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Zasu A, Hishima F, Thauvin M, Yoneyama Y, Kitani Y, Hakuno F, Volovitch M, Takahashi SI, Vriz S, Rampon C, Kamei H. NADPH-Oxidase Derived Hydrogen Peroxide and Irs2b Facilitate Re-oxygenation-Induced Catch-Up Growth in Zebrafish Embryo. Front Endocrinol (Lausanne) 2022; 13:929668. [PMID: 35846271 PMCID: PMC9283716 DOI: 10.3389/fendo.2022.929668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 05/31/2022] [Indexed: 11/30/2022] Open
Abstract
Oxygen deprivation induces multiple changes at the cellular and organismal levels, and its re-supply also brings another special physiological status. We have investigated the effects of hypoxia/re-oxygenation on embryonic growth using the zebrafish model: hypoxia slows embryonic growth, but re-oxygenation induces growth spurt or catch-up growth. The mitogen-activated kinase (MAPK)-pathway downstream insulin-like growth factor (IGF/Igf) has been revealed to positively regulate the re-oxygenation-induced catch-up growth, and the role of reactive oxygen species generated by environmental oxygen fluctuation is potentially involved in the phenomenon. Here, we report the role of NADPH-oxidase (Nox)-dependent hydrogen peroxide (H2O2) production in the MAPK-activation and catch-up growth. The inhibition of Nox significantly blunted catch-up growth and MAPK-activity. Amongst two zebrafish insulin receptor substrate 2 genes (irs2a and irs2b), the loss of irs2b, but not its paralog irs2a, resulted in blunted MAPK-activation and catch-up growth. Furthermore, irs2b forcedly expressed in mammalian cells allowed IGF-MAPK augmentation in the presence of H2O2, and the irs2b deficiency completely abolished the somatotropic action of Nox in re-oxygenation condition. These results indicate that redox signaling alters IGF/Igf signaling to facilitate hypoxia/re-oxygenation-induced embryonic growth compensation.
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Affiliation(s)
- Ayaka Zasu
- Faculty of Biological Science and Technology, Institute of Science and Engineering, Kanazawa University, Noto, Japan
| | - Futa Hishima
- Faculty of Biological Science and Technology, Institute of Science and Engineering, Kanazawa University, Noto, Japan
| | - Marion Thauvin
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, Centre national de la recherche scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Paris Sciences et Lettres (PSL) Research University, Paris, France
- Sorbonne Université, Ecole Doctorale 515-Complexité du Vivant, Paris, France
| | - Yosuke Yoneyama
- Departments of Animal Sciences and Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Institute of Research, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yoichiro Kitani
- Noto Marine Laboratory, Division of Marine Environmental Studies, Institute of Nature and Environmental Technology, Kanazawa University, Noto, Japan
| | - Fumihiko Hakuno
- Departments of Animal Sciences and Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Michel Volovitch
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, Centre national de la recherche scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Paris Sciences et Lettres (PSL) Research University, Paris, France
- Department of Biology, École Normale Supérieure, Paris Sciences et Lettres (PSL) Research University, Paris, France
- Laboratoire des BioMolécules (LBM), Département de Chimie, Sorbonne Université, École Normale Supérieure, Paris Sciences et Lettres (PSL) University, Sorbonne Université, Centre national de la recherche scientifique (CNRS), Paris, France
| | - Shin-Ichiro Takahashi
- Departments of Animal Sciences and Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Sophie Vriz
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, Centre national de la recherche scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Paris Sciences et Lettres (PSL) Research University, Paris, France
- Laboratoire des BioMolécules (LBM), Département de Chimie, Sorbonne Université, École Normale Supérieure, Paris Sciences et Lettres (PSL) University, Sorbonne Université, Centre national de la recherche scientifique (CNRS), Paris, France
- Université Paris-Cité, Faculty of Sciences, Paris, France
| | - Christine Rampon
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, Centre national de la recherche scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Paris Sciences et Lettres (PSL) Research University, Paris, France
- Laboratoire des BioMolécules (LBM), Département de Chimie, Sorbonne Université, École Normale Supérieure, Paris Sciences et Lettres (PSL) University, Sorbonne Université, Centre national de la recherche scientifique (CNRS), Paris, France
- Université Paris-Cité, Faculty of Sciences, Paris, France
| | - Hiroyasu Kamei
- Faculty of Biological Science and Technology, Institute of Science and Engineering, Kanazawa University, Noto, Japan
- *Correspondence: Hiroyasu Kamei,
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Abstract
Reduction of insulin/insulin-like growth factor 1 (IGF1) signaling (IIS) extends the lifespan of various species. So far, several longevity mouse models have been developed containing mutations related to growth signaling deficiency by targeting growth hormone (GH), IGF1, IGF1 receptor, insulin receptor, and insulin receptor substrate. In addition, p70 ribosomal protein S6 kinase 1 (S6K1) knockout leads to lifespan extension. S6K1 encodes an important kinase in the regulation of cell growth. S6K1 is regulated by mechanistic target of rapamycin (mTOR) complex 1. The v-myc myelocytomatosis viral oncogene homolog (MYC)-deficient mice also exhibits a longevity phenotype. The gene expression profiles of these mice models have been measured to identify their longevity mechanisms. Here, we summarize our knowledge of long-lived mouse models related to growth and discuss phenotypic characteristics, including organ-specific gene expression patterns.
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Affiliation(s)
- Seung-Soo Kim
- Institute of Animal Molecular Biotechnology, Korea University, Seoul 02841, Korea
| | - Cheol-Koo Lee
- Institute of Animal Molecular Biotechnology, Korea University, Seoul 02841; Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02481, Korea
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Abstract
PURPOSE OF REVIEW Inadequate insulin-producing pancreatic β-cell mass is a key feature of both type 1 and type 2 diabetes. Efforts to regenerate β-cell mass from pancreatic precursors may thus ameliorate absolute or relative insulin deficiency, thereby improving glucose homeostasis. A clear understanding of the processes that govern the generation of new β-cells in the mature pancreas will be fundamental to success in this effort. This review discusses the current state of knowledge regarding β-cell regeneration and emphasizes recent studies of significance. RECENT FINDINGS Recent reports demonstrate regenerative potential in the adult human pancreas. Further, they build on the strong existing evidence that proliferation of preexisting β-cells is the predominant source of new β-cells in adulthood by dissecting the cell cycle machinery components and critical signaling pathways required for β-cell proliferation. Finally, β-cell trophic peptides have demonstrated preclinical potential as pharmacologic regenerative agents and may form the basis for clinical interventions in the future. SUMMARY Efforts to augment β-cell regeneration by enhancing β-cell viability and proliferation may lead to novel therapeutic approaches for type 1 and type 2 diabetes. An intimate understanding of the molecular mechanisms underlying the regulation of β-cell proliferation and survival will be fundamental to the optimization of endogenous β-cell regeneration.
