Adipose triglyceride lipase contributes to cancer-associated cachexia

Pan-cancer secreted proteome and skeletal muscle regulation: insight from a proteogenomic data-driven knowledge base

Large-scale, pan-cancer analysis is enabled by data driven knowledge bases that link tumor molecular profiles with phenotypes. A debilitating cancer-related phenotype is skeletal muscle loss, or cachexia, which occurs partly from tumor products secreted into circulation. Using the LinkedOmicsKB knowledge base assembled from the Clinical Proteomics Tumor Analysis Consortium proteogenomic analysis, along with catalogs of human secretome proteins, ligand-receptor pairs and molecular signatures, we sought to identify candidate pan-cancer proteins secreted to blood that could regulate skeletal muscle phenotypes in multiple solid cancers. Tumor proteins having significant pan-cancer associations with muscle were referenced against secretome proteins secreted to blood from the Human Protein Atlas, then verified as increased in paired tumor vs. normal tissues in pan-cancer manner. This workflow revealed seven secreted proteins from cancers afflicting kidneys, head and neck, lungs and pancreas that classified as protein-binding activity modulator, extracellular matrix protein or intercellular signaling molecule. Concordance of these biomarkers with validated molecular signatures of cachexia and senescence supported relevance to muscle and cachexia disease biology, and high tumor expression of the biomarker set associated with lower overall survival. In this article, we discuss avenues by which skeletal muscle and cachexia may be regulated by these candidate pan-cancer proteins secreted to blood, and conceptualize a strategy that considers them collectively as a biomarker signature with potential for refinement by data analytics and radiogenomics for predictive testing of future risk in a non-invasive, blood-based panel amenable to broad uptake and early management.

Systemic metabolic crosstalk as driver of cancer cachexia

Cachexia is a complex metabolic disorder characterized by negative energy balance due to increased consumption and lowered intake, leading to progressive tissue wasting and inefficient energy distribution. Once considered as passive bystander, metabolism is now acknowledged as a regulator of biological functions and disease progression. This shift in perspective mirrors the evolving understanding of cachexia itself, no longer viewed merely as a secondary consequence of cancer but as an active process. However, metabolic dysregulations in cachexia are currently studied in an organ-specific manner, failing to be fully integrated into a comprehensive framework that explains their functional roles in disease progression. Thus, in this review, we aim to provide a general overview of the various metabolic alterations with a potential systemic impact.

Theoretical framework and emerging challenges of lipid metabolism in cancer

Elevated lipid metabolism is one of hallmarks of malignant tumors. Lipids not only serve as essential structural components of biological membranes but also provide energy and substrates for the proliferation of cancer cells and tumor growth. Cancer cells meet their lipid needs by coordinating the processes of lipid absorption, synthesis, transport, storage, and catabolism. As research in this area continues to deepen, numerous new discoveries have emerged, making it crucial for scientists to stay informed about the developments of cancer lipid metabolism. In this review, we first discuss relevant concepts and theories or assumptions that help us understand the lipid metabolism and -based cancer therapies. We then systematically summarize the latest advancements in lipid metabolism including new mechanisms, novel targets, and up-to-date pre-clinical and clinical investigations of anti-cancer treatment with lipid metabolism targeted drugs. Finally, we emphasize emerging research directions and therapeutic strategies, and discuss future prospective and emerging challenges. This review aims to provide the latest insights and guidance for research in the field of cancer lipid metabolism.

The RNA-binding protein HuR impairs adipose tissue anabolism in pancreatic cancer cachexia

Background

Cachexia is defined by chronic loss of fat and muscle, is a frequent complication of pancreatic ductal adenocarcinoma (PDAC), and negatively impacts patient outcomes. Nutritional supplementation cannot fully reverse tissue wasting, and the mechanisms underlying this phenotype are unclear. This work aims to define the relative contributions of catabolism and anabolism to adipose wasting in PDAC-bearing mice. Human antigen R (HuR) is an RNA-binding protein recently shown to suppress adipogenesis. We hypothesize that fat wasting results from a loss of adipose anabolism driven by increased HuR activity in adipocytes of PDAC-bearing mice.

Methods

Adult C57BL/6J mice received orthotopic PDAC cell (Kras G12D ; p53 R172H/+ ; Pdx1-cre) (OT-PDAC) or PBS (sham) injections. Mice exhibiting moderate cachexia (9 days after injection) were fasted for 24h, or fasted 24h and refed 24h before euthanasia. A separate cohort of PDAC mice were treated with an established HuR inhibitor (KH-3, 100 mg/kg) and subjected to the fast/refeed paradigm. We analyzed body mass, gross fat pad mass, and adipose tissue mRNA expression. We quantified lipolytic rate as the normalized quantity of glycerol released from 3T3-L1 adipocytes in vitro, and gonadal fat pads (gWAT) ex vivo.

Results

3T3-L1 adipocytes treated with PDAC cell conditioned media (CM) liberated less triglyceride into the culture media than control-treated adipocytes (-28.1%) and had lower expression of lipolysis and lipogenesis genes than control cells. PDAC gWAT cultured ex vivo displayed decreased lipolysis compared to sham gWAT (-54.7%). PDAC and sham mice lost equivalent fat mass after a 24h fast, however, PDAC mice could not restore inguinal fat pads (iWAT) (-40.5%) or gWAT (-31.8%) mass after refeeding. RNAseq revealed 572 differentially expressed genes in gWAT from PDAC compared to sham mice. Downregulated genes (n=126) were associated with adipogenesis (adj p=0.05), and expression of adipogenesis master regulators Pparg and Cebpa were reduced in gWAT from PDAC mice. Immunohistochemistry revealed increased HuR staining in gWAT (+74.9%) and iWAT (+41.2%) from PDAC mice. Inhibiting HuR binding restored lipogenesis in refed animals with a concomitant increase in iWAT mass (+131.7%) and genes regulating adipogenesis (Pparγ, Cebpa, Retn, Adipoq, Fasn).

Conclusions

Our work highlights deficient adipose anabolism as a driver of wasting in 3T3-L1 adipocytes treated with PDAC conditioned media and OT-PDAC mice. The small molecule KH3, which disrupts HuR binding, was sufficient to restore adipogenic and lipogenic gene expression and prevent adipose wasting. This highlights HuR as a potentially targetable regulatory node for adipose anabolism in cancer cachexia.

Liposomal Codelivery of Doxorubicin and Curcumin Sensitizes Antitumor Activity and Reduces Tumor Metastasis

Multidrug resistance (MDR) is a major obstacle to traditional cancer treatment using chemotherapeutic agents like doxorubicin (DOX). MDR affects drug dosage regimens and enables the recurrence and metastasis of cancer. Because DOX causes severe side effects at high dosages, it is important to use an MDR modulator to make cancer cells sensitive to DOX. This work focused on a liposome-based codelivery system containing curcumin (CUR) and DOX, focusing on CUR as an MDR modulator. The synergistic effect was maximized when the ratio of DOX and CUR was 1:1, and the synthesis of liposomal drugs was successfully verified. In addition, a successful MDR reversal effect was demonstrated through rhodamine 123 assay, Western blotting, and immunofluorescence. Compared to the conventional DOX treatment, the dual-drug treatment exhibits a significantly improved anticancer effect. In the murine metastasis 4T1 IP tumor model, the dual-drug-encapsulating liposomes successfully suppressed tumor growth and reversed the tumoral effect (omental tumor metastasis, fat, and muscle weight loss) into a normal state.

Cancer cachexia: multilevel metabolic dysfunction

Cancer cachexia is a complex metabolic disorder marked by unintentional body weight loss or 'wasting' of body mass, driven by multiple aetiological factors operating at various levels. It is associated with many malignancies and significantly contributes to cancer-related morbidity and mortality. With emerging recognition of cancer as a systemic disease, there is increasing awareness that understanding and treatment of cancer cachexia may represent a crucial cornerstone for improved management of cancer. Here, we describe the metabolic changes contributing to body wasting in cachexia and explain how the entangled action of both tumour-derived and host-amplified processes induces these metabolic changes. We discuss energy homeostasis and possible ways that the presence of a tumour interferes with or hijacks physiological energy conservation pathways. In that context, we highlight the role played by metabolic cross-talk mechanisms in cachexia pathogenesis. Lastly, we elaborate on the challenges and opportunities in the treatment of this devastating paraneoplastic phenomenon that arise from the complex and multifaceted metabolic cross-talk mechanisms and provide a status on current and emerging therapeutic approaches.

