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Zhang Q, Linke V, Overmyer KA, Traeger LL, Kasahara K, Miller IJ, Manson DE, Polaske TJ, Kerby RL, Kemis JH, Trujillo EA, Reddy TR, Russell JD, Schueler KL, Stapleton DS, Rabaglia ME, Seldin M, Gatti DM, Keele GR, Pham DT, Gerdt JP, Vivas EI, Lusis AJ, Keller MP, Churchill GA, Blackwell HE, Broman KW, Attie AD, Coon JJ, Rey FE. Author Correction: Genetic mapping of microbial and host traits reveals production of immunomodulatory lipids by Akkermansia muciniphila in the murine gut. Nat Microbiol 2023; 8:745. [PMID: 36973420 PMCID: PMC10066032 DOI: 10.1038/s41564-023-01366-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Affiliation(s)
- Qijun Zhang
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Vanessa Linke
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
- IMol Polish Academy of Sciences, Warsaw, Poland
- ReMedy International Research Agenda Unit, IMol Polish Academy of Sciences, Warsaw, Poland
| | - Katherine A Overmyer
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA
- Morgridge Institute for Research, Madison, WI, USA
| | - Lindsay L Traeger
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Kazuyuki Kasahara
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Ian J Miller
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Daniel E Manson
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Thomas J Polaske
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Robert L Kerby
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Julia H Kemis
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Edna A Trujillo
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Thiru R Reddy
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Jason D Russell
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Kathryn L Schueler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Donald S Stapleton
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Mary E Rabaglia
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Marcus Seldin
- Departments of Microbiology, Immunology and Molecular Genetics, and Human Genetics, University of California, Los Angeles, Los Angeles, CA, USA
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | | | | | - Duy T Pham
- The Jackson Laboratory, Bar Harbor, ME, USA
| | - Joseph P Gerdt
- Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Eugenio I Vivas
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Aldons J Lusis
- Departments of Microbiology, Immunology and Molecular Genetics, and Human Genetics, University of California, Los Angeles, Los Angeles, CA, USA
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | | | - Helen E Blackwell
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Karl W Broman
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI, USA
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Joshua J Coon
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA
- Morgridge Institute for Research, Madison, WI, USA
| | - Federico E Rey
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
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2
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Emfinger CH, de Klerk E, Schueler KL, Rabaglia ME, Stapleton DS, Simonett SP, Mitok KA, Wang Z, Liu X, Paulo JA, Yu Q, Cardone RL, Foster HR, Lewandowski SL, Perales JC, Kendziorski CM, Gygi SP, Kibbey RG, Keller MP, Hebrok M, Merrins MJ, Attie AD. β Cell-specific deletion of Zfp148 improves nutrient-stimulated β cell Ca2+ responses. JCI Insight 2022; 7:e154198. [PMID: 35603790 PMCID: PMC9220824 DOI: 10.1172/jci.insight.154198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 04/20/2022] [Indexed: 12/05/2022] Open
Abstract
Insulin secretion from pancreatic β cells is essential for glucose homeostasis. An insufficient response to the demand for insulin results in diabetes. We previously showed that β cell-specific deletion of Zfp148 (β-Zfp148KO) improves glucose tolerance and insulin secretion in mice. Here, we performed Ca2+ imaging of islets from β‑Zfp148KO and control mice fed both a chow and a Western-style diet. β-Zfp148KO islets demonstrated improved sensitivity and sustained Ca2+ oscillations in response to elevated glucose levels. β-Zfp148KO islets also exhibited elevated sensitivity to amino acid-induced Ca2+ influx under low glucose conditions, suggesting enhanced mitochondrial phosphoenolpyruvate-dependent (PEP-dependent), ATP-sensitive K+ channel closure, independent of glycolysis. RNA-Seq and proteomics of β-Zfp148KO islets revealed altered levels of enzymes involved in amino acid metabolism (specifically, SLC3A2, SLC7A8, GLS, GLS2, PSPH, PHGDH, and PSAT1) and intermediary metabolism (namely, GOT1 and PCK2), consistent with altered PEP cycling. In agreement with this, β-Zfp148KO islets displayed enhanced insulin secretion in response to l-glutamine and activation of glutamate dehydrogenase. Understanding pathways controlled by ZFP148 may provide promising strategies for improving β cell function that are robust to the metabolic challenge imposed by a Western diet.
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Affiliation(s)
| | | | - Kathryn L. Schueler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Mary E. Rabaglia
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Donnie S. Stapleton
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Shane P. Simonett
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Kelly A. Mitok
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Ziyue Wang
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, Durham, North Carolina, USA
| | - Xinyue Liu
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Joao A. Paulo
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Qing Yu
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Rebecca L. Cardone
- Department of Internal Medicine (Endocrinology), Yale University, New Haven, Connecticut, USA
| | - Hannah R. Foster
- Department of Medicine, Division of Endocrinology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Sophie L. Lewandowski
- Department of Medicine, Division of Endocrinology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - José C. Perales
- Department of Physiological Sciences, School of Medicine, University of Barcelona, L’Hospitalet del Llobregat, Barcelona, Spain
| | - Christina M. Kendziorski
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Steven P. Gygi
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Richard G. Kibbey
- Department of Internal Medicine (Endocrinology), Yale University, New Haven, Connecticut, USA
- Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, USA
| | - Mark P. Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | | | - Matthew J. Merrins
- Department of Medicine, Division of Endocrinology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin, USA
| | - Alan D. Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
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3
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Simonett SP, Shin S, Herring JA, Bacher R, Smith LA, Dong C, Rabaglia ME, Stapleton DS, Schueler KL, Choi J, Bernstein MN, Turkewitz DR, Perez-Cervantes C, Spaeth J, Stein R, Tessem JS, Kendziorski C, Keleş S, Moskowitz IP, Keller MP, Attie AD. Identification of direct transcriptional targets of NFATC2 that promote β cell proliferation. J Clin Invest 2021; 131:e144833. [PMID: 34491912 PMCID: PMC8553569 DOI: 10.1172/jci144833] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 09/02/2021] [Indexed: 12/13/2022] Open
Abstract
The transcription factor NFATC2 induces β cell proliferation in mouse and human islets. However, the genomic targets that mediate these effects have not been identified. We expressed active forms of Nfatc2 and Nfatc1 in human islets. By integrating changes in gene expression with genomic binding sites for NFATC2, we identified approximately 2200 transcriptional targets of NFATC2. Genes induced by NFATC2 were enriched for transcripts that regulate the cell cycle and for DNA motifs associated with the transcription factor FOXP. Islets from an endocrine-specific Foxp1, Foxp2, and Foxp4 triple-knockout mouse were less responsive to NFATC2-induced β cell proliferation, suggesting the FOXP family works to regulate β cell proliferation in concert with NFATC2. NFATC2 induced β cell proliferation in both mouse and human islets, whereas NFATC1 did so only in human islets. Exploiting this species difference, we identified approximately 250 direct transcriptional targets of NFAT in human islets. This gene set enriches for cell cycle-associated transcripts and includes Nr4a1. Deletion of Nr4a1 reduced the capacity of NFATC2 to induce β cell proliferation, suggesting that much of the effect of NFATC2 occurs through its induction of Nr4a1. Integration of noncoding RNA expression, chromatin accessibility, and NFATC2 binding sites enabled us to identify NFATC2-dependent enhancer loci that mediate β cell proliferation.
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Affiliation(s)
- Shane P. Simonett
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Sunyoung Shin
- Department of Mathematical Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Jacob A. Herring
- Nutrition, Dietetics and Food Science Department, Brigham Young University, Provo, Utah, USA
| | - Rhonda Bacher
- Department of Biostatistics, University of Florida, Gainesville, Florida, USA
| | - Linsin A. Smith
- Departments of Pediatrics, Pathology, and Human Genetics, University of Chicago, Chicago, Illinois, USA
| | - Chenyang Dong
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Mary E. Rabaglia
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Donnie S. Stapleton
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Kathryn L. Schueler
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Jeea Choi
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | | | - Daniel R. Turkewitz
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Carlos Perez-Cervantes
- Departments of Pediatrics, Pathology, and Human Genetics, University of Chicago, Chicago, Illinois, USA
| | - Jason Spaeth
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Roland Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Jeffery S. Tessem
- Nutrition, Dietetics and Food Science Department, Brigham Young University, Provo, Utah, USA
| | - Christina Kendziorski
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Sündüz Keleş
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Ivan P. Moskowitz
- Departments of Pediatrics, Pathology, and Human Genetics, University of Chicago, Chicago, Illinois, USA
| | - Mark P. Keller
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Alan D. Attie
- Biochemistry Department, University of Wisconsin–Madison, Madison, Wisconsin, USA
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4
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Linke V, Overmyer KA, Miller IJ, Brademan DR, Hutchins PD, Trujillo EA, Reddy TR, Russell JD, Cushing EM, Schueler KL, Stapleton DS, Rabaglia ME, Keller MP, Gatti DM, Keele GR, Pham D, Broman KW, Churchill GA, Attie AD, Coon JJ. A large-scale genome-lipid association map guides lipid identification. Nat Metab 2020; 2:1149-1162. [PMID: 32958938 PMCID: PMC7572687 DOI: 10.1038/s42255-020-00278-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 08/11/2020] [Indexed: 12/13/2022]
Abstract
Despite the crucial roles of lipids in metabolism, we are still at the early stages of comprehensively annotating lipid species and their genetic basis. Mass spectrometry-based discovery lipidomics offers the potential to globally survey lipids and their relative abundances in various biological samples. To discover the genetics of lipid features obtained through high-resolution liquid chromatography-tandem mass spectrometry, we analysed liver and plasma from 384 diversity outbred mice, and quantified 3,283 molecular features. These features were mapped to 5,622 lipid quantitative trait loci and compiled into a public web resource termed LipidGenie. The data are cross-referenced to the human genome and offer a bridge between genetic associations in humans and mice. Harnessing this resource, we used genome-lipid association data as an additional aid to identify a number of lipids, for example gangliosides through their association with B4galnt1, and found evidence for a group of sex-specific phosphatidylcholines through their shared locus. Finally, LipidGenie's ability to query either mass or gene-centric terms suggests acyl-chain-specific functions for proteins of the ABHD family.
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Affiliation(s)
- Vanessa Linke
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Katherine A Overmyer
- Morgridge Institute for Research, Madison, WI, USA
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Ian J Miller
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Dain R Brademan
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Paul D Hutchins
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Edna A Trujillo
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Thiru R Reddy
- Morgridge Institute for Research, Madison, WI, USA
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | | | - Emily M Cushing
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Kathryn L Schueler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Donald S Stapleton
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Mary E Rabaglia
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | | | | | - Duy Pham
- The Jackson Laboratory, Bar Harbor, ME, USA
| | - Karl W Broman
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI, USA
| | | | - Alan D Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Joshua J Coon
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
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5
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Kemis JH, Linke V, Barrett KL, Boehm FJ, Traeger LL, Keller MP, Rabaglia ME, Schueler KL, Stapleton DS, Gatti DM, Churchill GA, Amador-Noguez D, Russell JD, Yandell BS, Broman KW, Coon JJ, Attie AD, Rey FE. Genetic determinants of gut microbiota composition and bile acid profiles in mice. PLoS Genet 2019; 15:e1008073. [PMID: 31465442 PMCID: PMC6715156 DOI: 10.1371/journal.pgen.1008073] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 06/14/2019] [Indexed: 02/03/2023] Open
Abstract
The microbial communities that inhabit the distal gut of humans and other mammals exhibit large inter-individual variation. While host genetics is a known factor that influences gut microbiota composition, the mechanisms underlying this variation remain largely unknown. Bile acids (BAs) are hormones that are produced by the host and chemically modified by gut bacteria. BAs serve as environmental cues and nutrients to microbes, but they can also have antibacterial effects. We hypothesized that host genetic variation in BA metabolism and homeostasis influence gut microbiota composition. To address this, we used the Diversity Outbred (DO) stock, a population of genetically distinct mice derived from eight founder strains. We characterized the fecal microbiota composition and plasma and cecal BA profiles from 400 DO mice maintained on a high-fat high-sucrose diet for ~22 weeks. Using quantitative trait locus (QTL) analysis, we identified several genomic regions associated with variations in both bacterial and BA profiles. Notably, we found overlapping QTL for Turicibacter sp. and plasma cholic acid, which mapped to a locus containing the gene for the ileal bile acid transporter, Slc10a2. Mediation analysis and subsequent follow-up validation experiments suggest that differences in Slc10a2 gene expression associated with the different strains influences levels of both traits and revealed novel interactions between Turicibacter and BAs. This work illustrates how systems genetics can be utilized to generate testable hypotheses and provide insight into host-microbe interactions.
