Aerobic glycolysis: beyond proliferation

Taking over Cellular Energy-Metabolism for TBSV Replication: The High ATP Requirement of an RNA Virus within the Viral Replication Organelle

Recent discoveries on virus-driven hijacking and compartmentalization of the cellular glycolytic and fermentation pathways to support robust virus replication put the spotlight on the energy requirement of viral processes. The active recruitment of glycolytic enzymes in combination with fermentation enzymes by the viral replication proteins emphasizes the advantages of producing ATP locally within viral replication structures. This leads to a paradigm shift in our understanding of how viruses take over host metabolism to support the virus’s energy needs during the replication process. This review highlights our current understanding of how a small plant virus, Tomato bushy stunt virus, exploits a conserved energy-generating cellular pathway during viral replication. The emerging picture is that viruses not only rewire cellular metabolic pathways to obtain the necessary resources from the infected cells but the fast replicating viruses might have to actively hijack and compartmentalize the energy-producing enzymes to provide a readily available source of ATP for viral replication process.

Metabolic Plasticity of Tumor Cells: How They Do Adapt to Food Deprivation

Dysregulated metabolism is a key hallmark of cancer cells and an enticing target for cancer treatment. Since the last 10 years, research on cancer metabolism has moved from pathway attention to network consideration. This metabolic complexity continuously adapt to new constraints in the tumor microenvironment. In this review, we will highlight striking changes in cancer cell metabolism compared to normal cells. Understanding this tumor metabolic plasticity suggests potential new targets and innovative combinatorial treatments for fighting cancer.

Long non-coding RNA GAS5 acts as proliferation "brakes" in CD133+ cells responsible for tumor recurrence

Presence of quiescent, therapy evasive population often described as cancer stem cells (CSC) or tumor initiating cells (TIC) is often attributed to extreme metastasis and tumor recurrence. This population is typically enriched in a tumor as a result of microenvironment or chemotherapy induced stress. The TIC population adapts to this stress by turning on cell cycle arrest programs that is a “fail-safe” mechanism to prevent expansion of malignant cells to prevent further injury. Upon removal of the “stress” conditions, these cells restart their cell cycle and regain their proliferative nature thereby resulting in tumor relapse. Growth Arrest Specific 5 (GAS5) is a long-non-coding RNA that plays a vital role in this process. In pancreatic cancer, CD133+ population is a typical representation of the TIC population that is responsible for tumor relapse. In this study, we show for the first time that emergence of CD133+ population coincides with upregulation of GAS5, that reprograms the cell cycle to slow proliferation by inhibiting GR mediated cell cycle control. The CD133+ population further routed metabolites like glucose to shunt pathways like pentose phosphate pathway, that were predominantly biosynthetic in spite of being quiescent in nature but did not use it immediately for nucleic acid synthesis. Upon inhibiting GAS5, these cells were released from their growth arrest and restarted the nucleic acid synthesis and proliferation. Our study thus showed that GAS5 acts as a molecular switch for regulating quiescence and growth arrest in CD133+ population, that is responsible for aggressive biology of pancreatic tumors.

The Effects of Meldonium on the Renal Acute Ischemia/Reperfusion Injury in Rats

Acute renal ischemia/reperfusion (I/R) injury is a clinical condition that is challenging to treat. Meldonium is an anti-ischemic agent that shifts energy production from fatty acid oxidation to less oxygen-consuming glycolysis. Thus, in this study we investigated the effects of a four-week meldonium pre-treatment (300 mg/kg b.m./day) on acute renal I/R in male rats (Wistar strain). Our results showed that meldonium decreased animal body mass gain, food and water intake, and carnitine, glucose, and lactic acid kidney content. In kidneys of animals subjected to I/R, meldonium increased phosphorylation of mitogen-activated protein kinase p38 and protein kinase B, and increased the expression of nuclear factor erythroid 2-related factor 2 and haeme oxygenase 1, causing manganese superoxide dismutase expression and activity to increase, as well as lipid peroxidation, cooper-zinc superoxide dismutase, glutathione peroxidase, and glutathione reductase activities to decrease. By decreasing the kidney Bax/Bcl2 expression ratio and kidney and serum high mobility group box 1 protein content, meldonium reduced apoptotic and necrotic events in I/R, as confirmed by kidney histology. Meldonium increased adrenal noradrenaline content and serum, adrenal, hepatic, and renal ascorbic/dehydroascorbic acid ratio, which caused complex changes in renal lipidomics. Taken together, our results have confirmed that meldonium pre-treatment protects against I/R-induced oxidative stress and apoptosis/necrosis.

