1
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Zhao F, Hang K, Zhou Q, Shao L, Li H, Li W, Lin S, Dai A, Cai X, Liu Y, Xu Y, Feng W, Yang D, Wang MW. Molecular basis of signal transduction mediated by the human GIPR splice variants. Proc Natl Acad Sci U S A 2023; 120:e2306145120. [PMID: 37792509 PMCID: PMC10576055 DOI: 10.1073/pnas.2306145120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Accepted: 08/07/2023] [Indexed: 10/06/2023] Open
Abstract
Glucose-dependent insulinotropic polypeptide receptor (GIPR) is a potential drug target for metabolic disorders. It works with glucagon-like peptide-1 receptor and glucagon receptor in humans to maintain glucose homeostasis. Unlike the other two receptors, GIPR has at least 13 reported splice variants (SVs), more than half of which have sequence variations at either C or N terminus. To explore their roles in endogenous peptide-mediated GIPR signaling, we determined the cryoelectron microscopy (cryo-EM) structures of the two N terminus-altered SVs (referred as GIPR-202 and GIPR-209 in the Ensembl database, SV1 and SV2 here, respectively) and investigated the outcome of coexpressing each of them in question with GIPR in HEK293T cells with respect to ligand binding, receptor expression, cAMP (adenosine 3,5-cyclic monophosphate) accumulation, β-arrestin recruitment, and cell surface localization. It was found that while both N terminus-altered SVs of GIPR neither bound to the hormone nor elicited signal transduction per se, they suppressed ligand binding and cAMP accumulation of GIPR. Meanwhile, SV1 reduced GIPR-mediated β-arrestin 2 responses. The cryo-EM structures of SV1 and SV2 showed that they reorganized the extracellular halves of transmembrane helices 1, 6, and 7 and extracellular loops 2 and 3 to adopt a ligand-binding pocket-occupied conformation, thereby losing binding ability to the peptide. The results suggest a form of signal bias that is constitutive and ligand-independent, thus expanding our knowledge of biased signaling beyond pharmacological manipulation (i.e., ligand specific) as well as constitutive and ligand-independent (e.g., SV1 of the growth hormone-releasing hormone receptor).
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Affiliation(s)
- Fenghui Zhao
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
| | - Kaini Hang
- iHuman Institute, ShanghaiTech University, Shanghai201210, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai201210, China
| | - Qingtong Zhou
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai200032, China
- Research Center for Deepsea Bioresources, Sanya, Hainan572025, China
| | - Lijun Shao
- iHuman Institute, ShanghaiTech University, Shanghai201210, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai201210, China
| | - Hao Li
- Research Center for Deepsea Bioresources, Sanya, Hainan572025, China
| | - Wenzhuo Li
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
| | - Shi Lin
- Research Center for Deepsea Bioresources, Sanya, Hainan572025, China
| | - Antao Dai
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
| | - Xiaoqing Cai
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
| | - Yanyun Liu
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing210023, China
| | - Yingna Xu
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai200032, China
| | - Wenbo Feng
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai200032, China
| | - Dehua Yang
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
- Research Center for Deepsea Bioresources, Sanya, Hainan572025, China
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing210023, China
| | - Ming-Wei Wang
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai200032, China
- Research Center for Deepsea Bioresources, Sanya, Hainan572025, China
- Department of Chemistry, School of Science, The University of Tokyo, Tokyo113-0033, Japan
- School of Pharmacy, Hainan Medical University, Haikou570228, China
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2
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Hammoud R, Drucker DJ. Beyond the pancreas: contrasting cardiometabolic actions of GIP and GLP1. Nat Rev Endocrinol 2023; 19:201-216. [PMID: 36509857 DOI: 10.1038/s41574-022-00783-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/17/2022] [Indexed: 12/14/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP1) exhibit incretin activity, meaning that they potentiate glucose-dependent insulin secretion. The emergence of GIP receptor (GIPR)-GLP1 receptor (GLP1R) co-agonists has fostered growing interest in the actions of GIP and GLP1 in metabolically relevant tissues. Here, we update concepts of how these hormones act beyond the pancreas. The actions of GIP and GLP1 on liver, muscle and adipose tissue, in the control of glucose and lipid homeostasis, are discussed in the context of plausible mechanisms of action. Both the GIPR and GLP1R are expressed in the central nervous system, wherein receptor activation produces anorectic effects enabling weight loss. In preclinical studies, GIP and GLP1 reduce atherosclerosis. Furthermore, GIPR and GLP1R are expressed within the heart and immune system, and GLP1R within the kidney, revealing putative mechanisms linking GIP and GLP1R agonism to cardiorenal protection. We interpret the clinical and mechanistic data obtained for different agents that enable weight loss and glucose control for the treatment of obesity and type 2 diabetes mellitus, respectively, by activating or blocking GIPR signalling, including the GIPR-GLP1R co-agonist tirzepatide, as well as the GIPR antagonist-GLP1R agonist AMG-133. Collectively, we update translational concepts of GIP and GLP1 action, while highlighting gaps, areas of uncertainty and controversies meriting ongoing investigation.
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Affiliation(s)
- Rola Hammoud
- Department of Medicine, Lunenfeld-Tanenbaum Research Institute, Mt Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Daniel J Drucker
- Department of Medicine, Lunenfeld-Tanenbaum Research Institute, Mt Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.
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3
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Ko J, Jang S, Kwon W, Kim SY, Jang S, Kim E, Ji YR, Park S, Kim MO, Choi SK, Cho DH, Lee HS, Lim SG, Ryoo ZY. Protective Effect of GIP against Monosodium Glutamate-Induced Ferroptosis in Mouse Hippocampal HT-22 Cells through the MAPK Signaling Pathway. Antioxidants (Basel) 2022; 11:antiox11020189. [PMID: 35204073 PMCID: PMC8868324 DOI: 10.3390/antiox11020189] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/10/2022] [Accepted: 01/17/2022] [Indexed: 02/08/2023] Open
Abstract
The effect of glucose-dependent insulinotropic polypeptide (GIP) on cells under oxidative stress induced by glutamate, a neurotransmitter, and the underlying molecular mechanisms were assessed in the present study. We found that in the pre-treatment of HT-22 cells with glutamate in a dose-dependent manner, intracellular ROS were excessively generated, and additional cell damage occurred in the form of lipid peroxidation. The neurotoxicity caused by excessive glutamate was found to be ferroptosis and not apoptosis. Other factors (GPx-4, Nrf2, Nox1 and Hspb1) involved in ferroptosis were also identified. In other words, it was confirmed that GIP increased the activity of sub-signalling molecules in the process of suppressing ferroptosis as an antioxidant and maintained a stable cell cycle even under glutamate-induced neurotoxicity. At the same time, in HT-22 cells exposed to ferroptosis as a result of excessive glutamate accumulation, GIP sustained cell viability by activating the mitogen-activated protein kinase (MAPK) signalling pathway. These results suggest that the overexpression of the GIP gene increases cell viability by regulating mechanisms related to cytotoxicity and reactive oxygen species production in hippocampal neuronal cell lines.
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Affiliation(s)
- Jiwon Ko
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Soyoung Jang
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Wookbong Kwon
- Core Protein Resources Center, DGIST, Daegu 42988, Korea; (W.K.); (S.-K.C.)
- Division of Biotechnology, DGIST, Daegu 42988, Korea
| | - Si-Yong Kim
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Soyeon Jang
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Eungyung Kim
- Department of Animal Science and Biotechnology, Kyungpook National University, Sangju-si 37224, Korea; (E.K.); (M.-O.K.)
| | - Young-Rae Ji
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
- Section on Sensory Cell Regeneration and Development, Laboratory of Molecular Biology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sijun Park
- School of Life Science, Kyungpook National University, Daegu 42988, Korea;
| | - Myoung-Ok Kim
- Department of Animal Science and Biotechnology, Kyungpook National University, Sangju-si 37224, Korea; (E.K.); (M.-O.K.)
| | - Seong-Kyoon Choi
- Core Protein Resources Center, DGIST, Daegu 42988, Korea; (W.K.); (S.-K.C.)
- Division of Biotechnology, DGIST, Daegu 42988, Korea
| | - Dong-Hyung Cho
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
- Brain Science and Engineering Institute, Kyungpook National University, Daegu 42988, Korea
| | - Hyun-Shik Lee
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Su-Geun Lim
- School of Life Science, Kyungpook National University, Daegu 42988, Korea;
- Correspondence: (S.-G.L.); (Z.-Y.R.)
| | - Zae-Young Ryoo
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
- Correspondence: (S.-G.L.); (Z.-Y.R.)
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4
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Liu T, Ji RL, Tao YX. Naturally occurring mutations in G protein-coupled receptors associated with obesity and type 2 diabetes mellitus. Pharmacol Ther 2021; 234:108044. [PMID: 34822948 DOI: 10.1016/j.pharmthera.2021.108044] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/15/2021] [Accepted: 11/15/2021] [Indexed: 12/12/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of membrane receptors involved in the regulation of almost all known physiological processes. Dysfunctions of GPCR-mediated signaling have been shown to cause various diseases. The prevalence of obesity and type 2 diabetes mellitus (T2DM), two strongly associated disorders, is increasing worldwide, with tremendous economical and health burden. New safer and more efficacious drugs are required for successful weight reduction and T2DM treatment. Multiple GPCRs are involved in the regulation of energy and glucose homeostasis. Mutations in these GPCRs contribute to the development and progression of obesity and T2DM. Therefore, these receptors can be therapeutic targets for obesity and T2DM. Indeed some of these receptors, such as melanocortin-4 receptor and glucagon-like peptide 1 receptor, have provided important new drugs for treating obesity and T2DM. This review will focus on the naturally occurring mutations of several GPCRs associated with obesity and T2DM, especially incorporating recent large genomic data and insights from structure-function studies, providing leads for future investigations.
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Affiliation(s)
- Ting Liu
- Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL 36849, United States
| | - Ren-Lei Ji
- Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL 36849, United States.
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5
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Murata Y, Harada N, Kishino S, Iwasaki K, Ikeguchi-Ogura E, Yamane S, Kato T, Kanemaru Y, Sankoda A, Hatoko T, Kiyobayashi S, Ogawa J, Hirasawa A, Inagaki N. Medium-chain triglycerides inhibit long-chain triglyceride-induced GIP secretion through GPR120-dependent inhibition of CCK. iScience 2021; 24:102963. [PMID: 34466786 PMCID: PMC8382997 DOI: 10.1016/j.isci.2021.102963] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 01/14/2021] [Accepted: 08/05/2021] [Indexed: 12/13/2022] Open
Abstract
Long-chain triglycerides (LCTs) intake strongly stimulates GIP secretion from enteroendocrine K cells and induces obesity and insulin resistance partly due to GIP hypersecretion. In this study, we found that medium-chain triglycerides (MCTs) inhibit GIP secretion after single LCT ingestion and clarified the mechanism underlying MCT-induced inhibition of GIP secretion. MCTs reduced the CCK effect after single LCT ingestion in wild-type (WT) mice, and a CCK agonist completely reversed MCT-induced inhibition of GIP secretion. In vitro studies showed that medium-chain fatty acids (MCFAs) inhibit long-chain fatty acid (LCFA)-stimulated CCK secretion and increase in intracellular Ca2+ concentrations through inhibition of GPR120 signaling. Long-term administration of MCTs reduced obesity and insulin resistance in high-LCT diet-fed WT mice, but not in high-LCT diet-fed GIP-knockout mice. Thus, MCT-induced inhibition of GIP hypersecretion reduces obesity and insulin resistance under high-LCT diet feeding condition.
