bims-glucam Biomed News
on Glutamine cancer metabolism
Issue of 2021‒02‒07
twenty papers selected by
Sreeparna Banerjee
Middle East Technical University


  1. J Diabetes Metab Disord. 2020 Dec;19(2): 1731-1775
    Vadlakonda L, Indracanti M, Kalangi SK, Gayatri BM, Naidu NG, Reddy ABM.
      Purpose: Re-examine the current metabolic models.Methods: Review of literature and gene networks.
    Results: Insulin activates Pi uptake, glutamine metabolism to stabilise lipid membranes. Tissue turnover maintains the metabolic health. Current model of intermediary metabolism (IM) suggests glucose is the source of energy, and anaplerotic entry of fatty acids and amino acids into mitochondria increases the oxidative capacity of the TCA cycle to produce the energy (ATP). The reduced cofactors, NADH and FADH2, have different roles in regulating the oxidation of nutrients, membrane potentials and biosynthesis. Trans-hydrogenation of NADH to NADPH activates the biosynthesis. FADH2 sustains the membrane potential during the cell transformations. Glycolytic enzymes assume the non-canonical moonlighting functions, enter the nucleus to remodel the genetic programmes to affect the tissue turnover for efficient use of nutrients. Glycosylation of the CD98 (4F2HC) stabilises the nutrient transporters and regulates the entry of cysteine, glutamine and BCAA into the cells. A reciprocal relationship between the leucine and glutamine entry into cells regulates the cholesterol and fatty acid synthesis and homeostasis in cells. Insulin promotes the Pi transport from the blood to tissues, activates the mitochondrial respiratory activity, and glutamine metabolism, which activates the synthesis of cholesterol and the de novo fatty acids for reorganising and stabilising the lipid membranes for nutrient transport and signal transduction in response to fluctuations in the microenvironmental cues. Fatty acids provide the lipid metabolites, activate the second messengers and protein kinases. Insulin resistance suppresses the lipid raft formation and the mitotic slippage activates the fibrosis and slow death pathways.
    Keywords:  CD98; Fatty acids; Glutamine; Leucine; Mitochondrial pyruvate carrier proteins (MPC1&2); Tissue turnover; mTORC1
    DOI:  https://doi.org/10.1007/s40200-020-00566-5
  2. Front Oncol. 2020 ;10 617190
    Ye X, Wei X, Liao J, Chen P, Li X, Chen Y, Yang Y, Zhao Q, Sun H, Pan L, Chen G, He X, Lyu J, Fang H.
      Tumor cells develop a series of metabolic reprogramming mechanisms to meet the metabolic needs for tumor progression. As metabolic hubs in cells, mitochondria play a significant role in this process, including energy production, biosynthesis, and redox hemostasis. In this study, we show that 4-hydroxyphenylpyruvate dioxygenase-like protein (HPDL), a previously uncharacterized protein, is positively associated with the development of pancreatic ductal adenocarcinoma (PDAC) and disease prognosis. We found that overexpression of HPDL in PDAC cells promotes tumorigenesis in vitro, whereas knockdown of HPDL inhibits cell proliferation and colony formation. Mechanistically, we found that HPDL is a mitochondrial intermembrane space localized protein that positively regulates mitochondrial bioenergetic processes and adenosine triphosphate (ATP) generation in a glutamine dependent manner. Our results further reveal that HPDL protects cells from oxidative stress by reprogramming the metabolic profile of PDAC cells toward glutamine metabolism. In short, we conclude that HPDL promotes PDAC likely through its effects on glutamine metabolism and redox balance.
    Keywords:  glutamine; metabolic reprogramming; mitochondria; pancreatic ductal adenocarcinoma; redox balance
    DOI:  https://doi.org/10.3389/fonc.2020.617190
  3. Int J Biochem Cell Biol. 2021 Jan 30. pii: S1357-2725(21)00019-4. [Epub ahead of print] 105935
    Smith H, De Souza D, Tull D, McConville M, Pellagatti A, Boultwood J, Board M, Callaghan R.
