PKM2 promotes cell metastasis and inhibits autophagy via the JAK/STAT3 pathway in hepatocellular carcinoma

MicroRNA-122 regulates inflammatory and autophagic proteins by downregulating pyruvate kinase M2 in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the serious global health concerns, leading to non-alcoholic steatohepatitis (NASH), and to hepatocellular carcinoma (HCC). Despite its prevalence, the molecular mechanisms regulating NAFLD progression remain elusive. The present study aims to determine role of microRNA-122-mediated regulation of pyruvate kinase M2 (PKM2) on regulating inflammatory and autophagic proteins during the pathogenesis of NAFLD. Huh7 cells were incubated with free fatty acids (FFAs) or transfected with single guide RNA to PKM2 containing CRISPR-Cas9 system or miR-122 for up to 72 h. C57BL/6 mice were fed with sham-operated control, choline sufficient L-amino acid defined (CSAA) or choline-deficient L-amino acid defined (CDAA) diet for 6, 18, 32 and 54 weeks. The RNA or protein was isolated from the Huh7 cells and the liver tissue of the mice. RT-PCR was performed for miR-122 expression and Western blots were performed for PKM2, iNOS, COX2, Beclin-1, Atg7 and LC3-II. FFAs induced the expression of PKM2, iNOS and COX2, while decreased the expression of miR-122, Beclin-1, Atg7 and LC3-II. Overexpression of miR-122 resulted in decreased PKM2, iNOS and COX2 and increased Beclin-1, Atg7 and LC3-II. Silencing of PKM2 led to decreased iNOS and COX2 and increased Beclin-1, Atg7 and LC3-II. In CDAA fed-mice, there was a significant increase in PKM2, iNOS and COX2 and decreased miR-122, Beclin-1, Atg7 and LC3-II. The data showed that FFAs downregulated miR-122 expression, which resulted in the upregulation of PKM2, which in turn upregulated inflammatory proteins and downregulated autophagic proteins during the pathogenesis of NAFLD.

Progress of Pyruvate Kinase M2 in Hepatocellular Carcinoma-Associated Signaling Pathway

Hepatocellular carcinoma (HCC) is an aggressive liver tumor with a unique metabolic profile and a shift to glycolytic metabolism. This review discusses the contribution of pyruvate kinase M2 (PKM2) to HCC development and its potential as a target for therapy. We carried out a broad literature review on PKM2, focusing on its role in the glycolytic pathway and special interactions with key signaling pathways like Phosphoinositide 3-kinase/Protein kinase B/Mammalian target of rapamycin (PI3K/AKT/mTOR) and Mitogen-activated protein kinase (MAPK). PKM2 also performs a dual role in energy metabolism and signal transduction in HCC. PKM2 is paramount in the induction of HCC by regulating cellular metabolism and oncogenic signaling pathways. It promotes tumor growth, survival, and metastasis through interaction with the PI3K/AKT/mTOR and MAPK pathways. PKM2 is a key factor in HCC pathogenesis, with a dual impact on metabolism and signaling. Its properties may open the way for developing novel therapeutic interventions against HCC. Thus, PKM2 inhibition may offer further opportunities for tumor growth blockade, which could meaningfully improve patients' clinical outcomes.

Extracellular vesicle-packaged PKM2 from endometriotic stromal cells promotes endometrial collagen I deposition by inhibiting autophagy in endometriosis

Aberrant endometrial collagen I deposition during the implantation window impairs endometrial stromal cell (ESC) decidualization, which may contribute to lower pregnancy rate in endometriosis (EMs) patients with in vitro fertilization (IVF) treatment. However, the underlying mechanism of eutopic aberrant endometrium collagen I deposition in EMs remains unclear. In this study, we found increased endometrial collagen I and defective decidualization in the mid-secretory phase of EMs patients, while the level of eutopic ESCs' autophagy was decreased, which was an important mechanism of intracellular collagen degradation. Lower ESCs' autophagy level may cause the endometrial collagen I deposition in EMs. Furthermore, in vivo and in vitro studies showed that the extracellular vesicles derived from the ectopic ESCs of EMs patients (EMs-EVs) encapsulated higher PKM2 inhibited autophagy of the ESCs accompanied by an increase of collagen I. We also found that the constructed EMs-EVsAd-PKM2 with PKM2 overexpression inhibited ESCs' autophagy by activating the Akt/mTOR signaling pathway. And the expressions of PKM2, p-Akt and p-mTOR were also increased in the endometrium of EMs patients. Collectively, these data showed that EMs-EVs delivering PKM2 inhibited autophagy inducing aberrant endometrial collagen I deposition via the Akt/mTOR signaling pathway to impair decidualization, which provided a potential therapeutic target for improving the IVF pregnancy rate in EMs patients.