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Affiliation(s)
- Julia H. Kemis
- Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Vanessa Linke
- Department of Chemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Kelsey L. Barrett
- Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Frederick J. Boehm
- Department of Statistics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Lindsay L. Traeger
- Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Mark P. Keller
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Mary E. Rabaglia
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Kathryn L. Schueler
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Donald S. Stapleton
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Daniel M. Gatti
- Jackson Laboratory, Bar Harbor, Maine, United States of America
| | | | - Daniel Amador-Noguez
- Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Jason D. Russell
- Department of Chemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Brian S. Yandell
- Department of Statistics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Karl W. Broman
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Joshua J. Coon
- Department of Chemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- Morgridge Institute for Research, Madison, Wisconsin, United States of America
- Department of Biomolecular Chemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Alan D. Attie
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Federico E. Rey
- Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
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6
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Keller MP, Rabaglia ME, Schueler KL, Stapleton DS, Gatti DM, Vincent M, Mitok KA, Wang Z, Ishimura T, Simonett SP, Emfinger CH, Das R, Beck T, Kendziorski C, Broman KW, Yandell BS, Churchill GA, Attie AD. Gene loci associated with insulin secretion in islets from non-diabetic mice. J Clin Invest 2019; 129:4419-4432. [PMID: 31343992 DOI: 10.1172/jci129143] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Genetic susceptibility to type 2 diabetes is primarily due to β-cell dysfunction. However, a genetic study to directly interrogate β-cell function ex vivo has never been previously performed. We isolated 233,447 islets from 483 Diversity Outbred (DO) mice maintained on a Western-style diet, and measured insulin secretion in response to a variety of secretagogues. Insulin secretion from DO islets ranged >1,000-fold even though none of the mice were diabetic. The insulin secretory response to each secretagogue had a unique genetic architecture; some of the loci were specific for one condition, whereas others overlapped. Human loci that are syntenic to many of the insulin secretion QTL from mouse are associated with diabetes-related SNPs in human genome-wide association studies. We report on three genes, Ptpn18, Hunk and Zfp148, where the phenotype predictions from the genetic screen were fulfilled in our studies of transgenic mouse models. These three genes encode a non-receptor type protein tyrosine phosphatase, a serine/threonine protein kinase, and a Krϋppel-type zinc-finger transcription factor, respectively. Our results demonstrate that genetic variation in insulin secretion that can lead to type 2 diabetes is discoverable in non-diabetic individuals.
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Affiliation(s)
- Mark P Keller
- University of Wisconsin-Madison, Biochemistry Department, Madison, Wisconsin, USA
| | - Mary E Rabaglia
- University of Wisconsin-Madison, Biochemistry Department, Madison, Wisconsin, USA
| | - Kathryn L Schueler
- University of Wisconsin-Madison, Biochemistry Department, Madison, Wisconsin, USA
| | - Donnie S Stapleton
- University of Wisconsin-Madison, Biochemistry Department, Madison, Wisconsin, USA
| | | | | | - Kelly A Mitok
- University of Wisconsin-Madison, Biochemistry Department, Madison, Wisconsin, USA
| | - Ziyue Wang
- University of Wisconsin-Madison, Department of Biostatistics and Medical Informatics, Madison, Wisconsin, USA
| | | | - Shane P Simonett
- University of Wisconsin-Madison, Biochemistry Department, Madison, Wisconsin, USA
| | | | - Rahul Das
- University of Wisconsin-Madison, Biochemistry Department, Madison, Wisconsin, USA
| | - Tim Beck
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Christina Kendziorski
- University of Wisconsin-Madison, Department of Biostatistics and Medical Informatics, Madison, Wisconsin, USA
| | - Karl W Broman
- University of Wisconsin-Madison, Department of Biostatistics and Medical Informatics, Madison, Wisconsin, USA
| | - Brian S Yandell
- University of Wisconsin-Madison, Department of Horticulture, Madison, Wisconsin, USA
| | | | - Alan D Attie
- University of Wisconsin-Madison, Biochemistry Department, Madison, Wisconsin, USA
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7
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Mitok KA, Freiberger EC, Schueler KL, Rabaglia ME, Stapleton DS, Kwiecien NW, Malec PA, Hebert AS, Broman AT, Kennedy RT, Keller MP, Coon JJ, Attie AD. Islet proteomics reveals genetic variation in dopamine production resulting in altered insulin secretion. J Biol Chem 2018; 293:5860-5877. [PMID: 29496998 DOI: 10.1074/jbc.ra117.001102] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 01/29/2018] [Indexed: 12/11/2022] Open
Abstract
The mouse is a critical model in diabetes research, but most research in mice has been limited to a small number of mouse strains and limited genetic variation. Using the eight founder strains and both sexes of the Collaborative Cross (C57BL/6J (B6), A/J, 129S1/SvImJ (129), NOD/ShiLtJ (NOD), NZO/HILtJ (NZO), PWK/PhJ (PWK), WSB/EiJ (WSB), and CAST/EiJ (CAST)), we investigated the genetic dependence of diabetes-related metabolic phenotypes and insulin secretion. We found that strain background is associated with an extraordinary range in body weight, plasma glucose, insulin, triglycerides, and insulin secretion. Our whole-islet proteomic analysis of the eight mouse strains demonstrates that genetic background exerts a strong influence on the islet proteome that can be linked to the differences in diabetes-related metabolic phenotypes and insulin secretion. We computed protein modules consisting of highly correlated proteins that enrich for biological pathways and provide a searchable database of the islet protein expression profiles. To validate the data resource, we identified tyrosine hydroxylase (Th), a key enzyme in catecholamine synthesis, as a protein that is highly expressed in β-cells of PWK and CAST islets. We show that CAST islets synthesize elevated levels of dopamine, which suppresses insulin secretion. Prior studies, using only the B6 strain, concluded that adult mouse islets do not synthesize l-3,4-dihydroxyphenylalanine (l-DOPA), the product of Th and precursor of dopamine. Thus, the choice of the CAST strain, guided by our islet proteomic survey, was crucial for these discoveries. In summary, we provide a valuable data resource to the research community, and show that proteomic analysis identified a strain-specific pathway by which dopamine synthesized in β-cells inhibits insulin secretion.
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Affiliation(s)
| | | | | | | | | | | | - Paige A Malec
- the Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109
| | - Alexander S Hebert
- the Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, Wisconsin 53706 and
| | | | - Robert T Kennedy
- the Department of Chemistry, University of Michigan-Ann Arbor, Ann Arbor, Michigan 48109
| | | | - Joshua J Coon
- Chemistry, and .,the Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, Wisconsin 53706 and
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8
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Kreznar JH, Keller MP, Traeger LL, Rabaglia ME, Schueler KL, Stapleton DS, Zhao W, Vivas EI, Yandell BS, Broman AT, Hagenbuch B, Attie AD, Rey FE. Host Genotype and Gut Microbiome Modulate Insulin Secretion and Diet-Induced Metabolic Phenotypes. Cell Rep 2017; 18:1739-1750. [PMID: 28199845 DOI: 10.1016/j.celrep.2017.01.062] [Citation(s) in RCA: 118] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 12/09/2016] [Accepted: 01/24/2017] [Indexed: 12/14/2022] Open
Abstract
Genetic variation drives phenotypic diversity and influences the predisposition to metabolic disease. Here, we characterize the metabolic phenotypes of eight genetically distinct inbred mouse strains in response to a high-fat/high-sucrose diet. We found significant variation in diabetes-related phenotypes and gut microbiota composition among the different mouse strains in response to the dietary challenge and identified taxa associated with these traits. Follow-up microbiota transplant experiments showed that altering the composition of the gut microbiota modifies strain-specific susceptibility to diet-induced metabolic disease. Animals harboring microbial communities with enhanced capacity for processing dietary sugars and for generating hydrophobic bile acids showed increased susceptibility to metabolic disease. Notably, differences in glucose-stimulated insulin secretion between different mouse strains were partially recapitulated via gut microbiota transfer. Our results suggest that the gut microbiome contributes to the genetic and phenotypic diversity observed among mouse strains and provide a link between the gut microbiome and insulin secretion.
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Affiliation(s)
- Julia H Kreznar
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Lindsay L Traeger
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Mary E Rabaglia
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Kathryn L Schueler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Donald S Stapleton
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Wen Zhao
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Eugenio I Vivas
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Brian S Yandell
- Department of Statistics, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Horticulture, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Aimee Teo Broman
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Bruno Hagenbuch
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas, Kansas City, KS 66160, USA
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
| | - Federico E Rey
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.
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9
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Keller MP, Paul PK, Rabaglia ME, Stapleton DS, Schueler KL, Broman AT, Ye SI, Leng N, Brandon CJ, Neto EC, Plaisier CL, Simonett SP, Kebede MA, Sheynkman GM, Klein MA, Baliga NS, Smith LM, Broman KW, Yandell BS, Kendziorski C, Attie AD. The Transcription Factor Nfatc2 Regulates β-Cell Proliferation and Genes Associated with Type 2 Diabetes in Mouse and Human Islets. PLoS Genet 2016; 12:e1006466. [PMID: 27935966 PMCID: PMC5147809 DOI: 10.1371/journal.pgen.1006466] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 11/04/2016] [Indexed: 12/22/2022] Open
Abstract
Human genome-wide association studies (GWAS) have shown that genetic variation at >130 gene loci is associated with type 2 diabetes (T2D). We asked if the expression of the candidate T2D-associated genes within these loci is regulated by a common locus in pancreatic islets. Using an obese F2 mouse intercross segregating for T2D, we show that the expression of ~40% of the T2D-associated genes is linked to a broad region on mouse chromosome (Chr) 2. As all but 9 of these genes are not physically located on Chr 2, linkage to Chr 2 suggests a genomic factor(s) located on Chr 2 regulates their expression in trans. The transcription factor Nfatc2 is physically located on Chr 2 and its expression demonstrates cis linkage; i.e., its expression maps to itself. When conditioned on the expression of Nfatc2, linkage for the T2D-associated genes was greatly diminished, supporting Nfatc2 as a driver of their expression. Plasma insulin also showed linkage to the same broad region on Chr 2. Overexpression of a constitutively active (ca) form of Nfatc2 induced β-cell proliferation in mouse and human islets, and transcriptionally regulated more than half of the T2D-associated genes. Overexpression of either ca-Nfatc2 or ca-Nfatc1 in mouse islets enhanced insulin secretion, whereas only ca-Nfatc2 was able to promote β-cell proliferation, suggesting distinct molecular pathways mediating insulin secretion vs. β-cell proliferation are regulated by NFAT. Our results suggest that many of the T2D-associated genes are downstream transcriptional targets of NFAT, and may act coordinately in a pathway through which NFAT regulates β-cell proliferation in both mouse and human islets. Genome-wide association studies (GWAS) and linkage studies provide a powerful way to establish a causal connection between a gene locus and a physiological or pathophysiological phenotype. We wondered if candidate genes associated with type 2 diabetes in human populations, in addition to being causal for the disease, could also be intermediate traits in a pathway leading to disease. In addition, we wished to know if there were any regulatory loci that could coordinately drive the expression of these genes in pancreatic islets and thus complete a pathway; i.e. Driver → GWAS candidate expression → type 2 diabetes. Using data from a mouse intercross between a diabetes-susceptible and a diabetes-resistant mouse strain, we found that the expression of ~40% of >130 candidate GWAS genes genetically mapped to a hot spot on mouse chromosome 2. Using a variety of statistical methods, we identified the transcription factor Nfatc2 as the candidate driver. Follow-up experiments showed that overexpression of Nfatc2 does indeed affect the expression of the GWAS genes and regulates β-cell proliferation and insulin secretion. The work shows that in addition to being causal, GWAS candidate genes can be intermediate traits in a pathway leading to disease. Model organisms can be used to explore these novel causal pathways.
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Affiliation(s)
- Mark P. Keller
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Pradyut K. Paul
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Mary E. Rabaglia
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Donnie S. Stapleton
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Kathryn L. Schueler
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Aimee Teo Broman
- Department of Biostatistics & Medical Informatics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Shuyun Isabella Ye
- Department of Statistics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Ning Leng
- Department of Biostatistics & Medical Informatics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Christopher J. Brandon
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | | | | | - Shane P. Simonett
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Melkam A. Kebede
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Gloria M. Sheynkman
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Mark A. Klein
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | | | - Lloyd M. Smith
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Karl W. Broman
- Department of Biostatistics & Medical Informatics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Brian S. Yandell
- Department of Statistics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Christina Kendziorski
- Department of Biostatistics & Medical Informatics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Alan D. Attie
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
- * E-mail:
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10
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Krautkramer KA, Kreznar JH, Romano KA, Vivas EI, Barrett-Wilt GA, Rabaglia ME, Keller MP, Attie AD, Rey FE, Denu JM. Diet-Microbiota Interactions Mediate Global Epigenetic Programming in Multiple Host Tissues. Mol Cell 2016; 64:982-992. [PMID: 27889451 DOI: 10.1016/j.molcel.2016.10.025] [Citation(s) in RCA: 323] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Revised: 09/22/2016] [Accepted: 10/18/2016] [Indexed: 02/07/2023]
Abstract
Histone-modifying enzymes regulate transcription and are sensitive to availability of endogenous small-molecule metabolites, allowing chromatin to respond to changes in environment. The gut microbiota produces a myriad of metabolites that affect host physiology and susceptibility to disease; however, the underlying molecular events remain largely unknown. Here we demonstrate that microbial colonization regulates global histone acetylation and methylation in multiple host tissues in a diet-dependent manner: consumption of a "Western-type" diet prevents many of the microbiota-dependent chromatin changes that occur in a polysaccharide-rich diet. Finally, we demonstrate that supplementation of germ-free mice with short-chain fatty acids, major products of gut bacterial fermentation, is sufficient to recapitulate chromatin modification states and transcriptional responses associated with colonization. These findings have profound implications for understanding the complex functional interactions between diet, gut microbiota, and host health.
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Affiliation(s)
- Kimberly A Krautkramer
- Wisconsin Institute for Discovery, Madison, WI 53715, USA; Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health - Madison, Madison, WI 53706, USA
| | - Julia H Kreznar
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI 53706, USA
| | - Kymberleigh A Romano
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI 53706, USA
| | - Eugenio I Vivas
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI 53706, USA
| | | | - Mary E Rabaglia
- Department of Biochemistry, University of Wisconsin - Madison, Madison, WI 53706, USA
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin - Madison, Madison, WI 53706, USA
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin - Madison, Madison, WI 53706, USA
| | - Federico E Rey
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI 53706, USA.
| | - John M Denu
- Wisconsin Institute for Discovery, Madison, WI 53715, USA; Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health - Madison, Madison, WI 53706, USA; Morgridge Institute for Research, Madison, WI 53715, USA.
