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Hawes EM, Rahim M, Haratipour Z, Orun AR, O'Rourke ML, Oeser JK, Kim K, Claxton DP, Blind RD, Young JD, O'Brien RM. Biochemical and metabolic characterization of a G6PC2 inhibitor. Biochimie 2024; 222:109-122. [PMID: 38431189 DOI: 10.1016/j.biochi.2024.02.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 02/28/2024] [Accepted: 02/29/2024] [Indexed: 03/05/2024]
Abstract
Three glucose-6-phosphatase catalytic subunits, that hydrolyze glucose-6-phosphate (G6P) to glucose and inorganic phosphate, have been identified, designated G6PC1-3, but only G6PC1 and G6PC2 have been implicated in the regulation of fasting blood glucose (FBG). Elevated FBG has been associated with multiple adverse clinical outcomes, including increased risk for type 2 diabetes and various cancers. Therefore, G6PC1 and G6PC2 inhibitors that lower FBG may be of prophylactic value for the prevention of multiple conditions. The studies described here characterize a G6PC2 inhibitor, designated VU0945627, previously identified as Compound 3. We show that VU0945627 preferentially inhibits human G6PC2 versus human G6PC1 but activates human G6PC3. VU0945627 is a mixed G6PC2 inhibitor, increasing the Km but reducing the Vmax for G6P hydrolysis. PyRx virtual docking to an AlphaFold2-derived G6PC2 structural model suggests VU0945627 binds two sites in human G6PC2. Mutation of residues in these sites reduces the inhibitory effect of VU0945627. VU0945627 does not inhibit mouse G6PC2 despite its 84% sequence identity with human G6PC2. Mutagenesis studies suggest this lack of inhibition of mouse G6PC2 is due, in part, to a change in residue 318 from histidine in human G6PC2 to proline in mouse G6PC2. Surprisingly, VU0945627 still inhibited glucose cycling in the mouse islet-derived βTC-3 cell line. Studies using intact mouse liver microsomes and PyRx docking suggest that this observation can be explained by an ability of VU0945627 to also inhibit the G6P transporter SLC37A4. These data will inform future computational modeling studies designed to identify G6PC isoform-specific inhibitors.
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Affiliation(s)
- Emily M Hawes
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Mohsin Rahim
- Department of Chemical and Biomolecular Engineering, Vanderbilt School of Engineering, Nashville, TN, 37232, USA
| | - Zeinab Haratipour
- Austin Peay State University, 601 College St, Clarksville, TN 37044, USA; Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Abigail R Orun
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Margaret L O'Rourke
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - James K Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Kwangho Kim
- Department of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN, 37232, USA
| | - Derek P Claxton
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Ray D Blind
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Jamey D Young
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA; Department of Chemical and Biomolecular Engineering, Vanderbilt School of Engineering, Nashville, TN, 37232, USA
| | - Richard M O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA.
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2
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Zhang Z, Su H, Li Q, Li M. Transcriptome Profiling Reveals the Response of Seed Germination of Peganum harmala to Drought Stress. PLANTS (BASEL, SWITZERLAND) 2024; 13:1649. [PMID: 38931081 PMCID: PMC11207268 DOI: 10.3390/plants13121649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2024] [Revised: 06/06/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024]
Abstract
Peganum harmala L. is a perennial herbaceous plant that plays critical roles in protecting the ecological environment in arid, semi-arid, and desert areas. Although the seed germination characteristics of P. harmala in response to environmental factors (i.e., drought, temperature, and salt) have been investigated, the response mechanism of seed germination to drought conditions has not yet been revealed. In this study, the changes in the physiological characteristics and transcriptional profiles in seed germination were examined under different polyethylene glycol (PEG) concentrations (0-25%). The results show that the seed germination rate was significantly inhibited with an increase in the PEG concentration. Totals of 3726 and 10,481 differentially expressed genes (DEGs) were, respectively, generated at 5% and 25% PEG vs. the control (C), with 1642 co-expressed DEGs, such as drought stress (15), stress response (175), and primary metabolism (261). The relative expression levels (RELs) of the key genes regulating seed germination in response to drought stress were in accordance with the physiological changes. These findings will pave the way to increase the seed germination rate of P. harmala in drought conditions.
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Affiliation(s)
- Zhen Zhang
- State Key Laboratory of Aridland Crop Science, Gansu Agricultural University, Lanzhou 730070, China; (Z.Z.); (H.S.)
| | - Hongyan Su
- State Key Laboratory of Aridland Crop Science, Gansu Agricultural University, Lanzhou 730070, China; (Z.Z.); (H.S.)
| | - Qingen Li
- Station of Forestry and Grassland, Alxa Right Banner 737300, China;
| | - Mengfei Li
- State Key Laboratory of Aridland Crop Science, Gansu Agricultural University, Lanzhou 730070, China; (Z.Z.); (H.S.)
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3
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Hawes E, Claxton D, Oeser J, O’Brien R. Identification of structural motifs critical for human G6PC2 function informed by sequence analysis and an AlphaFold2-predicted model. Biosci Rep 2024; 44:BSR20231851. [PMID: 38095063 PMCID: PMC10776900 DOI: 10.1042/bsr20231851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 11/22/2023] [Accepted: 12/12/2023] [Indexed: 01/10/2024] Open
Abstract
G6PC2 encodes a glucose-6-phosphatase (G6Pase) catalytic subunit, primarily expressed in pancreatic islet β cells, which modulates the sensitivity of insulin secretion to glucose and thereby regulates fasting blood glucose (FBG). Mutational analyses were conducted to validate an AlphaFold2 (AF2)-predicted structure of human G6PC2 in conjunction with a novel method to solubilize and purify human G6PC2 from a heterologous expression system. These analyses show that residues forming a predicted intramolecular disulfide bond are essential for G6PC2 expression and that residues forming part of a type 2 phosphatidic acid phosphatase (PAP2) motif are critical for enzyme activity. Additional mutagenesis shows that residues forming a predicted substrate cavity modulate enzyme activity and substrate specificity and residues forming a putative cholesterol recognition amino acid consensus (CRAC) motif influence protein expression or enzyme activity. This CRAC motif begins at residue 219, the site of a common G6PC2 non-synonymous single-nucleotide polymorphism (SNP), rs492594 (Val219Leu), though the functional impact of this SNP is disputed. In microsomal membrane preparations, the L219 variant has greater activity than the V219 variant, but this difference disappears when G6PC2 is purified in detergent micelles. We hypothesize that this was due to a differential association of the two variants with cholesterol. This concept was supported by the observation that the addition of cholesteryl hemi-succinate to the purified enzymes decreased the Vmax of the V219 and L219 variants ∼8-fold and ∼3 fold, respectively. We anticipate that these observations should support the rational development of G6PC2 inhibitors designed to lower FBG.
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Affiliation(s)
- Emily M. Hawes
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, U.S.A
| | - Derek P. Claxton
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, U.S.A
| | - James K. Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, U.S.A
| | - Richard M. O’Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, U.S.A
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4
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Veiga-da-Cunha M, Wortmann SB, Grünert SC, Van Schaftingen E. Treatment of the Neutropenia Associated with GSD1b and G6PC3 Deficiency with SGLT2 Inhibitors. Diagnostics (Basel) 2023; 13:diagnostics13101803. [PMID: 37238286 DOI: 10.3390/diagnostics13101803] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/12/2023] [Accepted: 05/17/2023] [Indexed: 05/28/2023] Open
Abstract
Glycogen storage disease type Ib (GSD1b) is due to a defect in the glucose-6-phosphate transporter (G6PT) of the endoplasmic reticulum, which is encoded by the SLC37A4 gene. This transporter allows the glucose-6-phosphate that is made in the cytosol to cross the endoplasmic reticulum (ER) membrane and be hydrolyzed by glucose-6-phosphatase (G6PC1), a membrane enzyme whose catalytic site faces the lumen of the ER. Logically, G6PT deficiency causes the same metabolic symptoms (hepatorenal glycogenosis, lactic acidosis, hypoglycemia) as deficiency in G6PC1 (GSD1a). Unlike GSD1a, GSD1b is accompanied by low neutrophil counts and impaired neutrophil function, which is also observed, independently of any metabolic problem, in G6PC3 deficiency. Neutrophil dysfunction is, in both diseases, due to the accumulation of 1,5-anhydroglucitol-6-phosphate (1,5-AG6P), a potent inhibitor of hexokinases, which is slowly formed in the cells from 1,5-anhydroglucitol (1,5-AG), a glucose analog that is normally present in blood. Healthy neutrophils prevent the accumulation of 1,5-AG6P due to its hydrolysis by G6PC3 following transport into the ER by G6PT. An understanding of this mechanism has led to a treatment aimed at lowering the concentration of 1,5-AG in blood by treating patients with inhibitors of SGLT2, which inhibits renal glucose reabsorption. The enhanced urinary excretion of glucose inhibits the 1,5-AG transporter, SGLT5, causing a substantial decrease in the concentration of this polyol in blood, an increase in neutrophil counts and function and a remarkable improvement in neutropenia-associated clinical signs and symptoms.
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Affiliation(s)
- Maria Veiga-da-Cunha
- Metabolic Research Group, de Duve Institute and UCLouvain, B-1200 Brussels, Belgium
| | - Saskia B Wortmann
- University Children's Hospital, Paracelsus Medical University, 5020 Salzburg, Austria
- Amalia Children's Hospital, Radboudumc, 6525 Nijmegen, The Netherlands
| | - Sarah C Grünert
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Center, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
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5
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Cao J, Markel A, Hanahoe E, Ketova T, Mihai C, Zalinger Z, Marquardt D, Amato NJ, Cheng YM, Reid DW, Dousis A, Giangrande PH, Schultz JR, Martini PGV, Finn PF. Amnio acid substitution at position 298 of human glucose-6 phosphatase-α significantly impacts its stability in mammalian cells. Amino Acids 2023:10.1007/s00726-023-03263-8. [PMID: 36944899 DOI: 10.1007/s00726-023-03263-8] [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: 12/06/2022] [Accepted: 03/09/2023] [Indexed: 03/23/2023]
Abstract
Glucose-6-phosphatase-α (G6Pase-α) catalyzes the hydrolysis of glucose-6-phosphate to glucose and functions as a key regulator in maintaining blood glucose homeostasis. Deficiency in G6Pase-α causes glycogen storage disease 1a (GSD1a), an inherited disorder characterized by life-threatening hypoglycemia and other long-term complications. We have developed a potential mRNA-based therapy for GSD1a and demonstrated that a human G6Pase-α (hG6Pase-α) variant harboring a single serine (S) to cysteine (C) substitution at the amino acid site 298 (S298C) had > twofold increase in protein expression, resulting in improved in vivo efficacy. Here, we sought to investigate the mechanisms contributing to the increased expression of the S298C variant. Mutagenesis of hG6Pase-α identified distinct protein variants at the 298 amino acid position with substantial reduction in protein expression in cultured cells. Kinetic analysis of expression and subcellular localization in mammalian cells, combined with cell-free in vitro translation assays, revealed that altered protein expression stemmed from differences in cellular protein stability rather than biosynthetic rates. Site-specific mutagenesis studies targeting other cysteines of the hG6Pase-α S298C variant suggest the observed improvements in stability are not due to additional disulfide bond formation. The glycosylation at Asparagine (N)-96 is critical in maintaining enzymatic activity and mutations at position 298 mainly affected glycosylated forms of hG6Pase-α. Finally, proteasome inhibition by lactacystin improved expression levels of unstable hG6Pase-α variants. Taken together, these data uncover a critical role for a single amino acid substitution impacting the stability of G6Pase-α and provide insights into the molecular genetics of GSD1a and protein engineering for therapeutic development.
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Affiliation(s)
- Jingsong Cao
- Rare Diseases, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Arianna Markel
- Rare Diseases, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Erin Hanahoe
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Tatiana Ketova
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Cosmin Mihai
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Zach Zalinger
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - David Marquardt
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Nicholas J Amato
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Yi Min Cheng
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - David W Reid
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Athanasios Dousis
- Platform, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
- Current Address: Tessera Therapeutics, Somerville, MA, USA
| | - Paloma H Giangrande
- Rare Diseases, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
- Current Address: Wave Life Sciences, Cambridge, MA, USA
| | - Joshua R Schultz
- Rare Diseases, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA
| | - Paolo G V Martini
- Rare Diseases, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA.
| | - Patrick F Finn
- Rare Diseases, Moderna, Inc., 200 Technology Square, Cambridge, MA, 02139, USA.
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6
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Udhaya Kumar S, Kamaraj B, Varghese RP, Preethi VA, Bithia R, George Priya Doss C. Mutations in G6PC2 gene with increased risk for development of type 2 diabetes: Understanding via computational approach. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2022; 130:351-373. [PMID: 35534112 DOI: 10.1016/bs.apcsb.2022.02.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
An increase in the fast blood glucose (FBG) levels has been linked to an increased risk of developing a chronic condition, type 2 diabetes (T2D). The mutation in the G6PC2 gene was identified to have a lead role in the modulation of FBG levels. The abnormal regulation of this enzyme influences glucose-stimulated insulin secretion (GSIS), which controls the insulin levels corresponding to the system's glucose level. This study focuses on the mutations at the G6PC2 gene, which cause the variation from normal expression levels and increase the risk of T2D. We examined the non-synonymous single nucleotide polymorphisms (nsSNPs) present in the G6PC2 and subjected them to pathogenicity, stability, residue conservation, and membrane simulation. The individual representation of surrounding amino acids in the mutant (I63T) model showed the loss of hydrophobic interactions compared to the native G6PC2. In addition, the trajectory results from the membrane simulation exhibited reduced stability, and the least compactness was identified for the I63T mutant model. Our study shed light on the structural and conformational changes at the transmembrane region due to the I63T mutation in G6PC2. Additionally, the Gibbs free energy landscape analysis against the two principal components showed structural differences and decreased the conformational stability of the I63T mutant model compared to the native. Like those presented in this study, dynamical simulations may indeed be crucial to comprehending the structural insights of G6PC2 mutations in cardiovascular-associated mortality and T2D.
