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Jin L, Alesi GN, Kang S. Glutaminolysis as a target for cancer therapy. Oncogene 2016; 35:3619-25. [PMID: 26592449 PMCID: PMC5225500 DOI: 10.1038/onc.2015.447] [Citation(s) in RCA: 272] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 10/15/2015] [Accepted: 10/22/2015] [Indexed: 02/06/2023]
Abstract
Cancer cells display an altered metabolic circuitry that is directly regulated by oncogenic mutations and loss of tumor suppressors. Mounting evidence indicates that altered glutamine metabolism in cancer cells has critical roles in supporting macromolecule biosynthesis, regulating signaling pathways, and maintaining redox homeostasis, all of which contribute to cancer cell proliferation and survival. Thus, intervention in these metabolic processes could provide novel approaches to improve cancer treatment. This review summarizes current findings on the role of glutaminolytic enzymes in human cancers and provides an update on the development of small molecule inhibitors to target glutaminolysis for cancer therapy.
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Affiliation(s)
- L Jin
- Department of Hematology and Medical Oncology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
| | - G N Alesi
- Department of Hematology and Medical Oncology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
| | - S Kang
- Department of Hematology and Medical Oncology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
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Zhang W, Zhu M, Wang F, Cao D, Ruan JJ, Su W, Ruan BH. Mono-sulfonated tetrazolium salt based NAD(P)H detection reagents suitable for dehydrogenase and real-time cell viability assays. Anal Biochem 2016; 509:33-40. [PMID: 27387057 DOI: 10.1016/j.ab.2016.06.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 06/21/2016] [Accepted: 06/27/2016] [Indexed: 02/02/2023]
Abstract
Glutamate dehydrogenase (GDH) catalyzes the oxidative deamination of L-glutamate and is important for several biological processes. For GDH inhibitor screening, we developed a novel mono-sulfonated tetrazolium salt (EZMTT), which can be synthesized using H2O2 oxidation and purified easily on silica gel in large quantities. The EZMTT detection method showed linear dose responses to NAD(P)H, dehydrogenase concentration and cell numbers. In E. coli GDH assay, the EZMTT method showed excellent assay reproducibility with a Z factor of 0.9 and caused no false positives in the presence of antioxidants (such as BME). Using the EZMTT-formazan-NAD(P)H system, we showed that EGCG is a potent E. coli GDH inhibitor (IC50 45 nM) and identified that Ebselen, a multifunctional thioredoxin reductase inhibitor, inactivated E. coli GDH (IC50 213 nM). In cell-based assays at 0.5 mM tetrazolium concentration, EZMTT showed essentially no toxicity after a 3-day incubation, whereas 40% of inhibition was observed for WST-8. In conclusion, EZMTT is a novel tetrazolium salt which provides improved features that are suitable for dehydrogenases and real-time cell-based high-throughput screening (HTS).
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Affiliation(s)
- Wei Zhang
- College of Pharmaceutical Science, Collaborative Innovation Center of Yangtza River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, China; Department of Urology, Zhejiang Cancer Hospital, Hangzhou, China
| | - Min Zhu
- College of Pharmaceutical Science, Collaborative Innovation Center of Yangtza River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, China
| | - Feng Wang
- College of Pharmaceutical Science, Collaborative Innovation Center of Yangtza River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, China
| | - Danhui Cao
- College of Pharmaceutical Science, Collaborative Innovation Center of Yangtza River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, China
| | | | - Weike Su
- College of Pharmaceutical Science, Collaborative Innovation Center of Yangtza River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, China
| | - Benfang Helen Ruan
- College of Pharmaceutical Science, Collaborative Innovation Center of Yangtza River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, China.
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Argininosuccinate synthetase regulates hepatic AMPK linking protein catabolism and ureagenesis to hepatic lipid metabolism. Proc Natl Acad Sci U S A 2016; 113:E3423-30. [PMID: 27247419 DOI: 10.1073/pnas.1606022113] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
A key sensor of cellular energy status, AMP-activated protein kinase (AMPK), interacts allosterically with AMP to maintain an active state. When active, AMPK triggers a metabolic switch, decreasing the activity of anabolic pathways and enhancing catabolic processes such as lipid oxidation to restore the energy balance. Unlike oxidative tissues, in which AMP is generated from adenylate kinase during states of high energy demand, the ornithine cycle enzyme argininosuccinate synthetase (ASS) is a principle site of AMP generation in the liver. Here we show that ASS regulates hepatic AMPK, revealing a central role for ureagenesis flux in the regulation of metabolism via AMPK. Treatment of primary rat hepatocytes with amino acids increased gluconeogenesis and ureagenesis and, despite nutrient excess, induced both AMPK and acetyl-CoA carboxylase (ACC) phosphorylation. Antisense oligonucleotide knockdown of hepatic ASS1 expression in vivo decreased liver AMPK activation, phosphorylation of ACC, and plasma β-hydroxybutyrate concentrations. Taken together these studies demonstrate that increased amino acid flux can activate AMPK through increased AMP generated by ASS, thus providing a novel link between protein catabolism, ureagenesis, and hepatic lipid metabolism.
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Nagashima H, Tanaka K, Sasayama T, Irino Y, Sato N, Takeuchi Y, Kyotani K, Mukasa A, Mizukawa K, Sakata J, Yamamoto Y, Hosoda K, Itoh T, Sasaki R, Kohmura E. Diagnostic value of glutamate with 2-hydroxyglutarate in magnetic resonance spectroscopy for IDH1 mutant glioma. Neuro Oncol 2016; 18:1559-1568. [PMID: 27154922 DOI: 10.1093/neuonc/now090] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 03/30/2016] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Mutations in the isocitrate dehydrogenase 1 (IDH1) gene that are frequently observed in low-grade glioma are strongly associated with the accumulation of 2-hydroxyglutarate (2HG), which is a valuable diagnostic and prognostic biomarker of IDH1 mutant glioma. However, conventional MR spectroscopy (MRS)-based noninvasive detection of 2HG is challenging. In this study, we aimed to determine the additional value of other metabolites in predicting IDH1 mutations with conventional MRS. METHODS Forty-seven patients with glioma underwent conventional single voxel short echo time MRS prior to surgery. A stereotactic navigation-guided operation was performed to resect tumor tissues in the center of the MRS voxel. MRS-based measurements of metabolites were validated with gas chromatography-mass spectrometry. We also conducted integrated analyses of glioma cell lines and clinical samples to examine the other metabolite levels and molecular findings in IDH1 mutant gliomas. RESULTS A metabolomic analysis demonstrated higher levels of 2HG in IDH1 mutant glioma cells and surgical tissues. Interestingly, glutamate levels were significantly decreased in IDH1 mutant gliomas. Through an analysis of metabolic enzyme genes in glutamine pathways, it was shown that the expressions of branched-chain amino acid transaminase 1 were reduced and glutamate dehydrogenase levels were elevated in IDH1 mutant gliomas. Conventional MRS detection of glutamate and 2HG resulted in a high diagnostic accuracy (sensitivity 72%, specificity 96%) for IDH1 mutant glioma. CONCLUSIONS IDH1 mutations alter glutamate metabolism. Combining glutamate levels optimizes the 2HG-based monitoring of IDH1 mutations via MRS and represents a reliable clinical application for diagnosing IDH1 mutant gliomas.
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Affiliation(s)
- Hiroaki Nagashima
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Kazuhiro Tanaka
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Takashi Sasayama
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Yasuhiro Irino
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Naoko Sato
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Yukiko Takeuchi
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Katsusuke Kyotani
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Akitake Mukasa
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Katsu Mizukawa
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Junichi Sakata
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Yusuke Yamamoto
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Kohkichi Hosoda
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Tomoo Itoh
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Ryohei Sasaki
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
| | - Eiji Kohmura
- Department of Neurosurgery, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (H.N., K.T., T.S., N.S., K.M., J.S., Y.Y., K.H., E.K.); Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (Y.I., Y.T.); Center for Radiology and Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (K.K.); Department of Diagnostic Pathology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (T.I.); Division of Radiation Oncology, Kobe University Graduate School of Medicine and Kobe University Hospital, Kobe, Japan (R.S.); Department of Neurosurgery, University of Tokyo Hospital, Tokyo, Japan (A.M.)
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Kerimi A, Williamson G. At the interface of antioxidant signalling and cellular function: Key polyphenol effects. Mol Nutr Food Res 2016; 60:1770-88. [PMID: 26887821 PMCID: PMC5021119 DOI: 10.1002/mnfr.201500940] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/09/2016] [Accepted: 02/10/2016] [Indexed: 12/18/2022]
Abstract
The hypothesis that dietary (poly)phenols promote well‐being by improving chronic disease‐risk biomarkers, such as endothelial dysfunction, chronic inflammation and plasma uric acid, is the subject of intense current research, involving human interventions studies, animal models and in vitro mechanistic work. The original claim that benefits were due to the direct antioxidant properties of (poly)phenols has been mostly superseded by detailed mechanistic studies on specific molecular targets. Nevertheless, many proposed mechanisms in vivo and in vitro are due to modulation of oxidative processes, often involving binding to specific proteins and effects on cell signalling. We review the molecular mechanisms for 3 actions of (poly)phenols on oxidative processes where there is evidence in vivo from human intervention or animal studies. (1) Effects of (poly) phenols on pathways of chronic inflammation leading to prevention of some of the damaging effects associated with the metabolic syndrome. (2) Interaction of (poly)phenols with endothelial cells and smooth muscle cells, leading to effects on blood pressure and endothelial dysfunction, and consequent reduction in cardiovascular disease risk. (3) The inhibition of xanthine oxidoreductase leading to modulation of intracellular superoxide and plasma uric acid, a risk factor for developing type 2 diabetes.
