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Lee J, Kim WK. Applications of Enteroendocrine Cells (EECs) Hormone: Applicability on Feed Intake and Nutrient Absorption in Chickens. Animals (Basel) 2023; 13:2975. [PMID: 37760373 PMCID: PMC10525316 DOI: 10.3390/ani13182975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/09/2023] [Accepted: 09/13/2023] [Indexed: 09/29/2023] Open
Abstract
This review focuses on the role of hormones derived from enteroendocrine cells (EECs) on appetite and nutrient absorption in chickens. In response to nutrient intake, EECs release hormones that act on many organs and body systems, including the brain, gallbladder, and pancreas. Gut hormones released from EECs play a critical role in the regulation of feed intake and the absorption of nutrients such as glucose, protein, and fat following feed ingestion. We could hypothesize that EECs are essential for the regulation of appetite and nutrient absorption because the malfunction of EECs causes severe diarrhea and digestion problems. The importance of EEC hormones has been recognized, and many studies have been carried out to elucidate their mechanisms for many years in other species. However, there is a lack of research on the regulation of appetite and nutrient absorption by EEC hormones in chickens. This review suggests the potential significance of EEC hormones on growth and health in chickens under stress conditions induced by diseases and high temperature, etc., by providing in-depth knowledge of EEC hormones and mechanisms on how these hormones regulate appetite and nutrient absorption in other species.
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Affiliation(s)
| | - Woo Kyun Kim
- Department of Poultry Science, University of Georgia, Athens, GA 30602, USA;
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2
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Irwin DM. Molecular evolution of GIP and Exendin and their receptors. Peptides 2020; 125:170158. [PMID: 31582191 DOI: 10.1016/j.peptides.2019.170158] [Citation(s) in RCA: 3] [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: 07/16/2019] [Revised: 09/11/2019] [Accepted: 09/18/2019] [Indexed: 01/31/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is a product of the Gip gene and acts as an incretin hormone in mammals. Gip is most closely related to the proglucagon (Gcg) and Exendin genes and diverged from these very early in vertebrate evolution. In mammals, GIP acts through its specific receptor, encoded by the Gipr gene, which belongs to a subfamily of 7-transmembrane G-protein coupled receptor (GPCR) genes that also includes those for the proglucagon-derived peptides (Gcgr, Glp1r, and Glp2r), and the receptor for Exendin (Grlr). Gip, Gipr, Exendin, and Grlr genes are found in species from most vertebrate classes. While most species that have a Gip gene also have a Gipr gene, two classes of vertebrates, cartilaginous fish and birds, retain conserved Gip genes but lack Gipr genes. This raises the possibility the GIP signals through other receptors in some vertebrates. Exendin genes and the gene for its receptor, Grlr, are also found in diverse vertebrates, with the notable exception of mammals. Both GIP and Exendin likely have important roles in vertebrate physiology, but their roles are either dispensable or can be replaced by other hormones.
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Affiliation(s)
- David M Irwin
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada; Banting and Best Diabetes Centre, University of Toronto, Toronto, Canada.
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Herwig E, Schwean-Lardner K, Van Kessel A, Savary RK, Classen HL. Assessing the effect of starch digestion characteristics on ileal brake activation in broiler chickens. PLoS One 2020; 15:e0228647. [PMID: 32032378 PMCID: PMC7006927 DOI: 10.1371/journal.pone.0228647] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 01/20/2020] [Indexed: 01/10/2023] Open
Abstract
The objective of this research was to evaluate activation of the ileal brake in broiler chickens using diets containing semi-purified wheat (WS; rapidly and highly digested) and pea (PS; slowly and poorly digested) starch. Diets were formulated to contain six WS:PS ratios (100:0, 80:20, 60:40, 40:60, 20:80, 0:100) and each starch ratio was fed to 236 Ross 308 male broilers housed in 4 litter floor pens. At 28 d of age, the effect of PS concentration was assessed on starch digestion, digestive tract morphology, and digesta pH and short-chain fatty acid (SCFA) concentration. Glucagon-like peptide-1 (GLP-1) and peptide tyrosine-tyrosine (PYY) status were assessed in serum (ELISA) and via gene expression in jejunal and ileal tissue (proglucagon for GLP-1). Data were analyzed using regression analyses, and significance was accepted at P ≤ 0.05. Increasing dietary PS resulted in reduced starch digestibility in the small intestine, but had no effect in the colon. Crop content pH responded quadratically to PS level with an estimated minimum at 55% PS. Total SCFA increased linearly in the crop with PS level, but changed in a quadratic fashion in the ileum (estimated maximum at 62% PS). Ceacal SCFA concentrations were highest for the 80 and 100% PS levels. The relative empty weight (crop, small intestine, colon), length (small intestine) and content (crop jejunum, Ileum) of digestive tract sections increased linearly with increasing PS concentration. Dietary treatment did not affect serum GLP-1 or PYY or small intestine transcript abundance. In conclusion, feeding PS increased the presence of L-cell activators (starch, SCFA) and increased trophic development and content of the digestive tract, suggestive of L-cell activation. However, no direct evidence of ileal brake activation was found by measuring venous blood levels of GLP-1 or PYY or corresponding gene expression in small intestine tissue.
