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An M, Akyuz M, Capik O, Yalcin C, Bertram R, Karatas EA, Karatas OF, Yildirim V. Gain of function mutation in K(ATP) channels and resulting upregulation of coupling conductance are partners in crime in the impairment of Ca 2+ oscillations in pancreatic ß-cells. Math Biosci 2024; 374:109224. [PMID: 38821258 DOI: 10.1016/j.mbs.2024.109224] [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: 01/20/2024] [Revised: 04/30/2024] [Accepted: 05/28/2024] [Indexed: 06/02/2024]
Abstract
Gain of function mutations in the pore forming Kir6 subunits of the ATP sensitive K+ channels (K(ATP) channels) of pancreatic β-cells are the major cause of neonatal diabetes in humans. In this study, we show that in insulin secreting mouse β-cell lines, gain of function mutations in Kir6.1 result in a significant connexin36 (Cx36) overexpression, which form gap junctional connections and mediate electrical coupling between β-cells within pancreatic islets. Using computational modeling, we show that upregulation in Cx36 might play a functional role in the impairment of glucose stimulated Ca2+ oscillations in a cluster of β-cells with Kir6.1 gain of function mutations in their K(ATP) channels (GoF-K(ATP) channels). Our results show that without an increase in Cx36 expression, a gain of function mutation in Kir6.1 might not be sufficient to diminish glucose stimulated Ca2+ oscillations in a β-cell cluster. We also show that a reduced Cx36 expression, which leads to loss of coordination in a wild-type β-cell cluster, restores coordinated Ca2+ oscillations in a β-cell cluster with GoF-K(ATP) channels. Our results indicate that in a heterogenous β-cell cluster with GoF-K(ATP) channels, there is an inverted u-shaped nonmonotonic relation between the cluster activity and Cx36 expression. These results show that in a neonatal diabetic β-cell model, gain of function mutations in the Kir6.1 cause Cx36 overexpression, which aggravates the impairment of glucose stimulated Ca2+ oscillations.
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Affiliation(s)
- Murat An
- Department of Basic Sciences, Erzurum Technical University, Erzurum, Turkey
| | - Mesut Akyuz
- Department of Molecular Biology and Genetics, Erzurum Technical University, Erzurum, Turkey
| | - Ozel Capik
- Department of Molecular Biology and Genetics, Erzurum Technical University, Erzurum, Turkey
| | - Cigdem Yalcin
- Department of Mathematics, Erzurum Technical University, Erzurum, Turkey
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida, United States
| | - Elanur Aydin Karatas
- Department of Molecular Biology and Genetics, Erzurum Technical University, Erzurum, Turkey
| | - Omer Faruk Karatas
- Department of Molecular Biology and Genetics, Erzurum Technical University, Erzurum, Turkey
| | - Vehpi Yildirim
- Department of Mathematics, Erzurum Technical University, Erzurum, Turkey; Department of Cardiology, Erasmus University Medical Center, Rotterdam, The Netherlands.
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Kamat V, Sweet IR. Hypertonicity during a rapid rise in D-glucose mediates first-phase insulin secretion. Front Endocrinol (Lausanne) 2024; 15:1395028. [PMID: 38989001 PMCID: PMC11233695 DOI: 10.3389/fendo.2024.1395028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2024] [Accepted: 06/10/2024] [Indexed: 07/12/2024] Open
Abstract
Introduction Biphasic insulin secretion is an intrinsic characteristic of the pancreatic islet and has clinical relevance due to the loss of first-phase in patients with Type 2 diabetes. As it has long been shown that first-phase insulin secretion only occurs in response to rapid changes in glucose, we tested the hypothesis that islet response to an increase in glucose is a combination of metabolism plus an osmotic effect where hypertonicity is driving first-phase insulin secretion. Methods Experiments were performed using perifusion analysis of rat, mouse, and human islets. Insulin secretion rate (ISR) and other parameters associated with its regulation were measured in response to combinations of D-glucose and membrane-impermeable carbohydrates (L-glucose or mannitol) designed to dissect the effect of hypertonicity from that of glucose metabolism. Results Remarkably, the appearance of first-phase responses was wholly dependent on changes in tonicity: no first-phase in NAD(P)H, cytosolic calcium, cAMP secretion rate (cAMP SR), or ISR was observed when increased D-glucose concentration was counterbalanced by decreases in membrane-impermeable carbohydrates. When D-glucose was greater than 8 mM, rapid increases in L-glucose without any change in D-glucose resulted in first-phase responses in all measured parameters that were kinetically similar to D-glucose. First-phase ISR was completely abolished by H89 (a non-specific inhibitor of protein kinases) without affecting first-phase calcium response. Defining first-phase ISR as the difference between glucose-stimulated ISR with and without a change in hypertonicity, the peak of first-phase ISR occurred after second-phase ISR had reached steady state, consistent with the well-established glucose-dependency of mechanisms that potentiate glucose-stimulated ISR. Discussion The data collected in this study suggests a new model of glucose-stimulated biphasic ISR where first-phase ISR derives from (and after) a transitory amplification of second-phase ISR and driven by hypertonicity-induced rise in H89-inhibitable kinases likely driven by first-phase responses in cAMP, calcium, or a combination of both.
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Affiliation(s)
| | - Ian R. Sweet
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA, United States
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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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Kim YK, Won KC, Sussel L. Glucose metabolism partially regulates β-cell function through epigenomic changes. J Diabetes Investig 2024; 15:649-655. [PMID: 38436511 PMCID: PMC11143420 DOI: 10.1111/jdi.14173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Revised: 02/12/2024] [Accepted: 02/14/2024] [Indexed: 03/05/2024] Open
Abstract
The β-cell relies predominantly on glucose utilization to generate adenosine triphosphate, which is crucial for both cell viability and insulin secretion. The β-cell has evolved remarkable metabolic flexibility to productively respond to shifts in environmental conditions and changes in glucose availability. Although these adaptive responses are important for maintaining optimal cellular function, there is emerging evidence that the resulting changes in cellular metabolites can impact the epigenome, causing transient and lasting alterations in gene expression. This review explores the intricate interplay between metabolism and the epigenome, providing valuable insights into the molecular mechanisms leading to β-cell dysfunction in diabetes. Understanding these mechanisms will be critical for developing targeted therapeutic strategies to preserve and enhance β-cell function, offering potential avenues for interventions to improve glycemic control in individuals with diabetes.
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Affiliation(s)
- Yong Kyung Kim
- Barbara Davis Center for DiabetesUniversity of Colorado Anschutz Medical CampusAuroraColoradoUSA
| | - Kyu Chang Won
- Department of Internal MedicineYeungnam University College of MedicineDaeguKorea
| | - Lori Sussel
- Barbara Davis Center for DiabetesUniversity of Colorado Anschutz Medical CampusAuroraColoradoUSA
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Satin LS, Corradi J, Sherman AS. Do We Need a New Hypothesis for KATP Closure in β-Cells? Distinguishing the Baby From the Bathwater. Diabetes 2024; 73:844-848. [PMID: 38640066 PMCID: PMC11109778 DOI: 10.2337/db24-0131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 03/15/2024] [Indexed: 04/21/2024]
Affiliation(s)
- Leslie Sherwin Satin
- Department of Pharmacology and Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, Brehm Diabetes Center and Caswell Diabetes Institute, University of Michigan Medical School, Ann Arbor, MI
| | - Jeremías Corradi
- Department of Pharmacology and Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, Brehm Diabetes Center and Caswell Diabetes Institute, University of Michigan Medical School, Ann Arbor, MI
| | - Arthur Stewart Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
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Lv X, Gao J, Yang J, Zou Y, Chen J, Sun Y, Song J, Liu Y, Wang L, Xia L, Yu S, Wei Z, Chen L, Hou X. Clinical and functional characterization of a novel KCNJ11 (c.101G > A, p.R34H) mutation associated with maturity-onset diabetes mellitus of the young type 13. Endocrine 2024:10.1007/s12020-024-03873-6. [PMID: 38761346 DOI: 10.1007/s12020-024-03873-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 05/09/2024] [Indexed: 05/20/2024]
Abstract
PURPOSE This study aimed to describe the clinical features, diagnostic and therapeutic course of a patient with MODY13 caused by KCNJ11 (c.101G > A, p.R34H) and how it contributes to the pathogenesis of MODY13, and to explore new therapeutic targets. METHODS Whole-exome sequencing was used to screen prediagnosed individuals and family members with clinically suspected KCNJ11 mutations. Real-time fluorescence quantitative PCR, western blotting, thallium flux of potassium channels, glucose-stimulated insulin secretion (GSIS), and immunofluorescence assays were used to analyze the regulation of insulin secretion by the KCNJ11 mutant in MIN6 cells. Daily blood glucose levels were continuously monitored for 14 days in the proband using the ambulatory blood glucose meter (SIBIONICS). RESULTS Mutation screening of the entire exon of the gene identified a heterozygous KCNJ11 (c.101G > A, p.R34H) mutation in the proband and his mother. Cell-based GSIS assays after transfection of MIN6 using wild-type and mutant plasmids revealed that this mutation impaired insulin secretory function. Furthermore, we found that this impaired secretory function is associated with reduced functional activity of the mutant KCNJ11 protein and reduced expression of the insulin secretion-associated exocytosis proteins STXBP1 and SNAP25. CONCLUSION For the first time, we revealed the pathogenic mechanism of KCNJ11 (c.101G > A, p.R34H) associated with MODY13. This mutant can cause alterations in KATP channel activity, reduce sensitivity to glucose stimulation, and impair pancreatic β-cell secretory function by downregulating insulin secretion-associated exocytosis proteins. Therefore, oral sulfonylurea drugs can lower blood glucose levels through pro-insulinotropic effects and are more favorable for patients with this mutation.
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Affiliation(s)
- Xiaoyu Lv
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Jing Gao
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Jingwen Yang
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Ying Zou
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Jun Chen
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Yujing Sun
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Jia Song
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Yiran Liu
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Liming Wang
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Longqing Xia
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Shijia Yu
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Zichun Wei
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Li Chen
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
- Institute of Endocrine and Metabolic Diseases of Shandong University, Jinan, 250012, Shandong, China
- Key Laboratory of Endocrine and Metabolic Diseases, Shandong Province Medicine & Health, Jinan, 250012, Shandong, China
- Jinan Clinical Research Center for Endocrine and Metabolic Disease, Jinan, 250012, Shandong, China
| | - Xinguo Hou
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China.
- Institute of Endocrine and Metabolic Diseases of Shandong University, Jinan, 250012, Shandong, China.
- Key Laboratory of Endocrine and Metabolic Diseases, Shandong Province Medicine & Health, Jinan, 250012, Shandong, China.
- Jinan Clinical Research Center for Endocrine and Metabolic Disease, Jinan, 250012, Shandong, China.
