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Csajbók ÉA, Kocsis ÁK, Faragó N, Furdan S, Kovács B, Lovas S, Molnár G, Likó I, Zvara Á, Puskás LG, Patócs A, Tamás G. Expression of GLP-1 receptors in insulin-containing interneurons of rat cerebral cortex. Diabetologia 2019; 62:717-725. [PMID: 30637442 DOI: 10.1007/s00125-018-4803-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 11/30/2018] [Indexed: 01/12/2023]
Abstract
AIMS/HYPOTHESIS Glucagon-like peptide 1 (GLP-1) receptors are expressed by pancreatic beta cells and GLP-1 receptor signalling promotes insulin secretion. GLP-1 receptor agonists have neural effects and are therapeutically promising for mild cognitive impairment and Alzheimer's disease. Our previous results showed that insulin is released by neurogliaform neurons in the cerebral cortex, but the expression of GLP-1 receptors on insulin-producing neocortical neurons has not been tested. In this study, we aimed to determine whether GLP-1 receptors are present in insulin-containing neurons. METHODS We harvested the cytoplasm of electrophysiologically and anatomically identified neurogliaform interneurons during patch-clamp recordings performed in slices of rat neocortex. Using single-cell digital PCR, we determined copy numbers of Glp1r mRNA and other key genes in neurogliaform cells harvested in conditions corresponding to hypoglycaemia (0.5 mmol/l glucose) and hyperglycaemia (10 mmol/l glucose). In addition, we performed whole-cell patch-clamp recordings on neurogliaform cells to test the effects of GLP-1 receptor agonists for functional validation of single-cell digital PCR results. RESULTS Single-cell digital PCR revealed GLP-1 receptor expression in neurogliaform cells and showed that copy numbers of mRNA of the Glp1r gene in hyperglycaemia exceeded those in hypoglycaemia by 9.6 times (p < 0.008). Moreover, single-cell digital PCR confirmed co-expression of Glp1r and Ins2 mRNA in neurogliaform cells. Functional expression of GLP-1 receptors was confirmed with whole-cell patch-clamp electrophysiology, showing a reversible effect of GLP-1 on neurogliaform cells. This effect was prevented by pre-treatment with the GLP-1 receptor-specific antagonist exendin-3(9-39) and was absent in hypoglycaemia. In addition, single-cell digital PCR of neurogliaform cells revealed that the expression of transcription factors (Pdx1, Isl1, Mafb) are important in beta cell development. CONCLUSIONS/INTERPRETATION Our results provide evidence for the functional expression of GLP-1 receptors in neurons known to release insulin in the cerebral cortex. Hyperglycaemia increases the expression of GLP-1 receptors in neurogliaform cells, suggesting that endogenous incretins and therapeutic GLP-1 receptor agonists might have effects on these neurons, similar to those in pancreatic beta cells.
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Affiliation(s)
- Éva A Csajbók
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép fasor 52, Szeged, H-6726, Hungary
- 1st Department of Internal Medicine, University of Szeged, Szeged, Hungary
| | - Ágnes K Kocsis
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép fasor 52, Szeged, H-6726, Hungary
| | - Nóra Faragó
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép fasor 52, Szeged, H-6726, Hungary
- Laboratory of Functional Genomics, Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary
- Avidin Ltd, Szeged, Hungary
| | - Szabina Furdan
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép fasor 52, Szeged, H-6726, Hungary
| | - Balázs Kovács
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép fasor 52, Szeged, H-6726, Hungary
| | - Sándor Lovas
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép fasor 52, Szeged, H-6726, Hungary
| | - Gábor Molnár
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép fasor 52, Szeged, H-6726, Hungary
| | - István Likó
- MTA Lendület Hereditary Endocrine Tumors Research Group, Semmelweis University, Budapest, Hungary
| | - Ágnes Zvara
- Laboratory of Functional Genomics, Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary
| | - László G Puskás
- Laboratory of Functional Genomics, Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary
- Avidin Ltd, Szeged, Hungary
| | - Attila Patócs
- MTA Lendület Hereditary Endocrine Tumors Research Group, Semmelweis University, Budapest, Hungary
| | - Gábor Tamás
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép fasor 52, Szeged, H-6726, Hungary.
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Abstract
Recent results suggest that insulin is synthesised by a subpopulation of neurons in the cerebral cortex and neural progenitor cells of the hippocampus. Supplementing the slow supply of insulin to the brain by pancreatic beta cells, the insulin locally released by neurons provides a rapid means of regulating local microcircuits, effectively modulating synaptic transmission and on-demand energy homeostasis of neural networks. Modulation of insulin production by brain neurons via glucagon-like peptide 1 (GLP-1) agonists might be useful in counteracting diabetes, obesity and neurodegenerative diseases. Replacement of lost pancreatic beta cells by autologous transplantation of insulin-producing neural progenitor cells could be a viable therapy for diabetes.
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Affiliation(s)
- Éva A Csajbók
- Endocrine Unit, 1st Department of Internal Medicine, University of Szeged, Szeged, Hungary
| | - Gábor Tamás
- MTA-SZTE Research Group for Cortical Microcircuits, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Közép Fasor 52, Szeged, 6726, Hungary.
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McNay EC, Recknagel AK. Reprint of: 'Brain insulin signaling: A key component of cognitive processes and a potential basis for cognitive impairment in type 2 diabetes'. Neurobiol Learn Mem 2011; 96:517-28. [PMID: 22085799 DOI: 10.1016/j.nlm.2011.11.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Understanding of the role of insulin in the brain has gradually expanded, from initial conceptions of the brain as insulin-insensitive through identification of a role in regulation of feeding, to recent demonstration of insulin as a key component of hippocampal memory processes. Conversely, systemic insulin resistance such as that seen in type 2 diabetes is associated with a range of cognitive and neural deficits. Here we review the evidence for insulin as a cognitive and neural modulator, including potential effector mechanisms, and examine the impact that type 2 diabetes has on these mechanisms in order to identify likely bases for the cognitive impairments seen in type 2 diabetic patients.
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Affiliation(s)
- Ewan C McNay
- Behavioral Neuroscience and Center for Neuroscience Research, University at Albany (SUNY), SS399, 1400 Washington Avenue, Albany, NY 12222, USA.
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McNay EC, Recknagel AK. Brain insulin signaling: a key component of cognitive processes and a potential basis for cognitive impairment in type 2 diabetes. Neurobiol Learn Mem 2011; 96:432-42. [PMID: 21907815 DOI: 10.1016/j.nlm.2011.08.005] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2011] [Revised: 07/09/2011] [Accepted: 08/12/2011] [Indexed: 12/16/2022]
Abstract
Understanding of the role of insulin in the brain has gradually expanded, from initial conceptions of the brain as insulin-insensitive through identification of a role in regulation of feeding, to recent demonstration of insulin as a key component of hippocampal memory processes. Conversely, systemic insulin resistance such as that seen in type 2 diabetes is associated with a range of cognitive and neural deficits. Here we review the evidence for insulin as a cognitive and neural modulator, including potential effector mechanisms, and examine the impact that type 2 diabetes has on these mechanisms in order to identify likely bases for the cognitive impairments seen in type 2 diabetic patients.
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Affiliation(s)
- Ewan C McNay
- Behavioral Neuroscience and Center for Neuroscience Research, University at Albany (SUNY), SS399, 1400 Washington Avenue, Albany, NY 12222, USA.
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