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Dobson JR, Jacobson DA. Disrupted Endoplasmic Reticulum Ca 2+ Handling: A Harβinger of β-Cell Failure. BIOLOGY 2024; 13:379. [PMID: 38927260 PMCID: PMC11200644 DOI: 10.3390/biology13060379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 05/17/2024] [Accepted: 05/17/2024] [Indexed: 06/28/2024]
Abstract
The β-cell workload increases in the setting of insulin resistance and reduced β-cell mass, which occurs in type 2 and type 1 diabetes, respectively. The prolonged elevation of insulin production and secretion during the pathogenesis of diabetes results in β-cell ER stress. The depletion of β-cell Ca2+ER during ER stress activates the unfolded protein response, leading to β-cell dysfunction. Ca2+ER is involved in many pathways that are critical to β-cell function, such as protein processing, tuning organelle and cytosolic Ca2+ handling, and modulating lipid homeostasis. Mutations that promote β-cell ER stress and deplete Ca2+ER stores are associated with or cause diabetes (e.g., mutations in ryanodine receptors and insulin). Thus, improving β-cell Ca2+ER handling and reducing ER stress under diabetogenic conditions could preserve β-cell function and delay or prevent the onset of diabetes. This review focuses on how mechanisms that control β-cell Ca2+ER are perturbed during the pathogenesis of diabetes and contribute to β-cell failure.
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Affiliation(s)
| | - David A. Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA;
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2
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Ramanadham S, Turk J, Bhatnagar S. Noncanonical Regulation of cAMP-Dependent Insulin Secretion and Its Implications in Type 2 Diabetes. Compr Physiol 2023; 13:5023-5049. [PMID: 37358504 PMCID: PMC10809800 DOI: 10.1002/cphy.c220031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
Abstract
Impaired glucose tolerance (IGT) and β-cell dysfunction in insulin resistance associated with obesity lead to type 2 diabetes (T2D). Glucose-stimulated insulin secretion (GSIS) from β-cells occurs via a canonical pathway that involves glucose metabolism, ATP generation, inactivation of K ATP channels, plasma membrane depolarization, and increases in cytosolic concentrations of [Ca 2+ ] c . However, optimal insulin secretion requires amplification of GSIS by increases in cyclic adenosine monophosphate (cAMP) signaling. The cAMP effectors protein kinase A (PKA) and exchange factor activated by cyclic-AMP (Epac) regulate membrane depolarization, gene expression, and trafficking and fusion of insulin granules to the plasma membrane for amplifying GSIS. The widely recognized lipid signaling generated within β-cells by the β-isoform of Ca 2+ -independent phospholipase A 2 enzyme (iPLA 2 β) participates in cAMP-stimulated insulin secretion (cSIS). Recent work has identified the role of a G-protein coupled receptor (GPCR) activated signaling by the complement 1q like-3 (C1ql3) secreted protein in inhibiting cSIS. In the IGT state, cSIS is attenuated, and the β-cell function is reduced. Interestingly, while β-cell-specific deletion of iPLA 2 β reduces cAMP-mediated amplification of GSIS, the loss of iPLA 2 β in macrophages (MØ) confers protection against the development of glucose intolerance associated with diet-induced obesity (DIO). In this article, we discuss canonical (glucose and cAMP) and novel noncanonical (iPLA 2 β and C1ql3) pathways and how they may affect β-cell (dys)function in the context of impaired glucose intolerance associated with obesity and T2D. In conclusion, we provide a perspective that in IGT states, targeting noncanonical pathways along with canonical pathways could be a more comprehensive approach for restoring β-cell function in T2D. © 2023 American Physiological Society. Compr Physiol 13:5023-5049, 2023.
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Affiliation(s)
- Sasanka Ramanadham
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Alabama, USA
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Alabama, USA
| | - John Turk
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Sushant Bhatnagar
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Alabama, USA
- Department of Medicine, University of Alabama at Birmingham, Alabama, USA
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Lin S, Chen C, Ouyang P, Cai Z, Liu X, Abdurahman A, Peng J, Li Y, Zhang Z, Song GL. SELENOM Knockout Induces Synaptic Deficits and Cognitive Dysfunction by Influencing Brain Glucose Metabolism. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:1607-1619. [PMID: 36635091 DOI: 10.1021/acs.jafc.2c07491] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Selenium, a trace element associated with memory impairment and glucose metabolism, mainly exerts its function through selenoproteins. SELENOM is a selenoprotein located in the endoplasmic reticulum (ER) lumen. Our study demonstrates for the first time that SELENOM knockout decreases synaptic plasticity and causes memory impairment in 10-month-old mice. In addition, SELENOM knockout causes hyperglycaemia and disturbs glucose metabolism, which is essential for synapse formation and transmission in the brain. Further research reveals that SELENOM knockout leads to inhibition of the brain insulin signaling pathway [phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR/p70 S6 kinase pathway], which may impair synaptic plasticity in mice. High-fat diet (HFD) feeding suppresses the brain insulin signaling pathway in SELENOM knockout mice and leads to earlier onset of cognitive impairment at 5 months of age. In general, our study demonstrates that SELENOM knockout induces synaptic deficits via the brain insulin signaling pathway, thus leading to cognitive dysfunction in mice. These data strongly suggest that SELENOM plays a vital role in brain glucose metabolism and contributes substantially to synaptic plasticity.
