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Ahrén B, Yamada Y, Seino Y. The Insulin Response to Oral Glucose in GIP and GLP-1 Receptor Knockout Mice: Review of the Literature and Stepwise Glucose Dose Response Studies in Female Mice. Front Endocrinol (Lausanne) 2021; 12:665537. [PMID: 34122340 PMCID: PMC8190331 DOI: 10.3389/fendo.2021.665537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 04/21/2021] [Indexed: 12/31/2022] Open
Abstract
A key factor for the insulin response to oral glucose is the pro-glucagon derived incretin hormone glucagon-like peptide-1 (GLP-1), together with the companion incretin hormone, glucose-dependent insulinotropic polypeptide (GIP). Studies in GIP and GLP-1 receptor knockout (KO) mice have been undertaken in several studies to examine this role of the incretin hormones. In the present study, we reviewed the literature on glucose and insulin responses to oral glucose in these mice. We found six publications with such studies reporting results of thirteen separate study arms. The results were not straightforward, since glucose intolerance in GIP or GLP-1 receptor KO mice were reported only in eight of the arms, whereas normal glucose tolerance was reported in five arms. A general potential weakness of the published study is that each of them have examined effects of only one single dose of glucose. In a previous study in mice with genetic deletion of both GLP-1 and GIP receptors we showed that these mice have impaired insulin response to oral glucose after large but not small glucose loads, suggesting that the relevance of the incretin hormones may be dependent on the glucose load. To further test this hypothesis, we have now performed a stepwise glucose administration through a gastric tube (from zero to 125mg) in model experiments in anesthetized female wildtype, GLP-1 receptor KO and GIP receptor KO mice. We show that GIP receptor KO mice exhibit glucose intolerance in the presence of impaired insulin response after 100 and 125 mg glucose, but not after lower doses of glucose. In contrast, GLP-1 receptor KO mice have normal glucose tolerance after all glucose loads, in the presence of a compensatory increase in the insulin response. Therefore, based on these results and the literature survey, we suggest that GIP and GLP-1 receptor KO mice retain normal glucose tolerance after oral glucose, except after large glucose loads in GIP receptor KO mice, and we also show an adaptive mechanism in GLP-1 receptor KO mice, which needs to be further examined.
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Affiliation(s)
- Bo Ahrén
- Department of Clinical Sciences Lund, Lund University, Lund, Sweden
| | - Yuichiro Yamada
- Department of Endocrinology, Diabetes and Geriatric Medicine, Graduate School of Medicine, Akita University, Akita, Japan
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Lynggaard MB, Gasbjerg LS, Christensen MB, Knop FK. GIP(3-30)NH 2 - a tool for the study of GIP physiology. Curr Opin Pharmacol 2020; 55:31-40. [PMID: 33053504 DOI: 10.1016/j.coph.2020.08.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [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: 06/10/2020] [Revised: 08/12/2020] [Accepted: 08/25/2020] [Indexed: 12/25/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is a gut hormone impacting glucose, lipid and bone metabolism through the GIP receptor (GIPR). The GIP system has key species differences complicating the translation of findings from rodent to human physiology. Furthermore, the effects of endogenous GIP in humans have been difficult to tease out due to the lack of a suitable GIPR antagonist. The naturally occurring GIP(3-30)NH2 has turned out to constitute a safe and efficacious GIPR antagonist for rodent and human use. To study GIP physiology, it is recommended to use the species-specific GIP(3-30)NH2 peptide sequence, and for human intravenous infusions, an antagonist:agonist ratio of a minimum of 600 with a 20min infusion time before the intervention of interest is recommended. Several studies using GIP(3-30)NH2 are coming, hopefully providing new insights into the physiology of GIP, the pathophysiologic involvement of GIP in several diseases and the therapeutic potential of the GIPR.
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Affiliation(s)
- Mads Bank Lynggaard
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | - Lærke Smidt Gasbjerg
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mikkel Bring Christensen
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Clinical Pharmacology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Filip Krag Knop
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Steno Diabetes Center Copenhagen, Gentofte, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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Fu Y, Kaneko K, Lin HY, Mo Q, Xu Y, Suganami T, Ravn P, Fukuda M. Gut Hormone GIP Induces Inflammation and Insulin Resistance in the Hypothalamus. Endocrinology 2020; 161:5865317. [PMID: 32603429 PMCID: PMC7410368 DOI: 10.1210/endocr/bqaa102] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 06/24/2020] [Indexed: 02/08/2023]
Abstract
The hypothalamus plays a critical role in controlling energy balance. High-fat diet (HFD) feeding increases the gene expression of proinflammatory mediators and decreases insulin actions in the hypothalamus. Here, we show that a gut-derived hormone, glucose-dependent insulinotropic polypeptide (GIP), whose levels are elevated during diet-induced obesity, promotes and mediates hypothalamic inflammation and insulin resistance during HFD-induced obesity. Unbiased ribonucleic acid sequencing of GIP-stimulated hypothalami revealed that hypothalamic pathways most affected by intracerebroventricular (ICV) GIP stimulation were related to inflammatory-related responses. Subsequent analysis demonstrated that GIP administered either peripherally or centrally, increased proinflammatory-related factors such as Il-6 and Socs3 in the hypothalamus, but not in the cortex of C57BL/6J male mice. Consistently, hypothalamic activation of IκB kinase-β inflammatory signaling was induced by ICV GIP. Further, hypothalamic levels of proinflammatory cytokines and Socs3 were significantly reduced by an antagonistic GIP receptor (GIPR) antibody and by GIPR deficiency. Additionally, centrally administered GIP reduced anorectic actions of insulin in the brain and diminished insulin-induced phosphorylation of Protein kinase B and Glycogen synthase kinase 3β in the hypothalamus. Collectively, these findings reveal a previously unrecognized role for brain GIP signaling in diet-induced inflammation and insulin resistance in the hypothalamus.
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Affiliation(s)
- Yukiko Fu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
- Department of Molecular Medicine and Metabolism, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan
| | - Kentaro Kaneko
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Hsiao-Yun Lin
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Qianxing Mo
- Dan L Duncan Cancer Center and Center for Cell Gene & Therapy, Baylor College of Medicine, Houston, Texas
- Present address: Department of Biostatistics & Bioinformatics, H. Lee Moffitt Cancer Center & Research Institute, Tampa, Florida 33612
| | - Yong Xu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas
| | - Takayoshi Suganami
- Department of Molecular Medicine and Metabolism, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan
| | - Peter Ravn
- AstraZeneca, R&D BioPharmaceuticals Unit, Department of Antibody Discovery and Protein Engineering, Cambridge, UK
| | - Makoto Fukuda
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
- Correspondence: Makoto Fukuda, Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA. E-mail:
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Abstract
Glucose-dependent insulinotropic polypeptide (GIP) receptor knockout (KO) mice are tools for studying GIP physiology. Previous results have demonstrated that these mice have impaired insulin response to oral glucose. In this study, we examined the insulin response to intravenous glucose by measuring glucose, insulin and C-peptide after intravenous glucose (0.35 g/kg) in 5-h fasted female GIP receptor KO mice and their wild-type (WT) littermates. The 1 min insulin and C-peptide responses to intravenous glucose were significantly enhanced in GIP receptor KO mice (n = 26) compared to WT mice (n = 30) as was beta cell function (area under the 50 min C-peptide curve divided by area under the 50 min curve for glucose) (P = 0.001). Beta cell function after intravenous glucose was also enhanced in GIP receptor KO mice in the presence of the glucagon-like peptide-1 receptor antagonist exendin 9 (30 nmol/kg; P = 0.007), the muscarinic antagonist atropine (5 mg/kg; P = 0.007) and the combination of the alpha-adrenoceptor antagonist yohimbine (1.4 mg/kg) and the beta-adrenoceptor antagonist propranolol (2.5 mg/kg; P = 0.042). Analysis of the regression between fasting glucose (6.8 ± 0.1 mmol/l in GIP receptor KO mice and 7.5 ± 0.2 mmol/l in WT mice, P = 0.003) and the 1 min C-peptide response to intravenous glucose showed a negative linear regression between these variables in both WT (n = 60; r = -0.425, P = 0.001) and GIP receptor KO mice (n = 56; r = -0.474, P < 0.001). We conclude that there is a beta cell adaptation in GIP receptor KO mice resulting in enhanced insulin secretion after intravenous glucose to which slight long-term reduction in circulating glucose in these mice may contribute.
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Affiliation(s)
- Bo Ahrén
- Department of Clinical Sciences Lund, Lund university, Lund, Sweden.
| | - Yuchiro Yamada
- Department of Endocrinology, Diabetes and Geriatric Medicine, Graduate School of Medicine, Akita University, Akita, Japan
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Kruse M, Keyhani-Nejad F, Osterhoff MA, Pfeiffer AFH. Sexually dimorphic metabolic responses to exposure of a high fat diet during pregnancy, lactation and early adulthood in Gipr -/- mice. Peptides 2020; 125:170250. [PMID: 31917165 DOI: 10.1016/j.peptides.2019.170250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 12/22/2019] [Accepted: 12/26/2019] [Indexed: 12/25/2022]
Abstract
Obesity has a multifactorial origin. It is known that alterations of the intra uterine milieu induce developmental programming effects leading to metabolic diseases in offspring. Obesity is diminished in mice lacking the glucose-dependent insulinotropic polypeptide receptor (Gipr-/-) when exposed to a high fat diet (HFD). We investigated whether Gipr-/- mice are still protected from obesity when additionally exposure to a HFD during pregnancy and lactation occurs. Male and female wild type (WT) and Gipr-/- offspring received either a control/ low fat diet or HFD during pregnancy and lactation and were then either left on this diet or placed on the opposite diet after weaning until 24 weeks of life. Female WT mice showed increased body weight and adiposity when exposed to a HFD during pregnancy and lactation and post-weaning compared to female WT that received the HFD after weaning only. This exacerbated effect of a HFD during pregnancy and lactation was abolished in female Gipr-/- mice. Male Gipr-/- mice were protected from obesity to a much lesser extent. Male Gipr-/- mice exposed to a HFD during pregnancy and lactation and after weaning exhibited significantly increased fed serum glucose compared to Gipr-/- mice exposed to a HFD after weaning only. In female Gipr-/- mice no differences in fed blood glucose were observed between these groups. Our data indicate that female Gipr-/- mice are more protected from obesity. This protection is preserved in female Gipr-/- mice when additional deleterious effects of a HFD occur during fetal development.
