1
|
Yan LS, Cheng BCY, Zhang SF, Luo G, Zhang C, Wang QG, Fu XQ, Wang YW, Zhang Y. Tibetan Medicine for Diabetes Mellitus: Overview of Pharmacological Perspectives. Front Pharmacol 2021; 12:748500. [PMID: 34744728 PMCID: PMC8566911 DOI: 10.3389/fphar.2021.748500] [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] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 10/04/2021] [Indexed: 11/13/2022] Open
Abstract
Diabetes mellitus (DM) and its complications pose a major public health threat which is approaching epidemic proportions globally. Current drug options may not provide good efficacy and even cause serious adverse effects. Seeking safe and effective agents for DM treatment has been an area of intensive interest. As a healing system originating in Tibet, Traditional Tibetan Medicine (TTM) has been widely used by Tibetan people for the prevention and treatment of DM and its complications for hundreds of years. Tibetan Materia Medica (TMM) including the flower of Edgeworthia gardneri (Wall.) Meisn., Phyllanthi Fructus, Chebulae Fructus, Huidouba, and Berberidis Cortex are most frequently used and studied. These TMMs possess hypoglycemic, anti-insulin resistant, anti-glycation, lipid lowering, anti-inflammatory, and anti-oxidative effects. The underlying mechanisms of these actions may be related to their α-glucosidase inhibitory, insulin signaling promoting, PPARs-activating, gut microbiota modulation, islet β cell-preserving, and TNF-α signaling suppressive properties. This review presents a comprehensive overview of the mode and mechanisms of action of various active constituents, extracts, preparations, and formulas from TMM. The dynamic beneficial effects of the products prepared from TMM for the management of DM and its complications are summarized. These TMMs are valuable materia medica which have the potential to be developed as safe and effective anti-DM agents.
Collapse
Affiliation(s)
- Li-Shan Yan
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, China
| | - Brian Chi-Yan Cheng
- College of Professional and Continuing Education, Hong Kong Polytechnic University, Hong Kong, China
| | - Shuo-Feng Zhang
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, China
| | - Gan Luo
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, China
| | - Chao Zhang
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, China
| | - Qing-Gao Wang
- First Affiliated Hospital, Guangxi University of Chinese Medicine, Guangxi, China
| | - Xiu-Qiong Fu
- Centre for Cancer and Inflammation Research, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China
| | - Yi-Wei Wang
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, China
| | - Yi Zhang
- School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, China
| |
Collapse
|
2
|
Navarro JA, Decara J, Medina-Vera D, Tovar R, Suarez J, Pavón J, Serrano A, Vida M, Gutierrez-Adan A, Sanjuan C, Baixeras E, de Fonseca FR. D-Pinitol from Ceratonia siliqua Is an Orally Active Natural Inositol That Reduces Pancreas Insulin Secretion and Increases Circulating Ghrelin Levels in Wistar Rats. Nutrients 2020; 12:nu12072030. [PMID: 32650579 PMCID: PMC7400942 DOI: 10.3390/nu12072030] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 07/03/2020] [Accepted: 07/06/2020] [Indexed: 12/18/2022] Open
Abstract
To characterize the metabolic actions of D-Pinitol, a dietary inositol, in male Wistar rats, we analyzed its oral pharmacokinetics and its effects on (a) the secretion of hormones regulating metabolism (insulin, glucagon, IGF-1, ghrelin, leptin and adiponectin), (b) insulin signaling in the liver and (c) the expression of glycolytic and neoglucogenesis enzymes. Oral D-Pinitol administration (100 or 500 mg/Kg) resulted in its rapid absorption and distribution to plasma and liver compartments. Its administration reduced insulinemia and HOMA-IR, while maintaining glycaemia thanks to increased glucagon activity. In the liver, D-Pinitol reduced the key glycolytic enzyme pyruvate kinase and decreased the phosphorylation of the enzymes AKT and GSK-3. These observations were associated with an increase in ghrelin concentrations, a known inhibitor of insulin secretion. The profile of D-Pinitol suggests its potential use as a pancreatic protector decreasing insulin secretion through ghrelin upregulation, while sustaining glycaemia through the liver-based mechanisms of glycolysis control.
