Molecular link between glucose and glutamine consumption in cancer cells mediated by CtBP and SIRT4

NUAKs promote mTOR/c-Myc-induced glucose and glutamine reprogramming for cell growth and metastasis in breast cancer cells

Breast cancer progression and metastasis are closely connected to changes in glucose and glutamine metabolism. While Novel (nua) kinase family 1 (NUAK1) and Novel (nua) kinase family 2 (NUAK2), which are two members of the AMPK-related kinases, have been associated with breast tumorigenesis, their role in the metabolic reprogramming that occurs during breast cancer progression remains unclear. Our research uncovers that NUAKs expression is significantly higher in breast cancer tissues and cell lines, and it is positively related to glycolysis, the pentose phosphate pathway (PPP), glutamine metabolism, and a poor prognosis for breast cancer patients. We show that NUAKs significantly increase metabolic reprogramming, including aerobic glycolysis, PPP, and glutamine metabolism in triple negative breast cancer subtypes but only induce aerobic glycolysis and PPP in luminal breast cancer subtypes to meet the anabolic demands of rapidly dividing breast cancer cells. In contrast, the depletion of NUAKs has the opposite effect. Mechanistic insights reveal that NUAKs activate mammalian target of rapamycin (mTOR) signaling, which in turn upregulates the c-Myc transcription factor, a crucial regulator of glucose and glutamine metabolic gene expression. Moreover, we demonstrate that NUAKs enhance mTOR/c-Myc signaling pathways, leading to increased glucose and glutamine reprogramming, which supports rapid cell proliferation and metastatic potential in breast cancer cells. Importantly, pretreating breast cancer cells with mTOR inhibitors blocked the metabolic reprogramming and tumor-promoting effect of NUAK1/2. Therefore, targeting NUAKs may represent a novel therapeutic strategy for the treatment of breast cancer.

Sirtuin insights: bridging the gap between cellular processes and therapeutic applications

The greatest challenges that organisms face today are effective responses or detection of life-threatening environmental changes due to an obvious semblance of stress and metabolic fluctuations. These are associated with different pathological conditions among which cancer is most important. Sirtuins (SIRTs; NAD+-dependent enzymes) are versatile enzymes with diverse substrate preferences, cellular locations, crucial for cellular processes and pathological conditions. This article describes in detail the distinct roles of SIRT isoforms, unveiling their potential as either cancer promoters or suppressors and also explores how both natural and synthetic compounds influence the SIRT function, indicating promise for therapeutic applications. We also discussed the inhibitors/activators tailored to specific SIRTs, holding potential for diseases lacking effective treatments. It may uncover the lesser-studied SIRT isoforms (e.g., SIRT6, SIRT7) and their unique functions. This article also offers a comprehensive overview of SIRTs, linking them to a spectrum of diseases and highlighting their potential for targeted therapies, combination approaches, disease management, and personalized medicine. We aim to contribute to a transformative era in healthcare and innovative treatments by unraveling the intricate functions of SIRTs.

Norovirus NS1/2 protein increases glutaminolysis for efficient viral replication

Viruses are obligate intracellular parasites that rely on host cell metabolism for successful replication. Thus, viruses rewire host cell pathways involved in central carbon metabolism to increase the availability of building blocks for successful propagation. However, the underlying mechanisms of virus-induced alterations to host metabolism are largely unknown. Noroviruses (NoVs) are highly prevalent pathogens that cause sporadic and epidemic viral gastroenteritis. In the present study, we uncovered several strain-specific and shared host cell metabolic requirements of three murine norovirus (MNV) strains, MNV-1, CR3, and CR6. While all three strains required glycolysis, glutaminolysis, and the pentose phosphate pathway for optimal infection of macrophages, only MNV-1 relied on host oxidative phosphorylation. Furthermore, the first metabolic flux analysis of NoV-infected cells revealed that both glycolysis and glutaminolysis are upregulated during MNV-1 infection of macrophages. Glutamine deprivation affected the viral lifecycle at the stage of genome replication, resulting in decreased non-structural and structural protein synthesis, viral assembly, and egress. Mechanistic studies further showed that MNV infection and overexpression of the non-structural protein NS1/2 increased the enzymatic activity of the rate-limiting enzyme glutaminase. In conclusion, the inaugural investigation of NoV-induced alterations to host glutaminolysis identified NS1/2 as the first viral molecule for RNA viruses that regulates glutaminolysis either directly or indirectly. This increases our fundamental understanding of virus-induced metabolic alterations and may lead to improvements in the cultivation of human NoVs.

SIRT4 promotes neuronal apoptosis in models of Alzheimer's disease via the STAT2-SIRT4-mTOR pathway

Alzheimer's disease (AD) is the leading cause of dementia and presents a considerable disease burden. Its pathology involves substantial neuronal loss, primarily attributed to neuronal apoptosis. Although sirtuin 4 (SIRT4) has been implicated in regulating apoptosis in various diseases, the role of SIRT4 in AD pathology remains unclear. The study used APP/PS1 mice as an animal model of AD and amyloid-β (Aβ)1-42-treated HT-22 cells as an AD cell model. SIRT4 expression was determined by quantitative real-time polymerase chain reaction, Western blot, and immunofluorescence. A Sirt4 knockdown model was established by intracranial injection of lentivirus-packaged sh-SIRT4 and cellular lentivirus transfection. Immunohistochemistry and flow cytometry were used to examine Aβ deposition in mice and apoptosis, respectively. Protein expression was assessed by Western blot analysis. The UCSC and JASPAR databases were used to predict upstream transcription factors of Sirt4. Subsequently, the binding of transcription factors to Sirt4 was analyzed using a dual-luciferase assay and chromatin immunoprecipitation. SIRT4 expression was upregulated in both APP/PS1 mice and Aβ-treated HT-22 cells compared with their respective control groups. Sirt4 knockdown in animal and cellular models of AD resulted in reduced apoptosis, decreased Aβ deposition, and amelioration of learning and memory impairments in mice. Mechanistically, SIRT4 modulates apoptosis via the mTOR pathway and is negatively regulated by the transcription factor signal transducer and activator of transcription 2 (STAT2). Our study findings suggest that targeting the STAT2-SIRT4-mTOR axis may offer a new treatment approach for AD.NEW & NOTEWORTHY The study reveals that in Alzheimer's disease models, SIRT4 expression increases, contributing to neuronal apoptosis and amyloid-β deposition. Reducing SIRT4 lessens apoptosis and amyloid-β accumulation, improving memory in mice. This process involves the mTOR pathway, regulated by STAT2 transcription factor. These findings suggest targeting the STAT2-SIRT4-mTOR axis as a potential Alzheimer's treatment strategy.

Identification and characterization of a new potent inhibitor targeting CtBP1/BARS in melanoma cells

BACKGROUND

The C-terminal-binding protein 1/brefeldin A ADP-ribosylation substrate (CtBP1/BARS) acts both as an oncogenic transcriptional co-repressor and as a fission inducing protein required for membrane trafficking and Golgi complex partitioning during mitosis, hence for mitotic entry. CtBP1/BARS overexpression, in multiple cancers, has pro-tumorigenic functions regulating gene networks associated with "cancer hallmarks" and malignant behavior including: increased cell survival, proliferation, migration/invasion, epithelial-mesenchymal transition (EMT). Structurally, CtBP1/BARS belongs to the hydroxyacid-dehydrogenase family and possesses a NAD(H)-binding Rossmann fold, which, depending on ligands bound, controls the oligomerization of CtBP1/BARS and, in turn, its cellular functions. Here, we proposed to target the CtBP1/BARS Rossmann fold with small molecules as selective inhibitors of mitotic entry and pro-tumoral transcriptional activities.

METHODS

Structured-based screening of drug databases at different development stages was applied to discover novel ligands targeting the Rossmann fold. Among these identified ligands, N-(3,4-dichlorophenyl)-4-{[(4-nitrophenyl)carbamoyl]amino}benzenesulfonamide, called Comp.11, was selected for further analysis. Fluorescence spectroscopy, isothermal calorimetry, computational modelling and site-directed mutagenesis were employed to define the binding of Comp.11 to the Rossmann fold. Effects of Comp.11 on the oligomerization state, protein partners binding and pro-tumoral activities were evaluated by size-exclusion chromatography, pull-down, membrane transport and mitotic entry assays, Flow cytometry, quantitative real-time PCR, motility/invasion, and colony assays in A375MM and B16F10 melanoma cell lines. Effects of Comp.11 on tumor growth in vivo were analyzed in mouse tumor model.

