1
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Zhang X, Luo S, Wang M, Huang Q, Fang W, Li J, Liu T, Zhang Y, Deng Z, Liu CL, Guan S, Ayala JE, Flavell RA, Kulkarni RN, Libby P, Guo J, Liu Z, Shi GP. IL18 signaling causes islet β cell development and insulin secretion via different receptors on acinar and β cells. Dev Cell 2022; 57:1496-1511.e6. [DOI: 10.1016/j.devcel.2022.05.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 12/31/2021] [Accepted: 05/16/2022] [Indexed: 12/13/2022]
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2
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Sajan MP, Hansen BC, Acevedo‐Duncan M, Kindy MS, Cooper DR, Farese RV. Roles of hepatic atypical protein kinase C hyperactivity and hyperinsulinemia in insulin-resistant forms of obesity and type 2 diabetes mellitus. MedComm (Beijing) 2021; 2:3-16. [PMID: 34766133 PMCID: PMC8491214 DOI: 10.1002/mco2.54] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 12/21/2020] [Accepted: 12/28/2020] [Indexed: 11/10/2022] Open
Abstract
Diet-induced obesity, the metabolic syndrome, type 2 diabetes (DIO/MetS/T2DM), and their adverse sequelae have reached pandemic levels. In mice, DIO/MetS/T2DM initiation involves diet-dependent increases in lipids that activate hepatic atypical PKC (aPKC) and thereby increase lipogenic enzymes and proinflammatory cytokines. These or other hepatic aberrations, via adverse liver-to-muscle cross talk, rapidly impair postreceptor insulin signaling to glucose transport in muscle. The ensuing hyperinsulinemia further activates hepatic aPKC, which first blocks the ability of Akt to suppress gluconeogenic enzyme expression, and later impairs Akt activation, further increasing hepatic glucose production. Recent findings suggest that hepatic aPKC also increases a proteolytic enzyme that degrades insulin receptors. Fortunately, all hepatic aberrations and muscle impairments are prevented/reversed by inhibition or deficiency of hepatic aPKC. But, in the absence of treatment, hyperinsulinemia induces adverse events, some by using "spare receptors" to bypass receptor defects. Thus, in brain, hyperinsulinemia increases Aβ-plaque precursors and Alzheimer risk; in kidney, hyperinsulinemia activates the renin-angiotensin-adrenal axis, thus increasing vasoconstriction, sodium retention, and cardiovascular risk; and in liver, hyperinsulinemia increases lipogenesis, obesity, hepatosteatosis, hyperlipidemia, and cardiovascular risk. In summary, increases in hepatic aPKC are critically required for development of DIO/MetS/T2DM and its adverse sequelae, and therapeutic approaches that limit hepatic aPKC may be particularly effective.
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Affiliation(s)
- Mini P. Sajan
- Department of Internal MedicineUniversity of South Florida College of MedicineTampaFloridaUSA
- Research ServiceJames AHaley Veterans Administration Medical CenterTampaFloridaUSA
| | - Barbara C. Hansen
- Department of Internal MedicineUniversity of South Florida College of MedicineTampaFloridaUSA
| | - Mildred Acevedo‐Duncan
- Department of ChemistryCollege of Arts and SciencesUniversity of South FloridaTampaFloridaUSA
| | - Mark S. Kindy
- Research ServiceJames AHaley Veterans Administration Medical CenterTampaFloridaUSA
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of South FloridaTampaFloridaUSA
| | - Denise R. Cooper
- Research ServiceJames AHaley Veterans Administration Medical CenterTampaFloridaUSA
- Department of Molecular MedicineUniversity of South FloridaTampaFloridaUSA
| | - Robert V. Farese
- Department of Internal MedicineUniversity of South Florida College of MedicineTampaFloridaUSA
- Research ServiceJames AHaley Veterans Administration Medical CenterTampaFloridaUSA
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3
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Kanno A, Asahara SI, Furubayashi A, Masuda K, Yoshitomi R, Suzuki E, Takai T, Kimura-Koyanagi M, Matsuda T, Bartolome A, Hirota Y, Yokoi N, Inaba Y, Inoue H, Matsumoto M, Inoue K, Abe T, Wei FY, Tomizawa K, Ogawa W, Seino S, Kasuga M, Kido Y. GCN2 regulates pancreatic β cell mass by sensing intracellular amino acid levels. JCI Insight 2020; 5:128820. [PMID: 32376799 DOI: 10.1172/jci.insight.128820] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 04/01/2020] [Indexed: 01/09/2023] Open
Abstract
EIF2AK4, which encodes the amino acid deficiency-sensing protein GCN2, has been implicated as a susceptibility gene for type 2 diabetes in the Japanese population. However, the mechanism by which GCN2 affects glucose homeostasis is unclear. Here, we show that insulin secretion is reduced in individuals harboring the risk allele of EIF2AK4 and that maintenance of GCN2-deficient mice on a high-fat diet results in a loss of pancreatic β cell mass. Our data suggest that GCN2 senses amino acid deficiency in β cells and limits signaling by mechanistic target of rapamycin complex 1 to prevent β cell failure during the consumption of a high-fat diet.
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Affiliation(s)
- Ayumi Kanno
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Shun-Ichiro Asahara
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Ayuko Furubayashi
- Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Science, Kobe, Japan
| | - Katsuhisa Masuda
- Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Science, Kobe, Japan
| | - Risa Yoshitomi
- Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Science, Kobe, Japan
| | - Emi Suzuki
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Tomoko Takai
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | | | - Tomokazu Matsuda
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Alberto Bartolome
- Naomi Berrie Diabetes Center and Department of Medicine, Columbia University, New York, New York, USA
| | - Yushi Hirota
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Norihide Yokoi
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yuka Inaba
- Metabolism and Nutrition Research Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa, Ishikawa, Japan
| | - Hiroshi Inoue
- Metabolism and Nutrition Research Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa, Ishikawa, Japan
| | - Michihiro Matsumoto
- Department of Molecular Metabolic Regulation, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | | | - Takaya Abe
- Laboratory for Animal Resource Development and.,Laboratory for Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Fan-Yan Wei
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Wataru Ogawa
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Masato Kasuga
- National Center for Global Health and Medicine, Tokyo, Japan
| | - Yoshiaki Kido
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and.,Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Science, Kobe, Japan
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4
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SUZUKI EMI, MATSUDA TOMOKAZU, KAWAMOTO TAKESHI, TAKAHASHI HIROAKI, MIEDA YUSUKE, MATSUURA YUKI, TAKAI TOMOKO, KANNO AYUMI, KOYANAGI-KIMURA MAKI, ASAHARA SHUNICHIRO, INOUE HIROSHI, OGAWA WATARU, KIDO YOSHIAKI. Docosahexaenoic Acid Reduces Palmitic Acid-Induced Endoplasmic Reticulum Stress in Pancreatic Β Cells. THE KOBE JOURNAL OF MEDICAL SCIENCES 2018; 64:E43-E55. [PMID: 30381726 PMCID: PMC6347050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 03/13/2018] [Indexed: 06/08/2023]
Abstract
Endoplasmic reticulum (ER) stress leads to peripheral insulin resistance and the progression of pancreatic beta cell failure in type 2 diabetes. Although ER stress plays an important role in the pathogenesis of diabetes, it is indispensable for cellular activity. Therefore, when assessing the pathological significance of ER stress, it is important to monitor and quantify ER stress levels. Here, we have established a novel system to monitor ER stress levels quickly and sensitively, and using this method, we have clarified the effect of differences in glucose concentration and various fatty acids on the ER of pancreatic β cells. First, we developed a cell system that secretes Gaussia luciferase in culture medium depending on the activation of the GRP78 promoter. This system could sensitively monitor ER stress levels that could not be detected with real-time RT-PCR and immunoblotting. This system revealed that hyperglycemia does not induce unfolded protein response (UPR) in a short period of time in MIN6 cells, a mouse pancreatic β cell line. Physiological concentrations of palmitic acid, a saturated fatty acid, induced ER stress quickly, while physiological concentrations of oleic acid, an unsaturated fatty acid, did not. Docosahexaenoic acid, an n-3 unsaturated fatty acid, inhibited palmitic acid-induced ER stress. In this study, we have established a system that can sensitively detect ER stress levels of living cells in a short period of time. This system can be used to monitor the state of the ER in living cells and lead to the investigation of the significance of physiological or pathological ER stress levels.
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Affiliation(s)
- EMI SUZUKI
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - TOMOKAZU MATSUDA
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - TAKESHI KAWAMOTO
- Division of Medical Chemistry, Department of Metabolism and Diseases, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - HIROAKI TAKAHASHI
- Division of Medical Chemistry, Department of Metabolism and Diseases, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - YUSUKE MIEDA
- Division of Medical Chemistry, Department of Metabolism and Diseases, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - YUKI MATSUURA
- Division of Medical Chemistry, Department of Metabolism and Diseases, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - TOMOKO TAKAI
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - AYUMI KANNO
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - MAKI KOYANAGI-KIMURA
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - SHUN-ICHIRO ASAHARA
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - HIROSHI INOUE
- Department of Physiology and Metabolism, Brain/Liver Interface Medicine Research Center, Kanazawa University, Kanazawa, Japan
| | - WATARU OGAWA
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - YOSHIAKI KIDO
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
- Division of Medical Chemistry, Department of Metabolism and Diseases, Kobe University Graduate School of Health Sciences, Kobe, Japan
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5
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Xie Y, Cui C, Nie A, Wang Y, Ni Q, Liu Y, Yin Q, Zhang H, Li Y, Wang Q, Gu Y, Ning G. The mTORC2/PKC pathway sustains compensatory insulin secretion of pancreatic β cells in response to metabolic stress. Biochim Biophys Acta Gen Subj 2017; 1861:2039-2047. [DOI: 10.1016/j.bbagen.2017.04.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 03/31/2017] [Accepted: 04/18/2017] [Indexed: 12/24/2022]
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6
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Trexler AJ, Taraska JW. Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells. Cell Calcium 2017; 67:1-10. [PMID: 29029784 DOI: 10.1016/j.ceca.2017.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 12/27/2022]
Abstract
The control of insulin release from pancreatic beta cells helps ensure proper blood glucose level, which is critical for human health. Protein kinase C has been shown to be one key control mechanism for this process. After glucose stimulation, calcium influx into beta cells triggers exocytosis of insulin-containing dense-core granules and activates protein kinase C via calcium-dependent phospholipase C-mediated generation of diacylglycerol. Activated protein kinase C potentiates insulin release by enhancing the calcium sensitivity of exocytosis, likely by affecting two main pathways that could be linked: (1) the reorganization of the cortical actin network, and (2) the direct phosphorylation of critical exocytotic proteins such as munc18, SNAP25, and synaptotagmin. Here, we review what is currently known about the molecular mechanisms of protein kinase C action on each of these pathways and how these effects relate to the control of insulin release by exocytosis. We identify remaining challenges in the field and suggest how these challenges might be addressed to advance our understanding of the regulation of insulin release in health and disease.