Chloride intracellular channel 6 inhibits hepatocellular carcinoma progression by modulating immune cell balance and promoting tumor cell apoptosis

Objective

Chloride intracellular channel 6 (CLIC6) is essential for the development of cancer, and it is widely studied for the treatment of various cancers. This study aimed to explore the potential mechanisms of CLIC6 in the treatment of hepatocellular carcinoma (HCC).

Material and Methods

Initially, a subcutaneous xenograft model of HCC was established. The model groups were treated with varying levels of CLIC6 recombinant protein. After 21 days, tumor and liver tissues were harvested. Tumor size and weight were measured, and hematoxylin-eosin staining was used to assess histopathological changes in the tumor tissues. Terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick-end labeling staining was employed to evaluate apoptosis in tumor tissue cells. Quantitative real-time polymerase chain reaction and Western blot were utilized to analyze cytokine messenger ribonucleic acid ( mRNA) levels in the liver or tumor tissues, and immunohistochemistry was conducted to assess cytokine expression.

Results

CLIC6 significantly inhibits tumor proliferation and enhances apoptosis in tumor tissue cells. CLIC6 markedly reduces the mRNA levels of interleukin (IL)-6, IL-1β, interferon-γ, tumor necrosis factor-α, and IL-17A in liver tissue when increasing transforming growth factor-β and IL-4 mRNA levels. CLIC6 potentially modulates Th cell balance by regulating forkhead box protein P3, GATA-binding protein 3, T-box expressed in T cell, and retinoic acid receptor-related orphan receptor γt (ROR-γt) expression, thereby restraining HCC progression in mice. Moreover, CLIC6 mitigates hepatic oxidative damage via the Janus tyrosine kinase 1/signal transducer and activator of the transcription pathway, attenuates c-Jun N-terminal kinase (JNK) phosphorylation, and modulates apoptosis-related proteins, effectively hindering HCC development.

Conclusion

CLIC6 demonstrates potent antitumor effects in HCC through inhibition of proliferation, promotion of apoptosis, modulation of cytokine levels, regulation of immune cell balance, and attenuation of oxidative stress pathways.

Mannich Base Derived from Lawsone Inhibits PKM2 and Induces Neoplastic Cell Death

Background/Objectives: Pyruvate kinase M2, a central regulator of cancer cell metabolism, has garnered significant attention as a promising target for disrupting the metabolic adaptability of tumor cells. This study explores the potential of the Mannich base derived from lawsone (MB-6a) to interfere with PKM2 enzymatic activity both in vitro and in silico. Methods: The antiproliferative potential of MB-6a was tested using MTT assay in various cell lines, including SCC-9, Hep-G2, HT-29, B16-F10, and normal human gingival fibroblast (HGF). The inhibition of PKM2 mediated by MB-6a was assessed using an LDH-coupled assay and by measuring ATP production. Docking studies and molecular dynamics calculations were performed using Autodock 4 and GROMACS, respectively, on the tetrameric PKM2 crystallographic structure. Results: The Mannich base 6a demonstrated selective cytotoxicity against all cancer cell lines tested without affecting cell migration, with the highest selectivity index (SI) of 4.63 in SCC-9, followed by B16-F10 (SI = 3.9), Hep-G2 (SI = 3.4), and HT-29 (SI = 2.03). The compound effectively inhibited PKM2 glycolytic activity, leading to a reduction of ATP production both in the enzymatic reaction and in cells treated with this naphthoquinone derivative. MB-6a showed favorable binding to PKM2 in the ATP-bound monomers through docking studies (PDB ID: 4FXF; binding affinity scores ranging from -6.94 to -9.79 kcal/mol) and MD simulations, revealing binding affinities stabilized by key interactions including hydrogen bonds, halogen bonds, and hydrophobic contacts. Conclusions: The findings suggest that MB-6a exerts its antiproliferative activity by disrupting cell glucose metabolism, consequently reducing ATP production and triggering energetic collapse in cancer cells. This study highlights the potential of MB-6a as a lead compound targeting PKM2 and warrants further investigation into its mechanism of action and potential clinical applications.