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11
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Paul PK, Rabaglia ME, Wang CY, Stapleton DS, Leng N, Kendziorski C, Lewis PW, Keller MP, Attie AD. Histone chaperone ASF1B promotes human β-cell proliferation via recruitment of histone H3.3. Cell Cycle 2016; 15:3191-3202. [PMID: 27753532 DOI: 10.1080/15384101.2016.1241914] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Anti-silencing function 1 (ASF1) is a histone H3-H4 chaperone involved in DNA replication and repair, and transcriptional regulation. Here, we identify ASF1B, the mammalian paralog to ASF1, as a proliferation-inducing histone chaperone in human β-cells. Overexpression of ASF1B led to distinct transcriptional signatures consistent with increased cellular proliferation and reduced cellular death. Using multiple methods of monitoring proliferation and mitotic progression, we show that overexpression of ASF1B is sufficient to induce human β-cell proliferation. Co-expression of histone H3.3 further augmented β-cell proliferation, whereas suppression of endogenous H3.3 attenuated the stimulatory effect of ASF1B. Using the histone binding-deficient mutant of ASF1B (V94R), we show that histone binding to ASF1B is required for the induction of β-cell proliferation. In contrast to H3.3, overexpression of histone H3 variants H3.1 and H3.2 did not have an impact on ASF1B-mediated induction of proliferation. Our findings reveal a novel role of ASF1B in human β-cell replication and show that ASF1B and histone H3.3A synergistically stimulate human β-cell proliferation.
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Affiliation(s)
- Pradyut K Paul
- a Department of Biochemistry , University of Wisconsin , Madison , WI , USA
| | - Mary E Rabaglia
- a Department of Biochemistry , University of Wisconsin , Madison , WI , USA
| | - Chen-Yu Wang
- a Department of Biochemistry , University of Wisconsin , Madison , WI , USA
| | - Donald S Stapleton
- a Department of Biochemistry , University of Wisconsin , Madison , WI , USA
| | - Ning Leng
- b Department of Statistics , University of Wisconsin , Madison , WI , USA
| | - Christina Kendziorski
- c Department of Biostatistics and Medical Informatics , University of Wisconsin , Madison , WI , USA
| | - Peter W Lewis
- d Department of Biomolecular Chemistry , University of Wisconsin , Madison , WI , USA
| | - Mark P Keller
- a Department of Biochemistry , University of Wisconsin , Madison , WI , USA
| | - Alan D Attie
- a Department of Biochemistry , University of Wisconsin , Madison , WI , USA
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12
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Baughman JM, Rose CM, Kolumam G, Webster JD, Wilkerson EM, Merrill AE, Rhoads TW, Noubade R, Katavolos P, Lesch J, Stapleton DS, Rabaglia ME, Schueler KL, Asuncion R, Domeyer M, Zavala-Solorio J, Reich M, DeVoss J, Keller MP, Attie AD, Hebert AS, Westphall MS, Coon JJ, Kirkpatrick DS, Dey A. NeuCode Proteomics Reveals Bap1 Regulation of Metabolism. Cell Rep 2016; 16:583-595. [PMID: 27373151 PMCID: PMC5546211 DOI: 10.1016/j.celrep.2016.05.096] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 04/14/2016] [Accepted: 05/28/2016] [Indexed: 12/13/2022] Open
Abstract
We introduce neutron-encoded (NeuCode) amino acid labeling of mice as a strategy for multiplexed proteomic analysis in vivo. Using NeuCode, we characterize an inducible knockout mouse model of Bap1, a tumor suppressor and deubiquitinase whose in vivo roles outside of cancer are not well established. NeuCode proteomics revealed altered metabolic pathways following Bap1 deletion, including profound elevation of cholesterol biosynthetic machinery coincident with reduced expression of gluconeogenic and lipid homeostasis proteins in liver. Bap1 loss increased pancreatitis biomarkers and reduced expression of mitochondrial proteins. These alterations accompany a metabolic remodeling with hypoglycemia, hypercholesterolemia, hepatic lipid loss, and acinar cell degeneration. Liver-specific Bap1 null mice present with fully penetrant perinatal lethality, severe hypoglycemia, and hepatic lipid deficiency. This work reveals Bap1 as a metabolic regulator in liver and pancreas, and it establishes NeuCode as a reliable proteomic method for deciphering in vivo biology.
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Affiliation(s)
- Joshua M Baughman
- Department of Protein Chemistry, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Christopher M Rose
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Ganesh Kolumam
- Department of Molecular Biology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Joshua D Webster
- Department of Pathology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Emily M Wilkerson
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Anna E Merrill
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Timothy W Rhoads
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Rajkumar Noubade
- Department of Immunology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Paula Katavolos
- Department of Safety Assessment, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Justin Lesch
- Department of Translational Immunology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Donald S Stapleton
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Mary E Rabaglia
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Kathy L Schueler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Raymond Asuncion
- Department of Transgenic Technology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Melanie Domeyer
- Department of Transgenic Technology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Jose Zavala-Solorio
- Department of Molecular Biology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Michael Reich
- Department of Laboratory Animal Resources, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Jason DeVoss
- Department of Translational Immunology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Alexander S Hebert
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Michael S Westphall
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Joshua J Coon
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA; Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI 53706, USA.
| | - Donald S Kirkpatrick
- Department of Protein Chemistry, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA.
| | - Anwesha Dey
- Department of Discovery Oncology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA.
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13
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Soni MS, Rabaglia ME, Bhatnagar S, Shang J, Ilkayeva O, Mynatt R, Zhou YP, Schadt EE, Thornberry NA, Muoio DM, Keller MP, Attie AD. Downregulation of carnitine acyl-carnitine translocase by miRNAs 132 and 212 amplifies glucose-stimulated insulin secretion. Diabetes 2014; 63:3805-14. [PMID: 24969106 PMCID: PMC4207388 DOI: 10.2337/db13-1677] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We previously demonstrated that micro-RNAs (miRNAs) 132 and 212 are differentially upregulated in response to obesity in two mouse strains that differ in their susceptibility to obesity-induced diabetes. Here we show the overexpression of miRNAs 132 and 212 enhances insulin secretion (IS) in response to glucose and other secretagogues including nonfuel stimuli. We determined that carnitine acyl-carnitine translocase (CACT; Slc25a20) is a direct target of these miRNAs. CACT is responsible for transporting long-chain acyl-carnitines into the mitochondria for β-oxidation. Small interfering RNA-mediated knockdown of CACT in β-cells led to the accumulation of fatty acyl-carnitines and enhanced IS. The addition of long-chain fatty acyl-carnitines promoted IS from rat insulinoma β-cells (INS-1) as well as primary mouse islets. The effect on INS-1 cells was augmented in response to suppression of CACT. A nonhydrolyzable ether analog of palmitoyl-carnitine stimulated IS, showing that β-oxidation of palmitoyl-carnitine is not required for its stimulation of IS. These studies establish a link between miRNA-dependent regulation of CACT and fatty acyl-carnitine-mediated regulation of IS.
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Affiliation(s)
- Mufaddal S Soni
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | - Mary E Rabaglia
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | | | - Jin Shang
- Department of Metabolic Disorders-Diabetes, Merck Research Laboratories, Rahway, NJ
| | - Olga Ilkayeva
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, NC
| | - Randall Mynatt
- Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA
| | - Yun-Ping Zhou
- Department of Metabolic Disorders-Diabetes, Merck Research Laboratories, Rahway, NJ
| | - Eric E Schadt
- Institute for Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, NY
| | - Nancy A Thornberry
- Department of Metabolic Disorders-Diabetes, Merck Research Laboratories, Rahway, NJ
| | - Deborah M Muoio
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, NC Departments of Medicine and Pharmacology and Cancer Biology, Duke University, Durham, NC
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin, Madison, WI
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14
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Johnson LM, Barrick S, Hager MV, McFedries A, Homan EA, Rabaglia ME, Keller MP, Attie AD, Saghatelian A, Bisello A, Gellman SH. A potent α/β-peptide analogue of GLP-1 with prolonged action in vivo. J Am Chem Soc 2014; 136:12848-51. [PMID: 25191938 PMCID: PMC4183665 DOI: 10.1021/ja507168t] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
![]()
Glucagon-like peptide-1 (GLP-1) is
a natural agonist for GLP-1R,
a G protein-coupled receptor (GPCR) on the surface of pancreatic β
cells. GLP-1R agoinsts are attractive for treatment of type 2 diabetes,
but GLP-1 itself is rapidly degraded by peptidases in vivo. We describe a design strategy for retaining GLP-1-like activity
while engendering prolonged activity in vivo, based
on strategic replacement of native α residues with conformationally
constrained β-amino acid residues. This backbone-modification
approach may be useful for developing stabilized analogues of other
peptide hormones.
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Affiliation(s)
- Lisa M Johnson
- Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
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15
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Bhatnagar S, Soni MS, Wrighton LS, Hebert AS, Zhou AS, Paul PK, Gregg T, Rabaglia ME, Keller MP, Coon JJ, Attie AD. Phosphorylation and degradation of tomosyn-2 de-represses insulin secretion. J Biol Chem 2014; 289:25276-86. [PMID: 25002582 DOI: 10.1074/jbc.m114.575985] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The abundance and functional activity of proteins involved in the formation of the SNARE complex are tightly regulated for efficient exocytosis. Tomosyn proteins are negative regulators of exocytosis. Tomosyn causes an attenuation of insulin secretion by limiting the formation of the SNARE complex. We hypothesized that glucose-dependent stimulation of insulin secretion from β-cells must involve reversing the inhibitory action of tomosyn. Here, we show that glucose increases tomosyn protein turnover. Within 1 h of exposure to 15 mM glucose, ~50% of tomosyn was degraded. The degradation of tomosyn in response to high glucose was blocked by inhibitors of the proteasomal pathway. Using (32)P labeling and mass spectrometry, we showed that tomosyn-2 is phosphorylated in response to high glucose, phorbol esters, and analogs of cAMP, all key insulin secretagogues. We identified 11 phosphorylation sites in tomosyn-2. Site-directed mutagenesis was used to generate phosphomimetic (Ser → Asp) and loss-of-function (Ser → Ala) mutants. The Ser → Asp mutant had enhanced protein turnover compared with the Ser → Ala mutant and wild type tomosyn-2. Additionally, the Ser → Asp tomosyn-2 mutant was ineffective at inhibiting insulin secretion. Using a proteomic screen for tomosyn-2-binding proteins, we identified Hrd-1, an E3-ubiquitin ligase. We showed that tomosyn-2 ubiquitination is increased by Hrd-1, and knockdown of Hrd-1 by short hairpin RNA resulted in increased abundance in tomosyn-2 protein levels. Taken together, our results reveal a mechanism by which enhanced phosphorylation of a negative regulator of secretion, tomosyn-2, in response to insulin secretagogues targets it to degradation by the Hrd-1 E3-ubiquitin ligase.
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Affiliation(s)
| | | | | | - Alexander S Hebert
- Chemistry and Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706
| | | | | | | | | | | | - Joshua J Coon
- Chemistry and Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706
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16
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Tu Z, Keller MP, Zhang C, Rabaglia ME, Greenawalt DM, Yang X, Wang IM, Dai H, Bruss MD, Lum PY, Zhou YP, Kemp DM, Kendziorski C, Yandell BS, Attie AD, Schadt EE, Zhu J. Integrative analysis of a cross-loci regulation network identifies App as a gene regulating insulin secretion from pancreatic islets. PLoS Genet 2012; 8:e1003107. [PMID: 23236292 PMCID: PMC3516550 DOI: 10.1371/journal.pgen.1003107] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Accepted: 10/04/2012] [Indexed: 01/20/2023] Open
Abstract
Complex diseases result from molecular changes induced by multiple genetic factors and the environment. To derive a systems view of how genetic loci interact in the context of tissue-specific molecular networks, we constructed an F2 intercross comprised of >500 mice from diabetes-resistant (B6) and diabetes-susceptible (BTBR) mouse strains made genetically obese by the Leptinob/ob mutation (Lepob). High-density genotypes, diabetes-related clinical traits, and whole-transcriptome expression profiling in five tissues (white adipose, liver, pancreatic islets, hypothalamus, and gastrocnemius muscle) were determined for all mice. We performed an integrative analysis to investigate the inter-relationship among genetic factors, expression traits, and plasma insulin, a hallmark diabetes trait. Among five tissues under study, there are extensive protein–protein interactions between genes responding to different loci in adipose and pancreatic islets that potentially jointly participated in the regulation of plasma insulin. We developed a novel ranking scheme based on cross-loci protein-protein network topology and gene expression to assess each gene's potential to regulate plasma insulin. Unique candidate genes were identified in adipose tissue and islets. In islets, the Alzheimer's gene App was identified as a top candidate regulator. Islets from 17-week-old, but not 10-week-old, App knockout mice showed increased insulin secretion in response to glucose or a membrane-permeant cAMP analog, in agreement with the predictions of the network model. Our result provides a novel hypothesis on the mechanism for the connection between two aging-related diseases: Alzheimer's disease and type 2 diabetes. Alzheimer's disease and type 2 diabetes are two common aging-related diseases. Numerous studies have shown that the two diseases are associated. However, the mechanisms of such connection are not clear. Both diseases are complex diseases that are induced by multiple genetic factors and the environment. To understand the molecular network regulated by complex genetic factors causing type 2 diabetes, we constructed an F2 intercross comprised of >500 mice from diabetes-resistant and diabetic mouse strains. We measured genotypes, clinical traits, and expression profiling in five tissues for each mouse. We then performed an integrative analysis to investigate the inter-relationship among genetic factors, expression traits, and plasma insulin, a hallmark diabetes trait, and developed a novel method for inferring key regulators for regulating plasma insulin. In islets, the Alzheimer's gene App was identified as a top candidate regulator. Islets from 17-week-old, but not 10-week-old, App knockout mice showed increased insulin secretion in response to glucose, in agreement with the predictions of the network model. Our result provides a novel hypothesis on the mechanism for the connection between two aging-related diseases: Alzheimer's disease and type 2 diabetes.