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Affiliation(s)
- Asimina Kerimi
- School of Food Science and Nutrition, University of Leeds, Leeds, UK
| | - Gary Williamson
- School of Food Science and Nutrition, University of Leeds, Leeds, UK
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Hussain J, Schlachterman A, Kamel A, Gupte A. Hyperinsulinism Hyperammonemia Syndrome, a Rare Clinical Constellation. J Investig Med High Impact Case Rep 2016; 4:2324709616632552. [PMID: 26962538 PMCID: PMC4765817 DOI: 10.1177/2324709616632552] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 01/21/2016] [Accepted: 01/23/2016] [Indexed: 12/30/2022] Open
Abstract
We present the unique case of adult hyperinsulinism hyperammonemia syndrome (HI/HA). This condition is rarely seen in children and even more infrequently in adults. A 27-year-old female with HI/HA, generalized tonic-clonic seizures, staring spells, and gastroesophageal reflux disease presented with diffuse abdominal pain, hypoglycemia, confusion, and sweating. She reported a history of significant nausea, vomiting, and diarrhea, which had been present intermittently over the past year. On examination, she was found to have a soft, nontender, and mildly distended abdomen without splenomegaly or masses. She had a normal blood pressure and was tachycardic (130 bpm). Her initial complete blood count and basic metabolic panel, excluding glucose, were within normal limits. She was found to have an elevated peripherally drawn venous ammonia (171 mmol/L) and near hypoglycemia (blood glucose 61 mg/dL), which were drawn given her history of HI/HA. She was continued on home carglumic acid and diazoxide, glucose was supplemented intravenously, and she was started on levetiracetam for seizure prophylaxis. An upper endoscopy (esophagogastroduodenoscopy [EGD]) was performed and was unremarkable, and biopsies taken were within normal limits. Following the EGD, she underwent a gastric emptying study that showed delayed emptying (216 minutes), consistent with a new diagnosis of gastroparesis, the likely etiology of her initial abdominal pain on presentation. This was subsequently treated with azithromycin oral solution. We present this case to raise awareness of this rarely encountered syndrome and to provide the basic principles of treatment.
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Affiliation(s)
| | | | - Amir Kamel
- University of Florida, Gainesville, FL, USA
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58
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Brandvold KR, Morimoto RI. The Chemical Biology of Molecular Chaperones--Implications for Modulation of Proteostasis. J Mol Biol 2015; 427:2931-47. [PMID: 26003923 DOI: 10.1016/j.jmb.2015.05.010] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 05/09/2015] [Accepted: 05/13/2015] [Indexed: 12/14/2022]
Abstract
Protein homeostasis (proteostasis) is inextricably tied to cellular health and organismal lifespan. Aging, exposure to physiological and environmental stress, and expression of mutant and metastable proteins can cause an imbalance in the protein-folding landscape, which results in the formation of non-native protein aggregates that challenge the capacity of the proteostasis network (PN), increasing the risk for diseases associated with misfolding, aggregation, and aberrant regulation of cell stress responses. Molecular chaperones have central roles in each of the arms of the PN (protein synthesis, folding, disaggregation, and degradation), leading to the proposal that modulation of chaperone function could have therapeutic benefits for the large and growing family of diseases of protein conformation including neurodegeneration, metabolic diseases, and cancer. In this review, we will discuss the current strategies used to tune the PN through targeting molecular chaperones and assess the potential of the chemical biology of proteostasis.
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Affiliation(s)
- Kristoffer R Brandvold
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, IL 60208, USA
| | - Richard I Morimoto
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, IL 60208, USA.
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59
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Jin L, Li D, Alesi GN, Fan J, Kang HB, Lu Z, Boggon TJ, Jin P, Yi H, Wright ER, Duong D, Seyfried NT, Egnatchik R, DeBerardinis RJ, Magliocca KR, He C, Arellano ML, Khoury HJ, Shin DM, Khuri FR, Kang S. Glutamate dehydrogenase 1 signals through antioxidant glutathione peroxidase 1 to regulate redox homeostasis and tumor growth. Cancer Cell 2015; 27:257-70. [PMID: 25670081 PMCID: PMC4325424 DOI: 10.1016/j.ccell.2014.12.006] [Citation(s) in RCA: 242] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 09/29/2014] [Accepted: 12/15/2014] [Indexed: 12/14/2022]
Abstract
How mitochondrial glutaminolysis contributes to redox homeostasis in cancer cells remains unclear. Here we report that the mitochondrial enzyme glutamate dehydrogenase 1 (GDH1) is commonly upregulated in human cancers. GDH1 is important for redox homeostasis in cancer cells by controlling the intracellular levels of its product alpha-ketoglutarate and subsequent metabolite fumarate. Mechanistically, fumarate binds to and activates a reactive oxygen species scavenging enzyme glutathione peroxidase 1. Targeting GDH1 by shRNA or a small molecule inhibitor R162 resulted in imbalanced redox homeostasis, leading to attenuated cancer cell proliferation and tumor growth.
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Affiliation(s)
- Lingtao Jin
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Dan Li
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Gina N Alesi
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Jun Fan
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Hee-Bum Kang
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Zhou Lu
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Titus J Boggon
- Department of Pharmacology, Yale University, New Haven, CT 06520, USA
| | - Peng Jin
- Department of Human Genetics, Emory University, Atlanta, GA 30322, USA
| | - Hong Yi
- Robert P. Apkarian Integrated Electron Microscopy Core, Emory University, Atlanta, GA 30322, USA
| | - Elizabeth R Wright
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Duc Duong
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Nicholas T Seyfried
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
| | | | | | - Kelly R Magliocca
- Department of Pathology & Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Chuan He
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Martha L Arellano
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Hanna J Khoury
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Dong M Shin
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Fadlo R Khuri
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Sumin Kang
- Winship Cancer Institute, Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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Synthetic lethality of combined glutaminase and Hsp90 inhibition in mTORC1-driven tumor cells. Proc Natl Acad Sci U S A 2015; 112:E21-9. [PMID: 25524627 PMCID: PMC4291663 DOI: 10.1073/pnas.1417015112] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) integrates multiple signals from growth factors, nutrients, and cellular energy status to control a wide range of metabolic processes, including mRNA biogenesis; protein, nucleotide, and lipid synthesis; and autophagy. Deregulation of the mTORC1 pathway is found in cancer as well as genetic disorders such as tuberous sclerosis complex (TSC) and sporadic lymphangioleiomyomatosis. Recent studies have shown that the mTORC1 inhibitor rapamycin and its analogs generally suppress proliferation rather than induce apoptosis. Therefore, it is critical to use alternative strategies to induce death of cells with activated mTORC1. In this study, a small-molecule screen has revealed that the combination of glutaminase (GLS) and heat shock protein 90 (Hsp90) inhibitors selectively triggers death of TSC2-deficient cells. At a mechanistic level, high mTORC1-driven translation rates in TSC1/2-deficient cells, unlike wild-type cells, sensitizes these cells to endoplasmic reticulum (ER) stress. Thus, Hsp90 inhibition drives accumulation of unfolded protein and ER stress. When combining proteotoxic stress with oxidative stress by depletion of the intracellular antioxidant glutathione by GLS inhibition, acute cell death is observed in cells with activated mTORC1 signaling. This study suggests that this combination strategy may have the potential to be developed into a therapeutic use for the treatment of mTORC1-driven tumors.
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61
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Kaneko YK, Takii M, Kojima Y, Yokosawa H, Ishikawa T. Structure-Dependent Inhibitory Effects of Green Tea Catechins on Insulin Secretion from Pancreatic β-Cells. Biol Pharm Bull 2015; 38:476-81. [DOI: 10.1248/bpb.b14-00789] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Yukiko K. Kaneko
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, University of Shizuoka
| | - Miki Takii
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, University of Shizuoka
| | - Yumiko Kojima
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, University of Shizuoka
| | - Hiroko Yokosawa
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, University of Shizuoka
| | - Tomohisa Ishikawa
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, University of Shizuoka
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62
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Jia G, Sowers JR. Interaction of islet α-cell and β-cell in the regulation of glucose homeostasis in HI/HA syndrome patients with the GDH(H454Y) mutation. Diabetes 2014; 63:4008-10. [PMID: 25414017 PMCID: PMC4237997 DOI: 10.2337/db14-1243] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Guanghong Jia
- Endocrinology, Diabetes and Metabolism, Diabetes Cardiovascular Center, University of Missouri, Columbia, MO Harry S. Truman Memorial Veterans' Hospital, Columbia, MO
| | - James R Sowers
- Endocrinology, Diabetes and Metabolism, Diabetes Cardiovascular Center, University of Missouri, Columbia, MO Harry S. Truman Memorial Veterans' Hospital, Columbia, MO Departments of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
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63
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Chandran S, Yap F, Hussain K. Molecular mechanisms of protein induced hyperinsulinaemic hypoglycaemia. World J Diabetes 2014; 5:666-677. [PMID: 25317244 PMCID: PMC4138590 DOI: 10.4239/wjd.v5.i5.666] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 04/23/2014] [Accepted: 05/29/2014] [Indexed: 02/05/2023] Open
Abstract
The interplay between glucose metabolism and that of the two other primary nutrient classes, amino acids and fatty acids is critical for regulated insulin secretion. Mitochondrial metabolism of glucose, amino acid and fatty acids generates metabolic coupling factors (such as ATP, NADPH, glutamate, long chain acyl-CoA and diacylglycerol) which trigger insulin secretion. The observation of protein induced hypoglycaemia in patients with mutations in GLUD1 gene, encoding the enzyme glutamate dehydrogenase (GDH) and HADH gene, encoding for the enzyme short-chain 3-hydroxyacyl-CoA dehydrogenase has provided new mechanistic insights into the regulation of insulin secretion by amino acid and fatty acid metabolism. Metabolic signals arising from amino acid and fatty acid metabolism converge on the enzyme GDH which integrates both signals from both pathways and controls insulin secretion. Hence GDH seems to play a pivotal role in regulating both amino acid and fatty acid metabolism.
