1
|
André S, Verteneuil S, Ris L, Kahvecioglu ZC, Nonclercq D, De Winter J, Vander Elst L, Laurent S, Muller RN, Burtea C. Modulation of Cytosolic Phospholipase A2 as a Potential Therapeutic Strategy for Alzheimer's Disease. J Alzheimers Dis Rep 2023; 7:1395-1426. [PMID: 38225969 PMCID: PMC10789292 DOI: 10.3233/adr-230075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 11/17/2023] [Indexed: 01/17/2024] Open
Abstract
Background Alzheimer's disease (AD) is a neurodegenerative disorder lacking any curative treatment up to now. Indeed, actual medication given to the patients alleviates only symptoms. The cytosolic phospholipase A2 (cPLA2-IVA) appears as a pivotal player situated at the center of pathological pathways leading to AD and its inhibition could be a promising therapeutic approach. Objective A cPLA2-IVA inhibiting peptide was identified in the present work, aiming to develop an original therapeutic strategy. Methods We targeted the cPLA2-IVA using the phage display technology. The hit peptide PLP25 was first validated in vitro (arachidonic acid dosage [AA], cPLA2-IVA cellular translocation) before being tested in vivo. We evaluated spatial memory using the Barnes maze, amyloid deposits by MRI and immunohistochemistry (IHC), and other important biomarkers such as the cPLA2-IVA itself, the NMDA receptor, AβPP and tau by IHC after i.v. injection in APP/PS1 mice. Results Showing a high affinity for the C2 domain of this enzyme, the peptide PLP25 exhibited an inhibitory effect on cPLA2-IVA activity by blocking its binding to its substrate, resulting in a decreased release of AA. Coupled to a vector peptide (LRPep2) in order to optimize brain access, we showed an improvement of cognitive abilities of APP/PS1 mice, which also exhibited a decreased number of amyloid plaques, a restored expression of cPLA2-IVA, and a favorable effect on NMDA receptor expression and tau protein phosphorylation. Conclusions cPLA2-IVA inhibition through PLP25 peptide could be a promising therapeutic strategy for AD.
Collapse
Affiliation(s)
- Séverine André
- General, Organic and Biomedical Chemistry Unit, NMR and Molecular Imaging Laboratory, University of Mons, Mons, Belgium
| | - Sébastien Verteneuil
- General, Organic and Biomedical Chemistry Unit, NMR and Molecular Imaging Laboratory, University of Mons, Mons, Belgium
| | - Laurence Ris
- Department of Neurosciences, University of Mons, Research Institute for Health Science and Technologies, Mons, Belgium
| | - Zehra-Cagla Kahvecioglu
- General, Organic and Biomedical Chemistry Unit, NMR and Molecular Imaging Laboratory, University of Mons, Mons, Belgium
| | | | - Julien De Winter
- Organic Synthesis and Mass Spectrometry Laboratory (SMOs), University of Mons-UMONS, Mons, Belgium
| | - Luce Vander Elst
- General, Organic and Biomedical Chemistry Unit, NMR and Molecular Imaging Laboratory, University of Mons, Mons, Belgium
| | - Sophie Laurent
- General, Organic and Biomedical Chemistry Unit, NMR and Molecular Imaging Laboratory, University of Mons, Mons, Belgium
- Center for Microscopy and Molecular Imaging, Gosselies, Belgium
| | - Robert N. Muller
- General, Organic and Biomedical Chemistry Unit, NMR and Molecular Imaging Laboratory, University of Mons, Mons, Belgium
- Center for Microscopy and Molecular Imaging, Gosselies, Belgium
| | - Carmen Burtea
- General, Organic and Biomedical Chemistry Unit, NMR and Molecular Imaging Laboratory, University of Mons, Mons, Belgium
| |
Collapse
|
2
|
Ramanadham S, Turk J, Bhatnagar S. Noncanonical Regulation of cAMP-Dependent Insulin Secretion and Its Implications in Type 2 Diabetes. Compr Physiol 2023; 13:5023-5049. [PMID: 37358504 PMCID: PMC10809800 DOI: 10.1002/cphy.c220031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
Abstract