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Rodríguez-Rivera NS, Barrera-Oviedo D. Exploring the Pathophysiology of ATP-Dependent Potassium Channels in Insulin Resistance. Int J Mol Sci 2024; 25:4079. [PMID: 38612888 PMCID: PMC11012456 DOI: 10.3390/ijms25074079] [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: 02/02/2024] [Revised: 03/15/2024] [Accepted: 03/29/2024] [Indexed: 04/14/2024] Open
Abstract
Ionic channels are present in eucaryotic plasma and intracellular membranes. They coordinate and control several functions. Potassium channels belong to the most diverse family of ionic channels that includes ATP-dependent potassium (KATP) channels in the potassium rectifier channel subfamily. These channels were initially described in heart muscle and then in other tissues such as pancreatic, skeletal muscle, brain, and vascular and non-vascular smooth muscle tissues. In pancreatic beta cells, KATP channels are primarily responsible for maintaining the membrane potential and for depolarization-mediated insulin release, and their decreased density and activity may be related to insulin resistance. KATP channels' relationship with insulin resistance is beginning to be explored in extra-pancreatic beta tissues like the skeletal muscle, where KATP channels are involved in insulin-dependent glucose recapture and their activation may lead to insulin resistance. In adipose tissues, KATP channels containing Kir6.2 protein subunits could be related to the increase in free fatty acids and insulin resistance; therefore, pathological processes that promote prolonged adipocyte KATP channel inhibition might lead to obesity due to insulin resistance. In the central nervous system, KATP channel activation can regulate peripheric glycemia and lead to brain insulin resistance, an early peripheral alteration that can lead to the development of pathologies such as obesity and Type 2 Diabetes Mellitus (T2DM). In this review, we aim to discuss the characteristics of KATP channels, their relationship with clinical disorders, and their mechanisms and potential associations with peripheral and central insulin resistance.
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Affiliation(s)
- Nidia Samara Rodríguez-Rivera
- Laboratorio de Farmacología y Bioquímica Clínica, Departamento de Farmacología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico;
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Chen Y, Hu X, Zhao M. Clinical and genetic characteristics of maturity-onset diabetes of the young type 13: A systematic review of the literature. J Diabetes 2024; 16:e13520. [PMID: 38095268 PMCID: PMC10925878 DOI: 10.1111/1753-0407.13520] [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: 02/21/2023] [Revised: 07/26/2023] [Accepted: 11/27/2023] [Indexed: 03/12/2024] Open
Abstract
OBJECTIVE Maturity-onset diabetes of the young type 13 (MODY13), a rare type of monogenic diabetes, is often misdiagnosed as type 1 or type 2 diabetes. To improve early diagnosis and precise treatment, we performed a systematic review and analysis of the literature about MODY13. METHODS PubMed, Cochrane, Embase, China National Knowledge Infrastructure (CNKI), Chinese BioMedical (CBM) Literature Database, and Wanfang Database were searched using the following search terms: "MODY13," "KCNJ11 maturity-onset diabetes of the young," "KCNJ11-MODY," "maturity-onset diabetes of the young type 13," and "neonatal diabetes mellitus KCNJ11." The demography, clinical characteristics, and gene mutations of patients were expressed with descriptive statistical methods. RESULTS A total of 33 reports were included in this study, including 75 patients and 28 types of mutations. Thirty-six patients were male. The mean onset age was 25.20 ± 15.26 years. The averages of recorded body mass index, glycated hemoglobin (HbA1c), and fasting C-peptide were 23.45 ± 4.56kg/m2 , 10.07 ± 1.96%, and 0.31 ± 0.23nmol/L, respectively. Most of the mutation sites were located in the cytosolic region of N- and C-terminal domains of Kir6.2. Seven patients were reported to have diabetic chronic complications. CONCLUSION MODY13 was diagnosed later than other types of MODY and was associated with low fasting C-peptide. Mutation sites of MODY13 were mostly concentrated in N- and C-terminal intracellular domains. The majority of KCNJ11 gene mutations causing MODY 13 were from G to A. The incidence rates of chronic complications were lower than type 1 and type 2 diabetes.
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Affiliation(s)
- Yaning Chen
- Department of EndocrinologyThe Sixth Medical Center of Chinese PLA General HospitalBeijingChina
| | - Xiaodong Hu
- Department of EndocrinologyThe Sixth Medical Center of Chinese PLA General HospitalBeijingChina
| | - Mingwei Zhao
- Department of EndocrinologyThe Sixth Medical Center of Chinese PLA General HospitalBeijingChina
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Longden TA, Lederer WJ. Electro-metabolic signaling. J Gen Physiol 2024; 156:e202313451. [PMID: 38197953 PMCID: PMC10783436 DOI: 10.1085/jgp.202313451] [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: 07/26/2023] [Revised: 10/27/2023] [Accepted: 12/14/2023] [Indexed: 01/11/2024] Open
Abstract
Precise matching of energy substrate delivery to local metabolic needs is essential for the health and function of all tissues. Here, we outline a mechanistic framework for understanding this critical process, which we refer to as electro-metabolic signaling (EMS). All tissues exhibit changes in metabolism over varying spatiotemporal scales and have widely varying energetic needs and reserves. We propose that across tissues, common signatures of elevated metabolism or increases in energy substrate usage that exceed key local thresholds rapidly engage mechanisms that generate hyperpolarizing electrical signals in capillaries that then relax contractile elements throughout the vasculature to quickly adjust blood flow to meet changing needs. The attendant increase in energy substrate delivery serves to meet local metabolic requirements and thus avoids a mismatch in supply and demand and prevents metabolic stress. We discuss in detail key examples of EMS that our laboratories have discovered in the brain and the heart, and we outline potential further EMS mechanisms operating in tissues such as skeletal muscle, pancreas, and kidney. We suggest that the energy imbalance evoked by EMS uncoupling may be central to cellular dysfunction from which the hallmarks of aging and metabolic diseases emerge and may lead to generalized organ failure states-such as diverse flavors of heart failure and dementia. Understanding and manipulating EMS may be key to preventing or reversing these dysfunctions.
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Affiliation(s)
- Thomas A. Longden
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Laboratory of Neurovascular Interactions, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - W. Jonathan Lederer
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Laboratory of Molecular Cardiology, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
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Veluthakal R, Esparza D, Hoolachan JM, Balakrishnan R, Ahn M, Oh E, Jayasena CS, Thurmond DC. Mitochondrial Dysfunction, Oxidative Stress, and Inter-Organ Miscommunications in T2D Progression. Int J Mol Sci 2024; 25:1504. [PMID: 38338783 PMCID: PMC10855860 DOI: 10.3390/ijms25031504] [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: 12/22/2023] [Revised: 01/15/2024] [Accepted: 01/23/2024] [Indexed: 02/12/2024] Open
Abstract
Type 2 diabetes (T2D) is a heterogenous disease, and conventionally, peripheral insulin resistance (IR) was thought to precede islet β-cell dysfunction, promoting progression from prediabetes to T2D. New evidence suggests that T2D-lean individuals experience early β-cell dysfunction without significant IR. Regardless of the primary event (i.e., IR vs. β-cell dysfunction) that contributes to dysglycemia, significant early-onset oxidative damage and mitochondrial dysfunction in multiple metabolic tissues may be a driver of T2D onset and progression. Oxidative stress, defined as the generation of reactive oxygen species (ROS), is mediated by hyperglycemia alone or in combination with lipids. Physiological oxidative stress promotes inter-tissue communication, while pathological oxidative stress promotes inter-tissue mis-communication, and new evidence suggests that this is mediated via extracellular vesicles (EVs), including mitochondria containing EVs. Under metabolic-related stress conditions, EV-mediated cross-talk between β-cells and skeletal muscle likely trigger mitochondrial anomalies leading to prediabetes and T2D. This article reviews the underlying molecular mechanisms in ROS-related pathogenesis of prediabetes, including mitophagy and mitochondrial dynamics due to oxidative stress. Further, this review will describe the potential of various therapeutic avenues for attenuating oxidative damage, reversing prediabetes and preventing progression to T2D.
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Affiliation(s)
- Rajakrishnan Veluthakal
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes & Metabolism Research Institute, City of Hope Beckman Research Institute, 1500 E. Duarte Rd, Duarte, CA 91010, USA; (D.E.); (J.M.H.); (R.B.); (M.A.); (E.O.); (C.S.J.)
| | | | | | | | | | | | | | - Debbie C. Thurmond
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes & Metabolism Research Institute, City of Hope Beckman Research Institute, 1500 E. Duarte Rd, Duarte, CA 91010, USA; (D.E.); (J.M.H.); (R.B.); (M.A.); (E.O.); (C.S.J.)
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Kahn SE, Woods SC, Halter JB, Taborsky GJ, Schwartz MW. Daniel Porte Jr., 13 August 1931-13 May 2023. Diabetes 2024; 73:5-10. [PMID: 38118001 PMCID: PMC10784651 DOI: 10.2337/db23-0787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Affiliation(s)
- Steven E. Kahn
- VA Puget Sound Health Care System and University of Washington, Seattle, WA
| | | | - Jeffrey B. Halter
- University of Michigan, Ann Arbor, MI
- National University of Singapore, Singapore
| | - Gerald J. Taborsky
- VA Puget Sound Health Care System and University of Washington, Seattle, WA
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Corradi J, Thompson B, Fletcher PA, Bertram R, Sherman AS, Satin LS. K ATP channel activity and slow oscillations in pancreatic beta cells are regulated by mitochondrial ATP production. J Physiol 2023; 601:5655-5667. [PMID: 37983196 PMCID: PMC10842208 DOI: 10.1113/jp284982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 10/16/2023] [Indexed: 11/22/2023] Open
Abstract
Pancreatic beta cells secrete insulin in response to plasma glucose. The ATP-sensitive potassium channel (KATP ) links glucose metabolism to islet electrical activity in these cells by responding to increased cytosolic [ATP]/[ADP]. It was recently proposed that pyruvate kinase (PK) in close proximity to beta cell KATP locally produces the ATP that inhibits KATP activity. This proposal was largely based on the observation that applying phosphoenolpyruvate (PEP) and ADP to the cytoplasmic side of excised inside-out patches inhibited KATP . To test the relative contributions of local vs. mitochondrial ATP production, we recorded KATP activity using mouse beta cells and INS-1 832/13 cells. In contrast to prior reports, we could not replicate inhibition of KATP activity by PEP + ADP. However, when the pH of the PEP solutions was not corrected for the addition of PEP, strong channel inhibition was observed as a result of the well-known action of protons to inhibit KATP . In cell-attached recordings, perifusing either a PK activator or an inhibitor had little or no effect on KATP channel closure by glucose, further suggesting that PK is not an important regulator of KATP . In contrast, addition of mitochondrial inhibitors robustly increased KATP activity. Finally, by measuring the [ATP]/[ADP] responses to imposed calcium oscillations in mouse beta cells, we found that oxidative phosphorylation could raise [ATP]/[ADP] even when ADP was at its nadir during the burst silent phase, in agreement with our mathematical model. These results indicate that ATP produced by mitochondrial oxidative phosphorylation is the primary controller of KATP in pancreatic beta cells. KEY POINTS: Phosphoenolpyruvate (PEP) plus adenosine diphosphate does not inhibit KATP activity in excised patches. PEP solutions only inhibit KATP activity if the pH is unbalanced. Modulating pyruvate kinase has minimal effects on KATP activity. Mitochondrial inhibition, in contrast, robustly potentiates KATP activity in cell-attached patches. Although the ADP level falls during the silent phase of calcium oscillations, mitochondria can still produce enough ATP via oxidative phosphorylation to close KATP . Mitochondrial oxidative phosphorylation is therefore the main source of the ATP that inhibits the KATP activity of pancreatic beta cells.