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Affiliation(s)
- Michael Kruse
- Department of Clinical Nutrition, German Institute of Human Nutrition, Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany; Department for Endocrinology, Diabetes and Nutrition, Charité - University of Medicine, Hindenburgdamm 30, 12200 Berlin, Germany
| | - Farnaz Keyhani-Nejad
- Department of Clinical Nutrition, German Institute of Human Nutrition, Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany; Department for Endocrinology, Diabetes and Nutrition, Charité - University of Medicine, Hindenburgdamm 30, 12200 Berlin, Germany
| | - Martin A Osterhoff
- Department of Clinical Nutrition, German Institute of Human Nutrition, Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany; Department for Endocrinology, Diabetes and Nutrition, Charité - University of Medicine, Hindenburgdamm 30, 12200 Berlin, Germany
| | - Andreas F H Pfeiffer
- Department of Clinical Nutrition, German Institute of Human Nutrition, Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany; Department for Endocrinology, Diabetes and Nutrition, Charité - University of Medicine, Hindenburgdamm 30, 12200 Berlin, Germany; German Center for Diabetes Research, Germany.
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Zhang CY, Boylan MO, Arakawa H, Wolfe MM. Effects of gastric inhibitory polypeptide (GIP) immunoneutralization on mouse motor coordination and memory. Peptides 2020; 125:170227. [PMID: 31805296 DOI: 10.1016/j.peptides.2019.170227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 11/27/2019] [Accepted: 11/29/2019] [Indexed: 11/20/2022]
Abstract
Gastric inhibitory polypeptide (GIP) is a regulatory peptide expressed in the mammalian upper small intestine, and both GIP and its receptor (GIPR) are expressed in the cortex and hippocampus regions of the brain as well. While learning and memory deficits have been observed in GIPR-/- mice, the effects of peripheral GIP immunoneutralization on motor-coordination, learning, and memory have not been examined. In the present study, adult GIPR-/- mice (KO) and age-matched wild-type C57BL/6 J mice (WT) received weekly vehicle PBS injections for 12 weeks, while a third group of wild-type mice were injected weekly for 12 weeks with 30 mg/kg body weight humanized GIP-mAb (AB) to assess the possibility of long-term effects of peripheral GIP antagonism on rodent memory and behavior. All mice groups then underwent a battery of tests that evaluated motor behavior, body coordination, and memory. Performance deficits in several memory studies after 12 weeks of treatment were demonstrated in KO, but not in AB or WT mice. Body coordination performance showed no significant differences among the 3 groups. A similar short-term study (3 injections over 9 days) was also conducted and the results were similar to those from the long-term study. Thus, short-term and long-term peripheral GIP antagonism by GIP-mAb did not appear to affect learning and memory in mice, consistent with the notion that the GIP-mAb does not cross the blood brain barrier. Furthermore, our studies indicate that GIP signaling in the brain appears to involve local neurocrine pathways.
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Affiliation(s)
- Claire Y Zhang
- Division of Gastroenterology, MetroHealth Medical Center, Case Western Reserve University, Cleveland, OH, United States
| | - Michael O Boylan
- Division of Gastroenterology, MetroHealth Medical Center, Case Western Reserve University, Cleveland, OH, United States
| | - Hiroyuki Arakawa
- Department of Neuroscience, Case Western Reserve University, Cleveland, OH, United States
| | - M Michael Wolfe
- Division of Gastroenterology, MetroHealth Medical Center, Case Western Reserve University, Cleveland, OH, United States; Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, United States.
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Wu N, Meng F, Zhou T, Venter J, Giang TK, Kyritsi K, Wu C, Alvaro D, Onori P, Mancinelli R, Gaudio E, Francis H, Alpini G, Glaser S, Franchitto A. The Secretin/Secretin Receptor Axis Modulates Ductular Reaction and Liver Fibrosis through Changes in Transforming Growth Factor-β1-Mediated Biliary Senescence. Am J Pathol 2018; 188:2264-2280. [PMID: 30036520 PMCID: PMC6168967 DOI: 10.1016/j.ajpath.2018.06.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/26/2018] [Accepted: 06/19/2018] [Indexed: 12/12/2022]
Abstract
Activation of the secretin (Sct)/secretin receptor (SR) axis stimulates ductular reaction and liver fibrosis, which are hallmarks of cholangiopathies. Our aim was to define the role of Sct-regulated cellular senescence, and we demonstrated that both ductular reaction and liver fibrosis are significantly reduced in Sct-/-, SR-/-, and Sct-/-/SR-/- bile duct ligated (BDL) mice compared with BDL wild-type mice. The reduction in hepatic fibrosis in Sct-/-, SR-/-, and Sct-/-/SR-/- BDL mice was accompanied by reduced transforming growth factor-β1 levels in serum and cholangiocyte supernatant, as well as decreased expression of markers of cellular senescence in cholangiocytes in contrast to enhanced cellular senescence in hepatic stellate cells compared with BDL wild-type mice. Secretin directly stimulated the senescence of cholangiocytes and regulated, by a paracrine mechanism, the senescence of hepatic stellate cells and liver fibrosis via modulation of transforming growth factor-β1 biliary secretion. Targeting senescent cholangiocytes may represent a novel therapeutic approach for ameliorating hepatic fibrosis during cholestatic liver injury.
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Affiliation(s)
- Nan Wu
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Fanyin Meng
- Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Baylor Scott & White Health Care, Temple, Texas
| | - Tianhao Zhou
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Julie Venter
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Thao K Giang
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Konstantina Kyritsi
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Chaodong Wu
- Department of Nutrition and Food Science, Texas A&M University, College Station, Texas
| | | | - Paolo Onori
- Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Sapienza, Rome, Italy
| | - Romina Mancinelli
- Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Sapienza, Rome, Italy
| | - Eugenio Gaudio
- Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Sapienza, Rome, Italy
| | - Heather Francis
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas; Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Baylor Scott & White Health Care, Temple, Texas
| | - Gianfranco Alpini
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas; Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Baylor Scott & White Health Care, Temple, Texas.
| | - Shannon Glaser
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas; Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Baylor Scott & White Health Care, Temple, Texas
| | - Antonio Franchitto
- Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Sapienza, Rome, Italy; Department of Medicine, Sapienza, Rome, Italy; Eleonora Lorillard Spencer Cenci Foundation, Rome, Italy
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Shimizu T, Sato T, Tsukiyama K, Fujita H, Kato S, Hoizumi M, Shirasawa H, Narita T, Terada Y, Seino Y, Yamada Y. Food Intake Affects Sperm-Egg Fusion Through the GIP/PSG17 Axis in Mice. Endocrinology 2017; 158:2134-2144. [PMID: 28430907 DOI: 10.1210/en.2016-1861] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [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: 11/22/2016] [Accepted: 04/14/2017] [Indexed: 12/30/2022]
Abstract
In addition to overeating, starvation also reduces fecundity in mammals. However, little is known about the molecular mechanisms linking food intake to fertility, especially in males. Gastric inhibitory polypeptide (GIP), which is released from intestinal K-cells after meal ingestion, stimulates insulin secretion from pancreatic β-cells through the action of incretin and has several extrapancreatic effects. Here, we identified GIP receptor (Gipr) expression in mouse spermatids. Microarray analysis revealed that pregnancy-specific glycoprotein 17 (Psg17), a potential CD9-binding partner, was significantly decreased in GIP receptor-knockout (Gipr-/-) testes. Glycosylphosphatidylinositol-anchored PSG17 was expressed on the surface of acrosome-reacted sperm, and Gipr-/- sperm led to a lower fertilization rate in vitro, compared with that of Gipr+/+ sperm, both in the absence and presence of the zona pellucida. Plasma GIP concentrations and Psg17 messenger RNA (mRNA) were immediately increased in the testis after a single meal, whereas ingestion of a chronic high-fat diet markedly decreased Gipr and Psg17 mRNA. These results suggest that reduced GIP signaling, by decreased GIP levels or the downregulation of Gipr, is associated with the reduction of fecundity due to starvation or overeating. Thus, proper regulation of GIP signaling in the testis could be a potential unique therapeutic target for male infertility in obese and diabetic individuals.
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Affiliation(s)
- Tatsunori Shimizu
- Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Takehiro Sato
- Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Katsushi Tsukiyama
- Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Hiroki Fujita
- Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Shunsuke Kato
- Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Manabu Hoizumi
- Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Hiromitsu Shirasawa
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Takuma Narita
- Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Yukihiro Terada
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita 010-8543, Japan
| | - Yutaka Seino
- Kansai Electric Power Medical Research Institute, Osaka 553-0003, Japan
| | - Yuichiro Yamada
- Department of Endocrinology, Diabetes, and Geriatric Medicine, Akita University Graduate School of Medicine, Akita 010-8543, Japan
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Malbert CH. [The brain-gut axis: insights from the obese pig model]. Bull Acad Natl Med 2013; 197:1683-1699. [PMID: 26137814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The pig, which shares several similarities with humans, is increasingly used for biomedical research, particularly in nutrition and neurosciences. Recent studies in minipigs have shown that a deleterious nutritional environment (e.g. a high-fat and high-sugar diet) induces obesity which, as in humans, is associated with increased adiposity, insulin resistance, modified eating behaviour, and altered gastric function and intestinal sensitivity. These changes are accompanied by differences in the activation matrices and metabolic activity of several brain areas. Using this animal model, we have revisited the concept of dual hedonic and homeostatic control of food intake. We have thus developed a minimally invasive and potentially reversible surgical approach to the control of food intake, as an alternative to bariatric surgery, based on chronic vagal stimulation at the abdominal level.
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Affiliation(s)
- Charles-Henri Malbert
- Unité Alimentation & Adaptations Digestives, Nerveuses et Comportementales, INRA, Domaine de la Prise - 35590 Saint-Gilles, France.
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Gaudin-Audrain C, Irwin N, Mansur S, Flatt PR, Thorens B, Baslé M, Chappard D, Mabilleau G. Glucose-dependent insulinotropic polypeptide receptor deficiency leads to modifications of trabecular bone volume and quality in mice. Bone 2013; 53:221-30. [PMID: 23220186 DOI: 10.1016/j.bone.2012.11.039] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [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: 07/13/2012] [Revised: 11/13/2012] [Accepted: 11/28/2012] [Indexed: 12/12/2022]
Abstract
A role for the gastro-intestinal tract in controlling bone remodeling is suspected since serum levels of bone remodeling markers are affected rapidly after a meal. Glucose-dependent insulinotropic polypeptide (GIP) represents a suitable candidate in mediating this effect. The aim of the present study was to investigate the effect of total inhibition of GIP signaling on trabecular bone volume, microarchitecture and quality. We used GIP receptor (GIPR) knockout mice and investigated trabecular bone volume and microarchitecture by microCT and histomorphometry. GIPR-deficient animals at 16 weeks of age presented with a significant (20%) increase in trabecular bone mass accompanied by an increase (17%) in trabecular number. In addition, the number of osteoclasts and bone formation rate was significantly reduced and augmented, respectively in these animals when compared with wild-type littermates. These modifications of trabecular bone microarchitecture are linked to a remodeling in the expression pattern of adipokines in the GIPR-deficient mice. On the other hand, despite significant enhancement in bone volume, intrinsic mechanical properties of the bone matrix was reduced as well as the distribution of bone mineral density and the ratio of mature/immature collagen cross-links. Taken together, these results indicate an increase in trabecular bone volume in GIPR KO animals associated with a reduction in bone quality.
