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Xiao W, Chen Y, Wang C. Quantitative Chemoproteomic Methods for Reactive Cysteinome Profiling. Isr J Chem 2023. [DOI: 10.1002/ijch.202200100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Weidi Xiao
- Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education College of Chemistry and Molecular Engineering Peking University 100871 Peking China
- Peking-Tsinghua Center for Life Sciences Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 China
| | - Ying Chen
- Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education College of Chemistry and Molecular Engineering Peking University 100871 Peking China
- Peking-Tsinghua Center for Life Sciences Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 China
| | - Chu Wang
- Synthetic and Functional Biomolecules Center Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education College of Chemistry and Molecular Engineering Peking University 100871 Peking China
- Peking-Tsinghua Center for Life Sciences Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 China
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2
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Mlozen MM, Van Marwijk J, Wilhelmi BS, Whiteley C. Comparative Analysis of the Interaction of Silver Nanoparticles with Hexokinase from Trypanosoma brucei and Humans. Int J Nanomedicine 2023; 18:1399-1411. [PMID: 36992823 PMCID: PMC10041994 DOI: 10.2147/ijn.s401319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 03/14/2023] [Indexed: 03/31/2023] Open
Abstract
Background Regardless of the efforts to ease cases of human African trypanosomiasis (HAT), an increased number of cases get reported annually. This is because of drug resistant Trypanosoma brucei (Tb), the causative agent of the illness. This has renewed the need for creative methods to find new anti-trypanosomal drugs. The blood stream form (BSF) of the parasite depends exclusively on the glycolytic pathway for energy production while it is in the human host. Interruptions in this pathway efficiently kills the parasite. Trypanosoma brucei hexokinase (TbHK) is the first enzyme in glycolysis, and any effectors or inhibitors of TbHK would have potential as anti-trypanosomal agents. Methods TbHK and human glucokinase (hGCK) were over-expressed with a 6 histidine-tag in E. coli BL21(DE3) cells having the pRARE2 plasmid. Results TbHK had thermal and pH stability between 30°C and 55°C and 7.5 and 8.5, respectively, while hGCK exhibited thermal and pH stability between 30°C and 40°C and 7.0 and 8.0, respectively. Kinetically, TbHK had a Km of 39.3 µM, Vmax of 0.066 µmol.min-1.mL-1, kcat of 2.05 min-1 and kcat/Km of 0.0526 min-1.µmol-1. hGCK exhibited a Km of 4.5 µM, Vmax of 0.032 µnmol.min-1.mL-1, kcat of 11.25 min-1, and kcat/Km of 2.5 min-1.µmol-1. Interaction kinetic studies of silver nanoparticles (AgNPs) (0.1 µM) of average size of 6 nm with TbHK and hGCK were conducted. AgNPs selectively inhibited TbHK over hGCK. TbHK showed a non-competitive inhibition with a 50% and 28% decrease in Vmax, and kcat/km, respectively. HsGCK showed a 33% increase in affinity, 9% decrease in Vmax, and a 50% increase in enzyme efficiency. Conclusion The observed pattern of hGCK and AgNPs falls under the uncompetitive inhibition. The observed highly selective inhibitory effects of AgNPs between TbHK and hGCK may be used in development of new anti-trypanosomal drugs.
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Affiliation(s)
- Madalitso M Mlozen
- Department of Biochemistry and Microbiology, Rhodes University, Makhanda (Grahamstown), South Africa
- Malawi Adventist University, Malamulo Campus, Department of Biomedical Sciences, Makwasa, Malawi
- Correspondence: Madalitso M Mlozen, Malawi Adventist University, Malamulo campus, Department of Biomedical Sciences, P.O.Box 55, Makwasa, Tel +265 884628334, Email
| | - Jacqueline Van Marwijk
- Department of Biochemistry and Microbiology, Rhodes University, Makhanda (Grahamstown), South Africa
| | - Brendan Shane Wilhelmi
- Department of Biochemistry and Microbiology, Rhodes University, Makhanda (Grahamstown), South Africa
| | - Chris Whiteley
- Department of Biochemistry and Microbiology, Rhodes University, Makhanda (Grahamstown), South Africa
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Doğan M, Eröz R, Bolu S, Yüce H, Gezdirici A, Arslanoğlu İ, Teralı K. Study of ten causal genes in Turkish patients with clinically suspected maturity-onset diabetes of the young (MODY) using a targeted next-generation sequencing panel. Mol Biol Rep 2022; 49:7483-7495. [PMID: 35733065 DOI: 10.1007/s11033-022-07552-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 04/10/2022] [Accepted: 05/03/2022] [Indexed: 11/29/2022]
Abstract
BACKGROUND Maturity-onset diabetes of the young (MODY), which is the most common cause of monogenic diabetes, has an autosomal dominant pattern of inheritance and exhibits marked clinical and genetic heterogeneity. The aim of the current study was to investigate molecular defects in patients with clinically suspected MODY using a next-generation sequencing (NGS)-based targeted gene panel. METHODS Candidate patients with clinical suspicion of MODY and their parents were included in the study. Molecular genetic analyses were performed on genomic DNA by using NGS. A panel of ten MODY-causal genes involving GCK, HNF1A, HNF1B, HNF4A, ABCC8, CEL, INS, KCNJ11, NEUROD1, PDX1 was designed and subsequently implemented to screen 40 patients for genetic variants. RESULTS Ten different pathogenic or likely pathogenic variants were identified in MODY-suspected patients, with a diagnostic rate of 25%. Three variants of uncertain significance were also detected in the same screen. A novel pathogenic variant in the gene HNF1A (c.505_506delAA [p.Lys169AlafsTer18]) was described for the first time in this report. Intriguingly, we were able to detect variants associated with rare forms of MODY in our study population. CONCLUSIONS Our results suggest that in heterogenous diseases such as MODY, NGS analysis enables accurate identification of underlying molecular defects in a timely and cost-effective manner. Although MODY accounts for 2-5% of all diabetic cases, molecular genetic diagnosis of MODY is necessary for optimal long-term treatment and prognosis as well as for effective genetic counseling.
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Affiliation(s)
- Mustafa Doğan
- Department of Medical Genetics, Genetic Diseases Center, Basaksehir Cam and Sakura City Hospital, 34480, Istanbul, Turkey.
| | - Recep Eröz
- Department of Medical Genetics, Faculty of Medicine, Aksaray University, 81620, Aksaray, Turkey
| | - Semih Bolu
- Department of Pediatric Endocrinology, Faculty of Medicine, Bolu Abant İzzet Baysal University, 14030, Bolu, Turkey
| | - Hüseyin Yüce
- Department of Medical Genetics, Faculty of Medicine, Aksaray University, 81620, Aksaray, Turkey
| | - Alper Gezdirici
- Department of Medical Genetics, Genetic Diseases Center, Basaksehir Cam and Sakura City Hospital, 34480, Istanbul, Turkey
| | - İlknur Arslanoğlu
- Department of Pediatrics Endocrinology, Faculty of Medicine, Duzce University, 81620, Duzce, Turkey
| | - Kerem Teralı
- Department of Medical Biochemistry, Faculty of Medicine, Girne American University, 99428, Kyrenia, Cyprus
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Zhou HL, Premont RT, Stamler JS. The manifold roles of protein S-nitrosylation in the life of insulin. Nat Rev Endocrinol 2022; 18:111-128. [PMID: 34789923 PMCID: PMC8889587 DOI: 10.1038/s41574-021-00583-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/08/2021] [Indexed: 02/04/2023]
Abstract
Insulin, which is released by pancreatic islet β-cells in response to elevated levels of glucose in the blood, is a critical regulator of metabolism. Insulin triggers the uptake of glucose and fatty acids into the liver, adipose tissue and muscle, and promotes the storage of these nutrients in the form of glycogen and lipids. Dysregulation of insulin synthesis, secretion, transport, degradation or signal transduction all cause failure to take up and store nutrients, resulting in type 1 diabetes mellitus, type 2 diabetes mellitus and metabolic dysfunction. In this Review, we make the case that insulin signalling is intimately coupled to protein S-nitrosylation, in which nitric oxide groups are conjugated to cysteine thiols to form S-nitrosothiols, within effectors of insulin action. We discuss the role of S-nitrosylation in the life cycle of insulin, from its synthesis and secretion in pancreatic β-cells, to its signalling and degradation in target tissues. Finally, we consider how aberrant S-nitrosylation contributes to metabolic diseases, including the roles of human genetic mutations and cellular events that alter S-nitrosylation of insulin-regulating proteins. Given the growing influence of S-nitrosylation in cellular metabolism, the field of metabolic signalling could benefit from renewed focus on S-nitrosylation in type 2 diabetes mellitus and insulin-related disorders.
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Affiliation(s)
- Hua-Lin Zhou
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - Richard T Premont
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - Jonathan S Stamler
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
- Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA.
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Langer S, Waterstradt R, Hillebrand G, Santer R, Baltrusch S. The novel GCK variant p.Val455Leu associated with hyperinsulinism is susceptible to allosteric activation and is conducive to weight gain and the development of diabetes. Diabetologia 2021; 64:2687-2700. [PMID: 34532767 PMCID: PMC8563668 DOI: 10.1007/s00125-021-05553-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 06/21/2021] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS The mammalian enzyme glucokinase (GK), expressed predominantly in liver and pancreas, plays an essential role in carbohydrate metabolism. Monogenic GK disorders emphasise the role of GK in determining the blood glucose set point. METHODS A family with congenital hyperinsulinism (CHI) was examined for GCK gene variants by Sanger sequencing. A combined approach, involving kinetic analysis (also using GK activators and inhibitors), intracellular translocation assays, insulin secretion measurements and structural modelling, was used to investigate the novel variant compared with known variants. RESULTS We report on the novel gain-of-function GCK variant p.Val455Leu (V455L), inherited as an autosomal dominant trait in a German family with CHI and concomitant obesity (fasting blood glucose 2.1 mmol/l, BMI 45.0 kg/m2, HOMA-IR 1.5 in an adult female family member); one male family member developed type 2 diabetes until age 35 years (with fasting glucose 2.8-3.7 mmol/l, BMI 38.9 kg/m2, HOMA-IR 4.6). Kinetic characterisation of the V455L variant revealed a significant increase in glucose affinity (glucose concentration at which reaction rate is half its maximum rate [S0.5]: mutant 2.4 ± 0.3 mmol/l vs wild-type 7.6 ± 1.0 mmol/l), accompanied by a distinct additive susceptibility to both the endogenous activator fructose 2,6-bisphosphatase and the synthetic allosteric activator RO-28-1675. The effect of RO-28-1675 was more pronounced when compared with the previously known GK variants V455M and V455E. Binding to the inhibitor glucokinase regulatory protein was unimpaired for V455L and V455E but was reduced for V455M, whereas mannoheptulose inhibited all GK variants and the wild-type enzyme. Structural analyses suggested a role for residue 455 in rearrangements between the inactive and active conformations of GK and also in allosteric activation. Comparison with V455M and V455E and an overview of activating GK variants provided a context for the novel sequence aberration in terms of altered GK enzyme characteristics caused by single amino acid changes. CONCLUSION/INTERPRETATION We provide new knowledge on the structure-function relationship of GK, with special emphasis on enzyme activation, potentially yielding fresh strategic insights into breaking the vicious circle of fluctuating blood glucose levels and the attendant risk of long-lasting metabolic changes in both CHI and type 2 diabetes.
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Affiliation(s)
- Sara Langer
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Rostock, Rostock, Germany
| | - Rica Waterstradt
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Rostock, Rostock, Germany
| | - Georg Hillebrand
- Department of Pediatrics, University Medical Center Eppendorf, Hamburg, Germany
- Department of Pediatrics, Medical Center Itzehoe, Itzehoe, Germany
| | - René Santer
- Department of Pediatrics, University Medical Center Eppendorf, Hamburg, Germany
| | - Simone Baltrusch
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Rostock, Rostock, Germany.