Co-opting the fermentation pathway for tombusvirus replication: Compartmentalization of cellular metabolic pathways for rapid ATP generation

The viral replication proteins of plus-stranded RNA viruses orchestrate the biogenesis of the large viral replication compartments, including the numerous viral replicase complexes, which represent the sites of viral RNA replication. The formation and operation of these virus-driven structures require subversion of numerous cellular proteins, membrane deformation, membrane proliferation, changes in lipid composition of the hijacked cellular membranes and intensive viral RNA synthesis. These virus-driven processes require plentiful ATP and molecular building blocks produced at the sites of replication or delivered there. To obtain the necessary resources from the infected cells, tomato bushy stunt virus (TBSV) rewires cellular metabolic pathways by co-opting aerobic glycolytic enzymes to produce ATP molecules within the replication compartment and enhance virus production. However, aerobic glycolysis requires the replenishing of the NAD+ pool. In this paper, we demonstrate the efficient recruitment of pyruvate decarboxylase (Pdc1) and alcohol dehydrogenase (Adh1) fermentation enzymes into the viral replication compartment. Depletion of Pdc1 in combination with deletion of the homologous PDC5 in yeast or knockdown of Pdc1 and Adh1 in plants reduced the efficiency of tombusvirus replication. Complementation approach revealed that the enzymatically functional Pdc1 is required to support tombusvirus replication. Measurements with an ATP biosensor revealed that both Pdc1 and Adh1 enzymes are required for efficient generation of ATP within the viral replication compartment. In vitro reconstitution experiments with the viral replicase show the pro-viral function of Pdc1 during the assembly of the viral replicase and the activation of the viral p92 RdRp, both of which require the co-opted ATP-driven Hsp70 protein chaperone. We propose that compartmentalization of the co-opted fermentation pathway in the tombusviral replication compartment benefits the virus by allowing for the rapid production of ATP locally, including replenishing of the regulatory NAD+ pool by the fermentation pathway. The compartmentalized production of NAD+ and ATP facilitates their efficient use by the co-opted ATP-dependent host factors to support robust tombusvirus replication. We propose that compartmentalization of the fermentation pathway gives an evolutionary advantage for tombusviruses to replicate rapidly to speed ahead of antiviral responses of the hosts and to outcompete other pathogenic viruses. We also show the dependence of turnip crinkle virus, bamboo mosaic virus, tobacco mosaic virus and the insect-infecting Flock House virus on the fermentation pathway, suggesting that a broad range of viruses might induce this pathway to support rapid replication.

Erythroid differentiation displays a peak of energy consumption concomitant with glycolytic metabolism rearrangements

Our previous single-cell based gene expression analysis pointed out significant variations of LDHA level during erythroid differentiation. Deeper investigations highlighted that a metabolic switch occurred along differentiation of erythroid cells. More precisely we showed that self-renewing progenitors relied mostly upon lactate-productive glycolysis, and required LDHA activity, whereas differentiating cells, mainly involved mitochondrial oxidative phosphorylation (OXPHOS). These metabolic rearrangements were coming along with a particular temporary event, occurring within the first 24h of erythroid differentiation. The activity of glycolytic metabolism and OXPHOS rose jointly with oxgene consumption dedicated to ATP production at 12-24h of the differentiation process before lactate-productive glycolysis sharply fall down and energy needs decline. Finally, we demonstrated that the metabolic switch mediated through LDHA drop and OXPHOS upkeep might be necessary for erythroid differentiation. We also discuss the possibility that metabolism, gene expression and epigenetics could act together in a circular manner as a driving force for differentiation.

Hyperglycemia-Induced Aberrant Cell Proliferation; A Metabolic Challenge Mediated by Protein O-GlcNAc Modification

Chronic hyperglycemia has been associated with an increased prevalence of pathological conditions including cardiovascular disease, cancer, or various disorders of the immune system. In some cases, these associations may be traced back to a common underlying cause, but more often, hyperglycemia and the disturbance in metabolic balance directly facilitate pathological changes in the regular cellular functions. One such cellular function crucial for every living organism is cell cycle regulation/mitotic activity. Although metabolic challenges have long been recognized to influence cell proliferation, the direct impact of diabetes on cell cycle regulatory elements is a relatively uncharted territory. Among other "nutrient sensing" mechanisms, protein O-linked β-N-acetylglucosamine (O-GlcNAc) modification emerged in recent years as a major contributor to the deleterious effects of hyperglycemia. An increasing amount of evidence suggest that O-GlcNAc may significantly influence the cell cycle and cellular proliferation. In our present review, we summarize the current data available on the direct impact of metabolic changes caused by hyperglycemia in pathological conditions associated with cell cycle disorders. We also review published experimental evidence supporting the hypothesis that O-GlcNAc modification may be one of the missing links between metabolic regulation and cellular proliferation.