RESULTS

We identify Comp.11 as a new, potent and selective inhibitor of CtBP1/BARS (but not CtBP2). Comp.11 directly binds to the CtBP1/BARS Rossmann fold affecting the oligomerization state of the protein (unlike other known CtBPs inhibitors), which, in turn, hinders interactions with relevant partners, resulting in the inhibition of both CtBP1/BARS cellular functions: i) membrane fission, with block of mitotic entry and cellular secretion; and ii) transcriptional pro-tumoral effects with significantly hampered proliferation, EMT, migration/invasion, and colony-forming capabilities. The combination of these effects impairs melanoma tumor growth in mouse models.  CONCLUSIONS: This study identifies a potent and selective inhibitor of CtBP1/BARS active in cellular and melanoma animal models revealing new opportunities to study the role of CtBP1/BARS in tumor biology and to develop novel melanoma treatments.

Joint modeling of association networks and longitudinal biomarkers: An application to childhood obesity

The prevalence of chronic non-communicable diseases such as obesity has noticeably increased in the last decade. The study of these diseases in early life is of paramount importance in determining their course in adult life and in supporting clinical interventions. Recently, attention has been drawn to approaches that study the alteration of metabolic pathways in obese children. In this work, we propose a novel joint modeling approach for the analysis of growth biomarkers and metabolite associations, to unveil metabolic pathways related to childhood obesity. Within a Bayesian framework, we flexibly model the temporal evolution of growth trajectories and metabolic associations through the specification of a joint nonparametric random effect distribution, with the main goal of clustering subjects, thus identifying risk sub-groups. Growth profiles as well as patterns of metabolic associations determine the clustering structure. Inclusion of risk factors is straightforward through the specification of a regression term. We demonstrate the proposed approach on data from the Growing Up in Singapore Towards healthy Outcomes cohort study, based in Singapore. Posterior inference is obtained via a tailored MCMC algorithm, involving a nonparametric prior with mixed support. Our analysis has identified potential key pathways in obese children that allow for the exploration of possible molecular mechanisms associated with childhood obesity.

Cancer risk according to fasting blood glucose trajectories: a population-based cohort study

INTRODUCTION

Diabetes mellitus is known to increase the risk of cancer. Fasting blood glucose (FBG) levels can be changed over time. However, the association between FBG trajectory and cancer risk has been insufficiently studied. This research aims to examine the relationship between FBG trajectories and cancer risk in the Korean population.

RESEARCH DESIGN AND METHODS

We analyzed data from the National Health Insurance Service-National Health Screening Cohort collected between 2002 and 2015. Group-based trajectory modeling was performed on 256,271 Koreans aged 40-79 years who had participated in health examinations at least three times from 2002 to 2007. After excluding patients with cancer history before 2008, we constructed a cancer-free cohort. The Cox proportional hazards model was applied to examine the association between FBG trajectories and cancer incidence by cancer type, after adjustments for covariates. Cancer case was defined as a person who was an outpatient thrice or was hospitalized once or more with a cancer diagnosis code within the first year of the claim.

RESULTS

During the follow-up time (2008-2015), 18,991 cancer cases were identified. Four glucose trajectories were found: low-stable (mean of FBG at each wave <100 mg/dL), elevated-stable (113-124 mg/dL), elevated-high (104-166 mg/dL), and high-stable (>177 mg/dL). The high-stable group had a higher risk of multiple myeloma, liver cancer and gastrointestinal cancer than the low-stable group, with HR 4.09 (95% CI 1.40 to 11.95), HR 1.68 (95% CI 1.25 to 2.26) and HR 1.27 (95% CI 1.11 to 1.45), respectively. In elevated-stable trajectory, the risk increased for all cancer (HR 1.08, 95% CI 1.02 to 1.16) and stomach cancer (HR 1.24, 95% CI 1.07 to 1.43). Significant associations were also found in the elevated-high group with oral (HR 2.13, 95% CI 1.01 to 4.47), liver (HR 1.50, 95% CI 1.08 to 2.08) and pancreatic cancer (HR 1.99, 95% CI 1.20 to 3.30).

CONCLUSIONS

Our study highlights that the uncontrolled high glucose level for many years may increase the risk of cancer.

Norovirus NS1/2 protein increases glutaminolysis for efficient viral replication

Viruses are obligate intracellular parasites that rely on host cell metabolism for successful replication. Thus, viruses rewire host cell pathways involved in central carbon metabolism to increase the availability of building blocks for replication. However, the underlying mechanisms of virus-induced alterations to host metabolism are largely unknown. Noroviruses (NoVs) are highly prevalent pathogens that cause sporadic and epidemic viral gastroenteritis. In the present study, we uncovered several strain-specific and shared host cell metabolic requirements of three murine norovirus (MNV) strains, the acute MNV-1 strain and the persistent CR3 and CR6 strains. While all three strains required glycolysis, glutaminolysis, and the pentose phosphate pathway for optimal infection of macrophages, only MNV-1 relied on host oxidative phosphorylation. Furthermore, the first metabolic flux analysis of NoV-infected cells revealed that both glycolysis and glutaminolysis are upregulated during MNV-1 infection of macrophages. Glutamine deprivation affected the MNV lifecycle at the stage of genome replication, resulting in decreased non-structural and structural protein synthesis, viral assembly, and egress. Mechanistic studies further showed that MNV infection and overexpression of the MNV non-structural protein NS1/2 increased the enzymatic activity of the rate-limiting enzyme glutaminase. In conclusion, the inaugural investigation of NoV-induced alterations to host glutaminolysis identified the first viral regulator of glutaminolysis for RNA viruses, which increases our fundamental understanding of virus-induced metabolic alterations.

Monocarboxylate Transporter-1 (MCT1)-Mediated Lactate Uptake Protects Pancreatic Adenocarcinoma Cells from Oxidative Stress during Glutamine Scarcity Thereby Promoting Resistance against Inhibitors of Glutamine Metabolism

Metabolic compartmentalization of stroma-rich tumors, like pancreatic ductal adenocarcinoma (PDAC), greatly contributes to malignancy. This involves cancer cells importing lactate from the microenvironment (reverse Warburg cells) through monocarboxylate transporter-1 (MCT1) along with substantial phenotype alterations. Here, we report that the reverse Warburg phenotype of PDAC cells compensated for the shortage of glutamine as an essential metabolite for redox homeostasis. Thus, oxidative stress caused by glutamine depletion led to an Nrf2-dependent induction of MCT1 expression in pancreatic T3M4 and A818-6 cells. Moreover, greater MCT1 expression was detected in glutamine-scarce regions within tumor tissues from PDAC patients. MCT1-driven lactate uptake supported the neutralization of reactive oxygen species excessively produced under glutamine shortage and the resulting drop in glutathione levels that were restored by the imported lactate. Consequently, PDAC cells showed greater survival and growth under glutamine depletion when utilizing lactate through MCT1. Likewise, the glutamine uptake inhibitor V9302 and glutaminase-1 inhibitor CB839 induced oxidative stress in PDAC cells, along with cell death and cell cycle arrest that were again compensated by MCT1 upregulation and forced lactate uptake. Our findings show a novel mechanism by which PDAC cells adapt their metabolism to glutamine scarcity and by which they develop resistance against anticancer treatments based on glutamine uptake/metabolism inhibition.

Hypoxia and lactate influence VOC production in A549 lung cancer cells

Introduction: Cancer cells emit characteristic volatile organic compounds (VOCs), which are potentially generated from ROS-based lipid peroxidation of polyunsaturated fatty acids. The metabolism of such VOCs and their regulation remain to be fully investigated. In fact, the enzymes involved in the synthesis of these VOCs have not been described yet. Methods: In this study, we firstly conducted in vitro enzyme assays and demonstrated that recombinant alcohol dehydrogenase (ADH) converted Trans 2-hexenal into Trans 2-hexenol. The latter has previously been reported as a cancer VOC. To study VOC metabolism, 14 different culture conditions were compared in view of Trans 2-hexenol production. Results and discussion: The data indicate that hypoxia and the addition of lactate positively influenced Trans 2-hexenol production in A549 cancer cells. The RNAseq data suggested certain gene expressions in the VOC pathway and in lactate signaling, parallel to VOC production. This implies that hypoxia and lactate signaling with a VOC production can be characteristic for cancer in vitro.