Impaired glucose tolerance (IGT) and β-cell dysfunction in insulin resistance associated with obesity lead to type 2 diabetes (T2D). Glucose-stimulated insulin secretion (GSIS) from β-cells occurs via a canonical pathway that involves glucose metabolism, ATP generation, inactivation of K ATP channels, plasma membrane depolarization, and increases in cytosolic concentrations of [Ca 2+ ] c . However, optimal insulin secretion requires amplification of GSIS by increases in cyclic adenosine monophosphate (cAMP) signaling. The cAMP effectors protein kinase A (PKA) and exchange factor activated by cyclic-AMP (Epac) regulate membrane depolarization, gene expression, and trafficking and fusion of insulin granules to the plasma membrane for amplifying GSIS. The widely recognized lipid signaling generated within β-cells by the β-isoform of Ca 2+ -independent phospholipase A 2 enzyme (iPLA 2 β) participates in cAMP-stimulated insulin secretion (cSIS). Recent work has identified the role of a G-protein coupled receptor (GPCR) activated signaling by the complement 1q like-3 (C1ql3) secreted protein in inhibiting cSIS. In the IGT state, cSIS is attenuated, and the β-cell function is reduced. Interestingly, while β-cell-specific deletion of iPLA 2 β reduces cAMP-mediated amplification of GSIS, the loss of iPLA 2 β in macrophages (MØ) confers protection against the development of glucose intolerance associated with diet-induced obesity (DIO). In this article, we discuss canonical (glucose and cAMP) and novel noncanonical (iPLA 2 β and C1ql3) pathways and how they may affect β-cell (dys)function in the context of impaired glucose intolerance associated with obesity and T2D. In conclusion, we provide a perspective that in IGT states, targeting noncanonical pathways along with canonical pathways could be a more comprehensive approach for restoring β-cell function in T2D. © 2023 American Physiological Society. Compr Physiol 13:5023-5049, 2023.
Collapse
Affiliation(s)
- Sasanka Ramanadham
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Alabama, USA
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Alabama, USA
| | - John Turk
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Sushant Bhatnagar
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Alabama, USA
- Department of Medicine, University of Alabama at Birmingham, Alabama, USA
| |
Collapse
|
3
|
Mohanty S, Rashid MHA, Mohanty C, Swayamsiddha S. Modern computational intelligence based drug repurposing for diabetes epidemic. Diabetes Metab Syndr 2021; 15:102180. [PMID: 34186343 DOI: 10.1016/j.dsx.2021.06.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 06/12/2021] [Accepted: 06/14/2021] [Indexed: 12/18/2022]
Abstract
BACKGROUND AND AIM Objectives are to explore recent advances in discovery of new antidiabetic agents using repurposing strategies and to discuss modern technologies used for drug repurposing highlighting diabetic specific web portal. METHODS Recent literature were studied and analyzed from various sources such as Scopus, PubMed, and IEEE Xplore databases. RESULTS Drugs like Niclosamideethanolamine, Methazolamide, Diacerein, Berberine, Clobetasol, etc. with possibility of repurposing to curb diabetes can be potential late-stage clinical candidates, providing access to information on pharmacology, formulation, and probable toxicity if any. CONCLUSIONS With collaboration of artificial intelligence (AI) with pharmacology, the efficiency of drug repurposing can improve significantly.
Collapse
Affiliation(s)
- Sweta Mohanty
- School of Applied Science, KIIT University, Bhubaneswar, Odisha, India
| | | | - Chandana Mohanty
- School of Applied Science, KIIT University, Bhubaneswar, Odisha, India.
| | - Swati Swayamsiddha
- School of Electronics Engineering, KIIT University, Bhubaneswar, Odisha, India.