HSF2 regulates aerobic glycolysis by suppression of FBP1 in hepatocellular carcinoma

Heat shock factors (HSFs) are essential for all organisms to survive exposures to acute stress. Recent years have witnessed the progress in uncovering the importance of HSFs in cancer cell oncogenesis, progression and metastasis. However, their roles in hepatocellular carcinoma (HCC) proliferation and the underlying mechanism have seldom been discussed. The present study aims to uncover the two important HSFs members HSF1 and HSF2 in hepatocellular carcinoma (HCC). By using the Cancer Genome Atlas (TCGA) dataset analysis, we investigated the prognosis value of HSF1 and HSF2 in HCC and identified HSF2 as a prediction factor of overall survival of HCC. In vitro cell line studies demonstrated that silencing HSF2 expression could decrease the proliferation in HCC cells. In depth mechanism analysis demonstrated that HSF2 promoted cell proliferation via positive regulation of aerobic glycolysis, and HSF2 interacted with euchromatic histone lysine methyltransferase 2 (EHMT2) to epigenetically silence fructose-bisphosphatase 1 (FBP1), which is a tumor suppressor and negative regulator of aerobic glycolysis in HCC. HSF2 expression indicated unfavorable prognosis of HCC patients and it could regulate aerobic glycolysis by suppression of FBP1 to support uncontrolled proliferation of HCC cells.

Oleanolic acid reduces aerobic glycolysis-associated proliferation by inhibiting yes-associated protein in gastric cancer cells

Gastric cancer represents a common malignancy of digestive tract with high incidence and mortality. Increasing evidence suggests that the growth of gastric tumor cells relies largely on aerobic glycolysis. Currently, many potential anti-cancer candidates are derived from natural products. Here, we evaluated the effects of oleanolic acid (OA), a triterpenoid component widely found in the plants of Oleaceae family, on aerobic glycolysis and proliferation in human MKN-45 and SGC-7901 gastric cancer cells. Our results demonstrated that OA reduced the viability and proliferation of gastric cancer cells and inhibited the expression of cyclin A and cyclin-dependent kinase 2. OA blocked glycolysis in these cells evidenced by decreases in the uptake and consumption of glucose, intracellular lactate levels and extracellular acidification rate. Glycolysis inhibitor 2-deoxy-d-glucose, similar to OA, suppressed gastric cancer cell proliferation. OA also decreased the expression and intracellular activities of glycolysis rate-limiting enzymes hexokinase 2 (HK2) and phosphofructokinase 1 (PFK1). Moreover, OA downregulated the expression of hypoxia inducible factor-1α (HIF-1α) and decreased its nuclear abundance. Upregulation of HIF-1α by deferoxamine rescued OA-inhibited HK2 and PFK1. Furthermore, OA reduced the nuclear abundance of yes-associated protein (YAP) in gastric tumor cells. YAP inhibitor verteporfin, similar to OA, downregulated the expression of HIF-1α and glycolytic enzymes in gastric cancer cells; whereas overexpression of YAP abrogated all these effects of OA. Collectively, inhibition of YAP was responsible for OA blockade of HIF-1α-mediated aerobic glycolysis and proliferation in human gastric tumor cells. OA could be developed as a promising candidate for gastric cancer treatment.

The Post-amyloid Era in Alzheimer's Disease: Trust Your Gut Feeling

The amyloid hypothesis, the assumption that beta-amyloid toxicity is the primary cause of neuronal and synaptic loss, has been the mainstream research concept in Alzheimer's disease for the past two decades. Currently, this model is quietly being replaced by a more holistic, “systemic disease” paradigm which, like the aging process, affects multiple body tissues and organs, including the gut microbiota. It is well-established that inflammation is a hallmark of cellular senescence; however, the infection-senescence link has been less explored. Microbiota-induced senescence is a gradually emerging concept promoted by the discovery of pathogens and their products in Alzheimer's disease brains associated with senescent neurons, glia, and endothelial cells. Infectious agents have previously been associated with Alzheimer's disease, but the cause vs. effect issue could not be resolved. A recent study may have settled this debate as it shows that gingipain, a Porphyromonas gingivalis toxin, can be detected not only in Alzheimer's disease but also in the brains of older individuals deceased prior to developing the illness. In this review, we take the position that gut and other microbes from the body periphery reach the brain by triggering intestinal and blood-brain barrier senescence and disruption. We also surmise that novel Alzheimer's disease findings, including neuronal somatic mosaicism, iron dyshomeostasis, aggressive glial phenotypes, and loss of aerobic glycolysis, can be explained by the infection-senescence model. In addition, we discuss potential cellular senescence targets and therapeutic strategies, including iron chelators, inflammasome inhibitors, senolytic antibiotics, mitophagy inducers, and epigenetic metabolic reprograming.

Development of a neurotoxicity assay that is tuned to detect mitochondrial toxicants