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Affiliation(s)
- S Udhaya Kumar
- Laboratory of Integrative Genomics, Department of Integrative Biology, School of Bio Sciences and Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - Balu Kamaraj
- Department of Neuroscience Technology, College of Applied Medical Sciences, Imam Abdulrahman Bin Faisal University, Jubail, Saudi Arabia
| | - Rinku Polachirakkal Varghese
- Laboratory of Integrative Genomics, Department of Integrative Biology, School of Bio Sciences and Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - V Anu Preethi
- School of Computer Science and Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - R Bithia
- Laboratory of Integrative Genomics, Department of Integrative Biology, School of Bio Sciences and Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - C George Priya Doss
- Laboratory of Integrative Genomics, Department of Integrative Biology, School of Bio Sciences and Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, India.
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7
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Overway EM, Bosma KJ, Claxton DP, Oeser JK, Singh K, Breidenbach LB, Mchaourab HS, Davis LK, O'Brien RM. Nonsynonymous single-nucleotide polymorphisms in the G6PC2 gene affect protein expression, enzyme activity, and fasting blood glucose. J Biol Chem 2022; 298:101534. [PMID: 34954144 PMCID: PMC8800118 DOI: 10.1016/j.jbc.2021.101534] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/16/2021] [Accepted: 12/17/2021] [Indexed: 12/30/2022] Open
Abstract
G6PC2 encodes a glucose-6-phosphatase (G6Pase) catalytic subunit that modulates the sensitivity of insulin secretion to glucose and thereby regulates fasting blood glucose (FBG). A common single-nucleotide polymorphism (SNP) in G6PC2, rs560887 is an important determinant of human FBG variability. This SNP has a subtle effect on G6PC2 RNA splicing, which raises the question as to whether nonsynonymous SNPs with a major impact on G6PC2 stability or enzyme activity might have a broader disease/metabolic impact. Previous attempts to characterize such SNPs were limited by the very low inherent G6Pase activity and expression of G6PC2 protein in islet-derived cell lines. In this study, we describe the use of a plasmid vector that confers high G6PC2 protein expression in islet cells, allowing for a functional analysis of 22 nonsynonymous G6PC2 SNPs, 19 of which alter amino acids that are conserved in mouse G6PC2 and the human and mouse variants of the related G6PC1 isoform. We show that 16 of these SNPs markedly impair G6PC2 protein expression (>50% decrease). These SNPs have variable effects on the stability of human and mouse G6PC1, despite the high sequence homology between these isoforms. Four of the remaining six SNPs impaired G6PC2 enzyme activity. Electronic health record-derived phenotype analyses showed an association between high-impact SNPs and FBG, but not other diseases/metabolites. While homozygous G6pc2 deletion in mice increases the risk of hypoglycemia, these human data reveal no evidence that the beneficial use of partial G6PC2 inhibitors to lower FBG would be associated with unintended negative consequences.
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Affiliation(s)
- Emily M Overway
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Karin J Bosma
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Derek P Claxton
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - James K Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Kritika Singh
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Lindsay B Breidenbach
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Lea K Davis
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Richard M O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
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8
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Mizusawa N, Harada N, Iwata T, Ohigashi I, Itakura M, Yoshimoto K. Identification of protease serine S1 family member 53 as a mitochondrial protein in murine islet beta cells. Islets 2022; 14:1-13. [PMID: 34636707 PMCID: PMC8812782 DOI: 10.1080/19382014.2021.1982325] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The aim of this study was to identify genes that are specifically expressed in pancreatic islet β-cells (hereafter referred to as β-cells). Large-scale complementary DNA-sequencing analysis was performed for 3,429 expressed sequence tags derived from murine MIN6 β-cells, through homology comparisons using the GenBank database. Three individual ESTs were found to code for protease serine S1 family member 53 (Prss53). Prss53 mRNA is processed into both a short and long form, which encode 482 and 552 amino acids, respectively. Transient overexpression of myc-tagged Prss53 in COS-7 cells showed that Prss53 was strongly associated with the luminal surfaces of organellar membranes and that it underwent signal peptide cleavage and N-glycosylation. Immunoelectron microscopy and western blotting revealed that Prss53 localized to mitochondria in MIN6 cells. Short hairpin RNA-mediated Prss53 knockdown resulted in Ppargc1a downregulation and Ucp2 and Glut2 upregulation. JC-1 staining revealed that the mitochondria were depolarized in Prss53-knockdown MIN6 cells; however, no change was observed in glucose-stimulated insulin secretion. Our results suggest that mitochondrial Prss53 expression plays an important role in maintaining the health of β-cells.
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Affiliation(s)
- Noriko Mizusawa
- Department of Medical Pharmacology, Institute of Biomedical Sciences, Tokushima University, Tokushima, Japan
- CONTACT Noriko Mizusawa Department of Oral Bioscience, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-Kuramoto-cho, Tokushima City770-8504, Japan
| | - Nagakatsu Harada
- Department of Health and Nutrition, Faculty of Nursing and Nutrition, The University of Shimane, Shimane, Japan
| | - Takeo Iwata
- Department of Functional Morphology, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, Niigata, Japan
| | - Izumi Ohigashi
- Division of Experimental Immunology, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| | - Mitsuo Itakura
- Division of Genetic Information, Institute for Genome Research, Tokushima University, Tokushima, Japan
| | - Katsuhiko Yoshimoto
- Department of Medical Pharmacology, Institute of Biomedical Sciences, Tokushima University, Tokushima, Japan
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9
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Zusi C, Rinaldi E, Bonetti S, Boselli ML, Trabetti E, Malerba G, Bonora E, Bonadonna RC, Trombetta M. Haplotypes of the genes (GCK and G6PC2) underlying the glucose/glucose-6-phosphate cycle are associated with pancreatic beta cell glucose sensitivity in patients with newly diagnosed type 2 diabetes from the VNDS study (VNDS 11). J Endocrinol Invest 2021; 44:2567-2574. [PMID: 34128214 DOI: 10.1007/s40618-020-01483-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 12/07/2020] [Indexed: 10/21/2022]
Abstract
BACKGROUND Elevated fasting plasma glucose has been associated with increased risk for development of type 2 diabetes (T2D). The balance between glucokinase (GCK) and glucose-6-phosphate catalytic subunit 2 (G6PC2) activity are involved in glucose homeostasis through glycolytic flux, and subsequent insulin secretion. AIM In this study, we evaluated the association between the genetic variability of G6PC2 and GCK genes and T2D-related quantitative traits. METHODS In 794 drug-naïve, GADA-negative, newly diagnosed T2D patients (VNDS; NTC01526720) we performed: genotyping of 6 independent tag-SNPs within GCK gene and 5 tag-SNPs within G6PC2 gene; euglycaemic insulin clamp to assess insulin sensitivity; OGTT to estimate beta-cell function (derivative and proportional control; DC, PC) by mathematical modeling. Genetic association analysis has been conducted using Plink software. RESULTS Two SNPs within GCK gene (rs882019 and rs1303722) were associated to DC in opposite way (both p < 0.004). Two G6PC2 variants (rs13387347 and rs560887) were associated to both parameters of insulin secretion (DC and PC) and to fasting C-peptide levels (all p < 0.038). Moreover, subjects carrying the A allele of rs560887 showed higher values of 2h-plasma glucose (2hPG) (p = 0.033). Haplotype analysis revealed that GCK (AACAAA) haplotype was associated to decreased fasting C-peptide levels, whereas, the most frequent haplotype of G6PC2 (GGAAG) was associated with higher fasting C-peptide levels (p = 0.001), higher PC (β = 6.87, p = 0.022) and the lower 2hPG (p = 0.012). CONCLUSION Our findings confirmed the role of GCK and G6PC2 in regulating the pulsatility in insulin secretion thereby influencing insulin-signaling and leading to a gradual modulation in glucose levels in Italian patients with newly diagnosed T2D.
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Affiliation(s)
- C Zusi
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University and Hospital Trust of Verona, Piazzale Stefani 1, 37126, Verona, Italy
| | - E Rinaldi
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University and Hospital Trust of Verona, Piazzale Stefani 1, 37126, Verona, Italy
| | - S Bonetti
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University and Hospital Trust of Verona, Piazzale Stefani 1, 37126, Verona, Italy
| | - M L Boselli
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University and Hospital Trust of Verona, Piazzale Stefani 1, 37126, Verona, Italy
| | - E Trabetti
- Department of Neuroscience, Biomedicine and Movement Sciences, Section of Biology and Genetics, University of Verona, Verona, Italy
| | - G Malerba
- Department of Neuroscience, Biomedicine and Movement Sciences, Section of Biology and Genetics, University of Verona, Verona, Italy
| | - E Bonora
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University and Hospital Trust of Verona, Piazzale Stefani 1, 37126, Verona, Italy
| | - R C Bonadonna
- Department of Medicine and Surgery, University of Parma, Parma, Italy
- Division of Endocrinology and Metabolic Diseases, Azienda Ospedaliero-Universitaria di Parma, Parma, Italy
| | - M Trombetta
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University and Hospital Trust of Verona, Piazzale Stefani 1, 37126, Verona, Italy.
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10
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Chung RH, Chiu YF, Wang WC, Hwu CM, Hung YJ, Lee IT, Chuang LM, Quertermous T, Rotter JI, Chen YDI, Chang IS, Hsiung CA. Multi-omics analysis identifies CpGs near G6PC2 mediating the effects of genetic variants on fasting glucose. Diabetologia 2021; 64:1613-1625. [PMID: 33842983 DOI: 10.1007/s00125-021-05449-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 02/08/2021] [Indexed: 10/21/2022]
Abstract
AIMS/HYPOTHESIS An elevated fasting glucose level in non-diabetic individuals is a key predictor of type 2 diabetes. Genome-wide association studies (GWAS) have identified hundreds of SNPs for fasting glucose but most of their functional roles in influencing the trait are unclear. This study aimed to identify the mediation effects of DNA methylation between SNPs identified as significant from GWAS and fasting glucose using Mendelian randomisation (MR) analyses. METHODS We first performed GWAS analyses for three cohorts (Taiwan Biobank with 18,122 individuals, the Healthy Aging Longitudinal Study in Taiwan with 1989 individuals and the Stanford Asia-Pacific Program for Hypertension and Insulin Resistance with 416 individuals) with individuals of Han Chinese ancestry in Taiwan, followed by a meta-analysis for combining the three GWAS analysis results to identify significant and independent SNPs for fasting glucose. We determined whether these SNPs were methylation quantitative trait loci (meQTLs) by testing their associations with DNA methylation levels at nearby CpG sites using a subsample of 1775 individuals from the Taiwan Biobank. The MR analysis was performed to identify DNA methylation with causal effects on fasting glucose using meQTLs as instrumental variables based on the 1775 individuals. We also used a two-sample MR strategy to perform replication analysis for CpG sites with significant MR effects based on literature data. RESULTS Our meta-analysis identified 18 significant (p < 5 × 10-8) and independent SNPs for fasting glucose. Interestingly, all 18 SNPs were meQTLs. The MR analysis identified seven CpGs near the G6PC2 gene that mediated the effects of a significant SNP (rs2232326) in the gene on fasting glucose. The MR effects for two CpGs were replicated using summary data based on the European population, using an exonic SNP rs2232328 in G6PC2 as the instrument. CONCLUSIONS/INTERPRETATION Our analysis results suggest that rs2232326 and rs2232328 in G6PC2 may affect DNA methylation at CpGs near the gene and that the methylation may have downstream effects on fasting glucose. Therefore, SNPs in G6PC2 and CpGs near G6PC2 may reside along the pathway that influences fasting glucose levels. This is the first study to report CpGs near G6PC2, an important gene for regulating insulin secretion, mediating the effects of GWAS-significant SNPs on fasting glucose.
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Affiliation(s)
- Ren-Hua Chung
- Division of Biostatistics and Bioinformatics, Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Taiwan.
| | - Yen-Feng Chiu
- Division of Biostatistics and Bioinformatics, Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Taiwan
| | - Wen-Chang Wang
- The Ph.D. Program for Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Chii-Min Hwu
- Section of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
- School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Yi-Jen Hung
- Division of Endocrine and Metabolism, Tri-Service General Hospital, Taipei, Taiwan
- Institute of Preventive Medicine, National Defense Medical Center, Taipei, Taiwan
| | - I-Te Lee
- School of Medicine, National Yang-Ming University, Taipei, Taiwan
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan
- School of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Lee-Ming Chuang
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
- Institutes of Molecular Medicine, Collage of Medicine, National Taiwan University, Taipei, Taiwan
| | - Thomas Quertermous
- Division of Cardiovascular Medicine and Stanford Cardiovascular Institute, Falk Cardiovascular Research Center, Stanford University, Stanford, CA, USA
| | - Jerome I Rotter
- Institute for Translational Genomics and Population Sciences, the Lundquist Institute, Harbor-UCLA Medical Center, Torrance, CA, USA
- Department of Pediatrics, Harbor-UCLA Medical Center, Torrance, CA, USA
| | - Yii-Der I Chen
- Institute for Translational Genomics and Population Sciences, the Lundquist Institute, Harbor-UCLA Medical Center, Torrance, CA, USA
- Department of Pediatrics, Harbor-UCLA Medical Center, Torrance, CA, USA
| | - I-Shou Chang
- National Institute of Cancer Research, National Health Research Institutes, Zhunan, Taiwan
| | - Chao A Hsiung
- Division of Biostatistics and Bioinformatics, Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Taiwan.
