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Hellman B, Dansk H, Grapengiesser E. Somatostatin promotes glucose generation of Ca2+oscillations in pancreatic islets both in the absence and presence of tolbutamide. Cell Calcium 2018; 74:35-42. [DOI: 10.1016/j.ceca.2018.05.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 05/15/2018] [Accepted: 05/30/2018] [Indexed: 11/22/2022]
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Abstract
Serotonin (5-hydroxytryptamine or 5-HT) once most extensively studied as a neurotransmitter of the central nervous system, is seen to be predominantly secreted in the gut. About 95% of 5-HT is estimated to be found in gut mainly within the enterochromaffin cells whereas about 5% is found in the brain. 5-HT is an important enteric signaling molecule and is well known for playing a key role in sensory-motor and secretory functions in the gut. In recent times, studies uncovering various new functions of gut-derived 5-HT indicate that many more are yet to be discovered in coming days. Recent studies revealed that 5-HT plays a pivotal role in immune cell activation and generation/perpetuation of inflammation in the gut. In addition to its various roles in the gut, there are now emerging evidences that suggest an important role of gut-derived 5-HT in other biological processes beyond the gut, such as bone remodeling and metabolic homeostasis. This review focuses to briefly summarize the accumulated and newly updated role of 5-HT in the maintenance of normal gut physiology and in the pathogenesis of inflammation in the gut. The collected information about this multifaceted signaling molecule may aid in distinguishing its good and bad effects which may lead to the development of novel strategies to overcome the unwanted effect, such as in inflammatory bowel disease.
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Affiliation(s)
- Suhrid Banskota
- Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, ON, Canada; Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
| | - Jean-Eric Ghia
- Department of Immunology and Internal Medicine, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Waliul I Khan
- Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, ON, Canada; Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.
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Martin AM, Young RL, Leong L, Rogers GB, Spencer NJ, Jessup CF, Keating DJ. The Diverse Metabolic Roles of Peripheral Serotonin. Endocrinology 2017; 158:1049-1063. [PMID: 28323941 DOI: 10.1210/en.2016-1839] [Citation(s) in RCA: 139] [Impact Index Per Article: 19.9] [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] [Received: 11/13/2016] [Accepted: 02/23/2017] [Indexed: 02/07/2023]
Abstract
Serotonin (5-hydroxytryptamine or 5-HT) is a multifunctional bioamine with important signaling roles in a range of physiological pathways. Almost all of the 5-HT in our bodies is synthesized in specialized enteroendocrine cells within the gastrointestinal (GI) mucosa called enterochromaffin (EC) cells. These cells provide all of our circulating 5-HT. We have long appreciated the important contributions of 5-HT within the gut, including its role in modulating GI motility. However, evidence of the physiological and clinical significance of gut-derived 5-HT outside of the gut has recently emerged, implicating 5-HT in regulation of glucose homeostasis, lipid metabolism, bone density, and diseases associated with metabolic syndrome, such as obesity and type 2 diabetes. Although a new picture has developed in the last decade regarding the various metabolic roles of peripheral serotonin, so too has our understanding of the physiology of EC cells. Given that they are scattered throughout the lining of the GI tract within the epithelial cell layer, these cells are typically difficult to study. Advances in isolation procedures now allow the study of pure EC-cell cultures and single cells, enabling studies of EC-cell physiology to occur. EC cells are sensory cells that are capable of integrating cues from ingested nutrients, the enteric nervous system, and the gut microbiome. Thus, levels of peripheral 5-HT can be modulated by a multitude of factors, resulting in both local and systemic effects for the regulation of a raft of physiological pathways related to metabolism and obesity.