The Role of Pyruvate Kinase M2 Posttranslational Modification in the Occurrence and Development of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the deadly malignant tumors that directly leads to the death of nearly one million people worldwide every year, causing a serious burden on society. In the presence of sufficient oxygen, HCC cells rapidly generate energy through aerobic glycolysis, which promotes tumor cell proliferation, immune evasion, metastasis, angiogenesis, and drug resistance. Pyruvate kinase M2 (PKM2) is a key rate-limiting enzyme in glycolysis. In recent years, studies have found that PKM2 not only exerts pyruvate kinase activity in the process of glucose metabolism, but also exerts protein kinase activity in non-metabolic pathways to affect tumor cell processes, and its activity is flexibly regulated by various posttranslational modifications such as acetylation, phosphorylation, lactylation, ubiquitination, SUMOylation, and so forth. This review summarizes the role of posttranslational modifications of PKM2-related sites in the development of HCC.

The interaction between lncRNAs and transcription factors regulating autophagy in human cancers: A comprehensive and therapeutical survey

Autophagy, as a highly conserved cellular process, participates in cellular homeostasis by degradation and recycling of damaged organelles and proteins. Besides, autophagy has been evidenced to play a dual role through cancer initiation and progression. In the early stage, it may have a tumor-suppressive function through inducing apoptosis and removing damaged cells and organelles. However, late stages promote tumor progression by maintaining stemness features and induction of chemoresistance. Therefore, identifying and targeting molecular mechanisms involved in autophagy is a potential therapeutic strategy for human cancers. Multiple transcription factors (TFs) are involved in the regulation of autophagy by modulating the expression of autophagy-related genes (ATGs). In addition, a wide array of long noncoding RNAs (lncRNAs), a group of regulatory ncRNAs, have been evidenced to regulate the function of these autophagy-related TFs through tumorigenesis. Subsequently, the lncRNAs/TFs/ATGs axis shows great potential as a therapeutic target for human cancers. Therefore, this review aimed to summarize new findings about the role of lncRNAs in regulating autophagy-related TFs with therapeutic perspectives.

Targeting PKM2 improves the gemcitabine sensitivity of intrahepatic cholangiocarcinoma cells via inhibiting β-catenin signaling pathway

Gemcitabine is considered the standard first-line chemotherapeutic agent for patients with intrahepatic cholangiocarcinoma (ICC). However, its therapeutic efficacy is hampered by the development of chemoresistance. Pyruvate kinase M2 (PKM2), a crucial mediator of the final step in glycolysis, has been implicated in the origination and advancement of diverse malignancies. Its expression is increased in many tumor types and this may correlate with increased drug sensitivity. However, the specific effect of PKM2 on the gemcitabine sensitivity in ICC remains to be elucidated. In this research, we aimed to elucidate the role and functional significance of PKM2 in ICC, as well as the heightened susceptibility of ICC cells to gemcitabine by targeting PKM2 and the underlying molecular mechanisms. Immunohistochemical and immunofluorescence analyses revealed elevated expression of PKM2 in both tumor cells and macrophages in human ICC tissues. Reducing PKM2 levels significantly restrained the proliferation of tumor cells, impeded cell cycle advance, induced programmed cell death, and suppressed metastasis. In addition, knockdown or pharmacological inhibition of PKM2 could enhance the response of ICC cells to gemcitabine in vitro. Interestingly, conditioned medium co-culture system suggested that conditioned medium from M2 macrophages increased gemcitabine sensitivity of ICC cells. However, silencing PKM2 or pharmacological inhibition of PKM2 in M2 macrophages did not ameliorate the gemcitabine resistance mediated by M2 macrophages derived conditioned medium. Mechanistically, downregulation of PKM2 repressed the expression of β-catenin and its downstream transcriptional targets, thereby hindering the propagation of β-catenin signaling cascade. Finally, the results of the subcutaneous xenograft experiment in nude mice provided compelling evidence of a synergistic interaction between PKM2-IN-1 and gemcitabine in vivo. In summary, we reported that PKM2 may function as an advantageous target for increasing the sensitivity of ICC to gemcitabine treatment. Targeting PKM2 improves the gemcitabine sensitivity of ICC cells via inhibiting β-catenin signaling pathway.

