O-GlcNAc transferase promotes fatty liver-associated liver cancer through inducing palmitic acid and activating endoplasmic reticulum stress

Bacillus amyloliquefaciens attenuates the intestinal permeability, oxidative stress and endoplasmic reticulum stress: transcriptome and microbiome analyses in weaned piglets

Endoplasmic reticulum (ER) stress is related to oxidative stress (OS) and leads to intestinal injury. Bacillus amyloliquefaciens SC06 (SC06) can regulate OS, but its roles in intestinal ER stress remains unclear. Using a 2 × 2 factorial design, 32 weaned piglets were treated by two SC06 levels (0 or 1 × 108 CFU/g), either with or without diquat (DQ) injection. We found that SC06 increased growth performance, decreased ileal permeability, OS and ER stress in DQ-treated piglets. Transcriptome showed that differentially expressed genes (DEGs) induced by DQ were enriched in NF-κB signaling pathway. DEGs between DQ- and SC06 + DQ-treated piglets were enriched in glutathione metabolism pathway. Ileal microbiome revealed that the SC06 + DQ treatment decreased Clostridium and increased Actinobacillus. Correlations were found between microbiota and ER stress genes. In conclusion, dietary SC06 supplementation increased the performance, decreased the permeability, OS and ER stress in weaned piglets by regulating ileal genes and microbiota.

Biological Functions and Potential Therapeutic Significance of O-GlcNAcylation in Hepatic Cellular Stress and Liver Diseases

O-linked-β-D-N-acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation), which is dynamically regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), is a post-translational modification involved in multiple cellular processes. O-GlcNAcylation of proteins can regulate their biological functions via crosstalk with other post-translational modifications, such as phosphorylation, ubiquitination, acetylation, and methylation. Liver diseases are a major cause of death worldwide; yet, key pathological features of the disease, such as inflammation, fibrosis, steatosis, and tumorigenesis, are not fully understood. The dysregulation of O-GlcNAcylation has been shown to be involved in some severe hepatic cellular stress, viral hepatitis, liver fibrosis, nonalcoholic fatty acid liver disease (NAFLD), malignant progression, and drug resistance of hepatocellular carcinoma (HCC) through multiple molecular signaling pathways. Here, we summarize the emerging link between O-GlcNAcylation and hepatic pathological processes and provide information about the development of therapeutic strategies for liver diseases.

Sugar-coated bullets: Unveiling the enigmatic mystery 'sweet arsenal' in osteoarthritis

Glycosylation is a crucial post-translational modification process where sugar molecules (glycans) are covalently linked to proteins, lipids, or other biomolecules. In this highly regulated and complex process, a series of enzymes are involved in adding, modifying, or removing sugar residues. This process plays a pivotal role in various biological functions, influencing the structure, stability, and functionality of the modified molecules. Glycosylation is essential in numerous biological processes, including cell adhesion, signal transduction, immune response, and biomolecular recognition. Dysregulation of glycosylation is associated with various diseases. Glycation, a post-translational modification characterized by the non-enzymatic attachment of sugar molecules to proteins, has also emerged as a crucial factor in various diseases. This review comprehensively explores the multifaceted role of glycation in disease pathogenesis, with a specific focus on its implications in osteoarthritis (OA). Glycosylation and glycation alterations wield a profound influence on OA pathogenesis, intertwining with disease onset and progression. Diverse studies underscore the multifaceted role of aberrant glycosylation in OA, particularly emphasizing its intricate relationship with joint tissue degradation and inflammatory cascades. Distinct glycosylation patterns, including N-glycans and O-glycans, showcase correlations with inflammatory cytokines, matrix metalloproteinases, and cellular senescence pathways, amplifying the degenerative processes within cartilage. Furthermore, the impact of advanced glycation end-products (AGEs) formation in OA pathophysiology unveils critical insights into glycosylation-driven chondrocyte behavior and extracellular matrix remodeling. These findings illuminate potential therapeutic targets and diagnostic markers, signaling a promising avenue for targeted interventions in OA management. In this comprehensive review, we aim to thoroughly examine the significant impact of glycosylation or AGEs in OA and explore its varied effects on other related conditions, such as liver-related diseases, immune system disorders, and cancers, among others. By emphasizing glycosylation's role beyond OA and its implications in other diseases, we uncover insights that extend beyond the immediate focus on OA, potentially revealing novel perspectives for diagnosing and treating OA.

Palmitic acid activates NLRP3 inflammasome through NF-κB and AMPK-mitophagy-ROS pathways to induce IL-1β production in large yellow croaker (Larimichthys crocea)

Studies on marine fish showed that vegetable oils substituted for excessive fish oil increased interleukin-1β (IL-1β) production. However, whether the nucleotide-binding oligomerization domain, leucine-rich repeat-containing family, pyrin domain-containing-3 (NLRP3) inflammasome has a substantial role in fatty acid-induced IL-1β production in fish remains unclear. The associated specific mechanism is also unknown. In this study, nlrp3, caspase-1 and apoptosis-associated speck-like protein containing a CARD (asc) were successfully cloned, and NLRP3 inflammasome consisted of NLRP3, caspase-1 and ASC in large yellow croaker. Primary hepatocytes of fish incubated with palmitic acid (PA) exhibited the highest expression of pro-inflammatory genes (il-1β and tnfα) and NLRP3 inflammasome related genes (nlrp3, caspase-1 and asc), caspase-1 activity and IL-1β production among different treatments. Furthermore, PA-induced NLRP3 inflammasome activation was confirmed to require two signals: the first signal was that PA promoted the NF-κB (P65) protein into the nucleus, and NF-κB increased NLRP3 promoter activity and nlrp3 transcription. The second signal was that PA inhibited AMPK phosphorylation and decreased mitophagy by inhibiting the expression of PINK and parkin proteins, thereby damaging the mitochondria that could not be effectively cleared. Mitochondrial damage generated excessive amounts of reactive oxygen species, which activated the NLRP3 inflammasome and then induced caspase-1 activity and IL-1β production. Therefore, excessive dietary PA activated NLRP3 inflammasome through NF-κB and AMPK-mitophagy-ROS pathways to induce IL-1β production, thereby leading to inflammation in fish.

Spatial proteomics of immune microenvironment in nonalcoholic steatohepatitis-associated hepatocellular carcinoma

BACKGROUND AND AIMS

NASH-HCC is inherently resistant to immune checkpoint blockade, but its tumor immune microenvironment is largely unknown.

APPROACH AND RESULTS

We applied the imaging mass cytometry to construct a spatially resolved single-cell atlas from the formalin-fixed and paraffin-embedded tissue sections from patients with NASH-HCC, virus-HCC (HBV-HCC and HCV-HCC), and healthy donors. Based on 35 biomarkers, over 750,000 individual cells were categorized into 13 distinct cell types, together with the expression of key immune functional markers. Higher infiltration of T cells, myeloid-derived suppressor cell (MDSCs), and tumor-associated macrophages (TAMs) in HCC compared to controls. The distribution of immune cells in NASH-HCC is spatially heterogeneous, enriched at adjacent normal tissues and declined toward tumors. Cell-cell connections analysis revealed the interplay of MDSCs and TAMs with CD8 + T cells in NASH-HCC. In particular, exhausted programmed cell death 1 (PD-1 + )CD8 + T cells connected with programmed cell death-ligand 1 (PD-L1 + )/inducible T cell costimulator (ICOS + ) MDSCs and TAMs in NASH-HCC, but not in viral HCC. In contrast, CD4 + /CD8 + T cells with granzyme B positivity were reduced in NASH-HCC. Tumor cells expressed low PD-L1 and showed few connections with immune cells.

CONCLUSIONS

Our work provides the first detailed spatial map of single-cell phenotypes and multicellular connections in NASH-HCC. We demonstrate that interactions between MDSCs and TAMs with effector T cells underlie immunosuppression in NASH-HCC and are an actionable target.

Protein O-GlcNAcylation: The sweet hub in liver metabolic flexibility from a (patho)physiological perspective

O-GlcNAcylation is a dynamic, reversible and atypical O-glycosylation that regulates various cellular physiological processes via conformation, stabilisation, localisation, chaperone interaction or activity of target proteins. The O-GlcNAcylation cycle is precisely controlled by collaboration between O-GlcNAc transferase and O-GlcNAcase. Uridine-diphosphate-N-acetylglucosamine, the sole donor of O-GlcNAcylation produced by the hexosamine biosynthesis pathway, is controlled by the input of glucose, glutamine, acetyl coenzyme A and uridine triphosphate, making it a sensor of the fluctuation of molecules, making O-GlcNAcylation a pivotal nutrient sensor for the metabolism of carbohydrates, amino acids, lipids and nucleotides. O-GlcNAcylation, particularly prevalent in liver, is the core hub for controlling systemic glucose homeostasis due to its nutritional sensitivity and precise spatiotemporal regulation of insulin signal transduction. The pathology of various liver diseases has highlighted hepatic metabolic disorder and dysfunction, and abnormal O-GlcNAcylation also plays a specific pathological role in these processes. Therefore, this review describes the unique features of O-GlcNAcylation and its dynamic homeostasis maintenance. Additionally, it explains the underlying nutritional sensitivity of O-GlcNAcylation and discusses its mechanism of spatiotemporal modulation of insulin signal transduction and liver metabolic homeostasis during the fasting and feeding cycle. This review emphasises the pathophysiological implications of O-GlcNAcylation in nonalcoholic fatty liver disease, nonalcoholic steatohepatitis and hepatic fibrosis, and focuses on the adverse effects of hyper O-GlcNAcylation on liver cancer progression and metabolic reprogramming.