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Affiliation(s)
- Yuki Murata
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Shigenobu Kishino
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Kanako Iwasaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Eri Ikeguchi-Ogura
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Shunsuke Yamane
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Tomoko Kato
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Yoshinori Kanemaru
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Akiko Sankoda
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Tomonobu Hatoko
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Sakura Kiyobayashi
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Jun Ogawa
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Akira Hirasawa
- Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
- Corresponding author
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6
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Kanemaru Y, Harada N, Shimazu-Kuwahara S, Yamane S, Ikeguchi E, Murata Y, Kiyobayashi S, Hatoko T, Inagaki N. Absence of GIP secretion alleviates age-related obesity and insulin resistance. J Endocrinol 2020; 245:13-20. [PMID: 31977316 PMCID: PMC7040458 DOI: 10.1530/joe-19-0477] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 01/23/2020] [Indexed: 12/25/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is an incretin secreted from enteroendocine K cells after nutrient ingestion. Fat strongly induces GIP secretion, and GIP hypersecretion is involved in high-fat diet-induced obesity and insulin resistance. Aging also induces GIP hypersecretion, but its effect on body weight gain and insulin sensitivity remains unclear. In the present study, we investigated the effect of GIP on age-related body weight gain and insulin resistance using GIP-knockout homozygous (GIP-/-) and heterozygous (GIP+/-) mice, which have entirely absent and 50% reduced GIP secretion compared to wild-type (WT) mice, respectively. Under 12% fat-containing normal diet feeding condition, body weight was significantly lower in GIP-/- mice compared to that in WT and GIP+/- mice from 38 weeks of age, while there was no significant difference between WT and GIP+/- mice. Visceral and s.c. fat mass were also significantly lower in GIP-/- mice compared to those in WT and GIP+/- mice. During oral glucose tolerance test, blood glucose levels did not differ among the three groups. Insulin levels were significantly lower in GIP-/- mice than those in WT and GIP+/- mice. During insulin tolerance test, GIP-/- mice showed higher insulin sensitivity than that of WT and GIP+/- mice. Adiponectin mRNA levels were increased and leptin mRNA levels tended to be decreased in adipose tissue of GIP-/- mice. These results demonstrate that GIP is involved in age-related obesity and insulin resistance and that inhibition of GIP secretion alleviates age-related fat mass gain and insulin resistance under carbohydrate-based diet feeding condition.
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Affiliation(s)
- Yoshinori Kanemaru
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Satoko Shimazu-Kuwahara
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Preemptive Medicine and Lifestyle Related Disease Research Center, Kyoto University Hospital, Kyoto, Japan
| | - Shunsuke Yamane
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Eri Ikeguchi
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Yuki Murata
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Sakura Kiyobayashi
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Tomonobu Hatoko
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Correspondence should be addressed to N Inagaki:
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7
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GIP as a Potential Therapeutic Target for Atherosclerotic Cardiovascular Disease-A Systematic Review. Int J Mol Sci 2020; 21:ijms21041509. [PMID: 32098413 PMCID: PMC7073149 DOI: 10.3390/ijms21041509] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 02/20/2020] [Accepted: 02/21/2020] [Indexed: 02/06/2023] Open
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are gut hormones that are secreted from enteroendocrine L cells and K cells in response to digested nutrients, respectively. They are also referred to incretin for their ability to stimulate insulin secretion from pancreatic beta cells in a glucose-dependent manner. Furthermore, GLP-1 exerts anorexic effects via its actions in the central nervous system. Since native incretin is rapidly inactivated by dipeptidyl peptidase-4 (DPP-4), DPP-resistant GLP-1 receptor agonists (GLP-1RAs), and DPP-4 inhibitors are currently used for the treatment of type 2 diabetes as incretin-based therapy. These new-class agents have superiority to classical oral hypoglycemic agents such as sulfonylureas because of their low risks for hypoglycemia and body weight gain. In addition, a number of preclinical studies have shown the cardioprotective properties of incretin-based therapy, whose findings are further supported by several randomized clinical trials. Indeed, GLP-1RA has been significantly shown to reduce the risk of cardiovascular and renal events in patients with type 2 diabetes. However, the role of GIP in cardiovascular disease remains to be elucidated. Recently, pharmacological doses of GIP receptor agonists (GIPRAs) have been found to exert anti-obesity effects in animal models. These observations suggest that combination therapy of GLP-1R and GIPR may induce superior metabolic and anti-diabetic effects compared with each agonist individually. Clinical trials with GLP-1R/GIPR dual agonists are ongoing in diabetic patients. Therefore, in this review, we summarize the cardiovascular effects of GIP and GIPRAs in cell culture systems, animal models, and humans.
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8
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Grandl G, Novikoff A, DiMarchi R, Tschöp MH, Müller TD. Gut Peptide Agonism in the Treatment of Obesity and Diabetes. Compr Physiol 2019; 10:99-124. [PMID: 31853954 DOI: 10.1002/cphy.c180044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Obesity is a global healthcare challenge that gives rise to devastating diseases such as the metabolic syndrome, type-2 diabetes (T2D), and a variety of cardiovascular diseases. The escalating prevalence of obesity has led to an increased interest in pharmacological options to counteract excess weight gain. Gastrointestinal hormones such as glucagon, amylin, and glucagon-like peptide-1 (GLP-1) are well recognized for influencing food intake and satiety, but the therapeutic potential of these native peptides is overall limited by a short half-life and an often dose-dependent appearance of unwanted effects. Recent clinical success of chemically optimized GLP-1 mimetics with improved pharmacokinetics and sustained action has propelled pharmacological interest in using bioengineered gut hormones to treat obesity and diabetes. In this article, we summarize the basic biology and signaling mechanisms of selected gut peptides and discuss how they regulate systemic energy and glucose metabolism. Subsequently, we focus on the design and evaluation of unimolecular drugs that combine the beneficial effects of selected gut hormones into a single entity to optimize the beneficial impact on systems metabolism. © 2020 American Physiological Society. Compr Physiol 10:99-124, 2020.
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Affiliation(s)
- Gerald Grandl
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Aaron Novikoff
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Richard DiMarchi
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Matthias H Tschöp
- German Center for Diabetes Research (DZD), Neuherberg, Germany.,Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - Timo D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany.,German Center for Diabetes Research (DZD), Neuherberg, Germany.,Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, Tübingen, Germany
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9
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Murata Y, Harada N, Yamane S, Iwasaki K, Ikeguchi E, Kanemaru Y, Harada T, Sankoda A, Shimazu-Kuwahara S, Joo E, Poudyal H, Inagaki N. Medium-chain triglyceride diet stimulates less GIP secretion and suppresses body weight and fat mass gain compared with long-chain triglyceride diet. Am J Physiol Endocrinol Metab 2019; 317:E53-E64. [PMID: 30990747 DOI: 10.1152/ajpendo.00200.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Gastric inhibitory polypeptide (GIP) is an incretin secreted from enteroendocrine K cells and potentiates insulin secretion from pancreatic β-cells. GIP also enhances long-chain triglyceride (LCT) diet-induced obesity and insulin resistance. Long-term intake of medium-chain triglyceride (MCT) diet is known to induce less body weight and fat mass gain than that of LCT diet. However, the effect of MCT diet feeding on GIP secretion and the effect of GIP on body weight and fat mass under MCT diet-feeding condition are unknown. In this study, we evaluated the effect of single MCT oil administration on GIP secretion and compared the effect of long-term MCT and LCT diet on body weight and fat mass gain in wild-type (WT) and GIP-knockout (GIP KO) mice. Single administration of LCT oil induced GIP secretion but that of MCT oil did not in WT mice. Long-term intake of LCT diet induced GIP hypersecretion and significant body weight and fat mass gain compared with that of control fat (CF) diet in WT mice. In contrast, MCT diet did not induce GIP hypersecretion, and MCT diet-fed mice showed smaller increase in body weight and fat mass gain compared with CF diet-fed mice. In GIP KO mice, body weight and fat mass were markedly attenuated in LCT diet-fed mice but not in MCT diet-fed mice. Our results suggest that long-term intake of MCT diet stimulates less GIP secretion and suppresses body weight and fat mass gain compared with that of LCT diet.
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Affiliation(s)
- Yuki Murata
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Shunsuke Yamane
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Kanako Iwasaki
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Eri Ikeguchi
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Yoshinori Kanemaru
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Takanari Harada
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Akiko Sankoda
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Satoko Shimazu-Kuwahara
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Erina Joo
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Hemant Poudyal
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
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10
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Yamane S, Harada N. Gastric inhibitory polypeptide/glucose-dependent insulinotropic polypeptide signaling in adipose tissue. J Diabetes Investig 2018; 10:3-5. [PMID: 30248247 PMCID: PMC6319611 DOI: 10.1111/jdi.12942] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
GIPR signaling in adipose tissue plays an important role in HFD‐induced insulin resistance and hepatic steatosis in vivo, with no direct effect on fat accumulation, through IL‐6 signaling
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Affiliation(s)
- Shunsuke Yamane
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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11
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Ikeguchi E, Harada N, Kanemaru Y, Sankoda A, Yamane S, Iwasaki K, Imajo M, Murata Y, Suzuki K, Joo E, Inagaki N. Transcriptional factor Pdx1 is involved in age-related GIP hypersecretion in mice. Am J Physiol Gastrointest Liver Physiol 2018; 315:G272-G282. [PMID: 29723041 DOI: 10.1152/ajpgi.00054.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Fat accumulation with aging is a serious problem; glucose-dependent insulinotropic polypeptide/gastric inhibitory polypeptide (GIP) is an incretin that plays an important role in fat accumulation. GIP receptor knockout mice show reduced fat mass and improved insulin sensitivity associated with aging. Therefore, GIP is involved in fat accumulation and insulin resistance with aging. However, age-related changes of GIP secretion remain unclear. The present study aimed to elucidate age-related changes of GIP secretion and enteroendocrine K cells using GIP reporter [GIP-green fluorescent protein (GFP) knock-in heterozygous (GIPgfp/+)] mice. Aged 1-yr-old GIPgfp/+ mice exhibited a phenotype of fat accumulation, insulin resistance, and GIP hypersecretion compared with young (3-4 mo old) GIPgfp/+ mice. In aged mice, K-cell number in the small intestine and the mRNA expression levels of GIP and transcriptional factor pancreatic and duodenal homeobox-1 (Pdx1) in K cells were increased. K-cell number, GIP mRNA expression and content in small intestine, and GIP secretion were decreased after posteriori suppression of Pdx1 using intestine-specific gene transfer. Thus, Pdx1 positively regulates GIP mRNA and K-cell number in small intestine. Increased Pdx1 expression might be involved in GIP hypersecretion with aging. NEW & NOTEWORTHY Age-related changes of glucose-dependent insulinotropic polypeptide/gastric inhibitory polypeptide (GIP) secretion and K cells were investigated. We found that K-cell number and GIP and pancreatic and duodenal homeobox-1 (Pdx1) expression in K cells were increased in aged mice, which showed greater GIP secretion compared with young mice. In addition, we have succeeded in posteriori suppression of Pdx1 in small intestine using the method of intestine-specific gene transfer, and showed that K-cell number, GIP expression, and GIP secretion were decreased in the Pdx1-knockdown intestine.