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Albury-Warren TM, Pandey V, Spinel LP, Masternak MM, Altomare DA. Prediabetes linked to excess glucagon in transgenic mice with pancreatic active AKT1. J Endocrinol 2016; 228:49-59. [PMID: 26487674 PMCID: PMC4803065 DOI: 10.1530/joe-15-0288] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/20/2015] [Indexed: 12/31/2022]
Abstract
Protein kinase B/AKT has three isoforms (AKT1-3) and is renowned for its central role in the regulation of cell growth and proliferation, due to its constitutive activation in various cancers. AKT2, which is highly expressed in insulin-responsive tissues, has been identified as a primary regulator of glucose metabolism as Akt2 knockout mice (Akt2(-/-)) are glucose-intolerant and insulin-resistant. However, the role of AKT1 in glucose metabolism is not as clearly defined. We previously showed that mice with myristoylated Akt1 (AKT1(Myr)) expressed through a bicistronic Pdx1-TetA and TetO-MyrAkt1 system were susceptible to islet cell carcinomas, and in this study we characterized an early onset, prediabetic phenotype. Beginning at weaning (3 weeks of age), the glucose-intolerant AKT1(Myr) mice exhibited non-fasted hyperglycemia, which progressed to fasted hyperglycemia by 5 months of age. The glucose intolerance was attributed to a fasted hyperglucagonemia, and hepatic insulin resistance detectable by reduced phosphorylation of the insulin receptor following insulin injection into the inferior vena cava. In contrast, treatment with doxycycline diet to turn off the transgene caused attenuation of the non-fasted and fasted hyperglycemia, thus affirming AKT1 hyperactivation as the trigger. Collectively, this model highlights a novel glucagon-mediated mechanism by which AKT1 hyperactivation affects glucose homeostasis and provides an avenue to better delineate the molecular mechanisms responsible for diabetes mellitus and the potential association with pancreatic cancer.
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Affiliation(s)
- Toya M Albury-Warren
- Burnett School of Biomedical SciencesCollege of Medicine, University of Central Florida, 6900 Lake Nona Boulevard, Orlando, Florida 32827, USADepartment of Head and Neck SurgeryThe Greater Poland Cancer Centre, 61-866 Poznan, Poland
| | - Veethika Pandey
- Burnett School of Biomedical SciencesCollege of Medicine, University of Central Florida, 6900 Lake Nona Boulevard, Orlando, Florida 32827, USADepartment of Head and Neck SurgeryThe Greater Poland Cancer Centre, 61-866 Poznan, Poland
| | - Lina P Spinel
- Burnett School of Biomedical SciencesCollege of Medicine, University of Central Florida, 6900 Lake Nona Boulevard, Orlando, Florida 32827, USADepartment of Head and Neck SurgeryThe Greater Poland Cancer Centre, 61-866 Poznan, Poland
| | - Michal M Masternak
- Burnett School of Biomedical SciencesCollege of Medicine, University of Central Florida, 6900 Lake Nona Boulevard, Orlando, Florida 32827, USADepartment of Head and Neck SurgeryThe Greater Poland Cancer Centre, 61-866 Poznan, Poland Burnett School of Biomedical SciencesCollege of Medicine, University of Central Florida, 6900 Lake Nona Boulevard, Orlando, Florida 32827, USADepartment of Head and Neck SurgeryThe Greater Poland Cancer Centre, 61-866 Poznan, Poland
| | - Deborah A Altomare
- Burnett School of Biomedical SciencesCollege of Medicine, University of Central Florida, 6900 Lake Nona Boulevard, Orlando, Florida 32827, USADepartment of Head and Neck SurgeryThe Greater Poland Cancer Centre, 61-866 Poznan, Poland
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Dhindsa S, Ghanim H, Batra M, Kuhadiya ND, Abuaysheh S, Sandhu S, Green K, Makdissi A, Hejna J, Chaudhuri A, Punyanitya M, Dandona P. Insulin Resistance and Inflammation in Hypogonadotropic Hypogonadism and Their Reduction After Testosterone Replacement in Men With Type 2 Diabetes. Diabetes Care 2016; 39:82-91. [PMID: 26622051 PMCID: PMC4686848 DOI: 10.2337/dc15-1518] [Citation(s) in RCA: 179] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Accepted: 10/04/2015] [Indexed: 02/03/2023]
Abstract
OBJECTIVE One-third of men with type 2 diabetes have hypogonadotropic hypogonadism (HH). We conducted a randomized placebo-controlled trial to evaluate the effect of testosterone replacement on insulin resistance in men with type 2 diabetes and HH. RESEARCH DESIGN AND METHODS A total of 94 men with type 2 diabetes were recruited into the study; 50 men were eugonadal, while 44 men had HH. Insulin sensitivity was calculated from the glucose infusion rate (GIR) during hyperinsulinemic-euglycemic clamp. Lean body mass and fat mass were measured by DEXA and MRI. Subcutaneous fat samples were taken to assess insulin signaling genes. Men with HH were randomized to receive intramuscular testosterone (250 mg) or placebo (1 mL saline) every 2 weeks for 24 weeks. RESULTS Men with HH had higher subcutaneous and visceral fat mass than eugonadal men. GIR was 36% lower in men with HH. GIR increased by 32% after 24 weeks of testosterone therapy but did not change after placebo (P = 0.03 for comparison). There was a decrease in subcutaneous fat mass (-3.3 kg) and increase in lean mass (3.4 kg) after testosterone treatment (P < 0.01) compared with placebo. Visceral and hepatic fat did not change. The expression of insulin signaling genes (IR-β, IRS-1, AKT-2, and GLUT4) in adipose tissue was significantly lower in men with HH and was upregulated after testosterone treatment. Testosterone treatment also caused a significant fall in circulating concentrations of free fatty acids, C-reactive protein, interleukin-1β, tumor necrosis factor-α, and leptin (P < 0.05 for all). CONCLUSIONS Testosterone treatment in men with type 2 diabetes and HH increases insulin sensitivity, increases lean mass, and decreases subcutaneous fat.
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Affiliation(s)
- Sandeep Dhindsa
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY Division of Endocrinology, Diabetes and Metabolism, Texas Tech University Health Sciences Center, Odessa, TX
| | - Husam Ghanim
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | - Manav Batra
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | - Nitesh D Kuhadiya
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | - Sanaa Abuaysheh
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | - Sartaj Sandhu
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | - Kelly Green
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | - Antoine Makdissi
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | - Jeanne Hejna
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | - Ajay Chaudhuri
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
| | | | - Paresh Dandona
- Division of Endocrinology, Diabetes and Metabolism, State University of New York at Buffalo, Buffalo, NY
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IRS2 and PTEN are key molecules in controlling insulin sensitivity in podocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:3224-34. [PMID: 26384875 DOI: 10.1016/j.bbamcr.2015.09.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 09/01/2015] [Accepted: 09/14/2015] [Indexed: 01/03/2023]
Abstract
Insulin signaling to the glomerular podocyte is important for normal kidney function and is implicated in the pathogenesis of diabetic nephropathy (DN). This study determined the role of the insulin receptor substrate 2 (IRS2) in this system. Conditionally immortalized murine podocytes were generated from wild-type (WT) and insulin receptor substrate 2-deficient mice (Irs2(-/-)). Insulin signaling, glucose transport, cellular motility and cytoskeleton rearrangement were then analyzed. Within the glomerulus IRS2 is enriched in the podocyte and is preferentially phosphorylated by insulin in comparison to IRS1. Irs2(-/-) podocytes are significantly insulin resistant in respect to AKT signaling, insulin-stimulated GLUT4-mediated glucose uptake, filamentous actin (F-actin) cytoskeleton remodeling and cell motility. Mechanistically, we discovered that Irs2 deficiency causes insulin resistance through up-regulation of the phosphatase and tensin homolog (PTEN). Importantly, suppressing PTEN in Irs2(-/-) podocytes rescued insulin sensitivity. In conclusion, this study has identified for the first time IRS2 as a critical molecule for sensitizing the podocyte to insulin actions through its ability to modulate PTEN expression. This finding reveals two potential molecular targets in the podocyte for modulating insulin sensitivity and treating DN.