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Affiliation(s)
- Adam J Trexler
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Justin W Taraska
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States.
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7
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Wuttke A, Yu Q, Tengholm A. Autocrine Signaling Underlies Fast Repetitive Plasma Membrane Translocation of Conventional and Novel Protein Kinase C Isoforms in β Cells. J Biol Chem 2016; 291:14986-95. [PMID: 27226533 PMCID: PMC4946917 DOI: 10.1074/jbc.m115.698456] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Indexed: 01/08/2023] Open
Abstract
PKC signaling has been implicated in the regulation of many cell functions, including metabolism, cell death, proliferation, and secretion. Activation of conventional and novel PKC isoforms is associated with their Ca2+- and/or diacylglycerol (DAG)-dependent translocation to the plasma membrane. In β cells, exocytosis of insulin granules evokes brief (<10 s) local DAG elevations (“spiking”) at the plasma membrane because of autocrine activation of P2Y1 purinoceptors by ATP co-released with insulin. Using total internal reflection microscopy, fluorescent protein-tagged PKCs, and signaling biosensors, we investigated whether DAG spiking causes membrane recruitment of PKCs and whether different classes of PKCs show characteristic responses. Glucose stimulation of MIN6 cells triggered DAG spiking with concomitant repetitive translocation of the novel isoforms PKCδ, PKCϵ, and PKCη. The conventional PKCα, PKCβI, and PKCβII isoforms showed a more complex pattern with both rapid and slow translocation. K+ depolarization-induced PKCϵ translocation entirely mirrored DAG spiking, whereas PKCβI translocation showed a sustained component, reflecting the subplasma membrane Ca2+ concentration ([Ca2+]pm), with additional effect during DAG spikes. Interference with DAG spiking by purinoceptor inhibition prevented intermittent translocation of PKCs and reduced insulin secretion but did not affect [Ca2+]pm elevation or sustained PKCβI translocation. The muscarinic agonist carbachol induced pronounced transient PKCβI translocation and sustained recruitment of PKCϵ. When rise of [Ca2+]pm was prevented, the carbachol-induced DAG and PKCϵ responses were somewhat reduced, but PKCβI translocation was completely abolished. We conclude that exocytosis-induced DAG spikes efficiently recruit both conventional and novel PKCs to the β cell plasma membrane. PKC signaling is thus implicated in autocrine regulation of β cell function.
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Affiliation(s)
- Anne Wuttke
- From the Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, 75123 Uppsala, Sweden
| | - Qian Yu
- From the Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, 75123 Uppsala, Sweden
| | - Anders Tengholm
- From the Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, 75123 Uppsala, Sweden
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8
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Schmit SL, Schumacher FR, Edlund CK, Conti DV, Ihenacho U, Wan P, Van Den Berg D, Casey G, Fortini BK, Lenz HJ, Tusié-Luna T, Aguilar-Salinas CA, Moreno-Macías H, Huerta-Chagoya A, Ordóñez-Sánchez ML, Rodríguez-Guillén R, Cruz-Bautista I, Rodríguez-Torres M, Muñóz-Hernández LL, Arellano-Campos O, Gómez D, Alvirde U, González-Villalpando C, González-Villalpando ME, Le Marchand L, Haiman CA, Figueiredo JC. Genome-wide association study of colorectal cancer in Hispanics. Carcinogenesis 2016; 37:547-556. [PMID: 27207650 PMCID: PMC4876992 DOI: 10.1093/carcin/bgw046] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 04/13/2016] [Indexed: 01/01/2023] Open
Abstract
This manuscript describes the first large-scale genome-wide association study of colorectal cancer in Hispanics and Latinos. Our results demonstrate the broad replication of known susceptibility regions and the importance of fine-mapping in ethnic minority populations. Genome-wide association studies (GWAS) have identified 58 susceptibility alleles across 37 regions associated with the risk of colorectal cancer (CRC) with P < 5×10−8. Most studies have been conducted in non-Hispanic whites and East Asians; however, the generalizability of these findings and the potential for ethnic-specific risk variation in Hispanic and Latino (HL) individuals have been largely understudied. We describe the first GWAS of common genetic variation contributing to CRC risk in HL (1611 CRC cases and 4330 controls). We also examine known susceptibility alleles and implement imputation-based fine-mapping to identify potential ethnicity-specific association signals in known risk regions. We discovered 17 variants across 4 independent regions that merit further investigation due to suggestive CRC associations (P < 1×10−6) at 1p34.3 (rs7528276; Odds Ratio (OR) = 1.86 [95% confidence interval (CI): 1.47–2.36); P = 2.5×10−7], 2q23.3 (rs1367374; OR = 1.37 (95% CI: 1.21–1.55); P = 4.0×10−7), 14q24.2 (rs143046984; OR = 1.65 (95% CI: 1.36–2.01); P = 4.1×10−7) and 16q12.2 [rs142319636; OR = 1.69 (95% CI: 1.37–2.08); P=7.8×10−7]. Among the 57 previously published CRC susceptibility alleles with minor allele frequency ≥1%, 76.5% of SNPs had a consistent direction of effect and 19 (33.3%) were nominally statistically significant (P < 0.05). Further, rs185423955 and rs60892987 were identified as novel secondary susceptibility variants at 3q26.2 (P = 5.3×10–5) and 11q12.2 (P = 6.8×10−5), respectively. Our findings demonstrate the importance of fine mapping in HL. These results are informative for variant prioritization in functional studies and future risk prediction modeling in minority populations.
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Affiliation(s)
- Stephanie L Schmit
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA.,Department of Cancer Epidemiology, Moffitt Cancer Center, Tampa, FL 33612, USA
| | - Fredrick R Schumacher
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Christopher K Edlund
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - David V Conti
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Ugonna Ihenacho
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Peggy Wan
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Graham Casey
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Barbara K Fortini
- Department of Biology, Claremont McKenna College, Claremont, CA 91711, USA
| | - Heinz-Josef Lenz
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Teresa Tusié-Luna
- Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Sección XVI, Tlalpan, 14000 México City, México.,Instituto de Investigaciones Biomédicas, UNAM. Unidad de Biología Molecular y Medicina Genómica, UNAM/INCMNSZ, Coyoacán, 04510 México City, México
| | - Carlos A Aguilar-Salinas
- Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Sección XVI, Tlalpan, 14000 México City, México
| | | | - Alicia Huerta-Chagoya
- Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Sección XVI, Tlalpan, 14000 México City, México.,Instituto de Investigaciones Biomédicas, UNAM. Unidad de Biología Molecular y Medicina Genómica, UNAM/INCMNSZ, Coyoacán, 04510 México City, México
| | | | | | | | | | | | - Olimpia Arellano-Campos
- Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Sección XVI, Tlalpan, 14000 México City, México
| | - Donají Gómez
- Universidad Autónoma Metropolitana, Tlalpan 14387, México City, México
| | - Ulices Alvirde
- Universidad Autónoma Metropolitana, Tlalpan 14387, México City, México
| | - Clicerio González-Villalpando
- Unidad de Investigación en Diabetes, Instituto Nacional de Salud Pública, México City, México.,Centro de Estudios en Diabetes, 01120 México City, México and
| | | | - Loic Le Marchand
- Epidemiology Program, University of Hawaii Cancer Center, Honolulu, HI 96813, USA
| | - Christopher A Haiman
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Jane C Figueiredo
- Department of Preventive Medicine.,University of Southern California Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
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9
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Matsuda T, Takahashi H, Mieda Y, Shimizu S, Kawamoto T, Matsuura Y, Takai T, Suzuki E, Kanno A, Koyanagi-Kimura M, Asahara SI, Bartolome A, Yokoi N, Inoue H, Ogawa W, Seino S, Kido Y. Regulation of Pancreatic β Cell Mass by Cross-Interaction between CCAAT Enhancer Binding Protein β Induced by Endoplasmic Reticulum Stress and AMP-Activated Protein Kinase Activity. PLoS One 2015; 10:e0130757. [PMID: 26091000 PMCID: PMC4474801 DOI: 10.1371/journal.pone.0130757] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 05/22/2015] [Indexed: 01/05/2023] Open
Abstract
During the development of type 2 diabetes, endoplasmic reticulum (ER) stress leads to not only insulin resistance but also to pancreatic beta cell failure. Conversely, cell function under various stressed conditions can be restored by reducing ER stress by activating AMP-activated protein kinase (AMPK). However, the details of this mechanism are still obscure. Therefore, the current study aims to elucidate the role of AMPK activity during ER stress-associated pancreatic beta cell failure. MIN6 cells were loaded with 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide (AICAR) and metformin to assess the relationship between AMPK activity and CCAAT enhancer binding protein β (C/EBPβ) expression levels. The effect of C/EBPβ phosphorylation on expression levels was also investigated. Vildagliptin and metformin were administered to pancreatic beta cell-specific C/EBPβ transgenic mice to investigate the relationship between C/EBPβ expression levels and AMPK activity in the pancreatic islets. When pancreatic beta cells are exposed to ER stress, the accumulation of the transcription factor C/EBPβ lowers the AMP/ATP ratio, thereby decreasing AMPK activity. In an opposite manner, incubation of MIN6 cells with AICAR or metformin activated AMPK, which suppressed C/EBPβ expression. In addition, administration of the dipeptidyl peptidase-4 inhibitor vildagliptin and metformin to pancreatic beta cell-specific C/EBPβ transgenic mice decreased C/EBPβ expression levels and enhanced pancreatic beta cell mass in proportion to the recovery of AMPK activity. Enhanced C/EBPβ expression and decreased AMPK activity act synergistically to induce ER stress-associated pancreatic beta cell failure.
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Affiliation(s)
- Tomokazu Matsuda
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroaki Takahashi
- Division of Medical Chemistry, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - Yusuke Mieda
- Division of Medical Chemistry, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - Shinobu Shimizu
- Division of Medical Chemistry, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - Takeshi Kawamoto
- Division of Medical Chemistry, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - Yuki Matsuura
- Division of Medical Chemistry, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe, Japan
| | - Tomoko Takai
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Emi Suzuki
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Ayumi Kanno
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Maki Koyanagi-Kimura
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shun-ichiro Asahara
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Alberto Bartolome
- Naomi Berrie Diabetes Center, Department of Medicine, Columbia University, New York, United States of America
| | - Norihide Yokoi
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroshi Inoue
- Department of Physiology and Metabolism, Brain/Liver Interface Medicine Research Center, Kanazawa University, Kanazawa, Japan
| | - Wataru Ogawa
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Susumu Seino
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yoshiaki Kido
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
- Division of Medical Chemistry, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe, Japan
- * E-mail:
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10
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Kanno A, Asahara SI, Masuda K, Matsuda T, Kimura-Koyanagi M, Seino S, Ogawa W, Kido Y. Compensatory hyperinsulinemia in high-fat diet-induced obese mice is associated with enhanced insulin translation in islets. Biochem Biophys Res Commun 2015; 458:681-686. [PMID: 25686499 DOI: 10.1016/j.bbrc.2015.02.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 02/04/2015] [Indexed: 02/03/2023]
Abstract
A high-fat diet (HF) is associated with obesity, insulin resistance, and hyperglycemia. Animal studies have shown compensatory mechanisms in pancreatic β-cells after high fat load, such as increased pancreatic β-cell mass, enhanced insulin secretion, and exocytosis. However, the effects of high fat intake on insulin synthesis are obscure. Here, we investigated whether insulin synthesis was altered in correlation with an HF diet, for the purpose of obtaining further understanding of the compensatory mechanisms in pancreatic β-cells. Mice fed an HF diet are obese, insulin resistant, hyperinsulinemic, and glucose intolerant. In islets of mice fed an HF diet, more storage of insulin was identified. We analyzed insulin translation in mouse islets, as well as in INS-1 cells, using non-radioisotope chemicals. We found that insulin translational levels were significantly increased in islets of mice fed an HF diet to meet systemic demand, without altering its transcriptional levels. Our data showed that not only increased pancreatic β-cell mass and insulin secretion but also elevated insulin translation is the major compensatory mechanism of pancreatic β-cells.
