mechanisms of CC using preclinical models. However, the mechanisms of cachexia appear to differ across several variables including tumor type and model and biologic variables such as sex. These differences may be exacerbated by variance in experimental approaches and data reporting. This review examines literature spanning from 2011 to March 2024, focusing on common preclinical models of CC, including Lewis Lung Carcinoma, pancreatic KPC, and colorectal colon-26 and Apcmin/+ models. Our analysis reveals considerable heterogeneity in phenotypic outcomes, and investigated mechanisms within each model, with particular attention to sex differences that may be exacerbated through methodological differences. Although searching for unified mechanisms is critical, we posit that effective treatment approaches are likely to leverage the heterogeneity presented by the tumor and pertinent biological variables to direct specific interventions. In exploring this heterogeneity, it becomes critical to consider methodological and data reporting approaches to best inform further research.

Photobiomodulation therapy moderates cancer cachexia-associated muscle wasting through activating PI3K/AKT/FoxO3a pathway

Cancer cachexia-associated muscle wasting as a multifactorial wasting syndrome, is an important factor affecting the long-term survival rate of tumor patients. Photobiomodulation therapy (PBMT) has emerged as a promising tool to cure and prevent many diseases. However, the effect of PBMT on skeletal muscle atrophy during cancer progression has not been fully demonstrated yet. Here, we found PBMT alleviated the atrophy of myotube diameter induced by cancer cells in vitro, and prevented cancer-associated muscle atrophy in mice bearing tumor. Mechanistically, the alleviation of muscle wasting by PBMT was found to be involved in inhibiting E3 ubiquitin ligases MAFbx and MuRF-1. In addition, transcriptomic analysis using RNA-seq and GSEA revealed that PI3K/AKT pathway might be involved in PBMT-prevented muscle cachexia. Next, we showed the protective effect of PBMT against muscle cachexia was totally blocked by AKT inhibitor in vitro and in vivo. Moreover, PBMT-activated AKT promoted FoxO3a phosphorylation and thus inhibiting the nucleus entry of FoxO3a. Lastly, in cisplatin-treated muscle cachexia model, PBMT had also been shown to ameliorate muscle atrophy through enhancing PI3K/AKT pathway to suppress MAFbx and MuRF-1 expression. These novel findings revealed that PBMT could be a promising therapeutic approach in treating muscle cachexia induced by cancer.

Anemoside B4 ameliorates dextran sulfate sodium (DSS)-induced colitis through inhibiting NLRP3 inflammasome and modulating gut microbiota

Ulcerative colitis (UC) has been recognized as a chronic and relapsing inflammatory disease of the gastrointestinal tract. Clinically, aminosalicylates, immunosuppressants and biological agents are commonly used to treat UC at different stages of the disease. However, these drugs often have side effects. Here, we investigated the anti-UC activity of Anemoside B4 (AB4) in mice with dextran sulfate sodium (DSS) induced colitis. Colon tissues, serum, and colonic contents were collected for assessment of intestinal barrier function, inflammatory cytokines production and microenvironment of intestinal microbiota. Results showed that AB4 alleviated colon shortening, weight lossing and histopathological damage in DSS-induced mice. In addition, we demonstrated both in vivo and in vitro that AB4 remarkably ameliorated colonic inflammation through suppressing NLRP3 pathway. Moreover, AB4 strengthened the intestinal epithelial barrier by regulating myosin light chain kinase (MLCK)-phosphorylated myosin light chain 2 (pMLC2) signaling pathway. Furthermore, we performed 16 S rRNA gene sequencing and fecal microbiome transplantation (FMT) experiments to demonstrate that AB4 alleviated colitis through regulating dysbiosis of intestinal microbiota. These results revealed that AB4 effectively ameliorate experimental UC mainly through regulating MLCK/pMLC2 pathway, NLRP3 pathway and dysbiosis of microbiota, provided new insights into the development of novel anti-UC drugs.

Mechanisms of Ovarian Cancer-Associated Cachexia

Cancer-associated cachexia occurs in 50% to 80% of cancer patients and is responsible for 20% to 30% of cancer-related deaths. Cachexia limits survival and treatment outcomes, and is a major contributor to morbidity and mortality during cancer. Ovarian cancer is one of the leading causes of cancer-related deaths in women, and recent studies have begun to highlight the prevalence and clinical impact of cachexia in this population. Here, we review the existing understanding of cachexia pathophysiology and summarize relevant studies assessing ovarian cancer-associated cachexia in clinical and preclinical studies. In clinical studies, there is increased evidence that reduced skeletal muscle mass and quality associate with worse outcomes in subjects with ovarian cancer. Mouse models of ovarian cancer display cachexia, often characterized by muscle and fat wasting alongside inflammation, although they remain underexplored relative to other cachexia-associated cancer types. Certain soluble factors have been identified and successfully targeted in these models, providing novel therapeutic targets for mitigating cachexia during ovarian cancer. However, given the relatively low number of studies, the translational relevance of these findings is yet to be determined and requires more research. Overall, our current understanding of ovarian cancer-associated cachexia is insufficient and this review highlights the need for future research specifically aimed at exploring mechanisms of ovarian cancer-associated cachexia by using unbiased approaches and animal models representative of the clinical landscape of ovarian cancer.

Targeting IL-23 for the interception of obesity-associated colorectal cancer

Inflammation and obesity are two major factors that promote Colorectal cancer (CRC). Our recent data suggests that interleukin (IL)-23, is significantly elevated in CRC tumors and correlates with patient obesity, tumor grade and survival. Thus, we hypothesize that obesity and CRC may be linked via inflammation and IL-23 may be a potential target for intervention in high-risk patients. TCGA dataset and patient sera were evaluated for IL-23A levels. IL-23A [IL-23 p19-/-] knockout (KO) mice were crossed to Apcmin/+ mice and progeny were fed low-fat or high-fat diets. At termination intestines were evaluated for tumorigenesis. Tumors, serum, and fecal contents were analyzed for protein biomarkers, cytokines, and microbiome profile respectively. IL-23A levels are elevated in the sera of patients with obesity and colon tumors. Genetic ablation of IL-23A significantly suppressed colonic tumor multiplicity (76-96 %) and incidence (72-95 %) in male and female mice. Similarly, small-intestinal tumor multiplicity and size were also significantly reduced in IL-23A KO mice. IL-23A knockdown in Apcmin/+ mice fed high-fat diet, also resulted in significant suppression of colonic (50-58 %) and SI (41-48 %) tumor multiplicity. Cytokine profiling showed reduction in several circulating pro-inflammatory cytokines including loss of IL-23A. Biomarker analysis suggested reduced tumor cell proliferation and immune modulation with an increase in tumor-infiltrating CD4+ and CD8+ T-lymphocytes in the IL-23A KO mice compared to controls. Fecal microbiome analysis revealed potentially beneficial changes in the bacterial population profile. In summary, our data indicates a tumor promoting role for IL-23 in CRC including diet-induced obesity. With several IL-23 targeted therapies in clinical trials, there is a great potential for targeting this cytokine for CRC prevention and therapy.

Cancer Cachexia: Underlying Mechanisms and Potential Therapeutic Interventions

Cancer cachexia, a multifactorial metabolic syndrome developed during malignant tumor growth, is characterized by an accelerated loss of body weight accompanied by the depletion of skeletal muscle mass. This debilitating condition is associated with muscle degradation, impaired immune function, reduced functional capacity, compromised quality of life, and diminished survival in cancer patients. Despite the lack of the known capability of fully reversing or ameliorating this condition, ongoing research is shedding light on promising preclinical approaches that target the disrupted mechanisms in the pathophysiology of cancer cachexia. This comprehensive review delves into critical aspects of cancer cachexia, including its underlying pathophysiological mechanisms, preclinical models for studying the progression of cancer cachexia, methods for clinical assessment, relevant biomarkers, and potential therapeutic strategies. These discussions collectively aim to contribute to the evolving foundation for effective, multifaceted counteractive strategies against this challenging condition.