Many neurotoxicants affect energy metabolism in man, but currently available test methods may still fail to predict mito- and neurotoxicity. We addressed this issue using LUHMES cells, i.e., human neuronal precursors that easily differentiate into mature neurons. Within the NeuriTox assay, they have been used to screen for neurotoxicants. Our new approach is based on culturing the cells in either glucose or galactose (Glc-Gal-NeuriTox) as the main carbohydrate source during toxicity testing. Using this Glc-Gal-NeuriTox assay, 52 mitochondrial and non-mitochondrial toxicants were tested. The panel of chemicals comprised 11 inhibitors of mitochondrial respiratory chain complex I (cI), 4 inhibitors of cII, 8 of cIII, and 2 of cIV; 8 toxicants were included as they are assumed to be mitochondrial uncouplers. In galactose, cells became more dependent on mitochondrial function, which made them 2-3 orders of magnitude more sensitive to various mitotoxicants. Moreover, galactose enhanced the specific neurotoxicity (destruction of neurites) compared to a general cytotoxicity (plasma membrane lysis) of the toxicants. The Glc-Gal-NeuriTox assay worked particularly well for inhibitors of cI and cIII, while the toxicity of uncouplers and non-mitochondrial toxicants did not differ significantly upon glucose ↔ galactose exchange. As a secondary assay, we developed a method to quantify the inhibition of all mitochondrial respiratory chain functions/complexes in LUHMES cells. The combination of the Glc-Gal-NeuriTox neurotoxicity screening assay with the mechanistic follow up of target site identification allowed both, a more sensitive detection of neurotoxicants and a sharper definition of the mode of action of mitochondrial toxicants.

MiR-150-5p regulates melanoma proliferation, invasion and metastasis via SIX1-mediated Warburg Effect

Aerobic glycolysis is a hallmark of cancer. Sine oculis homeobox 1 (SIX1), a key transcription factor in terms of regulating aerobic glycolysis (the Warburg Effect), plays a critical role in tumorigenesis of various cancer types, including breast cancer, liver cancer, and lung cancer. However, the upstream regulating mechanisms of SIX1 in melanoma remain to be determined. MicroRNAs (miRNAs) have emerged as key regulators in tumorigenesis and progression. Here, we initially showed that microRNA-150-5p (miR-150-5p) inhibits SIX1 expression by directly targeting its 3'-UTR in melanoma cells. miR-150-5p suppressed melanoma cell proliferation, migration, and invasion through inhibition of SIX1. Mechanistically, miR-150-5p dampens glycolysis by decreasing the glucose uptake, lactate production, ATP generation, and extracellular acidification rate (ECAR), and increasing oxygen consumption rate (OCR) by targeting SIX1. Importantly, glycolysis regulated by miR-150-5p/SIX1 axis is critical for its regulation of melanoma growth and metastasis both in vitro and in vivo. Collectively, our study demonstrates the importance of miR-150-5p/SIX1 axis in melanoma, which could be a promising therapeutic target in melanoma.

Fructose 1,6-bisphosphate inhibits osteoclastogenesis by attenuating RANKL-induced NF-κB/NFATc-1

BACKGROUND

Although some glycolytic intermediates have been shown to modulate several cell type formation and activation, the functional role of fructose 1,6-bisphosphate (FBP) on osteoclastogenesis is still unknown.

METHODS

Osteoclastogenesis was evaluated on bone marrow preosteoclasts cultured with M-CSF - 30 ng/ml, RANKL - 10 ng/ml, and two concentrations of FBP (100 and 300 µM). TRAP-positive stained cells were counted, and osteoclastogenic marker genes expression were evaluated by qPCR. Osteoclasts resorption capacity was evaluated by the expression of specific enzymes and capacity to resorb a mineralized matrix. The NF-κB activation was detected using RAW 264.7, stably expressing luciferase on the NF-κB responsive promoter.

RESULTS

We show that FBP, the product of the first stage of glycolysis, inhibited RANKL-induced osteoclasts differentiation and TRAP activity. The treatment of preosteoclasts with FBP attenuated osteoclast fusion and formation, without affecting cell viability. Moreover, the inhibition of several osteoclastogenic marker genes expression (TRAP, OSCAR, DC-STAMP, Integrin αv, NFATc1) by FBP correlates with a reduction of mineralized matrix resorption capacity. The mechanism underlying FBP-inhibition of osteoclastogenesis involves NF-κB/NFATc1 signaling pathway inhibition.

CONCLUSION

Altogether these data show a protective role of a natural glycolytic intermediate in bone homeostasis that may have therapeutic benefit for osteolytic diseases.

Cellular Metabolism Is a Major Determinant of HIV-1 Reservoir Seeding in CD4+ T Cells and Offers an Opportunity to Tackle Infection

HIV persists in long-lived infected cells that are not affected by antiretroviral treatment. These HIV reservoirs are mainly located in CD4⁺ T cells, but their distribution is variable in the different subsets. Susceptibility to HIV-1 increases with CD4⁺ T cell differentiation. We evaluated whether the metabolic programming that supports the differentiation and function of CD4⁺ T cells affected their susceptibility to HIV-1. We found that differences in HIV-1 susceptibility between naive and more differentiated subsets were associated with the metabolic activity of the cells. Indeed, HIV-1 selectively infected CD4⁺ T cells with high oxidative phosphorylation and glycolysis, independent of their activation phenotype. Moreover, partial inhibition of glycolysis (1) impaired HIV-1 infection in vitro in all CD4⁺ T cell subsets, (2) decreased the viability of preinfected cells, and (3) precluded HIV-1 amplification in cells from HIV-infected individuals. Our results elucidate the link between cell metabolism and HIV-1 infection and identify a vulnerability in tackling HIV reservoirs.

