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Leblanc C, Langlois M, Coulombe G, Vaillancourt‐Lavigueur V, Jones C, Carrier JC, Boudreau F, Rivard N. Epithelial Src homology region 2 domain–containing phosphatase‐1 restrains intestinal growth, secretory cell differentiation, and tumorigenesis. FASEB J 2017; 31:3512-3526. [DOI: 10.1096/fj.201601378r] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
Affiliation(s)
- Caroline Leblanc
- Département d'Anatomie et de Biologie CellulaireFaculté de Médecine et des Sciences de la SantéUniversité de Sherbrooke Sherbrooke Quebec Canada
| | - Marie‐Josée Langlois
- Département d'Anatomie et de Biologie CellulaireFaculté de Médecine et des Sciences de la SantéUniversité de Sherbrooke Sherbrooke Quebec Canada
| | - Geneviève Coulombe
- Département d'Anatomie et de Biologie CellulaireFaculté de Médecine et des Sciences de la SantéUniversité de Sherbrooke Sherbrooke Quebec Canada
| | - Vanessa Vaillancourt‐Lavigueur
- Département d'Anatomie et de Biologie CellulaireFaculté de Médecine et des Sciences de la SantéUniversité de Sherbrooke Sherbrooke Quebec Canada
| | - Christine Jones
- Département d'Anatomie et de Biologie CellulaireFaculté de Médecine et des Sciences de la SantéUniversité de Sherbrooke Sherbrooke Quebec Canada
| | - Julie C. Carrier
- Département d'Anatomie et de Biologie CellulaireFaculté de Médecine et des Sciences de la SantéUniversité de Sherbrooke Sherbrooke Quebec Canada
| | - François Boudreau
- Département d'Anatomie et de Biologie CellulaireFaculté de Médecine et des Sciences de la SantéUniversité de Sherbrooke Sherbrooke Quebec Canada
| | - Nathalie Rivard
- Département d'Anatomie et de Biologie CellulaireFaculté de Médecine et des Sciences de la SantéUniversité de Sherbrooke Sherbrooke Quebec Canada
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Yang X, Wang Y, Yao J, Yang X. Mechanistic study of signalling pathways in intestinal B lymphocytes using eicosapentaenoic and docosahexaenoic acid in broiler chickens. FOOD AGR IMMUNOL 2015. [DOI: 10.1080/09540105.2015.1104652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Terry NA, Walp ER, Lee RA, Kaestner KH, May CL. Impaired enteroendocrine development in intestinal-specific Islet1 mouse mutants causes impaired glucose homeostasis. Am J Physiol Gastrointest Liver Physiol 2014; 307:G979-91. [PMID: 25214396 PMCID: PMC4233286 DOI: 10.1152/ajpgi.00390.2013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Enteroendocrine cells secrete over a dozen different hormones responsible for coordinating digestion, absorption, metabolism, and gut motility. Loss of enteroendocrine cells is a known cause of severe congenital diarrhea. Furthermore, enteroendocrine cells regulate glucose metabolism, with the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) playing critical roles in stimulating insulin release by pancreatic β-cells. Islet1 (Isl1) is a LIM-homeodomain transcription factor expressed specifically in an array of intestinal endocrine cells, including incretin-expressing cells. To examine the impact of intestinal Isl1 on glycemic control, we set out to explore the role of intestinal Isl1 in hormone cell specification and organismal physiology. Mice with intestinal epithelial-specific ablation of Isl1 were obtained by crossing Villin-Cre transgenic animals with mice harboring a Isl1(loxP) allele (Isl1(int) model). Gene ablation of Isl1 in the intestine results in loss of GLP-1, GIP, cholecystokinin (CCK), and somatostatin-expressing cells and an increase in 5-HT (serotonin)-producing cells, while the chromogranin A population was unchanged. This dramatic change in hormonal milieu results in animals with lipid malabsorption and females smaller than their littermate controls. Interestingly, when challenged with oral, not intraperitoneal glucose, the Isl-1 intestinal-deficient animals (Isl1(int)) display impaired glucose tolerance, indicating loss of the incretin effect. Thus the Isl1(int) model confirms that intestinal biology is essential for organism physiology in glycemic control and susceptibility to diabetes.