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Oliveira JM, Rebuffat SA, Gasa R, Gomis R. Targeting type 2 diabetes: lessons from a knockout model of insulin receptor substrate 2. Can J Physiol Pharmacol 2014; 92:613-20. [DOI: 10.1139/cjpp-2014-0114] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Insulin receptor substrate 2 (IRS2) is a widely expressed protein that regulates crucial biological processes including glucose metabolism, protein synthesis, and cell survival. IRS2 is part of the insulin – insulin-like growth factor (IGF) signaling pathway and mediates the activation of the phosphotidylinositol 3-kinase (PI3K)–Akt and the Ras–mitogen-activated protein kinase (MAPK) cascades in insulin target tissues and in the pancreas. The best evidence of this is that systemic elimination of the Irs2 in mice (Irs2−/−) recapitulates the pathogenesis of type 2 diabetes (T2D), in that diabetes arises as a consequence of combined insulin resistance and beta-cell failure. Indeed, work using this knockout mouse has confirmed the importance of IRS2 in the control of glucose homeostasis and especially in the survival and function of pancreatic beta-cells. These studies have shown that IRS2 is critically required for beta-cell compensation in conditions of increased insulin demand. Importantly, islets isolated from T2D patients exhibit reduced IRS2 expression, which supports the likely contribution of altered IRS2-dependent signaling to beta-cell failure in human T2D. For all these reasons, the Irs2−/− mouse has been and will be essential for elucidating the inter-relationship between beta-cell function and insulin resistance, as well as to delineate therapeutic strategies to protect beta-cells during T2D progression.
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Affiliation(s)
- Joana Moitinho Oliveira
- Diabetes and Obesity Research Laboratory, Institut d’Investigations Biomediques August Pi i Sunyer, Centre Esther Koplowitz, C/Rosselló, 149-153 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Sandra A. Rebuffat
- Diabetes and Obesity Research Laboratory, Institut d’Investigations Biomediques August Pi i Sunyer, Centre Esther Koplowitz, C/Rosselló, 149-153 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Rosa Gasa
- Diabetes and Obesity Research Laboratory, Institut d’Investigations Biomediques August Pi i Sunyer, Centre Esther Koplowitz, C/Rosselló, 149-153 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Ramon Gomis
- Diabetes and Obesity Research Laboratory, Institut d’Investigations Biomediques August Pi i Sunyer, Centre Esther Koplowitz, C/Rosselló, 149-153 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- University of Barcelona, Hospital Clínic, Barcelona, Spain
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Affiliation(s)
- Aaron Bender
- Diabetes, Obesity and Metabolism Institute, The Icahn School of Medicine at Mount Sinai, Atran 5, 1 Gustave L. Levy Place, Box 1152, New York, NY, 10029, USA
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Yang KT, Bayan JA, Zeng N, Aggarwal R, He L, Peng Z, Kassa A, Kim M, Luo Z, Shi Z, Medina V, Boddupally K, Stiles BL. Adult-onset deletion of Pten increases islet mass and beta cell proliferation in mice. Diabetologia 2014; 57:352-61. [PMID: 24162585 PMCID: PMC3918745 DOI: 10.1007/s00125-013-3085-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 09/27/2013] [Indexed: 12/31/2022]
Abstract
AIMS/HYPOTHESIS Adult beta cells have a diminished ability to proliferate. Phosphatase and tensin homologue (PTEN) is a lipid phosphatase that antagonises the function of the mitogenic phosphatidylinositol 3-kinase (PI3K) pathway. The objective of this study was to understand the role of PTEN and PI3K signalling in the maintenance of beta cells postnatally. METHODS We developed a Pten (lox/lox); Rosa26 (lacZ); RIP-CreER (+) model that permitted us to induce Pten deletion by treatment with tamoxifen in mature animals. We evaluated islet mass and function as well as beta cell proliferation in 3- and 12-month-old mice treated with tamoxifen (Pten deleted) vs mice treated with vehicle (Pten control). RESULTS Deletion of Pten in juvenile (3-month-old) beta cells significantly induced their proliferation and increased islet mass. The expansion of islet mass occurred concomitantly with the enhanced ability of the Pten-deleted mice to maintain euglycaemia in response to streptozotocin treatment. In older mice (>12 months of age), deletion of Pten similarly increased islet mass and beta cell proliferation. This novel finding suggests that PTEN-regulated mechanisms may override the age-onset diminished ability of beta cells to respond to mitogenic stimulation. We also found that proteins regulating G1/S cell-cycle transition, such as cyclin D1, cyclin D2, p27 and p16, were altered when PTEN was lost, suggesting that they may play a role in PTEN/PI3K-regulated beta cell proliferation in adult tissue. CONCLUSIONS/INTERPRETATION The signals regulated by the PTEN/PI3K pathway are important for postnatal maintenance of beta cells and regulation of their proliferation in adult tissues.
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Affiliation(s)
- Kai-Ting Yang
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA, USA
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Zhao X, Tang YG, Wu SV, Wang C, Perfetti R, Khoury N, Cai D, He F, Su X, Go VLW, Hui H. The global transcriptional response of isolated human islets of langerhans to glucagon-like Peptide-1 receptor agonist liraglutide. ISRN ENDOCRINOLOGY 2012; 2012:608672. [PMID: 23056957 PMCID: PMC3465925 DOI: 10.5402/2012/608672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 08/20/2012] [Indexed: 12/24/2022]
Abstract
GLP-1 and its analog have been used in diabetes treatment; however, the direct alteration of gene expression profile in human islets induced by GLP-1 has not been reported. In present study, transcriptional gene expression in the liraglutide-treated human islets was analyzed with 12 human U133A chips including 23000 probe sets. The data compared between liraglutide and control groups showed a significant difference on glucose-induced insulin secretion, rather than viability. Microarray analysis identified 7000 genes expressed in human islets. Eighty genes were found to be modulated by liraglutide treatment. Furthermore, the products of these genes are proteins involved in binding capability, enzyme activity, transporter function, signal transduction, cell proliferation, apoptosis, and cell differentiation. Our data provides a set of information in the complex events, following the activation of the GLP-1 receptor in the islets of Langerhans.