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Affiliation(s)
- Ayumi Kanno
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
| | - Shun-Ichiro Asahara
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
| | - Katsuhisa Masuda
- Division of Medical Chemistry, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe 654-0142, Japan.
| | - Tomokazu Matsuda
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
| | - Maki Kimura-Koyanagi
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0047, Japan.
| | - Wataru Ogawa
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
| | - Yoshiaki Kido
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan; Division of Medical Chemistry, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe 654-0142, Japan.
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11
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Tellkamp F, Vorhagen S, Niessen CM. Epidermal polarity genes in health and disease. Cold Spring Harb Perspect Med 2014; 4:a015255. [PMID: 25452423 DOI: 10.1101/cshperspect.a015255] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The epidermis of the skin is a highly polarized, metabolic tissue with important innate immune functions. The polarity of the epidermis is, for example, reflected in controlled changes in cell shape that accompany differentiation, oriented cell division, and the planar orientation of hair follicles and cilia. The establishment and maintenance of polarity is organized by a diverse set of polarity proteins that include transmembrane adhesion proteins, cytoskeletal scaffold proteins, and kinases. Although polarity proteins have been extensively studied in cell culture and in vivo in simple epithelia of lower organisms, their role in mammalian tissue biology is only slowly evolving. This article will address the importance of polarizing processes and their molecular regulators in epidermal morphogenesis and homeostasis and discuss how alterations in polarity may contribute to skin disease.
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Affiliation(s)
- Frederik Tellkamp
- Department of Dermatology, Center for Molecular Medicine Cologne, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Susanne Vorhagen
- Department of Dermatology, Center for Molecular Medicine Cologne, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Carien M Niessen
- Department of Dermatology, Center for Molecular Medicine Cologne, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
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12
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Rajagopal S, Fields BL, Kamatchi GL. Contribution of protein kinase Cα in the stimulation of insulin by the down-regulation of Cavβ subunits. Endocrine 2014; 47:463-71. [PMID: 24452871 PMCID: PMC4176602 DOI: 10.1007/s12020-013-0149-y] [Citation(s) in RCA: 4] [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: 10/03/2013] [Accepted: 12/14/2013] [Indexed: 12/23/2022]
Abstract
Voltage-gated calcium (Cav) channels and protein kinase C (PKC) isozymes are involved in insulin secretion. In addition, Cavβ, one of the auxiliary subunits of Cav channels, also regulates the secretion of insulin as knockout of Cavβ3 (β3(-/-)) subunits in mice led to efficient glucose homeostasis and increased insulin levels. We examined whether other types of Cavβ subunits also have similar properties. In this regard, we used small interfering RNA (siRNA) of these subunits (20 μg each) to down-regulate them and examined blood glucose, serum insulin and PKC translocation in isolated pancreatic β cells of mice. While the down-regulation of Cavβ2 and β3 subunits increased serum insulin levels and caused efficient glucose homeostasis, the down-regulation of Cavβ1 and β4 subunits failed to affect both these parameters. Examination of PKC isozymes in the pancreatic β-cells of Cavβ2- or β3 siRNA-injected mice showed that three PKC isozymes, viz., PKC α, βII and θ, translocated to the membrane. This suggests that when present, Cavβ2 and β3 subunits inhibited PKC activation. Among these three isozymes, only PKCα siRNA inhibited insulin and increased glucose concentrations. It is possible that the activation of PKCs βII and θ is not sufficient for the release of insulin and PKCα is the mediator of insulin secretion under the control of Cavβ subunits. Since Cavβ subunits are present intracellularly, it is possible that they (1) inhibited the translocation of PKC isozymes to the membrane and (2) decreased the interaction between Cav channels and PKC isozymes and thus the secretion of insulin.
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Affiliation(s)
- Senthilkumar Rajagopal
- Department of Zoology, Nizam College, Osmania University, Hyderabad, 500001, Andhra Pradesh, India
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13
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Rajagopal S, Fields B, Burton B, On C, Reeder A, Kamatchi G. Inhibition of protein kinase C (PKC) response of voltage-gated calcium (Cav)2.2 channels expressed in Xenopus oocytes by Cavβ subunits. Neuroscience 2014; 280:1-9. [DOI: 10.1016/j.neuroscience.2014.08.049] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 08/27/2014] [Accepted: 08/28/2014] [Indexed: 01/12/2023]
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14
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Yoshida Y, Fuchita M, Kimura-Koyanagi M, Kanno A, Matsuda T, Asahara SI, Hashimoto N, Isagawa T, Ogawa W, Aburatani H, Noda T, Seino S, Kasuga M, Kido Y. Contribution of insulin signaling to the regulation of pancreatic beta-cell mass during the catch-up growth period in a low birth weight mouse model. Diabetol Int 2013. [DOI: 10.1007/s13340-013-0127-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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15
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Asahara S, Shibutani Y, Teruyama K, Inoue HY, Kawada Y, Etoh H, Matsuda T, Kimura-Koyanagi M, Hashimoto N, Sakahara M, Fujimoto W, Takahashi H, Ueda S, Hosooka T, Satoh T, Inoue H, Matsumoto M, Aiba A, Kasuga M, Kido Y. Ras-related C3 botulinum toxin substrate 1 (RAC1) regulates glucose-stimulated insulin secretion via modulation of F-actin. Diabetologia 2013; 56:1088-97. [PMID: 23412604 PMCID: PMC3622740 DOI: 10.1007/s00125-013-2849-5] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 01/17/2013] [Indexed: 11/03/2022]
Abstract
AIMS/HYPOTHESIS The small G-protein ras-related C3 botulinum toxin substrate 1 (RAC1) plays various roles in mammalian cells, such as in the regulation of cytoskeletal organisation, cell adhesion, migration and morphological changes. The present study examines the effects of RAC1 ablation on pancreatic beta cell function. METHODS Isolated islets from pancreatic beta cell-specific Rac1-knockout (betaRac1(-/-)) mice and RAC1 knockdown INS-1 insulinoma cells treated with small interfering RNA were used to investigate insulin secretion and cytoskeletal organisation in pancreatic beta cells. RESULTS BetaRac1(-/-) mice showed decreased glucose-stimulated insulin secretion, while there were no apparent differences in islet morphology. Isolated islets from the mice had blunted insulin secretion in response to high glucose levels. In RAC1 knockdown INS-1 cells, insulin secretion was also decreased in response to high glucose levels, consistent with the phenotype of betaRac1(-/-) mice. Even under high glucose levels, RAC1 knockdown INS-1 cells remained intact with F-actin, which inhibits the recruitment of the insulin granules, resulting in an inhibition of insulin secretion. CONCLUSIONS/INTERPRETATION In RAC1-deficient pancreatic beta cells, F-actin acts as a barrier for insulin granules and reduces glucose-stimulated insulin secretion.
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Affiliation(s)
- S. Asahara
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Y. Shibutani
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - K. Teruyama
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - H. Y. Inoue
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - Y. Kawada
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - H. Etoh
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - T. Matsuda
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - M. Kimura-Koyanagi
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - N. Hashimoto
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - M. Sakahara
- Cancer Institute, Japanese Foundation of Cancer Research, Tokyo, Japan
| | - W. Fujimoto
- Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - H. Takahashi
- Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - S. Ueda
- Kobe University Graduate School of Agricultural Science, Kobe, Japan
| | - T. Hosooka
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - T. Satoh
- Division of Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - H. Inoue
- Department of Physiology and Metabolism, Brain/Liver Interface Medicine Research Center, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - M. Matsumoto
- Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - A. Aiba
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - M. Kasuga
- Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Y. Kido
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
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16
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Henquin JC, Sempoux C, Marchandise J, Godecharles S, Guiot Y, Nenquin M, Rahier J. Congenital hyperinsulinism caused by hexokinase I expression or glucokinase-activating mutation in a subset of β-cells. Diabetes 2013; 62:1689-96. [PMID: 23274908 PMCID: PMC3636634 DOI: 10.2337/db12-1414] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Congenital hyperinsulinism causes persistent hypoglycemia in neonates and infants. Most often, uncontrolled insulin secretion (IS) results from a lack of functional K(ATP) channels in all β-cells or only in β-cells within a resectable focal lesion. In more rare cases, without K(ATP) channel mutations, hyperfunctional islets are confined within few lobules, whereas hypofunctional islets are present throughout the pancreas. They also can be cured by selective partial pancreatectomy; however, unlike those with a K(ATP) focal lesion, they show clinical sensitivity to diazoxide. Here, we characterized in vitro IS by fragments of pathological and adjacent normal pancreas from six such cases. Responses of normal pancreas were unremarkable. In pathological region, IS was elevated at 1 mmol/L and was further increased by 15 mmol/L glucose. Diazoxide suppressed IS and tolbutamide antagonized the inhibition. The most conspicuous anomaly was a large stimulation of IS by 1 mmol/L glucose. In five of six cases, immunohistochemistry revealed undue presence of low-K(m) hexokinase-I in β-cells of hyperfunctional islets only. In one case, an activating mutation of glucokinase (I211F) was found in pathological islets only. Both abnormalities, attributed to somatic genetic events, may account for inappropriate IS at low glucose levels by a subset of β-cells. They represent a novel cause of focal congenital hyperinsulinism.
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Affiliation(s)
- Jean-Claude Henquin
- Unit of Endocrinology and Metabolism, University of Louvain, Faculty of Medicine, Brussels, Belgium.