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Heinzlmann A, Kiss G, Tóth ZE, Dochnal R, Pál Á, Sipos I, Manczinger M, Szabó G, Hashimoto H, Köves K. Intranasal application of secretin, similarly to intracerebroventricular administration, influences the motor behavior of mice probably through specific receptors. J Mol Neurosci 2012; 48:558-64. [PMID: 22752505 DOI: 10.1007/s12031-012-9839-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [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: 03/27/2012] [Accepted: 06/11/2012] [Indexed: 11/27/2022]
Abstract
Secretin and its receptors show wide distribution in the central nervous system. It was demonstrated previously that intravenous (i.v.) and intracerebroventricular (i.c.v.) application of secretin influenced the behavior of rat, mouse, and human. In our previous experiment, we used a special animal model, Japanese waltzing mice (JWM). These animals run around without stopping (the ambulation distance is very limited) and they do not bother with their environment. The i.c.v. secretin attenuated this hyperactive repetitive movement. In the present work, the effect of i.c.v. and intranasal (i.n.) application of secretin was compared. We have also looked for the presence of secretin receptors in the brain structures related to motor functions. Two micrograms of i.c.v. secretin improved the horizontal movement of JWM, enhancing the ambulation distance. It was nearly threefold higher in treated than in control animals. The i.n. application of secretin to the left nostril once or twice a day or once for 3 days more effectively enhanced the ambulation distance than i.c.v. administration. When secretin was given twice a day for 3 days it had no effect. Secretin did not improve the explorative behavior (the rearing), of JWM. With the use of in situ hybridization, we have found very dense secretin receptor labeling in the cerebellum. In the primary motor cortex and in the striatum, only a few labeled cells were seen. It was supposed that secretin exerted its effect through specific receptors, mainly present in the cerebellum.
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MESH Headings
- Administration, Intranasal
- Animals
- Cerebellum/chemistry
- Cerebellum/drug effects
- Corpus Striatum/chemistry
- Drug Evaluation, Preclinical
- Exploratory Behavior/drug effects
- Female
- Hyperkinesis/drug therapy
- Hyperkinesis/genetics
- In Situ Hybridization
- Injections, Intraventricular
- Male
- Mice
- Mice, Neurologic Mutants
- Motor Activity/drug effects
- Motor Activity/physiology
- Motor Cortex/chemistry
- Nerve Tissue Proteins/agonists
- Nerve Tissue Proteins/analysis
- Nerve Tissue Proteins/physiology
- Rats
- Rats, Sprague-Dawley
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/analysis
- Receptors, G-Protein-Coupled/physiology
- Receptors, Gastrointestinal Hormone/agonists
- Receptors, Gastrointestinal Hormone/analysis
- Receptors, Gastrointestinal Hormone/physiology
- Secretin/administration & dosage
- Secretin/pharmacology
- Secretin/therapeutic use
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Affiliation(s)
- Andrea Heinzlmann
- Department of Human Morphology and Developmental Biology, Semmelweis University, Tűzoltó u. 58, Budapest 1094, Hungary
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12
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Bates HE, Campbell JE, Ussher JR, Baggio LL, Maida A, Seino Y, Drucker DJ. Gipr is essential for adrenocortical steroidogenesis; however, corticosterone deficiency does not mediate the favorable metabolic phenotype of Gipr(-/-) mice. Diabetes 2012; 61:40-8. [PMID: 22043004 PMCID: PMC3237652 DOI: 10.2337/db11-1060] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) promotes glucose-dependent insulin secretion. However, GIP also enhances glucocorticoid secretion and promotes adiposity. Because obesity and diabetes are glucocorticoid dependent, we examined whether the effects of GIP on energy balance and glycemia are regulated by glucocorticoids using pharmacological activation of GIP receptor (GIPR) signaling with [d-Ala(2)]GIP in mice and in Y1 adrenocortical cells. Genetic elimination of GIPR activity was also studied in normal- and high-fat (HF)-fed Gipr-deficient (Gipr(-/-)) mice. [d-Ala(2)]GIP increased murine corticosterone levels in a GIPR-dependent manner. Conversely, basal corticosterone levels were reduced, whereas food deprivation resulted in significantly enhanced plasma corticosterone levels in Gipr(-/-) mice. [d-Ala(2)]GIP increased cAMP levels, activated extracellular signal\x{2013}related kinase (ERK)1/2, increased expression of steroidogenic genes, and increased neutral lipid storage in Y1GIPR cells. Gipr(-/-) adrenal glands demonstrated a twofold upregulation of the ACTH receptor mRNA and increased sensitivity to ACTH ex vivo. Although HF-fed Gipr(-/-) mice exhibited significantly lower plasma corticosterone, glucocorticoid-treated HF-fed Gipr(-/-) mice had similar energy balance and glycemia compared with Gipr(+)(/+) controls. Hence, although the Gipr is essential for adrenal steroidogenesis and links HF feeding to increased levels of corticosterone, reduced glucocorticoid levels do not significantly contribute to the enhanced metabolic phenotypes in HF-fed Gipr(-/-) mice.
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Affiliation(s)
- Holly E. Bates
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Jonathan E. Campbell
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - John R. Ussher
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Laurie L. Baggio
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Adriano Maida
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | | | - Daniel J. Drucker
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
- Corresponding author: Daniel J. Drucker,
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13
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Waget A, Cabou C, Masseboeuf M, Cattan P, Armanet M, Karaca M, Castel J, Garret C, Payros G, Maida A, Sulpice T, Holst JJ, Drucker DJ, Magnan C, Burcelin R. Physiological and pharmacological mechanisms through which the DPP-4 inhibitor sitagliptin regulates glycemia in mice. Endocrinology 2011; 152:3018-29. [PMID: 21673098 DOI: 10.1210/en.2011-0286] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Inhibition of dipeptidyl peptidase-4 (DPP-4) activity improves glucose homeostasis through a mode of action related to the stabilization of the active forms of DPP-4-sensitive hormones such as the incretins that enhance glucose-induced insulin secretion. However, the DPP-4 enzyme is highly expressed on the surface of intestinal epithelial cells; hence, the role of intestinal vs. systemic DPP-4 remains unclear. To analyze mechanisms through which the DPP-4 inhibitor sitagliptin regulates glycemia in mice, we administered low oral doses of the DPP-4 inhibitor sitagliptin that selectively reduced DPP-4 activity in the intestine. Glp1r(-/-) and Gipr(-/-) mice were studied and glucagon-like peptide (GLP)-1 receptor (GLP-1R) signaling was blocked by an i.v. infusion of the corresponding receptor antagonist exendin (9-39). The role of the dipeptides His-Ala and Tyr-Ala as DPP-4-generated GLP-1 and glucose-dependent insulinotropic peptide (GIP) degradation products was studied in vivo and in vitro on isolated islets. We demonstrate that very low doses of oral sitagliptin improve glucose tolerance and plasma insulin levels with selective reduction of intestinal but not systemic DPP-4 activity. The glucoregulatory action of sitagliptin was associated with increased vagus nerve activity and was diminished in wild-type mice treated with the GLP-1R antagonist exendin (9-39) and in Glp1r(-/-) and Gipr(-/-) mice. Furthermore, the dipeptides liberated from GLP-1 (His-Ala) and GIP (Tyr-Ala) deteriorated glucose tolerance, reduced insulin, and increased portal glucagon levels. The predominant mechanism through which DPP-4 inhibitors regulate glycemia involves local inhibition of intestinal DPP-4 activity, activation of incretin receptors, reduced liberation of bioactive dipeptides, and activation of the gut-to-pancreas neural axis.
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Affiliation(s)
- Aurélie Waget
- Institut de Recherche sur les Maladies Métaboliques et Cardiovasculaires de l'Hôpital Rangueil, Inserm U1048, BP 84225, 31432 Toulouse Cedex 4, France
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14
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Harada N. [Structure and function of incretin receptor]. Nihon Rinsho 2011; 69:813-820. [PMID: 21595264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
G protein-coupled receptor (GPCR) is integral membrane protein with seven alfa-helices and most diverse families of protein in mammals. It is located on cell membrane and activated by binding neurotransmit proteins and hormones. It has critical role of functional regulation in central nerve system and peripheral organs. Recently, many orphan GPCRs have been identified from the data of genomic sequence in human genomic project. GIP receptor and GLP-1 receptor belong to glucagon receptor subfamily of class B and are widely expressed in many organs. GIP receptor is expressed in intestine, adipose tissue, brain, adrenal gland, and bone, while GLP-1 receptor is expressed in intestine, CNS, lung, kidney and heart. GIP and GLP-1 have not only pancreatic effect, such as potentiation of insulin secretion but also many extrapancreatic effects.
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Affiliation(s)
- Norio Harada
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University
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15
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Gupta D, Peshavaria M, Monga N, Jetton TL, Leahy JL. Physiologic and pharmacologic modulation of glucose-dependent insulinotropic polypeptide (GIP) receptor expression in beta-cells by peroxisome proliferator-activated receptor (PPAR)-gamma signaling: possible mechanism for the GIP resistance in type 2 diabetes. Diabetes 2010; 59:1445-50. [PMID: 20332343 PMCID: PMC2874705 DOI: 10.2337/db09-1655] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
OBJECTIVE We previously showed that peroxisome proliferator-activated receptor (PPAR)-gamma in beta-cells regulates pdx-1 transcription through a functional PPAR response element (PPRE). Gene Bank blast for a homologous nucleotide sequence revealed the same PPRE within the rat glucose-dependent insulinotropic polypeptide receptor (GIP-R) promoter sequence. We investigated the role of PPARgamma in GIP-R transcription. RESEARCH DESIGN AND METHODS Chromatin immunoprecipitation assay, siRNA, and luciferase gene transcription assay in INS-1 cells were performed. Islet GIP-R expression and immunohistochemistry studies were performed in pancreas-specific PPARgamma knockout mice (PANC PPARgamma(-/-)), normoglycemic 60% pancreatectomy rats (Px), normoglycemic and hyperglycemic Zucker fatty (ZF) rats, and mouse islets incubated with troglitazone. RESULTS In vitro studies of INS-1 cells confirmed that PPAR-gamma binds to the putative PPRE sequence and regulates GIP-R transcription. In vivo verification was shown by a 70% reduction in GIP-R protein expression in islets from PANC PPARgamma(-/-) mice and a twofold increase in islets of 14-day post-60% Px Sprague-Dawley rats that hyperexpress beta-cell PPARgamma. Thiazolidinedione activation (72 h) of this pathway in normal mouse islets caused a threefold increase of GIP-R protein and a doubling of insulin secretion to 16.7 mmol/l glucose/10 nmol/l GIP. Islets from obese normoglycemic ZF rats had twofold increased PPARgamma and GIP-R protein levels versus lean rats, with both lowered by two-thirds in ZF rats made hyperglycemic by 60% Px. CONCLUSIONS Our studies have shown physiologic and pharmacologic regulation of GIP-R expression in beta-cells by PPARgamma signaling. Also disruption of this signaling pathway may account for the lowered beta-cell GIP-R expression and resulting GIP resistance in type 2 diabetes.
