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Arunagiri A, Alam M, Haataja L, Draz H, Alasad B, Samy P, Sadique N, Tong Y, Cai Y, Shakeri H, Fantuzzi F, Ibrahim H, Jang I, Sidarala V, Soleimanpour SA, Satin LS, Otonkoski T, Cnop M, Itkin‐Ansari P, Kaufman RJ, Liu M, Arvan P. Proinsulin folding and trafficking defects trigger a common pathological disturbance of endoplasmic reticulum homeostasis. Protein Sci 2024; 33:e4949. [PMID: 38511500 PMCID: PMC10955614 DOI: 10.1002/pro.4949] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 01/23/2024] [Accepted: 02/14/2024] [Indexed: 03/22/2024]
Abstract
Primary defects in folding of mutant proinsulin can cause dominant-negative proinsulin accumulation in the endoplasmic reticulum (ER), impaired anterograde proinsulin trafficking, perturbed ER homeostasis, diminished insulin production, and β-cell dysfunction. Conversely, if primary impairment of ER-to-Golgi trafficking (which also perturbs ER homeostasis) drives misfolding of nonmutant proinsulin-this might suggest bi-directional entry into a common pathological phenotype (proinsulin misfolding, perturbed ER homeostasis, and deficient ER export of proinsulin) that can culminate in diminished insulin storage and diabetes. Here, we've challenged β-cells with conditions that impair ER-to-Golgi trafficking, and devised an accurate means to assess the relative abundance of distinct folded/misfolded forms of proinsulin using a novel nonreducing SDS-PAGE/immunoblotting protocol. We confirm abundant proinsulin misfolding upon introduction of a diabetogenic INS mutation, or in the islets of db/db mice. Whereas blockade of proinsulin trafficking in Golgi/post-Golgi compartments results in intracellular accumulation of properly-folded proinsulin (bearing native disulfide bonds), impairment of ER-to-Golgi trafficking (regardless whether such impairment is achieved by genetic or pharmacologic means) results in decreased native proinsulin with more misfolded proinsulin. Remarkably, reversible ER-to-Golgi transport defects (such as treatment with brefeldin A or cellular energy depletion) upon reversal quickly restore the ER folding environment, resulting in the disappearance of pre-existing misfolded proinsulin while preserving proinsulin bearing native disulfide bonds. Thus, proper homeostatic balance of ER-to-Golgi trafficking is linked to a more favorable proinsulin folding (as well as trafficking) outcome.
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Affiliation(s)
- Anoop Arunagiri
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Maroof Alam
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Leena Haataja
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Hassan Draz
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Bashiyer Alasad
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Praveen Samy
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Nadeed Sadique
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Yue Tong
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Ying Cai
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Hadis Shakeri
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Federica Fantuzzi
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Hazem Ibrahim
- Stem Cells and Metabolism Research Program, Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | - Insook Jang
- Degenerative Diseases ProgramCenter for Genetic Disorders and Aging Research, Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Vaibhav Sidarala
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Scott A. Soleimanpour
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Leslie S. Satin
- Department of PharmacologyUniversity of Michigan Medical SchoolAnn ArborMichiganUSA
| | - Timo Otonkoski
- Stem Cells and Metabolism Research Program, Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | - Miriam Cnop
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Pamela Itkin‐Ansari
- Development, Aging and Regeneration ProgramCenter for Genetic Disorders and Aging Research, Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Randal J. Kaufman
- Degenerative Diseases ProgramCenter for Genetic Disorders and Aging Research, Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Ming Liu
- Department of Endocrinology and MetabolismTianjin Medical University General HospitalTianjinChina
| | - Peter Arvan
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
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Corradi J, Thompson B, Fletcher PA, Bertram R, Sherman AS, Satin LS. K ATP channel activity and slow oscillations in pancreatic beta cells are regulated by mitochondrial ATP production. J Physiol 2023; 601:5655-5667. [PMID: 37983196 PMCID: PMC10842208 DOI: 10.1113/jp284982] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 10/16/2023] [Indexed: 11/22/2023] Open
Abstract
Pancreatic beta cells secrete insulin in response to plasma glucose. The ATP-sensitive potassium channel (KATP ) links glucose metabolism to islet electrical activity in these cells by responding to increased cytosolic [ATP]/[ADP]. It was recently proposed that pyruvate kinase (PK) in close proximity to beta cell KATP locally produces the ATP that inhibits KATP activity. This proposal was largely based on the observation that applying phosphoenolpyruvate (PEP) and ADP to the cytoplasmic side of excised inside-out patches inhibited KATP . To test the relative contributions of local vs. mitochondrial ATP production, we recorded KATP activity using mouse beta cells and INS-1 832/13 cells. In contrast to prior reports, we could not replicate inhibition of KATP activity by PEP + ADP. However, when the pH of the PEP solutions was not corrected for the addition of PEP, strong channel inhibition was observed as a result of the well-known action of protons to inhibit KATP . In cell-attached recordings, perifusing either a PK activator or an inhibitor had little or no effect on KATP channel closure by glucose, further suggesting that PK is not an important regulator of KATP . In contrast, addition of mitochondrial inhibitors robustly increased KATP activity. Finally, by measuring the [ATP]/[ADP] responses to imposed calcium oscillations in mouse beta cells, we found that oxidative phosphorylation could raise [ATP]/[ADP] even when ADP was at its nadir during the burst silent phase, in agreement with our mathematical model. These results indicate that ATP produced by mitochondrial oxidative phosphorylation is the primary controller of KATP in pancreatic beta cells. KEY POINTS: Phosphoenolpyruvate (PEP) plus adenosine diphosphate does not inhibit KATP activity in excised patches. PEP solutions only inhibit KATP activity if the pH is unbalanced. Modulating pyruvate kinase has minimal effects on KATP activity. Mitochondrial inhibition, in contrast, robustly potentiates KATP activity in cell-attached patches. Although the ADP level falls during the silent phase of calcium oscillations, mitochondria can still produce enough ATP via oxidative phosphorylation to close KATP . Mitochondrial oxidative phosphorylation is therefore the main source of the ATP that inhibits the KATP activity of pancreatic beta cells.
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Affiliation(s)
- Jeremías Corradi
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Benjamin Thompson
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Patrick A. Fletcher
- Laboratory of Biological Modeling, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida, USA
| | - Arthur S. Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Leslie S. Satin
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
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Bertram R, Marinelli I, Fletcher PA, Satin LS, Sherman AS. Deconstructing the integrated oscillator model for pancreatic β-cells. Math Biosci 2023; 365:109085. [PMID: 37802364 PMCID: PMC10991200 DOI: 10.1016/j.mbs.2023.109085] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 09/12/2023] [Accepted: 09/26/2023] [Indexed: 10/10/2023]
Abstract
Electrical bursting oscillations in the β-cells of pancreatic islets have been a focus of investigation for more than fifty years. This has been aided by mathematical models, which are descendants of the pioneering Chay-Keizer model. This article describes the key biophysical and mathematical elements of this model, and then describes the path forward from there to the Integrated Oscillator Model (IOM). It is both a history and a deconstruction of the IOM that describes the various elements that have been added to the model over time, and the motivation for adding them. Finally, the article is a celebration of the 40th anniversary of the publication of the Chay-Keizer model.
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Affiliation(s)
- Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, FL, United States.
| | - Isabella Marinelli
- Centre for Systems Modeling and Quantitative Biomedicine, University of Birmingham, United Kingdom
| | - Patrick A Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
| | - Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
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Jo S, Beetch M, Gustafson E, Wong A, Oribamise E, Chung G, Vadrevu S, Satin LS, Bernal-Mizrachi E, Alejandro EU. Sex Differences in Pancreatic β-Cell Physiology and Glucose Homeostasis in C57BL/6J Mice. J Endocr Soc 2023; 7:bvad099. [PMID: 37873500 PMCID: PMC10590649 DOI: 10.1210/jendso/bvad099] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Indexed: 10/25/2023] Open
Abstract
The importance of sexual dimorphism has been highlighted in recent years since the National Institutes of Health's mandate on considering sex as a biological variable. Although recent studies have taken strides to study both sexes side by side, investigations into the normal physiological differences between males and females are limited. In this study, we aimed to characterized sex-dependent differences in glucose metabolism and pancreatic β-cell physiology in normal conditions using C57BL/6J mice, the most common mouse strain used in metabolic studies. Here, we report that female mice have improved glucose and insulin tolerance associated with lower nonfasted blood glucose and insulin levels compared with male mice at 3 and 6 months of age. Both male and female animals show β-cell mass expansion from embryonic day 17.5 to adulthood, and no sex differences were observed at embryonic day 17.5, newborn, 1 month, or 3 months of age. However, 6-month-old males displayed increased β-cell mass in response to insulin resistance compared with littermate females. Molecularly, we uncovered sexual dimorphic alterations in the protein levels of nutrient sensing proteins O-GlcNAc transferase and mTOR, as well as differences in glucose-stimulus coupling mechanisms that may underlie the differences in sexually dimorphic β-cell physiology observed in C57BL/6J mice.
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Affiliation(s)
- Seokwon Jo
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Megan Beetch
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Eric Gustafson
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Alicia Wong
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Eunice Oribamise
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Grace Chung
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Suryakiran Vadrevu
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Leslie S Satin
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Ernesto Bernal-Mizrachi
- Diabetes, VA Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA
- Miami VA Healthcare System and Division Endocrinology, Metabolism and Diabetes, University of Miami, Miami, FL 33125, USA
| | - Emilyn U Alejandro
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
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Zhang IX, Herrmann A, Leon J, Jeyarajan S, Arunagiri A, Arvan P, Gilon P, Satin LS. ER stress increases expression of intracellular calcium channel RyR1 to modify Ca 2+ homeostasis in pancreatic beta cells. J Biol Chem 2023; 299:105065. [PMID: 37468098 PMCID: PMC10448220 DOI: 10.1016/j.jbc.2023.105065] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 07/13/2023] [Accepted: 07/14/2023] [Indexed: 07/21/2023] Open
Abstract
Pancreatic beta cells maintain glucose homeostasis by secreting pulses of insulin in response to a rise in plasma glucose. Pulsatile insulin secretion occurs as a result of glucose-induced oscillations in beta-cell cytosolic Ca2+. The endoplasmic reticulum (ER) helps regulate beta-cell cytosolic Ca2+, and ER stress can lead to ER Ca2+ reduction, beta-cell dysfunction, and an increased risk of type 2 diabetes. However, the mechanistic effects of ER stress on individual calcium channels are not well understood. To determine the effects of tunicamycin-induced ER stress on ER inositol 1,4,5-triphosphate receptors (IP3Rs) and ryanodine receptors (RyRs) and their involvement in subsequent Ca2+ dysregulation, we treated INS-1 832/13 cells and primary mouse islets with ER stress inducer tunicamycin (TM). We showed TM treatment increased RyR1 mRNA without affecting RyR2 mRNA and decreased both IP3R1 and IP3R3 mRNA. Furthermore, we found stress reduced ER Ca2+ levels, triggered oscillations in cytosolic Ca2+ under subthreshold glucose conditions, and increased apoptosis and that these changes were prevented by cotreatment with the RyR1 inhibitor dantrolene. In addition, we demonstrated silencing RyR1-suppressed TM-induced subthreshold cytosolic Ca2+ oscillations, but silencing RyR2 did not affect these oscillations. In contrast, inhibiting IP3Rs with xestospongin-C failed to suppress the TM-induced cytosolic Ca2+ oscillations and did not protect beta cells from TM-induced apoptosis although xestospongin-C inclusion did prevent ER Ca2+ reduction. Taken together, these results show changes in RyR1 play a critical role in ER stress-induced Ca2+ dysfunction and beta-cell apoptosis.