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Affiliation(s)
- Shujing Lin
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
- Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong518000, People's Republic of China
| | - Chen Chen
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
| | - Pei Ouyang
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
| | - Zhiyu Cai
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
| | - Xibei Liu
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
| | - Anwar Abdurahman
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
| | - Jiaying Peng
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
| | - Yu Li
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
| | - Zhonghao Zhang
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
| | - Guo-Li Song
- Shenzhen Key Laboratory of Marine Bioresources and Ecology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong518060, People's Republic of China
- Shenzhen Bay Laboratory, Shenzhen, Guangdong518000, People's Republic of China
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Wen XP, Wan QQ. Regulatory effect of insulin on the structure, function and metabolism of Na +/K +-ATPase (Review). Exp Ther Med 2021; 22:1243. [PMID: 34539839 PMCID: PMC8438676 DOI: 10.3892/etm.2021.10678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 08/04/2021] [Indexed: 11/14/2022] Open
Abstract
Na+/K+-ATPase is an ancient enzyme, the role of which is to maintain Na+ and K+ gradients across cell membranes, thus preserving intracellular ion homeostasis. The regulation of Na+/K+-ATPase is affected by several regulatory factors through a number of pathways, with hormones serving important short-term and long-term regulatory functions. Na+/K+-ATPase can also be degraded through activation of the ubiquitin proteasome and autophagy-lysosomal pathways, thereby affecting its abundance and enzymatic activity. As regards the regulatory effect of insulin, it has been found to upregulate the relative abundance of Na+/K+-ATPase and restore the transport efficiency in multiple in vitro and in vivo experiments. Therefore, elucidating the role of insulin in the regulation Na+/K+-ATPase may help uncover new drug targets for the treatment of related diseases. The aim of the present study was to review the structure and function of Na+/K+-ATPase and to discuss the possible mechanisms through which it may be regulated by insulin, in order to investigate the possibility of designing new therapies for related diseases.
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Affiliation(s)
- Xu-Peng Wen
- Transplantation Center, The Third Xiangya Hospital, Central South University, Changsha, Hunan 410013, P.R. China
| | - Qi-Quan Wan
- Transplantation Center, The Third Xiangya Hospital, Central South University, Changsha, Hunan 410013, P.R. China
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5
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Calcium Signaling in ß-cell Physiology and Pathology: A Revisit. Int J Mol Sci 2019; 20:ijms20246110. [PMID: 31817135 PMCID: PMC6940736 DOI: 10.3390/ijms20246110] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 11/28/2019] [Accepted: 12/02/2019] [Indexed: 12/12/2022] Open
Abstract
Pancreatic beta (β) cell dysfunction results in compromised insulin release and, thus, failed regulation of blood glucose levels. This forms the backbone of the development of diabetes mellitus (DM), a disease that affects a significant portion of the global adult population. Physiological calcium (Ca2+) signaling has been found to be vital for the proper insulin-releasing function of β-cells. Calcium dysregulation events can have a dramatic effect on the proper functioning of the pancreatic β-cells. The current review discusses the role of calcium signaling in health and disease in pancreatic β-cells and provides an in-depth look into the potential role of alterations in β-cell Ca2+ homeostasis and signaling in the development of diabetes and highlights recent work that introduced the current theories on the connection between calcium and the onset of diabetes.
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Schaar A, Sun Y, Sukumaran P, Rosenberger TA, Krout D, Roemmich JN, Brinbaumer L, Claycombe-Larson K, Singh BB. Ca 2+ entry via TRPC1 is essential for cellular differentiation and modulates secretion via the SNARE complex. J Cell Sci 2019; 132:jcs.231878. [PMID: 31182642 PMCID: PMC6633397 DOI: 10.1242/jcs.231878] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 05/27/2019] [Indexed: 12/17/2022] Open
Abstract
Properties of adipocytes, including differentiation and adipokine secretion, are crucial factors in obesity-associated metabolic syndrome. Here, we provide evidence that Ca2+ influx in primary adipocytes, especially upon Ca2+ store depletion, plays an important role in adipocyte differentiation, functionality and subsequently metabolic regulation. The endogenous Ca2+ entry channel in both subcutaneous and visceral adipocytes was found to be dependent on TRPC1–STIM1, and blocking Ca2+ entry with SKF96365 or using TRPC1−/− knockdown adipocytes inhibited adipocyte differentiation. Additionally, TRPC1−/− mice have decreased organ weight, but increased adipose deposition and reduced serum adiponectin and leptin concentrations, without affecting total adipokine expression. Mechanistically, TRPC1-mediated Ca2+ entry regulated SNARE complex formation, and agonist-mediated secretion of adipokine-loaded vesicles was inhibited in TRPC1−/− adipose. These results suggest an unequivocal role of TRPC1 in adipocyte differentiation and adiponectin secretion, and that loss of TRPC1 disturbs metabolic homeostasis. This article has an associated First Person interview with the first author of the paper. Summary: TRPC1 modulates Ca2+ entry, which is essential in adipocyte differentiation and adiponectin secretion, through facilitating SNARE complex formation, thereby maintaining metabolic homeostasis.