| |
Collapse
|
4
|
Zulyniak M, Fuller H, Iles M. Investigation of the Causal Association between Long-Chain n-6 Polyunsaturated Fatty Acid Synthesis and the Risk of Type 2 Diabetes: A Mendelian Randomization Analysis. Lifestyle Genom 2020; 13:146-153. [DOI: 10.1159/000509663] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 06/18/2020] [Indexed: 11/19/2022] Open
|
5
|
Abstract
PURPOSE Group X (GX) and group V (GV) secretory phospholipase A2 (sPLA2) potently release arachidonic acid (AA) from the plasma membrane of intact cells. We previously demonstrated that GX sPLA2 negatively regulates glucose-stimulated insulin secretion (GSIS) by a prostaglandin E2 (PGE2)-dependent mechanism. In this study we investigated whether GV sPLA2 similarly regulates GSIS. METHODS GSIS and pancreatic islet-size were assessed in wild-type (WT) and GV sPLA2-knock out (GV KO) mice. GSIS was also assessed ex vivo in isolated islets and in vitro using MIN6 pancreatic beta cell lines with or without GV sPLA2 overexpression or silencing. RESULTS GSIS was significantly decreased in islets isolated from GV KO mice compared to WT mice and in MIN6 cells with siRNA-mediated GV sPLA2 suppression. MIN6 cells overexpressing GV sPLA2 (MIN6-GV) showed a significant increase in GSIS compared to control cells. Though the amount of AA released into the media by MIN6-GV cells was significantly higher, PGE2 production was not enhanced or cAMP content decreased compared to control MIN6 cells. Surprisingly, GV KO mice exhibited a significant increase in plasma insulin levels following i.p. injection of glucose compared to WT mice. This increase in GSIS in GV KO mice was associated with a significant increase in pancreatic islet size and number of proliferating cells in β-islets compared to WT mice. CONCLUSIONS Deficiency of GV sPLA2 results in diminished GSIS in isolated pancreatic beta-cells. However, the reduced GSIS in islets lacking GV sPLA2 appears to be compensated by increased islet mass in GV KO mice.
Collapse
Affiliation(s)
- Preetha Shridas
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA.
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY, 40536, USA.
| | - Victoria P Noffsinger
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY, 40536, USA
| | - Andrea C Trumbauer
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
| | - Nancy R Webb
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
- Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington, KY, 40536, USA
| |
Collapse
|
6
|
Caporarello N, Salmeri M, Scalia M, Motta C, Parrino C, Frittitta L, Olivieri M, Toscano MA, Anfuso CD, Lupo G. Role of cytosolic and calcium independent phospholipases A(2) in insulin secretion impairment of INS-1E cells infected by S. aureus. FEBS Lett 2015; 589:3969-76. [PMID: 26632509 DOI: 10.1016/j.febslet.2015.11.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 11/19/2015] [Indexed: 10/22/2022]
Abstract
Cytosolic PLA2 (cPLA2) and Ca(2+)-independent PLA2 (iPLA2) play a significant role in insulin β-cells secretion. Bacterial infections may be responsible of the onset of diabetes. The mechanism by which Staphylococcus aureus infection of INS-1 cells alters glucose-induced insulin secretion has been examined. After acute infection, insulin secretion and PLA2 activities significantly increased. Moreover, increased expressions of phospho-cPLA2, phospho-PKCα and phospho-ERK 1/2 were observed. Chronic infection causes a decrease in insulin release and a significant increase of iPLA2 and COX-2 protein expression. Moreover, insulin secretion in infected cells could be restored using specific siRNAs against iPLA2 isoform and specific COX-2 inhibitor.
Collapse
Affiliation(s)
- N Caporarello
- Dept. of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Italy
| | - M Salmeri
- Dept. of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Italy
| | - M Scalia
- Dept. of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Italy
| | - C Motta
- Dept. of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Italy
| | - C Parrino
- Dept. of Clinical and Experimental Medicine, School of Medicine, University of Catania, Italy
| | - L Frittitta
- Dept. of Clinical and Experimental Medicine, School of Medicine, University of Catania, Italy
| | - M Olivieri
- Dept. of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Italy
| | - M A Toscano
- Dept. of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Italy
| | - C D Anfuso
- Dept. of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Italy
| | - G Lupo
- Dept. of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Italy.