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Affiliation(s)
- Zhidong Tu
- Institute of Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, New York, United States of America
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Mark P. Keller
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Chunsheng Zhang
- Merck Research Laboratories, Boston, Massachusetts, United States of America
| | - Mary E. Rabaglia
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | | | - Xia Yang
- Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, California, United States of America
| | - I-Ming Wang
- Merck Research Laboratories, Rahway, New Jersey, United States of America
| | - Hongyue Dai
- Merck Research Laboratories, Boston, Massachusetts, United States of America
| | - Matthew D. Bruss
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Pek Y. Lum
- Department of Genetics, Rosetta Inpharmatics, Merck, Seattle, Washington, United States of America
| | - Yun-Ping Zhou
- Merck Research Laboratories, Rahway, New Jersey, United States of America
| | - Daniel M. Kemp
- Merck Research Laboratories, Rahway, New Jersey, United States of America
| | - Christina Kendziorski
- Department of Biostatistics and Medical Informatics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Brian S. Yandell
- Department of Statistics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Alan D. Attie
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Eric E. Schadt
- Institute of Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, New York, United States of America
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
- Graduate School of Biological Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
- Pacific Biosciences, Menlo Park, California, United States of America
| | - Jun Zhu
- Institute of Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, New York, United States of America
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
- Graduate School of Biological Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
- * E-mail:
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17
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Wang CY, Stapleton DS, Schueler KL, Rabaglia ME, Oler AT, Keller MP, Kendziorski CM, Broman KW, Yandell BS, Schadt EE, Attie AD. Tsc2, a positional candidate gene underlying a quantitative trait locus for hepatic steatosis. J Lipid Res 2012; 53:1493-501. [PMID: 22628617 DOI: 10.1194/jlr.m025239] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Nonalchoholic fatty liver disease (NAFLD) is the most common cause of liver dysfunction and is associated with metabolic diseases, including obesity, insulin resistance, and type 2 diabetes. We mapped a quantitative trait locus (QTL) for NAFLD to chromosome 17 in a cross between C57BL/6 (B6) and BTBR mouse strains made genetically obese with the Lep(ob/ob) mutation. We identified Tsc2 as a gene underlying the chromosome 17 NAFLD QTL. Tsc2 functions as an inhibitor of mammalian target of rapamycin, which is involved in many physiological processes, including cell growth, proliferation, and metabolism. We found that Tsc2(+/-) mice have increased lipogenic gene expression in the liver in an insulin-dependent manner. The coding single nucleotide polymorphism between the B6 and BTBR strains leads to a change in the ability to inhibit the expression of lipogenic genes and de novo lipogenesis in AML12 cells and to promote the proliferation of Ins1 cells. This difference is due to a different affinity of binding to Tsc1, which affects the stability of Tsc2.
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Affiliation(s)
- Chen-Yu Wang
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
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18
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Bhatnagar S, Oler AT, Rabaglia ME, Stapleton DS, Schueler KL, Truchan NA, Worzella SL, Stoehr JP, Clee SM, Yandell BS, Keller MP, Thurmond DC, Attie AD. Positional cloning of a type 2 diabetes quantitative trait locus; tomosyn-2, a negative regulator of insulin secretion. PLoS Genet 2011; 7:e1002323. [PMID: 21998599 PMCID: PMC3188574 DOI: 10.1371/journal.pgen.1002323] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 08/11/2011] [Indexed: 01/19/2023] Open
Abstract
We previously mapped a type 2 diabetes (T2D) locus on chromosome 16 (Chr 16) in an F2 intercross from the BTBR T (+) tf (BTBR) Lepob/ob and C57BL/6 (B6) Lepob/ob mouse strains. Introgression of BTBR Chr 16 into B6 mice resulted in a consomic mouse with reduced fasting plasma insulin and elevated glucose levels. We derived a panel of sub-congenic mice and narrowed the diabetes susceptibility locus to a 1.6 Mb region. Introgression of this 1.6 Mb fragment of the BTBR Chr 16 into lean B6 mice (B6.16BT36–38) replicated the phenotypes of the consomic mice. Pancreatic islets from the B6.16BT36–38 mice were defective in the second phase of the insulin secretion, suggesting that the 1.6 Mb region encodes a regulator of insulin secretion. Within this region, syntaxin-binding protein 5-like (Stxbp5l) or tomosyn-2 was the only gene with an expression difference and a non-synonymous coding single nucleotide polymorphism (SNP) between the B6 and BTBR alleles. Overexpression of the b-tomosyn-2 isoform in the pancreatic β-cell line, INS1 (832/13), resulted in an inhibition of insulin secretion in response to 3 mM 8-bromo cAMP at 7 mM glucose. In vitro binding experiments showed that tomosyn-2 binds recombinant syntaxin-1A and syntaxin-4, key proteins that are involved in insulin secretion via formation of the SNARE complex. The B6 form of tomosyn-2 is more susceptible to proteasomal degradation than the BTBR form, establishing a functional role for the coding SNP in tomosyn-2. We conclude that tomosyn-2 is the major gene responsible for the T2D Chr 16 quantitative trait locus (QTL) we mapped in our mouse cross. Our findings suggest that tomosyn-2 is a key negative regulator of insulin secretion. Humans carry many genetic variants that confer small effects on metabolic traits relevant to type 2 diabetes. These effects are amplified by environmental stressors like obesity. We used morbid obesity as a sensitizer to identify genes that contribute to the diabetes susceptibility of the BTBR mouse strain. Using mapping and breeding strategies, we were able to narrow a genetic region to one containing just 13 genes. One of these genes, tomosyn-2, emerged as a prime candidate. Our functional studies showed that tomosyn-2 is an inhibitor of insulin secretion, and it binds to the proteins involved in the fusion of insulin containing granules with the plasma membrane. We found a coding mutation and demonstrated that this mutation affects the stability of the protein product. Our work with Tomosyn-2 provides new insights into the regulation of insulin secretion and emphasizes that negative regulation is critical for avoiding insulin-induced hypoglycemia.
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Affiliation(s)
- Sushant Bhatnagar
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Angie T. Oler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Mary E. Rabaglia
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Donald S. Stapleton
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Kathryn L. Schueler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Nathan A. Truchan
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Sara L. Worzella
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Jonathan P. Stoehr
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Susanne M. Clee
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada
| | - Brian S. Yandell
- Department of Statistics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Mark P. Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Debbie C. Thurmond
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Alan D. Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail:
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19
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Raines SM, Richards OC, Schneider LR, Schueler KL, Rabaglia ME, Oler AT, Stapleton DS, Genové G, Dawson JA, Betsholtz C, Attie AD. Loss of PDGF-B activity increases hepatic vascular permeability and enhances insulin sensitivity. Am J Physiol Endocrinol Metab 2011; 301:E517-26. [PMID: 21673305 PMCID: PMC3174531 DOI: 10.1152/ajpendo.00241.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hepatic vasculature is not thought to pose a permeability barrier for diffusion of macromolecules from the bloodstream to hepatocytes. In contrast, in extrahepatic tissues, the microvasculature is critically important for insulin action, because transport of insulin across the endothelial cell layer is rate limiting for insulin-stimulated glucose disposal. However, very little is known concerning the role in this process of pericytes, the mural cells lining the basolateral membrane of endothelial cells. PDGF-B is a growth factor involved in the recruitment and function of pericytes. We studied insulin action in mice expressing PDGF-B lacking the proteoglycan binding domain, producing a protein with a partial loss of function (PDGF-B(ret/ret)). Insulin action was assessed through measurements of insulin signaling and insulin and glucose tolerance tests. PDGF-B deficiency enhanced hepatic vascular transendothelial transport. One outcome of this change was an increase in hepatic insulin signaling. This correlated with enhanced whole body glucose homeostasis and increased insulin clearance from the circulation during an insulin tolerance test. In obese mice, PDGF-B deficiency was associated with an 80% reduction in fasting insulin and drastically reduced insulin secretion. These mice did not have significantly higher glucose levels, reflecting a dramatic increase in insulin action. Our findings show that, despite already having a high permeability, hepatic transendothelial transport can be further enhanced. To the best of our knowledge, this is the first study to connect PDGF-B-induced changes in hepatic sinusoidal transport to changes in insulin action, demonstrating a link between PDGF-B signaling and insulin sensitivity.
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20
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Lavine JA, Raess PW, Stapleton DS, Rabaglia ME, Suhonen JI, Schueler KL, Koltes JE, Dawson JA, Yandell BS, Samuelson LC, Beinfeld MC, Davis DB, Hellerstein MK, Keller MP, Attie AD. Cholecystokinin is up-regulated in obese mouse islets and expands beta-cell mass by increasing beta-cell survival. Endocrinology 2010; 151:3577-88. [PMID: 20534724 PMCID: PMC2940525 DOI: 10.1210/en.2010-0233] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
An absolute or functional deficit in beta-cell mass is a key factor in the pathogenesis of diabetes. We model obesity-driven beta-cell mass expansion by studying the diabetes-resistant C57BL/6-Leptin(ob/ob) mouse. We previously reported that cholecystokinin (Cck) was the most up-regulated gene in obese pancreatic islets. We now show that islet cholecystokinin (CCK) is up-regulated 500-fold by obesity and expressed in both alpha- and beta-cells. We bred a null Cck allele into the C57BL/6-Leptin(ob/ob) background and investigated beta-cell mass and metabolic parameters of Cck-deficient obese mice. Loss of CCK resulted in decreased islet size and reduced beta-cell mass through increased beta-cell death. CCK deficiency and decreased beta-cell mass exacerbated fasting hyperglycemia and reduced hyperinsulinemia. We further investigated whether CCK can directly affect beta-cell death in cell culture and isolated islets. CCK was able to directly reduce cytokine- and endoplasmic reticulum stress-induced cell death. In summary, CCK is up-regulated by islet cells during obesity and functions as a paracrine or autocrine factor to increase beta-cell survival and expand beta-cell mass to compensate for obesity-induced insulin resistance.
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Affiliation(s)
- Jeremy A Lavine
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
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21
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Davis DB, Lavine JA, Suhonen JI, Krautkramer KA, Rabaglia ME, Sperger JM, Fernandez LA, Yandell BS, Keller MP, Wang IM, Schadt EE, Attie AD. FoxM1 is up-regulated by obesity and stimulates beta-cell proliferation. Mol Endocrinol 2010; 24:1822-34. [PMID: 20660304 DOI: 10.1210/me.2010-0082] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
beta-Cell mass expansion is one mechanism by which obese animals compensate for insulin resistance and prevent diabetes. FoxM1 is a transcription factor that can regulate the expression of multiple cell cycle genes and is necessary for the maintenance of adult beta-cell mass, beta-cell proliferation, and glucose homeostasis. We hypothesized that FoxM1 is up-regulated by nondiabetic obesity and initiates a transcriptional program leading to beta-cell proliferation. We performed gene expression analysis on islets from the nondiabetic C57BL/6 Leptin(ob/ob) mouse, the diabetic BTBR Leptin(ob/ob) mouse, and an F2 Leptin(ob/ob) population derived from these strains. We identified obesity-driven coordinated up-regulation of islet Foxm1 and its target genes in the nondiabetic strain, correlating with beta-cell mass expansion and proliferation. This up-regulation was absent in the diabetic strain. In the F2 Leptin(ob/ob) population, increased expression of Foxm1 and its target genes segregated with higher insulin and lower glucose levels. We next studied the effects of FOXM1b overexpression on isolated mouse and human islets. We found that FoxM1 stimulated mouse and human beta-cell proliferation by activating many cell cycle phases. We asked whether FOXM1 expression is also responsive to obesity in human islets by collecting RNA from human islet donors (body mass index range: 24-51). We found that the expression of FOXM1 and its target genes is positively correlated with body mass index. Our data suggest that beta-cell proliferation occurs in adult obese humans in an attempt to expand beta-cell mass to compensate for insulin resistance, and that the FoxM1 transcriptional program plays a key role in this process.
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Affiliation(s)
- Dawn Belt Davis
- Department of Medicine, University of Wisconsin, Madison, WI, USA.
