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Brown GC. Bioenergetic myths of energy transduction in eukaryotic cells. Front Mol Biosci 2024; 11:1402910. [PMID: 38952719 PMCID: PMC11215017 DOI: 10.3389/fmolb.2024.1402910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Accepted: 04/15/2024] [Indexed: 07/03/2024] Open
Abstract
The study of energy transduction in eukaryotic cells has been divided between Bioenergetics and Physiology, reflecting and contributing to a variety of Bioenergetic myths considered here: 1) ATP production = energy production, 2) energy transduction is confined to mitochondria (plus glycolysis and chloroplasts), 3) mitochondria only produce heat when required, 4) glycolysis is inefficient compared to mitochondria, and 5) mitochondria are the main source of reactive oxygen species (ROS) in cells. These myths constitute a 'mitocentric' view of the cell that is wrong or unbalanced. In reality, mitochondria are the main site of energy dissipation and heat production in cells, and this is an essential function of mitochondria in mammals. Energy transduction and ROS production occur throughout the cell, particularly the cytosol and plasma membrane, and all cell membranes act as two-dimensional energy conduits. Glycolysis is efficient, and produces less heat per ATP than mitochondria, which might explain its increased use in muscle and cancer cells.
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Affiliation(s)
- Guy C. Brown
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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2
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Muñoz F, Fex M, Moritz T, Mulder H, Cataldo LR. Unique features of β-cell metabolism are lost in type 2 diabetes. Acta Physiol (Oxf) 2024; 240:e14148. [PMID: 38656044 DOI: 10.1111/apha.14148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 02/28/2024] [Accepted: 04/05/2024] [Indexed: 04/26/2024]
Abstract
Pancreatic β cells play an essential role in the control of systemic glucose homeostasis as they sense blood glucose levels and respond by secreting insulin. Upon stimulating glucose uptake in insulin-sensitive tissues post-prandially, this anabolic hormone restores blood glucose levels to pre-prandial levels. Maintaining physiological glucose levels thus relies on proper β-cell function. To fulfill this highly specialized nutrient sensor role, β cells have evolved a unique genetic program that shapes its distinct cellular metabolism. In this review, the unique genetic and metabolic features of β cells will be outlined, including their alterations in type 2 diabetes (T2D). β cells selectively express a set of genes in a cell type-specific manner; for instance, the glucose activating hexokinase IV enzyme or Glucokinase (GCK), whereas other genes are selectively "disallowed", including lactate dehydrogenase A (LDHA) and monocarboxylate transporter 1 (MCT1). This selective gene program equips β cells with a unique metabolic apparatus to ensure that nutrient metabolism is coupled to appropriate insulin secretion, thereby avoiding hyperglycemia, as well as life-threatening hypoglycemia. Unlike most cell types, β cells exhibit specialized bioenergetic features, including supply-driven rather than demand-driven metabolism and a high basal mitochondrial proton leak respiration. The understanding of these unique genetically programmed metabolic features and their alterations that lead to β-cell dysfunction is crucial for a comprehensive understanding of T2D pathophysiology and the development of innovative therapeutic approaches for T2D patients.
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Affiliation(s)
- Felipe Muñoz
- Clinical Research Center, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund, Sweden
| | - Malin Fex
- Clinical Research Center, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund, Sweden
| | - Thomas Moritz
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hindrik Mulder
- Clinical Research Center, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund, Sweden
| | - Luis Rodrigo Cataldo
- Clinical Research Center, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund, Sweden
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Merrins MJ, Kibbey RG. Glucose Regulation of β-Cell KATP Channels: It Is Time for a New Model! Diabetes 2024; 73:856-863. [PMID: 38768366 PMCID: PMC11109790 DOI: 10.2337/dbi23-0032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 01/04/2024] [Indexed: 05/22/2024]
Abstract
An agreed-upon consensus model of glucose-stimulated insulin secretion from healthy β-cells is essential for understanding diabetes pathophysiology. Since the discovery of the KATP channel in 1984, an oxidative phosphorylation (OxPhos)-driven rise in ATP has been assumed to close KATP channels to initiate insulin secretion. This model lacks any evidence, genetic or otherwise, that mitochondria possess the bioenergetics to raise the ATP/ADP ratio to the triggering threshold, and conflicts with genetic evidence demonstrating that OxPhos is dispensable for insulin secretion. It also conflates the stoichiometric yield of OxPhos with thermodynamics, and overestimates OxPhos by failing to account for established features of β-cell metabolism, such as leak, anaplerosis, cataplerosis, and NADPH production that subtract from the efficiency of mitochondrial ATP production. We have proposed an alternative model, based on the spatial and bioenergetic specializations of β-cell metabolism, in which glycolysis initiates insulin secretion. The evidence for this model includes that 1) glycolysis has high control strength over insulin secretion; 2) glycolysis is active at the correct time to explain KATP channel closure; 3) plasma membrane-associated glycolytic enzymes control KATP channels; 4) pyruvate kinase has favorable bioenergetics, relative to OxPhos, for raising ATP/ADP; and 5) OxPhos stalls before membrane depolarization and increases after. Although several key experiments remain to evaluate this model, the 1984 model is based purely on circumstantial evidence and must be rescued by causal, mechanistic experiments if it is to endure.
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Affiliation(s)
- Matthew J. Merrins
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Wisconsin—Madison
- William S. Middleton Memorial Veterans Hospital, Madison, WI
| | - Richard G. Kibbey
- Departments of Internal Medicine (Endocrinology) and Cellular & Molecular Physiology, Yale University, New Haven, CT
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Rutter GA, Sweet IR. Glucose Regulation of β-Cell KATP Channels: Is a New Model Needed? Diabetes 2024; 73:849-855. [PMID: 38768365 PMCID: PMC11109788 DOI: 10.2337/dbi23-0031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 12/18/2023] [Indexed: 05/22/2024]
Abstract
The canonical model of glucose-induced increase in insulin secretion involves the metabolism of glucose via glycolysis and the citrate cycle, resulting in increased ATP synthesis by the respiratory chain and the closure of ATP-sensitive K+ (KATP) channels. The resulting plasma membrane depolarization, followed by Ca2+ influx through L-type Ca2+ channels, then induces insulin granule fusion. Merrins and colleagues have recently proposed an alternative model whereby KATP channels are controlled by pyruvate kinase, using glycolytic and mitochondrial phosphoenolpyruvate (PEP) to generate microdomains of high ATP/ADP immediately adjacent to KATP channels. This model presents several challenges. First, how mitochondrially generated PEP, but not ATP produced abundantly by the mitochondrial F1F0-ATP synthase, can gain access to the proposed microdomains is unclear. Second, ATP/ADP fluctuations imaged immediately beneath the plasma membrane closely resemble those in the bulk cytosol. Third, ADP privation of the respiratory chain at high glucose, suggested to drive alternating, phased-locked generation by mitochondria of ATP or PEP, has yet to be directly demonstrated. Finally, the approaches used to explore these questions may be complicated by off-target effects. We suggest instead that Ca2+ changes, well known to affect both ATP generation and consumption, likely drive cytosolic ATP/ADP oscillations that in turn regulate KATP channels and membrane potential. Thus, it remains to be demonstrated that a new model is required to replace the existing, mitochondrial bioenergetics-based model.
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Affiliation(s)
- Guy A. Rutter
- Centre de Recherche du CHUM, Faculté de Médicine, Université de Montréal, Montréal, Québéc, Canada
- Department of Metabolism, Digestion, and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, U.K
- Lee Kong Chian Imperial Medical School, Nanyang Technological University, Singapore
| | - Ian R. Sweet
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA
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Jacovetti C, Donnelly C, Menoud V, Suleiman M, Cosentino C, Sobel J, Wu K, Bouzakri K, Marchetti P, Guay C, Kayser B, Regazzi R. The mitochondrial tRNA-derived fragment, mt-tRF-Leu TAA, couples mitochondrial metabolism to insulin secretion. Mol Metab 2024; 84:101955. [PMID: 38704026 PMCID: PMC11112368 DOI: 10.1016/j.molmet.2024.101955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 04/29/2024] [Accepted: 04/29/2024] [Indexed: 05/06/2024] Open
Abstract
OBJECTIVE The contribution of the mitochondrial electron transfer system to insulin secretion involves more than just energy provision. We identified a small RNA fragment (mt-tRF-LeuTAA) derived from the cleavage of a mitochondrially-encoded tRNA that is conserved between mice and humans. The role of mitochondrially-encoded tRNA-derived fragments remains unknown. This study aimed to characterize the impact of mt-tRF-LeuTAA, on mitochondrial metabolism and pancreatic islet functions. METHODS We used antisense oligonucleotides to reduce mt-tRF-LeuTAA levels in primary rat and human islet cells, as well as in insulin-secreting cell lines. We performed a joint transcriptome and proteome analysis upon mt-tRF-LeuTAA inhibition. Additionally, we employed pull-down assays followed by mass spectrometry to identify direct interactors of the fragment. Finally, we characterized the impact of mt-tRF-LeuTAA silencing on the coupling between mitochondrial metabolism and insulin secretion using high-resolution respirometry and insulin secretion assays. RESULTS Our study unveils a modulation of mt-tRF-LeuTAA levels in pancreatic islets in different Type 2 diabetes models and in response to changes in nutritional status. The level of the fragment is finely tuned by the mechanistic target of rapamycin complex 1. Located within mitochondria, mt-tRF-LeuTAA interacts with core subunits and assembly factors of respiratory complexes of the electron transfer system. Silencing of mt-tRF-LeuTAA in islet cells limits the inner mitochondrial membrane potential and impairs mitochondrial oxidative phosphorylation, predominantly by affecting the Succinate (via Complex II)-linked electron transfer pathway. Lowering mt-tRF-LeuTAA impairs insulin secretion of rat and human pancreatic β-cells. CONCLUSIONS Our findings indicate that mt-tRF-LeuTAA interacts with electron transfer system complexes and is a pivotal regulator of mitochondrial oxidative phosphorylation and its coupling to insulin secretion.
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Affiliation(s)
- Cecile Jacovetti
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland.
| | - Chris Donnelly
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Véronique Menoud
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Mara Suleiman
- Department of Clinical and Experimental Medicine, Diabetes Unit, University of Pisa, Pisa, Italy
| | - Cristina Cosentino
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Jonathan Sobel
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Kejing Wu
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Karim Bouzakri
- UMR DIATHEC, EA 7294, Centre Européen d'Etude du Diabète, Université de Strasbourg, Fédération de Médecine Translationnelle de Strasbourg, Strasbourg, France
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, Diabetes Unit, University of Pisa, Pisa, Italy
| | - Claudiane Guay
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Bengt Kayser
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Romano Regazzi
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland; Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
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Rivera Nieves AM, Wauford BM, Fu A. Mitochondrial bioenergetics, metabolism, and beyond in pancreatic β-cells and diabetes. Front Mol Biosci 2024; 11:1354199. [PMID: 38404962 PMCID: PMC10884328 DOI: 10.3389/fmolb.2024.1354199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 01/17/2024] [Indexed: 02/27/2024] Open
Abstract
In Type 1 and Type 2 diabetes, pancreatic β-cell survival and function are impaired. Additional etiologies of diabetes include dysfunction in insulin-sensing hepatic, muscle, and adipose tissues as well as immune cells. An important determinant of metabolic health across these various tissues is mitochondria function and structure. This review focuses on the role of mitochondria in diabetes pathogenesis, with a specific emphasis on pancreatic β-cells. These dynamic organelles are obligate for β-cell survival, function, replication, insulin production, and control over insulin release. Therefore, it is not surprising that mitochondria are severely defective in diabetic contexts. Mitochondrial dysfunction poses challenges to assess in cause-effect studies, prompting us to assemble and deliberate the evidence for mitochondria dysfunction as a cause or consequence of diabetes. Understanding the precise molecular mechanisms underlying mitochondrial dysfunction in diabetes and identifying therapeutic strategies to restore mitochondrial homeostasis and enhance β-cell function are active and expanding areas of research. In summary, this review examines the multidimensional role of mitochondria in diabetes, focusing on pancreatic β-cells and highlighting the significance of mitochondrial metabolism, bioenergetics, calcium, dynamics, and mitophagy in the pathophysiology of diabetes. We describe the effects of diabetes-related gluco/lipotoxic, oxidative and inflammation stress on β-cell mitochondria, as well as the role played by mitochondria on the pathologic outcomes of these stress paradigms. By examining these aspects, we provide updated insights and highlight areas where further research is required for a deeper molecular understanding of the role of mitochondria in β-cells and diabetes.
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Affiliation(s)
- Alejandra María Rivera Nieves
- Diabetes Center of Excellence, University of Massachusetts Chan Medical School, Worcester, MA, United States
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, United States
| | - Brian Michael Wauford
- Diabetes Center of Excellence, University of Massachusetts Chan Medical School, Worcester, MA, United States
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, United States
| | - Accalia Fu
- Diabetes Center of Excellence, University of Massachusetts Chan Medical School, Worcester, MA, United States
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, United States
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Paliwal A, Paliwal V, Jain S, Paliwal S, Sharma S. Current Insight on the Role of Glucokinase and Glucokinase Regulatory Protein in Diabetes. Mini Rev Med Chem 2024; 24:674-688. [PMID: 37612862 DOI: 10.2174/1389557523666230823151927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 06/19/2023] [Accepted: 07/13/2023] [Indexed: 08/25/2023]
Abstract
The glucokinase regulator (GCKR) gene encodes an inhibitor of the glucokinase enzyme (GCK), found only in hepatocytes and responsible for glucose metabolism. A common GCKR coding variation has been linked to various metabolic traits in genome-wide association studies. Rare GCKR polymorphisms influence GKRP activity, expression, and localization. Despite not being the cause, these variations are linked to hypertriglyceridemia. Because of their crystal structures, we now better understand the molecular interactions between GKRP and the GCK. Finally, small molecules that specifically bind to GKRP and decrease blood sugar levels in diabetic models have been identified. GCKR allelic spectrum changes affect lipid and glucose homeostasis. GKRP dysfunction has been linked to a variety of molecular causes, according to functional analysis. Numerous studies have shown that GKRP dysfunction is not the only cause of hypertriglyceridemia, implying that type 2 diabetes could be treated by activating liver-specific GCK via small molecule GKRP inhibition. The review emphasizes current discoveries concerning the characteristic roles of glucokinase and GKRP in hepatic glucose metabolism and diabetes. This information has influenced the growth of directed molecular therapies for diabetes, which has improved our understanding of lipid and glucose physiology.