Hyperactive browning and hypermetabolism: potentially dangerous element in critical illness

Brown/beige adipose tissue has attracted much attention in previous studies because it can improve metabolism and combat obesity through non-shivering thermogenesis. However, recent studies have also indicated that especially in critical illness, overactivated brown adipose tissue or extensive browning of white adipose tissue may bring damage to individuals mainly by exacerbating hypermetabolism. In this review, the phenomenon of fat browning in critical illness will be discussed, along with the potential harm, possible regulatory mechanism and corresponding clinical treatment options of the induction of fat browning. The current research on fat browning in critical illness will offer more comprehensive understanding of its biological characteristics, and inspire researchers to develop new complementary treatments for the hypermetabolic state that occurs in critically ill patients.

Bidirectional association between perioperative skeletal muscle and subcutaneous fat in colorectal cancer patients and their prognostic significance

Introduction

Low skeletal muscle mass and high adipose tissue coexist across the body weight spectrum and independently predict the survival ratio of colorectal cancer (CRC) patients. This combination may lead to a mutually exacerbating vicious cycle. Tumor-associated metabolic conditions primarily affect subcutaneous adipose tissue, but the nature and direction of its relationship with skeletal muscle are unclear. This study aims to examine the bidirectional causal relationship between skeletal muscle index (SMI) and subcutaneous fat index (SFI) during the perioperative period in CRC patients; as well as to validate the association between perioperative SMI, SFI, and CRC prognosis.

Methods

This population-based retrospective cohort study included patients with stage I-III colorectal cancer who underwent radical resection at the Third Affiliated Hospital of Kunming Medical University between September 2012 and February 2019. Based on inclusion and exclusion criteria, 1,448 patients were analyzed. Preoperative (P1), 2 months postoperative (P2), and 5 months postoperative (P3) CT scans were collected to evaluate the skeletal muscle index (SMI; muscle area at the third lumbar vertebra divided by height squared) and subcutaneous fat index (SFI; subcutaneous fat area at the third lumbar vertebra divided by height squared). A random intercept cross-lagged panel model (RI-CLPM) was used to examine the intra-individual relationship between SMI and SFI, and Cox regression was employed to assess the association between SMI, SFI, recurrence-free survival (RFS), and overall survival (OS).

Results

The median age at diagnosis was 59.00 years (IQR: 51.00-66.00), and 587 patients (40.54%) were female. RI-CLPM analysis revealed a negative correlation between SFI and subsequent SMI at the individual level: P1-P2 (β = -0.372, p = 0.038) and P2-P3 (β = -0.363, p = 0.001). SMI and SFI showed a negative correlation during P1-P2 (β = -0.363, p = 0.001) but a positive correlation during P2-P3 (β = 0.357, p = 0.006). No significant correlation was found between the random intercepts of SFI and SMI at the between-person level (r = 0.157, p = 0.603). The Cox proportional hazards multivariate regression model identified that patients with elevated SFI had poorer recurrence-free survival (HR, 1.24; 95% CI: 1.00-1.55). Compared to patients with normal preoperative SMI and SFI, those with low SMI or high SFI had poorer recurrence-free survival (HR, 1.26; 95% CI: 1.03-1.55) and overall survival (HR, 1.39; 95% CI: 1.04-1.87). However, no significant association between SMI and SFI and the prognosis of colorectal cancer patients was observed postoperatively.

Conclusion

In CRC patients, preoperative muscle loss leads to postoperative fat accumulation, exacerbating muscle loss in a feedback loop. Elevated preoperative SFI predicts poorer survival outcomes. Monitoring SMI and SFI is crucial as prognostic indicators, despite non-significant postoperative associations. Further research is needed to improve patient outcomes.

Lipolysis engages CD36 to promote ZBP1-mediated necroptosis-impairing lung regeneration in COPD

Lung parenchyma destruction represents a severe condition commonly found in chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality worldwide. Promoting lung regeneration is crucial for achieving clinical improvement. However, no therapeutic drugs are approved to improve the regeneration capacity due to incomplete understanding of the underlying pathogenic mechanisms. Here, we identify a positive feedback loop formed between adipose triglyceride lipase (ATGL)-mediated lipolysis and overexpression of CD36 specific to lung epithelial cells, contributing to disease progression. Genetic deletion of CD36 in lung epithelial cells and pharmacological inhibition of either ATGL or CD36 effectively reduce COPD pathogenesis and promote lung regeneration in mice. Mechanistically, disruption of the ATGL-CD36 loop rescues Z-DNA binding protein 1 (ZBP1)-induced cell necroptosis and restores WNT/β-catenin signaling. Thus, we uncover a crosstalk between lipolysis and lung epithelial cells, suggesting the regenerative potential for therapeutic intervention by targeting the ATGL-CD36-ZBP1 axis in COPD.

IL36G-producing neutrophil-like monocytes promote cachexia in cancer

Most patients with advanced cancer develop cachexia, a multifactorial syndrome characterized by progressive skeletal muscle wasting. Despite its catastrophic impact on survival, the critical mediators responsible for cancer cachexia development remain poorly defined. Here, we show that a distinct subset of neutrophil-like monocytes, which we term cachexia-inducible monocytes (CiMs), emerges in the advanced cancer milieu and promotes skeletal muscle loss. Unbiased transcriptome analysis reveals that interleukin 36 gamma (IL36G)-producing CD38+ CiMs are induced in chronic monocytic blood cancer characterized by prominent cachexia. Notably, the emergence of CiMs and the activation of CiM-related gene signatures in monocytes are confirmed in various advanced solid cancers. Stimuli of toll-like receptor 4 signaling are responsible for the induction of CiMs. Genetic inhibition of IL36G-mediated signaling attenuates skeletal muscle loss and rescues cachexia phenotypes in advanced cancer models. These findings indicate that the IL36G-producing subset of neutrophil-like monocytes could be a potential therapeutic target in cancer cachexia.

Cancer cachexia: biomarkers and the influence of age

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

The Different Shades of Thermogenic Adipose Tissue

PURPOSE OF REVIEW

By providing a concise overview of adipose tissue types, elucidating the regulation of adipose thermogenic capacity in both physiological contexts and chronic wasting diseases (a protracted hypermetabolic state that precipitates sustained catabolism and consequent progressive corporeal atrophy), and most importantly, delving into the ongoing discourse regarding the role of adipose tissue thermogenic activation in chronic wasting diseases, this review aims to provide researchers with a comprehensive understanding of the field.

RECENT FINDINGS

Adipose tissue, traditionally classified as white, brown, and beige (brite) based on its thermogenic activity and potential, is intricately regulated by complex mechanisms in response to exercise or cold exposure. This regulation is adipose depot-specific and dependent on the duration of exposure. Excessive thermogenic activation of adipose tissue has been observed in chronic wasting diseases and has been considered a pathological factor that accelerates disease progression. However, this conclusion may be confounded by the detrimental effects of excessive lipolysis. Recent research also suggests that such activation may play a beneficial role in the early stages of chronic wasting disease and provide potential therapeutic effects. A more comprehensive understanding of the changes in adipose tissue thermogenesis under physiological and pathological conditions, as well as the underlying regulatory mechanisms, is essential for the development of novel interventions to improve health and prevent disease.

A molecular pathway for cancer cachexia-induced muscle atrophy revealed at single-nucleus resolution

Cancer cachexia is a prevalent and often fatal wasting condition that cannot be fully reversed with nutritional interventions. Muscle atrophy is a central component of the syndrome, but the mechanisms whereby cancer leads to skeletal muscle atrophy are not well understood. We performed single-nucleus multi-omics on skeletal muscles from a mouse model of cancer cachexia and profiled the molecular changes in cachexic muscle. Our results revealed the activation of a denervation-dependent gene program that upregulates the transcription factor myogenin. Further studies showed that a myogenin-myostatin pathway promotes muscle atrophy in response to cancer cachexia. Short hairpin RNA inhibition of myogenin or inhibition of myostatin through overexpression of its endogenous inhibitor follistatin prevented cancer cachexia-induced muscle atrophy in mice. Our findings uncover a molecular basis of muscle atrophy associated with cancer cachexia and highlight potential therapeutic targets for this disorder.

Epinephrine promotes breast cancer metastasis through a ubiquitin-specific peptidase 22-mediated lipolysis circuit

Chronic stress-induced epinephrine (EPI) accelerates breast cancer progression and metastasis, but the molecular mechanisms remain unclear. Herein, we found a strong positive correlation between circulating EPI levels and the tumoral expression of ubiquitin-specific peptidase 22 (USP22) in patients with breast cancer. USP22 facilitated EPI-induced breast cancer progression and metastasis by enhancing adipose triglyceride lipase (ATGL)-mediated lipolysis. Targeted USP22 deletion decreased ATGL expression and lipolysis, subsequently inhibiting EPI-mediated breast cancer lung metastasis. USP22 acts as a bona fide deubiquitinase for the Atgl gene transcription factor FOXO1, and EPI architects a lipolysis signaling pathway to stabilize USP22 through AKT-mediated phosphorylation. Notably, USP22 phosphorylation levels are positively associated with EPI and with downstream pathways involving both FOXO1 and ATGL in breast cancers. Pharmacological USP22 inhibition synergized with β-blockers in treating preclinical xenograft breast cancer models. This study reveals a molecular pathway behind EPI's tumor-promoting effects and provides a strong rationale for combining USP22 inhibition with β-blockers to treat aggressive breast cancer.