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Affiliation(s)
- Eri Ikeguchi
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Yoshinori Kanemaru
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Akiko Sankoda
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Shunsuke Yamane
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Kanako Iwasaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Masamichi Imajo
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University , Kyoto , Japan
| | - Yuki Murata
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Kazuyo Suzuki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Erina Joo
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
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12
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Maekawa R, Ogata H, Murase M, Harada N, Suzuki K, Joo E, Sankoda A, Iida A, Izumoto T, Tsunekawa S, Hamada Y, Oiso Y, Inagaki N, Arima H, Hayashi Y, Seino Y. Glucose-dependent insulinotropic polypeptide is required for moderate high-fat diet- but not high-carbohydrate diet-induced weight gain. Am J Physiol Endocrinol Metab 2018; 314:E572-E583. [PMID: 29406782 DOI: 10.1152/ajpendo.00352.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Both high-fat (HFD) and high-carbohydrate (ST) diets are known to induce weight gain. Glucose-dependent insulinotropic polypeptide (GIP) is secreted mainly from intestinal K cells upon stimuli by nutrients such as fat and glucose, and it potentiates glucose-induced insulin secretion. GIP is well known to contribute to HFD-induced obesity. In this study, we analyzed the effect of ST feeding on GIP secretion and metabolic parameters to explore the role of GIP in ST-induced weight gain. Both wild-type (WT) and GIP receptor deficient ( GiprKO) mice were fed normal chow (NC), ST, or moderate (m)HFD for 22 wk. Body weight was measured, and then glucose tolerance tests were performed. Insulin secretion from isolated islets also was analyzed. WT mice fed ST or mHFD displayed weight gain concomitant with increased plasma GIP levels compared with WT mice fed NC. WT mice fed mHFD showed improved glucose tolerance due to enhanced insulin secretion during oral glucose tolerance tests compared with WT mice fed NC or ST. GiprKO mice fed mHFD did not display weight gain. On the other hand, GiprKO mice fed ST showed weight gain and did not display obvious glucose intolerance. Glucose-induced insulin secretion was enhanced during intraperitoneal glucose tolerance tests and from isolated islets in both WT and GiprKO mice fed ST compared with those fed NC. In conclusion, enhanced GIP secretion induced by mHFD-feeding contributes to increased insulin secretion and body weight gain, whereas GIP is marginally involved in weight gain induced by ST-feeding.
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Affiliation(s)
- Ryuya Maekawa
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Hidetada Ogata
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Masatoshi Murase
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Kazuyo Suzuki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Erina Joo
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Akiko Sankoda
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Atsushi Iida
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Takako Izumoto
- Department of Oral and Maxillofacial Surgery, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Shin Tsunekawa
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Yoji Hamada
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
- Department of Metabolic Medicine, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Yutaka Oiso
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan
| | - Hiroshi Arima
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Yoshitaka Hayashi
- Department of Genetics, Division of Stress Adaptation and Protection, Research Institute of Environmental Medicine, Nagoya University , Nagoya , Japan
| | - Yusuke Seino
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine , Nagoya , Japan
- Department of Metabolic Medicine, Nagoya University Graduate School of Medicine , Nagoya , Japan
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13
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Ussher JR, Campbell JE, Mulvihill EE, Baggio LL, Bates HE, McLean BA, Gopal K, Capozzi M, Yusta B, Cao X, Ali S, Kim M, Kabir MG, Seino Y, Suzuki J, Drucker DJ. Inactivation of the Glucose-Dependent Insulinotropic Polypeptide Receptor Improves Outcomes following Experimental Myocardial Infarction. Cell Metab 2018; 27:450-460.e6. [PMID: 29275960 DOI: 10.1016/j.cmet.2017.11.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 10/15/2017] [Accepted: 11/15/2017] [Indexed: 12/15/2022]
Abstract
Incretin hormones exert pleiotropic metabolic actions beyond the pancreas. Although the heart expresses both incretin receptors, the cardiac biology of GIP receptor (GIPR) action remains incompletely understood. Here we show that GIPR agonism did not impair the response to cardiac ischemia. In contrast, genetic elimination of the Gipr reduced myocardial infarction (MI)-induced ventricular injury and enhanced survival associated with reduced hormone sensitive lipase (HSL) phosphorylation; it also increased myocardial triacylglycerol (TAG) stores. Conversely, direct GIPR agonism in the isolated heart reduced myocardial TAG stores and increased fatty acid oxidation. The cardioprotective phenotype in Gipr-/- mice was partially reversed by pharmacological activation or genetic overexpression of HSL. Selective Gipr inactivation in cardiomyocytes phenocopied Gipr-/- mice, resulting in improved survival and reduced adverse remodeling following experimental MI. Hence, the cardiomyocyte GIPR regulates fatty acid metabolism and the adaptive response to ischemic cardiac injury. These findings have translational relevance for developing GIPR-based therapeutics.
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Affiliation(s)
- John R Ussher
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada; Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Jonathan E Campbell
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada; Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA
| | - Erin E Mulvihill
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Laurie L Baggio
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Holly E Bates
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Brent A McLean
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Keshav Gopal
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Megan Capozzi
- Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA
| | - Bernardo Yusta
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Xiemin Cao
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Safina Ali
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Minsuk Kim
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - M Golam Kabir
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Yutaka Seino
- Kansai Electric Power Hospital and Medical Research Institute, 2-1-7 Fukushima-ku, Osaka 553-0003, Japan
| | - Jinya Suzuki
- Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Daniel J Drucker
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada.
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14
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Shalaby SM, Zidan HE, Shokry A, Saeed J, El-Sokkary RH. Association of incretin receptors genetic polymorphisms with type 2 diabetes mellitus in Egyptian patients. J Gene Med 2017; 19:e2973. [DOI: 10.1002/jgm.2973] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
Affiliation(s)
- Sally M. Shalaby
- Medical Biochemistry Department, Faculty of Medicine; Zagazig University; Zagazig Egypt
| | - Haidy E. Zidan
- Medical Biochemistry Department, Faculty of Medicine; Zagazig University; Zagazig Egypt
| | - Amira Shokry
- Internal Medicine Department, Faculty of Medicine; Zagazig University; Zagazig Egypt
| | - Jehan Saeed
- Internal Medicine Department, Faculty of Medicine; Zagazig University; Zagazig Egypt
| | - Rehab H. El-Sokkary
- Microbiology & Immunolgy Department, Faculty of Medicine; Zagazig University; Zagazig Egypt
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15
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Wang T, Ma X, Tang T, Higuchi K, Peng D, Zhang R, Chen M, Yan J, Wang S, Yan D, He Z, Jiang F, Bao Y, Jia W, Ishida K, Hu C. The effect of glucose-dependent insulinotropic polypeptide (GIP) variants on visceral fat accumulation in Han Chinese populations. Nutr Diabetes 2017; 7:e278. [PMID: 28530680 PMCID: PMC5518809 DOI: 10.1038/nutd.2017.28] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/05/2017] [Accepted: 04/06/2017] [Indexed: 11/09/2022] Open
Abstract
Objectives: We aim to validate the effects of glucose-dependent insulinotropic polypeptide (GIP) on fat distribution and glucose metabolism in Han Chinese populations. Methods: We genotyped six tag single-nucleotide polymorphisms (SNPs) of GIP and four tag SNPs of glucose-dependent insulinotropic polypeptide receptor (GIPR) among 2884 community-based individuals from Han Chinese populations. Linear analysis was applied to test the associations of these variants with visceral fat area (VFA) and subcutaneous fat area (SFA) quantified by magnetic resonance imaging as well as glucose-related traits. Results: We found that the C allele of rs4794008 of GIP tended to increase the VFA and the VFA/SFA ratio in all subjects (P=0.050 and P=0.054, respectively), and rs4794008 was associated with the VFA/SFA ratio in males (P=0.041) after adjusting for the BMI. The VFA-increasing allele of rs4794008 was not related to any glucose metabolism traits. However, rs9904288 of GIP was associated with the SFA in males as well as glucose-related traits in all subjects (P range, 0.004–0.049), and the GIPR variants displayed associations with both fat- and glucose-related traits. Conclusions: The results could provide the evidence that GIP might modulate visceral fat accumulation via incretin function or independent of incretin.
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Affiliation(s)
- T Wang
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - X Ma
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - T Tang
- Laboratory of Cardiovascular Immunology, Institute of Cardiology, Union Hospital, Tongji Medical College of Huazhong University of Science and Technology, Wuhan, China
| | - K Higuchi
- Kao (China) Research &Development Center Company Limited, Shanghai, China
| | - D Peng
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - R Zhang
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - M Chen
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - J Yan
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - S Wang
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - D Yan
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Z He
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - F Jiang
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Y Bao
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - W Jia
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - K Ishida
- Kao (China) Research &Development Center Company Limited, Shanghai, China
| | - C Hu
- Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.,Institute for Metabolic Diseases, Department of Endocrinology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital South Campus, Shanghai, China
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16
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Müller TD, Finan B, Clemmensen C, DiMarchi RD, Tschöp MH. The New Biology and Pharmacology of Glucagon. Physiol Rev 2017; 97:721-766. [PMID: 28275047 DOI: 10.1152/physrev.00025.2016] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In the last two decades we have witnessed sizable progress in defining the role of gastrointestinal signals in the control of glucose and energy homeostasis. Specifically, the molecular basis of the huge metabolic benefits in bariatric surgery is emerging while novel incretin-based medicines based on endogenous hormones such as glucagon-like peptide 1 and pancreas-derived amylin are improving diabetes management. These and related developments have fostered the discovery of novel insights into endocrine control of systemic metabolism, and in particular a deeper understanding of the importance of communication across vital organs, and specifically the gut-brain-pancreas-liver network. Paradoxically, the pancreatic peptide glucagon has reemerged in this period among a plethora of newly identified metabolic macromolecules, and new data complement and challenge its historical position as a gut hormone involved in metabolic control. The synthesis of glucagon analogs that are biophysically stable and soluble in aqueous solutions has promoted biological study that has enriched our understanding of glucagon biology and ironically recruited glucagon agonism as a central element to lower body weight in the treatment of metabolic disease. This review summarizes the extensive historical record and the more recent provocative direction that integrates the prominent role of glucagon in glucose elevation with its under-acknowledged effects on lipids, body weight, and vascular health that have implications for the pathophysiology of metabolic diseases, and the emergence of precision medicines to treat metabolic diseases.
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Affiliation(s)
- T D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - B Finan
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - C Clemmensen
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - R D DiMarchi
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - M H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
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17
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Joo E, Harada N, Yamane S, Fukushima T, Taura D, Iwasaki K, Sankoda A, Shibue K, Harada T, Suzuki K, Hamasaki A, Inagaki N. Inhibition of Gastric Inhibitory Polypeptide Receptor Signaling in Adipose Tissue Reduces Insulin Resistance and Hepatic Steatosis in High-Fat Diet-Fed Mice. Diabetes 2017; 66:868-879. [PMID: 28096257 DOI: 10.2337/db16-0758] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 01/11/2017] [Indexed: 11/13/2022]
Abstract
Gastric inhibitory polypeptide receptor (GIPR) directly induces energy accumulation in adipose tissue in vitro. However, the importance of the direct effect of GIPR signaling on adipose tissue in vivo remains unclear. In the current study, we generated adipose tissue-specific GIPR knockout (GIPRadipo-/-) mice and investigated the direct actions of GIP in adipose tissue. Under high-fat diet (HFD)-fed conditions, GIPRadipo-/- mice had significantly lower body weight and lean body mass compared with those in floxed GIPR (GIPRfl/fl) mice, although the fat volume was not significantly different between the two groups. Interestingly, insulin resistance, liver weight, and hepatic steatosis were reduced in HFD-fed GIPRadipo-/- mice. Plasma levels of interleukin-6 (IL-6), a proinflammatory cytokine that induces insulin resistance, were reduced in HFD-fed GIPRadipo-/- mice compared with those in HFD-fed GIPRfl/fl mice. Suppressor of cytokine signaling 3 (SOCS3) signaling is located downstream of the IL-6 receptor and is associated with insulin resistance and hepatic steatosis. Expression levels of SOCS3 mRNA were significantly lower in adipose and liver tissues of HFD-fed GIPRadipo-/- mice compared with those of HFD-fed GIPRfl/fl mice. Thus, GIPR signaling in adipose tissue plays a critical role in HFD-induced insulin resistance and hepatic steatosis in vivo, which may involve IL-6 signaling.