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Affiliation(s)
- Ajita Paliwal
- Department of Pharmacy, Banasthali Vidyapith, Banasthali, Rajasthan, India
| | - Vartika Paliwal
- Department of Pharmacy, Banasthali Vidyapith, Banasthali, Rajasthan, India
| | - Smita Jain
- Department of Pharmacy, Banasthali Vidyapith, Banasthali, Rajasthan, India
| | - Sarvesh Paliwal
- Department of Pharmacy, Banasthali Vidyapith, Banasthali, Rajasthan, India
| | - Swapnil Sharma
- Department of Pharmacy, Banasthali Vidyapith, Banasthali, Rajasthan, India
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Tarfeen N, Nisa KU, Ahmad MB, Waza AA, Ganai BA. Metabolic and Genetic Association of Vitamin D with Calcium Signaling and Insulin Resistance. Indian J Clin Biochem 2023; 38:407-417. [PMID: 37746541 PMCID: PMC10516840 DOI: 10.1007/s12291-022-01105-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 11/29/2022] [Indexed: 12/14/2022]
Abstract
Various evidences have unveiled the significance of Vitamin D in diverse processes which include its action in prevention of immune dysfunction, cancer and cardiometabolic disorders. Studies have confirmed the function of VD in controlling the expression of approximately nine hundred genes including gene expression of insulin. VD insufficiency may be linked with the pathogenesis of diseases that are associated with insulin resistance (IR) including diabetes as well as obesity. Thus, VD lowers IR-related disorders such as inflammation and oxidative stress. This review provides an insight regarding the molecular mechanism manifesting, how insufficiency of VD may be connected with the IR and diabetes. It also discusses the effect of VD in maintaining the Ca2+ levels in beta cells of the pancreas and in the tissues that are responsive to insulin.
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Affiliation(s)
- Najeebul Tarfeen
- Centre of Research for Development, University of Kashmir, Srinagar, India
| | - Khair Ul Nisa
- Department of Environmental Science, University of Kashmir, Srinagar, India
| | - Mir Bilal Ahmad
- Department of Biochemistry, University of Kashmir, Srinagar, India
| | - Ajaz Ahmad Waza
- Multidisciplinary Research Unit (MRU), Government Medical Collage (GMC) Srinagar, Srinagar, J & K 190010 India
| | - Bashir Ahmad Ganai
- Centre of Research for Development, University of Kashmir, Srinagar, India
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Zhu K, Mukherjee K, Wei C, Hayek SS, Collins A, Gu C, Corapi K, Altintas MM, Wang Y, Waikar SS, Bianco AC, Koch A, Tacke F, Reiser J, Sever S. The D2D3 form of uPAR acts as an immunotoxin and may cause diabetes and kidney disease. Sci Transl Med 2023; 15:eabq6492. [PMID: 37729431 DOI: 10.1126/scitranslmed.abq6492] [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] [Received: 04/21/2022] [Accepted: 08/31/2023] [Indexed: 09/22/2023]
Abstract
Soluble urokinase plasminogen activator receptor (suPAR) is a risk factor for kidney diseases. In addition to suPAR, proteolysis of membrane-bound uPAR results in circulating D1 and D2D3 proteins. We showed that when exposed to a high-fat diet, transgenic mice expressing D2D3 protein developed progressive kidney disease marked by microalbuminuria, elevated serum creatinine, and glomerular hypertrophy. D2D3 transgenic mice also exhibited insulin-dependent diabetes mellitus evidenced by decreased levels of insulin and C-peptide, impaired glucose-stimulated insulin secretion, decreased pancreatic β cell mass, and high fasting blood glucose. Injection of anti-uPAR antibody restored β cell mass and function in D2D3 transgenic mice. At the cellular level, the D2D3 protein impaired β cell proliferation and inhibited the bioenergetics of β cells, leading to dysregulated cytoskeletal dynamics and subsequent impairment in the maturation and trafficking of insulin granules. D2D3 protein was predominantly detected in the sera of patients with nephropathy and insulin-dependent diabetes mellitus. These sera inhibited glucose-stimulated insulin release from human islets in a D2D3-dependent manner. Our study showed that D2D3 injures the kidney and pancreas and suggests that targeting this protein could provide a therapy for kidney diseases and insulin-dependent diabetes mellitus.
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Affiliation(s)
- Ke Zhu
- Department of Medicine, Rush University Medical Center, Chicago, IL 60612, USA
| | - Kamalika Mukherjee
- Harvard Medical School and Division of Nephrology, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Changli Wei
- Department of Medicine, Rush University Medical Center, Chicago, IL 60612, USA
| | - Salim S Hayek
- Division of Cardiology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Agnieszka Collins
- Harvard Medical School and Division of Nephrology, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Changkyu Gu
- Harvard Medical School and Division of Nephrology, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Kristin Corapi
- Harvard Medical School and Division of Nephrology, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Mehmet M Altintas
- Department of Medicine, Rush University Medical Center, Chicago, IL 60612, USA
| | - Yong Wang
- Department of Surgery, University of Virginia, Charlottesville, VA 22903, USA
| | - Sushrut S Waikar
- Section of Nephrology, Boston University Chobanian & Avedisian School of Medicine and Boston Medical Center, Boston, MA 02129, USA
| | - Antonio C Bianco
- Division of Endocrinology, Department of Medicine, University of Chicago, Chicago, IL 60637, USA
| | - Alexander Koch
- Department of Gastroenterology, Metabolic Diseases and Internal Intensive Care Medicine, University Hospital Aachen, 52072 Aachen, Germany
| | - Frank Tacke
- Department of Hepatology and Gastroenterology, Charité - Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Jochen Reiser
- Department of Medicine, Rush University Medical Center, Chicago, IL 60612, USA
| | - Sanja Sever
- Harvard Medical School and Division of Nephrology, Massachusetts General Hospital, Charlestown, MA 02129, USA
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Barsby T, Vähäkangas E, Ustinov J, Montaser H, Ibrahim H, Lithovius V, Kuuluvainen E, Chandra V, Saarimäki-Vire J, Katajisto P, Hietakangas V, Otonkoski T. Aberrant metabolite trafficking and fuel sensitivity in human pluripotent stem cell-derived islets. Cell Rep 2023; 42:112970. [PMID: 37556323 DOI: 10.1016/j.celrep.2023.112970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 06/09/2023] [Accepted: 07/26/2023] [Indexed: 08/11/2023] Open
Abstract
Pancreatic islets regulate blood glucose homeostasis through the controlled release of insulin; however, current metabolic models of glucose-sensitive insulin secretion are incomplete. A comprehensive understanding of islet metabolism is integral to studies of endocrine cell development as well as diabetic islet dysfunction. Human pluripotent stem cell-derived islets (SC-islets) are a developmentally relevant model of human islet function that have great potential in providing a cure for type 1 diabetes. Using multiple 13C-labeled metabolic fuels, we demonstrate that SC-islets show numerous divergent patterns of metabolite trafficking in proposed insulin release pathways compared with primary human islets but are still reliant on mitochondrial aerobic metabolism to derive function. Furthermore, reductive tricarboxylic acid cycle activity and glycolytic metabolite cycling occur in SC-islets, suggesting that non-canonical coupling factors are also present. In aggregate, we show that many facets of SC-islet metabolism overlap with those of primary islets, albeit with a retained immature signature.
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Affiliation(s)
- Tom Barsby
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
| | - Eliisa Vähäkangas
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jarkko Ustinov
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Hossam Montaser
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Hazem Ibrahim
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Väinö Lithovius
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Emilia Kuuluvainen
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Vikash Chandra
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jonna Saarimäki-Vire
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Pekka Katajisto
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Ville Hietakangas
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Timo Otonkoski
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.
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11
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Yanai H, Adachi H, Hakoshima M, Katsuyama H. Glucose-Lowering Effects of Imeglimin and Its Possible Beneficial Effects on Diabetic Complications. BIOLOGY 2023; 12:biology12050726. [PMID: 37237539 DOI: 10.3390/biology12050726] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 04/27/2023] [Accepted: 05/15/2023] [Indexed: 05/28/2023]
Abstract
Mitochondrial dysfunction is a prominent pathological feature of type 2 diabetes, which contributes to β-cell mass reduction and insulin resistance. Imeglimin is a novel oral hypoglycemic agent with a unique mechanism of action targeting mitochondrial bioenergetics. Imeglimin reduces reactive oxygen species production, improves mitochondrial function and integrity, and also improves the structure and function of endoplasmic reticulum (ER), changes which enhance glucose-stimulated insulin secretion and inhibit the apoptosis of β-cells, leading to β-cell mass preservation. Further, imeglimin inhibits hepatic glucose production and ameliorates insulin sensitivity. Clinical trials into the effects of imeglimin monotherapy and combination therapy exhibited an excellent hypoglycemic efficacy and safety profile in type 2 diabetic patients. Mitochondrial impairment is closely associated with endothelial dysfunction, which is a very early event in atherosclerosis. Imeglimin improved endothelial dysfunction in patients with type 2 diabetes via both glycemic control-dependent and -independent mechanisms. In experimental animals, imeglimin improved cardiac and kidney function via an improvement in mitochondrial and ER function or/and an improvement in endothelial function. Furthermore, imeglimin reduced ischemia-induced brain damage. In addition to glucose-lowering effects, imeglimin can be a useful therapeutic option for diabetic complications in type 2 diabetic patients.
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Affiliation(s)
- Hidekatsu Yanai
- Department of Diabetes, Endocrinology and Metabolism, National Center for Global Health and Medicine Kohnodai Hospital, 1-7-1 Kohnodai, Chiba 272-8516, Japan
| | - Hiroki Adachi
- Department of Diabetes, Endocrinology and Metabolism, National Center for Global Health and Medicine Kohnodai Hospital, 1-7-1 Kohnodai, Chiba 272-8516, Japan
| | - Mariko Hakoshima
- Department of Diabetes, Endocrinology and Metabolism, National Center for Global Health and Medicine Kohnodai Hospital, 1-7-1 Kohnodai, Chiba 272-8516, Japan
| | - Hisayuki Katsuyama
- Department of Diabetes, Endocrinology and Metabolism, National Center for Global Health and Medicine Kohnodai Hospital, 1-7-1 Kohnodai, Chiba 272-8516, Japan
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12
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Liu J, Fu H, Kang F, Ning G, Ni Q, Wang W, Wang Q. β-Cell glucokinase expression was increased in type 2 diabetes subjects with better glycemic control. J Diabetes 2023; 15:409-418. [PMID: 36942376 PMCID: PMC10172022 DOI: 10.1111/1753-0407.13380] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 02/22/2023] [Accepted: 02/26/2023] [Indexed: 03/23/2023] Open
Abstract
BACKGROUND Type 2 diabetes (T2D) is characterized by a progressive deterioration of β-cell function with a continuous decline in insulin secretion. Glucokinase (GCK) facilitates the rate-limiting step of glycolysis in pancreatic β-cells, to acquire the proper glucose-stimulated insulin secretion. Multiple glucokinase activators (GKAs) have been developed and clinically tested. However, the dynamic change of human pancreatic GCK expression during T2D progression has not been investigated. METHODS We evaluated GCK expression by measuring the average immunoreactivity of GCK in insulin+ or glucagon+ cells from pancreatic sections of 11 nondiabetic subjects (ND), 10 subjects with impaired fasting glucose (IFG), 9 with well-controlled T2D (wT2D), and 5 individuals with poorly controlled T2D (uT2D). We also assessed the relationship between GCK expression and adaptive unfolded protein response (UPR) in human diabetic β-cells. RESULTS We did not detect changes of GCK expression in IFG islets. However, we found β-cell GCK levels were significantly increased in T2D with adequate glucose control (wT2D) but not in T2D with poor glucose control (uT2D). Furthermore, there was a strong positive correlation between GCK expression and adaptive UPR (spliced X-box binding protein 1 [XBP1s] and activating transcription factor 4 [ATF4]), as well as functional maturity marker (urocortin-3 [UCN3]) in human diabetic β-cells. CONCLUSIONS Our study demonstrates that inductions of GCK enhanced adaptive UPR and UCN3 in human β-cells, which might be an adaptive mechanism during T2D progression. This finding provides a rationale for exploring novel molecules that activate β-cell GCK and thereby improve pharmacological treatment of T2D.