      Solid tumours modify their metabolic strategy to ensure sufficient biomass and energy to maintain a high rate of proliferation. However, solid tumours are characterised by a high proportion of quiescent cells and little is known about their metabolic profile. A tumour spheroid model with DLD1 cells was used to investigate the influence of a quiescent state on the cellular utilisation of glucose and glutamine. Quiescent DLD1 spheroids displayed increased depletion of both nutrients from the bathing medium compared to their proliferative counterparts and displayed highly active overall metabolism. A combination of biochemical and metabolomics approaches demonstrated that glucose utilisation resulted in an increased production of the 3-carbon intermediates lactate and alanine in quiescent spheroids. In addition, glutamine metabolism was directed to anabolic pathways; including the "reverse TCA cycle" to produce citrate for fatty-acid synthesis. These metabolic adaptations in DLD1 spheroids may propose a metabolic altruism of quiescent regions in solid tumours to provide biosynthetic intermediates required to sustain tumour growth, angiogenesis and metastasis.
    Keywords:  Tumour metabolism; glucose metabolism; glutamine metabolism; glutaminolysis; glycolysis; metabolomics; quiescence; tumour spheroid
    DOI:  https://doi.org/10.1016/j.biocel.2021.105935
  4. Biomedicines. 2021 Feb 03. pii: 147. [Epub ahead of print]9(2):
    Du W, Ren L, Hamblin MH, Fan Y.
      Angiogenesis, a process of new blood vessel formation from the pre-existing vascular bed, is a critical event in various physiological and pathological settings. Over the last few years, the role of endothelial cell (EC) metabolism in angiogenesis has received considerable attention. Accumulating studies suggest that ECs rely on aerobic glycolysis, rather than the oxidative phosphorylation pathway, to produce ATP during angiogenesis. To date, numerous critical regulators of glucose metabolism, fatty acid oxidation, and glutamine metabolism have been identified to modulate the EC angiogenic switch and pathological angiogenesis. The unique glycolytic feature of ECs is critical for cell proliferation, migration, and responses to environmental changes. In this review, we provide an overview of recent EC glucose metabolism studies, particularly glycolysis, in quiescent and angiogenic ECs. We also summarize and discuss potential therapeutic strategies that take advantage of EC metabolism. The elucidation of metabolic regulation and the precise underlying mechanisms could facilitate drug development targeting EC metabolism to treat angiogenesis-related diseases.
    Keywords:  angiogenesis; endothelial cell; glycolysis; metabolism; pathological angiogenesis; tumor microenvironment
    DOI:  https://doi.org/10.3390/biomedicines9020147
  5. PeerJ. 2021 ;9 e10648
    Hinow P, Pinter G, Yan W, Wang SE.
      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.
    Keywords:  Cancer-associated fibroblasts; Glutamine/ammonium metabolism; Mathematical modeling
    DOI:  https://doi.org/10.7717/peerj.10648
  6. Cancers (Basel). 2021 Feb 02. pii: 569. [Epub ahead of print]13(3):
    Benyahia Z, Blackman MCNM, Hamelin L, Zampieri LX, Capeloa T, Bedin ML, Vazeille T, Schakman O, Sonveaux P.
      To survive and proliferate in solid tumors, cancer cells adapt and evolve rapidly in microenvironments where oxygen and substrate bioavailability fluctuates over time and space. This creates metabolic heterogeneity. Cancer cells can further cooperate metabolically, for example by swapping glycolytic end-product lactate for blood-borne glucose. This type of cooperation can be targeted therapeutically, since transmembrane lactate exchanges are facilitated by lactate-proton symporters of the monocarboxylate (MCT) family. Among new drugs, AZD3965 is a first-in-class selective MCT1 inhibitor currently tested in Phase I/II clinical trials for patients with different types of cancers. Because MCT1 can function bidirectionally, we tested here whether and how malignant and nonmalignant cells adapt their metabolism and MCT repertoire when AZD3965 inhibits either lactate import or export. Using breast-associated malignant and nonmalignant cell lines as models, we report that AZD3965 is not directly cytotoxic. In the presence of glucose and glutamine, oxidative cells can survive when lactate uptake is blocked, and proliferating cells compensate MCT1 inhibition by overexpressing MCT4, a specialized facilitator of lactate export. Phenotypic characterization of mice focusing on metabolism, muscle and brain physiology found partial and transient memory retention defect as sole consequence of MCT1 inhibition by AZD3965. We therefore conclude that AZD3965 is compatible with anticancer therapy.