Exosomal miRNA 16-5p/29a-3p from pancreatic cancer induce adipose atrophy by inhibiting adipogenesis and promoting lipolysis

Over 80% of the patients with pancreatic ductal adenocarcinoma (PDAC) have cachexia/wasting syndrome. Cachexia is associated with reduced survival, decreased quality of life, and higher metastasis rates. Here, we demonstrate that fat loss is the earliest feature of PDAC-exosome-induced cachexia. MicroRNA sequencing of exosomal components from normal and cancer-derived exosomes revealed enrichment of miR-16-5p, miR-21-5p, miR-29a-3p, and miR-125b-5p in serum exosomes of mice harboring PDAC and patients with PDAC. Further, miR-16-5p and miR-29a-3p inhibited adipogenesis through decreasing Erlin2 and Cmpk1 expression which downregulates C/EBPβ and PPARγ. Synergistically, miR-29a-3p promotes lipolysis through increasing ATGL expression by suppressing MCT1 expression. Furthermore, PDAC-exosomes deprived of miR-16-5p and miR-29a-3p fail to induce fat loss. Hence, miR-16-5p and miR-29a-3p exosomal miRs are essential for PDAC-induced fat loss. Thus, we unravel that PDAC induces adipose atrophy via exosomal miRs. This knowledge may provide new diagnostic and therapeutic strategies for PDAC-induced cachexia.

Epigallocatechin gallate protects against fat and muscle atrophy in B16BL6 melanoma-bearing mice on a high-fat diet

AIMS

Epidemiological evidence indicates that there is a substantial association between body mass index (BMI) and at least ten forms of cancer, including melanoma, and BMI imbalance contributes to the poor survival rate of cancer patients before and after therapy. Nevertheless, few pharmacological studies on models of obesity and cancer have been reported. In this study, we administered epigallocatechin gallate (EGCG) to B16BL6 tumor-bearing mice that received a high-fat diet (HFD) to examine its impact.

METHODS

B16BL6 tumor-bearing mice were fed a HFD. Body weight and food intake were documented every week. We conducted a Western blot analysis to examine the protein levels in the tumor, gastrocnemius (GAS), and tibialis anterior (TA) muscles, as well as the inguinal and epididymal white adipose tissues (iWAT and eWAT).

KEY FINDINGS

EGCG has been shown to have anti-cancer effects equivalent to those of cisplatin, a chemotherapy drug. Furthermore, EGCG protected against the loss of epidydimal white adipose tissue by regulating protein levels of lipolysis factors of adipose triglyceride lipase and hormone-sensitive lipase as well as WAT browning factors of uncoupling protein 1, as opposed to cisplatin. EGCG was shown to reduce the protein levels of muscular atrophy factors of muscle RING-finger protein-1, whereas cisplatin did not contribute to rescuing the atrophy of TA and GAS muscles.

CONCLUSION

Taken together, our findings indicate that EGCG has a preventive effect against cachexia symptoms and has anti-cancer effects similar to those of cisplatin in tumor-bearing mice fed a high-fat diet.

The effect of hyperlipidemia on overall survival in patients with cancer was differentiated by BMI and hyperlipidemia type

BACKGROUND AND AIMS

The impact of lipids on the overall survival (OS) of patients with malignancy has not yet been clarified. This study aimed to evaluate the effect of hyperlipidemia on the OS among Chinese patients based on Body Mass Index (BMI) stratifications and hyperlipidemia types.

METHOD

The patients in this study were derived from the Investigation of the Nutrition Status and Clinical Outcome of Common Cancers (INSCOC) trial. Kaplan-Meier was used to draw the survival curve, and the log-rank test was used to estimate the survival rates between each group. Cox proportional hazards regression models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

A total of 9054 patients were included in the final study, with a median age of 59 years, and 55.3% (5004) of them were males. Regarding types of hyperlipidemia, only low high-density lipoprotein was an independent risk factor for the prognosis of all patients (HR = 1.35, 95% CI: 1.25-1.45, P < 0.001), while high total cholesterol (HR = 1.01, 95% CI: 0.90-1.15, P = 0.839) and high low-density lipoprotein (HR = 1.03, 95%CI: 0.91-1.16, P = 0.680) were not. In terms of BMI stratification, the effect of triglycerides on prognosis varied; high triglycerides were an independent risk factor for the prognosis of underweight patients (HR = 1.56, 95% CI:1.05-2.32, P = 0.027) and a protective factor for overweight patients (HR = 0.75, 95% CI: 0.63-0.89, P = 0.001). However, for normal-weight patients, there was no significant statistical difference (HR = 0.88, 95%CI: 0.75-1.03, P = 0.108).

CONCLUSIONS

The impact of hyperlipidemia on the OS among patients with cancer varied by different BMI and hyperlipidemia types. BMI and hyperlipidemia type ought to be considered in combination to estimate the prognosis of patients with malignancy.

AMPK as a mediator of tissue preservation: time for a shift in dogma?

Ground-breaking discoveries have established 5'-AMP-activated protein kinase (AMPK) as a central sensor of metabolic stress in cells and tissues. AMPK is activated through cellular starvation, exercise and drugs by either directly or indirectly affecting the intracellular AMP (or ADP) to ATP ratio. In turn, AMPK regulates multiple processes of cell metabolism, such as the maintenance of cellular ATP levels, via the regulation of fatty acid oxidation, glucose uptake, glycolysis, autophagy, mitochondrial biogenesis and degradation, and insulin sensitivity. Moreover, AMPK inhibits anabolic processes, such as lipogenesis and protein synthesis. These findings support the notion that AMPK is a crucial regulator of cell catabolism. However, studies have revealed that AMPK's role in cell homeostasis might not be as unidirectional as originally thought. This Review explores emerging evidence for AMPK as a promoter of cell survival and an enhancer of anabolic capacity in skeletal muscle and adipose tissue during catabolic crises. We discuss AMPK-activating interventions for tissue preservation during tissue wasting in cancer-associated cachexia and explore the clinical potential of AMPK activation in wasting conditions. Overall, we provide arguments that call for a shift in the current dogma of AMPK as a mere regulator of cell catabolism, concluding that AMPK has an unexpected role in tissue preservation.

Low expression of ELOVL6 may be involved in fat loss in white adipose tissue of cancer-associated cachexia

BACKGROUND

Cancer-associated cachexia (CAC) arises from malignant tumors and leads to a debilitating wasting syndrome. In the pathophysiology of CAC, the depletion of fat plays an important role. The mechanisms of CAC-induced fat loss include the enhancement of lipolysis, inhibition of lipogenesis, and browning of white adipose tissue (WAT). However, few lipid-metabolic enzymes have been reported to be involved in CAC. This study hypothesized that ELOVL6, a critical enzyme for the elongation of fatty acids, may be involved in fat loss in CAC.

METHODS

Transcriptome sequencing technology was used to identify CAC-related genes in the WAT of a CAC rodent model. Then, the expression level of ELOVL6 and the fatty acid composition were analyzed in a large clinical sample. Elovl6 was knocked down by siRNA in 3T3-L1 mouse preadipocytes to compare with wild-type 3T3-L1 cells treated with tumor cell conditioned medium.

RESULTS

In the WAT of patients with CAC, a significant decrease in the expression of ELOVL6 was found, which was linearly correlated with the extent of body mass reduction. Gas chromatographic analysis revealed an increase in palmitic acid (C16:0) and a decrease in linoleic acid (C18:2n-6) in these tissue samples. After treatment with tumor cell-conditioned medium, 3T3-L1 mouse preadipocytes showed a decrease in Elovl6 expression, and Elovl6-knockdown cells exhibited a reduction in preadipocyte differentiation and lipogenesis. Similarly, the knockdown of Elovl6 in 3T3-L1 cells resulted in a significant increase in palmitic acid (C16:0) and a marked decrease in oleic acid (C18:1n-9) content.

CONCLUSION

Overall, the expression of ELOVL6 was decreased in the WAT of CAC patients. Decreased expression of ELOVL6 might induce fat loss in CAC patients by potentially altering the fatty acid composition of adipocytes. These findings suggest that ELOVL6 may be used as a valuable biomarker for the early diagnosis of CAC and may hold promise as a target for future therapies.

