1
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He Y, Su J, Gao H, Li J, Feng Z, Yin Y. Untargeted Metabolomics Reveals the Function of GPRC6A in Amino Acid and Lipid Metabolism in Mice. Metabolites 2022; 12:metabo12090776. [PMID: 36144181 PMCID: PMC9502419 DOI: 10.3390/metabo12090776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 08/22/2022] [Accepted: 08/22/2022] [Indexed: 11/16/2022] Open
Abstract
GPRC6A is an amino acid sensor in the cytomembrane. Despite substantial evidence for the role of GPRC6A in metabolism, the specific effects and mechanism by which this gene acts on metabolic processes are still unresolved. In this study, serum biochemical parameters related to liver and kidney function and serum amino acid levels were determined in GPRC6A wild-type (WT) and knockout (KO) mice. An untargeted serum metabolomics analysis was also conducted for the first time, to the best of our knowledge, to decipher the function of GPRC6A in metabolic processes. GPRC6A was involved in lipid and amino acid metabolism, mainly by affecting liver function. A loss of GPRC6A function may perturb bile acid metabolism, thus leading to abnormal unsaturated fatty acid metabolism. GPRC6A KO may lead to excessive protein breakdown under starvation, and the loss of GPRC6A had a significant effect on phenylalanine metabolism-related pathways. Our metabolomics data provide a novel basis for further functional studies of GPRC6A.
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Affiliation(s)
- Yumin He
- Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Hunan Provincial Engineering Research Canter for Healthy Livestock and Poultry Production, Scientific Observational and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha 410125, China(
- Animal Nutrition and Human Health Laboratory, College of Life Sciences, Hunan Normal University, Changsha 410081, China
| | - Jingyun Su
- Animal Nutrition and Human Health Laboratory, College of Life Sciences, Hunan Normal University, Changsha 410081, China
| | - Hongrui Gao
- Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Hunan Provincial Engineering Research Canter for Healthy Livestock and Poultry Production, Scientific Observational and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha 410125, China(
- College of Veterinary Medicine, Hunan Agricultural University, Changsha 410128, China
| | - Jianzhong Li
- Animal Nutrition and Human Health Laboratory, College of Life Sciences, Hunan Normal University, Changsha 410081, China
- Correspondence: (J.L.); (Z.F.)
| | - Zemeng Feng
- Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Hunan Provincial Engineering Research Canter for Healthy Livestock and Poultry Production, Scientific Observational and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha 410125, China(
- Correspondence: (J.L.); (Z.F.)
| | - Yulong Yin
- Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Hunan Provincial Engineering Research Canter for Healthy Livestock and Poultry Production, Scientific Observational and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha 410125, China(
- Animal Nutrition and Human Health Laboratory, College of Life Sciences, Hunan Normal University, Changsha 410081, China
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2
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GPRC6A Mediates Glucose and Amino Acid Homeostasis in Mice. Metabolites 2022; 12:metabo12080740. [PMID: 36005612 PMCID: PMC9415337 DOI: 10.3390/metabo12080740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 08/03/2022] [Accepted: 08/08/2022] [Indexed: 11/29/2022] Open
Abstract
GPRC6A, an important member of the G-protein-coupled receptor superfamily, has been widely studied in body health maintenance and related diseases. However, it is still controversial whether GPRC6A plays a vital role in glucose homeostasis, and the role of GPRC6A on amino acid homeostasis has not been reported. In this study, GPRC6A was knocked out in C57BL6 mice, and we found that GPRC6A plays an important role in the glucose metabolism, mainly affecting the glucose clearance capacity and gluconeogenesis in mice. GPRC6A plays an important role in maintaining amino acid homeostasis under dietary restrictions, and this may be realized by participating in the regulation of autophagy. Since a large amount of amino acid is lost from urine in aged GPRC6A−/− mice, it is possible that GPRC6A regulates amino acid homeostasis by affecting the integrity of tissue structure. GPRC6A is involved in the regulation of mTORC1 activation but is not necessary for mTORC1 activation under sufficient nutritional supply. In the absence of exogenous amino acids, the loss of GPRC6A induces the GCN2 pathway activation and excessive autophagy of cells, leading to the overactivation of mTORC1, which may be detrimental to body health and cell survival. In summary, this study provides a theoretical and experimental basis for the metabolic process of GPRC6A in body growth and health.
