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Dalle Nogare M, D'Annunzio S, Vazza G, Regazzo D, Picello L, Denaro L, Voltan G, Scaroni C, Ceccato F, Occhi G. The Methylation Analysis of the Glucose-Dependent Insulinotropic Polypeptide Receptor (GIPR) Locus in GH-Secreting Pituitary Adenomas. Int J Mol Sci 2023; 24:ijms24119264. [PMID: 37298217 DOI: 10.3390/ijms24119264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/19/2023] [Accepted: 05/19/2023] [Indexed: 06/12/2023] Open
Abstract
The glucose-dependent insulinotropic polypeptide receptor (GIPR) is aberrantly expressed in about one-third of GH-secreting pituitary adenomas (GH-PAs) and has been associated with a paradoxical increase of GH after a glucose load. The reason for such an overexpression has not yet been clarified. In this work, we aimed to evaluate whether locus-specific changes in DNA methylation patterns could contribute to this phenomenon. By cloning bisulfite-sequencing PCR, we compared the methylation pattern of the GIPR locus in GIPR-positive (GIPR+) and GIPR-negative (GIPR-) GH-PAs. Then, to assess the correlation between Gipr expression and locus methylation, we induced global DNA methylation changes by treating the lactosomatotroph GH3 cells with 5-aza-2'-deoxycytidine. Differences in methylation levels were observed between GIPR+ and GIPR- GH-PAs, both within the promoter (31.9% vs. 68.2%, p < 0.05) and at two gene body regions (GB_1 20.7% vs. 9.1%; GB_2 51.2% vs. 65.8%, p < 0.05). GH3 cells treated with 5-aza-2'-deoxycytidine showed a ~75% reduction in Gipr steady-state level, possibly associated with the observed decrease in CpGs methylation. These results indicate that epigenetic regulation affects GIPR expression in GH-PAs, even though this possibly represents only a part of a much more complex regulatory mechanism.
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Affiliation(s)
| | - Sarah D'Annunzio
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, 38123 Trento, Italy
| | - Giovanni Vazza
- Department of Biology, University of Padova, 35128 Padova, Italy
| | - Daniela Regazzo
- Endocrinology Unit, Department of Medicine, Padova University Hospital, 35121 Padova, Italy
| | - Luna Picello
- Department of Biology, University of Padova, 35128 Padova, Italy
| | - Luca Denaro
- Academic Neurosurgery, Department of Neurosciences, Padova University Hospital, 35121 Padova, Italy
| | - Giacomo Voltan
- Endocrinology Unit, Department of Medicine, Padova University Hospital, 35121 Padova, Italy
| | - Carla Scaroni
- Endocrinology Unit, Department of Medicine, Padova University Hospital, 35121 Padova, Italy
| | - Filippo Ceccato
- Endocrinology Unit, Department of Medicine, Padova University Hospital, 35121 Padova, Italy
| | - Gianluca Occhi
- Department of Biology, University of Padova, 35128 Padova, Italy
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Kizilkaya HS, Sørensen KV, Kibsgaard CJ, Gasbjerg LS, Hauser AS, Sparre-Ulrich AH, Grarup N, Rosenkilde MM. Loss of Function Glucose-Dependent Insulinotropic Polypeptide Receptor Variants Are Associated With Alterations in BMI, Bone Strength and Cardiovascular Outcomes. Front Cell Dev Biol 2021; 9:749607. [PMID: 34760890 PMCID: PMC8573201 DOI: 10.3389/fcell.2021.749607] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 09/16/2021] [Indexed: 12/25/2022] Open
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) and its receptor (GIPR) are involved in multiple physiological systems related to glucose metabolism, bone homeostasis and fat deposition. Recent research has surprisingly indicated that both agonists and antagonists of GIPR may be useful in the treatment of obesity and type 2 diabetes, as both result in weight loss when combined with GLP-1 receptor activation. To understand the receptor signaling related with weight loss, we examined the pharmacological properties of two rare missense GIPR variants, R190Q (rs139215588) and E288G (rs143430880) linked to lower body mass index (BMI) in carriers. At the molecular and cellular level, both variants displayed reduced G protein coupling, impaired arrestin recruitment and internalization, despite maintained high GIP affinity. The physiological phenotyping revealed an overall impaired bone strength, increased systolic blood pressure, altered lipid profile, altered fat distribution combined with increased body impedance in human carriers, thereby substantiating the role of GIP in these physiological processes.