Tumoral acidosis promotes adipose tissue depletion by fostering adipocyte lipolysis

OBJECTIVE

Tumour progression drives profound alterations in host metabolism, such as adipose tissue depletion, an early event of cancer cachexia. As fatty acid consumption by cancer cells increases upon acidosis of the tumour microenvironment, we reasoned that fatty acids derived from distant adipose lipolysis may sustain tumour fatty acid craving, leading to the adipose tissue loss observed in cancer cachexia.

METHODS

To evaluate the pro-lipolytic capacities of acid-exposed cancer cells, primary mouse adipocytes from subcutaneous and visceral adipose tissue were exposed to pH-matched conditioned medium from human and murine acid-exposed cancer cells (pH 6.5), compared to naive cancer cells (pH 7.4). To further address the role of tumoral acidosis on adipose tissue loss, a pH-low insertion peptide was injected into tumour-bearing mice, and tumoral acidosis was neutralised with a sodium bicarbonate buffer. Prolipolytic mediators were identified by transcriptomic approaches and validated on murine and human adipocytes.

RESULTS

Here, we reveal that acid-exposed cancer cells promote lipolysis from subcutaneous and visceral adipocytes and that dampening acidosis in vivo inhibits adipose tissue depletion. We further found a set of well-known prolipolytic factors enhanced upon acidosis adaptation and unravelled a role for β-glucuronidase (GUSB) as a promising new actor in adipocyte lipolysis.

CONCLUSIONS

Tumoral acidosis promotes the mobilization of fatty acids derived from adipocytes via the release of soluble factors by cancer cells. Our work paves the way for therapeutic approaches aimed at tackling cachexia by targeting the tumour acidic compartment.

Impaired Remodeling of White Adipose Tissue in Obesity and Aging: From Defective Adipogenesis to Adipose Organ Dysfunction

The adipose organ adapts and responds to internal and environmental stimuli by remodeling both its cellular and extracellular components. Under conditions of energy surplus, the subcutaneous white adipose tissue (WAT) is capable of expanding through the enlargement of existing adipocytes (hypertrophy), followed by de novo adipogenesis (hyperplasia), which is impaired in hypertrophic obesity. However, an impaired hyperplastic response may result from various defects in adipogenesis, leading to different WAT features and metabolic consequences, as discussed here by reviewing the results of the studies in animal models with either overexpression or knockdown of the main molecular regulators of the two steps of the adipogenesis process. Moreover, impaired WAT remodeling with aging has been associated with various age-related conditions and reduced lifespan expectancy. Here, we delve into the latest advancements in comprehending the molecular and cellular processes underlying age-related changes in WAT function, their involvement in common aging pathologies, and their potential as therapeutic targets to influence both the health of elderly people and longevity. Overall, this review aims to encourage research on the mechanisms of WAT maladaptation common to conditions of both excessive and insufficient fat tissue. The goal is to devise adipocyte-targeted therapies that are effective against both obesity- and age-related disorders.

Excessive fat expenditure in MCT-induced heart failure rats is associated with BMAL1/REV-ERBα circadian rhythmic loop disruption

Fat loss predicts adverse outcomes in advanced heart failure (HF). Disrupted circadian clocks are a primary cause of lipid metabolic issues, but it's unclear if this disruption affects fat expenditure in HF. To address this issue, we investigated the effects of disruption of the BMAL1/REV-ERBα circadian rhythmic loop on adipose tissue metabolism in HF.50 Wistar rats were initially divided into control (n = 10) and model (n = 40) groups. The model rats were induced with HF via monocrotaline (MCT) injections, while the control group received equivalent solvent injections. After establishing the HF model, the model group was further subdivided into four groups: normal rhythm (LD), inverted rhythm (DL), lentivirus vector carrying Bmal1 short hairpin RNA (LV-Bmal1 shRNA), and empty lentivirus vector control (LV-Control shRNA) groups, each with 10 rats. The DL subgroup was exposed to a reversed light-dark cycle of 8 h: 16 h (dark: light), while the rest adhered to normal light-dark conditions (light: dark 12 h: 12 h). Histological analyses were conducted using H&E, Oil Red O, and Picrosirius red stains to examine adipose and liver tissues. Immunohistochemical staining, RT-qPCR, and Western blotting were performed to detect markers of lipolysis, lipogenesis, and beiging of white adipose tissue (WAT), while thermogenesis indicators were detected in brown adipose tissue (BAT). The LD group rats exhibited decreased levels of BMAL1 protein, increased levels of REV-ERBα protein, and disrupted circadian circuits in adipose tissue compared to controls. Additionally, HF rats showed reduced adipose mass and increased ectopic lipid deposition, along with smaller adipocytes containing lower lipid content and fibrotic adipose tissue. In the LD group WAT, expression of ATGL, HSL, PKA, and p-PKA proteins increased, alongside elevated mRNA levels of lipase genes (Hsl, Atgl, Peripilin) and FFA β-oxidation genes (Cpt1, acyl-CoA). Conversely, lipogenic gene expression (Scd1, Fas, Mgat, Dgat2) decreased, while beige adipocyte markers (Cd137, Tbx-1, Ucp-1, Zic-1) and UCP-1 protein expression increased. In BAT, HF rats exhibited elevated levels of PKA, p-PKA, and UCP-1 proteins, along with increased expression of thermogenic genes (Ucp-1, Pparγ, Pgc-1α) and lipid transportation genes (Cd36, Fatp-1, Cpt-1). Plasma NT-proBNP levels were higher in LD rats, accompanied by elevated NE and IL-6 levels in adipose tissue. Remarkably, morphologically, the adipocytes in the DL and LV-Bmal1 shRNA groups showed reduced size and lower lipid content, while lipid deposition in the liver was more pronounced in these groups compared to the LD group. At the gene/protein level, the BMAL1/REV-ERBα circadian loop exhibited severe disruption in LV-Bmal1 shRNA rats compared to LD rats. Additionally, there was increased expression of lipase genes, FFA β oxidation genes, and beige adipocyte markers in WAT, as well as higher expression of thermogenic genes and lipid transportation genes in BAT. Furthermore, plasma NT-proBNP levels and adipose tissue levels of NE and IL-6 were elevated in LV-Bmal1 shRNA rats compared with LD rats. The present study demonstrates that disruption of the BMAL1/REV-ERBα circadian rhythmic loop is associated with fat expenditure in HF. This result suggests that restoring circadian rhythms in adipose tissue may help counteract disorders of adipose metabolism and reduce fat loss in HF.

Activation of GPR81 by lactate drives tumour-induced cachexia

Cachexia affects 50-80% of patients with cancer and accounts for 20% of cancer-related death, but the underlying mechanism driving cachexia remains elusive. Here we show that circulating lactate levels positively correlate with the degree of body weight loss in male and female patients suffering from cancer cachexia, as well as in clinically relevant mouse models. Lactate infusion per se is sufficient to trigger a cachectic phenotype in tumour-free mice in a dose-dependent manner. Furthermore, we demonstrate that adipose-specific G-protein-coupled receptor (GPR)81 ablation, similarly to global GPR81 deficiency, ameliorates lactate-induced or tumour-induced adipose and muscle wasting in male mice, revealing adipose GPR81 as the major mediator of the catabolic effects of lactate. Mechanistically, lactate/GPR81-induced cachexia occurs independently of the well-established protein kinase A catabolic pathway, but it is mediated by a signalling cascade sequentially activating Gi-Gβγ-RhoA/ROCK1-p38. These findings highlight the therapeutic potential of targeting GPR81 for the treatment of this life-threatening complication of cancer.

[Cancer-associated cachexia: an unresolved disease]

Cachexia is a systemic wasting condition associated to advanced phases of many cancers, which contributes to significant morbidity and mortality. It is mainly characterized by involuntary weight loss due to muscle wasting often associated with loss of adipose tissue, possibly leading to inanition and death, without treatment to date. Symptomatology covers a complex array of disorders (fatigue, inflammation, pain, anorexia, depression) related to multisystemic impairments progressively affecting numerous organs and tissues (muscle, adipose tissue, brain, immune system, gastrointestinal tract). The mechanisms of induction and progression of the disease, still poorly understood, involve inflammatory, metabolic, and neuroendocrine drivers, triggered by a variety of mediators originating from tumor, tumor-host interactions, and inter-organ crosstalk.