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Affiliation(s)
- Irina X Zhang
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Andrea Herrmann
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Juan Leon
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida, USA
| | - Sivakumar Jeyarajan
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Anoop Arunagiri
- Department of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan, USA
| | - Peter Arvan
- Department of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan, USA
| | - Patrick Gilon
- Pole of Endocrinology, Diabetes and Nutrition (EDIN), Institute of Experimental and Clinical Research (IREC), Université Catholique de Louvain, Brussels, Belgium
| | - Leslie S Satin
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA.
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Fletcher PA, Thompson B, Liu C, Bertram R, Satin LS, Sherman AS. Ca 2+ Release or Ca 2+ Entry, that is the Question: What Governs Ca 2+ Oscillations in Pancreatic Beta Cells? Am J Physiol Endocrinol Metab 2023; 324:E477-E487. [PMID: 37074988 DOI: 10.1152/ajpendo.00030.2023] [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] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/20/2023]
Abstract
The standard model for Ca2+ oscillations in insulin-secreting pancreatic beta cells centers on Ca2+ entry through voltage-activated Ca2+ channels. These work in combination with ATP-dependent K+ channels, which are the bridge between the metabolic state of the cells and plasma membrane potential. This partnership underlies the ability of the beta cells to secrete insulin appropriately on a minute-to-minute time scale to control whole-body plasma glucose. Though this model, developed over more than 40 years through many cycles of experimentation and mathematical modeling, has been very successful, it has been challenged by a hypothesis that calcium-induced calcium release from the endoplasmic reticulum through ryanodine or IP3 receptors is instead the key driver of islet oscillations. We show here that the alternative model is in fact incompatible with a large body of established experimental data and that the new observations offered in support of it can be better explained by the standard model.
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Affiliation(s)
- Patrick A Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
| | - Benjamin Thompson
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan-Ann Arbor, Ann Arbor, MI, United States
| | - Chanté Liu
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan-Ann Arbor, Ann Arbor, MI, United States
| | - Richard Bertram
- Department of Mathematics, Florida State University, Tallahassee, FL, United States
| | - Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan-Ann Arbor, Ann Arbor, MI, United States
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
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Jeyarajan S, Zhang IX, Arvan P, Lentz SI, Satin LS. Simultaneous Measurement of Changes in Mitochondrial and Endoplasmic Reticulum Free Calcium in Pancreatic Beta Cells. Biosensors (Basel) 2023; 13:382. [PMID: 36979594 PMCID: PMC10046164 DOI: 10.3390/bios13030382] [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] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 02/28/2023] [Accepted: 03/08/2023] [Indexed: 05/28/2023]
Abstract
The free calcium (Ca2+) levels in pancreatic beta cell organelles have been the subject of many recent investigations. Under pathophysiological conditions, disturbances in these pools have been linked to altered intracellular communication and cellular dysfunction. To facilitate studies of subcellular Ca2+ signaling in beta cells and, particularly, signaling between the endoplasmic reticulum (ER) and mitochondria, we designed a novel dual Ca2+ sensor which we termed DS-1. DS-1 encodes two stoichiometrically fluorescent proteins within a single plasmid, G-CEPIA-er, targeted to the ER and R-CEPIA3-mt, targeted to mitochondria. Our goal was to simultaneously measure the ER and mitochondrial Ca2+ in cells in real time. The Kds of G-CEPIA-er and R-CEPIA3-mt for Ca2+ are 672 and 3.7 μM, respectively. Confocal imaging of insulin-secreting INS-1 832/13 expressing DS-1 confirmed that the green and red fluorophores correctly colocalized with organelle-specific fluorescent markers as predicted. Further, we tested whether DS-1 exhibited the functional properties expected by challenging an INS-1 cell to glucose concentrations or drugs having well-documented effects on the ER and mitochondrial Ca2+ handling. The data obtained were consistent with those seen using other single organelle targeted probes. These results taken together suggest that DS-1 is a promising new approach for investigating Ca2+ signaling within multiple organelles of the cell.
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Affiliation(s)
- Sivakumar Jeyarajan
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48105, USA; (S.J.)
| | - Irina X Zhang
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48105, USA; (S.J.)
| | - Peter Arvan
- Department of Internal Medicine, Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Stephen I. Lentz
- Department of Internal Medicine, Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Leslie S. Satin
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48105, USA; (S.J.)
- Department of Internal Medicine, Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA
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Zhang IX, Hermann A, Leon J, Arunagiri A, Arvan P, Satin LS. Upregulation of ryanodine receptor 1 is involved in ER stress-induced disruption of beta cell calcium homeostasis. Biophys J 2023; 122:234a-235a. [PMID: 36783148 DOI: 10.1016/j.bpj.2022.11.1379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Irina X Zhang
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Andrea Hermann
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Juan Leon
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Anoop Arunagiri
- Department of Internal Medicine, Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Peter Arvan
- Department of Internal Medicine, Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Leslie S Satin
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
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9
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Marinelli I, Thompson BM, Parekh VS, Fletcher PA, Gerardo-Giorda L, Sherman AS, Satin LS, Bertram R. Oscillations in K(ATP) conductance drive slow calcium oscillations in pancreatic β-cells. Biophys J 2022; 121:1449-1464. [PMID: 35300967 PMCID: PMC9072586 DOI: 10.1016/j.bpj.2022.03.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [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] [Received: 08/24/2021] [Revised: 10/07/2021] [Accepted: 03/11/2022] [Indexed: 11/26/2022] Open
Abstract
ATP-sensitive K+ (K(ATP)) channels were first reported in the β-cells of pancreatic islets in 1984, and it was soon established that they are the primary means by which the blood glucose level is transduced to cellular electrical activity and consequently insulin secretion. However, the role that the K(ATP) channels play in driving the bursting electrical activity of islet β-cells, which drives pulsatile insulin secretion, remains unclear. One difficulty is that bursting is abolished when several different ion channel types are blocked pharmacologically or genetically, making it challenging to distinguish causation from correlation. Here, we demonstrate a means for determining whether activity-dependent oscillations in K(ATP) conductance play the primary role in driving electrical bursting in β-cells. We use mathematical models to predict that if K(ATP) is the driver, then contrary to intuition, the mean, peak, and nadir levels of ATP/ADP should be invariant to changes in glucose within the concentration range that supports bursting. We test this in islets using Perceval-HR to image oscillations in ATP/ADP. We find that mean, peak, and nadir levels are indeed approximately invariant, supporting the hypothesis that oscillations in K(ATP) conductance are the main drivers of the slow bursting oscillations typically seen at stimulatory glucose levels in mouse islets. In conclusion, we provide, for the first time to our knowledge, causal evidence for the role of K(ATP) channels not only as the primary target for glucose regulation but also for their role in driving bursting electrical activity and pulsatile insulin secretion.
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Affiliation(s)
- Isabella Marinelli
- Centre for Systems Modelling & Quantitative Biomedicine (SMQB), University of Birmingham, Birmingham, UK
| | - Benjamin M Thompson
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Vishal S Parekh
- Chemical Biology and Therapeutics Science Program, Broad Institute, Cambridge, Massachusetts
| | - Patrick A Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland
| | - Luca Gerardo-Giorda
- Institute for Mathematical Methods in Medicine and Data Based Modeling, Johannes Kepler University, Linz, Austria; Johann Radon Institute for Computational and Applied Mathematics (RICAM), Austrian Academy of Sciences, Linz, Austria
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland
| | - Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida.
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Marinelli I, Parekh V, Fletcher P, Thompson B, Ren J, Tang X, Saunders TL, Ha J, Sherman A, Bertram R, Satin LS. Slow oscillations persist in pancreatic beta cells lacking phosphofructokinase M. Biophys J 2022; 121:692-704. [PMID: 35131294 PMCID: PMC8948000 DOI: 10.1016/j.bpj.2022.01.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [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] [Received: 08/18/2021] [Revised: 12/07/2021] [Accepted: 01/28/2022] [Indexed: 11/22/2022] Open
Abstract
Pulsatile insulin secretion by pancreatic beta cells is necessary for tight glucose control in the body. Glycolytic oscillations have been proposed as the mechanism for generating the electrical oscillations underlying pulsatile insulin secretion. The glycolytic enzyme 6-phosphofructokinase-1 (PFK) synthesizes fructose-1,6-bisphosphate (FBP) from fructose-6-phosphate. It has been proposed that the slow electrical and Ca2+ oscillations (periods of 3-5 min) observed in islets result from allosteric feedback activation of PFKM by FBP. Pancreatic beta cells express three PFK isozymes: PFKL, PFKM, and PFKP. A prior study of mice that were engineered to lack PFKM using a gene-trap strategy to delete Pfkm produced a mosaic reduction in global Pfkm expression, but the islets isolated from the mice still exhibited slow Ca2+ oscillations. However, these islets still expressed residual PFKM protein. Thus, to more fully test the hypothesis that beta cell PFKM is responsible for slow islet oscillations, we made a beta-cell-specific knockout mouse that completely lacked PFKM. While PFKM deletion resulted in subtle metabolic changes in vivo, islets that were isolated from these mice continued to exhibit slow oscillations in electrical activity, beta cell Ca2+ concentrations, and glycolysis, as measured using PKAR, an FBP reporter/biosensor. Furthermore, simulations obtained with a mathematical model of beta cell activity shows that slow oscillations can persist despite PFKM loss provided that one of the other PFK isoforms, such as PFKP, is present, even if its level of expression is unchanged. Thus, while we believe that PFKM may be the main regulator of slow oscillations in wild-type islets, PFKP can provide functional redundancy. Our model also suggests that PFKM likely dominates, in vivo, because it outcompetes PFKP with its higher FBP affinity and lower ATP affinity. We thus propose that isoform redundancy may rescue key physiological processes of the beta cell in the absence of certain critical genes.
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Affiliation(s)
- Isabella Marinelli
- Centre for Systems Modelling & Quantitative Biomedicine (SMQB), University of Birmingham, Birmingham, UK
| | - Vishal Parekh
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Patrick Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Bethesda
| | - Benjamin Thompson
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Jinhua Ren
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Xiaoqing Tang
- Department of Biological Sciences, Michigan Technological University, Houghton, Michigan
| | - Thomas L Saunders
- Division of Medical Medicine and Genetics, Department of Internal Medicine, Transgenic Animal Model Core, University of Michigan Medical School, Ann Arbor, Michigan
| | - Joon Ha
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Bethesda
| | - Arthur Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Bethesda
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida
| | - Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan.