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Affiliation(s)
- Anne Schaar
- Department of Biomedical Science, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA
| | - Yuyang Sun
- Department of Biomedical Science, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA
| | - Pramod Sukumaran
- Department of Biomedical Science, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA
| | - Thad A Rosenberger
- Department of Biomedical Science, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA
| | - Danielle Krout
- US Department of Agriculture-Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58203, USA
| | - James N Roemmich
- US Department of Agriculture-Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58203, USA
| | - Lutz Brinbaumer
- Neurobiology Laboratory, NIHES, NIH, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA.,Institute of Biomedical Research, (BIOMED) Catholic University of Argentina, Av. Alicia Moreau de Justo 1300, Edificio San Jose Piso 3, Buenos Aires C1107AAZ, Argentina
| | - Kate Claycombe-Larson
- US Department of Agriculture-Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58203, USA
| | - Brij B Singh
- Department of Biomedical Science, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA
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Sabatini PV, Speckmann T, Lynn FC. Friend and foe: β-cell Ca 2+ signaling and the development of diabetes. Mol Metab 2019; 21:1-12. [PMID: 30630689 PMCID: PMC6407368 DOI: 10.1016/j.molmet.2018.12.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 12/03/2018] [Accepted: 12/19/2018] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND The divalent cation Calcium (Ca2+) regulates a wide range of processes in disparate cell types. Within insulin-producing β-cells, increases in cytosolic Ca2+ directly stimulate insulin vesicle exocytosis, but also initiate multiple signaling pathways. Mediated through activation of downstream kinases and transcription factors, Ca2+-regulated signaling pathways leverage substantial influence on a number of critical cellular processes within the β-cell. Additionally, there is evidence that prolonged activation of these same pathways is detrimental to β-cell health and may contribute to Type 2 Diabetes pathogenesis. SCOPE OF REVIEW This review aims to briefly highlight canonical Ca2+ signaling pathways in β-cells and how β-cells regulate the movement of Ca2+ across numerous organelles and microdomains. As a main focus, this review synthesizes experimental data from in vitro and in vivo models on both the beneficial and detrimental effects of Ca2+ signaling pathways for β-cell function and health. MAJOR CONCLUSIONS Acute increases in intracellular Ca2+ stimulate a number of signaling cascades, resulting in (de-)phosphorylation events and activation of downstream transcription factors. The short-term stimulation of these Ca2+ signaling pathways promotes numerous cellular processes critical to β-cell function, including increased viability, replication, and insulin production and secretion. Conversely, chronic stimulation of Ca2+ signaling pathways increases β-cell ER stress and results in the loss of β-cell differentiation status. Together, decades of study demonstrate that Ca2+ movement is tightly regulated within the β-cell, which is at least partially due to its dual roles as a potent signaling molecule.
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Affiliation(s)
- Paul V Sabatini
- Diabetes Research Group, BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada; Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada; Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Thilo Speckmann
- Diabetes Research Group, BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada; Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Francis C Lynn
- Diabetes Research Group, BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada; Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada; Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
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8
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Jayanarayanan S, Anju TR, Smijin S, Paulose CS. Vitamin D3 supplementation increases insulin level by regulating altered IP3 and AMPA receptor expression in the pancreatic islets of streptozotocin-induced diabetic rat. J Nutr Biochem 2015; 26:1041-9. [PMID: 26054778 DOI: 10.1016/j.jnutbio.2015.04.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 04/13/2015] [Accepted: 04/26/2015] [Indexed: 12/17/2022]
Abstract
Pancreatic islets, particularly insulin-secreting β cells, share common characteristics with neurons. Glutamate is one of the major excitatory neurotransmitter in the brain and pancreas, and its action is mediated through glutamate receptors. In the present work, we analysed the role of vitamin D3 in the modulation of AMPA receptor subunit and their functional role in insulin release. Radio receptor binding study in diabetic rats showed a significant increase in AMPA receptor density. Insulin AMPA colabelling study showed an altered AMPA GluR2 and GluR4 subunit expression in the pancreatic beta cells. We also found lowered IP3 content and decreased IP3 receptor in pancreas of diabetic rats. The alterations in AMPA and IP3 receptor resulted in reduced cytosolic calcium level concentration, which further blocks Ca(2+)-mediated insulin release. Vitamin D3 supplementation restored the alteration in vitamin D receptor expression, AMPA receptor density and AMPA and IP3 receptor expression in the pancreatic islets that helps to restore the calcium-mediated insulin secretion. Our study reveals the antidiabetic property of vitamin D3 that is suggested to have therapeutic role through regulating glutamatergic function in diabetic rats.