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11
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Bosma KJ, Rahim M, Oeser JK, McGuinness OP, Young JD, O'Brien RM. G6PC2 confers protection against hypoglycemia upon ketogenic diet feeding and prolonged fasting. Mol Metab 2020; 41:101043. [PMID: 32569842 PMCID: PMC7369601 DOI: 10.1016/j.molmet.2020.101043] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 05/26/2020] [Accepted: 06/16/2020] [Indexed: 12/14/2022] Open
Abstract
Objective G6PC2 is predominantly expressed in pancreatic islet beta cells. G6PC2 hydrolyzes glucose-6-phosphate to glucose and inorganic phosphate, thereby creating a futile substrate cycle that opposes the action of glucokinase. This substrate cycle determines the sensitivity of glucose-stimulated insulin secretion to glucose and hence regulates fasting blood glucose (FBG) but not fasting plasma insulin (FPI) levels. Our objective was to explore the physiological benefit this cycle confers. Methods We investigated the response of wild type (WT) and G6pc2 knockout (KO) mice to changes in nutrition. Results Pancreatic G6pc2 expression was little changed by ketogenic diet feeding but was inhibited by 24 hr fasting and strongly induced by high fat feeding. When challenged with either a ketogenic diet or 24 hr fasting, blood glucose fell to 70 mg/dl or less in G6pc2 KO but not WT mice, suggesting that G6PC2 may have evolved, in part, to prevent hypoglycemia. Prolonged ketogenic diet feeding reduced the effect of G6pc2 deletion on FBG. The hyperglycemia associated with high fat feeding was partially blunted in G6pc2 KO mice, suggesting that under these conditions the presence of G6PC2 is detrimental. As expected, FPI changed but did not differ between WT and KO mice in response to fasting, ketogenic and high fat feeding. Conclusions Since elevated FBG levels are associated with increased risk for cardiovascular-associated mortality (CAM), these studies suggest that, while G6PC2 inhibitors would be useful for lowering FBG and the risk of CAM, partial inhibition will be important to avoid the risk of hypoglycemia. G6pc2 deletion lowers fasting blood glucose (FBG) in chow and high fat fed mice. Elevated FBG increases the risk of cardiovascular-associated mortality (CAM). G6pc2 deletion results in hypoglycemia in mice on a ketogenic diet. G6pc2 deletion results in hypoglycemia in mice following prolonged fasting. G6PC2 inhibitors may prevent CAM but increase risk of hypoglycemia.
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Affiliation(s)
- Karin J Bosma
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Mohsin Rahim
- Department of Chemical and Biomolecular Engineering, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - James K Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Owen P McGuinness
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Jamey D Young
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Department of Chemical and Biomolecular Engineering, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Richard M O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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12
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Bosma KJ, Rahim M, Singh K, Goleva SB, Wall ML, Xia J, Syring KE, Oeser JK, Poffenberger G, McGuinness OP, Means AL, Powers AC, Li WH, Davis LK, Young JD, O’Brien RM. Pancreatic islet beta cell-specific deletion of G6pc2 reduces fasting blood glucose. J Mol Endocrinol 2020; 64:235-248. [PMID: 32213654 PMCID: PMC7331801 DOI: 10.1530/jme-20-0031] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 03/13/2020] [Indexed: 12/25/2022]
Abstract
The G6PC1, G6PC2 and G6PC3 genes encode distinct glucose-6-phosphatase catalytic subunit (G6PC) isoforms. In mice, germline deletion of G6pc2 lowers fasting blood glucose (FBG) without affecting fasting plasma insulin (FPI) while, in isolated islets, glucose-6-phosphatase activity and glucose cycling are abolished and glucose-stimulated insulin secretion (GSIS) is enhanced at submaximal but not high glucose. These observations are all consistent with a model in which G6PC2 regulates the sensitivity of GSIS to glucose by opposing the action of glucokinase. G6PC2 is highly expressed in human and mouse islet beta cells however, various studies have shown trace G6PC2 expression in multiple tissues raising the possibility that G6PC2 also affects FBG through non-islet cell actions. Using real-time PCR we show here that expression of G6pc1 and/or G6pc3 are much greater than G6pc2 in peripheral tissues, whereas G6pc2 expression is much higher than G6pc3 in both pancreas and islets with G6pc1 expression not detected. In adult mice, beta cell-specific deletion of G6pc2 was sufficient to reduce FBG without changing FPI. In addition, electronic health record-derived phenotype analyses showed no association between G6PC2 expression and phenotypes clearly unrelated to islet function in humans. Finally, we show that germline G6pc2 deletion enhances glycolysis in mouse islets and that glucose cycling can also be detected in human islets. These observations are all consistent with a mechanism by which G6PC2 action in islets is sufficient to regulate the sensitivity of GSIS to glucose and hence influence FBG without affecting FPI.
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Affiliation(s)
- Karin J. Bosma
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Mohsin Rahim
- Department of Chemical and Biomolecular Engineering, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Kritika Singh
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Slavina B. Goleva
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Martha L. Wall
- Department of Chemical and Biomolecular Engineering, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Jing Xia
- Departments of Cell Biology and of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| | - Kristen E. Syring
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - James K. Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Greg Poffenberger
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Owen P. McGuinness
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Anna L. Means
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Alvin C. Powers
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232
- VA Tennessee Valley Healthcare System, Nashville, TN 37232
| | - Wen-hong Li
- Departments of Cell Biology and of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| | - Lea K. Davis
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Jamey D. Young
- Department of Chemical and Biomolecular Engineering, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Richard M. O’Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
- To whom correspondence should be addressed: Department of Molecular Physiology and Biophysics, 8415 MRB IV, 2213 Garland Ave, Vanderbilt University Medical School, Nashville, TN 37232-0615,
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Westermeier F, Holyoak T, Gatica R, Martínez F, Negrón M, Yáñez AJ, Nahmias D, Nualart F, Burbulis I, Bertinat R. Cytosolic phosphoenolpyruvate carboxykinase is expressed in α-cells from human and murine pancreas. J Cell Physiol 2019; 235:166-175. [PMID: 31180589 DOI: 10.1002/jcp.28955] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 05/24/2019] [Indexed: 12/16/2022]
Abstract
The pancreatic islets of Langerhans, mainly formed by glucagon-producing α-cells and insulin-producing β-cells, are critical for glucose homeostasis. Insulin and glucagon oppositely modulate blood glucose levels in health, but a combined decline in insulin secretion together with increased glucagon secretion contribute to hyperglycemia in diabetes. Despite this bi-hormonal dysregulation, most studies have focused on insulin secretion and much less is known about glucagon secretion. Therefore, a deeper understanding of α-cell metabolism and glucagon secretion is of great interest. Here, we show that phosphoenolpyruvate carboxykinase (PCK1), an essential cataplerotic enzyme involved in metabolism and long considered to be absent from the pancreatic islet, is expressed in pancreatic α-cells of both murine and human. Furthermore, PCK1 transcription is induced by fasting and diabetes in rat pancreas, which indicates that the PCK1 activity is required for α-cell adaptation to different metabolic states. To our knowledge, this is the first evidence implicating PCK1 expression in α-cell metabolism.
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Affiliation(s)
- Francisco Westermeier
- FH JOANNEUM Gesellschaft mbH University of Applied Sciences, Institute of Biomedical Science, Department of Health Studies, Graz, Austria
| | - Todd Holyoak
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Rodrigo Gatica
- Escuela de Veterinaria, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Fernando Martínez
- Centro de Microscopía Avanzada, CMA-BIO BIO, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Marianne Negrón
- Centro de Microscopía Avanzada, CMA-BIO BIO, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Alejandro J Yáñez
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Daniel Nahmias
- Anatomía patológica, Hospital Puerto Montt, Puerto Montt, Chile
| | - Francisco Nualart
- Centro de Microscopía Avanzada, CMA-BIO BIO, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Ian Burbulis
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Virginia, Charlottesville, Virginia.,Escuela de Medicina, Universidad San Sebastián, Sede de la Patagonia, Puerto Montt, Chile
| | - Romina Bertinat
- Centro de Microscopía Avanzada, CMA-BIO BIO, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
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Rudhira/BCAS3 is essential for mouse development and cardiovascular patterning. Sci Rep 2018; 8:5632. [PMID: 29618843 PMCID: PMC5884795 DOI: 10.1038/s41598-018-24014-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 03/22/2018] [Indexed: 01/23/2023] Open
Abstract
Rudhira/Breast Carcinoma Amplified Sequence 3 (BCAS3) is a cytoskeletal protein that promotes directional cell migration and angiogenesis in vitro and is implicated in human carcinomas and coronary artery disease. To study the role of Rudhira during development in vivo, we generated the first knockout mouse for rudhira and show that Rudhira is essential for mouse development. Rudhira null embryos die at embryonic day (E) 9.5 accompanied by severe vascular patterning defects in embryonic and extra-embryonic tissues. To identify the molecular processes downstream of rudhira, we analyzed the transcriptome of intact knockout yolk sacs. Genome-wide transcriptome analysis showed that Rudhira functions in angiogenesis and its related processes such as cell adhesion, extracellular matrix organization, peptidase activity and TGFβ signaling. Since Rudhira is also expressed in endothelial cells (ECs), we further generated Tie2Cre-mediated endothelial knockout (CKO) of rudhira. CKO embryos survive to E11.5 and similar to the global knockout, display gross vascular patterning defects, showing that endothelial Rudhira is vital for development. Further, Rudhira knockdown ECs in culture fail to sprout in a spheroid-sprouting assay, strongly supporting its role in vascular patterning. Our study identifies an essential role for Rudhira in blood vessel remodeling and provides a mouse model for cardiovascular development.
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15
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Meta-analyses of the association of G6PC2 allele variants with elevated fasting glucose and type 2 diabetes. PLoS One 2017; 12:e0181232. [PMID: 28704540 PMCID: PMC5509327 DOI: 10.1371/journal.pone.0181232] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 06/28/2017] [Indexed: 12/19/2022] Open
Abstract
Objective To collectively evaluate the association of glucose-6-phosphatase catalytic unit 2 (G6PC2) allele variants with elevated fasting glucose (FG) and type 2 diabetes (T2D). Design Meta-analysis Data sources PubMed, Web of Knowledge and Embase databases. Study selection Full text articles of studies that identified an association of G6PC2 with T2D and elevated FG. Patient involvement There was no T2D patient involvement in the analyses on the association of FG with G6PC2, there were T2D patients and non-diabetes patient involvement in the analyses on the association of T2D with G6PC2. Statistical analysis Random-effects meta-analyses were used to calculate the pool effect sizes. I2 metric and H2 tests were used to calculate the heterogeneity. Begg's funnel plot and Egger’s linear regression test were done to assess publication bias. Results Of the 423 studies identified, 21 were eligible and included. Data on three loci (rs560887, rs16856187 and rs573225) were available. The G allele at rs560887 in three ethnicities, the C allele at rs16856187 and the A allele at rs573225 all had a positive association with elevated FG. Per increment of G allele at rs560887 and A allele at rs573225 resulted in a FG 0.070 mmol/l and 0.075 mmol/l higher (ß (95% CI) = 0.070 (0.060, 0.079), p = 4.635e-50 and 0.075 (0.065, 0.085), p = 5.856e-48, respectively). With regard to the relationship of rs16856187 and FG, an increase of 0.152 (95% CI: 0.034–0.270; p = 0.011) and 0.317 (95% CI: 0.193–0.442, p = 6.046e-07) was found in the standardized mean difference (SMD) of FG for the AC and CC genotypes, respectively, when compared with the AA reference genotype. However, the G-allele of rs560887 in Caucasians under the additive model and the C-allele of rs16856187 under the allele and dominant models were associated with a decreased risk of T2D (OR (95% CI) = 0.964 (0.947, 0.981), p = 0.570e-4; OR (95% CI) = 0.892 (0.832, 0.956), p = 0.001; and OR (95% CI) = 0.923(0.892, 0.955), p = 5.301e-6, respectively). Conclusions Our meta-analyses demonstrate that all three allele variants of G6PC2 (rs560887, rs16856187 and rs573225) are associated with elevated FG, with two variants (rs560887 in the Caucasians subgroup and rs16856187 under the allele and dominant model) being associated with T2D as well. Further studies utilizing larger sample sizes and different ethnic populations are needed to extend and confirm these findings.