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3
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Park D, Kim DY, Byun MR, Hwang H, Ko SH, Baek JH, Baek K. Undercarboxylated, but not Carboxylated, Osteocalcin suppresses TNF-α induced inflammatory signaling pathway in Myoblast. J Endocr Soc 2022; 6:bvac084. [PMID: 35702666 PMCID: PMC9188654 DOI: 10.1210/jendso/bvac084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Indexed: 11/19/2022] Open
Abstract
Undercarboxylated osteocalcin (ucOCN) has been considered to be an important endocrine factor, especially to regulate bone and energy metabolism. Even with the mounting evidence showing the consistent inverse correlation of ucOCN levels in chronic inflammatory diseases, however, the mechanism underlying the involvement of ucOCN in the muscular inflammation has not been fully understood. In the present study, we explored 1) the endocrine role of ucOCN in the regulation of inflammation in C2C12 myoblasts and primary myoblasts and the underlying intracellular signaling mechanisms, and 2) whether G protein–coupled receptor family C group 6 member A (GPRC6A) is the ucOCN-sensing receptor associated with the ucOCN-mediated anti-inflammatory signaling pathway in myoblasts. ucOCN suppressed the tumor necrosis factor-α (TNF-α)–induced expressions of major inflammatory cytokines, including interleukin-1β (IL-1β) and inhibited the TNF-α–stimulated activities of transcription factors, including NF-κB, in C2C12 and primary myoblasts. Both knockdown and knockout of GPRC6A, by using siRNA or a CRISPR/CAS9 system, respectively, did not reverse the effect of ucOCN on IL-1β expression in myoblasts. Interestingly, TNF-α–induced IL-1β expression was inhibited by knockdown or deletion of GPRC6A itself, regardless of the ucOCN treatment. ucOCN was rapidly internalized into the cytoplasmic region via caveolae-mediated endocytosis, suggesting the presence of new target proteins in the cell membrane and/or in the cytoplasm for interaction with ucOCN in myoblasts. Taken together, these findings indicate that ucOCN suppresses the TNF-α–induced inflammatory signaling pathway in myoblasts. GPRC6A is not a sensing receptor associated with the ucOCN-mediated anti-inflammatory signaling pathway in myoblasts.
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Affiliation(s)
- Danbi Park
- Department of Pharmacology, College of Dentistry and Research Institute of Oral Science, Gangneung-Wonju National University , Gangwondo 25457, Republic of Korea
| | - Do-Yeon Kim
- Department of Pharmacology, School of Dentistry, Kyungpook National University , Daegu 41940, Republic of Korea
| | - Mi Ran Byun
- Department of Pharmacology, College of Pharmacy, Kyung Hee University , Seoul 02447, Republic of Korea
| | - Hyorin Hwang
- Department of Pharmacology, College of Dentistry and Research Institute of Oral Science, Gangneung-Wonju National University , Gangwondo 25457, Republic of Korea
| | - Seong Hee Ko
- Department of Pharmacology, College of Dentistry and Research Institute of Oral Science, Gangneung-Wonju National University , Gangwondo 25457, Republic of Korea
| | - Jeong-Hwa Baek
- Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University , Seoul 08826, Republic of Korea
| | - Kyunghwa Baek
- Department of Pharmacology, College of Dentistry and Research Institute of Oral Science, Gangneung-Wonju National University , Gangwondo 25457, Republic of Korea
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The Potential of L-Arginine in Prevention and Treatment of Disturbed Carbohydrate and Lipid Metabolism—A Review. Nutrients 2022; 14:nu14050961. [PMID: 35267936 PMCID: PMC8912821 DOI: 10.3390/nu14050961] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/16/2022] [Accepted: 02/22/2022] [Indexed: 01/27/2023] Open