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11
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Marinelli I, Fletcher PA, Sherman AS, Satin LS, Bertram R. Symbiosis of Electrical and Metabolic Oscillations in Pancreatic β-Cells. Front Physiol 2021; 12:781581. [PMID: 34925070 PMCID: PMC8682964 DOI: 10.3389/fphys.2021.781581] [Citation(s) in RCA: 13] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/08/2021] [Indexed: 11/13/2022] Open
Abstract
Insulin is secreted in a pulsatile pattern, with important physiological ramifications. In pancreatic β-cells, which are the cells that synthesize insulin, insulin exocytosis is elicited by pulses of elevated intracellular Ca2+ initiated by bursts of electrical activity. In parallel with these electrical and Ca2+ oscillations are oscillations in metabolism, and the periods of all of these oscillatory processes are similar. A key question that remains unresolved is whether the electrical oscillations are responsible for the metabolic oscillations via the effects of Ca2+, or whether the metabolic oscillations are responsible for the electrical oscillations due to the effects of ATP on ATP-sensitive ion channels? Mathematical modeling is a useful tool for addressing this and related questions as modeling can aid in the design of well-focused experiments that can test the predictions of particular models and subsequently be used to improve the models in an iterative fashion. In this article, we discuss a recent mathematical model, the Integrated Oscillator Model (IOM), that was the product of many years of development. We use the model to demonstrate that the relationship between calcium and metabolism in beta cells is symbiotic: in some contexts, the electrical oscillations drive the metabolic oscillations, while in other contexts it is the opposite. We provide new insights regarding these results and illustrate that what might at first appear to be contradictory data are actually compatible when viewed holistically with the IOM.
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Affiliation(s)
- Isabella Marinelli
- Centre for Systems Modelling and Quantitative Biomedicine (SMQB), University of Birmingham, Birmingham, United Kingdom
| | - Patrick A Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
| | - Leslie S Satin
- Department of Pharmacology, Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Richard Bertram
- Programs in Neuroscience and Molecular Biophysics, Department of Mathematics, Florida State University, Tallahassee, FL, United States
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12
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Abstract
Beta cells of the pancreatic islet express many different types of ion channels. These channels reside in the β-cell plasma membrane as well as subcellular organelles and their coordinated activity and sensitivity to metabolism regulate glucose-dependent insulin secretion. Here, we review the molecular nature, expression patterns, and functional roles of many β-cell channels, with an eye toward explaining the ionic basis of glucose-induced insulin secretion. Our primary focus is on KATP and voltage-gated Ca2+ channels as these primarily regulate insulin secretion; other channels in our view primarily help to sculpt the electrical patterns generated by activated β-cells or indirectly regulate metabolism. Lastly, we discuss why understanding the physiological roles played by ion channels is important for understanding the secretory defects that occur in type 2 diabetes. © 2021 American Physiological Society. Compr Physiol 11:1-21, 2021.
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13
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Yong J, Parekh VS, Reilly SM, Nayak J, Chen Z, Lebeaupin C, Jang I, Zhang J, Prakash TP, Sun H, Murray S, Guo S, Ayala JE, Satin LS, Saltiel AR, Kaufman RJ. Chop/ Ddit3 depletion in β cells alleviates ER stress and corrects hepatic steatosis in mice. Sci Transl Med 2021; 13:13/604/eaba9796. [PMID: 34321322 DOI: 10.1126/scitranslmed.aba9796] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 04/07/2021] [Accepted: 06/23/2021] [Indexed: 12/21/2022]
Abstract
Type 2 diabetes (T2D) is a metabolic disorder characterized by hyperglycemia, hyperinsulinemia, and insulin resistance (IR). During the early phase of T2D, insulin synthesis and secretion by pancreatic β cells is enhanced, which can lead to proinsulin misfolding that aggravates endoplasmic reticulum (ER) protein homeostasis in β cells. Moreover, increased circulating insulin may contribute to fatty liver disease. Medical interventions aimed at alleviating ER stress in β cells while maintaining optimal insulin secretion are therefore an attractive therapeutic strategy for T2D. Previously, we demonstrated that germline Chop gene deletion preserved β cells in high-fat diet (HFD)-fed mice and in leptin receptor-deficient db/db mice. In the current study, we further investigated whether targeting Chop/Ddit3 specifically in murine β cells conferred therapeutic benefits. First, we showed that Chop deletion in β cells alleviated β cell ER stress and delayed glucose-stimulated insulin secretion (GSIS) in HFD-fed mice. Second, β cell-specific Chop deletion prevented liver steatosis and hepatomegaly in aged HFD-fed mice without affecting basal glucose homeostasis. Third, we provide mechanistic evidence that Chop depletion reduces ER Ca2+ buffering capacity and modulates glucose-induced islet Ca2+ oscillations, leading to transcriptional changes of ER chaperone profile ("ER remodeling"). Last, we demonstrated that a GLP1-conjugated Chop antisense oligonucleotide strategy recapitulated the reduction in liver triglycerides and pancreatic insulin content. In summary, our results demonstrate that Chop depletion in β cells provides a therapeutic strategy to alleviate dysregulated insulin secretion and consequent fatty liver disease in T2D.
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Affiliation(s)
- Jing Yong
- Division of Metabolism and Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA. .,Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA
| | - Vishal S Parekh
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA.,Department of Pharmacology, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA
| | - Shannon M Reilly
- Department of Pharmacology, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA.,Division of Metabolism and Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Jonamani Nayak
- Division of Metabolism and Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA.,Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA
| | - Zhouji Chen
- Division of Metabolism and Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA.,Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA
| | - Cynthia Lebeaupin
- Division of Metabolism and Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA.,Department of Pharmacology, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA.,Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA.,Division of Metabolism and Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Insook Jang
- Division of Metabolism and Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA.,Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA
| | - Jiangwei Zhang
- Cardiometabolic Phenotyping Core, Sanford-Burnham Medical Research Institute, 6400 Sanger Road, Orlando, FL 32827, USA.,Department of Antisense Drug Discovery, Ionis Pharmaceuticals Inc., 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Thazha P Prakash
- Cardiometabolic Phenotyping Core, Sanford-Burnham Medical Research Institute, 6400 Sanger Road, Orlando, FL 32827, USA.,Department of Antisense Drug Discovery, Ionis Pharmaceuticals Inc., 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Hong Sun
- Cardiometabolic Phenotyping Core, Sanford-Burnham Medical Research Institute, 6400 Sanger Road, Orlando, FL 32827, USA.,Department of Antisense Drug Discovery, Ionis Pharmaceuticals Inc., 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Sue Murray
- Cardiometabolic Phenotyping Core, Sanford-Burnham Medical Research Institute, 6400 Sanger Road, Orlando, FL 32827, USA.,Department of Antisense Drug Discovery, Ionis Pharmaceuticals Inc., 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Shuling Guo
- Cardiometabolic Phenotyping Core, Sanford-Burnham Medical Research Institute, 6400 Sanger Road, Orlando, FL 32827, USA.,Department of Antisense Drug Discovery, Ionis Pharmaceuticals Inc., 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Julio E Ayala
- Department of Molecular Physiology & Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.,Cardiometabolic Phenotyping Core, Sanford-Burnham Medical Research Institute, 6400 Sanger Road, Orlando, FL 32827, USA.,Department of Molecular Physiology & Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Leslie S Satin
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA.,Department of Pharmacology, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA
| | - Alan R Saltiel
- Department of Pharmacology, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA.,Division of Metabolism and Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA.,Department of Pharmacology, University of California San Diego, La Jolla, CA 92093, USA
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA.
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14
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Abstract
Both type 1 and type 2 diabetes mellitus are advancing at exponential rates, placing significant burdens on health care networks worldwide. Although traditional pharmacologic therapies such as insulin and oral antidiabetic stalwarts like metformin and the sulfonylureas continue to be used, newer drugs are now on the market targeting novel blood glucose-lowering pathways. Furthermore, exciting new developments in the understanding of beta cell and islet biology are driving the potential for treatments targeting incretin action, islet transplantation with new methods for immunologic protection, and the generation of functional beta cells from stem cells. Here we discuss the mechanistic details underlying past, present, and future diabetes therapies and evaluate their potential to treat and possibly reverse type 1 and 2 diabetes in humans. SIGNIFICANCE STATEMENT: Diabetes mellitus has reached epidemic proportions in the developed and developing world alike. As the last several years have seen many new developments in the field, a new and up to date review of these advances and their careful evaluation will help both clinical and research diabetologists to better understand where the field is currently heading.
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Affiliation(s)
- Leslie S Satin
- Department of Pharmacology (L.S.S.), Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine (L.S.S., S.A.S., E.M.W.), and Brehm Diabetes Center (L.S.S., S.A.S., E.M.W.), University of Michigan Medical School, Ann Arbor, Michigan; and VA Ann Arbor Healthcare System, Ann Arbor, Michigan (S.A.S.) ; ;
| | - Scott A Soleimanpour
- Department of Pharmacology (L.S.S.), Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine (L.S.S., S.A.S., E.M.W.), and Brehm Diabetes Center (L.S.S., S.A.S., E.M.W.), University of Michigan Medical School, Ann Arbor, Michigan; and VA Ann Arbor Healthcare System, Ann Arbor, Michigan (S.A.S.)
| | - Emily M Walker
- Department of Pharmacology (L.S.S.), Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine (L.S.S., S.A.S., E.M.W.), and Brehm Diabetes Center (L.S.S., S.A.S., E.M.W.), University of Michigan Medical School, Ann Arbor, Michigan; and VA Ann Arbor Healthcare System, Ann Arbor, Michigan (S.A.S.) ; ;
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15
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Wang Z, Mohan R, Chen X, Matson K, Waugh J, Mao Y, Zhang S, Li W, Tang X, Satin LS, Tang X. microRNA-483 Protects Pancreatic β-Cells by Targeting ALDH1A3. Endocrinology 2021; 162:6132087. [PMID: 33564883 PMCID: PMC7951052 DOI: 10.1210/endocr/bqab031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Indexed: 12/14/2022]
Abstract
Pancreatic β-cell dysfunction is central to the development and progression of type 2 diabetes. Dysregulation of microRNAs (miRNAs) has been associated with pancreatic islet dysfunction in type 2 diabetes. Previous study has shown that miR-483 is expressed relatively higher in β-cells than in α-cells. To explore the physiological function of miR-483, we generated a β-cell-specific knockout mouse model of miR-483. Loss of miR-483 enhances high-fat diet-induced hyperglycemia and glucose intolerance by the attenuation of diet-induced insulin release. Intriguingly, mice with miR-483 deletion exhibited loss of β-cell features, as indicated by elevated expression of aldehyde dehydrogenase family 1, subfamily A3 (Aldh1a3), a marker of β-cell dedifferentiation. Moreover, Aldh1a3 was validated as a direct target of miR-483 and overexpression of miR-483 repressed Aldh1a3 expression. Genetic ablation of miR-483 also induced alterations in blood lipid profile. Collectively, these data suggest that miR-483 is critical in protecting β-cell function by repressing the β-cell disallowed gene Aldh1a3. The dysregulated miR-483 may impair insulin secretion and initiate β-cell dedifferentiation during the development of type 2 diabetes.
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Affiliation(s)
- Zhihong Wang
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Ramkumar Mohan
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Xinqian Chen
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Katy Matson
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Jackson Waugh
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Yiping Mao
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Shungang Zhang
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Wanzhen Li
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Xiaohu Tang
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Leslie S Satin
- Department of Pharmacology, Brehm Center for Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Xiaoqing Tang
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
- Correspondence: Xiaoqing Tang, PhD, Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931, USA.