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Affiliation(s)
- Jingwen Liu
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory for Endocrine Tumor, State Key Laboratory of Medical Genomics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Hui Fu
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory for Endocrine Tumor, State Key Laboratory of Medical Genomics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fuyun Kang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory for Endocrine Tumor, State Key Laboratory of Medical Genomics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Guang Ning
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory for Endocrine Tumor, State Key Laboratory of Medical Genomics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Sino-French Research Center for Life Sciences and Genomics Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qicheng Ni
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory for Endocrine Tumor, State Key Laboratory of Medical Genomics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Weiqing Wang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory for Endocrine Tumor, State Key Laboratory of Medical Genomics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qidi Wang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory for Endocrine Tumor, State Key Laboratory of Medical Genomics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Sino-French Research Center for Life Sciences and Genomics Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
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13
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Crowder JJ, Zeng Z, Novak AN, Alves NJ, Linnemann AK. Stabilization protects islet integrity during respirometry in the Oroboros Oxygraph-2K analyzer. Islets 2022; 14:128-138. [PMID: 35331085 PMCID: PMC8959522 DOI: 10.1080/19382014.2022.2054251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Metabolic dysfunction of β-cells has been implicated as a contributor to diabetes pathogenesis, and efforts are ongoing to optimize analytical techniques that evaluate islet metabolism. High-resolution respirometry offers sensitive measurements of the respiratory effects of metabolic substrates and customizable manipulation of electron transport chain components, though the delicate nature of islets can pose challenges to conventional analyses. An affordable and reliable option for respirometry is the Oroboros Oxygraph-2 K system, which utilizes a stir bar to circulate reagents around cells. While this technique may be suitable for individual cells or mitochondria, the continual force exerted by the stir bar can have damaging effects on islet integrity. Herein, we demonstrate the protective benefits of a novel 3D-printed islet stabilization device and highlight the destructive effects of conventional Oxygraph analysis on islet integrity. Islet containment did not inhibit cellular responses to metabolic modulatory drugs, as indicated by robust fluctuations in oxygen consumption rates. The average size of wild-type mouse islets was significantly reduced following a standard Mito Stress Test within Oxygraph chambers, with a clear disruption in islet morphology and viability. Alternatively, containment of the islets within the interior chamber of the islet stabilization device yielded preservation of both islet morphology and increased cell viability/survival after respirometry analysis. Collectively, our study introduces a new and easily accessible tool to improve conventional Oxygraph respirometry of pancreatic islets by preserving natural islet structure and function throughout metabolic analysis.
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Affiliation(s)
- Justin J. Crowder
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Ziqian Zeng
- Department of Emergency Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Alissa N. Novak
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Nathan J. Alves
- Department of Emergency Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
- Amelia K. Linnemann Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Amelia K. Linnemann
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
- Indiana Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN, USA
- CONTACT Nathan J. Alves
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14
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Mustafa A, Shekhar C. Association between serum 25-hydroxyvitamin-D and Triglycerides-Glucose index among Indian adolescents. BMC Nutr 2022; 8:69. [PMID: 35879737 PMCID: PMC9310494 DOI: 10.1186/s40795-022-00568-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 07/19/2022] [Indexed: 12/02/2022] Open
Abstract
Background Vitamin D deficiency has been found to associated with numerous skeletal and non-skeletal diseases including Diabetes Mellitus. Insulin Resistance (IR) is considered as one of the primary reasons of Type-2 Diabetes Mellitus (T2DM). The association between vitamin D deficiency and IR has been extensively explore in previous studies, but none of them focused on Indian adolescents, and none of them used the TyG index as IR marker. Hence, this population-based cross-sectional study investigates the relationship between insulin resistance (IR) assessed using the Triglycerides Glucose Index (TyG index) and vitamin D measured by serum 25-hydroxyvitamin-D (25(OH)D). Methods For this study, we utilized data from the Comprehensive National Nutrition Survey (CNNS, 2016–18). The study is based on a sample size of 10,167 adolescents aged 10–19 years. The TyG index cut-off value of 4.65 was used to classify IR. We examined associations between the TyG index and serum 25(OH)D using multiple linear regression models adjusted for potential confounders. Odds of Insulin Resistance among vitamin D deficient/insufficient adolescents were assessed using multivariable logistic regression. Results A significant negative association was found between serum 25(OH)D and the TyG index, where a 10% increase in serum 25(OH)D was associated with 0.56 (95% CI = -0.67, -0.45) unit decrement in the TyG index. The odds of having IR were 90% higher among vitamin D deficient adolescents (OR: 1.90; 95% CI = 1.62—2.23) compared to adolescents with adequate levels of vitamin D. The association between vitamin D deficiency and IR was independent of sex; in other words, the association between vitamin D and IR was significant in both the sexes. Conclusion Independent of sex, this study found a significant inverse association between vitamin D and insulin resistance in Indian adolescents. The findings of this study highlight the utility of TyG index and the importance of vitamin D in lowering the risk of T2DM in future generations of the country.
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15
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Onikanni SA, Lawal B, Oyinloye BE, Ajiboye BO, Ulziijargal S, Wang CH, Emran TB, Simal-Gandara J. Mitochondrial defects in pancreatic beta-cell dysfunction and neurodegenerative diseases: Pathogenesis and therapeutic applications. Life Sci 2022; 312:121247. [PMID: 36450327 DOI: 10.1016/j.lfs.2022.121247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 11/12/2022] [Accepted: 11/24/2022] [Indexed: 11/29/2022]
Abstract
Mitochondria malfunction is linked to the development of β-cell failure and a variety of neurodegenerative disorders. Pancreatic β-cells are normally configured to detect glucose and other food secretagogues in order to adjust insulin exocytosis and maintain glucose homeostasis. As a result of the increased glucose level, mitochondria metabolites and nucleotides are produced, which operate in concert with cytosolic Ca2+ to stimulate insulin secretion. Furthermore, mitochondria are the primary generators of adenosine triphosphate (ATP), reactive oxygen species (ROS), and apoptosis regulation. Mitochondria are concentrated in synapses, and any substantial changes in synaptic mitochondria location, shape, quantity, or function might cause oxidative stress, resulting in faulty synaptic transmission, a symptom of various degenerative disorders at an early stage. However, a greater understanding of the role of mitochondria in the etiology of β-cell dysfunction and neurodegenerative disorder should pave the way for a more effective approach to addressing these health issues. This review looks at the widespread occurrence of mitochondria depletion in humans, and its significance to mitochondria biogenesis in signaling and mitophagy. Proper understanding of the processes might be extremely beneficial in ameliorating the rising worries about mitochondria biogenesis and triggering mitophagy to remove depleted mitochondria, therefore reducing disease pathogenesis.
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Affiliation(s)
- Sunday Amos Onikanni
- Graduate Institute of Biomedical Science, College of Medicine, China Medical University, Taichung, Taiwan; Department of Chemical Sciences, Biochemistry Unit, Afe Babalola University, Ado-Ekiti, Ekiti State, Nigeria.
| | - Bashir Lawal
- PhD Program for Cancer Molecular Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University and Academia Sinica, Taipei 11031, Taiwan; Graduate Institute for Cancer Biology & Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei 11031, Taiwan
| | - Babatunji Emmanuel Oyinloye
- Department of Chemical Sciences, Biochemistry Unit, Afe Babalola University, Ado-Ekiti, Ekiti State, Nigeria; Biotechnology and Structural Biology (BSB) Group, Department of Biochemistry and Microbiology, University of Zululand, KwaDlangezwa 3886, South Africa; Institute of Drug Research and Development, SE Bogoro Center, Afe Babalola University, PMB 5454, Ado-Ekiti 360001, Nigeria
| | - Basiru Olaitan Ajiboye
- Institute of Drug Research and Development, SE Bogoro Center, Afe Babalola University, PMB 5454, Ado-Ekiti 360001, Nigeria; Phytomedicine and Molecular Toxicology Research Laboratory, Department of Biochemistry, Federal University of Technology, Oye-Ekiti, Ekiti State, Nigeria
| | - Sukhbat Ulziijargal
- Graduate Institute of Biomedical Science, College of Medicine, China Medical University, Taichung, Taiwan
| | - Chih-Hao Wang
- Graduate Institute of Biomedical Science, College of Medicine, China Medical University, Taichung, Taiwan
| | - Talha Bin Emran
- Department of Pharmacy, BGC Trust University Bangladesh, Chittagong 4381, Bangladesh; Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh.
| | - Jesus Simal-Gandara
- Universidade de Vigo, Nutrition and Bromatology Group, Analytical Chemistry and Food Science Department, Faculty of Science, E32004 Ourense, Spain.
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16
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Gelbach PE, Zheng D, Fraser SE, White KL, Graham NA, Finley SD. Kinetic and data-driven modeling of pancreatic β-cell central carbon metabolism and insulin secretion. PLoS Comput Biol 2022; 18:e1010555. [PMID: 36251711 PMCID: PMC9612825 DOI: 10.1371/journal.pcbi.1010555] [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] [Received: 10/11/2021] [Revised: 10/27/2022] [Accepted: 09/08/2022] [Indexed: 11/06/2022] Open
Abstract
Pancreatic β-cells respond to increased extracellular glucose levels by initiating a metabolic shift. That change in metabolism is part of the process of glucose-stimulated insulin secretion and is of particular interest in the context of diabetes. However, we do not fully understand how the coordinated changes in metabolic pathways and metabolite products influence insulin secretion. In this work, we apply systems biology approaches to develop a detailed kinetic model of the intracellular central carbon metabolic pathways in pancreatic β-cells upon stimulation with high levels of glucose. The model is calibrated to published metabolomics datasets for the INS1 823/13 cell line, accurately capturing the measured metabolite fold-changes. We first employed the calibrated mechanistic model to estimate the stimulated cell's fluxome. We then used the predicted network fluxes in a data-driven approach to build a partial least squares regression model. By developing the combined kinetic and data-driven modeling framework, we gain insights into the link between β-cell metabolism and glucose-stimulated insulin secretion. The combined modeling framework was used to predict the effects of common anti-diabetic pharmacological interventions on metabolite levels, flux through the metabolic network, and insulin secretion. Our simulations reveal targets that can be modulated to enhance insulin secretion. The model is a promising tool to contextualize and extend the usefulness of metabolomics data and to predict dynamics and metabolite levels that are difficult to measure in vitro. In addition, the modeling framework can be applied to identify, explain, and assess novel and clinically-relevant interventions that may be particularly valuable in diabetes treatment.
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Affiliation(s)
- Patrick E. Gelbach
- Department of Biomedical Engineering, USC, Los Angeles, California, United States of America
| | - Dongqing Zheng
- Mork Family Department of Chemical Engineering and Materials Science, USC, Los Angeles, California, United States of America
| | - Scott E. Fraser
- Translational Imaging Center, University of Southern California, Los Angeles, California, United States of America
| | - Kate L. White
- Departments of Biological Sciences and Chemistry, Bridge Institute, USC Michelson Center, USC, Los Angeles, California, United States of America
| | - Nicholas A. Graham
- Mork Family Department of Chemical Engineering and Materials Science, USC, Los Angeles, California, United States of America
| | - Stacey D. Finley
- Department of Biomedical Engineering, USC, Los Angeles, California, United States of America
- Mork Family Department of Chemical Engineering and Materials Science, USC, Los Angeles, California, United States of America
- Department of Quantitative and Computational Biology, USC, Los Angeles, California, United States of America
- * E-mail:
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17
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Yin X, Chen JY, Huang XJ, Lai JH, Huang C, Yao W, Li NX, Huang WC, Guo XG. Association between vitamin D serum levels and insulin resistance assessed by HOMA-IR among non-diabetic adults in the United States: Results from NHANES 2007-2014. Front Nutr 2022; 9:883904. [PMID: 36313112 PMCID: PMC9614433 DOI: 10.3389/fnut.2022.883904] [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: 02/25/2022] [Accepted: 08/08/2022] [Indexed: 11/13/2022] Open
Abstract
Insulin resistance, a pathological response to insulin hormone in insulin-dependent cells, is characterized by the presence of high glucose and insulin concentrations. The homeostasis model of insulin resistance (HOMA-IR) is one of the most used indexes to estimate insulin resistance by assessing the fasting glucose and insulin levels. An association was observed between vitamin D levels and insulin resistance, which varied in different ethnic groups, and there is some evidence that vitamin D supplementation could contribute to the improvement of insulin resistance. This study assessed the association between 25-hydroxyvitamin D (25[OH]D) concentration and HOMA-IR in American adults aged 20 years and older, without diabetes and other chronic diseases that can influence insulin resistance. The data from the National Health and Nutrition Examination Survey (NHANES) 2007–2014 were used by exploiting the free and publicly-accessible web datasets. Linear regression models were performed to evaluate the association between serum 25(OH)D concentration and HOMA-IR, and a negative association was observed, which remained significant following the adjustment for age, gender, race/ethnicity, education, body mass index (BMI), physical activity, the season of examination, current smoking, hypertension, the use of drugs which can influence insulin resistance, serum bicarbonates, triglycerides, and calcium and phosphorus levels. Only in non-Hispanic Blacks was this inverse association between vitamin D and HOMA-IR not observed in the fully adjusted model. Further studies are needed to explain the mechanisms of the observed ethnic/racial differences in the association of vitamin D levels with HOMA-IR.
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Affiliation(s)
- Xin Yin
- Department of Clinical Laboratory Medicine, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China,Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, China
| | - Jia-Yu Chen
- Department of Clinical Medicine, The Third Clinical School of Guangzhou Medical University, Guangzhou, China
| | - Xiang-Jie Huang
- School of Computer Science and Engineering, Central South University, Changsha, China
| | - Jia-Hong Lai
- Department of Clinical Medicine, The Third Clinical School of Guangzhou Medical University, Guangzhou, China
| | - Chang Huang
- Department of Clinical Medicine, The Third Clinical School of Guangzhou Medical University, Guangzhou, China
| | - Wang Yao
- Department of Clinical Medicine, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Nan-Xi Li
- Department of Psychiatric Medicine, The Mental Health College of Guangzhou Medical University, Guangzhou, China
| | - Wei-Chao Huang
- Department of Clinical Medicine, The Second Clinical School of Guangzhou Medical University, Guangzhou, China
| | - Xu-Guang Guo
- Department of Clinical Laboratory Medicine, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China,Department of Clinical Medicine, The Third Clinical School of Guangzhou Medical University, Guangzhou, China,Guangdong Provincial Key Laboratory of Major Obstetric Diseases, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China,Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China,Guangzhou Key Laboratory for Clinical Rapid Diagnosis and Early Warning of Infectious Diseases, KingMed School of Laboratory Medicine, Guangzhou Medical University, Guangzhou, China,*Correspondence: Xu-Guang Guo
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18
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Monitoring glycolytic dynamics in single cells using a fluorescent biosensor for fructose 1,6-bisphosphate. Proc Natl Acad Sci U S A 2022; 119:e2204407119. [PMID: 35881794 PMCID: PMC9351453 DOI: 10.1073/pnas.2204407119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cellular metabolism is regulated over space and time to ensure that energy production is efficiently matched with consumption. Fluorescent biosensors are useful tools for studying metabolism as they enable real-time detection of metabolite abundance with single-cell resolution. For monitoring glycolysis, the intermediate fructose 1,6-bisphosphate (FBP) is a particularly informative signal as its concentration is strongly correlated with flux through the whole pathway. Using GFP insertion into the ligand-binding domain of the Bacillus subtilis transcriptional regulator CggR, we developed a fluorescent biosensor for FBP termed HYlight. We demonstrate that HYlight can reliably report the real-time dynamics of glycolysis in living cells and tissues, driven by various metabolic or pharmacological perturbations, alone or in combination with other physiologically relevant signals. Using this sensor, we uncovered previously unknown aspects of β-cell glycolytic heterogeneity and dynamics.