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Affiliation(s)
- Alyce M Martin
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
| | - Richard L Young
- Nutrition and Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide 5001, Australia
- Adelaide Medical School, University of Adelaide, Adelaide 5005, Australia
| | - Lex Leong
- Infection and Immunity, SAHMRI, Adelaide 5001, Australia
- SAHMRI Microbiome Research Laboratory, School of Medicine, Flinders University of South Australia, Adelaide 5042, Australia
| | - Geraint B Rogers
- Infection and Immunity, SAHMRI, Adelaide 5001, Australia
- SAHMRI Microbiome Research Laboratory, School of Medicine, Flinders University of South Australia, Adelaide 5042, Australia
| | - Nick J Spencer
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
| | - Claire F Jessup
- Adelaide Medical School, University of Adelaide, Adelaide 5005, Australia
- Discipline of Anatomy and Histology, Flinders University of South Australia, Adelaide 5042, Australia
| | - Damien J Keating
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
- Nutrition and Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide 5001, Australia
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Almaça J, Molina J, Menegaz D, Pronin AN, Tamayo A, Slepak V, Berggren PO, Caicedo A. Human Beta Cells Produce and Release Serotonin to Inhibit Glucagon Secretion from Alpha Cells. Cell Rep 2016; 17:3281-3291. [PMID: 28009296 PMCID: PMC5217294 DOI: 10.1016/j.celrep.2016.11.072] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 10/24/2016] [Accepted: 11/23/2016] [Indexed: 12/11/2022] Open
Abstract
In the pancreatic islet, serotonin is an autocrine signal increasing beta cell mass during metabolic challenges such as those associated with pregnancy or high-fat diet. It is still unclear whether serotonin is relevant for regular islet physiology and hormone secretion. Here, we show that human beta cells produce and secrete serotonin when stimulated with increases in glucose concentration. Serotonin secretion from beta cells decreases cyclic AMP (cAMP) levels in neighboring alpha cells via 5-HT1F receptors and inhibits glucagon secretion. Without serotonergic input, alpha cells lose their ability to regulate glucagon secretion in response to changes in glucose concentration, suggesting that diminished serotonergic control of alpha cells can cause glucose blindness and the uncontrolled glucagon secretion associated with diabetes. Supporting this model, pharmacological activation of 5-HT1F receptors reduces glucagon secretion and has hypoglycemic effects in diabetic mice. Thus, modulation of serotonin signaling in the islet represents a drug intervention opportunity.
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Affiliation(s)
- Joana Almaça
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | - Judith Molina
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Danusa Menegaz
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Alexey N Pronin
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Alejandro Tamayo
- Diabetes Research Institute, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Vladlen Slepak
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; Program in Neuroscience, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Per-Olof Berggren
- Diabetes Research Institute, University of Miami Miller School of Medicine, Miami, FL 33136, USA; Rolf Luft Research Center for Diabetes & Endocrinology, Karolinska Institutet, Stockholm SE-17177, Sweden; Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Alejandro Caicedo
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA; Program in Neuroscience, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
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Alshahrani S, Almutairi MM, Kursan S, Dias-Junior E, Almiahuob MM, Aguilar-Bryan L, Di Fulvio M. Increased Slc12a1 expression in β-cells and improved glucose disposal in Slc12a2 heterozygous mice. J Endocrinol 2015; 227:153-65. [PMID: 26400961 PMCID: PMC4623298 DOI: 10.1530/joe-15-0327] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/23/2015] [Indexed: 12/26/2022]
Abstract
The products of the Slc12a1 and Slc12a2 genes, commonly known as Na(+)-dependent K(+)2Cl(-) co-transporters NKCC2 and NKCC1, respectively, are the targets for the diuretic bumetanide. NKCCs are implicated in the regulation of intracellular chloride concentration ([Cl(-)]i) in pancreatic β-cells, and as such, they may play a role in glucose-stimulated plasma membrane depolarization and insulin secretion. Unexpectedly, permanent elimination of NKCC1 does not preclude insulin secretion, an event potentially linked to the homeostatic regulation of additional Cl(-) transporters expressed in β-cells. In this report we provide evidence for such a mechanism. Mice lacking a single allele of Slc12a2 exhibit lower fasting glycemia, increased acute insulin response (AIR) and lower blood glucose levels 15-30 min after a glucose load when compared to mice harboring both alleles of the gene. Furthermore, heterozygous expression or complete absence of Slc12a2 associates with increased NKCC2 protein expression in rodent pancreatic β-cells. This has been confirmed by using chronic pharmacological down-regulation of NKCC1 with bumetanide in the mouse MIN6 β-cell line or permanent molecular silencing of NKCC1 in COS7 cells, which results in increased NKCC2 expression. Furthermore, MIN6 cells chronically pretreated with bumetanide exhibit increased initial rates of Cl(-) uptake while preserving glucose-stimulated insulin secretion. Together, our results suggest that NKCCs are involved in insulin secretion and that a single Slc12a2 allele may protect β-cells from failure due to increased homeostatic expression of Slc12a1.