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Affiliation(s)
- Jeremías Corradi
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Benjamin Thompson
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Patrick A. Fletcher
- Laboratory of Biological Modeling, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida, USA
| | - Arthur S. Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Leslie S. Satin
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
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13
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Kamat V, Grumbine MK, Bao K, Mokate K, Khalil G, Cook D, Clearwater B, Hirst R, Harman J, Boeck M, Fu Z, Smith LEH, Goswami M, Wubben TJ, Walker EM, Zhu J, Soleimanpour SA, Scarlett JM, Robbings BM, Hass D, Hurley JB, Sweet IR. A versatile pumpless multi-channel fluidics system for maintenance and real-time functional assessment of tissue and cells. CELL REPORTS METHODS 2023; 3:100642. [PMID: 37963464 PMCID: PMC10694526 DOI: 10.1016/j.crmeth.2023.100642] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/24/2023] [Accepted: 10/20/2023] [Indexed: 11/16/2023]
Abstract
To address the needs of the life sciences community and the pharmaceutical industry in pre-clinical drug development to both maintain and continuously assess tissue metabolism and function with simple and rapid systems, we improved on the initial BaroFuse to develop it into a fully functional, pumpless, scalable multi-channel fluidics instrument that continuously measures changes in oxygen consumption and other endpoints in response to test compounds. We and several other laboratories assessed it with a wide range of tissue types including retina, pancreatic islets, liver, and hypothalamus with both aqueous and gaseous test compounds. The setup time was less than an hour for all collaborating groups, and there was close agreement between data obtained from the different laboratories. This easy-to-use system reliably generates real-time metabolic and functional data from tissue and cells in response to test compounds that will address a critical need in basic and applied research.
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Affiliation(s)
- Varun Kamat
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA
| | | | - Khang Bao
- EnTox Sciences, Inc., Mercer Island, WA 98040, USA
| | - Kedar Mokate
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA
| | - Gamal Khalil
- EnTox Sciences, Inc., Mercer Island, WA 98040, USA
| | - Daniel Cook
- EnTox Sciences, Inc., Mercer Island, WA 98040, USA
| | | | - Richard Hirst
- Technical Assembly Service Corporation, Seattle, WA 98109, USA
| | - Jarrod Harman
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Myriam Boeck
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Eye Center, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
| | - Zhongjie Fu
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Lois E H Smith
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Moloy Goswami
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
| | - Thomas J Wubben
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
| | - Emily M Walker
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 98195, USA
| | - Jie Zhu
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 98195, USA
| | - Scott A Soleimanpour
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 98195, USA
| | - Jarrad M Scarlett
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA; Department of Pediatric Gastroenterology and Hepatology, Seattle Children's Hospital, Seattle, WA 98145, USA
| | - Brian M Robbings
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA; Department of Biochemistry, University of Washington, Seattle, WA 98109, USA
| | - Daniel Hass
- Department of Biochemistry, University of Washington, Seattle, WA 98109, USA
| | - James B Hurley
- Department of Biochemistry, University of Washington, Seattle, WA 98109, USA
| | - Ian R Sweet
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA; EnTox Sciences, Inc., Mercer Island, WA 98040, USA.
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14
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Bertram R, Marinelli I, Fletcher PA, Satin LS, Sherman AS. Deconstructing the integrated oscillator model for pancreatic β-cells. Math Biosci 2023; 365:109085. [PMID: 37802364 PMCID: PMC10991200 DOI: 10.1016/j.mbs.2023.109085] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 09/12/2023] [Accepted: 09/26/2023] [Indexed: 10/10/2023]
Abstract
Electrical bursting oscillations in the β-cells of pancreatic islets have been a focus of investigation for more than fifty years. This has been aided by mathematical models, which are descendants of the pioneering Chay-Keizer model. This article describes the key biophysical and mathematical elements of this model, and then describes the path forward from there to the Integrated Oscillator Model (IOM). It is both a history and a deconstruction of the IOM that describes the various elements that have been added to the model over time, and the motivation for adding them. Finally, the article is a celebration of the 40th anniversary of the publication of the Chay-Keizer model.
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Affiliation(s)
- Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, FL, United States.
| | - Isabella Marinelli
- Centre for Systems Modeling and Quantitative Biomedicine, University of Birmingham, United Kingdom
| | - Patrick A Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
| | - Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
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15
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Kong CC, Cheng JD, Wang W. Neurotransmitters regulate β cells insulin secretion: A neglected factor. World J Clin Cases 2023; 11:6670-6679. [PMID: 37901031 PMCID: PMC10600852 DOI: 10.12998/wjcc.v11.i28.6670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 07/17/2023] [Accepted: 08/31/2023] [Indexed: 09/25/2023] Open
Abstract
β cells are the main cells responsible for the hypoglycemic function of pancreatic islets, and the insulin secreted by these cells is the only hormone that lowers blood glucose levels in the human body. β cells are regulated by various factors, among which neurotransmitters make an important contribution. This paper discusses the effects of neurotransmitters secreted by various sympathetic and parasympathetic nerves on β cells and summarizes the mechanisms by which various neurotransmitters regulate insulin secretion. Many neurotransmitters do not have a single source and are not only released from nerve terminals but also synthesized by β cells themselves, allowing them to synergistically regulate insulin secretion. Almost all of these neurotransmitters depend on the presence of glucose to function, and their actions are mostly related to the Ca2+ and cAMP concentrations. Although neurotransmitters have been extensively studied, many of their mechanisms remain unclear and require further exploration by researchers.
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Affiliation(s)
- Chu-Chu Kong
- Department of Endocrinology, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen 361100, Fujian Province, China
| | - Ji-Dong Cheng
- Department of Endocrinology, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen 361100, Fujian Province, China
| | - Wei Wang
- Department of Endocrinology, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen 361100, Fujian Province, China
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16
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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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17
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Khajavi N, Riçku K, Schreier PCF, Gentz T, Beyerle P, Cruz E, Breit A, Reinach PS, Gudermann T. Chronic Mg 2+ Deficiency Does Not Impair Insulin Secretion in Mice. Cells 2023; 12:1790. [PMID: 37443824 PMCID: PMC10340716 DOI: 10.3390/cells12131790] [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: 06/02/2023] [Revised: 06/28/2023] [Accepted: 07/03/2023] [Indexed: 07/15/2023] Open
Abstract
Magnesium is an essential mediator of a vast number of critical enzymatic cellular reactions in the human body. Some clinical epidemiological studies suggest that hypomagnesemia accounts for declines in insulin secretion in patients with type 2 diabetes (T2D); however, the results of various experimental studies do not support this notion. To address this discrepancy, we assessed the short- and long-term effects of hypomagnesemia on β-cell function and insulin secretion in primary mouse islets of Langerhans and in a mouse model of hypomagnesemia known as Trpm6Δ17 /fl;Villin1-Cre mice. We found that lowering the extracellular Mg2+ concentration from 1.2 mM to either 0.6 or 0.1 mM remarkably increased glucose-induced insulin secretion (GIIS) in primary islets isolated from C57BL/6 mice. Similarly, both the plasma insulin levels and GIIS rose in isolated islets of Trpm6Δ17 /fl;Villin1-Cre mice. We attribute these rises to augmented increases in intracellular Ca2+ oscillations in pancreatic β-cells. However, the glycemic metabolic profile was not impaired in Trpm6Δ17 /fl;Villin1-Cre mice, suggesting that chronic hypomagnesemia does not lead to insulin resistance. Collectively, the results of this study suggest that neither acute nor chronic Mg2+ deficiency suppresses glucose-induced rises in insulin secretion. Even though hypomagnesemia can be symptomatic of T2D, such deficiency may not account for declines in insulin release in this disease.
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Affiliation(s)
- Noushafarin Khajavi
- Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, 80539 Munich, Germany; (K.R.); (P.C.F.S.); (T.G.); (P.B.); (E.C.); (A.B.)
| | - Klea Riçku
- Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, 80539 Munich, Germany; (K.R.); (P.C.F.S.); (T.G.); (P.B.); (E.C.); (A.B.)
| | - Pascale C. F. Schreier
- Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, 80539 Munich, Germany; (K.R.); (P.C.F.S.); (T.G.); (P.B.); (E.C.); (A.B.)
| | - Tanja Gentz
- Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, 80539 Munich, Germany; (K.R.); (P.C.F.S.); (T.G.); (P.B.); (E.C.); (A.B.)
| | - Philipp Beyerle
- Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, 80539 Munich, Germany; (K.R.); (P.C.F.S.); (T.G.); (P.B.); (E.C.); (A.B.)
| | - Emmanuel Cruz
- Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, 80539 Munich, Germany; (K.R.); (P.C.F.S.); (T.G.); (P.B.); (E.C.); (A.B.)
| | - Andreas Breit
- Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, 80539 Munich, Germany; (K.R.); (P.C.F.S.); (T.G.); (P.B.); (E.C.); (A.B.)
| | - Peter S. Reinach
- Ophthalmology Department, Wenzhou Medical University, Wenzhou 325015, China;
| | - Thomas Gudermann
- Walther Straub Institute of Pharmacology and Toxicology, LMU Munich, 80539 Munich, Germany; (K.R.); (P.C.F.S.); (T.G.); (P.B.); (E.C.); (A.B.)
- German Center for Lung Research, 81377 Munich, Germany
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18
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Fletcher PA, Thompson B, Liu C, Bertram R, Satin LS, Sherman AS. Ca 2+ release or Ca 2+ entry, that is the question: what governs Ca 2+ oscillations in pancreatic β cells? Am J Physiol Endocrinol Metab 2023; 324:E477-E487. [PMID: 37074988 PMCID: PMC10228667 DOI: 10.1152/ajpendo.00030.2023] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 04/06/2023] [Accepted: 04/07/2023] [Indexed: 04/20/2023]
Abstract
The standard model for Ca2+ oscillations in insulin-secreting pancreatic β cells centers on Ca2+ entry through voltage-activated Ca2+ channels. These work in combination with ATP-dependent K+ channels, which are the bridge between the metabolic state of the cells and plasma membrane potential. This partnership underlies the ability of the β cells to secrete insulin appropriately on a minute-to-minute time scale to control whole body plasma glucose. Though this model, developed over more than 40 years through many cycles of experimentation and mathematical modeling, has been very successful, it has been challenged by a hypothesis that calcium-induced calcium release from the endoplasmic reticulum through ryanodine or inositol trisphosphate (IP3) receptors is instead the key driver of islet oscillations. We show here that the alternative model is in fact incompatible with a large body of established experimental data and that the new observations offered in support of it can be better explained by the standard model.