    Keywords:  CD147/basigin; brain; breast cancer; cancer metabolism; heart; monocarboxylate transporters (MCTs); muscle; oxidative pathway of lactate; oxidative phosphorylation (OXPHOS); preclinical toxicology
    DOI:  https://doi.org/10.3390/cancers13030569
  7. Adv Nutr. 2021 Feb 02. pii: nmaa174. [Epub ahead of print]
    Icard P, Loi M, Wu Z, Ginguay A, Lincet H, Robin E, Coquerel A, Berzan D, Fournel L, Alifano M.
      The tumor microenvironment is a complex mix of cancerous and noncancerous cells (especially immune cells and fibroblasts) with distinct metabolisms. These cells interact with each other and are influenced by the metabolic disorders of the host. In this review, we discuss how metabolic pathways that sustain biosynthesis in cancer cells could be targeted to increase the effectiveness of cancer therapies by limiting the nutrient uptake of the cell, inactivating metabolic enzymes (key regulatory ones or those linked to cell cycle progression), and inhibiting ATP production to induce cell death. Furthermore, we describe how the microenvironment could be targeted to activate the immune response by redirecting nutrients toward cytotoxic immune cells or inhibiting the release of waste products by cancer cells that stimulate immunosuppressive cells. We also examine metabolic disorders in the host that could be targeted to inhibit cancer development. To create future personalized therapies for targeting each cancer tumor, novel techniques must be developed, such as new tracers for positron emission tomography/computed tomography scan and immunohistochemical markers to characterize the metabolic phenotype of cancer cells and their microenvironment. Pending personalized strategies that specifically target all metabolic components of cancer development in a patient, simple metabolic interventions could be tested in clinical trials in combination with standard cancer therapies, such as short cycles of fasting or the administration of sodium citrate or weakly toxic compounds (such as curcumin, metformin, lipoic acid) that target autophagy and biosynthetic or signaling pathways.
    Keywords:  body composition; drug resistance; glycolysis; immunity; metabolism; tumor microenvironment
    DOI:  https://doi.org/10.1093/advances/nmaa174
  8. Front Oncol. 2020 ;10 591342
    Wu S, Kuang H, Ke J, Pi M, Yang DH.
      Tumor cells rewire metabolism to meet their increased nutritional demands, allowing the maintenance of tumor survival, proliferation, and expansion. Enhancement of glycolysis and glutaminolysis is identified in most, if not all cancers, including multiple myeloma (MM), which interacts with a hypoxic, acidic, and nutritionally deficient tumor microenvironment (TME). In this review, we discuss the metabolic changes including generation, depletion or accumulation of metabolites and signaling pathways, as well as their relationship with the TME in MM cells. Moreover, we describe the crosstalk among metabolism, TME, and changing function of immune cells during cancer progression. The overlapping metabolic phenotype between MM and immune cells is discussed. In this sense, targeting metabolism of MM cells is a promising therapeutic approach. We propose that it is important to define the metabolic signatures that may regulate the function of immune cells in TME in order to improve the response to immunotherapy.
    Keywords:  immune cell dysfunction; metabolic reprogramming; multiple myeloma; signaling pathways; tumor microenvironment
    DOI:  https://doi.org/10.3389/fonc.2020.591342
  9. J Biol Chem. 2020 Jan 03. pii: S0021-9258(17)49553-6. [Epub ahead of print]295(1): 111-124
    Liberti MV, Allen AE, Ramesh V, Dai Z, Singleton KR, Guo Z, Liu JO, Wood KC, Locasale JW.