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64
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Regulation of autophagy by amino acids and MTOR-dependent signal transduction. Amino Acids 2014; 47:2037-63. [PMID: 24880909 PMCID: PMC4580722 DOI: 10.1007/s00726-014-1765-4] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Accepted: 05/12/2014] [Indexed: 01/05/2023]
Abstract
Amino acids not only participate in intermediary metabolism but also stimulate insulin-mechanistic target of rapamycin (MTOR)-mediated signal transduction which controls the major metabolic pathways. Among these is the pathway of autophagy which takes care of the degradation of long-lived proteins and of the elimination of damaged or functionally redundant organelles. Proper functioning of this process is essential for cell survival. Dysregulation of autophagy has been implicated in the etiology of several pathologies. The history of the studies on the interrelationship between amino acids, MTOR signaling and autophagy is the subject of this review. The mechanisms responsible for the stimulation of MTOR-mediated signaling, and the inhibition of autophagy, by amino acids have been studied intensively in the past but are still not completely clarified. Recent developments in this field are discussed.
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Divakaruni AS, Rogers GW, Murphy AN. Measuring Mitochondrial Function in Permeabilized Cells Using the Seahorse XF Analyzer or a Clark-Type Oxygen Electrode. ACTA ACUST UNITED AC 2014; 60:25.2.1-16. [PMID: 24865646 DOI: 10.1002/0471140856.tx2502s60] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Measurements of mitochondrial respiration in intact cells can help define metabolism and its dysregulation in fields such as cancer, metabolic disease, immunology, and neurodegeneration. Although cells can be offered various substrates in the assay medium, many cell types can oxidize stored pools of energy substrates. A general bioenergetic profile can therefore be obtained using intact cells, but the inability to control substrate provision to the mitochondria can restrict an in-depth, mechanistic understanding. Mitochondria can be isolated from intact cells, but the yield and quality of the end product is often poor and prone to subselection during isolation. Plasma membrane permeabilization of cells provides a solution to this challenge, allowing experimental control of the medium surrounding the mitochondria. This unit describes techniques to measure respiration in permeabilized adherent cells using a Seahorse XF Analyzer or permeabilized suspended cells in a Hansatech Oxygraph.
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Affiliation(s)
- Ajit S Divakaruni
- Department of Pharmacology, University of California, San Diego, La Jolla, California
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66
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Abstract
Hypoglycemia in the pediatric population is a common finding important to recognize and manage to prevent brain injury. Recent advances in molecular genetics have provided new insight into its biochemical and physiologic basis and have led to more appropriate and specific treatment. Although a major cause of brain injury in pediatrics, the ability to predict the long-term outcome in these patients remains difficult. Identification of these at-risk individuals is important. The physiologic adaptations associated with transition from fetal to neonatal life are now better understood thus allowing for improved surveillance and management. Despite these advances, analytical limitations of point-of-care testing instruments at low glucose concentration continue to persist, This review aims to address these questions and provide an overview of pediatric hypoglycemia and the molecular pathways involved.
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67
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Peek J, Shi T, Christendat D. Identification of Novel Polyphenolic Inhibitors of Shikimate Dehydrogenase (AroE). ACTA ACUST UNITED AC 2014; 19:1090-8. [DOI: 10.1177/1087057114527127] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 02/17/2014] [Indexed: 11/15/2022]
Abstract
Shikimate dehydrogenase (AroE) is an attractive target for herbicides and antimicrobial agents due to its conserved and essential nature in plants, fungi, and bacteria. Here, we have performed an in vitro screen using a collection of more than 5500 compounds and identified 24 novel inhibitors of AroE from Pseudomonas putida. The IC50 values for the two most potent inhibitors we identified, epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), were 3.0 ± 0.2 µM and 3.7 ± 0.5 µM, respectively. Based on the high level of structural conservation between AroE orthologs, we predicted that the identified compounds would also inhibit AroE enzymes from other organisms. Consistent with this hypothesis, we found that EGCG and ECG inhibit the AroE domain of the bifunctional dehydroquinate dehydratase-shikimate dehydrogenase (DHQ-SDH) from Arabidopsis thaliana with IC50 values of 2.1 ± 0.3 µM and 2.0 ± 0.2 µM, respectively.
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Affiliation(s)
- James Peek
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Thomas Shi
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Dinesh Christendat
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, ON, Canada
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68
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Li M, Li C, Allen A, Stanley CA, Smith TJ. Glutamate dehydrogenase: structure, allosteric regulation, and role in insulin homeostasis. Neurochem Res 2013; 39:433-45. [PMID: 24122080 DOI: 10.1007/s11064-013-1173-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 09/26/2013] [Accepted: 10/03/2013] [Indexed: 02/02/2023]
Abstract
Glutamate dehydrogenase (GDH) is a homohexameric enzyme that catalyzes the reversible oxidative deamination of L-glutamate to 2-oxoglutarate. Only in the animal kingdom is this enzyme heavily allosterically regulated by a wide array of metabolites. The major activators are ADP and leucine and inhibitors include GTP, palmitoyl CoA, and ATP. Spontaneous mutations in the GTP inhibitory site that lead to the hyperinsulinism/hyperammonemia (HHS) syndrome have shed light as to why mammalian GDH is so tightly regulated. Patients with HHS exhibit hypersecretion of insulin upon consumption of protein and concomitantly extremely high levels of ammonium in the serum. The atomic structures of four new inhibitors complexed with GDH complexes have identified three different allosteric binding sites. Using a transgenic mouse model expressing the human HHS form of GDH, at least three of these compounds blocked the dysregulated form of GDH in pancreatic tissue. EGCG from green tea prevented the hyper-response to amino acids in whole animals and improved basal serum glucose levels. The atomic structure of the ECG-GDH complex and mutagenesis studies is directing structure-based drug design using these polyphenols as a base scaffold. In addition, all of these allosteric inhibitors are elucidating the atomic mechanisms of allostery in this complex enzyme.
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Affiliation(s)
- Ming Li
- Donald Danforth Plant Science Center, 975 North Warson Road, Saint Louis, MO, 63132, USA
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69
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Hensley CT, Wasti AT, DeBerardinis RJ. Glutamine and cancer: cell biology, physiology, and clinical opportunities. J Clin Invest 2013. [DOI: 10.1172/jci69600 pmid:239994422013-09-01]] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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70
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Hensley CT, Wasti AT, DeBerardinis RJ. Glutamine and cancer: cell biology, physiology, and clinical opportunities. J Clin Invest 2013; 123:3678-84. [PMID: 23999442 DOI: 10.1172/jci69600] [Citation(s) in RCA: 867] [Impact Index Per Article: 78.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Glutamine is an abundant and versatile nutrient that participates in energy formation, redox homeostasis, macromolecular synthesis, and signaling in cancer cells. These characteristics make glutamine metabolism an appealing target for new clinical strategies to detect, monitor, and treat cancer. Here we review the metabolic functions of glutamine as a super nutrient and the surprising roles of glutamine in supporting the biological hallmarks of malignancy. We also review recent efforts in imaging and therapeutics to exploit tumor cell glutamine dependence, discuss some of the challenges in this arena, and suggest a disease-focused paradigm to deploy these emerging approaches.
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Affiliation(s)
- Christopher T Hensley
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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71
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Sáez-Ayala M, Fernández-Pérez MP, Chazarra S, Mchedlishvili N, Tárraga-Tomás A, Rodríguez-López JN. Factors influencing the antifolate activity of synthetic tea-derived catechins. Molecules 2013; 18:8319-41. [PMID: 23863773 PMCID: PMC6270263 DOI: 10.3390/molecules18078319] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 07/05/2013] [Accepted: 07/12/2013] [Indexed: 11/16/2022] Open
Abstract
Novel tea catechin derivatives have been synthesized, and a structure-activity study, related to the capacity of these and other polyphenols to bind dihydrofolate reductase (DHFR), has been performed. The data showed an effective binding between all molecules and the free enzyme, and the dissociation constants of the synthetic compounds and of the natural analogues were on the same order. Polyphenols with a catechin configuration were better DHFR inhibitors than those with an epicatechin configuration. Antiproliferative activity was also studied in cultured tumour cells, and the data showed that the activity of the novel derivatives was higher in catechin isomers. Derivatives with a hydroxyl group para on the ester-bonded gallate moiety presented a high in vitro binding to DHFR, but exhibited transport problems in cell culture due to ionization at physiologic pHs. The impact of the binding of catechins to serum albumin on their biological activity was also evaluated. The information provided in this study could be important for the design of novel medicinal active compounds derived from tea catechins. The data suggest that changes in their structure to avoid serum albumin interactions and to facilitate plasmatic membrane transport are essential for the intracellular functions of catechins.