Platelet status in cancer cachexia progression in ApcMin/+ mice

Cachexia, a complex wasting syndrome, significantly affects the quality of life and treatment options for cancer patients. Studies have reported a strong correlation between high platelet count and decreased survival in cachectic individuals. Therefore, this study aimed to investigate the immunopathogenesis of cancer cachexia using the ApcMin/+ mouse model of spontaneous colorectal cancer. The research focused on identifying cellular elements in the blood at different stages of cancer cachexia, assessing inflammatory markers and fibrogenic factors in the skeletal muscle, and studying the behavioral and metabolic phenotype of ApcMin/+ mice at the pre-cachectic and severely cachectic stages. Platelet measurements were also obtained from other animal models of cancer cachexia - Lewis Lung Carcinoma and Colon 26 adenocarcinoma. Our study revealed that platelet number is elevated prior to cachexia development in ApcMin/+ mice and can become activated during its progression. We also observed increased expression of TGFβ2, TGFβ3, and SMAD3 in the skeletal muscle of pre-cachectic ApcMin/+ mice. In severely cachectic mice, we observed an increase in Ly6g, CD206, and IL-10 mRNA. Meanwhile, IL-1β gene expression was elevated in the pre-cachectic stage. Our behavioral and metabolic phenotyping results indicate that pre-cachectic ApcMin/+ mice exhibit decreased physical activity. Additionally, we found an increase in anemia at pre-cachectic and severely cachectic stages. These findings highlight the altered platelet status during early and late stages of cachexia and provide a basis for further investigation of platelets in the field of cancer cachexia.

[Gut Microbiome and Colorectal Cancer]

Colorectal cancer (CRC) is one of the most common cancers in Korea. A majority of CRCs are caused by progressive genomic alterations referred to as the adenoma-carcinoma sequence. The factors that may increase the risk of CRC include obesity and consumption of a high-fat diet, red meat, processed meat, and alcohol. Recently, the role of gut microbiota in the formation, progression and treatment of CRCs has been investigated in depth. An altered gut microbiota can drive carcinogenesis and cause the development of CRC. Studies have also shown the role of gut microbiota in the prevention of CRC and the impact of therapies involving gut microbiota on CRC. Herein, we summarize the current understanding of the role of the gut microbiota in the development of CRC and its therapeutic potential, including the prevention of CRC and in enhancing efficacy of chemotherapy and immunotherapy.

Cancer cachexia: molecular mechanisms and treatment strategies

Muscle wasting is a consequence of physiological changes or a pathology characterized by increased catabolic activity that leads to progressive loss of skeletal muscle mass and strength. Numerous diseases, including cancer, organ failure, infection, and aging-associated diseases, are associated with muscle wasting. Cancer cachexia is a multifactorial syndrome characterized by loss of skeletal muscle mass, with or without the loss of fat mass, resulting in functional impairment and reduced quality of life. It is caused by the upregulation of systemic inflammation and catabolic stimuli, leading to inhibition of protein synthesis and enhancement of muscle catabolism. Here, we summarize the complex molecular networks that regulate muscle mass and function. Moreover, we describe complex multi-organ roles in cancer cachexia. Although cachexia is one of the main causes of cancer-related deaths, there are still no approved drugs for cancer cachexia. Thus, we compiled recent ongoing pre-clinical and clinical trials and further discussed potential therapeutic approaches for cancer cachexia.

β-Carotene suppresses cancer cachexia by regulating the adipose tissue metabolism and gut microbiota dysregulation

Cancer cachexia is a metabolic disease affecting multiple organs and characterized by loss adipose and muscle tissues. Metabolic dysregulated of adipose tissue has a crucial role in cancer cachexia. β-Carotene (BC) is stored in adipose tissues and increases muscle mass and differentiation. However, its regulatory effects on adipose tissues in cancer cachexia have not been investigated yet. In this study, we found that BC supplementations could inhibit several cancer cachexia-related changes, including decreased carcass-tumor (carcass weight after tumor removal), adipose weights, and muscle weights in CT26-induced cancer cachexia mice. Moreover, BC supplementations suppressed cancer cachexia-induced lipolysis, fat browning, hepatic gluconeogenesis, and systemic inflammation. Altered diversity and composition of gut microbiota in cancer cachexia were restored by the BC supplementations. BC treatments could reverse the down-regulated adipogenesis and dysregulated mitochondrial respiration and glycolysis in adipocytes and colon cancer organoid co-culture systems. Taken together, these results suggest that BC can be a potential therapeutic strategy for cancer cachexia.

Implication of Obesity and Gut Microbiome Dysbiosis in the Etiology of Colorectal Cancer

The complexity and variety of gut microbiomes within and among individuals have been extensively studied in recent years in connection to human health and diseases. Our growing understanding of the bidirectional communication between metabolic diseases and the gut microbiome has also highlighted the significance of gut microbiome dysbiosis in the genesis and development of obesity-related cancers. Therefore, it is crucial to comprehend the possible role of the gut microbiota in the crosstalk between obesity and colorectal cancer (CRC). Through the induction of gut microbial dysbiosis, gut epithelial barrier impairment, metabolomic dysregulation, chronic inflammation, or dysregulation in energy harvesting, obesity may promote the development of colorectal tumors. It is well known that strategies for cancer prevention and treatment are most effective when combined with a healthy diet, physical activity, and active lifestyle choices. Recent studies also suggest that an improved understanding of the complex linkages between the gut microbiome and various cancers as well as metabolic diseases can potentially improve cancer treatments and overall outcomes. In this context, we herein review and summarize the clinical and experimental evidence supporting the functional role of the gut microbiome in the pathogenesis and progression of CRC concerning obesity and its metabolic correlates, which may pave the way for the development of novel prognostic tools for CRC prevention. Therapeutic approaches for restoring the microbiome homeostasis in conjunction with cancer treatments are also discussed herein.

The protective effect of cannabinoids against colorectal cancer cachexia through modulation of inflammation and immune responses

Cancer cachexia is a multifactorial disorder characterized by weight loss and muscle wasting, and there are currently no FDA-approved medications. In the present study, upregulation of six cytokines was observed in serum samples from patients with colorectal cancer (CRC) and in mouse models. A negative correlation between the levels of the six cytokines and body mass index in CRC patients was seen. Gene Ontology analysis revealed that these cytokines were involved in regulating T cell proliferation. The infiltration of CD8⁺ T cells was found to be associated with muscle atrophy in mice with CRC. Adoptive transfer of CD8⁺ T cells isolated from CRC mice resulted in muscle wasting in recipients. The Genotype-Tissue Expression database showed that negative correlations between the expression of cachexia markers and cannabinoid receptor 2 (CB2) in human skeletal muscle tissues. Pharmacological treatment with Δ⁹-tetrahydrocannabinol (Δ⁹-THC), a selective CB2 agonist or overexpression of CB2 attenuated CRC-associated muscle atrophy. In contrast, knockout of CB2 with a CRISPR/Cas9-based strategy or depletion of CD8⁺ T cells in CRC mice abolished the Δ⁹-THC-mediated effects. This study demonstrates that cannabinoids ameliorate CD8⁺ T cell infiltration in CRC-associated skeletal muscle atrophy via a CB2-mediated pathway. Serum levels of the six-cytokine signature might serve as a potential biomarker to detect the therapeutic effects of cannabinoids in CRC-associated cachexia.

