scholarly journals BCAT1 affects mitochondrial metabolism independently of leucine transamination in activated human macrophages

2020 ◽  
Vol 133 (22) ◽  
pp. jcs247957
Author(s):  
Jeong-Hun Ko ◽  
Antoni Olona ◽  
Adonia E. Papathanassiu ◽  
Norzawani Buang ◽  
Kwon-Sik Park ◽  
...  
Keyword(s):  
Macrophage Activation ◽  
Polarization State ◽  
Tca Cycle ◽  
Metabolic Adaptation ◽  
Human Macrophages ◽  
Relative Contribution ◽  
The Tca Cycle ◽  
Nutrient Consumption ◽  
Anti Oxidant ◽  
Branched Chain

ABSTRACTIn response to environmental stimuli, macrophages change their nutrient consumption and undergo an early metabolic adaptation that progressively shapes their polarization state. During the transient, early phase of pro-inflammatory macrophage activation, an increase in tricarboxylic acid (TCA) cycle activity has been reported, but the relative contribution of branched-chain amino acid (BCAA) leucine remains to be determined. Here, we show that glucose but not glutamine is a major contributor of the increase in TCA cycle metabolites during early macrophage activation in humans. We then show that, although uptake of BCAAs is not altered, their transamination by BCAT1 is increased following 8 h lipopolysaccharide (LPS) stimulation. Of note, leucine is not metabolized to integrate into the TCA cycle in basal or stimulated human macrophages. Surprisingly, the pharmacological inhibition of BCAT1 reduced glucose-derived itaconate, α-ketoglutarate and 2-hydroxyglutarate levels without affecting succinate and citrate levels, indicating a partial inhibition of the TCA cycle. This indirect effect is associated with NRF2 (also known as NFE2L2) activation and anti-oxidant responses. These results suggest a moonlighting role of BCAT1 through redox-mediated control of mitochondrial function during early macrophage activation.

scholarly journals Ammonia inhibits energy metabolism in astrocytes in a rapid and glutamate dehydrogenase 2-dependent manner

2020 ◽  
Vol 13 (10) ◽  
pp. dmm047134
Author(s):  
Leonie Drews ◽  
Marcel Zimmermann ◽  
Philipp Westhoff ◽  
Dominik Brilhaus ◽  
Rebecca E. Poss ◽  
...  
Keyword(s):  
Amino Acids ◽  
Energy Metabolism ◽  
Glutamate Dehydrogenase ◽  
Mitochondrial Respiration ◽  
Tca Cycle ◽  
Dependent Manner ◽  
Independent Manner ◽  
The Tca Cycle ◽  
Branched Chain ◽  
Tca Cycle Intermediates

ABSTRACTAstrocyte dysfunction is a primary factor in hepatic encephalopathy (HE) impairing neuronal activity under hyperammonemia. In particular, the early events causing ammonia-induced toxicity to astrocytes are not well understood. Using established cellular HE models, we show that mitochondria rapidly undergo fragmentation in a reversible manner upon hyperammonemia. Further, in our analyses, within a timescale of minutes, mitochondrial respiration and glycolysis were hampered, which occurred in a pH-independent manner. Using metabolomics, an accumulation of glucose and numerous amino acids, including branched chain amino acids, was observed. Metabolomic tracking of 15N-labeled ammonia showed rapid incorporation of 15N into glutamate and glutamate-derived amino acids. Downregulating human GLUD2 [encoding mitochondrial glutamate dehydrogenase 2 (GDH2)], inhibiting GDH2 activity by SIRT4 overexpression, and supplementing cells with glutamate or glutamine alleviated ammonia-induced inhibition of mitochondrial respiration. Metabolomic tracking of 13C-glutamine showed that hyperammonemia can inhibit anaplerosis of tricarboxylic acid (TCA) cycle intermediates. Contrary to its classical anaplerotic role, we show that, under hyperammonemia, GDH2 catalyzes the removal of ammonia by reductive amination of α-ketoglutarate, which efficiently and rapidly inhibits the TCA cycle. Overall, we propose a critical GDH2-dependent mechanism in HE models that helps to remove ammonia, but also impairs energy metabolism in mitochondria rapidly.