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Affiliation(s)
- Natalie A. Terry
- 1The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; ,2Division of Gastroenterology and Nutrition, Department of Pediatrics, Philadelphia, Pennsylvania; ,3Department of Pathology and Laboratory Medicine, Philadelphia, Pennsylvania; and
| | - Erik R. Walp
- 1The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; ,3Department of Pathology and Laboratory Medicine, Philadelphia, Pennsylvania; and
| | - Randall A. Lee
- 1The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; ,2Division of Gastroenterology and Nutrition, Department of Pediatrics, Philadelphia, Pennsylvania;
| | - Klaus H. Kaestner
- 4Perelman School of Medicine at the University of Pennsylvania, Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Philadelphia, Pennsylvania
| | - Catherine Lee May
- 1The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; ,2Division of Gastroenterology and Nutrition, Department of Pediatrics, Philadelphia, Pennsylvania; ,3Department of Pathology and Laboratory Medicine, Philadelphia, Pennsylvania; and
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Chowdhury S, Reeds DN, Crimmins DL, Patterson BW, Laciny E, Wang S, Tran HD, Griest TA, Rometo DA, Dunai J, Wallendorf MJ, Ladenson JH, Polonsky KS, Wice BM. Xenin-25 delays gastric emptying and reduces postprandial glucose levels in humans with and without type 2 diabetes. Am J Physiol Gastrointest Liver Physiol 2014; 306:G301-9. [PMID: 24356886 PMCID: PMC3920124 DOI: 10.1152/ajpgi.00383.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Xenin-25 (Xen) is a neurotensin-related peptide secreted by a subset of glucose-dependent insulinotropic polypeptide (GIP)-producing enteroendocrine cells. In animals, Xen regulates gastrointestinal function and glucose homeostasis, typically by initiating neural relays. However, little is known about Xen action in humans. This study determines whether exogenously administered Xen modulates gastric emptying and/or insulin secretion rates (ISRs) following meal ingestion. Fasted subjects with normal (NGT) or impaired (IGT) glucose tolerance and Type 2 diabetes mellitus (T2DM; n = 10-14 per group) ingested a liquid mixed meal plus acetaminophen (ACM; to assess gastric emptying) at time zero. On separate occasions, a primed-constant intravenous infusion of vehicle or Xen at 4 (Lo-Xen) or 12 (Hi-Xen) pmol · kg(-1) · min(-1) was administered from zero until 300 min. Some subjects with NGT received 30- and 90-min Hi-Xen infusions. Plasma ACM, glucose, insulin, C-peptide, glucagon, Xen, GIP, and glucagon-like peptide-1 (GLP-1) levels were measured and ISRs calculated. Areas under the curves were compared for treatment effects. Infusion with Hi-Xen, but not Lo-Xen, similarly delayed gastric emptying and reduced postprandial glucose levels in all groups. Infusions for 90 or 300 min, but not 30 min, were equally effective. Hi-Xen reduced plasma GLP-1, but not GIP, levels without altering the insulin secretory response to glucose. Intense staining for Xen receptors was detected on PGP9.5-positive nerve fibers in the longitudinal muscle of the human stomach. Thus Xen reduces gastric emptying in humans with and without T2DM, probably via a neural relay. Moreover, endogenous GLP-1 may not be a major enhancer of insulin secretion in healthy humans under physiological conditions.
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Affiliation(s)
- Sara Chowdhury
- 1Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Dominic N. Reeds
- 2Division of Nutritional Science, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Dan L. Crimmins
- 3Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri;
| | - Bruce W. Patterson
- 2Division of Nutritional Science, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Erin Laciny
- 1Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Songyan Wang
- 1Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Hung D. Tran
- 1Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Terry A. Griest
- 3Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri;
| | - David A. Rometo
- 1Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Judit Dunai
- 1Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Michael J. Wallendorf
- 4Division of Biostatistics, Washington University School of Medicine, St. Louis, Missouri; and
| | - Jack H. Ladenson
- 3Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri;
| | - Kenneth S. Polonsky
- 1Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri; ,5Division of the Biological Sciences and Pritzker School of Medicine, The University of Chicago, Chicago, Illinois
| | - Burton M. Wice
- 1Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri;
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Chowdhury S, Wang S, Patterson BW, Reeds DN, Wice BM. The combination of GIP plus xenin-25 indirectly increases pancreatic polypeptide release in humans with and without type 2 diabetes mellitus. ACTA ACUST UNITED AC 2013; 187:42-50. [PMID: 24183983 DOI: 10.1016/j.regpep.2013.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 10/07/2013] [Accepted: 10/23/2013] [Indexed: 12/25/2022]
Abstract
Xenin-25 (Xen) is a 25-amino acid neurotensin-related peptide that activates neurotensin receptor-1 (NTSR1). We previously showed that Xen increases the effect of glucose-dependent insulinotropic polypeptide (GIP) on insulin release 1) in hyperglycemic mice via a cholinergic relay in the periphery independent from the central nervous system and 2) in humans with normal or impaired glucose tolerance, but not type 2 diabetes mellitus (T2DM). Since this blunted response to Xen defines a novel defect in T2DM, it is important to understand how Xen regulates islet physiology. On separate visits, subjects received intravenous graded glucose infusions with vehicle, GIP, Xen, or GIP plus Xen. The pancreatic polypeptide response was used as an indirect measure of cholinergic input to islets. The graded glucose infusion itself had little effect on the pancreatic polypeptide response whereas administration of Xen equally increased the pancreatic polypeptide response in humans with normal glucose tolerance, impaired glucose tolerance, and T2DM. The pancreatic polypeptide response to Xen was similarly amplified by GIP in all 3 groups. Antibody staining of human pancreas showed that NTSR1 is not detectable on islet endocrine cells, sympathetic neurons, blood vessels, or endothelial cells but is expressed at high levels on PGP9.5-positive axons in the exocrine tissue and at low levels on ductal epithelial cells. PGP9.5 positive nerve fibers contacting beta cells in the islet periphery were also observed. Thus, a neural relay, potentially involving muscarinic acetylcholine receptors, indirectly increases the effects of Xen on pancreatic polypeptide release in humans.