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16
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Sidarala V, Pearson GL, Parekh VS, Thompson B, Christen L, Gingerich MA, Zhu J, Stromer T, Ren J, Reck EC, Chai B, Corbett JA, Mandrup-Poulsen T, Satin LS, Soleimanpour SA. Mitophagy protects β cells from inflammatory damage in diabetes. JCI Insight 2020; 5:141138. [PMID: 33232298 PMCID: PMC7819751 DOI: 10.1172/jci.insight.141138] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 11/11/2020] [Indexed: 12/14/2022] Open
Abstract
Inflammatory damage contributes to β cell failure in type 1 and 2 diabetes (T1D and T2D, respectively). Mitochondria are damaged by inflammatory signaling in β cells, resulting in impaired bioenergetics and initiation of proapoptotic machinery. Hence, the identification of protective responses to inflammation could lead to new therapeutic targets. Here, we report that mitophagy serves as a protective response to inflammatory stress in both human and rodent β cells. Utilizing in vivo mitophagy reporters, we observed that diabetogenic proinflammatory cytokines induced mitophagy in response to nitrosative/oxidative mitochondrial damage. Mitophagy-deficient β cells were sensitized to inflammatory stress, leading to the accumulation of fragmented dysfunctional mitochondria, increased β cell death, and hyperglycemia. Overexpression of CLEC16A, a T1D gene and mitophagy regulator whose expression in islets is protective against T1D, ameliorated cytokine-induced human β cell apoptosis. Thus, mitophagy promotes β cell survival and prevents diabetes by countering inflammatory injury. Targeting this pathway has the potential to prevent β cell failure in diabetes and may be beneficial in other inflammatory conditions.
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Affiliation(s)
- Vaibhav Sidarala
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and
| | - Gemma L Pearson
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and
| | - Vishal S Parekh
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Benjamin Thompson
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Lisa Christen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Morgan A Gingerich
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and.,Program in Biological Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Jie Zhu
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and
| | - Tracy Stromer
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and
| | - Jianhua Ren
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Emma C Reck
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and
| | - Biaoxin Chai
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and
| | - John A Corbett
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | | | - Leslie S Satin
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and.,Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Scott A Soleimanpour
- Division of Metabolism, Endocrinology and Diabetes and Department of Internal Medicine, and.,VA Ann Arbor Healthcare System, Ann Arbor, Michigan, USA
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17
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Satin LS, Rorsman P. Response to Comment on Satin et al. "Take Me To Your Leader": An Electrophysiological Appraisal of the Role of Hub Cells in Pancreatic Islets. Diabetes 2020;69:830-836. Diabetes 2020; 69:e12-e13. [PMID: 32820057 PMCID: PMC7809710 DOI: 10.2337/dbi20-0027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Leslie S Satin
- Department of Pharmacology, Brehm Center for Diabetes Research, Medical School, University of Michigan, Ann Arbor, MI
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, and Churchill Hospital, Oxford, U.K
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18
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Satin LS, Zhang Q, Rorsman P. "Take Me To Your Leader": An Electrophysiological Appraisal of the Role of Hub Cells in Pancreatic Islets. Diabetes 2020; 69:830-836. [PMID: 32312899 PMCID: PMC7171959 DOI: 10.2337/dbi19-0012] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [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] [Received: 06/25/2019] [Accepted: 02/10/2020] [Indexed: 12/26/2022]
Abstract
The coordinated electrical activity of β-cells within the pancreatic islet drives oscillatory insulin secretion. A recent hypothesis postulates that specially equipped "hub" or "leader" cells within the β-cell network drive islet oscillations and that electrically silencing or optically ablating these cells suppresses coordinated electrical activity (and thus insulin secretion) in the rest of the islet. In this Perspective, we discuss this hypothesis in relation to established principles of electrophysiological theory. We conclude that whereas electrical coupling between β-cells is sufficient for the propagation of excitation across the islet, there is no obvious electrophysiological mechanism that explains how hyperpolarizing a hub cell results in widespread inhibition of islet electrical activity and disruption of their coordination. Thus, intraislet diffusible factors should perhaps be considered as an alternate mechanism.
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Affiliation(s)
- Leslie S Satin
- Department of Pharmacology, Brehm Center for Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford, U.K
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford, U.K
- Metabolic Physiology, Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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19
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Zhang IX, Ren J, Vadrevu S, Raghavan M, Satin LS. ER stress increases store-operated Ca 2+ entry (SOCE) and augments basal insulin secretion in pancreatic beta cells. J Biol Chem 2020; 295:5685-5700. [PMID: 32179650 PMCID: PMC7186166 DOI: 10.1074/jbc.ra120.012721] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [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: 01/21/2020] [Revised: 03/06/2020] [Indexed: 12/13/2022] Open
Abstract
Type 2 diabetes mellitus (T2DM) is characterized by impaired glucose-stimulated insulin secretion and increased peripheral insulin resistance. Unremitting endoplasmic reticulum (ER) stress can lead to beta-cell apoptosis and has been linked to type 2 diabetes. Although many studies have attempted to link ER stress and T2DM, the specific effects of ER stress on beta-cell function remain incompletely understood. To determine the interrelationship between ER stress and beta-cell function, here we treated insulin-secreting INS-1(832/13) cells or isolated mouse islets with the ER stress-inducer tunicamycin (TM). TM induced ER stress as expected, as evidenced by activation of the unfolded protein response. Beta cells treated with TM also exhibited concomitant alterations in their electrical activity and cytosolic free Ca2+ oscillations. As ER stress is known to reduce ER Ca2+ levels, we tested the hypothesis that the observed increase in Ca2+ oscillations occurred because of reduced ER Ca2+ levels and, in turn, increased store-operated Ca2+ entry. TM-induced cytosolic Ca2+ and membrane electrical oscillations were acutely inhibited by YM58483, which blocks store-operated Ca2+ channels. Significantly, TM-treated cells secreted increased insulin under conditions normally associated with only minimal release, e.g. 5 mm glucose, and YM58483 blocked this secretion. Taken together, these results support a critical role for ER Ca2+ depletion-activated Ca2+ current in mediating Ca2+-induced insulin secretion in response to ER stress.
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Affiliation(s)
- Irina X Zhang
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Jianhua Ren
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | | | - Malini Raghavan
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Leslie S Satin
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan 48105.
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20
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Thompson BM, Marinelli I, Bertram R, Sherman A, Satin LS. Multiple Feedback Mechanisms Underlying Beta Cell Secretory Oscillations. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.3067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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21
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Abstract
The endoplasmic reticulum (ER) mediates the first steps of protein assembly within the secretory pathway and is the site where protein folding and quality control are initiated. The storage and release of Ca2+ are critical physiological functions of the ER. Disrupted ER homeostasis activates the unfolded protein response (UPR), a pathway which attempts to restore cellular equilibrium in the face of ER stress. Unremitting ER stress, and insufficient compensation for it results in beta-cell apoptosis, a process that has been linked to both type 1 diabetes (T1D) and type 2 diabetes (T2D). Both types are characterized by progressive beta-cell failure and a loss of beta-cell mass, although the underlying causes are different. The reduction of mass occurs secondary to apoptosis in the case of T2D, while beta cells undergo autoimmune destruction in T1D. In this review, we examine recent findings that link the UPR pathway and ER Ca2+ to beta cell dysfunction. We also discuss how UPR activation in beta cells favors cell survival versus apoptosis and death, and how ER protein chaperones are involved in regulating ER Ca2+ levels. Abbreviations: BiP, Binding immunoglobulin Protein ER; endoplasmic reticulum; ERAD, ER-associated protein degradation; IFN, interferon; IL, interleukin; JNK, c-Jun N-terminal kinase; KHE, proton-K+ exchanger; MODY, maturity-onset diabetes of young; PERK, PRKR-like ER kinase; SERCA, Sarco/Endoplasmic Reticulum Ca2+-ATPases; T1D, type 1 diabetes; T2D, type 2 diabetes; TNF, tumor necrosis factor; UPR, unfolded protein response; WRS, Wolcott-Rallison syndrome.
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Affiliation(s)
- Irina X Zhang
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan, Ann Arbor, MI
| | - Malini Raghavan
- Department of Microbiology and Immunology Michigan Medicine, University of Michigan, Ann Arbor, MI
| | - Leslie S Satin
- Department of Pharmacology and Brehm Diabetes Research Center, University of Michigan, Ann Arbor, MI
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22
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Scarl RT, Corbin KL, Vann NW, Smith HM, Satin LS, Sherman A, Nunemaker CS. Intact pancreatic islets and dispersed beta-cells both generate intracellular calcium oscillations but differ in their responsiveness to glucose. Cell Calcium 2019; 83:102081. [PMID: 31563790 DOI: 10.1016/j.ceca.2019.102081] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 09/12/2019] [Accepted: 09/14/2019] [Indexed: 01/19/2023]
Abstract
Pancreatic islets produce pulses of insulin and other hormones that maintain normal glucose homeostasis. These micro-organs possess exquisite glucose-sensing capabilities, allowing for precise changes in pulsatile insulin secretion in response to small changes in glucose. When communication among these cells is disrupted, precision glucose sensing falters. We measured intracellular calcium patterns in 6-mM-steps between 0 and 16 mM glucose, and also more finely in 2-mM-steps from 8 to 12 mM glucose, to compare glucose sensing systematically among intact islets and dispersed islet cells derived from the same mouse pancreas in vitro. The calcium activity of intact islets was uniformly low (quiescent) below 4 mM glucose and active above 8 mM glucose, whereas dispersed beta-cells displayed a broader activation range (2-to-10 mM). Intact islets exhibited calcium oscillations with 2-to-5-min periods, yet beta-cells exhibited longer 7-10 min periods. In every case, intact islets showed changes in activity with each 6-mM-glucose step, whereas dispersed islet cells displayed a continuum of calcium responses ranging from islet-like patterns to stable oscillations unaffected by changes in glucose concentration. These differences were also observed for 2-mM-glucose steps. Despite the diversity of dispersed beta-cell responses to glucose, the sum of all activity produced a glucose dose-response curve that was surprisingly similar to the curve for intact islets, arguing against the importance of "hub cells" for function. Beta-cells thus retain many of the features of islets, but some are more islet-like than others. Determining the molecular underpinnings of these variations could be valuable for future studies of stem-cell-derived beta-cell therapies.
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Affiliation(s)
- Rachel T Scarl
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States
| | - Kathryn L Corbin
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States; Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States
| | - Nicholas W Vann
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, United States
| | - Hallie M Smith
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States
| | - Leslie S Satin
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, MI, United States; Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Arthur Sherman
- Laboratory of Biological Modeling, NIDDK, NIH, Bethesda, MD, United States
| | - Craig S Nunemaker
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States; Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States.
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23
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Poitout V, Satin LS, Kahn SE, Stoffers DA, Marchetti P, Gannon M, Verchere CB, Herold KC, Myers MG, Marshall SM. A Call for Improved Reporting of Human Islet Characteristics in Research Articles. Diabetes 2019; 68:239-240. [PMID: 30552106 DOI: 10.2337/dbi18-0055] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, Centre de recherche du centre hospitalier de l'Université de Montréal (CRCHUM), Montréal, Québec, Canada
- Department of Medicine, University of Montreal, Québec, Canada
| | - Leslie S Satin
- Brehm Diabetes Center, University of Michigan, Ann Arbor, MI
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI
| | - Steven E Kahn
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, WA
| | - Doris A Stoffers
- Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
- Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Maureen Gannon
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - C Bruce Verchere
- BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
- Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kevan C Herold
- Department of Immunobiology and Internal Medicine, Yale University, New Haven, CT
| | - Martin G Myers
- Brehm Diabetes Center, University of Michigan, Ann Arbor, MI
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
| | - Sally M Marshall
- Institute of Cellular Medicine, Faculty of Clinical Medical Sciences, Newcastle University, Newcastle upon Tyne, U.K
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24
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Poitout V, Satin LS, Kahn SE, Stoffers DA, Marchetti P, Gannon M, Verchere CB, Herold KC, Myers MG, Marshall SM. A call for improved reporting of human islet characteristics in research articles. Diabetologia 2019; 62:209-211. [PMID: 30547229 PMCID: PMC7259467 DOI: 10.1007/s00125-018-4784-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 11/12/2018] [Indexed: 10/27/2022]
Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, Centre de recherche du centre hospitalier de l'Université de Montréal (CRCHUM), 900 rue Saint-Denis, Office R05-406, Montréal, QC, H2X 0A9, Canada.