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Affiliation(s)
- Xiaoning Zhao
- Center of Metabolic Diseases, Beijiao Hospital, Southern Medical University, North 1838 Guangzhou Road, Guangzhou 510515, China ; International Center for Metabolic Diseases, Southern Medical University (SMU), 8 Floor, Life Science Build, North 1838 Guangzhou Road, Guangzhou 510515, China ; Department of Medicine, Cedar-Sinai Medical Center, Los Angeles, CA 90048, USA
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Inflammation-Mediated Regulation of MicroRNA Expression in Transplanted Pancreatic Islets. J Transplant 2012; 2012:723614. [PMID: 22655170 PMCID: PMC3359768 DOI: 10.1155/2012/723614] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 02/09/2012] [Accepted: 02/20/2012] [Indexed: 12/22/2022] Open
Abstract
Nonspecific inflammation in the transplant microenvironment results in β-cell dysfunction and death influencing negatively graft outcome. MicroRNA (miRNA) expression and gene target regulation in transplanted islets are not yet well characterized. We evaluated the impact of inflammation on miRNA expression in transplanted rat islets. Islets exposed in vitro to proinflammatory cytokines and explanted syngeneic islet grafts were evaluated by miRNA arrays. A subset of 26 islet miRNAs was affected by inflammation both in vivo and in vitro. Induction of miRNAs was dependent on NF-κB, a pathway linked with cytokine-mediated islet cell death. RT-PCR confirmed expression of 8 miRNAs. The association between these miRNAs and mRNA target-predicting algorithms in genome-wide RNA studies of β-cell inflammation identified 238 potential miRNA gene targets. Several genes were ontologically associated with regulation of insulin signaling and secretion, diabetes, and islet physiology. One of the most activated miRNAs was miR-21. Overexpression of miR-21 in insulin-secreting MIN6 cells downregulated endogenous expression of the tumor suppressor Pdcd4 and of Pclo, a Ca2+ sensor protein involved in insulin secretion. Bioinformatics identified both as potential targets. The integrated analysis of miRNA and mRNA expression profiles revealed potential targets that may identify molecular targets for therapeutic interventions.
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Abstract
New therapeutic approaches to counter the increasing prevalence of obesity and type 2 diabetes mellitus are in high demand. Deregulation of the phosphoinositide-3-kinase (PI3K)/v-akt murine thymoma viral oncogene homologue (AKT), mitogen-activated protein kinase (MAPK) and AMP-activated protein kinase (AMPK) pathways, which are essential for glucose homeostasis, often results in obesity and diabetes. Thus, these pathways should be attractive therapeutic targets. However, with the exception of metformin, which is considered to function mainly by activating AMPK, no treatment for the metabolic syndrome based on targeting protein kinases has yet been developed. By contrast, therapies based on the inhibition of the PI3K/AKT and MAPK pathways are already successful in the treatment of diverse cancer types and inflammatory diseases. This contradiction prompted us to review the signal transduction mechanisms of PI3K/AKT, MAPK and AMPK and their roles in glucose homeostasis, and we also discuss current clinical implications.
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Galli C, Passeri G, Macaluso GM. FoxOs, Wnts and oxidative stress-induced bone loss: new players in the periodontitis arena? J Periodontal Res 2011; 46:397-406. [PMID: 21332475 DOI: 10.1111/j.1600-0765.2011.01354.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND AND OBJECTIVE Chronic periodontitis is a widespread disease affecting tooth-supporting structures that can lead to extensive loss of periodontal ligament and bone, ultimately resulting in tooth loss. Extensive evidence has demonstrated a strong association between age, metabolic disorders such as type II diabetes, oxidative stress and alveolar bone loss. The molecular players controlling bone maintenance and underlying age-related bone loss and its links to the general metabolism are currently the object of intense research. MATERIAL AND METHODS Recent findings are summarized to elucidate the molecular mechanisms linking oxidative stress, bone loss and metabolic factors. RESULTS It is well known that reactive oxygen species are an inevitable consequence of cellular respiration and that organisms have developed an efficient array of defenses against them. The core of this complex defense line is a family of transcription factors, known as FoxOs, which can bind to β-catenin and initiate a transcriptional programme regulating cell apoptosis, DNA repair and degradation of reactive oxygen species. An increase in reactive oxygen species due, for example, to age or insulin resistance, generates a situation in which bone formation is impaired by activation of FoxO, and a decrease in Wnt signaling and bone resorption are promoted. CONCLUSION The balance between FoxO and the Wnt pathway is finely tuned by systemic and local factors, creating a far-reaching mechanism that dictates the fate of mesenchymal progenitors and regulates the homeostasis of bone, providing a rationale for the impairment of systemic and alveolar bone maintenance clinically observed with age and metabolic diseases.
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Affiliation(s)
- C Galli
- Department of Internal Medicine Unit of Periodontology, University of Parma, Parma, Italy.
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Hay N. Akt isoforms and glucose homeostasis - the leptin connection. Trends Endocrinol Metab 2011; 22:66-73. [PMID: 20947368 PMCID: PMC3427792 DOI: 10.1016/j.tem.2010.09.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 09/10/2010] [Accepted: 09/13/2010] [Indexed: 12/31/2022]
Abstract
The serine/threonine kinase Akt, also known as protein kinase B, has been the focus of substantial attention, largely because it is frequently activated in human cancers. However, relatively little is known about the roles of Akt, particularly the individual isoforms of Akt, in glucose homeostasis in vivo. This review summarizes data on the role of Akt isoforms in glucose homeostasis and diabetes. Emphasis is given to the observation that certain combinations of whole-body Akt1 and Akt2 deficiencies reduce circulating levels of leptin and that restoration of leptin levels restores normal glucose homeostasis in diabetic Akt-deficient mice. The significance of these findings, together with recent observations suggesting that leptin emulates insulin action, is also discussed.
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Affiliation(s)
- Nissim Hay
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA.
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Abstract
The Insulin Receptor/PI 3-kinase (INSR/PI3K) signalling pathway is a key regulator of cell and organismal metabolism. Phosphoinositides generated by PI 3-kinases following insulin and other metabolic hormone receptor activation give rise to signalling cascades involving a multitude of effector molecules. The physiological roles of these molecules have been dissected with the use of both pharmacological and genetic tools. Furthermore, tissue-specific mutagenesis has revealed the extent to which individual insulin-target organs and signalling molecules contribute to whole-body carbohydrate and lipid homeostasis. These studies have generated important information with respect to the function of these molecules in normal physiology and their implication in the development of metabolic diseases such as type-2 diabetes and obesity.
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16
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Norquay LD, D'Aquino KE, Opare-Addo LM, Kuznetsova A, Haas M, Bluestone JA, White MF. Insulin receptor substrate-2 in beta-cells decreases diabetes in nonobese diabetic mice. Endocrinology 2009; 150:4531-40. [PMID: 19574401 PMCID: PMC2754683 DOI: 10.1210/en.2009-0395] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Insulin receptor substrate-2 (Irs2) integrates insulin-like signals with glucose and cAMP agonists to regulate beta-cell growth, function, and survival. This study investigated whether increased Irs2 concentration in beta-cells could reduce beta-cell destruction and the incidence of type 1 diabetes in nonobese diabetic (NOD) mice. NOD mice were intercrossed with C57BL/6 mice overexpressing Irs2 specifically in beta-cells to create NOD(Irs2) mice. After backcrossing NOD(Irs2) mice for 12 generations, glucose homeostasis and diabetes incidence were compared against NOD littermates. Compared with 12-wk-old NOD mice, the progression of severe insulitis was reduced and islet mass was increased in NOD(Irs2) mice. Moreover, the risk of diabetes decreased 50% in NOD(Irs2) mice until the experiment was terminated at 40 wk of age. Nondiabetic NOD(Irs2) mice displayed better glucose tolerance than nondiabetic NOD mice throughout the duration of the study and up to the age of 18 months. The effect of Irs2 to increase islet mass and improve glucose tolerance raised the possibility that NOD(Irs2) mice might have an increased capacity to respond to anti-CD3 antibody, which can induce remission of overt diabetes in some NOD mice. Anti-CD3 antibody injections restored glucose tolerance in newly diabetic NOD and NOD(Irs2) mice; however, anti-CD3-treated NOD(Irs2) mice were less likely than NOD mice to relapse during the experimental period because they displayed 10-fold greater beta-cell mass and mitogenesis. In conclusion, increased Irs2 attenuated the progression of beta-cell destruction, promoted beta-cell mitogenesis, and reduced diabetes incidence in NOD(Irs2) mice.