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Affiliation(s)
- Sadanandan Jayanarayanan
- Molecular Neurobiology and Cell Biology Unit, Centre for Neuroscience, Cochin University of Science and Technology, Cochin, 682 022, Kerala, India
| | - Thoppil R Anju
- Molecular Neurobiology and Cell Biology Unit, Centre for Neuroscience, Cochin University of Science and Technology, Cochin, 682 022, Kerala, India
| | - Soman Smijin
- Molecular Neurobiology and Cell Biology Unit, Centre for Neuroscience, Cochin University of Science and Technology, Cochin, 682 022, Kerala, India
| | - Cheramadathikudiyil Skaria Paulose
- Molecular Neurobiology and Cell Biology Unit, Centre for Neuroscience, Cochin University of Science and Technology, Cochin, 682 022, Kerala, India.
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9
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Liang K, Du W, Lu J, Li F, Yang L, Xue Y, Hille B, Chen L. Alterations of the Ca²⁺ signaling pathway in pancreatic beta-cells isolated from db/db mice. Protein Cell 2014; 5:783-94. [PMID: 25053525 PMCID: PMC4180459 DOI: 10.1007/s13238-014-0075-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 04/20/2014] [Indexed: 11/16/2022] Open
Abstract
Upon glucose elevation, pancreatic beta-cells secrete insulin in a Ca2+-dependent manner. In diabetic animal models, different aspects of the calcium signaling pathway in beta-cells are altered, but there is no consensus regarding their relative contributions to the development of beta-cell dysfunction. In this study, we compared the increase in cytosolic Ca2+ ([Ca2+]i) via Ca2+ influx, Ca2+ mobilization from endoplasmic reticulum (ER) calcium stores, and the removal of Ca2+ via multiple mechanisms in beta-cells from both diabetic db/db mice and non-diabetic C57BL/6J mice. We refined our previous quantitative model to describe the slow [Ca2+]i recovery after depolarization in beta-cells from db/db mice. According to the model, the activity levels of the two subtypes of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) pump, SERCA2 and SERCA3, were severely down-regulated in diabetic cells to 65% and 0% of the levels in normal cells. This down-regulation may lead to a reduction in the Ca2+ concentration in the ER, a compensatory up-regulation of the plasma membrane Na+/Ca2+ exchanger (NCX) and a reduction in depolarization-evoked Ca2+ influx. As a result, the patterns of glucose-stimulated calcium oscillations were significantly different in db/db diabetic beta-cells compared with normal cells. Overall, quantifying the changes in the calcium signaling pathway in db/db diabetic beta-cells will aid in the development of a disease model that could provide insight into the adaptive transformations of beta-cell function during diabetes development.
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Affiliation(s)
- Kuo Liang
- Department of General Surgery, XuanWu Hospital, Capital Medical University, Beijing, 100053, China
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10
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Sun T, Guo J, Chen H, Zhang J, Zhang X, Jiang X, Wang F, Xu Z, Huang X, Sha J, Chan HC. Maternal caffeine exposure impairs insulin secretion by pancreatic β-cells and increases the risk of type II diabetes mellitus in offspring. Cell Biol Int 2014; 38:1183-93. [DOI: 10.1002/cbin.10321] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 04/25/2014] [Indexed: 12/31/2022]
Affiliation(s)
- Tingting Sun
- Epithelial Cell Biology Research Centre; School of Biomedical Sciences; The Chinese University of Hong Kong; Shatin NT Hong Kong
| | - Jinghui Guo
- Epithelial Cell Biology Research Centre; School of Biomedical Sciences; The Chinese University of Hong Kong; Shatin NT Hong Kong
| | - Hui Chen
- Epithelial Cell Biology Research Centre; School of Biomedical Sciences; The Chinese University of Hong Kong; Shatin NT Hong Kong
| | - Jieting Zhang
- Epithelial Cell Biology Research Centre; School of Biomedical Sciences; The Chinese University of Hong Kong; Shatin NT Hong Kong
| | - Xiaohu Zhang
- Epithelial Cell Biology Research Centre; School of Biomedical Sciences; The Chinese University of Hong Kong; Shatin NT Hong Kong
| | - Xiaohua Jiang
- Epithelial Cell Biology Research Centre; School of Biomedical Sciences; The Chinese University of Hong Kong; Shatin NT Hong Kong
| | - Fuqiang Wang
- Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing 210029 China
| | - Zhiyang Xu
- Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing 210029 China
| | - Xiaoyan Huang
- Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing 210029 China
| | - Jiahao Sha
- Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing 210029 China
| | - Hsiao Chang Chan
- Epithelial Cell Biology Research Centre; School of Biomedical Sciences; The Chinese University of Hong Kong; Shatin NT Hong Kong
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Abstract
Zinc (Zn2+) is an essential element crucial for growth and development, and also plays a role in cell signaling for cellular processes like cell division and apoptosis. In the mammalian pancreas, Zn2+ is essential for the correct processing, storage, secretion, and action of insulin in beta (β)-cells. Insulin is stored inside secretory vesicles or granules, where two Zn2+ ions coordinate six insulin monomers to form the hexameric-structure on which maturated insulin crystals are based. The total Zn2+ content of the mammalian pancreas is among the highest in the body, and Zn2+ concentration reach millimolar levels in the interior of the dense-core granule. Changes in Zn2+ levels in the pancreas have been found to be associated with diabetes. Hence, the relationship between co-stored Zn2+ and insulin undoubtedly is critical to normal β-cell function. The advances in the field of Zn2+ biology over the last decade have facilitated our understanding of Zn2+ trafficking, its intracellular distribution and its storage. When exocytosis of insulin occurs, insulin granules fuse with the β-cell plasma membrane and release their contents, i.e., insulin as well as substantial amount of free Zn2+, into the extracellular space and the local circulation. Studies increasingly indicate that secreted Zn2+ has autocrine or paracrine signaling in β-cells or the neighboring cells. This review discusses the Zn2+ homeostasis in β-cells with emphasis on the potential signaling role of Zn2+ to islet biology.