Collapse
Affiliation(s)
- Juan A. Navarro
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
- Facultad de Medicina, Universidad de Málaga, 29010 Málaga, Spain
| | - Juan Decara
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
| | - Dina Medina-Vera
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
- Facultad de Ciencias, Universidad de Málaga, 29010 Málaga, Spain
| | - Rubén Tovar
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
- Facultad de Medicina, Universidad de Málaga, 29010 Málaga, Spain
| | - Juan Suarez
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
| | - Javier Pavón
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
| | - Antonia Serrano
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
| | - Margarita Vida
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
| | - Alfonso Gutierrez-Adan
- Departamento de Reproducción Animal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28040 Madrid, Spain;
| | - Carlos Sanjuan
- Euronutra S.L. Calle Johannes Kepler, 3, 29590 Málaga, Spain
- Correspondence: (C.S.); (E.B.); (F.R.d.F.); Tel.: +34-655-373-093 (E.B.); +34-669-426-548 (F.R.d.F.)
| | - Elena Baixeras
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Málaga, 29010 Málaga, Spain
- Correspondence: (C.S.); (E.B.); (F.R.d.F.); Tel.: +34-655-373-093 (E.B.); +34-669-426-548 (F.R.d.F.)
| | - Fernando Rodríguez de Fonseca
- Laboratorio de Medicina Regenerativa, Instituto IBIMA de Málaga, Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain; (J.A.N.); (J.D.); (D.M.-V.); (R.T.); (J.S.); (J.P.); (A.S.); (M.V.)
- Correspondence: (C.S.); (E.B.); (F.R.d.F.); Tel.: +34-655-373-093 (E.B.); +34-669-426-548 (F.R.d.F.)
| |
Collapse
|
3
|
Integration of Rap1 and Calcium Signaling. Int J Mol Sci 2020; 21:ijms21051616. [PMID: 32120817 PMCID: PMC7084553 DOI: 10.3390/ijms21051616] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 02/24/2020] [Accepted: 02/25/2020] [Indexed: 02/07/2023] Open
Abstract
Ca2+ is a universal intracellular signal. The modulation of cytoplasmic Ca2+ concentration regulates a plethora of cellular processes, such as: synaptic plasticity, neuronal survival, chemotaxis of immune cells, platelet aggregation, vasodilation, and cardiac excitation–contraction coupling. Rap1 GTPases are ubiquitously expressed binary switches that alternate between active and inactive states and are regulated by diverse families of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Active Rap1 couples extracellular stimulation with intracellular signaling through secondary messengers—cyclic adenosine monophosphate (cAMP), Ca2+, and diacylglycerol (DAG). Much evidence indicates that Rap1 signaling intersects with Ca2+ signaling pathways to control the important cellular functions of platelet activation or neuronal plasticity. Rap1 acts as an effector of Ca2+ signaling when activated by mechanisms involving Ca2+ and DAG-activated (CalDAG-) GEFs. Conversely, activated by other GEFs, such as cAMP-dependent GEF Epac, Rap1 controls cytoplasmic Ca2+ levels. It does so by regulating the activity of Ca2+ signaling proteins such as sarcoendoplasmic reticulum Ca2+-ATPase (SERCA). In this review, we focus on the physiological significance of the links between Rap1 and Ca2+ signaling and emphasize the molecular interactions that may offer new targets for the therapy of Alzheimer’s disease, hypertension, and atherosclerosis, among other diseases.
Collapse
|
4
|
Mathiesen DS, Bagger JI, Bergmann NC, Lund A, Christensen MB, Vilsbøll T, Knop FK. The Effects of Dual GLP-1/GIP Receptor Agonism on Glucagon Secretion-A Review. Int J Mol Sci 2019; 20:E4092. [PMID: 31443356 PMCID: PMC6747202 DOI: 10.3390/ijms20174092] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/16/2019] [Accepted: 08/20/2019] [Indexed: 02/07/2023] Open
Abstract
The gut-derived incretin hormones glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are secreted after meal ingestion and work in concert to promote postprandial insulin secretion. Furthermore, GLP-1 inhibits glucagon secretion when plasma glucose concentrations are above normal fasting concentrations while GIP acts glucagonotropically at low glucose levels. A dual incretin receptor agonist designed to co-activate GLP-1 and GIP receptors was recently shown to elicit robust improvements of glycemic control (mean haemoglobin A1c reduction of 1.94%) and massive body weight loss (mean weight loss of 11.3 kg) after 26 weeks of treatment with the highest dose (15 mg once weekly) in a clinical trial including overweight/obese patients with type 2 diabetes. Here, we describe the mechanisms by which the two incretins modulate alpha cell secretion of glucagon, review the effects of co-administration of GLP-1 and GIP on glucagon secretion, and discuss the potential role of glucagon in the therapeutic effects observed with novel unimolecular dual GLP-1/GIP receptor agonists. For clinicians and researchers, this manuscript offers an understanding of incretin physiology and pharmacology, and provides mechanistic insight into future antidiabetic and obesity treatments.