Ferroptosis, a subtle talk between immune system and cancer cells: To be or not to be?

Ferroptosis, an established form of programmed cell death discovered in 2012, is characterized by an imbalance in iron metabolism, lipid metabolism, and antioxidant metabolism. Activated CD8 + T cells can trigger ferroptosis in tumor cells by releasing interferon-γ, which initiates the ferroptosis program. Despite the remarkable progress made in treating various tumors with immunotherapy, such as anti-PD1/PDL1, there are still significant challenges to overcome, including limited treatment options and drug resistance. In this review, we exam the potential biological significance of the ferroptosis phenotype using bioinformatics and review the latest advancements in understanding the mechanism of ferroptosis-mediated anti-tumor immunotherapy. Furthermore, we revisit the host immune system, immune microenvironment, ferroptotic defense system, metabolic reprogramming, and key genes that regulate the occurrence and resistance of ferroptosis of tumor cell. Additionally, several immune-combined ferroptosis treatment strategies were put forward to improve immunotherapy efficacy and to provide new insights into reversing anti-tumor immune drug resistance.

Non-ammoniagenic proliferation and differentiation media for cultivated adipose tissue

Ammonia (Amm), and its aqueous solved state, ammonium, which is produced from glutamine (Gln) metabolism, is a known inhibitor of stem cell proliferation in vitro. In the context of cultivated beef, primary bovine fibro-adipogenic progenitor cells (FAPs) need to be grown and differentiated for several weeks in vitro for the production of cultivated fat. In this study, the ammonium sensitivity of these cells was investigated by introducing ammonium chloride, which was found to inhibit their proliferation when above 5 mM and their adipogenic differentiation when above 2 mM. Novel serum-free proliferation and differentiation media were hence developed with the aim to suppress Amm production during expansion and adipogenesis. Glutamine substitutes, such as a-ketoglutarate (aKG), glutamate (Glt) and pyruvate (Pyr) were investigated. It was found that aKG based proliferation medium (PM) was the most effective in promoting and maintaining FAPs growth over several passages while the specific Amm production rate was reduced more than 5-fold. In terms of differentiation capacity, the substitution of glucose (Gluc) and Gln with galactose (Gal) and Pyr was shown to be the most effective in promoting FAPs differentiation into mature adipocytes, resulting in over 2-fold increase of fat volume per cell, while suppressing Amm production. Our findings suggest that FAPs do not require Gln as an essential nutrient but, on the contrary, possess all the necessary metabolic pathways to proliferate and subsequently differentiate in a Gln-free medium, resulting in decreased Amm production rates and seemingly synthesising glutamine de novo. These findings are important for prolonging the lifespan of culture medium, allowing for reduced costs and process interventions.

The mitochondrial chaperone TRAP-1 regulates the glutamine metabolism in tumor cells

Understanding cancer cell metabolism always provides information on hidden dimensions of tumor adaptations. Warburg's theory that cancer cells opt for aerobic glycolysis over the mitochondrial oxidative phosphorylation (OXPHOS) system is widely accepted. However, the hypothesis does not explain the mitochondrion's role in these cells. Here, we demonstrate that intact mitochondria are used for anaplerotic functions and ATP production by utilizing glutamine with the help of mitochondrial chaperone TRAP-1 (Tumor Necrosis Factor Receptor-associated Protein 1). TRAP-1 otherwise promotes aerobic glycolysis by lowering the mitochondrial OXPHOS in the presence of glucose. Here, we show that TRAP-1 maintains mitochondrial integrity and augments glutamine metabolism upon glucose deprivation to meet the cellular energy demand. The enhanced PER and ECAR correlating with increased ATP production suggest that glutamine fuels mitochondria in the presence of TRAP-1. We also found that TRAP1-dependent glutamine utilization involves the HIF2α-SLC1A5-GLS axis and is independent of hypoxia. Subsequently, we show that the metastatic potential of tumor cells is linked with glucose utilization, whereas the proliferative potential is linked with both glucose and glutamine utilization. Our findings establish that TRAP-1 contributes to enhanced glutamine utilization through the HIF2α-SLC1A5-GLS axis. Our results endow that TRAP-1 inhibitors can be potential drug candidates to combat tumor metabolism. Therefore, their use, either alone or in combination with existing chemotherapeutic agents, may target tumor metabolism and improve anticancer treatment response.

Metabolic modulation of CtBP dimeric status impacts the repression of DNA damage repair genes and the platinum sensitivity of ovarian cancer

Platinum drug-based chemotherapy plays a dominant role in OC (ovarian cancer) treatment. The expression of DNA damage repair (DDR) genes is critical in distinguishing drug-sensitive and drug-refractory patients, as well as in the development of drug resistance in long-term treated patients. CtBP is a highly expressed oncogene in OC and was found to repress DDR genes expression in our previous study. In the present study, the formation of CtBP dimers in live cells was studied, and the functional differences between monomeric and oligomeric CtBP were explored by CHIP-seq and RNA-seq. Besides, the dynamics of CtBP dimer formation in response to the metabolic modulation were investigated by the protein fragment complementation (PCA) assays. We show that dimerized CtBP, but not the dimerization-defective mutant, binds to and represses DDR gene expression in OC cells. Treatment of the mice tumors grown from engrafted OC cells by cisplatin disclosed that high-level CtBP expression promotes the CtBP dimerization and increases the therapeutic effect of cisplatin. Moreover, the CtBP dimerization is responsive to the intracellular metabolic status as represented by the free NADH abundance. Metformin was found to increase the dimerization of CtBP and potentiate the therapeutic effect of cisplatin in a CtBP dimerization-dependent manner. Our data suggest that the CtBP dimerization status is a potential biomarker to predict platinum drug sensitivity in patients with ovarian cancer and a target of metformin to improve the therapeutic effect of platinum drugs in OC treatment.

NEAT1 is essential for metabolic changes that promote breast cancer growth and metastasis

Accelerated glycolysis is the main metabolic change observed in cancer, but the underlying molecular mechanisms and their role in cancer progression remain poorly understood. Here, we show that the deletion of the long noncoding RNA (lncRNA) Neat1 in MMTV-PyVT mice profoundly impairs tumor initiation, growth, and metastasis, specifically switching off the penultimate step of glycolysis. Mechanistically, NEAT1 directly binds and forms a scaffold bridge for the assembly of PGK1/PGAM1/ENO1 complexes and thereby promotes substrate channeling for high and efficient glycolysis. Notably, NEAT1 is upregulated in cancer patients and correlates with high levels of these complexes, and genetic and pharmacological blockade of penultimate glycolysis ablates NEAT1-dependent tumorigenesis. Finally, we demonstrate that Pinin mediates glucose-stimulated nuclear export of NEAT1, through which it exerts isoform-specific and paraspeckle-independent functions. These findings establish a direct role for NEAT1 in regulating tumor metabolism, provide new insights into the Warburg effect, and identify potential targets for therapy.

Emerging Roles of Energy Metabolism in Ferroptosis Regulation of Tumor Cells

Ferroptosis is a new form of regulated cell death, which is characterized by the iron-dependent accumulation of lethal lipid peroxides and involved in many critical diseases. Recent reports revealed that cellular energy metabolism activities such as glycolysis, pentose phosphate pathway (PPP), and tricarboxylic acid cycle are involved in the regulation of key ferroptosis markers such as reduced nicotinamide adenine dinucleotide phosphate (NADPH), glutathione (GSH), and reactive oxygen species (ROS), therefore imposing potential regulatory roles in ferroptosis. Remarkably, tumor cells can activate adaptive metabolic responses to inhibit ferroptosis for self-preservation such as the upregulation of glycolysis and PPP. Due to the rapid proliferation of tumor cells and the intensified metabolic rate, tumor energy metabolism has become a target for disrupting the redox homeostasis and induce ferroptosis. Based on these emerging insights, regulatory impact of those-tumor specific metabolic aberrations is systematically characterized, such as rewired glucose metabolism and metabolic compensation through glutamine utilization on ferroptosis and analyzed the underlying molecular mechanisms. Additionally, those ferroptosis-based therapeutic strategies are also discussed by exploiting those metabolic vulnerabilities, which may open up new avenues for tumor treatment in a clinical context.