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Affiliation(s)
- Magalí Sáez-Ayala
- Department of Biochemistry and Molecular Biology A, School of Biology, Regional Campus of International Excellence “Campus Mare Nostrum”, University of Murcia, 30100, Murcia, Spain; E-Mails: (M.S.-A.); (M.P.F.-P.); (S.C.)
| | - María Piedad Fernández-Pérez
- Department of Biochemistry and Molecular Biology A, School of Biology, Regional Campus of International Excellence “Campus Mare Nostrum”, University of Murcia, 30100, Murcia, Spain; E-Mails: (M.S.-A.); (M.P.F.-P.); (S.C.)
| | - Soledad Chazarra
- Department of Biochemistry and Molecular Biology A, School of Biology, Regional Campus of International Excellence “Campus Mare Nostrum”, University of Murcia, 30100, Murcia, Spain; E-Mails: (M.S.-A.); (M.P.F.-P.); (S.C.)
| | - Nani Mchedlishvili
- Durmishidze Institute of Biochemistry and Biotechnology of Agrarian University of Georgia, 0131, Tbilisi, Georgia; E-Mail:
| | - Alberto Tárraga-Tomás
- Department of Organic Chemistry, Faculty of Chemistry, Regional Campus of International Excellence “Campus Mare Nostrum”, University of Murcia, 30100, Murcia, Spain; E-Mail:
| | - José Neptuno Rodríguez-López
- Department of Biochemistry and Molecular Biology A, School of Biology, Regional Campus of International Excellence “Campus Mare Nostrum”, University of Murcia, 30100, Murcia, Spain; E-Mails: (M.S.-A.); (M.P.F.-P.); (S.C.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +34-868-888-284; Fax: +34-868-884-782
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Csibi A, Fendt SM, Li C, Poulogiannis G, Choo AY, Chapski DJ, Jeong SM, Dempsey JM, Parkhitko A, Morrison T, Henske EP, Haigis MC, Cantley LC, Stephanopoulos G, Yu J, Blenis J. The mTORC1 pathway stimulates glutamine metabolism and cell proliferation by repressing SIRT4. Cell 2013; 153:840-54. [PMID: 23663782 DOI: 10.1016/j.cell.2013.04.023] [Citation(s) in RCA: 423] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 03/05/2013] [Accepted: 04/10/2013] [Indexed: 12/20/2022]
Abstract
Proliferating mammalian cells use glutamine as a source of nitrogen and as a key anaplerotic source to provide metabolites to the tricarboxylic acid cycle (TCA) for biosynthesis. Recently, mammalian target of rapamycin complex 1 (mTORC1) activation has been correlated with increased nutrient uptake and metabolism, but no molecular connection to glutaminolysis has been reported. Here, we show that mTORC1 promotes glutamine anaplerosis by activating glutamate dehydrogenase (GDH). This regulation requires transcriptional repression of SIRT4, the mitochondrial-localized sirtuin that inhibits GDH. Mechanistically, mTORC1 represses SIRT4 by promoting the proteasome-mediated destabilization of cAMP-responsive element binding 2 (CREB2). Thus, a relationship between mTORC1, SIRT4, and cancer is suggested by our findings. Indeed, SIRT4 expression is reduced in human cancer, and its overexpression reduces cell proliferation, transformation, and tumor development. Finally, our data indicate that targeting nutrient metabolism in energy-addicted cancers with high mTORC1 signaling may be an effective therapeutic approach.
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Affiliation(s)
- Alfred Csibi
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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Natural compounds as regulators of the cancer cell metabolism. Int J Cell Biol 2013; 2013:639401. [PMID: 23762063 PMCID: PMC3670510 DOI: 10.1155/2013/639401] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 04/22/2013] [Indexed: 01/08/2023] Open
Abstract
Even though altered metabolism is an "old" physiological mechanism, only recently its targeting became a therapeutically interesting strategy and by now it is considered an emerging hallmark of cancer. Nevertheless, a very poor number of compounds are under investigation as potential modulators of cell metabolism. Candidate agents should display selectivity of action towards cancer cells without side effects. This ideal favorable profile would perfectly overlap the requisites of new anticancer therapies and chemopreventive strategies as well. Nature represents a still largely unexplored source of bioactive molecules with a therapeutic potential. Many of these compounds have already been characterized for their multiple anticancer activities. Many of them are absorbed with the diet and therefore possess a known profile in terms of tolerability and bioavailability compared to newly synthetized chemical compounds. The discovery of important cross-talks between mediators of the most therapeutically targeted aberrancies in cancer (i.e., cell proliferation, survival, and migration) and the metabolic machinery allows to predict the possibility that many anticancer activities ascribed to a number of natural compounds may be due, in part, to their ability of modulating metabolic pathways. In this review, we attempt an overview of what is currently known about the potential of natural compounds as modulators of cancer cell metabolism.
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74
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Jeong SM, Xiao C, Finley LW, Lahusen T, Souza AL, Pierce K, Li YH, Wang X, Laurent G, German NJ, Xu X, Li C, Wang RH, Lee J, Csibi A, Cerione R, Blenis J, Clish CB, Kimmelman A, Deng CX, Haigis MC. SIRT4 has tumor-suppressive activity and regulates the cellular metabolic response to DNA damage by inhibiting mitochondrial glutamine metabolism. Cancer Cell 2013; 23:450-63. [PMID: 23562301 PMCID: PMC3650305 DOI: 10.1016/j.ccr.2013.02.024] [Citation(s) in RCA: 326] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 11/30/2012] [Accepted: 02/21/2013] [Indexed: 12/15/2022]
Abstract
DNA damage elicits a cellular signaling response that initiates cell cycle arrest and DNA repair. Here, we find that DNA damage triggers a critical block in glutamine metabolism, which is required for proper DNA damage responses. This block requires the mitochondrial SIRT4, which is induced by numerous genotoxic agents and represses the metabolism of glutamine into tricarboxylic acid cycle. SIRT4 loss leads to both increased glutamine-dependent proliferation and stress-induced genomic instability, resulting in tumorigenic phenotypes. Moreover, SIRT4 knockout mice spontaneously develop lung tumors. Our data uncover SIRT4 as an important component of the DNA damage response pathway that orchestrates a metabolic block in glutamine metabolism, cell cycle arrest, and tumor suppression.
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Affiliation(s)
- Seung Min Jeong
- Department of Cell Biology, Harvard Medical School, Boston, MA USA
| | - Cuiying Xiao
- Mammalian Genetics Section, Genetics of Development and Disease Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Lydia W.S Finley
- Department of Cell Biology, Harvard Medical School, Boston, MA USA
| | - Tyler Lahusen
- Mammalian Genetics Section, Genetics of Development and Disease Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Amanda L. Souza
- Metabolite Profiling Platform, Broad Institute of MIT and Harvard Cambridge, MA, USA
| | - Kerry Pierce
- Metabolite Profiling Platform, Broad Institute of MIT and Harvard Cambridge, MA, USA
| | - Ying-Hua Li
- Division of Genomic Stability and DNA Repair, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Xiaoxu Wang
- Division of Genomic Stability and DNA Repair, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Gaëlle Laurent
- Department of Cell Biology, Harvard Medical School, Boston, MA USA
| | | | - Xiaoling Xu
- Mammalian Genetics Section, Genetics of Development and Disease Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Cuiling Li
- Mammalian Genetics Section, Genetics of Development and Disease Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Rui-Hong Wang
- Mammalian Genetics Section, Genetics of Development and Disease Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Jaewon Lee
- Department of Cell Biology, Harvard Medical School, Boston, MA USA
| | - Alfredo Csibi
- Department of Cell Biology, Harvard Medical School, Boston, MA USA
| | - Richard Cerione
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - John Blenis
- Department of Cell Biology, Harvard Medical School, Boston, MA USA
| | - Clary B. Clish
- Metabolite Profiling Platform, Broad Institute of MIT and Harvard Cambridge, MA, USA
| | - Alec Kimmelman
- Division of Genomic Stability and DNA Repair, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Chu-Xia Deng
- Mammalian Genetics Section, Genetics of Development and Disease Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
- Correspondence: ;
| | - Marcia C. Haigis
- Department of Cell Biology, Harvard Medical School, Boston, MA USA
- Correspondence: ;
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75
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Lorin S, Tol MJ, Bauvy C, Strijland A, Poüs C, Verhoeven AJ, Codogno P, Meijer AJ. Glutamate dehydrogenase contributes to leucine sensing in the regulation of autophagy. Autophagy 2013; 9:850-60. [PMID: 23575388 PMCID: PMC3672295 DOI: 10.4161/auto.24083] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Amino acids, leucine in particular, are known to inhibit autophagy, at least in part by their ability to stimulate MTOR-mediated signaling. Evidence is presented showing that glutamate dehydrogenase, the central enzyme in amino acid catabolism, contributes to leucine sensing in the regulation of autophagy. The data suggest a dual mechanism by which glutamate dehydrogenase activity modulates autophagy, i.e., by activating MTORC1 and by limiting the formation of reactive oxygen species.
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Affiliation(s)
- Séverine Lorin
- EA4530, Faculty of Pharmacy, University Paris-Sud, Châtenay-Malabry, France
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76
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Divergent effects of sulforaphane on basal and glucose-stimulated insulin secretion in β-cells: role of reactive oxygen species and induction of endogenous antioxidants. Pharm Res 2013; 30:2248-59. [PMID: 23468051 DOI: 10.1007/s11095-013-1013-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 02/15/2013] [Indexed: 02/07/2023]
Abstract
PURPOSE Oxidative stress is implicated in pancreatic β-cell dysfunction, yet clinical outcomes of antioxidant therapies on diabetes are inconclusive. Since reactive oxygen species (ROS) can function as signaling intermediates for glucose-stimulated insulin secretion (GSIS), we hypothesize that exogenously boosting cellular antioxidant capacity dampens signaling ROS and GSIS. METHODS To test the hypothesis, we formulated a mathematical model of redox homeostatic control circuit comprising known feedback and feedforward loops and validated model predictions with plant-derived antioxidant sulforaphane (SFN). RESULTS SFN acutely (30-min treatment) stimulated basal insulin secretion in INS-1(832/13) cells and cultured mouse islets, which could be attributed to SFN-elicited ROS as N-acetylcysteine or glutathione ethyl ester suppressed SFN-stimulated insulin secretion. The mathematical model predicted an adapted redox state characteristic of strong induction of endogenous antioxidants but marginally increased ROS under prolonged SFN exposure, a state that attenuates rather than facilitates glucose-stimulated ROS and GSIS. We validated the prediction by demonstrating that although 24-h treatment of INS-1(832/13) cells with low, non-cytotoxic concentrations of SFN (2-10 μM) protected the cells from cytotoxicity by oxidative insult, it markedly suppressed insulin secretion stimulated by 20 mM glucose. CONCLUSIONS Our study indicates that adaptive induction of endogenous antioxidants by exogenous antioxidants, albeit cytoprotective, inhibits GSIS in β-cells.