The Anti-Tumorigenic Role of Cannabinoid Receptor 2 in Colon Cancer: A Study in Mice and Humans

The endocannabinoid system, particularly cannabinoid receptor 2 (CB2 in mice and CNR2 in humans), has controversial pathophysiological implications in colon cancer. Here, we investigate the role of CB2 in potentiating the immune response in colon cancer in mice and determine the influence of CNR2 variants in humans. Comparing wild-type (WT) mice to CB2 knockout (CB2^-/-) mice, we performed a spontaneous cancer study in aging mice and subsequently used the AOM/DSS model of colitis-associated colorectal cancer and a model for hereditary colon cancer (Apc^Min/+). Additionally, we analyzed genomic data in a large human population to determine the relationship between CNR2 variants and colon cancer incidence. Aging CB2^-/- mice exhibited a higher incidence of spontaneous precancerous lesions in the colon compared to WT controls. The AOM/DSS-treated CB2^-/- and Apc^Min/+CB2^-/- mice experienced aggravated tumorigenesis and enhanced splenic populations of immunosuppressive myeloid-derived suppressor cells along with abated anti-tumor CD8+ T cells. Importantly, corroborative genomic data reveal a significant association between non-synonymous variants of CNR2 and the incidence of colon cancer in humans. Taken together, the results suggest that endogenous CB2 activation suppresses colon tumorigenesis by shifting the balance towards anti-tumor immune cells in mice and thus portray the prognostic value of CNR2 variants for colon cancer patients.

Contribution of skeletal muscle to cancer immunotherapy: A focus on muscle function, inflammation, and microbiota

Sarcopenia, characterized by degenerative and systemic loss of skeletal muscle mass and function, is a multifactorial syndrome commonly observed in individuals with cancer. Additionally, it represents a poor nutritional status and indicates possible presence of cancer cachexia. Recently, with the extensive application of cancer immunotherapy, the effects of sarcopenia/cachexia on cancer immunotherapy, have gained attention. The aim of this review was to summarize the influence of low muscle mass (sarcopenia/cachexia) on the response and immune-related adverse events to immunotherapy from the latest literature. It was revealed that low muscle mass (sarcopenia/cachexia) has detrimental effects on cancer immunotherapy in most cases, although there were results that were not consistent with this finding. This review also discussed potential causes of the paradox, such as different measure methods, research types, muscle indicators, time point, and cancer type. Mechanically, chronic inflammation, immune cells, and microbiota may be critically involved in regulating the efficacy of immunotherapy under the condition of low muscle mass (sarcopenia/cachexia). Thus, nutritional interventions will likely be promising ways for individuals with cancer to increase the efficacy of immunotherapy in the future, for low muscle mass (sarcopenia/cachexia) is an important prognostic factor for cancer immunotherapy.

Pathological features of tissues and cell populations during cancer cachexia

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

Lipopolysaccharide-induced hypothalamic inflammation in cancer cachexia-anorexia is amplified by tumour-derived prostaglandin E2

BACKGROUND

Cachexia-anorexia syndrome is a complex metabolic condition characterized by skeletal muscle wasting, reduced food intake and prominent involvement of systemic and central inflammation. Here, the gut barrier function was investigated in pancreatic cancer-induced cachexia mouse models by relating intestinal permeability to the degree of cachexia. We further investigated the involvement of the gut-brain axis and the crosstalk between tumour, gut and hypothalamus in vitro.

METHODS

Two distinct mouse models of pancreatic cancer cachexia (KPC and 4662) were used. Intestinal inflammation and permeability were assessed through fluorescein isothiocyanate dextran (FITC-dextran) and lipopolysaccharide (LPS), and hypothalamic and systemic inflammation through mRNA expression and plasma cytokines, respectively. To simulate the tumour-gut-brain crosstalk, hypothalamic (HypoE-N46) cells were incubated with cachexia-inducing tumour secretomes and LPS. A synthetic mimic of C26 secretome was produced based on its secreted inflammatory mediators. Each component of the mimic was systematically omitted to narrow down the key mediator(s) with an amplifying inflammation. To substantiate its contribution, cyclooxygenase-2 (COX-2) inhibitor was used.

RESULTS

In vivo experiments showed FITC-dextran was enhanced in the KPC group (362.3 vs. sham 111.4 ng/mL, P < 0.001). LPS was increased to 140.9 ng/mL in the KPC group, compared with sham and 4662 groups (115.8 and 115.8 ng/mL, P < 0.05). Hypothalamic inflammatory gene expression of Ccl2 was up-regulated in the KPC group (6.3 vs. sham 1, P < 0.0001, 4662 1.3, P < 0.001), which significantly correlated with LPS concentration (r = 0.4948, P = 0.0226). These data suggest that intestinal permeability is positively related to the cachexic degree. Prostaglandin E2 (PGE2) was confirmed to be present in the plasma and PGE2 concentration (log10) in the KPC group was much higher than in 4662 group (1.85 and 0.56 ng/mL, P < 0.001), indicating a role for PGE2 in pancreatic cancer-induced cachexia. Parallel to in vivo findings, in vitro experiments revealed that the cachexia-inducing tumour secretomes (C26, LLC, KPC and 4662) amplified LPS-induced hypothalamic IL-6 secretion (419%, 321%, 294%, 160%). COX-2 inhibitor to the tumour cells reduced PGE2 content (from 10⁵ to 10²  pg/mL) in the secretomes and eliminated the amplified hypothalamic IL-6 production. Moreover, results could be reproduced by addition of PGE2 alone, indicating that the increased hypothalamic inflammation is directly related to the PGE2 from tumour.

CONCLUSIONS

PGE2 secreted by the tumour may play a role in amplifying the effects of bacteria-derived LPS on the inflammatory hypothalamic response. The cachexia-inducing potential of tumour mice models parallels the loss of intestinal barrier function. Tumour-derived PGE2 might play a key role in cancer-related cachexia-anorexia syndrome via tumour-gut-brain crosstalk.

Targeting cancer cachexia: Molecular mechanisms and clinical study

Cancer cachexia is a complex systemic catabolism syndrome characterized by muscle wasting. It affects multiple distant organs and their crosstalk with cancer constitute cancer cachexia environment. During the occurrence and progression of cancer cachexia, interactions of aberrant organs with cancer cells or other organs in a cancer cachexia environment initiate a cascade of stress reactions and destroy multiple organs including the liver, heart, pancreas, intestine, brain, bone, and spleen in metabolism, neural, and immune homeostasis. The role of involved organs turned from inhibiting tumor growth into promoting cancer cachexia in cancer progression. In this review, we depicted the complicated relationship of cancer cachexia with the metabolism, neural, and immune homeostasis imbalance in multiple organs in a cancer cachexia environment and summarized the treatment progress in recent years. And we discussed the molecular mechanism and clinical study of cancer cachexia from the perspective of multiple organs metabolic, neurological, and immunological abnormalities. Updated understanding of cancer cachexia might facilitate the exploration of biomarkers and novel therapeutic targets of cancer cachexia.

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.

From Mouth to Muscle: Exploring the Potential Relationship between the Oral Microbiome and Cancer-Related Cachexia

Cancer cachexia is a multifactorial wasting syndrome associated with skeletal muscle and adipose tissue loss, as well as decreased appetite. It affects approximately half of all cancer patients and leads to a decrease in treatment efficacy, quality of life, and survival. The human microbiota has been implicated in the onset and propagation of cancer cachexia. Dysbiosis, or the imbalance of the microbial communities, may lead to chronic systemic inflammation and contribute to the clinical phenotype of cachexia. Though the relationship between the gut microbiome, inflammation, and cachexia has been previously studied, the oral microbiome remains largely unexplored. As the initial point of digestion, the oral microbiome plays an important role in regulating systemic health. Oral dysbiosis leads to the upregulation of pro-inflammatory cytokines and an imbalance in natural flora, which in turn may contribute to muscle wasting associated with cachexia. Reinstating this equilibrium with the use of prebiotics and probiotics has the potential to improve the quality of life for patients suffering from cancer-related cachexia.

Poria cocos polysaccharides exert prebiotic function to attenuate the adverse effects and improve the therapeutic outcome of 5-FU in ApcMin/+ mice

BACKGROUND

As a first-line chemotherapeutic agent, 5-fluorouracil (5-FU) exhibits many side effects, weakening its efficacy in cancer treatment. In this study, we hypothesize that Poria cocos polysaccharides (PCP), a traditional Chinese herbal medicine with various bioactivities and prebiotic effects, might improve the therapeutic effect of 5-FU by restoring the homeostasis of the gut microenvironment and the commensal gut microflora.