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Affiliation(s)
- Erina Joo
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Shunsuke Yamane
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Toru Fukushima
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Daisuke Taura
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kanako Iwasaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akiko Sankoda
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kimitaka Shibue
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takanari Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kazuyo Suzuki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akihiro Hamasaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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18
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Pujadas G, Drucker DJ. Vascular Biology of Glucagon Receptor Superfamily Peptides: Mechanistic and Clinical Relevance. Endocr Rev 2016; 37:554-583. [PMID: 27732058 DOI: 10.1210/er.2016-1078] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Regulatory peptides produced in islet and gut endocrine cells, including glucagon, glucagon-like peptide-1 (GLP-1), GLP-2, and glucose-dependent insulinotropic polypeptide, exert actions with considerable metabolic importance and translational relevance. Although the clinical development of GLP-1 receptor agonists and dipeptidyl peptidase-4 inhibitors has fostered research into how these hormones act on the normal and diseased heart, less is known about the actions of these peptides on blood vessels. Here we review the effects of these peptide hormones on normal blood vessels and highlight their vascular actions in the setting of experimental and clinical vascular injury. The cellular localization and signal transduction properties of the receptors for glucagon, GLP-1, GLP-2, and glucose-dependent insulinotropic polypeptide are discussed, with emphasis on endothelial cells and vascular smooth muscle cells. The actions of these peptides on the control of blood flow, blood pressure, angiogenesis, atherosclerosis, and vascular inflammation are reviewed with a focus on elucidating direct and indirect mechanisms of action. How these peptides traverse the blood-brain barrier is highlighted, with relevance to the use of GLP-1 receptor agonists to treat obesity and neurodegenerative disorders. Wherever possible, we compare actions identified in cell lines and primary cell culture with data from preclinical studies and, when available, results of human investigation, including studies in subjects with diabetes, obesity, and cardiovascular disease. Throughout the review, we discuss pitfalls, limitations, and challenges of the existing literature and highlight areas of controversy and uncertainty. The increasing use of peptide-based therapies for the treatment of diabetes and obesity underscores the importance of understanding the vascular biology of peptide hormone action.
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Affiliation(s)
- Gemma Pujadas
- Department of Medicine, Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Daniel J Drucker
- Department of Medicine, Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, ON M5G 1X5, Canada
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19
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Rodríguez-Pérez JM, Blachman-Braun R, Pomerantz A, Vargas-Alarcón G, Posadas-Sánchez R, Pérez-Hernández N. Possible role of intronic polymorphisms in the PHACTR1 gene on the development of cardiovascular disease. Med Hypotheses 2016; 97:64-70. [PMID: 27876132 DOI: 10.1016/j.mehy.2016.10.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 10/19/2016] [Indexed: 11/24/2022]
Abstract
Cardiovascular disease (CVD) is a complex multifactorial and polygenetic disease in which the interaction of numerous genes, genetic variants, and environmental factors plays a major role in its development. In an attempt to demonstrate the association between certain genetic variants and CVD, researchers have run large genomic wild association studies (GWAS) in recent decades. These studies have correlated several genomic variants with the presence of CVD. Recently, certain polymorphisms in the phosphatase and actin regulator 1 (PHACTR1) gene have been shown to be associated with CVD (i.e., coronary artery disease, coronary artery calcification, early onset myocardial infarction, cervical artery dissection and hypertension) in different ethnic groups. It is important to state that all of the described PHACTR1 genetic variants associated with CVD are located in non-translating gene regions known as introns. Thus, the purpose of this article is to hypothesize the effect of certain intronic polymorphisms in the PHACTR1 gene on pathological processes in the cardiovascular system. In addition, we present compelling evidence that supports this hypothesis as well as a methodology that could be used to assess the allelic effect using in vitro and in vivo models, which will ultimately demonstrate the pathophysiological contribution of PHACTR1 intronic polymorphisms to the development of CVD.
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Affiliation(s)
- José Manuel Rodríguez-Pérez
- Department of Molecular Biology, National Institute of Cardiology "Ignacio Chávez", Mexico City 14080, Mexico
| | - Ruben Blachman-Braun
- Department of Molecular Biology, National Institute of Cardiology "Ignacio Chávez", Mexico City 14080, Mexico
| | - Alan Pomerantz
- Department of Oncology and Hematology, National Institute of Medical Sciences and Nutrition "Salvador Zubirán", Mexico City 14080, Mexico
| | - Gilberto Vargas-Alarcón
- Department of Molecular Biology, National Institute of Cardiology "Ignacio Chávez", Mexico City 14080, Mexico
| | - Rosalinda Posadas-Sánchez
- Department of Endocrinology, National Institute of Cardiology "Ignacio Chávez", Mexico City 14080, Mexico
| | - Nonanzit Pérez-Hernández
- Department of Molecular Biology, National Institute of Cardiology "Ignacio Chávez", Mexico City 14080, Mexico.
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20
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Finan B, Müller TD, Clemmensen C, Perez-Tilve D, DiMarchi RD, Tschöp MH. Reappraisal of GIP Pharmacology for Metabolic Diseases. Trends Mol Med 2016; 22:359-376. [DOI: 10.1016/j.molmed.2016.03.005] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 03/15/2016] [Accepted: 03/17/2016] [Indexed: 12/31/2022]
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Abstract
The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are important regulators of insulin and glucagon secretion as well as lipid metabolism and appetite. These biological functions make their respective receptors (GIPR and GLP-1R) attractive targets in the treatment of both type 2 diabetes mellitus (T2DM) and obesity. The use of these native peptides in the treatment of these conditions is limited by their short half-lives. However, long-acting GLP-1R agonists and inhibitors of the enzyme that rapidly inactivates GIP and GLP-1 (dipeptidyl peptidase IV) are in clinical use. Although there is a loss of response to both hormones in T2DM, this effect appears to be more pronounced for GIP. This has made targeting GIPR less successful than GLP-1R. Furthermore, results demonstrating that GIPR knockout mice were resistant to diet-induced obesity suggested that GIPR antagonists may prove to be useful therapeutics. More recently, molecules that activate both receptors have shown promise in terms of glycemic and body weight control. This review focused on recent advances in the understanding of the signaling mechanisms and regulation of these two clinically important receptors.
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Affiliation(s)
- Suleiman Al-Sabah
- *Dr. Suleiman Al-Sabah, Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, PO Box 24923, Safat 13110 (Kuwait), E-Mail
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22
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Renner S, Blutke A, Streckel E, Wanke R, Wolf E. Incretin actions and consequences of incretin-based therapies: lessons from complementary animal models. J Pathol 2015; 238:345-58. [DOI: 10.1002/path.4655] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 10/02/2015] [Accepted: 10/05/2015] [Indexed: 12/30/2022]
Affiliation(s)
- Simone Renner
- Gene Centre, Centre for Innovative Medical Models (CiMM) and German Centre for Diabetes Research (DZD); Ludwig-Maximilians-Universität München; Germany
| | - Andreas Blutke
- Institute of Veterinary Pathology, Centre for Clinical Veterinary Medicine; Ludwig-Maximilians-Universität München; Germany
| | - Elisabeth Streckel
- Gene Centre, Centre for Innovative Medical Models (CiMM) and German Centre for Diabetes Research (DZD); Ludwig-Maximilians-Universität München; Germany
| | - Rüdiger Wanke
- Institute of Veterinary Pathology, Centre for Clinical Veterinary Medicine; Ludwig-Maximilians-Universität München; Germany
| | - Eckhard Wolf
- Gene Centre, Centre for Innovative Medical Models (CiMM) and German Centre for Diabetes Research (DZD); Ludwig-Maximilians-Universität München; Germany
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23
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Skrombolas D, Wylie I, Maharaj S, Frelinger JG. Characterization of an IL-12 p40/p35 Truncated Fusion Protein That can Inhibit the Action of IL-12. J Interferon Cytokine Res 2015; 35:690-7. [PMID: 25938719 DOI: 10.1089/jir.2014.0176] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Interleukin-12 (IL-12), a potent inducer of interferon gamma (IFNγ), is a heterodimeric protein consisting of p40 and p35 subunits whose expression is regulated independently. IL-12 is part of a cytokine family (currently consisting of IL-12, IL-23, IL-27, and IL-35) that can have profoundly different immunologic effects, despite sharing subunits. In constructing a single-chain fusion of p40 and p35, we discovered an insert corresponding to an intron in the gene encoding the p35 subunit that would result in a truncated form of p35 if translated. To test its possible role, we constructed, expressed, and analyzed fusions of p40 with the full-length or the truncated form of p35. The fusion protein containing the truncated p35 did not stimulate the proliferation of the IL-12-responsive cell line CTLL-2 nor did it induce IFNγ or the chemokine IFNγ-inducible protein 10 (IP-10, CXCL10) or monokine induced by IFNγ (MIG, CXCL9) from spleen cells. In striking contrast, the full-length IL-12 p40/p35 fusion induced robust responses in both assays. Moreover, the truncated IL-12 fusion protein inhibited the action of the full-length IL-12 p40/p35 fusion in the proliferation assay and also blocked the induction of IFNγ. These findings raise the possibility that alternative splicing may provide an additional regulatory mechanism for IL-12.
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Affiliation(s)
- Denise Skrombolas
- Department of Microbiology and Immunology, University of Rochester Medical Center , Rochester, New York
| | - Isabel Wylie
- Department of Microbiology and Immunology, University of Rochester Medical Center , Rochester, New York
| | - Shivana Maharaj
- Department of Microbiology and Immunology, University of Rochester Medical Center , Rochester, New York
| | - John G Frelinger
- Department of Microbiology and Immunology, University of Rochester Medical Center , Rochester, New York
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Ravi S, Schilder RJ, Kimball SR. Role of precursor mRNA splicing in nutrient-induced alterations in gene expression and metabolism. J Nutr 2015; 145:841-6. [PMID: 25761502 PMCID: PMC4408736 DOI: 10.3945/jn.114.203216] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Precursor mRNA (pre-mRNA) splicing is a critical step in gene expression that results in the removal of intronic sequences from immature mRNA, leading to the production of mature mRNA that can be translated into protein. Alternative pre-mRNA splicing is the process whereby alternative exons and/or introns are selectively included or excluded, generating mature mRNAs that encode proteins that may differ in function. The resulting alterations in the pattern of protein isoform expression can result in changes in protein-protein interaction, subcellular localization, and flux through metabolic pathways. Although basic mechanisms of pre-mRNA splicing of introns and exons are reasonably well characterized, how these mechanisms are regulated remains poorly understood. The goal of this review is to highlight selected recent advances in our understanding of the regulation of pre-mRNA splicing by nutrients and modulation of nutrient metabolism that result from changes in pre-mRNA splicing.
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Affiliation(s)
- Suhana Ravi
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA; and
| | - Rudolf J Schilder
- Departments of Entomology and Biology, The Pennsylvania State University, State College, PA
| | - Scot R Kimball
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA; and
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Coon SD, Rajendran VM, Schwartz JH, Singh SK. Glucose-dependent insulinotropic polypeptide-mediated signaling pathways enhance apical PepT1 expression in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 2015; 308:G56-62. [PMID: 25377315 PMCID: PMC4281688 DOI: 10.1152/ajpgi.00168.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have shown recently that glucose-dependent insulinotropic polypeptide (GIP), but not glucagon-like peptide 1 (GLP-1) augments H(+) peptide cotransporter (PepT1)-mediated peptide absorption in murine jejunum. While we observed that inhibiting cAMP production decreased this augmentation of PepT1 activity by GIP, it was unclear whether PKA and/or other regulators of cAMP signaling pathway(s) were involved. This study utilized tritiated glycyl-sarcosine [(3)H-glycyl-sarcosine (Gly-Sar), a relatively nonhydrolyzable dipeptide] uptake to measure PepT1 activity in CDX2-transfected IEC-6 (IEC-6/CDX2) cells, an absorptive intestinal epithelial cell model. Similar to our earlier observations with mouse jejunum, GIP but not GLP-1 augmented Gly-Sar uptake (control vs. +GIP: 154 ± 22 vs. 454 ± 39 pmol/mg protein; P < 0.001) in IEC-6/CDX2 cells. Rp-cAMP (a PKA inhibitor) and wortmannin [phosophoinositide-3-kinase (PI3K) inhibitor] pretreatment completely blocked, whereas neither calphostin C (a potent PKC inhibitor) nor BAPTA (an intracellular Ca(2+) chelator) pretreatment affected the GIP-augmented Gly-Sar uptake in IEC-6/CDX2 cells. The downstream metabolites Epac (control vs. Epac agonist: 287 ± 22 vs. 711 ± 80 pmol/mg protein) and AKT (control vs. AKT inhibitor: 720 ± 50 vs. 75 ± 19 pmol/mg protein) were shown to be involved in GIP-augmented PepT1 activity as well. Western blot analyses revealed that both GIP and Epac agonist pretreatment enhance the PepT1 expression on the apical membranes, which is completely blocked by wortmannin in IEC-6/CDX2 cells. These observations demonstrate that both cAMP and PI3K signaling pathways augment GIP-induced peptide uptake through Epac and AKT-mediated pathways in intestinal epithelial cells, respectively. In addition, these observations also indicate that both Epac and AKT-mediated signaling pathways increase apical membrane expression of PepT1 in intestinal absorptive epithelial cells.