      Aerobic glycolysis or the Warburg effect (WE) is characterized by increased glucose uptake and incomplete oxidation to lactate. Although the WE is ubiquitous, its biological role remains controversial, and whether glucose metabolism is functionally different during fully oxidative glycolysis or during the WE is unknown. To investigate this question, here we evolved resistance to koningic acid (KA), a natural product that specifically inhibits glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a rate-controlling glycolytic enzyme, during the WE. We found that KA-resistant cells lose the WE but continue to conduct glycolysis and surprisingly remain dependent on glucose as a carbon source and also on central carbon metabolism. Consequently, this altered state of glycolysis led to differential metabolic activity and requirements, including emergent activities in and dependences on fatty acid metabolism. These findings reveal that aerobic glycolysis is a process functionally distinct from conventional glucose metabolism and leads to distinct metabolic requirements and biological functions.
    Keywords:  Warburg effect; cancer; glucose metabolism; glyceraldehyde-3-phosphate dehydrogenase GAPDH; glycolysis; mass spectrometry (MS); metabolic regulation; metabolic reprogramming; metabolomics; oxidative metabolism
    DOI:  https://doi.org/10.1074/jbc.RA119.010903
  10. Hepatology. 2021 Feb 02.
    Tao J, Krutsenko Y, Moghe A, Singh S, Poddar M, Bell A, Oertel M, Singhi AD, Geller D, Chen X, Lujambio A, Liu S, Monga SP.
      BACKGROUND: Hepatocellular cancer (HCC) remains a major unmet clinical need. Although activating CTNNB1 mutations are seen in prominent subsets of HCC cases, these by themselves are insufficient for hepatocarcinogenesis. Co-expression of mutant CTNNB1 with clinically relevant co-occurrence has yielded HCCs. Here, we identify cooperation between β-catenin and Nrf2 signaling in HCC.METHODS: Public HCC datasets were assessed for concomitant presence of CTNNB1 mutations and either mutations in NFE2L2 or KEAP1, or Nrf2 activation by gene signature. HCC development in mice and similarity to human HCC subsets was assessed following co-expression of T41A-CTNNB1 with either WT-, G31A- or T80K-NFE2L2. Based on mTORC1 activation in CTNNB1-mutated HCCs, response of preclinical HCC to mTOR inhibitor was investigated.
    RESULTS: Overall, 9% of HCC cases showed concomitant CTNNB1 mutations and Nrf2 activation, subsets of which were due to mutations in NFE2L2/KEAP1. Co-expression of mutated-CTNNB1 with mutant-NFE2L2 but not WT-NFE2L2 led to HCC development and mortality by 12-14 weeks. These HCCs were positive for β-catenin targets like Glutamine synthetase and Cyclin-D1, and Nrf2 targets like NAD(P)H Quinone Dehydrogenase 1 and peroxiredoxin 1. RNA-seq and pathway analysis showed high concordance of preclinical HCC to human HCC subset showing activation of unique (Iron Homeostasis and Glioblastoma Multiforme signaling) and expected (Glutamine Metabolism) pathways. NFE2L2-CTNNB1 HCC mice were treated with mTOR inhibitor everolimus (5mg/kg diet ad libitum), which led to >50% decrease in tumor burden. Conclusion Co-activation of β-catenin and Nrf2 is evident in 9% of all human HCCs. Co-expression of mutant-NFE2L2 and mutant-CTNNB1 led to clinically relevant HCC development in mice, which responded to mTOR inhibitors. Thus, this model has both biological and therapeutic implications.