METHODS

Apc^Min/+ mice were employed to evaluate the anti-cancer effect of 5-FU in conjunction with PCP treatment. Body weight and food consumption were monitored weekly. Polyp count was used to assess the anti-cancer effect of PCP and 5-FU. Expressions of mucosal cytokines and gut epithelial junction molecules were measured using qRT-PCR. 16S rRNA gene sequencing of fecal DNAs was used to evaluate the compositional changes of gut microbiota (GM). Transplantation of Lactobacillus johnsonii and Bifidobacterium animalis were performed to verify the prebiotic effects of PCP in improving the efficacy of 5-FU.

RESULTS

The results showed that PCP treatment alleviated the weight loss caused by 5-FU treatment and reduced the polyp burden in Apc^Min/+ mice. Additionally, PCP treatment eased the cytotoxic effects of 5-FU by reducing the expressions of pro-inflammatory cytokines, increasing the anti-inflammatory cytokines; and significantly improving the gut barriers by enhancing the tight junction proteins and associated adhesion molecules. Furthermore, 16S rRNA gene sequencing data showed that PCP alone or with 5-FU could stimulate the growth of probiotic bacteria (Bacteroides acidifaciens, Bacteroides intestinihominis, Butyricicoccus pullicaecorum, and the genera Lactobacillus, Bifidobacterium, Eubacterium). At the same time, it inhibited the growth of potential pathogens (e.g., Alistipes finegoldii, Alistipes massiliensis, Alistipes putredinis., Citrobacter spp., Desulfovibrio spp., and Desulfovibrio desulfuricans). Moreover, the results showed that transplantation of L.johnsonii and B.animalis effectively reduced the polyp burden in Apc^Min/+ mice being treated with 5-FU.

CONCLUSION

Our study showed that PCP could effectively improve the anti-cancer effect of 5-FU by attenuating its side effects, modulating intestinal inflammation, improving the gut epithelial barrier, and modulating the gut microbiota of Apc^Min/+ mice.

Cancer cachexia as a multiorgan failure: Reconstruction of the crime scene

Cachexia is a devastating syndrome associated with the end-stage of several diseases, including cancer, and characterized by body weight loss and severe muscle and adipose tissue wasting. Although different cancer types are affected to diverse extents by cachexia, about 80% of all cancer patients experience this comorbidity, which highly reduces quality of life and response to therapy, and worsens prognosis, accounting for more than 25% of all cancer deaths. Cachexia represents an urgent medical need because, despite several molecular mechanisms have been identified, no effective therapy is currently available for this devastating syndrome. Most studies focus on skeletal muscle, which is indeed the main affected and clinically relevant organ, but cancer cachexia is characterized by a multiorgan failure. In this review, we focus on the current knowledge on the multiple tissues affected by cachexia and on the biomarkers with the attempt to define a chronological pathway, which might be useful for the early identification of patients who will undergo cachexia. Indeed, it is likely that the inefficiency of current therapies might be attributed, at least in part, to their administration in patients at the late stages of cachexia.

Targeting the gut to prevent and counteract metabolic disorders and pathologies during aging

Impairment of gut function is one of the explanatory mechanisms of health status decline in elderly population. These impairments involve a decline in gut digestive physiology, metabolism and immune status, and associated to that, changes in composition and function of the microbiota it harbors. Continuous deteriorations are generally associated with the development of systemic dysregulations and ultimately pathologies that can worsen the initial health status of individuals. All these alterations observed at the gut level can then constitute a wide range of potential targets for development of nutritional strategies that can impact gut tissue or associated microbiota pattern. This can be key, in a preventive manner, to limit gut functionality decline, or in a curative way to help maintaining optimum nutrients bioavailability in a context on increased requirements, as frequently observed in pathological situations. The aim of this review is to give an overview on the alterations that can occur in the gut during aging and lead to the development of altered function in other tissues and organs, ultimately leading to the development of pathologies. Subsequently is discussed how nutritional strategies that target gut tissue and gut microbiota can help to avoid or delay the occurrence of aging-related pathologies.

Development of a Therapeutic Peptide for Cachexia Suggests a Platform Approach for Drug-like Peptides

During the development of a melanocortin (MC) peptide drug to treat the condition of cachexia (a hypermetabolic state producing lean body mass wasting), we were confronted with the need for peptide transport across the blood-brain barrier (BBB): the MC-4 receptors (MC4Rs) for metabolic rate control are located in the hypothalamus, i.e., behind the BBB. Using the term "peptides with BBB transport", we screened the medical literature like a peptide library. This revealed numerous "hits"-peptides with BBB transport and/or oral activity. We noted several features common to most peptides in this class, including a dipeptide sequence of nonpolar residues, primary structure cyclization (whole or partial), and a Pro-aromatic motif usually within the cyclized region. Based on this, we designed an MC4R antagonist peptide, TCMCB07, that successfully treated many forms of cachexia. As part of our pharmacokinetic characterization of TCMCB07, we discovered that hepatobiliary extraction from blood accounted for a majority of the circulating peptide's excretion. Further screening of the literature revealed that TCMCB07 is a member of a long-forgotten peptide class, showing active transport by a multi-specific bile salt carrier. Bile salt transport peptides have predictable pharmacokinetics, including BBB transport, but rapid hepatic clearance inhibited their development as drugs. TCMCB07 shares the general characteristics of the bile salt peptide class but with a much longer half-life of hours, not minutes. A change in its C-terminal amino acid sequence slows hepatic clearance. This modification is transferable to other peptides in this class, suggesting a platform approach for producing drug-like peptides.

Microbiota and body weight control: Weight watchers within?

BACKGROUND

Despite several decades of research, managing body weight remains an unsolved clinical problem. Health problems associated with dysregulated body weight, such as obesity and cachexia, exhibit several gut microbiota alterations. There is an increased interest in utilising the gut microbiota for body weight control, as it responds to intervention and plays an important role in energy extraction from food, as well as biotransformation of nutrients.

SCOPE OF THE REVIEW

This review provides an overview of the role of the gut microbiota in the physiological and metabolic alterations observed in two body weight dysregulation-related disorders, namely obesity and cachexia. Second, we assess the available evidence for different strategies, including caloric restriction, intermittent fasting, ketogenic diet, bariatric surgery, probiotics, prebiotics, synbiotics, high-fibre diet, and fermented foods - effects on body weight and gut microbiota composition. This approach was used to give insights into the possible link between body weight control and gut microbiota configuration.

MAJOR CONCLUSIONS

Despite extensive associations between body weight and gut microbiota composition, limited success could be achieved in the translation of microbiota-related interventions for body weight control in humans. Manipulation of the gut microbiota alone is insufficient to alter body weight and future research is needed with a combination of strategies to enhance the effects of lifestyle interventions.

Water-soluble dietary fiber alleviates cancer-induced muscle wasting through changes in gut microenvironment in mice

Cancer cachexia and the associated skeletal muscle wasting are considered poor prognostic factors, although effective treatment has not yet been established. Recent studies have indicated that the pathogenesis of skeletal muscle loss may involve dysbiosis of the gut microbiota and the accompanying chronic inflammation or altered metabolism. In this study, we evaluated the possible effects of modifying the gut microenvironment with partially hydrolyzed guar gum (PHGG), a soluble dietary fiber, on cancer‐related muscle wasting and its mechanism using a colon‐26 murine cachexia model. Compared with a fiber‐free (FF) diet, PHGG contained fiber‐rich (FR) diet–attenuated skeletal muscle loss in cachectic mice by suppressing the elevation of the major muscle‐specific ubiquitin ligases Atrogin‐1 and MuRF1, as well as the autophagy markers LC3 and Bnip3. Although tight‐junction markers were partially reduced in both FR and FF diet–fed cachectic mice, the abundance of Bifidobacterium, Akkermansia, and unclassified S24‐7 family increased by FR diet, contributing to the retention of the colonic mucus layer. The reinforcement of the gut barrier function resulted in the controlled entry of pathogens into the host system and reduced circulating levels of lipopolysaccharide‐binding protein (LBP) and IL‐6, which in turn led to the suppression of proteolysis by downregulating the ubiquitin‐proteasome system and autophagy pathway. These results suggest that dietary fiber may have the potential to alleviate skeletal muscle loss in cancer cachexia, providing new insights for developing effective strategies in the future.