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16
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Boortz KA, Syring KE, Pound LD, Mo H, Bastarache L, Oeser JK, McGuinness OP, Denny JC, O’Brien RM. Effects of G6pc2 deletion on body weight and cholesterol in mice. J Mol Endocrinol 2017; 58:127-139. [PMID: 28122818 PMCID: PMC5380368 DOI: 10.1530/jme-16-0202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 01/24/2017] [Indexed: 11/08/2022]
Abstract
Genome-wide association study (GWAS) data have linked the G6PC2 gene to variations in fasting blood glucose (FBG). G6PC2 encodes an islet-specific glucose-6-phosphatase catalytic subunit that forms a substrate cycle with the beta cell glucose sensor glucokinase. This cycle modulates the glucose sensitivity of insulin secretion and hence FBG. GWAS data have not linked G6PC2 to variations in body weight but we previously reported that female C57BL/6J G6pc2-knockout (KO) mice were lighter than wild-type littermates on both a chow and high-fat diet. The purpose of this study was to compare the effects of G6pc2 deletion on FBG and body weight in both chow-fed and high-fat-fed mice on two other genetic backgrounds. FBG was reduced in G6pc2 KO mice largely independent of gender, genetic background or diet. In contrast, the effect of G6pc2 deletion on body weight was markedly influenced by these variables. Deletion of G6pc2 conferred a marked protection against diet-induced obesity in male mixed genetic background mice, whereas in 129SvEv mice deletion of G6pc2 had no effect on body weight. G6pc2 deletion also reduced plasma cholesterol levels in a manner dependent on gender, genetic background and diet. An association between G6PC2 and plasma cholesterol was also observed in humans through electronic health record-derived phenotype analyses. These observations suggest that the action of G6PC2 on FBG is largely independent of the influences of environment, modifier genes or epigenetic events, whereas the action of G6PC2 on body weight and cholesterol are influenced by unknown variables.
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Affiliation(s)
- Kayla A. Boortz
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Kristen E. Syring
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Lynley D. Pound
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Huan Mo
- Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Lisa Bastarache
- Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - James K. Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Owen P. McGuinness
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Joshua C. Denny
- Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, TN 37232
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Richard M. O’Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
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Bian X, Wasserfall C, Wallstrom G, Wang J, Wang H, Barker K, Schatz D, Atkinson M, Qiu J, LaBaer J. Tracking the Antibody Immunome in Type 1 Diabetes Using Protein Arrays. J Proteome Res 2017; 16:195-203. [PMID: 27690455 DOI: 10.1021/acs.jproteome.6b00354] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We performed an unbiased proteome-scale profiling of humoral autoimmunity in recent-onset type 1 diabetes (T1D) patients and nondiabetic controls against ∼10 000 human proteins using a Nucleic Acid Programmable Protein Array (NAPPA) platform, complemented by a knowledge-based selection of proteins from genes enriched in human pancreas. Although the global response was similar between cases and controls, we identified and then validated six specific novel T1D-associated autoantibodies (AAbs) with sensitivities that ranged from 16 to 27% at 95% specificity. These included AAbs against PTPRN2, MLH1, MTIF3, PPIL2, NUP50 (from NAPPA screening), and QRFPR (by targeted ELISA). Immunohistochemistry demonstrated that NUP50 protein behaved differently in islet cells, where it stained both nucleus and cytoplasm, compared with only nuclear staining in exocrine pancreas. Conversely, PPIL2 staining was absent in islet cells, despite its presence in exocrine cells. The combination of anti-PTPRN2, -MLH1, -PPIL2, and -QRFPR had an AUC of 0.74 and 37.5% sensitivity at 95% specificity. These data indicate that these markers behave independently and support the use of unbiased screening to find biomarkers because the majority was not predicted based on predicted abundance. Our study enriches the knowledge of the "autoantibody-ome" in unprecedented breadth and width.
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Affiliation(s)
- Xiaofang Bian
- The Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University , Tempe, Arizona 85287, United States
| | - Clive Wasserfall
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida , Gainesville, Florida 32603, United States
| | - Garrick Wallstrom
- The Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University , Tempe, Arizona 85287, United States
| | - Jie Wang
- The Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University , Tempe, Arizona 85287, United States
| | - Haoyu Wang
- The Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University , Tempe, Arizona 85287, United States
| | - Kristi Barker
- The Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University , Tempe, Arizona 85287, United States
| | - Desmond Schatz
- Department of Pediatrics, College of Medicine, University of Florida , Gainesville, Florida 30607, United States
| | - Mark Atkinson
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida , Gainesville, Florida 32603, United States
| | - Ji Qiu
- The Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University , Tempe, Arizona 85287, United States
| | - Joshua LaBaer
- The Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University , Tempe, Arizona 85287, United States
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Functional Analysis of Mouse G6pc1 Mutations Using a Novel In Situ Assay for Glucose-6-Phosphatase Activity and the Effect of Mutations in Conserved Human G6PC1/G6PC2 Amino Acids on G6PC2 Protein Expression. PLoS One 2016; 11:e0162439. [PMID: 27611587 PMCID: PMC5017610 DOI: 10.1371/journal.pone.0162439] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Accepted: 08/23/2016] [Indexed: 11/19/2022] Open
Abstract
Elevated fasting blood glucose (FBG) has been associated with increased risk for development of type 2 diabetes. Single nucleotide polymorphisms (SNPs) in G6PC2 are the most important common determinants of variations in FBG in humans. Studies using G6pc2 knockout mice suggest that G6pc2 regulates the glucose sensitivity of insulin secretion. G6PC2 and the related G6PC1 and G6PC3 genes encode glucose-6-phosphatase catalytic subunits. This study describes a functional analysis of 22 non-synonymous G6PC2 SNPs, that alter amino acids that are conserved in human G6PC1, mouse G6pc1 and mouse G6pc2, with the goal of identifying variants that potentially affect G6PC2 activity/expression. Published data suggest strong conservation of catalytically important amino acids between all four proteins and the related G6PC3 isoform. Because human G6PC2 has very low glucose-6-phosphatase activity we used an indirect approach, examining the effect of these SNPs on mouse G6pc1 activity. Using a novel in situ functional assay for glucose-6-phosphatase activity we demonstrate that the amino acid changes associated with the human G6PC2 rs144254880 (Arg79Gln), rs149663725 (Gly114Arg) and rs2232326 (Ser324Pro) SNPs reduce mouse G6pc1 enzyme activity without affecting protein expression. The Arg79Gln variant alters an amino acid mutation of which, in G6PC1, has previously been shown to cause glycogen storage disease type 1a. We also demonstrate that the rs368382511 (Gly8Glu), rs138726309 (His177Tyr), rs2232323 (Tyr207Ser) rs374055555 (Arg293Trp), rs2232326 (Ser324Pro), rs137857125 (Pro313Leu) and rs2232327 (Pro340Leu) SNPs confer decreased G6PC2 protein expression. In summary, these studies identify multiple G6PC2 variants that have the potential to be associated with altered FBG in humans.
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A Severe Congenital Neutropenia Type 4 Case (G6PC3 Mutation) Presented With Large Platelets in the Peripheral Smear. J Pediatr Hematol Oncol 2016; 38:324-8. [PMID: 26808373 DOI: 10.1097/mph.0000000000000504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Severe congenital neutropenia type 4 is a disorder of the hematopoietic system associated with mutations in the glucose-6-phosphatase catabolic 3 (G6PC3) gene. This disorder is characterized by neutropenia, congenital heart defects, urogenital malformations, and prominent superficial veins. To our knowledge, although intermittent thrombocytopenia is observed in this mutation, the coexistence of large thrombocytes is rarely seen. Here we present a case of severe congenital neutropenia type 4 with G6PC3 mutation and large platelets in the peripheral smear.
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Wall ML, Pound LD, Trenary I, O'Brien RM, Young JD. Novel stable isotope analyses demonstrate significant rates of glucose cycling in mouse pancreatic islets. Diabetes 2015; 64:2129-37. [PMID: 25552595 PMCID: PMC4439557 DOI: 10.2337/db14-0745] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2014] [Accepted: 12/20/2014] [Indexed: 11/20/2022]
Abstract
A polymorphism located in the G6PC2 gene, which encodes an islet-specific glucose-6-phosphatase catalytic subunit, is the most important common determinant of variations in fasting blood glucose (FBG) levels in humans. Studies of G6pc2 knockout (KO) mice suggest that G6pc2 represents a negative regulator of basal glucose-stimulated insulin secretion (GSIS) that acts by hydrolyzing glucose-6-phosphate (G6P), thereby reducing glycolytic flux. However, this conclusion conflicts with the very low estimates for the rate of glucose cycling in pancreatic islets, as assessed using radioisotopes. We have reassessed the rate of glucose cycling in pancreatic islets using a novel stable isotope method. The data show much higher levels of glucose cycling than previously reported. In 5 mmol/L glucose, islets from C57BL/6J chow-fed mice cycled ∼16% of net glucose uptake. The cycling rate was further increased at 11 mmol/L glucose. Similar cycling rates were observed using islets from high fat-fed mice. Importantly, glucose cycling was abolished in G6pc2 KO mouse islets, confirming that G6pc2 opposes the action of the glucose sensor glucokinase by hydrolyzing G6P. The demonstration of high rates of glucose cycling in pancreatic islets explains why G6pc2 deletion enhances GSIS and why variants in G6PC2 affect FBG in humans.
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Affiliation(s)
- Martha L Wall
- Department of Chemical and Biomolecular Engineering, Vanderbilt School of Engineering, Nashville, TN
| | - Lynley D Pound
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, TN
| | - Irina Trenary
- Department of Chemical and Biomolecular Engineering, Vanderbilt School of Engineering, Nashville, TN
| | - Richard M O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, TN
| | - Jamey D Young
- Department of Chemical and Biomolecular Engineering, Vanderbilt School of Engineering, Nashville, TN Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, TN
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21
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Wang Y, Wang H, Li M, Gao Z, Zhang S. Identification, expression and regulation of amphioxus G6Pase gene with an emphasis on origin of liver. Gen Comp Endocrinol 2015; 214:9-16. [PMID: 25745818 DOI: 10.1016/j.ygcen.2014.12.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 12/25/2014] [Accepted: 12/28/2014] [Indexed: 10/23/2022]
Abstract
Vertebrate glucose-6-phosphatase (G6Pase) consists of three isozymes: G6Pase-I, G6Pase-II and G6Pase-III. Despite extensive study on G6Pases in vertebrates, information regarding expression and regulation of G6Pase genes is rather limited in invertebrates. Here we report the identification of G6Pase gene in amphioxus Branchiostoma japonicum, which is abundantly expressed in the digestive diverticulum and ovary in a tissue-specific manner. The phylogenetic and genomic structure analyses reveal that amphioxus G6Pase bears close resemblance to vertebrate G6Pase-III and represents the archetype of vertebrate G6Pase from which the vertebrate G6Pase isoforms may be originated by 2 rounds of genome duplication during vertebrate evolution. We also demonstrate that GH treatment induces a closely similar expression pattern and trend of g6pases in both zebrafish and amphioxus, and that G6Pase activity in amphioxus digestive diverticulum is subjected to regulation of feeding and fasting as observed in vertebrates. Collectively, all these provide functional evidences supporting the notion that the digestive diverticulum is the liver homologue playing a key role in maintaining the glucose homeostasis in amphioxus.
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Affiliation(s)
- Yu Wang
- Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China
| | - Hui Wang
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Mengyang Li
- Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China
| | - Zhan Gao
- Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China
| | - Shicui Zhang
- Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China.
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22
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Tousch D, Bidel LPR, Cazals G, Ferrare K, Leroy J, Faucanié M, Chevassus H, Tournier M, Lajoix AD, Azay-Milhau J. Chemical analysis and antihyperglycemic activity of an original extract from burdock root (Arctium lappa). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2014; 62:7738-7745. [PMID: 24933284 DOI: 10.1021/jf500926v] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In the present study, we obtained a dried burdock root extract (DBRE) rich in caffeoylquinic acids derivatives. We performed the chemical characterization of DBRE and explored its antihyperglycemic potential in both in vitro and in vivo experiments. Chemical analysis of DBRE using LC-MS and GC-MS revealed the presence of a great majority of dicaffeoylquinic acid derivatives (75.4%) of which 1,5-di-O-caffeoyl-4-O-maloylquinic acid represents 44% of the extract. In the in vitro experiments, DBRE is able to increase glucose uptake in cultured L6 myocytes and to decrease glucagon-induced glucose output from rat isolated hepatocytes together with a reduction of hepatic glucose 6-phosphatase activity. DBRE did not increase insulin secretion in the INS-1 pancreatic β-cell line. In vivo, DBRE improves glucose tolerance both after intraperitoneal and oral subchronic administration. In conclusion, our data demonstrate that DBRE constitutes an original set of caffeoylquinic acid derivatives displaying antihyperglycemic properties.