Curcuma xanthorrhiza extract and xanthorrhizol ameliorate cancer-induced adipose wasting in CT26-bearing mice by regulating lipid metabolism and adipose tissue browning

Background

Cancer cachexia-characterized by anorexia, body weight loss, skeletal muscle atrophy, and fat loss-affects nearly 80% of cancer patients and accounts for 20% of cancer deaths. Curcuma xanthorrhiza, known as Java turmeric, and its active compound xanthorrhizol (XAN) exhibit anticancer, anti-inflammatory, and antioxidant properties. However, the ameliorative effects of C. xanthorrhiza extract (CXE) and XAN on cancer-associated adipose atrophy remain unexplored. This study aimed to evaluate the therapeutic effects of CXE and XAN on cancer cachexia-induced adipose tissue wasting in CT26 tumor-bearing mice.

Methods

CT26 cells were injected subcutaneously into the right flank of BALB/c mice to establish a cancer cachexia model. To evaluate the inhibitory effects of CXE and XAN on cancer cachexia, 50 and 100 mg/kg CXE and 15 mg/kg XAN were administered orally every day for 1 week.

Results

CXE and XAN administration significantly attenuated the loss of body weight and epidydimal fat mass by cancer cachexia. In epididymal adipose tissues, administration of CXE or XAN inhibited white adipose tissue browning by repressing expression of the thermogenic genes. Simultaneously, CXE or XAN attenuated fat catabolism through the downregulation of lipolytic genes. The administration of CXE or XAN induced the expression of genes associated with adipogenesis and lipogenesis-related genes. Moreover, CXE or XAN treatment was associated with maintaining metabolic homeostasis; regulating the expression of adipokines and AMP-activated protein kinase (AMPK).

Conclusions

CXE and XAN mitigate cancer-induced adipose tissue atrophy, primarily by modulating lipid metabolism and WAT browning, indicating their therapeutic potential for cachectic cancer patients.

Energy preservation for skeletal muscles: Shenqi Fuzheng injection prevents tissue wasting and restores bioenergetic profiles in a mouse model of chemotherapy-induced cachexia

BACKGROUND

Energy deficiency is the characteristic of chemotherapy-induced cachexia (CIC) which is manifested by muscle wasting. glycolysis, tricarboxylic acid (TCA) cycle, and lipid metabolism are central to muscle bioenergy production, which is vulnerable to chemotherapy during cancer treatment. Recent investigations have spotlighted the potential of Shenqi Fuzheng injection (SQ), a Chinese proprietary medicine comprising Radix Codonopsis and Radix Astragali, in alleviating CIC. However, the specific effects of SQ on muscle energy metabolism remains less explored.

PURPOSE AND METHODS

Here, we integrated transcriptomics, spatial metabolomics, gas chromatography-mass spectrometry targeted quantitative analysis, and transmission electron microscopy techniques, combined with Seahorse live-cell metabolic analysis to reveal the changes in genes and pathways related to energy metabolism in the CIC model and SQ's protective effects at molecular and functional levels.

RESULTS

Our data showed that chemotherapeutic agents caused glycolysis imbalance, which further leads to metabolic derangements of TCA cycle intermediates. SQ maintained glycolysis balance by facilitating pyruvate fluxing to mitochondria for more efficient bioenergy production, which involved a dual effect on promoting functions of mitochondrial pyruvate dehydrogenase complexes and inhibiting lactate dehydrogenase for lactate production. As a result of the sustained pyruvate level achieved by SQ administration, glycolysis balance was maintained, which further led to the preservation of mitochondrial integrity and function of electron transport chain, thereby, ensuring the normal operation of the TCA cycle and the proper synthesis of adenosine triphosphate (ATP). The above results were further validated using the Seahorse live-cell assay.

CONCLUSION

In conclusion, our study highlights SQ as a promising strategy for CIC management, emphasizing its ability to harmonize the homeostasis of the muscle bioenergetic profile. Beyond its therapeutic implications, this study also offers a novel perspective for the development of innovative treatments in the realm of herbal medicine.

Progressive, multi-organ, and multi-layered nature of cancer cachexia

Cancer cachexia is a complex, multifaceted condition that negatively impacts the health, treatment efficacy, and economic status of cancer patients. The management of cancer cachexia is an essential clinical need. Cancer cachexia is currently defined mainly according to the severity of weight loss and sarcopenia (i.e., macrosymptoms). However, such macrosymptoms may be insufficient to give clinicians clues on how to manage this condition as these symptoms appear at the late stage of cancer. We need to understand earlier events during the progression of cancer cachexia so as not to miss a clinical opportunity to control this complex syndrome. Recent research indicates that cancer-induced changes in the host are much wider than previously recognized, including disruption of liver function and the immune system. Furthermore, such changes are observed before the occurrence of visible distant metastases (i.e., in early, localized cancers). In light of these findings, we propose to expand the definition of cancer cachexia to include all cancer-induced changes to host physiology, including changes caused by early, localized cancers. This new definition of cancer cachexia can provide a new perspective on this topic, which can stimulate the research and development of novel cancer cachexia therapies.

Hsa_circ_0021205 enhances lipolysis via regulating miR-195-5p/HSL axis and drives malignant progression of glioblastoma

Abnormal lipid metabolism is an essential hallmark of glioblastoma. Hormone sensitive lipase (HSL), an important rate-limiting enzyme contributed to lipolysis, which was involved in aberrant lipolysis of glioblastoma, however, its definite roles and the relevant regulatory pathway have not been fully elucidated. Our investigations disclosed high expression of HSL in glioblastoma. Knock-down of HSL restrained proliferation, migration, and invasion of glioblastoma cells while adding to FAs could significantly rescue the inhibitory effect of si-HSL on tumor cells. Overexpression of HSL further promoted tumor cell proliferation and invasion. Bioinformatics analysis and dual-luciferase reporter assay were performed to predict and verify the regulatory role of ncRNAs on HSL. Mechanistically, hsa_circ_0021205 regulated HSL expression by sponging miR-195-5p, which further promoted lipolysis and drove the malignant progression of glioblastoma. Besides, hsa_circ_0021205/miR-195-5p/HSL axis activated the epithelial-mesenchymal transition (EMT) signaling pathway. These findings suggested that hsa_circ_0021205 promoted tumorigenesis of glioblastoma through regulation of HSL, and targeting hsa_circ_0021205/miR-195-5p/HSL axis can serve as a promising new strategy against glioblastoma.

Elevated 18F-FDG uptake in subcutaneous adipose tissue correlates negatively with nutritional status and prognostic survival in cachexia patients with gastric cancer

BACKGROUND

Browning of white adipose tissue is a crucial factor contributing to adipose loss in cachexia patients, detectable via 18F-Fluorodeoxyglucose (18F-FDG) uptake. The present study elucidates the clinical relevance of 18F-FDG uptake in the subcutaneous adipose tissue of gastric cancer patients, specifically focusing on adipose browning and its implications on patient clinical parameters and prognosis.

METHODS

This investigation encompassed 770 gastric cancer patients, with PET-CT imaging and clinical data meticulously combined. The 18F-FDG uptake in subcutaneous adipose tissue at the third lumbar layer was quantified, and its correlation with clinical parameters, particularly those related to nutritional status and fat metabolism, was examined. Kaplan-Meier curves were subsequently employed to probe the relationship between 18F-FDG uptake and overall survival.

RESULTS

Of the 770 gastric cancer patients, 252 exhibited cancer-associated cachexia, while 518 did not. Cachectic patients demonstrated elevated 18F-FDG uptake in subcutaneous adipose tissue relative to non-cachectic patients (P < 0.001). Increased 18F-FDG uptake was also correlated with reduced plasma concentrations of albumin, prealbumin, hemoglobin, platelets, cholesterol, apolipoprotein A, low-density lipoprotein, and elevated IL-6 concentrations (all P < 0.05). A significant inverse correlation was observed between 18F-FDG uptake and BMI, albumin, low-density lipoprotein, cholesterol, and apolipoprotein A (all P < 0.05). Patients with higher 18F-FDG uptake exhibited diminished overall survival rates compared to those with lower 18F-FDG uptake (P = 0.0065). Furthermore, 18F-FDG uptake in subcutaneous adipose tissue was an independent prognostic indicator in gastric cancer patients (P = 0.028).

CONCLUSIONS

Browning of subcutaneous adipose tissue was markedly elevated in cachectic gastric cancer patients compared to non-cachectic counterparts. Increased 18F-FDG uptake in subcutaneous adipose tissue in cachectic gastric cancer patients was inversely correlated with nutritional status and survival prognosis.