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Affiliation(s)
- Yang V Li
- Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, 346 Irvine Hall, Athens, OH, 45701, USA,
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12
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Liang K, Du W, Zhu W, Liu S, Cui Y, Sun H, Luo B, Xue Y, Yang L, Chen L, Li F. Contribution of different mechanisms to pancreatic beta-cell hyper-secretion in non-obese diabetic (NOD) mice during pre-diabetes. J Biol Chem 2011; 286:39537-45. [PMID: 21914804 DOI: 10.1074/jbc.m111.295931] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The development of insulin-dependent diabetes mellitus (IDDM) results from the selective destruction of pancreatic beta-cells. Both humans and spontaneous models of IDDM, such as NOD mice, have an extended pre-diabetic stage. Dynamic changes in beta-cell mass and function during pre-diabetes, such as insulin hyper-secretion, remain largely unknown. In this paper, we evaluated pre-diabetic female NOD mice at different ages (6, 10, and 14 weeks old) to illustrate alterations in beta-cell mass and function as disease progressed. We found an increase in beta-cell mass in 6-week-old NOD mice that may account for improved glucose tolerance in these mice. As NOD mice aged, beta-cell mass progressively reduced with increasing insulitis. In parallel, secretory ability of individual beta-cells was enhanced due to an increase in the size of slowly releasable pool (SRP) of vesicles. Moreover, expression of both SERCA2 and SERCA3 genes were progressively down-regulated, which facilitated depolarization-evoked secretion by prolonging Ca(2+) elevation upon glucose stimulation. In summary, we propose that different mechanisms contribute to the insulin hyper-secretion at different ages of pre-diabetic NOD mice, which may provide some new ideas concerning the progression and management of type I diabetes.
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Affiliation(s)
- Kuo Liang
- Department of General Surgery, XuanWu Hospital, Capital Medical University, Beijing, 100053, PR China
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Thörn K, Hovsepyan M, Bergsten P. Reduced levels of SCD1 accentuate palmitate-induced stress in insulin-producing β-cells. Lipids Health Dis 2010; 9:108. [PMID: 20920255 PMCID: PMC2955640 DOI: 10.1186/1476-511x-9-108] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 09/29/2010] [Indexed: 01/09/2023] Open
Abstract
Background Stearoyl-CoA desaturase 1 (SCD1) is an ER resident enzyme introducing a double-bond in saturated fatty acids. Global knockout of SCD1 in mouse increases fatty acid oxidation and insulin sensitivity which makes the animal resistant to diet-induced obesity. Inhibition of SCD1 has therefore been proposed as a potential therapy of the metabolic syndrome. Much of the work has focused on insulin target tissue and very little is known about how reduced levels of SCD1 would affect the insulin-producing β-cell, however. The aim of the present study was therefore to investigate how reduced levels of SCD1 affect the β-cell. Results Insulin-secreting MIN6 cells with reduced levels of SCD1 were established by siRNA mediated knockdown. When fatty acid oxidation was measured, no difference between cells with reduced levels of SCD1 and mock-transfected cells were found. Also, reducing levels of SCD1 did not affect insulin secretion in response to glucose. To investigate how SCD1 knockdown affected cellular mechanisms, differentially regulated proteins were identified by a proteomic approach. Cells with reduced levels of SCD1 had higher levels of ER chaperones and components of the proteasome. The higher amounts did not protect the β-cell from palmitate-induced ER stress and apoptosis. Instead, rise in levels of p-eIF2α and CHOP after palmitate exposure was 2-fold higher in cells with reduced levels of SCD1 compared to mock-transfected cells. Accordingly, apoptosis rose to higher levels after exposure to palmitate in cells with reduced levels of SCD1 compared to mock-transfected cells. Conclusions In conclusion, reduced levels of SCD1 augment palmitate-induced ER stress and apoptosis in the β-cell, which is an important caveat when considering targeting this enzyme as a treatment of the metabolic syndrome.