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Affiliation(s)
- Dhananjay Gupta
- From the Division of Endocrinology, Diabetes, and Metabolism and the Department of Medicine, University of Vermont, Burlington, Vermont
| | - Mina Peshavaria
- From the Division of Endocrinology, Diabetes, and Metabolism and the Department of Medicine, University of Vermont, Burlington, Vermont
| | - Navjot Monga
- From the Division of Endocrinology, Diabetes, and Metabolism and the Department of Medicine, University of Vermont, Burlington, Vermont
| | - Thomas L. Jetton
- From the Division of Endocrinology, Diabetes, and Metabolism and the Department of Medicine, University of Vermont, Burlington, Vermont
| | - Jack L. Leahy
- From the Division of Endocrinology, Diabetes, and Metabolism and the Department of Medicine, University of Vermont, Burlington, Vermont
- Corresponding author: Jack L. Leahy,
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16
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Abstract
PURPOSE OF REVIEW This article highlights recent advances in our understanding of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) physiology and their various sites of action beyond the incretin effect. RECENT FINDINGS Both GLP-1 and GIP stimulate insulin secretion in a glucose-dependent manner and are thus classified as incretins. Beyond glucose-dependent insulin secretion, the peptides have common actions on islet beta cells, leading beta-cell proliferation and resistance to apoptosis. However, the action of GLP-1 and GIP is not limited to the islet cells; they have regulatory functions in many organs. Recent evidence has suggested that GLP-1 has important beneficial effects in the cardiovascular system and central nervous system. GIP may play a role in promoting energy storage in humans, enhances bone formation via stimulation of osteoblast proliferation and inhibition of apoptosis and may play a role in central nervous system function. SUMMARY These new findings suggest further application of these hormones for the treatment of conditions such as cardiovascular disease and obesity.
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Affiliation(s)
- Meena Asmar
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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17
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Abstract
GLP-1 protects β-cells against apoptosis by still incompletely understood mechanisms. In a recent study, we searched for novel anti-apoptotic pathways by performing comparative transcriptomic analysis of islets from Gipr-/-;Glp-1r-/- mice, which show increased susceptibility to cytokine-induced apoptosis. We observed a strong reduction in IGF-1R expression in the knockout islets suggesting a link between the gluco-incretin and IGF-1R signaling pathways. Using MIN6 and primary islet cells, we demonstrated that GLP-1 strongly stimulates IGF-1R expression and that activation of the IGF-1R/Akt signaling pathway required active secretion of IGF-2 by the β-cells. We showed that inactivation of the IGF-1 receptor gene in β-cells or preventing its up-regulation by GLP-1, as well as suppressing IGF-2 expression or action, blocked the protective effect of GLP-1 against cytokine-induced apoptosis. Thus, an IGF-2/IGF-1 receptor autocrine loop operates in β-cells and GLP-1 increases its activity by enhancing IGF-1R expression and by stimulating IGF-2 secretion. This mechanism is required for GLP-1 to protect β-cells against apoptosis.
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MESH Headings
- Animals
- Apoptosis/drug effects
- Apoptosis/genetics
- Autocrine Communication/genetics
- Autocrine Communication/physiology
- Cytoprotection/drug effects
- Cytoprotection/genetics
- Glucagon-Like Peptide 1/pharmacology
- Glucagon-Like Peptide-1 Receptor
- Insulin-Like Growth Factor II/metabolism
- Insulin-Like Growth Factor II/physiology
- Insulin-Secreting Cells/drug effects
- Insulin-Secreting Cells/metabolism
- Insulin-Secreting Cells/physiology
- Mice
- Mice, Knockout
- Receptor, IGF Type 1/genetics
- Receptor, IGF Type 1/metabolism
- Receptor, IGF Type 1/physiology
- Receptors, Gastrointestinal Hormone/genetics
- Receptors, Gastrointestinal Hormone/metabolism
- Receptors, Gastrointestinal Hormone/physiology
- Receptors, Glucagon/genetics
- Receptors, Glucagon/metabolism
- Receptors, Glucagon/physiology
- Up-Regulation/drug effects
- Up-Regulation/genetics
- Up-Regulation/physiology
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Affiliation(s)
- Marion Cornu
- Department of Physiology and Center for Integrative Genomics, University of Lausanne, Génopode Building, CH-1015 Lausanne, Switzerland
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18
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Isken F, Weickert MO, Tschöp MH, Nogueiras R, Möhlig M, Abdelrahman A, Klaus S, Thorens B, Pfeiffer AF. Metabolic effects of diets differing in glycaemic index depend on age and endogenous glucose-dependent insulinotrophic polypeptide in mice. Diabetologia 2009; 52:2159-68. [PMID: 19644669 DOI: 10.1007/s00125-009-1466-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [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: 06/06/2009] [Accepted: 06/24/2009] [Indexed: 12/22/2022]
Abstract
AIMS/HYPOTHESIS High- vs low-glycaemic index (GI) diets unfavourably affect body fat mass and metabolic markers in rodents. Different effects of these diets could be age-dependent, as well as mediated, in part, by carbohydrate-induced stimulation of glucose-dependent insulinotrophic polypeptide (GIP) signalling. METHODS Young-adult (16 weeks) and aged (44 weeks) male wild-type (C57BL/6J) and GIP-receptor knockout (Gipr ( -/- )) mice were exposed to otherwise identical high-carbohydrate diets differing only in GI (20-26 weeks of intervention, n = 8-10 per group). Diet-induced changes in body fat distribution, liver fat, locomotor activity, markers of insulin sensitivity and substrate oxidation were investigated, as well as changes in the gene expression of anorexigenic and orexigenic hypothalamic factors related to food intake. RESULTS Body weight significantly increased in young-adult high- vs low-GI fed mice (two-way ANOVA, p < 0.001), regardless of the Gipr genotype. The high-GI diet in young-adult mice also led to significantly increased fat mass and changes in metabolic markers that indicate reduced insulin sensitivity. Even though body fat mass also slightly increased in high- vs low-GI fed aged wild-type mice (p < 0.05), there were no significant changes in body weight and estimated insulin sensitivity in these animals. However, aged Gipr ( -/- ) vs wild-type mice on high-GI diet showed significantly lower cumulative net energy intake, increased locomotor activity and improved markers of insulin sensitivity. CONCLUSIONS/INTERPRETATION The metabolic benefits of a low-GI diet appear to be more pronounced in younger animals, regardless of the Gipr genotype. Inactivation of GIP signalling in aged animals on a high-GI diet, however, could be beneficial.
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Affiliation(s)
- F Isken
- Department of Clinical Nutrition, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany
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19
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Yamada Y. [Incretin and bone]. Clin Calcium 2009; 19:1312-1317. [PMID: 19721203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Gastrointestinal hormones including gastric inhibitory polypeptide (GIP) and glucagon-like peptide (GLP) -1 are incretin, which are secreted immediately after meal ingestion and stimulate insulin secretion from pancreatic beta-cells. Characterization of extra-pancreatic GIP and GLP-1 receptors has revealed that these hormones regulate bone turnover. GIP intermittently stimulates osteoblasts and GLP-1 suppresses osteoclasts through a calcitonin-dependent pathway to increase the bone volume.
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Affiliation(s)
- Yuichiro Yamada
- Department of Endocrinology, Diabetes and Geriatric Medicine, Akita University Graduate School of Medicine
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20
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Lampron A, Bourdeau I, Oble S, Godbout A, Schürch W, Arjane P, Hamet P, Lacroix A. Regulation of aldosterone secretion by several aberrant receptors including for glucose-dependent insulinotropic peptide in a patient with an aldosteronoma. J Clin Endocrinol Metab 2009; 94:750-6. [PMID: 19066304 DOI: 10.1210/jc.2008-1340] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [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] [Indexed: 11/19/2022]
Abstract
CONTEXT Primary adrenal Cushing's syndrome can result from the aberrant adrenal expression of several hormone receptors; this mechanism has not been explored in detail in aldosterone-producing tumors. OBJECTIVE The objective of the study was to evaluate a 56-yr-old male patient with an aldosteronoma for the regulation of aldosterone secretion by aberrant hormone receptors. RESULTS Renin-independent stimulation of aldosterone secretion was observed in vivo after a mixed meal, oral glucose, or administration of glucose-dependent insulinotropic peptide (GIP), vasopressin, and tegaserod. The mixed meal-mediated stimulation of aldosterone was not present in five other cases of aldosteronoma. A smaller response of aldosterone after GIP infusion was observed in a normal subject. Aldosterone secretion was stimulated by GIP in primary cultures of this patient's aldosteronoma. Increased expression of GIP receptor was found in this aldosteronoma by real-time RT-PCR and immunohistochemistry. The GIP receptor protein was also found at lower levels in zona glomerulosa cells of the normal adjacent adrenal gland. Increased expression of serotonin 4 and ACTH receptors was also present in this aldosteronoma. CONCLUSIONS This case report provides new evidence of the implication of aberrant hormone receptors in the regulation of this aldosteronoma and suggests that further detailed studies of the role of aberrant hormone receptors in this frequent pathology should be undertaken.
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Affiliation(s)
- Antoine Lampron
- Division of Endocrinology, Centre Hospitalier de l'Université de Montré al, Montré al, Qué bec, Canada H2W 1T8
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21
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Parker HE, Habib AM, Rogers GJ, Gribble FM, Reimann F. Nutrient-dependent secretion of glucose-dependent insulinotropic polypeptide from primary murine K cells. Diabetologia 2009; 52:289-298. [PMID: 19082577 PMCID: PMC4308617 DOI: 10.1007/s00125-008-1202-x] [Citation(s) in RCA: 246] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Accepted: 10/16/2008] [Indexed: 12/21/2022]
Abstract
AIMS/HYPOTHESIS Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone with anti-apoptotic effects on the pancreatic beta cell. The aim of this study was to generate transgenic mice with fluorescently labelled GIP-secreting K cells and to use these to investigate pathways by which K cells detect nutrients. METHODS Transgenic mice were generated in which the GIP promoter drives the expression of the yellow fluorescent protein Venus. Fluorescent cells were purified by flow cytometry and analysed by quantitative RT-PCR. GIP secretion was assayed in primary cultures of small intestine. RESULTS Expression of Venus in transgenic mice was restricted to K cells, as assessed by immunofluorescence and measurements of the Gip mRNA and GIP protein contents of purified cells. K cells expressed high levels of mRNA for Kir6.2 (also known as Kcnj11), Sur1 (also known as Abcc8), Sglt1 (also known as Slc5a1), and of the G-protein-coupled lipid receptors Gpr40 (also known as Ffar1), Gpr119 and Gpr120. In primary cultures, GIP release was stimulated by glucose, glutamine and linoleic acid, and potentiated by forskolin plus 3-isobutyl-1-methylxanthine (IBMX), but was unaffected by the artificial sweetener sucralose. Secretion was half-maximal at 0.6 mmol/l glucose and partially mimicked by alpha-methylglucopyranoside, suggesting the involvement of SGLT1. Tolbutamide triggered secretion under basal conditions, whereas diazoxide suppressed responses in forskolin/IBMX. CONCLUSIONS/INTERPRETATION These transgenic mice and primary culture techniques provide novel opportunities to interrogate the mechanisms of GIP secretion. Glucose-triggered GIP secretion was SGLT1-dependent and modulated by K(ATP) channel activity but not determined by sweet taste receptors. Synergistic stimulation by elevated cAMP and glucose suggests that targeting appropriate G-protein-coupled receptors may provide opportunities to modulate GIP release in vivo.