Computed tomography with segmentation and quantification of individual organs in a D. melanogaster tumor model

Drosophila melanogaster tumor models are growing in popularity, driven by the high degree of genetic as well as functional conservation to humans. The most common method to measure the effects of a tumor on distant organs of a human cancer patient is to use computed tomography (CT), often used in diagnosing cachexia, a debilitating cancer-induced syndrome most visibly characterized by loss of muscle mass. Successful application of high resolution micro-CT scanning of D. melanogaster was recently reported and we here present the segmentation of all visible larval organs at several stages of tumor development. We previously showed the strong expected reduction in muscle mass as the tumor develops, and we here report a surprisingly strong reduction also in gut and Malpighian tubules (kidney) volume. Time-point of tumor development was found to have a stronger correlation to cachectic organ volume loss than tumor volume, giving support to the previously proposed idea that tumor size does not directly determine degree of cachexia.

High-Fat Diet Promotes Colorectal Tumorigenesis Through Modulating Gut Microbiota and Metabolites

BACKGROUND AND AIMS

Dietary fat intake is associated with increased risk of colorectal cancer (CRC). We examined the role of high-fat diet (HFD) in driving CRC through modulating gut microbiota and metabolites.

METHODS

HFD or control diet was fed to mice littermates in CRC mouse models of an azoxymethane (AOM) model and Apcmin/+ model, with or without antibiotics cocktail treatment. Germ-free mice for fecal microbiota transplantation were used for validation. Gut microbiota and metabolites were detected using metagenomic sequencing and high-performance liquid chromatography-mass spectrometry, respectively. Gut barrier function was determined using lipopolysaccharides level and transmission electron microscopy.

RESULTS

HFD promoted colorectal tumorigenesis in both AOM-treated mice and Apcmin/+ mice compared with control diet-fed mice. Gut microbiota depletion using antibiotics attenuated colon tumor formation in HFD-fed mice. A significant shift of gut microbiota composition with increased pathogenic bacteria Alistipessp.Marseille-P5997 and Alistipessp.5CPEGH6, and depleted probiotic Parabacteroides distasonis, along with impaired gut barrier function was exhibited in HFD-fed mice. Moreover, HFD-modulated gut microbiota promotes colorectal tumorigenesis in AOM-treated germ-free mice, indicating gut microbiota was essential in HFD-associated colorectal tumorigenesis. Gut metabolites alteration, including elevated lysophosphatidic acid, which was confirmed to promote CRC cell proliferation and impair cell junction, was also observed in HFD-fed mice. Moreover, transfer of stools from HFD-fed mice to germ-free mice without interference increased colonic cell proliferation, impaired gut barrier function, and induced oncogenic genes expression.

CONCLUSIONS

HFD drives colorectal tumorigenesis through inducing gut microbial dysbiosis, metabolomic dysregulation with elevated lysophosphatidic acid, and gut barrier dysfunction in mice.

Bile acid metabolism dysregulation associates with cancer cachexia: roles of liver and gut microbiome

BACKGROUND

Cancer cachexia is a multifactorial metabolic syndrome in which bile acid (BA) metabolism might be involved. The aim of the present study was to clarify the contribution of liver and gut microbiota to BA metabolism disturbance in cancer cachexia and to check the possibility of targeting BA metabolism using agents such as tauroursodeoxycholic acid (TUDCA) for cancer cachexia therapy.

METHODS

The BA profiles in liver, intestine, and serum of mice with cancer cachexia induced by inoculation of colon C26 tumour cells were analysed using metabolomics methods and compared with that of control mice. Proteomic analysis of liver protein expression profile and 16S rRNA gene sequencing analysis of gut microbiota composition in cancer cachexia mice were conducted. Expression levels of genes related to farnesoid X receptor (FXR) signalling pathway in the intestine and liver tissues were analysed using RT-PCR analysis. The BA profiles in serum of clinical colon cancer patients with or without cachexia were also analysed and compared with that of healthy volunteers. The effects of TUDCA in treating cancer cachexia mice were observed.

RESULTS

In the liver of cancer cachexia mice, expression of BA synthesis enzymes was inhibited while the amount of total BAs increased (P < 0.05). The ratios of conjugated BAs/un-conjugated BAs significantly increased in cancer cachexia mice liver (P < 0.01). Gut microbiota dysbiosis such as decrease in Lachnospiraceae and increase in Enterobacteriaceae was observed in the intestine of cancer cachexia mice, and microbial metabolism of BAs was reduced. Increase in expression of FGF15 in intestine (P < 0.01) suggested the activation of FXR signalling pathway which might contribute to the regulation of BA synthesis enzymes, transporters, and metabolic enzymes. Increase in the BA conjugation was observed in the serum of cancer cachexia mice. Results of clinical patients showed changes in BA metabolism, especially the increase in BA conjugation, and also suggested compensatory mechanism in BA metabolism regulation. Oral administration of 50 mg/kg TUDCA could significantly ameliorate the decrease in body weight (P < 0.001), muscle loss (P < 0.001), and atrophy of heart and liver (P < 0.05) in cancer cachexia mice without influence on tumour growth.

CONCLUSIONS

Bile acid metabolism dysregulation such as decrease in BA synthesis, increase in BA conjugation, and decrease in BA microbial metabolism was involved in development of cancer cachexia in mice. Targeting BA metabolism using agents such as TUDCA might be helpful for cancer cachexia therapy.

Activation of the Complement System in Patients with Cancer Cachexia

Simple Summary

Patients with cancer often suffer from severe weight loss as a result of the wasting of skeletal muscle and fat tissue. This has a strong negative impact on the patient’s prognosis and quality of life. Inflammation is thought to contribute to weight loss in cancer. To enable the future targeting of inflammation in patients with cancer who experience weight loss, we set out to characterize an important pro-inflammatory component of the immune system: the complement system. The blood levels of several elements of the complement system were analyzed in patients with and without weight loss and inflammation. We found that complement factors were activated specifically in patients with both weight loss and inflammation. Since complement inhibitory drugs are already on the market, these findings may open new opportunities for treating inflammation-mediated weight loss in patients with cancer.

Abstract

Systemic inflammation is thought to underlie many of the metabolic manifestations of cachexia in cancer patients. The complement system is an important component of innate immunity that has been shown to contribute to metabolic inflammation. We hypothesized that systemic inflammation in patients with cancer cachexia was associated with complement activation. Systemic C3a levels were higher in cachectic patients with inflammation (n = 23, C-reactive protein (CRP) ≥ 10 mg/L) as compared to patients without inflammation (n = 26, CRP < 10 mg/L) or without cachexia (n = 13) (medians 102.4 (IQR 89.4–158.0) vs. 81.4 (IQR 47.9–124.0) vs. 61.6 (IQR 46.8–86.8) ng/mL, respectively, p = 0.0186). Accordingly, terminal complement complex (TCC) concentrations gradually increased in these patient groups (medians 2298 (IQR 2022–3058) vs. 1939 (IQR 1725–2311) vs. 1805 (IQR 1552–2569) mAU/mL, respectively, p = 0.0511). C3a and TCC concentrations were strongly correlated (r_s = 0.468, p = 0.0005). Although concentrations of C1q and mannose-binding lectin did not differ between groups, C1q levels were correlated with both C3a and TCC concentrations (r_s = 0.394, p = 0.0042 and r_s = 0.300, p = 0.0188, respectively). In conclusion, systemic inflammation in patients with cancer cachexia is associated with the activation of key effector complement factors. The correlations between C1q and C3a/TCC suggest that the classical complement pathway could play a role in complement activation in patients with pancreatic cancer.