- Department of Medicine, University of Montreal, Montreal, QC, Canada.
| | - Leslie S Satin
- Brehm Diabetes Center, University of Michigan, Ann Arbor, MI, USA
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Steven E Kahn
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, WA, USA
| | - Doris A Stoffers
- Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
- Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Maureen Gannon
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - C Bruce Verchere
- BC Children's Hospital Research Institute, Vancouver, BC, Canada
- Department of Surgery, University of British Columbia, Vancouver, BC, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Kevan C Herold
- Department of Immunobiology and Internal Medicine, Yale University, New Haven, CT, USA
| | - Martin G Myers
- Brehm Diabetes Center, University of Michigan, Ann Arbor, MI, USA
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Sally M Marshall
- Institute of Cellular Medicine, Faculty of Clinical Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
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25
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Abstract
Insulin secretion from pancreatic islet β-cells occurs in a pulsatile fashion, with a typical period of ∼5 min. The basis of this pulsatility in mouse islets has been investigated for more than four decades, and the various theories have been described as either qualitative or mathematical models. In many cases the models differ in their mechanisms for rhythmogenesis, as well as other less important details. In this Perspective, we describe two main classes of models: those in which oscillations in the intracellular Ca2+ concentration drive oscillations in metabolism, and those in which intrinsic metabolic oscillations drive oscillations in Ca2+ concentration and electrical activity. We then discuss nine canonical experimental findings that provide key insights into the mechanism of islet oscillations and list the models that can account for each finding. Finally, we describe a new model that integrates features from multiple earlier models and is thus called the Integrated Oscillator Model. In this model, intracellular Ca2+ acts on the glycolytic pathway in the generation of oscillations, and it is thus a hybrid of the two main classes of models. It alone among models proposed to date can explain all nine key experimental findings, and it serves as a good starting point for future studies of pulsatile insulin secretion from human islets.
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Affiliation(s)
- Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, FL
| | - Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, MI
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
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26
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Wedgwood KCA, Satin LS. Six degrees of depolarization: Comment on "Network science of biological systems at different scales: A review" by Marko Gosak et al. Phys Life Rev 2018; 24:136-139. [PMID: 29395878 DOI: 10.1016/j.plrev.2018.01.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Accepted: 01/18/2018] [Indexed: 11/17/2022]
Affiliation(s)
| | - Leslie S Satin
- University of Michigan Medical School, Ann Arbor, MI, USA
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27
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Satin LS, Parekh VS. CFTR: Ferreting Out Its Role in Cystic Fibrosis-Related Diabetes. Endocrinology 2017; 158:3319-3321. [PMID: 28977616 PMCID: PMC5659707 DOI: 10.1210/en.2017-00746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 08/14/2017] [Indexed: 11/19/2022]
Affiliation(s)
- Leslie S. Satin
- Department of Pharmacology and Brehm Diabetes Center,
University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Vishal S. Parekh
- Department of Pharmacology and Brehm Diabetes Center,
University of Michigan Medical School, Ann Arbor, Michigan 48105
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28
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Montemurro C, Vadrevu S, Gurlo T, Butler AE, Vongbunyong KE, Petcherski A, Shirihai OS, Satin LS, Braas D, Butler PC, Tudzarova S. Cell cycle-related metabolism and mitochondrial dynamics in a replication-competent pancreatic beta-cell line. Cell Cycle 2017; 16:2086-2099. [PMID: 28820316 DOI: 10.1080/15384101.2017.1361069] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [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: 12/21/2022] Open
Abstract
Cell replication is a fundamental attribute of growth and repair in multicellular organisms. Pancreatic beta-cells in adults rarely enter cell cycle, hindering the capacity for regeneration in diabetes. Efforts to drive beta-cells into cell cycle have so far largely focused on regulatory molecules such as cyclins and cyclin-dependent kinases (CDKs). Investigations in cancer biology have uncovered that adaptive changes in metabolism, the mitochondrial network, and cellular Ca2+ are critical for permitting cells to progress through the cell cycle. Here, we investigated these parameters in the replication-competent beta-cell line INS 832/13. Cell cycle synchronization of this line permitted evaluation of cell metabolism, mitochondrial network, and cellular Ca2+ compartmentalization at key cell cycle stages. The mitochondrial network is interconnected and filamentous at G1/S but fragments during the S and G2/M phases, presumably to permit sorting to daughter cells. Pyruvate anaplerosis peaks at G1/S, consistent with generation of biomass for daughter cells, whereas mitochondrial Ca2+ and respiration increase during S and G2/M, consistent with increased energy requirements for DNA and lipid synthesis. This synchronization approach may be of value to investigators performing live cell imaging of Ca2+ or mitochondrial dynamics commonly undertaken in INS cell lines because without synchrony widely disparate data from cell to cell would be expected depending on position within cell cycle. Our findings also offer insight into why replicating beta-cells are relatively nonfunctional secreting insulin in response to glucose. They also provide guidance on metabolic requirements of beta-cells for the transition through the cell cycle that may complement the efforts currently restricted to manipulating cell cycle to drive beta-cells through cell cycle.
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Affiliation(s)
- Chiara Montemurro
- a Larry L. Hillblom Islet Research Center , University of California, Los Angeles, David Geffen School of Medicine , Los Angeles , CA , USA
| | - Suryakiran Vadrevu
- b Department of Pharmacology and Brehm Diabetes Research Center , University of Michigan , Ann Arbor , MI , USA
| | - Tatyana Gurlo
- a Larry L. Hillblom Islet Research Center , University of California, Los Angeles, David Geffen School of Medicine , Los Angeles , CA , USA
| | - Alexandra E Butler
- a Larry L. Hillblom Islet Research Center , University of California, Los Angeles, David Geffen School of Medicine , Los Angeles , CA , USA
| | - Kenny E Vongbunyong
- a Larry L. Hillblom Islet Research Center , University of California, Los Angeles, David Geffen School of Medicine , Los Angeles , CA , USA
| | - Anton Petcherski
- c Division of Endocrinology, Department of Medicine, David Geffen School of Medicine , University of California, Los Angeles , Los Angeles , CA , USA
| | - Orian S Shirihai
- c Division of Endocrinology, Department of Medicine, David Geffen School of Medicine , University of California, Los Angeles , Los Angeles , CA , USA
| | - Leslie S Satin
- b Department of Pharmacology and Brehm Diabetes Research Center , University of Michigan , Ann Arbor , MI , USA
| | - Daniel Braas
- d Department of Molecular and Medical Pharmacology, Crump Institute for Molecular Imaging , University of California, Los Angeles, David Geffen School of Medicine , Los Angeles , CA , USA ; UCLA Metabolomics Center , University of California, Los Angeles , Los Angeles , CA , USA
| | - Peter C Butler
- a Larry L. Hillblom Islet Research Center , University of California, Los Angeles, David Geffen School of Medicine , Los Angeles , CA , USA
| | - Slavica Tudzarova
- a Larry L. Hillblom Islet Research Center , University of California, Los Angeles, David Geffen School of Medicine , Los Angeles , CA , USA.,e Jonsson Comprehensive Cancer Center , University of California, Los Angeles, David Geffen School of Medicine , Los Angeles , CA , USA
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29
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Yildirim V, Vadrevu S, Thompson B, Satin LS, Bertram R. Upregulation of an inward rectifying K+ channel can rescue slow Ca2+ oscillations in K(ATP) channel deficient pancreatic islets. PLoS Comput Biol 2017; 13:e1005686. [PMID: 28749940 PMCID: PMC5549769 DOI: 10.1371/journal.pcbi.1005686] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 08/08/2017] [Accepted: 07/16/2017] [Indexed: 12/02/2022] Open
Abstract
Plasma insulin oscillations are known to have physiological importance in the regulation of blood glucose. In insulin-secreting β-cells of pancreatic islets, K(ATP) channels play a key role in regulating glucose-dependent insulin secretion. In addition, they convey oscillations in cellular metabolism to the membrane by sensing adenine nucleotides, and are thus instrumental in mediating pulsatile insulin secretion. Blocking K(ATP) channels pharmacologically depolarizes the β-cell plasma membrane and terminates islet oscillations. Surprisingly, when K(ATP) channels are genetically knocked out, oscillations in islet activity persist, and relatively normal blood glucose levels are maintained. Compensation must therefore occur to overcome the loss of K(ATP) channels in K(ATP) knockout mice. In a companion study, we demonstrated a substantial increase in Kir2.1 protein occurs in β-cells lacking K(ATP) because of SUR1 deletion. In this report, we demonstrate that β-cells of SUR1 null islets have an upregulated inward rectifying K+ current that helps to compensate for the loss of K(ATP) channels. This current is likely due to the increased expression of Kir2.1 channels. We used mathematical modeling to determine whether an ionic current having the biophysical characteristics of Kir2.1 is capable of rescuing oscillations that are similar in period to those of wild-type islets. By experimentally testing a key model prediction we suggest that Kir2.1 current upregulation is a likely mechanism for rescuing the oscillations seen in islets from mice deficient in K(ATP) channels. Pulsatile insulin secretion is important for the proper regulation of blood glucose, and disruption of this pulsatility is a hallmark of type II diabetes. An ion channel was discovered more than three decades ago that conveys the metabolic state of insulin-secreting β-cells to the plasma membrane because it is blocked by ATP and opened by ADP, and thereby controls the activity of these electrically-excitable cells on a rapid time scale according to the prevailing blood glucose level. In addition to setting the appropriate level of insulin secretion, K(ATP) channels play a key role in generating the oscillations in cellular activity that underlie insulin pulsatility. It is therefore surprising that oscillations in activity persist in islets in which the K(ATP) channels are genetically knocked out. In this combined modeling and experimental study, we demonstrate that the role played by K(ATP) current in wild-type β-cells can be taken over by an inward-rectifying K+ current which, we show here, is upregulated in β-cells from SUR1 knockout mice. This result helps to resolve a mystery in the field that has remained elusive for more than a decade, since the first studies showing oscillations in SUR1-/- islets.