    Keywords:  CTNNB1; Glutamine synthetase; KEAP1; NFE2L2; Wnt pathway; liver tumors; mTOR inhibitor; mutations
    DOI:  https://doi.org/10.1002/hep.31730
  11. Nat Genet. 2021 Feb;53(2): 215-229
    Betto RM, Diamante L, Perrera V, Audano M, Rapelli S, Lauria A, Incarnato D, Arboit M, Pedretti S, Rigoni G, Guerineau V, Touboul D, Stirparo GG, Lohoff T, Boroviak T, Grumati P, Soriano ME, Nichols J, Mitro N, Oliviero S, Martello G.
      Naive epiblast and embryonic stem cells (ESCs) give rise to all cells of adults. Such developmental plasticity is associated with genome hypomethylation. Here, we show that LIF-Stat3 signaling induces genomic hypomethylation via metabolic reconfiguration. Stat3-/- ESCs show decreased α-ketoglutarate production from glutamine, leading to increased Dnmt3a and Dnmt3b expression and DNA methylation. Notably, genome methylation is dynamically controlled through modulation of α-ketoglutarate availability or Stat3 activation in mitochondria. Alpha-ketoglutarate links metabolism to the epigenome by reducing the expression of Otx2 and its targets Dnmt3a and Dnmt3b. Genetic inactivation of Otx2 or Dnmt3a and Dnmt3b results in genomic hypomethylation even in the absence of active LIF-Stat3. Stat3-/- ESCs show increased methylation at imprinting control regions and altered expression of cognate transcripts. Single-cell analyses of Stat3-/- embryos confirmed the dysregulated expression of Otx2, Dnmt3a and Dnmt3b as well as imprinted genes. Several cancers display Stat3 overactivation and abnormal DNA methylation; therefore, the molecular module that we describe might be exploited under pathological conditions.
    DOI:  https://doi.org/10.1038/s41588-020-00770-2
  12. J Cancer. 2021 ;12(5): 1563-1574
    Chen X, Yi C, Yang MJ, Sun X, Liu X, Ma H, Li Y, Li H, Wang C, He Y, Chen G, Chen S, Yu L, Yu D.
      Background: Most tumors have an enhanced glycolysis flux, even when oxygen is available, called the aerobic glycolysis or the Warburg effect. Metabolic reprogramming promotes cancer progression, and is even related to the tumorigenesis. However, it is not clear whether the observed metabolic changes act as a driver or a bystander in cancer development. Methods: In this study, the metabolic characteristics of oral precancerous cells and cervical precancerous lesions were analyzed by metabolomics, and the expression of glycolytic enzymes in cervical precancerous lesions was evaluated by RT-PCR and Western blot analysis. Results: In total, 115 and 23 metabolites with reliable signals were identified in oral cells and cervical tissues, respectively. Based on the metabolome, oral precancerous cell DOK could be clearly separated from normal human oral epithelial cells (HOEC) and oral cancer cells. Four critical differential metabolites (pyruvate, glutamine, methionine and lysine) were identified between DOK and HOEC. Metabolic profiles could clearly distinguish cervical precancerous lesions from normal cervical epithelium and cervical cancer. Compared with normal cervical epithelium, the glucose consumption and lactate production increased in cervical precancerous lesions. The expression of glycolytic enzymes LDHA, HK II and PKM2 showed an increased tendency in cervical precancerous lesions compared with normal cervical epithelium. Conclusions: Our findings suggest that cell metabolism may be reprogrammed at the early stage of tumorigenesis, implying the contribution of metabolic reprogramming to the development of tumor.
    Keywords:  glycolytic enzymes; metabolic reprogramming; metabolomics; precancerous lesions; the Warburg-like effect
    DOI:  https://doi.org/10.7150/jca.54252
  13. Int J Mol Sci. 2021 Feb 02. pii: 1470. [Epub ahead of print]22(3):
    Weglarz-Tomczak E, Rijlaarsdam DJ, Tomczak JM, Brul S.