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Affiliation(s)
- Sara Chowdhury
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, Saint Louis, MO, United States
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6
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Roy SAB, Langlois MJ, Carrier JC, Boudreau F, Rivard N, Perreault N. Dual regulatory role for phosphatase and tensin homolog in specification of intestinal endocrine cell subtypes. World J Gastroenterol 2012; 18:1579-89. [PMID: 22529686 PMCID: PMC3325523 DOI: 10.3748/wjg.v18.i14.1579] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Revised: 02/06/2012] [Accepted: 02/26/2012] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the impact of phosphatase and tensin homolog (Pten) in the specification of intestinal enteroendocrine subpopulations.
METHODS: Using the Cre/loxP system, a mouse with conditional intestinal epithelial Pten deficiency was generated. Pten mutant mice and controls were sacrificed and small intestines collected for immunofluorescence and quantitative real-time polymerase chain reaction. Blood was collected on 16 h fasted mice by cardiac puncture. Enzyme-linked immunosorbent assay was used to measure blood circulating ghrelin, somatostatin (SST) and glucose-dependent insulinotropic peptide (GIP) levels.
RESULTS: Results show an unexpected dual regulatory role for epithelial Pten signalling in the specification/differentiation of enteroendocrine cell subpopulations in the small intestine. Our data indicate that Pten positively regulates chromogranin A (CgA) expressing subpopulations, including cells expressing secretin, ghrelin, gastrin and cholecystokinin (CCK). In contrast, Pten negatively regulates the enteroendocrine subtype specification of non-expressing CgA cells such as GIP and SST expressing cells.
CONCLUSION: The present results demonstrate that Pten signalling favours the enteroendocrine progenitor to specify into cells expressing CgA including those producing CCK, gastrin and ghrelin.
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Bruen CM, O'Halloran F, Cashman KD, Giblin L. The effects of food components on hormonal signalling in gastrointestinal enteroendocrine cells. Food Funct 2012; 3:1131-43. [DOI: 10.1039/c2fo30086a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Bezençon C, Fürholz A, Raymond F, Mansourian R, Métairon S, Le Coutre J, Damak S. Murine intestinal cells expressing Trpm5 are mostly brush cells and express markers of neuronal and inflammatory cells. J Comp Neurol 2008; 509:514-25. [DOI: 10.1002/cne.21768] [Citation(s) in RCA: 172] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Althage MC, Ford EL, Wang S, Tso P, Polonsky KS, Wice BM. Targeted ablation of glucose-dependent insulinotropic polypeptide-producing cells in transgenic mice reduces obesity and insulin resistance induced by a high fat diet. J Biol Chem 2008; 283:18365-76. [PMID: 18420580 DOI: 10.1074/jbc.m710466200] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The K cell is a specific sub-type of enteroendocrine cell located in the proximal small intestine that produces glucose-dependent insulinotropic polypeptide (GIP), xenin, and potentially other unknown hormones. Because GIP promotes weight gain and insulin resistance, reducing hormone release from K cells could lead to weight loss and increased insulin sensitivity. However, the consequences of coordinately reducing circulating levels of all K cell-derived hormones are unknown. To reduce the number of functioning K cells, regulatory elements from the rat GIP promoter/gene were used to express an attenuated diphtheria toxin A chain in transgenic mice. K cell number, GIP transcripts, and plasma GIP levels were profoundly reduced in the GIP/DT transgenic mice. Other enteroendocrine cell types were not ablated. Food intake, body weight, and blood glucose levels in response to insulin or intraperitoneal glucose were similar in control and GIP/DT mice fed standard chow. In contrast to single or double incretin receptor knock-out mice, the incretin response was absent in GIP/DT animals suggesting K cells produce GIP plus an additional incretin hormone. Following high fat feeding for 21-35 weeks, the incretin response was partially restored in GIP/DT mice. Transgenic versus wild-type mice demonstrated significantly reduced body weight (25%), plasma leptin levels (77%), and daily food intake (16%) plus enhanced energy expenditure (10%) and insulin sensitivity. Regardless of diet, long term glucose homeostasis was not grossly perturbed in the transgenic animals. In conclusion, studies using GIP/DT mice demonstrate an important role for K cells in the regulation of body weight and insulin sensitivity.