- Department Life, Light & Matter, University of Rostock, Rostock, Germany.
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Abstract
BACKGROUND Hypoglycemia, the condition of low blood sugar, is a common occurance in people with diabetes using insulin therapy. Protecting against hypoglycaemia by engineering an insulin preparation that can auto-adjust its biological activity to fluctuating blood glucose levels has been pursued since the 1970s, but despite numerous publications, no system that works well enough for practical use has reached clinical practise. SCOPE OF REVIEW This review will summarise and scrutinise known approaches for producing glucose-sensitive insulin therapies. Notably, systems described in patent applications will be extensively covered, which has not been the case for earlier reviews of this area. MAJOR CONCLUSIONS The vast majority of published systems are not suitable for product development, but a few glucose-sensitive insulin concepts have recently reached clinical trials, and there is hope that glucose-sensitive insulin will become available to people with diabetes in the near future.
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Affiliation(s)
- Thomas Hoeg-Jensen
- Research Chemistry, Novo Nordisk A/S, Novo Nordisk Park H5.S.05, DK-2720 Maaloev, Denmark.
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Vincent O, Gutierrez-Nogués A, Trejo-Herrero A, Navas MA. A novel reverse two-hybrid method for the identification of missense mutations that disrupt protein-protein binding. Sci Rep 2020; 10:21043. [PMID: 33273586 PMCID: PMC7713115 DOI: 10.1038/s41598-020-77992-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/19/2020] [Indexed: 01/26/2023] Open
Abstract
The reverse two-hybrid system is a powerful method to select mutations that disrupt the interaction between two proteins and therefore to identify the residues involved in this interaction. However, the usefulness of this technique has been limited by its relative complexity when compared to the classical two-hybrid system, since an additional selection step is required to eliminate the high background of uninformative truncation mutants. We have developed a new method that combines the classical and reverse two-hybrid systems to select loss-of-binding missense mutations in a single step. The strategy used to select against truncation mutants is based on the two-hybrid interaction between a C-terminal fusion peptide and the Tsg101 protein. We have applied this method to identify mutations in human glucokinase (GK) that disrupt glucokinase regulatory protein (GKRP) binding. Our results indicate that this method is very efficient and eliminates all the truncation mutants and false positives. The mutated residues identified in GK are involved in the GKRP binding interface or in stabilizing the super-open conformation of GK that binds GKRP. This technique offers an improvement over existing methods in terms of speed, efficiency and simplicity and can be used to study any detectable protein interaction in the two-hybrid system.
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Affiliation(s)
- Olivier Vincent
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, 28029, Madrid, Spain.
| | - Angel Gutierrez-Nogués
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain
| | - Adrían Trejo-Herrero
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain
| | - María-Angeles Navas
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.
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Dautel DR, Champion JA. Protein Vesicles Self-Assembled from Functional Globular Proteins with Different Charge and Size. Biomacromolecules 2020; 22:116-125. [PMID: 32886493 DOI: 10.1021/acs.biomac.0c00671] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protein vesicles can be synthesized by mixing two fusion proteins: an elastin-like polypeptide (ELP) fused to an arginine-rich leucine zipper (ZR) with a globular, soluble protein fused to a glutamate-rich leucine zipper (ZE). Currently, only fluorescent proteins have been incorporated into vesicles; however, for protein vesicles to be useful for biocatalysis, drug delivery, or biosensing, vesicles must assemble from functional proteins that span an array of properties and functionalities. In this work, the globular protein was systematically changed to determine the effects of the surface charge and size on the self-assembly of protein vesicles. The formation of microphases, which included vesicles, coacervates, and hybrid structures, was monitored at different assembly conditions to determine the phase space for each globular protein. The results show that the protein surface charge has a small effect on vesicle self-assembly. However, increasing the size of the globular protein decreases the vesicle size and increases the stability at lower ZE/ZR molar ratios. The phase diagrams created can be used as guidelines to incorporate new functional proteins into vesicles. Furthermore, this work reports catalytically active enzyme vesicles, demonstrating the potential for the application of vesicles as biocatalysts or biosensors.
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Affiliation(s)
- Dylan R Dautel
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 950 Atlantic Drive NW, Atlanta, Georgia 30332, United States
| | - Julie A Champion
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 950 Atlantic Drive NW, Atlanta, Georgia 30332, United States
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Neonatal parenteral nutrition affects the metabolic flow of glucose in newborn and adult male Hartley guinea pigs' liver. J Dev Orig Health Dis 2020; 12:484-495. [PMID: 32741420 DOI: 10.1017/s2040174420000719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Extremely premature birth is associated with a permanent disruption of energy metabolism. The underlying mechanisms are poorly understood. The oxidative stress induced by parenteral nutrition (PN) during the first week of life is suspected to reprogram energy metabolism in the liver. Full-term male Hartley guinea pigs (to isolate PN from prematurity) receiving PN enriched or not with glutathione (to isolate PN effects from PN-induced oxidative stress effects) or an Oral Nutrition (ON) during the first week of life were used. At 1 week (neonatal) and 16 weeks (adult), measurements of liver glutathione (GSH and GSSG) and activities of three key enzymes of energy metabolism (glucokinase (GCK), phosphofructokinase (PFK), and acetyl-CoA carboxylase (ACC)) were performed. Differences between groups were reported if p ≤ 0.05 (Analysis of Variance). At 1 week, compared to ON, PN induced higher GSSG (oxidative stress), higher GCK activity, and lower PFK and ACC activity, the glutathione supplement prevented all PN effects. At 16 weeks, early PN induced lower GSSG (reductive stress) and lower GCK activity, which was prevented by added glutathione, and higher ACC activity independent of glutathione supplement. ACC was negatively associated (r2 = 0.33) with GSSG. Increased nicotinamide adenine dinucleotide phosphate levels confirmed the glucose-6-phosphate accumulation at 1 week, whereas our protocol failed to document lipid accumulation at 16 weeks. In adult male guinea pigs, neonatal exposure to PN affected glutathione metabolism leading to reductive stress (lower GSSG) and an altered metabolic flow of glucose. Partial prevention with glutathione supplementation suggests that, in addition to peroxides, other factors of PN are involved.
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Trefts E, Hughey CC, Lantier L, Lark DS, Boyd KL, Pozzi A, Zent R, Wasserman DH. Energy metabolism couples hepatocyte integrin-linked kinase to liver glucoregulation and postabsorptive responses of mice in an age-dependent manner. Am J Physiol Endocrinol Metab 2019; 316:E1118-E1135. [PMID: 30835508 PMCID: PMC6732653 DOI: 10.1152/ajpendo.00496.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Integrin-linked kinase (ILK) is a critical intracellular signaling node for integrin receptors. Its role in liver development is complex, as ILK deletion at E10.5 (before hepatocyte differentiation) results in biochemical and morphological differences that resolve as mice age. Nevertheless, mice with ILK depleted specifically in hepatocytes are protected from the hepatic insulin resistance during obesity. Despite the potential importance of hepatocyte ILK to metabolic health, it is unknown how ILK controls hepatic metabolism or glucoregulation. The present study tested the role of ILK in hepatic metabolism and glucoregulation by deleting it specifically in hepatocytes, using a cre-lox system that begins expression at E15.5 (after initiation of hepatocyte differentiation). These mice develop the most severe morphological and glucoregulatory abnormalities at 6 wk, but these gradually resolve with age. After identifying when the deletion of ILK caused a severe metabolic phenotype, in depth studies were performed at this time point to define the metabolic programs that coordinate control of glucoregulation that are regulated by ILK. We show that 6-wk-old ILK-deficient mice have higher glucose tolerance and decreased net glycogen synthesis. Additionally, ILK was shown to be necessary for transcription of mitochondrial-related genes, oxidative metabolism, and maintenance of cellular energy status. Thus, ILK is required for maintaining hepatic transcriptional and metabolic programs that sustain oxidative metabolism, which are required for hepatic maintenance of glucose homeostasis.
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Affiliation(s)
- Elijah Trefts
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee
| | - Curtis C Hughey
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee
| | - Louise Lantier
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee
- Mouse Metabolic Phenotyping Center, Vanderbilt University School of Medicine , Nashville, Tennessee
| | - Dan S Lark
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee
| | - Kelli L Boyd
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine , Nashville, Tennessee
| | - Ambra Pozzi
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee
- Department of Medicine, Vanderbilt University School of Medicine , Nashville, Tennessee
- Veterans Affairs Medical Center , Nashville, Tennessee
| | - Roy Zent
- Department of Medicine, Vanderbilt University School of Medicine , Nashville, Tennessee
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine , Nashville, Tennessee
- Veterans Affairs Medical Center , Nashville, Tennessee
| | - David H Wasserman
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee
- Mouse Metabolic Phenotyping Center, Vanderbilt University School of Medicine , Nashville, Tennessee
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Ben Lamine J, Boujbiha MA, Dahane S, Cherifa AB, Khlifi A, Chahdoura H, Yakoubi MT, Ferchichi S, El Ayeb N, Achour L. α-Amylase and α-glucosidase inhibitor effects and pancreatic response to diabetes mellitus on Wistar rats of Ephedra alata areal part decoction with immunohistochemical analyses. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:9739-9754. [PMID: 30729433 DOI: 10.1007/s11356-019-04339-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Accepted: 01/22/2019] [Indexed: 06/09/2023]
Abstract
Ephedra alata, known as a medicinal plant in China, was used in this study as aqueous extract from aerial parts, for diabetes mellitus treatment. This study was carried out on two parts, in vitro, we tested the effect of the studied extract on the inhibition of α-glucosidase and α-amylase activities, and in vivo on Wistar male rats receiving alloxan intraperitoneally at a rate of 125 mg/kg. Extract (100, 200, and 300 mg/kg of body weight) was administrated for 28 days by oral gavage. Blood glucose, amylase, lipase, and lipid profile level were determined. Oxidative stress was evaluated by enzymatic activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), and by estimation of lipid peroxidation and protein carbonyl (PC) level. Histopathological changes in pancreas were investigated under photonic microscopy using immunohistochemical procedure. Our findings showed that aqueous extract inhibited in vitro both α-glucosidase and α-amylase activities and its use in vivo at 300 mg/kg of body weight restored pancreas weight and weight gain, ameliorated significantly (p ˂ 0.05) biochemical parameters; it prevented the increase in lipid and protein oxidation and the decrease in enzymatic and non-enzymatic defense system. Histological study of treated animals showed a comparable healed regeneration of beta cells.
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Affiliation(s)
- Jihene Ben Lamine
- Institut Supérieur de Biotechnologie de Monastir, Laboratoire de Recherche : Bioressources, Biologie Intégrative & Valorisation, Université de Monastir, LR14ES06, BP 74, 5000, Monastir, Tunisia.
- Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092, Tunis, Tunisia.
| | - Mouhamed Ali Boujbiha
- Institut Supérieur de Biotechnologie de Monastir, Laboratoire de Recherche : Bioressources, Biologie Intégrative & Valorisation, Université de Monastir, LR14ES06, BP 74, 5000, Monastir, Tunisia
| | - Sabra Dahane
- Institut Supérieur de Biotechnologie de Monastir, Laboratoire de Recherche : Bioressources, Biologie Intégrative & Valorisation, Université de Monastir, LR14ES06, BP 74, 5000, Monastir, Tunisia
| | - Amal Ben Cherifa
- Institut Supérieur de Biotechnologie de Monastir, Laboratoire de Recherche : Bioressources, Biologie Intégrative & Valorisation, Université de Monastir, LR14ES06, BP 74, 5000, Monastir, Tunisia
- Faculté des Sciences de Gabes, Université de Gabes, Gabes, Tunisia
| | - Aida Khlifi
- Institut Supérieur de Biotechnologie de Monastir, Laboratoire de Recherche : Bioressources, Biologie Intégrative & Valorisation, Université de Monastir, LR14ES06, BP 74, 5000, Monastir, Tunisia
| | - Hassiba Chahdoura
- Institut Supérieur de Biotechnologie de Monastir, Laboratoire de Recherche : Bioressources, Biologie Intégrative & Valorisation, Université de Monastir, LR14ES06, BP 74, 5000, Monastir, Tunisia
| | - Mouhamed Taher Yakoubi
- Laboratoire d'anatomie et pathologie, Centre Hôpital Universitaire Farhat Hached, Sousse, Tunisia
| | - Salima Ferchichi
- Laboratoire de biochimie, Centre Hôpital Universitaire Farhat Hached, Sousse, Tunisia
| | - Nacer El Ayeb
- Institut Supérieur de Biotechnologie de Monastir, Laboratoire de Recherche : Bioressources, Biologie Intégrative & Valorisation, Université de Monastir, LR14ES06, BP 74, 5000, Monastir, Tunisia
| | - Lotfi Achour
- Institut Supérieur de Biotechnologie de Monastir, Laboratoire de Recherche : Bioressources, Biologie Intégrative & Valorisation, Université de Monastir, LR14ES06, BP 74, 5000, Monastir, Tunisia
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Zhao JG, Wang HY, Wei ZG, Zhang YQ. Therapeutic effects of ethanolic extract from the green cocoon shell of silkworm Bombyx mori on type 2 diabetic mice and its hypoglycaemic mechanism. Toxicol Res (Camb) 2019; 8:407-420. [PMID: 31160974 DOI: 10.1039/c8tx00294k] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 01/04/2019] [Indexed: 01/13/2023] Open
Abstract
Diabetes mellitus is a clinically complex disease characterized by hyperglycaemia with disturbances in carbohydrate, fat and protein metabolism. The aim of this study was to determine the therapeutic effect of ethanolic extract (EE) from the green cocoon sericin layer of silkworm Bombyx mori on mice with type 2 diabetes mellitus (T2DM) and its hypoglycaemic mechanisms. The results showed that oral EE for 7 weeks had significant ameliorative effects on all the biochemical parameters studied in vivo. The levels of oral glucose tolerance and insulin tolerance were significantly improved. The hypoglycaemic rate in the 350 mg kg-1 high dosage group was 39.38%. The levels of nuclear factor kappa B (NFκB), interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-α) in the high dosage EE-treated group were significantly reduced, while activities of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were obviously increased. The islet area and the number of insulin-positive beta cells increased significantly in the high dose group. Furthermore, expression levels of insulin receptor (IR), insulin receptor substrate (IRS), phosphatidylinositide 3-kinase (PI3K), p-Akt and phospho-glycogen synthase kinase-3β (p-GSK3β) involved in insulin signalling were increased. Adenosine 5'-monophosphate-activated protein kinase (AMPK) and glucose transporter 4 (GLUT4) also were activated to regulate glucose metabolism in EE-treated groups. The levels of glucose 6-phosphatase (G6pase) and phosphoenolpyruvate carboxykinase (PEPCK) decreased, while the glucokinase (GK) level increased to promote glycolysis. The results clearly indicated that oral EE, especially at a high dose, could improve the glucose metabolism of T2DM by reducing inflammatory reactions, enhancing the antioxidant capacity and insulin sensitivity, and regulating the balance between glycolysis and gluconeogenesis, which means that EE has potential ameliorative effects on T2DM mice.
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Affiliation(s)
- Jin-Ge Zhao
- Silk Biotechnology Laboratory , School of Biology and Basic Medical Sciences , Soochow University , China .
| | - Hai-Yan Wang
- Silk Biotechnology Laboratory , School of Biology and Basic Medical Sciences , Soochow University , China .
| | - Zheng-Guo Wei
- Silk Biotechnology Laboratory , School of Biology and Basic Medical Sciences , Soochow University , China .
| | - Yu-Qing Zhang
- Silk Biotechnology Laboratory , School of Biology and Basic Medical Sciences , Soochow University , China .
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Abstract
SIGNIFICANCE Hexokinases are key enzymes that are responsible for the first reaction of glycolysis, but they also moonlight other cellular processes, including mitochondrial redox signaling regulation. Modulation of hexokinase activity and spatiotemporal location by reactive oxygen and nitrogen species as well as other gasotransmitters serves as the basis for a unique, underexplored method of tight and flexible regulation of these fundamental enzymes. Recent Advances: Redox modifications of thiols serve as a molecular code that enables the precise and complex regulation of hexokinases. Redox regulation of hexokinases is also used by multiple parasites to cause widespread and severe diseases, including malaria, Chagas disease, and sleeping sickness. Redox-active molecules affect each other, and the moonlighting activity of hexokinases provides another feedback loop that affects the cellular redox status and is hijacked in malignantly transformed cells. CRITICAL ISSUES Several compounds affect the redox status of hexokinases in vivo. These include the dehydroascorbic acid (oxidized form of vitamin C), pyrrolidinium porrolidine-1-carbodithioate (contraceptive), peroxynitrite (product of ethanol metabolism), alloxan (a glucose analog), and isobenzothiazolinone ebselen. However, very limited information is available regarding which amino acid residues in hexokinases are affected by redox signaling. Except in cases of monogenic diabetes, direct evidence is absent for disease phenotypes that are associated with variations within motifs that are susceptible to redox signaling. FUTURE DIRECTIONS Further studies should address the propensity of hexokinases and their disease-associated variants to participate in redox regulation. Robust and straightforward proteomic methods are needed to understand the context and consequences of hexokinase-mediated redox regulation in health and disease.
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Affiliation(s)
- Petr Heneberg
- Third Faculty of Medicine, Charles University , Prague, Czech Republic
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Sternisha SM, Miller BG. Molecular and cellular regulation of human glucokinase. Arch Biochem Biophys 2019; 663:199-213. [PMID: 30641049 DOI: 10.1016/j.abb.2019.01.011] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 01/09/2019] [Accepted: 01/10/2019] [Indexed: 01/23/2023]
Abstract
Glucose metabolism in humans is tightly controlled by the activity of glucokinase (GCK). GCK is predominantly produced in the pancreas, where it catalyzes the rate-limiting step of insulin secretion, and in the liver, where it participates in glycogen synthesis. A multitude of disease-causing mutations within the gck gene have been identified. Activating mutations manifest themselves in the clinic as congenital hyperinsulinism, while loss-of-function mutations produce several diabetic conditions. Indeed, pharmaceutical companies have shown great interest in developing GCK-associated treatments for diabetic patients. Due to its essential role in maintaining whole-body glucose homeostasis, GCK activity is extensively regulated at multiple levels. GCK possesses a unique ability to self-regulate its own activity via slow conformational dynamics, which allows for a cooperative response to glucose. GCK is also subject to a number of protein-protein interactions and post-translational modification events that produce a broad range of physiological consequences. While significant advances in our understanding of these individual regulatory mechanisms have been recently achieved, how these strategies are integrated and coordinated within the cell is less clear. This review serves to synthesize the relevant findings and offer insights into the connections between molecular and cellular control of GCK.
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Affiliation(s)
- Shawn M Sternisha
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Brian G Miller
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA.
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15
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Hwang H, Rhim H. Functional significance of O-GlcNAc modification in regulating neuronal properties. Pharmacol Res 2017; 129:295-307. [PMID: 29223644 DOI: 10.1016/j.phrs.2017.12.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 11/17/2017] [Accepted: 12/04/2017] [Indexed: 12/22/2022]
Abstract
Post-translational modifications (PTMs) covalently modify proteins and diversify protein functions. Along with protein phosphorylation, another common PTM is the addition of O-linked β-N-acetylglucosamine (O-GlcNAc) to serine and/or threonine residues. O-GlcNAc modification is similar to phosphorylation in that it occurs to serine and threonine residues and cycles on and off with a similar time scale. However, a striking difference is that the addition and removal of the O-GlcNAc moiety on all substrates are mediated by the two enzymes regardless of proteins, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. O-GlcNAcylation can interact or potentially compete with phosphorylation on serine and threonine residues, and thus serves as an important molecular mechanism to modulate protein functions and activation. However, it has been challenging to address the role of O-GlcNAc modification in regulating protein functions at the molecular level due to the lack of convenient tools to determine the sites and degrees of O-GlcNAcylation. Studies in this field have only begun to expand significantly thanks to the recent advances in detection and manipulation methods such as quantitative proteomics and highly selective small-molecule inhibitors for OGT and OGA. Interestingly, multiple brain regions, especially hippocampus, express high levels of both OGT and OGA, and a number of neuron-specific proteins have been reported to undergo O-GlcNAcylation. This review aims to discuss the recent updates concerning the impacts of O-GlcNAc modification on neuronal functions at multiple levels ranging from intrinsic neuronal properties to synaptic plasticity and animal behaviors.
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Affiliation(s)
- Hongik Hwang
- Center for Neuroscience, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
| | - Hyewhon Rhim
- Center for Neuroscience, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Republic of Korea.
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Memory and synaptic plasticity are impaired by dysregulated hippocampal O-GlcNAcylation. Sci Rep 2017; 7:44921. [PMID: 28368052 PMCID: PMC5377249 DOI: 10.1038/srep44921] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 02/14/2017] [Indexed: 12/15/2022] Open
Abstract
O-GlcNAcylated proteins are abundant in the brain and are associated with neuronal functions and neurodegenerative diseases. Although several studies have reported the effects of aberrant regulation of O-GlcNAcylation on brain function, the roles of O-GlcNAcylation in synaptic function remain unclear. To understand the effect of aberrant O-GlcNAcylation on the brain, we used Oga+/− mice which have an increased level of O-GlcNAcylation, and found that Oga+/− mice exhibited impaired spatial learning and memory. Consistent with this result, Oga+/− mice showed a defect in hippocampal synaptic plasticity. Oga heterozygosity causes impairment of both long-term potentiation and long-term depression due to dysregulation of AMPA receptor phosphorylation. These results demonstrate a role for hyper-O-GlcNAcylation in learning and memory.
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Ou Y, Ren Z, Wang J, Yang X. Phycocyanin ameliorates alloxan-induced diabetes mellitus in mice: Involved in insulin signaling pathway and GK expression. Chem Biol Interact 2016; 247:49-54. [DOI: 10.1016/j.cbi.2016.01.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 01/14/2016] [Accepted: 01/22/2016] [Indexed: 11/16/2022]
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Francini F, Massa ML, Polo MP, Villagarcía H, Castro MC, Gagliardino JJ. Control of liver glucokinase activity: A potential new target for incretin hormones? Peptides 2015; 74:57-63. [PMID: 26524624 DOI: 10.1016/j.peptides.2015.10.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 10/13/2015] [Accepted: 10/26/2015] [Indexed: 12/27/2022]
Abstract
We tested the exendin-4 and des-fluoro-sitagliptin effects on fructose-induced increase in liver glucokinase activity in rats with impaired glucose tolerance and the exendin-4 effect on glucokinase activity in HepG2 cells incubated with fructose in the presence/absence of exendin-9-39. After 3 weeks of in vivo fructose administration we measured: (1) serum glucose, insulin and triglyceride levels; (2) liver and HepG2 cells glucokinase activity and (3) liver glucokinase and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase mRNA and protein levels. Fructose fed rats had: hypertriglyceridemia, hyperinsulinemia and high liver glucokinase activity (mainly located in the cytosolic fraction) together with higher glucokinase and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase mRNA and protein concentrations compared to control rats. Co-administration of either exendin-4 or des-fluoro-sitagliptin prevented serum and liver changes except glucokinase protein expression. Exendin-4 also prevented fructose-induced increase in glucokinase activity in cultured HepG2 cells, effect blunted by co-incubation with exendin-9-36. In conclusion exendin-4/des-fluro-sitagliptin prevented fructose-induced effect on glucokinase activity, mainly affecting enzyme activity modulators. Exendin 9-39 blunted in vitro protective exendin-4 effect on glucokinase activity, thus suggesting a direct effect of the later on hepatocytes through GLP-1 receptor. Alterations of glucokinase activity modulators could play a role in the pathogenesis of liver dysfunction, becoming a potential new treatment target for GLP-1 receptor agonists.