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17
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Spatial regulation of VEGF receptor endocytosis in angiogenesis. Nat Cell Biol 2013; 15:249-60. [PMID: 23354168 DOI: 10.1038/ncb2679] [Citation(s) in RCA: 191] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Accepted: 12/13/2012] [Indexed: 02/07/2023]
Abstract
Activities as diverse as migration, proliferation and patterning occur simultaneously and in a coordinated fashion during tissue morphogenesis. In the growing vasculature, the formation of motile, invasive and filopodia-carrying endothelial sprouts is balanced with the stabilization of blood-transporting vessels. Here, we show that sprouting endothelial cells in the retina have high rates of VEGF uptake, VEGF receptor endocytosis and turnover. These internalization processes are opposed by atypical protein kinase C activity in more stable and mature vessels. aPKC phosphorylates Dab2, a clathrin-associated sorting protein that, together with the transmembrane protein ephrin-B2 and the cell polarity regulator PAR-3, enables VEGF receptor endocytosis and downstream signal transduction. Accordingly, VEGF receptor internalization and the angiogenic growth of vascular beds are defective in loss-of-function mice lacking key components of this regulatory pathway. Our work uncovers how vessel growth is dynamically controlled by local VEGF receptor endocytosis and the activity of cell polarity proteins.
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18
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Wuttke A, Idevall-Hagren O, Tengholm A. P2Y₁ receptor-dependent diacylglycerol signaling microdomains in β cells promote insulin secretion. FASEB J 2013; 27:1610-20. [PMID: 23299857 DOI: 10.1096/fj.12-221499] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Diacylglycerol (DAG) controls numerous cell functions by regulating the localization of C1-domain-containing proteins, including protein kinase C (PKC), but little is known about the spatiotemporal dynamics of the lipid. Here, we explored plasma membrane DAG dynamics in pancreatic β cells and determined whether DAG signaling is involved in secretagogue-induced pulsatile release of insulin. Single MIN6 cells, primary mouse β cells, and human β cells within intact islets were transfected with translocation biosensors for DAG, PKC activity, or insulin secretion and imaged with total internal reflection fluorescence microscopy. Muscarinic receptor stimulation triggered stable, homogenous DAG elevations, whereas glucose induced short-lived (7.1 ± 0.4 s) but high-amplitude elevations (up to 109 ± 10% fluorescence increase) in spatially confined membrane regions. The spiking was mimicked by membrane depolarization and suppressed after inhibition of exocytosis or of purinergic P2Y₁, but not P2X receptors, reflecting involvement of autocrine purinoceptor activation after exocytotic release of ATP. Each DAG spike caused local PKC activation with resulting dissociation of its substrate protein MARCKS from the plasma membrane. Inhibition of spiking reduced glucose-induced pulsatile insulin secretion. Thus, stimulus-specific DAG signaling patterns appear in the plasma membrane, including distinct microdomains, which have implications for the kinetic control of exocytosis and other membrane-associated processes.
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Affiliation(s)
- Anne Wuttke
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Uppsala, Sweden
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19
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Kong LJ, Feng W, Wright M, Chen Y, Dallas-yang Q, Zhou YP, Berger JP. FGF21 suppresses hepatic glucose production through the activation of atypical protein kinase Cι/λ. Eur J Pharmacol 2013; 702:302-8. [PMID: 23305840 DOI: 10.1016/j.ejphar.2012.11.065] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 11/19/2012] [Accepted: 11/23/2012] [Indexed: 12/15/2022]
Abstract
Fibroblast growth factor 21 (FGF21) has been identified as a potent and robust metabolic regulator. Administration of recombinant FGF21 protein to rodents and rhesus monkeys exerts strong anti-diabetic effects. Previous studies have demonstrated that FGF21 inhibits glucose output in the rat H4IIE hepatoma cell line. We performed pharmacological studies to investigate the mechanisms by which FGF21 regulates glucose production in these cells. We found that both insulin and FGF21 suppressed gene expression of G6Pase and PEPCK. Accordingly, glucose production was inhibited. The FGF21 effects were phosphoinositide 3-kinase (PI3K)-dependent, and, unlike insulin, Akt-independent. Additionally, we found that FGF21 induced PKCι/λ phosphorylation in a PI3K-dependent manner; and that a non-isoform selective PKC inhibitor blocked FGF21 inhibition of glucose production, while an inhibitor of classical and novel PKC isoforms had no effect on FGF21 inhibitory activity. Furthermore, hepatic PKCι/λ phosphorylation was upregulated in FGF21-treated diabetic db/db mice.These data support the proposition that FGF21 inhibits hepatic glucose production by the PI3K-dependent activation of PKCι/λ.
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Affiliation(s)
- Ling-Jie Kong
- Merck Research Laboratories, RY80T-B119, Rahway, NJ 07065, USA.
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20
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Aronis KN, Mantzoros CS. A brief history of insulin resistance: from the first insulin radioimmunoassay to selectively targeting protein kinase C pathways. Metabolism 2012; 61:445-9. [PMID: 22304840 DOI: 10.1016/j.metabol.2012.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 01/03/2012] [Indexed: 12/29/2022]
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21
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Nagare T, Sakaue H, Matsumoto M, Cao Y, Inagaki K, Sakai M, Takashima Y, Nakamura K, Mori T, Okada Y, Matsuki Y, Watanabe E, Ikeda K, Taguchi R, Kamimura N, Ohta S, Hiramatsu R, Kasuga M. Overexpression of KLF15 transcription factor in adipocytes of mice results in down-regulation of SCD1 protein expression in adipocytes and consequent enhancement of glucose-induced insulin secretion. J Biol Chem 2011; 286:37458-69. [PMID: 21862590 DOI: 10.1074/jbc.m111.242651] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Krüppel-like factor 15 (KLF15), a member of the Krüppel-like factor family of transcription factors, has been found to play diverse roles in adipocytes in vitro. However, little is known of the function of KLF15 in adipocytes in vivo. We have now found that the expression of KLF15 in adipose tissue is down-regulated in obese mice, and we therefore generated adipose tissue-specific KLF15 transgenic (aP2-KLF15 Tg) mice to investigate the possible contribution of KLF15 to various pathological conditions associated with obesity in vivo. The aP2-KLF15 Tg mice manifest insulin resistance and are resistant to the development of obesity induced by maintenance on a high fat diet. However, they also exhibit improved glucose tolerance as a result of enhanced insulin secretion. Furthermore, this enhancement of insulin secretion was shown to result from down-regulation of the expression of stearoyl-CoA desaturase 1 (SCD1) in white adipose tissue and a consequent reduced level of oxidative stress. This is supported by the findings that restoration of SCD1 expression in white adipose tissue of aP2-KLF15 Tg mice exhibited increased oxidative stress in white adipose tissue and reduced insulin secretion with hyperglycemia. Our data thus provide an example of cross-talk between white adipose tissue and pancreatic β cells mediated through modulation of oxidative stress.
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Affiliation(s)
- Tomoki Nagare
- Department of Molecular Metabolic Regulation, National Center for Global Health and Medicine, Tokyo 162-8655, Japan
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Ablation of TSC2 enhances insulin secretion by increasing the number of mitochondria through activation of mTORC1. PLoS One 2011; 6:e23238. [PMID: 21886784 PMCID: PMC3158755 DOI: 10.1371/journal.pone.0023238] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 07/09/2011] [Indexed: 12/18/2022] Open
Abstract
Aim We previously found that chronic tuberous sclerosis protein 2 (TSC2) deletion induces activation of mammalian target of rapamycin Complex 1 (mTORC1) and leads to hypertrophy of pancreatic beta cells from pancreatic beta cell-specific TSC2 knockout (βTSC2−/−) mice. The present study examines the effects of TSC2 ablation on insulin secretion from pancreatic beta cells. Methods Isolated islets from βTSC2−/− mice and TSC2 knockdown insulin 1 (INS-1) insulinoma cells treated with small interfering ribonucleic acid were used to investigate insulin secretion, ATP content and the expression of mitochondrial genes. Results Activation of mTORC1 increased mitochondrial DNA expression, mitochondrial density and ATP production in pancreatic beta cells of βTSC2−/− mice. In TSC2 knockdown INS-1 cells, mitochondrial DNA expression, mitochondrial density and ATP production were increased compared with those in control INS-1 cells, consistent with the phenotype of βTSC2−/− mice. TSC2 knockdown INS-1 cells also exhibited augmented insulin secretory response to glucose. Rapamycin inhibited mitochondrial DNA expression and ATP production as well as insulin secretion in response to glucose. Thus, βTSC2−/− mice exhibit hyperinsulinemia due to an increase in the number of mitochondria as well as enlargement of individual beta cells via activation of mTORC1. Conclusion Activation of mTORC1 by TSC2 ablation increases mitochondrial biogenesis and enhances insulin secretion from pancreatic beta cells.
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Inoue T, Kido Y, Asahara SI, Matsuda T, Shibutani Y, Koyanagi M, Kasuga M. Effect of intrauterine undernutrition during late gestation on pancreatic beta cell mass. ACTA ACUST UNITED AC 2010; 30:325-30. [PMID: 20051640 DOI: 10.2220/biomedres.30.325] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We analyzed the effect of low birth weight on pancreatic beta cell mass. We used pregnant C57BL6J mice, and we reduced their food supply by 30% during the late gestational period and examined the changes in the metabolism and pancreatic beta cell mass. Pancreatic beta cell mass at birth was greatly decreased in the mice of the food restriction group (RG) as compared to the mice of the control group (CG). The body weight of RG mice exhibited a "catch-up growth" pattern and became equivalent to that of CG mice 7 days after birth, and thereafter exceeded that of CG mice; however, the pancreatic beta cell mass in RG mice remained lower than that in CG mice at the age of 4 weeks. A high-fat diet significantly increased the pancreatic beta cell mass in RG mice as compared to that in CG mice at 12 weeks of age. However, RG mice fed on high-fat diets tended to exhibit a decrease in the pancreatic beta cell mass at approximately 20 weeks of age. The plasma insulin concentrations also tended to be decreased in RG mice after 24 weeks of age as compared to those of CG mice. These results thus indicate that the growth of pancreatic beta cells is insufficient in RG mice, and pancreatic beta cell failure can easily develop as a consequence of insulin resistance.
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Affiliation(s)
- Tae Inoue
- Department of Internal Medicine, Division of Diabetes, Metabolism, and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
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Farese RV, Sajan MP. Metabolic functions of atypical protein kinase C: "good" and "bad" as defined by nutritional status. Am J Physiol Endocrinol Metab 2010; 298:E385-94. [PMID: 19996389 PMCID: PMC3774273 DOI: 10.1152/ajpendo.00608.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Atypical protein kinase C (aPKC) isoforms mediate insulin effects on glucose transport in muscle and adipose tissues and lipid synthesis in liver and support other metabolic processes, expression of enzymes needed for islet insulin secretion and hepatic glucose production/release, CNS appetite suppression, and inflammatory responses. In muscle, selective aPKC deficiency impairs glucose uptake and produces insulin resistance and hyperinsulinemia, which, by activating hepatic aPKC, provokes inordinate increases in lipid synthesis and produces typical "metabolic syndrome" features. In contrast, hepatic aPKC deficiency diminishes lipid synthesis and protects against metabolic syndrome features. Unfortunately, aPKC is deficient in muscle but paradoxically conserved in liver in obesity and type 2 diabetes mellitus; this combination is particularly problematic because it promotes lipid and carbohydrate abnormalities. Accordingly, metabolic effects of aPKCs can be "good" or "bad," depending upon nutritional status; thus, muscle glucose uptake, islet insulin secretion, hepatic glucose and lipid production/release, and adipose fat synthesis/storage would be important for survival during periods of limited food availability and therefore be "good." However, during times of food surfeit, excessive activation of hepatic aPKC, whether caused by overnutrition or impairments in extrahepatic effects of insulin, would lead to inordinate increases in hepatic lipid synthesis and metabolic syndrome features and therefore be "bad." In keeping with these ideas, the inhibition of hepatic aPKC markedly ameliorates lipid and carbohydrate abnormalities in experimental models of obesity and type 2 diabetes. We postulate that a similar approach may be useful for treating humans.