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Affiliation(s)
- Lisa D Norquay
- Division of Endocrinology, Children's Hospital Boston, Harvard Medical School, Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA
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17
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Elghazi L, Bernal-Mizrachi E. Akt and PTEN: beta-cell mass and pancreas plasticity. Trends Endocrinol Metab 2009; 20:243-51. [PMID: 19541499 PMCID: PMC4456182 DOI: 10.1016/j.tem.2009.03.002] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 03/02/2009] [Accepted: 03/03/2009] [Indexed: 12/31/2022]
Abstract
The capacity of pancreatic beta-cells to adapt to insulin resistance is crucial for glucose homeostasis and is a factor in the development of type 2 diabetes. The insulin receptor substrate (insulin receptor 2/phosphoinositide 3-kinase [PI3K]) pathway plays a crucial part in regulating beta-cell mass and function. The serine-threonine kinase Akt, also known as protein kinase B, is one of the major downstream targets of the PI3K pathway and is negatively regulated by phosphatase and tensin homologue deleted on chromosome 10. This Akt signaling pathway has recently been implicated in cell-cycle progression and survival of pancreatic beta-cells. Understanding the mechanisms that link Akt to modulation of beta-cell mass, function and plasticity will positively affect treatment of human diabetes.
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Affiliation(s)
- Lynda Elghazi
- Department of Internal Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine Saint-Louis, MO 63110, USA
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18
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Leptin deficiency and beta-cell dysfunction underlie type 2 diabetes in compound Akt knockout mice. Mol Cell Biol 2009; 29:3151-62. [PMID: 19289493 DOI: 10.1128/mcb.01792-08] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Phenotypic analyses of mice null for the individual Akt isoforms suggested that they are functionally distinct and that only Akt2 plays a role in diabetes. We show here that Akt isoforms play compensatory and complementary roles in glucose homeostasis and diabetes. Insulin resistance in Akt2(-/-) mice was inhibited by haplodeficiency of Pten, suggesting that other Akt isoforms can compensate for Akt2 function. Haplodeficiency of Akt1 in Akt2(-/-) mice, however, converts prediabetes to overt type 2 diabetes, which is also reversed by haplodeficiency of Pten. Akt3 does not appear to contribute significantly to diabetes. Overt type 2 diabetes in Akt1(+/-) Akt2(-/-) mice is manifested by hyperglycemia due to beta-cell dysfunction combined with impaired glucose homeostasis due to markedly decreased leptin levels. Restoring leptin levels was sufficient to restore normal blood glucose and insulin levels in Akt1(+/-) Akt2(-/-) and Akt2(-/-) mice, suggesting that leptin-deficiency is the predominant cause of diabetes in these mice. These results uncover a new mechanism linking Akt to diabetes, provide a therapeutic strategy, and show that diabetes induced as a consequence of cancer therapy, via Akt inhibition, could be reversed by leptin therapy.
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19
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Ikubo M, Wada T, Fukui K, Ishiki M, Ishihara H, Asano T, Tsuneki H, Sasaoka T. Impact of lipid phosphatases SHIP2 and PTEN on the time- and Akt-isoform-specific amelioration of TNF-alpha-induced insulin resistance in 3T3-L1 adipocytes. Am J Physiol Endocrinol Metab 2009; 296:E157-64. [PMID: 19001549 DOI: 10.1152/ajpendo.90581.2008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
TNF-alpha is a major contributor to the pathogenesis of insulin resistance associated with obesity and inflammation by serine phosphorylating and degrading insulin receptor substrate-1. Presently, we further found that pretreatment with TNF-alpha inhibited insulin-induced phosphorylation of Akt2 greater than Akt1. Since lipid phosphatases SH2-containing inositol 5'-phoshatase 2 (SHIP2) and phosphatase and tensin homologs deleted on chromosome 10 (PTEN) are negative regulators of insulin's metabolic signaling at the step downstream of phosphatidylinositol 3-kinase, we investigated the Akt isoform-specific properties of these phosphatases in the negative regulation after short- and long-term insulin treatment and examined the influence of inhibition on the amelioration of insulin resistance caused by TNF-alpha in 3T3-L1 adipocytes. Adenovirus-mediated overexpression of WT-SHIP2 decreased the phosphorylation of Akt2 greater than Akt1 after insulin stimulation up to 15 min. Expression of a dominant-negative DeltaIP-SHIP2 enhanced the phosphorylation of Akt2 up to 120 min. On the other hand, overexpression of WT-PTEN inhibited the phosphorylation of both Akt1 and Akt2 after short- but not long-term insulin treatment. The expression of DeltaIP-PTEN enhanced the phosphorylation of Akt1 at 120 min and that of Akt2 at 2 min. Interestingly, the expression of DeltaIP-SHIP2, but not DeltaIP-PTEN, protected against the TNF-alpha inhibition of insulin-induced phosphorylation of Akt2, GSK3, and AS160, whereas both improved the TNF-alpha inhibition of insulin-induced 2-deoxyglucose uptake. The results indicate that these lipid phosphatases possess different characteristics according to the time and preference of Akt isoform-dependent signaling in the negative regulation of the metabolic actions of insulin, whereas both inhibitions are effective in the amelioration of insulin resistance caused by TNF-alpha.
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Affiliation(s)
- Mariko Ikubo
- Department of Internal Medicine, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
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20
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Szabolcs M, Keniry M, Simpson L, Reid LJ, Koujak S, Schiff SC, Davidian G, Licata S, Gruvberger-Saal S, Murty VVVS, Nandula S, Efstratiadis A, Kushner JA, White MF, Parsons R. Irs2 inactivation suppresses tumor progression in Pten+/- mice. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 174:276-86. [PMID: 19095950 DOI: 10.2353/ajpath.2009.080086] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Mutations in the phosphatase and tensin homologue (PTEN)/phosphatidylinositol-3 kinase-alpha (PI3K) signaling pathway are frequently found in human cancer. In addition, Pten(+/-) mice develop tumors in multiple organs because of the activation of the PI3K signaling cascade. Because activation of PI3K signaling leads to feedback inhibition of insulin receptor substrate-2 (IRS2) expression, an upstream activator of PI3K, we therefore anticipated that IRS2 expression would be low in tumors that lack PTEN. Surprisingly, however, an elevation of IRS2 was often detected in tumor samples in which PTEN levels were compromised. To determine the potential contribution of Irs2 to tumor progression, Pten(+/-) mice were crossed with Irs2(+/-) mice. Deletion of Irs2 did not affect the initiation of neoplasia found in Pten(+/-) mice but suppressed cancer cell growth, proliferation, and invasion through the basement membrane. Deletion of Irs2 also attenuated the expression of Myc in prostatic intraepithelial neoplasia in Pten(+/-) mice. In addition, the expression levels of IRS2 and MYC were highly correlated in human prostate cancer, and IRS2 could stimulate MYC expression in cultured cells. Our findings provide evidence that the PI3K-activating adaptor Irs2 contributes to tumor progression in Pten(+/-) mice by stimulating both Myc and DNA synthesis.