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Affiliation(s)
- H E Parker
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
| | - A M Habib
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
| | - G J Rogers
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
| | - F M Gribble
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
| | - F Reimann
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
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22
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Peeters TL. Old and new targets for prokinetic drugs: motilin and ghrelin receptors. Eur Rev Med Pharmacol Sci 2008; 12 Suppl 1:136-137. [PMID: 18924456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- T L Peeters
- Center for Gastroenterological Research, University of Leuven, Leuven, Belgium.
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23
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Yamamoto I, Kaiya H, Tsutsui C, Sakai T, Tsukada A, Miyazato M, Tanaka M. Primary structure, tissue distribution, and biological activity of chicken motilin receptor. Gen Comp Endocrinol 2008; 156:509-14. [PMID: 18433751 DOI: 10.1016/j.ygcen.2008.03.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [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: 11/01/2007] [Revised: 03/10/2008] [Accepted: 03/11/2008] [Indexed: 10/22/2022]
Abstract
Motilin is a peptide hormone involved in gastrointestinal motility. GPR38, initially cloned as an orphan receptor, is now considered a specific receptor for motilin. Previously, molecular characterization of the motilin receptor had only been performed in mammalian and fish species. In this study, we cloned cDNA for chicken motilin receptor from the duodenum and characterized its primary structure, tissue distribution, and biological activity. The cDNA encoded 349 amino acids showing significant overall sequence identity to mammalian motilin receptors. Chicken motilin increased intracellular Ca2+ concentration in human embryonic kidney (HEK) 293 cells transiently expressing the recombinant chicken motilin receptor. Comparison of the cDNA sequence with the genomic sequence of chicken motilin receptor revealed that the chicken motilin receptor gene consists of two exons separated by an intron. Real-time PCR analysis showed that chicken motilin receptor mRNA is expressed in a wide range of tissues in 21-day-old chickens, with markedly high levels in the proventriculus, duodenum, and oviduct. The expression levels of the mRNA in the proventriculus and duodenum were highest just before hatching and rapidly decreased during post-hatch development. These results suggest that chicken motilin receptor is largely involved in gastrointestinal functions at pre- and post-hatch periods through an intracellular signaling pathway accompanied by an increase in Ca2+ levels.
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Affiliation(s)
- Ichiro Yamamoto
- High-Tech Research Center, Nippon Veterinary and Life Science University, Musashino, Tokyo 180-8602, Japan
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24
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Abstract
PURPOSE OF REVIEW Motilin is a hormone produced from endocrine cells of the duodenal mucosa to help regulate motility of the digestive tract. This review discusses new findings on the potential impact of motilin in human medicine. RECENT FINDINGS Motilin is a member of the peptide family that includes ghrelin whose cDNA also encodes a new candidate peptide, obestatin. Physiological interactions between these products will have to be explored. Pharmacological agents, agonists as well as antagonists, to motilin receptors are now emerging for clinical application. Motilin-receptor characterization, regarding its localization on nerves or muscles, as well as its biochemical mechanisms to sensitization for example, will be important steps in the design of future motilin agonists or antagonists. SUMMARY Motilin is a fascinating hormone for the physiologist. Its interaction with the family member ghrelin and with obestatin will open new areas for basic research. Motilin-receptor agonists or antagonists could soon be part of the therapeutic arsenal of the clinician to improve digestive dysmotility.
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25
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Flock G, Baggio LL, Longuet C, Drucker DJ. Incretin receptors for glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide are essential for the sustained metabolic actions of vildagliptin in mice. Diabetes 2007; 56:3006-13. [PMID: 17717280 DOI: 10.2337/db07-0697] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [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] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Dipeptidyl peptidase-4 (DPP4) inhibitors lower blood glucose in diabetic subjects; however, the mechanism of action through which these agents improve glucose homeostasis remains incompletely understood. Although glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP) represent important targets for DPP4 activity, whether additional substrates are important for the glucose-lowering actions of DPP4 inhibitors remains uncertain. RESEARCH DESIGN AND METHODS We examined the efficacy of continuous vildagliptin administration in wild-type (WT) and dual incretin receptor knockout (DIRKO) mice after 8 weeks of a high-fat diet. RESULTS Vildagliptin had no significant effect on food intake, energy expenditure, body composition, body weight gain, or insulin sensitivity in WT or DIRKO mice. However, glycemic excursion after oral glucose challenge was significantly reduced in WT but not in DIRKO mice after vildagliptin treatment. Moreover, vildagliptin increased levels of glucose-stimulated plasma insulin and reduced levels of cholesterol and triglycerides in WT but not in DIRKO mice. Vildagliptin treatment reduced the hepatic expression of genes important for cholesterol synthesis and fatty acid oxidation, including phospho-mevalonate kinase (Mvk), acyl-coenzyme dehydrogenase medium chain (Acadm), mevalonate (diphospho)decarboxylase (Mvd), and Acyl-CoA synthetase (Acsl1), in WT but not in DIRKO mice. However, vildagliptin also reduced levels of hepatic mRNA transcripts for farnesyl di-phosphate transferase (Fdft1), acetyl coenzyme A acyltransferase 1 (Acaa1), and carnitine palmitoyl transferase 1 (Cpt 1) in DIRKO mice. No direct effect of GLP-1 receptor agonists was detected on cholesterol or triglyceride synthesis and secretion in WT hepatocytes. CONCLUSIONS These findings illustrate that although GLP-1 and GIP receptors represent the dominant molecular mechanisms for transducing the glucoregulatory actions of DPP4 inhibitors, prolonged DPP4 inhibition modulates the expression of genes important for lipid metabolism independent of incretin receptor action in vivo.
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Affiliation(s)
- Grace Flock
- Samuel Lunenfeld Research Institute, Department of Medicine, Mount Sinai Hospital, University of Toronto, Toronto, Canada
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26
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Irwin N, Hunter K, Flatt PR. Comparison of the metabolic effects of GIP receptor antagonism and PYY(3-36) receptor activation in high fat fed mice. Peptides 2007; 28:2192-8. [PMID: 17884253 DOI: 10.1016/j.peptides.2007.08.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [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: 06/26/2007] [Revised: 08/10/2007] [Accepted: 08/14/2007] [Indexed: 11/22/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) and peptide YY (PYY) are secreted from the intestinal K- and L-cells, respectively, following a meal. Both peptides are believed to play a key role in glucose homeostasis and energy expenditure. This study investigated the effects of daily administration of the stable and specific GIP-R antagonist, (Pro(3))GIP (25 nmol/kg) and the endogenous truncated form of PYY, PYY(3-36) (50 nmol/kg), in mice fed with a high fat diet. Daily i.p. injection of (Pro(3))GIP, PYY(3-36) or combined peptide administration over 24 days significantly (P<0.05-0.01) decreased body weight compared with saline-treated controls without change in food intake. Plasma glucose levels and glucose tolerance were significantly (P<0.05) lowered by (Pro(3))GIP treatment alone, and in combination with PYY(3-36). These changes were accompanied by a slight improvement of insulin sensitivity in all of the treatment groups. (Pro(3))GIP treatment significantly reduced plasma corticosterone (P<0.05), while combined administration with PYY(3-36) significantly lowered serum glucagon (P<0.05). No appreciable changes were observed in either circulating or glucose-stimulated insulin secretion in all treatment groups. (Pro(3))GIP-treated mice had significantly (P<0.01) lowered fasting glucose levels and an improved (P<0.05) glycemic response to feeding. These comparative data indicate that chemical ablation of GIP receptor action using (Pro(3))GIP provides an especially effective means of countering obesity and related abnormalities induced by consumption of high fat energy rich diet.
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Affiliation(s)
- N Irwin
- School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK.
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27
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Winzell MS, Ahrén B. G-protein-coupled receptors and islet function-implications for treatment of type 2 diabetes. Pharmacol Ther 2007; 116:437-48. [PMID: 17900700 DOI: 10.1016/j.pharmthera.2007.08.002] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Accepted: 08/13/2007] [Indexed: 01/09/2023]
Abstract
Islet function is regulated by a number of different signals. A main signal is generated by glucose, which stimulates insulin secretion and inhibits glucagon secretion. The glucose effects are modulated by many factors, including hormones, neurotransmitters and nutrients. Several of these factors signal through guanine nucleotide-binding protein (G protein)-coupled receptors (GPCR). Examples of islet GPCR are GPR40 and GPR119, which are GPCR with fatty acids as ligands, the receptors for the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), the receptors for the islet hormones glucagon and somatostatin, the receptors for the classical neurotransmittors acetylcholine (ACh; M(3) muscarinic receptors) and noradrenaline (beta(2)- and alpha(2)-adrenoceptors) and for the neuropeptides pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP; PAC(1) and VPAC(2) receptors), cholecystokinin (CCK(A) receptors) and neuropeptide Y (NPY Y1 receptors). Other islet GPCR are the cannabinoid receptor (CB(1) receptors), the vasopressin receptors (V1(B) receptors) and the purinergic receptors (P(2Y) receptors). The islet GPCR couple mainly to adenylate cyclase and to phospholipase C (PLC). Since important pharmacological strategies for treatment of type 2 diabetes are stimulation of insulin secretion and inhibition of glucagon secretion, islet GPCR are potential drug targets. This review summarizes knowledge on islet GPCR.
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Affiliation(s)
- Maria Sörhede Winzell
- Department of Clinical Sciences, Division of Medicine, Lund University, Lund, Sweden.