| |
Collapse
|
7
|
Abstract
Drug repositioning has shorter developmental time, lower cost and less safety risk than traditional drug development process. The current study aims to repurpose marketed drugs and clinical candidates for new indications in diabetes treatment by mining clinical ‘omics’ data. We analyzed data from genome wide association studies (GWAS), proteomics and metabolomics studies and revealed a total of 992 proteins as potential anti-diabetic targets in human. Information on the drugs that target these 992 proteins was retrieved from the Therapeutic Target Database (TTD) and 108 of these proteins are drug targets with drug projects information. Research and preclinical drug targets were excluded and 35 of the 108 proteins were selected as druggable proteins. Among them, five proteins were known targets for treating diabetes. Based on the pathogenesis knowledge gathered from the OMIM and PubMed databases, 12 protein targets of 58 drugs were found to have a new indication for treating diabetes. CMap (connectivity map) was used to compare the gene expression patterns of cells treated by these 58 drugs and that of cells treated by known anti-diabetic drugs or diabetes risk causing compounds. As a result, 9 drugs were found to have the potential to treat diabetes. Among the 9 drugs, 4 drugs (diflunisal, nabumetone, niflumic acid and valdecoxib) targeting COX2 (prostaglandin G/H synthase 2) were repurposed for treating type 1 diabetes, and 2 drugs (phenoxybenzamine and idazoxan) targeting ADRA2A (Alpha-2A adrenergic receptor) had a new indication for treating type 2 diabetes. These findings indicated that ‘omics’ data mining based drug repositioning is a potentially powerful tool to discover novel anti-diabetic indications from marketed drugs and clinical candidates. Furthermore, the results of our study could be related to other disorders, such as Alzheimer’s disease.
Collapse
Affiliation(s)
- Ming Zhang
- Department of Medicine, Division of Neurology, Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, M5T 2S8, Canada
- * E-mail:
| | - Heng Luo
- University of Arkansas at Little Rock/University of Arkansas for Medical Sciences Bioinformatics Graduate Program, 2801 S. University Ave., Little Rock, AR, 72204, United States of America
| | - Zhengrui Xi
- Department of Medicine, Division of Neurology, Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, M5T 2S8, Canada
| | - Ekaterina Rogaeva
- Department of Medicine, Division of Neurology, Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, M5T 2S8, Canada
| |
Collapse
|
8
|
Shridas P, Zahoor L, Forrest KJ, Layne JD, Webb NR. Group X secretory phospholipase A2 regulates insulin secretion through a cyclooxygenase-2-dependent mechanism. J Biol Chem 2014; 289:27410-7. [PMID: 25122761 DOI: 10.1074/jbc.m114.591735] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Group X secretory phospholipase A2 (GX sPLA2) potently hydrolyzes membrane phospholipids to release arachidonic acid (AA). While AA is an activator of glucose-stimulated insulin secretion (GSIS), its metabolite prostaglandin E2 (PGE2) is a known inhibitor. In this study, we determined that GX sPLA2 is expressed in insulin-producing cells of mouse pancreatic islets and investigated its role in beta cell function. GSIS was measured in vivo in wild-type (WT) and GX sPLA2-deficient (GX KO) mice and ex vivo using pancreatic islets isolated from WT and GX KO mice. GSIS was also assessed in vitro using mouse MIN6 pancreatic beta cells with or without GX sPLA2 overexpression or exogenous addition. GSIS was significantly higher in islets isolated from GX KO mice compared with islets from WT mice. Conversely, GSIS was lower in MIN6 cells overexpressing GX sPLA2 (MIN6-GX) compared with control (MIN6-C) cells. PGE2 production was significantly higher in MIN6-GX cells compared with MIN6-C cells and this was associated with significantly reduced cellular cAMP. The effect of GX sPLA2 on GSIS was abolished when cells were treated with NS398 (a COX-2 inhibitor) or L-798,106 (a PGE2-EP3 receptor antagonist). Consistent with enhanced beta cell function, GX KO mice showed significantly increased plasma insulin levels following glucose challenge and were protected from age-related reductions in GSIS and glucose tolerance compared with WT mice. We conclude that GX sPLA2 plays a previously unrecognized role in negatively regulating pancreatic insulin secretion by augmenting COX-2-dependent PGE2 production.