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Affiliation(s)
- Patrick A Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland, United States
| | - Ben Thompson
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Chanté Liu
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida, United States
| | - Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland, United States
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19
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Ashcroft FM. KATP Channels and the Metabolic Regulation of Insulin Secretion in Health and Disease: The 2022 Banting Medal for Scientific Achievement Award Lecture. Diabetes 2023; 72:693-702. [PMID: 37815796 PMCID: PMC10202764 DOI: 10.2337/dbi22-0030] [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: 01/09/2023] [Accepted: 02/28/2023] [Indexed: 10/11/2023]
Abstract
Diabetes is characterized by elevation of plasma glucose due to an insufficiency of the hormone insulin and is associated with both inadequate insulin secretion and impaired insulin action. The Banting Medal for Scientific Achievement Commemorates the work of Sir Frederick Banting, a member of the team that first used insulin to treat a patient with diabetes almost exactly one hundred years ago on 11 January 1922. This article is based on my Banting lecture of 2022 and concerns the mechanism of glucose-stimulated insulin secretion from pancreatic β-cells, with an emphasis on the metabolic regulation of the KATP channel. This channel plays a central role in insulin release. Its closure in response to metabolically generated changes in the intracellular concentrations of ATP and MgADP stimulates β-cell electrical activity and insulin granule exocytosis. Activating mutations in KATP channel genes that impair the ability of the channel to respond to ATP give rise to neonatal diabetes. Impaired KATP channel regulation may also play a role in type 2 diabetes. I conjecture that KATP channel closure in response to glucose is reduced because of impaired glucose metabolism, which fails to generate a sufficient increase in ATP. Consequently, glucose-stimulated β-cell electrical activity is less. As ATP is also required for insulin granule exocytosis, both reduced exocytosis and less β-cell electrical activity may contribute to the reduction in insulin secretion. I emphasize that what follows is not a definitive review of the topic but a personal account of the contribution of my team to the field that is based on my Banting lecture.
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Affiliation(s)
- Frances M. Ashcroft
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, U.K
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20
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Ho T, Potapenko E, Davis DB, Merrins MJ. A plasma membrane-associated glycolytic metabolon is functionally coupled to K ATP channels in pancreatic α and β cells from humans and mice. Cell Rep 2023; 42:112394. [PMID: 37058408 PMCID: PMC10513404 DOI: 10.1016/j.celrep.2023.112394] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 02/25/2023] [Accepted: 03/30/2023] [Indexed: 04/15/2023] Open
Abstract
The ATP-sensitive K+ (KATP) channel is a key regulator of hormone secretion from pancreatic islet endocrine cells. Using direct measurements of KATP channel activity in pancreatic β cells and the lesser-studied α cells, from both humans and mice, we provide evidence that a glycolytic metabolon locally controls KATP channels on the plasma membrane. The two ATP-consuming enzymes of upper glycolysis, glucokinase and phosphofructokinase, generate ADP that activates KATP. Substrate channeling of fructose 1,6-bisphosphate through the enzymes of lower glycolysis fuels pyruvate kinase, which directly consumes the ADP made by phosphofructokinase to raise ATP/ADP and close the channel. We further show the presence of a plasma membrane-associated NAD+/NADH cycle whereby lactate dehydrogenase is functionally coupled to glyceraldehyde-3-phosphate dehydrogenase. These studies provide direct electrophysiological evidence of a KATP-controlling glycolytic signaling complex and demonstrate its relevance to islet glucose sensing and excitability.
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Affiliation(s)
- 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
| | - Dawn B Davis
- 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
| | - 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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21
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El-Meanawy SK, Dooge H, Wexler AC, Kosmach AC, Serban L, Santos EA, Alvarado FJ, Hacker TA, Ramratnam M. Overexpression of a Short Sulfonylurea Splice Variant Increases Cardiac Glucose Uptake and Uncouples Mitochondria by Regulating ROMK Activity. Life (Basel) 2023; 13:1015. [PMID: 37109544 PMCID: PMC10146620 DOI: 10.3390/life13041015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 04/04/2023] [Accepted: 04/12/2023] [Indexed: 04/29/2023] Open
Abstract
The mitochondrial splice variant of the sulfonylurea receptor (SUR2A-55) is associated with protection from myocardial ischemia-reperfusion (IR) injury, increased mitochondrial ATP sensitive K+ channel activity (mitoKATP) and altered glucose metabolism. While mitoKATP channels composed of CCDC51 and ABCB8 exist, the mitochondrial K+ pore regulated by SUR2A-55 is unknown. We explored whether SUR2A-55 regulates ROMK to form an alternate mitoKATP. We assessed glucose uptake in mice overexpressing SUR2A-55 (TGSUR2A-55) compared with WT mice during IR injury. We then examined the expression level of ROMK and the effect of ROMK modulation on mitochondrial membrane potential (Δψm) in WT and TGSUR2A-55 mice. TGSUR2A-55 had increased glucose uptake compared to WT mice during IR injury. The expression of ROMK was similar in WT compared to TGSUR2A-55 mice. ROMK inhibition hyperpolarized resting cardiomyocyte Δψm from TGSUR2A-55 mice but not from WT mice. In addition, TGSUR2A-55 and ROMK inhibitor treated WT isolated cardiomyocytes had enhanced mitochondrial uncoupling. ROMK inhibition blocked diazoxide induced Δψm depolarization and prevented preservation of Δψm from FCCP perfusion in WT and to a lesser degree TGSUR2A-55 mice. In conclusion, cardio-protection from SUR2A-55 is associated with ROMK regulation, enhanced mitochondrial uncoupling and increased glucose uptake.
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Affiliation(s)
- Sarah K. El-Meanawy
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; (S.K.E.-M.)
- Cardiology Section, Medical Service, William. S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
| | - Holly Dooge
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; (S.K.E.-M.)
- Cardiology Section, Medical Service, William. S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
| | - Allison C. Wexler
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; (S.K.E.-M.)
- Cardiology Section, Medical Service, William. S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
| | - Anna C. Kosmach
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; (S.K.E.-M.)
| | - Lara Serban
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; (S.K.E.-M.)
| | - Elizabeth A. Santos
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; (S.K.E.-M.)
| | - Francisco J. Alvarado
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; (S.K.E.-M.)
- Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Timothy A. Hacker
- Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Mohun Ramratnam
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; (S.K.E.-M.)
- Cardiology Section, Medical Service, William. S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
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22
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Martin GM, Patton BL, Shyng SL. K ATP channels in focus: Progress toward a structural understanding of ligand regulation. Curr Opin Struct Biol 2023; 79:102541. [PMID: 36807078 PMCID: PMC10023423 DOI: 10.1016/j.sbi.2023.102541] [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: 10/05/2022] [Revised: 12/11/2022] [Accepted: 01/14/2023] [Indexed: 02/21/2023]
Abstract
KATP channels are hetero-octameric complexes of four inward rectifying potassium channels, Kir6.1 or Kir6.2, and four sulfonylurea receptors, SUR1, SUR2A, or SUR2B from the ABC transporter family. This unique combination enables KATP channels to couple intracellular ATP/ADP ratios, through gating, with membrane excitability, thus regulating a broad range of cellular activities. The prominence of KATP channels in human physiology, disease, and pharmacology has long attracted research interest. Since 2017, a steady flow of high-resolution KATP cryoEM structures has revealed complex and dynamic interactions between channel subunits and their ligands. Here, we highlight insights from recent structures that begin to provide mechanistic explanations for decades of experimental data and discuss the remaining knowledge gaps in our understanding of KATP channel regulation.
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Affiliation(s)
- Gregory M Martin
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Bruce L Patton
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, 97239, USA.
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23
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Ho KH, Jayathilake A, Yagan M, Nour A, Osipovich AB, Magnuson MA, Gu G, Kaverina I. CAMSAP2 localizes to the Golgi in islet β-cells and facilitates Golgi-ER trafficking. iScience 2023; 26:105938. [PMID: 36718359 PMCID: PMC9883185 DOI: 10.1016/j.isci.2023.105938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 12/07/2022] [Accepted: 01/04/2023] [Indexed: 01/09/2023] Open
Abstract
Glucose stimulation induces the remodeling of microtubules, which potentiates insulin secretion in pancreatic β-cells. CAMSAP2 binds to microtubule minus ends to stabilize microtubules in several cultured clonal cells. Here, we report that the knockdown of CAMSAP2 in primary β-cells reduces total insulin content and attenuates GSIS without affecting the releasability of insulin vesicles. Surprisingly, CAMSAP2 knockdown does not change microtubule stability. Unlike in cultured insulinoma cells, CAMSAP2 in primary β-cells predominantly localizes to the Golgi apparatus instead of microtubule minus ends. This novel localization is specific to primary β- but not α-cells and is independent of microtubule binding. Consistent with its specific localization at the Golgi, CAMSAP2 promotes efficient Golgi-ER trafficking in primary β-cells. Moreover, primary β-cells and insulinoma cells likely express different CAMSAP2 isoforms. We propose that a novel CAMSAP2 isoform in primary β-cells has a non-canonical function, which promotes Golgi-ER trafficking to support efficient production of insulin and secretion.
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Affiliation(s)
- Kung-Hsien Ho
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Anissa Jayathilake
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Mahircan Yagan
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Aisha Nour
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Anna B. Osipovich
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Mark A. Magnuson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Guoqiang Gu
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Irina Kaverina
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
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24
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Müller M, Walkling J, Seemann N, Rustenbeck I. The Dynamics of Calcium Signaling in Beta Cells-A Discussion on the Comparison of Experimental and Modelling Data. Int J Mol Sci 2023; 24:ijms24043206. [PMID: 36834618 PMCID: PMC9960854 DOI: 10.3390/ijms24043206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/28/2023] [Accepted: 01/30/2023] [Indexed: 02/07/2023] Open
Abstract
The stimulus-secretion coupling of the pancreatic beta cell is particularly complex, as it integrates the availability of glucose and other nutrients with the neuronal and hormonal input to generate rates of insulin secretion that are appropriate for the entire organism. It is beyond dispute however, that the cytosolic Ca2+ concentration plays a particularly prominent role in this process, as it not only triggers the fusion of insulin granules with the plasma membrane, but also regulates the metabolism of nutrient secretagogues and affects the function of ion channels and transporters. In order to obtain a better understanding of the interdependence of these processes and, ultimately, of the entire beta cell as a working system, models have been developed based on a set of nonlinear ordinary differential equations, and were tested and parametrized on a limited set of experiments. In the present investigation, we have used a recently published version of the beta cell model to test its ability to describe further measurements from our own experimentation and from the literature. The sensitivity of the parameters is quantified and discussed; furthermore, the possible influence of the measuring technique is taken into account. The model proved to be powerful in correctly describing the depolarization pattern in response to glucose and the reaction of the cytosolic Ca2+ concentration to stepwise increases of the extracellular K+ concentration. Additionally, the membrane potential during a KATP channel block combined with a high extracellular K+ concentration could be reproduced. In some cases, however, a slight change of a single parameter led to an abrupt change in the cellular response, such as the generation of a Ca2+ oscillation with high amplitude and high frequency. This raises the question as to whether the beta cell may be a partially unstable system or whether further developments in modeling are needed to achieve a generally valid description of the stimulus-secretion coupling of the beta cell.
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Affiliation(s)
- Michael Müller
- Institute of Dynamics and Vibrations, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
- Correspondence: (M.M.); (I.R.); Tel.: +49-531-391-7005 (M.M.);+49-531-391-5670 (I.R.)
| | - Jonas Walkling
- Institute of Dynamics and Vibrations, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
| | - Nele Seemann
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
- Correspondence: (M.M.); (I.R.); Tel.: +49-531-391-7005 (M.M.);+49-531-391-5670 (I.R.)