Transcriptomics and Metabolomics Integration Reveals Redox-Dependent Metabolic Rewiring in Breast Cancer Cells

Rewiring glucose metabolism toward aerobic glycolysis provides cancer cells with a rapid generation of pyruvate, ATP, and NADH, while pyruvate oxidation to lactate guarantees refueling of oxidized NAD⁺ to sustain glycolysis. CtPB2, an NADH-dependent transcriptional co-regulator, has been proposed to work as an NADH sensor, linking metabolism to epigenetic transcriptional reprogramming. By integrating metabolomics and transcriptomics in a triple-negative human breast cancer cell line, we show that genetic and pharmacological down-regulation of CtBP2 strongly reduces cell proliferation by modulating the redox balance, nucleotide synthesis, ROS generation, and scavenging. Our data highlight the critical role of NADH in controlling the oncogene-dependent crosstalk between metabolism and the epigenetically mediated transcriptional program that sustains energetic and anabolic demands in cancer cells.

Mammalian SIRT4 is a tumor suppressor of clear cell renal cell carcinoma by inhibiting cancer proliferation, migration and invasion

OBJECTIVE

Sirtuins family are defined as class III histone deacetylases (HDACs). Recently, mammalian silent information regulator two 4 (SIRT4) has been reported to be a tumor suppressor gene in multiple cancers. The objective of the present study was to explore the potential role of SIRT4 in clear cell renal cell carcinoma (ccRCC).

METHODS

We estimated SIRT4 expression levels in ccRCC and its adjacent non-neoplastic tissue by Western blotting (WB), quantitative real-time polymerase chain reaction (qRT-PCR) and bioinformatics data, the clinical and survival data were also collected and analyzed. In vitro study, ccRCC cell lines were transfected with SIRT4-siRNA or lentivirus to downregulate or overexpress the expression level of SIRT4. Then, the proliferation capacity of tumor cell was assessed by 5-Ethynyl-2'-deoxyuridine (EDU) assay, cell migration and invasion capacity were assessed by Transwell assays.

RESULTS

Our results indicated that the expression level of SIRT4 in ccRCC was significantly lower than the corresponding normal tissues (P< 0.001). Meanwhile, bioinformatics data and the result of WB showed that low SIRT4 expression level was obviously involved with poor overall survival and advanced tumor stage in ccRCC patients. Biological experiments demonstrated that overexpression of SIRT4 significantly reduced the proliferation, migration and invasion ability of ccRCC cells. Conversely, downregulation of SIRT4 enhanced the proliferation, migration and invasion ability of ccRCC cells.

CONCLUSIONS

These findings support that SIRT4 acts as a tumor suppressor in ccRCC and might be a novel biomarker and new therapeutic target for ccRCC.

SIRT4 is the molecular switch mediating cellular proliferation in colorectal cancer through GLS mediated activation of AKT/GSK3β/CyclinD1 pathway

Mitochondria-localized sirtuin 4 (SIRT4) is associated with malignant phenotypes in colorectal cancer (CRC). However, the molecular mechanisms that drive SIRT4-mediated carcinogenesis are unclear. Initially, we confirmed expression of SIRT4 in CRC through public database and in CRC patient tissues using quantitative real-time reverse transcription PCR. We established HCT116 colorectal cells that overexpressed SIRT4 and HT29 cells were transfected with plasmids bearing a small interfering RNA construct to silence SIRT4. Assays to determine the malignant phenotypes (proliferation, invasion and migration) were performed. Xenograft in vivo models were also constructed. A protein interactome network was built using differentially expressed proteins identified using the liquid chromatography/tandem mass spectrophotometry, the findings of which were confirmed using co-immunoprecipitation, western blotting and phenotype rescue experiments. Decreased SIRT4 expression was associated with malignant phenotypes in vitro and in vivo. The ribosomal biogenesis pathway was enriched in the interactome network. SIRT4 suppression activated glutaminase, thereby initiating AKT activation. Our research provided novel insights into the molecular mechanisms underlying CRC, and identified that SIRT4 exerts its antitumor activity in CRC possibly dependent on glutaminase to inhibit proliferation, migration and invasion via the AKT/GSK3β/CyclinD1 pathway.

Mitochondrial sirtuins in stem cells and cancer

The mammalian sirtuin family consists of seven proteins, three of which (SIRT3, SIRT4, and SIRT5) localise specifically within mitochondria and preserve mitochondrial function and homeostasis. Mitochondrial sirtuins are involved in diverse functions such as deacetylation, ADP-ribosylation, demalonylation and desuccinylation, thus affecting various aspects of cell fate. Intriguingly, mitochondrial sirtuins are able to manage these delicate processes with accuracy mediated by crosstalk between the nucleus and mitochondria. Previous studies have provided ample information about their substrates and targets, whereas less is known about their role in cancer and stem cells. Here, we review and discuss recent advances in our understanding of the structural and functional properties of mitochondrial sirtuins, including their targets in cancer and stem cells. These advances could help to improve the understanding of their interplay with signalling cascades and pathways, leading to new avenues for developing novel drugs for sirtuin-related disease treatments. We also highlight the complex network of mitochondrial sirtuins in cancer and stem cells, which may be important in deciphering the molecular mechanism for their activation and inhibition.

Osmolality Effects on CHO Cell Growth, Cell Volume, Antibody Productivity and Glycosylation

The addition of nutrients and accumulation of metabolites in a fed-batch culture of Chinese hamster ovary (CHO) cells leads to an increase in extracellular osmolality in late stage culture. Herein, we explore the effect of osmolality on CHO cell growth, specific monoclonal antibody (mAb) productivity and glycosylation achieved with the addition of NaCl or the supplementation of a commercial feed. Although both methods lead to an increase in specific antibody productivity, they have different effects on cell growth and antibody production. Osmolality modulation using NaCl up to 470 mOsm kg^-1 had a consistently positive effect on specific antibody productivity and titre. The addition of the commercial feed achieved variable results: specific mAb productivity was increased, yet cell growth rate was significantly compromised at high osmolality values. As a result, Feed C addition to 410 mOsm kg^-1 was the only condition that achieved a significantly higher mAb titre compared to the control. Additionally, Feed C supplementation resulted in a significant reduction in galactosylated antibody structures. Cell volume was found to be positively correlated to osmolality; however, osmolality alone could not account for observed changes in average cell diameter without considering cell cycle variations. These results help delineate the overall effect of osmolality on titre and highlight the potentially negative effect of overfeeding on cell growth.

The pathways related to glutamine metabolism, glutamine inhibitors and their implication for improving the efficiency of chemotherapy in triple-negative breast cancer

Breast cancer (BC) is a heterogeneous cancer with multiple subtypes affecting women worldwide. Triple-negative breast cancer (TNBC) is a prominent subtype of BC with poor prognosis and an aggressive phenotype. Recent understanding of metabolic reprogramming supports its role in the growth of cancer cells and their adaptation to their microenvironment. The Warburg effect is characterized by the shift from oxidative to reductive metabolism and external secretion of lactate. The Warburg effect prevents the use of the required pyruvate in the tricarboxylic acid (TCA) cycle progressing through pyruvate dehydrogenase inactivation. Therefore, it is a major regulatory mechanism to promote glycolysis and disrupt the TCA cycle. Glutamine (Gln) can supply the complementary energy for cancer cells. Additionally, it is the main substrate to support bioenergetics and biosynthetic activities in cancer cells and plays a vital role in a wide array of other processes such as ferroptosis. Thus, the switching of glucose to Gln in the TCA cycle toward reductive Gln metabolism is carried out by hypoxia-inducible factors (HIFs) conducted through the Warburg effect. The literature suggests that the addiction of TNBC to Gln could facilitate the proliferation and invasiveness of these cancers. Thus, Gln metabolism inhibitors, such as CB-839, could be applied to manage the carcinogenic properties of TNBC. Such inhibitors, along with conventional chemotherapy agents, can potentially improve the efficiency and efficacy of TNBC treatment. In this review, we discuss the associations between glucose and Gln metabolism and control of cancer cell growth from the perspective that Gln metabolism inhibitors could improve the current chemotherapy drug effects.