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Affiliation(s)
- Eugenia Herwig
- Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Karen Schwean-Lardner
- Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Andrew Van Kessel
- Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Rachel K. Savary
- Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Henry L. Classen
- Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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4
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Prater CM, Harris BN, Carr JA. Tectal CRFR1 receptors modulate food intake and feeding behavior in the South African clawed frog Xenopus laevis. Horm Behav 2018; 105:86-94. [PMID: 30077740 DOI: 10.1016/j.yhbeh.2018.07.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 07/13/2018] [Accepted: 07/30/2018] [Indexed: 12/11/2022]
Abstract
The optic tectum and superior colliculus rapidly inhibit food intake when a visual threat is present. Previous work indicates that CRF, acting on CRFR1 receptors, may play a role in tectal inhibition of feeding behavior and food intake. Here we test the hypothesis that tectal CRFR1 receptors modulate food intake and feeding behavior in juvenile Xenopus laevis. We performed five experiments to test the following questions: 1) Does tectal CRF injection decrease food intake/feeding behavior? 2) Does a selective CRFR1 antagonist block CRF effects on feeding/feeding behavior? 3) Does a reactive stressor decrease food intake/feeding behavior? 4) Does a selective CRFR1 antagonist block reactive stress-induced decrease in feeding/feeding behavior? 5) Does food deprivation increase food intake/feeding behavior? Tectal CRF injections reduced food intake and influenced exploratory behavior, hindlimb kicks, and time in contact with food. These effects were blocked by the selective R1 antagonist NBI-27914. Exposure to a reactive stressor decreased food intake and this effect was blocked by NBI-27914. Neither food intake or feeding behavior changed following 1 wk of food deprivation. Overall, we conclude that activation of tectal CRFR1 inhibits food intake in juvenile X. laevis. Furthermore, tectal CRFR1 receptors appear to be involved in the reduction of food intake that occurs in response to a reactive stressor.
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Affiliation(s)
- Christine M Prater
- Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409-3131, United States of America
| | - Breanna N Harris
- Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409-3131, United States of America
| | - James A Carr
- Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409-3131, United States of America.
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Patel V, Joharapurkar A, Kshirsagar S, Sutariya B, Patel M, Patel H, Pandey D, Patel D, Bahekar R, Jain M. Central administration of coagonist of GLP-1 and glucagon receptors improves dyslipidemia. Biomed Pharmacother 2018; 98:364-371. [DOI: 10.1016/j.biopha.2017.12.068] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 11/29/2017] [Accepted: 12/15/2017] [Indexed: 12/25/2022] Open
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Tachibana T, Tsutsui K. Neuropeptide Control of Feeding Behavior in Birds and Its Difference with Mammals. Front Neurosci 2016; 10:485. [PMID: 27853416 PMCID: PMC5089991 DOI: 10.3389/fnins.2016.00485] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/10/2016] [Indexed: 12/29/2022] Open
Abstract
Feeding is an essential behavior for animals to sustain their lives. Over the past several decades, many neuropeptides that regulate feeding behavior have been identified in vertebrates. These neuropeptides are called “feeding regulatory neuropeptides.” There have been numerous studies on the role of feeding regulatory neuropeptides in vertebrates including birds. Some feeding regulatory neuropeptides show different effects on feeding behavior between birds and other vertebrates, particularly mammals. The difference is marked with orexigenic neuropeptides. For example, melanin-concentrating hormone, orexin, and motilin, which are regarded as orexigenic neuropeptides in mammals, have no effect on feeding behavior in birds. Furthermore, ghrelin and growth hormone-releasing hormone, which are also known as orexigenic neuropeptides in mammals, suppress feeding behavior in birds. Thus, it is likely that the feeding regulatory mechanism has changed during the evolution of vertebrates. This review summarizes the recent knowledge of peptidergic feeding regulatory factors in birds and discusses the difference in their action between birds and other vertebrates.