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Affiliation(s)
- Kristofer Thörn
- Department of Medical Cell Biology, Uppsala University, BMC Box 571, 75123 Uppsala, Sweden.
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Vandecaetsbeek I, Raeymaekers L, Wuytack F, Vangheluwe P. Factors controlling the activity of the SERCA2a pump in the normal and failing heart. Biofactors 2009; 35:484-99. [PMID: 19904717 DOI: 10.1002/biof.63] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Heart failure is the leading cause of death in western countries and is often associated with impaired Ca(2+) handling in the cardiomyocyte. In fact, cardiomyocyte relaxation and contraction are tightly controlled by the activity of the cardiac sarco(endo)plasmic reticulum (ER/SR) Ca(2+) pump SERCA2a, pumping Ca(2+) from the cytosol into the lumen of the ER/SR. This review addresses three important facets that control the SERCA2 activity in the heart. First, we focus on the alternative splicing of the SERCA2 messenger, which is strictly regulated in the developing heart. This splicing controls the formation of three SERCA2 splice variants with different enzymatic properties. Second, we will discuss the role and regulation of SERCA2a activity in the normal and failing heart. The two well-studied Ca(2+) affinity modulators phospholamban and sarcolipin control the activity of SERCA2a within a narrow window. An aberrantly high or low Ca(2+) affinity is often observed in and may even trigger cardiac failure. Correcting SERCA2a activity might therefore constitute a therapeutic approach to improve the contractility of the failing heart. Finally, we address the controversies and unanswered questions of other putative regulators of the cardiac Ca(2+) pump, such as sarcalumenin, HRC, S100A1, Bcl-2, HAX-1, calreticulin, calnexin, ERp57, IRS-1, and -2.
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Affiliation(s)
- Ilse Vandecaetsbeek
- Department of Molecular Cell Biology, Laboratory of Ca(2+)-transport ATPases, K.U.Leuven, Leuven, Belgium
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Lee SJ, Kim HE, Choi SE, Shin HC, Kwag WJ, Lee BK, Cho KW, Kang Y. Involvement of Ca2+/calmodulin kinase II (CaMK II) in genistein-induced potentiation of leucine/glutamine-stimulated insulin secretion. Mol Cells 2009; 28:167-74. [PMID: 19756396 DOI: 10.1007/s10059-009-0119-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 07/27/2009] [Accepted: 07/31/2009] [Indexed: 10/20/2022] Open
Abstract
Genistein has been reported to potentiate glucose-stimulated insulin secretion (GSIS). Inhibitory activity on tyrosine kinase or activation of protein kinase A (PKA) was shown to play a role in the genistein-induced potentiation effect on GSIS. The aim of the present study was to elucidate the mechanism of genistein-induced potentiation of insulin secretion. Genistein augmented insulin secretion in INS-1 cells stimulated by various energy-generating nutrients such as glucose, pyruvate, or leucine/glutamine (Leu/Gln), but not the secretion stimulated by depolarizing agents such as KCl and tolbutamide, or Ca(2+) channel opener Bay K8644. Genistein at a concentration of 50 μM showed a maximum potentiation effect on Leu/Gln-stimulated insulin secretion, but this was not sufficient to inhibit the activity of tyrosine kinase. Inhibitor studies as well as immunoblotting analysis demonstrated that activation of PKA was little involved in genistein-induced potentiation of Leu/Gln-stimulated insulin secretion. On the other hand, all the inhibitors of Ca(2+)/calmodulin kinase II tested, significantly diminished genistein-induced potentiation. Genistein also elevated the levels of [Ca(2+)]i and phospho-CaMK II. Furthermore, genistein augmented Leu/Gln-stimulated insulin secretion in CaMK II-overexpressing INS-1 cells. These data suggest that the activation of CaMK II played a role in genistein-induced potentiation of insulin secretion.
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Affiliation(s)
- Soo-Jin Lee
- Institute for Medical Science, Ajou University School of Medicine, Suwon, Korea
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16
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Regulation of glucose-dependent insulin secretion by insulin: Possible role of AMP-activated protein kinase. Life Sci 2009; 85:178-83. [DOI: 10.1016/j.lfs.2009.05.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 05/07/2009] [Accepted: 05/16/2009] [Indexed: 11/18/2022]
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Abstract
The appropriate function of insulin-producing pancreatic beta-cells is crucial for the regulation of glucose homeostasis, and its impairment leads to diabetes mellitus, the most common metabolic disorder in man. In addition to glucose, the major nutrient factor, inputs from the nervous system, humoral components, and cell-cell communication within the islet of Langerhans act together to guarantee the release of appropriate amounts of insulin in response to changes in blood glucose levels. Data obtained within the past decade in several laboratories have revitalized controversy over the autocrine feedback action of secreted insulin on beta-cell function. Although insulin historically has been suggested to exert a negative effect on beta-cells, recent data provide evidence for a positive role of insulin in transcription, translation, ion flux, insulin secretion, proliferation, and beta-cell survival. Current insights on the role of insulin on pancreatic beta-cell function are discussed.