Interaction Between Commensal Bacteria, Immune Response and the Intestinal Barrier in Inflammatory Bowel Disease

In inflammatory bowel disease (IBD), intestinal mucosa cell and intestinal epithelial cell are severely damaged, and then their susceptibility to bacteria increases, so many commensal bacteria become pathogenic. The pathogenic commensal bacteria can stimulate a series of compensatory immune responses in the intestine. However, the immune response prevents the intestinal tract from restoring homeostasis, which in turn produces an indispensable inflammatory response. On the contrary, in IBD, the fierce inflammatory response contributes to the development of IBD. However, the effect of commensal bacteria on inflammation in IBD has not been clearly studied. Therefore, we further summarize the changes brought about by the changes of commensal bacteria to the inflammation of the intestines and their mutual influence. This article reviews the protective mechanism of commensal bacteria in healthy people and the mechanism of commensal bacteria and immune response to the destruction of the intestinal barrier when IBD occurs. The treatment and prevention of IBD are also briefly summarized.

Precision strategies for cancer treatment by modifying the tumor-related bacteria

Research on the roles of the bacteria in tumor development and progression is a rapidly emerging field. Increasing evidence links bacteria with the modification of the tumor immune microenvironment, which greatly influences the antitumor response. In view of the individual immune effects of various bacteria in various tumors, developing personalized bacteria-modulating therapy may be a key to successful antitumor treatment. This review emphasizes the critical role of the bacteria in immune regulation, including both the tumor bacteria and gut bacteria. Aiming at tumor-related bacteria, we focus on various precise modulation strategies and discuss their impact and potential for tumor suppression. Finally, engineered bacteria with tumor-targeting ability could achieve precise delivery of various payloads into tumors, acting as a precision tool. Therefore, a precise tumor-related bacteria therapy may be a promising approach to suppress the development of tumors, as well as an adjuvant therapy to improve the antitumor efficacy of other approaches. KEY POINTS: • The mini-review updates the knowledge on complex effect of bacteria in TME. • Insight into the interaction and adjustment of bacteria in gut for TME. • Prospects and limitations of bacteria-related personalized therapy in the clinical anticancer therapy.

Gut microbiota and metabolic aspects of cancer cachexia

Cancer cachexia is a metabolic syndrome characterized by unintended weight loss and muscle wasting. It has a strong negative impact on survival. Its underlying mechanisms involve systemic inflammation and insulin resistance, which are known to be influenced by the gut microbiota. Preclinical studies support a role for the gut microbiota in cancer cachexia by demonstrating that cachectic mice display: 1) various gut microbiota composition changes; 2) increased gut permeability and translocation of pro-inflammatory microbial compounds; 3) muscle atrophy-related processes linked to gut microbiota properties; 4) positive effects of microbiota-modulating interventions. Data on the relationships between gut microbiota, insulin resistance, and hepatic/adipose tissue metabolism in cachexia models are lacking. Nevertheless, the available data and existing evidence for the impact of gut microbiota on metabolic aberrations in human obesity urge for exploration of its role in human cancer cachexia. We provide practical recommendations and discuss the challenges for such future clinical studies.

The Effect of Wheel Exercise on Functional Indices of Cachexia in Tumor-bearing Mice

INTRODUCTION

Cancer-related fatigue and muscle wasting have received significant attention over the last few decades with the goal of establishing interventions that can improve cancer patient life quality and survival. Increased physical activity has shown to reduce cancer-associated fatigue and has been proposed as a promising therapeutic to attenuate cancer-induced wasting. However, significant gaps remain in our understanding of how physical activity affects the compositional and functional changes that initiate muscle wasting. The purpose of the current study was to determine the effect of wheel exercise on body composition and functional indices of cancer cachexia before the development of significant wasting.

METHODS

Thirteen-week-old male Apc (MIN) and C57BL/6 (B6) mice were given free wheel access (W) or a locked wheel (Sed) for 5 wk.

RESULTS

Wheel activity was reduced in the MIN compared with B6; however, wheel access increased complex II expression in isolated skeletal muscle mitochondria regardless of genotype. Wheel access had no effect on tumor burden or plasma interleukin-6 in the MIN. MIN-W increased body weight and lean mass compared with MIN-Sed, and there was a direct correlation between wheel distance and lean mass change. MIN-W increased grip strength and treadmill time to fatigue compared with MIN-Sed. Within MIN-W mice, skeletal muscle fatigability was only improved in high runners (>60 min·d).

CONCLUSIONS

Our results suggest that there were therapeutic benefits of increased activity related to body composition, behavior, and whole-body function that were not dependent on exercise duration; however, there was an exercise threshold needed to improve skeletal muscle fatigability in tumor-bearing mice. Interestingly, wheel access was able to improve compositional and functional outcomes without mitigating tumor number or size.

Exercise-A Panacea of Metabolic Dysregulation in Cancer: Physiological and Molecular Insights

Metabolic dysfunction is a comorbidity of many types of cancers. Disruption of glucose metabolism is of concern, as it is associated with higher cancer recurrence rates and reduced survival. Current evidence suggests many health benefits from exercise during and after cancer treatment, yet only a limited number of studies have addressed the effect of exercise on cancer-associated disruption of metabolism. In this review, we draw on studies in cells, rodents, and humans to describe the metabolic dysfunctions observed in cancer and the tissues involved. We discuss how the known effects of acute exercise and exercise training observed in healthy subjects could have a positive outcome on mechanisms in people with cancer, namely: insulin resistance, hyperlipidemia, mitochondrial dysfunction, inflammation, and cachexia. Finally, we compile the current limited knowledge of how exercise corrects metabolic control in cancer and identify unanswered questions for future research.

Type I IFNs and CD8 T cells increase intestinal barrier permeability after chronic viral infection

Intestinal barrier leakage constitutes a potential therapeutic target for many inflammatory diseases and represents a disease progression marker during chronic viral infections. However, the causes of altered gut barrier remain mostly unknown. Using murine infection with lymphocytic choriomeningitis virus, we demonstrate that, in contrast to an acute viral strain, a persistent viral isolate leads to long-term viral replication in hematopoietic and mesenchymal cells, but not epithelial cells (IECs), in the intestine. Viral persistence drove sustained intestinal epithelial barrier leakage, which was characterized by increased paracellular flux of small molecules and was associated with enhanced colitis susceptibility. Type I IFN signaling caused tight junction dysregulation in IECs, promoted gut microbiome shifts and enhanced intestinal CD8 T cell responses. Notably, both type I IFN receptor blockade and CD8 T cell depletion prevented infection-induced barrier leakage. Our study demonstrates that infection with a virus that persistently replicates in the intestinal mucosa increases epithelial barrier permeability and reveals type I IFNs and CD8 T cells as causative factors of intestinal leakage during chronic infections.

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.

High levels of modified ceramides are a defining feature of murine and human cancer cachexia

BACKGROUND

Cancer cachexia (CCx) is a multifactorial energy-wasting syndrome reducing the efficiency of anti-cancer therapies, quality of life, and survival of cancer patients. In the past years, most studies focused on the identification of tumour and host-derived proteins contributing to CCx. However, there is still a lack of studies addressing the changes in bioactive lipids. The aim of this study was to identify specific lipid species as a hallmark of CCx by performing a broad range lipid analysis of plasma from well-established CCx mouse models as well as cachectic and weight stable cancer patients.

METHODS

Plasma from non-cachectic (PBS-injected mice, NC26 tumour-bearing mice), pre-cachectic and cachectic mice (C26 and LLC tumour-bearing mice, Apc^Min/+ mutant mice), and plasma from weight stable and cachectic patients with gastrointestinal cancer, were analysed using the Lipidyzer™ platform. In total, 13 lipid classes and more than 1100 lipid species, including sphingolipids, neutral and polar glycerolipids, were covered by the analysis. Correlation analysis between specific lipid species and readouts of CCx were performed. Lipidomics data were confirmed by gene expression analysis of metabolic organs to analyse enzymes involved in sphingolipid synthesis and degradation.