PC 18:1/18:1 mediates the anti-inflammatory effects of exercise and remodels tumor microenvironment of hepatocellular carcinoma

AIM

Phosphatidylcholine (PC) is essential for membrane structural integrity and lipid-dependent signaling pathways, and is an essential component required for cancer cell growth. Using hepatocellular carcinoma (HCC) as a tumor model, this study aims to further screen phospholipid biomarkers of the tumor microenvironment and explore the anti-tumor effects and mechanisms of aerobic exercise.

MAIN METHODS

The HCC of C57BL/6J mice was induced by the injection of the carcinogen diethylnitrosamine (DEN). Exercise was performed on an ungraded treadmill for weeks. The inflammation-related markers were detected by ELISA, PCR and immunohistochemistry, hepatic metabolic profile was analyzed by GC/MS, and lipid metabolism profile was further detected by lipid-targeted LC/MS. Cell culture was used to verify the anti-inflammatory effect of PC.

KEY FINDINGS

Exercise reduced hepatic inflammation, tumor incidence and volume. Metabolomics analysis showed that palmitic acid is a key metabolic marker for exercise to improve tumor microenvironment. Injection of exogenous palmitic acid following exercise impaired the anti-inflammatory and anti-tumor effects of exercise. Lipid metabolomics analysis further showed that metabolites for exercise were enriched in glycerol phospholipid metabolism, including 14 phosphatidylcholines (PCs), 18 phosphatidylethanolamines (PEs), and 6 triglycerides (TGs). These biomarkers contain different lengths of fatty acid chains and different numbers of unsaturated bonds, respectively. Cell culture verified that PC (18:1/18:1) mediated lipopolysaccharide (LPS)-induced inflammation in HepG2 cell.

SIGNIFICANCE

Our results suggest that exercise remodels glycerophospholipid metabolism and reduces hepatic palmitic acid loading and PC (18:1/18:1) level, thereby reconstructing a microenvironment that is hostile to HCC.

O-Linked N-Acetylglucosamine Transferase Regulates Bone Homeostasis Through Alkaline Phosphatase Pathway in Diabetic Periodontitis

Periodontitis is one of the most common complications of diabetes, which seriously affects patients' life quality. It is important to find the key factors and mechanisms to improve the treatment of periodontitis. In our study, high glucose (HG) and lipopolysaccharide (LPS) treated human periodontal ligament cells (hPDLCs) and LPS treated diabetic mice was used to establish the diabetic periodontitis model in vitro and in vivo. O-linked beta-N-acetylglucosamine glycosylation (O-GlcNAcylation) and O-linked N-acetylglucosamine transferase (OGT) protein levels were detected by western blot assay. Cell counting kit-8, alkaline phosphatase (ALP), and alizarin red staining (ARS) assays were used to observe the O-GlcNAcylation and OGT effects on cell viability and osteoblast differentiation. Co-immunoprecipitation (Co-IP) assay was used to detect the relationship between OGT and ALP. The results showed that the levels of OGT and O-GlcNAcylation were significantly increased in both cell and mouse models. ALP and ARS staining results showed that silencing of OGT or inhibition of O-glycosylation notably improved osteogenic differentiation, increased the osteoprotegerin (OPG) protein levels and decreased the receptor activator for nuclear factor-κB Ligand (RANKL) protein levels of the HG and LPS treated hPDLCs. In diabetic periodontitis mice, knockdown of OGT relieved the injury of gingival tissue, increased the ALP and OPG levels and decreased the RANKL levels. Besides, ALP interacted with OGT protein, and OGT protein was found to act on ALP serine 513 glycosylation. In conclusion, our study demonstrated that excessive O-GlcNAcylation could restrain osteoblast differentiation by O-glycosylation in ALP.

High dietary fructose promotes hepatocellular carcinoma progression by enhancing O-GlcNAcylation via microbiota-derived acetate

Emerging studies have addressed the tumor-promoting role of fructose in different cancers. The effects and pathological mechanisms of high dietary fructose on hepatocellular carcinoma (HCC) remain unclear. Here, we examined the effects of fructose supplementation on HCC progression in wild-type C57BL/6 mice using a spontaneous and chemically induced HCC mouse model. We show that elevated uridine diphospho-N-acetylglucosamine (UDP-GlcNAc) and O-GlcNAcylation levels induced by high dietary fructose contribute to HCC progression. Non-targeted metabolomics and stable isotope tracing revealed that under fructose treatment, microbiota-derived acetate upregulates glutamine and UDP-GlcNAc levels and enhances protein O-GlcNAcylation in HCC. Global profiling of O-GlcNAcylation revealed that hyper-O-GlcNAcylation of eukaryotic elongation factor 1A1 promotes cell proliferation and tumor growth. Targeting glutamate-ammonia ligase or O-linked N-acetylglucosamine transferase (OGT) remarkably impeded HCC progression in mice with high fructose intake. We propose that high dietary fructose promotes HCC progression through microbial acetate-induced hyper-O-GlcNAcylation.

Discovery of a novel OGT inhibitor through high-throughput screening based on Homogeneous Time-Resolved Fluorescence (HTRF)

O-GlcNAcylation is a specific type of post-translational glycosylation modification, which is regulated by two enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Aberrant overexpression of OGT is associated with the development of many solid tumors. In this study, we have developed and optimized a sensitive Homogeneous Time-Resolved Fluorescence (HTRF) assay then identified a novel OGT inhibitor CDDO (also called Bardoxolone) through a high-throughput screening (HTS) based on HTRF assay. Further characterization suggested that CDDO is an effective OGT inhibitor with an IC50 value of 6.56 ± 1.69 μM. CPMG-NMR analysis confirmed that CDDO is a direct binder of OGT with a binding affinity (Kd) of approximately 1.7 μM determined by the MST analysis. Moreover, HDX-MS analysis indicated that CDDO binds to the TPR domain and N-Terminal domain of OGT, which was further confirmed by the enzymatic competition experiments as the binding of CDDO to OGT was not affected by the catalytic site binding inhibitor OSMI-4. Our docking modeling analysis further predicted the possible interactions between CDDO and OGT, providing informative molecular basis for further optimization of the inhibitor in the future. Together, our results suggested CDDO is a new inhibitor of OGT with a distinct binding pocket from the reported OGT inhibitors. Our work paved a new direction for developing OGT inhibitors driven by novel mechanisms.

Unraveling the Role of Hepatic PGC1α in Breast Cancer Invasion: A New Target for Therapeutic Intervention?

Breast cancer (BC) is the most common cancer among women worldwide and the main cause of cancer deaths in women. Metabolic components are key risk factors for the development of non-alcoholic fatty liver disease (NAFLD), which may promote BC. Studies have reported that increasing PGC1α levels increases mitochondrial biogenesis, thereby increasing cell proliferation and metastasis. Moreover, the PGC1α/ERRα axis is a crucial regulator of cellular metabolism in various tissues, including BC. However, it remains unclear whether NAFLD is closely associated with the risk of BC. Therefore, the present study aimed to determine whether hepatic PGC1α promotes BC cell invasion via ERRα. Various assays, including ELISA, western blotting, and immunoprecipitation, have been employed to explore these mechanisms. According to the KM plot and TCGA data, elevated PGC1α expression was highly associated with a shorter overall survival time in patients with BC. High concentrations of palmitic acid (PA) promoted PGC1α expression, lipogenesis, and inflammatory processes in hepatocytes. Conditioned medium obtained from PA-treated hepatocytes significantly increased BC cell proliferation. Similarly, recombinant PGC1α in E0771 and MCF7 cells promoted cell proliferation, migration, and invasion in vitro. However, silencing PGC1α in both BC cell lines resulted in a decrease in this trend. As determined by immunoprecipitation assay, PCG1a interacted with ERRα, thereby facilitating the proliferation of BC cells. This outcome recognizes the importance of further investigations in exploring the full potential of hepatic PGC1α as a prognostic marker for BC development.