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Affiliation(s)
- Hüsün Sheyma Kizilkaya
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kimmie Vestergaard Sørensen
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Camilla J Kibsgaard
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Laerke Smidt Gasbjerg
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alexander S Hauser
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Alexander Hovard Sparre-Ulrich
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Antag Therapeutics ApS, Copenhagen, Denmark
| | - Niels Grarup
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Mette M Rosenkilde
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Gray SM, Xin Y, Ross EC, Chazotte BM, Capozzi ME, El K, Svendsen B, Ravn P, Sloop KW, Tong J, Gromada J, Campbell JE, D'Alessio DA. Discordance between GLP-1R gene and protein expression in mouse pancreatic islet cells. J Biol Chem 2020; 295:11529-11541. [PMID: 32554468 DOI: 10.1074/jbc.ra120.014368] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 06/16/2020] [Indexed: 12/22/2022] Open
Abstract
The insulinotropic actions of glucagon-like peptide 1 receptor (GLP-1R) in β-cells have made it a useful target to manage type 2 diabetes. Metabolic stress reduces β-cell sensitivity to GLP-1, yet the underlying mechanisms are unknown. We hypothesized that Glp1r expression is heterogeneous among β-cells and that metabolic stress decreases the number of GLP-1R-positive β-cells. Here, analyses of publicly available single-cell RNA-Seq sequencing (scRNASeq) data from mouse and human β-cells indicated that significant populations of β-cells do not express the Glp1r gene, supporting heterogeneous GLP-1R expression. To check these results, we used complementary approaches employing FACS coupled with quantitative RT-PCR, a validated GLP-1R antibody, and flow cytometry to quantify GLP-1R promoter activity, gene expression, and protein expression in mouse α-, β-, and δ-cells. Experiments with Glp1r reporter mice and a validated GLP-1R antibody indicated that >90% of the β-cells are GLP-1R positive, contradicting the findings with the scRNASeq data. α-cells did not express Glp1r mRNA and δ-cells expressed Glp1r mRNA but not protein. We also examined the expression patterns of GLP-1R in mouse models of metabolic stress. Multiparous female mice had significantly decreased β-cell Glp1r expression, but no reduction in GLP-1R protein levels or GLP-1R-mediated insulin secretion. These findings suggest caution in interpreting the results of scRNASeq for low-abundance transcripts such as the incretin receptors and indicate that GLP-1R is widely expressed in β-cells, absent in α-cells, and expressed at the mRNA, but not protein, level in δ-cells.