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Affiliation(s)
- Steven D. Coon
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Department of Medicine, Boston Veterans Affairs Healthcare System, Boston, Massachusetts; ,3Department of Medicine, Boston University Clinical & Translational Science Institute, Boston, Massachusetts; and
| | - Vazhaikkurichi M. Rajendran
- 4Department of Biochemistry and Molecular Biology, West Virginia University School of Medicine, Morgantown, West Virginia
| | - John H. Schwartz
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts;
| | - Satish K. Singh
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Department of Medicine, Boston Veterans Affairs Healthcare System, Boston, Massachusetts;
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26
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Nasteska D, Harada N, Suzuki K, Yamane S, Hamasaki A, Joo E, Iwasaki K, Shibue K, Harada T, Inagaki N. Chronic reduction of GIP secretion alleviates obesity and insulin resistance under high-fat diet conditions. Diabetes 2014; 63:2332-43. [PMID: 24584548 DOI: 10.2337/db13-1563] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Gastric inhibitory polypeptide (GIP) exhibits potent insulinotropic effects on β-cells and anabolic effects on bone formation and fat accumulation. We explored the impact of reduced GIP levels in vivo on glucose homeostasis, bone formation, and fat accumulation in a novel GIP-GFP knock-in (KI) mouse. We generated GIP-GFP KI mice with a truncated prepro-GIP gene. The phenotype was assessed in heterozygous and homozygous states in mice on a control fat diet and a high-fat diet (HFD) in vivo and in vitro. Heterozygous GIP-GFP KI mice (GIP-reduced mice [GIP(gfp/+)]) exhibited reduced GIP secretion; in the homozygous state (GIP-lacking mice [GIP(gfp/gfp)]), GIP secretion was undetectable. When fed standard chow, GIP(gfp/+) and GIP(gfp/gfp) mice showed mild glucose intolerance with decreased insulin levels; bone volume was decreased in GIP(gfp/gfp) mice and preserved in GIP(gfp/+) mice. Under an HFD, glucose levels during an oral glucose tolerance test were similar in wild-type, GIP(gfp/+), and GIP(gfp/gfp) mice, while insulin secretion remained lower. GIP(gfp/+) and GIP(gfp/gfp) mice showed reduced obesity and reduced insulin resistance, accompanied by higher fat oxidation and energy expenditure. GIP-reduced mice demonstrate that partial reduction of GIP does not extensively alter glucose tolerance, but it alleviates obesity and lessens the degree of insulin resistance under HFD conditions, suggesting a potential therapeutic value.
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Affiliation(s)
- Daniela Nasteska
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kazuyo Suzuki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Shunsuke Yamane
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akihiro Hamasaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Erina Joo
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kanako Iwasaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kimitaka Shibue
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takanari Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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27
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Abstract
Gastric inhibitory polypeptide (GIP) and glucagon‐like peptide‐1 (GLP‐1) are the two primary incretin hormones secreted from the intestine on ingestion of glucose or nutrients to stimulate insulin secretion from pancreatic β cells. GIP and GLP‐1 exert their effects by binding to their specific receptors, the GIP receptor (GIPR) and the GLP‐1 receptor (GLP‐1R), which belong to the G‐protein coupled receptor family. Receptor binding activates and increases the level of intracellular cyclic adenosine monophosphate in pancreatic β cells, thereby stimulating insulin secretion glucose‐dependently. In addition to their insulinotropic effects, GIP and GLP‐1 play critical roles in various biological processes in different tissues and organs that express GIPR and GLP‐1R, including the pancreas, fat, bone and the brain. Within the pancreas, GIP and GLP‐1 together promote β cell proliferation and inhibit apoptosis, thereby expanding pancreatic β cell mass, while GIP enhances postprandial glucagon response and GLP‐1 suppresses it. In adipose tissues, GIP but not GLP‐1 facilitates fat deposition. In bone, GIP promotes bone formation while GLP‐1 inhibits bone absorption. In the brain, both GIP and GLP‐1 are thought to be involved in memory formation as well as the control of appetite. In addition to these differences, secretion of GIP and GLP‐1 and their insulinotropic effects on β cells have been shown to differ in patients with type 2 diabetes compared to healthy subjects. We summarize here the similarities and differences of these two incretin hormones in secretion and metabolism, their insulinotropic action on pancreatic β cells, and their non‐insulinotropic effects, and discuss their potential in treatment of type 2 diabetes. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00022.x, 2010)
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Affiliation(s)
- Yutaka Seino
- The Division of Diabetes, Clinical Nutrition and Endocrinology, Kansai Electric Power Hospital, Osaka
| | - Mitsuo Fukushima
- The Division of Diabetes, Clinical Nutrition and Endocrinology, Kansai Electric Power Hospital, Osaka ; The Department of Nutritional Science, Okayama Prefectural University, Okayama, Japan
| | - Daisuke Yabe
- The Division of Diabetes, Clinical Nutrition and Endocrinology, Kansai Electric Power Hospital, Osaka
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Yamane S, Harada N, Hamasaki A, Muraoka A, Joo E, Suzuki K, Nasteska D, Tanaka D, Ogura M, Harashima SI, Inagaki N. Effects of glucose and meal ingestion on incretin secretion in Japanese subjects with normal glucose tolerance. J Diabetes Investig 2014; 3:80-5. [PMID: 24843549 PMCID: PMC4014936 DOI: 10.1111/j.2040-1124.2011.00143.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
UNLABELLED Aims/Introduction: Gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the major incretins; their secretion after various nutrient loads are well-evaluated in Caucasians. However, little is known of the relationship between incretin secretion and differing nutritional loading in Japanese subjects. In the present study, we evaluated GIP and GLP-1 secretion in Japanese subjects with normal glucose tolerance (NGT) after glucose loading (75 g glucose and 17 g glucose) and meal ingestion. MATERIALS AND METHODS A total of 10 Japanese NGT subjects participated in 75 g oral glucose tolerance test (OGTT), 17 g OGTT and meal tolerance test (MTT). Plasma glucose (PG), serum insulin (IRI), serum C-peptide (CPR), plasma total GIP, and plasma total GLP-1 levels during OGTT and MTT were determined. RESULTS Area under the curve (AUC)-GIP was increased in proportion to the amount of glucose, and was highest in MTT, showing that GIP secretion is also stimulated by nutrients other than glucose, such as lipid. In contrast, although the larger glucose load tended to induce a larger GLP-1 release, AUC-GLP-1 was not significantly different among the three loading tests (75 g OGTT, 17 g OGTT, MTT) irrespective of the kind or amount of nutrition load. CONCLUSIONS Our results suggest that nutritional composition might have a greater effect on GIP secretion than that on GLP-1 secretion in Japanese NGT subjects. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00143.x, 2012).
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Affiliation(s)
- Shunsuke Yamane
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Norio Harada
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akihiro Hamasaki
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Atsushi Muraoka
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Erina Joo
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kazuyo Suzuki
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Daniela Nasteska
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Daisuke Tanaka
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Masahito Ogura
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Shin-Ichi Harashima
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Nobuya Inagaki
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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Harada N, Hamasaki A, Yamane S, Muraoka A, Joo E, Fujita K, Inagaki N. Plasma gastric inhibitory polypeptide and glucagon-like peptide-1 levels after glucose loading are associated with different factors in Japanese subjects. J Diabetes Investig 2014; 2:193-9. [PMID: 24843483 PMCID: PMC4014918 DOI: 10.1111/j.2040-1124.2010.00078.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Aims/Introduction: Gastric inhibitory polypeptide (GIP) and glucagon‐like peptide‐1 (GLP‐1) are major incretins that potentiate insulin secretion from pancreatic β‐cells. The factors responsible for incretin secretion have been reported in Caucasian subjects, but have not been thoroughly evaluated in Japanese subjects. We evaluated the factors associated with incretin secretion during oral glucose tolerance test (OGTT) in Japanese subjects with normal glucose tolerance (NGT). Materials and Methods: We measured plasma GIP and GLP‐1 levels during OGTT in 17 Japanese NGT subjects and evaluated the factors associated with GIP and GLP‐1 secretion using simple and multiple regression analyses. Results: GIP secretion (AUC‐GIP) was positively associated with body mass index (P < 0.05), and area under the curve (AUC) of C‐peptide (P < 0.05) and glucagon (P < 0.01), whereas GLP‐1 secretion (AUC‐GLP‐1) was negatively associated with AUC of plasma glucose (P < 0.05). The insulinogenic index was most strongly associated with GIP secretion (P < 0.05); homeostasis model assessment β‐cell was the most the strongly associated factor in GLP‐1 secretion (P < 0.05) among the four indices of insulin secretion and insulin sensitivity. Conclusions: Several distinct factors might be associated with GIP and GLP‐1 secretion during OGTT in Japanese subjects. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00078.x, 2011)
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Affiliation(s)
- Norio Harada
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akihiro Hamasaki
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Shunsuke Yamane
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Atsushi Muraoka
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Erina Joo
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kazuyo Fujita
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Nobuya Inagaki
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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30
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Yamane S, Hamamoto Y, Harashima SI, Harada N, Hamasaki A, Toyoda K, Fujita K, Joo E, Seino Y, Inagaki N. GLP-1 receptor agonist attenuates endoplasmic reticulum stress-mediated β-cell damage in Akita mice. J Diabetes Investig 2014; 2:104-10. [PMID: 24843469 PMCID: PMC4015545 DOI: 10.1111/j.2040-1124.2010.00075.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Aims/Introduction: Endoplasmic reticulum (ER) stress is one of the contributing factors in the development of type 2 diabetes. To investigate the cytoprotective effect of glucagon‐like peptide 1 receptor (GLP‐1R) signaling in vivo, we examined the action of exendin‐4 (Ex‐4), a potent GLP‐1R agonist, on β‐cell apoptosis in Akita mice, an animal model of ER stress‐mediated diabetes. Materials and Methods: Ex‐4, phosphate‐buffered saline (PBS) or phlorizin were injected intraperitoneally twice a day from 3 to 5 weeks‐of‐age. We evaluated the changes in blood glucose levels, bodyweights, and pancreatic insulin‐positive area and number of islets. The effect of Ex‐4 on the numbers of C/EBP‐homologous protein (CHOP)‐, TdT‐mediated dUTP‐biotin nick‐end labeling (TUNEL)‐ or proliferating cell nuclear antigen‐positive β‐cells were also evaluated. Results: Ex‐4 significantly reduced blood glucose levels and increased both the insulin‐positive area and the number of islets compared with PBS‐treated mice. In contrast, there was no significant difference in the insulin‐positive area between PBS‐treated mice and phlorizin‐treated mice, in which blood glucose levels were controlled similarly to those in Ex‐4‐treated mice. Furthermore, treatment of Akita mice with Ex‐4 resulted in a significant decrease in the number of CHOP‐positive β‐cells and TUNEL‐positive β‐cells, and in CHOP mRNA levels in β‐cells, but there was no significant difference between the PBS‐treated group and the phlorizin‐treated group. Proliferating cell nuclear antigen staining showed no significant difference among the three groups in proliferation of β‐cells. Conclusions: These data suggest that Ex‐4 treatment can attenuate ER stress‐mediated β‐cell damage, mainly through a reduction of apoptotic cell death that is independent of lowered blood glucose levels. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00075.x, 2010)
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Affiliation(s)
- Shunsuke Yamane
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University
| | - Yoshiyuki Hamamoto
- Center for Diabetes and Endocrinology, Tazuke Kofukai Medical Research Institute, Kitano Hospital
| | - Shin-Ichi Harashima
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University
| | - Norio Harada
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University
| | - Akihiro Hamasaki
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University
| | - Kentaro Toyoda
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University
| | - Kazuyo Fujita
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University
| | - Erina Joo
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University
| | - Yutaka Seino
- Division of Diabetes, Clinical Nutrition and Endocrinology, Department of Medicine, Kansai Electric Power Hospital, Osaka, Japan
| | - Nobuya Inagaki
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University ; CREST of Japan Science and Technology (JST), Kyoto
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Coon SD, Schwartz JH, Rajendran VM, Jepeal L, Singh SK. Glucose-dependent insulinotropic polypeptide regulates dipeptide absorption in mouse jejunum. Am J Physiol Gastrointest Liver Physiol 2013; 305:G678-84. [PMID: 24072682 PMCID: PMC3840233 DOI: 10.1152/ajpgi.00098.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) secreted from jejunal mucosal K cells augments insulin secretion and plays a critical role in the pathogenesis of obesity and Type 2 diabetes mellitus. In recent studies, we have shown GIP directly activates Na-glucose cotransporter-1 (SGLT1) and enhances glucose absorption in mouse jejunum. It is not known whether GIP would also regulate other intestinal nutrient absorptive processes. The present study investigated the effect of GIP on proton-peptide cotransporter-1 (PepT1) that mediates di- and tripeptide absorption as well as peptidomimetic drugs. Immunohistochemistry studies localized both GIP receptor (GIPR) and PepT1 proteins on the basolateral and apical membranes of normal mouse jejunum, respectively. Anti-GIPR antibody detected 50-, 55-, 65-, and 70-kDa proteins, whereas anti-PepT1 detected a 70-kDa proteins in mucosal homogenates of mouse jejunum. RT-PCR analyses established the expression of GIPR- and PepT1-specific mRNA in mucosal cells of mouse jejunum. Absorption of Gly-Sar (a nondigestible dipeptide) measured under voltage-clamp conditions revealed that the imposed mucosal H(+) gradient-enhanced Gly-Sar absorption as an evidence for the presence of PepT1-mediated H(+):Gly-Sar cotransport on the apical membranes of mouse jejunum. H(+):Gly-Sar absorption was completely inhibited by cephalexin (a competitive inhibitor of PepT1) and was activated by GIP. The GIP-activated Gly-Sar absorption was completely inhibited by RP-cAMP (a cAMP antagonist). In contrast to GIP, the ileal L cell secreting glucagon-like peptide-1 (GLP-1) did not affect the H(+):Gly-Sar absorption in mouse jejunum. We conclude from these observations that GIP, but not GLP-1, directly activates PepT1 activity by a cAMP-dependent signaling pathway in jejunum.