The Role of APOE4 in Disrupting the Homeostatic Functions of Astrocytes and Microglia in Aging and Alzheimer's Disease

APOE4 is the greatest genetic risk factor for late-onset Alzheimer’s disease (AD), increasing the risk of developing the disease by 3-fold in the 14% of the population that are carriers. Despite 25 years of research, the exact mechanisms underlying how APOE4 contributes to AD pathogenesis remain incompletely defined. APOE in the brain is primarily expressed by astrocytes and microglia, cell types that are now widely appreciated to play key roles in the pathogenesis of AD; thus, a picture is emerging wherein APOE4 disrupts normal glial cell biology, intersecting with changes that occur during normal aging to ultimately cause neurodegeneration and cognitive dysfunction. This review article will summarize how APOE4 alters specific pathways in astrocytes and microglia in the context of AD and the aging brain. APOE itself, as a secreted lipoprotein without enzymatic activity, may prove challenging to directly target therapeutically in the classical sense. Therefore, a deeper understanding of the underlying pathways responsible for APOE4 toxicity is needed so that more tractable pathways and drug targets can be identified to reduce APOE4-mediated disease risk.

Targeting glycometabolic reprogramming to restore the sensitivity of leukemia drug-resistant K562/ADM cells to adriamycin

AIMS

Mounting studies have confirmed that cancer cells reprogram their metabolism during early carcinogenesis to develop many other hallmarks, and demonstrated a relationship between aerobic glycolysis and the occurrence of drug resistance. However, the molecular mechanisms and role in tumor drug resistance of aerobic glycolysis remain unclear.

MAIN METHODS

We analyzed differentially expressed genes (DEGs) at the RNA level between the multi-drug resistance (MDR) leukemia cell line K562/adriamycin (ADM) and its parental, drug-sensitive K562 cell line. Clustering and enrichment analysis of DEGs was performed. Oxamate, a lactic dehydrogenase inhibitor were used to assess the effect of glycolysis inhibition on ADM susceptibility and the expression of the enriched DEGs in K562/ADM cells.

KEY FINDINGS

A total of 1742 DEGs were detected between the K562/ADM and K562 cell lines. The differential expression of unigenes encoding enzymes involved in glycometabolism signifies that there was a greater aerobic glycolysis flux in K562/ADM cells. The PI3K-AKT signaling pathway, which is related to glucose metabolism, showed representative differential enrichment and up-regulation in K562/ADM cells. Oxamate improved and re-sensitized the therapeutic effect of ADM in ADM-resistant cells by inhibiting aerobic glycolysis either directly or indirectly by down-regulation of the AKT-mTOR pathway.

SIGNIFICANCE

Our findings suggest that ADM resistance mediated by the increase of aerobic glycolysis, which related to the over-activation of the AKT-mTOR-c-Myc pathway in MDR leukemia cells. Inhibition of aerobic glycolysis and down-regulation of signaling pathways involved in aerobic glycolysis represent a potential chemotherapeutic strategy for sensitizing leukemic cells and thereby overcoming MDR.

Aquaporin 9 Contributes to the Maturation Process and Inflammatory Cytokine Secretion of Murine Dendritic Cells

Dendritic cells (DCs) are the most potent antigen-presenting cells able to trigger the adaptive immune response to specific antigens. When non-self-antigens are captured, DCs switch from an “immature” to a “mature” state to fulfill their function. Among the several surface proteins involved in DCs maturation, the role of aquaporins (AQPs) is still poorly understood. Here we investigated the expression profile of Aqps in murine bone marrow derived dendritic cells (BMDCs). Among the Aqps analyzed, Aqp9 was the most expressed by DCs. Its expression level was significantly upregulated 6 h following LPS exposure. Chemical inhibition of Aqp9 led to a decreased inflammatory cytokines secretion. BMDCs from AQP9-KO mice release lower amount of inflammatory cytokines and chemokines and increased release of IL-10. Despite the reduced release of inflammatory cytokines, Aqp9-KO mice were not protected from DSS induced colitis. All together, our data indicate that AQP9 blockade can be an efficient strategy to reduce DCs inflammatory response but it is not sufficient to protect from acute inflammatory insults such as DSS induced colitis.

Epstein-Barr Virus-Induced Metabolic Rearrangements in Human B-Cell Lymphomas

Tumor metabolism has been the object of several studies in the past, leading to the pivotal observation of a consistent shift toward aerobic glycolysis (so-called Warburg effect). More recently, several additional investigations proved that tumor metabolism is profoundly affected during tumorigenesis, including glucose, lipid and amino-acid metabolism. It is noticeable that metabolic reprogramming can represent a suitable therapeutic target in many cancer types. Epstein–Barr virus (EBV) was the first virus linked with cancer in humans when Burkitt lymphoma (BL) was described. Besides other well-known effects, it was recently demonstrated that EBV can induce significant modification in cell metabolism, which may lead or contribute to neoplastic transformation of human cells. Similarly, virus-induced tumorigenesis is characterized by relevant metabolic abnormalities directly induced by the oncoviruses. In this article, the authors critically review the most recent literature concerning EBV-induced metabolism alterations in lymphomas.