Non-metabolic enzyme function of PKM2 in hepatocellular carcinoma: A review

Hepatocellular carcinoma (HCC) is one of the most malignant tumors with the highest incidence and mortality in the world, causing a serious burden on society. Pyruvate kinase M2 (PKM2) is one of the principal metabolic enzymes involved in glycolysis. Studies have shown that PKM2 is highly expressed in HCC and can be translocated to the nucleus, where it interacts with various transcription factors and proteins such as hypoxia-inducible factor-1α, sterol regulatory element-binding protein 1a, signal transducer and activator of transcription 3, nuclear factor erythroid 2-like 2 and histone H3, exerting non-metabolic enzyme functions to regulate the cell cycle, proliferation, apoptosis, immune escape, migration, and invasion, as well as HCC angiogenesis and tumor microenvironment. This review is focused on the recent progress of PKM2 interacting with various transcription factors and proteins affecting the onset and development of HCC, as well as natural drugs and noncoding RNA impacting diverse biological functions of liver cancer cells by regulating PKM2 non-metabolic enzyme functions, thereby providing valuable directions for the prognosis improvement and molecular targeted therapy of HCC in the future.

Glycolysis in Chronic Liver Diseases: Mechanistic Insights and Therapeutic Opportunities

Chronic liver diseases (CLDs) cover a spectrum of liver diseases, ranging from nonalcoholic fatty liver disease to liver cancer, representing a growing epidemic worldwide with high unmet medical needs. Glycolysis is a conservative and rigorous process that converts glucose into pyruvate and sustains cells with the energy and intermediate products required for diverse biological activities. However, abnormalities in glycolytic flux during CLD development accelerate the disease progression. Aerobic glycolysis is a hallmark of liver cancer and is responsible for a broad range of oncogenic functions including proliferation, invasion, metastasis, angiogenesis, immune escape, and drug resistance. Recently, the non-neoplastic role of aerobic glycolysis in immune activation and inflammatory disorders, especially CLD, has attracted increasing attention. Several key mediators of aerobic glycolysis, including HIF-1α and pyruvate kinase M2 (PKM2), are upregulated during steatohepatitis and liver fibrosis. The pharmacological inhibition or ablation of PKM2 effectively attenuates hepatic inflammation and CLD progression. In this review, we particularly focused on the glycolytic and non-glycolytic roles of PKM2 in the progression of CLD, highlighting the translational potential of a glycolysis-centric therapeutic approach in combating CLD.

A PKM2 inhibitor induces apoptosis and autophagy through JAK2 in human oral squamous cell carcinoma cells

The enzyme pyruvate kinase M2 (PKM2) is involved in glycolysis, which plays an important role in the regulation of tumor progression. In this study, we investigated the anti-tumor activity of N-(4-(3-(3-(methylamino)-3-oxopropyl)-5-(4'-(prop-2-yn-1-yloxy)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-1-yl)phenyl)propiolamide (MTP), a PKM2 inhibitor, in oral squamous cell carcinoma (OSCC) cells. Our results showed that MTP inhibited cell growth with IC50 values of 0.59 μM and 0.78 μM in SCC2095 and HSC3 OSCC cells, respectively. MTP induced caspase-dependent apoptosis, which was associated with the modulation of PKM2 and oncogenic biomarkers epidermal growth factor receptor and β-catenin. In addition, MTP increased the generation of reactive oxygen species (ROS) and modulated the expression of autophagic gene products, including LC3B-II and p62. Western blotting showed that MTP inhibited Janus kinase 2 (JAK2) signaling, and JAK2 overexpression partially reversed MTP-mediated cytotoxicity. Taken together, these data indicate the potential use of MTP as a therapeutic agent for OSCC.

Regulation of Autophagy via Carbohydrate and Lipid Metabolism in Cancer

Metabolic changes are an important component of tumor cell progression. Tumor cells adapt to environmental stresses via changes to carbohydrate and lipid metabolism. Autophagy, a physiological process in mammalian cells that digests damaged organelles and misfolded proteins via lysosomal degradation, is closely associated with metabolism in mammalian cells, acting as a meter of cellular ATP levels. In this review, we discuss the changes in glycolytic and lipid biosynthetic pathways in mammalian cells and their impact on carcinogenesis via the autophagy pathway. In addition, we discuss the impact of these metabolic pathways on autophagy in lung cancer.