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28
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Chu JYS, Chung SCK, Lam AKM, Tam S, Chung SK, Chow BKC. Phenotypes developed in secretin receptor-null mice indicated a role for secretin in regulating renal water reabsorption. Mol Cell Biol 2007; 27:2499-511. [PMID: 17283064 PMCID: PMC1899889 DOI: 10.1128/mcb.01088-06] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aquaporin 2 (AQP2) is responsible for regulating the concentration of urine in the collecting tubules of the kidney under the control of vasopressin (Vp). Studies using Vp-deficient Brattleboro rats, however, indicated the existence of substantial Vp-independent mechanisms for membrane insertion, as well as transcriptional regulation, of this water channel. The Vp-independent mechanism(s) is clinically relevant to patients with X-linked nephrogenic diabetes insipidus (NDI) by therapeutically bypassing the dysfunctional Vp receptor. On the basis of studies with secretin receptor-null (SCTR(-/-)) mice, we report here for the first time that mutation of the SCTR gene could lead to mild polydipsia and polyuria. Additionally, SCTR(-/-) mice were shown to have reduced renal expression of AQP2 and AQP4, as well as altered glomerular and tubular morphology, suggesting possible disturbances in the filtration and/or water reabsorption process in these animals. By using SCTR(-/-) mice as controls and comparing them with wild-type animals, we performed both in vivo and in vitro studies that demonstrated a role for secretin in stimulating (i) AQP2 translocation from intracellular vesicles to the plasma membrane in renal medullary tubules and (ii) expression of this water channel under hyperosmotic conditions. The present study therefore provides information for at least one of the Vp-independent mechanisms that modulate the process of renal water reabsorption. Future investigations in this direction should be important in developing therapeutic means for treating NDI patients.
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Affiliation(s)
- Jessica Y S Chu
- Department of Zoology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
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29
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Nishijima I, Yamagata T, Spencer CM, Weeber EJ, Alekseyenko O, Sweatt JD, Momoi MY, Ito M, Armstrong DL, Nelson DL, Paylor R, Bradley A. Secretin receptor-deficient mice exhibit impaired synaptic plasticity and social behavior. Hum Mol Genet 2006; 15:3241-50. [PMID: 17008357 PMCID: PMC2593392 DOI: 10.1093/hmg/ddl402] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Secretin is a peptide hormone released from the duodenum to stimulate the secretion of digestive juice by the pancreas. Secretin also functions as a neuropeptide hormone in the brain, and exogenous administration has been reported to alleviate symptoms in some patients with autism. We have generated secretin receptor-deficient mice to explore the relationship between secretin signaling in the brain and behavioral phenotypes. Secretin receptor-deficient mice are overtly normal and fertile; however, synaptic plasticity in the hippocampus is impaired and there are slightly fewer dendritic spines in the CA1 hippocampal pyramidal cells. Furthermore, secretin receptor-deficient mice show abnormal social and cognitive behaviors. These findings suggest that the secretin receptor system has an important role in the central nervous system relating to social behavior.
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Affiliation(s)
- Ichiko Nishijima
- Center for Molecular and Human Genetics, Columbus Children's Research Institute, The Ohio State University, Columbus, OH 43205, USA.
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30
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Liu G, Arnaud-Dabernat S, Kritzik MR, Kayali AG, Zhang YQ, Sarvetnick N. PYY in the expanding pancreatic epithelium. Endocrine 2006; 30:103-12. [PMID: 17185798 DOI: 10.1385/endo:30:1:103] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2006] [Revised: 06/19/2006] [Accepted: 06/21/2006] [Indexed: 11/11/2022]
Abstract
Gut peptide YY (PYY) plays an important role in regulating metabolism and is expressed during the ontogeny of the pancreas. However, its biological role during endocrine cell formation is not fully understood, and its role, if any, during pancreatic regeneration in the adult has not yet been explored. The knowledge of factors involved in beta cell renewal in adult animals is clearly relevant for the design of treatment strategies for type 1 diabetes. We therefore sought to determine if observations during fetal pancreas formation also apply to pancreatic growth in adult animals. Indeed, we have found marked expansion of the PYY-expressing population during pancreatic regeneration. In addition, we demonstrate the presence of cells co-expressing PYY and the critical pancreatic transcription factor pancreatic duodenal homeobox1 (PDX-1). Interestingly, these cells also co-expressed specific islet hormones during pancreatic development and re-growth, suggesting a developmental relationship. Furthermore, we have found that PYY can act in concert with IGF-1 to stimulate cellular responsiveness in pancreatic epithelial cells in vitro. Our data suggest that PYY may be a mediator of islet cell development, as well as a cofactor for growth factor responses, not only during fetal pancreas formation but also during regeneration in adult animals.
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Affiliation(s)
- Guoxun Liu
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA
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31
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Miyashita K, Itoh H, Nakao K. [ACTH-independent macronodular adrenal hyperplasia]. Nihon Rinsho 2006; Suppl 1:614-7. [PMID: 16776230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Affiliation(s)
- Kazutoshi Miyashita
- Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
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32
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Matsuura B, Dong M, Naik S, Miller LJ, Onji M. Differential Contributions of Motilin Receptor Extracellular Domains for Peptide and Non-peptidyl Agonist Binding and Activity. J Biol Chem 2006; 281:12390-6. [PMID: 16531413 DOI: 10.1074/jbc.m511921200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The family of G protein-coupled receptors that includes receptors for motilin, ghrelin, and growth hormone secretagogue has substantial potential importance as drug targets. Understanding of the molecular basis of hormone binding and receptor activation should provide insights that are helpful in the development of such drugs. We previously examined the unique second extracellular loop domain of the motilin receptor, identifying key epitopes in perimembranous locations at each end of this long loop (Matsuura, B., Dong, M., and Miller, L. J. (2002) J. Biol. Chem. 277, 9834-9839). Here, we have extended that work, examining the other predicted extracellular domains of the motilin receptor by using sequential deletions of segments ranging from one to six amino acid residues and site-directed alanine replacement mutagenesis approaches. Each construct was transiently expressed in COS cells, and characterized for motilin- and erythromycin-stimulated intracellular calcium responses and motilin radioligand binding. Only those receptor segments that included key Cys residues in positions 25, 30, and 111 or perimembranous regions at the ends of the amino terminus and the first and third extracellular loops disrupted motilin biological activity. Each of these Cys deletions also disrupted action of erythromycin. Alanine replacements for each of the potentially important amino acid residues in the perimembranous segments revealed that residues Gly36, Pro103, Leu109, and Phe332 were responsible for the selective negative impact on motilin biological activity, while responding normally to erythromycin. These results support the presence of functionally important disulfide bonds in the motilin receptor ectodomain and demonstrate that the structural determinants for binding and biological activity of peptide and non-peptidyl agonist ligands are distinct, with a broad extracellular perimembranous base contributing to normal motilin binding.
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Affiliation(s)
- Bunzo Matsuura
- Third Department of Internal Medicine, Ehime University School of Medicine, Shitsukawa 454, Tohon, Ehime 791-0295, Japan
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33
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Affiliation(s)
- Nicole Merten
- Institute of Biochemistry, Brüderstr. 34, 04103 Leipzig, Germany
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34
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Christopoulos S, Bourdeau I, Lacroix A. Clinical and Subclinical ACTH-Independent Macronodular Adrenal Hyperplasia and Aberrant Hormone Receptors. Horm Res Paediatr 2005; 64:119-31. [PMID: 16215323 DOI: 10.1159/000088818] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [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: 10/06/2005] [Indexed: 11/19/2022] Open
Abstract
ACTH-independent macronodular adrenal hyperplasia (AIMAH) is a very rare cause of endogenous Cushing's syndrome (CS). In this review, the clinical characteristics, the pathophysiology, and the management of AIMAH are described. AIMAH typically presents with overt CS, but subclinical oversecretion of cortisol has been increasingly described. The diagnosis is suspected by adrenal nodular enlargement on conventional imaging following the demonstration of ACTH-independent hypercortisolism. Final diagnosis is established by histological examination of the adrenal tissue. Bilateral adrenalectomy is the treatment of choice but unilateral adrenalectomy has been proposed in selected cases. In patients with subclinical CS, the decision to treat should be individualized. The pathophysiology of this condition has begun to be elucidated in recent years. Diverse aberrant membrane-bound receptors expressed in a non-mutated form in the adrenal gland have been found to be implicated in the regulation of steroidogenesis in AIMAH. When systematically screened, most patients with AIMAH and CS or subclinical CS exhibit an in vivo aberrant cortisol response to one or various ligands suggesting the presence of aberrant adrenal receptors. A protocol designed to screen patients for the presence of these aberrant receptors should be undertaken in all patients with AIMAH. The identification of these receptors provides the potential for novel pharmacological therapies by suppressing the endogenous ligands or blocking the receptor with specific antagonists.
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Affiliation(s)
- Stavroula Christopoulos
- Division of Endocrinology, Department of Medicine, Centre Hospitalier de l'Université de Montréal, Montréal, Canada
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35
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Nyberg J, Anderson MF, Meister B, Alborn AM, Ström AK, Brederlau A, Illerskog AC, Nilsson O, Kieffer TJ, Hietala MA, Ricksten A, Eriksson PS. Glucose-dependent insulinotropic polypeptide is expressed in adult hippocampus and induces progenitor cell proliferation. J Neurosci 2005; 25:1816-25. [PMID: 15716418 PMCID: PMC6725940 DOI: 10.1523/jneurosci.4920-04.2005] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The hippocampal dentate gyrus (DG) is an area of active proliferation and neurogenesis within the adult brain. The molecular events controlling adult cell genesis in the hippocampus essentially remain unknown. It has been reported previously that adult male and female rats from the strains Sprague Dawley (SD) and spontaneously hypertensive (SHR) have a marked difference in proliferation rates of cells in the hippocampal DG. To exploit this natural variability and identify potential regulators of cell genesis in the hippocampus, hippocampal gene expression from male SHR as well as male and female SD rats was analyzed using a cDNA array strategy. Hippocampal expression of the gene-encoding glucose-dependent insulinotropic polypeptide (GIP) varied strongly in parallel with cell-proliferation rates in the adult rat DG. Moreover, robust GIP immunoreactivity could be detected in the DG. The GIP receptor is expressed by cultured adult hippocampal progenitors and throughout the granule cell layer of the DG, including progenitor cells. Thus, these cells have the ability to respond to GIP. Indeed, exogenously delivered GIP induced proliferation of adult-derived hippocampal progenitors in vivo as well as in vitro, and adult GIP receptor knock-out mice exhibit a significantly lower number of newborn cells in the hippocampal DG compared with wild-type mice. This investigation demonstrates the presence of GIP in the brain for the first time and provides evidence for a regulatory function for GIP in progenitor cell proliferation.
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Affiliation(s)
- Jenny Nyberg
- The Arvid Carlsson Institute for Neuroscience at the Institute of Clinical Neuroscience, Göteborg University, Sahlgrenska University Hospital, 413 45 Göteborg, Sweden.