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Affiliation(s)
- Flavio Francini
- CENEXA (UNLP-CONICET CCT LA PLATA), PAHO/WHO Collaborating Centre for Diabetes, National University of La Plata School of Medicine, La Plata, Argentina.
| | - María Laura Massa
- CENEXA (UNLP-CONICET CCT LA PLATA), PAHO/WHO Collaborating Centre for Diabetes, National University of La Plata School of Medicine, La Plata, Argentina
| | | | - Hernán Villagarcía
- CENEXA (UNLP-CONICET CCT LA PLATA), PAHO/WHO Collaborating Centre for Diabetes, National University of La Plata School of Medicine, La Plata, Argentina
| | - María Cecilia Castro
- CENEXA (UNLP-CONICET CCT LA PLATA), PAHO/WHO Collaborating Centre for Diabetes, National University of La Plata School of Medicine, La Plata, Argentina
| | - Juan José Gagliardino
- CENEXA (UNLP-CONICET CCT LA PLATA), PAHO/WHO Collaborating Centre for Diabetes, National University of La Plata School of Medicine, La Plata, Argentina
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Gurgul-Convey E, Kaminski MT, Lenzen S. Physiological characterization of the human EndoC-βH1 β-cell line. Biochem Biophys Res Commun 2015; 464:13-9. [PMID: 26028562 DOI: 10.1016/j.bbrc.2015.05.072] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 05/20/2015] [Indexed: 12/11/2022]
Abstract
In the new human EndoC-βH1 β-cell line, a detailed analysis of the physiological characteristics was performed. This new human β-cell line expressed all target structures on the gene and protein level, which are crucial for physiological function and insulin secretion induced by glucose and other secretagogues. Glucose influx measurements revealed an excellent uptake capacity of EndoC-βH1 β-cells by the Glut1 and Glut2 glucose transporters. A high expression level of glucokinase enabled efficient glucose phosphorylation, increasing the ATP/ADP ratio along with stimulation of insulin secretion in the physiological glucose concentration range. The EC50 value of glucose for insulin secretion was 10.3 mM. Mannoheptulose, a specific glucokinase inhibitor, blocked glucose-induced insulin secretion (GSIS). The nutrient insulin secretagogues l-leucine and 2-ketoisocaproate also stimulated insulin secretion, with a potentiating effect of l-glutamine. The Kir 6.2 potassium channel blocker glibenclamide and Bay K 8644, an opener of the voltage-sensitive Ca(2+) channel significantly potentiated GSIS. Potentiation of GSIS by IBMX and forskolin went along with a strong stimulation of cAMP generation. In conclusion, the new human EndoC-βH1 β-cell line fully mirrors the analogous physiological characteristics of primary mouse, rat and human β-cells. Thus, this new human EndoC-βH1 β-cell line is very well suited for physiological β-cell studies.
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Affiliation(s)
- Ewa Gurgul-Convey
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Martin T Kaminski
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Sigurd Lenzen
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
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Azzouzi N, Barloy-Hubler F, Galibert F. Inventory of the cichlid olfactory receptor gene repertoires: identification of olfactory genes with more than one coding exon. BMC Genomics 2014; 15:586. [PMID: 25015101 PMCID: PMC4122780 DOI: 10.1186/1471-2164-15-586] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 07/01/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To help understand the molecular mechanisms underlying the remarkable phenotypic diversity displayed by cichlids, the genome sequences of O. niloticus, P. nyererei, H. burtoni, N. brichardi and M. zebra were recently determined. Here, we present the contents of the olfactory receptor (OR) repertoires in the genomes of these five fishes. RESULTS We performed an exhaustive TBLASTN search of the five cichlid genomes to identify their OR repertoires as completely as possible. We used as bait a set of ORs described in the literature. The cichlid repertoires thereby extracted contained large numbers of complete genes (O. niloticus 158; H. burtoni 90; M. zebra 102; N. brichardi 69; P. nyererei 88), a small numbers of pseudogenes and many "edge genes" corresponding to incomplete genes located at the ends of contigs. A phylogenetic tree was constructed and showed these repertoires include a large number of families and subfamilies. It also allowed the identification of a large number of OR analogues between cichlids with very high amino-acid identity (≥ 99%). Nearly 9% of the full-length cichlid OR genes are composed of several coding exons. This is very unusual for vertebrate OR genes. Nevertheless, the evidence is strong, and includes the donor and acceptor splice junction sequences; also, the positions of these genes in the phylogenetic tree indicate that they constitute subfamilies well apart from non-OR G protein-coupled receptor families. CONCLUSIONS Cichlid OR repertoires are made up of a larger number of genes and fewer pseudogenes than those in other teleosts except zebrafish. These ORs share all identified properties common to all fish ORs; however, the large number of families and subfamilies, each containing few ORs implies that they have evolved more rapidly. This high level of OR diversity is consistent with the substantial phenotypic diversity that characterizes cichlids.
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Affiliation(s)
| | | | - Francis Galibert
- Institut Génétique et Développement (UMR 6290) CNRS/Université de Rennes 1, Rennes, France.
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O-GlcNAcylation of AMPA receptor GluA2 is associated with a novel form of long-term depression at hippocampal synapses. J Neurosci 2014; 34:10-21. [PMID: 24381264 DOI: 10.1523/jneurosci.4761-12.2014] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Serine phosphorylation of AMPA receptor (AMPAR) subunits GluA1 and GluA2 modulates AMPAR trafficking during long-term changes in strength of hippocampal excitatory transmission required for normal learning and memory. The post-translational addition and removal of O-linked β-N-acetylglucosamine (O-GlcNAc) also occurs on serine residues. This, together with the high expression of the enzymes O-GlcNAc transferase (OGT) and β-N-acetylglucosamindase (O-GlcNAcase), suggests a potential role for O-GlcNAcylation in modifying synaptic efficacy and cognition. Furthermore, because key synaptic proteins are O-GlcNAcylated, this modification may be as important to brain function as phosphorylation, yet its physiological significance remains unknown. We report that acutely increasing O-GlcNAcylation in Sprague Dawley rat hippocampal slices induces an NMDA receptor and protein kinase C-independent long-term depression (LTD) at hippocampal CA3-CA1 synapses (O-GcNAc LTD). This LTD requires AMPAR GluA2 subunits, which we demonstrate are O-GlcNAcylated. Increasing O-GlcNAcylation interferes with long-term potentiation, and in hippocampal behavioral assays, it prevents novel object recognition and placement without affecting contextual fear conditioning. Our findings provide evidence that O-GlcNAcylation dynamically modulates hippocampal synaptic function and learning and memory, and suggest that altered O-GlcNAc levels could underlie cognitive dysfunction in neurological diseases.
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Abstract
Protein O-GlcNAcylation is an abundant, dynamic and reversible type of protein post-translational modification in animals that has been implicated in signalling processes linked to innate immunity, stress response, growth factor response, transcription, translation and proteosomal degradation. Only two enzymes, O-GlcNAc (O-linked N-acetylglucosamine) transferase and O-GlcNAcase, catalyse the reversible addition of the O-GlcNAc residue to over 1000 target proteins in the human cell. Recent advances in our understanding of the structures and mechanisms of these enzymes have resulted in the development of potent and selective inhibitors. The present review gives an overview of these inhibitors and how they have been used on cell lines, primary cells and animals to modulate O-GlcNAc levels and study the effects on signal transduction.
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Schermerhorn T. Normal glucose metabolism in carnivores overlaps with diabetes pathology in non-carnivores. Front Endocrinol (Lausanne) 2013; 4:188. [PMID: 24348462 PMCID: PMC3847661 DOI: 10.3389/fendo.2013.00188] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 11/19/2013] [Indexed: 12/15/2022] Open
Abstract
Carnivores, such as the dolphin and the domestic cat, have numerous adaptations that befit consumption of diets with high protein and fat content, with little carbohydrate content. Consequently, nutrient metabolism in carnivorous species differs substantially from that of non-carnivores. Important metabolic pathways known to differ between carnivores and non-carnivores are implicated in the development of diabetes and insulin resistance in non-carnivores: (1) the hepatic glucokinase (GCK) pathway is absent in healthy carnivores yet GCK deficiency may result in diabetes in rodents and humans, (2) healthy dolphins and cats are prone to periods of fasting hyperglycemia and exhibit insulin resistance, both of which are risk factors for diabetes in non-carnivores. Similarly, carnivores develop naturally occurring diseases such as hemochromatosis, fatty liver, obesity, and diabetes that have strong parallels with the same disorders in humans. Understanding how evolution, environment, diet, and domestication may play a role with nutrient metabolism in the dolphin and cat may also be relevant to human diabetes.
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Affiliation(s)
- Thomas Schermerhorn
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
- *Correspondence: Thomas Schermerhorn, Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, 1800 Denison Avenue, Manhattan, KS 66506-5606, USA e-mail:
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Meitzler JL, Hinde S, Bánfi B, Nauseef WM, Ortiz de Montellano PR. Conserved cysteine residues provide a protein-protein interaction surface in dual oxidase (DUOX) proteins. J Biol Chem 2013; 288:7147-57. [PMID: 23362256 DOI: 10.1074/jbc.m112.414797] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Intramolecular disulfide bond formation is promoted in oxidizing extracellular and endoplasmic reticulum compartments and often contributes to protein stability and function. DUOX1 and DUOX2 are distinguished from other members of the NOX protein family by the presence of a unique extracellular N-terminal region. These peroxidase-like domains lack the conserved cysteines that confer structural stability to mammalian peroxidases. Sequence-based structure predictions suggest that the thiol groups present are solvent-exposed on a single protein surface and are too distant to support intramolecular disulfide bond formation. To investigate the role of these thiol residues, we introduced four individual cysteine to glycine mutations in the peroxidase-like domains of both human DUOXs and purified the recombinant proteins. The mutations caused little change in the stabilities of the monomeric proteins, supporting the hypothesis that the thiol residues are solvent-exposed and not involved in disulfide bonds that are critical for structural integrity. However, the ability of the isolated hDUOX1 peroxidase-like domain to dimerize was altered, suggesting a role for these cysteines in protein-protein interactions that could facilitate homodimerization of the peroxidase-like domain or, in the full-length protein, heterodimeric interactions with a maturation protein. When full-length hDUOX1 was expressed in HEK293 cells, the mutations resulted in decreased H2O2 production that correlated with a decreased amount of the enzyme localized to the membrane surface rather than with a loss of activity or with a failure to synthesize the mutant proteins. These results support a role for the cysteine residues in intermolecular disulfide bond formation with the DUOX maturation factor DUOXA1.