      Cancer cell metabolism is dependent on cell-intrinsic factors, such as genetics, and cell-extrinsic factors, such nutrient availability. In this context, understanding how these two aspects interact and how diet influences cellular metabolism is important for developing personalized treatment. In order to achieve this goal, genome-scale metabolic models (GEMs) are used; however, genetics and nutrient availability are rarely considered together. Here, we propose integrated metabolic profiling, a framework that allows enriching GEMs with metabolic gene expression data and information about nutrients. First, the RNA-seq is converted into Reaction Activity Score (RAS) to further scale reaction bounds. Second, nutrient availability is converted to Maximal Uptake Rate (MUR) to modify exchange reactions in a GEM. We applied our framework to the human osteosarcoma cell line (U2OS). Osteosarcoma is a common and primary malignant form of bone cancer with poor prognosis, and, as indicated in our study, a glutamine-dependent type of cancer.
    Keywords:  genome-scale metabolic models; metabolism; nutrients; osteosarcoma; transcription
    DOI:  https://doi.org/10.3390/ijms22031470
  14. Nutrition. 2020 Nov 22. pii: S0899-9007(20)30370-1. [Epub ahead of print]85 111087
    de Freitas REM, Medeiros PHQS, Rodrigues FAP, Clementino MAF, Fernandes C, da Silva AVA, Prata MMG, Cavalcante PA, Lima AÂM, Havt A.
      OBJECTIVE: Vitamin A is commonly recommended as a treatment for diarrhea and undernutrition; however, little is known about the underlying cellular mechanisms. The aim of this study was to investigate the modulation of cell cycle by vitamin A derivatives (retinyl palmitate or retinol) in undernourished intestinal epithelial crypts (IEC-6).METHODS: IEC-6 cells were exposed to nutrient deprivation (no serum and no glutamine) and supplemented with retinyl palmitate or retinol at a range of 2 to 20 μM. Proliferation, apoptosis/necrosis, cell cycle process, and gene transcription were assessed.
    RESULTS: Nutrient deprivation for 6, 12, 24, or 48 h decreased cell proliferation, and retinyl palmitate further decreased it after 24 and 48 h. Apoptosis rates were reduced by undernourishment and further reduced by retinyl palmitate after 48 h; whereas necrosis rates were unaltered. Undernourishment induced overall cell quiescence, increased percentage of cells in G0/G1 phase and decreased percentage of cells in S phase after 12 h and in G2/M phases at 6, 12, and 24 h after treatment. Both retinoids also showed cell quiescence induction with less cells in G2/M phases after 48 h, whereas only retinol showed significant modulation of G0/G1 and S phases. Both retinoids also increased markers of cell differentiation Fabp and Iap gene transcriptions in about fivefold rates after 42 h. Furthermore, specific gene transcriptions related to MAP kinase signaling pathway regulation of cell differentiation and cell cycle regulation were triggered by retinoids in undernourished IEC-6, with higher levels of expression for Atf2 and C-jun genes.
    CONCLUSIONS: These findings indicated that both vitamin A derivatives induce further survival mechanisms in undernourished intestinal epithelial crypt cells. These mechanisms include increased cell quiescence, decreased apoptosis, increased cell differentiation, and transcription of genes related to MAP kinase signaling pathway.
    Keywords:  Cell cycle; Intestinal epithelium; Retinoids; Undernutrition; Vitamin A
    DOI:  https://doi.org/10.1016/j.nut.2020.111087
  15. Cancers (Basel). 2021 Feb 01. pii: 541. [Epub ahead of print]13(3):
    Sekine H, Motohashi H.
      Cancer cells exhibit unique metabolic features and take advantage of them to enhance their survival and proliferation. While the activation of NRF2 (nuclear factor erythroid 2-like 2; NFE2L2), a CNC (cap'n'collar) family transcription factor, is effective for the prevention and alleviation of various diseases, NRF2 contributes to cancer malignancy by promoting aggressive tumorigenesis and conferring therapeutic resistance. NRF2-mediated metabolic reprogramming and increased antioxidant capacity underlie the malignant behaviors of NRF2-activated cancer cells. Another member of the CNC family, NRF1, plays a key role in the therapeutic resistance of cancers. Since NRF1 maintains proteasome activity by inducing proteasome subunit genes in response to proteasome inhibitors, NRF1 protects cancer cells from proteotoxicity induced by anticancer proteasome inhibitors. An important metabolite that activates NRF1 is UDP-GlcNAc (uridine diphosphate N-acetylglucosamine), which is abundantly generated in many cancer cells from glucose and glutamine via the hexosamine pathway. Thus, the metabolic signatures of cancer cells are closely related to the oncogenic and tumor-promoting functions of CNC family members. In this review, we provide a brief overview of NRF2-mediated cancer malignancy and elaborate on NRF1-mediated drug resistance affected by an oncometabolite UDP-GlcNAc.