Collapse
Affiliation(s)
- Preetha Shridas
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Lubna Zahoor
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Kathy J Forrest
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Joseph D Layne
- From Saha Cardiovascular Research Center and Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington Kentucky 40536
| | - Nancy R Webb
- From Saha Cardiovascular Research Center and Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington Kentucky 40536
| |
Collapse
|
9
|
Hatlapatka K, Wienbergen A, Kühne C, Jörns A, Willenborg M, Rustenbeck I. Selective Enhancement of Nutrient-Induced Insulin Secretion by ATP-Sensitive K+ Channel-Blocking Imidazolines. J Pharmacol Exp Ther 2009; 331:1033-41. [DOI: 10.1124/jpet.109.152751] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
10
|
Abstract
OBJECTIVES Pancreatic beta cells respond to glucose stimulation with pulses of insulin release generated by oscillatory rises of the cytoplasmic Ca2+ concentration ([Ca2+]i). The observation that exposure to external ATP and other activators of cytoplasmic phospholipase A2 (cPLA2) rapidly induces rises of [Ca2+]i similar to ordinary oscillations made it important to analyze whether suppression of the cPLA2 activity affects glucose-induced [Ca2+]i rhythmicity in pancreatic beta cells. METHODS Ratiometric fura-2 technique was used for measuring [Ca2+]i in single beta cells and small aggregates prepared from ob/ob mouse islets. RESULTS Testing the effects of different inhibitors of cPLA2 in the presence of 20 mM glucose, it was found that N-(p-amylcinnamoyl)anthranilic acid (ACA) removed the oscillations at a concentration of 25 microM, arachidonyl trifluoromethyl ketone (AACOCF3) at 10 microM, and bromoenol lactone (BEL) at 10 to 15 microM. Withdrawal of ACA and BEL resulted in reappearance of the oscillations. Suppression of the arachidonic acid production by addition of 5 microM of the diacylglycerol lipase inhibitor 1,6-bis-(cyclohexyloximinocarbonylamino)-hexane (RHC 80267) effectively removed the [Ca2+]i oscillations, an effect reversed by removal of the inhibitor or addition of 100 microM tolbutamide. Suppression of the arachidonic acid production had a restrictive influence also on the transients of [Ca2+]i supposed to synchronize the beta-cell rhythmicity. Although less sensitive than the oscillations, most transients disappeared during exposure to 50 microM ACA or 35 microM RHC 80267. CONCLUSIONS The results support the idea that cyclic variations of cPLA2 activity are important for the generation and synchronization of the beta-cell [Ca2+]i oscillations responsible for pulsatile release of insulin.
Collapse
Affiliation(s)
- Gerd Larsson-Nyrén
- Department of Integrative Medical Biology, Section for Histology and Cell Biology, University of Umeå University, Umeå, Sweden.
| | | | | |
Collapse
|
11
|
Persaud SJ, Muller D, Belin VD, Papadimitriou A, Huang GC, Amiel SA, Jones PM. Expression and function of cyclooxygenase and lipoxygenase enzymes in human islets of Langerhans. Arch Physiol Biochem 2007; 113:104-9. [PMID: 17852048 DOI: 10.1080/13813450701531177] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Arachidonic acid (AA) is generated in pancreatic beta-cells through the activation of Ca2+-dependent cytosolic phospholipase A2 (cPLA2) and the consequent hydrolysis of membrane phospholipids in the sn-2 position of the glycerophospholipid backbone. AA acts as a second messenger in beta-cells to elevate cytosolic Ca2+ levels and stimulate insulin secretion, but it is not clear whether these are direct effects of AA or are dependent on its metabolism by cyclooxygenase (COX) and/or lipoxygenase (LOX) enzymes. In addition, much of the published data in this area have been generated using insulin-secreting cell lines or rodent islets, with very little information on AA generation and metabolism in human islets of Langerhans. This short review examines cPLA2, COX and LOX expression and function in insulin- secreting cell lines and rodent and human islets.