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Affiliation(s)
- Didier Tousch
- Université Montpellier I , 4 Boulevard Henri IV, Montpellier, France
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23
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Multi-tissue computational modeling analyzes pathophysiology of type 2 diabetes in MKR mice. PLoS One 2014; 9:e102319. [PMID: 25029527 PMCID: PMC4100879 DOI: 10.1371/journal.pone.0102319] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 06/18/2014] [Indexed: 12/25/2022] Open
Abstract
Computational models using metabolic reconstructions for in silico simulation of metabolic disorders such as type 2 diabetes mellitus (T2DM) can provide a better understanding of disease pathophysiology and avoid high experimentation costs. There is a limited amount of computational work, using metabolic reconstructions, performed in this field for the better understanding of T2DM. In this study, a new algorithm for generating tissue-specific metabolic models is presented, along with the resulting multi-confidence level (MCL) multi-tissue model. The effect of T2DM on liver, muscle, and fat in MKR mice was first studied by microarray analysis and subsequently the changes in gene expression of frank T2DM MKR mice versus healthy mice were applied to the multi-tissue model to test the effect. Using the first multi-tissue genome-scale model of all metabolic pathways in T2DM, we found out that branched-chain amino acids' degradation and fatty acids oxidation pathway is downregulated in T2DM MKR mice. Microarray data showed low expression of genes in MKR mice versus healthy mice in the degradation of branched-chain amino acids and fatty-acid oxidation pathways. In addition, the flux balance analysis using the MCL multi-tissue model showed that the degradation pathways of branched-chain amino acid and fatty acid oxidation were significantly downregulated in MKR mice versus healthy mice. Validation of the model was performed using data derived from the literature regarding T2DM. Microarray data was used in conjunction with the model to predict fluxes of various other metabolic pathways in the T2DM mouse model and alterations in a number of pathways were detected. The Type 2 Diabetes MCL multi-tissue model may explain the high level of branched-chain amino acids and free fatty acids in plasma of Type 2 Diabetic subjects from a metabolic fluxes perspective.
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O'Brien RM. Moving on from GWAS: functional studies on the G6PC2 gene implicated in the regulation of fasting blood glucose. Curr Diab Rep 2013; 13:768-77. [PMID: 24142592 PMCID: PMC4041587 DOI: 10.1007/s11892-013-0422-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Genome-wide association studies (GWAS) have shown that single-nucleotide polymorphisms (SNPs) in G6PC2 are the most important common determinants of variations in fasting blood glucose (FBG) levels. Molecular studies examining the functional impact of these SNPs on G6PC2 gene transcription and splicing suggest that they affect FBG by directly modulating G6PC2 expression. This conclusion is supported by studies on G6pc2 knockout (KO) mice showing that G6pc2 represents a negative regulator of basal glucose-stimulated insulin secretion that acts by hydrolyzing glucose-6-phosphate, thereby reducing glycolytic flux and opposing the action of glucokinase. Suppression of G6PC2 activity might, therefore, represent a novel therapy for lowering FBG and the risk of cardiovascular-associated mortality. GWAS and G6pc2 KO mouse studies also suggest that G6PC2 affects other aspects of beta cell function. The evolutionary benefit conferred by G6PC2 remains unclear, but it is unlikely to be related to its ability to modulate FBG.
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Affiliation(s)
- Richard M O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA,
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25
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Rydén AKE, Wesley JD, Coppieters KT, Von Herrath MG. Non-antigenic and antigenic interventions in type 1 diabetes. Hum Vaccin Immunother 2013; 10:838-46. [PMID: 24165565 PMCID: PMC4896560 DOI: 10.4161/hv.26890] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Type 1 diabetes (T1D) results from autoimmune destruction of the pancreatic β-cells. Current T1D therapies are exclusively focused on regulating glycemia rather than the underlying immune response. A handful of trials have sought to alter the clinical course of T1D using various broad immune-suppressors, e.g., cyclosporine A and azathioprine.1–3 The effect on β-cell preservation was significant, however, these therapies were associated with unacceptable side-effects. In contrast, more recent immunomodulators, such as anti-CD3 and antigenic therapies such as DiaPep277, provide a more targeted immunomodulation and have been generally well-tolerated and safe; however, as a monotherapy there appear to be limitations in terms of therapeutic benefit. Therefore, we argue that this new generation of immune-modifying agents will likely work best as part of a combination therapy. This review will summarize current immune-modulating therapies under investigation and discuss how to move the field of immunotherapy in T1D forward.
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Affiliation(s)
- Anna K E Rydén
- Type 1 Diabetes R&D Center; Novo Nordisk Inc.; Seattle, WA USA; Pacific Northwest Diabetes Research Institute; Seattle, WA USA
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26
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Yang T, Hohenstein AC, Lee CE, Hutton JC, Davidson HW. Mapping I-A(g7) restricted epitopes in murine G6PC2. Immunol Res 2013; 55:91-9. [PMID: 22983906 DOI: 10.1007/s12026-012-8368-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
G6PC2, also known as islet-specific glucose 6-phosphatase catalytic subunit-related protein (IGRP), is a major target of autoreactive CD8(+) T cells in both diabetic human subjects and the non-obese diabetic (NOD) mouse. However, in contrast to the abundant literature regarding the CD8(+) response to this antigen, much less is known about the potential involvement of IGRP-reactive CD4(+) T cells in diabetogenesis. The single previous study that examined this question in NOD mice was based upon a candidate epitope approach and identified three I-A(g7)-restricted epitopes that each elicited spontaneous responses in these animals. However, given the known inaccuracies of MHC class II epitope prediction algorithms, we hypothesized that additional specificities might also be targeted. To address this issue, we immunized NOD mice with membranes from insect cells overexpressing full-length recombinant mouse IGRP and measured recall responses of purified CD4(+) T cells using a library of overlapping peptides encompassing the entire 355-aa primary sequence. Nine peptides representing 8 epitopes gave recall responses, only 1 of which corresponded to any of the previously reported sequences. In each case proliferation was blocked by a monoclonal antibody to I-A(g7), but not the appropriate isotype control. Consistent with a role in diabetogenesis, proliferative responses to 4 of the 9 peptides (3 epitopes) were also detected in CD4(+) T cells purified from the pancreatic draining lymph nodes of pre-diabetic female animals, but not from peripheral lymph nodes or spleens of the same animals. Intriguingly, one of the newly identified spontaneously reactive epitopes (P8 [IGRP(55-72)]) is highly conserved between mice and man, suggesting that it might also be a target of HLA-DQ8-restricted T cells in diabetic human subjects, an hypothesis that we are currently testing.
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Affiliation(s)
- Tao Yang
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
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Baerenwald DA, Bonnefond A, Bouatia-Naji N, Flemming BP, Umunakwe OC, Oeser JK, Pound LD, Conley NL, Cauchi S, Lobbens S, Eury E, Balkau B, Lantieri O, Dadi PK, Jacobson DA, Froguel P, O’Brien RM. Multiple functional polymorphisms in the G6PC2 gene contribute to the association with higher fasting plasma glucose levels. Diabetologia 2013; 56:1306-16. [PMID: 23508304 PMCID: PMC4106008 DOI: 10.1007/s00125-013-2875-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 01/28/2013] [Indexed: 01/14/2023]
Abstract
AIMS/HYPOTHESIS We previously identified the G6PC2 locus as a strong determinant of fasting plasma glucose (FPG) and showed that a common G6PC2 intronic single nucleotide polymorphism (SNP) (rs560887) and two common G6PC2 promoter SNPs (rs573225 and rs13431652) are highly associated with FPG. However, these promoter SNPs have complex effects on G6PC2 fusion gene expression, and our data suggested that only rs13431652 is a potentially causative SNP. Here we examine the effect of rs560887 on G6PC2 pre-mRNA splicing and the contribution of an additional common G6PC2 promoter SNP, rs2232316, to the association signal. METHODS Minigene analyses were used to characterise the effect of rs560887 on G6PC2 pre-mRNA splicing. Fusion gene and gel retardation analyses characterised the effect of rs2232316 on G6PC2 promoter activity and transcription factor binding. The genetic association of rs2232316 with FPG variation was assessed using regression adjusted for age, sex and BMI in 4,220 Europeans with normal FPG. RESULTS The rs560887-G allele was shown to enhance G6PC2 pre-mRNA splicing, whereas the rs2232316-A allele enhanced G6PC2 transcription by promoting Foxa2 binding. Genetic analyses provide evidence for association of the rs2232316-A allele with increased FPG (β = 0.04 mmol/l; p = 4.3 × 10(-3)) as part of the same signal as rs560887, rs573225 and rs13431652. CONCLUSIONS/INTERPRETATION As with rs13431652, the in situ functional data with rs560887 and rs2232316 are in accord with the putative function of G6PC2 in pancreatic islets, and suggest that all three are potentially causative SNPs that contribute to the association between G6PC2 and FPG.
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Affiliation(s)
- D. A. Baerenwald
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
| | - A. Bonnefond
- CNRS-UMR-8199, Institut Pasteur de Lille, F-59019, Lille, France
- University Lille Nord de France, F-59019 Lille, France
| | - N. Bouatia-Naji
- CNRS-UMR-8199, Institut Pasteur de Lille, F-59019, Lille, France
- University Lille Nord de France, F-59019 Lille, France
- INSERM U970, Paris Cardiovascular Research Center PARCC, 56 rue Leblanc, F-75015 Paris, France
| | - B. P. Flemming
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
| | - O. C. Umunakwe
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
| | - J. K. Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
| | - L. D. Pound
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
| | - N. L. Conley
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
| | - S. Cauchi
- CNRS-UMR-8199, Institut Pasteur de Lille, F-59019, Lille, France
- University Lille Nord de France, F-59019 Lille, France
| | - S. Lobbens
- CNRS-UMR-8199, Institut Pasteur de Lille, F-59019, Lille, France
- University Lille Nord de France, F-59019 Lille, France
| | - E. Eury
- CNRS-UMR-8199, Institut Pasteur de Lille, F-59019, Lille, France
- University Lille Nord de France, F-59019 Lille, France
| | - B. Balkau
- INSERM, Centre for research in Epidemiology and Population Health (CESP), U1018, Epidemiology of diabetes, obesity and chronic renal disease over the lifecourse, F-94807, Villejuif, France
- Université Paris-Sud 11, UMRS 1018, F-94807 Villejuif, France
| | - O. Lantieri
- Institut inter-régional pour la santé (IRSA), F-37521 La Riche, France
| | - MAGIC Investigators
- Meta-Analysis of Glucose and Insulin related traits Consortium Investigators (http://www.magicinvestigators.org/)
| | - P. K. Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
| | - D. A. Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
| | - P. Froguel
- CNRS-UMR-8199, Institut Pasteur de Lille, F-59019, Lille, France
- University Lille Nord de France, F-59019 Lille, France
- Department of Genomics of Common Disease, School of Public Health, Imperial College London, W12 0NN London, UK
| | - R. M. O’Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee, USA
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Pound LD, Oeser JK, O’Brien TP, Wang Y, Faulman CJ, Dadi PK, Jacobson DA, Hutton JC, McGuinness OP, Shiota M, O’Brien RM. G6PC2: a negative regulator of basal glucose-stimulated insulin secretion. Diabetes 2013; 62:1547-56. [PMID: 23274894 PMCID: PMC3636628 DOI: 10.2337/db12-1067] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Elevated fasting blood glucose (FBG) is associated with increased risk for the development of type 2 diabetes and cardiovascular-associated mortality. Genome-wide association studies (GWAS) have linked polymorphisms in G6PC2 with variations in FBG and body fat, although not insulin sensitivity or glucose tolerance. G6PC2 encodes an islet-specific, endoplasmic reticulum-resident glucose-6-phosphatase catalytic subunit. A combination of in situ perfused pancreas, in vitro isolated islet, and in vivo analyses were used to explore the function of G6pc2 in mice. G6pc2 deletion had little effect on insulin sensitivity and glucose tolerance, whereas body fat was reduced in female G6pc2 knockout (KO) mice on both a chow and high-fat diet, observations that are all consistent with human GWAS data. G6pc2 deletion resulted in a leftward shift in the dose-response curve for glucose-stimulated insulin secretion (GSIS). As a consequence, under fasting conditions in which plasma insulin levels were identical, blood glucose levels were reduced in G6pc2 KO mice, again consistent with human GWAS data. Glucose-6-phosphatase activity was reduced, whereas basal cytoplasmic calcium levels were elevated in islets isolated from G6pc2 KO mice. These data suggest that G6pc2 represents a novel, negative regulator of basal GSIS that acts by hydrolyzing glucose-6-phosphate, thereby reducing glycolytic flux.
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Affiliation(s)
- Lynley D. Pound
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - James K. Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - Tracy P. O’Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - Yingda Wang
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - Chandler J. Faulman
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - Prasanna K. Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - David A. Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - John C. Hutton
- Barbara Davis Center for Childhood Diabetes, University of Colorado Health Sciences Center, Aurora, Colorado
| | - Owen P. McGuinness
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
| | - Richard M. O’Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee
- Corresponding author: Richard M. O’Brien,
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29
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Multiple roles of glucose-6-phosphatases in pathophysiology. Biochim Biophys Acta Gen Subj 2013; 1830:2608-18. [DOI: 10.1016/j.bbagen.2012.12.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 12/11/2012] [Accepted: 12/13/2012] [Indexed: 12/28/2022]
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30
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Boztug K, Klein C. Genetics and Pathophysiology of Severe Congenital Neutropenia Syndromes Unrelated to Neutrophil Elastase. Hematol Oncol Clin North Am 2013; 27:43-60, vii. [DOI: 10.1016/j.hoc.2012.11.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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31
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Arvan P, Pietropaolo M, Ostrov D, Rhodes CJ. Islet autoantigens: structure, function, localization, and regulation. Cold Spring Harb Perspect Med 2012; 2:cshperspect.a007658. [PMID: 22908193 DOI: 10.1101/cshperspect.a007658] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Islet autoantigens associated with autoimmune type 1 diabetes (T1D) are expressed in pancreatic β cells, although many show wider patterns of expression in the neuroendocrine system. Within pancreatic β cells, every T1D autoantigen is in one way or another linked to the secretory pathway. Together, these autoantigens play diverse roles in glucose regulation, metabolism of biogenic amines, as well as the regulation, formation, and packaging of secretory granules. The mechanism(s) by which immune tolerance to islet-cell antigens is lost during the development of T1D, remains unclear. Antigenic peptide creation for immune presentation may potentially link to the secretory biology of β cells in a number of ways, including proteasomal digestion of misfolded products, exocytosis and endocytosis of cell-surface products, or antigen release from dying β cells during normal or pathological turnover. In this context, we evaluate the biochemical nature and immunogenicity of the major autoantigens in T1D including (pro)insulin, GAD65, ZnT8, IA2, and ICA69.