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Affiliation(s)
- Vehpi Yildirim
- Department of Mathematics, Florida State University, Tallahassee, FL, United States of America
| | - Suryakiran Vadrevu
- Brehm Diabetes Center, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Benjamin Thompson
- Brehm Diabetes Center, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Leslie S. Satin
- Brehm Diabetes Center, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Richard Bertram
- Department of Mathematics and Programs in Molecular Biophysics and Neuroscience, Florida State University, Tallahassee, FL, United States of America
- * E-mail:
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30
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Kim SY, Lee JH, Merrins MJ, Gavrilova O, Bisteau X, Kaldis P, Satin LS, Rane SG. Loss of Cyclin-dependent Kinase 2 in the Pancreas Links Primary β-Cell Dysfunction to Progressive Depletion of β-Cell Mass and Diabetes. J Biol Chem 2017; 292:3841-3853. [PMID: 28100774 DOI: 10.1074/jbc.m116.754077] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [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: 08/25/2016] [Revised: 01/13/2017] [Indexed: 11/06/2022] Open
Abstract
The failure of pancreatic islet β-cells is a major contributor to the etiology of type 2 diabetes. β-Cell dysfunction and declining β-cell mass are two mechanisms that contribute to this failure, although it is unclear whether they are molecularly linked. Here, we show that the cell cycle regulator, cyclin-dependent kinase 2 (CDK2), couples primary β-cell dysfunction to the progressive deterioration of β-cell mass in diabetes. Mice with pancreas-specific deletion of Cdk2 are glucose-intolerant, primarily due to defects in glucose-stimulated insulin secretion. Accompanying this loss of secretion are defects in β-cell metabolism and perturbed mitochondrial structure. Persistent insulin secretion defects culminate in progressive deficits in β-cell proliferation, reduced β-cell mass, and diabetes. These outcomes may be mediated directly by the loss of CDK2, which binds to and phosphorylates the transcription factor FOXO1 in a glucose-dependent manner. Further, we identified a requirement for CDK2 in the compensatory increases in β-cell mass that occur in response to age- and diet-induced stress. Thus, CDK2 serves as an important nexus linking primary β-cell dysfunction to progressive β-cell mass deterioration in diabetes.
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Affiliation(s)
- So Yoon Kim
- From the Cell Growth and Metabolism Section, Diabetes, Endocrinology, and Obesity Branch and
| | - Ji-Hyeon Lee
- From the Cell Growth and Metabolism Section, Diabetes, Endocrinology, and Obesity Branch and
| | - Matthew J Merrins
- the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin, Madison, Wisconsin 53705
| | - Oksana Gavrilova
- the Mouse Metabolism Core Laboratory, NIDDK, National Institutes of Health, Clinical Research Center, Bethesda, Maryland 20892
| | - Xavier Bisteau
- the Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research), 61 Biopolis Drive, Proteos#3-09, Singapore 138673, Singapore
| | - Philipp Kaldis
- the Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research), 61 Biopolis Drive, Proteos#3-09, Singapore 138673, Singapore.,the Department of Biochemistry, National University of Singapore, Singapore 117597, Singapore, and
| | - Leslie S Satin
- the Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Sushil G Rane
- From the Cell Growth and Metabolism Section, Diabetes, Endocrinology, and Obesity Branch and
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31
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McKenna JP, Ha J, Merrins MJ, Satin LS, Sherman A, Bertram R. Ca2+ Effects on ATP Production and Consumption Have Regulatory Roles on Oscillatory Islet Activity. Biophys J 2017; 110:733-742. [PMID: 26840737 DOI: 10.1016/j.bpj.2015.11.3526] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/21/2015] [Accepted: 11/06/2015] [Indexed: 11/19/2022] Open
Abstract
Pancreatic islets respond to elevated blood glucose by secreting pulses of insulin that parallel oscillations in β-cell metabolism, intracellular Ca(2+) concentration, and bursting electrical activity. The mechanisms that maintain an oscillatory response are not fully understood, yet several models have been proposed. Only some can account for experiments supporting that metabolism is intrinsically oscillatory in β-cells. The dual oscillator model (DOM) implicates glycolysis as the source of oscillatory metabolism. In the companion article, we use recently developed biosensors to confirm that glycolysis is oscillatory and further elucidate the coordination of metabolic and electrical signals in the insulin secretory pathway. In this report, we modify the DOM by incorporating an established link between metabolism and intracellular Ca(2+) to reconcile model predictions with experimental observations from the companion article. With modification, we maintain the distinguishing feature of the DOM, oscillatory glycolysis, but introduce the ability of Ca(2+) influx to reshape glycolytic oscillations by promoting glycolytic efflux. We use the modified model to explain measurements from the companion article and from previously published experiments with islets.
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Affiliation(s)
- Joseph P McKenna
- Department of Mathematics, Florida State University, Tallahassee, Florida
| | - Joon Ha
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Matthew J Merrins
- Division of Endocrinology, Diabetes & Metabolism, Department of Medicine and Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin; William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin
| | - Leslie S Satin
- Department of Pharmacology and Brehm Diabetes Center, University of Michigan, Ann Arbor, Michigan
| | - Arthur Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Richard Bertram
- Department of Mathematics, Florida State University, Tallahassee, Florida; Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida.
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32
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Merrins MJ, Poudel C, McKenna JP, Ha J, Sherman A, Bertram R, Satin LS. Phase Analysis of Metabolic Oscillations and Membrane Potential in Pancreatic Islet β-Cells. Biophys J 2017; 110:691-699. [PMID: 26840733 DOI: 10.1016/j.bpj.2015.12.029] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 12/17/2015] [Accepted: 12/22/2015] [Indexed: 01/01/2023] Open
Abstract
Metabolism in islet β-cells displays oscillations that can trigger pulses of electrical activity and insulin secretion. There has been a decades-long debate among islet biologists about whether metabolic oscillations are intrinsic or occur in response to oscillations in intracellular Ca(2+) that result from bursting electrical activity. In this article, the dynamics of oscillatory metabolism were investigated using five different optical reporters. Reporter activity was measured simultaneously with membrane potential bursting to determine the phase relationships between the metabolic oscillations and electrical activity. Our experimental findings suggest that Ca(2+) entry into β-cells stimulates the rate of mitochondrial metabolism, accounting for the depletion of glycolytic intermediates during each oscillatory burst. We also performed Ca(2+) clamp tests in which we clamped membrane potential with the KATP channel-opener diazoxide and KCl to fix Ca(2+) at an elevated level. These tests confirm that metabolic oscillations do not require Ca(2+) oscillations, but show that Ca(2+) plays a larger role in shaping metabolic oscillations than previously suspected. A dynamical picture of the mechanisms of oscillations emerged that requires the restructuring of contemporary mathematical β-cell models, including our own dual oscillator model. In the companion article, we modified our model to account for these new data.
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Affiliation(s)
- Matthew J Merrins
- Division of Endocrinology, Diabetes & Metabolism, Department of Medicine and Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin; William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin
| | - Chetan Poudel
- Division of Endocrinology, Diabetes & Metabolism, Department of Medicine and Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin; William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin
| | - Joseph P McKenna
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida
| | - Joon Ha
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Arthur Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida
| | - Leslie S Satin
- Department of Pharmacology and Brehm Diabetes Center, University of Michigan, Ann Arbor, Michigan.
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33
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Affiliation(s)
- Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, MI Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Joon Ha
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
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Wynn ML, Yates JA, Evans CR, Van Wassenhove LD, Wu ZF, Bridges S, Bao L, Fournier C, Ashrafzadeh S, Merrins MJ, Satin LS, Schnell S, Burant CF, Merajver SD. RhoC GTPase Is a Potent Regulator of Glutamine Metabolism and N-Acetylaspartate Production in Inflammatory Breast Cancer Cells. J Biol Chem 2016; 291:13715-29. [PMID: 27129239 PMCID: PMC4919454 DOI: 10.1074/jbc.m115.703959] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [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: 11/12/2015] [Revised: 04/01/2016] [Indexed: 01/04/2023] Open
Abstract
Inflammatory breast cancer (IBC) is an extremely lethal cancer that rapidly metastasizes. Although the molecular attributes of IBC have been described, little is known about the underlying metabolic features of the disease. Using a variety of metabolic assays, including (13)C tracer experiments, we found that SUM149 cells, the primary in vitro model of IBC, exhibit metabolic abnormalities that distinguish them from other breast cancer cells, including elevated levels of N-acetylaspartate, a metabolite primarily associated with neuronal disorders and gliomas. Here we provide the first evidence of N-acetylaspartate in breast cancer. We also report that the oncogene RhoC, a driver of metastatic potential, modulates glutamine and N-acetylaspartate metabolism in IBC cells in vitro, revealing a novel role for RhoC as a regulator of tumor cell metabolism that extends beyond its well known role in cytoskeletal rearrangement.
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Affiliation(s)
- Michelle L Wynn
- From the Departments of Internal Medicine, Molecular and Integrative Physiology, and
| | | | | | | | - Zhi Fen Wu
- From the Departments of Internal Medicine
| | | | - Liwei Bao
- From the Departments of Internal Medicine
| | | | | | - Matthew J Merrins
- the Department of Medicine, University of Wisconsin, Madison, Wisconsin 53705, and the William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin 53705
| | - Leslie S Satin
- Pharmacology, University of Michigan, Ann Arbor, Michigan 48109
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Abstract
Type 2 diabetes (T2D) is generally thought to result from the combination of 2 metabolic defects, insulin resistance, which increases the level of insulin required to maintain glucose within the normal range, and failure of insulin-secreting pancreatic β-cells to compensate for the increased demand. We build on a mathematical model pioneered by Topp and colleagues to elucidate how compensation succeeds or fails. Their model added a layer of slow negative feedback to the classic insulin-glucose loop in the form of a slow, glucose-dependent birth and death law governing β-cell mass. We add to that model regulation of 2 aspects of β-cell function on intermediate time scales. The model quantifies the relative contributions of insulin action and insulin secretion defects to T2D and explains why prevention is easier than cure. The latter is a consequence of a threshold separating the normoglycemic and diabetic states (bistability), which also underlies the success of bariatric surgery and acute caloric restriction in rapidly reversing T2D. The threshold concept gives new insight into "Starling's Law of the Pancreas," whereby insulin secretion is higher for prediabetics and early diabetics than for normal individuals.
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Affiliation(s)
- Joon Ha
- Laboratory of Biological Modeling (J.H., A.S.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Pharmacology and Brehm Diabetes Research Center (L.S.S.), University of Michigan, Ann Arbor, Michigan 48105
| | - Leslie S Satin
- Laboratory of Biological Modeling (J.H., A.S.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Pharmacology and Brehm Diabetes Research Center (L.S.S.), University of Michigan, Ann Arbor, Michigan 48105
| | - Arthur S Sherman
- Laboratory of Biological Modeling (J.H., A.S.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Pharmacology and Brehm Diabetes Research Center (L.S.S.), University of Michigan, Ann Arbor, Michigan 48105
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Glynn E, Thompson B, Vadrevu S, Lu S, Kennedy RT, Ha J, Sherman A, Satin LS. Chronic Glucose Exposure Systematically Shifts the Oscillatory Threshold of Mouse Islets: Experimental Evidence for an Early Intrinsic Mechanism of Compensation for Hyperglycemia. Endocrinology 2016; 157:611-23. [PMID: 26697721 PMCID: PMC4733117 DOI: 10.1210/en.2015-1563] [Citation(s) in RCA: 23] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mouse islets exhibit glucose-dependent oscillations in electrical activity, intracellular Ca(2+) and insulin secretion. We developed a mathematical model in which a left shift in glucose threshold helps compensate for insulin resistance. To test this experimentally, we exposed isolated mouse islets to varying glucose concentrations overnight and monitored their glucose sensitivity the next day by measuring intracellular Ca(2+), electrical activity, and insulin secretion. Glucose sensitivity of all oscillation modes was increased when overnight glucose was greater than 2.8mM. To determine whether threshold shifts were a direct effect of glucose or involved secreted insulin, the KATP opener diazoxide (Dz) was coapplied with glucose to inhibit insulin secretion. The addition of Dz or the insulin receptor antagonist s961 increased islet glucose sensitivity, whereas the KATP blocker tolbutamide tended to reduce it. This suggests insulin and glucose have opposing actions on the islet glucose threshold. To test the hypothesis that the threshold shifts were due to changes in plasma membrane KATP channels, we measured cell KATP conductance, which was confirmed to be reduced by high glucose pretreatment and further reduced by Dz. Finally, treatment of INS-1 cells with glucose and Dz overnight reduced high affinity sulfonylurea receptor (SUR1) trafficking to the plasma membrane vs glucose alone, consistent with insulin increasing KATP conductance by altering channel number. The results support a role for metabolically regulated KATP channels in the maintenance of glucose homeostasis.