Collapse
Affiliation(s)
- Shanta J Persaud
- Beta Cell Development & Function Group, Division of Reproduction & Endocrinology, King's College London, London, UK.
| | | | | | | | | | | | | |
Collapse
|
12
|
Persaud SJ, Muller D, Belin VD, Kitsou-Mylona I, Asare-Anane H, Papadimitriou A, Burns CJ, Huang GC, Amiel SA, Jones PM. The role of arachidonic acid and its metabolites in insulin secretion from human islets of langerhans. Diabetes 2007; 56:197-203. [PMID: 17192482 DOI: 10.2337/db06-0490] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The roles played by arachidonic acid and its cyclooxygenase (COX)-generated and lipoxygenase (LOX)-generated metabolites have been studied using rodent islets and insulin-secreting cell lines, but very little is known about COX and LOX isoform expression and the effects of modulation of arachidonic acid generation and metabolism in human islets. We have used RT-PCR to identify mRNAs for cytosolic phospholipase A(2) (cPLA(2)), COX-1, COX-2, 5-LOX, and 12-LOX in isolated human islets. COX-3 and 15-LOX were not expressed by human islets. Perifusion experiments with human islets indicated that PLA(2) inhibition inhibited glucose-stimulated insulin secretion, whereas inhibitors of COX-2 and 12-LOX enzymes enhanced basal insulin secretion and also secretory responses induced by 20 mmol/l glucose or by 50 mumol/l arachidonic acid. Inhibition of COX-1 with 100 mumol/l acetaminophen did not significantly affect glucose-stimulated insulin secretion. These data indicate that the stimulation of insulin secretion from human islets in response to arachidonic acid does not require its metabolism through COX-2 and 5-/12-LOX pathways. The products of COX-2 and LOX activities have been implicated in cytokine-mediated damage of beta-cells, so selective inhibitors of these enzymes would be expected to have a dual protective role in diabetes: they would minimize beta-cell dysfunction while maintaining insulin secretion through enhancing endogenous arachidonic acid levels.
Collapse
Affiliation(s)
- Shanta J Persaud
- Beta Cell Development and Function Group, Division of Reproductive Health, Endocrinology, and Development, King's College London, UK.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Abstract
Fatty acids (FAs) and other lipid molecules are important for many cellular functions, including vesicle exocytosis. For the pancreatic beta-cell, while the presence of some FAs is essential for glucose-stimulated insulin secretion, FAs have enormous capacity to amplify glucose-stimulated insulin secretion, which is particularly operative in situations of beta-cell compensation for insulin resistance. In this review, we propose that FAs do this via three interdependent processes, which we have assigned to a "trident model" of beta-cell lipid signaling. The first two arms of the model implicate intracellular metabolism of FAs, whereas the third is related to membrane free fatty acid receptor (FFAR) activation. The first arm involves the AMP-activated protein kinase/malonyl-CoA/long-chain acyl-CoA (LC-CoA) signaling network in which glucose, together with other anaplerotic fuels, increases cytosolic malonyl-CoA, which inhibits FA partitioning into oxidation, thus increasing the availability of LC-CoA for signaling purposes. The second involves glucose-responsive triglyceride (TG)/free fatty acid (FFA) cycling. In this pathway, glucose promotes LC-CoA esterification to complex lipids such as TG and diacylglycerol, concomitant with glucose stimulation of lipolysis of the esterification products, with renewal of the intracellular FFA pool for reactivation to LC-CoA. The third arm involves FFA stimulation of the G-protein-coupled receptor GPR40/FFAR1, which results in enhancement of glucose-stimulated accumulation of cytosolic Ca2+ and consequently insulin secretion. It is possible that FFA released by the lipolysis arm of TG/FFA cycling is partly "secreted" and, via an autocrine/paracrine mechanism, is additive to exogenous FFAs in activating the FFAR1 pathway. Glucose-stimulated release of arachidonic acid from phospholipids by calcium-independent phospholipase A2 and/or from TG/FFA cycling may also be involved. Improved knowledge of lipid signaling in the beta-cell will allow a better understanding of the mechanisms of beta-cell compensation and failure in diabetes.