Unraveling the lost balance: Adrenergic dysfunction in cancer cachexia

Cancer cachexia, characterized by muscle wasting and widespread inflammation, poses a significant challenge for patients with cancer, profoundly impacting both their quality of life and treatment management. However, existing treatment modalities remain very limited, accentuating the necessity for innovative therapeutic interventions. Many recent studies demonstrated that changes in autonomic balance is a key driver of cancer cachexia. This review consolidates research findings from investigations into autonomic dysfunction across cancer cachexia, spanning animal models and patient cohorts. Moreover, we explore therapeutic strategies involving adrenergic receptor modulation through receptor blockers and agonists. Mechanisms underlying adrenergic hyperactivity in cardiac and adipose tissues, influencing tissue remodeling, are also examined. Looking ahead, we present a perspective for future research that delves into autonomic dysregulation in cancer cachexia. This comprehensive review highlights the urgency of advancing research to unveil innovative avenues for combatting cancer cachexia and improving patient well-being.

Leukemia inhibitory factor suppresses hepatic de novo lipogenesis and induces cachexia in mice

Cancer cachexia is a systemic metabolic syndrome characterized by involuntary weight loss, and muscle and adipose tissue wasting. Mechanisms underlying cachexia remain poorly understood. Leukemia inhibitory factor (LIF), a multi-functional cytokine, has been suggested as a cachexia-inducing factor. In a transgenic mouse model with conditional LIF expression, systemic elevation of LIF induces cachexia. LIF overexpression decreases de novo lipogenesis and disrupts lipid homeostasis in the liver. Liver-specific LIF receptor knockout attenuates LIF-induced cachexia, suggesting that LIF-induced functional changes in the liver contribute to cachexia. Mechanistically, LIF overexpression activates STAT3 to downregulate PPARα, a master regulator of lipid metabolism, leading to the downregulation of a group of PPARα target genes involved in lipogenesis and decreased lipogenesis in the liver. Activating PPARα by fenofibrate, a PPARα agonist, restores lipid homeostasis in the liver and inhibits LIF-induced cachexia. These results provide valuable insights into cachexia, which may help develop strategies to treat cancer cachexia.

Assessment of lipolysis biomarkers in adipose tissue of patients with gastrointestinal cancer

BACKGROUND

Adipose tissue metabolism may be impaired in patients with cancer. In particular, increased lipolysis was described in cancer-promoting adipose tissue atrophy. For this reason, we assessed the expression of the lipolysis-associated genes and proteins in subcutaneous adipose tissue (SAT) of gastrointestinal (GI) cancer patients compared to controls to verify their involvement in cancer, among different types of GI cancers, and in cachexia.

METHODS

We considered patients with GI cancer (gastric, pancreatic, and colorectal) at their first diagnosis, with/without cachexia, and controls with benign diseases. We collected SAT and total RNA was extracted and ATGL, HSL, PPARα, and MCP1 were analyzed by qRT-PCR. Western blot was performed to evaluate CGI-58, PLIN1 and PLIN5.

RESULTS

We found higher expression of ATGL and HSL in GI cancer patients with respect to controls (p ≤ 0.008) and a trend of increase for PPARα (p = 0.055). We found an upregulation of ATGL in GI cancer patients with cachexia (p = 0.033) and without cachexia (p = 0.017) vs controls. HSL was higher in patients with cachexia (p = 0.020) and without cachexia (p = 0.021), compared to controls. ATGL was upregulated in gastric cancer vs controls (p = 0.014) and higher HSL was found in gastric (p = 0.008) and in pancreatic cancer (p = 0.033) vs controls. At the protein level, we found higher CGI-58 in cancer vs controls (p = 0.019) and in cachectic vs controls (p = 0.029), as well as in gastric cancer vs controls (p = 0.027).

CONCLUSION

In our cohort of GI cancer patients, we found a modulation in the expression of genes and proteins involved in lipolysis, and differences were interestingly detected according to cancer type.

Convergent insulin and TGF-β signalling drives cancer cachexia by promoting aberrant fat body ECM accumulation in a Drosophila tumour model

In this study, we found that in the adipose tissue of wildtype animals, insulin and TGF-β signalling converge via a BMP antagonist short gastrulation (sog) to regulate ECM remodelling. In tumour bearing animals, Sog also modulates TGF-β signalling to regulate ECM accumulation in the fat body. TGF-β signalling causes ECM retention in the fat body and subsequently depletes muscles of fat body-derived ECM proteins. Activation of insulin signalling, inhibition of TGF-β signalling, or modulation of ECM levels via SPARC, Rab10 or Collagen IV in the fat body, is able to rescue tissue wasting in the presence of tumour. Together, our study highlights the importance of adipose ECM remodelling in the context of cancer cachexia.

Targeting dysregulated lipid metabolism in the tumor microenvironment

The reprogramming of lipid metabolism and its association with oncogenic signaling pathways within the tumor microenvironment (TME) have emerged as significant hallmarks of cancer. Lipid metabolism is defined as a complex set of molecular processes including lipid uptake, synthesis, transport, and degradation. The dysregulation of lipid metabolism is affected by enzymes and signaling molecules directly or indirectly involved in the lipid metabolic process. Regulation of lipid metabolizing enzymes has been shown to modulate cancer development and to avoid resistance to anticancer drugs in tumors and the TME. Because of this, understanding the metabolic reprogramming associated with oncogenic progression is important to develop strategies for cancer treatment. Recent advances provide insight into fundamental mechanisms and the connections between altered lipid metabolism and tumorigenesis. In this review, we explore alterations to lipid metabolism and the pivotal factors driving lipid metabolic reprogramming, which exacerbate cancer progression. We also shed light on the latest insights and current therapeutic approaches based on small molecular inhibitors and phytochemicals targeting lipid metabolism for cancer treatment. Further investigations are worthwhile to fully understand the underlying mechanisms and the correlation between altered lipid metabolism and carcinogenesis.

A novel antidiuretic hormone governs tumour-induced renal dysfunction

Maintenance of renal function and fluid transport are essential for vertebrates and invertebrates to adapt to physiological and pathological challenges. Human patients with malignant tumours frequently develop detrimental renal dysfunction and oliguria, and previous studies suggest the involvement of chemotherapeutic toxicity and tumour-associated inflammation1,2. However, how tumours might directly modulate renal functions remains largely unclear. Here, using conserved tumour models in Drosophila melanogaster3, we characterized isoform F of ion transport peptide (ITPF) as a fly antidiuretic hormone that is secreted by a subset of yki3SA gut tumour cells, impairs renal function and causes severe abdomen bloating and fluid accumulation. Mechanistically, tumour-derived ITPF targets the G-protein-coupled receptor TkR99D in stellate cells of Malpighian tubules-an excretory organ that is equivalent to renal tubules4-to activate nitric oxide synthase-cGMP signalling and inhibit fluid excretion. We further uncovered antidiuretic functions of mammalian neurokinin 3 receptor (NK3R), the homologue of fly TkR99D, as pharmaceutical blockade of NK3R efficiently alleviates renal tubular dysfunction in mice bearing different malignant tumours. Together, our results demonstrate a novel antidiuretic pathway mediating tumour-renal crosstalk across species and offer therapeutic opportunities for the treatment of cancer-associated renal dysfunction.

Deliberation on debilitating condition of cancer cachexia: Skeletal muscle wasting

BACKGROUND

Cancer cachexia is a debilitating syndrome associated with marked body loss because of muscular atrophy and fat loss. There are several mechanisms contributing to the pathogenesis of cachexia. The presence of the tumor releases cytokines from inflammatory and immune cells, which play a significant role in activating and deactivating certain pathways associated with protein, carbohydrate, and lipid metabolism. This review focuses on various cascades involving an imbalance between protein synthesis and degradation in the skeletal muscles.

OBJECTIVES

This study aimed to elucidate the mechanisms involved in skeletal muscle wasting phenomenon over the last few years.

METHODS

This article briefly overviews different pathways responsible for muscle atrophy in cancer cachexia. Studies published up to April 2023 were included. Important findings and study contributions were chosen and compiled using several databases including PubMed, Google Scholar, Science Direct, and ClinicalTrials.gov using relevant keywords.

RESULTS

Cancer cachexia is a complex disease involving multiple factors resulting in atrophy of skeletal muscles. Systemic inflammation, altered energy balance and carbohydrate metabolism, altered lipid and protein metabolism, and adipose tissue browning are some of the major culprits in cancer cachexia. Increased protein degradation and decreased protein synthesis lead to muscle atrophy. Changes in signaling pathway like ubiquitin-proteasome, autophagy, mTOR, AMPK, and IGF-1 also lead to muscle wasting. Physical exercise, nutritional supplementation, steroids, myostatin inhibitors, and interventions targeting on inflammation have been investigated to treat cancer cachexia. Some therapy showed positive results in preclinical and clinical settings, although more research on the efficacy and safety of the treatment should be done.

CONCLUSION

Muscle atrophy in cancer cachexia is the result of multiple complex mechanisms; as a result, a lot more research has been done to describe the pathophysiology of the disease. Targeted therapy and multimodal interventions can improve clinical outcomes for patients.