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Affiliation(s)
- Eric Glynn
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Benjamin Thompson
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Suryakiran Vadrevu
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Shusheng Lu
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Robert T Kennedy
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Joon Ha
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Arthur Sherman
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Leslie S Satin
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
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Alejandro EU, Bozadjieva N, Kumusoglu D, Abdulhamid S, Levine H, Haataja L, Vadrevu S, Satin LS, Arvan P, Bernal-Mizrachi E. Disruption of O-linked N-Acetylglucosamine Signaling Induces ER Stress and β Cell Failure. Cell Rep 2015; 13:2527-2538. [PMID: 26673325 PMCID: PMC4839001 DOI: 10.1016/j.celrep.2015.11.020] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [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] [Received: 06/12/2015] [Revised: 09/22/2015] [Accepted: 11/03/2015] [Indexed: 11/30/2022] Open
Abstract
Nutrient levels dictate the activity of O-linked N-acetylglucosamine transferase (OGT) to regulate O-GlcNAcylation, a post-translational modification mechanism to "fine-tune" intracellular signaling and metabolic status. However, the requirement of O-GlcNAcylation for maintaining glucose homeostasis by regulating pancreatic β cell mass and function is unclear. Here, we reveal that mice lacking β cell OGT (βOGT-KO) develop diabetes and β cell failure. βOGT-KO mice demonstrated increased ER stress and distended ER architecture, and these changes ultimately caused the loss of β cell mass due to ER-stress-induced apoptosis and decreased proliferation. Akt1/2 signaling was also dampened in βOGT-KO islets. The mechanistic role of these processes was demonstrated by rescuing the phenotype of βOGT-KO mice with concomitant Chop gene deletion or genetic reconstitution of Akt2. These findings identify OGT as a regulator of β cell mass and function and provide a direct link between O-GlcNAcylation and β cell survival by regulation of ER stress responses and modulation of Akt1/2 signaling.
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Affiliation(s)
- Emilyn U Alejandro
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Nadejda Bozadjieva
- Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Doga Kumusoglu
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Sarah Abdulhamid
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Hannah Levine
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Leena Haataja
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Suryakiran Vadrevu
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Leslie S Satin
- Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Peter Arvan
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI 48109-0678, USA
| | - Ernesto Bernal-Mizrachi
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI 48109-0678, USA; VA Ann Arbor Healthcare System, Ann Arbor, MI 48109-0678, USA.
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Xu H, Abuhatzira L, Carmona GN, Vadrevu S, Satin LS, Notkins AL. The Ia-2β intronic miRNA, miR-153, is a negative regulator of insulin and dopamine secretion through its effect on the Cacna1c gene in mice. Diabetologia 2015; 58:2298-306. [PMID: 26141787 PMCID: PMC6754265 DOI: 10.1007/s00125-015-3683-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [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] [Received: 12/30/2014] [Accepted: 06/11/2015] [Indexed: 12/23/2022]
Abstract
AIMS/HYPOTHESIS miR-153 is an intronic miRNA embedded in the genes that encode IA-2 (also known as PTPRN) and IA-2β (also known as PTPRN2). Islet antigen (IA)-2 and IA-2β are major autoantigens in type 1 diabetes and are important transmembrane proteins in dense core and synaptic vesicles. miR-153 and its host genes are co-regulated in pancreas and brain. The present experiments were initiated to decipher the regulatory network between miR-153 and its host gene Ia-2β (also known as Ptprn2). METHODS Insulin secretion was determined by ELISA. Identification of miRNA targets was assessed using luciferase assays and by quantitative real-time PCR and western blots in vitro and in vivo. Target protector was also employed to evaluate miRNA target function. RESULTS Functional studies revealed that miR-153 mimic suppresses both glucose- and potassium-induced insulin secretion (GSIS and PSIS, respectively), whereas miR-153 inhibitor enhances both GSIS and PSIS. A similar effect on dopamine secretion also was observed. Using miRNA target prediction software, we found that miR-153 is predicted to target the 3'UTR region of the calcium channel gene, Cacna1c. Further studies confirmed that Cacna1c mRNA and protein are downregulated by miR-153 mimics and upregulated by miR-153 inhibitors in insulin-secreting freshly isolated mouse islets, in the insulin-secreting mouse cell line MIN6 and in the dopamine-secreting cell line PC12. CONCLUSIONS/INTERPRETATION miR-153 is a negative regulator of both insulin and dopamine secretion through its effect on Cacna1c expression, which suggests that IA-2β and miR-153 have opposite functional effects on the secretory pathway.
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Affiliation(s)
- Huanyu Xu
- Experimental Medicine Section, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Liron Abuhatzira
- Experimental Medicine Section, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Gilberto N Carmona
- Experimental Medicine Section, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Suryakiran Vadrevu
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Leslie S Satin
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Abner L Notkins
- Experimental Medicine Section, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA.
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Satin LS, Schnell S. Evidence for Residual and Partly Reparable Insulin Secretory Function and Maintained β-Cell Gene Expression in Islets From Patients With Type 1 Diabetes. Diabetes 2015; 64:2335-7. [PMID: 26106195 PMCID: PMC4477347 DOI: 10.2337/db15-0434] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Leslie S Satin
- Department of Pharmacology, Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, MI
| | - Santiago Schnell
- Department of Molecular & Integrative Physiology, Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, MI
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Watts M, Fendler B, Merrins MJ, Satin LS, Bertram R, Sherman A. Calcium and Metabolic Oscillations in Pancreatic Islets: Who's Driving the Bus? *. SIAM J Appl Dyn Syst 2015; 13:683-703. [PMID: 25698909 PMCID: PMC4331037 DOI: 10.1137/130920198] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Pancreatic islets exhibit bursting oscillations in response to elevated blood glucose. These oscillations are accompanied by oscillations in the free cytosolic Ca2+ concentration (Cac ), which drives pulses of insulin secretion. Both islet Ca2+ and metabolism oscillate, but there is some debate about their interrelationship. Recent experimental data show that metabolic oscillations in some cases persist after the addition of diazoxide (Dz), which opens K(ATP) channels, hyperpolarizing β-cells and preventing Ca2+ entry and Ca2+ oscillations. Further, in some islets in which metabolic oscillations were eliminated with Dz, increasing the cytosolic Ca2+ concentration by the addition of KCl could restart the metabolic oscillations. Here we address why metabolic oscillations persist in some islets but not others, and why raising Cac restarts oscillations in some islets but not others. We answer these questions using the dual oscillator model (DOM) for pancreatic islets. The DOM can reproduce the experimental data and shows that the model supports two different mechanisms for slow metabolic oscillations, one that requires calcium oscillations and one that does not.
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Affiliation(s)
- Margaret Watts
- National Institutes of Health, Bethesda, MD 20892. The first and sixth authors’ research was supported by the NIH/NIDDK Intramural Research Program
| | - Bernard Fendler
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724. This author’s research was supported by the Simons Foundation and the Starr Cancer Consortium (I3-A123)
| | - Matthew J. Merrins
- University of Michigan, Ann Arbor, MI 48105. The third author’s research was supported by the National Institutes of Health (F32-DK085960), and the fourth author’s research was supported by the National Institutes of Health (R01-DK46409)
| | - Leslie S. Satin
- University of Michigan, Ann Arbor, MI 48105. The third author’s research was supported by the National Institutes of Health (F32-DK085960), and the fourth author’s research was supported by the National Institutes of Health (R01-DK46409)
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, FL 32306. This author’s research was supported by the National Institutes of Health (DK080714)
| | - Arthur Sherman
- National Institutes of Health, Bethesda, MD 20892. The first and sixth authors’ research was supported by the NIH/NIDDK Intramural Research Program
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Vadrevu S, Ren J, Zhang M, Glynn EJ, Sherman A, Satin LS. Kir2.1 Channels Compensate for the Loss of KATP Channels in SUR1 Null Islets. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.2375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Benninger RKP, Hutchens T, Head WS, McCaughey MJ, Zhang M, Le Marchand SJ, Satin LS, Piston DW. Intrinsic islet heterogeneity and gap junction coupling determine spatiotemporal Ca²⁺ wave dynamics. Biophys J 2014; 107:2723-33. [PMID: 25468351 DOI: 10.1016/j.bpj.2014.10.048] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 09/09/2014] [Accepted: 10/08/2014] [Indexed: 10/24/2022] Open
Abstract
Insulin is released from the islets of Langerhans in discrete pulses that are linked to synchronized oscillations of intracellular free calcium ([Ca(2+)]i). Associated with each synchronized oscillation is a propagating calcium wave mediated by Connexin36 (Cx36) gap junctions. A computational islet model predicted that waves emerge due to heterogeneity in β-cell function throughout the islet. To test this, we applied defined patterns of glucose stimulation across the islet using a microfluidic device and measured how these perturbations affect calcium wave propagation. We further investigated how gap junction coupling regulates spatiotemporal [Ca(2+)]i dynamics in the face of heterogeneous glucose stimulation. Calcium waves were found to originate in regions of the islet having elevated excitability, and this heterogeneity is an intrinsic property of islet β-cells. The extent of [Ca(2+)]i elevation across the islet in the presence of heterogeneity is gap-junction dependent, which reveals a glucose dependence of gap junction coupling. To better describe these observations, we had to modify the computational islet model to consider the electrochemical gradient between neighboring β-cells. These results reveal how the spatiotemporal [Ca(2+)]i dynamics of the islet depend on β-cell heterogeneity and cell-cell coupling, and are important for understanding the regulation of coordinated insulin release across the islet.
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Affiliation(s)
- Richard K P Benninger
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee; Department of Bioengineering, University of Colorado, Aurora, Colorado; Barbara Davis Center, University of Colorado, Aurora, Colorado.
| | - Troy Hutchens
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee
| | - W Steven Head
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Michael J McCaughey
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Min Zhang
- Department of Pharmacology, Virginia Commonwealth University, Richmond, Virginia
| | - Sylvain J Le Marchand
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Leslie S Satin
- Department of Pharmacology, Virginia Commonwealth University, Richmond, Virginia; Department of Pharmacology, University of Michigan, Ann Arbor, Michigan; Brehm Diabetes Center, University of Michigan, Ann Arbor, Michigan
| | - David W Piston
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee.