Abstract
L-arginine, an endogenous amino acid, is a safe substance that can be found in food. The compound is involved in synthesis of various products responsible for regulatory functions in the body. Particularly noteworthy is, among others, nitric oxide, a signaling molecule regulating carbohydrate and lipid metabolism. The increasing experimental and clinical data indicate that L-arginine supplementation may be helpful in managing disturbed metabolism in obesity, regulate arterial blood pressure or alleviate type 2 diabetes symptoms, but the mechanisms underlying these effects have not been sufficiently elucidated. This review aims to present the up-to-date information regarding the current uses and health-promoting potential of L-arginine, its effects on nitric oxide, carbohydrate and lipid metabolisms, based on the results of in vivo, in vitro studies, and clinical human trials. Available literature suggests that L-arginine may have beneficial effects on human health. However, some studies found that higher dietary L-arginine is associated with worsening of an existing disease or may be potential risk factor for development of some diseases. The mechanisms of regulatory effects of L-arginine on carbohydrate and lipid metabolism have not been fully understood and are currently under investigation.
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5
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Pi M, Nishimoto SK, Darryl Quarles L. Explaining Divergent Observations Regarding Osteocalcin/GPRC6A Endocrine Signaling. Endocrinology 2021; 162:6104945. [PMID: 33474566 PMCID: PMC7880225 DOI: 10.1210/endocr/bqab011] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Indexed: 12/13/2022]
Abstract
A new schema proposes that the bone-derived osteocalcin (Ocn) peptide hormone activates the G-protein-coupled receptor GPRC6A to directly regulate glucose and fat metabolism in liver, muscle, and fat, and to stimulate the release of metabolism-regulating hormones, including insulin, fibroblast growth factor 21, glucagon-like peptide 1, testosterone, and interleukin 6. Ocn/GPRC6A activation has also been implicated in cancer progression. GPRC6A is activated by cations, amino acids, and testosterone. The multiligand specificity, the regulation of energy metabolism in diverse tissues, and the coordinated release of metabolically active hormones make the GPRC6A endocrine networks unique. Recently, the significance of Ocn/GPRCA has been questioned. There is a lack of metabolic abnormalities in newly created genetically engineered Ocn- and Gprc6a-deficient mouse models. There are also paradoxical observations that GPRC6A may function as a tumor suppressor. In addition, discordant published studies have cast doubt on the function of the most prevalent uniquely human GPRC6A-KGKY polymorphism. Explanations for these divergent findings are elusive. We provide evidence that the metabolic susceptibility of genetically engineered Ocn- and Gprc6a-deficient mice is influenced by environmental challenges and genetic differences in mouse strains. In addition, the GPRC6A-KGKY polymorphism appears to be a gain-of-function variant. Finally, alternatively spliced isoforms of GPRC6A may alter ligand specificity and signaling that modulate oncogenic effects. Thus, genetic, post-translational and environmental factors likely account for the variable results regarding the functions of GPRC6A in animal models. Pending additional information, GPRC6A should remain a potential therapeutic target for regulating energy and fat metabolism, hormone production, and cancer progression.