    Keywords:  CNC proteins; NRF1; NRF2; O-GlcNAcylation; proteasome
    DOI:  https://doi.org/10.3390/cancers13030541
  16. Biomed Res Int. 2021 ;2021 8621464
    Zhang M, Fu Y, Chen Y, Ma Y, Guo Z, Wang Y, Hao H, Fu Q, Wang Z.
      In addition to serving as the building blocks for protein synthesis, amino acids can be used as an energy source, through catabolism. The transamination, oxidative deamination, and decarboxylation processes that occur during amino acid catabolism are catalyzed by specific enzymes, including aspartate aminotransferase (AST), glutamate dehydrogenase (GDH), glutamic acid decarboxylase (GAD), and ornithine decarboxylase (ODC); however, the overall molecular mechanisms through which amino acid catabolism occurs remain largely unknown. To examine the role of mechanistic target of rapamycin complex 1 (mTORC1) on amino acid catabolism, mTORC1 was inactivated by rapamycin or shRNA targeting Raptor, versus activated by overexpressing Rheb or amino acids in human hepatocytes. The expression of amino acid catabolic genes and related transcription factor was investigated by RT/real-time PCR and western blot analysis. A few types of amino acid metabolite were examined by ELISA and HPLC analysis. The data showed that inactivated mTORC1 resulted in inhibition of NF-κB and the expression of AST, GDH, GAD, and ODC, whereas activated mTORC1 enhanced NF-κB activation and the expression levels of the catabolism-associated genes. Further, inhibition of NF-κB reduced the expression levels of AST, GDH, GAD, and ODC. mTORC1 upregulated NF-κB activation and the expression of AST and ODC in response to glutamate and ornithine treatments, whereas rapamycin inhibited the utilization of glutamate and ornithine in hepatocytes. Taken together, these results indicated that the mTORC1/NF-κB axis modulates the rate of amino acid catabolism by regulating the expression of key catabolic enzymes in hepatocytes.
    DOI:  https://doi.org/10.1155/2021/8621464
  17. Cell Rep. 2021 Feb 02. pii: S2211-1247(21)00036-X. [Epub ahead of print]34(5): 108723
    Gonzalez-Menendez P, Romano M, Yan H, Deshmukh R, Papoin J, Oburoglu L, Daumur M, Dumé AS, Phadke I, Mongellaz C, Qu X, Bories PN, Fontenay M, An X, Dardalhon V, Sitbon M, Zimmermann VS, Gallagher PG, Tardito S, Blanc L, Mohandas N, Taylor N, Kinet S.
      The metabolic changes controlling the stepwise differentiation of hematopoietic stem and progenitor cells (HSPCs) to mature erythrocytes are poorly understood. Here, we show that HSPC development to an erythroid-committed proerythroblast results in augmented glutaminolysis, generating alpha-ketoglutarate (αKG) and driving mitochondrial oxidative phosphorylation (OXPHOS). However, sequential late-stage erythropoiesis is dependent on decreasing αKG-driven OXPHOS, and we find that isocitrate dehydrogenase 1 (IDH1) plays a central role in this process. IDH1 downregulation augments mitochondrial oxidation of αKG and inhibits reticulocyte generation. Furthermore, IDH1 knockdown results in the generation of multinucleated erythroblasts, a morphological abnormality characteristic of myelodysplastic syndrome and congenital dyserythropoietic anemia. We identify vitamin C homeostasis as a critical regulator of ineffective erythropoiesis; oxidized ascorbate increases mitochondrial superoxide and significantly exacerbates the abnormal erythroblast phenotype of IDH1-downregulated progenitors, whereas vitamin C, scavenging reactive oxygen species (ROS) and reprogramming mitochondrial metabolism, rescues erythropoiesis. Thus, an IDH1-vitamin C crosstalk controls terminal steps of human erythroid differentiation.