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22
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Hudkins KL, Pichaiwong W, Wietecha T, Kowalewska J, Banas MC, Spencer MW, Mühlfeld A, Koelling M, Pippin JW, Shankland SJ, Askari B, Rabaglia ME, Keller MP, Attie AD, Alpers CE. BTBR Ob/Ob mutant mice model progressive diabetic nephropathy. J Am Soc Nephrol 2010; 21:1533-42. [PMID: 20634301 DOI: 10.1681/asn.2009121290] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
There remains a need for robust mouse models of diabetic nephropathy (DN) that mimic key features of advanced human DN. The recently developed mouse strain BTBR with the ob/ob leptin-deficiency mutation develops severe type 2 diabetes, hypercholesterolemia, elevated triglycerides, and insulin resistance, but the renal phenotype has not been characterized. Here, we show that these obese, diabetic mice rapidly develop morphologic renal lesions characteristic of both early and advanced human DN. BTBR ob/ob mice developed progressive proteinuria beginning at 4 weeks. Glomerular hypertrophy and accumulation of mesangial matrix, characteristic of early DN, were present by 8 weeks, and glomerular lesions similar to those of advanced human DN were present by 20 weeks. By 22 weeks, we observed an approximately 20% increase in basement membrane thickness and a >50% increase in mesangial matrix. Diffuse mesangial sclerosis (focally approaching nodular glomerulosclerosis), focal arteriolar hyalinosis, mesangiolysis, and focal mild interstitial fibrosis were present. Loss of podocytes was present early and persisted. In summary, BTBR ob/ob mice develop a constellation of abnormalities that closely resemble advanced human DN more rapidly than most other murine models, making this strain particularly attractive for testing therapeutic interventions.
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Affiliation(s)
- Kelly L Hudkins
- Department of Pathology, University of Washington, Seattle, Washington, USA
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23
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Lavine JA, Raess PW, Davis DB, Rabaglia ME, Presley BK, Keller MP, Beinfeld MC, Kopin AS, Newgard CB, Attie AD. Contamination with E1A-positive wild-type adenovirus accounts for species-specific stimulation of islet cell proliferation by CCK: a cautionary note. Mol Endocrinol 2010; 24:464-7. [PMID: 20081104 DOI: 10.1210/me.2009-0384] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We have previously reported that adenovirus-mediated expression of preprocholecystokin (CCK) stimulates human and mouse islet cell proliferation. In follow-up studies, we became concerned that the CCK adenovirus might have been contaminated with a wild-type E1A-containing adenovirus. Here we show conclusively that the proliferative effects reported in the original paper in mouse and human islets were not due to CCK expression but rather to a contaminating E1A-expressing wild-type adenovirus. We also show, however, that CCK expression does have a proliferative effect in rat islets. We hope that our report of the steps taken to detect the wild-type virus contamination, and purification of the contributing viral stocks, will be helpful to other investigators, and that our experience will serve as a cautionary tale for use of adenovirus vectors, especially for studies on cellular replication.
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Affiliation(s)
- Jeremy A Lavine
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
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24
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Zhao E, Keller MP, Rabaglia ME, Oler AT, Stapleton DS, Schueler KL, Neto EC, Moon JY, Wang P, Wang IM, Lum PY, Ivanovska I, Cleary M, Greenawalt D, Tsang J, Choi YJ, Kleinhanz R, Shang J, Zhou YP, Howard AD, Zhang BB, Kendziorski C, Thornberry NA, Yandell BS, Schadt EE, Attie AD. Obesity and genetics regulate microRNAs in islets, liver, and adipose of diabetic mice. Mamm Genome 2010. [PMID: 19727952 DOI: 10.1007/00335-009-9217-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Type 2 diabetes results from severe insulin resistance coupled with a failure of b cells to compensate by secreting sufficient insulin. Multiple genetic loci are involved in the development of diabetes, although the effect of each gene on diabetes susceptibility is thought to be small. MicroRNAs (miRNAs) are noncoding 19-22-nucleotide RNA molecules that potentially regulate the expression of thousands of genes. To understand the relationship between miRNA regulation and obesity-induced diabetes, we quantitatively profiled approximately 220 miRNAs in pancreatic islets, adipose tissue, and liver from diabetes-resistant (B6) and diabetes-susceptible (BTBR) mice. More than half of the miRNAs profiled were expressed in all three tissues, with many miRNAs in each tissue showing significant changes in response to genetic obesity. Furthermore, several miRNAs in each tissue were differentially responsive to obesity in B6 versus BTBR mice, suggesting that they may be involved in the pathogenesis of diabetes. In liver there were approximately 40 miRNAs that were downregulated in response to obesity in B6 but not BTBR mice, indicating that genetic differences between the mouse strains play a critical role in miRNA regulation. In order to elucidate the genetic architecture of hepatic miRNA expression, we measured the expression of miRNAs in genetically obese F2 mice. Approximately 10% of the miRNAs measured showed significant linkage (miR-eQTLs), identifying loci that control miRNA abundance. Understanding the influence that obesity and genetics exert on the regulation of miRNA expression will reveal the role miRNAs play in the context of obesity-induced type 2 diabetes.
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Affiliation(s)
- Enpeng Zhao
- Biochemistry Department, University of Wisconsin, Madison, WI 53706, USA
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25
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Zhao E, Keller MP, Rabaglia ME, Oler AT, Stapleton DS, Schueler KL, Neto EC, Moon JY, Wang P, Wang IM, Lum PY, Ivanovska I, Cleary M, Greenawalt D, Tsang J, Choi YJ, Kleinhanz R, Shang J, Zhou YP, Howard AD, Zhang BB, Kendziorski C, Thornberry NA, Yandell BS, Schadt EE, Attie AD. Obesity and genetics regulate microRNAs in islets, liver, and adipose of diabetic mice. Mamm Genome 2010; 20:476-85. [PMID: 19727952 DOI: 10.1007/s00335-009-9217-2] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Accepted: 08/14/2009] [Indexed: 01/01/2023]
Abstract
Type 2 diabetes results from severe insulin resistance coupled with a failure of b cells to compensate by secreting sufficient insulin. Multiple genetic loci are involved in the development of diabetes, although the effect of each gene on diabetes susceptibility is thought to be small. MicroRNAs (miRNAs) are noncoding 19-22-nucleotide RNA molecules that potentially regulate the expression of thousands of genes. To understand the relationship between miRNA regulation and obesity-induced diabetes, we quantitatively profiled approximately 220 miRNAs in pancreatic islets, adipose tissue, and liver from diabetes-resistant (B6) and diabetes-susceptible (BTBR) mice. More than half of the miRNAs profiled were expressed in all three tissues, with many miRNAs in each tissue showing significant changes in response to genetic obesity. Furthermore, several miRNAs in each tissue were differentially responsive to obesity in B6 versus BTBR mice, suggesting that they may be involved in the pathogenesis of diabetes. In liver there were approximately 40 miRNAs that were downregulated in response to obesity in B6 but not BTBR mice, indicating that genetic differences between the mouse strains play a critical role in miRNA regulation. In order to elucidate the genetic architecture of hepatic miRNA expression, we measured the expression of miRNAs in genetically obese F2 mice. Approximately 10% of the miRNAs measured showed significant linkage (miR-eQTLs), identifying loci that control miRNA abundance. Understanding the influence that obesity and genetics exert on the regulation of miRNA expression will reveal the role miRNAs play in the context of obesity-induced type 2 diabetes.
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Affiliation(s)
- Enpeng Zhao
- Biochemistry Department, University of Wisconsin, Madison, WI 53706, USA
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26
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Lavine JA, Raess PW, Davis DB, Rabaglia ME, Presley BK, Keller MP, Beinfeld MC, Kopin AS, Newgard CB, Attie AD. Overexpression of pre-pro-cholecystokinin stimulates beta-cell proliferation in mouse and human islets with retention of islet function. Mol Endocrinol 2008; 22:2716-28. [PMID: 18845673 DOI: 10.1210/me.2008-0255] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Type 1 and type 2 diabetes result from a deficit in insulin production and beta-cell mass. Methods to expand beta-cell mass are under intensive investigation for the treatment of type 1 and type 2 diabetes. We tested the hypothesis that cholecystokinin (CCK) can promote beta-cell proliferation. We treated isolated mouse and human islets with an adenovirus containing the CCK cDNA (AdCMV-CCK). We measured [(3)H]thymidine and BrdU incorporation into DNA and additionally, performed flow cytometry analysis to determine whether CCK overexpression stimulates beta-cell proliferation. We studied islet function by measuring glucose-stimulated insulin secretion and investigated the cell cycle regulation of proliferating beta-cells by quantitative RT-PCR and Western blot analysis. Overexpression of CCK stimulated [(3)H]thymidine incorporation into DNA 5.0-fold and 15.8-fold in mouse and human islets, respectively. AdCMV-CCK treatment also stimulated BrdU incorporation into DNA 10-fold and 21-fold in mouse and human beta-cells, respectively. Glucose-stimulated insulin secretion was unaffected by CCK expression. Analysis of cyclin and cdk mRNA and protein abundance revealed that CCK overexpression increased cyclin A, cyclin B, cyclin E, cdk1, and cdk2 with no change in cyclin D1, cyclin D2, cyclin D3, cdk4, or cdk6 in mouse and human islets. Additionally, AdCMV-CCK treatment of CCK receptor knockout and wild-type mice resulted in equal [(3)H]thymidine incorporation. CCK is a beta-cell proliferative factor that is effective in both mouse and human islets. CCK triggers beta-cell proliferation without disrupting islet function, up-regulates a distinct set of cell cycle regulators in islets, and signals independently of the CCK receptors.
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Affiliation(s)
- Jeremy A Lavine
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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27
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Keller MP, Choi Y, Wang P, Davis DB, Rabaglia ME, Oler AT, Stapleton DS, Argmann C, Schueler KL, Edwards S, Steinberg HA, Chaibub Neto E, Kleinhanz R, Turner S, Hellerstein MK, Schadt EE, Yandell BS, Kendziorski C, Attie AD. A gene expression network model of type 2 diabetes links cell cycle regulation in islets with diabetes susceptibility. Genome Res 2008; 18:706-16. [PMID: 18347327 DOI: 10.1101/gr.074914.107] [Citation(s) in RCA: 279] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Insulin resistance is necessary but not sufficient for the development of type 2 diabetes. Diabetes results when pancreatic beta-cells fail to compensate for insulin resistance by increasing insulin production through an expansion of beta-cell mass or increased insulin secretion. Communication between insulin target tissues and beta-cells may initiate this compensatory response. Correlated changes in gene expression between tissues can provide evidence for such intercellular communication. We profiled gene expression in six tissues of mice from an obesity-induced diabetes-resistant and a diabetes-susceptible strain before and after the onset of diabetes. We studied the correlation structure of mRNA abundance and identified 105 co-expression gene modules. We provide an interactive gene network model showing the correlation structure between the expression modules within and among the six tissues. This resource also provides a searchable database of gene expression profiles for all genes in six tissues in lean and obese diabetes-resistant and diabetes-susceptible mice, at 4 and 10 wk of age. A cell cycle regulatory module in islets predicts diabetes susceptibility. The module predicts islet replication; we found a strong correlation between (2)H(2)O incorporation into islet DNA in vivo and the expression pattern of the cell cycle module. This pattern is highly correlated with that of several individual genes in insulin target tissues, including Igf2, which has been shown to promote beta-cell proliferation, suggesting that these genes may provide a link between insulin resistance and beta-cell proliferation.
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Affiliation(s)
- Mark P Keller
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53076, USA
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28
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Flowers JB, Rabaglia ME, Schueler KL, Flowers MT, Lan H, Keller MP, Ntambi JM, Attie AD. Loss of stearoyl-CoA desaturase-1 improves insulin sensitivity in lean mice but worsens diabetes in leptin-deficient obese mice. Diabetes 2007; 56:1228-39. [PMID: 17369521 DOI: 10.2337/db06-1142] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The lipogenic gene stearoyl-CoA desaturase (SCD)1 appears to be a promising new target for obesity-related diabetes, as mice deficient in this enzyme are resistant to diet- and leptin deficiency-induced obesity. The BTBR mouse strain replicates many features of insulin resistance found in humans with excess visceral adiposity. Using the hyperinsulinemic-euglycemic clamp technique, we determined that insulin sensitivity was improved in heart, soleus muscle, adipose tissue, and liver of BTBR SCD1-deficient mice. We next determined whether SCD1 deficiency could prevent diabetes in leptin-deficient BTBR mice. Loss of SCD1 in leptin(ob/ob) mice unexpectedly accelerated the progression to severe diabetes; 6-week fasting glucose increased approximately 70%. In response to a glucose challenge, Scd1(-/-) leptin(ob/ob) mice had insufficient insulin secretion, resulting in glucose intolerance. A morphologically distinct class of islets isolated from the Scd1(-/-) leptin(ob/ob) mice had reduced insulin content and increased triglycerides, free fatty acids, esterified cholesterol, and free cholesterol and also a much higher content of saturated fatty acids. We believe the accumulation of lipid is due to an upregulation of lipoprotein lipase (20-fold) and Cd36 (167-fold) and downregulation of lipid oxidation genes in this class of islets. Therefore, although loss of Scd1 has beneficial effects on adiposity, this benefit may come at the expense of beta-cells, resulting in an increased risk of diabetes.