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Affiliation(s)
- Jennifer L Meitzler
- Laboratory of Molecular Pharmacology of the Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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Dhanesha N, Joharapurkar A, Shah G, Dhote V, Kshirsagar S, Bahekar R, Jain M. Exendin-4 ameliorates diabetic symptoms through activation of glucokinase. J Diabetes 2012; 4:369-77. [PMID: 22356440 DOI: 10.1111/j.1753-0407.2012.00193.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Glucagon-like peptide-1 (GLP-1) and its stable analogue exendin-4 maintain glucose homeostasis by modulating insulin secretion from pancreatic β-cells and controlling hepatic glucose output. Glucokinase (GK), by catalysing the first step in glycolysis, plays an important role in glucose-stimulated insulin secretion and hepatic glucose metabolism. In the present study, we investigated the effects of exendin-4 on GK in high fat-fed and alloxan-treated diabetic mice. METHODS The effects of alloxan (5, 10 and 20 μmol/L) on insulin release from isolated murine islets, as well as glycogen synthesis by isolated murine hepatocytes, were assessed. The effects of exendin-4 (10 nmol/kg, twice daily for 4 weeks) were assessed in high fat-fed, alloxan (50 mg/kg, i.v.)-treated C57 mice. Glucokinase activity was assessed in the same model. RESULTS Pretreatment with exendin-4 attenuated alloxan-induced decreases in insulin release and glycogen synthesis in islets and hepatocytes. The alloxan-induced decrease in the GK activity in islets and hepatocytes was also ameliorated by exendin-4 treatment. Pretreatment with the GLP-1 receptor antagonist exendin-9 (100 nmol/L) blocked the effects of exendin-4 on the liver and pancreas. Treatment of high-fat fed, alloxan-treated diabetic mice with exendin-4 (10 nmol/L, i.p.) reduced the severity of diabetic symptoms. Specifically, exendin-4 treatment reduced serum glucose by 50% and %HbA1c by 24% compared with control and significantly decreased HOMA-IR by 39% and increased HOMA-β by 150%. In addition, exendin-4 treatment significantly reduced body weight by 6.8% and serum triglycerides by 35%. CONCLUSIONS The results indicate that glucose-stimulated insulin release and glycogen synthesis are decreased by alloxan due to reduced GK activity. These findings provide further insight into the mechanism by which exendin-4 regulates glucose homeostasis.
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Affiliation(s)
- Nirav Dhanesha
- Department of Pharmacology and Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Ahmedabad, India
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Ou Y, Lin L, Pan Q, Yang X, Cheng X. Preventive effect of phycocyanin from Spirulina platensis on alloxan-injured mice. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2012; 34:721-726. [PMID: 23121873 DOI: 10.1016/j.etap.2012.09.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 09/27/2012] [Accepted: 09/30/2012] [Indexed: 06/01/2023]
Abstract
The preventive effect of phycocyanin (obtained from Spirulina platensis) on alloxan-injured mice is investigated. Oral administration of phycocyanin was started two weeks before an alloxan injury and continued until four weeks later. Tests resulted in the following positive results of oral phycocyanin administration on alloxan-injured mice: decrease fasting blood glucose and glycosylated serum protein (GSP); maintain total antioxidative capability (T-AOC); avert malondialdehyde (MDA) formation in the liver, kidney, and pancreas; decrease total cholesterol (TC) level and triglycerides (TG) level in serum and liver; increase the levels of hepatic glycogen level; maintain glucokinase (GK) expression in the liver and decrease p53 expression in the pancreas at mRNA level. The histological observations also supported the above results. Acute toxicity study further shows that phycocyanin is relatively safe. These results led to the conclusion that phycocyanin has significant preventive effect on alloxan-injured mice. The inhibition of p53 pathway could be one of the mechanisms that led to the protection of pancreatic islets from alloxan injury. We also proposed that GK expression that functions to promote liver glycogen synthesis could be the reason for reduced blood glucose level. The encouraging results are the first step in studying the potential of phycocyanin as a clinical measure in preventing diabetes.
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Affiliation(s)
- Yu Ou
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China.
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Prabakaran D, Ashokkumar N. Antihyperglycemic effect of esculetin modulated carbohydrate metabolic enzymes activities in streptozotocin induced diabetic rats. J Funct Foods 2012. [DOI: 10.1016/j.jff.2012.05.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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Markwardt ML, Nkobena A, Ding SY, Rizzo MA. Association with nitric oxide synthase on insulin secretory granules regulates glucokinase protein levels. Mol Endocrinol 2012; 26:1617-29. [PMID: 22771492 PMCID: PMC3434526 DOI: 10.1210/me.2012-1183] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 06/19/2012] [Indexed: 11/19/2022] Open
Abstract
Glucokinase (GCK) association with insulin-secretory granules is controlled by interaction with nitric oxide synthase (NOS) and is reversed by GCK S-nitrosylation. Nonetheless, the function of GCK sequestration on secretory granules is unknown. Here we report that the S-nitrosylation blocking V367M mutation prevents GCK accumulation on secretory granules by inhibiting association with NOS. Expression of this mutant is reduced compared with a second S-nitrosylation blocking GCK mutant (C371S) that accumulates to secretory granules and is expressed at levels greater than wild type. Even so, the rate of degradation for wild type and mutant GCK proteins were not significantly different from one another, and neither mutation disrupted the ability of GCK to be ubiquitinated. Furthermore, gene silencing of NOS reduced endogenous GCK content but did not affect β-actin content. Treatment of GCK(C371S) expressing cells with short interfering RNA specific for NOS also blocked accumulation of this protein to secretory granules and reduced expression levels to that of GCK(V367M). Conversely, cotransfection of catalytically inactive NOS increased GCK-mCherry levels. Expression of GCK(C371S) in βTC3 cells enhanced glucose metabolism compared with untransfected cells and cells expressing wild type GCK, even though this mutant has slightly reduced enzymatic activity in vitro. Finally, molecular dynamics simulations revealed that V367M induces conformational changes in GCK that are similar to S-nitrosylated GCK, thereby suggesting a mechanism for V367M-inhibition of NOS association. Our findings suggest that sequestration of GCK on secretory granules regulates cellular GCK protein content, and thus cellular GCK activity, by acting as a storage pool for GCK proteins.
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Affiliation(s)
- Michele L Markwardt
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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29
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Casiopeina II-gly and bromo-pyruvate inhibition of tumor hexokinase, glycolysis, and oxidative phosphorylation. Arch Toxicol 2012; 86:753-66. [DOI: 10.1007/s00204-012-0809-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 01/31/2012] [Indexed: 10/28/2022]
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Cullen KS, Matschinsky FM, Agius L, Arden C. Susceptibility of glucokinase-MODY mutants to inactivation by oxidative stress in pancreatic β-cells. Diabetes 2011; 60:3175-85. [PMID: 22028181 PMCID: PMC3219952 DOI: 10.2337/db11-0423] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 08/31/2011] [Indexed: 12/19/2022]
Abstract
OBJECTIVE The posttranslational regulation of glucokinase (GK) differs in hepatocytes and pancreatic β-cells. We tested the hypothesis that GK mutants that cause maturity-onset diabetes of the young (GK-MODY) show compromised activity and posttranslational regulation in β-cells. RESEARCH DESIGN AND METHODS Activity and protein expression of GK-MODY and persistent hyperinsulinemic hypoglycemia of infancy (PHHI) mutants were studied in β-cell (MIN6) and non-β-cell (H4IIE) models. Binding of GK to phosphofructo-2-kinase, fructose-2,6-bisphosphatase (PFK2/FBPase2) was studied by bimolecular fluorescence complementation in cell-based models. RESULTS Nine of 11 GK-MODY mutants that have minimal effect on enzyme kinetics in vitro showed decreased specific activity relative to wild type when expressed in β-cells. A subset of these were stable in non-β-cells but showed increased inactivation in conditions of oxidative stress and partial reversal of inactivation by dithiothreitol. Unlike the GK-MODY mutants, four of five GK-PHHI mutants had similar specific activity to wild type and Y214C had higher activity than wild type. The GK-binding protein PFK2/FBPase2 protected wild-type GK from oxidative inactivation and the decreased stability of GK-MODY mutants correlated with decreased interaction with PFK2/FBPase2. CONCLUSIONS Several GK-MODY mutants show posttranslational defects in β-cells characterized by increased susceptibility to oxidative stress and/or protein instability. Regulation of GK activity through modulation of thiol status may be a physiological regulatory mechanism for the control of GK activity in β-cells.
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Affiliation(s)
- Kirsty S. Cullen
- Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, U.K
| | - Franz M. Matschinsky
- Department of Biochemistry and Biophysics and Institute for Diabetes, Obesity and Metabolism, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Loranne Agius
- Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, U.K
| | - Catherine Arden
- Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, U.K
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31
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Ding SY, Nkobena A, Kraft CA, Markwardt ML, Rizzo MA. Glucagon-like peptide 1 stimulates post-translational activation of glucokinase in pancreatic beta cells. J Biol Chem 2011; 286:16768-74. [PMID: 21454584 DOI: 10.1074/jbc.m110.192799] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucagon-like peptide 1 (GLP-1) potentiates glucose-stimulated insulin secretion from pancreatic β cells, yet does not directly stimulate secretion. The mechanisms underlying this phenomenon are incompletely understood. Here, we report that GLP-1 augments glucose-dependent rises in NAD(P)H autofluorescence in both βTC3 insulinoma cells and islets in a manner consistent with post-translational activation of glucokinase (GCK). GLP-1 treatment increased GCK activity and enhanced GCK S-nitrosylation in βTC3 cells. A 2-fold increase in S-nitrosylated GCK was also observed in mouse islets. Furthermore, GLP-1 activated a FRET-based GCK reporter in living cells. Activation of this reporter was sensitive to inhibition of nitric-oxide synthase (NOS), and incorporating the S-nitrosylation-blocking V367M mutation into this sensor prevented activation by GLP-1. GLP-1 potentiation of the glucose-dependent increase in islet NAD(P)H autofluorescence was also sensitive to a NOS inhibitor, whereas NOS inhibition did not affect the response to glucose alone. Expression of the GCK(V367M) mutant also blocked GLP-1 potentiation of the NAD(P)H response to glucose in βTC3 cells, but did not significantly affect metabolism of glucose in the absence of GLP-1. Co-expression of WT or mutant GCK proteins with a sensor for insulin secretory granule fusion also revealed that blockade of post-translational GCK S-nitrosylation diminished the effects of GLP-1 on granule exocytosis by ∼40% in βTC3 cells. These results suggest that post-translational activation of GCK is an important mechanism for mediating the insulinotropic effects of GLP-1.
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Affiliation(s)
- Shi-Ying Ding
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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32
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Chatham JC, Marchase RB. The role of protein O-linked beta-N-acetylglucosamine in mediating cardiac stress responses. BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1800:57-66. [PMID: 19607882 PMCID: PMC2814923 DOI: 10.1016/j.bbagen.2009.07.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Revised: 07/01/2009] [Accepted: 07/06/2009] [Indexed: 11/24/2022]
Abstract
The modification of serine and threonine residues of nuclear and cytoplasmic proteins by O-linked beta-N-acetylglucosamine (O-GlcNAc) has emerged as a highly dynamic post-translational modification that plays a critical role in regulating numerous biological processes. Much of our understanding of the mechanisms underlying the role of O-GlcNAc on cellular function has been in the context of its adverse effects in mediating a range of chronic disease processes, including diabetes, cancer and neurodegenerative diseases. However, at the cellular level it has been shown that O-GlcNAc levels are increased in response to stress; augmentation of this response improved cell survival while attenuation decreased cell viability. Thus, it has become apparent that strategies that augment O-GlcNAc levels are pro-survival, whereas those that reduce O-GlcNAc levels decrease cell survival. There is a long history demonstrating the effectiveness of acute glucose-insulin-potassium (GIK) treatment and to a lesser extent glutamine in protecting against a range of stresses, including myocardial ischemia. A common feature of these approaches for metabolic cardioprotection is that they both have the potential to stimulate O-GlcNAc synthesis. Consequently, here we examine the links between metabolic cardioprotection with the ischemic cardioprotection associated with acute increases in O-GlcNAc levels. Some of the protective mechanisms associated with activation of O-GlcNAcylation appear to be transcriptionally mediated; however, there is also strong evidence to suggest that transcriptionally independent mechanisms also play a critical role. In this context we discuss the potential link between O-GlcNAcylation and cardiomyocyte calcium homeostasis including the role of non-voltage gated, capacitative calcium entry as a potential mechanism contributing to this protection.