Autophagy orchestrates resistance in hepatocellular carcinoma cells

Treatment resistance is one of the major barriers for therapeutic strategies in hepatocellular carcinoma (HCC). Many studies have indicated that chemotherapy and radiotherapy induce autophagy machinery (cell protective autophagy) in HCC cells. In addition, many experiments report a remarkable crosstalk between treatment resistance and autophagy pathways. Thus, autophagy could be one of the key factors enabling tumor cells to hinder induced cell death after medical interventions. Therefore, extensive research on the molecular pathways involved in resistance induction and autophagy have been conducted to achieve the desired therapeutic response. The key molecular pathways related to the therapy resistance are TGF-β, MAPK, NRF2, NF-κB, and non-coding RNAs. In addition, EMT, drug transports, apoptosis evasion, DNA repair, cancer stem cells, and hypoxia could have considerable impact on the hepatoma cell's response to therapies. These mechanisms protect tumor cells against various treatments and many studies have shown that each of them is connected to the molecular pathways of autophagy induction in HCC. Hence, autophagy inhibition may be an effective strategy to improve therapeutic outcome in HCC patients. In this review, we further highlight how autophagy leads to poor response during treatment through a complex molecular network and how it enhances resistance in primary liver cancer. We propose that combinational regimens of approved HCC therapeutic protocols plus autophagy inhibitors may overcome drug resistance in HCC therapy.

STAT proteins in cancer: orchestration of metabolism

Reprogrammed metabolism is a hallmark of cancer. However, the metabolic dependency of cancer, from tumour initiation through disease progression and therapy resistance, requires a spectrum of distinct reprogrammed cellular metabolic pathways. These pathways include aerobic glycolysis, oxidative phosphorylation, reactive oxygen species generation, de novo lipid synthesis, fatty acid β-oxidation, amino acid (notably glutamine) metabolism and mitochondrial metabolism. This Review highlights the central roles of signal transducer and activator of transcription (STAT) proteins, notably STAT3, STAT5, STAT6 and STAT1, in orchestrating the highly dynamic metabolism not only of cancer cells but also of immune cells and adipocytes in the tumour microenvironment. STAT proteins are able to shape distinct metabolic processes that regulate tumour progression and therapy resistance by transducing signals from metabolites, cytokines, growth factors and their receptors; defining genetic programmes that regulate a wide range of molecules involved in orchestration of metabolism in cancer and immune cells; and regulating mitochondrial activity at multiple levels, including energy metabolism and lipid-mediated mitochondrial integrity. Given the central role of STAT proteins in regulation of metabolic states, they are potential therapeutic targets for altering metabolic reprogramming in cancer.

The Role of PKM2 in the Regulation of Mitochondrial Function: Focus on Mitochondrial Metabolism, Oxidative Stress, Dynamic, and Apoptosis. PKM2 in Mitochondrial Function

The M2 isoform of pyruvate kinase (PKM2) is one isoform of pyruvate kinase (PK). PKM2 is expressed at high levels during embryonic development and tumor progression and is subject to complex allosteric regulation. PKM2 is a special glycolytic enzyme that regulates the final step of glycolysis; the role of PKM2 in the metabolism, survival, and apoptosis of cancer cells has received increasing attention. Mitochondria are directly or indirectly involved in the regulation of energy metabolism, susceptibility to oxidative stress, and cell death; however, the role of PKM2 in mitochondrial functions remains unclear. Herein, we review the related mechanisms of the role of PKM2 in the regulation of mitochondrial functions from the aspects of metabolism, reactive oxygen species (ROS), dynamic, and apoptosis, which can be highlighted as a target for the clinical management of cardiovascular and metabolic diseases.