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Affiliation(s)
- Robert V Farese
- James A. Haley Veteran's Administration Medical Center, Tampa, FL 33612, USA.
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25
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Matsuda T, Kido Y, Asahara SI, Kaisho T, Tanaka T, Hashimoto N, Shigeyama Y, Takeda A, Inoue T, Shibutani Y, Koyanagi M, Hosooka T, Matsumoto M, Inoue H, Uchida T, Koike M, Uchiyama Y, Akira S, Kasuga M. Ablation of C/EBPbeta alleviates ER stress and pancreatic beta cell failure through the GRP78 chaperone in mice. J Clin Invest 2009; 120:115-26. [PMID: 19955657 DOI: 10.1172/jci39721] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Accepted: 10/07/2009] [Indexed: 11/17/2022] Open
Abstract
Pancreatic beta cell failure is thought to underlie the progression from glucose intolerance to overt diabetes, and ER stress is implicated in such beta cell dysfunction. We have now shown that the transcription factor CCAAT/enhancer-binding protein beta (C/EBPbeta) accumulated in the islets of diabetic animal models as a result of ER stress before the onset of hyperglycemia. Transgenic overexpression of C/EBPbeta specifically in beta cells of mice reduced beta cell mass and lowered plasma insulin levels, resulting in the development of diabetes. Conversely, genetic ablation of C/EBPbeta in the beta cells of mouse models of diabetes, including Akita mice, which harbor a heterozygous mutation in Ins2 (Ins2WT/C96Y), and leptin receptor-deficient (Lepr-/-) mice, resulted in an increase in beta cell mass and ameliorated hyperglycemia. The accumulation of C/EBPbeta in pancreatic beta cells reduced the abundance of the molecular chaperone glucose-regulated protein of 78 kDa (GRP78) as a result of suppression of the transactivation activity of the transcription factor ATF6alpha, thereby increasing the vulnerability of these cells to excess ER stress. Our results thus indicate that the accumulation of C/EBPbeta in pancreatic beta cells contributes to beta cell failure in mice by enhancing susceptibility to ER stress.
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Affiliation(s)
- Tomokazu Matsuda
- Department of Internal Medicine, Division of Diabetes, Metabolism, and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
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Piquer S, Casas S, Quesada I, Nadal A, Julià M, Novials A, Gomis R. Role of iduronate-2-sulfatase in glucose-stimulated insulin secretion by activation of exocytosis. Am J Physiol Endocrinol Metab 2009; 297:E793-801. [PMID: 19602578 DOI: 10.1152/ajpendo.90878.2008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Iduronate-2-sulfatase (IDS) is a lysosomal enzyme expressed in pancreatic islets responsible for the degradation of proteoglycans such as perlecan and dermatan sulfate. Previous findings of our group demonstrated the involvement of IDS in the normal pathway of lysosomal degradation of secretory peptides, suggesting a role of this enzyme in beta-cell secretory functionality. The present study was undertaken to characterize the effect of IDS overexpression on insulin release. INS1E cells were transiently transfected with a construct encoding human IDS (hIDS). hIDS overexpression was associated with a gain of function detected by a reduction in heparan sulfate content. hIDS potentiated the glucose-stimulated insulin secretory response compared with controls (61%) with no changes in insulin mRNA levels or insulin peptide content. Results on quantification of the exocytotic process showed a significant increase in hIDS-transfected cells compared with controls. Furthermore, ultramorphological analysis demonstrated an increase in the number of granules in the immediate vicinity of the plasma membrane in hIDS-transfected cells and a decrease in total vesicles per square micrometer. hIDS overexpression induced phosphorylation of protein kinase C (PKC) alpha and its newly myristoylated alanine-rich C kinase substrate, MARCKS. We conclude that IDS has a role in glucose-stimulated insulin secretion via a mechanism that involves the activation of exocytosis through phosphorylation of PKCalpha and MARCKS.
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Affiliation(s)
- S Piquer
- Endocrinology and Diabetes Unit, Laboratory of Diabetes and Obesity, Institut d' Investigacions Biomediques August Pi iSunyer-Fundació Clínic, Hospital Clínic, Barcelona, Spain
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Moscat J, Diaz-Meco MT, Wooten MW. Of the atypical PKCs, Par-4 and p62: recent understandings of the biology and pathology of a PB1-dominated complex. Cell Death Differ 2009; 16:1426-37. [PMID: 19713972 DOI: 10.1038/cdd.2009.119] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The recent identification of a novel protein-protein interaction module, termed PB1, in critical signaling molecules such as p62 (also known as sequestosome1), the atypical PKCs, and Par-6, has unveiled the existence of a new set of signaling complexes, which can be central to several biological processes from development to cancer. In this review, we will discuss the most recent advances on the role that the different components of these complexes have in vivo and that are relevant to human disease. In particular, we will review what we are learning from new data from knockout mice, and the indications from human mutations on the real role of these proteins in the physiology and biology of human diseases. The role that PKCzeta, PKClambda/iota, and Par-4 have in lung and prostate cancer in vivo and in humans will be extensively covered in this article, as will the multifunctional role of p62 as a novel hub in cell signaling during cancer and inflammation, and the mechanistic details and controversial data published on its potential role in aggregate formation and signaling. All this published information is shedding new light on the proposed pathological implications of these PB1-regulators in disease and shows their important role in cell physiology.
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Affiliation(s)
- J Moscat
- Department of Cancer and Cell Biology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, USA.
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Hamada S, Hara K, Hamada T, Yasuda H, Moriyama H, Nakayama R, Nagata M, Yokono K. Upregulation of the mammalian target of rapamycin complex 1 pathway by Ras homolog enriched in brain in pancreatic beta-cells leads to increased beta-cell mass and prevention of hyperglycemia. Diabetes 2009; 58:1321-32. [PMID: 19258434 PMCID: PMC2682691 DOI: 10.2337/db08-0519] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Components of insulin/IGF-1 receptor-mediated signaling pathways in pancreatic beta-cells have been implicated in the development of diabetes, in part through the regulation of beta-cell mass in vivo. Studies in vitro have shown that the protein Ras homolog enriched in brain (Rheb) plays a key role as a positive upstream regulator of the mammalian target of rapamycin complex 1 (mTORC1) pathway in integrating inputs from nutrients and growth factors for cell growth. Our objective was to investigate the role of the mTORC1 pathway in the regulation of beta-cell mass in vivo. RESEARCH DESIGN AND METHODS We generated transgenic mice that overexpress Rheb in beta-cells. We examined the activation of the mTORC1 pathway and its effects on beta-cell mass, on glucose metabolism, and on protection against hyperglycemia. RESULTS Immunoblots of islet extracts revealed that the phosphorylation levels of ribosomal protein S6 and eukaryotic initiation factor 4E binding protein 1, downstream effectors for mTORC1, were upregulated in transgenic beta-cells. Immunostaining of the pancreatic sections with anti-phospho-S6 antibody confirmed upregulation of the mTORC1 pathway in beta-cells in vivo. The mice showed improved glucose tolerance with higher insulin secretion. This arose from increased beta-cell mass accompanied by increased cell size. The mice also exhibited resistance to hyperglycemia induced by streptozotocin and obesity. CONCLUSIONS Activation of the mTORC1 pathway by Rheb led to increased beta-cell mass in this mouse model without producing obvious unfavorable effects, giving a potential approach for the treatment of beta-cell failure and diabetes.
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Affiliation(s)
- Suirin Hamada
- Department of Internal and Geriatric Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Kenta Hara
- Department of Internal and Geriatric Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
- Corresponding author: Kenta Hara,
| | - Takeshi Hamada
- Department of Internal and Geriatric Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hisafumi Yasuda
- Department of Internal and Geriatric Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroaki Moriyama
- Department of Internal and Geriatric Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Rika Nakayama
- Laboratory for Animal Resources and Genetic Engineering, Center for Developmental Biology (CDB), RIKEN, Kobe, Japan
| | - Masao Nagata
- Department of Internal and Geriatric Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Koichi Yokono
- Department of Internal and Geriatric Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
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Sajan MP, Standaert ML, Rivas J, Miura A, Kanoh Y, Soto J, Taniguchi CM, Kahn CR, Farese RV. Role of atypical protein kinase C in activation of sterol regulatory element binding protein-1c and nuclear factor kappa B (NFkappaB) in liver of rodents used as a model of diabetes, and relationships to hyperlipidaemia and insulin resistance. Diabetologia 2009; 52:1197-207. [PMID: 19357831 PMCID: PMC4766834 DOI: 10.1007/s00125-009-1336-5] [Citation(s) in RCA: 49] [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: 01/22/2009] [Accepted: 02/25/2009] [Indexed: 02/06/2023]
Abstract
AIMS/HYPOTHESIS Previous findings in rodents used as a model of diabetes suggest that insulin activation of atypical protein kinase C (aPKC) is impaired in muscle, but, unexpectedly, conserved in liver, despite impaired hepatic protein kinase B (PKB/Akt) activation. Moreover, aPKC at least partly regulates two major transactivators: (1) hepatic sterol receptor binding protein-1c (SREBP-1c), which controls lipid synthesis; and (2) nuclear factor kappa B (NFkappaB), which promotes inflammation and systemic insulin resistance. METHODS In Goto-Kakizaki rats used as a model of type 2 diabetes, we examined: (1) whether differences in hepatic aPKC and PKB activation reflect differences in activation of IRS-1- and IRS-2-dependent phosphatidylinositol 3-kinase (PI3K); (2) whether hepatic SREBP-1c and NFkappaB are excessively activated by aPKC; and (3) metabolic consequences of excessive activation of hepatic aPKC, SREBP-1c and NFkappaB. RESULTS In liver, as well as in muscle, IRS-2/PI3K activation by insulin was intact, whereas IRS-1/PI3K activation by insulin was impaired. Moreover, hepatic IRS-2 is known to control hepatic aPKC during insulin activation. Against this background, selective inhibition of hepatic aPKC by adenoviral-mediated expression of mRNA encoding kinase-inactive aPKC or short hairpin RNA targeting Irs2 mRNA and partially depleting hepatic IRS-2 diminished hepatic SREBP-1c production and NFkappaB activities, concomitantly improving serum lipids and insulin signalling in muscle and liver. Similar improvements in SREBP-1c, NFkappaB and insulin signalling were seen in ob/ob mice following inhibition of hepatic aPKC. CONCLUSIONS/INTERPRETATION In diabetic rodent liver, diminished PKB activation may largely reflect impaired IRS-1/PI3K activation, while conserved aPKC activation reflects retained IRS-2/PI3K activity. Hepatic aPKC may also contribute importantly to excessive SREPB-1c and NFkappaB activities. Excessive hepatic aPKC-dependent activation of SREBP-1c and NFkappaB may contribute importantly to hyperlipidaemia and systemic insulin resistance.