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77
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Zhang T, Li C. Mechanisms of amino acid-stimulated insulin secretion in congenital hyperinsulinism. Acta Biochim Biophys Sin (Shanghai) 2013; 45:36-43. [PMID: 23212075 DOI: 10.1093/abbs/gms107] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The role of amino acids in the regulation of insulin secretion in pancreatic beta-cells is highlighted in three forms of congenital hyperinsulinism (HI), namely gain-of-function mutations of glutamate dehydrogenase (GDH), loss-of-function mutations of ATP-dependent potassium channels, and a deficiency of short-chain 3-hydroxyacyl-CoA dehydrogenase. Studies on disease mouse models of HI suggest that amino acid oxidation and signaling effects are the major mechanisms of amino acid-stimulated insulin secretion. Amino acid oxidation via GDH produces ATP and triggers insulin secretion. The signaling effect of amino acids amplifies insulin release after beta-cell depolarization and elevation of cytosolic calcium.
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Affiliation(s)
- Tingting Zhang
- Division of Endocrinology, Department of Pediatrics, The Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Whitelaw BS, Robinson MB. Inhibitors of glutamate dehydrogenase block sodium-dependent glutamate uptake in rat brain membranes. Front Endocrinol (Lausanne) 2013; 4:123. [PMID: 24062726 PMCID: PMC3775299 DOI: 10.3389/fendo.2013.00123] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 08/30/2013] [Indexed: 02/02/2023] Open
Abstract
We recently found evidence for anatomic and physical linkages between the astroglial Na(+)-dependent glutamate transporters (GLT-1/EAAT2 and GLAST/EAAT1) and mitochondria. In these same studies, we found that the glutamate dehydrogenase (GDH) inhibitor, epigallocatechin-monogallate (EGCG), inhibits both glutamate oxidation and Na(+)-dependent glutamate uptake in astrocytes. In the present study, we extend this finding by exploring the effects of EGCG on Na(+)-dependent l-[(3)H]-glutamate (Glu) uptake in crude membranes (P2) prepared from rat brain cortex. In this preparation, uptake is almost exclusively mediated by GLT-1. EGCG inhibited l-[(3)H]-Glu uptake in cortical membranes with an IC50 value of 230 μM. We also studied the effects of two additional inhibitors of GDH, hexachlorophene (HCP) and bithionol (BTH). Both of these compounds also caused concentration-dependent inhibition of glutamate uptake in cortical membranes. Pre-incubating with HCP for up to 15 min had no greater effect than that observed with no pre-incubation, showing that the effects occur rapidly. HCP decreased the V max for glutamate uptake without changing the K m, consistent with a non-competitive mechanism of action. EGCG, HCP, and BTH also inhibited Na(+)-dependent transport of d-[(3)H]-aspartate (Asp), a non-metabolizable transporter substrate, and [(3)H]-γ-aminobutyric acid (GABA). In contrast to the forebrain, glutamate uptake in crude cerebellar membranes (P2) is likely mediated by GLAST (EAAT1). Therefore, the effects of these compounds were examined in cerebellar membranes. In this region, none of these compounds had any effect on uptake of either l-[(3)H]-Glu or d-[(3)H]-Asp, but they all inhibited [(3)H]-GABA uptake. Together these studies suggest that GDH is preferentially required for glutamate uptake in forebrain as compared to cerebellum, and GDH may be required for GABA uptake as well. They also provide further evidence for a functional linkage between glutamate transport and mitochondria.
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Affiliation(s)
- Brendan S. Whitelaw
- Children’s Hospital of Philadelphia Research Institute, Philadelphia, PA, USA
| | - Michael B. Robinson
- Children’s Hospital of Philadelphia Research Institute, Philadelphia, PA, USA
- Departments of Pediatrics and Pharmacology, University of Pennsylvania, Philadelphia, PA, USA
- *Correspondence: Michael B. Robinson, Department of Pediatrics, University of Pennsylvania, 502N Abramson Pediatric Research Building, 3615 Civic Center Boulevard, Philadelphia, PA 19104-4318, USA e-mail:
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79
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Kim EA, Yang SJ, Choi SY, Lee WJ, Cho SW. Inhibition of glutamate dehydrogenase and insulin secretion by KHG26377 does not involve ADP-ribosylation by SIRT4 or deacetylation by SIRT3. BMB Rep 2012; 45:458-63. [PMID: 22917030 DOI: 10.5483/bmbrep.2012.45.8.040] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We investigated the mechanisms involved in KHG26377 regulation of glutamate dehydrogenase (GDH) activity, focusing on the roles of SIRT4 and SIRT3. Intraperitoneal injection of mice with KHG26377 reduced GDH activity with concomitant repression of glucose-induced insulin secretion. Consistent with their known functions, SIRT4 ribosylated GDH and reduced its activity, and SIRT3 deacetylated GDH, increasing its activity. However, KHG26377 did not affect SIRT4-mediated ADP-ribosylation/ inhibition or SIRT3-mediated deacetylation/activation of GDH. KHG26377 had no effect on SIRT4 protein levels, and did not alter total GDH, acetylated GDH, or SIRT3 protein levels in pancreatic mitochondrial lysates. These results suggest that the mechanism by which KHG26377 inhibits GDH activity and insulin secretion does not involve ADP-ribosylation of GDH by SIRT4 or deacetylation of GDH by SIRT3.
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Affiliation(s)
- Eun-A Kim
- Department of Biochemistry and Molecular Biology, University of Ulsan College of Medicine, Seoul, Korea
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80
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Komlos D, Mann KD, Zhuo Y, Ricupero CL, Hart RP, Liu AYC, Firestein BL. Glutamate dehydrogenase 1 and SIRT4 regulate glial development. Glia 2012; 61:394-408. [PMID: 23281078 DOI: 10.1002/glia.22442] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 10/22/2012] [Indexed: 01/10/2023]
Abstract
Congenital hyperinsulinism/hyperammonemia (HI/HA) syndrome is caused by an activation mutation of glutamate dehydrogenase 1 (GDH1), a mitochondrial enzyme responsible for the reversible interconversion between glutamate and α-ketoglutarate. The syndrome presents clinically with hyperammonemia, significant episodic hypoglycemia, seizures, and frequent incidences of developmental and learning defects. Clinical research has implicated that although some of the developmental and neurological defects may be attributed to hypoglycemia, some characteristics cannot be ascribed to low glucose and as hyperammonemia is generally mild and asymptomatic, there exists the possibility that altered GDH1 activity within the brain leads to some clinical changes. GDH1 is allosterically regulated by many factors, and has been shown to be inhibited by the ADP-ribosyltransferase sirtuin 4 (SIRT4), a mitochondrially localized sirtuin. Here we show that SIRT4 is localized to mitochondria within the brain. SIRT4 is highly expressed in glial cells, specifically astrocytes, in the postnatal brain and in radial glia during embryogenesis. Furthermore, SIRT4 protein decreases in expression during development. We show that factors known to allosterically regulate GDH1 alter gliogenesis in CTX8 cells, a novel radial glial cell line. We find that SIRT4 and GDH1 overexpression play antagonistic roles in regulating gliogenesis and that a mutant variant of GDH1 found in HI/HA patients accelerates the development of glia from cultured radial glia cells.
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Affiliation(s)
- Daniel Komlos
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
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81
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Cocoa polyphenols and their potential benefits for human health. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2012; 2012:906252. [PMID: 23150750 PMCID: PMC3488419 DOI: 10.1155/2012/906252] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 05/18/2012] [Accepted: 05/31/2012] [Indexed: 12/20/2022]
Abstract
This paper compiles the beneficial effects of cocoa polyphenols on human health, especially with regard to cardiovascular and inflammatory diseases, metabolic disorders, and cancer prevention. Their antioxidant properties may be responsible for many of their pharmacological effects, including the inhibition of lipid peroxidation and the protection of LDL-cholesterol against oxidation, and increase resistance to oxidative stress. The phenolics from cocoa also modify the glycemic response and the lipid profile, decreasing platelet function and inflammation along with diastolic and systolic arterial pressures, which, taken together, may reduce the risk of cardiovascular mortality. Cocoa polyphenols can also modulate intestinal inflammation through the reduction of neutrophil infiltration and expression of different transcription factors, which leads to decreases in the production of proinflammatory enzymes and cytokines. The phenolics from cocoa may thus protect against diseases in which oxidative stress is implicated as a causal or contributing factor, such as cancer. They also have antiproliferative, antimutagenic, and chemoprotective effects, in addition to their anticariogenic effects.
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82
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Spanaki C, Zaganas I, Kounoupa Z, Plaitakis A. The complex regulation of human glud1 and glud2 glutamate dehydrogenases and its implications in nerve tissue biology. Neurochem Int 2012; 61:470-81. [PMID: 22658952 DOI: 10.1016/j.neuint.2012.05.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2012] [Revised: 05/20/2012] [Accepted: 05/21/2012] [Indexed: 12/01/2022]
Abstract
Mammalian glutamate dehydrogenase (GDH) is a housekeeping mitochondrial enzyme (hGDH1 in the human) that catalyses the reversible inter-conversion of glutamate to α-ketoglutarate and ammonia, thus interconnecting amino acid and carbohydrate metabolism. It displays an energy sensing mechanism, which permits enzyme activation under low cellular energy states. As GDH is at the crossroads of important metabolic pathways, a tight control of its activity is essential. Indeed, to fulfill its role in metabolism and cellular energetics, mammalian GDH has evolved into a highly regulated enzyme subject to allosteric modulation by diverse compounds. The recent emergence (<23 million years ago) in apes and humans of a hGDH2 isoenzyme with distinct regulatory properties, as well as, the detection of gain-of-function variants in hGDH1 and hGDH2 that affect the nervous system, have introduced additional complexities. The properties of the two highly homologous human GDHs were studied using purified recombinant hGDH1 and hGDH2 obtained by expression of the corresponding cDNAs in Sf21 cells. Results showed that, in contrast to hGDH1 that maintains substantial basal activity (35-40% of its maximal capacity), hGDH2 displays low basal activity (3-8% of maximal) that is remarkably responsive to activation by rising levels of ADP and/or l-leucine. This is primarily due to the Arg443Ser evolutionary change, which also made hGDH2 markedly sensitive to estrogens and neuroleptic drugs. In contrast to hGDH1, which is subject to potent GTP inhibition, hGDH2 has dissociated its function from this energy switch, being able to metabolize glutamate even when the Krebs cycle generates GTP levels sufficient to inactivate the housekeeping hGDH1. Our data also show that spermidine, a polyamine thought to reduce oxidative stress and to prolong survival, and EGCG, a green tea polyphenol, inhibit hGDH2 at lower concentrations than hGDH1. The implications of these findings in nerve tissue biology are discussed.