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36
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Liu M, Dong L, Zhu WY. [Distribution and role of motilin receptor in the amygdala of rats]. Di Yi Jun Yi Da Xue Xue Bao 2005; 25:1100-4. [PMID: 16174573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
OBJECTIVE To explore the distribution and role of motilin receptor in the amygdala of rats. METHODS The distribution of motilin receptor in the amygdala was detected by immunohistochemistry in adult SD rats of either sex. The duodenal interdigestive migrating myoelectric complex (MMC) was recorded and analyzed for investigating the role of motilin receptor in the amygdala. RESULTS Motilin receptors were detected in the amygdala of rats. The medial amygdaloid nucleus contained the greatest amount of motilin receptors, which was also abound in the basolateral nucleus of the amygdala but less abundant in the basomedial nucleus of the amygdala, central amygdaloid nucleus and lateral amygdaloid nucleus. The binding of motilin receptors and motilin in the amygdala caused shortening of duodenal MMC cycle duration and increased amplitude and frequency of phase III. The effects were completely abolished by subdiaphragmal vagotomy but not by intravenous injection of atropine, phentolamine or propranolol. Anti-motilin serum partially abolished these effects, and destruction of the basolateral nucleus of the amygdala had no effects on duodenal MMC. CONCLUSIONS Motilin receptors are present in all the subnuclei of the amygdala. The effects of microinjection of motilin in the amygdala on duodenal MMC might rely on either the effects of noncholinergic and nonadrenergic neurons on the duodenal smooth muscle, or increase in local motilin via amygdala-hypothalamus-brain stem-vagus pathway, indicating the important role of motilin receptor in the amygdala in duodenal MMC regulation.
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Affiliation(s)
- Mei Liu
- Department of Gastroenterology, Second Hospital of Xi'an Jiaotong University, Xi'an 710004, China.
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37
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Kim SJ, Choi WS, Han JSM, Warnock G, Fedida D, McIntosh CHS. A Novel Mechanism for the Suppression of a Voltage-gated Potassium Channel by Glucose-dependent Insulinotropic Polypeptide. J Biol Chem 2005; 280:28692-700. [PMID: 15955806 DOI: 10.1074/jbc.m504913200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The mechanisms involved in glucose regulation of insulin secretion by ATP-sensitive (K(ATP)) and calcium-activated (K(CA)) potassium channels have been extensively studied, but less is known about the role of voltage-gated (K(V)) potassium channels in pancreatic beta-cells. The incretin hormone, glucose-dependent insulinotropic polypeptide (GIP) stimulates insulin secretion by potentiating events underlying membrane depolarization and exerting direct effects on exocytosis. In the present study, we identified a novel role for GIP in regulating K(V)1.4 channel endocytosis. In GIP receptor-expressing HEK293 cells, GIP reduced A-type peak ionic current amplitude of K(V)1.4 via activation of protein kinase A (PKA). Using mutant forms of K(V)1.4 with Ala-Ser/Thr substitutions in a potential PKA phosphorylation site, C-terminal phosphorylation was shown to be linked to GIP-mediated current amplitude decreases. Proteinase K digestion and immunocytochemical studies on mutant K(V)1.4 localization following GIP stimulation demonstrated phosphorylation-dependent rapid endocytosis of K(V)1.4. Expression of K(V)1.4 protein was also demonstrated in human beta-cells; GIP treatment resulting in similar decreases in A-type potassium current peak amplitude to those in HEK293 cells. Transient overexpression in INS-1 beta-cells (clone 832/13) of wild-type (WT) K(V)1.4, or a T601A mutant form resistant to PKA phosphorylation, resulted in reduced glucose-stimulated insulin secretion; WT K(V)1.4 overexpression potentiated GIP-induced insulin secretion, whereas this response was absent in T601A cells. These results strongly support an important novel role for GIP in regulating K(V)1.4 cell surface expression and modulation of A-type potassium currents, which is likely to be critically important for its insulinotropic action.
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Affiliation(s)
- Su-Jin Kim
- Department of Cellular & Physiological Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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38
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Fujisawa T, Ogihara T. [Motilin]. Nihon Rinsho 2005; 63 Suppl 8:517-20. [PMID: 16149566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Affiliation(s)
- Tomomi Fujisawa
- Department of Geriatric Medicine, Osaka University Graduate School of Medicine
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39
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Irwin N, Green BD, Mooney MH, Greer B, Harriott P, Bailey CJ, Gault VA, O'Harte FPM, Flatt PR. A Novel, Long-Acting Agonist of Glucose-Dependent Insulinotropic Polypeptide Suitable for Once-Daily Administration in Type 2 Diabetes. J Pharmacol Exp Ther 2005; 314:1187-94. [PMID: 15923344 DOI: 10.1124/jpet.105.086082] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone with a potentially therapeutic role in type 2 diabetes. Rapid degradation by dipeptidylpeptidase IV has prompted the development of enzyme-resistant N-terminally modified analogs, but renal clearance still limits in vivo bioactivity. In this study, we report long-term antidiabetic effects of a novel, N-terminally protected, fatty acid-derivatized analog of GIP, N-AcGIP(LysPAL(37)), in obese diabetic (ob/ob) mice. Once-daily injections of N-AcGIP(LysPAL(37)) over a 14-day period significantly decreased plasma glucose, glycated hemoglobin, and improved glucose tolerance compared with ob/ob mice treated with saline or native GIP. Plasma insulin and pancreatic insulin content were significantly increased by N-AcGIP(LysPAL(37)). This was accompanied by a significant enhancement in the insulin response to glucose together with a notable improvement of insulin sensitivity. No evidence was found for GIP receptor desensitization and the metabolic effects of N-AcGIP(LysPAL(37)) were independent of any change in feeding or body weight. Similar daily injections of native GIP did not affect any of the parameters measured. These data demonstrate the ability of once-daily injections of N-terminally modified, fatty acid-derivatized analogs of GIP, such as N-AcGIP(LysPAL(37)), to improve diabetes control and to offer a new class of agents for the treatment of type 2 diabetes.
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Affiliation(s)
- Nigel Irwin
- School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK
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40
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Herbach N, Goeke B, Schneider M, Hermanns W, Wolf E, Wanke R. Overexpression of a dominant negative GIP receptor in transgenic mice results in disturbed postnatal pancreatic islet and beta-cell development. ACTA ACUST UNITED AC 2005; 125:103-17. [PMID: 15582721 DOI: 10.1016/j.regpep.2004.08.021] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [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: 03/24/2004] [Revised: 07/27/2004] [Accepted: 08/16/2004] [Indexed: 12/20/2022]
Abstract
The expression of a dominant negative glucose-dependent insulinotropic polypeptide receptor (GIPRdn) under the control of the rat pro-insulin gene promoter induces severe diabetes mellitus in transgenic mice. This study aims to gain further insight into the effect of the expression of a dominant negative GIPR on glucose homeostasis and postnatal development of the endocrine pancreas. The diabetic phenotype of GIPRdn transgenic animals was first observed between 14 and 21 days of age (urine glucose>1000 mg/dl). After onset of diabetes, serum glucose was significantly higher and insulin values were significantly lower in GIPRdn transgenic mice vs. non-transgenic littermate controls. Morphometric studies of pancreatic islets and their endocrine cell types were carried out at 10, 30 and 90 days of age. The total islet and total beta-cell volume of transgenic mice was severely reduced as compared to control mice, irrespective of the age at sampling (p<0.05). The total volume of isolated insulin positive cells that were not contained within established islets was significantly reduced in transgenic mice, indicating disturbed islet neogenesis. These findings demonstrate in vivo evidence that intact signaling of G-protein coupled receptors is involved in postnatal islet and beta-cell development and neogenesis of the pancreatic islets.
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Affiliation(s)
- Nadja Herbach
- Institute of Veterinary Pathology, Veterinaerstrasse 13, 80539 Munich, Germany.
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41
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Thielemans L, Depoortere I, Perret J, Robberecht P, Liu Y, Thijs T, Carreras C, Burgeon E, Peeters TL. Desensitization of the Human Motilin Receptor by Motilides. J Pharmacol Exp Ther 2005; 313:1397-405. [PMID: 15764739 DOI: 10.1124/jpet.104.081497] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tachyphylaxis may have contributed to the failure of the motilide ABT-229 [N-ethyl, N-methyl 4'' deoxy erythromycin (EM)-B enolether] in clinical trials. We compared the desensitizing potency of structurally related motilides [EM-A, EM-A enolether (ME4), N-ethyl, N-methyl EM-A (ME36), EM-B enolether (ME67), N-ethyl, N-methyl EM-A enolether (EM523), ABT-229 and 4'' deoxy EM-A enolether (KOS1326)] in a Chinese hamster ovary (CHO)-K1 cell line expressing the human motilin receptor (MTLR) and in rabbit duodenal segments. CHO-MTLR cells were preincubated with motilides prior to stimulation with motilin. The negative logarithm of the preincubation concentration reducing the maximal motilin-induced Ca(2+) flux to 50% was calculated (pDC(50)). Internalization was visualized in CHO-K1 cells containing an enhanced green fluorescent protein (EGFP)-tagged MTLR and quantified in binding experiments. The contractile response of repeated stimulations was measured in duodenal segments. In CHO-MTLR cells, the pDC(50) was ABT-229 (8.78) > motilin (7.77) > EM-A (4.78), different from their order of potency to induce Ca(2+) release (pEC(50)): motilin (9.39) > ABT-229 (8.46) > EM-A (7.11). In cells with the EGFP-tagged MTLR, ABT-229 decreased membrane fluorescence by 25 +/- 2% compared with 16 +/- 2% for motilin and 8 +/- 2% for EM-A. Binding studies confirmed that EM-A did not induce MTLR internalization (residual binding 96 +/- 4% compared with motilin, 31 +/- 3% and ABT-229, 21 +/- 1%). Comparison of the pDC(50) and pEC(50) values of the other motilides ME4 (5.90; 8.08), ME67 (6.03; 8.12), ME36 (3.32; 6.62), EM-523 (6.02; 8.22), and KOS1326 (7.32; 8.14) suggested that the strong desensitizing properties of ABT-229 are mostly related to the removal of the 4''-OH of the cladinose sugar. The decline of the contractile response in duodenal segments correlated with the pDC(50). The ability to desensitize and internalize the MTLR is not only determined by potency. This may be an important criterion for the development of a clinically useful compound.
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Affiliation(s)
- Leen Thielemans
- Gut Hormone Lab, Center for Gastroenterological Research, Department of Pathophysiology, Katholieke Universiteit Leuven, Belgium
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Claeys I, Poels J, Simonet G, Franssens V, Van Loy T, Van Hiel MB, Breugelmans B, Vanden Broeck J. Insect Neuropeptide and Peptide Hormone Receptors: Current Knowledge and Future Directions. Vitamins & Hormones 2005; 73:217-82. [PMID: 16399412 DOI: 10.1016/s0083-6729(05)73007-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Peptides form a very versatile class of extracellular messenger molecules that function as chemical communication signals between the cells of an organism. Molecular diversity is created at different levels of the peptide synthesis scheme. Peptide messengers exert their biological functions via specific signal-transducing membrane receptors. The evolutionary origin of several peptide precursor and receptor gene families precedes the divergence of the important animal Phyla. In this chapter, current knowledge is reviewed with respect to the analysis of peptide receptors from insects, incorporating many recent data that result from the sequencing of different insect genomes. Therefore, detailed information is provided on six different peptide receptor families belonging to two distinct receptor categories (i.e., the heptahelical and the single transmembrane receptors). In addition, the remaining problems, the emerging concepts, and the future prospects in this area of research are discussed.