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Affiliation(s)
- John C Chatham
- Department of Medicine, Division of Cardiovascular Disease, Center for Free Radical Biology, Center for Aging and Clinical Nutrition Research Center, University of Alabama at Birmingham, Birmingham, AL, USA.
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33
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Ding SY, Tribble ND, Kraft CA, Markwardt M, Gloyn AL, Rizzo MA. Naturally occurring glucokinase mutations are associated with defects in posttranslational S-nitrosylation. Mol Endocrinol 2009; 24:171-7. [PMID: 19934346 DOI: 10.1210/me.2009-0138] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Posttranslational activation of glucokinase (GCK) through S-nitrosylation has been recently observed in the insulin-secreting pancreatic beta-cell; however, the function of this molecular mechanism in regulating the physiology of insulin secretion is not well understood. To more fully understand the function of posttranslational regulation of GCK, we examined two naturally occurring GCK mutations that map to residues proximal to the S-nitrosylated cysteine and cause mild fasting hyperglycemia (maturity-onset diabetes of the young; subtype glucokinase). The kinetics of recombinantly generated GCK-R369P and GCK-V367M were assessed in vitro. The GCK-R369P protein has greatly reduced catalytic activity (relative activity index 0.05 vs. 1.00 for wild type), whereas the GCK-V367M has near normal kinetics (relative activity index 1.26 vs. 1.00 for wild type). Quantitative imaging and biochemical assays were used to assess the effect of these mutants on the metabolic response to glucose, GCK activation, and S-nitrosylation of GCK in betaTC3 insulinoma cells. Expression of either mutant in betaTC3 cells did not affect the metabolic response to 5 mM glucose. However, expression of either mutant blocked the effects of insulin on glucose-stimulated nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate reduction, suggesting defects in posttranslational regulation of GCK. Each of these mutations blocked GCK activation, and prevented posttranslational cysteine S-nitrosylation. Our findings link defects in hormone-regulated GCK S-nitrosylation to hyperglycemia and support a role for posttranslational regulation of GCK S-nitrosylation as a vital regulatory mechanism for glucose-stimulated insulin secretion.
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Affiliation(s)
- Shi-Ying Ding
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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Francini F, Castro MC, Gagliardino JJ, Massa ML. Regulation of liver glucokinase activity in rats with fructose-induced insulin resistance and impaired glucose and lipid metabolism. Can J Physiol Pharmacol 2009; 87:702-10. [DOI: 10.1139/y09-064] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We evaluated the relative role of different regulatory mechanisms, particularly 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (PFK2/FBPase-2), in liver glucokinase (GK) activity in intact animals with fructose-induced insulin resistance and impaired glucose and lipid metabolism. We measured blood glucose, triglyceride and insulin concentration, glucose tolerance, liver triglyceride content, GK activity, and GK and PFK2 protein and gene expression in fructose-rich diet (FRD) and control rats. After 3 weeks, FRD rats had significantly higher blood glucose, insulin and triglyceride levels, and liver triglyceride content, insulin resistance, and impaired glucose tolerance. FRD rats also had significantly higher GK activity in the cytosolic fraction (18.3 ± 0.35 vs. 11.27 ± 0.34 mU/mg protein). Differences in GK protein concentration (116% and 100%) were not significant, suggesting a potentially impaired GK translocation in FRD rats. Although GK transcription level was similar, PFK2 gene expression and protein concentration were 4- and 5-fold higher in the cytosolic fraction of FRD animals. PFK2 immunological blockage significantly decreased GK activity in control and FRD rats; in the latter, this blockage decreased GK activity to control levels. Results suggest that increased liver GK activity might participate in the adaptative response to fructose overload to maintain glucose/triglyceride homeostasis in intact animals. Under these conditions, PFK2 increase would be the main enhancer of GK activity.
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Affiliation(s)
- Flavio Francini
- CENEXA / Center for Experimental and Applied Endocrinology (UNLP-CONICET, PAHO/WHO Collaborating Center for Diabetes), National University of La Plata, School of Medicine, 1900 La Plata, Argentina
| | - María C. Castro
- CENEXA / Center for Experimental and Applied Endocrinology (UNLP-CONICET, PAHO/WHO Collaborating Center for Diabetes), National University of La Plata, School of Medicine, 1900 La Plata, Argentina
| | - Juan J. Gagliardino
- CENEXA / Center for Experimental and Applied Endocrinology (UNLP-CONICET, PAHO/WHO Collaborating Center for Diabetes), National University of La Plata, School of Medicine, 1900 La Plata, Argentina
| | - María L. Massa
- CENEXA / Center for Experimental and Applied Endocrinology (UNLP-CONICET, PAHO/WHO Collaborating Center for Diabetes), National University of La Plata, School of Medicine, 1900 La Plata, Argentina
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35
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Contarteze RVL, de Alencar Mota CS, de Oliveira CAM, de Almeida Leme JAC, Bottcher LB, de Mello MAR, Luciano E. Exercise test and glucose homeostasis in rats treated with alloxan during the neonatal period or fed a high calorie diet. J Diabetes 2009; 1:65-72. [PMID: 20923522 DOI: 10.1111/j.1753-0407.2008.00003.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Animal models appear well-suited for studies into the role of exercise in the prevention of non-insulin-dependent diabetes mellitus (NIDDM). The aim of the present study was to analyze glucose homeostasis and blood lactate during an exercise swimming test in rats treated with alloxan during the neonatal period and/or fed a high calorie diet from weaning onwards. METHODS Rats were injected with alloxan (200 mg/kg, i.p.) or vehicle (citrate buffer) at 6 days of age. After weaning, rats were divided into four groups and fed either a balanced diet or a high-caloric diet as follows: C, control group (vehicle + normal diet); A, alloxan-treated rats fed the normal diet; H, vehicle-treated rats fed the high-caloric diet; and HA, alloxan-treated rats fed the high-caloric diet. RESULTS Fasting serum glucose levels were higher in groups A and AH compared with the control group. The Homeostatic Model Assessment index varied in the groups as follows: H>A>HA = C. There were no differences in free fatty acids or blood lactate concentrations during the swim test. CONCLUSIONS Alloxan-treated rats fed a normal or high-caloric diet have the potential to be used in studies analyzing the role physical exercise plays in the prevention of NIDDM.
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MESH Headings
- Age Factors
- Aging
- Animals
- Animals, Newborn
- Biomarkers/blood
- Blood Glucose/metabolism
- Diabetes Mellitus, Experimental/blood
- Diabetes Mellitus, Experimental/etiology
- Diabetes Mellitus, Experimental/physiopathology
- Diabetes Mellitus, Experimental/prevention & control
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/etiology
- Diabetes Mellitus, Type 2/prevention & control
- Energy Intake
- Fatty Acids, Nonesterified/blood
- Glucose Intolerance/blood
- Glucose Intolerance/etiology
- Glucose Intolerance/prevention & control
- Glucose Tolerance Test
- Homeostasis
- Insulin/blood
- Insulin Resistance
- Lactic Acid/blood
- Male
- Physical Exertion
- Rats
- Rats, Wistar
- Swimming
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Zhang X, Liang W, Mao Y, Li H, Yang Y, Tan H. Hepatic glucokinase activity is the primary defect in alloxan-induced diabetes of mice. Biomed Pharmacother 2009; 63:180-6. [PMID: 17768029 DOI: 10.1016/j.biopha.2007.07.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Accepted: 07/18/2007] [Indexed: 10/22/2022] Open
Abstract
Alloxan is a classical diabetogen which is used to achieve beta-cell destruction and type 1 diabetes due to its selective cytotoxic effect on pancreatic beta-cells. Although alloxan-induced diabetes is widely used in the laboratory to mimic diabetic pathology and for screening antidiabetic drugs, there has not been any comprehensive research in vivo on its diabetogenicity. In our study, alloxan-induced diabetic mice were generated by a single intravenous injection of alloxan (100 mg/kg). Our data show that these mice possess hyperglycemia, hypoinsulinism and morphological characteristics of impaired pancreas that are consistent with the accepted diabetogenic effects of alloxan. Alloxan is believed to confer its diabetogenic effect by inhibiting pancreatic glucokinase activity, leading to pancreatic beta-cell death. We examined the effects of alloxon on the other major site of glucokinase expression, the liver. Our results show that alloxan treatment led to an 81% reduction in glucokinase immunoreactivity and a greater than 90% reduction in glucokinase enzymatic activity in the liver, suggesting that alloxan's toxicity is not specific to the pancreas. Given the important role of glucokinase as a glucose sensor, and our findings on the effects of alloxon on liver glucokinase activity we propose that the effects on the liver are the primary contributor to pathogenesis in alloxan-induced diabetes. Alloxan-induced diabetes is thus a multifactor-promoted diabetes model which still could be used to examine the antidiabetic effects of compounds prompting insulin secretion and increasing liver-specific glucokinase activity. Despite alloxan-induced diabetes being inconsistent with the natural pathogenesis of human diabetes, further research on the causes of decreased glucokinase activity will help us to unravel the pathogenesis of diabetes and its complications.
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Affiliation(s)
- Xuemei Zhang
- Department of Pharmacology, College of Medicine, Dalian University, Dalian 116622, PR China
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Abstract
3-BrPA (3-bromopyruvate) is an alkylating agent with anti-tumoral activity on hepatocellular carcinoma. This compound inhibits cellular ATP production owing to its action on glycolysis and oxidative phosphorylation; however, the specific metabolic steps and mechanisms of 3-BrPA action in human hepatocellular carcinomas, particularly its effects on mitochondrial energetics, are poorly understood. In the present study it was found that incubation of HepG2 cells with a low concentration of 3-BrPA for a short period (150 microM for 30 min) significantly affected both glycolysis and mitochondrial respiratory functions. The activity of mitochondrial hexokinase was not inhibited by 150 microM 3-BrPA, but this concentration caused more than 70% inhibition of GAPDH (glyceraldehyde-3-phosphate dehydrogenase) and 3-phosphoglycerate kinase activities. Additionally, 3-BrPA treatment significantly impaired lactate production by HepG2 cells, even when glucose was withdrawn from the incubation medium. Oxygen consumption of HepG2 cells supported by either pyruvate/malate or succinate was inhibited when cells were pre-incubated with 3-BrPA in glucose-free medium. On the other hand, when cells were pre-incubated in glucose-supplemented medium, oxygen consumption was affected only when succinate was used as the oxidizable substrate. An increase in oligomycin-independent respiration was observed in HepG2 cells treated with 3-BrPA only when incubated in glucose-supplemented medium, indicating that 3-BrPA induces mitochondrial proton leakage as well as blocking the electron transport system. The activity of succinate dehydrogenase was inhibited by 70% by 3-BrPA treatment. These results suggest that the combined action of 3-BrPA on succinate dehydrogenase and on glycolysis, inhibiting steps downstream of the phosphorylation of glucose, play an important role in HepG2 cell death.