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Affiliation(s)
- Cleanthe Spanaki
- Department of Neurology, Medical School, University of Crete, Heraklion, Crete, Greece
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83
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da Silva PMR, Batista TM, Ribeiro RA, Zoppi CC, Boschero AC, Carneiro EM. Decreased insulin secretion in islets from protein malnourished rats is associated with impaired glutamate dehydrogenase function: effect of leucine supplementation. Metabolism 2012; 61:721-32. [PMID: 22078937 DOI: 10.1016/j.metabol.2011.09.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 08/27/2011] [Accepted: 09/27/2011] [Indexed: 02/06/2023]
Abstract
We herein studied the role of glutamate dehydrogenase (GDH), in response to leucine (LEU) supplementation, upon insulin secretion of malnourished rats. Weaned male Wistar rats were fed normal-protein (17%) or low-protein diet (6%, LP) for 8 weeks. Half of the rats of each group were supplemented with LEU (1.5%) in the drinking water for the following 4 weeks. Gene and protein expressions, static insulin secretion, and cytoplasmic Ca(2+) oscillations were measured. Glutamate dehydrogenase messenger RNA was 58% lower in LP islets, and LEU supplementation augmented it in 28%. The LP islets secreted less insulin when exposed to 20 mmol/L LEU, 20 mmol/L LEU + 2 mmol/L glutamine (with or without 5 mmol/L aminooxyacetic acid, a branched chain aminotransferase inhibitor, or 20 μmol/L epigallocatechin gallate, a GDH inhibitor), 20 mmol/L α-ketoisocaproate, glutamine + 20 mmol/L β-2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (a GDH activator), and 22.2 mmol/L glucose. Leucine supplementation augmented insulin secretion to levels found in normal-protein islets in all the above conditions, an effect that was blunted when islets were incubated with epigallocatechin gallate. The glutamine + β-2-aminobicyclo[2.2.1]heptane-2-carboxylic acid-induced increased [Ca(2+)](i) and oscillations were higher than those for LP islets. Leucine supplementation normalized these parameters in LP islets. Impaired GDH function was associated with lower insulin release in LP islets, and LEU supplementation normalized insulin secretion via restoration of GDH function. In addition, GDH may contribute to insulin secretion through ameliorations of Ca(2+) handling in LP islets.
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Affiliation(s)
- Priscilla Muniz Ribeiro da Silva
- Department of Anatomy, Cellular Biology and Physiology and Biophysics, Institute of Biology, University of Campinas,PO Box 6109, CEP 13083-970 Campinas, SP, Brazil
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84
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Lu YX, Zhang Q, Li J, Sun YX, Wang LY, Cheng WM, Hu XY. Antidiabetic Effects of Total Flavonoids from Litsea Coreana leve on Fat-Fed, Streptozotocin-Induced Type 2 Diabetic Rats. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2012; 38:713-25. [DOI: 10.1142/s0192415x10008184] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study was initiated to determine the possible antidiabetic effects of total flavonoids of Litsea Coreana leve (TFLC), an alcohol extract from the dried leaves of Litsea Coreana leve, on type 2 diabetic rats. Male Sprague-Dawley rats ( n = 40, 160–180 g) were divided into two groups and fed with normal chow diet (Normal Control group) or high-fat diet (HFD) for a period of 4 weeks. After 4 weeks of dietary manipulation, the HFD-fed rats were injected with 30 mg/kg streptozocin (STZ) to induce diabetes 72 hours after STZ injection. These diabetic rats were randomly divided into 3 groups ( n = 10): Diabetic Control group, Diabetic + TFLC group and Diabetic + PIO group. Diabetic + TFLC group and Diabetic + PIO group were orally administered with 400 mg/kg TFLC or 10 mg/kg pioglitazone (all suspended in 0.5% CMC-Na) respectively for 6 weeks. All rats were examined for body weight, serum and hepatic biochemical indices, content of malondialdehyde (MDA), activities of superoxide dismutase (SOD) and pathological changes in liver and pancreas, as well as protein tyrosine phosphatase 1B (PTP1B) expression in liver. The diabetic rats became obese, insulin resistant, hyperglycemic and hyperlipidemic. Treatment with TFLC showed a significant increase in insulin sensitivity, serum HDL-C level and SOD activities, meanwhile marked decrease in body weight, serum FFA, TC, TG, LDL-C, CRP, MDA content. TFLC also attenuated pathologic alterations in liver and pancreatic islet. Furthermore, TFLC was found to decrease the expression of PTP1B in diabetic rat liver. These results suggested that TFLC could ameliorate hyperglycemia, hyperlipoidemia, inflammation and oxidation stress, as well as insulin resistance of type 2 diabetic rats.
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Affiliation(s)
- Yun-Xia Lu
- School of Pharmacy, Anhui Medical University, Hefei 230032, P. R. China
- Department of Biochemistry, Anhui Medical University, Hefei 230032, P. R. China
| | - Qiu Zhang
- School of Pharmacy, Anhui Medical University, Hefei 230032, P. R. China
| | - Jun Li
- School of Pharmacy, Anhui Medical University, Hefei 230032, P. R. China
| | - Yu-Xiu Sun
- Department of Biochemistry, Anhui Medical University, Hefei 230032, P. R. China
| | - Ling-Yun Wang
- Department of Biochemistry, Anhui Medical University, Hefei 230032, P. R. China
| | - Wen-Ming Cheng
- School of Pharmacy, Anhui Medical University, Hefei 230032, P. R. China
| | - Xiang-Yang Hu
- Department of Pathology, Anhui Medical University, Hefei 230032, P. R. China
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85
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Bauer DE, Jackson JG, Genda EN, Montoya MM, Yudkoff M, Robinson MB. The glutamate transporter, GLAST, participates in a macromolecular complex that supports glutamate metabolism. Neurochem Int 2012; 61:566-74. [PMID: 22306776 DOI: 10.1016/j.neuint.2012.01.013] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 01/11/2012] [Accepted: 01/12/2012] [Indexed: 01/25/2023]
Abstract
GLAST is the predominant glutamate transporter in the cerebellum and contributes substantially to glutamate transport in forebrain. This astroglial glutamate transporter quickly binds and clears synaptically released glutamate and is principally responsible for ensuring that synaptic glutamate concentrations remain low. This process is associated with a significant energetic cost. Compartmentalization of GLAST with mitochondria and proteins involved in energy metabolism could provide energetic support for glutamate transport. Therefore, we performed immunoprecipitation and co-localization experiments to determine if GLAST might co-compartmentalize with proteins involved in energy metabolism. GLAST was immunoprecipitated from rat cerebellum and subunits of the Na(+)/K(+) ATPase, glycolytic enzymes, and mitochondrial proteins were detected. GLAST co-localized with mitochondria in cerebellar tissue. GLAST also co-localized with mitochondria in fine processes of astrocytes in organotypic hippocampal slice cultures. From these data, we hypothesized that mitochondria participate in a macromolecular complex with GLAST to support oxidative metabolism of transported glutamate. To determine the functional metabolic role of this complex, we measured CO(2) production from radiolabeled glutamate in cultured astrocytes and compared it to overall glutamate uptake. Within 15 min, 9% of transported glutamate was converted to CO(2). This CO(2) production was blocked by inhibitors of glutamate transport and glutamate dehydrogenase, but not by an inhibitor of glutamine synthetase. Our data support a model in which GLAST exists in a macromolecular complex that allows transported glutamate to be metabolized in mitochondria to support energy production.
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Affiliation(s)
- Deborah E Bauer
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA 19104, United States
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86
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Li M, Li C, Allen A, Stanley CA, Smith TJ. The structure and allosteric regulation of mammalian glutamate dehydrogenase. Arch Biochem Biophys 2011; 519:69-80. [PMID: 22079166 DOI: 10.1016/j.abb.2011.10.015] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 10/19/2011] [Accepted: 10/25/2011] [Indexed: 01/10/2023]
Abstract
Glutamate dehydrogenase (GDH) is a homohexameric enzyme that catalyzes the reversible oxidative deamination of l-glutamate to 2-oxoglutarate. Only in the animal kingdom is this enzyme heavily allosterically regulated by a wide array of metabolites. The major activators are ADP and leucine, while the most important inhibitors include GTP, palmitoyl CoA, and ATP. Recently, spontaneous mutations in the GTP inhibitory site that lead to the hyperinsulinism/hyperammonemia (HHS) syndrome have shed light as to why mammalian GDH is so tightly regulated. Patients with HHS exhibit hypersecretion of insulin upon consumption of protein and concomitantly extremely high levels of ammonium in the serum. The atomic structures of four new inhibitors complexed with GDH complexes have identified three different allosteric binding sites. Using a transgenic mouse model expressing the human HHS form of GDH, at least three of these compounds were found to block the dysregulated form of GDH in pancreatic tissue. EGCG from green tea prevented the hyper-response to amino acids in whole animals and improved basal serum glucose levels. The atomic structure of the ECG-GDH complex and mutagenesis studies is directing structure-based drug design using these polyphenols as a base scaffold. In addition, all of these allosteric inhibitors are elucidating the atomic mechanisms of allostery in this complex enzyme.