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Affiliation(s)
- Matthew C Althage
- Department of Internal Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, Saint Louis, MO 63110, USA
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Sutherland K, Young RL, Cooper NJ, Horowitz M, Blackshaw LA. Phenotypic characterization of taste cells of the mouse small intestine. Am J Physiol Gastrointest Liver Physiol 2007; 292:G1420-8. [PMID: 17290008 DOI: 10.1152/ajpgi.00504.2006] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Nutrient-evoked gastrointestinal reflexes are likely initiated by specialized epithelial cells located in the small intestine that detect luminal stimuli and release mediators that activate vagal endings. The G-protein alpha-gustducin, a key signal molecule in lingual taste detection, has been identified in mouse small intestine, where it may also subserve nutrient detection; however, the phenotype of alpha-gustducin cells is unknown. Immunohistochemistry was performed throughout the mouse small intestine for alpha-gustducin, enteroendocrine cell markers 5-HT and glucagon-like peptide-1 (GLP-1), and brush cell markers neuronal nitric oxide synthase and Ulex europaeus agglutinin-1 (UEA-1) lectin binding, singly, and in combination. alpha-Gustducin was expressed in solitary epithelial cells of the mid to upper villus, which were distributed in a regional manner with most occurring within the midjejunum. Here, 27% of alpha-gustducin cells colabeled for 5-HT and 15% for GLP-1; 57% of alpha-gustducin cells colabeled UEA-1, with no triple labeling. alpha-Gustducin cells that colabeled for 5-HT or GLP-1 were of distinct morphology and exhibited a different alpha-gustducin immunolabeling pattern to those colabeled with UEA-1. Neuronal nitric oxide synthase was absent from intestinal epithelium despite strong labeling in the myenteric plexus. We conclude that subsets of enteroendocrine cells in the midjejunum and brush cells (more generally distributed) are equipped to utilize alpha-gustducin signaling in mice. Intestinal taste modalities may be signaled by these enteroendocrine cells via the release of 5-HT, GLP-1, or coexpressed mediators or by brush cells via a nonnitrergic mediator in distinct regions of the intestine.
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Affiliation(s)
- Kate Sutherland
- Discipline of Physiology, School of Molecular and Biomedical Sciences, University of Adelaide, Australia
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Lobo-da-Cunha A, Batista-Pinto C. Ultrastructural, histochemical and cytochemical characterization of intestinal epithelial cells in Aplysia depilans (Gastropoda, Opisthobranchia). ACTA ZOOL-STOCKHOLM 2007. [DOI: 10.1111/j.1463-6395.2007.00268.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Lomax AE, Linden DR, Mawe GM, Sharkey KA. Effects of gastrointestinal inflammation on enteroendocrine cells and enteric neural reflex circuits. Auton Neurosci 2006; 126-127:250-7. [PMID: 16616704 DOI: 10.1016/j.autneu.2006.02.015] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Revised: 02/20/2006] [Accepted: 02/27/2006] [Indexed: 01/29/2023]
Abstract
Inflammation of the gastrointestinal (GI) tract has pronounced effects on GI function. Many of the functions of the GI tract are subject to neural regulation by the enteric nervous system (ENS) and its extrinsic connections. Therefore, it is possible that inflammatory effects on the ENS contribute to altered function during GI inflammation. The reflex circuitry of the ENS is comprised of sensory transducers in the mucosa (enteroendocrine cells), afferent neurons, interneurons and motor neurons. This review focuses on recent data that describe inflammation-induced changes to the ENS and mucosal enteroendocrine cells. Studies of tissues from patients with inflammatory bowel disease (IBD) and from animal models of IBD have demonstrated marked changes in mucosal enteroendocrine cell signaling. These changes, which have been studied most intensely in 5-HT-containing enterochromaffin cells, involve changes in the number of cells, their signaling molecule content or their means of signal termination. Morphological evidence of enteric neuropathy during inflammation has been obtained from human samples and animal models of IBD. The neuropathy can reduce the number of enteric neurons in the inflamed region and is often accompanied by a change in the neurochemical coding of enteric neurons, both in the inflamed region and at distant sites. Electrophysiological recordings have been made from enteric neurons in inflamed regions of the colon of animal models of IBD. These studies have consistently found that inflammation increases excitability of intrinsic primary afferent neurons and alters synaptic transmission to interneurons and motor neurons. These data set the stage for a comprehensive examination of the role of altered neuronal and enteroendocrine cell signaling in symptom generation during GI inflammation.