scholarly journals Reactive Oxygen Species, Metabolic Plasticity, and Drug Resistance in Cancer

2020 ◽  
Vol 21 (10) ◽  
pp. 3412 ◽  
Author(s):  
Vikas Bhardwaj ◽  
Jun He
Keyword(s):  
Reactive Oxygen Species ◽  
Cancer Cells ◽  
Reactive Oxygen ◽  
Tca Cycle ◽  
Metabolic Adaptation ◽  
Oxygen Species ◽  
Metabolic Plasticity ◽  
The Tca Cycle ◽  
Clinical Benefits ◽  
High Level

The metabolic abnormality observed in tumors is characterized by the dependence of cancer cells on glycolysis for their energy requirements. Cancer cells also exhibit a high level of reactive oxygen species (ROS), largely due to the alteration of cellular bioenergetics. A highly coordinated interplay between tumor energetics and ROS generates a powerful phenotype that provides the tumor cells with proliferative, antiapoptotic, and overall aggressive characteristics. In this review article, we summarize the literature on how ROS impacts energy metabolism by regulating key metabolic enzymes and how metabolic pathways e.g., glycolysis, PPP, and the TCA cycle reciprocally affect the generation and maintenance of ROS homeostasis. Lastly, we discuss how metabolic adaptation in cancer influences the tumor’s response to chemotherapeutic drugs. Though attempts of targeting tumor energetics have shown promising preclinical outcomes, the clinical benefits are yet to be fully achieved. A better understanding of the interaction between metabolic abnormalities and involvement of ROS under the chemo-induced stress will help develop new strategies and personalized approaches to improve the therapeutic efficiency in cancer patients.

scholarly journals Flavonoid-mediated immunomodulation of human macrophages involves key metabolites and metabolic pathways

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Luís F. Mendes ◽  
Vítor M. Gaspar ◽  
Tiago A. Conde ◽  
João F. Mano ◽  
Iola F. Duarte
Keyword(s):  
Metabolic Pathways ◽  
Tca Cycle ◽  
Immunomodulatory Activity ◽  
Human Macrophages ◽  
Biological Targets ◽  
Glycolytic Activity ◽  
The Tca Cycle ◽  
M1 Phenotype ◽  
Biochemical Level

Abstract The ability of flavonoids to attenuate macrophage pro-inflammatory activity and to promote macrophage-mediated resolution of inflammation is still poorly understood at the biochemical level. In this study, we have employed NMR metabolomics to assess how therapeutically promising flavonoids (quercetin, naringenin and naringin) affect the metabolism of human macrophages, with a view to better understand their biological targets and activity. In vitro-cultured human macrophages were polarized to the pro-inflammatory M1 phenotype, through incubation with LPS + IFN-γ, and subsequently treated with each flavonoid. The metabolic signatures of pro-inflammatory polarization and of flavonoid incubations were then characterized and compared. The results showed that all flavonoids modulated the cells endometabolome with the strongest impact being observed for quercetin. Many of the flavonoid-induced metabolic variations were in the opposite sense to those elicited by pro-inflammatory stimulation. In particular, the metabolic processes proposed to reflect flavonoid-mediated immunomodulation of macrophages included the downregulation of glycolytic activity, observed for all flavonoids, anti-inflammatory reprogramming of the TCA cycle (mainly quercetin), increased antioxidant protection (quercetin), osmoregulation (naringin), and membrane modification (naringenin). This work revealed key metabolites and metabolic pathways involved in macrophage responses to quercetin, naringenin and naringin, providing novel insights into their immunomodulatory activity.