Modeling the bidirectional glutamine/ammonium conversion between cancer cells and cancer-associated fibroblasts

Like in an ecosystem, cancer and other cells residing in the tumor microenvironment engage in various modes of interactions to buffer the negative effects of environmental changes. One such change is the consumption of common nutrients (such as glutamine/Gln) and the consequent accumulation of toxic metabolic byproducts (such as ammonium/NH4). Ammonium is a waste product of cellular metabolism whose accumulation causes cell stress. In tumors, it is known that it can be recycled into nutrients by cancer associated fibroblasts (CAFs). Here we present monoculture and coculture growth of cancer cells and CAFs on different substrates: glutamine and ammonium. We propose a mathematical model to aid our understanding. We find that cancer cells are able to survive on ammonium and recycle it to glutamine for limited periods of time. CAFs are able to even grow on ammonium. In coculture, the presence of CAFs results in an improved survival of cancer cells compared to their monoculture when exposed to ammonium. Interestingly, the ratio between the two cell populations is maintained under various concentrations of NH4, suggesting the ability of the mixed cell system to survive temporary metabolic stress and sustain the size and cell composition as a stable entity.

Research Progress of Sirtuin4 in Cancer

Sirtuins (SIRTs) are members of the silent information regulator-2 family. They are a conserved family of nicotinamide adenine dinucleotide-dependent protein lysine deacylases. SIRTS are involved in intricate cellular processes. There are seven subtypes of SIRTs (1–7) in mammals. SIRT4 is located mainly in mitochondria and has various catalytic activities. These enzyme activities give it a diverse range of important biologic functions, such as energy metabolism, oxidative stress, and aging. Cancer is characterized as reprogramming of energy metabolism and redox imbalance, and SIRT4 can affect tumorigenesis. Here, we review the structure, localization, and enzyme activity of SIRT4 and its role in various neoplasms.

Upregulation of PI3K/AKT/PTEN pathway is correlated with glucose and glutamine metabolic dysfunction during tamoxifen resistance development in MCF-7 cells

Tamoxifen resistance is emerging as a big challenge in endocrine therapy of luminal A breast cancer patients. In this study, we aimed to determine the molecular changes of PI3K/AKT/PTEN signaling pathway during tamoxifen-resistance development using gradually increased doses of tamoxifen in one model, while fixing tamoxifen treatment dose at 35 μM for several times in the second model. An upregulation of AKT/PI3K genes was noticed at 30 μM tamoxifen concentration in cells treated with a gradual increase of tamoxifen doses. In the second model, significant upregulation of AKT1 was seen in cells treated with 35 μM tamoxifen for three times. All genes studied showed a significant increase in expression in resistant cells treated with 50 µM and 35 µM six times tamoxifen. These genes’ upregulation was accompanied by PTEN and GSK3 ß genes’ down-regulation, and it was in correlation to the changes in the metabolic rate of glucose in tamoxifen-resistant models. A significant increase in glucose consumption rate from culture media was observed in tamoxifen resistant cells with the highest consumption rate reported in the first day of culturing. Increased glucose consumption rates were also correlated with GLUL significant gene expression and non-significant change in c-MYC gene expression that may lead to increased endogenous glutamine synthesis. As a result, several molecular and metabolic changes precede acquired tamoxifen resistance could be used as resistance biomarkers or targets to reverse tamoxifen resistance.

Glutamine metabolism in adipocytes: a bona fide epigenetic modulator of inflammation

A chronic low-grade inflammation of white adipose tissue (WAT) is one of the hallmarks of obesity and is proposed to contribute to insulin resistance and type 2 diabetes. Despite this, the causal mechanisms underlying WAT inflammation remain unclear. Based on metabolomic analyses of human WAT, Petrus et al. showed that the amino acid glutamine was the most markedly reduced polar metabolite in the obese state. Reduced glutamine levels in adipocytes induce an increase of Uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) levels via induction of glycolysis and the hexosamine biosynthetic pathways. This promotes nuclear O-GlcNAcylation, a posttranslational modification that activates the transcription of pro-inflammatory genes. Conversely, glutamine supplementation in vitro and in vivo, reversed these effects. Altogether, dysregulation of intracellular glutamine metabolism in WAT establishes an epigenetic link between adipocytes and inflammation. This commentary discusses these findings and their possibly therapeutic relevance in relation to insulin resistance and type 2 diabetes.

The emerging potential of SIRT-3 in oxidative stress-inflammatory axis associated increased neuroinflammatory component for metabolically impaired neural cell

People suffering from conditions like epilepsy, where there is an excess of neuron excitement, stroke, and cardiac arrest, where there are oxygen and glucose deprivation, Alzheimer, Parkinson, and Huntington's disease that causes metabolic and also oxidative stress-inflammatory axis; are known to be more vulnerable to disturbances in the metabolism, and there is a lot of inadequacy in defining the inflammation's mechanistic connections, as well as neurodegeneration and the bioenergetic deficiencies in the CNS. We retrieved relevant studies from PubMed/ScienceDirect/Medline/Public library of science/Mendeley/Springer link as well as Google Scholar. We used various keywords both individually and in combination with the literature search. 'Epidemiology of neurodegenerative disorders', 'neurodegenerative diseases associated hyper inflammation', 'Mechanism of inflammation in neuronal cell', 'Involvement of SIRTin inflammation', 'Pathogenesis of mitochondrial associated metabolic impairment in neurons', 'Reactive oxygen species-mediated mitochondrial dysfunction' were a few of the keywords used for the search. PINCH, which is a chronic neuro-inflammatory component that cannot be detected in matured neurons which are healthy, though expressed in oxidative stress inflammatory axis related tauopathy and diseases that cause neurodegeneration. We attempted to study the regulatory mechanisms that cause changes in the bioenergetics and its neuronal defects and mitochondrial subcellular localization that are PINCH protein-mediated on the other handSIRT1, the most intensively studied sirtuin, in oxidative stress-mediated inflammatory consequence for many diseases but very few research data explore the role of SIRT-3 for correction of the chronic neuroinflammatory component. Thus, in this review, we investigate the very recently identified molecules involving in the pathogenesis during stimulated oxidative stress-inflammatory axis in the excitatory neuronal cell which changes brain metabolism. Simultaneously, in CNS neurons of diseases with a component of chronic neuroinflammation which exhibit neuroprotective response, the consequences (mechanistic and biological) of SIRT-3, could be emerging future targets for neurodegenerative disorder treatment with impaired metabolisms.

p53-dependent glutamine usage determines susceptibility to oxidative stress in radioresistant head and neck cancer cells

The manner in which p53 maintains redox homeostasis and the means by which two key metabolic elements, glucose and glutamine, contribute to p53-dependent redox stability remain unclear. To elucidate the manner in which p53 deals with glucose-deprived, reactive oxygen species (ROS)-prone conditions in this regard, two isogenic cancer subclones (HN3R-A and HN3R-B) bearing distinct p53 mutations as an in vitro model of intratumoral p53 heterogeneity were identified. Following cumulative irradiation, the subclones showed a similar metabolic shift to aerobic glycolysis and increasing NADPH biogenesis for cellular defense against oxidative damage irrespective of p53 status. The radioresistant cancer cells became more sensitive to glycolysis-targeting drugs. However, in glucose-deprived and ROS-prone conditions, HN3R-B, the subclone with the original p53 increased the utilization of glutamine by GLS2, thereby maintaining redox homeostasis and ATP. Conversely, HN3R-A, the p53-deficient radioresistant subclone displayed an impairment in glutamine usage and high susceptibility to metabolic stresses as well as ROS-inducing agents despite the increased ROS scavenging system. Collectively, our findings suggest that p53 governs the alternative utilization of metabolic ingredients, such as glucose and glutamine, in ROS-prone conditions. Thus, p53 status may be an important biomarker for selecting cancer treatment strategies, including metabolic drugs and ROS-inducing agents, for recurrent cancers after radiotherapy.