Identification of a diketopiperazine-based O-GlcNAc transferase inhibitor sensitizing hepatocellular carcinoma to CDK9 inhibition

O-GlcNAcylation (O-linked β-N-acetylglucosaminylation) is an important post-translational and metabolic process in cells that is implicated in a wide range of physiological processes. O-GlcNAc transferase (OGT) is ubiquitously present in cells and is the only enzyme that catalyses the transfer of O-GlcNAc to nucleocytoplasmic proteins. Aberrant glycosylation by OGT has been linked to a variety of diseases including cancer, neurodegenerative disorders and diabetes. Previously, we and others demonstrated that O-GlcNAcylation is notably elevated in hepatocellular carcinoma (HCC). The overexpression of O-GlcNAcylation promotes cancer progression and metastasis. Here, we report the identification of HLY838, a novel diketopiperazine-based OGT inhibitor with the ability to induce a global decrease in cellular O-GlcNAc. HLY838 enhances the in vitro and in vivo anti-HCC activity of CDK9 inhibitor by downregulating c-Myc and downstream E2F1 expression. Mechanistically, c-Myc is regulated by the CDK9 at the transcript level, and stabilized by OGT at the protein level. This work therefore demonstrates that HLY838 potentiates the antitumor responses of CDK9 inhibitor, providing an experimental rationale for developing OGT inhibitor as a sensitizing agent in cancer therapeutics.

The deubiquitinase EIF3H promotes hepatocellular carcinoma progression by stabilizing OGT and inhibiting ferroptosis

Hepatocellular carcinoma (HCC) is one of the most prevalent and lethal human malignancies, and with quite limited treatment alternatives. The proteasome is responsible for most of the protein degradation in eukaryotic cells and required for the maintenance of intracellular homeostasis. However, its potential role in HCC is largely unknown. In the current study, we identified eukaryotic translation initiation factor 3 subunit H (EIF3H), belonging to the JAB1/MPN/MOV34 (JAMM) superfamily, as a bona fide deubiquitylase of O-GlcNAc transferase (OGT) in HCC. We explored that EIF3H was positively associated with OGT in HCC and was related to the unfavorable prognosis. EIF3H could interact with, deubiquitylate, and stabilize OGT in a deubiquitylase-dependent manner. Specifically, EIF3H was associated with the GT domain of ERα via its JAB/MP domain, thus inhibiting the K48-linked ubiquitin chain on OGT. Besides, we demonstrated that the knockdown of EIF3H significantly reduced OGT protein expression, cell proliferation and invasion, and caused G1/S arrest of HCC. We also found that the deletion of EIF3H prompted ferroptosis in HCC cells. Finally, the effects of EIF3H depletion could be reversed by further OGT overexpression, implying that the OGT status is indispensable for EIF3H function in HCC carcinogenesis. In summary, our study described the oncogenic function of EIF3H and revealed an interesting post-translational mechanism between EIF3H, OGT, and ferroptosis in HCC. Targeting the EIF3H may be a promising approach in HCC. Video Abstract.

Hepatocyte-specific O-GlcNAc transferase downregulation ameliorates nonalcoholic steatohepatitis by improving mitochondrial function

O-GlcNAcylation is a post-translational modification that directly couples the processes of nutrient sensing, metabolism, and signal transduction, affecting protein function and localization, since the O-linked N-acetylglucosamine moiety comes directly from the metabolism of glucose, lipids, and amino acids. De addition and removal of O-GlcNAc of target proteins is mediated by two highly conserved enzymes: O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) and O-GlcNAcase (OGA), respectively. Deregulation of O-GlcNAcylation has been reported to be associated with various human diseases such as cancer, diabetes, and cardiovascular diseases. The contribution of deregulated O-GlcNAcylation to the progression and pathogenesis of NAFLD remains intriguing, and a better understanding of its roles in this pathophysiological context is required to uncover novel avenues for therapeutic intervention. By using a translational approach, our aim is to describe the role of OGT and O-GlcNAcylation in the pathogenesis of NAFLD. We used primary mouse hepatocytes, human hepatic cell lines and in vivo mouse models of steatohepatitis to manipulate O-GlcNAc transferase (OGT). We also studied OGT and O-GlcNAcylation in liver samples from different cohorts of people with NAFLD. O-GlcNAcylation was upregulated in the liver of people and animal models with steatohepatitis. Downregulation of OGT in NAFLD-hepatocytes improved diet-induced liver injury in both in vivo and in vitro models. Proteomics studies revealed that mitochondrial proteins were hyper-O-GlcNAcylated in the liver of mice with steatohepatitis. Inhibition of OGT is able to restore mitochondrial oxidation and decrease hepatic lipid content in in vitro and in vivo models of NAFLD. These results demonstrate that deregulated hyper-O-GlcNAcylation favors NAFLD progression by reducing mitochondrial oxidation and promoting hepatic lipid accumulation.

Chromatin-associated OGT promotes the malignant progression of hepatocellular carcinoma by activating ZNF263

Reversible and dynamic O-GlcNAcylation regulates vast networks of highly coordinated cellular and nuclear processes. Although dysregulation of the sole enzyme O-GlcNAc transferase (OGT) was shown to be associated with the progression of hepatocellular carcinoma (HCC), the mechanisms by which OGT controls the cis-regulatory elements in the genome and performs transcriptional functions remain unclear. Here, we demonstrate that elevated OGT levels enhance HCC proliferation and metastasis, in vitro and in vivo, by orchestrating the transcription of numerous regulators of malignancy. Diverse transcriptional regulators are recruited by OGT in HCC cells undergoing malignant progression, which shapes genome-wide OGT chromatin cis-element occupation. Furthermore, an unrecognized cooperation between ZNF263 and OGT is crucial for activating downstream transcription in HCC cells. We reveal that O-GlcNAcylation of Ser662 is responsible for the chromatin association of ZNF263 at candidate gene promoters and the OGT-facilitated HCC malignant phenotypes. Our data establish the importance of aberrant OGT activity and ZNF263 O-GlcNAcylation in the malignant progression of HCC and support the investigation of OGT as a therapeutic target for HCC.

Development and validation of a selenium metabolism regulators associated prognostic model for hepatocellular carcinoma

BACKGROUND

Selenium metabolism has been implicated in human health. This study aimed to identify a selenium metabolism regulator-based prognostic signature for hepatocellular carcinoma (HCC) and validate the role of INMT in HCC.

METHODS

Transcriptome sequencing data and clinical information related to selenium metabolism regulators in TCGA liver cancer dataset were analysed. Next, a selenium metabolism model was constructed by multiple machine learning algorithms, including univariate, least absolute shrinkage and selection operator, and multivariate Cox regression analyses. Then, the potential of this model for predicting the immune landscape of different risk groups was evaluated. Finally, INMT expression was examined in different datasets. After knockdown of INMT, cell proliferation and colony formation assays were conducted.

RESULTS

A selenium metabolism model containing INMT and SEPSECS was established and shown to be an independent predictor of prognosis. The survival time of low-risk patients was significantly longer than that of high-risk patients. These two groups had different immune environments. In different datasets, including TCGA, GEO, and our PUMCH dataset, INMT was significantly downregulated in HCC tissues. Moreover, knockdown of INMT significantly promoted HCC cell proliferation.

CONCLUSIONS

The current study established a risk signature of selenium metabolism regulators for predicting the prognosis of HCC patients. INMT was identified as a biomarker for poor prognosis of HCC.

O-GlcNAcylation enhances Reticulon 2 protein stability and its promotive effects on gastric cancer progression

Our previous study indicated that Reticulon 2 (RTN2) was upregulated and facilitated the progression of gastric cancer. Protein O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) is a general feature during tumorigenesis, and regulates protein activity and stability through post-translational modification on serine/threonine. However, the relationship between RTN2 and O-GlcNAcylation have never been determined. In this study, we explored the influence of O-GlcNAcylation on RTN2 expression and its promotive role in gastric cancer. We found that RTN2 interacted with O-GlcNAc transferase (OGT) and was modified by O-GlcNAc. O-GlcNAcylation enhanced RTN2 protein stability via attenuating its lysosomal degradation in gastric cancer cells. Furthermore, our results demonstrated that RTN2-induced activation of ERK signalling was dependent on O-GlcNAcylation. Consistently, the stimulative effects of RTN2 on cellular proliferation and migration were abrogated by OGT inhibition. Tissue microarray with immumohistochemical staining also confirmed that the expression of RTN2 was positively correlated with the level of total O-GlcNAcylation as well as the phosphorylation level of ERK. Besides, combined RTN2 and O-GlcNAc staining intensity could improve predictive accuracy for gastric cancer patients' survival compared with each alone. Altogether, these findings suggest that O-GlcNAcylation on RTN2 was pivotal for its oncogenic functions in gastric cancer. Targeting RTN2 O-GlcNAcylation might provide new ideas for gastric cancer therapies.