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19
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Inoue R, Tsuno T, Togashi Y, Okuyama T, Sato A, Nishiyama K, Kyohara M, Li J, Fukushima S, Kin T, Miyashita D, Shiba Y, Atobe Y, Kiyonari H, Bando K, Shapiro AJ, Funakoshi K, Kulkarni RN, Terauchi Y, Shirakawa J. Uncoupling protein 2 and aldolase B impact insulin release by modulating mitochondrial function and Ca 2+ release from the ER. iScience 2022; 25:104603. [PMID: 35800776 PMCID: PMC9253497 DOI: 10.1016/j.isci.2022.104603] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 03/25/2022] [Accepted: 06/08/2022] [Indexed: 02/02/2023] Open
Abstract
Uncoupling protein 2 (UCP2), a mitochondrial protein, is known to be upregulated in pancreatic islets of patients with type 2 diabetes (T2DM); however, the pathological significance of this increase in UCP2 expression is unclear. In this study, we highlight the molecular link between the increase in UCP2 expression in β-cells and β-cell failure by using genetically engineered mice and human islets. β-cell-specific UCP2-overexpressing transgenic mice (βUCP2Tg) exhibited glucose intolerance and a reduction in insulin secretion. Decreased mitochondrial function and increased aldolase B (AldB) expression through oxidative-stress-mediated pathway were observed in βUCP2Tg islets. AldB, a glycolytic enzyme, was associated with reduced insulin secretion via mitochondrial dysfunction and impaired calcium release from the endoplasmic reticulum (ER). Taken together, our findings provide a new mechanism of β-cell dysfunction by UCP2 and AldB. Targeting the UCP2/AldB axis is a promising approach for the recovery of β-cell function.
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Affiliation(s)
- Ryota Inoue
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Takahiro Tsuno
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yu Togashi
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Tomoko Okuyama
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Aoi Sato
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
| | - Kuniyuki Nishiyama
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Mayu Kyohara
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Jinghe Li
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Setsuko Fukushima
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
| | - Tatsuya Kin
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, AB T6G2C8, Canada
| | - Daisuke Miyashita
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yusuke Shiba
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yoshitoshi Atobe
- Department of Neuroanatomy, Yokohama City University School of Medicine, Yokohama 236-0004, Japan
| | - Hiroshi Kiyonari
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - Kana Bando
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - A.M. James Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, AB T6G2C8, Canada
| | - Kengo Funakoshi
- Department of Neuroanatomy, Yokohama City University School of Medicine, Yokohama 236-0004, Japan
| | - Rohit N. Kulkarni
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Yasuo Terauchi
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Jun Shirakawa
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
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Lipotoxicity in a Vicious Cycle of Pancreatic Beta Cell Exhaustion. Biomedicines 2022; 10:biomedicines10071627. [PMID: 35884932 PMCID: PMC9313354 DOI: 10.3390/biomedicines10071627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 07/05/2022] [Accepted: 07/05/2022] [Indexed: 02/07/2023] Open
Abstract
Hyperlipidemia is a common metabolic disorder in modern society and may precede hyperglycemia and diabetes by several years. Exactly how disorders of lipid and glucose metabolism are related is still a mystery in many respects. We analyze the effects of hyperlipidemia, particularly free fatty acids, on pancreatic beta cells and insulin secretion. We have developed a computational model to quantitatively estimate the effects of specific metabolic pathways on insulin secretion and to assess the effects of short- and long-term exposure of beta cells to elevated concentrations of free fatty acids. We show that the major trigger for insulin secretion is the anaplerotic pathway via the phosphoenolpyruvate cycle, which is affected by free fatty acids via uncoupling protein 2 and proton leak and is particularly destructive in long-term chronic exposure to free fatty acids, leading to increased insulin secretion at low blood glucose and inadequate insulin secretion at high blood glucose. This results in beta cells remaining highly active in the “resting” state at low glucose and being unable to respond to anaplerotic signals at high pyruvate levels, as is the case with high blood glucose. The observed fatty-acid-induced disruption of anaplerotic pathways makes sense in the context of the physiological role of insulin as one of the major anabolic hormones.
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21
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Metabolic cycles and signals for insulin secretion. Cell Metab 2022; 34:947-968. [PMID: 35728586 PMCID: PMC9262871 DOI: 10.1016/j.cmet.2022.06.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 06/01/2022] [Accepted: 06/04/2022] [Indexed: 02/03/2023]
Abstract
In this review, we focus on recent developments in our understanding of nutrient-induced insulin secretion that challenge a key aspect of the "canonical" model, in which an oxidative phosphorylation-driven rise in ATP production closes KATP channels. We discuss the importance of intrinsic β cell metabolic oscillations; the phasic alignment of relevant metabolic cycles, shuttles, and shunts; and how their temporal and compartmental relationships align with the triggering phase or the secretory phase of pulsatile insulin secretion. Metabolic signaling components are assigned regulatory, effectory, and/or homeostatic roles vis-à-vis their contribution to glucose sensing, signal transmission, and resetting the system. Taken together, these functions provide a framework for understanding how allostery, anaplerosis, and oxidative metabolism are integrated into the oscillatory behavior of the secretory pathway. By incorporating these temporal as well as newly discovered spatial aspects of β cell metabolism, we propose a much-refined MitoCat-MitoOx model of the signaling process for the field to evaluate.
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22
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Rodrigues-dos-Santos K, Roy G, Binns DD, Grzemska MG, Barella LF, Armoo F, McCoy MK, Huynh AV, Yang JZ, Posner BA, Cobb MH, Kalwat MA. Small Molecule-mediated Insulin Hypersecretion Induces Transient ER Stress Response and Loss of Beta Cell Function. Endocrinology 2022; 163:6596276. [PMID: 35641126 PMCID: PMC9225822 DOI: 10.1210/endocr/bqac081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Indexed: 11/19/2022]
Abstract
Pancreatic islet beta cells require a fine-tuned endoplasmic reticulum (ER) stress response for normal function; abnormal ER stress contributes to diabetes pathogenesis. Here, we identified a small molecule, SW016789, with time-dependent effects on beta cell ER stress and function. Acute treatment with SW016789 potentiated nutrient-induced calcium influx and insulin secretion, while chronic exposure to SW016789 transiently induced ER stress and shut down secretory function in a reversible manner. Distinct from the effects of thapsigargin, SW016789 did not affect beta cell viability or apoptosis, potentially due to a rapid induction of adaptive genes, weak signaling through the eIF2α kinase PERK, and lack of oxidative stress gene Txnip induction. We determined that SW016789 acted upstream of voltage-dependent calcium channels (VDCCs) and potentiated nutrient- but not KCl-stimulated calcium influx. Measurements of metabolomics, oxygen consumption rate, and G protein-coupled receptor signaling did not explain the potentiating effects of SW016789. In chemical cotreatment experiments, we discovered synergy between SW016789 and activators of protein kinase C and VDCCs, suggesting involvement of these pathways in the mechanism of action. Finally, chronically elevated calcium influx was required for the inhibitory impact of SW016789, as blockade of VDCCs protected human islets and MIN6 beta cells from hypersecretion-induced dysfunction. We conclude that beta cells undergoing this type of pharmacological hypersecretion have the capacity to suppress their function to mitigate ER stress and avoid apoptosis. These results have the potential to uncover beta cell ER stress mitigation factors and add support to beta cell rest strategies to preserve function.
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Affiliation(s)
| | | | | | | | - Luiz F Barella
- Lilly Diabetes Center of Excellence, Indiana Biosciences Research Institute, Indianapolis, IN, USA
| | - Fiona Armoo
- Lilly Diabetes Center of Excellence, Indiana Biosciences Research Institute, Indianapolis, IN, USA
| | - Melissa K McCoy
- Departments of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Andy V Huynh
- Departments of Pharmacology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Jonathan Z Yang
- Departments of Pharmacology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Bruce A Posner
- Departments of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Melanie H Cobb
- Departments of Pharmacology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Michael A Kalwat
- Correspondence: Michael A. Kalwat, PhD, Lilly Diabetes Center of Excellence, Indiana Biosciences Research Institute, 1210 Waterway Blvd Ste, 2000 Indianapolis, IN 46202, USA. or
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23
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Abstract
The ability to maintain normoglycaemia, through glucose-sensitive insulin release, is a key aspect of postnatal beta cell function. However, terminally differentiated beta cell identity does not necessarily imply functional maturity. Beta cell maturation is therefore a continuation of beta cell development, albeit a process that occurs postnatally in mammals. Although many important features have been identified in the study of beta cell maturation, as of yet no unified mechanistic model of beta cell functional maturity exists. Here, we review recent findings about the underlying mechanisms of beta cell functional maturation. These findings include systemic hormonal and nutritional triggers that operate through energy-sensing machinery shifts within beta cells, resulting in primed metabolic states that allow for appropriate glucose trafficking and, ultimately, insulin release. We also draw attention to the expansive synergistic nature of these pathways and emphasise that beta cell maturation is dependent on overlapping regulatory and metabolic networks.
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Affiliation(s)
- Tom Barsby
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
| | - Timo Otonkoski
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
- Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.
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24
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Is Type 2 Diabetes a Primary Mitochondrial Disorder? Cells 2022; 11:cells11101617. [PMID: 35626654 PMCID: PMC9140179 DOI: 10.3390/cells11101617] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/27/2022] [Accepted: 04/20/2022] [Indexed: 02/06/2023] Open
Abstract
Diabetes mellitus is the most common endocrine disturbance in inherited mitochondrial diseases. It is essential to increase awareness of the correct diagnosis and treatment of diabetes in these patients and screen for the condition in family members, as diabetes might appear with distinctive clinical features, complications and at different ages of onset. The severity of mitochondrial-related diabetes is likely to manifest on a large scale of phenotypes depending on the location of the mutation and whether the number of affected mitochondria copies (heteroplasmy) reaches a critical threshold. Regarding diabetes treatment, the first-choice treatment for type 2 diabetes (T2D), metformin, is not recommended because of the risk of lactic acidosis. The preferred treatment for diabetes in patients with mitochondrial disorders is SGLT-2i and mitochondrial GLP-1-related substances. The tight relationship between mitochondrial dysfunction, reduced glucose-stimulated insulin secretion (GSIS), and diabetes development in human patients is acknowledged. However, despite the well-characterized role of mitochondria in GSIS, there is a relative lack of data in humans implicating mitochondrial dysfunction as a primary defect in T2D. Our recent studies have provided data supporting the significant role of the mitochondrial respiratory-chain enzyme, cytochrome c oxidase (COX), in regulating GSIS in a rodent model of T2D, the Cohen diabetic sensitive (CDs) rat. The nutritionally induced diabetic CDs rat demonstrates several features of mitochondrial diseases: markedly reduced COX activity in several tissues, increased reactive oxygen production, decreased ATP generation, and increased lactate dehydrogenase expression in islets. Moreover, our data demonstrate that reduced islet-COX activity precedes the onset of diabetes, suggesting that islet-COX deficiency is the primary defect causing diabetes in this model. This review examines the possibility of including T2D as a primary mitochondrial-related disease. Understanding the critical interdependence between diabetes and mitochondrial dysfunction, centering on the role of COX, may open novel avenues to diagnose and treat diabetes in patients with mitochondrial diseases and mitochondrial dysfunction in diabetic patients.
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25
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Morriseau TS, Doucette CA, Dolinsky VW. More than meets the islet: aligning nutrient and paracrine inputs with hormone secretion in health and disease. Am J Physiol Endocrinol Metab 2022; 322:E446-E463. [PMID: 35373587 DOI: 10.1152/ajpendo.00411.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pancreatic islet is responsive to an array of endocrine, paracrine, and nutritional inputs that adjust hormone secretion to ensure accurate control of glucose homeostasis. Although the mechanisms governing glucose-coupled insulin secretion have received the most attention, there is emerging evidence for a multitude of physiological signaling pathways and paracrine networks that collectively regulate insulin, glucagon, and somatostatin release. Moreover, the modulation of these pathways in conditions of glucotoxicity or lipotoxicity are areas of both growing interest and controversy. In this review, the contributions of external, intrinsic, and paracrine factors in pancreatic β-, α-, and δ-cell secretion across the full spectrum of physiological (i.e., fasting and fed) and pathophysiological (gluco- and lipotoxicity; diabetes) environments will be critically discussed.