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MESH Headings
- Animals
- Drosophila/genetics
- Drosophila/physiology
- Drosophila Proteins/genetics
- Drosophila Proteins/physiology
- Forecasting
- Frizzled Receptors/genetics
- Frizzled Receptors/physiology
- Insecta/genetics
- Insecta/physiology
- Invertebrate Hormones/genetics
- Invertebrate Hormones/physiology
- Receptor Protein-Tyrosine Kinases/physiology
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/physiology
- Receptors, Gastrointestinal Hormone/genetics
- Receptors, Gastrointestinal Hormone/physiology
- Receptors, Guanylate Cyclase-Coupled/genetics
- Receptors, Guanylate Cyclase-Coupled/physiology
- Receptors, Invertebrate Peptide/genetics
- Receptors, Invertebrate Peptide/physiology
- Receptors, Peptide/genetics
- Receptors, Peptide/physiology
- Receptors, Tachykinin/genetics
- Receptors, Tachykinin/physiology
- Receptors, Transforming Growth Factor beta/physiology
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Affiliation(s)
- Ilse Claeys
- Laboratory for Developmental Physiology, Genomics and Proteomics Department of Animal Physiology and Neurobiology, Zoological Institute K.U.Leuven, Naamsestraat 59, B-3000 Leuven, Belgium
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Huang J, Zhou H, Mahavadi S, Sriwai W, Lyall V, Murthy KS. Signaling pathways mediating gastrointestinal smooth muscle contraction and MLC20 phosphorylation by motilin receptors. Am J Physiol Gastrointest Liver Physiol 2005; 288:G23-31. [PMID: 15591586 DOI: 10.1152/ajpgi.00305.2004] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The signaling cascades initiated by motilin receptors in gastric and intestinal smooth muscle cells were characterized. Motilin bound with high affinity (IC(50) 0.7 +/- 0.2 nM) to receptors on smooth muscle cells; the receptors were rapidly internalized via G protein-coupled receptor kinase 2 (GRK2). Motilin selectively activated G(q) and G(13), stimulated G alpha(q)-dependent phosphoinositide (PI) hydrolysis and 1,4,5-trisphosphate (IP(3))-dependent Ca(2+) release, and increased cytosolic free Ca(2+). PI hydrolysis was blocked by expression of G alpha(q) minigene and augmented by overexpression of dominant negative RGS4(N88S) or GRK2(K220R). Motilin induced a biphasic, concentration-dependent contraction (EC(50) = 1.0 +/- 0.2 nM), consisting of an initial peak followed by a sustained contraction. The initial Ca(2+)-dependent contraction and myosin light-chain (MLC)(20) phosphorylation were inhibited by the PLC inhibitor U-73122 and the MLC kinase inhibitor ML-9 but were not affected by the Rho kinase inhibitor Y27632 or the PKC inhibitor bisindolylmaleimide. Sustained contraction and MLC(20) phosphorylation were RhoA dependent and mediated by two downstream messengers: PKC and Rho kinase. The latter was partly inhibited by expression of G alpha(q) or G alpha(13) minigene and abolished by coexpression of both minigenes. Sustained contraction and MLC(20) phosphorylation were partly inhibited by Y27632 and bisindolylmaleimide and abolished by a combination of both inhibitors. The inhibition reflected phosphorylation of two MLC phosphatase inhibitors: CPI-17 via PKC and MYPT1 via Rho kinase. We conclude that motilin initiates a G alpha(q)-mediated cascade involving Ca(2+)/calmodulin activation of MLC kinase and transient MLC(20) phosphorylation and contraction as well as a sustained G alpha(q)- and G alpha(13)-mediated, RhoA-dependent cascade involving phosphorylation of CPI-17 by PKC and MYPT1 by Rho kinase, leading to inhibition of MLC phosphatase and sustained MLC(20) phosphorylation and contraction.
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Affiliation(s)
- Jiean Huang
- Department of Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA
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Clement HW, Pschibul A, Schulz E. Effects of secretin on extracellular GABA and other amino acid concentrations in the rat hippocampus. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 71:239-71. [PMID: 16512354 DOI: 10.1016/s0074-7742(05)71011-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Affiliation(s)
- Hans-Willi Clement
- Department of Child and Adolescent Psychiatry, University of Freiburg, Germany
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Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone that is secreted in response to food intake and modulates beta cell function. It may also regulate beta cell fate. Released from the nutrient-sensing K-cells of the upper intestine, GIP acts on various tissues, including pancreatic beta cells, via interaction with its G-protein-coupled receptor. Perhaps the most important effect of GIP is its potentiation of insulin secretion. Indeed, pharmacological blockade or genetic knockout of its receptor delays glucose-dependent insulin secretion. Exposure to GIP also enhances the beta cell response to future nutrient stimulation and upregulates transcription of key beta cell genes. There is emerging evidence that like the related hormone glucagon-like peptide-1, GIP may function as a beta cell growth factor and anti-apoptotic agent, further supporting a role for this hormone in balancing beta cell function to changing metabolic conditions. Overproduction of GIP in response to increased nutrient loads may, however, contribute to the pathophysiology of obesity. Interestingly, its insulinotropic effect is lost in type 2 diabetes, perhaps because of hyperglycemia-induced receptor desensitization. A better understanding of GIP's effects on the beta cell under normal and pathological conditions may facilitate the design of GIP derivatives for the treatment of metabolic disorders.
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Affiliation(s)
- R D Wideman
- Departments of Physiology and Surgery, University of British Columbia, Vancouver, B.C. V6T 1Z3, Canada
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Abstract
A much greater insulin response is observed after oral glucose load than after intravenous injection of glucose. The hormonal factor(s) implicated as transmitters of signals from the gut to pancreatic beta-cells was referred to incretin; gastric inhibitory polypeptide or glucose-dependent insulinotropic polypeptide (GIP) is identified as one of the incretins. GIP exerts its effects by binding to its specific receptor, the GIP receptor, which is expressed in various tissues including pancreatic islets, adipose tissue, and brain. However, the physiological role of GIP has been generally thought to stimulate insulin secretion from pancreatic beta-cells, and the other actions of GIP have received little attention. We have bred and characterized mice with a targeted mutation of the GIP receptor gene. From these studies, we now know that GIP not only mediates early insulin secretion by acting on pancreatic beta-cells, but also links overnutrition to obesity by acting on adipocytes.
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Affiliation(s)
- Y Yamada
- Department of Diabetes and Clinical Nutrition, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
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Affiliation(s)
- H L Waldum
- Norwegian University of Science and Technology, Dept. of Medicine, Section of Gastroenterology, University Hospital of Trondheim, Norway.
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Hansotia T, Baggio LL, Delmeire D, Hinke SA, Yamada Y, Tsukiyama K, Seino Y, Holst JJ, Schuit F, Drucker DJ. Double incretin receptor knockout (DIRKO) mice reveal an essential role for the enteroinsular axis in transducing the glucoregulatory actions of DPP-IV inhibitors. Diabetes 2004; 53:1326-35. [PMID: 15111503 DOI: 10.2337/diabetes.53.5.1326] [Citation(s) in RCA: 245] [Impact Index Per Article: 12.3] [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] [Indexed: 11/13/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are gut-derived incretins that potentiate glucose clearance following nutrient ingestion. Elimination of incretin receptor action in GIPR(-/-) or GLP-1R(-/-) mice produces only modest impairment in glucose homeostasis, perhaps due to compensatory upregulation of the remaining incretin. We have now studied glucose homeostasis in double incretin receptor knockout (DIRKO) mice. DIRKO mice exhibit normal body weight and fail to exhibit an improved glycemic response after exogenous administration of GIP or the GLP-1R agonist exendin-4. Plasma glucagon and the hypoglycemic response to exogenous insulin were normal in DIRKO mice. Glycemic excursion was abnormally increased and levels of glucose-stimulated insulin secretion were decreased following oral but not intraperitoneal glucose challenge in DIRKO compared with GIPR(-/-) or GLP-1R(-/-) mice. Similarly, glucose-stimulated insulin secretion and the response to forskolin were well preserved in perifused DIRKO islets. Although the dipeptidyl peptidase-IV (DPP-IV) inhibitors valine pyrrolidide (Val-Pyr) and SYR106124 lowered glucose and increased plasma insulin in wild-type and single incretin receptor knockout mice, the glucose-lowering actions of DPP-IV inhibitors were eliminated in DIRKO mice. These findings demonstrate that glucose-stimulated insulin secretion is maintained despite complete absence of both incretin receptors, and they delineate a critical role for incretin receptors as essential downstream targets for the acute glucoregulatory actions of DPP-IV inhibitors.
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Affiliation(s)
- Tanya Hansotia
- Banting and Best Diabetes Centre, Department of Medicine, Toronto General Hospital, University of Toronto, 200 Elizabeth Street, Toronto, Ontario, Canada M5G 2C4
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Thorens B. [GIP and GLP-1: multiplicity of regulator mechanisms for insulin secretion]. Journ Annu Diabetol Hotel Dieu 2004:111-25. [PMID: 15259310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Affiliation(s)
- B Thorens
- Institut de Pharmacologie et Toxicologie, Lausanne, Suisse
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Irwin N, Gault VA, Green BD, Greer B, McCluskey JT, Harriott P, O'Harte FPM, Flatt PR. Effects of short-term chemical ablation of the GIP receptor on insulin secretion, islet morphology and glucose homeostasis in mice. Biol Chem 2004; 385:845-52. [PMID: 15493880 DOI: 10.1515/bc.2004.110] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone secreted by endocrine K-cells in response to nutrient absorption. In this study we have utilized a specific and enzymatically stable GIP receptor antagonist, (Pro3)GIP, to evaluate the contribution of endogenous GIP to insulin secretion and glucose homeostasis in mice. Daily injection of (Pro3)GIP (25 nmol/kg body weight) for 11 days had no effect on food intake or body weight. Non-fasting plasma glucose concentrations were significantly raised (p<0.05) by day 11, while plasma insulin concentrations were not significantly different from saline treated controls. After 11 days, intraperitoneal glucose tolerance was significantly impaired in the (Pro3)GIP treated mice compared to control (p<0.01). Glucose-mediated insulin secretion was not significantly different between the two groups. Insulin sensitivity of 11-day (Pro3)GIP treated mice was slightly impaired 60 min post injection compared with controls. Following a 15 min refeeding period in 18 h fasted mice, food intake was not significantly different in (Pro3)GIP treated mice and controls. However, (Pro3)GIP treated mice displayed significantly elevated plasma glucose levels 30 and 60 min post feeding (p<0.05, in both cases). Postprandial insulin secretion was not significantly different and no changes in pancreatic insulin content or islet morphology were observed in (Pro3)GIP treated mice. The observed biological effects of (Pro3)GIP were reversed following cessation of treatment for 9 days. These data indicate that ablation of GIP signaling causes a readily reversible glucose intolerance without appreciable change of insulin secretion.
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Affiliation(s)
- Nigel Irwin
- Diabetes Research Group, School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, Northern Ireland, UK.
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