Excess body weight: Novel insights into its roles in obesity comorbidities

Excess body weight is a global health problem due to sedentary lifestyle and unhealthy diet, affecting 2 billion population worldwide. Obesity is a major risk factor for metabolic diseases. Notably, the metabolic risk of obesity largely depends on body weight distribution, of which visceral adipose tissues but not subcutaneous fats are closely associated with obesity comorbidities, including type 2 diabetes, non-alcoholic fatty liver disease, cardiovascular disease and certain types of cancer. Latest multi-omics and mechanistical studies reported the crucial involvement of genetic and epigenetic alterations, adipokines dysregulation, immunity changes, imbalance of white and brown adipose tissues, and gut microbial dysbiosis in mediating the pathogenic association between visceral adipose tissues and comorbidities. In this review, we explore the epidemiology of excess body weight and the up-to-date mechanism of how excess body weight and obesity lead to chronic complications. We also examine the utilization of visceral fat measurement as an accurate clinical parameter for risk assessment in healthy individuals and clinical outcome prediction in obese subjects. In addition, current approaches for the prevention and treatment of excess body weight and its related metabolic comorbidities are further discussed. DATA AVAILABILITY: No data was used for the research described in the article.

Astragalus Polysaccharide Promotes Doxorubicin-Induced Apoptosis by Reducing O-GlcNAcylation in Hepatocellular Carcinoma

The toxicity and side effects of chemotherapeutic drugs remain a crucial obstacle to the clinical treatment of hepatocellular carcinoma (HCC). Identifying combination therapy from Chinese herbs to enhance the sensitivity of tumors to chemotherapeutic drugs is of particular interest. Astragalus polysaccharide (APS), one of the natural active components in Astragalus membranaceus, has been reported to exhibit anti-tumor properties in diverse cancer cell lines. The aim of this study was to determine the effect of APS on Doxorubicin (Dox)-induced apoptosis in HCC and the underlying mechanism. The results showed that APS dose-dependently promoted Dox-induced apoptosis and enhanced endoplasmic reticulum (ER) stress. Additionally, APS decreased the mRNA level and protein stability of O-GlcNAc transferase (OGT), and increased the O-GlcNAcase (OGA) expression. Furthermore, OGT lentiviral transfection or PugNAc (OGA inhibitor) treatment reversed the ER stress and apoptosis induced by the combination of Dox and APS. A xenograft tumor mouse model confirmed that the combination of APS and Dox showed an advantage in inhibiting tumor growth in vivo. These findings suggested that APS promoted Dox-induced apoptosis in HCC cells through reducing the O-GlcNAcylation, which led to the exacerbation of ER stress and activation of apoptotic pathways.

O-GlcNAcylation of SPOP promotes carcinogenesis in hepatocellular carcinoma

Aberrantly elevated O-GlcNAcylation level is commonly observed in human cancer patients, and has been proposed as a potential therapeutic target. Speckle-type POZ protein (SPOP), an important substrate adaptor of cullin3-RING ubiquitin ligase, plays a key role in the initiation and development of various cancers. However, the regulatory mechanisms governing SPOP and its function during hepatocellular carcinoma (HCC) progression remain unclear. Here, we show that, in HCC, SPOP is highly O-GlcNAcylated by O-GlcNAc transferase (OGT) at Ser96. In normal liver cells, the SPOP protein mainly localizes in the cytoplasm and mediates the ubiquitination of the oncoprotein neurite outgrowth inhibitor-B (Nogo-B) (also known as reticulon 4 B) by recognizing its N-terminal SPOP-binding consensus (SBC) motifs. However, O-GlcNAcylation of SPOP at Ser96 increases the nuclear positioning of SPOP in hepatoma cells, alleviating the ubiquitination of the Nogo-B protein, thereby promoting HCC progression in vitro and in vivo. In addition, ablation of O-GlcNAcylation by an S96A mutation increased the cytoplasmic localization of SPOP, thereby inhibiting the Nogo-B/c-FLIP cascade and HCC progression. Our findings reveal a novel post-translational modification of SPOP and identify a novel SPOP substrate, Nogo-B, in HCC. Intervention with the hyper O-GlcNAcylation of SPOP may provide a novel strategy for HCC treatment.

N6-Methyladenosine-Mediated Up-Regulation of FZD10 Regulates Liver Cancer Stem Cells' Properties and Lenvatinib Resistance Through WNT/β-Catenin and Hippo Signaling Pathways

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide, but there is a deficiency of early diagnosis biomarkers and therapeutic targets. Drug resistance accounts for most HCC-related deaths, yet the mechanisms underlying drug resistance remain poorly understood.

METHODS

Expression of Frizzled-10 (FZD10) in liver cancer stem cells (CSCs) was identified by means of RNA sequencing and validated by means of real-time polymerase chain reaction and immunohistochemistry. In vitro and in vivo experiments were used to assess the effect of FZD10 on liver CSC expansion and lenvatinib resistance. RNA sequencing, RNA binding protein immunoprecipitation, and luciferase report assays were applied to explore the mechanism underlying FZD10-mediated liver CSCs expansion and lenvatinib resistance.

RESULTS

Activation of FZD10 in liver CSCs was mediated by METTL3-dependent N6-methyladenosine methylation of FZD10 messenger RNA. Functional studies revealed that FZD10 promotes self-renewal, tumorigenicity, and metastasis of liver CSCs via activating β-catenin and YAP1. The FZD10-β-catenin/YAP1 axis is activated in liver CSCs and predicts poor prognosis. Moreover, FZD10-β-catenin/c-Jun axis transcriptionally activates METTL3 expression, forming a positive feedback loop. Importantly, the FZD10/β-catenin/c-Jun/MEK/ERK axis determines the responses of hepatoma cells to lenvatinib treatment. Analysis of patient cohort, patient-derived tumor organoids, and patient-derived xenografts further suggest that FZD10 might predict lenvatinib clinical benefit in patients with HCC. Furthermore, treatment of lenvatinib-resistant HCC with adeno-associated virus targeting FZD10 or a β-catenin inhibitor restored lenvatinib response.

CONCLUSIONS

Elevated FZD10 expression promotes expansion of liver CSCs and lenvatinib resistance, indicating that FZD10 expression is a novel prognostic biomarker and therapeutic target for human HCC.

Emerging Role of Protein O-GlcNAcylation in Liver Metabolism: Implications for Diabetes and NAFLD

O-linked b-N-acetyl-glucosaminylation (O-GlcNAcylation) is one of the most common post-translational modifications of proteins, and is established by modifying the serine or threonine residues of nuclear, cytoplasmic, and mitochondrial proteins. O-GlcNAc signaling is considered a critical nutrient sensor, and affects numerous proteins involved in cellular metabolic processes. O-GlcNAcylation modulates protein functions in different patterns, including protein stabilization, enzymatic activity, transcriptional activity, and protein interactions. Disrupted O-GlcNAcylation is associated with an abnormal metabolic state, and may result in metabolic disorders. As the liver is the center of nutrient metabolism, this review provides a brief description of the features of the O-GlcNAc signaling pathway, and summarizes the regulatory functions and underlying molecular mechanisms of O-GlcNAcylation in liver metabolism. Finally, this review highlights the role of O-GlcNAcylation in liver-associated diseases, such as diabetes and nonalcoholic fatty liver disease (NAFLD). We hope this review not only benefits the understanding of O-GlcNAc biology, but also provides new insights for treatments against liver-associated metabolic disorders.

LncRNA EBLN3P attributes methotrexate resistance in osteosarcoma cells through miR-200a-3p/O-GlcNAc transferase pathway

BACKGROUND

Osteosarcoma is highly malignant. The migration, invasion, and chemoresistance contribute to poor prognosis of osteosarcoma. Research reported that endogenous bornavirus-like nucleoprotein 3 pseudogene (EBLN3P) promotes the progression of osteosarcoma.

METHODS

In this study, the expression of EBLN3P in osteosarcoma tissue with different methotrexate (MTX) treatment responses was measured. Osteosarcoma cell lines with MTX resistance were constructed, and bioinformatic analysis was performed to explore the potential involved targets and pathways.

RESULTS

Higher EBLN3P was associated with MTX resistance. Downregulation of LncEBLN3P decreased the MTX resistance of osteosarcoma cells by sponging miR-200a-3p, an important microRNA that affects epithelial-mesenchymal transition (EMT). The decreased miR-200a-3p resulted in the upregulation of its target gene O-GlcNAc transferase (OGT), which in turn promoted the EMT process of osteosarcoma cells. Further analysis confirmed that the loss of OGT and over-expression of miR-200a-3p could partly abolish the MTX resistance induced by LncEBLN3P.

CONCLUSION

LncEBLN3P is upregulated in osteosarcoma and increases the MTX resistance in osteosarcoma cells through downregulating miR-200a-3p, which in turn promoted the EMT process of osteosarcoma cells by increasing the OGT.