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Affiliation(s)
- Alan E Lomax
- Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University, Kingston, Ontario, Canada K7L 5G2, and Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA.
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Li L, Wice BM. Bombesin and nutrients independently and additively regulate hormone release from GIP/Ins cells. Am J Physiol Endocrinol Metab 2005; 288:E208-15. [PMID: 15383372 DOI: 10.1152/ajpendo.00346.2004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) regulates glucose homeostasis and high-fat diet-induced obesity and insulin resistance. Therefore, elucidating the mechanisms that regulate GIP release is important. GIP is produced by K cells, a specific subtype of small intestinal enteroendocrine (EE) cell. Bombesin-like peptides produced by enteric neurons and luminal nutrients stimulate GIP release in vivo. We previously showed that PMA, bombesin, meat hydrolysate, glyceraldehyde, and methylpyruvate increase hormone release from a GIP-producing EE cell line (GIP/Ins cells). Here we demonstrate that bombesin and nutrients additively stimulate hormone release from GIP/Ins cells. In various cell systems, bombesin and PMA regulate cell physiology by activating PKD signaling in a PKC-dependent fashion, whereas nutrients regulate cell physiology by inhibiting AMPK signaling. Western blot analyses of GIP/Ins cells using antibodies specific for activated and/or phosphorylated forms of PKD and AMPK and one substrate for each kinase revealed that bombesin and PMA, but not nutrients, activated PKC, but not PKD. Conversely, nutrients, but not bombesin or PMA, inhibited AMPK activity. Pharmacological studies showed that PKC inhibition blocked bombesin- and PMA-stimulated hormone release, but AMPK activation failed to suppress nutrient-stimulated hormone secretion. Forced expression of constitutively active vs. dominant negative PKDs or AMPKs failed to perturb bombesin- or nutrient-stimulated hormone release. Thus, in GIP/Ins cells, PKC regulates bombesin-stimulated hormone release, whereas nutrients may control hormone release by regulating the activity of AMPK-related kinases, rather than AMPK itself. These results strongly suggest that K cells in vivo independently respond to neuronal vs. nutritional stimuli via two distinct signaling pathways.
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Affiliation(s)
- Lin Li
- Department of Internal Medicine, Division of Endocrinology, Diabetes & Metabolism, Washington University School of Medicine, St. Louis, MO 63110, USA
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Paspalas CD, Goldman-Rakic PS. Microdomains for dopamine volume neurotransmission in primate prefrontal cortex. J Neurosci 2004; 24:5292-300. [PMID: 15190100 PMCID: PMC6729299 DOI: 10.1523/jneurosci.0195-04.2004] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The explicit yet enigmatic involvement of dopamine in cortical physiology is in part volumetric (beyond the synapse), as is apparently the action of neuroleptics targeting dopamine receptors. The notion that nonsynaptic neuronal membranes would translate extracellular dopamine into receptor-specific spatiotemporal downstream signaling, similar to the chemical synapse, is intriguing. Here, we report that dopamine D5 (but not D1 or D2) receptors in the perisomatic plasma membrane of prefrontal cortical neurons form discrete and exclusively extrasynaptic microdomains with inositol 1,4,5-trisphosphate-gated calcium stores of subsurface cisterns and mitochondria. These findings introduce a novel dopaminoceptive substratum in the brain and a unique D5 receptor-specific signaling paradigm.
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Affiliation(s)
- Constantinos D Paspalas
- Yale University School of Medicine, Department of Neurobiology, Sterling Hall of Medicine B408, 333 Cedar Street, New Haven, CT 0651, USA.
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