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38
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Lenzen S. The mechanisms of alloxan- and streptozotocin-induced diabetes. Diabetologia 2008; 51:216-26. [PMID: 18087688 DOI: 10.1007/s00125-007-0886-7] [Citation(s) in RCA: 1137] [Impact Index Per Article: 71.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2007] [Accepted: 10/08/2007] [Indexed: 12/17/2022]
Abstract
Alloxan and streptozotocin are toxic glucose analogues that preferentially accumulate in pancreatic beta cells via the GLUT2 glucose transporter. In the presence of intracellular thiols, especially glutathione, alloxan generates reactive oxygen species (ROS) in a cyclic redox reaction with its reduction product, dialuric acid. Autoxidation of dialuric acid generates superoxide radicals, hydrogen peroxide and, in a final iron-catalysed reaction step, hydroxyl radicals. These hydroxyl radicals are ultimately responsible for the death of the beta cells, which have a particularly low antioxidative defence capacity, and the ensuing state of insulin-dependent 'alloxan diabetes'. As a thiol reagent, alloxan also selectively inhibits glucose-induced insulin secretion through its ability to inhibit the beta cell glucose sensor glucokinase. Following its uptake into the beta cells, streptozotocin is split into its glucose and methylnitrosourea moiety. Owing to its alkylating properties, the latter modifies biological macromolecules, fragments DNA and destroys the beta cells, causing a state of insulin-dependent diabetes. The targeting of mitochondrial DNA, thereby impairing the signalling function of beta cell mitochondrial metabolism, also explains how streptozotocin is able to inhibit glucose-induced insulin secretion.
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Affiliation(s)
- S Lenzen
- Institute of Clinical Biochemistry, Hannover Medical School, 30623, Hannover, Germany
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39
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Arden C, Trainer A, de la Iglesia N, Scougall KT, Gloyn AL, Lange AJ, Shaw JAM, Matschinsky FM, Agius L. Cell biology assessment of glucokinase mutations V62M and G72R in pancreatic beta-cells: evidence for cellular instability of catalytic activity. Diabetes 2007; 56:1773-82. [PMID: 17389332 DOI: 10.2337/db06-1151] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations in the glucokinase (GK) gene cause defects in blood glucose homeostasis. In some cases (V62M and G72R), the phenotype cannot be explained by altered enzyme kinetics or protein instability. We used transient and stable expression of green fluorescent protein (GFP) GK chimaeras in MIN6 beta-cells to study the phenotype defect of V62M and G72R. GK activity in lysates of MIN6 cell lines stably expressing wild-type or mutant GFP GK showed the expected affinity for glucose and response to pharmacological activators, indicating the expression of catalytically active enzymes. MIN6 cells stably expressing GFP V62M or GFP G72R had a lower GK activity-to-GK immunoreactivity ratio and GK activity-to-GK mRNA ratio but not GK immunoreactivity-to-GK mRNA ratio than wild-type GFP GK. Heterologous expression of liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK2/FDP2) in cell lines increased GK activity for wild-type GK and V62M but not for G72R, whereas expression of liver GK regulatory protein (GKRP) increased GK activity for wild type but not V62M or G72R. Lack of interaction of these mutants with GKRP was also evident in hepatocyte transfections from the lack of nuclear accumulation. These results suggest that cellular loss of GK catalytic activity rather than impaired translation or enhanced protein degradation may account for the hyperglycemia in subjects with V62M and G72R mutations.
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Affiliation(s)
- Catherine Arden
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK
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40
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Kappler-Tanudyaya N, Schmitt H, Tippkötter N, Meyer L, Lenzen S, Ulber R. Combination of biotransformation and chromatography for the isolation and purification of mannoheptulose. Biotechnol J 2007; 2:692-9. [PMID: 17492712 DOI: 10.1002/biot.200700004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Mannoheptulose is a seven-carbon sugar. It is an inhibitor of glucose-induced insulin secretion due to its ability to selectively inhibit the enzyme glucokinase. An improved procedure for mannoheptulose isolation from avocados is described in this study (based upon the original method by La Forge). The study focuses on the combination of biotransformation and downstream processing (preparative chromatography) as an efficient method to produce a pure extract of mannoheptulose. The experiments were divided into two major phases. In the first phase, several methods and parameters were compared to optimize the mannoheptulose extraction with respect to efficiency and purity. In the second phase, a mass balance of mannoheptulose over the whole extraction process was undertaken to estimate the yield and efficiency of the total extraction process. The combination of biotransformation and preparative chromatography allowed the production of a pure mannoheptulose extract. In a biological test, the sugar inhibited the glucokinase enzyme activity efficiently.
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Affiliation(s)
- Nathalie Kappler-Tanudyaya
- Fachbereich Maschinenbau und Verfahrenstechnik, Technische Universität Kaiserslautern, Kaiserslautern, Germany
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Liu J, Marchase RB, Chatham JC. Glutamine-induced protection of isolated rat heart from ischemia/reperfusion injury is mediated via the hexosamine biosynthesis pathway and increased protein O-GlcNAc levels. J Mol Cell Cardiol 2006; 42:177-85. [PMID: 17069847 PMCID: PMC1779903 DOI: 10.1016/j.yjmcc.2006.09.015] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 08/31/2006] [Accepted: 09/20/2006] [Indexed: 11/29/2022]
Abstract
It has been shown that glutamine protects the heart from ischemia/reperfusion (I/R) injury; however, the mechanisms underlying this protection have not been identified. Glutamine:fructose-6-phosphate amidotransferase (GFAT) regulates the entry of glucose into the hexosamine biosynthesis pathway (HBP), and activation of this pathway has been shown to be cardioprotective. Glutamine is required for metabolism of glucose via GFAT; therefore, the goal of this study was to determine whether glutamine cardioprotection could be attributed to increased flux through the HBP and elevated levels of O-linked N-acetylglucosamine (O-GlcNAc) on proteins. Hearts from male rats were isolated and perfused with Krebs-Henseliet buffer containing 5 mM glucose, and global, no-flow ischemia was induced for 20 min followed by 60 min of reperfusion. Thirty-minute pre-treatment with 2.5 mM glutamine significantly improved functional recovery (RPP: 15.6+/-5.7% vs. 59.4+/-6.1%; p<0.05) and decreased cardiac troponin I release (25.4+/-3.0 vs. 4.7+/-1.9 ng/ml; p<0.05) during reperfusion. This protection was associated with a significant increase in the levels of protein O-GlcNAc and ATP. Pre-treatment with 80 muM azaserine, an inhibitor of GFAT, completely reversed the protection seen with glutamine and prevented the increase in protein O-GlcNAc. O-GlcNAc transferase (OGT) catalyzes the formation of O-GlcNAc, and inhibition of OGT with 5 mM alloxan also reversed the protection associated with glutamine. These data support the hypothesis that in the ex vivo perfused heart glutamine cardioprotection is due, at least in part, to enhanced flux through the HBP and increased protein O-GlcNAc levels.
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Affiliation(s)
| | | | - John C. Chatham
- Department of Cell Biology
- Department of Medicine, University of Alabama at Birmingham,
Birmingham, AL 35294
- Address correspondence to: John C. Chatham,
Department of Medicine, 684 MCLM Building, University of Alabama at Birmingham,
Birmingham, AL 35294-0005, Tel: 205 934-0240, Fax: 205 934-0950, e-mail:
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42
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Lee TN, Alborn WE, Knierman MD, Konrad RJ. Alloxan is an inhibitor of O-GlcNAc-selective N-acetyl-beta-D-glucosaminidase. Biochem Biophys Res Commun 2006; 350:1038-43. [PMID: 17045574 DOI: 10.1016/j.bbrc.2006.09.155] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Accepted: 09/27/2006] [Indexed: 11/30/2022]
Abstract
We have previously shown that streptozotocin (STZ) inhibits O-GlcNAc-selective N-acetyl-beta-d-glucosaminidase (O-GlcNAcase), the enzyme that removes O-GlcNAc from proteins. In light of this observation, we explored the possibility that the diabetogenic toxin alloxan, an O-GlcNAc transferase (OGT) inhibitor, might also inhibit O-GlcNAcase. Alloxan inhibited islet O-GlcNAcase with a dose-response much like that of STZ. Similar to STZ, islet O-GlcNAcase was more susceptible to alloxan inhibition than was brain O-GlcNAcase. Alloxan directly inhibited recombinant O-GlcNAcase activity with a dose-response very similar to that of STZ. Subsequent LC/MS/MS analysis revealed that alloxan modified the tryptic digest pattern of the enzyme. One tryptic peptide LGCFEIAK(894-901) was modified by alloxan. Two other tryptic peptides, LDQVSQFGCR(158-167) and SFALLFDDIDHNMCAADK(168-185), both N-terminal active site peptides, were absent after alloxan treatment. Together, these data demonstrate that alloxan is an inhibitor of O-GlcNAc-selective N-acetyl-beta-d-glucosaminidase, with inhibition corresponding to an altered tryptic digest pattern of N-terminal active site peptides.
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Affiliation(s)
- Thomas N Lee
- Eli Lilly and Company, Indianapolis, IN 46285, USA
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43
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Elsner M, Gurgul-Convey E, Lenzen S. Relative importance of cellular uptake and reactive oxygen species for the toxicity of alloxan and dialuric acid to insulin-producing cells. Free Radic Biol Med 2006; 41:825-34. [PMID: 16895803 DOI: 10.1016/j.freeradbiomed.2006.06.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 05/31/2006] [Accepted: 06/02/2006] [Indexed: 10/24/2022]
Abstract
The diabetogenic agent alloxan is selectively accumulated in insulin-producing cells through uptake via the GLUT2 glucose transporter in the plasma membrane. In the presence of intracellular thiols, especially glutathione, alloxan generates "reactive oxygen species" (ROS) in a cyclic reaction between this substance and its reduction product, dialuric acid. The cytotoxic action of alloxan is initiated by free radicals formed in this redox reaction. Autoxidation of dialuric acid generates superoxide radicals (O(2)(*-)) and hydrogen peroxide (H(2)O(2)), and finally hydroxyl radicals ((*)OH). Thus, while superoxide dismutase (SOD) only reduced the toxicity, catalase, in particular in the presence of SOD, provided complete protection of insulin-producing cells against the cytotoxic action of alloxan and dialuric acid due to H(2)O(2) destruction and the prevention of hydroxyl radical ((*)OH) formation, indicating that it is the hydroxyl radical ((*)OH) which is the ROS ultimately responsible for cell death. After selective accumulation in pancreatic beta cells, which are weakly protected against oxidative stress, the cytotoxic glucose analogue alloxan destroys these insulin-producing cells and causes a state of insulin-dependent diabetes mellitus through ROS-mediated toxicity in rodents and in other animal species, which express this glucose transporter isoform in their beta cells.
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Affiliation(s)
- Matthias Elsner
- Institute of Clinical Biochemistry, Hannover Medical School, 30623 Hannover, Germany
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44
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Champattanachai V, Marchase RB, Chatham JC. Glucosamine protects neonatal cardiomyocytes from ischemia-reperfusion injury via increased protein-associated O-GlcNAc. Am J Physiol Cell Physiol 2006; 292:C178-87. [PMID: 16899550 DOI: 10.1152/ajpcell.00162.2006] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Increased levels of protein O-linked N-acetylglucosamine (O-GlcNAc) have been shown to increase cell survival following stress. Therefore, the goal of this study was to determine whether in isolated neonatal rat ventricular myocytes (NRVMs) an increase in protein O-GlcNAcylation resulted in improved survival and viability following ischemia-reperfusion (I/R). NRVMs were exposed to 4 h of ischemia and 16 h of reperfusion, and cell viability, necrosis, apoptosis, and O-GlcNAc levels were assessed. Treatment of cells with glucosamine, hyperglycemia, or O-(2-acetamido-2-deoxy-D-glucopyranosylidene)-amino-N-phenylcarbamate(PUGNAc), an inhibitor of O-GlcNAcase, significantly increased O-GlcNAc levels and improved cell viability, as well as reducing both necrosis and apoptosis compared with untreated cells following I/R. Alloxan, an inhibitor of O-GlcNAc transferase, markedly reduced O-GlcNAc levels and exacerbated I/R injury. The improved survival with hyperglycemia was attenuated by azaserine, which inhibits glucose metabolism via the hexosamine biosynthesis pathway. Reperfusion in the absence of glucose reduced O-GlcNAc levels on reperfusion compared with normal glucose conditions and decreased cell viability. O-GlcNAc levels significantly correlated with cell viability during reperfusion. The effects of glucosamine and PUGNAc on cellular viability were associated with reduced calcineurin activation as measured by translocation of nuclear factor of activated T cells, suggesting that increased O-GlcNAc levels may attenuate I/R induced increase in cytosolic Ca(2+). These data support the concept that activation of metabolic pathways leading to an increase in O-GlcNAc levels is an endogenous stress-activated response and that augmentation of this response improves cell survival. Thus strategies designed to activate these pathways may represent novel interventions for inducing cardioprotection.