Altered Gut Microbial Profile Accompanied by Abnormal Fatty Acid Metabolism Activity Exacerbates Endometrial Cancer Progression

Endometrial cancer (EC) is the most prevalent gynecological malignancy, with a higher risk in obese woman, indicating the possibility of gut microbiota involvement in EC progression. However, no direct evidence of a relationship between EC and gut microbiota in humans has been discovered. Here, we performed 16S rRNA sequencing to explore the relationship between dysbiosis of gut microbiota and cancer development in different types of EC patients. The results clearly show the differential profiles of gut microbiota between EC patients and normal participants as well as the association between gut microbiota and EC progression. Targeted metabolomics of plasma revealed an increased level of C16:1 and C20:2, which was positively associated with the abundance of Ruminococcus sp. N15.MGS-57. The higher richness of Ruminococcus sp. N15.MGS-57 in EC subjects not only was positively associated with blood C16:1 and C20:2 but also was negatively correlated with betalain and indole alkaloid biosynthesis. Furthermore, the combined marker panel of gut bacteria, blood metabolites, and clinical indices could distinguish the EC patients under lean and overweight conditions from normal subjects with high accuracy in both discovery and validation sets. In addition, the alteration of tumor microenvironment metabolism of EC was characterized by imaging mass microscopy. Spatial visualization of fatty acids showed that C16:1 and C18:1 obviously accumulate in tumor tissue, and C16:1 may promote EC cell invasion and metastasis through mTOR signaling. The aberrant fecal microbiome, more specifically, Ruminococcus sp. N15.MGS-57 and spatially distributed C16:1 in EC tissues, can be used as a biomarker of clinical features and outcomes and provide a new therapeutic target for clinical treatment. IMPORTANCE A growing number of studies have shown the connection between gut microbiota, obesity, and cancer. However, to our knowledge, the association between gut microbiota and endometrial cancer progression in humans has not been studied. We recruited EC and control individuals as research participants and further subgrouped subjects by body mass index to examine the association between gut microbiota, metabolites, and clinical indices. The higher richness of Ruminococcus sp. N15.MGS-57 in EC subjects was not only positively associated with blood C16:1 but also negatively correlated with betalain and indole alkaloid biosynthesis. Spatial visualization of fatty acids by imaging mass microscopy showed that C16:1 obviously accumulates in tumor tissue, and C16:1 may promote the EC cell invasion and metastasis through mTOR signaling. The aberrant fecal microbiome, more specifically, Ruminococcus sp. N15.MGS-57 and spatially distributed C16:1, can be used as a biomarker of clinical features and outcomes and provide a new therapeutic target for clinical treatment.

O-GlcNAcylation: an important post-translational modification and a potential therapeutic target for cancer therapy

O-linked β-d-N-acetylglucosamine (O-GlcNAc) is an important post-translational modification of serine or threonine residues on thousands of proteins in the nucleus and cytoplasm of all animals and plants. In eukaryotes, only two conserved enzymes are involved in this process. O-GlcNAc transferase is responsible for adding O-GlcNAc to proteins, while O-GlcNAcase is responsible for removing it. Aberrant O-GlcNAcylation is associated with a variety of human diseases, such as diabetes, cancer, neurodegenerative diseases, and cardiovascular diseases. Numerous studies have confirmed that O-GlcNAcylation is involved in the occurrence and progression of cancers in multiple systems throughout the body. It is also involved in regulating multiple cancer hallmarks, such as metabolic reprogramming, proliferation, invasion, metastasis, and angiogenesis. In this review, we first describe the process of O-GlcNAcylation and the structure and function of O-GlcNAc cycling enzymes. In addition, we detail the occurrence of O-GlcNAc in various cancers and the role it plays. Finally, we discuss the potential of O-GlcNAc as a promising biomarker and novel therapeutic target for cancer diagnosis, treatment, and prognosis.

Endoplasmic Reticulum Stress in Hepatitis B Virus and Hepatitis C Virus Infection

Endoplasmic reticulum (ER) stress, a type of cellular stress, always occurs when unfolded or misfolded proteins accumulating in the ER exceed the protein folding capacity. Because of the demand for rapid viral protein synthesis after viral infection, viral infections become a risk factor for ER stress. The hepatocyte is a cell with large and well-developed ER, and hepatitis virus infection is widespread in the population, indicating the interaction between hepatitis viruses and ER stress may have significance for managing liver diseases. In this paper, we review the process that is initiated by the hepatocyte through ER stress against HBV and HCV infection and explain how this information can be helpful in the treatment of HBV/HCV-related diseases.

O-GlycNacylation Remission Retards the Progression of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a metabolic disease spectrum associated with insulin resistance (IR), from non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma (HCC). O-GlcNAcylation is a posttranslational modification, regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Abnormal O-GlcNAcylation plays a key role in IR, fat deposition, inflammatory injury, fibrosis, and tumorigenesis. However, the specific mechanisms and clinical treatments of O-GlcNAcylation and NAFLD are yet to be elucidated. The modification contributes to understanding the pathogenesis and development of NAFLD, thus clarifying the protective effect of O-GlcNAcylation inhibition on liver injury. In this review, the crucial role of O-GlcNAcylation in NAFLD (from NAFL to HCC) is discussed, and the effect of therapeutics on O-GlcNAcylation and its potential mechanisms on NAFLD have been highlighted. These inferences present novel insights into the pathogenesis and treatments of NAFLD.

Protein O-GlcNAcylation in Metabolic Modulation of Skeletal Muscle: A Bright but Long Way to Go

O-GlcNAcylation is an atypical, dynamic and reversible O-glycosylation that is critical and abundant in metazoan. O-GlcNAcylation coordinates and receives various signaling inputs such as nutrients and stresses, thus spatiotemporally regulating the activity, stability, localization and interaction of target proteins to participate in cellular physiological functions. Our review discusses in depth the involvement of O-GlcNAcylation in the precise regulation of skeletal muscle metabolism, such as glucose homeostasis, insulin sensitivity, tricarboxylic acid cycle and mitochondrial biogenesis. The complex interaction and precise modulation of O-GlcNAcylation in these nutritional pathways of skeletal muscle also provide emerging mechanical information on how nutrients affect health, exercise and disease. Meanwhile, we explored the potential role of O-GlcNAcylation in skeletal muscle pathology and focused on its benefits in maintaining proteostasis under atrophy. In general, these understandings of O-GlcNAcylation are conducive to providing new insights into skeletal muscle (patho) physiology.

The O-GlcNAcylation and its promotion to hepatocellular carcinoma

O-GlcNAcylation is a posttranslational modification that attaches O-linked β-N-acetylglucosamine (O-GlcNAc) to the serine and threonine residues of proteins. Such a glycosylation would alter the activities, stabilities, and interactions of target proteins that are functional in a wide range of biological processes and diseases. Accumulating evidence indicates that O-GlcNAcylation is tightly associated with hepatocellular carcinoma (HCC) in its onset, growth, invasion and metastasis, drug resistance, and stemness. Here we summarize the discoveries of the role of O-GlcNAcylation in HCC and its function mechanism, aiming to deepen our understanding of HCC pathology, generate more biomarkers for its diagnosis and prognosis, and offer novel molecular targets for its treatment.

Comparison of effectiveness and safety of camrelizumab between HBV-related and non-B, non-C hepatocellular carcinoma: A retrospective study in China

Purpose: This study aimed to compare the clinical outcomes of camrelizumab in hepatitis B virus-related hepatocellular carcinoma (HBV–HCC) patients and non-HBV, non-HCV hepatocellular carcinoma (NBNC–HCC) patients in China.

Materials and methods: A total of 54 patients with hepatocellular carcinoma who received camrelizumab were included in this retrospective study from January 2019 to December 2021. The patients were assigned to the HBV–HCC group (n = 28) and the NBNC–HCC group (n = 26). The primary endpoints were overall survival (OS) and progression-free survival (PFS), and the secondary endpoints were the objective response rate (ORR), disease control rate (DCR), and adverse events (AEs). Multivariate analysis using Cox proportional hazard regression was used to identify independent prognostic factors. A nomogram model was subsequently established based on independent prognostic factors.

Results: The mean duration of follow-up was 12.7 ± 3.6 months. The median OS was not determined. The median PFS in the HBV–HCC group was significantly longer than that in the NBNC–HCC group (9.2 vs. 6.7 months, p = 0.003). The ORR and DCR in the HBV–HCC group were significantly higher than those in the NBNC–HCC group (ORR, 28.6% vs. 7.7%, p = 0.048; DCR, 71.4% vs. 42.3%, p = 0.031). No significant differences in the total incidence of AEs were found between the HBV–HCC group and the NBNC–HCC group (75.0% vs. 69.2%, p = 0.224). Multivariate regression analysis identified etiology, AFP level, and vascular invasion as independent prognostic factors (all p < 0.05).

Conclusion: Our findings demonstrate that camrelizumab is more effective in HBV–HCC patients than in NBNC–HCC patients, with manageable safety.