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Affiliation(s)
- Jessica B Flowers
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 537606, USA
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Clee SM, Yandell BS, Schueler KM, Rabaglia ME, Richards OC, Raines SM, Kabara EA, Klass DM, Mui ETK, Stapleton DS, Gray-Keller MP, Young MB, Stoehr JP, Lan H, Boronenkov I, Raess PW, Flowers MT, Attie AD. Positional cloning of Sorcs1, a type 2 diabetes quantitative trait locus. Nat Genet 2006; 38:688-93. [PMID: 16682971 DOI: 10.1038/ng1796] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Accepted: 04/06/2006] [Indexed: 11/08/2022]
Abstract
We previously mapped the type 2 diabetes mellitus-2 locus (T2dm2), which affects fasting insulin levels, to distal chromosome 19 in a leptin-deficient obese F2 intercross derived from C57BL/6 (B6) and BTBR T+ tf/J (BTBR) mice. Introgression of a 7-Mb segment of the B6 chromosome 19 into the BTBR background (strain 1339A) replicated the reduced insulin linked to T2dm2. The 1339A mice have markedly impaired insulin secretion in vivo and disrupted islet morphology. We used subcongenic strains derived from 1339A to localize the T2dm2 quantitative trait locus (QTL) to a 242-kb segment comprising the promoter, first exon and most of the first intron of the Sorcs1 gene. This was the only gene in the 1339A strain for which we detected amino acid substitutions and expression level differences between mice carrying B6 and BTBR alleles of this insert, thereby identifying variation within the Sorcs1 gene as underlying the phenotype associated with the T2dm2 locus. SorCS1 binds platelet-derived growth factor, a growth factor crucial for pericyte recruitment to the microvasculature, and may thus have a role in expanding or maintaining the islet vasculature. Our identification of the Sorcs1 gene provides insight into the pathway underlying the pathophysiology of obesity-induced type 2 diabetes mellitus.
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Affiliation(s)
- Susanne M Clee
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Rabaglia ME, Gray-Keller MP, Frey BL, Shortreed MR, Smith LM, Attie AD. Alpha-Ketoisocaproate-induced hypersecretion of insulin by islets from diabetes-susceptible mice. Am J Physiol Endocrinol Metab 2005; 289:E218-24. [PMID: 15741243 DOI: 10.1152/ajpendo.00573.2004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Most patients at risk for developing type 2 diabetes are hyperinsulinemic. Hyperinsulinemia may be a response to insulin resistance, but another possible abnormality is insulin hypersecretion. BTBR mice are insulin resistant and hyperinsulinemic. When the leptin(ob) mutation is introgressed into BTBR mice, they develop severe diabetes. We compared the responsiveness of lean B6 and BTBR mouse islets to various insulin secretagogues. The transamination product of leucine, alpha-ketoisocaproate (KIC), elicited a dramatic insulin secretory response in BTBR islets. The KIC response was blocked by methyl-leucine or aminooxyacetate, inhibitors of branched-chain amino transferase. When dimethylglutamate was combined with KIC, the fractional insulin secretion was identical in islets from both mouse strains, predicting that the amine donor is rate-limiting for KIC-induced insulin secretion. Consistent with this prediction, glutamate levels were higher in BTBR than in B6 islets. The transamination product of glutamate, alpha-ketoglutarate, elicited insulin secretion equally from B6 and BTBR islets. Thus formation of alpha-ketoglutarate is a requisite step in the response of mouse islets to KIC. alpha-Ketoglutarate can be oxidized to succinate. However, succinate does not stimulate insulin secretion in mouse islets. Our data suggest that alpha-ketoglutarate may directly stimulate insulin secretion and that increased formation of alpha-ketoglutarate leads to hyperinsulinemia.
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Affiliation(s)
- Mary E Rabaglia
- Dept. of Biochemistry, Univ. of Wisconsin-Madison, Madison, WI 53706, USA
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Minn AH, Lan H, Rabaglia ME, Harlan DM, Peculis BA, Attie AD, Shalev A. Increased insulin translation from an insulin splice-variant overexpressed in diabetes, obesity, and insulin resistance. Mol Endocrinol 2004; 19:794-803. [PMID: 15550470 DOI: 10.1210/me.2004-0119] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Type 2 diabetes occurs when pancreatic beta-cells become unable to compensate for the underlying insulin resistance. Insulin secretion requires beta-cell insulin stores to be replenished by insulin biosynthesis, which is mainly regulated at the translational level. Such translational regulation often involves the 5'-untranslated region. Recently, we identified a human insulin splice-variant (SPV) altering only the 5'-untranslated region and conferring increased translation efficiency. We now describe a mouse SPV (mSPV) that is found in the cytoplasm and exhibits increased translation efficiency resulting in more normal (prepro)insulin protein per RNA. The RNA stability of mSPV is not increased, but the predicted secondary RNA structure is altered, which may facilitate translation. To determine the role of mSPV in insulin resistance and diabetes, mSPV expression was measured by quantitative real-time RT-PCR in islets from three diabetic and/or insulin-resistant, obese and nonobese, mouse models (BTBRob/ob, C57BL/6ob/ob, and C57BL/6azip). Interestingly, mSPV expression was significantly higher in all diabetic/insulin-resistant mice compared with wild-type littermates and was dramatically induced in primary mouse islets incubated at high glucose. This raises the possibility that the mSPV may represent a compensatory beta-cell mechanism to enhance insulin biosynthesis when insulin requirements are elevated by hyperglycemia/insulin resistance.
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Affiliation(s)
- Alexandra H Minn
- Department of Medicine, University of Wisconsin-Madison, H4/526 Clinical Science Center, 600 Highland Avenue, Madison, Wisconsin 53792, USA
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Lan H, Rabaglia ME, Schueler KL, Mata C, Yandell BS, Attie AD. Distinguishing covariation from causation in diabetes: a lesson from the protein disulfide isomerase mRNA abundance trait. Diabetes 2004; 53:240-4. [PMID: 14693722 DOI: 10.2337/diabetes.53.1.240] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Protein disulfide isomerase (Pdi) is reported to be an insulin-regulated gene whose expression level is increased in the livers of rats with streptozotocin-induced diabetes. We found that Pdi mRNA is approximately 20-fold more abundant in the diabetes-susceptible BTBR mouse strain relative to the diabetes-resistant C56BL/6 (B6) strain. A genetic analysis was carried out to determine whether there is a causal relationship between elevated Pdi expression and diabetes phenotype in BTBR-ob/ob mice. We mapped Pdi mRNA abundance as a quantitative trait in 108 (B6 x BTBR)F(2)-ob/ob mice segregating for diabetes. We detected a single linkage at the telomeric end of chromosome 11, where the Pdi gene itself resides (logarithm of odds score >30.0). No linkage was detected for the Pdi mRNA trait in the regions where we have previously identified quantitative trait loci for diabetes traits. Sequencing of the Pdi promoter and cDNA revealed several single nucleotide polymorphisms between these two mouse strains. We conclude that in our experimental model, elevated Pdi expression is cis regulated and is not linked to diabetes susceptibility. Genetic analysis is a powerful tool for distinguishing covariation from causation in expression array studies of disease traits.
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Affiliation(s)
- Hong Lan
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
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33
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Lan H, Rabaglia ME, Stoehr JP, Nadler ST, Schueler KL, Zou F, Yandell BS, Attie AD. Gene expression profiles of nondiabetic and diabetic obese mice suggest a role of hepatic lipogenic capacity in diabetes susceptibility. Diabetes 2003; 52:688-700. [PMID: 12606510 DOI: 10.2337/diabetes.52.3.688] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Obesity is a strong risk factor for the development of type 2 diabetes. We have previously reported that in adipose tissue of obese (ob/ob) mice, the expression of adipogenic genes is decreased. When made genetically obese, the BTBR mouse strain is diabetes susceptible and the C57BL/6J (B6) strain is diabetes resistant. We used DNA microarrays and RT-PCR to compare the gene expression in BTBR-ob/ob versus B6-ob/ob mice in adipose tissue, liver, skeletal muscle, and pancreatic islets. Our results show: 1) there is an increased expression of genes involved in inflammation in adipose tissue of diabetic mice; 2) lipogenic gene expression was lower in adipose tissue of diabetes-susceptible mice, and it continued to decrease with the development of diabetes, compared with diabetes-resistant obese mice; 3) hepatic expression of lipogenic enzymes was increased and the hepatic triglyceride content was greatly elevated in diabetes-resistant obese mice; 4) hepatic expression of gluconeogenic genes was suppressed at the prediabetic stage but not at the onset of diabetes; and 5) genes normally not expressed in skeletal muscle and pancreatic islets were expressed in these tissues in the diabetic mice. We propose that increased hepatic lipogenic capacity protects the B6-ob/ob mice from the development of type 2 diabetes.
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Affiliation(s)
- Hong Lan
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706, USA
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Abstract
Insulin stimulates muscle and adipose tissue to absorb glucose through a signaling cascade that is incompletely understood. Insulin resistance, the inability of insulin to appropriately stimulate glucose uptake, is a hallmark of type 2 diabetes mellitus. The development of experimental systems that model human insulin resistance is important in elucidating the defects responsible for the development of type 2 diabetes. When two strains of mice, BTBR and C57BL/6J (B6), are crossed, the resultant male offspring (BtB6) demonstrate insulin resistance in muscle tissue. Here, we report an insulin resistance phenotype in adipose tissue from lean, nondiabetic BtB6 mice similar to that observed in human muscle. Adipocytes isolated from insulin-resistant male mice display 65% less insulin-stimulated glucose uptake compared with insulin-sensitive female mice. Similarly, adipocytes from insulin-resistant mice have diminished insulin-stimulated IRS-1 phosphorylation and phosphatidylinositol 3-kinase (PI3K) activation. However, normal activation of protein kinase B (Akt/PKB) by insulin is observed. Thus BtB6 mice demonstrate the dissociation of insulin-stimulated PI3K activity and Akt/PKB activation and represent a useful model to investigate the causes of insulin resistance in humans.
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Affiliation(s)
- S T Nadler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Stoehr JP, Nadler ST, Schueler KL, Rabaglia ME, Yandell BS, Metz SA, Attie AD. Genetic obesity unmasks nonlinear interactions between murine type 2 diabetes susceptibility loci. Diabetes 2000; 49:1946-54. [PMID: 11078464 DOI: 10.2337/diabetes.49.11.1946] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Nonlinear interactions between obesity and genetic risk factors are thought to determine susceptibility to type 2 diabetes. We used genetic obesity as a tool to uncover latent differences in diabetes susceptibility between two mouse strains, C57BL/6J (B6) and BTBR. Although both BTBR and B6 lean mice are euglycemic and glucose tolerant, lean BTBR x B6 F1 male mice are profoundly insulin resistant. We hypothesized that the genetic determinants of the insulin resistance syndrome might also predispose genetically obese mice to severe diabetes. Introgressing the ob allele into BTBR revealed large differences in diabetes susceptibility between the strain backgrounds. In a population of F2-ob/ob mice segregating for BTBR and B6 alleles, we observed large variation in pancreatic compensation for the underlying insulin resistance. We also detected two loci that substantially modify diabetes severity, and a third locus that strongly links to fasting plasma insulin levels. Amplification of the genetic signal from these latent diabetes susceptibility alleles in F2-ob/ob mice permitted discovery of an interaction between the two loci that substantially increased the risk of severe type 2 diabetes.
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Affiliation(s)
- J P Stoehr
- Department of Biochemistry, University of Wisconsin-Madison, USA
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36
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Abstract
A widely accepted genetically determined rodent model for human type 2 diabetes is the Goto-Kakizaki (GK) rat; however, the lesion(s) in the pancreatic islets of these rats has not been identified. Herein, intact islets from GK rats (aged 8-14 weeks) were studied, both immediately after isolation and after 18 h in tissue culture. Despite intact contents of insulin and protein, GK islets had markedly deficient insulin release in response to glucose, as well as to pure mitochondrial fuels or a non-nutrient membrane-depolarizing stimulus (40 mmol/l K+). In contrast, mastoparan (which activates GTP-binding proteins [GBPs]) completely circumvented any secretory defect. Basal and stimulated levels of adenine and guanine nucleotides, the activation of phospholipase C by Ca2+ or glucose, the secretory response to pertussis toxin, and the activation of selected low-molecular weight GBPs were not impaired. Defects were found, however, in the autophosphorylation and catalytic activity of cytosolic nucleoside diphosphokinase (NDPK), which may provide compartmentalized GTP pools to activate G-proteins; a deficient content of phosphoinositides was also detected. These studies identify novel, heretofore unappreciated, defects late in signal transduction in the islets of our colony of GK rats, possibly occurring at the site of activation by NDPK of a mastoparan-sensitive G-protein-dependent step in exocytosis.
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Affiliation(s)
- S A Metz
- Pacific Northwest Research Institute, Seattle, Washington 98122, USA.
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37
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Abstract
Inhibitors of IMP dehydrogenase, such as mycophenolic acid (MPA) and mizoribine, which deplete cellular GTP, are used clinically as immunosuppressive drugs. The prolonged effect of such agents on insulin-secreting beta-cells (HIT-T15 and INS-1) was investigated. Both MPA and mizoribine inhibited mitogenesis, as reflected by [3H]thymidine incorporation. Cell number, DNA and protein contents, and cell (metabolic) viability were decreased by about 30%, 60%, and 80% after treatment of HIT cells with clinically relevant concentrations (e.g. 1 microg/ml) of MPA for 1, 2, and 4 days, respectively. Mizoribine (48 h) similarly induced the death of HIT cells. INS-1 cells also were damaged by prolonged MPA treatment. MPA-treated HIT cells displayed a strong and localized staining with a DNA-binding dye (propidium iodide), suggesting condensation and fragmentation of DNA, which were confirmed by detection of DNA laddering in multiples of about 180 bp. DNA fragmentation was observed after 24-h MPA treatment and was dose dependent (29%, 49%, and 70% of cells were affected after 48-h exposure to 1, 3, and 10 microg/ml MPA, respectively). Examination of MPA-treated cells by electron microscopy revealed typical signs of apoptosis: condensed and marginated chromatin, apoptotic bodies, cytosolic vacuolization, and loss of microvilli. MPA-induced cell death was almost totally prevented by supplementation with guanosine, but not with adenosine or deoxyguanosine, indicating a specific effect of GTP depletion. An inhibitor of protein isoprenylation (lovastatin, 10-100 microM for 2-3 days) induced cell death and DNA degradation similar to those induced by sustained GTP depletion, suggesting a mediatory role of posttranslationally modified GTP-binding proteins. Indeed, impeding the function of G proteins of the Rho family (via glucosylation using Clostridium difficile toxin B), although not itself inducing apoptosis, potentiated cell death induced by MPA or lovastatin. These findings indicate that prolonged depletion of GTP induces beta-cell death compatible with apoptosis; this probably involves a direct impairment of GTP-dependent RNA-primed DNA synthesis, but also appears to be modulated by small GTP-binding proteins. Treatment of intact adult rat islets (the beta-cells of which replicate slowly) induced a modest, but definite, death by apoptosis over 1- to 3-day periods. Thus, more prolonged use of the new generation of immunosuppressive agents exemplified by MPA might have deleterious effects on the survival of islet or pancreas grafts.