Collapse
Affiliation(s)
- David S Mathiesen
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
| | - Jonatan I Bagger
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
- Steno Diabetes Center Copenhagen, 2820 Gentofte, Denmark
| | - Natasha C Bergmann
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
| | - Asger Lund
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
| | - Mikkel B Christensen
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
- Department of Clinical Pharmacology, Bispebjerg Hospital, University of Copenhagen, 2400 Copenhagen, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Tina Vilsbøll
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
- Steno Diabetes Center Copenhagen, 2820 Gentofte, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Filip K Knop
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark.
- Steno Diabetes Center Copenhagen, 2820 Gentofte, Denmark.
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark.
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark.
| |
Collapse
|
5
|
Brouwer S, Hoffmeister T, Gresch A, Schönhoff L, Düfer M. Resveratrol Influences Pancreatic Islets by Opposing Effects on Electrical Activity and Insulin Release. Mol Nutr Food Res 2019; 62. [PMID: 29341416 DOI: 10.1002/mnfr.201700902] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 12/19/2017] [Indexed: 01/27/2023]
Abstract
SCOPE Resveratrol is suggested to improve glycemic control by activation of sirtuin 1 (SIRT1) and has already been tested clinically. Our investigation characterizes the targets of resveratrol in pancreatic beta cells and their contribution to short- and long-term effects on insulin secretion. METHODS AND RESULTS Islets or beta cells are isolated from C57BL/6N mice. Electrophysiology is performed with microelectrode arrays and patch-clamp technique, insulin secretion and content are determined by radioimmunoassay, cAMP is measured by enzyme-linked immunosorbent assay, and cytosolic Ca2+ concentration by fluorescence methods. Resveratrol (25 μmol L-1 ) elevates [Ca2+ ]c and potentiates glucose-stimulated insulin secretion. These effects are associated with increased intracellular cAMP and are sensitive to the SIRT1 blocker Ex-527. Inhibition of EPAC1 by CE3F4 also abolishes the stimulatory effect of resveratrol. The underlying mechanism does not involve membrane depolarization as resveratrol even reduces electrical activity despite blocking KATP channels. Importantly, after prolonged exposure to resveratrol (14 days), the beneficial influence of the polyphenol on insulin release is lost. CONCLUSION Resveratrol addresses multiple targets in pancreatic islets. Potentiation of insulin secretion is mediated by SIRT1-dependent activation of cAMP/EPAC1. Considering resveratrol as therapeutic supplement for patients with type 2 diabetes mellitus, the inhibitory influence on electrical excitability attenuates positive effects.
Collapse
Affiliation(s)
- Simone Brouwer
- University of Münster, Pharmaceutical and Medicinal Chemistry, Dept. of Pharmacology, Münster, Germany
| | - Theresa Hoffmeister
- University of Münster, Pharmaceutical and Medicinal Chemistry, Dept. of Pharmacology, Münster, Germany
| | - Anne Gresch
- University of Münster, Pharmaceutical and Medicinal Chemistry, Dept. of Pharmacology, Münster, Germany
| | - Lisa Schönhoff
- University of Münster, Pharmaceutical and Medicinal Chemistry, Dept. of Pharmacology, Münster, Germany
| | - Martina Düfer
- University of Münster, Pharmaceutical and Medicinal Chemistry, Dept. of Pharmacology, Münster, Germany
| |
Collapse
|
6
|
Frank JA, Broichhagen J, Yushchenko DA, Trauner D, Schultz C, Hodson DJ. Optical tools for understanding the complexity of β-cell signalling and insulin release. Nat Rev Endocrinol 2018; 14:721-737. [PMID: 30356209 DOI: 10.1038/s41574-018-0105-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Following stimulation, pancreatic β-cells must orchestrate a plethora of signalling events to ensure the appropriate release of insulin and maintenance of normal glucose homeostasis. Failure at any point in this cascade leads to impaired insulin secretion, elevated blood levels of glucose and eventually type 2 diabetes mellitus. Likewise, β-cell replacement or regeneration strategies for the treatment of both type 1 and type 2 diabetes mellitus might fail if the correct cell signalling phenotype cannot be faithfully recreated. However, current understanding of β-cell function is complicated because of the highly dynamic nature of their intracellular and intercellular signalling as well as insulin release itself. β-Cells must precisely integrate multiple signals stemming from multiple cues, often with differing intensities, frequencies and cellular and subcellular localizations, before converging these signals onto insulin exocytosis. In this respect, optical approaches with high resolution in space and time are extremely useful for properly deciphering the complexity of β-cell signalling. An increased understanding of β-cell signalling might identify new mechanisms underlying insulin release, with relevance for future drug therapy and de novo stem cell engineering of functional islets.