Comparison of two anti-diabetic monoestolides regarding effects on intact murine liver tissue

CONTEXT

Monoestolides belonging to the fatty acid-hydroxy fatty acid (FAHFA) family have recently emerged as promising insulin sensitizers.

OBJECTIVE

To investigate and compare impact of two selected FAHFA isomers, namely 9-hexadecanoyloxy-octadecanoic acid [9-PAHSA] and 9-(9Z-octadecenoyloxy)-octadecanoic acid [9-OAHSA], on intact livers in C57BL/6J mice.

MATERIALS AND METHODS

Short-term in vivo study with intragastric gavage of 13 mg/kg of substances. Morphological, biochemical and high-resolution respirometric assessment of plasma and liver tissue or homogenates thereof.

RESULTS

The 9-OAHSA-gavaged mice had the highest final total body weight, the lowest free fatty acid circulating levels and the highest plasma activities of both ALT and AST. No significant changes of ambient glycaemia were found, however 9-PAHSA-gavaged mice tended to have lower glycaemia than other animals. Respirometry proved no substance-dependent differences.

DISCUSSION AND CONCLUSION

9-PAHSA was more metabolically beneficial and less hepatotoxic than 9-OAHSA. Bioenergetic machinery of liver homogenates seemed unaffected at our FAHFA dose.

Biofluids Metabolic Profiling Based on PS@Fe3O4-NH2 Magnetic Beads-Assisted LDI-MS for Liver Cancer Screening

Liver cancer (LC) is the third frequent cause of death worldwide, so early diagnosis of liver cancer patients is crucial for disease management. Herein, we applied NH₂-coated polystyrene@Fe₃O₄ magnetic beads (PS@Fe₃O₄-NH₂ MBs) as a matrix material in laser desorption/ionization mass spectrometry (LDI-MS). Rapid, sensitive, and selective metabolic profiling of the native biofluids was achieved without any inconvenient enrichment or purification. Then, based on the selected m/z features, LC patients were discriminated from healthy controls (HCs) by machine learning, with the high area under the curve (AUC) values for urine and serum assessments (0.962 and 0.935). Moreover, initial-diagnosed and subsequent-visited LC patients were also differentiated, which indicates potential applications of this method in early diagnosis. Furthermore, among these identified compounds by FT-ICR MS, the expression level of some metabolites changed from HCs to LCs, including 29 and 12 characteristic metabolites in human urine and serum samples, respectively. These results suggest that PS@Fe₃O₄-NH₂ MBs-assisted LDI-MS coupled with machine learning is feasible for LC clinical diagnosis.

Interferon-a potentiates anti-PD-1 efficacy by remodeling glucose metabolism in the hepatocellular carcinoma microenvironment

The overall response rate for anti-PD-1 therapy remains modest in hepatocellular carcinoma (HCC). We found that a combination of interferon alpha (IFN-a) and anti-PD-1-based immunotherapy resulted in enhanced antitumor activity in unresectable HCC patients. In both immunocompetent orthotopic and spontaneous HCC models, IFN-a therapy synergized with anti-PD-1 and the combination treatment led to significant enrichment of cytotoxic CD27+ CD8+ T cells. Mechanistically, IFN-a suppressed HIF1a signaling by inhibiting FosB transcription in HCC cells, resulting in reduced glucose consumption capacity and consequentially establishing the high-glucose microenvironment that fostered transcription of the T cell costimulatory molecule Cd27 via mTOR-FOXM1 signaling in infiltrating CD8+ T cells. Together, these data reveal that IFN-a reprograms glucose metabolism within HCC tumor microenvironment, thereby liberating T cell cytotoxic capacities and potentiating the PD-1 blockade-induced immune response. Our findings suggest that IFN-a and anti-PD-1 cotreatment is an effective novel combination strategy for HCC patients.

O-GlcNAcylation and Its Role in Cancer-Associated Inflammation

Cancer cells, as well as surrounding stromal and inflammatory cells, form an inflammatory tumor microenvironment (TME) to promote all stages of carcinogenesis. As an emerging post-translational modification (PTM) of serine and threonine residues of proteins, O-linked-N-Acetylglucosaminylation (O-GlcNAcylation) regulates diverse cancer-relevant processes, such as signal transduction, transcription, cell division, metabolism and cytoskeletal regulation. Recent studies suggest that O-GlcNAcylation regulates the development, maturation and functions of immune cells. However, the role of protein O-GlcNAcylation in cancer-associated inflammation has been less explored. This review summarizes the current understanding of the influence of protein O-GlcNAcylation on cancer-associated inflammation and the mechanisms whereby O-GlcNAc-mediated inflammation regulates tumor progression. This will provide a theoretical basis for further development of anti-cancer therapies.

Discovery of a New Drug-Like Series of OGT Inhibitors by Virtual Screening

O-GlcNAcylation is an essential post-translational modification installed by the enzyme O-β-N-acetyl-d-glucosaminyl transferase (OGT). Modulating this enzyme would be extremely valuable to better understand its role in the development of serious human pathologies, such as diabetes and cancer. However, the limited availability of potent and selective inhibitors hinders the validation of this potential therapeutic target. To explore new chemotypes that target the active site of OGT, we performed virtual screening of a large library of commercially available compounds with drug-like properties. We purchased samples of the most promising virtual hits and used enzyme assays to identify authentic leads. Structure-activity relationships of the best identified OGT inhibitor were explored by generating a small library of derivatives. Our best hit displays a novel uridine mimetic scaffold and inhibited the recombinant enzyme with an IC50 value of 7 µM. The current hit represents an excellent starting point for designing and developing a new set of OGT inhibitors that may prove useful for exploring the biology of OGT.

Histone H1.2 promotes hepatocarcinogenesis by regulating STAT3 signaling

Linker histone H1.2 (H1.2), encoded by HIST1H1C (H1C), is a major H1 variant in somatic cells. Among five histone H1 somatic variants, upregulated H1.2 was found in human hepatocellular carcinoma (HCC) samples and in a diethylnitrosamine (DEN)‐induced HCC mouse model. In vitro, H1.2 overexpression accelerated proliferation of HCC cell lines, whereas H1.2 knockdown (KD) had the opposite effect. In vivo, H1.2 insufficiency or deficiency (H1c KD or H1c KO) alleviated inflammatory response and HCC development in DEN‐treated mice. Mechanistically, H1.2 regulated the activation of signal transducer and activator of transcription 3 (STAT3), which in turn positively regulated H1.2 expression by binding to its promoter. Moreover, upregulation of the H1.2/STAT3 axis was observed in human HCC samples, and was confirmed in mouse models of methionine‐choline‐deficient diet induced nonalcoholic steatohepatitis or lipopolysaccharide induced acute inflammatory liver injury. Disrupting this feed‐forward loop by KD of STAT3 or treatment with STAT3 inhibitors rescued H1.2 overexpression‐induced proliferation. Moreover, STAT3 inhibitor treatment‐ameliorated H1.2 overexpression promoted xenograft tumor growth. Therefore, H1.2 plays a novel role in inflammatory response by regulating STAT3 activation in HCC, thus, blockade of the H1.2/STAT3 loop is a potential strategy against HCC.

Dihydroartemisinin alleviates steatosis and inflammation in nonalcoholic steatohepatitis by decreasing endoplasmic reticulum stress and oxidative stress

Nonalcoholic steatohepatitis (NASH) is a severely inflammatory subtype of nonalcoholic fatty liver. Endoplasmic reticulum stress (ERS) and oxidative stress (OS) cause metabolic abnormalities, promote liver steatosis and inflammation, and are central to the development of NASH. Dihydroartemisinin (DHA) is a compound extracted from Artemisia annua that is often used in the treatment of malaria. Recent studies have shown that DHA also has a wide range of pharmacological effects, acting on various organs throughout the body to exert anti-inflammatory, antioxidant, and anti-fibrotic effects. In this study, we demonstrated in vitro that the anti-inflammatory effect of DHA is effective against NASH and reduces liver steatosis. DHA treatment decreased the synthesis of lipids, such as cholesterol and free fatty acids, and the expression of nuclear factor kappa-B. This is accomplished by inhibiting the unfolded protein response and reducing the production of reactive oxygen species, thereby inhibiting OS and ERS. This study reveals DHA's therapeutic effect and potential mechanism in NASH, implying that DHA could be a new and promising candidate for NASH therapy.