α-Aminoadipate aminotransferase from an extremely thermophilic bacterium, Thermus thermophilus

Microbiology ◽  
2004 ◽  
Vol 150 (7) ◽  
pp. 2327-2334 ◽  
Author(s):  
Takashi Miyazaki ◽  
Junichi Miyazaki ◽  
Hisakazu Yamane ◽  
Makoto Nishiyama
Keyword(s):  
Thermus Thermophilus ◽  
Tca Cycle ◽  
Thermophilic Bacterium ◽  
Multiple Roles ◽  
Lysine Biosynthesis ◽  
Lag Phase ◽  
Gene Encoding ◽  
Branched Chain Amino Acid ◽  
The Tca Cycle ◽  
Branched Chain

The extremely thermophilic bacterium Thermus thermophilus HB27 synthesizes lysine through α-aminoadipate (AAA). In this study, a T. thermophilus gene encoding the enzyme that catalyses transamination of AAA was cloned as a mammalian kynurenine/AAA aminotransferase (Kat2) gene homologue. A T. thermophilus mutant with disruption of the Kat2 homologue required a longer lag phase for growth and showed slower growth in minimal medium. Furthermore, addition of AAA or lysine shortened the lag phase and improved the growth rate. The Kat2 homologue was therefore termed lysN. LysN recognizes not only 2-oxoadipate, an intermediate of lysine biosynthesis, but also 2-oxoisocaproate, 2-oxoisovalerate and 2-oxo-3-methylvalerate, intermediates of leucine, valine and isoleucine biosyntheses, respectively, along with oxaloacetate, a compound in the TCA cycle, as an amino acceptor. These results suggest multiple roles of LysN in several cellular metabolic pathways including lysine and branched-chain amino acid biosyntheses.

scholarly journals Novel insights into development of diabetic bladder disorder provided by metabolomic analysis of the rat nondiabetic and diabetic detrusor and urothelial layer

2016 ◽  
Vol 311 (2) ◽  
pp. E471-E479 ◽  
Author(s):  
Yi Wang ◽  
Gary G. Deng ◽  
Kelvin P. Davies
Keyword(s):  
Degradation Products ◽  
Tca Cycle ◽  
Pentose Phosphate ◽  
Branched Chain Amino Acid ◽  
The Tca Cycle ◽  
Glycation End Products ◽  
Markers Of Oxidative Stress ◽  
Branched Chain ◽  
Diabetic Bladder ◽  
Bladder Disorder

There are at present no published studies providing a global overview of changes in bladder metabolism resulting from diabetes. Such studies have the potential to provide mechanistic insight into the development of diabetic bladder disorder (DBD). In the present study, we compared the metabolome of detrusor and urothelial layer in a 1-mo streptozotocin-induced rat model of type 1 diabetes with nondiabetic controls. Our studies revealed that diabetes caused both common and differential changes in the detrusor and urothelial layer's metabolome. Diabetes resulted in similar changes in the levels of previously described diabetic markers in both tissues, such as glucose, lactate, 2-hydroxybutyrate, branched-chain amino acid degradation products, bile acids, and 1,5-anhydroglucitol, as well as markers of oxidative stress. In the detrusor (but not the urothelial layer), diabetes caused activation of the pentose-phosphate and polyol pathways, concomitant with a reduction in the TCA cycle and β-oxidation. Changes in detrusor energy-generating pathways resulted in an accumulation of sorbitol that, through generation of advanced glycation end products, is likely to play a central role in the development of DBD. In the diabetic urothelial layer there was decreased flux of glucose via glycolysis and changes in lipid metabolism, particularly prostaglandin synthesis, which also potentially contributes to detrusor dysfunction.

scholarly journals Mycobacterium tuberculosis induces decelerated bioenergetic metabolism in human macrophages

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Bridgette M Cumming ◽  
Kelvin W Addicott ◽  
John H Adamson ◽  
Adrie JC Steyn
Keyword(s):  
Fatty Acids ◽  
Mycobacterium Tuberculosis ◽  
Human Monocyte ◽  
Tca Cycle ◽  
Metabolic Reprogramming ◽  
Flux Analysis ◽  
Human Macrophages ◽  
Extracellular Flux ◽  
The Tca Cycle ◽  
Bioenergetic Metabolism