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Affiliation(s)
- Min Pi
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Satoru Kenneth Nishimoto
- Department of Microbiology, Immunology & Biochemistry, University of Tennessee Health Science Center, Memphis, TN, USA
| | - L Darryl Quarles
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
- Correspondence: L. Darryl Quarles, MD, University of Tennessee Health Sciences Center, Memphis, TN, USA. . Current Affiliation: 965 Court Ave, Suite B226, Memphis, TN 38163, USA
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6
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Wang H, Li J, Xu Z, Wu F, Zhang H, Yang C, Chen J, Ding B, Sui X, Guo Z, Li Y, Dai Z. Undercarboxylated osteocalcin inhibits the early differentiation of osteoclast mediated by Gprc6a. PeerJ 2021; 9:e10898. [PMID: 33717684 PMCID: PMC7934677 DOI: 10.7717/peerj.10898] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 01/13/2021] [Indexed: 11/20/2022] Open
Abstract
Osteocalcin (OCN) was the most abundant noncollagen protein and considered as an endocrine factor. However, the functions of Undercarboxylated osteocalcin (ucOCN) on osteoclast and bone resorption are not well understood. In the present study, preosteoclast RAW264.7 cells and bone marrow mononuclear cells (BMMs) were treated with ucOCN purified from prokaryotic bacteria. Our results showed that ucOCN attenuated the proliferation of RAW264.7 cells with a concentration dependant manner by MTS assay. Scrape wounding assay revealed the decreased motility of RAW264.7 cells after ucOCN treatment. RT-qPCR results manifested the inhibitory effects of ucOCN on the expression of osteoclastic marker genes in RAW264.7 cells during inducing differentiation of RANKL. It was also observed that ucOCN inhibited the formation of multinucleated cells from RAW264.7 cells and BMMs detected by TRAP staining. The number and area of bone resorb pits were also decreased after treatment with ucOCN during their osteoclast induction by toluidine blue staining. The formation and integrity of the osteoclast actin ring were impaired by ucOCN by immunofluorescent staining. Time dependant treatment of ucOCN during osteoclastic induction demonstrated the inhibitory effects mainly occurred at the early stage of osteoclastogenesis. Signaling analysis of luciferase activity of the CRE or SRE reporter and ERK1/2 phosphorylation showed the selective inhibitor or siRNA of Gprc6a (a presumptive ucOCN receptor) could attenuate the promotion of ucOCN on CRE-luciferase activity. Taken together, we provided the first evidence that ucOCN had negative effects on the early differentiation and bone resorption of osteoclasts via Gprc6a.
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Affiliation(s)
- Hailong Wang
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Jinqiao Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China.,Space Engineering University, Beijing, China
| | - Zihan Xu
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Feng Wu
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Hongyu Zhang
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Chao Yang
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Jian Chen
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China.,Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Bai Ding
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Xiukun Sui
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Zhifeng Guo
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Yinghui Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - Zhongquan Dai
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
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7
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Functions of Osteocalcin in Bone, Pancreas, Testis, and Muscle. Int J Mol Sci 2020; 21:ijms21207513. [PMID: 33053789 PMCID: PMC7589887 DOI: 10.3390/ijms21207513] [Citation(s) in RCA: 121] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/05/2020] [Accepted: 10/10/2020] [Indexed: 12/12/2022] Open
Abstract
Osteocalcin (Ocn), which is specifically produced by osteoblasts, and is the most abundant non-collagenous protein in bone, was demonstrated to inhibit bone formation and function as a hormone, which regulates glucose metabolism in the pancreas, testosterone synthesis in the testis, and muscle mass, based on the phenotype of Ocn-/- mice by Karsenty's group. Recently, Ocn-/- mice were newly generated by two groups independently. Bone strength is determined by bone quantity and quality. The new Ocn-/- mice revealed that Ocn is not involved in the regulation of bone formation and bone quantity, but that Ocn regulates bone quality by aligning biological apatite (BAp) parallel to the collagen fibrils. Moreover, glucose metabolism, testosterone synthesis and spermatogenesis, and muscle mass were normal in the new Ocn-/- mice. Thus, the function of Ocn is the adjustment of growth orientation of BAp parallel to the collagen fibrils, which is important for bone strength to the loading direction of the long bone. However, Ocn does not play a role as a hormone in the pancreas, testis, and muscle. Clinically, serum Ocn is a marker for bone formation, and exercise increases bone formation and improves glucose metabolism, making a connection between Ocn and glucose metabolism.