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Affiliation(s)
- Ingo B Leibiger
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden.
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18
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Activation of the Na+/K+-ATPase by insulin and glucose as a putative negative feedback mechanism in pancreatic beta-cells. Pflugers Arch 2008; 457:1351-60. [PMID: 18836740 DOI: 10.1007/s00424-008-0592-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 09/14/2008] [Accepted: 09/18/2008] [Indexed: 10/21/2022]
Abstract
Pancreatic beta-cells of sulfonylurea receptor type 1 knock-out (SUR1(-/-)) mice exhibit an oscillating membrane potential (V (m)) demonstrating that hyper-polarisation occurs despite the lack of K(ATP) channels. We hypothesize that glucose activates the Na(+)/K(+)-ATPase thus increasing a hyper-polarising current. Elevating glucose in SUR1(-/-) beta-cells resulted in a transient fall in V (m) and [Ca(2+)](c) independent of sarcoplasmic and endoplasmic reticulum Ca(2+)-activated ATPase (SERCA) activation. This was not affected by K(+) channel blockade but inhibited by ATP depletion and by ouabain. Increasing glucose also reduced [Na(+)](c), an effect reversed by ouabain. Exogenously applied insulin decreased [Na(+)](c) and hyper-polarised V (m). Inhibiting insulin signalling in SUR1(-/-) beta-cells blunted the glucose-induced decrease of [Ca(2+)](c). Tolbutamide (1 mmol/l) disclosed the SERCA-independent effect of glucose on [Ca(2+)](c) in wild-type beta-cells. The data show that in SUR1(-/-) beta-cells, glucose activates the Na(+)/K(+)-ATPase presumably by increasing [ATP](c). Insulin can also stimulate the pump and potentiate the effect of glucose. Pathways involving the pump may thus serve as potential drug targets in certain metabolic disorders.
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Vangheluwe P, Raeymaekers L, Dode L, Wuytack F. Modulating sarco(endo)plasmic reticulum Ca2+ ATPase 2 (SERCA2) activity: cell biological implications. Cell Calcium 2008; 38:291-302. [PMID: 16105684 DOI: 10.1016/j.ceca.2005.06.033] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 11/20/2022]
Abstract
Of the three mammalian members belonging to the sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) family, SERCA2 is evolutionary the oldest and shows the most wide tissue-expression pattern. Two major SERCA2 splice variants are well-characterized: the muscle-specific isoform SERCA2a and the housekeeping isoform SERCA2b. Recently, several interacting proteins and post-translational modifications of SERCA2 were identified which may modulate the activity of the Ca2+ pump. This review aims to give an overview of the vast literature concerning the cell biological implications of the SERCA2 isoform diversity and the factors regulating SERCA2. Proteins reported to interact with SERCA2 from the cytosolic domain involve the anti-apoptotic Bcl-2, the insulin receptor substrates IRS1/2, the EF-hand Ca2+-binding protein S100A1 and acylphosphatase. We will focus on the very particular position of SERCA2 as an enzyme functioning in a thin, highly fluid, leaky and cholesterol-poor membrane. Possible differential interactions of SERCA2b and SERCA2a with calreticulin, calnexin and ERp57, which could occur within the lumen of the endoplasmic reticulum will be discussed. Reported post-translational modifications possibly affecting pump activity involve N-glycosylation, glutathionylation and Ca2+/calmodulin kinase II-dependent phosphorylation. Finally, the pronounced vulnerability to oxidative damage of SERCA2 appears to be pivotal in the etiology of various pathologies.
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Affiliation(s)
- Peter Vangheluwe
- Laboratory of Physiology, O.&N. Gasthuisberg, K.U. Leuven, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium
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Glauser DA, Schlegel W. Sequential actions of ERK1/2 on the AP‐1 transcription factor allow temporal integration of metabolic signals in pancreatic β cells. FASEB J 2007; 21:3240-9. [PMID: 17504975 DOI: 10.1096/fj.06-7798com] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The AP-1 transcription factor composed of fos and jun gene products mediates transcriptional responses to hormonal and metabolic stimulations of pancreatic beta cells. Here, we investigated the mechanisms that dynamically control expression of AP-1 subunit proteins. In MIN6 cells, glucose and GLP-1 raised c-FOS protein with biphasic kinetics, an initial peak being followed by a plateau that persisted as long as stimuli were maintained. ERK1/2 activation paralleled c-FOS expression. Whereas initial induction of c-FOS protein required ERK1/2-dependent activation of c-fos transcription and de novo protein synthesis, persistent accumulation of c-FOS under sustained stimulation did not. Indeed, dependent on ERK1/2 activation, c-FOS accumulated in its hyperphosphorylated form protected from degradation through the proteasome pathway. The implication of ERK1/2 in the accumulation of c-FOS protein was confirmed in rat primary beta cells, and the functional consequences of this mechanism were demonstrated with DNA-binding and reporter assays. Altogether these findings reveal a sequential regulation of AP-1 by ERK1/2, which initially increases transcription of c-fos and, if stimulation persists, stabilizes freshly synthesized c-FOS protein to efficiently activate the transcription of AP-1-regulated genes. This ERK1/2-AP-1 module can function as a temporal integrator converting metabolic stimuli of different durations into differential transcriptional outputs.