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25
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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: 44] [Impact Index Per Article: 22.0] [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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26
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Multi target interactions of essential oil nanoemulsion of Cinnamomum travancoricum against diabetes mellitus via in vitro, in vivo and in silico approaches. Process Biochem 2022. [DOI: 10.1016/j.procbio.2022.04.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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27
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Wang M, Wu JX, Chen L. Structural Insights Into the High Selectivity of the Anti-Diabetic Drug Mitiglinide. Front Pharmacol 2022; 13:929684. [PMID: 35847046 PMCID: PMC9279661 DOI: 10.3389/fphar.2022.929684] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 05/25/2022] [Indexed: 11/13/2022] Open
Abstract
Mitiglinide is a highly selective fast-acting anti-diabetic drug that induces insulin secretion by inhibiting pancreatic KATP channels. However, how mitiglinide binds KATP channels remains unknown. Here, we show the cryo-EM structure of the SUR1 subunit complexed with mitiglinide. The structure reveals that mitiglinide binds inside the common insulin secretagogue-binding site of SUR1, which is surrounded by TM7, TM8, TM16, and TM17. Mitiglinide locks SUR1 in the NBD-separated inward-facing conformation. The detailed structural analysis of the mitiglinide-binding site uncovers the molecular basis of its high selectivity.
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Affiliation(s)
- Mengmeng Wang
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- National Biomedical Imaging Center, Peking University, Beijing, China
| | - Jing-Xiang Wu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing, China
- National Biomedical Imaging Center, Peking University, Beijing, China
| | - Lei Chen
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- National Biomedical Imaging Center, Peking University, Beijing, China
- *Correspondence: Lei Chen,
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28
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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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29
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Ježek P, Holendová B, Jabůrek M, Dlasková A, Plecitá-Hlavatá L. Contribution of Mitochondria to Insulin Secretion by Various Secretagogues. Antioxid Redox Signal 2022; 36:920-952. [PMID: 34180254 PMCID: PMC9125579 DOI: 10.1089/ars.2021.0113] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Significance: Mitochondria determine glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells by elevating ATP synthesis. As the metabolic and redox hub, mitochondria provide numerous links to the plasma membrane channels, insulin granule vesicles (IGVs), cell redox, NADH, NADPH, and Ca2+ homeostasis, all affecting insulin secretion. Recent Advances: Mitochondrial redox signaling was implicated in several modes of insulin secretion (branched-chain ketoacid [BCKA]-, fatty acid [FA]-stimulated). Mitochondrial Ca2+ influx was found to enhance GSIS, reflecting cytosolic Ca2+ oscillations induced by action potential spikes (intermittent opening of voltage-dependent Ca2+ and K+ channels) or the superimposed Ca2+ release from the endoplasmic reticulum (ER). The ATPase inhibitory factor 1 (IF1) was reported to tune the glucose sensitivity range for GSIS. Mitochondrial protein kinase A was implicated in preventing the IF1-mediated inhibition of the ATP synthase. Critical Issues: It is unknown how the redox signal spreads up to the plasma membrane and what its targets are, what the differences in metabolic, redox, NADH/NADPH, and Ca2+ signaling, and homeostasis are between the first and second GSIS phase, and whether mitochondria can replace ER in the amplification of IGV exocytosis. Future Directions: Metabolomics studies performed to distinguish between the mitochondrial matrix and cytosolic metabolites will elucidate further details. Identifying the targets of cell signaling into mitochondria and of mitochondrial retrograde metabolic and redox signals to the cell will uncover further molecular mechanisms for insulin secretion stimulated by glucose, BCKAs, and FAs, and the amplification of secretion by glucagon-like peptide (GLP-1) and metabotropic receptors. They will identify the distinction between the hub β-cells and their followers in intact and diabetic states. Antioxid. Redox Signal. 36, 920-952.
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Affiliation(s)
- Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Blanka Holendová
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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30
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Marinelli I, Thompson BM, Parekh VS, Fletcher PA, Gerardo-Giorda L, Sherman AS, Satin LS, Bertram R. Oscillations in K(ATP) conductance drive slow calcium oscillations in pancreatic β-cells. Biophys J 2022; 121:1449-1464. [PMID: 35300967 PMCID: PMC9072586 DOI: 10.1016/j.bpj.2022.03.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 10/07/2021] [Accepted: 03/11/2022] [Indexed: 11/26/2022] Open
Abstract
ATP-sensitive K+ (K(ATP)) channels were first reported in the β-cells of pancreatic islets in 1984, and it was soon established that they are the primary means by which the blood glucose level is transduced to cellular electrical activity and consequently insulin secretion. However, the role that the K(ATP) channels play in driving the bursting electrical activity of islet β-cells, which drives pulsatile insulin secretion, remains unclear. One difficulty is that bursting is abolished when several different ion channel types are blocked pharmacologically or genetically, making it challenging to distinguish causation from correlation. Here, we demonstrate a means for determining whether activity-dependent oscillations in K(ATP) conductance play the primary role in driving electrical bursting in β-cells. We use mathematical models to predict that if K(ATP) is the driver, then contrary to intuition, the mean, peak, and nadir levels of ATP/ADP should be invariant to changes in glucose within the concentration range that supports bursting. We test this in islets using Perceval-HR to image oscillations in ATP/ADP. We find that mean, peak, and nadir levels are indeed approximately invariant, supporting the hypothesis that oscillations in K(ATP) conductance are the main drivers of the slow bursting oscillations typically seen at stimulatory glucose levels in mouse islets. In conclusion, we provide, for the first time to our knowledge, causal evidence for the role of K(ATP) channels not only as the primary target for glucose regulation but also for their role in driving bursting electrical activity and pulsatile insulin secretion.
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Affiliation(s)
- Isabella Marinelli
- Centre for Systems Modelling & Quantitative Biomedicine (SMQB), University of Birmingham, Birmingham, UK
| | - Benjamin M Thompson
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Vishal S Parekh
- Chemical Biology and Therapeutics Science Program, Broad Institute, Cambridge, Massachusetts
| | - Patrick A Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland
| | - Luca Gerardo-Giorda
- Institute for Mathematical Methods in Medicine and Data Based Modeling, Johannes Kepler University, Linz, Austria; Johann Radon Institute for Computational and Applied Mathematics (RICAM), Austrian Academy of Sciences, Linz, Austria
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland
| | - Leslie S Satin
- Department of Pharmacology and Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida.
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31
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Guérineau NC, Campos P, Le Tissier PR, Hodson DJ, Mollard P. Cell Networks in Endocrine/Neuroendocrine Gland Function. Compr Physiol 2022; 12:3371-3415. [PMID: 35578964 DOI: 10.1002/cphy.c210031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Reproduction, growth, stress, and metabolism are determined by endocrine/neuroendocrine systems that regulate circulating hormone concentrations. All these systems generate rhythms and changes in hormone pulsatility observed in a variety of pathophysiological states. Thus, the output of endocrine/neuroendocrine systems must be regulated within a narrow window of effective hormone concentrations but must also maintain a capacity for plasticity to respond to changing physiological demands. Remarkably most endocrinologists still have a "textbook" view of endocrine gland organization which has emanated from 20th century histological studies on thin 2D tissue sections. However, 21st -century technological advances, including in-depth 3D imaging of specific cell types have vastly changed our knowledge. We now know that various levels of multicellular organization can be found across different glands, that organizational motifs can vary between species and can be modified to enhance or decrease hormonal release. This article focuses on how the organization of cells regulates hormone output using three endocrine/neuroendocrine glands that present different levels of organization and complexity: the adrenal medulla, with a single neuroendocrine cell type; the anterior pituitary, with multiple intermingled cell types; and the pancreas with multiple intermingled cell types organized into distinct functional units. We give an overview of recent methodologies that allow the study of the different components within endocrine systems, particularly their temporal and spatial relationships. We believe the emerging findings about network organization, and its impact on hormone secretion, are crucial to understanding how homeostatic regulation of endocrine axes is carried out within endocrine organs themselves. © 2022 American Physiological Society. Compr Physiol 12:3371-3415, 2022.
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Affiliation(s)
| | - Pauline Campos
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
| | - Paul R Le Tissier
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland, UK
| | - David J Hodson
- Institute of Metabolism and Systems Research (IMSR), University of Birmingham, Edgbaston, UK.,Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK.,COMPARE University of Birmingham and University of Nottingham Midlands, UK.,Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), NIHR Oxford Biomedical Research Centre, Churchill Hospital, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Patrice Mollard
- IGF, University of Montpellier, CNRS, INSERM, Montpellier, France
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32
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Pirotte B, Florence X, Goffin E, Leleux F, Lebrun P. Research Advancements on Fluorinated and Non-Fluorinated 4-Phenyl(thio)ureido-Substituted 2,2-Dimethylchromans Acting as Inhibitors of Insulin Release and Smooth Muscle Relaxants. Med Chem 2022; 18:884-894. [PMID: 35189799 DOI: 10.2174/1573406418666220221145500] [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: 10/22/2021] [Revised: 11/29/2021] [Accepted: 12/21/2021] [Indexed: 11/22/2022]
Abstract
AIMS The present study aimed at characterizing the impact of the presence or absence of fluorine atoms on the phenyl and benzopyran rings of 4-phenyl(thio)ureido-substituted 2,2-dimethylchromans on their ability to inhibit insulin release from pancreatic -cells or to relax vascular smooth muscle cells. METHODS Most compounds were found to inhibit insulin secretion and to provoke a marked myorelaxant activity. RESULTS The lack of a fluorine or a chlorine atom at the 6-position of the 2,2-dimethylchroman core structure reduced the inhibitory activity on the pancreatic endocrine tissue. One of the most active compounds on both tissues, compound 11h (BPDZ 678), was selected for further pharmacological investigations. CONCLUSION The biological data suggested that 11h mainly expressed the profile of a KATP channel opener on pancreatic -cells, although a calcium entry blockade effect was also observed. On vascular smooth muscle cells, 11h behaved as a calcium entry blocker.
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Affiliation(s)
- Bernard Pirotte
- Laboratoire de Chimie Pharmaceutique, Center for Interdisciplinary Research on Medicines (CIRM), Université de Liège, Quartier Hôpital, Avenue Hippocrate 15, B-4000 Liège, Belgium
| | - Xavier Florence
- Laboratoire de Chimie Pharmaceutique, Center for Interdisciplinary Research on Medicines (CIRM), Université de Liège, Quartier Hôpital, Avenue Hippocrate 15, B-4000 Liège, Belgium
- Laboratoire de Physiologie et Pharmacologie, Université Libre de Bruxelles, Faculté de Médecine, 808 Route de Lennik, B-1070 Bruxelles, Belgium
| | - Eric Goffin
- Laboratoire de Chimie Pharmaceutique, Center for Interdisciplinary Research on Medicines (CIRM), Université de Liège, Quartier Hôpital, Avenue Hippocrate 15, B-4000 Liège, Belgium
| | - Fabienne Leleux
- Laboratoire de Physiologie et Pharmacologie, Université Libre de Bruxelles, Faculté de Médecine, 808 Route de Lennik, B-1070 Bruxelles, Belgium
| | - Philippe Lebrun
- Laboratoire de Physiologie et Pharmacologie, Université Libre de Bruxelles, Faculté de Médecine, 808 Route de Lennik, B-1070 Bruxelles, Belgium
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33
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Park JE, Kim SY, Han JS. Scopoletin stimulates the secretion of insulin via a KATP channel-dependent pathway in INS-1 pancreatic β cells. J Pharm Pharmacol 2022; 74:1274-1281. [PMID: 35099527 DOI: 10.1093/jpp/rgab143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 12/23/2021] [Indexed: 12/17/2022]
Abstract
OBJECTIVES In this study, we investigated whether scopoletin stimulated the secretion of insulin in pancreatic β cells as well as the underlying mechanism involved in this process. METHODS We incubated the INS-1 pancreatic β cells with various concentrations of glucose (1.1, 5.6 or 16.7 mM) in the presence or absence of scopoletin. We then analysed the secretion of insulin in the cells treated with insulin secretion inhibitors or secretagogues. The intracellular influx of calcium induced by scopoletin was also analysed using the Fluo-2 AM dye. KEY FINDINGS We found that scopoletin (1-20 µM) markedly induced the secretion of insulin in a glucose concentration-dependent manner compared with the control. At depolarizing concentrations of potassium chloride (KCl), scopoletin markedly enhanced the insulin secretion compared with the cells which were treated only with KCl. Moreover, the treatment with diazoxide-opening K+ATP channel and verapamil blocking Ca2+ channel significantly decreased the scopoletin-induced increase in insulin secretion. After the pre-treatment of cells with a Ca2+ fluorescent dye, treatment with 20 µM scopoletin resulted in a significant increase in the influx of intracellular Ca2+, exhibiting fluorescence changes in various spectra. CONCLUSIONS Scopoletin stimulates the secretion of insulin via a K+ATP channel-dependent pathway in the INS-1 pancreatic β cells.