RESULTS

A decrease in several lysophosphatidylcholine (LPC) species and an increase in numerous sphingolipids including sphingomyelins (SMs), ceramides (CERs), hexosyl-ceramides (HCERs) and lactosyl-ceramides (LCERs), were mutual features of CCx in both mice and cancer patients. Notably, sphingolipid levels gradually increased during cachexia development. Key enzymes involved in ceramide synthesis were elevated in liver but not in adipose, muscle, or tumour tissues, suggesting that ceramide turnover in the liver is a major contributor to elevated sphingolipid levels in CCx. LPC(16:1), LPC(20:3), SM(16:0), SM(24:1), CER(16:0), CER(24:1), HCER(16:0), and HCER(24:1) were the most consistently affected lipid species between mice and humans and correlated negatively (LPCs) or positively (SMs, CERs and HCERs) with the severity of body weight loss.

CONCLUSIONS

High levels of sphingolipids, specifically ceramides and modified ceramides, are a defining feature of murine and human CCx and may contribute to tissue wasting and skeletal muscle atrophy through the inhibition of anabolic signals. The progressive increase in sphingolipids during cachexia development supports their potential as early biomarkers for CCx.

Development and progression of cancer cachexia: Perspectives from bench to bedside

Cancer cachexia (CC) is a devastating syndrome characterized by weight loss, reduced fat mass and muscle mass that affects approximately 80% of cancer patients and is responsible for 22%-30% of cancer-associated deaths. Understanding underlying mechanisms for the development of CC are crucial to advance therapies to treat CC and improve cancer outcomes. CC is a multi-organ syndrome that results in extensive skeletal muscle and adipose tissue wasting; however, CC can impair other organs such as the liver, heart, brain, and bone as well. A considerable amount of CC research focuses on changes that occur within the muscle, but cancer-related impairments in other organ systems are understudied. Furthermore, metabolic changes in organ systems other than muscle may contribute to CC. Therefore, the purpose of this review is to address degenerative mechanisms which occur during CC from a whole-body perspective. Outlining the information known about metabolic changes that occur in response to cancer is necessary to develop and enhance therapies to treat CC. As much of the current evidences in CC are from pre-clinical models we should note the majority of the data reviewed here are from preclinical models.

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.

Interaction of alcohol with time of eating on markers of circadian dyssynchrony and colon tissue injury

BACKGROUND

Alcohol increases the risk of developing colon cancer (CRC), in part via tissue inflammation and impaired barrier integrity. Circadian dyssynchrony (CD) is an understudied but common lifestyle associated factor that increases the risk of multi-organ tissue injury and number of malignancies including CRC. Our prior studies showed that the shift in light-dark cycle exacerbates barrier dysfunction and colonic inflammation in the setting of alcohol treatment, and increases the risk of CRC. Here we studied the interaction of alcohol with an abnormal eating pattern on markers of CD and colonic barrier integrity.

METHOD

Mice were subjected to day (rest-phase = wrong-time WT) or night-time (active-phase = right-time RT) access to food in combination with access to water or 15% alcohol for total duration of 10 weeks. The food and liquid intake was measured. The locomotor activity data was recorded throughout the study, using a beam-break system. Mice were euthanized at two time points (ZT2 and ZT14). Time variation in the expression of the molecular marker of circadian clock (per2 gene) was measured in the central (hypothalamus) and intestinal (colon) tissue. Colonic protein expression of barrier markers (Occludin and Claudin-1) was studied.

RESULTS

No significant differences were present in the weight gain and alcohol intake among the groups over the study period. We observed an interaction of WT eating with alcohol on behavioral markers of circadian rhythm. Compared to the RT + Water treated animals ("reference group"), combination of WT eating and alcohol consumption (WT + Alcohol) significantly changed the per2 oscillatory pattern, that was different between the colon and hypothalamus, indicative of worsening circadian dyssynchrony. This was associated with an overall impaired expression of barrier integrity markers in the colon.

CONCLUSIONS

Alcohol induces circadian dyssynchrony which is worsened by abnormal food timing, associated with impaired barrier integrity in the colon. Future studies on the interaction of alcohol and food timing could provide further insights into alcohol associated CRC pathophysiology.

Systemic inflammation is associated with circulating cell death released keratin 18 fragments in colorectal cancer

Systemic inflammation is a stage-independent marker of poor prognosis in colorectal cancer (CRC), activated in a complex, multifactorial process. It has been proposed that one of the main factors driving systemic inflammation may be tumor necrosis. Keratin 18 (KRT18) fragments are released from dead cells and their serum levels are markers for apoptotic and necrotic cell death. In CRC, high KRT18 levels associate with advanced disease, but their relationship with tumor necrosis and systemic inflammation is unknown. In this study, serum total soluble KRT18 (tKRT18) and apoptosis-related, caspase-cleaved fragment (aKRT18) levels were measured preoperatively from 328 CRC patients, and their difference was calculated to assess necrosis related KRT18 (nKRT18) levels. The relationships of these markers with tumor necrosis, clinicopathologic features, systemic inflammation markers (C-reactive protein, albumin, and 13 cytokines), and survival were analyzed. High serum tKRT18, aKRT18, and nKRT18 levels showed association with a higher extent of tumor necrosis, distant metastasis, and increased levels of several markers of systemic inflammation, including CXCL8. High serum tKRT18 (multivariable HR 1.94, 95% CI 1.28-2.95, p = .002) and nKRT18 (multivariable HR 1.87, 95% CI 1.24-2.82, p = .003) levels were associated with poor overall survival independent of potential confounding factors. Our results show that tumor necrosis in CRC contributes to serum levels of KRT18 fragments, and both necrosis and KRT18 levels associate with systemic inflammation. Moreover, we show that serum tKRT18 and nKRT18 levels have independent prognostic value in CRC. Our observations confirm the link between cell death and systemic inflammation.

Gut microbiota modulation: a novel strategy for prevention and treatment of colorectal cancer

Research about the role of gut microbiome in colorectal cancer (CRC) is a newly emerging field of study. Gut microbiota modulation, with the aim to reverse established microbial dysbiosis, is a novel strategy for prevention and treatment of CRC. Different strategies including probiotics, prebiotics, postbiotics, antibiotics, and fecal microbiota transplantation (FMT) have been employed. Although these strategies show promising results, mechanistically by correcting microbiota composition, modulating innate immune system, enhancing gut barrier function, preventing pathogen colonization and exerting selective cytotoxicity against tumor cells, it should be noted that they are accompanied by risks and controversies that can potentially introduce clinical complications. During bench-to-bedside translation, evaluation of risk-and-benefit ratio, as well as patient selection, should be carefully performed. In view of the individualized host response to gut microbiome intervention, developing personalized microbiome therapy may be the key to successful clinical treatment.

Adaptogenic flower buds exert cancer preventive effects by enhancing the SCFA-producers, strengthening the epithelial tight junction complex and immune responses

Microbiome therapy has attracted a keen interest from both research and business sectors. Our lab has been applying this "second genome" platform to assess the functionality of herbal medicines with fulfilling results. In this study, we applied this platform to assess the potential cancer-preventive effects of three selected adaptogenic plants. The flower buds from these plants were used to constitute Preparations SL and FSP according to the receipts of two commonly consumed Chinese medicinal decoctions for gastrointestinal discomfort. Preparation SL contains Sophorae japonica and Lonicerae Japonicae, and Preparation FSP contains Sophorae japonica and Gardenia Jasminoides. SL and FSP extracts significantly (p < 0.001) lowered the polyp burden, as well as the expressions of oncogenic signaling molecules, such as MAPK/ERK, PI3K/AKT, and STAT3 in Apc^Min/+ mice. The inflamed gut was alleviated by shifting M1 to M2 macrophage phenotypes and the associated immune cytokines. The other remarkable change was on the extracellular tight junction protein complex, where the occludin, ZO-1, ICAM-1, E-cadherin were significantly (p < 0.05) upregulated while the N-cadherin and β-catenin were downregulated in the treated mice. The above physiological changes in the gut epithelial barrier were companied with the changes in gut microbiome. The 16S Sequencing data revealed a marked decrease in the potential pathogens (especially Helicobacter species and hydrogen sulfide producing-bacteria) and the increase in beneficial bacteria (especially for species from the genera of Akkermansia, Barnesiella, Coprococcus, Lachnoclostridium, and Ruminococcus). The majority of which were the short-chain fatty acids (SCFAs) producers. Meanwhile SCFAs-sensing G protein-coupled receptors (GPCRs), including GPR41, GPR43, and GPR109a were also significantly upregulated. In a recent report, we proved that the bacteria-derived SCFAs plays an essential role to the anti-cancer effects of the mushroom polysaccharides and saponins in Apc^Min/+ mice. In this study, we further demonstrated that butyrate treatment could enhance the extracellular tight junction protein complex as effective as the treatments with SL and FSP to the Apc^Min/+ mice. Our findings provide strong evidence of the vital role of the SCFA-producers and their metabolites to the cancer-preventive properties of the SL and FSP preparations.