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Affiliation(s)
- Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
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Liu J, Zhou L, Xiong K, Godlewski G, Mukhopadhyay B, Tam J, Yin S, Gao P, Shan X, Pickel J, Bataller R, O'Hare J, Scherer T, Buettner C, Kunos G. Hepatic cannabinoid receptor-1 mediates diet-induced insulin resistance via inhibition of insulin signaling and clearance in mice. Gastroenterology 2012; 142:1218-1228.e1. [PMID: 22307032 PMCID: PMC3482511 DOI: 10.1053/j.gastro.2012.01.032] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Revised: 01/18/2012] [Accepted: 01/24/2012] [Indexed: 12/15/2022]
Abstract
BACKGROUND & AIMS Obesity-related insulin resistance contributes to cardiovascular disease. Cannabinoid receptor-1 (CB(1)) blockade improves insulin sensitivity in obese animals and people, suggesting endocannabinoid involvement. We explored the role of hepatic CB(1) in insulin resistance and inhibition of insulin signaling pathways. METHODS Wild-type mice and mice with disruption of CB(1) (CB(1)(-/-) mice) or with hepatocyte-specific deletion or transgenic overexpression of CB(1) were maintained on regular chow or a high-fat diet (HFD) to induce obesity and insulin resistance. Hyperinsulinemic-euglycemic clamp analysis was used to analyze the role of the liver and hepatic CB(1) in HFD-induced insulin resistance. The cellular mechanisms of insulin resistance were analyzed in mouse and human isolated hepatocytes using small interfering or short hairpin RNAs and lentiviral knockdown of gene expression. RESULTS The HFD induced hepatic insulin resistance in wild-type mice, but not in CB(1)(-/-) mice or mice with hepatocyte-specific deletion of CB(1). CB(1)(-/-) mice that overexpressed CB(1) specifically in hepatocytes became hyperinsulinemic as a result of reduced insulin clearance due to down-regulation of the insulin-degrading enzyme. However, they had increased hepatic glucose production due to increased glycogenolysis, indicating hepatic insulin resistance; this was further increased by the HFD. In mice with hepatocytes that express CB(1), the HFD or CB(1) activation induced the endoplasmic reticulum stress response via activation of the Bip-PERK-eIF2α protein translation pathway. In hepatocytes isolated from human or mouse liver, CB(1) activation caused endoplasmic reticulum stress-dependent suppression of insulin-induced phosphorylation of akt-2 via phosphorylation of IRS1 at serine-307 and by inducing the expression of the serine and threonine phosphatase Phlpp1. Expression of CB(1) was up-regulated in samples from patients with nonalcoholic fatty liver disease. CONCLUSIONS Endocannabinoids contribute to diet-induced insulin resistance in mice via hepatic CB(1)-mediated inhibition of insulin signaling and clearance.
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Affiliation(s)
- Jie Liu
- Laboratory of Physiologic Studies, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892-9413, USA.
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Hayee B, Antonopoulos A, Murphy EJ, Rahman FZ, Sewell G, Smith BN, McCartney S, Furman M, Hall G, Bloom SL, Haslam SM, Morris HR, Boztug K, Klein C, Winchester B, Pick E, Linch DC, Gale RE, Smith AM, Dell A, Segal AW. G6PC3 mutations are associated with a major defect of glycosylation: a novel mechanism for neutrophil dysfunction. Glycobiology 2011; 21:914-24. [PMID: 21385794 PMCID: PMC3110488 DOI: 10.1093/glycob/cwr023] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2010] [Revised: 02/03/2011] [Accepted: 03/02/2011] [Indexed: 01/18/2023] Open
Abstract
Glucose-6-phosphatase, an enzyme localized in the endoplasmic reticulum (ER), catalyzes the hydrolysis of glucose-6-phosphate (G6P) to glucose and inorganic phosphate. In humans, there are three differentially expressed glucose-6-phosphatase catabolic genes (G6PC1-3). Recently, it has been shown that mutations in the G6PC3 gene result in a syndrome associating congenital neutropenia and various organ malformations. The enzymatic function of G6PC3 is dependent on G6P transport into the ER, mediated by G6P translocase (G6PT). Mutations in the gene encoding G6PT result in glycogen storage disease type-1b (GSD-1b). Interestingly, GSD-1b patients exhibit a similar neutrophil dysfunction to that observed in G6PC3-deficient patients. To better understand the causes of neutrophil dysfunction in both diseases, we have studied the neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase of patients with G6PC3 and G6PT syndromes. Unexpectedly, sodium dodecyl sulfate-polyacrylamide gel electrophoresis experiments indicated hypo-glycosylation of gp91(phox), the electron-transporting component of the NADPH oxidase, in all of these patients. Rigorous mass spectrometric glycomic profiling showed that most of the complex-type antennae which characterize the neutrophil N-glycome of healthy individuals were severely truncated in the patients' neutrophils. A comparable truncation of the core 2 antenna of the O-glycans was also observed. This aberrant neutrophil glycosylation is predicted to have profound effects on the neutrophil function and merit designation of both syndromes as a new class of congenital disorders of glycosylation.
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Affiliation(s)
- Bu'Hussain Hayee
- Department of Molecular Medicine, and
- Research Department of Haematology, University College London, London WC1E 6BT, UK
| | | | | | | | | | - Bradley N Smith
- Department of Gastroenterology, UCLH NHS Foundation Trust, London NW1 2BU, UK
| | - Sara McCartney
- Research Department of Haematology, University College London, London WC1E 6BT, UK
| | - Mark Furman
- Department of Paediatric Gastroenterology, Royal Free Hampstead NHS Trust, London WC1N 3JH, UK
| | - Georgina Hall
- Paediatric Haematology/Oncology Unit, Oxford Children's Hospital, John Radcliffe Hospital, Oxford, UK
| | - Stuart L Bloom
- Research Department of Haematology, University College London, London WC1E 6BT, UK
| | - Stuart M Haslam
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, UK
| | - Howard R Morris
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, UK
| | - Kaan Boztug
- Department of Pediatric Hematology/Oncology, Hannover Medical School, Hannover, Germany
- Center for Molecular Medicine (CeMM) of the Austrian Academy of Sciences, A-1080 Vienna, Austria
| | - Christoph Klein
- Department of Pediatric Hematology/Oncology, Hannover Medical School, Hannover, Germany
| | - Bryan Winchester
- Biochemistry Research Group, UCL Institute of Child Health, London WC1N 1EH, UK
| | - Edgar Pick
- Julius Friedrich Cohnheim Laboratory of Phagocyte Research, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - David C Linch
- Department of Gastroenterology, UCLH NHS Foundation Trust, London NW1 2BU, UK
| | - Rosemary E Gale
- Department of Gastroenterology, UCLH NHS Foundation Trust, London NW1 2BU, UK
| | | | - Anne Dell
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, UK
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Klein C. Genetic defects in severe congenital neutropenia: emerging insights into life and death of human neutrophil granulocytes. Annu Rev Immunol 2011; 29:399-413. [PMID: 21219176 DOI: 10.1146/annurev-immunol-030409-101259] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The discovery of genetic defects causing congenital neutropenia has illuminated mechanisms controlling differentiation, circulation, and decay of neutrophil granulocytes. Deficiency of the mitochondrial proteins HAX1 and AK2 cause premature apoptosis of myeloid progenitor cells associated with dissipation of the mitochondrial membrane potential, whereas mutations in ELA2/ELANE and G6PC3 are associated with signs of increased endoplasmic reticulum stress. Mutations in the transcriptional repressor GFI1 and the cytoskeletal regulator WASP also lead to defective neutrophil production. This unexpected diversity of factors suggests that multiple pathways are involved in the pathogenesis of congenital neutropenia.
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Affiliation(s)
- Christoph Klein
- Department of Pediatric Hematology/Oncology, Hannover Medical School, Germany.
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Moessinger C, Kuerschner L, Spandl J, Shevchenko A, Thiele C. Human lysophosphatidylcholine acyltransferases 1 and 2 are located in lipid droplets where they catalyze the formation of phosphatidylcholine. J Biol Chem 2011; 286:21330-9. [PMID: 21498505 DOI: 10.1074/jbc.m110.202424] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Phosphatidylcholine (PC) is synthesized by two different pathways, the Lands cycle and the Kennedy pathway. The recently identified key enzymes of the Lands cycle, lysophosphatidylcholine acyltransferase 1 and 2 (LPCAT1 and -2), were reported to localize to the endoplasmic reticulum and to function in lung surfactant production and in inflammation response. Here, we show in various mammalian cell lines that both enzymes additionally localize to lipid droplets (LDs), which consist of a core of neutral lipids surrounded by a monolayer of phospholipid, mainly PC. This dual localization is enabled by the monotopic topology of these enzymes demonstrated in this study. Furthermore, we show that LDs have the ability to locally synthesize PC and that this activity correlates with the LPCAT1 and -2 expression level. This suggests that LPCAT1 and -2 have, in addition to their known function in specialized cells, a ubiquitous role in LD-associated lipid metabolism.
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Affiliation(s)
- Christine Moessinger
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307 Dresden, Germany
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36
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Bouatia-Naji N, Bonnefond A, Baerenwald DA, Marchand M, Bugliani M, Marchetti P, Pattou F, Printz RL, Flemming BP, Umunakwe OC, Conley NL, Vaxillaire M, Lantieri O, Balkau B, Marre M, Lévy-Marchal C, Elliott P, Jarvelin MR, Meyre D, Dina C, Oeser JK, Froguel P, O'Brien RM. Genetic and functional assessment of the role of the rs13431652-A and rs573225-A alleles in the G6PC2 promoter that are strongly associated with elevated fasting glucose levels. Diabetes 2010; 59:2662-71. [PMID: 20622168 PMCID: PMC3279535 DOI: 10.2337/db10-0389] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE Genome-wide association studies have identified a single nucleotide polymorphism (SNP), rs560887, located in a G6PC2 intron that is highly correlated with variations in fasting plasma glucose (FPG). G6PC2 encodes an islet-specific glucose-6-phosphatase catalytic subunit. This study examines the contribution of two G6PC2 promoter SNPs, rs13431652 and rs573225, to the association signal. RESEARCH DESIGN AND METHODS We genotyped 9,532 normal FPG participants (FPG <6.1 mmol/l) for three G6PC2 SNPs, rs13431652 (distal promoter), rs573225 (proximal promoter), rs560887 (3rd intron). We used regression analyses adjusted for age, sex, and BMI to assess the association with FPG and haplotype analyses to assess comparative SNP contributions. Fusion gene and gel retardation analyses characterized the effect of rs13431652 and rs573225 on G6PC2 promoter activity and transcription factor binding. RESULTS Genetic analyses provide evidence for a strong contribution of the promoter SNPs to FPG variability at the G6PC2 locus (rs13431652: β = 0.075, P = 3.6 × 10(-35); rs573225 β = 0.073 P = 3.6 × 10(-34)), in addition to rs560887 (β = 0.071, P = 1.2 × 10(-31)). The rs13431652-A and rs573225-A alleles promote increased NF-Y and Foxa2 binding, respectively. The rs13431652-A allele is associated with increased FPG and elevated promoter activity, consistent with the function of G6PC2 in pancreatic islets. In contrast, the rs573225-A allele is associated with elevated FPG but reduced promoter activity. CONCLUSIONS Genetic and in situ functional data support a potential role for rs13431652, but not rs573225, as a causative SNP linking G6PC2 to variations in FPG, though a causative role for rs573225 in vivo cannot be ruled out.