How Mycobacterium tuberculosis (Mtb) rewires macrophage energy metabolism to facilitate survival is poorly characterized. Here, we used extracellular flux analysis to simultaneously measure the rates of glycolysis and respiration in real time. Mtb infection induced a quiescent energy phenotype in human monocyte-derived macrophages and decelerated flux through glycolysis and the TCA cycle. In contrast, infection with the vaccine strain, M. bovis BCG, or dead Mtb induced glycolytic phenotypes with greater flux. Furthermore, Mtb reduced the mitochondrial dependency on glucose and increased the mitochondrial dependency on fatty acids, shifting this dependency from endogenous fatty acids in uninfected cells to exogenous fatty acids in infected macrophages. We demonstrate how quantifiable bioenergetic parameters of the host can be used to accurately measure and track disease, which will enable rapid quantifiable assessment of drug and vaccine efficacy. Our findings uncover new paradigms for understanding the bioenergetic basis of host metabolic reprogramming by Mtb.

scholarly journals UK5099 inhibits macrophage activation independent of mitochondrial pyruvate carrier mediated metabolism

2021 ◽  
Author(s):  
Linyu Ran ◽  
Song Zhang ◽  
Pei Zhao ◽  
Jiaqi Zhou ◽  
Haiyun Gan ◽  
...  
Keyword(s):  
Macrophage Activation ◽  
Cytokine Production ◽  
Inflammatory Responses ◽  
Tca Cycle ◽  
Metabolic Reprogramming ◽  
M1 Macrophages ◽  
Inflammatory Cytokine Production ◽  
The Tca Cycle ◽  
Mitochondrial Pyruvate Carrier ◽  
High Doses

Abstract Glycolysis is essential for the classical activation of macrophages (M1), but how glycolytic pathway metabolites engage in this process remains to be elucidated. Glycolysis culminates in the production of pyruvate, which can be transported into the mitochondria by the mitochondrial pyruvate carrier (MPC) followed by conversion to citrate and utilization in the TCA cycle. Alternatively, pyruvate can be metabolized to lactate under aerobic conditions, which had been considered to be the dominant route in the setting of classical macrophage activation. However, based on studies that used UK5099 as a MPC inhibitor and showed reduction in key inflammatory cytokines, the mitochondrial route has been considered to be of significance for M1 activation as well. Herein, using a genetic depletion model, we found that MPC is dispensable for metabolic reprogramming and the activation of M1. While UK5099 reaches maximal MPC inhibitory capacity at approximately 2–5µM, higher concentrations are required to inhibit inflammatory cytokine production in M1 and this is independent of MPC expression. Apart from MPC inhibition, UK5099 at high doses impairs glutamate oxidation, mitochondrial membrane potential and HIF-1α stabilization. Taken together, UK5099 inhibits inflammatory responses in M1 macrophages due to effects other than MPC inhibition.

scholarly journals BCKDK regulates the TCA cycle through PDC to ensure embryonic development in the absence of PDK family

2020 ◽  
Author(s):  
Lia Heinemann-Yerushalmi ◽  
Lital Bentovim ◽  
Neta Felsenthal ◽  
Ron Carmel Vinestock ◽  
Nofar Michaeli ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Tca Cycle ◽  
Bioinformatic Analysis ◽  
Compensatory Mechanism ◽  
The Tca Cycle ◽  
Early Embryonic Lethality ◽  
Branched Chain ◽  
Ketoacid Dehydrogenase