Collapse
|
14
|
Song K, Zhang X, Zhao C, Ang NT, Ma ZA. Inhibition of Ca2+-independent phospholipase A2 results in insufficient insulin secretion and impaired glucose tolerance. Mol Endocrinol 2004; 19:504-15. [PMID: 15471944 PMCID: PMC2917620 DOI: 10.1210/me.2004-0169] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Islet Ca2+-independent phospholipase A2 (iPLA2) is postulated to mediate insulin secretion by releasing arachidonic acid in response to insulin secretagogues. However, the significance of iPLA2 signaling in insulin secretion in vivo remains unexplored. Here we investigated the physiological role of iPLA2 in beta-cell lines, isolated islets, and mice. We showed that small interfering RNA-specific silencing of iPLA2 expression in INS-1 cells significantly reduced insulin-secretory responses of INS-1 cells to glucose. Immunohistochemical analysis revealed that mouse islet cells expressed significantly higher levels of iPLA2 than pancreatic exocrine acinar cells. Bromoenol lactone (BEL), a selective inhibitor of iPLA2, inhibited glucose-stimulated insulin secretion from isolated mouse islets; this inhibition was overcome by exogenous arachidonic acid. We also showed that iv BEL administration to mice resulted in sustained hyperglycemia and reduced insulin levels during glucose tolerance tests. Clamp experiments demonstrated that the impaired glucose tolerance was due to insufficient insulin secretion rather than decreased insulin sensitivity. Short-term administration of BEL to mice had no effect on fasting glucose levels and caused no apparent pathological changes of islets in pancreas sections. These results unambiguously demonstrate that iPLA2 signaling plays an important role in glucose-stimulated insulin secretion under physiological conditions.
Collapse
Affiliation(s)
- Keying Song
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, New York 10029, USA
| | | | | | | | | |
Collapse
|
15
|
Grapengiesser E, Dansk H, Hellman B. Pulses of external ATP aid to the synchronization of pancreatic beta-cells by generating premature Ca(2+) oscillations. Biochem Pharmacol 2004; 68:667-74. [PMID: 15276074 DOI: 10.1016/j.bcp.2004.04.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 04/23/2004] [Indexed: 10/26/2022]
Abstract
Pancreatic beta-cells respond to glucose stimulation with increase of the cytoplasmic Ca(2+) concentration ([Ca(2+)](i)), manifested as membrane-derived slow oscillations sometimes superimposed with transients of intracellular origin. The effect of external ATP on the oscillatory Ca(2+) signal for pulsatile insulin release was studied by digital imaging of fura-2 loaded beta-cells and small aggregates isolated from islets of ob/ob-mice. Addition of ATP (0.01-100 microM) to media containing 20mM glucose temporarily synchronized the [Ca(2+)](i) rhythmicity in the absence of cell contact by eliciting premature oscillations. External ATP triggered premature [Ca(2+)](i) oscillations also when the sarcoendoplasmic reticulum Ca(2+)-ATPase was inhibited with 50 microM cyclopiazonic acid and phospholipase C inhibited with 10 microM U-73122. The effect of ATP was mimicked by other activators of cytoplasmic phospholipase A(2) (10nM acetylcholine, 0.1-1 micro M of the C-terminal octapeptide of cholecystokinin and 2 microg/ml melittin) and suppressed by an inhibitor of the enzyme (50 microM p-amylcinnamoylanthranilic acid). Premature oscillations generated by pulses of ATP sometimes triggered subsequent oscillations. However, prolonged exposure to high concentrations of the nucleotide (10-100 microM) had a suppressive action on the beta-cell rhythmicity. The early effects of ATP included generation of transients induced by inositol (1,4,5) trisphosphate and superimposed on the premature oscillation or on an ordinary oscillation induced by glucose. The results support the idea that purinergic activation of phospholipase A(2) has a co-ordinating effect on the beta-cell rhythmicity by triggering premature [Ca(2+)](i) oscillations mediated by closure of ATP-sensitive K(+) channels.
Collapse
Affiliation(s)
- Eva Grapengiesser
- Department of Medical Cell Biology, Uppsala University, Biomedicum, SE-75123 Uppsala, Sweden
| | | | | |
Collapse
|