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Affiliation(s)
- Taylor S Morriseau
- Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme of the Children's Hospital Research Institute of Manitoba, Winnipeg, Manitoba, Canada
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Christine A Doucette
- Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme of the Children's Hospital Research Institute of Manitoba, Winnipeg, Manitoba, Canada
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Vernon W Dolinsky
- Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme of the Children's Hospital Research Institute of Manitoba, Winnipeg, Manitoba, Canada
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba, Canada
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26
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Aharon-Hananel G, Romero-Afrima L, Saada A, Mantzur C, Raz I, Weksler-Zangen S. Cytochrome c Oxidase Activity as a Metabolic Regulator in Pancreatic Beta-Cells. Cells 2022; 11:cells11060929. [PMID: 35326380 PMCID: PMC8946064 DOI: 10.3390/cells11060929] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/01/2022] [Accepted: 03/03/2022] [Indexed: 02/06/2023] Open
Abstract
Pancreatic β-cells couple glucose-stimulated insulin secretion (GSIS) with oxidative phosphorylation via cytochrome c oxidase (COX), a mitochondrial respiratory-chain enzyme. The Cohen diabetic-sensitive (CDs) rats exhibit hyperglycemia when fed a diabetogenic diet but maintain normoglycemia on a regular diet. We have previously reported a decreased COX activity in CDs rats and explored its relevance for type 2 diabetes (T2D). In this study, we investigated the relation between COX activity in islets, peripheral-blood mononuclear cells (PBMCs), and GSIS during diabetes development in CDs rats fed a diabetogenic diet for 4, 11, 20, and 30 days and during reversion to normoglycemia in hyperglycemic CDs rats fed a reversion diet for 7, 11, and 20 days. An oral glucose-tolerance test was performed at different periods of the diets measuring blood glucose and insulin concentrations. COX activity was determined in islets and PBMCs isolated from rats at the different periods of the diets. We demonstrated a progressive reduction in COX activity in CDs-islets that correlated positively with the decreasing GSIS (R2 = 0.9691, p < 0.001) and inversely with the elevation in blood glucose levels (R2 = 0.8396, p < 0.001). Hyperglycemia was initiated when islet COX activity decreased below 46%. The reversion diet restored >46% of the islet COX activity and GSIS while re-establishing normoglycemia. Interestingly, COX activity in PBMCs correlated significantly with islet COX activity (R2 = 0.8944, p < 0.001). Our data support islet COX activity as a major metabolic regulator of β-cells function. The correlation between COX activity in PBMCs and islets may serve as a noninvasive biomarker to monitor β-cell dysfunction in diabetes.
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Affiliation(s)
- Genya Aharon-Hananel
- The Hadassah Diabetes Center, Hadassah Medical Center, Jerusalem 9112102, Israel; (G.A.-H.); (L.R.-A.); (C.M.); (I.R.)
- Division of Endocrinology, Diabetes and Metabolism, The Chaim Sheba Medical Center, Tel Hashomer, Ramat-Gan 5266202, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
- The Department of Genetics, Hadassah Medical Center, Jerusalem 9112102, Israel;
| | - Leonor Romero-Afrima
- The Hadassah Diabetes Center, Hadassah Medical Center, Jerusalem 9112102, Israel; (G.A.-H.); (L.R.-A.); (C.M.); (I.R.)
- The Department of Genetics, Hadassah Medical Center, Jerusalem 9112102, Israel;
| | - Ann Saada
- The Department of Genetics, Hadassah Medical Center, Jerusalem 9112102, Israel;
- Faculty of Medicine Hebrew, University of Jerusalem, Jerusalem 9112102, Israel
| | - Carmit Mantzur
- The Hadassah Diabetes Center, Hadassah Medical Center, Jerusalem 9112102, Israel; (G.A.-H.); (L.R.-A.); (C.M.); (I.R.)
| | - Itamar Raz
- The Hadassah Diabetes Center, Hadassah Medical Center, Jerusalem 9112102, Israel; (G.A.-H.); (L.R.-A.); (C.M.); (I.R.)
- Faculty of Medicine Hebrew, University of Jerusalem, Jerusalem 9112102, Israel
| | - Sarah Weksler-Zangen
- The Hadassah Diabetes Center, Hadassah Medical Center, Jerusalem 9112102, Israel; (G.A.-H.); (L.R.-A.); (C.M.); (I.R.)
- Faculty of Medicine Hebrew, University of Jerusalem, Jerusalem 9112102, Israel
- The Liver Research Laboratory, Hadassah Medical Center, Jerusalem 9112102, Israel
- Correspondence: ; Tel.: +972-50-5172008
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27
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Balboa D, Barsby T, Lithovius V, Saarimäki-Vire J, Omar-Hmeadi M, Dyachok O, Montaser H, Lund PE, Yang M, Ibrahim H, Näätänen A, Chandra V, Vihinen H, Jokitalo E, Kvist J, Ustinov J, Nieminen AI, Kuuluvainen E, Hietakangas V, Katajisto P, Lau J, Carlsson PO, Barg S, Tengholm A, Otonkoski T. Functional, metabolic and transcriptional maturation of human pancreatic islets derived from stem cells. Nat Biotechnol 2022; 40:1042-1055. [PMID: 35241836 PMCID: PMC9287162 DOI: 10.1038/s41587-022-01219-z] [Citation(s) in RCA: 122] [Impact Index Per Article: 61.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 01/11/2022] [Indexed: 12/19/2022]
Abstract
Transplantation of pancreatic islet cells derived from human pluripotent stem cells is a promising treatment for diabetes. Despite progress in the generation of stem-cell-derived islets (SC-islets), no detailed characterization of their functional properties has been conducted. Here, we generated functionally mature SC-islets using an optimized protocol and benchmarked them comprehensively against primary adult islets. Biphasic glucose-stimulated insulin secretion developed during in vitro maturation, associated with cytoarchitectural reorganization and the increasing presence of alpha cells. Electrophysiology, signaling and exocytosis of SC-islets were similar to those of adult islets. Glucose-responsive insulin secretion was achieved despite differences in glycolytic and mitochondrial glucose metabolism. Single-cell transcriptomics of SC-islets in vitro and throughout 6 months of engraftment in mice revealed a continuous maturation trajectory culminating in a transcriptional landscape closely resembling that of primary islets. Our thorough evaluation of SC-islet maturation highlights their advanced degree of functionality and supports their use in further efforts to understand and combat diabetes. Pancreatic islets derived from stem cells are benchmarked against primary cells.
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Affiliation(s)
- Diego Balboa
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Bioinformatics and Genomics Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Barcelona, Spain
| | - Tom Barsby
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Väinö Lithovius
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jonna Saarimäki-Vire
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | | | - Oleg Dyachok
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Hossam Montaser
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Per-Eric Lund
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Mingyu Yang
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Hazem Ibrahim
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Anna Näätänen
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Vikash Chandra
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Helena Vihinen
- Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Jouni Kvist
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jarkko Ustinov
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Anni I Nieminen
- Metabolomics Unit, Institute for Molecular Medicine Finland, Helsinki, Finland
| | - Emilia Kuuluvainen
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Ville Hietakangas
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.,Molecular and Integrative Bioscience Research Program, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Pekka Katajisto
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.,Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
| | - Joey Lau
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Per-Ola Carlsson
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Timo Otonkoski
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland. .,Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.
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28
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Xiong Y, Wu L, Shao L, Wang Y, Huang Z, Huang X, Li C, Wu A, Liu Z, Fan X, Zhou P. Dynamic Alterations of the Gut Microbial Pyrimidine and Purine Metabolism in the Development of Liver Cirrhosis. Front Mol Biosci 2022; 8:811399. [PMID: 35155569 PMCID: PMC8832137 DOI: 10.3389/fmolb.2021.811399] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 12/22/2021] [Indexed: 12/02/2022] Open
Abstract
Background: Liver cirrhosis is the common end-stage of liver disease which lacks effective treatment, thus studies to determine prevention targets are an urgent need. The intestinal microbiota (IM) play important roles in modulating liver diseases which are mediated by microbial metabolites. Despite decades of growing microbial studies, whether IM contribute to the development of cirrhosis and the intimate metabolic link remain obscure. Here, we aimed to reveal the dynamic alterations of microbial composition and metabolic signatures in carbon tetrachloride (CCl4)-induced liver cirrhosis mice. Methods: CCl4-treated mice or normal control (NC) were sacrificed (n = 10 per group) after 5 and 15 weeks of intervention. The disease severity was confirmed by Masson’s trichrome or Sirius red staining. Metagenomics sequencing and fecal untargeted metabolomics were performed to evaluate the composition and metabolic function of IM in parallel with the development of cirrhosis. Results: The CCl4-treated mice presented liver fibrosis at 5 weeks and liver cirrhosis at 15 weeks indicated by collagen deposition and pseudo-lobule formation, respectively. Mice with liver cirrhosis showed distinct microbial composition from NC, even in the earlier fibrosis stage. Importantly, both of the liver fibrosis and cirrhosis mice were characterized with the depletion of Deltaproteobacteria (p < 0.05) and enrichment of Akkermansia (p < 0.05). Furthermore, fecal metabolomics revealed distinguished metabolomics profiles of mice with liver fibrosis and cirrhosis from the NC. Notably, pathway enrichment analysis pointed to remarkable disturbance of purine (p < 0.001 at 5 weeks, p = 0.034 at 15 weeks) and pyrimidine metabolic pathways (p = 0.005 at 5 weeks, p = 0.006 at 15 weeks) during the development of liver cirrhosis. Interestingly, the disorders of pyrimidine and purine metabolites like the known microbial metabolites thymidine and 2′-deoxyuridine had already occurred in liver fibrosis and continued in cirrhosis. Conclusion: These novel findings indicated the crucial role of IM-modulated pyrimidine and purine metabolites in the development of liver cirrhosis, which provides microbial targets for disease prevention.
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Affiliation(s)
- Yinghui Xiong
- The Hunan Provincial Key Laboratory of Viral Hepatitis, Department of Infectious Diseases, Xiangya Hospital, Central South University, Changsha, China
- Department of Infectious Diseases, Infection Control Center, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Li Wu
- The Hunan Provincial Key Laboratory of Viral Hepatitis, Department of Infectious Diseases, Xiangya Hospital, Central South University, Changsha, China
| | - Li Shao
- Institute of Translational Medicine, The Affiliated Hospital of Hangzhou Normal University, Hangzhou, China
| | - Yang Wang
- The Hunan Provincial Key Laboratory of Viral Hepatitis, Department of Infectious Diseases, Xiangya Hospital, Central South University, Changsha, China
- Institute of Integrative Medicine, Department of Integrated Traditional Chinese and Western Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - Zebing Huang
- The Hunan Provincial Key Laboratory of Viral Hepatitis, Department of Infectious Diseases, Xiangya Hospital, Central South University, Changsha, China
| | - Xun Huang
- Infection Control Center, Xiangya Hospital, Central South University, Changsha, China
| | - Chunhui Li
- Infection Control Center, Xiangya Hospital, Central South University, Changsha, China
| | - Anhua Wu
- Infection Control Center, Xiangya Hospital, Central South University, Changsha, China
| | - Zhenguo Liu
- Department of Infectious Diseases, Infection Control Center, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Xuegong Fan
- The Hunan Provincial Key Laboratory of Viral Hepatitis, Department of Infectious Diseases, Xiangya Hospital, Central South University, Changsha, China
- *Correspondence: Xuegong Fan, ; Pengcheng Zhou,
| | - Pengcheng Zhou
- Department of Infectious Diseases, Infection Control Center, The Third Xiangya Hospital, Central South University, Changsha, China
- Infection Control Center, Xiangya Hospital, Central South University, Changsha, China
- *Correspondence: Xuegong Fan, ; Pengcheng Zhou,
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29
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Murao N, Yokoi N, Takahashi H, Hayami T, Minami Y, Seino S. Increased glycolysis affects β-cell function and identity in aging and diabetes. Mol Metab 2021; 55:101414. [PMID: 34871777 PMCID: PMC8732780 DOI: 10.1016/j.molmet.2021.101414] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 11/25/2021] [Accepted: 12/01/2021] [Indexed: 12/24/2022] Open
Abstract
Objective Age is a risk factor for type 2 diabetes (T2D). We aimed to elucidate whether β-cell glucose metabolism is altered with aging and contributes to T2D. Methods We used senescence-accelerated mice (SAM), C57BL/6J (B6) mice, and ob/ob mice as aging models. As a diabetes model, we used db/db mice. The glucose responsiveness of insulin secretion and the [U-13C]-glucose metabolic flux were examined in isolated islets. We analyzed the expression of β-cell-specific genes in isolated islets and pancreatic sections as molecular signatures of β-cell identity. β cells defective in the malate-aspartate (MA) shuttle were previously generated from MIN6-K8 cells by the knockout of Got1, a component of the shuttle. We analyzed Got1 KO β cells as a model of increased glycolysis. Results We identified hyperresponsiveness to glucose and compromised cellular identity as dysfunctional phenotypes shared in common between aged and diabetic mouse β cells. We also observed a metabolic commonality between aged and diabetic β cells: hyperactive glycolysis through the increased expression of nicotinamide mononucleotide adenylyl transferase 2 (Nmnat2), a cytosolic nicotinamide adenine dinucleotide (NAD)-synthesizing enzyme. Got1 KO β cells showed increased glycolysis, β-cell dysfunction, and impaired cellular identity, phenocopying aging and diabetes. Using Got1 KO β cells, we show that attenuation of glycolysis or Nmnat2 activity can restore β-cell function and identity. Conclusions Our study demonstrates that hyperactive glycolysis is a metabolic signature of aged and diabetic β cells, which may underlie age-related β-cell dysfunction and loss of cellular identity. We suggest Nmnat2 suppression as an approach to counteract age-related T2D. Glucose hypersensitivity and impaired identity are common features of aged and diabetic β cells. Metabolic tracing reveals increased glycolysis and altered NAD production in aged and diabetic β cells. Increased glycolysis induces β-cell dysfunction and loss of identity. NAD production by Nmnat2 can be targeted to restore β-cell phenotypes.