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Johnson JS, Kono T, Tong X, Yamamoto WR, Zarain-Herzberg A, Merrins MJ, Satin LS, Gilon P, Evans-Molina C. Pancreatic and duodenal homeobox protein 1 (Pdx-1) maintains endoplasmic reticulum calcium levels through transcriptional regulation of sarco-endoplasmic reticulum calcium ATPase 2b (SERCA2b) in the islet β cell. J Biol Chem 2014; 289:32798-810. [PMID: 25271154 DOI: 10.1074/jbc.m114.575191] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [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: 12/25/2022] Open
Abstract
Although the pancreatic duodenal homeobox 1 (Pdx-1) transcription factor is known to play an indispensable role in β cell development and secretory function, recent data also implicate Pdx-1 in the maintenance of endoplasmic reticulum (ER) health. The sarco-endoplasmic reticulum Ca(2+) ATPase 2b (SERCA2b) pump maintains a steep Ca(2+) gradient between the cytosol and ER lumen. In models of diabetes, our data demonstrated loss of β cell Pdx-1 that occurs in parallel with altered SERCA2b expression, whereas in silico analysis of the SERCA2b promoter revealed multiple putative Pdx-1 binding sites. We hypothesized that Pdx-1 loss under inflammatory and diabetic conditions leads to decreased SERCA2b levels and activity with concomitant alterations in ER health. To test this, siRNA-mediated knockdown of Pdx-1 was performed in INS-1 cells. The results revealed reduced SERCA2b expression and decreased ER Ca(2+), which was measured using fluorescence lifetime imaging microscopy. Cotransfection of human Pdx-1 with a reporter fused to the human SERCA2 promoter increased luciferase activity 3- to 4-fold relative to an empty vector control, and direct binding of Pdx-1 to the proximal SERCA2 promoter was confirmed by chromatin immunoprecipitation. To determine whether restoration of SERCA2b could rescue ER stress induced by Pdx-1 loss, Pdx1(+/-) mice were fed a high-fat diet. Isolated islets demonstrated an increased spliced-to-total Xbp1 ratio, whereas SERCA2b overexpression reduced the Xbp1 ratio to that of wild-type controls. Together, these results identify SERCA2b as a novel transcriptional target of Pdx-1 and define a role for altered ER Ca(2+) regulation in Pdx-1-deficient states.
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Affiliation(s)
| | | | - Xin Tong
- Cellular and Integrative Physiology and
| | | | - Angel Zarain-Herzberg
- the Departamento de Bioquimica, Facultad de Medicina, National Autonomous University of México, México City, 04510 México
| | - Matthew J Merrins
- the Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, and Department of Biomolecular Chemistry, University of Wisconsin Madison School of Medicine and Public Health, Madison, Wisconsin 53705
| | - Leslie S Satin
- the Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Patrick Gilon
- the Pôle d'Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, 1348 Belgium, and
| | - Carmella Evans-Molina
- From the Departments of Biochemistry and Molecular Biology, Medicine, and Cellular and Integrative Physiology and the Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202, the Roudebush Veterans Affairs Medical Center, Indianapolis, Indiana 46202
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Alejandro EU, Gregg B, Wallen T, Kumusoglu D, Meister D, Chen A, Merrins MJ, Satin LS, Liu M, Arvan P, Bernal-Mizrachi E. Maternal diet-induced microRNAs and mTOR underlie β cell dysfunction in offspring. J Clin Invest 2014; 124:4395-410. [PMID: 25180600 DOI: 10.1172/jci74237] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 07/24/2014] [Indexed: 01/07/2023] Open
Abstract
A maternal diet that is low in protein increases the susceptibility of offspring to type 2 diabetes by inducing long-term alterations in β cell mass and function. Nutrients and growth factor signaling converge through mTOR, suggesting that this pathway participates in β cell programming during fetal development. Here, we revealed that newborns of dams exposed to low-protein diet (LP0.5) throughout pregnancy exhibited decreased insulin levels, a lower β cell fraction, and reduced mTOR signaling. Adult offspring of LP0.5-exposed mothers exhibited glucose intolerance as a result of an insulin secretory defect and not β cell mass reduction. The β cell insulin secretory defect was distal to glucose-dependent Ca2+ influx and resulted from reduced proinsulin biosynthesis and insulin content. Islets from offspring of LP0.5-fed dams exhibited reduced mTOR and increased expression of a subset of microRNAs, and blockade of microRNA-199a-3p and -342 in these islets restored mTOR and insulin secretion to normal. Finally, transient β cell activation of mTORC1 signaling in offspring during the last week of pregnancy of mothers fed a LP0.5 rescued the defect in the neonatal β cell fraction and metabolic abnormalities in the adult. Together, these findings indicate that a maternal low-protein diet alters microRNA and mTOR expression in the offspring, influencing insulin secretion and glucose homeostasis.
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Abstract
Rhythms govern many endocrine functions. Examples of such rhythmic systems include the insulin-secreting pancreatic beta-cell, which regulates blood glucose, and the gonadotropin-releasing hormone (GnRH) neuron, which governs reproductive function. Although serving very different functions within the body, these cell types share many important features. Both GnRH neurons and beta-cells, for instance, are hypothesized to generate at least two rhythms endogenously: (1) a burst firing electrical rhythm and (2) a slower rhythm involving metabolic or other intracellular processes. This review discusses the importance of hormone rhythms to both physiology and disease and compares and contrasts the rhythms generated by each system.
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Affiliation(s)
- Craig S. Nunemaker
- Division of Endocrinology and Metabolism, Department of, Medicine, University of Virginia, P.O. Box 801413, Charlottesville, VA 22901, USA,
| | - Leslie S. Satin
- Pharmacology Department, University of Michigan Medical School, 5128 Brehm Tower, Ann Arbor, MI 48105, USA
- Brehm Diabetes Research Center, University of Michigan, Medical School, 5128 Brehm Tower, Ann Arbor, MI 48105, USA
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Merrins MJ, Satin LS. Ca2+ has a Permissive Effect on Glycolytic Oscillations in Pancreatic Beta Cells. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.2937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Merrins MJ, Van Dyke AR, Mapp AK, Rizzo MA, Satin LS. Direct measurements of oscillatory glycolysis in pancreatic islet β-cells using novel fluorescence resonance energy transfer (FRET) biosensors for pyruvate kinase M2 activity. J Biol Chem 2013; 288:33312-22. [PMID: 24100037 DOI: 10.1074/jbc.m113.508127] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [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: 01/05/2023] Open
Abstract
Pulses of insulin released from pancreatic β-cells maintain blood glucose in a narrow range, although the source of these pulses is unclear. We and others have proposed that positive feedback mediated by the glycolytic enzyme phosphofructokinase-1 (PFK1) enables β-cells to generate metabolic oscillations via autocatalytic activation by its product fructose 1,6-bisphosphate (FBP). Although much indirect evidence has accumulated in favor of this hypothesis, a direct measurement of oscillating glycolytic intermediates has been lacking. To probe glycolysis directly, we engineered a family of inter- and intramolecular FRET biosensors based on the glycolytic enzyme pyruvate kinase M2 (PKAR; pyruvate kinase activity reporter), which multimerizes and is activated upon binding FBP. When introduced into Min6 β-cells, PKAR FRET efficiency increased rapidly in response to glucose. Importantly, however, metabolites entering downstream of PFK1 (glyceraldehyde, pyruvate, and ketoisocaproate) failed to activate PKAR, consistent with sensor activation by FBP; the dependence of PKAR on FBP was further confirmed using purified sensor in vitro. Using a novel imaging modality for monitoring mitochondrial flavin fluorescence in mouse islets, we show that slow oscillations in mitochondrial redox potential stimulated by 10 mm glucose are in phase with glycolytic efflux through PKM2, measured simultaneously from neighboring islet β-cells expressing PKAR. These results indicate that PKM2 activity in β-cells is oscillatory and are consistent with pulsatile PFK1 being the mediator of slow glycolytic oscillations.
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Affiliation(s)
- Matthew J Merrins
- From the Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan 48105
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Ren J, Sherman A, Bertram R, Goforth PB, Nunemaker CS, Waters CD, Satin LS. Slow oscillations of KATP conductance in mouse pancreatic islets provide support for electrical bursting driven by metabolic oscillations. Am J Physiol Endocrinol Metab 2013; 305:E805-17. [PMID: 23921138 PMCID: PMC3798703 DOI: 10.1152/ajpendo.00046.2013] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [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: 01/19/2023]
Abstract
We used the patch clamp technique in situ to test the hypothesis that slow oscillations in metabolism mediate slow electrical oscillations in mouse pancreatic islets by causing oscillations in KATP channel activity. Total conductance was measured over the course of slow bursting oscillations in surface β-cells of islets exposed to 11.1 mM glucose by either switching from current clamp to voltage clamp at different phases of the bursting cycle or by clamping the cells to -60 mV and running two-second voltage ramps from -120 to -50 mV every 20 s. The membrane conductance, calculated from the slopes of the ramp current-voltage curves, oscillated and was larger during the silent phase than during the active phase of the burst. The ramp conductance was sensitive to diazoxide, and the oscillatory component was reduced by sulfonylureas or by lowering extracellular glucose to 2.8 mM, suggesting that the oscillatory total conductance is due to oscillatory KATP channel conductance. We demonstrate that these results are consistent with the Dual Oscillator model, in which glycolytic oscillations drive slow electrical bursting, but not with other models in which metabolic oscillations are secondary to calcium oscillations. The simulations also confirm that oscillations in membrane conductance can be well estimated from measurements of slope conductance and distinguished from gap junction conductance. Furthermore, the oscillatory conductance was blocked by tolbutamide in isolated β-cells. The data, combined with insights from mathematical models, support a mechanism of slow (∼5 min) bursting driven by oscillations in metabolism, rather than by oscillations in the intracellular free calcium concentration.
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Affiliation(s)
- Jianhua Ren
- Department of Pharmacology and Brehm Diabetes Center, University of Michigan Medical School, Ann Arbor, Michigan
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Ferrario CR, Ndukwe BO, Ren J, Satin LS, Goforth PB. Stretch injury selectively enhances extrasynaptic, GluN2B-containing NMDA receptor function in cortical neurons. J Neurophysiol 2013; 110:131-40. [PMID: 23576693 DOI: 10.1152/jn.01011.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alterations in the function and expression of NMDA receptors are observed after in vivo and in vitro traumatic brain injury. We recently reported that mechanical stretch injury in cortical neurons transiently increases the contribution of NMDA receptors to network activity and results in an increase in calcium-permeable AMPA (CP-AMPA) receptor-mediated transmission 4 h postinjury (Goforth et al. 2011). Here, we evaluated changes in the function of synaptic vs. extrasynaptic GluN2B-containing NMDA receptors after injury. We also determined whether postinjury treatment with the GluN2B-selective antagonist Ro 25-6981 or memantine prevents injury-induced increases in CP-AMPA receptor activity. We found that injury increased extrasynaptic, GluN2B-containing NMDA receptor-mediated whole cell currents. In contrast, we found no differences in synaptic NMDA receptor-mediated transmission after injury. Furthermore, treatment with Ro 25-6981 or memantine after injury prevented injury-induced increases in CP-AMPA receptor-mediated activity. Together, our data suggest that increased NMDA receptor activity after injury is predominantly due to alterations in extrasynaptic, GluN2B-containing NMDA receptors and that activation of these receptors may contribute to the appearance of CP-AMPA receptors after injury.
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Affiliation(s)
- Carrie R Ferrario
- Department of Pharmacology, The University of Michigan, Ann Arbor, Michigan 48105, USA
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Merrins MJ, Kim SY, Rane SG, Satin LS. Cyclin Dependent Kinase 2 (CDK2) Regulates Secretory Function in Pancreatic Beta-Cells. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.3435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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