Collapse
Affiliation(s)
- James A Frank
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Johannes Broichhagen
- Department of Chemical Biology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Dmytro A Yushchenko
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Dirk Trauner
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Chemistry, New York University, New York, NY, USA
| | - Carsten Schultz
- European Molecular Biology Laboratory (EMBL), Cell Biology and Biophysics Unit, Heidelberg, Germany.
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA.
| | - David J Hodson
- Institute of Metabolism and Systems Research (IMSR) and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, UK.
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK.
| |
Collapse
|
7
|
Robichaux WG, Cheng X. Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development. Physiol Rev 2018; 98:919-1053. [PMID: 29537337 PMCID: PMC6050347 DOI: 10.1152/physrev.00025.2017] [Citation(s) in RCA: 135] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 09/05/2017] [Accepted: 09/06/2017] [Indexed: 12/13/2022] Open
Abstract
This review focuses on one family of the known cAMP receptors, the exchange proteins directly activated by cAMP (EPACs), also known as the cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs). Although EPAC proteins are fairly new additions to the growing list of cAMP effectors, and relatively "young" in the cAMP discovery timeline, the significance of an EPAC presence in different cell systems is extraordinary. The study of EPACs has considerably expanded the diversity and adaptive nature of cAMP signaling associated with numerous physiological and pathophysiological responses. This review comprehensively covers EPAC protein functions at the molecular, cellular, physiological, and pathophysiological levels; and in turn, the applications of employing EPAC-based biosensors as detection tools for dissecting cAMP signaling and the implications for targeting EPAC proteins for therapeutic development are also discussed.
Collapse
Affiliation(s)
- William G Robichaux
- Department of Integrative Biology and Pharmacology, Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center , Houston, Texas
| | - Xiaodong Cheng
- Department of Integrative Biology and Pharmacology, Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center , Houston, Texas
| |
Collapse
|
8
|
Algarni AS, Hargreaves AJ, Dickenson JM. Role of transglutaminase 2 in PAC 1 receptor mediated protection against hypoxia-induced cell death and neurite outgrowth in differentiating N2a neuroblastoma cells. Biochem Pharmacol 2017; 128:55-73. [PMID: 28065858 DOI: 10.1016/j.bcp.2017.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 01/03/2017] [Indexed: 01/09/2023]
Abstract
The PAC1 receptor and tissue transglutaminase (TG2) play important roles in neurite outgrowth and modulation of neuronal cell survival. In this study, we investigated the regulation of TG2 activity by the PAC1 receptor in retinoic acid-induced differentiating N2a neuroblastoma cells. TG2 transamidase activity was determined using an amine incorporation and a peptide cross linking assay. In situ TG2 activity was assessed by visualising the incorporation of biotin-X-cadaverine using confocal microscopy. TG2 phosphorylation was monitored via immunoprecipitation and Western blotting. The role of TG2 in PAC1 receptor-induced cytoprotection and neurite outgrowth was investigated by monitoring hypoxia-induced cell death and appearance of axonal-like processes, respectively. The amine incorporation and protein crosslinking activity of TG2 increased in a time and concentration-dependent manner following stimulation with pituitary adenylate cyclase-activating polypeptide-27 (PACAP-27). PACAP-27 mediated increases in TG2 activity were abolished by the TG2 inhibitors Z-DON and R283 and by pharmacological inhibition of protein kinase A (KT 5720 and Rp-cAMPs), protein kinase C (Ro 31-8220), MEK1/2 (PD 98059), and removal of extracellular Ca2+. Fluorescence microscopy demonstrated PACAP-27 induced in situ TG2 activity. TG2 inhibition blocked PACAP-27 induced attenuation of hypoxia-induced cell death and outgrowth of axon-like processes. TG2 activation and cytoprotection were also observed in human SH-SY5Y cells. Together, these results demonstrate that TG2 activity was stimulated downstream of the PAC1 receptor via a multi protein kinase dependent pathway. Furthermore, PAC1 receptor-induced cytoprotection and neurite outgrowth are dependent upon TG2. These results highlight the importance of TG2 in the cellular functions of the PAC1 receptor.