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Affiliation(s)
- Steven D. Coon
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Veterans Affairs Boston Healthcare System, Boston, Massachusetts; ,3Boston University Clinical and Translational Science Institute, Boston, Massachusetts; and
| | - John H. Schwartz
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts;
| | - Vazhaikkurichi M. Rajendran
- 4Department of Biochemistry and Molecular Biology, West Virginia University School of Medicine, Morgantown, West Virginia
| | - Lisa Jepeal
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Veterans Affairs Boston Healthcare System, Boston, Massachusetts;
| | - Satish K. Singh
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Veterans Affairs Boston Healthcare System, Boston, Massachusetts;
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Abstract
Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones that control the secretion of insulin, glucagon, and somatostatin to facilitate glucose disposal. The actions of incretin hormones are terminated via enzymatic cleavage by dipeptidyl peptidase-4 (DPP-4) and through renal clearance. GLP-1 and GIP promote β-cell proliferation and survival in rodents. DPP-4 inhibitors expand β-cell mass, reduce α-cell mass, and inhibit glucagon secretion in preclinical studies; however, whether incretin-based therapies sustain functional β-cell mass in human diabetic subjects remains unclear. GLP-1 and GIP exert their actions predominantly through unique G protein-coupled receptors expressed on β-cells and other pancreatic cell types. Accurate localization of incretin receptor expression in pancreatic ductal or acinar cells in normal or diabetic human pancreas is challenging because antisera used for detection of the GLP-1 receptor often are neither sufficiently sensitive nor specific to yield reliable data. This article reviews recent advances and controversies in incretin hormone action in the pancreas and contrasts established mechanisms with areas of uncertainty. Furthermore, methodological challenges and pitfalls are highlighted and key areas requiring additional scientific investigation are outlined.
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Cox RH, Fromme SJ. A naturally occurring truncated Cav1.2 α1-subunit inhibits Ca2+ current in A7r5 cells. Am J Physiol Cell Physiol 2013; 305:C896-905. [PMID: 23926129 DOI: 10.1152/ajpcell.00217.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Alternative splicing of the voltage-gated Ca(2+) (CaV) α1-subunit adds to the functional diversity of Ca(2+) channels. A variant with a 73-nt deletion in exon 15 of the Cav1.2 α1-subunit (Cav1.2Δ73) produced by alternative splicing that predicts a truncated protein has been described, but its function, if any, is unknown. We sought to determine if, by analogy to other truncated CaV α1-subunits, Cav1.2Δ73 acts as an inhibitor of wild-type Cav1.2 currents. HEK-293 cells were transfected with Cav1.2Δ73 in a pIRES vector with CD8 or in pcDNA3.1 with a V5/his COOH-terminal tag plus β2 and α2δ1 accessory subunits and pEGFP. Production of Cav1.2Δ73 protein was confirmed by Western blotting and immunofluorescence. Voltage-clamp studies revealed the absence of functional channels in transfected cells. In contrast, cells transfected with full-length Cav1.2 plus accessory subunits and pEGFP exhibited robust Ca(2+) currents. A7r5 cells exhibited endogenous Cav1.2-based currents that were greatly reduced (>80%) without a change in voltage-dependent activation when transfected with Cav1.2Δ73-IRES-CD8 compared with empty vector or pIRES-CD8 controls. Transfection of A7r5 cells with an analogous Cav2.3Δ73-IRES-CD8 had no effect on Ca(2+) currents. Immunofluorescence showed intracellular, but not plasma membrane, localization of Cav1.2Δ73-V5/his, as well as colocalization with an endoplasmic reticulum marker, ER Organelle Lights. Expression of Cav1.2Δ73 α1-subunits in A7r5 cells inhibits endogenous Cav1.2 currents. The fact that this variant arises naturally by alternative splicing raises the possibility that it may represent a physiological mechanism to modulate Cav1.2 functional activity.
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Affiliation(s)
- Robert H Cox
- Program in Cardiovascular Studies, Lankenau Institute for Medical Research, Main Line Health System, Wynnewood, Pennsylvania
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Ahlqvist E, Osmark P, Kuulasmaa T, Pilgaard K, Omar B, Brøns C, Kotova O, Zetterqvist AV, Stančáková A, Jonsson A, Hansson O, Kuusisto J, Kieffer TJ, Tuomi T, Isomaa B, Madsbad S, Gomez MF, Poulsen P, Laakso M, Degerman E, Pihlajamäki J, Wierup N, Vaag A, Groop L, Lyssenko V. Link between GIP and osteopontin in adipose tissue and insulin resistance. Diabetes 2013; 62:2088-94. [PMID: 23349498 PMCID: PMC3661641 DOI: 10.2337/db12-0976] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Low-grade inflammation in obesity is associated with accumulation of the macrophage-derived cytokine osteopontin (OPN) in adipose tissue and induction of local as well as systemic insulin resistance. Since glucose-dependent insulinotropic polypeptide (GIP) is a strong stimulator of adipogenesis and may play a role in the development of obesity, we explored whether GIP directly would stimulate OPN expression in adipose tissue and thereby induce insulin resistance. GIP stimulated OPN protein expression in a dose-dependent fashion in rat primary adipocytes. The level of OPN mRNA was higher in adipose tissue of obese individuals (0.13 ± 0.04 vs. 0.04 ± 0.01, P < 0.05) and correlated inversely with measures of insulin sensitivity (r = -0.24, P = 0.001). A common variant of the GIP receptor (GIPR) (rs10423928) gene was associated with a lower amount of the exon 9-containing isoform required for transmembrane activity. Carriers of the A allele with a reduced receptor function showed lower adipose tissue OPN mRNA levels and better insulin sensitivity. Together, these data suggest a role for GIP not only as an incretin hormone but also as a trigger of inflammation and insulin resistance in adipose tissue. Carriers of the GIPR rs10423928 A allele showed protective properties via reduced GIP effects. Identification of this unprecedented link between GIP and OPN in adipose tissue might open new avenues for therapeutic interventions.
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Affiliation(s)
- Emma Ahlqvist
- Department of Clinical Sciences, Diabetes, and Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - Peter Osmark
- Department of Clinical Sciences, Diabetes, and Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - Tiina Kuulasmaa
- Department of Clinical Nutrition, University of Eastern Finland, Kuopio, Finland
| | | | - Bilal Omar
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
| | | | - Olga Kotova
- Vascular ET-Coupling, Department of Clinical Sciences, University Hospital Malmö, Lund University, Malmö, Sweden
| | - Anna V. Zetterqvist
- Vascular ET-Coupling, Department of Clinical Sciences, University Hospital Malmö, Lund University, Malmö, Sweden
| | - Alena Stančáková
- Department of Medicine, University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland
| | - Anna Jonsson
- Department of Clinical Sciences, Diabetes, and Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - Ola Hansson
- Department of Clinical Sciences, Diabetes, and Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - Johanna Kuusisto
- Department of Medicine, University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland
| | - Timothy J. Kieffer
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tiinamaija Tuomi
- Folkhalsan Research Centre, Helsinki, Finland
- Department of Medicine, Helsinki University Central Hospital, and Research Program of Molecular Medicine, University of Helsinki, Helsinki, Finland
| | - Bo Isomaa
- Folkhalsan Research Centre, Helsinki, Finland
- Department of Social Services and Health Care, Jakobstad, Finland
| | - Sten Madsbad
- Department of Endocrinology, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Maria F. Gomez
- Vascular ET-Coupling, Department of Clinical Sciences, University Hospital Malmö, Lund University, Malmö, Sweden
| | | | - Markku Laakso
- Department of Medicine, University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland
| | - Eva Degerman
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
| | - Jussi Pihlajamäki
- Department of Clinical Nutrition, University of Eastern Finland, Kuopio, Finland
- Department of Medicine, University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland
| | - Nils Wierup
- Unit of Neuroendocrine Cell Biology, Department of Clinical Sciences, Lund University, Malmö, Sweden
| | - Allan Vaag
- Steno Diabetes Center, Gentofte, Denmark
- Department of Endocrinology, Rigshospitalet and Copenhagen University, Copenhagen, Denmark
| | - Leif Groop
- Department of Clinical Sciences, Diabetes, and Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
- Finnish Institute of Molecular Medicine, Helsinki University, Helsinki, Finland
| | - Valeriya Lyssenko
- Department of Clinical Sciences, Diabetes, and Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
- Corresponding author: Valeriya Lyssenko,
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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] [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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36
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Kelemen O, Convertini P, Zhang Z, Wen Y, Shen M, Falaleeva M, Stamm S. Function of alternative splicing. Gene 2013; 514:1-30. [PMID: 22909801 PMCID: PMC5632952 DOI: 10.1016/j.gene.2012.07.083] [Citation(s) in RCA: 488] [Impact Index Per Article: 44.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/21/2012] [Accepted: 07/30/2012] [Indexed: 12/15/2022]
Abstract
Almost all polymerase II transcripts undergo alternative pre-mRNA splicing. Here, we review the functions of alternative splicing events that have been experimentally determined. The overall function of alternative splicing is to increase the diversity of mRNAs expressed from the genome. Alternative splicing changes proteins encoded by mRNAs, which has profound functional effects. Experimental analysis of these protein isoforms showed that alternative splicing regulates binding between proteins, between proteins and nucleic acids as well as between proteins and membranes. Alternative splicing regulates the localization of proteins, their enzymatic properties and their interaction with ligands. In most cases, changes caused by individual splicing isoforms are small. However, cells typically coordinate numerous changes in 'splicing programs', which can have strong effects on cell proliferation, cell survival and properties of the nervous system. Due to its widespread usage and molecular versatility, alternative splicing emerges as a central element in gene regulation that interferes with almost every biological function analyzed.