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Affiliation(s)
- Jae Eun Park
- Department of Food Science and Nutrition, Pusan National University, Busan, Republic of Korea
| | - Seon Young Kim
- Department of Food Science and Nutrition, Pusan National University, Busan, Republic of Korea
| | - Ji Sook Han
- Department of Food Science and Nutrition, Pusan National University, Busan, Republic of Korea
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34
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Foster HR, Ho T, Potapenko E, Sdao SM, Huang SM, Lewandowski SL, VanDeusen HR, Davidson SM, Cardone RL, Prentki M, Kibbey RG, Merrins MJ. β-cell deletion of the PKm1 and PKm2 isoforms of pyruvate kinase in mice reveals their essential role as nutrient sensors for the K ATP channel. eLife 2022; 11:79422. [PMID: 35997256 PMCID: PMC9444242 DOI: 10.7554/elife.79422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 08/23/2022] [Indexed: 02/03/2023] Open
Abstract
Pyruvate kinase (PK) and the phosphoenolpyruvate (PEP) cycle play key roles in nutrient-stimulated KATP channel closure and insulin secretion. To identify the PK isoforms involved, we generated mice lacking β-cell PKm1, PKm2, and mitochondrial PEP carboxykinase (PCK2) that generates mitochondrial PEP. Glucose metabolism was found to generate both glycolytic and mitochondrially derived PEP, which triggers KATP closure through local PKm1 and PKm2 signaling at the plasma membrane. Amino acids, which generate mitochondrial PEP without producing glycolytic fructose 1,6-bisphosphate to allosterically activate PKm2, signal through PKm1 to raise ATP/ADP, close KATP channels, and stimulate insulin secretion. Raising cytosolic ATP/ADP with amino acids is insufficient to close KATP channels in the absence of PK activity or PCK2, indicating that KATP channels are primarily regulated by PEP that provides ATP via plasma membrane-associated PK, rather than mitochondrially derived ATP. Following membrane depolarization, the PEP cycle is involved in an 'off-switch' that facilitates KATP channel reopening and Ca2+ extrusion, as shown by PK activation experiments and β-cell PCK2 deletion, which prolongs Ca2+ oscillations and increases insulin secretion. In conclusion, the differential response of PKm1 and PKm2 to the glycolytic and mitochondrial sources of PEP influences the β-cell nutrient response, and controls the oscillatory cycle regulating insulin secretion.
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Affiliation(s)
- Hannah R Foster
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-MadisonMadisonUnited States
| | - Thuong Ho
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-MadisonMadisonUnited States
| | - Evgeniy Potapenko
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-MadisonMadisonUnited States
| | - Sophia M Sdao
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-MadisonMadisonUnited States
| | - Shih Ming Huang
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-MadisonMadisonUnited States
| | - Sophie L Lewandowski
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-MadisonMadisonUnited States
| | - Halena R VanDeusen
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-MadisonMadisonUnited States
| | - Shawn M Davidson
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of TechnologyCambridgeUnited States,Lewis-Sigler Institute for Integrative Genomics, Princeton UniversityPrincetonUnited States
| | - Rebecca L Cardone
- Department of Internal Medicine, Yale UniversityNew HavenUnited States
| | - Marc Prentki
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, and Departments of Nutrition, Biochemistry and Molecular Medicine, Université de MontréalMontréalCanada
| | - Richard G Kibbey
- Department of Internal Medicine, Yale UniversityNew HavenUnited States,Department of Cellular & Molecular Physiology, Yale UniversityNew HavenUnited States
| | - Matthew J Merrins
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-MadisonMadisonUnited States,William S. Middleton Memorial Veterans HospitalMadisonUnited States
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35
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Zhu C, Zhang S, Liu D, Wang Q, Yang N, Zheng Z, Wu Q, Zhou Y. A Novel Gene Prognostic Signature Based on Differential DNA Methylation in Breast Cancer. Front Genet 2021; 12:742578. [PMID: 34956313 PMCID: PMC8693898 DOI: 10.3389/fgene.2021.742578] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 11/15/2021] [Indexed: 12/11/2022] Open
Abstract
Background: DNA methylation played essential roles in regulating gene expression. The impact of DNA methylation status on the occurrence and development of cancers has been well demonstrated. However, little is known about its prognostic role in breast cancer (BC). Materials: The Illumina Human Methylation450 array (450k array) data of BC was downloaded from the UCSC xena database. Transcriptomic data of BC was downloaded from the Cancer Genome Atlas (TCGA) database. Firstly, we used univariate and multivariate Cox regression analysis to screen out independent prognostic CpGs, and then we identified methylation-associated prognosis subgroups by consensus clustering. Next, a methylation prognostic model was developed using multivariate Cox analysis and was validated with the Illumina Human Methylation27 array (27k array) dataset of BC. We then screened out differentially expressed genes (DEGs) between methylation high-risk and low-risk groups and constructed a methylation-based gene prognostic signature. Further, we validated the gene signature with three subgroups of the TCGA-BRCA dataset and an external dataset GSE146558 from the Gene Expression Omnibus (GEO) database. Results: We established a methylation prognostic signature and a methylation-based gene prognostic signature, and there was a close positive correlation between them. The gene prognostic signature involved six genes: IRF2, KCNJ11, ZDHHC9, LRP11, PCMT1, and TMEM70. We verified their expression in mRNA and protein levels in BC. Both methylation and methylation-based gene prognostic signatures showed good prognostic stratification ability. The AUC values of 3-years, 5-years overall survival (OS) were 0.737, 0.744 in the methylation signature and 0.725, 0.715 in the gene signature, respectively. In the validation groups, high-risk patients were confirmed to have poorer OS. The AUC values of 3 years were 0.757, 0.735, 0.733 in the three subgroups of TCGA dataset and 0.635 in GSE146558 dataset. Conclusion: This study revealed the DNA methylation landscape and established promising methylation and methylation-based gene prognostic signatures that could serve as potential prognostic biomarkers and therapeutic targets.
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Affiliation(s)
- Chunmei Zhu
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Shuyuan Zhang
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Di Liu
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Qingqing Wang
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China.,Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Ningning Yang
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China.,Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Zhewen Zheng
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China.,Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Qiuji Wu
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China.,Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China.,Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Yunfeng Zhou
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China.,Hubei Key Laboratory of Tumor Biological Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China.,Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China
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36
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Hughson BN. The Glucagon-Like Adipokinetic Hormone in Drosophila melanogaster - Biosynthesis and Secretion. Front Physiol 2021; 12:710652. [PMID: 35002748 PMCID: PMC8733639 DOI: 10.3389/fphys.2021.710652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 09/16/2021] [Indexed: 11/13/2022] Open
Abstract
Metabolic homeostasis requires the precise regulation of circulating sugar titers. In mammals, homeostatic control of circulating sugar titers requires the coordinated secretion and systemic activities of glucagon and insulin. Metabolic homeostasis is similarly regulated in Drosophila melanogaster through the glucagon-like adipokinetic hormone (AKH) and the Drosophila insulin-like peptides (DILPs). In flies and mammals, glucagon and AKH are biosynthesized in and secreted from specialized endocrine cells. KATP channels borne on these cells respond to fluctuations in circulating glucose titers and thereby regulate glucagon secretion. The influence of glucagon in the pathogenesis of type 2 diabetes mellitus is now recognized, and a crucial mechanism that regulates glucagon secretion was reported nearly a decade ago. Ongoing efforts to develop D. melanogaster models for metabolic syndrome must build upon this seminal work. These efforts make a critical review of AKH physiology timely. This review focuses on AKH biosynthesis and the regulation of glucose-responsive AKH secretion through changes in CC cell electrical activity. Future directions for AKH research in flies are discussed, including the development of models for hyperglucagonemia and epigenetic inheritance of acquired metabolic traits. Many avenues of AKH physiology remain to be explored and thus present great potential for improving the utility of D. melanogaster in metabolic research.
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Affiliation(s)
- Bryon N. Hughson
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
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37
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Marinelli I, Fletcher PA, Sherman AS, Satin LS, Bertram R. Symbiosis of Electrical and Metabolic Oscillations in Pancreatic β-Cells. Front Physiol 2021; 12:781581. [PMID: 34925070 PMCID: PMC8682964 DOI: 10.3389/fphys.2021.781581] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/08/2021] [Indexed: 11/13/2022] Open
Abstract
Insulin is secreted in a pulsatile pattern, with important physiological ramifications. In pancreatic β-cells, which are the cells that synthesize insulin, insulin exocytosis is elicited by pulses of elevated intracellular Ca2+ initiated by bursts of electrical activity. In parallel with these electrical and Ca2+ oscillations are oscillations in metabolism, and the periods of all of these oscillatory processes are similar. A key question that remains unresolved is whether the electrical oscillations are responsible for the metabolic oscillations via the effects of Ca2+, or whether the metabolic oscillations are responsible for the electrical oscillations due to the effects of ATP on ATP-sensitive ion channels? Mathematical modeling is a useful tool for addressing this and related questions as modeling can aid in the design of well-focused experiments that can test the predictions of particular models and subsequently be used to improve the models in an iterative fashion. In this article, we discuss a recent mathematical model, the Integrated Oscillator Model (IOM), that was the product of many years of development. We use the model to demonstrate that the relationship between calcium and metabolism in beta cells is symbiotic: in some contexts, the electrical oscillations drive the metabolic oscillations, while in other contexts it is the opposite. We provide new insights regarding these results and illustrate that what might at first appear to be contradictory data are actually compatible when viewed holistically with the IOM.