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Affiliation(s)
- G Li
- Medical Service, Middleton Veterans Administration Hospital, Madison, Wisconsin 53705, USA.
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38
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Kowluru A, Li G, Rabaglia ME, Segu VB, Hofmann F, Aktories K, Metz SA. Evidence for differential roles of the Rho subfamily of GTP-binding proteins in glucose- and calcium-induced insulin secretion from pancreatic beta cells. Biochem Pharmacol 1997; 54:1097-108. [PMID: 9464452 DOI: 10.1016/s0006-2952(97)00314-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We utilized clostridial toxins (with known specificities for inhibition of GTPases) to ascertain the contribution of candidate GTPases in physiologic insulin secretion from beta cells. Exposure of normal rat islets or isolated beta (HIT-T15) cells to Clostridium difficile toxins A and B catalyzed the glucosylation (and thereby the inactivation) of Rac, Cdc42, and Rho endogenous to beta cells; concomitantly, either toxin reduced glucose- or potassium-induced insulin secretion from rat islets and HIT cells. Treatment of beta cells with Clostridium sordellii lethal toxin (LT; which modified only Ras, Rap, and Rac) also reduced glucose- or potassium-induced secretion. However, clostridial toxin C3-exoenzyme (which ADP-ribosylates and inactivates only Rho) was without any effect on either glucose- or potassium-induced insulin secretion. These data suggest that Cdc42, Rac, Ras, and/or Rap (but not Rho) may be needed for glucose- or potassium-mediated secretion. The effects of these toxins appear to be specific on stimulus-secretion coupling, since no difference in metabolic viability (assessed colorimetrically by quantitating the conversion of the tetrazolium salt into a formazan in a reduction reaction driven by nutrient metabolism) was demonstrable between control and toxin (A or LT)-treated beta cells. Toxin (A or LT) treatment also did not alter glucose- or potassium-mediated rises in cytosolic free calcium concentrations ([Ca2+]i), suggesting that these GTPases are involved in steps distal to elevations in [Ca2+]i. Recent findings indicate that the carboxyl methylation of Cdc42 is stimulated by only glucose, whereas that of Rap (Kowluru et al., J Clin Invest 98: 540-555, 1996) and Rac (present study) are regulated by glucose or potassium. Together, these findings provide direct evidence, for the first time, that the Rho subfamily of GTPases plays a key regulatory role(s) in insulin secretion, and they suggest that Cdc42 may be required for early steps in glucose stimulation of insulin release, whereas Rap and/or Rac may be required for a later step(s) in the stimulus-secretion coupling cascade (i.e. Ca2+-induced exocytosis of insulin).
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Affiliation(s)
- A Kowluru
- Medical and Research Services, William S. Middleton Memorial VA Medical Center, Madison, WI 53705, USA.
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39
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Abstract
Although interleukin-1 beta (IL-1 beta) reduces pancreatic islet content of ATP and GTP, the distal events that mediate its inhibitory effects on insulin secretion remain poorly understood. Herein, the activation of phospholipase C (PLC) was quantified during islet perifusions. An 18-h exposure to IL-1 beta (100 pM) totally vitiated activation of PLC induced by glucose, an effect that requires ATP and GTP and closure of the ATP-dependent K+ (KATP) channel. Surprisingly, however, when islets were depolarized directly using either of two agonists, glyburide (which does not act via generation of purine nucleotides) or 40 mM K+ (which acts distal to KATP channel), PLC and insulin secretion were again obliterated by IL-1 beta. IL-1 beta also reduced the labeling of phosphoinositide substrates; however, this effect was insufficient to explain the inhibition of PLC, since the effects on substrate labeling, but not on PLC, were prevented by coprovision of guanosine or adenosine. Furthermore, when IL-1 beta-treated islets were exposed to 100 microM carbachol (which activates PLC partially independent of extracellular Ca2+), the effects were still obliterated by IL-1 beta. These data (together with the finding that IL-1 beta inhibited Ca(2+)-induced insulin release) suggest that, in addition to its effects on ATP synthesis and thereby on the KATP channel, IL-1 beta has at least two undescribed, distal effects to block both PLC as well as Ca(2+)-induced exocytosis. The latter correlated best with IL-1 beta's effect to impede phosphoinositide synthesis, since it also was reversed by guanosine or adenosine.
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Affiliation(s)
- J Vadakekalam
- Section of Endocrinology, Middleton Veterans Affairs Medical Center, Madison, Wisconsin 53705, USA
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40
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Vadakekalam J, Rabaglia ME, Metz SA. Roles of GTP and phospholipase C in the potentiation of Ca(2+)-induced insulin secretion by glucose in rat pancreatic islets. J Endocrinol 1997; 153:61-71. [PMID: 9135570 DOI: 10.1677/joe.0.1530061] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Glucose can augment insulin secretion independently of K+ channel closure, provided cytoplasmic free Ca2+ concentration is elevated. A role for phospholipase C (PLC) in this phenomenon has been both claimed and refuted. Recently, we have shown a role for GTP in the secretory effect of glucose as well as in glucose-induced PLC activation, using islets pre-treated with GTP synthesis inhibitors such as mycophenolic acid (MPA). Therefore, in the current studies, we examined first, whether glucose augments Ca(2+)-induced PLC activation and second, whether GTP is required for this effect, when K+(ATP) channels are kept open using diazoxide. Isolated rat islets pre-labeled with [3H]myo-inositol were studied with or without first priming with glucose. There was a 98% greater augmentation of insulin secretion by 16.7 mM glucose (in the presence of diazoxide and 40 mM K+) in primed islets; however, the ability of high glucose to augment PLC activity bore no relationship to the secretory response. MPA markedly inhibited PLC in both conditions; however, insulin secretion was only inhibited (by 46%) in primed islets. None of these differences were attributable to alterations in labeling of phosphoinositides or levels of GTP or ATP. These data indicate that an adequate level of GTP is critical for glucose's potentiation of Ca(2+)-induced insulin secretion in primed islets but that PLC activation can clearly be dissociated from insulin secretion and therefore cannot be the major cause of glucose's augmentation of Ca(2+)-induced insulin secretion.
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Affiliation(s)
- J Vadakekalam
- William S Middleton Veterans' Administration Hospital, Department of Medicine, University of Wisconsin-Madison 53792, USA
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Abstract
Interleukin-1beta (IL-1beta) has been shown to inhibit glucose-induced insulin secretion from rat islets and purified beta-cells, primarily through the generation of nitric oxide (NO). However, the mechanisms by which NO exerts its effects remain unclear. To examine the role of purine nucleotides, we cultured intact rat islets or INS-1 (glucose-responsive transformed rat) beta-cells for 18 h in the presence or absence of IL-1beta. In islets, the exposure to IL-1beta (100 pmol/l) inhibited subsequent glucose-induced insulin secretion by 91% with no significant effect on insulin content or basal insulin release. IL-1beta also diminished insulin secretion induced by pure mitochondrial fuels, 40 mmol/l K+, or a phorbol ester. Concomitantly, IL-1beta significantly decreased islet ATP (-45%), GTP (-33%), ATP/ADP (-54%), and GTP/GDP (-46%). These effects were totally reversed by provision of N(omega)-nitro-L-arginine methyl ester (NAME) in arginine-free media that inhibited NO production. In contrast, in INS-1 cells, IL-1beta (10 or 100 pmol/l) reduced both basal and glucose-induced insulin secretion by 50%, but insulin content was also reduced by 35%. Therefore, the INS-1 cells were still able to respond to glucose stimulation with a 1.8-2.0-fold increase in insulin release in either the presence or absence of IL-1beta. Concomitantly, in INS-1 cells, IL-1beta had no effect on ATP/ADP or GTP/GDP ratios, although it modestly decreased ATP (-25%) and GTP (-22%). As in islets, all effects of IL-1beta in INS-1 cells were prevented by NAME. Thus, in rat islets, IL-1beta (via the generation of NO) abolishes insulin exocytosis in association with large decreases in the ATP/ADP (and GTP/GDP) ratio, implying the impairment of mitochondrial function. Furthermore, IL-1beta inhibits cytosolic synthesis of new purine nucleotides (via the salvage pathway), as assessed by a decrease in their specific activity after labeling with [3H]hypoxanthine. In contrast, in INS-1 cells, IL-1beta appears to impair cytosolic synthesis of purine nucleotides and insulin biosynthesis selectively (both possibly reflecting decreased glycolysis) with little direct effect on insulin exocytosis itself.
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Affiliation(s)
- M Meredith
- Department of Medicine, University of Wisconsin, William S. Middleton Veteran's Administration Hospital, Madison, USA
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42
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Kowluru A, Seavey SE, Li G, Sorenson RL, Weinhaus AJ, Nesher R, Rabaglia ME, Vadakekalam J, Metz SA. Glucose- and GTP-dependent stimulation of the carboxyl methylation of CDC42 in rodent and human pancreatic islets and pure beta cells. Evidence for an essential role of GTP-binding proteins in nutrient-induced insulin secretion. J Clin Invest 1996; 98:540-55. [PMID: 8755667 PMCID: PMC507460 DOI: 10.1172/jci118822] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Several GTP-binding proteins (G-proteins) undergo post-translational modifications (isoprenylation and carboxyl methylation) in pancreatic beta cells. Herein, two of these were identified as CDC42 and rap 1, using Western blotting and immunoprecipitation. Confocal microscopic data indicated that CDC42 is localized only in islet endocrine cells but not in acinar cells of the pancreas. CDC42 undergoes a guanine nucleotide-specific membrane association and carboxyl methylation in normal rat islets, human islets, and pure beta (HIT or INS-1) cells. GTPgammaS-dependent carboxyl methylation of a 23-kD protein was also demonstrable in secretory granule fractions from normal islets or beta cells. AFC (a specific inhibitor of prenyl-cysteine carboxyl methyl transferases) blocked the carboxyl methylation of CDC42 in five types of insulin-secreting cells, without blocking GTPgammaS-induced translocation, implying that methylation is a consequence (not a cause) of transfer to membrane sites. High glucose (but not a depolarizing concentration of K+) induced the carboxyl methylation of CDC42 in intact cells, as assessed after specific immunoprecipitation. This effect was abrogated by GTP depletion using mycophenolic acid and was restored upon GTP repletion by coprovision of guanosine. In contrast, although rap 1 was also carboxyl methylated, it was not translocated to the particulate fraction by GTPgammaS; furthermore, its methylation was also stimulated by 40 mM K+ (suggesting a role which is not specific to nutrient stimulation). AFC also impeded nutrient-induced (but not K+-induced) insulin secretion from islets and beta cells under static or perifusion conditions, whereas an inactive structural analogue of AFC failed to inhibit insulin release. These effects were reproduced not only by S-adenosylhomocysteine (another methylation inhibitor), but also by GTP depletion. Thus, the glucose- and GTP-dependent carboxyl methylation of G-proteins such as CDC42 is an obligate step in the stimulus-secretion coupling of nutrient-induced insulin secretion, but not in the exocytotic event itself. Furthermore, AFC blocked glucose-activated phosphoinositide turnover, which may provide a partial biochemical explanation for its effect on secretion, and implies that certain G-proteins must be carboxyl methylated for their interaction with signaling effector molecules, a step which can be regulated by intracellular availability of GTP.
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Affiliation(s)
- A Kowluru
- Department of Medicine and Division of Endocrinology, University of Wisconsin School of Medicine, Madison, Wisconsin 53792, USA
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43
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Abstract
We have previously demonstrated a permissive role for GTP in insulin secretion; in the current studies, we examined the effect of GTP on phospholipase C (PLC) activation to explore one possible mechanism for that observation. In rat islets preexposed to the GTP synthesis inhibitors mycophenolic acid (MPA) or mizoribine (MZ), PLC activation induced by 16.7 mM glucose (or by 20 mM alpha-ketoisocaproic acid) was inhibited 63% without altering the labeling of phosphoinositide substrates. Provision of guanine, which normalizes islet GTP content and insulin release, prevented the inhibition of PLC by MPA. Glucose-induced phosphoinositide hydrolysis was blocked by removal of extracellular Ca2+ or by diazoxide. PLC induced directly by Ca2+ influx (i.e., 40 mM K+) was reduced 42% in MPA-pretreated islets but without inhibition of the concomitant insulin release. These data indicate that glucose-induced PLC activation largely reflects Ca2+ entry and demonstrate (for the first time in intact cells) that adequate GTP is necessary for glucose (and Ca(2+)-)-induced PLC activation but not for maximal Ca(2+)-induced exocytosis.