The B-Cell-Specific Ablation of B4GALT1 Reduces Cancer Formation and Reverses the Changes in Serum IgG Glycans during the Induction of Mouse Hepatocellular Carcinoma

Simple Summary

As serum IgG glycosylation is associated with various cancers, our goal is to explore whether serum IgG galactosylation and its associated glycans could be used as tumor markers associated with hepatocellular carcinoma (HCC). At the same time, we explore the effect of the B-cell-specific ablation of B4GALT1 on HCC and finally analyze whether the low incidence of female cancer was related to the findings from the above perspective. The results demonstrate that the tumor marker of serum IgG glycosylation is galactosylation and its associated glycans and that the B-cell-specific ablation of B4GALT1 reduces HCC formation by reducing serum IgG galactosylation levels and by modulating the associated glycans, meaning that the lower incidence of cancer in women may be related to minor changes in the B-cell B4GALT1 and unchanged serum IgG galactosylation levels. This study aims to provide a theoretical basis for the early diagnosis and prevention of HCC and to determine why it has such a high incidence in males.

Abstract

Serum immunoglobulin G (IgG) glycosylation, especially galactosylation, has been found to be related to a variety of tumors, including hepatocellular carcinoma (HCC). However, whether IgG glycan changes occur in the early stages of HCC formation remains unclear. We found that the galactosylation level increased and that the related individual glycans showed regular changes over the course of HCC induction. Then, the effect of the B-cell-specific ablation of β1,4galactosyltransferase 1 (CKO B4GALT1) and B4GALT1 defects on the IgG glycans that were modified during the model induction process and HCC formation is investigated in this study. CKO B4GALT1 reduces serum IgG galactosylation levels and reduces cancer formation. Furthermore, insignificant changes in the B-cell B4GALT1 and unchanged serum IgG galactosylation levels were found during cancer induction in female mice, which might contribute to the lower cancer incidence in female mice than in male mice. The gender differences observed during glycan and B4GALT1 modification also add more evidence that the B4GALT1 in B cells and in serum IgG galactosylation may play an important role in HCC. Therefore, the findings of the present research can be used to determine the methods for the early detection of HCC as well as for prevention.

O-GlcNAcylation regulation of cellular signaling in cancer

O-GlcNAcylation is a post-translational modification occurring on serine/threonine residues of nuclear and cytoplasmic proteins, mediated by the enzymes OGT and OGA which catalyze the addition or removal of the UDP-GlcNAc moieties, respectively. Structural changes brought by this modification lead to alternations of protein stability, protein-protein interactions, and phosphorylation. Importantly, O-GlcNAcylation is a nutrient sensor by coupling nutrient sensing with cellular signaling. Elevated levels of OGT and O-GlcNAc have been reported in a variety of cancers and has been linked to regulation of multiple cancer signaling pathways. In this review, we discuss the most recent findings on the role of O-GlcNAcylation as a metabolic sensor in signaling pathways and immune response in cancer.

Regulation of Liver Regeneration by Hepatocyte O-GlcNAcylation in Mice

BACKGROUND & AIMS

The liver has a unique capacity to regenerate after injury in a highly orchestrated and regulated manner. Here, we report that O-GlcNAcylation, an intracellular post-translational modification regulated by 2 enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), is a critical termination signal for liver regeneration following partial hepatectomy (PHX).

METHODS

We studied liver regeneration after PHX on hepatocyte specific OGT and OGA knockout mice (OGT-KO and OGA-KO), which caused a significant decrease (OGT-KO) and increase (OGA-KO) in hepatic O-GlcNAcylation, respectively.

RESULTS

OGA-KO mice had normal regeneration, but the OGT-KO mice exhibited substantial defects in termination of liver regeneration with increased liver injury, sustained cell proliferation resulting in significant hepatomegaly, hepatic dysplasia, and appearance of small nodules at 28 days after PHX. This was accompanied by a sustained increase in expression of cyclins along with significant induction in pro-inflammatory and pro-fibrotic gene expression in the OGT-KO livers. RNA-sequencing studies revealed inactivation of hepatocyte nuclear 4 alpha (HNF4α), the master regulator of hepatic differentiation and a known termination signal, in OGT-KO mice at 28 days after PHX, which was confirmed by both Western blot and immunohistochemistry analysis. Furthermore, a significant decrease in HNFα target genes was observed in OGT-KO mice, indicating a lack of hepatocyte differentiation following decreased hepatic O-GlcNAcylation. Immunoprecipitation experiments revealed HNF4α is O-GlcNAcylated in normal differentiated hepatocytes.

CONCLUSIONS

These studies show that O-GlcNAcylation plays a critical role in the termination of liver regeneration via regulation of HNF4α in hepatocytes.

A nexus of lipid and O-Glcnac metabolism in physiology and disease

Although traditionally considered a glucose metabolism-associated modification, the O-linked β-N-Acetylglucosamine (O-GlcNAc) regulatory system interacts extensively with lipids and is required to maintain lipid homeostasis. The enzymes of O-GlcNAc cycling have molecular properties consistent with those expected of broad-spectrum environmental sensors. By direct protein-protein interactions and catalytic modification, O-GlcNAc cycling enzymes may provide both acute and long-term adaptation to stress and other environmental stimuli such as nutrient availability. Depending on the cell type, hyperlipidemia potentiates or depresses O-GlcNAc levels, sometimes biphasically, through a diversity of unique mechanisms that target UDP-GlcNAc synthesis and the availability, activity and substrate selectivity of the glycosylation enzymes, O-GlcNAc Transferase (OGT) and O-GlcNAcase (OGA). At the same time, OGT activity in multiple tissues has been implicated in the homeostatic regulation of systemic lipid uptake, storage and release. Hyperlipidemic patterns of O-GlcNAcylation in these cells are consistent with both transient physiological adaptation and feedback uninhibited obesogenic and metabolic dysregulation. In this review, we summarize the numerous interconnections between lipid and O-GlcNAc metabolism. These links provide insights into how the O-GlcNAc regulatory system may contribute to lipid-associated diseases including obesity and metabolic syndrome.

Pleiotropic actions of IP6K1 mediate hepatic metabolic dysfunction to promote nonalcoholic fatty liver disease and steatohepatitis

OBJECTIVE

Obesity and insulin resistance greatly increase the risk of nonalcoholic fatty liver disease and steatohepatitis (NAFLD/NASH). We have previously discovered that whole-body and adipocyte-specific Ip6k1deletion protects mice from high-fat-diet-induced obesity and insulin resistance due to improved adipocyte thermogenesis and insulin signaling. Here, we aimed to determine the impact of hepatocyte-specific and whole-body Ip6k1 deletion (HKO and Ip6k1-KO or KO) on liver metabolism and NAFLD/NASH.

METHODS

Body weight and composition; energy expenditure; glycemic profiles; and serum and liver metabolic, inflammatory, fibrotic and toxicity parameters were assessed in mice fed Western and high-fructose diet (HFrD) (WD: 40% kcal fat, 1.25% cholesterol, no added choline and HFrD: 60% kcal fructose). Mitochondrial oxidative capacity was evaluated in isolated hepatocytes. RNA-Seq was performed in liver samples. Livers from human NASH patients were analyzed by immunoblotting and mass spectrometry.

RESULTS

HKO mice displayed increased hepatocyte mitochondrial oxidative capacity and improved insulin sensitivity but were not resistant to body weight gain. Improved hepatocyte metabolism partially protected HKO mice from NAFLD/NASH. In contrast, enhanced whole-body metabolism and reduced body fat accumulation significantly protected whole-body Ip6k1-KO mice from NAFLD/NASH. Mitochondrial oxidative pathways were upregulated, whereas gluconeogenic and fibrogenic pathways were downregulated in Ip6k1-KO livers. Furthermore, IP6K1 was upregulated in human NASH livers and interacted with the enzyme O-GlcNAcase that reduces protein O-GlcNAcylation. Protein O-GlcNAcylation was found to be reduced in Ip6k1-KO and HKO mouse livers.

CONCLUSION

Pleiotropic actions of IP6K1 in the liver and other metabolic tissues mediate hepatic metabolic dysfunction and NAFLD/NASH, and thus IP6K1 deletion may be a potential treatment target for this disease.

Lipid response of hepatocellular carcinoma cells to anticancer drug detected on nanostructure-assisted LDI-MS platform

High heterogeneity of hepatocellular carcinoma (HCC) tumor has become an obstacle to select effective therapy for the treatment of HCC patients. Methods that can guide the decision on therapy choice for HCC treatment are highly demanded. Evaluating the drug response of heterogeneous tumor cells at the molecular level can help to reveal the toxicity mechanism of anticancer drugs and provide more information than current cell-based chemosensitivity assays. In the present work, nanostructure-assisted laser desorption/ionization mass spectrometry (NALDI-MS) was used to investigate the lipid response of HCC cells to anticancer drugs. Three types of HCC cells (LM3, Hep G2, Huh7) were treated with sorafenib, doxorubicin hydro-chloride, and cisplatin. We found that the lipid profiles of HCC cells changed a lot after the drug treatment, and the degree of lipid changes was related to the cell viability. Two pairs of fatty acids C16:1/C16:0 and C18:1/C18:0 were found to be strongly related to the viability of HCC cells after drug treatment, and were more sensitive than Methyl-thiazolyl tetrazolium (MTT) assay. Accordingly, they can act as sensitive and comprehensive indexes to evaluate the drug susceptibility of HCC cells. In addition, the peak ratio of several neighboring phospholipids displayed high correlation with drug response of specific cell subtype to specific drug. The ratio of neighboring lipids may be traced back to the activity of enzyme and gene expression which regulate the lipidomic pathway. This method provides drug response of heterogenous tumor cells at molecular level and could be a potential candidate to precise tumor chemosensitivity assay.