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Affiliation(s)
- Sarah M Gray
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | - Yurong Xin
- Regeneron Pharmaceuticals, Tarrytown, New York, USA
| | - Elizabeth C Ross
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | - Bryanna M Chazotte
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | - Megan E Capozzi
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | - Kimberley El
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | - Berit Svendsen
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | - Peter Ravn
- Antibody Discovery and Protein Engineering, BioPharmaceuticals R&D, AstraZeneca, Cambridge, United Kingdom
| | - Kyle W Sloop
- Diabetes and Complications, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Jenny Tong
- Department of Medicine, Division of Metabolism, Endocrinology and Nutrition, University of Washington, Seattle, Washington, USA
| | | | - Jonathan E Campbell
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA.,Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, USA.,Department of Medicine, Division of Endocrinology, Duke University, Durham, North Carolina, USA
| | - David A D'Alessio
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA david.d'.,Department of Medicine, Division of Endocrinology, Duke University, Durham, North Carolina, USA
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Jacobi SF, Khajavi N, Kleinau G, Teumer A, Scheerer P, Homuth G, Völzke H, Wiegand S, Kühnen P, Krude H, Gong M, Raile K, Biebermann H. Evaluation of a rare glucose-dependent insulinotropic polypeptide receptor variant in a patient with diabetes. Diabetes Obes Metab 2019; 21:1168-1176. [PMID: 30784161 DOI: 10.1111/dom.13634] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Revised: 12/23/2018] [Accepted: 01/04/2019] [Indexed: 12/14/2022]
Abstract
AIMS Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone that augments insulin secretion in pancreatic β-cells via its glucose-dependent insulinotropic polypeptide receptor (GIPR). Recent genome-wide association studies identified a single nucleotide variant (SNV) in the GIPR encoding gene (GIPR), rs1800437, that is associated with obesity and insulin resistance. In the present study, we tested whether GIPR variants contribute to obesity and disturb glucose homeostasis or diabetes in specific patient populations. MATERIALS AND METHODS Exon sequencing of GIPR was performed in 164 children with obesity and insulin resistance and in 80 children with paediatric-onset diabetes of unknown origin. The Study of Health in Pomerania (SHIP) cohort, comprising 8320 adults, was screened for the GIPR variant Arg217Leu. GIPR variants were expressed in COS-7 cells and cAMP production was measured upon stimulation with GIP. Cell surface expression was determined by ELISA. Protein homology modelling of the GIPR variants was performed to extract three-dimensional information of the receptor. RESULTS A heterozygous missense GIPR variant Arg217Leu (rs200485112) was identified in a patient of Asian ancestry. Functional characterization of Arg217Leu revealed reduced surface expression and signalling after GIP challenge. The homology model of the GIPR structure supports the observed functional relevance of Arg217Leu. CONCLUSION In vitro functional studies and protein homology modelling indicate a potential relevance of the GIPR variant Arg217Leu in receptor function. The heterozygous variant displayed partial co-segregation with diabetes. Based on these findings, we suggest that GIPR variants may play a role in disturbed glucose homeostasis and may be of clinical relevance in homozygous patients.
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Affiliation(s)
- Simon F Jacobi
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; Institute of Experimental Pediatric Endocrinology, Berlin, Germany
- University Heart Center Freiburg-Bad Krozingen, Department of Congenital Heart Disease and Pediatric Cardiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Noushafarin Khajavi
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; Institute of Experimental Pediatric Endocrinology, Berlin, Germany
| | - Gunnar Kleinau
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; Institute of Experimental Pediatric Endocrinology, Berlin, Germany
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health; Institut für Medizinische Physik und Biophysik, Group Protein X-ray Crystallography and Signal Transduction, Berlin, Germany
| | - Alexander Teumer
- Department SHIP/Clinical-Epidemiological Research, Institute for Community Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Patrick Scheerer
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health; Institut für Medizinische Physik und Biophysik, Group Protein X-ray Crystallography and Signal Transduction, Berlin, Germany
| | - Georg Homuth
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine, University Greifswald, Greifswald, Germany
| | - Henry Völzke
- Department SHIP/Clinical-Epidemiological Research, Institute for Community Medicine, University Medicine Greifswald, Greifswald, Germany
- German Center for Diabetes Research (DZD), Site Greifswald, Greifswald, Germany
| | - Susanna Wiegand
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; Institute of Experimental Pediatric Endocrinology, Berlin, Germany
| | - Peter Kühnen
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; Institute of Experimental Pediatric Endocrinology, Berlin, Germany
| | - Heiko Krude
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; Institute of Experimental Pediatric Endocrinology, Berlin, Germany
| | - Maolian Gong
- Experimental and Clinical Research Center (ECRC), a joint collaboration of Charité and Max-Delbrück-Center of Molecular Medicine, Berlin, Germany
| | - Klemens Raile
- Experimental and Clinical Research Center (ECRC), a joint collaboration of Charité and Max-Delbrück-Center of Molecular Medicine, Berlin, Germany
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; Department of Paediatric Endocrinology and Diabetology, Berlin, Germany
| | - Heike Biebermann
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; Institute of Experimental Pediatric Endocrinology, Berlin, Germany
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