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Affiliation(s)
- Tetsuya Tachibana
- Laboratory of Animal Production, Department of Agrobiological Science, Faculty of Agriculture, Ehime University Matsuyama, Japan
| | - Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University Tokyo, Japan
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Honda K. Glucagon-related peptides and the regulation of food intake in chickens. Anim Sci J 2016; 87:1090-8. [PMID: 27150835 PMCID: PMC5084811 DOI: 10.1111/asj.12619] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 12/01/2015] [Accepted: 12/07/2015] [Indexed: 01/17/2023]
Abstract
The regulatory mechanisms underlying food intake in chickens have been a focus of research in recent decades to improve production efficiency when raising chickens. Lines of evidence have revealed that a number of brain‐gut peptides function as a neurotransmitter or peripheral satiety hormone in the regulation of food intake both in mammals and chickens. Glucagon, a 29 amino acid peptide hormone, has long been known to play important roles in maintaining glucose homeostasis in mammals and birds. However, the glucagon gene encodes various peptides that are produced by tissue‐specific proglucagon processing: glucagon is produced in the pancreas, whereas oxyntomodulin (OXM), glucagon‐like peptide (GLP)‐1 and GLP‐2 are produced in the intestine and brain. Better understanding of the roles of these peptides in the regulation of energy homeostasis has led to various physiological roles being proposed in mammals. For example, GLP‐1 functions as an anorexigenic neurotransmitter in the brain and as a postprandial satiety hormone in the peripheral circulation. There is evidence that OXM and GLP‐2 also induce anorexia in mammals. Therefore, it is possible that the brain‐gut peptides OXM, GLP‐1 and GLP‐2 play physiological roles in the regulation of food intake in chickens. More recently, a novel GLP and its specific receptor were identified in the chicken brain. This review summarizes current knowledge about the role of glucagon‐related peptides in the regulation of food intake in chickens.
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Affiliation(s)
- Kazuhisa Honda
- Graduate School of Agricultural Science, Kobe University, Kobe, Japan
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Busby ER, Mommsen TP. Proglucagons in vertebrates: Expression and processing of multiple genes in a bony fish. Comp Biochem Physiol B Biochem Mol Biol 2016; 199:58-66. [PMID: 26927880 DOI: 10.1016/j.cbpb.2016.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 02/17/2016] [Accepted: 02/17/2016] [Indexed: 11/16/2022]
Abstract
In contrast to mammals, where a single proglucagon (PG) gene encodes three peptides: glucagon, glucagon-like peptide 1 and glucagon-like peptide 2 (GLP-1; GLP-2), many non-mammalian vertebrates carry multiple PG genes. Here, we investigate proglucagon mRNA sequences, their tissue expression and processing in a diploid bony fish. Copper rockfish (Sebastes caurinus) express two independent genes coding for distinct proglucagon sequences (PG I, PG II), with PG II lacking the GLP-2 sequence. These genes are differentially transcribed in the endocrine pancreas, the brain, and the gastrointestinal tract. Alternative splicing identified in rockfish is only one part of this complex regulation of the PG transcripts: the system has the potential to produce two glucagons, four GLP-1s and a single GLP-2, or any combination of these peptides. Mass spectrometric analysis of partially purified PG-derived peptides in endocrine pancreas confirms translation of both PG transcripts and differential processing of the resulting peptides. The complex differential regulation of the two PG genes and their continued presence in this extant teleostean fish strongly suggests unique and, as yet largely unidentified, roles for the peptide products encoded in each gene.