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Affiliation(s)
- Naoya Murao
- Division of Molecular and Metabolic Medicine, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan
| | - Norihide Yokoi
- Division of Molecular and Metabolic Medicine, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan; Laboratory of Animal Breeding and Genetics, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Kyoto 606-8502, Japan
| | - Harumi Takahashi
- Division of Molecular and Metabolic Medicine, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan.
| | - Tomohide Hayami
- Division of Molecular and Metabolic Medicine, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan; Division of Diabetes, Department of Internal Medicine, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
| | - Yasuhiro Minami
- Division of Cell Physiology, Graduate School of Medicine, Kobe University, Chuo-ku, Kobe, Hyogo 650-0017, Japan
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan
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30
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Close AF, Chae H, Jonas JC. The lack of functional nicotinamide nucleotide transhydrogenase only moderately contributes to the impairment of glucose tolerance and glucose-stimulated insulin secretion in C57BL/6J vs C57BL/6N mice. Diabetologia 2021; 64:2550-2561. [PMID: 34448880 DOI: 10.1007/s00125-021-05548-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 05/26/2021] [Indexed: 12/31/2022]
Abstract
AIMS/HYPOTHESIS Nicotinamide nucleotide transhydrogenase (NNT) is involved in mitochondrial NADPH production and its spontaneous inactivating mutation (NntTr [Tr, truncated]) is usually considered to be the main cause of the lower glucose tolerance of C57BL/6J vs C57BL/6N mice. However, the impact of this mutation on glucose tolerance remains disputed. Here, we singled out the impact of NntTr from that of other genetic variants between C57BL/6J and C57BL/6N mice on mitochondrial glutathione redox state (EGSH), glucose-stimulated insulin secretion (GSIS) and glucose tolerance. METHODS Male and female N5BL/6J mice that express wild-type Nnt (NntWT) or NntTr (N5-WT and N5-Tr mice) on the C57BL/6J genetic background were obtained by crossing N5BL/6J NntWT/Tr heterozygous mice. C57BL/6J and C57BL/6N mice were from Janvier Labs. The Nnt genotype was confirmed by PCR and the genetic background by whole genome sequencing of one mouse of each type. Glucose tolerance was assessed by IPGTT, ITT and fasting/refeeding tests. Stimulus-secretion coupling events and GSIS were measured in isolated pancreatic islets. Cytosolic and mitochondrial EGSH were measured using the fluorescent redox probe GRX1-roGFP2 (glutaredoxin 1 fused to redox-sensitive enhanced GFP). RESULTS The Nnt genotype and genetic background of each type of mouse were confirmed. As reported previously in C57BL/6N vs C57BL/6J islets, the glucose regulation of mitochondrial (but not cytosolic) EGSH and of NAD(P)H autofluorescence was markedly improved in N5-WT vs N5-Tr islets, confirming the role of NNT in mitochondrial redox regulation. However, ex vivo GSIS was only 1.2-1.4-times higher in N5-WT vs N5-Tr islets, while it was 2.4-times larger in C57BL/6N vs N5-WT islets, questioning the role of NNT in GSIS. In vivo, the ITT results did not differ between N5-WT and N5-Tr or C57BL/6N mice. However, the glucose excursion during an IPGTT was only 15-20% lower in female N5-WT mice than in N5-Tr and C57BL/6J mice and remained 3.5-times larger than in female C57BL/6N mice. Similar observations were made during a fasting/refeeding test. A slightly larger (~30%) impact of NNT on glucose tolerance was found in males. CONCLUSIONS/INTERPRETATION Although our results confirm the importance of NNT in the regulation of mitochondrial redox state by glucose, they markedly downsize the role of NNT in the alteration of GSIS and glucose tolerance in C57BL/6J vs C57BL/6N mice. Therefore, documenting an NntWT genotype in C57BL/6 mice does not provide proof that their glucose tolerance is as good as in C57BL/6N mice.
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Affiliation(s)
- Anne-Françoise Close
- Secteur des sciences de la santé, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Université catholique de Louvain, Brussels, Belgium
| | - Heeyoung Chae
- Secteur des sciences de la santé, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Université catholique de Louvain, Brussels, Belgium
| | - Jean-Christophe Jonas
- Secteur des sciences de la santé, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Université catholique de Louvain, Brussels, Belgium.
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Walker JT, Saunders DC, Brissova M, Powers AC. The Human Islet: Mini-Organ With Mega-Impact. Endocr Rev 2021; 42:605-657. [PMID: 33844836 PMCID: PMC8476939 DOI: 10.1210/endrev/bnab010] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Indexed: 02/08/2023]
Abstract
This review focuses on the human pancreatic islet-including its structure, cell composition, development, function, and dysfunction. After providing a historical timeline of key discoveries about human islets over the past century, we describe new research approaches and technologies that are being used to study human islets and how these are providing insight into human islet physiology and pathophysiology. We also describe changes or adaptations in human islets in response to physiologic challenges such as pregnancy, aging, and insulin resistance and discuss islet changes in human diabetes of many forms. We outline current and future interventions being developed to protect, restore, or replace human islets. The review also highlights unresolved questions about human islets and proposes areas where additional research on human islets is needed.
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Affiliation(s)
- John T Walker
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Diane C Saunders
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Marcela Brissova
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Alvin C Powers
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.,Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA.,VA Tennessee Valley Healthcare System, Nashville, Tennessee, USA
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Vishnu N, Hamilton A, Bagge A, Wernersson A, Cowan E, Barnard H, Sancak Y, Kamer KJ, Spégel P, Fex M, Tengholm A, Mootha VK, Nicholls DG, Mulder H. Mitochondrial clearance of calcium facilitated by MICU2 controls insulin secretion. Mol Metab 2021; 51:101239. [PMID: 33932586 PMCID: PMC8163986 DOI: 10.1016/j.molmet.2021.101239] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/20/2021] [Accepted: 04/21/2021] [Indexed: 01/20/2023] Open
Abstract
OBJECTIVE Transport of Ca2+ into pancreatic β cell mitochondria facilitates nutrient-mediated insulin secretion. However, the underlying mechanism is unclear. Recent establishment of the molecular identity of the mitochondrial Ca2+ uniporter (MCU) and associated proteins allows modification of mitochondrial Ca2+ transport in intact cells. We examined the consequences of deficiency of the accessory protein MICU2 in rat and human insulin-secreting cells and mouse islets. METHODS siRNA silencing of Micu2 in the INS-1 832/13 and EndoC-βH1 cell lines was performed; Micu2-/- mice were also studied. Insulin secretion and mechanistic analyses utilizing live confocal imaging to assess mitochondrial function and intracellular Ca2+ dynamics were performed. RESULTS Silencing of Micu2 abrogated GSIS in the INS-1 832/13 and EndoC-βH1 cells. The Micu2-/- mice also displayed attenuated GSIS. Mitochondrial Ca2+ uptake declined in MICU2-deficient INS-1 832/13 and EndoC-βH1 cells in response to high glucose and high K+. MICU2 silencing in INS-1 832/13 cells, presumably through its effects on mitochondrial Ca2+ uptake, perturbed mitochondrial function illustrated by absent mitochondrial membrane hyperpolarization and lowering of the ATP/ADP ratio in response to elevated glucose. Despite the loss of mitochondrial Ca2+ uptake, cytosolic Ca2+ was lower in siMICU2-treated INS-1 832/13 cells in response to high K+. It was hypothesized that Ca2+ accumulated in the submembrane compartment in MICU2-deficient cells, resulting in desensitization of voltage-dependent Ca2+ channels, lowering total cytosolic Ca2+. Upon high K+ stimulation, MICU2-silenced cells showed higher and prolonged increases in submembrane Ca2+ levels. CONCLUSIONS MICU2 plays a critical role in β cell mitochondrial Ca2+ uptake. β cell mitochondria sequestered Ca2+ from the submembrane compartment, preventing desensitization of voltage-dependent Ca2+ channels and facilitating GSIS.
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Affiliation(s)
- N Vishnu
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden
| | - A Hamilton
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden
| | - A Bagge
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden
| | - A Wernersson
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden
| | - E Cowan
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden
| | - H Barnard
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden
| | - Y Sancak
- Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - K J Kamer
- Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - P Spégel
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden
| | - M Fex
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden
| | - A Tengholm
- Department of Medical Cell Biology, Uppsala University, Uppsala SE-751 23, Sweden
| | - V K Mootha
- Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - D G Nicholls
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden; Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - H Mulder
- Unit of Molecular Metabolism, Lund University Diabetes Center, Lund University, Malmö SE-205 02, Sweden.
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Stožer A, Skelin Klemen M, Gosak M, Križančić Bombek L, Pohorec V, Slak Rupnik M, Dolenšek J. Glucose-dependent activation, activity, and deactivation of beta cell networks in acute mouse pancreas tissue slices. Am J Physiol Endocrinol Metab 2021; 321:E305-E323. [PMID: 34280052 DOI: 10.1152/ajpendo.00043.2021] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 07/09/2021] [Indexed: 12/14/2022]
Abstract
Many details of glucose-stimulated intracellular calcium changes in β cells during activation, activity, and deactivation, as well as their concentration-dependence, remain to be analyzed. Classical physiological experiments indicated that in islets, functional differences between individual cells are largely attenuated, but recent findings suggest considerable intercellular heterogeneity, with some cells possibly coordinating the collective responses. To address the above with an emphasis on heterogeneity and describing the relations between classical physiological and functional network properties, we performed functional multicellular calcium imaging in mouse pancreas tissue slices over a wide range of glucose concentrations. During activation, delays to activation of cells and any-cell-to-first-responder delays are shortened, and the sizes of simultaneously responding clusters increased with increasing glucose concentrations. Exactly the opposite characterized deactivation. The frequency of fast calcium oscillations during activity increased with increasing glucose up to 12 mM glucose concentration, beyond which oscillation duration became longer, resulting in a homogenous increase in active time. In terms of functional connectivity, islets progressed from a very segregated network to a single large functional unit with increasing glucose concentration. A comparison between classical physiological and network parameters revealed that the first-responders during activation had longer active times during plateau and the most active cells during the plateau tended to deactivate later. Cells with the most functional connections tended to activate sooner, have longer active times, and deactivate later. Our findings provide a common ground for recent differing views on β cell heterogeneity and an important baseline for future studies of stimulus-secretion and intercellular coupling.NEW & NOTEWORTHY We assessed concentration-dependence in coupled β cells, degree of functional heterogeneity, and uncovered possible specialized subpopulations during the different phases of the response to glucose at the level of many individual cells. To this aim, we combined acute mouse pancreas tissue slices with functional multicellular calcium imaging over a wide range from threshold (7 mM) and physiological (8 and 9 mM) to supraphysiological (12 and 16 mM) glucose concentrations, classical physiological, and advanced network analyses.
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Affiliation(s)
- Andraž Stožer
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
| | - Maša Skelin Klemen
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
| | - Marko Gosak
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia
| | | | - Viljem Pohorec
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
| | - Marjan Slak Rupnik
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
- Alma Mater Europaea-European Center Maribor, Maribor, Slovenia
| | - Jurij Dolenšek
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia
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Rustenbeck I, Schulze T, Morsi M, Alshafei M, Panten U. What Is the Metabolic Amplification of Insulin Secretion and Is It (Still) Relevant? Metabolites 2021; 11:metabo11060355. [PMID: 34199454 PMCID: PMC8229681 DOI: 10.3390/metabo11060355] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 05/27/2021] [Accepted: 05/31/2021] [Indexed: 12/24/2022] Open
Abstract
The pancreatic beta-cell transduces the availability of nutrients into the secretion of insulin. While this process is extensively modified by hormones and neurotransmitters, it is the availability of nutrients, above all glucose, which sets the process of insulin synthesis and secretion in motion. The central role of the mitochondria in this process was identified decades ago, but how changes in mitochondrial activity are coupled to the exocytosis of insulin granules is still incompletely understood. The identification of ATP-sensitive K+-channels provided the link between the level of adenine nucleotides and the electrical activity of the beta cell, but the depolarization-induced Ca2+-influx into the beta cells, although necessary for stimulated secretion, is not sufficient to generate the secretion pattern as produced by glucose and other nutrient secretagogues. The metabolic amplification of insulin secretion is thus the sequence of events that enables the secretory response to a nutrient secretagogue to exceed the secretory response to a purely depolarizing stimulus and is thus of prime importance. Since the cataplerotic export of mitochondrial metabolites is involved in this signaling, an orienting overview on the topic of nutrient secretagogues beyond glucose is included. Their judicious use may help to define better the nature of the signals and their mechanism of action.
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Affiliation(s)
- Ingo Rustenbeck
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, D38106 Braunschweig, Germany; (T.S.); (M.M.); (M.A.); (U.P.)
- Correspondence: ; Tel.: +49-(0)53-139-156-70
| | - Torben Schulze
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, D38106 Braunschweig, Germany; (T.S.); (M.M.); (M.A.); (U.P.)
| | - Mai Morsi
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, D38106 Braunschweig, Germany; (T.S.); (M.M.); (M.A.); (U.P.)
- Department of Pharmacology, Faculty of Pharmacy, Assiut University, Assiut 71526, Egypt
| | - Mohammed Alshafei
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, D38106 Braunschweig, Germany; (T.S.); (M.M.); (M.A.); (U.P.)
| | - Uwe Panten
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, D38106 Braunschweig, Germany; (T.S.); (M.M.); (M.A.); (U.P.)
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35
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Nicholls DG. Mitochondrial proton leaks and uncoupling proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148428. [PMID: 33798544 DOI: 10.1016/j.bbabio.2021.148428] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 03/15/2021] [Accepted: 03/25/2021] [Indexed: 01/02/2023]
Abstract
Non-shivering thermogenesis in brown adipose tissue is mediated by uncoupling protein 1 (UCP1), which provides a carefully regulated proton re-entry pathway across the mitochondrial inner membrane operating in parallel to the ATP synthase and allowing respiration, and hence thermogenesis, to be released from the constraints of respiratory control. In the 40 years since UCP1 was first described, an extensive, and frequently contradictory, literature has accumulated, focused on the acute physiological regulation of the protein by fatty acids, purine nucleotides and possible additional factors. The purpose of this review is to examine, in detail, the experimental evidence underlying these proposed mechanisms. Emphasis will be placed on the methodologies employed and their relation to the physiological constraints under which the protein functions in the intact cell. The nature of the endogenous, UCP1-independent, proton leak will also be discussed. Finally, the troubled history of the putative novel uncoupling proteins, UCP2 and UCP3, will be evaluated.