Comparative proteomic profiling reveals a pathogenic role for the O-GlcNAcylated AIMP2-PARP1 complex in aging-related hepatic steatosis in mice

The prevalence of non-alcoholic fatty liver disease (NAFLD) increases with aging. However, the mechanism of aging-related NAFLD remains unclear. Herein, we constructed an aging-related hepatic steatosis model and analyzed the differentially expressed proteins (DEPs) in livers from young and old mice using liquid chromatography-mass spectrometry. Five hundred and eighty-eight aging-related DEPs and novel pathways were identified. Aminoacyl tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2), the most significantly upregulated protein, promoted poly(ADP-ribose) polymerase 1 (PARP1) activation in aging-related hepatic steatosis. Additionally, mice liver-specific O-GlcNAcase knockout promoted AIMP2 and PARP1 expression. O-GlcNAc transferase (OGT) overexpression and O-GlcNAcase inhibition by genetic or pharmaceutical manipulations increased AIMP2 and PARP1 levels in vitro. Mechanistically, O-GlcNAcylation increased AIMP2 protein stability, leading to its aggregation. Our study reveals O-GlcNAcylated AIMP2 as a novel pathogenic regulator of aging-related hepatic steatosis.

Alterations in Faecal Metagenomics and Serum Metabolomics Indicate Management Strategies for Patients With Budd-Chiari Syndrome

We investigated the effects of gut microbiota and serum metabolite levels in patients with Budd-Chiari syndrome (B-CS) and their importance for guiding clinical management strategies. In total, 214 B-CS patients (93 untreated and 121 treated) and 41 healthy controls were enrolled. Gut microbiota and serum metabolome were analysed using shotgun metagenomics and liquid chromatography-mass spectrometry. The gut microbiota of the patients showed abundance of Campylobacter and low levels of Saccharomyces, Deinococcus, and Thiomonas (P < 0.05). Thirty metabolites, including taurocholate and (R)-3-hydroxybutyric acid, were identified in the patients (VIP > 1, P < 0.05 and FC > 1.2 or FC < 0.83). Random forest (RF) models showed that serum metabolome could effectively identify B-CS from healthy controls and RF-metabolomics exhibited perfect discrimination (AUC = 100%, 95% CI: 100% – 100%), which was significantly higher than that achieved by RF-metagenomics (AUC = 58.48%, 95% CI: 38.46% – 78.5%). Campylobacter concisus and taurocholate showed significant positive correlation in patients with clinical manifestations (P < 0.05). Actinobacteria levels were significantly higher in untreated patients than in treated patients (P < 0.05). Campylobacter and Veillonella levels were significantly higher in treated patients than in healthy controls (P < 0.05). We identified major alterations in the gut microbiota and serum metabolome of patients with B-CS. Faecal metagenomics- and serum metabolomics-guided management strategies are required for patients with B-CS.

O-GlcNAc Transferase (OGT) Protects Cerebral Neurons from Death During Ischemia/Reperfusion (I/R) Injury by Modulating Drp1 in Mice

Previous studies have demonstrated that increased O-linked N-acetylglucosamine (O-GlcNAc) level could promote cell survival following environmental stresses. This study aimed to explore the role of O-GlcNAc transferase (OGT) during cerebral ischemia/reperfusion (I/R) injury. The mouse model with cerebral I/R injury was induced by middle cerebral artery occlusion/reperfusion (MCAO/R). The expression of ogt in brain tissues was detected by qRT-PCR, Western blot, and immunohistochemistry (IHC) staining assay. Neurological deficit was evaluated using a modified scoring system. The infarct volume was assessed by TTC staining assay. Neuronal apoptosis in brain tissues was evaluated by TUNEL staining assay. The level of cleaved caspase-3 in brain tissues was detected by Western blot and IHC staining assay. The expression of critical proteins involved in mitochondrial fission, including OPA1, Mfn1, and Mfn2, as well as Mff and Drp1 was detected by Western blot and IHC, respectively. The expression of ogt during cerebral I/R injury was significantly upregulated. Ogt knockdown significantly increased neurological score and infarct volume in I/R-induced mice. Meanwhile, ogt knockdown significantly enhanced neuronal apoptosis and cleaved caspase-3 level in brain tissues of I/R-induced mice. In addition, ogt knockdown markedly decreased serine 637 phosphorylation level of mitochondrial fission protein dynamin-related protein 1 (Drp1) and promoted Drp1 translocation from the cytosol to the mitochondria. Moreover, the specific Drp1 inhibitor mdivi-1 effectively attenuated ogt knockdown-induced brain injury of I/R-stimulated mice in vivo. Our study revealed that OGT protects against cerebral I/R injury by inhibiting the function of Drp1 in mice, suggesting that ogt may be a potential therapeutic target for cerebral I/R injury.

Role and Function of O-GlcNAcylation in Cancer

Simple Summary

Despite the rapid advancement in immunotherapy and targeted agents, many patients diagnosed with cancer have poor prognosis with dismal overall survival. One of the key hallmarks of cancer is the ability of cancer cells to reprogram their energy metabolism. O-GlcNAcylation is an emerging potential mechanism for cancer cells to induce proliferation and progression of tumor cells and resistance to chemotherapy. This review summarizes the mechanism behind O-GlcNAcylation and discusses the role of O-GlcNAcylation, including its function with receptor tyrosine kinase and chemo-resistance in cancer, and immune response to cancer and as a prognostic factor. Further pre-clinical studies on O-GlcNAcylation are warranted to assess the clinical efficacy of agents targeting O-GlcNAcylation.

Abstract

Cancer cells are able to reprogram their glucose metabolism and retain energy via glycolysis even under aerobic conditions. They activate the hexosamine biosynthetic pathway (HBP), and the complex interplay of O-linked N-acetylglucosaminylation (O-GlcNAcylation) via deprivation of nutrients or increase in cellular stress results in the proliferation, progression, and metastasis of cancer cells. Notably, cancer is one of the emerging diseases associated with O-GlcNAcylation. In this review, we summarize studies that delineate the role of O-GlcNAcylation in cancer, including its modulation in metastasis, function with receptor tyrosine kinases, and resistance to chemotherapeutic agents, such as cisplatin. In addition, we discuss the function of O-GlcNAcylation in eliciting immune responses associated with immune surveillance in the tumor microenvironment. O-GlcNAcylation is increasingly accepted as one of the key players involved in the activation and differentiation of T cells and macrophages. Finally, we discuss the prognostic role of O-GlcNAcylation and potential therapeutic agents such as O-linked β-N-acetylglucosamine-transferase inhibitors, which may help overcome the resistance mechanism associated with the reprogramming of glucose metabolism.

P53 suppresses the progression of hepatocellular carcinoma via miR-15a by decreasing OGT expression and EZH2 stabilization

Existing literature has highlighted the tumour suppressive capacity of microRNA-15a (miR-15a); however, its role in hepatocellular carcinoma (HCC) remains relatively unknown. This study aimed to investigate the role of miR-15a in HCC and the associated underlying mechanism. Initially, RT-qPCR was performed to detect the expression of miR-15a in HCC tissues and cells. Bioinformatics analysis, Pearson correlation coefficient, dual-luciferase reporter assay, and molecular approaches were all conducted to ascertain the interaction between miR-15a and O-linked N-acetylglucosamine (GlcNAc) transferase (OGT). PUGNAc treatment and cycloheximide (CHX) assay were performed to evaluate O-GlcNAc and the stabilization of the enhancer of zeste homolog 2 (EZH2). Finally, gain- and loss-of-function studies were employed to elucidate the role of P53 and the miR-15a/OGT/EZH2 axis in the progression of HCC, followed by in vivo experiments based on tumour-bearing nude mice. Our results demonstrated that the miR-15a expression was decreased in the HCC tissues and cells. P53 upregulated miR-15a expression, which inhibited the proliferation, migration and invasion of HCC cells, while inducing apoptosis and triggering a G0/G1 cell cycle phase arrest. OGT stabilized EZH2 via catalysing O-GlcNAc, which reversed the effect of P53 and miR-15a. The results of our in vivo study provided evidence demonstrating that P53 could suppress the development of HCC via the miR-15a/OGT/EZH2 axis. P53 was found to inhibit the OGT expression by promoting the expression of miR-15a, which destabilized EZH2 and suppressed the development of HCC. The key findings of our study highlight a promising novel therapeutic strategy for the treatment of HCC.