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Affiliation(s)
- Nabila Bouatia-Naji
- CNRS-UMR-8199, Institut Pasteur de Lille, Lille, France
- University Lille Nord de France, Lille, France
| | - Amélie Bonnefond
- CNRS-UMR-8199, Institut Pasteur de Lille, Lille, France
- University Lille Nord de France, Lille, France
| | - Devin A. Baerenwald
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Marion Marchand
- CNRS-UMR-8199, Institut Pasteur de Lille, Lille, France
- University Lille Nord de France, Lille, France
| | - Marco Bugliani
- Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy
| | - Piero Marchetti
- Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy
| | - François Pattou
- INSERM U859, Université de Lille-Nord de France, Centre Hospitalier Regional et Universitaire de Lille, Lille, France
| | - Richard L. Printz
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Brian P. Flemming
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Obi C. Umunakwe
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Nicholas L. Conley
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Martine Vaxillaire
- CNRS-UMR-8199, Institut Pasteur de Lille, Lille, France
- University Lille Nord de France, Lille, France
| | | | | | - Michel Marre
- Department of Endocrinology, Diabetology and Nutrition, Bichat-Claude Bernard University Hospital, Assistance Publique des Hôpitaux de Paris, Paris, France; INSERM U695, Université Paris 7, Paris, France
| | - Claire Lévy-Marchal
- INSERM U690, Robert Debré Hospital, Paris; Paris Diderot University, Paris, France
| | - Paul Elliott
- Department of Epidemiology and Public Health, Imperial College London, London, U.K
| | - Marjo-Riitta Jarvelin
- Department of Epidemiology and Public Health, Imperial College London, London, U.K
- Institute of Health Sciences, University of Oulu, Department of Child and Adolescent Health, National Public Health Institute, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - David Meyre
- CNRS-UMR-8199, Institut Pasteur de Lille, Lille, France
- University Lille Nord de France, Lille, France
| | - Christian Dina
- CNRS-UMR-8199, Institut Pasteur de Lille, Lille, France
- University Lille Nord de France, Lille, France
| | - James K. Oeser
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Philippe Froguel
- CNRS-UMR-8199, Institut Pasteur de Lille, Lille, France
- University Lille Nord de France, Lille, France
- Department of Genomics of Common Disease, School of Public Health, Imperial College London, London, U.K
| | - Richard M. O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
- Corresponding author: Richard M. O'Brien,
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Wenzlau JM, Walter M, Gardner TJ, Frisch LM, Yu L, Eisenbarth GS, Ziegler AG, Davidson HW, Hutton JC. Kinetics of the post-onset decline in zinc transporter 8 autoantibodies in type 1 diabetic human subjects. J Clin Endocrinol Metab 2010; 95:4712-9. [PMID: 20610599 PMCID: PMC3050104 DOI: 10.1210/jc.2010-0169] [Citation(s) in RCA: 53] [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: 01/11/2023]
Abstract
CONTEXT Zinc transporter 8 (ZnT8) is a newly discovered islet autoantigen in human type 1A diabetes (T1D). OBJECTIVE The objective was to document changes in ZnT8 autoantibody (ZnT8A) titer and prevalence after onset of disease in relationship to 65 kDa glutamate decarboxylase antibody (GADA) and islet cell antigen antibody (IA2A). DESIGN/PATIENTS Autoantibody radioimmunoprecipitation assays were performed on sera from three groups: 21 individuals monitored every 3 months from diagnosis for 2.5 yr; 61 individuals monitored at six monthly intervals for 5-12 yr; and a cross-sectional study of 424 patients with T1D of 20-57 yr duration. Circulating C-peptide was determined as an index of residual β-cell function. RESULTS ZnT8A titers declined exponentially from clinical onset of T1D with a t(1/2) ranging from 26 to 530 wk, similar to C-peptide (23-300 wk). Life-table analysis of antibody prevalence to 12 yr indicated that ZnT8A measured with either Arg325 or Trp325 probes persisted for a shorter interval than IA2A. Although prevalence of ZnT8A, IA2A, and GADA were comparable at disease onset (70.4 vs. 73.4 vs. 64%), only 6.7% of individuals remained ZnT8A positive after 25 yr compared with 19.5% for IA2A and 25.9% for GADA. Titers of ZnT8A and IA2A in seropositive individuals decreased progressively, whereas GADA remained elevated consistent with periodic reactivation of GADA humoral autoimmunity. CONCLUSIONS ZnT8 humoral autoreactivity declines rapidly in the first years after disease onset and is less persistent than IA2A or GADA in the longer term. ZnT8A determination may be a useful measure of therapeutic efficacy in the context of immune-based clinical interventions.
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Affiliation(s)
- J M Wenzlau
- Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Aurora, Colorado 80045, USA
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De Silva NMG, Frayling TM. Novel biological insights emerging from genetic studies of type 2 diabetes and related metabolic traits. Curr Opin Lipidol 2010; 21:44-50. [PMID: 19956073 DOI: 10.1097/mol.0b013e328334fdb6] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
PURPOSE OF REVIEW In the past 3 years, genome-wide association studies have identified many tens of common genetic variants associated with metabolic diseases and traits. Although much further research is needed to identify the target genes, the associations between gene variants and diseases are already providing biological insights. The purpose of this review is to update the reader with the most relevant findings, with a particular emphasis on type 2 diabetes (T2D) and glucose metabolism, and discuss some of the biological implications of the genetic findings. RECENT FINDINGS Largely through recent genome-wide association studies, we now know of approximately 20 gene variants associated with T2D, 10 with body mass index (BMI) and obesity, four with fasting glucose levels in the normoglycaemic population and over 30 with lipid levels. These findings are stimulating many new important areas of research related to metabolic diseases. For T2D and glucose metabolism, we discuss a number of aspects and implications of the genetic findings, including the observations that T2D gene variants are not usually in or near obvious candidate genes, highlighting the poor prior knowledge of the biology of the disease; most T2D gene variants are associated with beta-cell function rather than insulin resistance; there is a difference between genes that influence variation in normal glucose levels compared with those influencing onset and progression of diabetes; and there is a genetic link between diabetes and foetal growth. SUMMARY Genetic studies in the past 3 years have provided a greatly increased knowledge of the regions of the genome involved in adverse metabolic consequences. There are now over 100 common genetic variants reproducibly associated with metabolic traits, including reduced beta-cell function, obesity, increased lipid levels and increased glucose levels. These genetic findings are already altering perceptions of how these traits develop and interact to result in diseases such as T2D.
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Affiliation(s)
- N Maneka G De Silva
- Genetics of Complex Traits, Institute of Biomedical and Clinical Science, Peninsula College of Medicine and Dentistry, University of Exeter, Exeter, UK
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Hutton JC, Davidson HW. Cytokine-induced dicing and splicing in the beta-cell and the immune response in type 1 diabetes. Diabetes 2010; 59:335-6. [PMID: 20103713 PMCID: PMC2809971 DOI: 10.2337/db09-1767] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- John C Hutton
- Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA.
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40
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Rose CS, Grarup N, Krarup NT, Poulsen P, Wegner L, Nielsen T, Banasik K, Faerch K, Andersen G, Albrechtsen A, Borch-Johnsen K, Clausen JO, Jørgensen T, Vaag A, Pedersen O, Hansen T. A variant in the G6PC2/ABCB11 locus is associated with increased fasting plasma glucose, increased basal hepatic glucose production and increased insulin release after oral and intravenous glucose loads. Diabetologia 2009; 52:2122-9. [PMID: 19669124 DOI: 10.1007/s00125-009-1463-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Accepted: 06/29/2009] [Indexed: 01/05/2023]
Abstract
AIMS/HYPOTHESIS An association between elevated fasting plasma glucose and the common rs560887 G allele in the G6PC2/ABCB11 locus has been reported. In Danes we aimed to examine rs560887 in relation to plasma glucose and serum insulin responses following oral and i.v. glucose loads and in relation to hepatic glucose production during a hyperinsulinaemic-euglycaemic clamp. Furthermore, we examined rs560887 for association with impaired fasting glycaemia (IFG), impaired glucose tolerance (IGT), type 2 diabetes and components of the metabolic syndrome. METHODS rs560887 was genotyped in the Inter99 cohort (n = 5,899), in 366 young, healthy Danes, in non-diabetic relatives of type 2 diabetic patients (n = 196), and in young and elderly twins (n = 159). Participants underwent an OGTT, an IVGTT or a 2 h hyperinsulinaemic-euglycaemic clamp. RESULTS The rs560887 G allele associated with elevated fasting plasma glucose (p = 2 x 10(-14)) but not with plasma glucose levels at 30 min (p = 0.9) or 120 min (p = 0.9) during an OGTT. G allele carriers had elevated levels of serum insulin at 30 min during an OGTT (p = 1 x 10(-4)) and relatives of type 2 diabetes patients carrying the G allele had an increased acute insulin response (p = 4 x 10(-4)) during an IVGTT. Among elderly twins, G allele carriers had higher basal hepatic glucose production (p = 0.04). Finally, the G allele associated with the risk of having IFG (OR 1.26, 95% CI 1.08-1.47, p = 0.002), but not with IGT (OR 0.94, 95% CI 0.82-1.08, p = 0.4) or type 2 diabetes (OR 0.93, 95% CI 0.84-1.04, p = 0.2). CONCLUSIONS/INTERPRETATION The common rs560887 G allele in the G6PC2/ABCB11 locus is associated with increased fasting glycaemia and increased risk of IFG, associations that may be partly related to an increased basal hepatic glucose production rate.
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Affiliation(s)
- C S Rose
- Hagedorn Research Institute, Gentofte, Denmark
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Boztug K, Klein C. Novel genetic etiologies of severe congenital neutropenia. Curr Opin Immunol 2009; 21:472-80. [PMID: 19782549 DOI: 10.1016/j.coi.2009.09.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2009] [Revised: 08/24/2009] [Accepted: 09/10/2009] [Indexed: 11/19/2022]
Abstract
Severe congenital neutropenia (SCN) comprises a heterogenous group of primary immunodeficiency disorders collectively characterized by paucity of mature neutrophils. In recent years, progress has been made with respect to the elucidation of genetic causes underlying syndromic and non-syndromic variants of SCN. Most cases of autosomal dominant SCN are associated with mutations in the neutrophil elastase (ELA-2/ELANE) gene, autosomal recessive forms of this disorder can be caused by mutations in the gene encoding the mitochondrial protein HAX-1. Rarely, SCN can be caused by mutations in the gene encoding the transcription factor GFI1 or activating mutations in the Wiskott-Aldrich syndrome (WAS) gene, respectively. More recently, a complex disorder associating SCN and developmental aberrations was identified, caused by mutations in the glucose-6-phosphatase catalytic subunit 3 (G6PC3) gene. Despite our increasing knowledge of the genetic etiologies of SCN, the molecular pathophysiology underlying these disorders remains only partially understood.
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Affiliation(s)
- Kaan Boztug
- Department of Pediatric Hematology/Oncology, Hannover Medical School, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
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Abstract
Glucose-6-phosphatase catalyzes the hydrolysis of glucose 6-phosphate (G6P) to glucose and inorganic phosphate. It is a multicomponent system located in the endoplasmic reticulum that comprises several integral membrane proteins, namely a catalytic subunit (G6PC) and transporters for G6P, inorganic phosphate, and glucose. The G6PC gene family contains three members, designated G6PC, G6PC2, and G6PC3. The tissue-specific expression patterns of these genes differ, and mutations in all three genes have been linked to distinct diseases in humans. This minireview discusses the disease association and transcriptional regulation of the G6PC genes as well as the biological functions of the encoded proteins.
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Affiliation(s)
- John C Hutton
- Barbara Davis Center for Childhood Diabetes, University of Colorado at Denver, Aurora, Colorado 80045, USA
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43
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Wenzlau JM, Frisch LM, Gardner TJ, Sarkar S, Hutton JC, Davidson HW. Novel antigens in type 1 diabetes: the importance of ZnT8. Curr Diab Rep 2009; 9:105-12. [PMID: 19323954 DOI: 10.1007/s11892-009-0019-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The presence of circulating islet cell autoantibodies distinguishes type 1A diabetes (T1D) from other diabetic syndromes and determination of autoantigen genes and proteins is instrumental in understanding T1D as a clinical entity and in investigating the pathogenesis of the disease. ZnT8 was recently defined as a candidate autoantigen based on a -bioinformatics analysis focused on discovery of beta-cell-specific proteins associated with the regulatory pathway of secretion. The native molecule does not lend itself easily to solution-phase autoantibody assays, but ligands based on the predicted domain structure and molecular modeling have led to robust diagnostic procedures showing high specificities and sensitivities that complement current T1D autoantibody assays and add to the predictive value of their measurement. The incorporation of genetic and structural epitope analysis into ZnT8A determinations adds a further dimension to its diagnostic value and understanding of its role in the autoimmune disease process.
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Affiliation(s)
- Janet M Wenzlau
- Barbara Davis Center for Childhood Diabetes, University of Colorado at Denver and Health Sciences Center, PO Box 6511, 1775 North Ursula Court, Aurora, CO 80045, USA
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44
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Hu C, Zhang R, Wang C, Ma X, Wang C, Fang Q, Bao Y, Xiang K, Jia W. A genetic variant of G6PC2 is associated with type 2 diabetes and fasting plasma glucose level in the Chinese population. Diabetologia 2009; 52:451-6. [PMID: 19082990 DOI: 10.1007/s00125-008-1241-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Accepted: 11/20/2008] [Indexed: 01/05/2023]
Abstract
AIMS/HYPOTHESIS Single nucleotide polymorphisms (SNPs) in G6PC2 have been reported to be associated with fasting plasma glucose level in several populations of European descent. However, whether G6PC2 variants have a similar effect in other ethnic groups is unknown. The aim of this study was to investigate the effect of common variants of G6PC2 on type 2 diabetes and related clinical features in a Chinese population. METHODS We selected four SNPs, rs13387347, rs2232316, rs492594 and rs16856187, tagging all the common variants spanning the G6PC2 gene (r(2) >or= 0.8) based on HapMap Chinese data, and genotyped them in a group of 3,676 Shanghai Chinese individuals, comprising 1,876 cases and 1,800 controls. RESULTS Three SNPs were nominally associated with type 2 diabetes, with rs16856187 showing the strongest evidence for association (p = 0.0009, empirical p = 0.0047). Further conditional analysis revealed that the association signal arose from an individual SNP, rs16856187. This SNP was also associated with fasting plasma glucose level in participants with normal glucose regulation (p = 0.0002), with the fasting plasma glucose level observed to increase by 0.067 mmol/l with each copy of the rare C allele. CONCLUSIONS/INTERPRETATION In this study we identified a novel risk-conferring G6PC2 SNP for type 2 diabetes in a Chinese population and confirmed the previous finding that G6PC2 variants are associated with fasting plasma glucose concentration.