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Affiliation(s)
- Matthias Szabolcs
- Institute for Cancer Genetics, College of Physicians and Surgeons, Columbia University, New York, New York, USA
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21
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Abstract
Insulin-like signaling is critical for nutrient homeostasis, growth and survival. However, work with lower metazoans-Caenorhabditis elegans and Drosophila-shows that reduced insulin-like signaling extends life span. In addition, reduced insulin signaling in higher animals-rodents and humans-causes glucose intolerance and hyperinsulinemia that progresses to diabetes and shortens the life span of affected individuals. Hyperinsulinemia usually develops to maintain glucose homeostasis and prevent the progression toward life-threatening type 2 diabetes; however, increased circulating insulin may have negative effects on the brain that promote age-related disease. We discuss the possibility that the brain is the site where reduced insulin-like signaling can consistently extend mammalian life span-just as reduced insulin-like signaling extends the life span of lower metazoans.
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Affiliation(s)
- Akiko Taguchi
- Howard Hughes Medical Institute, Division of Endocrinology, Children's Hospital Boston, Harvard Medical School, Karp Family Research Laboratories, Boston, MA 02115, USA
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22
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Abstract
Forkhead proteins, and FoxO1 in particular, play a significant role in regulating whole body energy metabolism. Glucose homeostasis is achieved by adjusting endogenous glucose production as well as glucose uptake by peripheral tissues in response to insulin. In the fasted state, the liver is primarily responsible for maintaining glucose levels, with FoxO1 playing a key role in promoting the expression of gluconeogenic enzymes. Following feeding, pancreatic beta cells secrete insulin, which promotes the uptake of glucose by peripheral tissues including skeletal muscle and adipose tissue, and can in part suppress gluconeogenic enzyme expression in the liver. In addition to directly regulating metabolism, FoxO1 also plays a role in the formation of both adipose tissue and skeletal muscle, two major organs that are critical for maintaining energy homeostasis. The importance of FoxO1 in energy homeostasis is particularly striking under conditions of metabolic dysfunction or insulin resistance. In obese or diabetic states, FoxO1-dependent gene expression promotes some of the deleterious characteristics associated with these conditions, including hyperglycemia and glucose intolerance. In addition, the increase in pancreatic beta cell mass that normally occurs in response to a rise in insulin demand is blunted by nuclear FoxO1 expression. However, under these same pathophysiological conditions, FoxO1 expression may help drive the expression of genes involved in combating oxidative stress, thereby preserving cellular function. FoxO1 may also be involved in promoting the switch from carbohydrate to fatty acid as the major energy source during starvation.
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23
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Park S, Hong SM, Sung SR. Exendin-4 and exercise promotes β-cell function and mass through IRS2 induction in islets of diabetic rats. Life Sci 2008; 82:503-11. [PMID: 18237751 DOI: 10.1016/j.lfs.2007.12.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 11/21/2007] [Accepted: 12/08/2007] [Indexed: 12/19/2022]
Affiliation(s)
- Sunmin Park
- Department of Food & Nutrition, College of Natural Science, Hoseo University, Asan-Si, South Korea.
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24
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Vinciguerra M, Veyrat-Durebex C, Moukil MA, Rubbia-Brandt L, Rohner-Jeanrenaud F, Foti M. PTEN down-regulation by unsaturated fatty acids triggers hepatic steatosis via an NF-kappaBp65/mTOR-dependent mechanism. Gastroenterology 2008; 134:268-80. [PMID: 18166358 DOI: 10.1053/j.gastro.2007.10.010] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Accepted: 09/28/2007] [Indexed: 12/13/2022]
Abstract
BACKGROUND & AIMS Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a tumor suppressor and a regulator of insulin sensitivity in peripheral tissues. In the liver, PTEN deletion increases insulin sensitivity, but induces steatosis, steatohepatitis, and hepatocellular carcinoma. Here, we investigated the pathophysiologic mechanisms regulating PTEN expression in the liver and the development of steatosis. METHODS PTEN expression was evaluated in the liver of rats and human beings having metabolic syndrome. Signaling pathways regulating PTEN expression and lipid accumulation in hepatocytes were examined in vitro. RESULTS PTEN expression is down-regulated in the liver of rats having steatosis and high plasma levels of fatty acids, as well as in steatotic human livers. Unsaturated fatty acids inhibited PTEN expression in HepG2 cells via activation of a signaling complex formed by the mammalian target of rapamycin (mTOR) and nuclear factor-kappaB (NF-kappaB). Down-regulation of PTEN expression induced steatosis by affecting import, esterification, and extracellular release of fatty acids. CONCLUSIONS Hepatic steatosis can be mediated by alterations of PTEN expression in hepatocytes exposed to high levels of unsaturated fatty acids. Furthermore, our data revealed interaction between mTOR and NF-kappaB, suggesting cross-talk between these 2 pathways.
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Affiliation(s)
- Manlio Vinciguerra
- Department of Cell Physiology and Metabolism, Geneva Medical Faculty, Geneva University Hospital, Switzerland
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25
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Grempler R, Leicht S, Kischel I, Eickelmann P, Redemann N. Inhibition of SH2-domain containing inositol phosphatase 2 (SHIP2) in insulin producing INS1E cells improves insulin signal transduction and induces proliferation. FEBS Lett 2007; 581:5885-90. [DOI: 10.1016/j.febslet.2007.11.066] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Revised: 10/25/2007] [Accepted: 11/20/2007] [Indexed: 12/31/2022]
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26
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Abstract
The functions ascribed to PTEN have become more diverse since its discovery as a putative phosphatase mutated in many human tumors. Although it can dephosphorylate lipids and proteins, it also has functions independent of phosphatase activity in normal and pathological states. In addition, control of PTEN function is very complex. It is positively and negatively regulated at the transcriptional level, as well as post-translationally by phosphorylation, ubiquitylation, oxidation and acetylation. Although most of its tumor suppressor activity is likely to be caused by lipid dephosphorylation at the plasma membrane, PTEN also resides in the cytoplasm and nucleus, and its subcellular distribution is under strict control. Deregulation of PTEN function is implicated in other human diseases in addition to cancer, including diabetes and autism.
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Affiliation(s)
- Tanja Tamguney
- UCSF Cancer Research Institute, 2340 Sutter Street, San Francisco, CA 94115, USA
| | - David Stokoe
- UCSF Cancer Research Institute, 2340 Sutter Street, San Francisco, CA 94115, USA
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27
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Elghazi L, Rachdi L, Weiss AJ, Cras-Méneur C, Bernal-Mizrachi E. Regulation of beta-cell mass and function by the Akt/protein kinase B signalling pathway. Diabetes Obes Metab 2007; 9 Suppl 2:147-57. [PMID: 17919189 DOI: 10.1111/j.1463-1326.2007.00783.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The insulin receptor substrate-2/phosphoinositide 3-kinase (PI3K) pathway plays a critical role in the regulation of beta-cell mass and function, demonstrated both in vitro and in vivo. The serine threonine kinase Akt is one of the promising downstream molecules of this pathway that has been identified as a potential target to regulate function and induce proliferation and survival of beta cells. Here we summarize some of the molecular mechanisms, downstream signalling pathways and critical components involved in the regulation of beta-cell mass and function by Akt.