Insulin specifically regulates expression of liver and muscle phosphofructokinase isoforms

Phosphofructokinase (PFK) is a key regulatory enzyme of glycolysis, being considered the pacemaker of this pathway. In mammals, this enzyme exists as three different isoforms, PFKM, PFKL and PFKP, presenting different regulatory and catalytic properties. The expression of these isoforms is tissue-specific and vary according to the cell differentiation and signalization. Although it is known that the expression of the different PFK isoforms directly affects cell function, the information regarding the regulation of PFK isoforms expression is scarce. In the present work, we evaluate the role of insulin signalization on the expression of three PFK isoforms on skeletal muscle, liver, and epididymal white adipose tissue (eWAT) of mice. For this, Swiss mice were treated with streptozotocin (STZ) to disrupt pancreatic ß-cells and, thus, insulin production. Control group were treated with citrate buffer (STZ vehicle). These groups were then treated with insulin or saline twice a day for ten consecutive days when animals were euthanized and tissues used for the evaluation of PFK isoforms expression by quantitative PCR (qPCR). Our results revealed that the lack of insulin significantly impacted the expression of PFKL, presenting mild effects on PFKM and no effects on PFKP. The decrease of PFKL and PFKM mRNA levels observed on the group treated with STZ was reversed by the treatment with insulin. In conclusion, insulin, the most known regulator of glucose consumption, specifically regulates the expression of PFKL and PFKM, which impact the regulation of glycolysis in the cell.

Role of SLC7A5 in Metabolic Reprogramming of Human Monocyte/Macrophage Immune Responses

Amino acids (AAs) are necessary nutrients which act not only as building blocks in protein synthesis but also in crucial anabolic cellular signaling pathways. It has been demonstrated that SLC7A5 is a critical transporter that mediates uptake of several essential amino acids in highly proliferative tumors and activated T cells. However, the dynamics and relevance of SLC7A5 activity in monocytes/macrophages is still poorly understood. We provide evidence that SLC7A5-mediated leucine influx contributes to pro-inflammatory cytokine production via mTOR complex 1 (mTORC1)-induced glycolytic reprograming in activated human monocytes/macrophages. Moreover, expression of SLC7A5 is significantly elevated in monocytes derived from patients with rheumatoid arthritis (RA), a chronic inflammatory disease, and was also markedly induced by LPS stimulation of both monocytes and macrophages from healthy individuals. Further, pharmacological blockade or silencing of SLC7A5 led to a significant reduction of IL-1β downstream of leucine-mediated mTORC1 activation. Inhibition of SLC7A5-mediated leucine influx was linked to downregulation of glycolytic metabolism as evidenced by the decreased extracellular acidification rate, suggesting a regulatory role for this molecule in glycolytic reprograming. Furthermore, the expression of SLC7A5 on circulating monocytes from RA patients positively correlated with clinical parameters, suggesting that SLC7A5-mediated AA influx is related to inflammatory conditions.

MPC1, a key gene in cancer metabolism, is regulated by COUPTFII in human prostate cancer

Mitochondrial pyruvate carrier 1 (MPC1) and MPC 2 form a transporter complex in cells to control pyruvate transportation into mitochondria. Reduced expression of MPC1 disrupts the transporter function, induces metabolic shift to increase glycolysis, and thus plays important roles in several diseases, including cancer. However, the role of MPC1 in prostate cancer and the underlying mechanism causing the down-regulation of MPC1 in tumor cells remain to be defined. Here, we show that MPC1 serves as a critical regulator of glycolysis in prostate cancer cells, which in turn controls cancer cell growth, invasion, and the tumorigenic capability. More importantly, we identified that chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII), a steroid receptor superfamily member, transcriptionally regulates the expression of MPC1. We further demonstrate that COUP-TFII, which is upregulated in the prostate cancer patient, regulates MPC1 and glycolysis to promote tumor growth and metastasis. Our findings reveal that COUP-TFII represses MPC1 expression in prostate cancer cells to facilitate a metabolism switch to increase glycolysis and promote cancer progression. This observation raises an intriguing possibility of targeting COUP-TFII to modulate cancer cell metabolism for prostate cancer intervention.

Long Noncoding RNA Cancer Susceptibility Candidate 8 Suppresses the Proliferation of Bladder Cancer Cells via Regulating Glycolysis

Increasing evidence highlights the critical regulatory role of long noncoding RNAs (lncRNAs) in carcinogenesis. Bladder cancer has become the most prevalent urologic malignancy, which is commonly diagnosed among adults. In this study, we showed that the lncRNA cancer susceptibility candidate 8 (CASC8) is significantly downregulated in bladder cancers and associated with the advanced stage of bladder cancer patients. Overexpression of CASC8 remarkably suppressed the bladder cancer cell proliferation. Mechanistically, we illustrated that CASC8 reduced the glycolysis of bladder cancer cells via interacting with the fibroblast growth factor receptor 1 (FGFR1). The binding of CASC8 with FGFR1 inhibits FGFR1-mediated lactate dehydrogenase A phosphorylation, which attenuates the conversion of pyruvate into lactate. Collectively, our findings uncovered the pivotal role of CASC8 in bladder tumorigenesis and suggested that CASC8 may function as a candidate biomarker for the diagnosis of bladder cancer.