STAT3 Signalling Drives LDH Up-Regulation and Adiponectin Down-Regulation in Cachectic Adipocytes

Cachexia is a devastating pathology that worsens the quality of life and antineoplastic treatment outcomes of oncologic patients. Herein, we report that the secretome from murine colon carcinoma CT26 induces cachectic features in both murine and human adipocytes that are associated with metabolic alterations such as enhanced lactate production and decreased oxygen consumption. The use of oxamate, which inhibits lactate dehydrogenase activity, hinders the effects induced by CT26 secretome. Interestingly, the CT26 secretome elicits an increased level of lactate dehydrogenase and decreased expression of adiponectin. These modifications are driven by the STAT3 signalling cascade since the inhibition of STAT3 with WP1066 impedes the formation of the cachectic condition and the alteration of lactate dehydrogenase and adiponectin levels. Collectively, these findings show that STAT3 is responsible for the altered lactate dehydrogenase and adiponectin levels that, in turn, could participate in the worsening of this pathology and highlight a step forward in the comprehension of the mechanisms underlying the onset of the cachectic condition in adipocytes.

Carnosol analogue WK-63 alleviated cancer cachexia by inhibiting NF-κB and activating AKT pathways in muscle while inhibiting NF-κB and AMPK pathways in adipocyte

Cancer cachexia is a systemic metabolic disorder syndrome characterized by severe wasting of muscle and adipose tissues while is lack of effective therapeutic approaches. Carnosol (CS) was found in our previous study to exhibit ameliorating effects on cancer cachexia. In the present study, we designed and synthesized 49 CS analogues by structural modification of CS. Results of activity screening revealed that, among the analogues, WK-63 exhibited better effects than CS in ameliorating atrophy of C2C12 myotubes induced by conditioned medium of C26 tumor cells. WK-63 could also dose-dependently alleviate adipocyte lipolysis of mature 3 T3-L1 cells induced by C26 tumor cell conditioned medium. WK-63 alleviated myotube atrophy by inhibiting Nuclear Factor kappa-B (NF-κB) and activating the Protein Kinase B (AKT) signaling pathway, and also alleviated fat loss by inhibiting NF-κB and Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathways. Results of pharmacokinetic (PK) assay showed that, compared with other analogues, WK-63 exhibited longer half-life (T1/2) and mean residence time (MRTs), as well as a larger concentration curve area (AUC0-t). These findings suggested that WK-63 might exert optimal effects in vivo. In the C26 tumor-bearing mice model, administration of WK-63 ameliorated the body weight loss and also improved the weight loss of epididymal adipose tissue. WK-63 is expected to be a novel therapeutic option for the treatment of cancer cachexia.

Adipocyte lipolysis protects mice against Trypanosoma brucei infection

Trypanosoma brucei causes African trypanosomiasis, colonizing adipose tissue and inducing weight loss. Here we investigated the molecular mechanisms responsible for adipose mass loss and its impact on disease pathology. We found that lipolysis is activated early in infection. Mice lacking B and T lymphocytes fail to upregulate adipocyte lipolysis, resulting in higher fat mass retention. Genetic ablation of the rate-limiting adipose triglyceride lipase specifically from adipocytes (AdipoqCre/+-Atglfl/fl) prevented the stimulation of adipocyte lipolysis during infection, reducing fat mass loss. Surprisingly, these mice succumbed earlier and presented a higher parasite burden in the gonadal adipose tissue, indicating that host lipolysis limits parasite growth. Consistently, free fatty acids comparable with those of adipose interstitial fluid induced loss of parasite viability. Adipocyte lipolysis emerges as a mechanism controlling local parasite burden and affecting the loss of fat mass in African trypanosomiasis.

Prognostic role of body composition in peritoneal carcinomatosis patients undergoing cytoreduction and hyperthermic intraperitoneal chemotherapy

BACKGROUND

Bioelectric impedance analysis (BIA)-measured body composition and nutritional status have been used as prognostic indicators in various cancer cohorts. This study investigated whether BIA could provide information on prognosis in peritoneal carcinomatosis patients undergoing cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC).

METHODS

We retrospectively analyzed the data of 99 patients with preoperative BIA data among those who underwent CRS and HIPEC. The association between BIA-derived parameters and intraoperative peritoneal cancer index (PCI) score was assessed. Predictive analysis for the occurrence of postoperative morbidities including major complications (Clavien-Dindo classification 3-4) and re-admission within 30 days after surgery as well as 1 year mortality was also performed.

RESULTS

BIA-derived mineral (r = 0.224, p = 0.027), fat (r =  - 0.202, p = 0.048), and total body water (TBW)/fat-free mass (FFM) (r =  - 0.280, p = 0.005) showed significant associations with intraoperative PCI score. Lower TBW/FFM was an independent predictor of major postoperative complications (OR 0.047, 95% CI 0.003-0.749, p = 0.031) and re-admission (OR 0.094, 95% CI 0.014-0.657, p = 0.017) within 30 days after surgery. Higher fat mass was also independently associated with a higher risk of major postoperative complications (OR 1.120, 95% CI 1.006-1.248, p = 0.039) and re-admission (OR 1.123, 95% CI 1.024-1.230, p = 0.013). Intraoperative PCI score > 20 (OR 4.489, 95% CI 1.191-16.917, p = 0.027) and re-admission within 30 days after surgery (OR 5.269, 95% CI 1.288-21.547, p = 0.021) independently predicted postoperative 1-year mortality.

CONCLUSIONS

We demonstrate that preoperative BIA-derived TBW/FFM and fat mass were significantly correlated with metastatic extent, assessed by PCI score, in patients with peritoneal carcinomatosis. In addition, BIA-derived TBW/FFM and fat mass showed independent predictability for postoperative 30-day major complications and re-admission in patients undergoing CRS and HIPEC. Our findings suggest that assessment of BIA may improve discrete risk stratification in patients who are planned to receive CRS and HIPEC.

Lipocalin-2 promotes adipose-macrophage interactions to shape peripheral and central inflammatory responses in experimental autoimmune encephalomyelitis

OBJECTIVE

Accumulating evidence suggests that dysfunctional adipose tissue (AT) plays a major role in the risk of developing multiple sclerosis (MS), the most common immune-mediated and demyelinating disease of the central nervous system. However, the contribution of adipose tissue to the etiology and progression of MS is still obscure. This study aimed at deciphering the responses of AT in experimental autoimmune encephalomyelitis (EAE), the best characterized animal model of MS.

RESULTS AND METHODS

We observed a significant AT loss in EAE mice at the onset of disease, with a significant infiltration of M1-like macrophages and fibrosis in the AT, resembling a cachectic phenotype. Through an integrative and multilayered approach, we identified lipocalin2 (LCN2) as the key molecule released by dysfunctional adipocytes through redox-dependent mechanism. Adipose-derived LCN2 shapes the pro-inflammatory macrophage phenotype, and the genetic deficiency of LCN2 specifically in AT reduced weight loss as well as inflammatory macrophage infiltration in spinal cord in EAE mice. Mature adipocytes downregulating LCN2 reduced lipolytic response to inflammatory stimuli (e.g. TNFα) through an ATGL-mediated mechanism.

CONCLUSIONS

Overall data highlighted a role LCN2 in exacerbating inflammatory phenotype in EAE model, suggesting a pathogenic role of dysfunctional AT in MS.

Identification of an alternative triglyceride biosynthesis pathway

Triacylglycerols (TAGs) are the main source of stored energy in the body, providing an important substrate pool for mitochondrial beta-oxidation. Imbalances in the amount of TAGs are associated with obesity, cardiac disease and various other pathologies1,2. In humans, TAGs are synthesized from excess, coenzyme A-conjugated fatty acids by diacylglycerol O-acyltransferases (DGAT1 and DGAT2)3. In other organisms, this activity is complemented by additional enzymes4, but whether such alternative pathways exist in humans remains unknown. Here we disrupt the DGAT pathway in haploid human cells and use iterative genetics to reveal an unrelated TAG-synthesizing system composed of a protein we called DIESL (also known as TMEM68, an acyltransferase of previously unknown function) and its regulator TMX1. Mechanistically, TMX1 binds to and controls DIESL at the endoplasmic reticulum, and loss of TMX1 leads to the unconstrained formation of DIESL-dependent lipid droplets. DIESL is an autonomous TAG synthase, and expression of human DIESL in Escherichia coli endows this organism with the ability to synthesize TAG. Although both DIESL and the DGATs function as diacylglycerol acyltransferases, they contribute to the cellular TAG pool under specific conditions. Functionally, DIESL synthesizes TAG at the expense of membrane phospholipids and maintains mitochondrial function during periods of extracellular lipid starvation. In mice, DIESL deficiency impedes rapid postnatal growth and affects energy homeostasis during changes in nutrient availability. We have therefore identified an alternative TAG biosynthetic pathway driven by DIESL under potent control by TMX1.