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Affiliation(s)
- Ellen R Busby
- Department of Biochemistry and Microbiology, and Department of Biology, University of Victoria, Victoria, BC, Canada.
| | - Thomas P Mommsen
- Department of Biochemistry and Microbiology, and Department of Biology, University of Victoria, Victoria, BC, Canada
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Patel V, Joharapurkar AA, Kshirsagar SG, Patel KN, Bahekar R, Shah G, Jain MR. Central GLP-1 receptor activation improves cholesterol metabolism partially independent of its effect on food intake. Can J Physiol Pharmacol 2016; 94:161-167. [DOI: 10.1139/cjpp-2014-0457] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) receptor agonists modulate lipid metabolism, apart from controlling glucose homeostasis. We investigated the role of central GLP-1 receptor (GLP-1R) agonism in regulation of hepatic lipid metabolism in cholesterol-fed hamsters. Cholesterol-fed hamsters were treated by intracerebroventricular (i.c.v.) route with exendin-4, as acute or repeated dose regimen and compared with hamsters pair-fed to the exendin-treated hamsters and with hamsters co-treated with GLP-1 antagonist exendin-9. Effect of acute treatment was observed on food intake, tyloxapol-induced hypertriglyceridemia, and corn oil induced post prandial lipemia. Plasma and hepatic lipids and changes in the expression of hepatic genes involved in lipid metabolism were assessed after chronic administration. Acute, as well as repeated dose, treatment of exendin-4 showed significant changes in hepatic lipids, circulating fatty acids, triglycerides, LDL, and cholesterol. Expression of SREBP-1c was reduced while that of LDLR and CYP7A1 was increased after the repeated dose treatment, and there was no change in HMG CoA reductase. These changes were blocked by co-treatment of exendin-9, and not replicated by pair feeding to the significant extent. Central GLP-1 receptor activation showed profound effects on peripheral lipid metabolism, which were partially independent of its effect on food intake.
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Affiliation(s)
- Vishal Patel
- Department of Pharmacology & Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Sarkhej-Bavla N.H.No.8A, Moraiya, Ahmedabad 382210, India
- K.B. Institute of Pharmaceutical Education and Research, Gandhinagar 382023, Gujarat
| | - Amit Arvind Joharapurkar
- Department of Pharmacology & Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Sarkhej-Bavla N.H.No.8A, Moraiya, Ahmedabad 382210, India
| | - Samadhan Govind Kshirsagar
- Department of Pharmacology & Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Sarkhej-Bavla N.H.No.8A, Moraiya, Ahmedabad 382210, India
| | - Kartikkumar Navinchandra Patel
- Department of Pharmacology & Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Sarkhej-Bavla N.H.No.8A, Moraiya, Ahmedabad 382210, India
| | - Rajesh Bahekar
- Department of Medicinal Chemistry, Zydus Research Centre, Cadila Healthcare Limited, Sarkhej-Bavla N.H.No.8A, Moraiya, Ahmedabad 382210, India
| | - Gaurang Shah
- K.B. Institute of Pharmaceutical Education and Research, Gandhinagar 382023, Gujarat
| | - Mukul R. Jain
- Department of Pharmacology & Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Sarkhej-Bavla N.H.No.8A, Moraiya, Ahmedabad 382210, India
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Onrust L, Ducatelle R, Van Driessche K, De Maesschalck C, Vermeulen K, Haesebrouck F, Eeckhaut V, Van Immerseel F. Steering Endogenous Butyrate Production in the Intestinal Tract of Broilers as a Tool to Improve Gut Health. Front Vet Sci 2015; 2:75. [PMID: 26734618 PMCID: PMC4682374 DOI: 10.3389/fvets.2015.00075] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 11/30/2015] [Indexed: 12/11/2022] Open
Abstract
The ban on antimicrobial growth promoters and efforts to reduce therapeutic antibiotic usage has led to major problems of gastrointestinal dysbiosis in livestock production in Europe. Control of dysbiosis without the use of antibiotics requires a thorough understanding of the interaction between the microbiota and the host mucosa. The gut microbiota of the healthy chicken is highly diverse, producing various metabolic end products, including gases and fermentation acids. The distal gut knows an abundance of bacteria from within the Firmicutes Clostridium clusters IV and XIVa that produce butyric acid, which is one of the metabolites that are sensed by the host as a signal. The host responds by strengthening the epithelial barrier, reducing inflammation, and increasing the production of mucins and antimicrobial peptides. Stimulating the colonization and growth of butyrate-producing bacteria thus may help optimizing gut health. Various strategies are available to stimulate butyrate production in the distal gut. These include delivery of prebiotic substrates that are broken down by bacteria into smaller molecules which are then used by butyrate producers, a concept called cross-feeding. Xylo-oligosaccharides (XOS) are such compounds as they can be converted to lactate, which is further metabolized to butyrate. Probiotic lactic acid producers can be supplied to support the cross-feeding reactions. Direct feeding of butyrate-producing Clostridium cluster IV and XIVa strains are a future tool provided that large scale production of strictly anaerobic bacteria can be optimized. Current results of strategies that promote butyrate production in the gut are promising. Nevertheless, our current understanding of the intestinal ecosystem is still insufficient, and further research efforts are needed to fully exploit the capacity of these strategies.