LMP1-mediated glycolysis induces myeloid-derived suppressor cell expansion in nasopharyngeal carcinoma

Myeloid-derived suppressor cells (MDSCs) are expanded in tumor microenvironments, including that of Epstein–Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC). The link between MDSC expansion and EBV infection in NPC is unclear. Here, we show that EBV latent membrane protein 1 (LMP1) promotes MDSC expansion in the tumor microenvironment by promoting extra-mitochondrial glycolysis in malignant cells, which is a scenario for immune escape initially suggested by the frequent, concomitant detection of abundant LMP1, glucose transporter 1 (GLUT1) and CD33⁺ MDSCs in tumor sections. The full process has been reconstituted in vitro. LMP1 promotes the expression of multiple glycolytic genes, including GLUT1. This metabolic reprogramming results in increased expression of the Nod-like receptor family protein 3 (NLRP3) inflammasome, COX-2 and P-p65 and, consequently, increased production of IL-1β, IL-6 and GM-CSF. Finally, these changes in the environment of malignant cells result in enhanced NPC-derived MDSC induction. One key step is the physical interaction of LMP1 with GLUT1 to stabilize the GLUT1 protein by blocking its K48-ubiquitination and p62-dependent autolysosomal degradation. This work indicates that LMP1-mediated glycolysis regulates IL-1β, IL-6 and GM-CSF production through the NLRP3 inflammasome, COX-2 and P-p65 signaling pathways to enhance tumor-associated MDSC expansion, which leads to tumor immunosuppression in NPC.

The expression of the Epstein-Barr virus (EBV) oncogenic protein denoted latent membrane protein 1 (LMP1) varies in patients with NPC and is linked to tumorigenesis and tumor immunosuppression, but the molecular mechanism through which LMP1 leads to tumor immune escape remains unknown. Work to date suggests that the expansion of tumor-associated myeloid-derived suppressor cells (MDSCs) is the main cause of tumor immunosuppression such as that found in NPC. Here, we found that tumor LMP1 expression is correlated with glucose transporter 1 (GLUT1) levels, CD33⁺ MDSC number and unfavorable survival in patients with NPC. Based on the results of our in vitro analysis, LMP1 promotes GLUT1-dependent glycolysis in NPC cells, resulting in activation of the Nod-like receptor family protein 3 (NLRP3) inflammasome, COX-2 and P-p65 signaling pathways and subsequently increased IL-1β, IL-6 and GM-CSF production. Importantly, LMP1 interacts with GLUT1 to stabilize the GLUT1 protein by disrupting its K48-linked ubiquitination and autolysosomal degradation in a p62-dependent manner and up-regulating the GLUT1 mRNA and protein levels by inducing p65 activation. Therefore, we determined that GLUT1-dependent glycolysis is required for tumor-induced MDSC differentiation and that this process is associated with LMP1 expression. Based on our findings, LMP1-mediated glycolysis is a key process involved in controlling tumor immunosuppression and directly contributes to oncogenesis.

Metabolic switching and cell fate decisions: implications for pluripotency, reprogramming and development

Cell fate decisions are closely linked to changes in metabolic activity. Over recent years this connection has been implicated in mechanisms underpinning embryonic development, reprogramming and disease pathogenesis. In addition to being important for supporting the energy demands of different cell types, metabolic switching from aerobic glycolysis to oxidative phosphorylation plays a critical role in controlling biosynthetic processes, intracellular redox state, epigenetic status and reactive oxygen species levels. These processes extend beyond ATP synthesis by impacting cell proliferation, differentiation, enzymatic activity, ageing and genomic integrity. This review will focus on how metabolic switching impacts decisions made by multipotent cells and discusses mechanisms by which this occurs.

Kinetic analysis, size profiling, and bioenergetic association of DNA released by selected cell lines in vitro

Although circulating DNA (cirDNA) analysis shows great promise as a screening tool for a wide range of pathologies, numerous stumbling blocks hinder the rapid translation of research to clinical practice. This is related directly to the inherent complexity of the in vivo setting, wherein the influence of complex systems of interconnected cellular responses and putative DNA sources creates a seemingly arbitrary representation of the quantitative and qualitative properties of the cirDNA in the blood of any individual. Therefore, to evaluate the potential of in vitro cell cultures to circumvent the difficulties encountered in in vivo investigations, the purpose of this work was to elucidate the characteristics of the DNA released [cell-free DNA (cfDNA)] by eight different cell lines. This revealed three different forms of cfDNA release patterns and the presence of nucleosomal fragments as well as actively released forms of DNA, which are not only consistently observed in every tested cell line, but also in plasma samples. Correlations between cfDNA release and cellular origin, growth rate, and cancer status were also investigated by screening and comparing bioenergetics flux parameters. These results show statistically significant correlations between cfDNA levels and glycolysis, while no correlations between cfDNA levels and oxidative phosphorylation were observed. Furthermore, several correlations between growth rate, cancer status, and dependency on aerobic glycolysis were observed. Cell cultures can, therefore, successfully serve as closed-circuit models to either replace or be used in conjunction with biofluid samples, which will enable sharper focus on specific cell types or DNA origins.