Glutamine depletion disrupts mitochondrial integrity and impairs C2C12 myoblast proliferation, differentiation, and the heat-shock response

Glutamine and glucose are both oxidized in the mitochondria to supply the majority of usable energy for processes of cellular function. Low levels of plasma and skeletal muscle glutamine are associated with severe illness. We hypothesized that glutamine deficiency would disrupt mitochondrial integrity and impair cell function. C2C12 mouse myoblasts were cultured in control media supplemented with 5.6 mmol/L glucose and 2 mmol/L glutamine, glutamine depletion (Gln^-) or glucose depletion (Glc^-) media. We compared mitochondrial morphology and function, as well as cell proliferation, myogenic differentiation, and heat-shock response in these cells. Glc^- cells exhibited slightly elongated mitochondrial networks and increased mitochondrial mass, with normal membrane potential (ΔΨm). Mitochondria in Gln^- cells became hyperfused and swollen, which were accompanied by severe disruption of cristae and decreases in ΔΨm, mitochondrial mass, the inner mitochondrial membrane remodeling protein OPA1, electron transport chain complex IV protein expression, and markers of mitochondrial biogenesis and bioenergetics. In addition, Gln^- increased the autophagy marker LC3B-II on the mitochondrial membrane. Notably, basal mitochondrial respiration was increased in Glc^- cells as compared to control cells, whereas maximal respiration remained unchanged. In contrast, basal respiration, maximal respiration and reserve capacity were all decreased in Gln^- cells. Consistent with the aforementioned mitochondrial deficits, Gln^- cells had lower growth rates and myogenic differentiation, as well as a higher rate of cell death under heat stress conditions than Glc^- and control cells. We conclude that glutamine is essential for mitochondrial integrity and function; glutamine depletion impairs myoblast proliferation, differentiation, and the heat-shock response.

Functions of mammalian SIRT4 in cellular metabolism and research progress in human cancer

Sirtuins are mammalian homologs of yeast silent information regulator two (SIRT) and are a highly conserved family of proteins, which act as nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylases. The seven sirtuins (SIRT1-7) share a conserved catalytic core domain; however, they have different enzyme activities, biological functions, and subcellular localizations. Among them, mitochondrial SIRT4 possesses ADP-ribosyltransferase, NAD⁺-dependent deacetylase, lipoamidase, and long-chain deacylase activities and can modulate the function of substrate proteins via ADP-ribosylation, delipoylation, deacetylation and long-chain deacylation. SIRT4 has been shown to play a crucial role in insulin secretion, fatty acid oxidation, amino acid metabolism, ATP homeostasis, apoptosis, neurodegeneration, and cardiovascular diseases. In addition, recent studies have demonstrated that SIRT4 acts as a tumor suppressor. Here, the present review summarizes the enzymatic activities and biological functions of SIRT4, as well as its roles in cellular metabolism and human cancer, which are described in the current literature.

Protons and High-Linear Energy Transfer Radiation Induce Genetically Similar Lymphomas With High Penetrance in a Mouse Model of the Aging Human Hematopoietic System

PURPOSE

Humans are exposed to charged particles in different scenarios. The use of protons and high-linear energy transfer (LET) in cancer treatment is steadily growing. In outer space, astronauts will be exposed to a mixed radiation field composed of both protons and heavy ions, in particularly the long-term space missions outside of earth's magnetosphere. Thus, understanding the radiobiology and transforming potential of these types of ionizing radiation are of paramount importance.

METHODS AND MATERIALS

We examined the effect of 10 or 100 cGy of whole-body doses of protons or ²⁸Si ions on the hematopoietic system of a genetic model of aging based on recent studies that showed selective loss of the MLH1 protein in human hematopoietic stems with age.

RESULTS

We found that Mlh1 deficient animals are highly prone to develop lymphomas when exposed to either low doses of protons or ²⁸Si ions. The lymphomas that develop are genetically indistinguishable, in spite of different types of damage elicited by low- and high-LET radiation. RNA sequencing analyses reveal similar gene expression patterns, similar numbers of altered genes, similar numbers of single nucleotide variants and insertions and deletions, and similar activation of known leukemogenic loci.

CONCLUSIONS

Although the incidence of malignancy is related to radiation quality, and increased due to loss of Mlh1, the phenotype of the tumors is independent of LET.

Co-delivery of 2-Deoxyglucose and a glutamine metabolism inhibitor V9302 via a prodrug micellar formulation for synergistic targeting of metabolism in cancer

The unique metabolic demand of cancer cells suggests a new therapeutic strategy targeting the metabolism in cancers. V9302 is a recently reported inhibitor of ASCT2 amino acid transporter which shows promising antitumor activity by blocking glutamine uptake. However, its poor solubility in aqueous solutions and tumor cells' compensatory metabolic shift to glucose metabolism may limit the antitumor efficacy of V9302. 2-Deoxyglucose (2-DG), a derivative of glucose, has been developed as a potential antitumor agent through inhibiting glycolysis in tumor cells. In order to achieve enhanced antitumor effect by inhibiting both metabolic pathways, a 2-DG prodrug-based micellar carrier poly-(oligo ethylene glycol)-co-poly(4-((4-oxo-4-((4-vinylbenzyl)oxy)butyl)disulfaneyl)butanoic acid)-(2-deoxyglucose) (POEG-p-2DG) was developed. POEG-p-2DG well retained the pharmacological activity of 2-DG in vitro and in vivo, More importantly, POEG-p-2DG could self-assemble to form micelles that were capable of loading V9302 to achieve co-delivery of 2-DG and V9302. V9302-loaded POEG-p2DG micelles were small in sizes (~10 nm), showed a slow kinetics of drug release and demonstrated targeted delivery to tumor. In addition, V9302 loaded POEG-p-2DG micelles exhibited improved anti-tumor efficacy both in vitro and in vivo. Interestingly, 2-DG treatment further decreased the glutamine uptake when combined with V9302, likely due to inhibition of ASCT2 glycosylation. These results suggest that POEG-p2DG prodrug micelles may serve as a dual functional carrier for V9302 to achieve synergistic targeting of metabolism in cancers. STATEMENT OF SIGNIFICANCE: Unique cancer cell's metabolism profile denotes a new therapeutic strategy. V9302 is a recently reported glutamine metabolism inhibitor that shows promising antitumor activity. However, its poor waster solubility and tumor cell's compensatory metabolic network may limit its potential clinical application. 2-Deoxyglucose(2-DG) is a widely used glycolysis inhibitor. However, its clinical application is hindered by low efficacy as monotherapy. Thus, in this study, we developed a redox-sensitive, 2-DG-based prodrug polymer, as a dual-functional carrier for co-delivery of V9302 and 2-DG as a combination strategy. V9302 loaded POEG-p-2DG micelle showed significantly improved antitumor activity through synergistic targeting of both glutamine and glycolysis metabolism pathway. More interestingly, POEG-p-2DG itself further facilitates inhibition of glutamine metabolism, likely through inhibition of ASCT2 glycosylation.

SIRT4 prevents excitotoxicity via modulating glutamate metabolism in glioma cells

Excitotoxicity is the presence of excessive glutamate, which is normally taken up by glutamate transporters on astrocytes. Glutamate transporter 1 (GLT-1) is the major transporter on glia cells clearing more than 90% of the glutamate. Sirtuin 4 (SIRT4) is a mitochondrial sirtuin which is expressed in the brain. Previously, it was shown that loss of SIRT4 leads to a more severe reaction to kainic acid, an excitotoxic agent, and also decreased GLT-1 expression in the brain. In this study, we aimed to investigate whether overexpression of SIRT4 is protective against excitotoxicity in glia cells. We overexpressed SIRT4 in A172 glioma cell line and treated with kainic acid in order to induce excitotoxicity. We observed that SIRT4 overexpression increased the cell viability after kainic acid treatment. In addition, reduced glutamate was detected in glutamate assay with overexpression of SIRT4 after kainic acid treatment since SIRT4 decreased cell death by preventing excitotoxicity. Our results show that overexpression of SIRT4 increased the protein levels of GLT-1 and glutamate dehydrogenase (GDH) after kainic acid (KA) treatment so that excess glutamate can be absorbed. However, overexpression of SIRT4 decreased glutamine synthetase (GS) levels. These results demonstrate that, by inhibiting GS, SIRT4 prevents glutamine formation, which will be converted to glutamate in neurons. SIRT4 prevents excitotoxicity via upregulating glutamate metabolism. Finally, our results may show that SIRT4 might prevent excitotoxicity and related cell death via reducing GS expression and upregulating GLT-1 and GDH levels. Therefore, it is important to develop therapeutics against excitotoxicity through SIRT4-related pathways in the cell.

Monocarboxylate Transporter 1 in Brain Diseases and Cancers

Background:

Monocarboxylate Transporter 1 (MCT1), an important membrane transport protein, mediates the translocation of monocarboxylates together with protons across biological membranes. Due to its pathological significance, MCT1 plays an important role in the progression of some diseases, such as brain diseases and cancers.