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Affiliation(s)
- J Vadakekalam
- Department of Medicine, University of Wisconsin, Madison, USA
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Kowluru A, Seavey SE, Rabaglia ME, Nesher R, Metz SA. Carboxylmethylation of the catalytic subunit of protein phosphatase 2A in insulin-secreting cells: evidence for functional consequences on enzyme activity and insulin secretion. Endocrinology 1996; 137:2315-23. [PMID: 8641181 DOI: 10.1210/endo.137.6.8641181] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We report the carboxylmethylation of a 36-kDa protein in intact normal rat islets and clonal beta (INS-1) cells. This protein was predominantly cytosolic. Its carboxylmethylation, as assessed by vapor phase equilibration assay, was resistant to inhibition by N-acetyl-S-trans, trans-farnesyl-L-cysteine, a competitive substrate for cysteine methyl transferases. These data suggest that the methylated C-terminal amino acid is not cysteine. The methylated protein was identified as the catalytic subunit of protein phosphatase 2A (PP2Ac) by immunoblotting. The carboxylmethylation of the PP2Ac increased its catalytic activity, suggesting a key role in the functional regulation of PP2A. Therefore, we studied okadaic acid, a selective inhibitor of PP2A that acts by an unknown mechanism. Okadaic acid (but not 1-nor-okadaone, its inactive analog) inhibited (Ki = 10 nM) the carboxylmethylation of PP2Ac and phosphatase activity in the cytosolic fraction (from normal rat islets and clonal beta-cells) as well as in intact rat islets. Furthermore, methylated PP2Ac underwent rapid demethylation (t 1/2 = 40 min) catalyzed by a methyl esterase localized in islet homogenates. Ebelactone, a purported inhibitor of methyl esterases, significantly delayed (> 200 min) the demethylation of PP2Ac. Furthermore, ebelactone reversibly inhibited glucose- and ketoisocaproate-induced insulin secretion from normal rat islets. These data identify, for the first time, a methylation-demethylation cycle for PP2Ac in the beta-cell and suggest a key functional relationship between PP2A activity and the carboxylmethylation of its catalytic subunit. These findings thus suggest a negative modulatory role for PP2A in nutrient-induced insulin exocytosis.
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Affiliation(s)
- A Kowluru
- Section of Endocrinology, University of Wisconsin School of Medicine, Madison 53972, USA
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Meredith M, Rabaglia ME, Metz SA. Evidence of a role for GTP in the potentiation of Ca(2+)-induced insulin secretion by glucose in intact rat islets. J Clin Invest 1995; 96:811-21. [PMID: 7635976 PMCID: PMC185267 DOI: 10.1172/jci118127] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Glucose initiates insulin secretion by closing K(+)-ATP channels, leading to Ca2+ influx (E1); it also potentiates Ca(2+)-induced secretion (E2) when the K(+)-ATP channel is kept open using diazoxide and depolarizing concentrations of K+ are provided. To examine the roles of purine nucleotides in E2, we compared the effects of glucose to those of the mitochondrial fuel monomethylsuccinate. Either agonist could induce E2 accompanied by significant increases in ATP, ATP/ADP ratio, and GTP/GDP ratio; GTP increased significantly only with glucose. Mycophenolic acid (MPA), an inhibitor of cytosolic GTP synthesis, markedly inhibited glucose-induced E2 (either in perifusions or in static incubations) and decreased GTP and the GTP/GDP ratio, but did not alter the ATP/ADP ratio. Provision of guanine (but not adenine) reversed these changes pari passu. In contrast, MPA had no effect on succinate-induced E2, despite generally similar changes in nucleotides. A similar lack of effect of MPA on E2 was seen with a second mitochondrial fuel, alpha-ketoisocaproic acid (KIC). However, in the absence of diazoxide and K+, MPA blunted the secretory effects of either glucose, succinate, or KIC. These studies suggest that GTP plays a role in both glucose and succinate or KIC-induced insulin secretion at a step dependent on mitochondrial metabolism and the K(+)-ATP channel. In addition to mitochondrial effects, glucose appears to have extramitochondrial effects important to its potentiation of Ca(2+)-induced insulin secretion that are also dependent on GTP.
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Affiliation(s)
- M Meredith
- Division of Endocrinology, University of Wisconsin, Madison, USA
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Kowluru A, Seavey SE, Rabaglia ME, Metz SA. Non-specific stimulatory effects of mastoparan on pancreatic islet nucleoside diphosphokinase activity: dissociation from insulin secretion. Biochem Pharmacol 1995; 49:263-6. [PMID: 7840804 DOI: 10.1016/s0006-2952(94)00489-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We examined whether mastoparan (MAS)-induced insulin secretion might involve the activation of nucleoside diphosphokinase (NDP kinase), which catalyzes the conversion of GDP to GTP, a known permissive factor for insulin secretion. MAS and MAS 7 (which activate GTP-binding proteins), but not MAS 17 (an inactive analog), stimulated insulin secretion from normal rat islets. In contrast to their specific effects on insulin secretion, MAS, MAS 7 and MAS 17 each stimulated formation of the phosphoenzyme-intermediate of NDP kinase, as well as its catalytic activity. These effects were mimicked by several cationic drugs. Thus, caution is indicated in using MAS to study cellular regulation, since some of its effects appear to be non-specific, and may be due, in part, to its amphiphilic, cationic nature.
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Affiliation(s)
- A Kowluru
- Department of Medicine, University of Wisconsin School of Medicine, Madison 53792
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Kowluru A, Rabaglia ME, Muse KE, Metz SA. Subcellular localization and kinetic characterization of guanine nucleotide binding proteins in normal rat and human pancreatic islets and transformed beta cells. Biochim Biophys Acta 1994; 1222:348-59. [PMID: 8038203 DOI: 10.1016/0167-4889(94)90040-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The subcellular localization and the kinetics of the GTPase activities of monomeric and heterotrimeric GTP-binding proteins were investigated in normal rat and human pancreatic islets and were compared to those obtained using a transformed hamster beta cell line (HIT cells). The [alpha-32P]GTP overlay technique revealed the presence of at least four low-molecular-mass proteins (approx. 20-27 kDa) in normal rat islets, which were enriched in the secretory granule fraction compared to the membrane fraction (with little abundance of these proteins in the cytosolic fraction). In contrast, in HIT cells, these proteins (at least six) were predominantly cytosolic. Three of these proteins were immunologically identified as rab3A, rac2, and CDC42Hs in islets as well as in HIT cells. In addition, pertussis toxin augmented the ribosylation of at least one heterotrimeric G-protein of about 39 kDa (probably G(i) and/or G(o)) in the membrane and secretory granule fractions of normal rat and human islets, whereas at least three such Ptx substrates (36-39 kDa) were found in HIT cell membranes. Kinetic activities revealed the presence of at least three such activities (Km for GTP of 372 nM, 2.2 microM, and 724 microM) in islet homogenates which were differentially distributed in various subcellular fractions; similar activities were also demonstrable in HIT cell homogenates. Thus, these studies demonstrate the presence of both monomeric G-proteins intrinsic to the secretory granules of normal rat islets which can be ascribed to beta cells; since these G-proteins are regulated by insulinotropic lipids (as described in the accompanying article), such proteins may couple the activation of phospholipases (endogenous to islets) to the exocytotic secretion of insulin. These findings also suggest that caution is necessary in extrapolating data concerning G-proteins from cultured, transformed beta cell lines to the physiology of normal islets, in view of both qualitative and quantitative differences between the two preparations.
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Affiliation(s)
- A Kowluru
- Department of Medicine, University of Wisconsin School of Medicine, Madison 53792
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Metz SA, Rabaglia ME, Stock JB, Kowluru A. Modulation of insulin secretion from normal rat islets by inhibitors of the post-translational modifications of GTP-binding proteins. Biochem J 1993; 295 ( Pt 1):31-40. [PMID: 8216234 PMCID: PMC1134816 DOI: 10.1042/bj2950031] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Many GTP-binding proteins (GBPs) are modified by mevalonic acid (MVA)-dependent isoprenylation, carboxyl methylation or palmitoylation. The effects of inhibitors of these processes on insulin release were studied. Intact pancreatic islets were shown to synthesize and metabolize MVA and to prenylate several candidate proteins. Culture with lovastatin (to inhibit synthesis of endogenous MVA) caused the accumulation in the cytosol of low-M(r) GBPs (labelled by the [alpha-32P]GTP overlay technique), suggesting a disturbance of membrane association. Concomitantly, lovastatin pretreatment reduced glucose-induced insulin release by about 50%; co-provision of 100-200 microM MVA totally prevented this effect. Perillic acid, a purported inhibitor of the prenylation of small GBPs, also markedly reduced glucose-induced insulin secretion. Furthermore, both N-acetyl-S-trans,trans-farnesyl-L-cysteine (AFC), which inhibited the base-labile carboxyl methylation of GBPs in islets or in transformed beta-cells, and cerulenic acid, an inhibitor of protein palmitoylation, also reduced nutrient-induced secretion; an inactive analogue of AFC (which did not inhibit carboxyl methylation in islets) had no effect on secretion. In contrast with nutrients, the effects of agonists that induce secretion by directly activating distal components in signal transduction (such as a phorbol ester or mastoparan) were either unaffected or enhanced by lovastatin or AFC. These data are compatible with the hypothesis that post-translational modifications are required for one or more stimulatory GBPs to promote proximal step(s) in fuel-induced insulin secretion, whereas one or more inhibitory GBPs might reduce secretion at a more distal locus.
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Affiliation(s)
- S A Metz
- Section of Endocrinology, Middleton Veterans Hospital, Madison, WI
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Metz SA, Meredith M, Rabaglia ME, Kowluru A. Small elevations of glucose concentration redirect and amplify the synthesis of guanosine 5'-triphosphate in rat islets. J Clin Invest 1993; 92:872-82. [PMID: 8349822 PMCID: PMC294926 DOI: 10.1172/jci116662] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Recent studies suggest a permissive requirement for guanosine 5'-triphosphate (GTP) in insulin release, based on the use of GTP synthesis inhibitors (such as myocophenolic acid) acting at inosine monophosphate (IMP) dehydrogenase; herein, we examine the glucose dependency of GTP synthesis. Mycophenolic acid inhibited insulin secretion equally well after islet culture at 7.8 or 11.1 mM glucose (51% inhibition) but its effect was dramatically attenuated when provided at < or = 6.4 mM glucose (13% inhibition; P < 0.001). These observations were explicable by a stimulation of islet GTP synthesis derived from IMP since, at high glucose: (a) total GTP content was augmented; (b) a greater decrement in GTP (1.75 vs. 1.05 pmol/islet) was induced by mycophenolic acid; and (c) a smaller "pool" of residual GTP persisted after drug treatment. Glucose also accelerated GTP synthesis from exogenous guanine ("salvage" pathway) and increased content of a pyrimidine, uridine 5'-triphosphate (UTP), suggesting that glucose augments production of a common regulatory intermediate (probably 5-phosphoribosyl-1-pyrophosphate). Pathway-specific radiolabeling studies confirmed that glucose tripled both salvage and de novo synthesis of nucleotides. We conclude that steep changes in the biosynthesis of cytosolic pools of GTP occur at modest changes in glucose concentrations, a finding which may have relevance to the adaptive (patho) physiologic responses of islets to changes in ambient glucose levels.
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Affiliation(s)
- S A Metz
- Department of Medicine, University of Wisconsin, Madison 53792
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Metz SA, Rabaglia ME, Pintar TJ. Selective inhibitors of GTP synthesis impede exocytotic insulin release from intact rat islets. J Biol Chem 1992; 267:12517-27. [PMID: 1352288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2023] Open
Abstract
To investigate whether GTP concentrations can be a regulatory step in exocytotic hormone secretion, we treated isolated rat islets with mycophenolic acid (MPA) or mizoribine, two selective inhibitors of de novo GTP synthesis. When islets were cultured overnight in purine-free medium containing the drug, MPA reduced GTP levels by up to 81 +/- 1%; guanine circumvented this block via the nucleotide "salvage" pathway. MPA concomitantly inhibited glucose (16.7 mM)-induced insulin secretion in batch-type incubations (or perifusions), by up to 68% at 50 micrograms/ml. Although the inhibition of secretion occurred over a similar concentration range as the reduction in total GTP content, the two variables were not directly correlated. However, the secretory effects also were prevented by adding guanine, but not hypoxanthine or xanthine, to the culture medium. Similar results for GTP content and insulin release were seen using mizoribine. Insulin content was modestly (-18%) reduced by MPA but indices of fractional release (release/insulin content) were also markedly impaired. Although MPA also reduced ATP levels more modestly (-39%) and increased UTP (+87%), these were not the cause of the secretory defect since adenine restored ATP and UTP nearly to normal, but did not alter the reduction in GTP content or insulin secretion. MPA also inhibited secretion induced by amino acid or by a phorbol ester but had virtually no effect on release induced by a depolarizing concentration of K+, suggesting that GTP depletion does not merely impede Ca+ influx or directly block Ca(2+)-activated exocytosis. However, a severe reduction of GTP content did not prevent the pertussis toxin-sensitive inhibition of insulin release induced by epinephrine, suggesting that the function of heterotrimeric GTP-binding proteins is not limited by ambient GTP concentrations. Although these studies do not elucidate the exact site(s) in the exocytotic cascade which depend on intact GTP stores, they do provide the first direct evidence that GTP is required (and can be rate limiting) for insulin release.
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Affiliation(s)
- S A Metz
- Section of Endocrinology, University of Wisconsin, Madison
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