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Affiliation(s)
- Lonneke Onrust
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University , Merelbeke , Belgium
| | - Richard Ducatelle
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University , Merelbeke , Belgium
| | - Karolien Van Driessche
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University , Merelbeke , Belgium
| | - Celine De Maesschalck
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University , Merelbeke , Belgium
| | - Karen Vermeulen
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University , Merelbeke , Belgium
| | - Freddy Haesebrouck
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University , Merelbeke , Belgium
| | - Venessa Eeckhaut
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University , Merelbeke , Belgium
| | - Filip Van Immerseel
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University , Merelbeke , Belgium
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Honda K, Saneyasu T, Shimatani T, Aoki K, Yamaguchi T, Nakanishi K, Kamisoyama H. Intracerebroventricular administration of chicken glucagon-like peptide-2 potently suppresses food intake in chicks. Anim Sci J 2014; 86:312-8. [DOI: 10.1111/asj.12282] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 06/11/2014] [Indexed: 12/23/2022]
Affiliation(s)
- Kazuhisa Honda
- Department of Bioresource Science; Graduate School of Agricultural Science; Kobe University; Kobe Japan
| | - Takaoki Saneyasu
- Department of Bioresource Science; Graduate School of Agricultural Science; Kobe University; Kobe Japan
| | - Tomohiko Shimatani
- Department of Bioresource Science; Graduate School of Agricultural Science; Kobe University; Kobe Japan
| | - Koji Aoki
- Department of Bioresource Science; Graduate School of Agricultural Science; Kobe University; Kobe Japan
| | - Takuya Yamaguchi
- Department of Bioresource Science; Graduate School of Agricultural Science; Kobe University; Kobe Japan
| | - Kiwako Nakanishi
- Department of Bioresource Science; Graduate School of Agricultural Science; Kobe University; Kobe Japan
| | - Hiroshi Kamisoyama
- Department of Bioresource Science; Graduate School of Agricultural Science; Kobe University; Kobe Japan
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Huang G, He C, Meng F, Li J, Zhang J, Wang Y. Glucagon-like peptide (GCGL) is a novel potential TSH-releasing factor (TRF) in Chickens: I) Evidence for its potent and specific action on stimulating TSH mRNA expression and secretion in the pituitary. Endocrinology 2014; 155:4568-80. [PMID: 25076122 DOI: 10.1210/en.2014-1331] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Our recent study proposed that the novel glucagon-like peptide (GCGL), encoded by a glucagon-like gene identified in chickens and other lower vertebrates, is likely a hypophysiotropic factor in nonmammalian vertebrates. To test this hypothesis, in this study, we investigated the GCGL action on chicken pituitaries. The results showed that: 1) GCGL, but not TRH, potently and specifically stimulates TSH secretion in intact pituitaries incubated in vitro or in cultured pituitary cells monitored by Western blotting or a cell-based luciferase reporter assay; 2) GCGL (0.1nM-10nM) dose dependently induces the mRNA expression of TSHβ but not 5 other hormone genes in cultured pituitary cells examined by quantitative real-time RT-PCR, an action likely mediated by intracellular adenylate cyclase/cAMP/protein kinase A and phospholipase C/inositol 1,4,5-trisphosphate/Ca(2+) signaling pathways coupled to GCGL receptor (GCGLR); 3) GCGLR mRNA is mainly localized in pituitary cephalic lobe demonstrated by in situ hybridization, where TSH-cells reside, further supporting a direct action of GCGL on thyrotrophs. The potent and specific action of GCGL on pituitary TSH expression and secretion, together with the partial accordance shown among the temporal expression profiles of GCGL in the hypothalamus and GCGLR and TSHβ in the pituitary, provides the first collective evidence that hypothalamic GCGL is most likely to be a novel TSH-releasing factor functioning in chickens. The discovery of this novel potential TSH-releasing factor (GCGL) in a nonmammalian vertebrate species, ie, chickens, would facilitate our comprehensive understanding of the hypothalamic control of pituitary-thyroid axis across vertebrates.
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Affiliation(s)
- Guian Huang
- Key Laboratory of Bioresources and Ecoenvironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, People's Republic of China
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