    Keywords:  alpha-ketoglutarate; enucleation; erythropoiesis; hematopoietic stem and progenitor cell; human; isocitrate dehydrogenase; mitochondria; oxidative phosphorylation; redox stress; vitamin C
    DOI:  https://doi.org/10.1016/j.celrep.2021.108723
  18. World J Surg Oncol. 2021 Jan 31. 19(1): 35
    Gong Y, Qian Y, Luo G, Liu Y, Wang R, Deng S, Cheng H, Jin K, Ni Q, Yu X, Wu W, Liu C.
      BACKGROUND: Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) is the first rate-limiting enzyme of the hexosamine biosynthesis pathway (HBP), which plays a pivotal role in the progression of pancreatic ductal adenocarcinoma (PDAC). Therefore, we investigated the prognostic significance of GFPT1 expression in patients with resectable PDAC.METHODS: We analyzed public datasets to compare GFPT1 expression in tumor tissues and normal/adjacent pancreatic tissues. We measured the relative GFPT1 expression of 134 resected PDAC specimens in our institution, using real-time polymerase chain reaction (PCR). Survival was compared between high and low GFPT1 expression groups using Kaplan-Meier curves and log-rank tests. Multivariate analyses were estimated using Cox regression and logistic regression models.
    RESULTS: GFPT1 is generally upregulated in PDAC tissues, according to the analysis of public datasets. The data from our institution shows that high GFPT1 expression was correlated with a high rate of lymph node (LN) metastasis (p = 0.038) and was an independent risk factor for LN metastasis (odds ratio (OR) = 3.14, 95% confidence interval (CI) = 1.42 to 6.90, P = 0.005). High GFPT1 expression was significantly associated with poor overall survival (OS; P = 0.019) in patients with resected PDAC. The multivariable-adjusted hazard ratio (HR) for mortality when comparing patients with high and low GFPT1 expression was 2.54 (95% CI = 1.35 to 4.79, P = 0.004).
    CONCLUSIONS: GFPT1 is generally upregulated in PDAC tissue and is associated with a high risk of LN metastasis and an unfavorable outcome in patients with resectable PDAC, suggesting its crucial role in PDAC progression.
    Keywords:  Glutamine-fructose-6-phosphate transaminase 1; Hexosamine biosynthesis pathway (HBP); Prognosis; Survival
    DOI:  https://doi.org/10.1186/s12957-021-02147-z
  19. Biochem Soc Trans. 2021 Feb 05. pii: BST20190730. [Epub ahead of print]
    Heberle AM, Rehbein U, Rodríguez Peiris M, Thedieck K.
      Cells have evolved highly intertwined kinase networks to finely tune cellular homeostasis to the environment. The network converging on the mechanistic target of rapamycin (MTOR) kinase constitutes a central hub that integrates metabolic signals and adapts cellular metabolism and functions to nutritional changes and stress. Feedforward and feedback loops, crosstalks and a plethora of modulators finely balance MTOR-driven anabolic and catabolic processes. This complexity renders it difficult - if not impossible - to intuitively decipher signaling dynamics and network topology. Over the last two decades, systems approaches have emerged as powerful tools to simulate signaling network dynamics and responses. In this review, we discuss the contribution of systems studies to the discovery of novel edges and modulators in the MTOR network in healthy cells and in disease.
    Keywords:  amino acids; computational models; mechanistic target of rapamycin; protein kinase B; signaling; systems biology
    DOI:  https://doi.org/10.1042/BST20190730