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Affiliation(s)
- Saeed Alshahrani
- Department of Pharmacology and ToxicologyBoonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, 216 HSB, Dayton, Ohio 45435, USAPacific Northwest Diabetes Research InstituteSeattle, Washington 98122, USA
| | - Mohammed Mashari Almutairi
- Department of Pharmacology and ToxicologyBoonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, 216 HSB, Dayton, Ohio 45435, USAPacific Northwest Diabetes Research InstituteSeattle, Washington 98122, USA
| | - Shams Kursan
- Department of Pharmacology and ToxicologyBoonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, 216 HSB, Dayton, Ohio 45435, USAPacific Northwest Diabetes Research InstituteSeattle, Washington 98122, USA
| | - Eduardo Dias-Junior
- Department of Pharmacology and ToxicologyBoonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, 216 HSB, Dayton, Ohio 45435, USAPacific Northwest Diabetes Research InstituteSeattle, Washington 98122, USA
| | - Mohamed Mahmoud Almiahuob
- Department of Pharmacology and ToxicologyBoonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, 216 HSB, Dayton, Ohio 45435, USAPacific Northwest Diabetes Research InstituteSeattle, Washington 98122, USA
| | - Lydia Aguilar-Bryan
- Department of Pharmacology and ToxicologyBoonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, 216 HSB, Dayton, Ohio 45435, USAPacific Northwest Diabetes Research InstituteSeattle, Washington 98122, USA
| | - Mauricio Di Fulvio
- Department of Pharmacology and ToxicologyBoonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, 216 HSB, Dayton, Ohio 45435, USAPacific Northwest Diabetes Research InstituteSeattle, Washington 98122, USA
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Abstract
Exogenous dopamine inhibits insulin secretion from pancreatic β-cells, but the lack of dopaminergic neurons in pancreatic islets has led to controversy regarding the importance of this effect. Recent data, however, suggest a plausible physiologic role for dopamine in the regulation of insulin secretion. We review the literature underlying our current understanding of dopaminergic signaling that can down-regulate glucose-stimulated insulin secretion from pancreatic islets. In this negative feedback loop, dopamine is synthesized in the β-cells from circulating L-dopa, serves as an autocrine signal that is cosecreted with insulin, and causes a tonic inhibition on glucose-stimulated insulin secretion. On the whole animal scale, L-dopa is produced by cells in the gastrointestinal tract, and its concentration in the blood plasma increases following a mixed meal. By reviewing the outcome of certain types of bariatric surgery that result in rapid amelioration of glucose tolerance, we hypothesize that dopamine serves as an "antiincretin" signal that counterbalances the stimulatory effect of glucagon-like peptide 1.
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Affiliation(s)
- Alessandro Ustione
- Department of Molecular Physiology and Biophysics, Vanderbilt University, 702 Light Hall, Nashville, Tennessee 37232-0615, USA
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Abstract
Here, we outline how islet cells use autocrine and paracrine 'circuits' of classical neurotransmitters and their corresponding receptors and transporters to communicate with vicinal β-cells to regulate glucose-stimulated insulin secretion. Many of these same circuits operate in the central nervous system and can be visualized by molecular imaging. We discuss how these techniques might be applied to measuring the dynamics of β-cell function in real time.