Cancer cachexia and its pathophysiology: links with sarcopenia, anorexia and asthenia

Cancer cachexia is a multifactorial syndrome characterized by a progressive loss of skeletal muscle mass, along with adipose tissue wasting, systemic inflammation and other metabolic abnormalities leading to functional impairment. Cancer cachexia has long been recognized as a direct cause of complications in cancer patients, reducing quality of life and worsening disease outcomes. Some related conditions, like sarcopenia (age-related muscle wasting), anorexia (appetite loss) and asthenia (reduced muscular strength and fatigue), share some key features with cancer cachexia, such as weakness and systemic inflammation. Understanding the interplay and the differences between these conditions is critical to advance basic and translational research in this field, improving the accuracy of diagnosis and contributing to finally achieve effective therapies for affected patients.

Gut microbiota composition influences outcomes of skeletal muscle nutritional intervention via blended protein supplementation in posttransplant patients with hematological malignancies

BACKGROUND

Skeletal muscle atrophy is an important and independent predictor of survival after hematopoietic stem cell transplantation (HSCT). Our previous study found that soy-whey blended protein (SWP) can improve muscle mass in acute leukemia patients.

OBJECTIVE

We aimed to explore potential factors that influence muscle outcomes after nutritional intervention.

METHODS

In this case-control study, 13 patients who received HSCT and failed to improve muscle function within half a year were included. After two months of SWP intervention, the subjects were divided into two groups (MSI: muscle status improved; MNI: muscle status not improved). 16S rDNA sequencing, principal coordinate analysis (PCoA) and the PICRUSt algorithm were used to analyze the composition, structure and function of the intestinal microbiota between the groups. This study was registered in the Chinese Clinical Trial Registry (ChiCTR 1800017765).

RESULTS

SWP significantly improved muscle status (muscle area: from 330.4 mm² to 384.8 mm², p = 0.02; muscle strength: from 19.2 kg to 21.3 kg, p = 0.04). However, there were a small number of subjects whose muscle status was not effectively improved. After SWP intervention, the diversity (Shannon: from 1.7 to 3.8, p = 0.01; Simpson: from 0.6 to 0.8, p = 0.015) of the intestinal microbiota in the MSI group increased significantly, whereas that in the MNI group did not. Principal component analysis (PCA) revealed separate groupings of the microbiota of the Baseline-MSI and Endpoint-MSI time points in the MSI group. Opposite patterns of microbial abundance change were found between the MSI group (75% of changed genera were increased) and the MNI group (80% of changed genera were decreased). Three bacterial taxa (negative correlation: Streptococcus; positive correlations: Ruminococcus and Veillonella) were significantly related to muscle improvement outcomes. Both pentose phosphate (p = 0.048) and amino acid biosynthesis (p = 0.039), which are related to muscle metabolism, were found to be significantly changed in the MSI group through PICRUSt algorithm prediction.

CONCLUSIONS

Our results suggest that the intestinal microbiota plays important roles in the regulation of muscle metabolism.

Expression of Free Fatty Acid Receptor 2 by Dendritic Cells Prevents Their Expression of Interleukin 27 and Is Required for Maintenance of Mucosal Barrier and Immune Response Against Colorectal Tumors in Mice

BACKGROUND & AIMS

Intestinal microbes and their metabolites affect the development of colorectal cancer (CRC). Short-chain fatty acids are metabolites generated by intestinal microbes from dietary fiber. We investigated the mechanisms by which free fatty acid receptor 2 (FFAR2), a receptor for short-chain fatty acids that can affect the composition of the intestinal microbiome, contributes to the pathogenesis of CRC.

METHODS

We performed studies with ApcMin/+ mice, ApcMin/+Ffar2-/- mice, mice with conditional disruption of Ffar2 in dendritic cells (DCs) (Ffar2fl/flCD11c-Cre mice), ApcMin/+Ffar2fl/flCD11c-Cre mice, and Ffar2fl/fl mice (controls); some mice were given dextran sodium sulfate to induce colitis, with or without a FFAR2 agonist or an antibody against interleukin 27 (IL27). Colon and tumor tissues were analyzed by histology, quantitative polymerase chain reaction, and 16S ribosomal RNA gene sequencing; lamina propria and mesenteric lymph node tissues were analyzed by RNA sequencing and flow cytometry. Intestinal permeability was measured after gavage with fluorescently labeled dextran. We collected data on colorectal tumors from The Cancer Genome Atlas.

RESULTS

ApcMin/+Ffar2-/- mice developed significantly more spontaneous colon tumors than ApcMin/+ mice and had increased gut permeability before tumor development, associated with reduced expression of E-cadherin. Colon tumors from ApcMin/+Ffar2-/- mice had a higher number of bacteria than tumors from ApcMin/+ mice, as well as higher frequencies of CD39+CD8+ T cells and exhausted or dying T cells. DCs from ApcMin/+Ffar2-/- mice had an altered state of activation, increased death, and higher production of IL27. Administration of an antibody against IL27 reduced the numbers of colon tumors in ApcMin/+ mice with colitis. Frequencies of CD39+CD8+ T cells and IL27+ DCs were increased in colon lamina propria from Ffar2fl/flCD11c-Cre mice with colitis compared with control mice or mice without colitis. ApcMin/+Ffar2fl/flCD11c-Cre mice developed even more tumors than ApcMin/+Ffar2fl/fl mice, and their tumors had even higher numbers of IL27+ DCs. ApcMin/+ mice with colitis given the FFAR2 agonist developed fewer colon tumors, with fewer IL27+ DCs, than mice not given the agonist. DCs incubated with the FFAR2 agonist no longer had gene expression patterns associated with activation or IL27 production.

CONCLUSIONS

Loss of FFAR2 promotes colon tumorigenesis in mice by reducing gut barrier integrity, increasing tumor bacterial load, promoting exhaustion of CD8+ T cells, and overactivating DCs, leading to their death. Antibodies against IL27 and an FFAR2 agonist reduce tumorigenesis in mice and might be developed for the treatment of CRC.

Advances in cancer cachexia: Intersection between affected organs, mediators, and pharmacological interventions

Advanced cancer patients exhibit cachexia, a condition characterized by a significant reduction in the body weight predominantly from loss of skeletal muscle and adipose tissue. Cachexia is one of the major causes of morbidity and mortality in cancer patients. Decreased food intake and multi-organ energy imbalance in cancer patients worsen the cachexia syndrome. Cachectic cancer patients have a low tolerance for chemo- and radiation therapies and also have a reduced quality of life. The presence of tumors and the current treatment options for cancer further exacerbate the cachexia condition, which remains an unmet medical need. The onset of cachexia involves crosstalk between different organs leading to muscle wasting. Recent advancements in understanding the molecular mechanisms of skeletal muscle atrophy/hypertrophy and adipose tissue wasting/browning provide a platform for the development of new targeted therapies. Therefore, a better understanding of this multifactorial disorder will help to improve the quality of life of cachectic patients. In this review, we summarize the metabolic mediators of cachexia, their molecular functions, affected organs especially with respect to muscle atrophy and adipose browning and then discuss advanced therapeutic approaches to cancer cachexia.