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Affiliation(s)
- Ming Li
- Donald Danforth Plant Science Center, 975 North Warson Road, Saint Louis, MO 63132, USA
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87
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Li C, Li M, Chen P, Narayan S, Matschinsky FM, Bennett MJ, Stanley CA, Smith TJ. Green tea polyphenols control dysregulated glutamate dehydrogenase in transgenic mice by hijacking the ADP activation site. J Biol Chem 2011; 286:34164-74. [PMID: 21813650 PMCID: PMC3190766 DOI: 10.1074/jbc.m111.268599] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Revised: 07/04/2011] [Indexed: 12/28/2022] Open
Abstract
Glutamate dehydrogenase (GDH) catalyzes the oxidative deamination of L-glutamate and, in animals, is extensively regulated by a number of metabolites. Gain of function mutations in GDH that abrogate GTP inhibition cause the hyperinsulinism/hyperammonemia syndrome (HHS), resulting in increased pancreatic β-cell responsiveness to leucine and susceptibility to hypoglycemia following high protein meals. We have previously shown that two of the polyphenols from green tea (epigallocatechin gallate (EGCG) and epicatechin gallate (ECG)) inhibit GDH in vitro and that EGCG blocks GDH-mediated insulin secretion in wild type rat islets. Using structural and site-directed mutagenesis studies, we demonstrate that ECG binds to the same site as the allosteric regulator, ADP. Perifusion assays using pancreatic islets from transgenic mice expressing a human HHS form of GDH demonstrate that the hyperresponse to glutamine caused by dysregulated GDH is blocked by the addition of EGCG. As observed in HHS patients, these transgenic mice are hypersensitive to amino acid feeding, and this is abrogated by oral administration of EGCG prior to challenge. Finally, the low basal blood glucose level in the HHS mouse model is improved upon chronic administration of EGCG. These results suggest that this common natural product or some derivative thereof may prove useful in controlling this genetic disorder. Of broader clinical implication is that other groups have shown that restriction of glutamine catabolism via these GDH inhibitors can be useful in treating various tumors. This HHS transgenic mouse model offers a highly useful means to test these agents in vivo.
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Affiliation(s)
| | - Ming Li
- the Donald Danforth Plant Science Center, Saint Louis, Missouri 63132, and
| | - Pan Chen
- From the Division of Endocrinology and
| | - Srinivas Narayan
- the Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
| | - Franz M. Matschinsky
- the Diabetes Research Center and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Michael J. Bennett
- the Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
| | | | - Thomas J. Smith
- the Donald Danforth Plant Science Center, Saint Louis, Missouri 63132, and
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88
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Romanov V, Whyard T, Bonala R, Johnson F, Grollman A. Glutamate dehydrogenase requirement for apoptosis induced by aristolochic acid in renal tubular epithelial cells. Apoptosis 2011; 16:1217-28. [DOI: 10.1007/s10495-011-0646-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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89
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Karaca M, Frigerio F, Maechler P. From pancreatic islets to central nervous system, the importance of glutamate dehydrogenase for the control of energy homeostasis. Neurochem Int 2011; 59:510-7. [DOI: 10.1016/j.neuint.2011.03.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 03/21/2011] [Accepted: 03/23/2011] [Indexed: 11/25/2022]
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90
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Mereles D, Hunstein W. Epigallocatechin-3-gallate (EGCG) for clinical trials: more pitfalls than promises? Int J Mol Sci 2011; 12:5592-603. [PMID: 22016611 PMCID: PMC3189735 DOI: 10.3390/ijms12095592] [Citation(s) in RCA: 224] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 08/17/2011] [Accepted: 08/19/2011] [Indexed: 11/29/2022] Open
Abstract
Epigallocatechin-3-gallate (EGCG), the main and most significant polyphenol in green tea, has shown numerous health promoting effects acting through different pathways, as antioxidant, anti-inflammatory and anti-atherogenic agent, showing gene expression activity, functioning through growth factor-mediated pathways, the mitogen-activated protein kinase-dependent pathway, the ubiquitin/proteasome degradation pathway, as well as eliciting an amyloid protein remodeling activity. However, epidemiological inferences are sometimes conflicting and in vitro and in vivo studies may seem discrepant. Current knowledge on how to enhance bioavailability could be the answer to some of these issues. Furthermore, dose levels, administration frequency and potential side effects remain to be examined.
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Affiliation(s)
- Derliz Mereles
- Department of Cardiology, Angiology and Pneumology, University of Heidelberg, D-69120 Heidelberg, Germany
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +49-6221-568852; Fax: +49-6221-567436
| | - Werner Hunstein
- Faculty of Medicine, University of Heidelberg, D-69120, Heidelberg, Germany; E-Mail:
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91
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Abstract
Green tea is made from unfermented dried leaves from Camellia sinensis and has been consumed by humans for thousands of years. For nearly as long, it has been used as a folk remedy for a wide array of diseases. More recently, a large number of in-vitro and in-vivo scientific studies have supported this ancient contention that the polyphenols from green tea can provide a number of health benefits. Since these compounds are clearly safe for human consumption and ubiquitous in the food supply, they are highly attractive as lead compounds for drug discovery programs. However, as drugs, they are far from optimum. They are relatively unstable, poorly absorbed, and readily undergo a number of metabolic transformations by intestinal microbiota and human enzymes. Further, since these compounds target a wide array of biological systems, in-vivo testing is rather difficult since effects on alternative pathways need to be carefully eliminated. The purpose of this review is to discuss some of the challenges and benefits of pursuing this family of compounds for drug discovery.
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Affiliation(s)
- Thomas J Smith
- Donald Danforth Plant Science Center, 975 North Warson Road, Saint Louis, MO 63132 USA, Tel: (314)-587-1451
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92
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Cherniack EP. Polyphenols: planting the seeds of treatment for the metabolic syndrome. Nutrition 2011; 27:617-23. [PMID: 21367579 DOI: 10.1016/j.nut.2010.10.013] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 10/05/2010] [Accepted: 10/06/2010] [Indexed: 11/18/2022]
Abstract
Greater understanding about the pathogenesis of metabolic syndrome and potential causes suggests that plant polyphenols might be useful as a treatment. Dietary excess energy can be stored in adipocytes, leading to the release of proinflammatory cytokines and adipose-related hormones that cause vascular injury. Plant polyphenols, organic compounds found in numerous plant species and their fruits, are being actively studied as potential treatments for components of the metabolic syndrome. Individual polyphenols that have been examined include resveratrol, quercetin, epigallocathechin-3-gallate, and curcumin. Resveratrol lowers weight, blood pressure, glucose, and insulin resistance in rodents, and a human trial is currently underway. Quercetin decreases lipid and glucose levels in obese rats, and in a human investigation of subjects with the metabolic syndrome has lowered blood pressure without significant alteration of lipids. Epigallocathechin-3-gallate-induced weight loss has attenuated glucose levels and insulin resistance in rodents and improved hemoglobin A(1c) and lipid in human studies. Plant extracts also can be used. Grape seed and chokeberry extracts have decreased blood pressure and lipid levels in small human trials. Other human investigations have shown the beneficial effects of cocoa, coffee, carob, and Momordica charantia. Thus far, most studies have involved a small number of subjects and have been of short duration. Future studies should be designed to account for a disease process in which the pathogenic factors may take place for years before disease manifestations take place, the possibly limited bioavailability of polyphenols, and the potential need to provide combinations or modifications of polyphenols.
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Affiliation(s)
- E Paul Cherniack
- Geriatrics Institute, Division of Gerontology and Geriatric Medicine, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, USA.
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93
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Deng W, Dong XF, Tong JM, Xie TH, Zhang Q. Effects of an aqueous alfalfa extract on production performance, egg quality and lipid metabolism of laying hens. J Anim Physiol Anim Nutr (Berl) 2011; 96:85-94. [DOI: 10.1111/j.1439-0396.2010.01125.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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94
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Stanley CA. Two genetic forms of hyperinsulinemic hypoglycemia caused by dysregulation of glutamate dehydrogenase. Neurochem Int 2010; 59:465-72. [PMID: 21130127 DOI: 10.1016/j.neuint.2010.11.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 11/18/2010] [Accepted: 11/24/2010] [Indexed: 02/02/2023]
Abstract
Glutamate dehydrogenase (GDH) has recently been shown to be involved in two genetic disorders of hyperinsulinemic hypoglycemia in children. These include the hyperinsulinism/hyperammonemia syndrome caused by dominant activating mutations of GLUD1 which interfere with inhibitory regulation by GTP and hyperinsulinism due to recessive deficiency of short-chain 3-hydroxy-acyl-CoA dehydrogenase (SCHAD, encoded by HADH1). The clinical manifestations of the abnormalities in pancreatic ß-cell insulin regulation include fasting hypoglycemia, as well as protein-sensitive hypoglycemia. The latter is due to abnormally increased sensitivity of affected children to stimulation of insulin secretion by the amino acid, leucine. In patients with GDH activating mutations, mild hyperammonemia occurs in both the basal and protein-fed state, possibly due to increased renal ammoniagenesis. Some patients with GDH activating mutations appear to be at unusual risk of developmental delay and generalized epilepsy, perhaps reflecting consequences of increased GDH activity in the brain. Studies of these two disorders have been carried out in mouse models to define the mechanisms of insulin dysregulation. In SCHAD deficiency, the activation of GDH is due to loss of a direct inhibitory protein-protein interaction between SCHAD and GDH. These two novel human disorders demonstrate the important role of GDH in insulin regulation and illustrate unexpectedly important reasons for the unusually complex allosteric regulation of GDH.
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Affiliation(s)
- Charles A Stanley
- University of Pennsylvania School of Medicine, Endocrinology Division, The Children's Hospital of Philadelphia, Philadelphia, PA 19026, United States.