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Vagn Korsgaard T, Colding-Jørgensen M. Time-dependent mechanisms in beta-cell glucose sensing. J Biol Phys 2006; 32:289-306. [PMID: 19669468 DOI: 10.1007/s10867-006-9017-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 04/21/2006] [Accepted: 04/28/2006] [Indexed: 12/22/2022] Open
Abstract
The relation between plasma glucose and insulin release from pancreatic beta-cells is not stationary in the sense that a given glucose concentration leads to a specific rate of insulin secretion. A number of time-dependent mechanisms appear to exist that modify insulin release both on a short and a longer time scale. Typically, two phases are described. The first phase, lasting up to 10 min, is a pulse of insulin release in response to fast changes in glucose concentration. The second phase is a more steady increase of insulin release over minutes to hours, if the elevated glucose concentration is sustained. The paper describes the glucose sensing mechanism via the complex dynamics of the key enzyme glucokinase, which controls the first step in glucose metabolism: phosphorylation of glucose to glucose-6-phosphate. Three time-dependent phenomena (mechanisms) are described. The fastest, corresponding to the first phase, is a delayed negative feedback regulating the glucokinase activity. Due to the delay, a rapid glucose increase will cause a burst of activity in the glucose sensing system, before the glucokinase is down-regulated. The second mechanism corresponds to the translocation of glucokinase from an inactive to an active form. As the translocation is controlled by the product(s) of the glucokinase reaction rather than by the substrate glucose, this mechanism gives a positive, but saturable, feedback. Finally, the release of the insulin granules is assumed to be enhanced by previous glucose exposure, giving a so-called glucose memory to the beta-cells. The effect depends on the insulin release of the cells, and this mechanism constitutes a second positive, saturable feedback system. Taken together, the three phenomena describe most of the glucose sensing behaviour of the beta-cells. The results indicate that the insulin release is not a precise function of the plasma glucose concentration. It rather looks as if the beta-cells just increase the insulin production, until the plasma glucose has returned to normal. This type of integral control has the advantage that the precise glucose sensitivity of the beta-cells is not important for normal glucose homeostasis.
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Affiliation(s)
- Thomas Vagn Korsgaard
- Development Projects Management, Novo Nordisk A/S, Novo Allè, 2880 Bagsvaerd, Denmark
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Nunemaker CS, Zhang M, Satin LS. Insulin feedback alters mitochondrial activity through an ATP-sensitive K+ channel-dependent pathway in mouse islets and beta-cells. Diabetes 2004; 53:1765-72. [PMID: 15220200 DOI: 10.2337/diabetes.53.7.1765] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Recent work suggests that insulin may exert both positive and negative feedback directly on pancreatic beta-cells. To investigate the hypothesis that insulin modulates beta-cell metabolism, mouse islets and beta-cell clusters were loaded with rhodamine 123 to dynamically monitor mitochondrial membrane potential (DeltaPsi(m)). Spontaneous oscillations in DeltaPsi(m) (period: 218 +/- 26 s) were observed in 17 of 30 islets exposed to 11.1 mmol/l glucose. Acute insulin application (100 nmol/l) hyperpolarized DeltaPsi(m), indicating a change in mitochondrial activity. The ATP-sensitive K(+) (K(ATP)) channel opener diazoxide or the l-type calcium channel blocker nifedipine mimicked the effect of insulin, suggesting that insulin activates K(ATP) channels to hyperpolarize DeltaPsi(m) by inhibiting calcium influx. Treatment with forskolin, which increases endogenous insulin secretion, also mimicked the effect of exogenous insulin, suggesting physiological feedback. Pretreatment with nifedipine or the K(ATP) inhibitor glyburide prevented insulin action, further implicating a K(ATP) channel pathway. Together, these data suggest a feedback mechanism whereby insulin receptor activation opens K(ATP) channels to inhibit further secretion. The resulting reduction in beta-cell calcium increases the energy stored in the mitochondrial gradient that drives ATP production. Insulin feedback onto mitochondria may thus help to calibrate the energy needs of the beta-cell on a minute-to-minute basis.
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Affiliation(s)
- Craig S Nunemaker
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, USA
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