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Ali ES, Hua J, Wilson CH, Tallis GA, Zhou FH, Rychkov GY, Barritt GJ. The glucagon-like peptide-1 analogue exendin-4 reverses impaired intracellular Ca(2+) signalling in steatotic hepatocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2135-46. [PMID: 27178543 DOI: 10.1016/j.bbamcr.2016.05.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 04/20/2016] [Accepted: 05/04/2016] [Indexed: 02/07/2023]
Abstract
The release of Ca(2+) from the endoplasmic reticulum (ER) and subsequent replenishment of ER Ca(2+) by Ca(2+) entry through store-operated Ca(2+) channels (SOCE) play critical roles in the regulation of liver metabolism by adrenaline, glucagon and other hormones. Both ER Ca(2+) release and Ca(2+) entry are severely inhibited in steatotic hepatocytes. Exendin-4, a slowly-metabolised glucagon-like peptide-1 (GLP-1) analogue, is known to reduce liver glucose output and liver lipid, but the mechanisms involved are not well understood. The aim of this study was to determine whether exendin-4 alters intracellular Ca(2+) homeostasis in steatotic hepatocytes, and to evaluate the mechanisms involved. Exendin-4 completely reversed lipid-induced inhibition of SOCE in steatotic liver cells, but did not reverse lipid-induced inhibition of ER Ca(2+) release. The action of exendin-4 on Ca(2+) entry was rapid in onset and was mimicked by GLP-1 or dibutyryl cyclic AMP. In steatotic liver cells, exendin-4 caused a rapid decrease in lipid (half time 6.5min), inhibited the accumulation of lipid in liver cells incubated in the presence of palmitate plus the SOCE inhibitor BTP-2, and enhanced the formation of cyclic AMP. Hormone-stimulated accumulation of extracellular glucose in glycogen replete steatotic liver cells was inhibited compared to that in non-steatotic cells, and this effect of lipid was reversed by exendin-4. It is concluded that, in steatotic hepatocytes, exendin-4 reverses the lipid-induced inhibition of SOCE leading to restoration of hormone-regulated cytoplasmic Ca(2+) signalling. The mechanism may involve GLP-1 receptors, cyclic AMP, lipolysis, decreased diacylglycerol and decreased activity of protein kinase C.
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Affiliation(s)
- Eunüs S Ali
- Department of Medical Biochemistry and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia 5001, Australia
| | - Jin Hua
- Department of Medical Biochemistry and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia 5001, Australia
| | - Claire H Wilson
- Molecular Regulation Laboratory, Centre for Cancer Biology, Division of Health Sciences, University of South Australia, Adelaide, South Australia, 5001, Australia
| | - George A Tallis
- Medical Biochemistry, SA Pathology, Finders Medical Centre, Bedford Park, South Australia 5042, Australia
| | - Fiona H Zhou
- School of Medicine, The University of Adelaide, and South Australian Health and Medical Research Institute, Adelaide, South Australia 5005, Australia
| | - Grigori Y Rychkov
- School of Medicine, The University of Adelaide, and South Australian Health and Medical Research Institute, Adelaide, South Australia 5005, Australia
| | - Greg J Barritt
- Department of Medical Biochemistry and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia 5001, Australia.
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Sunil C, Duraipandiyan V, Agastian P, Ignacimuthu S. Antidiabetic effect of plumbagin isolated from Plumbago zeylanica L. root and its effect on GLUT4 translocation in streptozotocin-induced diabetic rats. Food Chem Toxicol 2012; 50:4356-63. [DOI: 10.1016/j.fct.2012.08.046] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 08/17/2012] [Accepted: 08/20/2012] [Indexed: 10/28/2022]
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Sunil C, Agastian P, Kumarappan C, Ignacimuthu S. In vitro antioxidant, antidiabetic and antilipidemic activities of Symplocos cochinchinensis (Lour.) S. Moore bark. Food Chem Toxicol 2012; 50:1547-53. [DOI: 10.1016/j.fct.2012.01.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 01/18/2012] [Accepted: 01/20/2012] [Indexed: 10/14/2022]
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Gandhi GR, Ignacimuthu S, Paulraj MG. Solanum torvum Swartz. fruit containing phenolic compounds shows antidiabetic and antioxidant effects in streptozotocin induced diabetic rats. Food Chem Toxicol 2011; 49:2725-33. [DOI: 10.1016/j.fct.2011.08.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 07/25/2011] [Accepted: 08/04/2011] [Indexed: 01/08/2023]
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