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Affiliation(s)
- Isabella Marinelli
- Centre for Systems Modelling and Quantitative Biomedicine (SMQB), University of Birmingham, Birmingham, United Kingdom
| | - Patrick A Fletcher
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
| | - Arthur S Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, MD, United States
| | - Leslie S Satin
- Department of Pharmacology, Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Richard Bertram
- Programs in Neuroscience and Molecular Biophysics, Department of Mathematics, Florida State University, Tallahassee, FL, United States
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38
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Tentonin 3/TMEM150C regulates glucose-stimulated insulin secretion in pancreatic β-cells. Cell Rep 2021; 37:110067. [PMID: 34852221 DOI: 10.1016/j.celrep.2021.110067] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 10/17/2021] [Accepted: 11/08/2021] [Indexed: 11/24/2022] Open
Abstract
Glucose homeostasis is initially regulated by the pancreatic hormone insulin. Glucose-stimulated insulin secretion in β-cells is composed of two cellular mechanisms: a high glucose concentration not only depolarizes the membrane potential of the β-cells by ATP-sensitive K+ channels but also induces cell inflation, which is sufficient to release insulin granules. However, the molecular identity of the stretch-activated cation channel responsible for the latter pathway remains unknown. Here, we demonstrate that Tentonin 3/TMEM150C (TTN3), a mechanosensitive channel, contributes to glucose-stimulated insulin secretion by mediating cation influx. TTN3 is expressed specifically in β-cells and mediates cation currents to glucose and hypotonic stimulations. The glucose-induced depolarization, firing activity, and Ca2+ influx of β-cells were significantly lower in Ttn3-/- mice. More importantly, Ttn3-/- mice show impaired glucose tolerance with decreased insulin secretion in vivo. We propose that TTN3, as a stretch-activated cation channel, contributes to glucose-stimulated insulin secretion.
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39
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Zhao C, MacKinnon R. Molecular structure of an open human K ATP channel. Proc Natl Acad Sci U S A 2021; 118:e2112267118. [PMID: 34815345 PMCID: PMC8640745 DOI: 10.1073/pnas.2112267118] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/02/2021] [Indexed: 11/18/2022] Open
Abstract
KATP channels are metabolic sensors that translate intracellular ATP/ADP balance into membrane excitability. The molecular composition of KATP includes an inward-rectifier potassium channel (Kir) and an ABC transporter-like sulfonylurea receptor (SUR). Although structures of KATP have been determined in many conformations, in all cases, the pore in Kir is closed. Here, we describe human pancreatic KATP (hKATP) structures with an open pore at 3.1- to 4.0-Å resolution using single-particle cryo-electron microscopy (cryo-EM). Pore opening is associated with coordinated structural changes within the ATP-binding site and the channel gate in Kir. Conformational changes in SUR are also observed, resulting in an area reduction of contact surfaces between SUR and Kir. We also observe that pancreatic hKATP exhibits the unique (among inward-rectifier channels) property of PIP2-independent opening, which appears to be correlated with a docked cytoplasmic domain in the absence of PIP2.
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Affiliation(s)
- Chen Zhao
- HHMI, The Rockefeller University, New York, NY 10065
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, New York, NY 10065
| | - Roderick MacKinnon
- HHMI, The Rockefeller University, New York, NY 10065;
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, New York, NY 10065
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40
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Expression of truncated Kir6.2 promotes insertion of functionally inverted ATP-sensitive K + channels. Sci Rep 2021; 11:21539. [PMID: 34728728 PMCID: PMC8564548 DOI: 10.1038/s41598-021-00988-y] [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: 05/18/2021] [Accepted: 10/06/2021] [Indexed: 11/12/2022] Open
Abstract
ATP-sensitive K+ (KATP) channels couple cellular metabolism to electrical activity in many cell types. Wild-type KATP channels are comprised of four pore forming (Kir6.x) and four regulatory (sulfonylurea receptor, SURx) subunits that each contain RKR endoplasmic reticulum retention sequences that serve to properly translocate the channel to the plasma membrane. Truncated Kir6.x variants lacking RKR sequences facilitate plasma membrane expression of functional Kir6.x in the absence of SURx; however, the effects of channel truncation on plasma membrane orientation have not been explored. To investigate the role of truncation on plasma membrane orientation of ATP sensitive K+ channels, three truncated variants of Kir6.2 were used (Kir6.2ΔC26, 6xHis-Kir6.2ΔC26, and 6xHis-EGFP-Kir6.2ΔC26). Oocyte expression of Kir6.2ΔC26 shows the presence of a population of inverted inserted channels in the plasma membrane, which is not present when co-expressed with SUR1. Immunocytochemical staining of intact and permeabilized HEK293 cells revealed that the N-terminus of 6xHis-Kir6.2ΔC26 was accessible on both sides of the plasma membrane at roughly equivalent ratios, whereas the N-terminus of 6xHis-EGFP-Kir6.2Δ26 was only accessible on the intracellular face. In HEK293 cells, whole-cell electrophysiological recordings showed a ca. 50% reduction in K+ current upon addition of ATP to the extracellular solution for 6xHis-Kir6.2ΔC26, though sensitivity to extracellular ATP was not observed in 6xHis-EGFP-Kir6.2ΔC26. Importantly, the population of channels that is inverted exhibited similar function to properly inserted channels within the plasma membrane. Taken together, these data suggest that in the absence of SURx, inverted channels can be formed from truncated Kir6.x subunits that are functionally active which may provide a new model for testing pharmacological modulators of Kir6.x, but also indicates the need for added caution when using truncated Kir6.2 mutants.
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41
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Chen Y, Hu X, Cui J, Zhao M, Yao H. A novel mutation KCNJ11 R136C caused KCNJ11-MODY. Diabetol Metab Syndr 2021; 13:91. [PMID: 34465386 PMCID: PMC8406974 DOI: 10.1186/s13098-021-00708-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Accepted: 08/11/2021] [Indexed: 11/16/2022] Open
Abstract
A young female patient, diagnosed with diabetes mellitus at the age of 28 years old in 2009, carries KCNJ11 R136C by whole exome sequencing and her daughter doesn't carry this mutation. Bioinformatics software predicted that the 136th amino acid is highly conservative and the mutation is deleterious. KCNJ11 R136C can result in the change of channel port structure of KATP channel. So she was diagnosed as KCNJ11-MODY.
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Affiliation(s)
- Yaning Chen
- Department of Endocrinology, Sixth Medical Center of PLA General Hospital, 6# Fucheng Road, Haidian District, Beijing, 100048, China
| | - Xiaodong Hu
- Department of Endocrinology, Sixth Medical Center of PLA General Hospital, 6# Fucheng Road, Haidian District, Beijing, 100048, China
| | - Jia Cui
- Department of Endocrinology, Sixth Medical Center of PLA General Hospital, 6# Fucheng Road, Haidian District, Beijing, 100048, China
| | - Mingwei Zhao
- Department of Endocrinology, Sixth Medical Center of PLA General Hospital, 6# Fucheng Road, Haidian District, Beijing, 100048, China
| | - Hebin Yao
- Department of Endocrinology, Sixth Medical Center of PLA General Hospital, 6# Fucheng Road, Haidian District, Beijing, 100048, China.
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42
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Metabolic Phenotypes and Step by Step Evolution of Type 2 Diabetes: A New Paradigm. Biomedicines 2021; 9:biomedicines9070800. [PMID: 34356863 PMCID: PMC8301386 DOI: 10.3390/biomedicines9070800] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 07/02/2021] [Accepted: 07/05/2021] [Indexed: 01/18/2023] Open
Abstract
Unlike bolus insulin secretion mechanisms, basal insulin secretion is poorly understood. It is essential to elucidate these mechanisms in non-hyperinsulinaemia healthy persons. This establishes a baseline for investigation into pathologies where these processes are dysregulated, such as in type 2 diabetes (T2DM), cardiovascular disease (CVD), certain cancers and dementias. Chronic hyperinsulinaemia enforces glucose fueling, depleting the NAD+ dependent antioxidant activity that increases mitochondrial reactive oxygen species (mtROS). Consequently, beta-cell mitochondria increase uncoupling protein expression, which decreases the mitochondrial ATP surge generation capacity, impairing bolus mediated insulin exocytosis. Excessive ROS increases the Drp1:Mfn2 ratio, increasing mitochondrial fission, which increases mtROS; endoplasmic reticulum-stress and impaired calcium homeostasis ensues. Healthy individuals in habitual ketosis have significantly lower glucagon and insulin levels than T2DM individuals. As beta-hydroxybutyrate rises, hepatic gluconeogenesis and glycogenolysis supply extra-hepatic glucose needs, and osteocalcin synthesis/release increases. We propose insulin’s primary role is regulating beta-hydroxybutyrate synthesis, while the role of bone regulates glucose uptake sensitivity via osteocalcin. Osteocalcin regulates the alpha-cell glucagon secretory profile via glucagon-like peptide-1 and serotonin, and beta-hydroxybutyrate synthesis via regulating basal insulin levels. Establishing metabolic phenotypes aids in resolving basal insulin secretion regulation, enabling elucidation of the pathological changes that occur and progress into chronic diseases associated with ageing.
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43
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von Molitor E, Riedel K, Krohn M, Hafner M, Rudolf R, Cesetti T. Sweet Taste Is Complex: Signaling Cascades and Circuits Involved in Sweet Sensation. Front Hum Neurosci 2021; 15:667709. [PMID: 34239428 PMCID: PMC8258107 DOI: 10.3389/fnhum.2021.667709] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 05/20/2021] [Indexed: 12/13/2022] Open
Abstract
Sweetness is the preferred taste of humans and many animals, likely because sugars are a primary source of energy. In many mammals, sweet compounds are sensed in the tongue by the gustatory organ, the taste buds. Here, a group of taste bud cells expresses a canonical sweet taste receptor, whose activation induces Ca2+ rise, cell depolarization and ATP release to communicate with afferent gustatory nerves. The discovery of the sweet taste receptor, 20 years ago, was a milestone in the understanding of sweet signal transduction and is described here from a historical perspective. Our review briefly summarizes the major findings of the canonical sweet taste pathway, and then focuses on molecular details, about the related downstream signaling, that are still elusive or have been neglected. In this context, we discuss evidence supporting the existence of an alternative pathway, independent of the sweet taste receptor, to sense sugars and its proposed role in glucose homeostasis. Further, given that sweet taste receptor expression has been reported in many other organs, the physiological role of these extraoral receptors is addressed. Finally, and along these lines, we expand on the multiple direct and indirect effects of sugars on the brain. In summary, the review tries to stimulate a comprehensive understanding of how sweet compounds signal to the brain upon taste bud cells activation, and how this gustatory process is integrated with gastro-intestinal sugar sensing to create a hedonic and metabolic representation of sugars, which finally drives our behavior. Understanding of this is indeed a crucial step in developing new strategies to prevent obesity and associated diseases.