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Affiliation(s)
- Voraratt Champattanachai
- University of Alabama at Birmingham, 1530 3rd Avenue South, MCLM 684, Birmingham, AL 35294-0005, USA
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45
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Fülöp N, Marchase RB, Chatham JC. Role of protein O-linked N-acetyl-glucosamine in mediating cell function and survival in the cardiovascular system. Cardiovasc Res 2006; 73:288-97. [PMID: 16970929 PMCID: PMC2848961 DOI: 10.1016/j.cardiores.2006.07.018] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Revised: 07/14/2006] [Accepted: 07/18/2006] [Indexed: 10/24/2022] Open
Abstract
There is growing recognition that the O-linked attachment of N-acetyl-glucosamine (O-GlcNAc) on serine and threonine residues of nuclear and cytoplasmic proteins is a highly dynamic post-translational modification that plays a key role in signal transduction pathways. Numerous proteins have been identified as targets of O-GlcNAc modifications including kinases, phosphatases, transcription factors, metabolic enzymes, chaperons, and cytoskeletal proteins. Modulation of O-GlcNAc levels has been shown to modify DNA binding, enzyme activity, protein-protein interactions, the half-life of proteins, and subcellular localization. The level of O-GlcNAc is regulated in part by the metabolism of glucose via the hexosamine biosynthesis pathway (HBP), and the metabolic abnormalities associated with insulin resistance and diabetes, such as hyperglycemia, hyperlipidemia, and hyperinsulinemia, are all associated with increased flux through the HBP and elevated O-GlcNAc levels. Increased HBP flux and O-GlcNAc levels have been implicated in the impaired relaxation of isolated cardiomyocytes, blunted response to angiotensin II and phenylephrine, hyperglycemia-induced cardiomyocyte apoptosis, and endothelial and vascular cell dysfunction. In contrast to these adverse effects, recent studies have also shown that O-GlcNAc levels increase in response to acute stress and that this is associated with increased cell survival. Thus, while the relationship between O-GlcNAc levels and cellular function is complex and not well-understood, it is clear that these pathways play a critical role in the regulation of cell function and survival in the cardiovascular system and may be implicated in the adverse effects of metabolic disease on the heart.
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Affiliation(s)
- Norbert Fülöp
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama
| | - Richard B. Marchase
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama
- Corresponding Author: John C. Chatham, University of Alabama at Birmingham, Department of Medicine, 1530 3 Avenue South, MCLM 684, Birmingham, AL 35294-0005. Telephone: (205) 934-0240;Fax: (205) 934-0950;
| | - John C. Chatham
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama
- Corresponding Author: John C. Chatham, University of Alabama at Birmingham, Department of Medicine, 1530 3 Avenue South, MCLM 684, Birmingham, AL 35294-0005. Telephone: (205) 934-0240;Fax: (205) 934-0950;
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46
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Baltrusch S, Francini F, Lenzen S, Tiedge M. Interaction of glucokinase with the liver regulatory protein is conferred by leucine-asparagine motifs of the enzyme. Diabetes 2005; 54:2829-37. [PMID: 16186382 DOI: 10.2337/diabetes.54.10.2829] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The glucokinase regulatory protein (GRP) plays a pivotal role in the regulation of metabolic flux in liver by the glucose-phosphorylating enzyme glucokinase. Random peptide phage display library screening for binding partners of GRP allowed the identification of an asparagine-leucine consensus motif. Asparagine-leucine motifs of glucokinase located in the hinge region, as well as in the large domain, were changed by site-directed mutagenesis. The L58R/N204Y and the L309R/N313Y glucokinase mutants showed a significantly reduced interaction with GRP. The L355R/N350Y mutant had a fivefold-higher binding affinity for GRP than wild-type glucokinase. Imaging of glucokinase and GRP fluorescence fusion proteins revealed that the L58R/N204Y glucokinase mutant lacked glucose-dependent translocation by GRP, whereas the L355R/N350Y glucokinase mutant was trapped in the nucleus due to high affinity for GRP. The results indicate that the L58/N204 motif in the hinge region confers binding to GRP, while the L355/N350 motif may modulate the binding affinity for GRP. This latter motif is part of the alpha10 helix of glucokinase and accessible to GRP in the free and complex conformation.
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Affiliation(s)
- Simone Baltrusch
- Institute of Clinical Biochemistry, Hannover Medical School, D-30623 Hannover, Germany.
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47
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Méndez JD, Hernández RDH. l-Arginine and polyamine administration protect β-cells against alloxan diabetogenic effect in Sprague–Dawley rats. Biomed Pharmacother 2005; 59:283-9. [PMID: 15996850 DOI: 10.1016/j.biopha.2005.05.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Indexed: 11/30/2022] Open
Abstract
In the searching for new substances with the capacity to protect beta-cells from the toxic effects of alloxan, we evaluated the effect of L-arginine and the polyamines putrescine, spermidine and spermine in a murine experimental model of diabetes. Diabetes was induced by the i.p. injection of either 200 mg/kg (24-h experiments) or 120 mg/kg (12 days experiments) body weight. L-Arginine and polyamines were administered 10 min before or 10 min after alloxan administration, once its half-life had elapsed, respectively. In the 24-h study, serum glucose (199.8+/-27.6 mg/dl) and triglyceride (54.6+/-4.9 mg/dl) concentrations showed a protective effect of spermine, as these parameters were not too high (P < or = 0.05), compared to the alloxan-treated group (415.4+/-47.8 and 90.2+/-11.6 mg/dl, respectively), and were closer to glucose (132.3+/-6.0 mg/dl) and similar to triglycerides (63.8+/-7.1 mg/dl) of the control group. A similar pattern was observed on the parameters measured when L-arginine and polyamines were administered daily for 12 days, starting 10 min after a single alloxan administration, which provides evidence that L-arginine and polyamines are effective in impeding the increase in serum glucose, triglyceride and cholesterol concentration showed on day 3 by the alloxan-treated group, as well as a higher acinar cell regenerative capacity as determined by immunohistochemical techniques. Spermine turning out to be more effective than L-arginine, putrescine or spermidine in counteracting the marked hyperglycemia and triglyceridemia showed by the alloxan-treated group and similar in effect when evaluating cholesterolemia. These results show a clear protective role of L-arginine and polyamines over the pancreatic beta-cell, in addition to the induction of neogenesis from both ductal and acinar cells that leads to the recovery of endocrine pancreatic function in rats with experimental diabetes.
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Affiliation(s)
- José D Méndez
- Medical Research Unit in Metabolic Diseases, National Medical Center, Mexican Institute of Social Security, P.O. Box A-047, Mexico City, 06703 D.F., Mexico.
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48
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Arden C, Harbottle A, Baltrusch S, Tiedge M, Agius L. Glucokinase is an integral component of the insulin granules in glucose-responsive insulin secretory cells and does not translocate during glucose stimulation. Diabetes 2004; 53:2346-52. [PMID: 15331544 DOI: 10.2337/diabetes.53.9.2346] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The association of glucokinase with insulin secretory granules has been shown by cell microscopy techniques. We used MIN6 insulin-secretory cells and organelle fractionation to determine the effects of glucose on the subcellular distribution of glucokinase. After permeabilization with digitonin, 50% of total glucokinase remained bound intracellularly, while 30% was associated with the 13,000g particulate fraction. After density gradient fractionation of the organelles, immunoreactive glucokinase was distributed approximately equally between dense insulin granules and low-density organelles that cofractionate with mitochondria. Although MIN6 cells show glucose-responsive insulin secretion, glucokinase association with the granules and low-density organelles was not affected by glucose. Subfractionation of the insulin granule components by hypotonic lysis followed by sucrose gradient centrifugation showed that glucokinase colocalized with the granule membrane marker phogrin and not with insulin. PFK2 (6-phosphofructo-2-kinase-2/fructose-2,6-bisphosphatase)/FDPase-2, a glucokinase-binding protein, and glyceraldehyde phosphate dehydrogenase, which has been implicated in granule fusion, also colocalized with glucokinase after hypotonic lysis or detergent extaction of the granules. The results suggest that glucokinase is an integral component of the granule and does not translocate during glucose stimulation.
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Affiliation(s)
- Catherine Arden
- School of Clinical Medical Sciences-Diabetes, The Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, UK
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49
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Fridlyand LE, Philipson LH. Does the glucose-dependent insulin secretion mechanism itself cause oxidative stress in pancreatic beta-cells? Diabetes 2004; 53:1942-8. [PMID: 15277370 DOI: 10.2337/diabetes.53.8.1942] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucose-dependent insulin secretion (GDIS), reactive oxygen species (ROS) production, and oxidative stress in pancreatic beta-cells may be tightly linked processes. Here we suggest that the same pathways used in the activation of GDIS (increased glycolytic flux, ATP-to-ADP ratio, and intracellular Ca2+ concentration) can dramatically enhance ROS production and manifestations of oxidative stress and, possibly, apoptosis. The increase in ROS production and oxidative stress produced by GDIS activation itself suggests a dual role for metabolic insulin secretagogues, as an initial sharp increase in insulin secretion rate can be accompanied by progressive beta-cell injury. We propose that therapeutic strategies targeting enhancement of GDIS should be carefully considered in light of possible loss of beta-cell function and mass.
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Affiliation(s)
- Leonid E Fridlyand
- Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA
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50
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Massa L, Baltrusch S, Okar DA, Lange AJ, Lenzen S, Tiedge M. Interaction of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) with glucokinase activates glucose phosphorylation and glucose metabolism in insulin-producing cells. Diabetes 2004; 53:1020-9. [PMID: 15047617 DOI: 10.2337/diabetes.53.4.1020] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) was recently identified as a new intracellular binding partner for glucokinase (GK). Therefore, we studied the importance of this interaction for the activity status of GK and glucose metabolism in insulin-producing cells by overexpression of the rat liver and pancreatic islet isoforms of PFK-2/FBPase-2. PFK-2/FBPase-2 overexpression in RINm5F-GK cells significantly increased the GK activity by 78% in cells expressing the islet isoform, by 130% in cells expressing the liver isoform, and by 116% in cells expressing a cAMP-insensitive liver S32A/H258A double mutant isoform. Only in cells overexpressing the wild-type liver PFK-2/FBPase-2 isoform was the increase of GK activity abolished by forskolin, apparently due to the regulatory site for phosphorylation by a cAMP-dependent protein kinase. In cells overexpressing any isoform of the PFK-2/FBPase-2, the increase of the GK enzyme activity was antagonized by treatment with anti-FBPase-2 antibody. Increasing the glucose concentration from 2 to 10 mmol/l had a significant stimulatory effect on the GK activity in RINm5F-GK cells overexpressing any isoform of PFK-2/FBPase-2. The interaction of GK with PFK-2/FBPase-2 takes place at glucose concentrations that are physiologically relevant for the activation of GK and the regulation of glucose-induced insulin secretion. This new mechanism of posttranslational GK regulation may also represent a new site for pharmacotherapeutic intervention in type 2 diabetes treatment.
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Affiliation(s)
- Laura Massa
- Institute of Clinical Biochemistry, Hannover Medical School, Hannover, Germany
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