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36
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Mitochondrial Calcium Signaling in Pancreatic β-Cell. Int J Mol Sci 2021; 22:ijms22052515. [PMID: 33802289 PMCID: PMC7959128 DOI: 10.3390/ijms22052515] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/22/2021] [Accepted: 02/26/2021] [Indexed: 12/13/2022] Open
Abstract
Accumulation of calcium in energized mitochondria of pancreatic β-cells is emerging as a crucial process for pancreatic β-cell function. β-cell mitochondria sense and shape calcium signals, linking the metabolism of glucose and other secretagogues to the generation of signals that promote insulin secretion during nutrient stimulation. Here, we describe the role of mitochondrial calcium signaling in pancreatic β-cell function. We report the latest pharmacological and genetic findings, including the first mitochondrial calcium-targeted intervention strategies developed to modulate pancreatic β-cell function and their potential relevance in the context of diabetes.
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37
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Bourgeois S, Sawatani T, Van Mulders A, De Leu N, Heremans Y, Heimberg H, Cnop M, Staels W. Towards a Functional Cure for Diabetes Using Stem Cell-Derived Beta Cells: Are We There Yet? Cells 2021; 10:cells10010191. [PMID: 33477961 PMCID: PMC7835995 DOI: 10.3390/cells10010191] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 01/12/2021] [Indexed: 02/06/2023] Open
Abstract
Diabetes mellitus is a pandemic metabolic disorder that results from either the autoimmune destruction or the dysfunction of insulin-producing pancreatic beta cells. A promising cure is beta cell replacement through the transplantation of islets of Langerhans. However, donor shortage hinders the widespread implementation of this therapy. Human pluripotent stem cells, including embryonic stem cells and induced pluripotent stem cells, represent an attractive alternative beta cell source for transplantation. Although major advances over the past two decades have led to the generation of stem cell-derived beta-like cells that share many features with genuine beta cells, producing fully mature beta cells remains challenging. Here, we review the current status of beta cell differentiation protocols and highlight specific challenges that are associated with producing mature beta cells. We address the challenges and opportunities that are offered by monogenic forms of diabetes. Finally, we discuss the remaining hurdles for clinical application of stem cell-derived beta cells and the status of ongoing clinical trials.
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Affiliation(s)
- Stephanie Bourgeois
- Beta Cell Neogenesis (BENE) Research Group, Vrije Universiteit Brussel (VUB), 1090 Brussels, Belgium; (S.B.); (A.V.M.); (N.D.L.); (Y.H.); (H.H.)
| | - Toshiaki Sawatani
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles, 1070 Brussels, Belgium; (T.S.); (M.C.)
| | - Annelore Van Mulders
- Beta Cell Neogenesis (BENE) Research Group, Vrije Universiteit Brussel (VUB), 1090 Brussels, Belgium; (S.B.); (A.V.M.); (N.D.L.); (Y.H.); (H.H.)
| | - Nico De Leu
- Beta Cell Neogenesis (BENE) Research Group, Vrije Universiteit Brussel (VUB), 1090 Brussels, Belgium; (S.B.); (A.V.M.); (N.D.L.); (Y.H.); (H.H.)
- Department of Endocrinology, University Hospital Brussels, 1090 Brussels, Belgium
- Department of Endocrinology, ASZ Aalst, 9300 Aalst, Belgium
| | - Yves Heremans
- Beta Cell Neogenesis (BENE) Research Group, Vrije Universiteit Brussel (VUB), 1090 Brussels, Belgium; (S.B.); (A.V.M.); (N.D.L.); (Y.H.); (H.H.)
| | - Harry Heimberg
- Beta Cell Neogenesis (BENE) Research Group, Vrije Universiteit Brussel (VUB), 1090 Brussels, Belgium; (S.B.); (A.V.M.); (N.D.L.); (Y.H.); (H.H.)
| | - Miriam Cnop
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles, 1070 Brussels, Belgium; (T.S.); (M.C.)
- Division of Endocrinology, Erasmus Hospital, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | - Willem Staels
- Beta Cell Neogenesis (BENE) Research Group, Vrije Universiteit Brussel (VUB), 1090 Brussels, Belgium; (S.B.); (A.V.M.); (N.D.L.); (Y.H.); (H.H.)
- Service of Pediatric Endocrinology, Department of Pediatrics, KidZ Health Castle, Universitair Ziekenhuis Brussel (UZ Brussel), 1090 Brussels, Belgium
- Correspondence: ; Tel.: +32-0-24774473
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Torres Dominguez EA, Meza Peñafiel A, Gómez Pedraza A, Martínez Leo EE. Molecular mechanisms from insulin-mimetic effect of vitamin D: treatment alternative in Type 2 diabetes mellitus. Food Funct 2021; 12:6682-6690. [PMID: 34165135 DOI: 10.1039/d0fo03230a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Diabetes mellitus is a complex and multifactorial disease with a global prevalence that exceeds 425 million people. Type 2 diabetes mellitus (T2DM) is characterized by a state of insulin resistance, which leads to metabolic alterations that aggravate the state of health of people. Vitamin D deficiency appears to play an important role in the triggering mechanisms of insulin resistance. In this review, an analysis is made of the biochemical mechanisms associated with the insulin-mimetic effect of vitamin D, its supplementation being a possible nutritional strategy for the T2DM treatment. The current scientific evidence is extensive regarding the dose of vitamin D used for an insulin-mimetic effect. However, clinical trials and systematic reviews show statistical differences on glucose, insulin, and glycated hemoglobin levels of patients with T2DM, associated with activation mechanisms of transcription factors related to genes of the glucide metabolism and the insulin receptor, and the regulation of intracellular Ca2+ insulin concentrations. Likewise, an indirect mechanism associated with antioxidant and anti-inflammatory effects has been shown that also leads to sensitivity to the insulin receptor. The use of a specific dose of vitamin D could be an effective alternative in the T2DM treatment, which would reduce the risk of complications derived from hyperglycemia.
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Balboa D, Iworima DG, Kieffer TJ. Human Pluripotent Stem Cells to Model Islet Defects in Diabetes. Front Endocrinol (Lausanne) 2021; 12:642152. [PMID: 33828531 PMCID: PMC8020750 DOI: 10.3389/fendo.2021.642152] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 02/03/2021] [Indexed: 12/17/2022] Open
Abstract
Diabetes mellitus is characterized by elevated levels of blood glucose and is ultimately caused by insufficient insulin production from pancreatic beta cells. Different research models have been utilized to unravel the molecular mechanisms leading to the onset of diabetes. The generation of pancreatic endocrine cells from human pluripotent stem cells constitutes an approach to study genetic defects leading to impaired beta cell development and function. Here, we review the recent progress in generating and characterizing functional stem cell-derived beta cells. We summarize the diabetes disease modeling possibilities that stem cells offer and the challenges that lie ahead to further improve these models.
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Affiliation(s)
- Diego Balboa
- Regulatory Genomics and Diabetes, Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Barcelona, Spain
- *Correspondence: Diego Balboa,
| | - Diepiriye G. Iworima
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
- School of Biomedical Engineering, The University of British Columbia, Vancouver, BC, Canada
| | - Timothy J. Kieffer
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
- School of Biomedical Engineering, The University of British Columbia, Vancouver, BC, Canada
- Department of Surgery, University of British Columbia, Vancouver, BC, Canada
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40
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Chareyron I, Christen S, Moco S, Valsesia A, Lassueur S, Dayon L, Wollheim CB, Santo Domingo J, Wiederkehr A. Augmented mitochondrial energy metabolism is an early response to chronic glucose stress in human pancreatic beta cells. Diabetologia 2020; 63:2628-2640. [PMID: 32960311 PMCID: PMC7641954 DOI: 10.1007/s00125-020-05275-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 08/04/2020] [Indexed: 01/15/2023]
Abstract
AIMS/HYPOTHESIS In islets from individuals with type 2 diabetes and in islets exposed to chronic elevated glucose, mitochondrial energy metabolism is impaired. Here, we studied early metabolic changes and mitochondrial adaptations in human beta cells during chronic glucose stress. METHODS Respiration and cytosolic ATP changes were measured in human islet cell clusters after culture for 4 days in 11.1 mmol/l glucose. Metabolomics was applied to analyse intracellular metabolite changes as a result of glucose stress conditions. Alterations in beta cell function were followed using insulin secretion assays or cytosolic calcium signalling after expression of the calcium probe YC3.6 specifically in beta cells of islet clusters. RESULTS At early stages of glucose stress, mitochondrial energy metabolism was augmented in contrast to the previously described mitochondrial dysfunction in beta cells from islets of diabetic donors. Following chronic glucose stress, mitochondrial respiration increased (by 52.4%, p < 0.001) and, as a consequence, the cytosolic ATP/ADP ratio in resting human pancreatic islet cells was elevated (by 27.8%, p < 0.05). Because of mitochondrial overactivation in the resting state, nutrient-induced beta cell activation was reduced. In addition, chronic glucose stress caused metabolic adaptations that resulted in the accumulation of intermediates of the glycolytic pathway, the pentose phosphate pathway and the TCA cycle; the most strongly augmented metabolite was glycerol 3-phosphate. The changes in metabolites observed are likely to be due to the inability of mitochondria to cope with continuous nutrient oversupply. To protect beta cells from chronic glucose stress, we inhibited mitochondrial pyruvate transport. Metabolite concentrations were partially normalised and the mitochondrial respiratory response to nutrients was markedly improved. Furthermore, stimulus-secretion coupling as assessed by cytosolic calcium signalling, was restored. CONCLUSION/INTERPRETATION We propose that metabolic changes and associated mitochondrial overactivation are early adaptations to glucose stress, and may reflect what happens as a result of poor blood glucose control. Inhibition of mitochondrial pyruvate transport reduces mitochondrial nutrient overload and allows beta cells to recover from chronic glucose stress. Graphical abstract.
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Affiliation(s)
- Isabelle Chareyron
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park, Lausanne, Switzerland
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Stefan Christen
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park, Lausanne, Switzerland
| | - Sofia Moco
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park, Lausanne, Switzerland
| | - Armand Valsesia
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park, Lausanne, Switzerland
| | - Steve Lassueur
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park, Lausanne, Switzerland
| | - Loïc Dayon
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park, Lausanne, Switzerland
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Claes B Wollheim
- Department of Cell Physiology and Metabolism, University Medical Center, Geneva, Switzerland
| | - Jaime Santo Domingo
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park, Lausanne, Switzerland
| | - Andreas Wiederkehr
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park, Lausanne, Switzerland.
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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41
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Jones AE, Sheng L, Acevedo A, Veliova M, Shirihai OS, Stiles L, Divakaruni AS. Forces, fluxes, and fuels: tracking mitochondrial metabolism by integrating measurements of membrane potential, respiration, and metabolites. Am J Physiol Cell Physiol 2020; 320:C80-C91. [PMID: 33147057 DOI: 10.1152/ajpcell.00235.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Assessing mitochondrial function in cell-based systems is a central component of metabolism research. However, the selection of an initial measurement technique may be complicated given the range of parameters that can be studied and the need to define the mitochondrial (dys)function of interest. This methods-focused review compares and contrasts the use of mitochondrial membrane potential measurements, plate-based respirometry, and metabolomics and stable isotope tracing. We demonstrate how measurements of 1) cellular substrate preference, 2) respiratory chain activity, 3) cell activation, and 4) mitochondrial biogenesis are enriched by integrating information from multiple methods. This manuscript is meant to serve as a perspective to help choose which technique might be an appropriate initial method to answer a given question, as well as provide a broad "roadmap" for designing follow-up assays to enrich datasets or resolve ambiguous results.
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Affiliation(s)
- Anthony E Jones
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California
| | - Li Sheng
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California
| | - Aracely Acevedo
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California
| | - Michaela Veliova
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California.,Department of Medicine, University of California, Los Angeles, California
| | - Orian S Shirihai
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California.,Department of Medicine, University of California, Los Angeles, California
| | - Linsey Stiles
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California.,Department of Medicine, University of California, Los Angeles, California
| | - Ajit S Divakaruni
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California
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42
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Kilanowska A, Ziółkowska A. Role of Phosphodiesterase in the Biology and Pathology of Diabetes. Int J Mol Sci 2020; 21:E8244. [PMID: 33153226 PMCID: PMC7662747 DOI: 10.3390/ijms21218244] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 12/12/2022] Open
Abstract
Glucose metabolism is the initiator of a large number of molecular secretory processes in β cells. Cyclic nucleotides as a second messenger are the main physiological regulators of these processes and are functionally divided into compartments in pancreatic cells. Their intracellular concentration is limited by hydrolysis led by one or more phosphodiesterase (PDE) isoenzymes. Literature data confirmed multiple expressions of PDEs subtypes, but the specific roles of each in pancreatic β-cell function, particularly in humans, are still unclear. Isoforms present in the pancreas are also found in various tissues of the body. Normoglycemia and its strict control are supported by the appropriate release of insulin from the pancreas and the action of insulin in peripheral tissues, including processes related to homeostasis, the regulation of which is based on the PDE- cyclic AMP (cAMP) signaling pathway. The challenge in developing a therapeutic solution based on GSIS (glucose-stimulated insulin secretion) enhancers targeted at PDEs is the selective inhibition of their activity only within β cells. Undeniably, PDEs inhibitors have therapeutic potential, but some of them are burdened with certain adverse effects. Therefore, the chance to use knowledge in this field for diabetes treatment has been postulated for a long time.