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Affiliation(s)
- M P Sajan
- Research Service, James A Haley Veterans Hospital, Tampa, FL 33612, USA
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30
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Asahara SI, Matsuda T, Kido Y, Kasuga M. Increased ribosomal biogenesis induces pancreatic beta cell failure in mice model of type 2 diabetes. Biochem Biophys Res Commun 2009; 381:367-71. [PMID: 19309774 DOI: 10.1016/j.bbrc.2009.02.047] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
AIM To study the changes in gene expression by pancreatic beta cells under insulin resistance conditions. METHOD An exhaustive gene expression analysis was performed, using isolated pancreatic islets of obese diabetic model Lepr(-/-) mice. Overexpression of cyclin D2 was induced in cells from the pancreatic beta cell line, namely, INS-1. RESULTS Through a gene expression analysis using islets isolated from db/db mice, we found a significant increase in the expression of ribosome-related molecules. In addition, increased expression of cyclin D2 was found at certain protein levels. As INS-1 cells were induced to overexpress cyclin D2, we found an increase in the expression of ribosome-related molecules. Concurrently, an increase in the expression of endoplasmic reticulum stress (ER stress)-related molecules was also found. CONCLUSION In cases of pancreatic beta cell hyperplasia associated with insulin resistance, ribosomal biogenesis is increased, and ER stress is induced.
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Affiliation(s)
- Shun-ichiro Asahara
- Department of Internal Medicine, Division of Diabetes, Metabolism, and Endocrinology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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31
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Roffey J, Rosse C, Linch M, Hibbert A, McDonald NQ, Parker PJ. Protein kinase C intervention: the state of play. Curr Opin Cell Biol 2009; 21:268-79. [PMID: 19233632 DOI: 10.1016/j.ceb.2009.01.019] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2009] [Accepted: 01/15/2009] [Indexed: 12/21/2022]
Abstract
Intervention in protein kinase C (PKC) has a chequered history, partly because of the poor selectivity of many inhibitors and partly a reflection of the sometimes antagonistic action of related PKC isoforms. Recent advances in targeting PKC isoforms have come from structural work on isolated kinase domains that have provided opportunities to drive selectivity through structure-based avenues. The promise of isoform selective inhibitors and the rationale for their development are discussed in the broader context of the PKC inhibitor arsenal.
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Affiliation(s)
- Jon Roffey
- Discovery Laboratory, Cancer Research Technology Limited, Wolfson Institute for Biomedical Research, London, UK
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32
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Hou LQ, Wang YH, Liu LJ, Guo J, Teng LP, Cao LH, Shi H, Yuan L, De W. Expression and localization of mesothelin in developing rat pancreas. Dev Growth Differ 2009; 50:531-41. [PMID: 18505465 DOI: 10.1111/j.1440-169x.2008.01047.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
To define a genetic network that regulates development of the pancreas, we used high-density microarray (Affymetrix) to generate transcriptional profiles of rat pancreas from five biologically significant stages of development: embryonic day 12.5 (E12.5), E15.5, E18.5, postnatal day 0 (P0) and adult. Many genes were notably highly expressed in the later gestation when islet architecture and function are gradually forming. The expression and localization of mesothelin, one of these genes, was further examined. Reverse transcription-polymerase chain reaction and Western blot analysis revealed that mRNA and protein levels of mesothelin were high from later gestation to 2-3 weeks after birth, and with relatively low but detectable expression levels in adult rat pancreas. Immunolocalization indicated that mesothelin localized not only in islet beta-cells but also in the mesenchyme of developing rat pancreas. Transient mesothelin expression was concomitant with the development of islets architecture formation, remodeling and maturation. These findings indicate that mesothelin is dynamically expressed in the developing rat pancreas and that mesothelin might be involved in some developmental events during development of rat pancreas.
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Affiliation(s)
- Liang-Qin Hou
- Department of Biochemistry and Molecular Biology, Nanjing Medical University, Hanzhong Road 140, 210029, Nanjing, China
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33
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Tengholm A, Gylfe E. Oscillatory control of insulin secretion. Mol Cell Endocrinol 2009; 297:58-72. [PMID: 18706473 DOI: 10.1016/j.mce.2008.07.009] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Revised: 05/30/2008] [Accepted: 07/10/2008] [Indexed: 11/17/2022]
Abstract
Pancreatic beta-cells possess an inherent ability to generate oscillatory signals that trigger insulin release. Coordination of the secretory activity among beta-cells results in pulsatile insulin secretion from the pancreas, which is considered important for the action of the hormone in the target tissues. This review focuses on the mechanisms underlying oscillatory control of insulin secretion at the level of the individual beta-cell. Recent studies have demonstrated that oscillations of the cytoplasmic Ca(2+) concentration are synchronized with oscillations in beta-cell metabolism, intracellular cAMP concentration, phospholipase C activity and plasma membrane phosphoinositide lipid concentrations. There are complex interdependencies between the different messengers and signalling pathways that contribute to amplitude regulation and shaping of the insulin secretory response to nutrient stimuli and neurohormonal modulators. Several of these pathways may be important pharmacological targets for improving pulsatile insulin secretion in type 2 diabetes.
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Affiliation(s)
- Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, SE-75123 Uppsala, Sweden.
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34
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Abstract
Members of the serine/threonine PKC (protein kinase C) family perform diverse functions in multiple cell types. All members of the family are activated in signalling cascades triggered by occupation of cell surface receptors, but the cPKC (conventional PKC) and nPKC (novel PKC) isoforms are also responsive to fatty acid metabolites. PKC isoforms are involved in various aspects of pancreatic beta-cell function, including cell proliferation, differentiation and death, as well as regulation of secretion in response to glucose and muscarinic receptor agonists. Recently, the nPKC isoform, PKCepsilon, has also been implicated in the loss of insulin secretory responsiveness that underpins the development of Type 2 diabetes.
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35
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Schmitz-Peiffer C, Biden TJ. Protein kinase C function in muscle, liver, and beta-cells and its therapeutic implications for type 2 diabetes. Diabetes 2008; 57:1774-83. [PMID: 18586909 PMCID: PMC2453608 DOI: 10.2337/db07-1769] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 04/15/2008] [Indexed: 01/27/2023]
Affiliation(s)
| | - Trevor J. Biden
- From the Garvan Institute of Medical Research, Darlinghurst, Australia
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36
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Biphasic response of pancreatic beta-cell mass to ablation of tuberous sclerosis complex 2 in mice. Mol Cell Biol 2008; 28:2971-9. [PMID: 18316403 DOI: 10.1128/mcb.01695-07] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Recent studies have demonstrated the importance of insulin or insulin-like growth factor 1 (IGF-1) for regulation of pancreatic beta-cell mass. Given the role of tuberous sclerosis complex 2 (TSC2) as an upstream molecule of mTOR (mammalian target of rapamycin), we examined the effect of TSC2 deficiency on beta-cell function. Here, we show that mice deficient in TSC2, specifically in pancreatic beta cells (betaTSC2(-/-) mice), manifest increased IGF-1-dependent phosphorylation of p70 S6 kinase and 4E-BP1 in islets as well as an initial increased islet mass attributable in large part to increases in the sizes of individual beta cells. These mice also exhibit hypoglycemia and hyperinsulinemia at young ages (4 to 28 weeks). After 40 weeks of age, however, the betaTSC2(-/-) mice develop progressive hyperglycemia and hypoinsulinemia accompanied by a reduction in islet mass due predominantly to a decrease in the number of beta cells. These results thus indicate that TSC2 regulates pancreatic beta-cell mass in a biphasic manner.
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37
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Beguinot F, Formisano P. Atypical protein kinase C dysfunction and the metabolic syndrome. Trends Endocrinol Metab 2008; 19:39-41. [PMID: 18294863 DOI: 10.1016/j.tem.2007.11.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 11/02/2007] [Accepted: 11/02/2007] [Indexed: 11/20/2022]
Abstract
Atypical protein kinase C isoforms are crucial mediators of glucose uptake in insulin-sensitive tissues. In humans, decreased muscular atypical protein kinase C activity has been found in insulin-resistant states. In a recent report by Farese et al., a novel mouse model is described, featuring selective ablation of an atypical protein kinase C, protein kinase Clambda, in muscle. Phenotyping of these mice demonstrated systemic insulin resistance, reduced glucose tolerance, abdominal obesity and dyslipidemia, thus mimicking human metabolic syndrome. Intriguingly, therefore, atypical protein kinase Clambda deficiency might be sufficient to induce metabolic syndrome in mice.
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Affiliation(s)
- Francesco Beguinot
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Federico II University of Naples Medical School, Via Sergio Pansini 5, Naples, Italy.
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Reddy NM, Kleeberger SR, Yamamoto M, Kensler TW, Scollick C, Biswal S, Reddy SP. Genetic dissection of the Nrf2-dependent redox signaling-regulated transcriptional programs of cell proliferation and cytoprotection. Physiol Genomics 2007; 32:74-81. [PMID: 17895394 DOI: 10.1152/physiolgenomics.00126.2007] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The beta zipper (bZip) transcription factor, nuclear factor erythroid 2, like 2 (Nrf2), acting via an antioxidant/electrophile response element, regulates the expression of several antioxidant enzymes and maintains cellular redox homeostasis. Nrf2 deficiency diminishes pulmonary expression of several antioxidant enzymes, rendering them highly susceptible to various mouse models of prooxidant-induced lung injury. We recently demonstrated that Nrf2 deficiency impairs primary cultured pulmonary epithelial cell proliferation and greatly enhances sensitivity to prooxidant-induced cell death. Glutathione (GSH) supplementation rescued cells from these defects associated with Nrf2 deficiency. To further delineate the mechanisms by which Nrf2, via redox signaling, regulates cellular protection and proliferation, we compared the global expression profiling of Nrf2-deficient cells with and without GSH supplementation. We found that GSH regulates the expression of various networks of transcriptional programs including 1) several antioxidant enzymes involved in cellular detoxification of reactive oxygen species and recycling of thiol status and 2) several growth factors, growth factor receptors, and integrins that are critical for cell growth and proliferation. We also found that Nrf2 deficiency enhances the expression levels of several genes encoding proinflammatory cytokines; however, GSH supplementation markedly suppressed their expression. Collectively, these findings uncover an important insight into the nature of genes regulated by Nrf2-dependent redox signaling through GSH that are involved in cellular detoxification and proliferation.