The pathophysiology of cancer-mediated cardiac cachexia and novel treatment strategies: A narrative review

SIGNIFICANCE

Two of the leading causes of death worldwide are cancer and cardiovascular diseases. Most cancer patients suffer from a metabolic wasting syndrome known as cancer-induced cardiac cachexia, resulting in death in up to 30% of cancer patients. Main symptoms of this disease are severe cardiac muscle wasting, cardiac remodeling, and cardiac dysfunction. Metabolic alterations, increased inflammation, and imbalance of protein homeostasis contribute to the progression of this multifactorial syndrome, ultimately resulting in heart failure and death. Cancer-induced cardiac cachexia is associated with decreased quality of life, increased fatiguability, and decreased tolerance to therapeutic interventions.

RECENT ADVANCES

While molecular mechanisms of this disease are not fully understood, researchers have identified different stages of progression of this disease, as well as potential biomarkers to detect and monitor the development. Preclinical and clinical studies have shown positive results when implementing certain pharmacological and non-pharmacological therapy interventions.

CRITICAL ISSUES

There are still no clear diagnostic criteria for cancer-mediated cardiac cachexia and the condition remains untreated, leaving cancer patients with irreversible effects of this syndrome. While traditional cardiovascular therapy interventions, such as beta-blockers, have shown some positive results in preclinical and clinical research studies, recent preclinical studies have shown more successful results with certain non-traditional treatment options that have not been further evaluated yet. There is still no clinical standard of care or approved FDA drug to aid in the prevention or treatment of cancer-induced cardiac cachexia. This review aims to revisit the still not fully understood pathophysiological mechanisms of cancer-induced cardiac cachexia and explore recent studies using novel treatment strategies.

FUTURE DIRECTIONS

While research has progressed, further investigations might provide novel diagnostic techniques, potential biomarkers to monitor the progression of the disease, as well as viable pharmacological and non-pharmacological treatment options to increase quality of life and reduce cancer-induced cardiac cachexia-related mortality.

Exploring the Therapeutic Potential of Ethyl 3-Hydroxybutyrate in Alleviating Skeletal Muscle Wasting in Cancer Cachexia

Cachexia (CAC) is a debilitating metabolic syndrome. Although dietary interventions are attractive, long-term adherence to specific diets is difficult to maintain and can lead to systemic side effects. Ethyl 3-hydroxybutyrate (EHB) is a commonly used food additive found in wine and Tribolium castaneum. In this study, we investigated the effects of EHB administration in cachectic mice. After a single intraperitoneal injection of EHB into mice, 3-hydroxybutyrate (3-HB) levels were significantly increased in the serum and gastrocnemius of mice. The administration of EHB alleviated cachexia-related symptoms, ameliorated skeletal muscle atrophy, and improved survival in cachectic mice. In addition, the supplementation of cachectic mice with 3-HB by EHB administration significantly reduced tumor weights, indicating the anti-tumor effects of 3-HB. Remarkably, the addition of 3-HB to the culture medium significantly attenuated the C2C12 myotube atrophy induced by the culture supernatant of CT26 cell lines, highlighting its potential to counteract the destructive effects of tumor-derived elements on muscle tissue. NMR-based metabolomics analysis provided insights into the underlying mechanisms and revealed that the anti-cachexia effects of 3-HB treatment can be attributed to three key mechanisms: the promotion of the TCA cycle and the attenuation of proteolysis, the promotion of protein synthesis and the improvement of metabolic homeostasis, and a reduction in inflammation and an enhancement of the antioxidant capacity. This study provided compelling evidence for the protective effects of 3-HB treatment on the cachectic gastrocnemius and highlighted the efficacy of EHB administration as a ketone supplementation approach to achieve nutritional ketosis without the need for dietary restriction.

You only waste twice: T cells in parasite-induced organ wasting

In this issue of Cell Reports, Redford et al.1 uncouple the role of CD4+ and CD8+ T cells in controlling anorexia and wasting of muscle and adipose tissue during chronic parasitic infections. These results shed light on the impact of adaptive immune cells on organ catabolism.

CD4+ T cells regulate sickness-induced anorexia and fat wasting during a chronic parasitic infection

Infections cause catabolism of fat and muscle stores. Traditionally, studies have focused on understanding how the innate immune system contributes to energy stores wasting, while the role of the adaptive immune system remains elusive. In the present study, we examine the role of the adaptive immune response in adipose tissue wasting and cachexia using a murine model of the chronic parasitic infection Trypanosoma brucei, the causative agent of sleeping sickness. We find that the wasting response occurs in two phases, with the first stage involving fat wasting caused by CD4+ T cell-induced anorexia and a second anorexia-independent cachectic stage that is dependent on CD8+ T cells. Fat wasting has no impact on host antibody-mediated resistance defenses or survival, while later-stage muscle wasting contributes to disease-tolerance defenses. Our work reveals a decoupling of adaptive immune-mediated resistance from the catabolic response during infection.

REPTOR and CREBRF encode key regulators of muscle energy metabolism

Metabolic flexibility of muscle tissue describes the adaptive capacity to use different energy substrates according to their availability. The disruption of this ability associates with metabolic disease. Here, using a Drosophila model of systemic metabolic dysfunction triggered by yorkie-induced gut tumors, we show that the transcription factor REPTOR is an important regulator of energy metabolism in muscles. We present evidence that REPTOR is activated in muscles of adult flies with gut yorkie-tumors, where it modulates glucose metabolism. Further, in vivo studies indicate that sustained activity of REPTOR is sufficient in wildtype muscles to repress glycolysis and increase tricarboxylic acid (TCA) cycle metabolites. Consistent with the fly studies, higher levels of CREBRF, the mammalian ortholog of REPTOR, reduce glycolysis in mouse myotubes while promoting oxidative metabolism. Altogether, our results define a conserved function for REPTOR and CREBRF as key regulators of muscle energy metabolism.

PRMT5 links lipid metabolism to contractile function of skeletal muscles

Skeletal muscle plays a key role in systemic energy homeostasis besides its contractile function, but what links these functions is poorly defined. Protein Arginine Methyl Transferase 5 (PRMT5) is a well-known oncoprotein but also expressed in healthy tissues with unclear physiological functions. As adult muscles express high levels of Prmt5, we generated skeletal muscle-specific Prmt5 knockout (Prmt5MKO ) mice. We observe reduced muscle mass, oxidative capacity, force production, and exercise performance in Prmt5MKO mice. The motor deficiency is associated with scarce lipid droplets in myofibers due to defects in lipid biosynthesis and accelerated degradation. Specifically, PRMT5 deletion reduces dimethylation and stability of Sterol Regulatory Element-Binding Transcription Factor 1a (SREBP1a), a master regulator of de novo lipogenesis. Moreover, Prmt5MKO impairs the repressive H4R3 symmetric dimethylation at the Pnpla2 promoter, elevating the level of its encoded protein ATGL, the rate-limiting enzyme catalyzing lipolysis. Accordingly, skeletal muscle-specific double knockout of Pnpla2 and Prmt5 normalizes muscle mass and function. Together, our findings delineate a physiological function of PRMT5 in linking lipid metabolism to contractile function of myofibers.

Development of a peptide drug restoring AMPK and adipose tissue functionality in cancer cachexia

Cancer cachexia is a severe systemic wasting disease that negatively affects quality of life and survival in patients with cancer. To date, treating cancer cachexia is still a major unmet clinical need. We recently discovered the destabilization of the AMP-activated protein kinase (AMPK) complex in adipose tissue as a key event in cachexia-related adipose tissue dysfunction and developed an adeno-associated virus (AAV)-based approach to prevent AMPK degradation and prolong cachexia-free survival. Here, we show the development and optimization of a prototypic peptide, Pen-X-ACIP, where the AMPK-stabilizing peptide ACIP is fused to the cell-penetrating peptide moiety penetratin via a propargylic glycine linker to enable late-stage functionalization using click chemistry. Pen-X-ACIP was efficiently taken up by adipocytes, inhibited lipolysis, and restored AMPK signaling. Tissue uptake assays showed a favorable uptake profile into adipose tissue upon intraperitoneal injection. Systemic delivery of Pen-X-ACIP into tumor-bearing animals prevented the progression of cancer cachexia without affecting tumor growth and preserved body weight and adipose tissue mass with no discernable side effects in other peripheral organs, thereby achieving proof of concept. As Pen-X-ACIP also exerted its anti-lipolytic activity in human adipocytes, it now provides a promising platform for further (pre)clinical development toward a novel, first-in-class approach against cancer cachexia.