Methods:

We summarize the general description of MCT1 and provide a comprehensive understanding of the role of MCT1 in brain diseases and cancers. Furthermore, this review discusses the opportunities and challenges of MCT1- targeting drug-delivery systems in the treatment of brain diseases and cancers.

Results:

In the brain, loss of MCT1 function is associated with pathologies of degeneration and injury of the nervous system. In tumors, MCT1 regulates the activity of signaling pathways and controls the exchange of monocarboxylates in aerobic glycolysis to affect tumor metabolism, proliferation and invasion. Meanwhile, MCT1 also acts as a good biomarker for the prediction and diagnosis of cancer progressions.

Conclusion:

MCT1 is an attractive transporter in brain diseases and cancers. Moreover, the development of MCT1- based small molecule drugs and MCT1 inhibitors in the clinic is promising. This review systematically summarizes the basic characteristics of MCT1 and its role in brain diseases and cancers, laying the foundation for further research on MCT1.

SIRT3 Regulation of Mitochondrial Quality Control in Neurodegenerative Diseases

Neurodegenerative diseases are disorders that are characterized by a progressive decline of motor and/or cognitive functions caused by the selective degeneration and loss of neurons within the central nervous system. The most common neurodegenerative diseases are Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). Neurons have high energy demands, and dysregulation of mitochondrial quality and function is an important cause of neuronal degeneration. Mitochondrial quality control plays an important role in maintaining mitochondrial integrity and ensuring normal mitochondrial function; thus, defects in mitochondrial quality control are also significant causes of neurodegenerative diseases. The mitochondrial deacetylase SIRT3 has been found to have a large effect on mitochondrial function. Recent studies have also shown that SIRT3 has a role in mitochondrial quality control, including in the refolding or degradation of misfolded/unfolded proteins, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis, all of which are affected in neurodegenerative diseases.

1H NMR-Based Metabolomics Reveals the Antitumor Mechanisms of Triptolide in BALB/c Mice Bearing CT26 Tumors

Triptolide, the main active ingredient in Tripterygium wilfordii Hook. f. (Celastraceae), has shown promising effects against a variety of tumors. However, the molecular pharmacological mechanisms explaining the action of triptolide remain unknown. In this study, the CT26 colon tumor cell line was inoculated subcutaneously into BALB/c mice, and plasma samples were subjected to ¹H NMR metabolomics analysis. The metabolic signature identified five metabolites whose levels were lower and 15 whose levels were higher in CT26 tumor-bearing mice than in normal control mice. Triptolide treatment significantly reversed the levels of nine of these metabolites, including isoleucine, glutamine, methionine, proline, 3-hydroxybutyric acid, 2-hydroxyisovalerate, 2-hydroxyisobutyrate, and low-density lipoprotein/very low-density lipoprotein. Based on the identities of these potential biomarkers, we conclude that the antitumor mechanism of triptolide might rely on correcting perturbations in branched-chain amino acid metabolism, serine/glycine/methionine biosynthesis, and ketone bodies metabolism.

SIRT4 enhances the sensitivity of ER-positive breast cancer to tamoxifen by inhibiting the IL-6/STAT3 signal pathway

Recent advances in endocrine therapy have improved the prospects for estrogen receptor‐positive breast cancer. Tamoxifen is an effective drug for patients with estrogen receptor‐positive breast cancer, but the development of resistance is common. Therefore, discovering ways to enhance the sensitivity of cancer cells to tamoxifen may help improve breast cancer treatment. We studied the biological role of sirtuin 4 (SIRT4) in tamoxifen‐treated MCF7 and T47D cells. The levels of the MYC proto‐oncogene (MYC) and cyclin D1 (CCND1) were detected by western blotting and quantitative reverse transcription‐polymerase chain reaction in breast cancer cells with SIRT4 overexpression or depletion. Immunofluorescence and western blotting were used to assess the phosphorylation status of signal transducer and activator of transcription 3 (STAT3). SIRT4 overexpression decreased the half maximal inhibitory concentration of tamoxifen in MCF7 and T47D cells, while its depletion increased it. Thus, SIRT4 enhances the sensitivity of breast cancer cells to tamoxifen. Moreover, western blotting revealed decreased STAT3 phosphorylation after SIRT4 transfection. The transcription and translation of MYC and CCND1, target genes of the STAT3 pathway, were also blocked. Immunofluorescence revealed that pathway activation and nuclear STAT4 translocation were suppressed when SIRT4 was overexpressed. Furthermore, the effects of SIRT4 overexpression or depletion on proliferation could be offset by STAT3 activation or inhibition. Taken together, these results demonstrate that SIRT4 enhances the tamoxifen sensitivity of breast cancer cells by inhibiting the STAT3 signaling pathway. With this knowledge, therapeutic strategies with reduced drug resistance risk may be developed.

Vacuolar H+-ATPase Subunit V0C Regulates Aerobic Glycolysis of Esophageal Cancer Cells via PKM2 Signaling

The vacuolar H+-adenosine triphosphatase (ATPase) subunit V0C (ATP6V0C), a proton-conducting, pore-forming subunit of vacuolar ATPase, maintains pH homeostasis and induces organelle acidification. The intracellular and extracellular pH of cancer cells affects their growth; however, the role of ATP6V0C in highly invasive esophageal cancer cells (ECCs) remains unclear. In this study, we examined the role of ATP6V0C in glucose metabolism in ECCs. The ATP6V0C depletion attenuated ECC proliferation, invasion, and suppressed glucose metabolism, as indicated by reduced glucose uptake and decreased lactate and adenosine triphosphate (ATP) production in cells. Consistent with this, expression of glycolytic enzyme and the extracellular acidification rate (ECAR) were also decreased by ATP6V0C knockdown. Mechanistically, ATP6V0C interacted with pyruvate kinase isoform M2 (PKM2), a key regulator of glycolysis in ECCs. The ATP6V0C depletion reduced PKM2 phosphorylation at tyrosine residue 105 (Tyr105), leading to inhibition of nuclear translocation of PKM2. In addition, ATP6V0C was recruited at hypoxia response element (HRE) sites in the lactate dehydrogenase A (LDHA) gene for glycolysis. Thus, our data suggest that ATP6V0C enhances aerobic glycolysis and motility in ECCs.

Diverse Roads Taken by 13C-Glucose-Derived Metabolites in Breast Cancer Cells Exposed to Limiting Glucose and Glutamine Conditions

In cancers, tumor cells are exposed to fluctuating nutrient microenvironments with limiting supplies of glucose and glutamine. While the metabolic program has been related to the expression of oncogenes, only fractional information is available on how variable precarious nutrient concentrations modulate the cellular levels of metabolites and their metabolic pathways. We thus sought to obtain an overview of the metabolic routes taken by ¹³C-glucose-derived metabolites in breast cancer MCF-7 cells growing in combinations of limiting glucose and glutamine concentrations. Isotopologue profiles of key metabolites were obtained by gas chromatography/mass spectrometry (GC/MS). They revealed that in limiting and standard saturating medium conditions, the same metabolic routes were engaged, including glycolysis, gluconeogenesis, as well as the TCA cycle with glutamine and pyruvate anaplerosis. However, the cellular levels of ¹³C-metabolites, for example, serine, alanine, glutamate, malate, and aspartate, were highly sensitive to the available concentrations and the ratios of glucose and glutamine. Notably, intracellular lactate concentrations did not reflect the Warburg effect. Also, isotopologue profiles of ¹³C-serine as well as ¹³C-alanine show that the same glucose-derived metabolites are involved in gluconeogenesis and pyruvate replenishment. Thus, anaplerosis and the bidirectional flow of central metabolic pathways ensure metabolic plasticity for adjusting to precarious nutrient conditions.

The risk trajectory between preoperative fasting glucose and common digestive tract cancer-specific mortality in the FIESTA cohort involving 6865 Chinese patients

Backgrounds: High blood glucose or hyperglycemia is an established risk factor for the development and progression of cancer at many sites, whereas data on the relevance between low blood glucose or hypoglycemia and cancer survival are lacking.

Aims: We aimed to assess the shape of risk trajectory between preoperative fasting glucose and postoperative digestive cancer-specific mortality in Chinese.