MPC1 and MPC2 expressions are associated with favorable clinical outcomes in prostate cancer

Background

Cancer cells exhibit an altered metabolism, which is characterized by a preference for aerobic glycolysis more than mitochondrial oxidation of pyruvate. Mitochondrial pyruvate carrier 1 (MPC1) and mitochondrial pyruvate carrier 2 (MPC2) play a bottleneck role by transporting pyruvate into mitochondrial through the mitochondrial inner membrane. Therefore, their protein expression in cancers may be of clinical consequences. There are studies showing low levels of MPC1 expression in colon, kidney and lung cancers, and the expression of MPC1 correlates with poor prognosis. However, the expression status of MPC1 and MPC2 in prostate cancer (PCA) is unclear.

Methods

In this study, expression of MPC1 and MPC2 in LNCaP and DU145 prostate cancer cell lines was examined by immunocytochemistry (ICC) and Western blotting. Compared to the LNCaP cells, lower levels of MPC1 and MPC2 expression in the DU145 cell line was identified. We then extended our study to 88 patients with prostate cancer who underwent transurethral electro-vaporization of prostate or radical prostatectomy at the First Affiliated Hospital of Zhengzhou University, Henan, China. Patient-derived paraffin embedded PCA specimens were collected for immunohistochemistry (IHC). Correlations with clinicopathologic factors were evaluated by Chi-square or Fisher´s exact probability tests. Overall survival (OS) rates were determined using the Kaplan-Meier estimator. The Cox proportional hazard regression model was used in univariate analysis and multivariate analysis to identify factors significantly correlated with prognosis.

Results

Linear regression analysis revealed that MPC1 expression level was positively correlated with MPC2 expression (r = 0.375, P = 0.006) in the prostate cancers. MPC1 expression was negatively associated with UICC stage (P = 0.031). While UICC stage (P < 0.001) and lymph node metastasis (P = 0.002) were negatively associated with MPC2 expression. Positive MPC1 or MPC2 expression in cancer tissues was significantly associated with higher OS (P < 0.05). The multivariate analysis showed that both MPC1 and MPC2 expressions in PCA were independent prognostic factors for higher OS (For MPC1: RR = 0.654, 95% CI: 0.621-0690, P < 0.001; For MPC2: RR = 0.696, 95% CI: 0.660-0.734, P < 0.001).

Conclusions

Our study indicates that MPC1 and MPC2 expressions are of prognostic values in PCAs and that positive expression of MPC1 or MPC2 is a predictor of favorable outcome.

Overexpression of ABCC3 promotes cell proliferation, drug resistance, and aerobic glycolysis and is associated with poor prognosis in urinary bladder cancer patients

Human urinary bladder cancer (UBC) is the one of the most common malignancies worldwide and occurs at a higher frequency in male individuals. ATP-binding cassette, subfamily C, member 3 (ABCC3), a member of the ABC transporter family, is highly expressed in tumor cells, where it actively effluxes a broad spectrum of metabolites. However, the expression and role of ABCC3 in human UBC remains unclear. Our study aimed to identify the expression status of ABCC3 in UBC cases and investigate the biological effects on UBC in cells. We found that both mRNA and protein levels of ABCC3 were significantly higher in UBC tissues than normal tissues. Immunochemistry evaluation of ABCC3 expression in 122 UBC clinical specimens showed that high expression of ABCC3 had a positive correlation with UBC tumor size, advanced tumor node metastasis stage, and malignant histology. Moreover, high ABCC3 expression was linked to poor overall survival in UBC. ABCC3 effects on cell proliferation and drug resistance were measured by colony formation and methylthiazolyldiphenyl-tetrazolium bromide (MTT) assays. ABCC3-knockdown cells showed a significant decrease in cell growth and drug resistance. RNA interference of ABCC3 also caused downregulation of lactate dehydrogenase A (LDHA), which positively correlated with ABCC3 expression in UBC specimens. In addition, cancer cell glycolytic ability was decreased upon ABCC3 knockdown. The activity of LDHA was also abrogated in ABCC3-deficient UBC cells, and the blockade of LDHA increased UBC cells sensitivity to Cis-diamine dichloroplatinum (CDDP). In summary, our study suggests ABCC3 is an important oncoprotein involved in glycolysis and drug resistance. These data also indicates that ABCC3 could be a potential prognostic marker and promising therapeutic target in UBC.