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95
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Li M, Li C, Allen A, Stanley CA, Smith TJ. The structure and allosteric regulation of glutamate dehydrogenase. Neurochem Int 2010; 59:445-55. [PMID: 21070828 DOI: 10.1016/j.neuint.2010.10.017] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 10/19/2010] [Accepted: 10/27/2010] [Indexed: 01/17/2023]
Abstract
Glutamate dehydrogenase (GDH) has been extensively studied for more than 50 years. Of particular interest is the fact that, while considered by most to be a 'housekeeping' enzyme, the animal form of GDH is heavily regulated by a wide array of allosteric effectors and exhibits extensive inter-subunit communication. While the chemical mechanism for GDH has remained unchanged through epochs of evolution, it was not clear how or why animals needed to evolve such a finely tuned form of this enzyme. As reviewed here, recent studies have begun to elucidate these issues. Allosteric regulation first appears in the Ciliates and may have arisen to accommodate evolutionary changes in organelle function. The occurrence of allosteric regulation appears to be coincident with the formation of an 'antenna' like feature rising off the tops of the subunits that may be necessary to facilitate regulation. In animals, this regulation further evolved as GDH became integrated into a number of other regulatory pathways. In particular, mutations in GDH that abrogate GTP inhibition result in dangerously high serum levels of insulin and ammonium. Therefore, allosteric regulation of GDH plays an important role in insulin homeostasis. Finally, several compounds have been identified that block GDH-mediated insulin secretion that may be to not only find use in treating these insulin disorders but to kill tumors that require glutamine metabolism for cellular energy.
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Affiliation(s)
- Ming Li
- Donald Danforth Plant Science Center, Saint Louis, MO 63132, United States
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96
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Yang J, Chi Y, Burkhardt BR, Guan Y, Wolf BA. Leucine metabolism in regulation of insulin secretion from pancreatic beta cells. Nutr Rev 2010; 68:270-9. [PMID: 20500788 DOI: 10.1111/j.1753-4887.2010.00282.x] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Leucine, a branched-chain amino acid that must be supplied in the daily diet, plays an important role in controlling protein synthesis and regulating cell metabolism in various cell types. In pancreatic beta cells, leucine acutely stimulates insulin secretion by serving as both metabolic fuel and allosteric activator of glutamate dehydrogenase to enhance glutaminolysis. Leucine has also been shown to regulate gene transcription and protein synthesis in pancreatic islet beta cells via both mTOR-dependent and -independent pathways at physiological concentrations. Long-term treatment with leucine has been shown to improve insulin secretory dysfunction of human diabetic islets via upregulation of certain key metabolic genes. In vivo, leucine administration improves glycemic control in humans and rodents with type 2 diabetes. This review summarizes and discusses the recent findings regarding the effects of leucine metabolism on pancreatic beta-cell function.
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Affiliation(s)
- Jichun Yang
- Department of Physiology and Pathophysiology, Peking University Diabetes Center, Peking University Health Science Center, Beijing, China.
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97
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Li C, Chen P, Palladino A, Narayan S, Russell LK, Sayed S, Xiong G, Chen J, Stokes D, Butt YM, Jones PM, Collins HW, Cohen NA, Cohen AS, Nissim I, Smith TJ, Strauss AW, Matschinsky FM, Bennett MJ, Stanley CA. Mechanism of hyperinsulinism in short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency involves activation of glutamate dehydrogenase. J Biol Chem 2010; 285:31806-18. [PMID: 20670938 DOI: 10.1074/jbc.m110.123638] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanism of insulin dysregulation in children with hyperinsulinism associated with inactivating mutations of short-chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD) was examined in mice with a knock-out of the hadh gene (hadh(-/-)). The hadh(-/-) mice had reduced levels of plasma glucose and elevated plasma insulin levels, similar to children with SCHAD deficiency. hadh(-/-) mice were hypersensitive to oral amino acid with decrease of glucose level and elevation of insulin. Hypersensitivity to oral amino acid in hadh(-/-) mice can be explained by abnormal insulin responses to a physiological mixture of amino acids and increased sensitivity to leucine stimulation in isolated perifused islets. Measurement of cytosolic calcium showed normal basal levels and abnormal responses to amino acids in hadh(-/-) islets. Leucine, glutamine, and alanine are responsible for amino acid hypersensitivity in islets. hadh(-/-) islets have lower intracellular glutamate and aspartate levels, and this decrease can be prevented by high glucose. hadh(-/-) islets also have increased [U-(14)C]glutamine oxidation. In contrast, hadh(-/-) mice have similar glucose tolerance and insulin sensitivity compared with controls. Perifused hadh(-/-) islets showed no differences from controls in response to glucose-stimulated insulin secretion, even with addition of either a medium-chain fatty acid (octanoate) or a long-chain fatty acid (palmitate). Pull-down experiments with SCHAD, anti-SCHAD, or anti-GDH antibodies showed protein-protein interactions between SCHAD and GDH. GDH enzyme kinetics of hadh(-/-) islets showed an increase in GDH affinity for its substrate, α-ketoglutarate. These studies indicate that SCHAD deficiency causes hyperinsulinism by activation of GDH via loss of inhibitory regulation of GDH by SCHAD.
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Affiliation(s)
- Changhong Li
- Division of Endocrinology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
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98
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Yang SJ, Hahn HG, Choi SY, Cho SW. Inhibitory effects of KHG26377 on glutamate dehydrogenase activity in cultured islets. BMB Rep 2010; 43:245-9. [PMID: 20423608 DOI: 10.5483/bmbrep.2010.43.4.245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
GDH has been known to be related with hyperinsulinismhyperammonemia syndrome. We have screened new drugs with a view to developing effective drugs modulating GDH activity. In the present work, we investigated the effects of a new drug, KHG26377 on glutamate formation and GDH activity in cultured rat islets. When KHG26377 was added to the culture medium for 24 h prior to kinetic analysis, the V(max) of GDH was decreased by 59% whereas K(m) is not significantly changed. The concentration of glutamate decreased by 50% and perfusion of islets with KHG26377 reduced insulin release by up to 55%. Our results show that KHG26377 regulates insulin release by inhibiting GDH activity in primary cultured islets and support the previous studies for the connection between GDH activity and insulin release. Further studies are required to determine in vivo effects and pharmacokinetics of the drug.
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Affiliation(s)
- Seung-Ju Yang
- 1Department of Biomedical Laboratory Science, Konyang University, Daejeon 302-718, USA
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99
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Tai KK, Truong DD. (-)-Epigallocatechin-3-gallate (EGCG), a green tea polyphenol, reduces dichlorodiphenyl-trichloroethane (DDT)-induced cell death in dopaminergic SHSY-5Y cells. Neurosci Lett 2010; 482:183-7. [PMID: 20542083 DOI: 10.1016/j.neulet.2010.06.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Revised: 05/07/2010] [Accepted: 06/05/2010] [Indexed: 12/21/2022]
Abstract
Results from epidemiological studies indicated that there exists an inverse correlation between consumption of green tea and neurodegenerative diseases including Parkinson's disease. We hypothesized that consumption of green tea would activate endogenous protective mechanisms against environmental toxin-induced cell injury, which is believed to play a causative role in the etiology of Parkinson's disease. Here, we found that epigallocatechin-3-gallate (EGCG), a major green tea polyphenol, concentration-dependently (1 microM, 3 microM and 10 microM) reduced dichlorodiphenyl-trichloroethane (DDT) (100 microM)-induced cell death in dopaminergic neuroblastoma SHSY-5Y cells. The cell viability was determined by trypan blue exclusion assays. We also found that preconditioning the SHSY-5Y cells with EGCG by multiple, brief, prior exposures of the cells to EGCG can subsequently protect the cells from DDT-induced cell death. The EGCG-induced protective effect positively correlated with the number of exposures to EGCG. These results suggest that EGCG has a protective effect against DDT-induced cell death, and that prior exposures to EGCG activate an endogenous protective mechanism in the dopaminergic cells which can mitigate organochlorine pesticide-induced cell injury.
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Affiliation(s)
- Kwok-Keung Tai
- The Parkinson's and Movement Disorder Research Laboratory, Long Beach Memorial Medical Center, 2801 Atlantic Ave., Long Beach, CA 90806, USA.
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100
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Choo AY, Kim SG, Vander Heiden MG, Mahoney SJ, Vu H, Yoon SO, Cantley LC, Blenis J. Glucose addiction of TSC null cells is caused by failed mTORC1-dependent balancing of metabolic demand with supply. Mol Cell 2010; 38:487-99. [PMID: 20513425 DOI: 10.1016/j.molcel.2010.05.007] [Citation(s) in RCA: 217] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 11/16/2009] [Accepted: 03/05/2010] [Indexed: 12/11/2022]
Abstract
The mTORC1-signaling pathway integrates environmental conditions into distinct signals for cell growth by balancing anabolic and catabolic processes. Accordingly, energetic stress inhibits mTORC1 signaling predominantly through AMPK-dependent activation of TSC1/2. Thus, TSC1/2-/- cells are hypersensitive to glucose deprivation, and this has been linked to increased p53 translation and activation of apoptosis. Herein, we show that mTORC1 inhibition during glucose deprivation prevented not only the execution of death, but also induction of energetic stress. mTORC1 inhibition during glucose deprivation decreased AMPK activation and allowed ATP to remain high, which was both necessary and sufficient for protection. This effect was not due to increased catabolic activities such as autophagy, but rather exclusively due to decreased anabolic processes, reducing energy consumption. Specifically, TSC1/2-/- cells become highly dependent on glutamate dehydrogenase-dependent glutamine metabolism via the TCA cycle for survival. Therefore, mTORC1 inhibition during energetic stress is primarily to balance metabolic demand with supply.
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Affiliation(s)
- Andrew Y Choo
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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