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Affiliation(s)
- Olga Kelemen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Paolo Convertini
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Zhaiyi Zhang
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Yuan Wen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Manli Shen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Marina Falaleeva
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Stefan Stamm
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
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Kaitaniemi S, Grön K, Elovaara H, Salmi M, Jalkanen S, Elima K. Functional modulation of vascular adhesion protein-1 by a novel splice variant. PLoS One 2013; 8:e54151. [PMID: 23349812 PMCID: PMC3548902 DOI: 10.1371/journal.pone.0054151] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 12/07/2012] [Indexed: 12/22/2022] Open
Abstract
Vascular Adhesion Protein-1 (VAP-1) is an endothelial adhesion molecule belonging to the primary amine oxidases. Upon inflammation it takes part in the leukocyte extravasation cascade facilitating transmigration of leukocytes into the inflamed tissue. Screening of a human lung cDNA library revealed the presence of an alternatively spliced shorter transcript of VAP-1, VAP-1Δ3. Here, we have studied the functional and structural characteristics of VAP-1Δ3, and show that the mRNA for this splice variant is expressed in most human tissues studied. In comparison to the parent molecule this carboxy-terminally truncated isoform lacks several of the amino acids important in the formation of the enzymatic groove of VAP-1. In addition, the conserved His684, which takes part in coordinating the active site copper, is missing from VAP-1Δ3. Assays using the prototypic amine substrates methylamine and benzylamine demonstrated that VAP-1Δ3 is indeed devoid of the semicarbazide-sensitive amine oxidase (SSAO) activity characteristic to VAP-1. When VAP-1Δ3-cDNA is transfected into cells stably expressing VAP-1, the surface expression of the full-length molecule is reduced. Furthermore, the SSAO activity of the co-transfectants is diminished in comparison to transfectants expressing only VAP-1. The observed down-regulation of both the expression and enzymatic activity of VAP-1 may result from a dominant-negative effect caused by heterodimerization between VAP-1 and VAP-1Δ3, which was detected in co-immunoprecipitation studies. This alternatively spliced transcript adds thus to the repertoire of potential regulatory mechanisms through which the cell-surface expression and enzymatic activity of VAP-1 can be modulated.
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Affiliation(s)
- Sam Kaitaniemi
- MediCity Research Laboratory, University of Turku, Turku, Finland
- Department of Microbiology and Immunology, University of Turku, Turku, Finland
| | - Kirsi Grön
- MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Heli Elovaara
- MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Marko Salmi
- MediCity Research Laboratory, University of Turku, Turku, Finland
- Department of Medical Biochemistry and Genetics, University of Turku, Turku, Finland
| | - Sirpa Jalkanen
- MediCity Research Laboratory, University of Turku, Turku, Finland
- Department of Microbiology and Immunology, University of Turku, Turku, Finland
| | - Kati Elima
- MediCity Research Laboratory, University of Turku, Turku, Finland
- Department of Medical Biochemistry and Genetics, University of Turku, Turku, Finland
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Suzuki K, Harada N, Yamane S, Nakamura Y, Sasaki K, Nasteska D, Joo E, Shibue K, Harada T, Hamasaki A, Toyoda K, Nagashima K, Inagaki N. Transcriptional regulatory factor X6 (Rfx6) increases gastric inhibitory polypeptide (GIP) expression in enteroendocrine K-cells and is involved in GIP hypersecretion in high fat diet-induced obesity. J Biol Chem 2013; 288:1929-38. [PMID: 23192339 PMCID: PMC3548501 DOI: 10.1074/jbc.m112.423137] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 11/28/2012] [Indexed: 11/06/2022] Open
Abstract
Gastric inhibitory polypeptide (GIP) is an incretin released from enteroendocrine K-cells in response to nutrient ingestion. GIP potentiates glucose-stimulated insulin secretion and induces energy accumulation into adipose tissue, resulting in obesity. Plasma GIP levels are reported to be increased in the obese state. However, the molecular mechanisms of GIP secretion and high fat diet (HFD)-induced GIP hypersecretion remain unclear, primarily due to difficulties in separating K-cells from other intestinal epithelial cells in vivo. In this study, GIP-GFP knock-in mice that enable us to visualize K-cells by enhanced GFP were established. Microarray analysis of isolated K-cells from these mice revealed that transcriptional regulatory factor X6 (Rfx6) is expressed exclusively in K-cells. In vitro experiments using the mouse intestinal cell line STC-1 showed that knockdown of Rfx6 decreased mRNA expression, cellular content, and secretion of GIP. Rfx6 bound to the region in the gip promoter that regulates gip promoter activity, and overexpression of Rfx6 increased GIP mRNA expression. HFD induced obesity and GIP hypersecretion in GIP-GFP heterozygous mice in vivo. Immunohistochemical and flow cytometry analysis showed no significant difference in K-cell number between control fat diet-fed (CFD) and HFD-fed mice. However, GIP content in the upper small intestine and GIP mRNA expression in K-cells were significantly increased in HFD-fed mice compared with those in CFD-fed mice. Furthermore, expression levels of Rfx6 mRNA were increased in K-cells of HFD-fed mice. These results suggest that Rfx6 increases GIP expression and content in K-cells and is involved in GIP hypersecretion in HFD-induced obesity.
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Affiliation(s)
- Kazuyo Suzuki
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Norio Harada
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Shunsuke Yamane
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Yasuhiko Nakamura
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Kazuki Sasaki
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Daniela Nasteska
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Erina Joo
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Kimitaka Shibue
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Takanari Harada
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Akihiro Hamasaki
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Kentaro Toyoda
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Kazuaki Nagashima
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Nobuya Inagaki
- From the Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
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Abstract
Background and Aims: Ingestion of food stimulates the secretion of incretin peptides glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 to ensure the proper absorption and storage of nutrients. Menin is the 67 kDa protein product of the MEN1 gene recently reported to have a role in metabolism. In this study, we will determine the regulation of menin in the proximal duodenum by food intake and diet in correlation with GIP levels in the proximal duodenum of mice after an 18 h fast followed by 4 and 7 h refeeding and 3 months of high-fat diet. Methods: A dual luciferase assay was used to determine GIP promoter activity and ELISA was used to measure the levels of GIP after inhibition of menin through small interfering RNA (siRNA) and exposure to MAPK and AKT inhibitors. Colocalization of menin and GIP were determined by immunofluorescence. Results: Menin and GIP expression are regulated by fasting, refeeding and diet in the proximal duodenum. Overexpression of menin in STC-1 cells significantly inhibited GIP mRNA and promoter activity, whereas menin siRNA upregulated GIP levels. Inhibition of GIP expression by the PI3/AKT inhibitor, LY294002, was abrogated in STC-1 cells with reduced menin levels, whereas the MAPK inhibitor, UO126, inhibited the expression of GIP independent of menin. Exposure of STC-1 cells to GIP reduced menin expression in a dose-dependent manner via PI3K-AKT signaling. Conclusion: Feeding and diet regulates the expression of menin, which inversely correlates with GIP levels in the proximal duodenum. In vitro assays indicate that menin is a negative regulator of GIP via inhibition of PI3K-AKT signaling. We show menin colocalizing with GIP in K cells of the proximal gut and hypothesize that downregulation of menin may serve as a mechanism by which GIP is regulated in response to food intake and diet.
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40
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Cho YM, Merchant CE, Kieffer TJ. Targeting the glucagon receptor family for diabetes and obesity therapy. Pharmacol Ther 2012; 135:247-78. [DOI: 10.1016/j.pharmthera.2012.05.009] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 05/15/2012] [Indexed: 12/11/2022]
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Wise H. The roles played by highly truncated splice variants of G protein-coupled receptors. J Mol Signal 2012; 7:13. [PMID: 22938630 PMCID: PMC3477067 DOI: 10.1186/1750-2187-7-13] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 07/29/2012] [Indexed: 01/08/2023] Open
Abstract
Alternative splicing of G protein-coupled receptor (GPCR) genes greatly increases the total number of receptor isoforms which may be expressed in a cell-dependent and time-dependent manner. This increased diversity of cell signaling options caused by the generation of splice variants is further enhanced by receptor dimerization. When alternative splicing generates highly truncated GPCRs with less than seven transmembrane (TM) domains, the predominant effect in vitro is that of a dominant-negative mutation associated with the retention of the wild-type receptor in the endoplasmic reticulum (ER). For constitutively active (agonist-independent) GPCRs, their attenuated expression on the cell surface, and consequent decreased basal activity due to the dominant-negative effect of truncated splice variants, has pathological consequences. Truncated splice variants may conversely offer protection from disease when expression of co-receptors for binding of infectious agents to cells is attenuated due to ER retention of the wild-type co-receptor. In this review, we will see that GPCRs retained in the ER can still be functionally active but also that highly truncated GPCRs may also be functionally active. Although rare, some truncated splice variants still bind ligand and activate cell signaling responses. More importantly, by forming heterodimers with full-length GPCRs, some truncated splice variants also provide opportunities to generate receptor complexes with unique pharmacological properties. So, instead of assuming that highly truncated GPCRs are associated with faulty transcription processes, it is time to reassess their potential benefit to the host organism.
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Affiliation(s)
- Helen Wise
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China.
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42
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Sanchez C, Escrieut C, Clerc P, Gigoux V, Waser B, Reubi JC, Fourmy D. Characterization of a novel five-transmembrane domain cholecystokinin-2 receptor splice variant identified in human tumors. Mol Cell Endocrinol 2012; 349:170-9. [PMID: 22040601 DOI: 10.1016/j.mce.2011.10.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 10/12/2011] [Accepted: 10/12/2011] [Indexed: 12/24/2022]
Abstract
The cholecystokinin-2 receptor (CCK2R), is expressed in cancers where it contributes to tumor progression. The CCK2R is over-expressed in a sub-set of tumors, allowing its use in tumor targeting with a radiolabel ligand. Since discrepancies between mRNA levels and CCK2R binding sites were noticed, we searched for abnormally spliced variants in tumors from various origins having been previously reported to frequently express cholecystokinin receptors, such as medullary thyroid carcinomas, gastrointestinal stromal tumors, leiomyomas and leiomyosarcomas, and gastroenteropancreatic tumors. A variant of the CCK2R coding for a putative five-transmembrane domains receptor has been cloned. This variant represented as much as 6% of CCK2R levels. Ectopic expression in COS-7 cells revealed that this variant lacks biological activity due to its sequestration in endoplasmic reticulum. When co-expressed with the CCK2R, this variant diminished membrane density of the CCK2R and CCK2R-mediated activity (phospholipase-C and ERK activation). In conclusion, a novel splice variant acting as a dominant negative on membrane density of the CCK2R may be of importance for the pathophysiology of certain tumors and for their in vivo CCK2R-targeting.