Collapse
Affiliation(s)
- Alanood S Algarni
- School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, United Kingdom
| | - Alan J Hargreaves
- School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, United Kingdom
| | - John M Dickenson
- School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, United Kingdom.
| |
Collapse
|
9
|
Exchange factors directly activated by cAMP mediate melanocortin 4 receptor-induced gene expression. Sci Rep 2016; 6:32776. [PMID: 27612207 PMCID: PMC5017209 DOI: 10.1038/srep32776] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 08/15/2016] [Indexed: 01/16/2023] Open
Abstract
Gs protein-coupled receptors regulate many vital body functions by activation of cAMP response elements (CRE) via cAMP-dependent kinase A (PKA)-mediated phosphorylation of the CRE binding protein (CREB). Melanocortin 4 receptors (MC4R) are prototypical Gs-coupled receptors that orchestrate the hypothalamic control of food-intake and metabolism. Remarkably, the significance of PKA for MC4R-induced CRE-dependent transcription in hypothalamic cells has not been rigorously interrogated yet. In two hypothalamic cell lines, we observed that blocking PKA activity had only weak or no effects on reporter gene expression. In contrast, inhibitors of exchange factors directly activated by cAMP-1/2 (EPAC-1/2) mitigated MC4R-induced CRE reporter activation and mRNA induction of the CREB-dependent genes c-fos and thyrotropin-releasing hormone. Furthermore, we provide first evidence that extracellular-regulated kinases-1/2 (ERK-1/2) activated by EPACs and not PKA are the elusive CREB kinases responsible for MC4R-induced CREB/CRE activation in hypothalamic cells. Overall, these data emphasize the pivotal role of EPACs rather than PKA in hypothalamic gene expression elicited by a prototypical Gs-coupled receptor.
Collapse
|
10
|
Velasco M, Díaz-García CM, Larqué C, Hiriart M. Modulation of Ionic Channels and Insulin Secretion by Drugs and Hormones in Pancreatic Beta Cells. Mol Pharmacol 2016; 90:341-57. [PMID: 27436126 DOI: 10.1124/mol.116.103861] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/18/2016] [Indexed: 12/11/2022] Open
Abstract
Pancreatic beta cells, unique cells that secrete insulin in response to an increase in glucose levels, play a significant role in glucose homeostasis. Glucose-stimulated insulin secretion (GSIS) in pancreatic beta cells has been extensively explored. In this mechanism, glucose enters the cells and subsequently the metabolic cycle. During this process, the ATP/ADP ratio increases, leading to ATP-sensitive potassium (KATP) channel closure, which initiates depolarization that is also dependent on the activity of TRP nonselective ion channels. Depolarization leads to the opening of voltage-gated Na(+) channels (Nav) and subsequently voltage-dependent Ca(2+) channels (Cav). The increase in intracellular Ca(2+) triggers the exocytosis of insulin-containing vesicles. Thus, electrical activity of pancreatic beta cells plays a central role in GSIS. Moreover, many growth factors, incretins, neurotransmitters, and hormones can modulate GSIS, and the channels that participate in GSIS are highly regulated. In this review, we focus on the principal ionic channels (KATP, Nav, and Cav channels) involved in GSIS and how classic and new proteins, hormones, and drugs regulate it. Moreover, we also discuss advances on how metabolic disorders such as metabolic syndrome and diabetes mellitus change channel activity leading to changes in insulin secretion.
Collapse
Affiliation(s)
- Myrian Velasco
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Carlos Manlio Díaz-García
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Carlos Larqué
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Marcia Hiriart
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| |
Collapse
|