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Affiliation(s)
- Narsa M Reddy
- Department of Environmental Health Sciences, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
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Vasavada RC, Wang L, Fujinaka Y, Takane KK, Rosa TC, Mellado-Gil JMD, Friedman PA, Garcia-Ocaña A. Protein kinase C-zeta activation markedly enhances beta-cell proliferation: an essential role in growth factor mediated beta-cell mitogenesis. Diabetes 2007; 56:2732-43. [PMID: 17686945 DOI: 10.2337/db07-0461] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Diabetes results from a deficiency of functional beta-cells. Previous studies have identified hepatocyte growth factor (HGF) and parathyroid hormone-related protein (PTHrP) as two potent beta-cell mitogens. The objective of this study is to determine 1) whether HGF and PTHrP have additive/synergistic effects on beta-cell growth and proliferation; 2) the signaling pathways through which these growth factors mediate beta-cell mitogenesis; and 3) whether activation of this/these signaling pathway(s) enhances human beta-cell replication. RESEARCH DESIGN AND METHODS We generated and phenotypically analyzed doubly transgenic mice overexpressing PTHrP and HGF in the beta-cell. INS-1 and primary mouse and human islet cells were used to identify mitogenic signaling pathways activated by HGF and/or PTHrP. RESULTS Combined overexpression of HGF and PTHrP in the beta-cell of doubly transgenic mice did not result in additive/synergistic effects on beta-cell growth and proliferation, suggesting potential cross-talk between signaling pathways activated by both growth factors. Examination of these signaling pathways in INS-1 cells revealed atypical protein kinase C (PKC) as a novel intracellular target activated by both HGF and PTHrP in beta-cells. Knockdown of PKC zeta, but not PKC iota/lambda, expression using specific small-interfering RNAs blocked growth factor-induced INS-1 cell proliferation. Furthermore, adenovirus-mediated delivery of kinase-dead PKC zeta completely inhibited beta-cell proliferation in primary islet cells overexpressing PTHrP and/or HGF. Finally, adenovirus-mediated delivery of constitutively active PKC zeta in mouse and human primary islet cells significantly enhanced beta-cell proliferation. CONCLUSIONS PKC zeta is essential for PTHrP- and HGF-induced beta-cell proliferation. PKC zeta activation could be useful in therapeutic strategies for expanding beta-cell mass in vitro and in vivo.
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Affiliation(s)
- Rupangi C Vasavada
- Department of Medicine, Division of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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Farese RV, Sajan MP, Yang H, Li P, Mastorides S, Gower WR, Nimal S, Choi CS, Kim S, Shulman GI, Kahn CR, Braun U, Leitges M. Muscle-specific knockout of PKC-lambda impairs glucose transport and induces metabolic and diabetic syndromes. J Clin Invest 2007. [PMID: 17641777 DOI: 10.1172/jci31408c1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Obesity, the metabolic syndrome, and type 2 diabetes mellitus (T2DM) are major global health problems. Insulin resistance is frequently present in these disorders, but the causes and effects of such resistance are unknown. Here, we generated mice with muscle-specific knockout of the major murine atypical PKC (aPKC), PKC-lambda, a postulated mediator for insulin-stimulated glucose transport. Glucose transport and translocation of glucose transporter 4 (GLUT4) to the plasma membrane were diminished in muscles of both homozygous and heterozygous PKC-lambda knockout mice and were accompanied by systemic insulin resistance; impaired glucose tolerance or diabetes; islet beta cell hyperplasia; abdominal adiposity; hepatosteatosis; elevated serum triglycerides, FFAs, and LDL-cholesterol; and diminished HDL-cholesterol. In contrast to the defective activation of muscle aPKC, insulin signaling and actions were intact in muscle, liver, and adipocytes. These findings demonstrate the importance of aPKC in insulin-stimulated glucose transport in muscles of intact mice and show that insulin resistance and resultant hyperinsulinemia owing to a specific defect in muscle aPKC is sufficient to induce abdominal obesity and other lipid abnormalities of the metabolic syndrome and T2DM. These findings are particularly relevant because humans who have obesity, impaired glucose tolerance, and T2DM reportedly have defective activation and/or diminished levels of muscle aPKC.
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Affiliation(s)
- Robert V Farese
- James A. Haley Veterans Medical Center, Tampa, Florida 33612, USA.
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Farese RV, Sajan MP, Yang H, Li P, Mastorides S, Gower WR, Nimal S, Choi CS, Kim S, Shulman GI, Kahn CR, Braun U, Leitges M. Muscle-specific knockout of PKC-lambda impairs glucose transport and induces metabolic and diabetic syndromes. J Clin Invest 2007; 117:2289-301. [PMID: 17641777 PMCID: PMC1913489 DOI: 10.1172/jci31408] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Accepted: 05/08/2007] [Indexed: 12/11/2022] Open
Abstract
Obesity, the metabolic syndrome, and type 2 diabetes mellitus (T2DM) are major global health problems. Insulin resistance is frequently present in these disorders, but the causes and effects of such resistance are unknown. Here, we generated mice with muscle-specific knockout of the major murine atypical PKC (aPKC), PKC-lambda, a postulated mediator for insulin-stimulated glucose transport. Glucose transport and translocation of glucose transporter 4 (GLUT4) to the plasma membrane were diminished in muscles of both homozygous and heterozygous PKC-lambda knockout mice and were accompanied by systemic insulin resistance; impaired glucose tolerance or diabetes; islet beta cell hyperplasia; abdominal adiposity; hepatosteatosis; elevated serum triglycerides, FFAs, and LDL-cholesterol; and diminished HDL-cholesterol. In contrast to the defective activation of muscle aPKC, insulin signaling and actions were intact in muscle, liver, and adipocytes. These findings demonstrate the importance of aPKC in insulin-stimulated glucose transport in muscles of intact mice and show that insulin resistance and resultant hyperinsulinemia owing to a specific defect in muscle aPKC is sufficient to induce abdominal obesity and other lipid abnormalities of the metabolic syndrome and T2DM. These findings are particularly relevant because humans who have obesity, impaired glucose tolerance, and T2DM reportedly have defective activation and/or diminished levels of muscle aPKC.
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Affiliation(s)
- Robert V Farese
- James A. Haley Veterans Medical Center, Tampa, Florida 33612, USA.
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42
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Miele C, Raciti GA, Cassese A, Romano C, Giacco F, Oriente F, Paturzo F, Andreozzi F, Zabatta A, Troncone G, Bosch F, Pujol A, Chneiweiss H, Formisano P, Beguinot F. PED/PEA-15 regulates glucose-induced insulin secretion by restraining potassium channel expression in pancreatic beta-cells. Diabetes 2007; 56:622-33. [PMID: 17327429 DOI: 10.2337/db06-1260] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes (ped/pea-15) gene is overexpressed in human diabetes and causes this abnormality in mice. Transgenic mice with beta-cell-specific overexpression of ped/pea-15 (beta-tg) exhibited decreased glucose tolerance but were not insulin resistant. However, they showed impaired insulin response to hyperglycemia. Islets from the beta-tg also exhibited little response to glucose. mRNAs encoding the Sur1 and Kir6.2 potassium channel subunits and their upstream regulator Foxa2 were specifically reduced in these islets. Overexpression of PED/PEA-15 inhibited the induction of the atypical protein kinase C (PKC)-zeta by glucose in mouse islets and in beta-cells of the MIN-6 and INS-1 lines. Rescue of PKC-zeta activity elicited recovery of the expression of the Sur1, Kir6.2, and Foxa2 genes and of glucose-induced insulin secretion in PED/PEA-15-overexpressing beta-cells. Islets from ped/pea-15-null mice exhibited a twofold increased activation of PKC-zeta by glucose; increased abundance of the Sur1, Kir6.2, and Foxa2 mRNAs; and enhanced glucose effect on insulin secretion. In conclusion, PED/PEA-15 is an endogenous regulator of glucose-induced insulin secretion, which restrains potassium channel expression in pancreatic beta-cells. Overexpression of PED/PEA-15 dysregulates beta-cell function and is sufficient to impair glucose tolerance in mice.
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Affiliation(s)
- Claudia Miele
- Department of Cellular and Molecular Biology and Pathology, Federico II University of Naples, via Sergio Pansini 5, Naples 80131, Italy
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43
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Goto Y, Nomura M, Tanaka K, Kondo A, Morinaga H, Okabe T, Yanase T, Nawata H, Takayanagi R, Li E. Genetic interactions between activin type IIB receptor and Smad2 genes in asymmetrical patterning of the thoracic organs and the development of pancreas islets. Dev Dyn 2007; 236:2865-74. [PMID: 17849440 DOI: 10.1002/dvdy.21303] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Signaling through activin type IIB receptor (ActRIIB) has been shown to regulate the axial formation and the development of foregut-derived organs such as the pancreas in mice. Here, we provide genetic evidence that ActRIIB and Smad2 genes cooperatively regulated asymmetrical patterning of the thoracic organs and pancreas development in mice. The loss of one allele of Smad2 on ActRIIB-/- background resulted in the increased severity of ActRIIB-/- phenotypes, including right pulmonary isomerism and complex cardiac malformations, and resulted in 100% frequency of death soon after birth. Of interest, 14% of compound heterozygous ActRIIB+/- Smad2+/- mice exhibited the ActRIIB-/- phenotypes and died soon after birth. In the pancreas, hypoplastic islets were found not only in ActRIIB-/- but also in Smad2+/- mice. A more severe phenotype was also found in ActRIIB+/- Smad2+/- mice. As well, these mutant mice exhibited impaired glucose tolerance in a gene dosage-sensitive manner. This genetic evidence strongly suggested that ActRIIB and Smad2 function in the same signaling pathway to regulate axial patterning and pancreas islet formation by means of a threshold mechanism.
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Affiliation(s)
- Yutaka Goto
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
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44
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Liu XJ, He AB, Chang YS, Fang FD. Atypical protein kinase C in glucose metabolism. Cell Signal 2006; 18:2071-6. [PMID: 16787739 DOI: 10.1016/j.cellsig.2006.04.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Accepted: 04/28/2006] [Indexed: 01/17/2023]
Abstract
Type 2 diabetes mellitus is a multigenic disease with evident genetic predisposition, and complex pathogenesis in which environmental and genetic factors interact. The disorder of body utilization glucose is a crucial reason for causing diabetes. Atypical PKCs, belonging to Ser/Thr protein kinase, have many important biological functions in vivo, and may be involved in the pathogenesis of diabetes mellitus. APKCs participate in glucose metabolism by regulating glucose transport and absorption, glycogen synthesis, and insulin secretion. The exact mechanism by which aPKCs participate in glucose metabolism remains unclear. So far, the clarification of which will be helpful for the prevention and cure of type 2 diabetes.