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Vischer HF, Watts AO, Nijmeijer S, Leurs R. G protein-coupled receptors: walking hand-in-hand, talking hand-in-hand? Br J Pharmacol 2011; 163:246-60. [PMID: 21244374 DOI: 10.1111/j.1476-5381.2011.01229.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Most cells express a panel of different G protein-coupled receptors (GPCRs) allowing them to respond to at least a corresponding variety of extracellular ligands. In order to come to an integrative well-balanced functional response these ligand-receptor pairs can often cross-regulate each other. Although most GPCRs are fully capable to induce intracellular signalling upon agonist binding on their own, many GPCRs, if not all, appear to exist and function in homomeric and/or heteromeric assemblies for at least some time. Such heteromeric organization offers unique allosteric control of receptor pharmacology and function between the protomers and might even unmask 'new' features. However, it is important to realize that some functional consequences that are proposed to originate from heteromeric receptor interactions may also be observed due to intracellular crosstalk between signalling pathways of non-associated GPCRs.
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Affiliation(s)
- Henry F Vischer
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
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Yabe D, Seino Y. Two incretin hormones GLP-1 and GIP: comparison of their actions in insulin secretion and β cell preservation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:248-56. [PMID: 21820006 DOI: 10.1016/j.pbiomolbio.2011.07.010] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Accepted: 07/20/2011] [Indexed: 12/16/2022]
Abstract
Gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the two primary incretin hormones secreted from the intestine upon ingestion of glucose or nutrients to stimulate insulin secretion from pancreatic β cells. GIP and GLP-1 exert their effects by binding to their specific receptors, the GIP receptor (GIPR) and the GLP-1 receptor (GLP-1R), which belong to the G-protein coupled receptor family. Receptor binding activates and increases the level of intracellular cAMP in pancreatic β cells, thereby stimulating insulin secretion glucose-dependently. In addition to their insulinotropic effects, GIP and GLP-1 have been shown to preserve pancreatic β cell mass by inhibiting apoptosis of β cells and enhancing their proliferation. Due to such characteristics, incretin hormones have been gaining mush attention as attractive targets for treatment of type 2 diabetes, and indeed incretin-based therapeutics have been rapidly disseminated worldwide. However, despites of plethora of rigorous studies, molecular mechanisms underlying how GIPR and GLP-1R activation leads to enhancement of glucose-dependent insulin secretion are still largely unknown. Here, we summarize the similarities and differences of these two incretin hormones in secretion and metabolism, their insulinotropic actions and their effects on pancreatic β cell preservation. We then try to discuss potential of GLP-1 and GIP in treatment of type 2 diabetes.
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Affiliation(s)
- Daisuke Yabe
- The Division of Diabetes, Clinical Nutrition and Endocrinology, Kansai Electric Power Hospital, 2-1-7 Fukushima, Fukushima-ku, Osaka 553-0003, Japan.
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Córdoba-Chacón J, Gahete MD, Durán-Prado M, Luque RM, Castaño JP. Truncated somatostatin receptors as new players in somatostatin-cortistatin pathophysiology. Ann N Y Acad Sci 2011; 1220:6-15. [PMID: 21388399 DOI: 10.1111/j.1749-6632.2011.05985.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Somatostatin (SST) and cortistatin (CORT) act through a family of seven transmembrane domain (TMD) receptors (sst1-5) to govern multiple functions, from growth hormone (GH) secretion to neurotransmission, metabolic homeostasis, gastrointestinal and immune function, and tumor cell growth. Thus, SST analogs are used to treat endocrine/tumoral pathologies. Yet, some SST/CORT actions cannot be explained by their interaction with known ssts. We recently identified novel sst5 variants in human, pig, mouse, and rat that lack one or more TMDs and display unique molecular/functional features: they exhibit distinct tissue distribution, divergent responses to SST/CORT, and intracellular localization as opposed to the typical plasma-membrane distribution of full-length ssts. When coexpressed in the same cell, truncated sst5 variants colocalize and physically interact with full-length ssts, providing a molecular basis to disrupt normal sst2/sst5 functioning. This may explain the inverse correlation between hsst5TMD4 expression in pituitary tumors and octreotide responsiveness in acromegaly. Discovery of these new truncated sst5 variants provides novel insights on SST/CORT/sst pathophysiology and suggests new research avenues for the therapeutic potential of this system.
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Affiliation(s)
- José Córdoba-Chacón
- Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba, Córdoba, Spain
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Morrison FS, Johnstone KA, Harries LW. Physiological effects of Type 2 diabetes on mRNA processing and gene expression. Expert Rev Endocrinol Metab 2011; 6:255-267. [PMID: 30290446 DOI: 10.1586/eem.10.76] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Characteristics of Type 2 diabetes include both high blood glucose (hyperglycemia) and raised cholesterol and triglycerides (hyperlipidemia). Several studies have now shown that both hyperglycemia and hyperlipidemia can alter gene expression by disrupting physiological mechanisms of gene regulation, including alternative mRNA splicing, epigenetic gene regulation and miRNA-mediated regulation of gene expression. These processes may also be influenced by intracellular oxidative stress, which is increased in diabetes and in response to hyperglycemia and hyperlipidemia. Many pathways relevant to diabetes are affected by altered gene expression, including lipid and glucose metabolism and oxidative phosphorylation. This article considers how hyperglycemia and hyperlipidemia can alter gene expression in diabetes, which could potentially contribute to the worsening of the diabetic phenotype and diabetic complications.
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Affiliation(s)
- Faer S Morrison
- a Institute of Biomedical and Clinical Science, Peninsula College of Medicine and Dentistry, University of Exeter, Exeter, EX2 5DW, UK
| | - Karen A Johnstone
- a Institute of Biomedical and Clinical Science, Peninsula College of Medicine and Dentistry, University of Exeter, Exeter, EX2 5DW, UK
| | - Lorna W Harries
- a Institute of Biomedical and Clinical Science, Peninsula College of Medicine and Dentistry, University of Exeter, Exeter, EX2 5DW, UK
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A GIP receptor agonist exhibits beta-cell anti-apoptotic actions in rat models of diabetes resulting in improved beta-cell function and glycemic control. PLoS One 2010; 5:e9590. [PMID: 20231880 PMCID: PMC2834736 DOI: 10.1371/journal.pone.0009590] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Accepted: 02/15/2010] [Indexed: 01/09/2023] Open
Abstract
AIMS The gastrointestinal hormone GIP promotes pancreatic islet function and exerts pro-survival actions on cultured beta-cells. However, GIP also promotes lipogenesis, thus potentially restricting its therapeutic use. The current studies evaluated the effects of a truncated GIP analog, D-Ala(2)-GIP(1-30) (D-GIP(1-30)), on glucose homeostasis and beta-cell mass in rat models of diabetes. MATERIALS AND METHODS The insulinotropic and pro-survival potency of D-GIP(1-30) was evaluated in perfused pancreas preparations and cultured INS-1 beta-cells, respectively, and receptor selectivity evaluated using wild type and GIP receptor knockout mice. Effects of D-GIP(1-30) on beta-cell function and glucose homeostasis, in vivo, were determined using Lean Zucker rats, obese Vancouver diabetic fatty rats, streptozotocin treated rats, and obese Zucker diabetic fatty rats, with effects on beta-cell mass determined in histological studies of pancreatic tissue. Lipogenic effects of D-GIP(1-30) were evaluated on cultured 3T3-L1 adipocytes. RESULTS Acutely, D-GIP(1-30) improved glucose tolerance and insulin secretion. Chronic treatment with D-GIP(1-30) reduced levels of islet pro-apoptotic proteins in Vancouver diabetic fatty rats and preserved beta-cell mass in streptozotocin treated rats and Zucker diabetic fatty rats, resulting in improved insulin responses and glycemic control in each animal model, with no change in body weight. In in vitro studies, D-GIP(1-30) exhibited equivalent potency to GIP(1-42) on beta-cell function and survival, but greatly reduced action on lipoprotein lipase activity in 3T3-L1 adipocytes. CONCLUSIONS These findings demonstrate that truncated forms of GIP exhibit potent anti-diabetic actions, without pro-obesity effects, and that the C-terminus contributes to the lipogenic actions of GIP.
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Underwood CR, Parthier C, Reedtz-Runge S. Structural basis for ligand recognition of incretin receptors. VITAMINS AND HORMONES 2010; 84:251-78. [PMID: 21094903 DOI: 10.1016/b978-0-12-381517-0.00009-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor are homologous G-protein-coupled receptors (GPCRs). Incretin receptor agonists stimulate the synthesis and secretion of insulin from pancreatic β-cells and are therefore promising agents for the treatment of type 2 diabetes. It is well established that the N-terminal extracellular domain (ECD) of incretin receptors is important for ligand binding and ligand specificity, whereas the transmembrane domain is involved in receptor activation. Structures of the ligand-bound ECD of incretin receptors have been solved recently by X-ray crystallography. The crystal structures reveal a similar fold of the ECD and a similar mechanism of ligand binding, where the ligand adopts an α-helical conformation. Residues in the C-terminal part of the ligand interact directly with the ECD and hydrophobic interactions appear to be the main driving force for ligand binding to the ECD of incretin receptors. Obviously, the-still missing-structures of full-length incretin receptors are required to construct a complete picture of receptor function at the molecular level. However, the progress made recently in structural analysis of the ECDs of incretin receptors and related GPCRs has shed new light on the process of ligand recognition and binding and provided a basis to disclose some of the mechanisms underlying receptor activation at high resolution.
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Affiliation(s)
- Christina Rye Underwood
- Department of Chemistry, MEMPHYS Center for Biomembrane Physics, Technical University of Denmark, Kgs. Lyngby, Denmark, GLP-1 and Obesity Biology, Novo Nordisk, Måløv, Denmark
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Markovic D, Challiss RAJ. Alternative splicing of G protein-coupled receptors: physiology and pathophysiology. Cell Mol Life Sci 2009; 66:3337-52. [PMID: 19629391 PMCID: PMC11115665 DOI: 10.1007/s00018-009-0093-4] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 06/30/2009] [Accepted: 07/03/2009] [Indexed: 12/16/2022]
Abstract
The G protein-coupled receptors (GPCRs) are a superfamily of transmembrane receptors that have a broad distribution and can collectively recognise a diverse array of ligands. Activation or inhibition of GPCR signalling can affect many (patho)physiological processes, and consequently they are a major target for existing and emerging drug therapies. A common observation has been that the pharmacological, signalling and regulatory properties of GPCRs can differ in a cell- and tissue-specific manner. Such "phenotypic" diversity might be attributable to post-translational modifications and/or association of GPCRs with accessory proteins, however, post-transcriptional mechanisms are also likely to contribute. Although approximately 50% of GPCR genes are intronless, those that possess introns can undergo alternative splicing, generating GPCR subtype isoforms that may differ in their pharmacological, signalling and regulatory properties. In this review we shall highlight recent research into GPCR splice variation and discuss the potential consequences this might have for GPCR function in health and disease.
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Affiliation(s)
- Danijela Markovic
- Department of Cell Physiology and Pharmacology, University of Leicester, Henry Wellcome Building, Leicester, UK.
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Focus on the splicing of secretin GPCRs transmembrane-domain 7. Trends Biochem Sci 2009; 34:443-52. [PMID: 19733082 DOI: 10.1016/j.tibs.2009.06.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Revised: 05/20/2009] [Accepted: 06/04/2009] [Indexed: 12/17/2022]
Abstract
The family of G-protein coupled receptors (GPCRs) is one of the largest protein families in the mammalian genome with a fundamental role in cell biology. GPCR activity is finely tuned by various transcriptional, post-transcriptional and post-translational mechanisms. Alternative pre-mRNA splicing is now emerging as a crucial process regulating GPCR biological function. Intriguingly, this mechanism appears to extensively target the Secretin family of GPCRs, especially the exon that encodes a 14 amino acid sequence that forms the distal part of 7th transmembrane helix, and exhibits an unusually high level of sequence conservation among most Secretin GPCRs. Do the "TMD7-short" receptor variants have a role as novel regulators of GPCR signallng and, if so, what are the implications for hormonal actions and physiology?
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