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Affiliation(s)
- L Elghazi
- Department of Internal Medicine, Division of Endocrinology, Washington University School of Medicine, Metabolism & Lipid Research, St Louis, MO 63110, USA
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28
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Affiliation(s)
- Mihaela M Mocanu
- The Hatter Cardiovascular Institute, University College London Hospital and Medical School, Chenies Mew, London, WC1E 6HX, UK
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29
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Mocanu MM, Yellon DM. PTEN, the Achilles' heel of myocardial ischaemia/reperfusion injury? Br J Pharmacol 2007; 150:833-8. [PMID: 17293884 PMCID: PMC2013879 DOI: 10.1038/sj.bjp.0707155] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Myocardial ischaemia/reperfusion injury leading to myocardial infarction is one of the most frequent causes of debilitation and death in man. Considerable research has been undertaken to investigate the possibility of reducing myocardial infarction and increasing cell survival by activating certain endogenous prosurvival signaling pathways. Thus, it has been established that the activation of the PI3K (Phosphoinositide-3 kinase)/Akt (Protein kinase B, PKB) signaling pathway is essential for protection against ischaemia/reperfusion injury. This pathway has been shown to be activated by mechanical procedures (e.g. pre and post conditioning) as well as by a number of pharmacological agents. Although the activation of this prosurvival signaling pathway induces the phosphorylation of a large number of substrates implicated in increased cell survival, when activated over a prolonged period this pathway can have detrimental consequences by facilitating unwanted growth and malignancies. Importantly PTEN (phosphatase and tensin homolog deleted on chromosome ten), is the main phosphatase which negatively regulates the PI3K/Akt pathway. In this review we discuss: a) the significance and the limitations of inhibiting PTEN in myocardial ischaemia/reperfusion injury; b) PTEN and its relationship to ischaemic preconditioning, c) the role of PTEN in the development of tolerance to chronic administration of drugs known to limit infarction by activating PI3K/Akt pathway when given acutely, and d) the possible role of PTEN in the ischaemic/reperfused diabetic heart. The experimental evidence discussed in this review illustrates the importance of PTEN inhibition in the protection of the heart against ischaemia/reperfusion injury.
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Affiliation(s)
- M M Mocanu
- The Hatter Cardiovascular Institute, Department of Medicine, UCL Chenies Mews, London, UK
| | - D M Yellon
- The Hatter Cardiovascular Institute, Department of Medicine, UCL Chenies Mews, London, UK
- Author for correspondence:
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30
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Xu J, Gowen L, Raphalides C, Hoyer KK, Weinger JG, Renard M, Troke JJ, Vaitheesyaran B, Lee WNP, Saad MF, Sleeman MW, Teitell MA, Kurland IJ. Decreased hepatic futile cycling compensates for increased glucose disposal in the Pten heterodeficient mouse. Diabetes 2006; 55:3372-80. [PMID: 17130482 DOI: 10.2337/db06-0002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Despite altered regulation of insulin signaling, Pten(+/-) heterodeficient standard diet-fed mice, approximately 4 months old, exhibit normal fasting glucose and insulin levels. We report here a stable isotope flux phenotyping study of this "silent" phenotype, in which tissue-specific insulin effects in whole-body Pten(+/-)-deficient mice were dissected in vivo. Flux phenotyping showed gain of function in Pten(+/-) mice, seen as increased peripheral glucose disposal, and compensation by a metabolic feedback mechanism that 1) decreases hepatic glucose recycling via suppression of glucokinase expression in the basal state to preserve hepatic glucose production and 2) increases hepatic responsiveness in the fasted-to-fed transition. In Pten(+/-) mice, hepatic gene expression of glucokinase was 10-fold less than wild-type (Pten(+/+)) mice in the fasted state and reached Pten(+/+) values in the fed state. Glucose-6-phosphatase expression was the same for Pten(+/-) and Pten(+/+) mice in the fasted state, and its expression for Pten(+/-) was 25% of Pten(+/+) in the fed state. This study demonstrates how intra- and interorgan flux compensations can preserve glucose homeostasis (despite a specific gene defect that accelerates glucose disposal) and how flux phenotyping can dissect these tissue-specific flux compensations in mice presenting with a "silent" phenotype.
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Affiliation(s)
- Jun Xu
- SUNY at Stony Brook, HSC T-15 Room 060, Stony Brook, NY 11794-8154, USA
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McKinnon CM, Ravier MA, Rutter GA. FoxO1 is required for the regulation of preproglucagon gene expression by insulin in pancreatic alphaTC1-9 cells. J Biol Chem 2006; 281:39358-69. [PMID: 17062568 DOI: 10.1074/jbc.m605022200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Forkhead/winged helix box gene, group O-1 (FoxO1) is a member of a family of nuclear transcription factors regulated by insulin-dependent phosphorylation and implicated in the development of the endocrine pancreas. We show here firstly that FoxO1 protein is expressed in both primary mouse islet alpha and beta cells. Examined in clonal alphaTC1-9 cells, insulin caused endogenous FoxO1 to translocate from the nucleus to the cytoplasm. Demonstrating the importance of nuclear exclusion of FoxO1 for the inhibition of preproglucagon gene expression, FoxO1 silencing by RNA interference reduced preproglucagon mRNA levels by >40% in the absence of insulin and abolished the decrease in mRNA levels elicited by the hormone. Electrophoretic mobility shift assay and chromatin immunoprecipitation revealed direct binding of FoxO1 to a forkhead consensus binding site, termed GL3, in the preproglucagon gene promoter region, localized -1798 bp upstream of the transcriptional start site. Deletion or mutation of this site diminished FoxO1 binding and eliminated transcriptional regulation by glucose or insulin. FoxO1 silencing also abolished the acute regulation by insulin, but not glucose, of glucagon secretion, demonstrating the importance of FoxO1 expression in maintaining the alpha-cell phenotype.
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Affiliation(s)
- Caroline M McKinnon
- Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol, BS8 1TD, United Kingdom
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32
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Nguyen KTT, Tajmir P, Lin CH, Liadis N, Zhu XD, Eweida M, Tolasa-Karaman G, Cai F, Wang R, Kitamura T, Belsham DD, Wheeler MB, Suzuki A, Mak TW, Woo M. Essential role of Pten in body size determination and pancreatic beta-cell homeostasis in vivo. Mol Cell Biol 2006; 26:4511-8. [PMID: 16738317 PMCID: PMC1489140 DOI: 10.1128/mcb.00238-06] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
PTEN (phosphatase with tensin homology) is a potent negative regulator of phosphoinositide 3-kinase (PI3K)/Akt signaling, an evolutionarily conserved pathway that signals downstream of growth factors, including insulin and insulin-like growth factor 1. In lower organisms, this pathway participates in fuel metabolism and body size regulation and insulin-like proteins are produced primarily by neuronal structures, whereas in mammals, the major source of insulin is the pancreatic beta cells. Recently, rodent insulin transcription was also shown in the brain, particularly the hypothalamus. The specific regulatory elements of the PI3K pathway in these insulin-expressing tissues that contribute to growth and metabolism in higher organisms are unknown. Here, we report PTEN as a critical determinant of body size and glucose metabolism when targeting is driven by the rat insulin promoter in mice. The partial deletion of PTEN in the hypothalamus resulted in significant whole-body growth restriction and increased insulin sensitivity. Efficient PTEN deletion in beta cells led to increased islet mass without compromise of beta-cell function. Parallel enhancement in PI3K signaling was found in PTEN-deficient hypothalamus and beta cells. Together, we have shown that PTEN in insulin-transcribing cells may play an integrative role in regulating growth and metabolism in vivo.