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Affiliation(s)
| | - Agnieszka Ziółkowska
- Department of Anatomy and Histology, Collegium Medicum, University of Zielona Gora, Zyty 28, 65-046 Zielona Gora, Poland;
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43
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Lewandowski SL, Cardone RL, Foster HR, Ho T, Potapenko E, Poudel C, VanDeusen HR, Sdao SM, Alves TC, Zhao X, Capozzi ME, de Souza AH, Jahan I, Thomas CJ, Nunemaker CS, Davis DB, Campbell JE, Kibbey RG, Merrins MJ. Pyruvate Kinase Controls Signal Strength in the Insulin Secretory Pathway. Cell Metab 2020; 32:736-750.e5. [PMID: 33147484 PMCID: PMC7685238 DOI: 10.1016/j.cmet.2020.10.007] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 06/30/2020] [Accepted: 10/09/2020] [Indexed: 12/14/2022]
Abstract
Pancreatic β cells couple nutrient metabolism with appropriate insulin secretion. Here, we show that pyruvate kinase (PK), which converts ADP and phosphoenolpyruvate (PEP) into ATP and pyruvate, underlies β cell sensing of both glycolytic and mitochondrial fuels. Plasma membrane-localized PK is sufficient to close KATP channels and initiate calcium influx. Small-molecule PK activators increase the frequency of ATP/ADP and calcium oscillations and potently amplify insulin secretion. PK restricts respiration by cyclically depriving mitochondria of ADP, which accelerates PEP cycling until membrane depolarization restores ADP and oxidative phosphorylation. Our findings support a compartmentalized model of β cell metabolism in which PK locally generates the ATP/ADP required for insulin secretion. Oscillatory PK activity allows mitochondria to perform synthetic and oxidative functions without any net impact on glucose oxidation. These findings suggest a potential therapeutic route for diabetes based on PK activation that would not be predicted by the current consensus single-state model of β cell function.
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Affiliation(s)
- Sophie L Lewandowski
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Rebecca L Cardone
- Department of Internal Medicine, Yale University, New Haven, CT 06520, USA
| | - Hannah R Foster
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Thuong Ho
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Evgeniy Potapenko
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Chetan Poudel
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Halena R VanDeusen
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Sophia M Sdao
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Tiago C Alves
- Department of Internal Medicine, Yale University, New Haven, CT 06520, USA
| | - Xiaojian Zhao
- Department of Internal Medicine, Yale University, New Haven, CT 06520, USA
| | - Megan E Capozzi
- Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - Arnaldo H de Souza
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Ishrat Jahan
- Department of Biomedical Sciences, Ohio University, Athens, OH 45701, USA
| | - Craig J Thomas
- National Center for Advancing Translational Sciences, Rockville, MD 20850, USA
| | - Craig S Nunemaker
- Department of Biomedical Sciences, Ohio University, Athens, OH 45701, USA
| | - Dawn Belt Davis
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | | | - Richard G Kibbey
- Department of Internal Medicine, Yale University, New Haven, CT 06520, USA; Department of Cellular & Molecular Physiology, Yale University, New Haven, CT 06520, USA.
| | - Matthew J Merrins
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA; William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA.
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44
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Sha W, Hu F, Bu S. Mitochondrial dysfunction and pancreatic islet β-cell failure (Review). Exp Ther Med 2020; 20:266. [PMID: 33199991 PMCID: PMC7664595 DOI: 10.3892/etm.2020.9396] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 07/17/2020] [Indexed: 02/07/2023] Open
Abstract
Pancreatic β-cells are the only source of insulin in humans. Mitochondria uses pyruvate to produce ATP as an intermediate link between glucose intake and insulin secretion in β-cells, in a process known as glucose-stimulated insulin secretion (GSIS). Previous studies have demonstrated that GSIS is negatively regulated by various factors in the mitochondria, including tRNALeu mutations, high p58 expression, reduced nicotinamide nucleotide transhydrogenase activity, abnormal levels of uncoupling proteins and reduced expression levels of transcription factors A, B1 and B2. Additionally, oxidative stress damages mitochondria and impairs antioxidant defense mechanisms, leading to the increased production of reactive oxygen species, which induces β-cell dysfunction. Inflammation in islets can also damage β-cell physiology. Inflammatory cytokines trigger the release of cytochrome c from the mitochondria via the NF-κB pathway. The present review examined the potential factors underlying mitochondrial dysfunction and their association with islet β-cell failure, which may offer novel insights regarding future strategies for the preservation of mitochondrial function and enhancement of antioxidant activity for individuals with diabetes mellitus.
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Affiliation(s)
- Wenxin Sha
- Diabetes Research Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Fei Hu
- Diabetes Research Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Shizhong Bu
- Diabetes Research Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
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45
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Morsi M, Schulze T, Früh E, Brüning D, Panten U, Rustenbeck I. Fresh and cultured mouse islets differ in their response to nutrient stimulation. Endocr Connect 2020; 9:769-782. [PMID: 32688335 PMCID: PMC7424343 DOI: 10.1530/ec-20-0289] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 07/19/2020] [Indexed: 12/25/2022]
Abstract
Observing different kinetics of nutrient-induced insulin secretion in fresh and cultured islets under the same condition we compared parameters of stimulus secretion coupling in freshly isolated and 22-h-cultured NMRI mouse islets. Stimulation of fresh islets with 30 mM glucose after perifusion without nutrient gave a continuously ascending secretion rate. In 22-h-cultured islets the same protocol produced a brisk first phase followed by a moderately elevated plateau, a pattern regarded to be typical for mouse islets. This was also the response of cultured islets to the nutrient secretagogue alpha-ketoisocaproic acid, whereas the secretion of fresh islets increased similarly fast but remained strongly elevated. The responses of fresh and cultured islets to purely depolarizing stimuli (tolbutamide or KCl), however, were closely similar. Signs of apoptosis and necrosis were rare in both preparations. In cultured islets, the glucose-induced rise of the cytosolic Ca2+ concentration started from a lower value and was larger as was the increase of the ATP/ADP ratio. The prestimulatory level of mitochondrial reducing equivalents, expressed as the NAD(P)H/FAD fluorescence ratio, was lower in cultured islets, but increased more strongly than in fresh islets. When culture conditions were modified by replacing RPMI with Krebs-Ringer medium and FCS with BSA, the amount of released insulin varied widely, but the kinetics always showed a predominant first phase. In conclusion, the secretion kinetics of fresh mouse islets is more responsive to variations of nutrient stimulation than cultured islets. The more uniform kinetics of the latter may be caused by a different use of endogenous metabolites.
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Affiliation(s)
- Mai Morsi
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Torben Schulze
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Eike Früh
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Dennis Brüning
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Uwe Panten
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
- Correspondence should be addressed to I Rustenbeck:
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46
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Abstract
Glucose-induced (physiological) insulin secretion from the islet β-cell involves interplay between cationic (i.e., changes in intracellular calcium) and metabolic (i.e., generation of hydrophobic and hydrophilic second messengers) events. A large body of evidence affirms support for novel regulation, by G proteins, of specific intracellular signaling events, including actin cytoskeletal remodeling, transport of insulin-containing granules to the plasma membrane for fusion, and secretion of insulin into the circulation. This article highlights the following aspects of GPCR-G protein biology of the islet. First, it overviews our current understanding of the identity of a wide variety of G protein regulators and their modulatory roles in GPCR-G protein-effector coupling, which is requisite for optimal β-cell function under physiological conditions. Second, it describes evidence in support of novel, noncanonical, GPCR-independent mechanisms of activation of G proteins in the islet. Third, it highlights the evidence indicating that abnormalities in G protein function lead to islet β-cell dysregulation and demise under the duress of metabolic stress and diabetes. Fourth, it summarizes observations of potential beneficial effects of GPCR agonists in preventing/halting metabolic defects in the islet β-cell under various pathological conditions (e.g., metabolic stress and inflammation). Lastly, it identifies knowledge gaps and potential avenues for future research in this evolving field of translational islet biology. Published 2020. Compr Physiol 10:453-490, 2020.
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Affiliation(s)
- Anjaneyulu Kowluru
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Center for Translational Research in Diabetes, Biomedical Research Service, John D. Dingell VA Medical Center, Wayne State University, Detroit, Michigan, USA
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47
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Metabolomics Analysis of Nutrient Metabolism in β-Cells. J Mol Biol 2020; 432:1429-1445. [DOI: 10.1016/j.jmb.2019.07.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 07/03/2019] [Accepted: 07/11/2019] [Indexed: 01/05/2023]
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48
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Grubelnik V, Zmazek J, Markovič R, Gosak M, Marhl M. Modelling of energy-driven switch for glucagon and insulin secretion. J Theor Biol 2020; 493:110213. [PMID: 32109481 DOI: 10.1016/j.jtbi.2020.110213] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 02/19/2020] [Accepted: 02/24/2020] [Indexed: 12/14/2022]
Abstract
We present a mathematical model of the energy-driven metabolic switch for glucagon and insulin secretion from pancreatic alpha and beta cells, respectively. The energy status related to hormone secretion is studied for various glucose concentrations. Additionally, the physiological response is studied with regards to the presence of other metabolites, particularly the free-fatty acids. At low glucose, the ATP production in alpha cells is high due to free-fatty acids oxidation in mitochondria, which enables glucagon secretion. When the glucose concentration is elevated above the threshold value, the glucagon secretion is switched off due to the contribution of glycolytic ATP production, representing an "anaerobic switch". On the other hand, during hypoglycemia, the ATP production in beta cells is low, reflecting a "waiting state" for glucose as the main metabolite. When glucose is elevated above the threshold value, the oxidative fate of glucose in mitochondria is the main source of energy required for effective insulin secretion, i.e. the "aerobic switch". Our results show the importance of well-regulated and fine-tuned energetic processes in pancreatic alpha and beta cells required for efficient hormone secretion and hence effective blood glucose regulation. These energetic processes have to be appropriately switched on and off based on the sensing of different metabolites by alpha and beta cells. Our computational results indicate that disturbances in cell energetics (e.g. mitochondrial dysfunction), and dysfunctional metabolite sensing and distribution throughout the cell might be related to pathologies such as metabolic syndrome and diabetes.
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Affiliation(s)
- Vladimir Grubelnik
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor SI-2000, Slovenia
| | - Jan Zmazek
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia
| | - Rene Markovič
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia
| | - Marko Gosak
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Medicine, University of Maribor, Maribor SI-2000, Slovenia
| | - Marko Marhl
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Medicine, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Education, University of Maribor, Maribor SI-2000, Slovenia.
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49
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Kahancová A, Sklenář F, Ježek P, Dlasková A. Overexpression of native IF1 downregulates glucose-stimulated insulin secretion by pancreatic INS-1E cells. Sci Rep 2020; 10:1551. [PMID: 32005857 PMCID: PMC6994519 DOI: 10.1038/s41598-020-58411-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 01/15/2020] [Indexed: 01/08/2023] Open
Abstract
We have previously reported that transient knock-down of ATPase inhibitory factor 1 (IF1) by siRNA upregulates ATP levels and subsequently augments insulin secretion in model pancreatic β-cells INS-1E. Here we investigated how long-term IF1-overexpression impacts pancreatic β-cell bioenergetics and insulin secretion. We generated INS-1E cell line stably overexpressing native IF1. We revealed that IF1 overexpression leads to a substantial decrease in ATP levels and reduced glucose-stimulated insulin secretion. A decrease in total cellular ATP content was also reflected in decreased free ATP cytosolic and mitochondrial levels, as monitored with ATeam biosensor. Consistently, cellular respiration of IF1-overexpressing cells was decreased. 3D structured illumination microscopy (SIM) revealed a higher amount of insulin granules with higher volume in IF1-overexpressing cells. Similar effects occurred when cells were incubated at low glucose concentrations. Noteworthy, activation of PKA by dibutyryl cAMP entirely abolished the inhibitory effect of IF1 overexpression on ATP production and insulin secretion. Mitochondrial network morphology and cristae ultrastructure in INS-1E overexpressing IF1 remained mostly unchanged. Finally, we show that INS-1E cells decrease their IF1 protein levels relative to ATP synthase α-subunit in response to increased glucose. In conclusion, IF1 actively downregulates INS-1E cellular metabolism and reduces their ability to secrete insulin.
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Affiliation(s)
- Anežka Kahancová
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology, The Czech Academy of Sciences, Prague, Czech Republic
| | - Filip Sklenář
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology, The Czech Academy of Sciences, Prague, Czech Republic
| | - Petr Ježek
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology, The Czech Academy of Sciences, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, No. 75, Institute of Physiology, The Czech Academy of Sciences, Prague, Czech Republic.
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50
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Rumala CZ, Liu J, Locasale JW, Corkey BE, Deeney JT, Rameh LE. Exposure of Pancreatic β-Cells to Excess Glucose Results in Bimodal Activation of mTORC1 and mTOR-Dependent Metabolic Acceleration. iScience 2020; 23:100858. [PMID: 32058969 PMCID: PMC7005503 DOI: 10.1016/j.isci.2020.100858] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 08/28/2019] [Accepted: 01/16/2020] [Indexed: 01/03/2023] Open
Abstract
Chronic exposure of pancreatic β-cells to excess glucose can lead to metabolic acceleration and loss of stimulus-secretion coupling. Here, we examined how exposure to excess glucose (defined here as concentrations above 5 mM) affects mTORC1 signaling and the metabolism of β-cells. Acute exposure to excess glucose stimulated glycolysis-dependent mTORC1 signaling, without changes in the PI3K or AMPK pathways. Prolonged exposure to excess glucose led to hyperactivation of mTORC1 and metabolic acceleration, characterized by higher basal respiration and maximal respiratory capacity, increased energy demand, and enhanced flux through mitochondrial pyruvate metabolism. Inhibition of pyruvate transport to the mitochondria decelerated the metabolism of β-cells chronically exposed to excess glucose and re-established glucose-dependent mTORC1 signaling, disrupting a positive feedback loop for mTORC1 hyperactivation. mTOR inhibition had positive and negative impacts on various metabolic pathways and insulin secretion, demonstrating a role for mTOR signaling in the long-term metabolic adaptation of β-cells to excess glucose. Acute glucose stimulates mTORC1 in β-cells through a glycolysis-dependent mechanism Chronic excess glucose promotes mTOR-dependent metabolic acceleration of β-cells Metabolic acceleration activates a positive feedback loop for mTORC1 hyperactivation mTOR hyperactivation disturbs the metabolism and insulin secretion patterns of β-cells
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Affiliation(s)
| | - Juan Liu
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Duke University, Durham, NC 27710, USA
| | - Jason Wei Locasale
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Duke University, Durham, NC 27710, USA
| | - Barbara Ellen Corkey
- Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA
| | - Jude Thaddeus Deeney
- Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA
| | - Lucia Egydio Rameh
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, USA; Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
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