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Affiliation(s)
- C Hu
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, People's Republic of China
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Boztug K, Appaswamy G, Ashikov A, Schäffer AA, Salzer U, Diestelhorst J, Germeshausen M, Brandes G, Lee-Gossler J, Noyan F, Gatzke AK, Minkov M, Greil J, Kratz C, Petropoulou T, Pellier I, Bellanné-Chantelot C, Rezaei N, Mönkemöller K, Irani-Hakimeh N, Bakker H, Gerardy-Schahn R, Zeidler C, Grimbacher B, Welte K, Klein C. A syndrome with congenital neutropenia and mutations in G6PC3. N Engl J Med 2009; 360:32-43. [PMID: 19118303 PMCID: PMC2778311 DOI: 10.1056/nejmoa0805051] [Citation(s) in RCA: 250] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND The main features of severe congenital neutropenia are the onset of severe bacterial infections early in life, a paucity of mature neutrophils, and an increased risk of leukemia. In many patients, the genetic causes of severe congenital neutropenia are unknown. METHODS We performed genomewide genotyping and linkage analysis on two consanguineous pedigrees with a total of five children affected with severe congenital neutropenia. Candidate genes from the linkage interval were sequenced. Functional assays and reconstitution experiments were carried out. RESULTS All index patients were susceptible to bacterial infections and had very few mature neutrophils in the bone marrow; structural heart defects, urogenital abnormalities, and venous angiectasia on the trunk and extremities were additional features. Linkage analysis of the two index families yielded a combined multipoint lod score of 5.74 on a linkage interval on chromosome 17q21. Sequencing of G6PC3, the candidate gene encoding glucose-6-phosphatase, catalytic subunit 3, revealed a homozygous missense mutation in exon 6 that abolished the enzymatic activity of glucose-6-phosphatase in all affected children in the two families. The patients' neutrophils and fibroblasts had increased susceptibility to apoptosis. The myeloid cells showed evidence of increased endoplasmic reticulum stress and increased activity of glycogen synthase kinase 3beta (GSK-3beta). We identified seven additional, unrelated patients who had severe congenital neutropenia with syndromic features and distinct biallelic mutations in G6PC3. CONCLUSIONS Defective function of glucose-6-phosphatase, catalytic subunit 3, underlies a severe congenital neutropenia syndrome associated with cardiac and urogenital malformations.
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Affiliation(s)
- Kaan Boztug
- Departments of Pediatric Hematology/Oncology, Hannover Medical School, Germany
| | | | - Angel Ashikov
- Departments of Cellular Chemistry, Hannover Medical School, Germany
| | | | - Ulrich Salzer
- Department of Rheumatology and Clinical Immunology, University Medical Center Freiburg, Freiburg, Germany
| | - Jana Diestelhorst
- Departments of Pediatric Hematology/Oncology, Hannover Medical School, Germany
| | | | - Gudrun Brandes
- Departments of Cell Biology, Hannover Medical School, Germany
| | | | - Fatih Noyan
- Departments of Pediatric Hematology/Oncology, Hannover Medical School, Germany
| | | | | | - Johann Greil
- Department of Pediatric Oncology, Hematology and Immunology, Children’s Hospital, University of Heidelberg, Germany
| | - Christian Kratz
- Division of, Pediatric Hematology/Oncology, Department of Pediatrics and Adolescent Medicine, University of Freiburg, Germany
| | - Theoni Petropoulou
- 1Department of Pediatrics, Aghia Sophia Children’s Hospital, University of Athens, Greece
| | - Isabelle Pellier
- Department of Pediatric Hematology, Immunology and Oncology, CHU Angers, France
| | | | - Nima Rezaei
- Immunology, Asthma and, Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Kirsten Mönkemöller
- Department of, General Pediatrics, Children’s Hospital Amsterdamer Straße, Cologne, Germany
| | - Noha Irani-Hakimeh
- Department of, Laboratory Medicine, Saint Georges University Hospital, Beirut, Lebanon
| | - Hans Bakker
- Departments of Cellular Chemistry, Hannover Medical School, Germany
| | | | - Cornelia Zeidler
- Departments of Pediatric Hematology/Oncology, Hannover Medical School, Germany
| | - Bodo Grimbacher
- Department of, Immunology, Royal Free Hospital and University College London, London, UK
| | - Karl Welte
- Departments of Pediatric Hematology/Oncology, Hannover Medical School, Germany
| | - Christoph Klein
- Departments of Pediatric Hematology/Oncology, Hannover Medical School, Germany
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Martin CC, Flemming BP, Wang Y, Oeser JK, O’Brien RM. Foxa2 and MafA regulate islet-specific glucose-6-phosphatase catalytic subunit-related protein gene expression. J Mol Endocrinol 2008; 41:315-28. [PMID: 18753309 PMCID: PMC2614309 DOI: 10.1677/jme-08-0062] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP/G6PC2) is a major autoantigen in both mouse and human type 1 diabetes. IGRP is selectively expressed in islet beta cells and polymorphisms in the IGRP gene have recently been associated with variations in fasting blood glucose levels and cardiovascular-associated mortality in humans. Chromatin immunoprecipitation (ChIP) assays have shown that the IGRP promoter binds the islet-enriched transcription factors Pax-6 and BETA2. We show here, again using ChIP assays, that the IGRP promoter also binds the islet-enriched transcription factors MafA and Foxa2. Single binding sites for these factors were identified in the proximal IGRP promoter, mutation of which resulted in decreased IGRP fusion gene expression in betaTC-3, Hamster insulinoma tumor (HIT), and Min6 cells. ChiP assays have shown that the islet-enriched transcription factor Pdx-1 also binds the IGRP promoter, but mutational analysis of four Pdx-1 binding sites in the proximal IGRP promoter revealed surprisingly little effect of Pdx-1 binding on IGRP fusion gene expression in betaTC-3 cells. In contrast, in both HIT and Min6 cells mutation of these four Pdx-1 binding sites resulted in a approximately 50% reduction in fusion gene expression. These data suggest that the same group of islet-enriched transcription factors, namely Pdx-1, Pax-6, MafA, BETA2, and Foxa2, directly or indirectly regulate expression of the two major autoantigens in type 1 diabetes.
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Affiliation(s)
| | | | | | | | - Richard M. O’Brien
- To whom correspondence should be addressed: Department of Molecular Physiology and Biophysics, 8415 MRB IV, 2213 Garland Ave, Vanderbilt University Medical School, Nashville, TN 37232-0615, Telephone (615) 936-1503; Facsimile (615) 322-7236, E-mail:
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Chen WM, Erdos MR, Jackson AU, Saxena R, Sanna S, Silver KD, Timpson NJ, Hansen T, Orrù M, Grazia Piras M, Bonnycastle LL, Willer CJ, Lyssenko V, Shen H, Kuusisto J, Ebrahim S, Sestu N, Duren WL, Spada MC, Stringham HM, Scott LJ, Olla N, Swift AJ, Najjar S, Mitchell BD, Lawlor DA, Smith GD, Ben-Shlomo Y, Andersen G, Borch-Johnsen K, Jørgensen T, Saramies J, Valle TT, Buchanan TA, Shuldiner AR, Lakatta E, Bergman RN, Uda M, Tuomilehto J, Pedersen O, Cao A, Groop L, Mohlke KL, Laakso M, Schlessinger D, Collins FS, Altshuler D, Abecasis GR, Boehnke M, Scuteri A, Watanabe RM. Variations in the G6PC2/ABCB11 genomic region are associated with fasting glucose levels. J Clin Invest 2008; 118:2620-8. [PMID: 18521185 DOI: 10.1172/jci34566] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Accepted: 04/23/2008] [Indexed: 12/19/2022] Open
Abstract
Identifying the genetic variants that regulate fasting glucose concentrations may further our understanding of the pathogenesis of diabetes. We therefore investigated the association of fasting glucose levels with SNPs in 2 genome-wide scans including a total of 5,088 nondiabetic individuals from Finland and Sardinia. We found a significant association between the SNP rs563694 and fasting glucose concentrations (P = 3.5 x 10(-7)). This association was further investigated in an additional 18,436 nondiabetic individuals of mixed European descent from 7 different studies. The combined P value for association in these follow-up samples was 6.9 x 10(-26), and combining results from all studies resulted in an overall P value for association of 6.4 x 10(-33). Across these studies, fasting glucose concentrations increased 0.01-0.16 mM with each copy of the major allele, accounting for approximately 1% of the total variation in fasting glucose. The rs563694 SNP is located between the genes glucose-6-phosphatase catalytic subunit 2 (G6PC2) and ATP-binding cassette, subfamily B (MDR/TAP), member 11 (ABCB11). Our results in combination with data reported in the literature suggest that G6PC2, a glucose-6-phosphatase almost exclusively expressed in pancreatic islet cells, may underlie variation in fasting glucose, though it is possible that ABCB11, which is expressed primarily in liver, may also contribute to such variation.
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Affiliation(s)
- Wei-Min Chen
- Department of Public Health Sciences, University of Virginia, Charlottesville, Virginia, USA
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Lindbloom S, Lecluyse M, Schermerhorn T. Cloning and comparative bioinformatic analysis of feline glucose-6-phosphatase catalytic subunit cDNA. ACTA ACUST UNITED AC 2008; 19:256-63. [PMID: 17852328 DOI: 10.1080/10425170701574920] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Glucose-6-phosphatase is a multicomponent enzyme composed of a transporter subunit and a catalytic subunit that is involved in hepatic glucose production. The objective of the present study was to determine the complete nucleotide sequence of feline hepatic glucose-6-phosphatase catalytic subunit (G6Pc) cDNA and to perform comparative analysis of the molecular features of the feline G6Pc cDNA and protein. Feline G6Pc cDNA contains 2261 bases and encodes a 357 aa protein. The feline cDNA and protein are highly conserved with overall identity ranging from 73-86% to 86-95%, respectively, among mammalian species. Membrane topology, phosphatase consensus sequence, ER retention sequence, N-glycosylation sites and active site residues are conserved in the feline protein. Analysis of the putative feline G6Pc protein did not reveal any species-specific features to explain the unusual in vivo regulation of G6Pase activity reported in feline liver.
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Affiliation(s)
- Sara Lindbloom
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506-5606, USA.
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Abstract
PURPOSE OF REVIEW The beta-cell-specific zinc transporter isoform 8 (SLC30A8) has recently emerged both as a major autoantigenic target of type 1 diabetes and also as a genetic marker for type 2 diabetes. We examine the hypothesis that the cell specificity and cellular localization of this granule membrane protein are significant factors in its contribution to the pathogenesis of these diseases. RECENT FINDINGS Both type 1 diabetes and type 2 diabetes are associated with islet functional failure and both diseases may be linked to stress responses and changes in the secretory pathway, which lead to cell apoptosis and thus directly to reduction of beta-cell mass or activation of underlying autoimmunity. In both cases, the common polymorphism at aa 325 has been implicated in disease, in type 1 diabetes by determining the autoantibody epitope specificity and in type 2 diabetes through association with altered beta-cell mass and impaired secretion. SUMMARY Functional studies of the transporter will be key to understanding the role of ZnT8 in type 2 diabetes. Investigation of the cellular immune response to ZnT8 will be essential in evaluating its contribution to type 1 diabetes. Measurement of autoantibodies to ZnT8 takes us a step closer to detection of prediabetes in the general population.
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Affiliation(s)
- Janet M Wenzlau
- Barbara Davis Center for Childhood Diabetes, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80045, USA
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Petyuk VA, Qian WJ, Hinault C, Gritsenko MA, Singhal M, Monroe ME, Camp DG, Kulkarni RN, Smith RD. Characterization of the mouse pancreatic islet proteome and comparative analysis with other mouse tissues. J Proteome Res 2008; 7:3114-26. [PMID: 18570455 DOI: 10.1021/pr800205b] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The pancreatic islets of Langerhans, and especially the insulin-producing beta cells, play a central role in the maintenance of glucose homeostasis. Alterations in the expression of multiple proteins in the islets that contribute to the maintenance of islet function are likely to underlie the pathogenesis of types 1 and 2 diabetes. To identify proteins that constitute the islet proteome, we provide the first comprehensive proteomic characterization of pancreatic islets for mouse, the most commonly used animal model in diabetes research. Using strong cation exchange fractionation coupled with reversed phase LC-MS/MS we report the confident identification of 17,350 different tryptic peptides covering 2612 proteins having at least two unique peptides per protein. The data set also identified approximately 60 post-translationally modified peptides including oxidative modifications and phosphorylation. While many of the identified phosphorylation sites corroborate those previously known, the oxidative modifications observed on cysteinyl residues reveal potentially novel information suggesting a role for oxidative stress in islet function. Comparative analysis with 15 available proteomic data sets from other mouse tissues and cells revealed a set of 133 proteins predominantly expressed in pancreatic islets. This unique set of proteins, in addition to those with known functions such as peptide hormones secreted from the islets, contains several proteins with as yet unknown functions. The mouse islet protein and peptide database accessible at (http://ncrr.pnl.gov), provides an important reference resource for the research community to facilitate research in the diabetes and metabolism fields.
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Affiliation(s)
- Vladislav A Petyuk
- Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA
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