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Affiliation(s)
- Kinh-Tung T Nguyen
- Department of Medicine, Medical Biophysics, Institute of Medical Science, Ontario Cancer Institute, University of Toronto, Toronto, Ontario, Canada
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33
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Sasaoka T, Wada T, Tsuneki H. Lipid phosphatases as a possible therapeutic target in cases of type 2 diabetes and obesity. Pharmacol Ther 2006; 112:799-809. [PMID: 16842857 DOI: 10.1016/j.pharmthera.2006.06.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2006] [Accepted: 06/05/2006] [Indexed: 11/26/2022]
Abstract
Phosphatidyl inositol 3-kinase (PI3-kinase) functions as a lipid kinase to produce PI(3,4,5)P(3) from PI(4,5)P(2) in vivo. PI(3,4,5)P(3) is crucial as a lipid second messenger in various metabolic effects of insulin. Lipid phosphatases, src homology 2 domain containing inositol 5'-phosphatase 2 (SHIP2) and skeletal muscle and kidney-enriched inositol phosphatase (SKIP) hydrolyze PI(3,4,5)P(3) to PI(3,4)P(2) and phosphatase and tensin homolog deleted on chromosome ten (PTEN) hydrolyzes PI(3,4,5)P(3) to PI(4,5)P(2). SHIP2 negatively regulates insulin signaling relatively specifically via its 5'-phosphatase activity. Targeted disruption of the SHIP2 gene in mice resulted in increased insulin sensitivity and conferred protection from obesity induced by a high-fat diet. Polymorphisms in the human SHIP2 gene are associated, at least in part, with the insulin resistance of type 2 diabetes. Importantly, inhibition of endogenous SHIP2 through the liver-specific expression of a dominant-negative SHIP2 improves glucose metabolism and insulin resistance in diabetic db/db mice. Overexpression of PTEN and SKIP also inhibited insulin-induced phosphorylation of Akt and the uptake of glucose in cultured cells. Although a homozygous disruption of the PTEN gene in mice results in embryonic lethality, either skeletal muscle or adipose tissue-specific disruption of PTEN ameliorated glucose metabolism without formation of tumors in animal models of diabetes. The role of SKIP in glucose metabolism remains to be further clarified in vivo. Taken together, inhibition of endogenous SHIP2 in the whole body appears to be effective at improving the insulin resistance associated with type 2 diabetes and/or obesity. Inhibition of PTEN in the tissues specifically targeted, including skeletal muscle and fat, may result in an amelioration of insulin resistance in type 2 diabetes, although caution against the formation of tumors is needed.
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Affiliation(s)
- Toshiyasu Sasaoka
- Department of Clinical Pharmacology, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan.
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34
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Li LX, MacDonald PE, Ahn DS, Oudit GY, Backx PH, Brubaker PL. Role of phosphatidylinositol 3-kinasegamma in the beta-cell: interactions with glucagon-like peptide-1. Endocrinology 2006; 147:3318-25. [PMID: 16574789 DOI: 10.1210/en.2006-0155] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) increases beta-cell function and growth through protein kinase A- and phosphatidylinositol-3-kinase (PI3-K)/protein kinase B, respectively. GLP-1 acts via a G protein-coupled receptor, and PI3-Kgamma is known to be activated by G(betagamma.) Therefore, the role of PI3-Kgamma in the chronic effects of GLP-1 on the beta-cell was investigated using PI3-Kgamma knockout (KO) mice treated with the GLP-1 receptor agonist, exendin-4 (Ex4; 1 nmol/kg sc every 24 h for 14 d). In vivo, glucose and insulin responses were similar in PBS- and Ex4-treated KO and wild-type (WT) mice. However, glucose-stimulated insulin secretion was markedly impaired in islets from PBS-KO mice (P < 0.05), and this was partially normalized by chronic Ex4 treatment (P < 0.05). In contrast, insulin content was increased in PBS-KO islets, and this was paradoxically decreased by Ex4 treatment, compared with the stimulatory effect of Ex4 on WT islets (P < 0.05-0.01). Transfection of INS-1E beta-cells with small interfering RNA for PI3-Kgamma similarly decreased glucose-stimulated insulin secretion (P < 0.01) and increased insulin content. Basal values for beta-cell mass, islet number and proliferation, glucose transporter 2, glucokinase, and insulin receptor substrate-2 were increased in PBS-KO mice (P < 0.05-0.001) and, although they were increased by Ex4 treatment of WT animals (P < 0.05), they were decreased in Ex4-KO mice (P < 0.05-0.01). These findings indicate that PI3-Kgamma deficiency impairs insulin secretion, resulting in compensatory islet growth to maintain normoglycemia. Chronic Ex4 treatment normalizes the secretory defect, thereby relieving the pressure for expansion of beta-cell mass. These studies reveal a new role for PI3-Kgamma as a positive regulator of insulin secretion, and reinforce the importance of GLP-1 for the maintenance of normal beta-cell function.
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Affiliation(s)
- Li-Xin Li
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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35
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Stiles BL, Kuralwalla-Martinez C, Guo W, Gregorian C, Wang Y, Tian J, Magnuson MA, Wu H. Selective deletion of Pten in pancreatic beta cells leads to increased islet mass and resistance to STZ-induced diabetes. Mol Cell Biol 2006; 26:2772-81. [PMID: 16537919 PMCID: PMC1430339 DOI: 10.1128/mcb.26.7.2772-2781.2006] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a lipid phosphatase. PTEN inhibits the action of phosphatidylinositol-3-kinase and reduces the levels of phosphatidylinositol triphosphate, a crucial second messenger for cell proliferation and survival, as well as insulin signaling. In this study, we deleted Pten specifically in the insulin producing beta cells during murine pancreatic development. Pten deletion leads to increased cell proliferation and decreased cell death, without significant alteration of beta-cell differentiation. Consequently, the mutant pancreas generates more and larger islets, with a significant increase in total beta-cell mass. PTEN loss also protects animals from developing streptozotocin-induced diabetes. Our data demonstrate that PTEN loss in beta cells is not tumorigenic but beneficial. This suggests that modulating the PTEN-controlled signaling pathway is a potential approach for beta-cell protection and regeneration therapies.
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Affiliation(s)
- Bangyan L Stiles
- Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, California 90095, USA
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Vinciguerra M, Foti M. PTEN and SHIP2 phosphoinositide phosphatases as negative regulators of insulin signalling. Arch Physiol Biochem 2006; 112:89-104. [PMID: 16931451 DOI: 10.1080/13813450600711359] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Insulin resistance in peripheral tissues is the primary cause responsible for onset of type II diabetes mellitus. Recently, the genetic and biochemical dissection of intracellular signalling pathways transducing the metabolic and mitogenic effects of insulin has contributed to the understanding of the molecular causes of this insulin resistance. In particular, important efforts have been developed to comprehend the role of negative regulators of insulin signalling, since they might represent future therapeutical targets to reduce insulin resistance in peripheral tissues. Herein, we will briefly review major intracellular signalling pathways activated by insulin and how they are negatively regulated by distinct mechanisms. In particular, the role of PTEN and SHIP2, two phosphoinositide phosphatases recently implicated as negative modulators of insulin signalling, is in focus. Current knowledge on the role of PTEN and SHIP2 in insulin resistance, type II diabetes and related disorders will also be discussed.
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Affiliation(s)
- Manlio Vinciguerra
- Department of Cellular Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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