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Affiliation(s)
- Xiao-Jun Liu
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences and School of Basic Medicine Peking Union Medical College, Beijing 100005, China
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45
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Bryan J, Muñoz A, Zhang X, Düfer M, Drews G, Krippeit-Drews P, Aguilar-Bryan L. ABCC8 and ABCC9: ABC transporters that regulate K+ channels. Pflugers Arch 2006; 453:703-18. [PMID: 16897043 DOI: 10.1007/s00424-006-0116-z] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Accepted: 06/08/2006] [Indexed: 11/28/2022]
Abstract
The sulfonylurea receptors (SURs) ABCC8/SUR1 and ABCC9/SUR2 are members of the C-branch of the transport adenosine triphosphatase superfamily. Unlike their brethren, the SURs have no identified transport function; instead, evolution has matched these molecules with K(+) selective pores, either K(IR)6.1/KCNJ8 or K(IR)6.2/KCNJ11, to assemble adenosine triphosphate (ATP)-sensitive K(+) channels found in endocrine cells, neurons, and both smooth and striated muscle. Adenine nucleotides, the major regulators of ATP-sensitive K(+) (K(ATP)) channel activity, exert a dual action. Nucleotide binding to the pore reduces the activity or channel open probability, whereas Mg-nucleotide binding and/or hydrolysis in the nucleotide-binding domains of SUR antagonize this inhibitory action to stimulate channel openings. Mutations in either subunit can alter this balance and, in the case of the SUR1/KIR6.2 channels found in neurons and insulin-secreting pancreatic beta cells, are the cause of monogenic forms of hyperinsulinemic hypoglycemia and neonatal diabetes. Additionally, the subtle dysregulation of K(ATP) channel activity by a K(IR)6.2 polymorphism has been suggested as a predisposing factor in type 2 diabetes mellitus. Studies on K(ATP) channel null mice are clarifying the roles of these metabolically sensitive channels in a variety of tissues.
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Affiliation(s)
- Joseph Bryan
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
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46
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Imai F, Hirai SI, Akimoto K, Koyama H, Miyata T, Ogawa M, Noguchi S, Sasaoka T, Noda T, Ohno S. Inactivation of aPKCλ results in the loss of adherens junctions in neuroepithelial cells without affecting neurogenesis in mouse neocortex. Development 2006; 133:1735-44. [PMID: 16571631 DOI: 10.1242/dev.02330] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In developing mammalian telencephalon, the loss of adherens junctions and cell cycle exit represent crucial steps in the differentiation of neuroepithelial cells into neurons, but the relationship between these cellular events remains obscure. Atypical protein kinase C (aPKC) is known to contribute to junction formation in epithelial cells and to cell fate determination for Drosophila neuroblasts. To elucidate the functions of aPKCλ, one out of two aPKC members, in mouse neocortical neurogenesis, a Nestin-Cre mediated conditional gene targeting system was employed. In conditional aPKCλ knockout mice, neuroepithelial cells of the neocortical region lost aPKCλ protein at embryonic day 15 and demonstrated a loss of adherens junctions, retraction of apical processes and impaired interkinetic nuclear migration that resulted in disordered neuroepithelial tissue architecture. These results are evidence that aPKCλ is indispensable for the maintenance of adherens junctions and may function in the regulation of adherens junction integrity upon differentiation of neuroepithelial cells into neurons. In spite of the loss of adherens junctions in the neuroepithelium of conditional aPKCλ knockout mice, neurons were produced at a normal rate. Therefore, we concluded that, at least in the later stages of neurogenesis, regulation of cell cycle exit is independent of adherens junctions.
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Affiliation(s)
- Fumiyasu Imai
- Department of Molecular Biology, Yokohama City University Graduate School of Medical Science, 3-9 Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan
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47
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Hashimoto N, Kido Y, Uchida T, Asahara SI, Shigeyama Y, Matsuda T, Takeda A, Tsuchihashi D, Nishizawa A, Ogawa W, Fujimoto Y, Okamura H, Arden KC, Herrera PL, Noda T, Kasuga M. Ablation of PDK1 in pancreatic beta cells induces diabetes as a result of loss of beta cell mass. Nat Genet 2006; 38:589-93. [PMID: 16642023 DOI: 10.1038/ng1774] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2005] [Accepted: 03/09/2006] [Indexed: 12/22/2022]
Abstract
The total mass of islets of Langerhans is reduced in individuals with type 2 diabetes, possibly contributing to the pathogenesis of this condition. Although the regulation of islet mass is complex, recent studies have suggested the importance of a signaling pathway that includes the insulin or insulin-like growth factor-1 receptors, insulin receptor substrate and phosphatidylinositol (PI) 3-kinase. 3-Phosphoinositide-dependent protein kinase 1 (PDK1) is a serine-threonine kinase that mediates signaling downstream of PI 3-kinase. Here we show that mice that lack PDK1 specifically in pancreatic beta cells (betaPdk1-/- mice) develop progressive hyperglycemia as a result of a loss of islet mass. The mice show reductions in islet density as well as in the number and size of cells. Haploinsufficiency of the gene for the transcription factor Foxo1 resulted in a marked increase in the number, but not the size, of cells and resulted in the restoration of glucose homeostasis in betaPdk1-/- mice. These results suggest that PDK1 is important in maintenance of pancreatic cell mass and glucose homeostasis.
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Affiliation(s)
- Naoko Hashimoto
- Department of Clinical Molecular Medicine, Division of Diabetes and Digestive and Kidney Diseases, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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48
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Warwar N, Efendic S, Ostenson CG, Haber EP, Cerasi E, Nesher R. Dynamics of glucose-induced localization of PKC isoenzymes in pancreatic beta-cells: diabetes-related changes in the GK rat. Diabetes 2006; 55:590-9. [PMID: 16505220 DOI: 10.2337/diabetes.55.03.06.db05-0001] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucose metabolism affects most major signal pathways in pancreatic beta-cells. Multiple protein kinases, including protein kinase C (PKC) isoenzymes, are involved in these effects; however, their role is poorly defined. Moreover, the dynamics of kinase isoenzyme activation in reference to the biphasic insulin secretion is unknown. In perfused pancreas of Wistar rats, PKCalpha staining was strongly associated with insulin staining, jointly accumulating in the vicinity of the plasma membrane during early first-phase insulin response. The signal declined before the onset of second phase and reappeared during second-phase insulin release as foci, only weekly associated with insulin staining; this signal persisted for at least 15 min after glucose stimulation. In the GK rat, glucose had minimal effect on beta-cell PKCalpha. In control beta-cells, PKCdelta stained as granulated foci with partial association with insulin staining; however, no glucose-dependent translocation was observed. In the GK rat, only minimal staining for PKCdelta was observed, increasing exclusively during early first-phase secretion. In Wistar beta-cells, PKCepsilon concentrated near the nucleus, strongly associated with insulin staining, with dynamics resembling that of biphasic insulin response, but persisting for 15 min after cessation of stimulation. In GK rats, PKCepsilon staining lacked glucose-dependent changes or association with insulin. PKCzeta exhibited bimodal dynamics in control beta-cells: during early first phase, accumulation near the cell membrane was observed, dispersing thereafter. This was followed by a gradual accumulation near the nucleus; 15 min after glucose stimulus, clear PKCzeta staining was observed within the nucleus. In the GK rat, a similar response was only occasionally observed. In control beta-cells, glucose stimulation led to a transient recruitment of PKCtheta, associated with first-phase insulin release, not seen in GK beta-cell. Data from this and related studies support a role for PKCalpha in glucose-induced insulin granule recruitment for exocytosis; a role for PKCepsilon in activation of insulin granules for exocytosis and/or in the glucose-generated time-dependent potentiation signal for insulin release; and a dual function for PKCzeta in initiating insulin release and in a regulatory role in the transcriptional machinery. Furthermore, diminished levels and/or activation of PKCalpha, PKCepsilon, PKCtheta, and PKCzeta could be part of the defective signals downstream to glucose metabolism responsible for the deranged insulin secretion in the GK rat.
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Affiliation(s)
- Nasim Warwar
- Endocrinology and Metabolism Service, Hebrew University, Hadassah Medical Center, Jerusalem, Israel
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49
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Lee JY, Ristow M, Lin X, White MF, Magnuson MA, Hennighausen L. RIP-Cre Revisited, Evidence for Impairments of Pancreatic β-Cell Function. J Biol Chem 2006; 281:2649-53. [PMID: 16326700 DOI: 10.1074/jbc.m512373200] [Citation(s) in RCA: 205] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The Cre/loxP recombinase system for performing conditional gene targeting experiments has been very useful in exploring genetic pathways that control both the development and function of pancreatic beta-cells. One particular line of transgenic mice (B6.Cg-Tg(Ins2-cre)25Mgn/J), commonly called RIP-Cre, in which expression of Cre recombinase is controlled by a short fragment of the rat insulin II gene promoter has been used in at least 21 studies on at least 17 genes. In most of these studies inactivation of the gene of interest was associated with either glucose intolerance or frank diabetes. Experimental evidence has been gradually emerging to suggest that RIP-Cre mice alone display glucose intolerance. In this study experiments from three laboratories demonstrate that RIP-Cre mice, in the absence of genes targeted by loxP sites, are glucose intolerant, possibly due to impaired insulin secretion. In addition, we review the use of RIP-Cre mice and discuss possible molecular underpinnings and ramifications of our findings.
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Affiliation(s)
- Ji-Yeon Lee
- Laboratory of Genetics and Physiology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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50
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Wada T, Nakashima T, Hiroshi N, Penninger JM. RANKL-RANK signaling in osteoclastogenesis and bone disease. Trends Mol Med 2005; 12:17-25. [PMID: 16356770 DOI: 10.1016/j.molmed.2005.11.007] [Citation(s) in RCA: 836] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Revised: 11/03/2005] [Accepted: 11/24/2005] [Indexed: 01/10/2023]
Abstract
Hundreds of millions of people worldwide are affected by bone-related diseases, such as osteoporosis and rheumatoid arthritis. Understanding the molecular mechanisms of bone metabolism is crucial for developing novel drugs for treating such diseases. In particular, genetic experiments showing that the receptor activator of NF-kappaB (RANK), its ligand RANKL, and the decoy receptor OPG are essential, central regulators of osteoclast development and osteoclast function were significant turning points in our understanding of bone diseases. RANKL-RANK signaling activates a variety of downstream signaling pathways required for osteoclast development. Moreover, molecular cross-talk between RANKL-RANK and other ligand-receptor systems fine-tunes bone homeostasis in normal physiology and disease. Designing novel drugs that target RANKL-RANK and their signaling pathways in osteoclasts could potentially revolutionize the treatment of many diseases associated with bone loss such as arthritis, tooth loss, cancer metastases or osteoporosis.
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Affiliation(s)
- Teiji Wada
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
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