Methods: In total, 6865 patients who underwent radical surgery for esophageal cancer (n=2535), gastric cancer (n=3012) and colorectal cancer (n=1318) during 2000-2010 were followed up as of December 2015. All patients received neither chemotherapy nor radiotherapy before and after the surgery. Optimal cutoff points were determined using survival tree analysis.

Results: The median follow-up time was 44.9 months (range: 0.5-188.9 months), with 1065 deaths from esophageal cancer, 1331 from gastric cancer and 412 from colorectal cancer. Using fasting glucose (4.36, 6.09] mmol/L as the reference group, hazard ratios for fasting glucose ≤4.36, (6.09, 8.95], (8.95, 11.5] and >11.5 mmol/L were 1.35 (95% confidence interval: 1.19, 1.54), 2.82 (2.57, 3.11), 3.56 (3.10, 4.08) and 4.27 (3.67, 4.97), respectively (p<0.001).

Conclusions: Our findings indicate a U-shaped risk trajectory between preoperative fasting glucose and digestive tract cancer-specific mortality in Chinese. Further external validation is warranted.

Applications of Protein Fragment Complementation Assays for Analyzing Biomolecular Interactions and Biochemical Networks in Living Cells

Protein-protein interactions (PPIs) are indispensable for the dynamic assembly of multiprotein complexes that are central players of nearly all of the intracellular biological processes, such as signaling pathways, metabolic pathways, formation of intracellular organelles, establishment of cytoplasmic skeletons, etc. Numerous approaches have been invented to study PPIs both in vivo and in vitro, including the protein-fragment complementation assay (PCA), which is a widely applied technology to study PPIs and biomolecular interactions. PCA is a technology based on the expression of the bait and prey proteins in fusion with two complementary reporter protein fragments, respectively, that will reassemble when in close proximity. The reporter protein can be the enzymes or fluorescent proteins. Recovery of the enzymatic activity or fluorescent signal can be the indicator of PPI between the bait and prey proteins. Significant effort has been invested in developing many derivatives of PCA, along with various applications, in order to address specific questions. Therefore, a prompt review of these applications is important. In this review, we will categorize these applications according to the scenarios that the PCAs were applied and expect to provide a reference guideline for the future selection of PCA methods in solving a specific problem.

Epigenetic and metabolic programming of innate immunity in sepsis

Sepsis, the 10th leading cause of death, is the most expensive condition in the United States. The immune response in sepsis transitions from hyperinflammatory to a hypoinflammatory and immunosuppressive phase; individual variations regarding timing and overlap between hyper- and hypoinflammation exist in a number of patients. While one third of the sepsis-related deaths occur during hyperinflammation, majority of the sepsis-mortality occurs during the hypoinflammatory phase. Currently, no phase-specific molecular-based therapies exist to treat sepsis. Coordinated epigenetic and metabolic perturbations orchestrate this shift from hyper- to hypoinflammation in innate immune cells during sepsis. These epigenetic and metabolic changes during sepsis progression and therapeutic opportunities they pose are described in this review.

Inhibition of glycolysis disrupts cellular antioxidant defense and sensitizes HepG2 cells to doxorubicin treatment

Increased glucose consumption is a known hallmark of cancer cells. Increased glycolysis provides ATP, reducing agents and substrates for macromolecular synthesis in intensely dividing cells. Therefore, inhibition of glycolysis is one strategy in anticancer therapy as well as in improved efficacy of conventional anticancer chemotherapeutic agents. One such agent is doxorubicin (DOX), but the mechanism of sensitization of tumor cells to DOX by inhibition of glycolysis has not been fully elucidated. As oxidative stress is an important phenomenon accompanying DOX action and antioxidant defense is closely related to energy metabolism, the aim of the study was the evaluation of oxidative stress markers and antioxidant abilities of cancer cells treated with DOX while glycolysis is inhibited. HepG2 cells were treated with DOX and one of three glycolysis inhibitors: 2-deoxyglucose, dichloroacetate or 3-promopyruvate. To evaluate the possible interaction mechanisms, we assessed mRNA expression of selected genes related to energy metabolism and antioxidant defense; oxidative stress markers; and reduced glutathione (GSH) and NADPH levels. Additionally, glutamine consumption was measured. It was demonstrated that the chemotherapeutic agent and glycolysis inhibitors induced oxidative stress and associated damage in HepG2 cells. However, simultaneous treatment with both agents resulted in even greater lipid peroxidation and a significant reduction in GSH and NADPH levels. Moreover, in the presence of the drug and an inhibitor, HepG2 cells had a reduced ability to take up glutamine. These results indicated that cells treated with DOX while glycolysis was inhibited had significantly reduced ability to produce NADPH and antioxidant defenses.

High Glucose Concentrations Negatively Regulate the IGF1R/Src/ERK Axis through the MicroRNA-9 in Colorectal Cancer

Studies have revealed that people with hyperglycemia have a high risk of colorectal cancer (CRC). Hyperglycemia may be responsible for supplying energy to CRC cells. However, the potential molecular mechanism for this association remains unclear. Furthermore, microRNA-9 (miR-9) has a tumor-suppressive function in CRC. Aberrant reduced expression of miR-9 is involved in the development and progression of malignancy caused by a high glucose (HG) concentration. In this study, we used an HG concentration to activate miR-9 downregulation in CRC cells. Our results indicated that miR-9 decreased the insulin-like growth factor-1 receptor (IGF1R)/Src signaling pathway and downstream cyclin B1 and N-cadherin but upregulated E-cadherin. The HG concentration not only promoted cell proliferation, increased the G1 population, and modulated epithelial-to-mesenchymal transition (EMT) protein expression and morphology but also promoted the cell migration and invasion ability of SW480 (low metastatic potential) and SW620 (high metastatic potential) cells. In addition, low glucose concentrations could reverse the effect of the HG concentration in SW480 and SW620 cells. In conclusion, our results provide new evidence for multiple signaling pathways being regulated through hyperglycemia in CRC. We propose that blood sugar control may serve as a potential strategy for the clinical management of CRC.

High Levels of Prebiotic Resistant Starch in Diet Modulate Gene Expression and Metabolomic Profile in Pancreatic Cancer Xenograft Mice

Cancer initiation and protection mainly derives from a systemic metabolic environment regulated by dietary patterns. Less is known about the impact of nutritional interventions in people with a diagnosis of cancer. The aim of our study was to investigate the effect of a diet rich in resistant starch (RS) on cell pathways modulation and metabolomic phenotype in pancreatic cancer xenograft mice. RNA-Seq experiments on tumor tissue showed that 25 genes resulted in dysregulated pancreatic cancer in mice fed with an RS diet, as compared to those fed with control diet. Moreover, in these two different mice groups, six serum metabolites were deregulated as detected by LC–MS analysis. A bioinformatic prediction analysis showed the involvement of the differentially expressed genes on insulin receptor signaling, circadian rhythm signaling, and cancer drug resistance among the three top canonical pathways, whilst cell death and survival, gene expression, and neurological disease were among the three top disease and biological functions. These findings shed light on the genomic and metabolic phenotype, contributing to the knowledge of the mechanisms through which RS may act as a potential supportive approach for enhancing the efficacy of existing cancer treatments.

Sirtuins and Immuno-Metabolism of Sepsis

Sepsis and septic shock are the leading causes of death in non-coronary intensive care units worldwide. During sepsis-associated immune dysfunction, the early/hyper-inflammatory phase transitions to a late/hypo-inflammatory phase as sepsis progresses. The majority of sepsis-related deaths occur during the hypo-inflammatory phase. There are no phase-specific therapies currently available for clinical use in sepsis. Metabolic rewiring directs the transition from hyper-inflammatory to hypo-inflammatory immune responses to protect homeostasis during sepsis inflammation, but the mechanisms underlying this immuno-metabolic network are unclear. Here, we review the roles of NAD+ sensing Sirtuin (SIRT) family members in controlling immunometabolic rewiring during the acute systemic inflammatory response associated with sepsis. We discuss individual contributions among family members SIRT 1, 2, 3, 4 and 6 in regulating the metabolic switch between carbohydrate-fueled hyper-inflammation to lipid-fueled hypo-inflammation. We further highlight the role of SIRT1 and SIRT2 as potential "druggable" targets for promoting immunometabolic homeostasis and increasing sepsis survival.