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Affiliation(s)
- P E Harris
- Division of Endocrinology, Department of Medicine, The Naomi Berrie Diabetes Center and Columbia University College of Physicians and Surgeons, New York, NY, USA.
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Abstract
The ATP-sensitive potassium (K(ATP)) channel plays a crucial role in insulin secretion and thus glucose homeostasis. K(ATP) channel activity in the pancreatic beta-cell is finely balanced; increased activity prevents insulin secretion, whereas reduced activity stimulates insulin release. The beta-cell metabolism tightly regulates K(ATP) channel gating, and if this coupling is perturbed, two distinct disease states can result. Diabetes occurs when the K(ATP) channel fails to close in response to increased metabolism, whereas congenital hyperinsulinism results when K(ATP) channels remain closed even at very low blood glucose levels. In general there is a good correlation between the magnitude of K(ATP) current and disease severity. Mutations that cause a complete loss of K(ATP) channels in the beta-cell plasma membrane produce a severe form of congenital hyperinsulinism, whereas mutations that partially impair channel function produce a milder phenotype. Similarly mutations that greatly reduce the ATP sensitivity of the K(ATP) channel lead to a severe form of neonatal diabetes with associated neurological complications, whilst mutations that cause smaller shifts in ATP sensitivity cause neonatal diabetes alone. This chapter reviews our current understanding of the pancreatic beta-cell K(ATP) channel and highlights recent structural, functional and clinical advances.
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Affiliation(s)
- Rebecca Clark
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.
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Heimes K, Feistel B, Verspohl EJ. Impact of the 5-HT3 receptor channel system for insulin secretion and interaction of ginger extracts. Eur J Pharmacol 2009; 624:58-65. [PMID: 19818348 DOI: 10.1016/j.ejphar.2009.09.049] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [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: 04/15/2009] [Revised: 09/15/2009] [Accepted: 09/28/2009] [Indexed: 11/22/2022]
Abstract
The relevance of serotonin and in particular that of 5-HT(3) receptors is unequivocal with respect to emetic/antiemetic effects, but it is controversial with respect to antidiabetic effects. The effects of tropisetron (5-HT(3) receptor antagonist) and various ginger (Zingiber officinale) extracts (known to interact with the 5-HT(3) receptor channel system) were investigated. Serotonin (32 to 500 microM) inhibits insulin release (RIA) from INS-1 cells which is reversed by tropisetron (10 to 100 microM) and two different ginger extracts (spissum and an oily extract). Their effects are obvious even in the absence of serotonin but are more pronounced in its presence (doubled to tripled). Specific 5-HT(3) binding sites are present in INS-1 cells using 0.4 nM [3H] GR65630 in displacement experiments. The in vitro data with respect to ginger are corroborated by in vivo data on glucose-loaded rats showing that blood glucose (Glucoquant) is decreased by approximately 35% and plasma insulin (RIA) is increased by approximately 10%. Both the spissum extract and the oily ginger extract are effective in two other models: they inhibit [(14)C] guanidinium uptake into N1E-115 cells (model of 5-HT(3) effects) and relax rat ileum both directly and as a serotonin antagonistic effect. Other receptors addressed by ginger are 5-HT(2) receptors as demonstrated by using methysergide and ketanserin. They weakly antagonize the serotonin effect as well. It may be concluded that serotonin and in particular the 5-HT(3) receptor channel system are involved in modulating insulin release and that tropisetron and various ginger extracts can be used to improve a diabetic situation.
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Affiliation(s)
- Katharina Heimes
- Department of Pharmacology, Institute of Medicinal Chemistry, Westfälische Wilhelms-University of Münster, Hittorfstrasse 58-62, 48149 Münster, Germany
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