Downregulation of STK25 promotes autophagy via the Janus kinase 2/signal transducer and activator of transcription 3 pathway in colorectal cancer

Autophagy plays a crucial role in colorectal cancer (CRC) development. Our previous study suggested that serine/threonine protein kinase 25 (STK25) regulates aerobic glycolysis in CRC cells. Glycolysis modulates cellular autophagy during tumor growth; however, the role of STK25 in autophagy remains unclear. In this study, we found that STK25 expression was decreased in CRC tissues and CRC patients with high STK25 expression had a favorable prognosis. Functional assays suggested that STK25 inhibition promoted autophagy in CRC cells. Overexpression of STK25 exhibited the opposite effects. Moreover, the results of western blot demonstrated that silencing STK25 induced autophagy by activating the JAK2/STAT3 pathway. Therefore, STK25 could be a potential indicator for therapies targeting the JAK2/STAT3 pathway in CRC.

The critical function of metabolic reprogramming in cancer metastasis

Cancer metastasis is the leading cause of cancer‐related death. It is a complex, inefficient, and multistep process related to poor prognosis and high mortality of patients. Increasing evidence has shown that metabolic programming is a recognized hallmarker of cancer, plays a critical role in cancer metastasis. Metabolism alterations of glucose, lipid, and amino acid provide cancer cells with energy and substances for biosynthesis, maintain biofunctions and significantly affect proliferation, invasion, and metastasis of cancer cells. Tumor microenvironment (TME) is a complex system formed by varieties of cellular and noncellular elements. Nontumor cells in TME also undergo metabolic reprogramming or respond to metabolites to promote migration and invasion of cancer cells. A comprehensive understanding of the regulatory mechanism in metastasis from the metabolic reprogramming aspect is required to develop new therapeutic strategies combatting cancer metastasis. This review illustrates the metabolic reprogramming and interaction of cancer cells and nontumor cells in the TME, and the development of treatment strategies targeting metabolism alterations.

Unfolding the role of autophagy in the cancer metabolism

Autophagy is considered an indispensable process that scavenges toxins, recycles complex macromolecules, and sustains the essential cellular functions. In addition to its housekeeping role, autophagy plays a substantial role in many pathophysiological processes such as cancer. Certainly, it adapts cancer cells to thrive in the stress conditions such as hypoxia and starvation. Cancer cells indeed have also evolved by exploiting the autophagy process to fulfill energy requirements through the production of metabolic fuel sources and fundamentally altered metabolic pathways. Occasionally autophagy as a foe impedes tumorigenesis and promotes cell death. The complex role of autophagy in cancer makes it a potent therapeutic target and has been actively tested in clinical trials. Moreover, the versatility of autophagy has opened new avenues of effective combinatorial therapeutic strategies. Thereby, it is imperative to comprehend the specificity of autophagy in cancer-metabolism. This review summarizes the recent research and conceptual framework on the regulation of autophagy by various metabolic pathways, enzymes, and their cross-talk in the cancer milieu, including the implementation of altered metabolism and autophagy in clinically approved and experimental therapeutics.

Anti-Inflammatory Effect of Muscle-Derived Interleukin-6 and Its Involvement in Lipid Metabolism

Interleukin (IL)-6 has been studied since its discovery for its role in health and diseases. It is one of the most important pro-inflammatory cytokines. IL-6 was reported as an exacerbating factor in coronavirus disease. In recent years, it has become clear that the function of muscle-derived IL-6 is different from what has been reported so far. Exercise is accompanied by skeletal muscle contraction, during which, several bioactive substances, collectively named myokines, are secreted from the muscles. Many reports have shown that IL-6 is the most abundant myokine. Interestingly, it was indicated that IL-6 plays opposing roles as a myokine and as a pro-inflammatory cytokine. In this review, we discuss why IL-6 has different functions, the signaling mode of hyper-IL-6 via soluble IL-6 receptor (sIL-6R), and the involvement of soluble glycoprotein 130 in the suppressive effect of hyper-IL-6. Furthermore, the involvement of a disintegrin and metalloprotease family molecules in the secretion of sIL-6R is described. One of the functions of muscle-derived IL-6 is lipid metabolism in the liver. However, the differences between the functions of IL-6 as a pro-inflammatory cytokine and the functions of muscle-derived IL-6 are unclear. Although the involvement of myokines in lipid metabolism in adipocytes was previously discussed, little is known about the direct relationship between nonalcoholic fatty liver disease and muscle-derived IL-6. This review is the first to discuss the relationship between the function of IL-6 in diseases and the function of muscle-derived IL-6, focusing on IL-6 signaling and lipid metabolism in the liver.