AbstractPyruvate dehydrogenase kinases (PDK1-4) inhibit the TCA cycle by phosphorylating pyruvate dehydrogenase complex (PDC). Here, we show that the PDK family is dispensable for the survival of murine embryonic development and that BCKDK serves as a compensatory mechanism by inactivating PDC.First, we knocked out all fourPdkgenes one by one. Surprisingly,Pdktotal KO embryos developed and were born in expected ratios, but died by postnatal day 4 due to hypoglycemia or ketoacidosis.Finding that PDC was phosphorylated in these embryos suggested that another kinase compensates for the PDK family. Bioinformatic analysis implicated brunch chain ketoacid dehydrogenase kinase (Bckdk), a key regulator of branched chain amino acids (BCAA) catabolism. Indeed, knockout ofBckdkand thePdkfamily led to loss of PDC phosphorylation, increment in PDC activity, elevation of Pyruvate flux into the TCA and early embryonic lethality. These findings reveal a new regulatory crosstalk hardwiring BCAA and glucose catabolic pathways, which feed the TCA cycle.

scholarly journals Pheochromocytomas and Paragangliomas: Bypassing Cellular Respiration

Cancers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 683 ◽  
Author(s):  
Alberto Cascón ◽  
Laura Remacha ◽  
Bruna Calsina ◽  
Mercedes Robledo
Keyword(s):  
Neurological Disorders ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Metabolic Adaptation ◽  
Cellular Respiration ◽  
Therapeutic Approaches ◽  
Molecular Alterations ◽  
The Tca Cycle ◽  
Number Of Genes ◽  
Genes Encoding

Pheochromocytomas and paragangliomas (PPGL) are rare neuroendocrine tumors that show the highest heritability of all human neoplasms and represent a paradoxical example of genetic heterogeneity. Amongst the elevated number of genes involved in the hereditary predisposition to the disease (at least nineteen) there are eleven tricarboxylic acid (TCA) cycle-related genes, some of which are also involved in the development of congenital recessive neurological disorders and other cancers such as cutaneous and uterine leiomyomas, gastrointestinal tumors and renal cancer. Somatic or germline mutation of genes encoding enzymes catalyzing pivotal steps of the TCA cycle not only disrupts cellular respiration, but also causes severe alterations in mitochondrial metabolite pools. These latter alterations lead to aberrant accumulation of “oncometabolites” that, in the end, may lead to deregulation of the metabolic adaptation of cells to hypoxia, inhibition of the DNA repair processes and overall pathological changes in gene expression. In this review, we will address the TCA cycle mutations leading to the development of PPGL, and we will discuss the relevance of these mutations for the transformation of neural crest-derived cells and potential therapeutic approaches based on the emerging knowledge of underlying molecular alterations.

scholarly journals Metabolic Fate of the Increased Yeast Amino Acid Uptake Subsequent to Catabolite Derepression

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
John S. Hothersall ◽  
Aamir Ahmed
Keyword(s):  
Amino Acid ◽  
Protein Expression ◽  
Citrate Synthase ◽  
Tca Cycle ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Leucine Oxidation ◽  
The Tca Cycle ◽  
Branched Chain ◽  
Ketoacid Dehydrogenase

Catabolite repression (CCR) regulates amino acid permeases in Saccharomyces cerevisiae via a TOR-kinase mediated mechanism. When glucose, the preferred fuel in S. cerevisiae, is substituted by galactose, amino acid uptake is increased. Here we have assessed the contribution and metabolic significance of this surfeit of amino acid in yeast undergoing catabolite derepression (CDR). L-[U-14C]leucine oxidation was increased 15 ± 1 fold in wild type (WT) strain grown in galactose compared to glucose. Under CDR, leucine oxidation was (i) proportional to uptake, as demonstrated by decreased uptake and oxidation of leucine in strains deleted of major leucine permeases and (ii) entirely dependent upon the TCA cycle, as cytochrome c1 (Cyt1) deleted strains could not grow in galactose. A regulator of amino acid carbon entry into the TCA cycle, branched chain ketoacid dehydrogenase, was also increased 29 ± 3 fold under CCR in WT strain. Protein expression of key TCA cycle enzymes, citrate synthase (Cs), and Cyt1 was increased during CDR. In summary, CDR upregulation of amino acid uptake is accompanied by increased utilization of amino acids for yeast growth. The mechanism for this is likely to be an increase in protein expression of key regulators of the TCA cycle.

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