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Affiliation(s)
- Elena von Molitor
- Institute of Molecular and Cell Biology, Hochschule Mannheim, Mannheim, Germany
| | | | | | - Mathias Hafner
- Institute of Molecular and Cell Biology, Hochschule Mannheim, Mannheim, Germany
| | - Rüdiger Rudolf
- Institute of Molecular and Cell Biology, Hochschule Mannheim, Mannheim, Germany.,Interdisciplinary Center for Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Tiziana Cesetti
- Institute of Molecular and Cell Biology, Hochschule Mannheim, Mannheim, Germany
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44
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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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45
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Glucose and NAADP trigger elementary intracellular β-cell Ca 2+ signals. Sci Rep 2021; 11:10714. [PMID: 34021189 PMCID: PMC8140081 DOI: 10.1038/s41598-021-88906-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 04/15/2021] [Indexed: 11/12/2022] Open
Abstract
Pancreatic β-cells release insulin upon a rise in blood glucose. The precise mechanisms of stimulus-secretion coupling, and its failure in Diabetes Mellitus Type 2, remain to be elucidated. The consensus model, as well as a class of currently prescribed anti-diabetic drugs, are based around the observation that glucose-evoked ATP production in β-cells leads to closure of cell membrane ATP-gated potassium (KATP) channels, plasma membrane depolarisation, Ca2+ influx, and finally the exocytosis of insulin granules. However, it has been demonstrated by the inactivation of this pathway using genetic and pharmacological means that closure of the KATP channel alone may not be sufficient to explain all β-cell responses to glucose elevation. We have previously proposed that NAADP-evoked Ca2+ release is an important step in stimulus-secretion coupling in pancreatic β-cells. Here we show using total internal reflection fluorescence (TIRF) microscopy that glucose as well as the Ca2+ mobilising messenger nicotinic acid adenine dinucleotide phosphate (NAADP), known to operate in β-cells, lead to highly localised elementary intracellular Ca2+ signals. These were found to be obscured by measurements of global Ca2+ signals and the action of powerful SERCA-based sequestration mechanisms at the endoplasmic reticulum (ER). Building on our previous work demonstrating that NAADP-evoked Ca2+ release is an important step in stimulus-secretion coupling in pancreatic β-cells, we provide here the first demonstration of elementary Ca2+ signals in response to NAADP, whose occurrence was previously suspected. Optical quantal analysis of these events reveals a unitary event amplitude equivalent to that of known elementary Ca2+ signalling events, inositol trisphosphate (IP3) receptor mediated blips, and ryanodine receptor mediated quarks. We propose that a mechanism based on these highly localised intracellular Ca2+ signalling events mediated by NAADP may initially operate in β-cells when they respond to elevations in blood glucose.
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46
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Zhang GF, Jensen MV, Gray SM, El K, Wang Y, Lu D, Becker TC, Campbell JE, Newgard CB. Reductive TCA cycle metabolism fuels glutamine- and glucose-stimulated insulin secretion. Cell Metab 2021; 33:804-817.e5. [PMID: 33321098 PMCID: PMC8115731 DOI: 10.1016/j.cmet.2020.11.020] [Citation(s) in RCA: 73] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 11/06/2020] [Accepted: 11/25/2020] [Indexed: 12/11/2022]
Abstract
Metabolic fuels regulate insulin secretion by generating second messengers that drive insulin granule exocytosis, but the biochemical pathways involved are incompletely understood. Here we demonstrate that stimulation of rat insulinoma cells or primary rat islets with glucose or glutamine + 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (Gln + BCH) induces reductive, "counter-clockwise" tricarboxylic acid (TCA) cycle flux of glutamine to citrate. Molecular or pharmacologic suppression of isocitrate dehydrogenase-2 (IDH2), which catalyzes reductive carboxylation of 2-ketoglutarate to isocitrate, results in impairment of glucose- and Gln + BCH-stimulated reductive TCA cycle flux, lowering of NADPH levels, and inhibition of insulin secretion. Pharmacologic suppression of IDH2 also inhibits insulin secretion in living mice. Reductive TCA cycle flux has been proposed as a mechanism for generation of biomass in cancer cells. Here we demonstrate that reductive TCA cycle flux also produces stimulus-secretion coupling factors that regulate insulin secretion, including in non-dividing cells.
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Affiliation(s)
- Guo-Fang Zhang
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA; Department of Medicine, Endocrinology and Metabolism Division, Duke University Medical Center, Durham, NC 27701, USA
| | - Mette V Jensen
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA
| | - Sarah M Gray
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA
| | - Kimberley El
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA
| | - You Wang
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA
| | - Danhong Lu
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA
| | - Thomas C Becker
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA; Department of Medicine, Endocrinology and Metabolism Division, Duke University Medical Center, Durham, NC 27701, USA
| | - Jonathan E Campbell
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA; Department of Medicine, Endocrinology and Metabolism Division, Duke University Medical Center, Durham, NC 27701, USA; Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27701, USA
| | - Christopher B Newgard
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA; Department of Medicine, Endocrinology and Metabolism Division, Duke University Medical Center, Durham, NC 27701, USA; Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27701, USA.
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47
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Senik MH, Abu IF, Fadhullah W. Analysis of K ATP Channels Opening Probability of Hippocampus Cells Treated with Kainic Acid. Malays J Med Sci 2021; 28:15-26. [PMID: 33679216 PMCID: PMC7909348 DOI: 10.21315/mjms2021.28.1.3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 12/12/2020] [Indexed: 01/14/2023] Open
Abstract
Background Kainic acid (KA)-induced seizures may be a valuable tool in the assessment of anti-epileptic drug efficacy in complex partial seizures. This study investigated the effects of KA on ATP-sensitive K+ (KATP) channels opening probability (NPo), which plays a crucial role in neuronal activities. Methods For the optimisation and validation protocol, β-cells were plated onto 35 mm plastic petri dishes and maintained in RPMI-1640 media supplemented with 10 mM glucose, 10% FCS and 25 mM of N-2-hydroxyethylpiperazine-N-ethanesulfonic acid (HEPES). The treatment effects of 10 mM glucose and 30 μM fluoxetine on KATP channels NPo of β-cells were assessed via cell-attached patch-clamp recordings. For hippocampus cell experiments, hippocampi were harvested from day 17 of maternal Lister-hooded rat foetus, and then transferred to a Ca2+ and Mg2+-free HEPES-buffered Hank's salt solution (HHSS). The dissociated cells were cultured and plated onto a 25 mm round cover glasses coated with poly-d-lysine (0.1 mg/mL) in a petri dish. The KATP channels NPo of hippocampus cells when perfused with 1 mM and 10 mM of KA were determined. Results NPo of β-cells showed significant decreasing patterns (P < 0.001) when treated with 10 mM glucose 0.048 (0.027) as well as 30 μM fluoxetine 0.190 (0.141) as compared to basal counterpart. In hippocampus cell experiment, a significant increase (P < 0.001) in mean NPo 2.148 (0.175) of neurons when applied with 1 mM of KA as compared to basal was observed. Conclusion The two concentrations of KA used in the study exerted contrasting effects toward the mean of NPo. It is hypothesised that KA at lower concentration (1 mM) opens more KATP channels, leading to hyperpolarisation of the neurons, which may prevent neuronal hyper excitability. No effect was shown in 10 mM KA treatment, suggesting that only lower than 10 mM KA produced significant changes in KATP channels. This implies further validation of KA concentration to be used in the future.
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Affiliation(s)
- Mohd Harizal Senik
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.,School of Life Sciences, Medical School, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - Izuddin Fahmy Abu
- Institute of Medical Science Technology, Universiti Kuala Lumpur, Kuala Lumpur, Malaysia
| | - Widad Fadhullah
- School of Industrial Technology, Universiti Sains Malaysia, Pulau Pinang, Malaysia
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48
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Conventional and Unconventional Mechanisms by which Exocytosis Proteins Oversee β-cell Function and Protection. Int J Mol Sci 2021; 22:ijms22041833. [PMID: 33673206 PMCID: PMC7918544 DOI: 10.3390/ijms22041833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/02/2021] [Accepted: 02/08/2021] [Indexed: 02/06/2023] Open
Abstract
Type 2 diabetes (T2D) is one of the prominent causes of morbidity and mortality in the United States and beyond, reaching global pandemic proportions. One hallmark of T2D is dysfunctional glucose-stimulated insulin secretion from the pancreatic β-cell. Insulin is secreted via the recruitment of insulin secretory granules to the plasma membrane, where the soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and SNARE regulators work together to dock the secretory granules and release insulin into the circulation. SNARE proteins and their regulators include the Syntaxins, SNAPs, Sec1/Munc18, VAMPs, and double C2-domain proteins. Recent studies using genomics, proteomics, and biochemical approaches have linked deficiencies of exocytosis proteins with the onset and progression of T2D. Promising results are also emerging wherein restoration or enhancement of certain exocytosis proteins to β-cells improves whole-body glucose homeostasis, enhances β-cell function, and surprisingly, protection of β-cell mass. Intriguingly, overexpression and knockout studies have revealed novel functions of certain exocytosis proteins, like Syntaxin 4, suggesting that exocytosis proteins can impact a variety of pathways, including inflammatory signaling and aging. In this review, we present the conventional and unconventional functions of β-cell exocytosis proteins in normal physiology and T2D and describe how these insights might improve clinical care for T2D.
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Zhao S, Wang M, Ma Z. Therapeutic potential of ATP-sensitive potassium channels in Parkinson's disease. Brain Res Bull 2021; 169:1-7. [PMID: 33434622 DOI: 10.1016/j.brainresbull.2021.01.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 12/19/2020] [Accepted: 01/04/2021] [Indexed: 11/19/2022]
Abstract
In the past decade, there was an increasing interest in the therapeutic potential targeting ATP-sensitive potassium (KATP) channels for an effective treatment of Parkinson's disease (PD). KATP channels are widely expressed in the central nervous system and were reported to mediate the degeneration and death of nigral dopamine neurons in the pathogenesis of PD. This review aims to address the pivotal roles of KATP channels played in the mechanisms underlying PD pathogenesis, and provide possible directions for further research from different perspectives, such as the vulnerability of dopamine neurons in the substantia nigra, neurotransmitter releasing, iron metabolism in the brain, α-synuclein secretion and mitochondrial dysfunction, which are off critical importance in the investigation of KATP channels-targeted precise therapeutic interventions for PD.
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Affiliation(s)
- Sha Zhao
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - MengZhen Wang
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - ZeGang Ma
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, China; Institute of Brain Science and Disorders, Qingdao University, Qingdao, China.
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50
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Campbell JE, Newgard CB. Mechanisms controlling pancreatic islet cell function in insulin secretion. Nat Rev Mol Cell Biol 2021; 22:142-158. [PMID: 33398164 DOI: 10.1038/s41580-020-00317-7] [Citation(s) in RCA: 251] [Impact Index Per Article: 83.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/19/2020] [Indexed: 02/07/2023]
Abstract
Metabolic homeostasis in mammals is tightly regulated by the complementary actions of insulin and glucagon. The secretion of these hormones from pancreatic β-cells and α-cells, respectively, is controlled by metabolic, endocrine, and paracrine regulatory mechanisms and is essential for the control of blood levels of glucose. The deregulation of these mechanisms leads to various pathologies, most notably type 2 diabetes, which is driven by the combined lesions of impaired insulin action and a loss of the normal insulin secretion response to glucose. Glucose stimulates insulin secretion from β-cells in a bi-modal fashion, and new insights about the underlying mechanisms, particularly relating to the second or amplifying phase of this secretory response, have been recently gained. Other recent work highlights the importance of α-cell-produced proglucagon-derived peptides, incretin hormones from the gastrointestinal tract and other dietary components, including certain amino acids and fatty acids, in priming and potentiation of the β-cell glucose response. These advances provide a new perspective for the understanding of the β-cell failure that triggers type 2 diabetes.
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Affiliation(s)
- Jonathan E Campbell
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC, USA.,Department of Medicine, Endocrinology and Metabolism Division, Duke University Medical Center, Durham, NC, USA.,Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Christopher B Newgard
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC, USA. .,Department of Medicine, Endocrinology and Metabolism Division, Duke University Medical Center, Durham, NC, USA. .,Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
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