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Riesner K, Cordes S, Peczynski C, Kalupa M, Schwarz C, Shi Y, Mertlitz S, Mengwasser J, van der Werf S, Peric Z, Koenecke C, Schoemans H, Duarte RF, Basak GW, Penack O. Reduced Calcium Signaling Is Associated With Severe Graft-Versus-Host Disease: Results From Preclinical Models and From a Prospective EBMT Study. Front Immunol 2020; 11:1983. [PMID: 32849661 PMCID: PMC7431962 DOI: 10.3389/fimmu.2020.01983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 07/22/2020] [Indexed: 11/24/2022] Open
Abstract
Despite its involvement in various immune functions, including the allogeneic activation of T-lymphocytes, the relevance of calcium (Ca2+) for GVHD pathobiology is largely unknown. To elucidate a potential association between Ca2+and GVHD, we analyzed Ca2+-sensing G-protein coupled receptor 6a (GPRC6a) signaling in preclinical GVHD models and conducted a prospective EBMT study on Ca2+ serum levels prior alloSCT including 363 matched sibling allogeneic peripheral blood stem cell transplantations (alloSCTs). In experimental models, we found decreased Gprc6a expression during intestinal GVHD. GPRC6a deficient alloSCT recipients had higher clinical and histopathological GVHD scores leading to increased mortality. As possible underlying mechanism, we found increased antigen presentation potential in GPRC6a–/– alloSCT recipients demonstrated by higher proliferation rates of T-lymphocytes. In patients with low Ca2+ serum levels (≤median 2.2 mmol/l) before alloSCT, we found a higher incidence of acute GVHD grades II-IV (HR = 2.3 Cl = 1.45–3.85 p = 0.0006), severe acute GVHD grades III-IV (HR = 3.3 CI = 1.59–7.14, p = 0.002) and extensive chronic GVHD (HR = 2.0 Cl = 1.04–3.85 p = 0.04). In conclusion, experimental and clinical data suggest an association of reduced Ca2+ signaling with increased severity of GVHD. Future areas of interest include the in depth analysis of involved molecular pathways and the investigation of Ca2+ signaling as a therapeutic target during GVHD.
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Affiliation(s)
- Katarina Riesner
- Department of Hematology, Oncology, and Tumor Immunology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Steffen Cordes
- Department of Hematology, Oncology, and Tumor Immunology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Christophe Peczynski
- EBMT Transplant Complications Working Party, Paris, France.,EBMT Statistical Unit, Paris, France
| | - Martina Kalupa
- Department of Hematology, Oncology, and Tumor Immunology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Constanze Schwarz
- Department of Hematology, Oncology, and Tumor Immunology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Yu Shi
- Department of Hematology, Oncology, and Tumor Immunology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Sarah Mertlitz
- Department of Hematology, Oncology, and Tumor Immunology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Jörg Mengwasser
- Department of Hematology, Oncology, and Tumor Immunology, Charité Universitätsmedizin Berlin, Berlin, Germany.,Department of Surgery, Charité Universitätsmedizin Berlin, Campus Charité Mitte/Campus Virchow Clinic, Berlin, Germany
| | | | - Zinaida Peric
- EBMT Transplant Complications Working Party, Paris, France.,University Hospital Center Rebro, Zagreb, Croatia
| | - Christian Koenecke
- EBMT Transplant Complications Working Party, Paris, France.,Hannover Medical School, Hanover, Germany
| | - Helene Schoemans
- EBMT Transplant Complications Working Party, Paris, France.,UZ Leuven, Leuven, Belgium
| | - Rafael F Duarte
- EBMT Transplant Complications Working Party, Paris, France.,Hospital Universitario Puerta de Hierro, Madrid, Spain
| | - Grzegorz W Basak
- EBMT Transplant Complications Working Party, Paris, France.,Medical University of Warsaw, Warsaw, Poland
| | - Olaf Penack
- Department of Hematology, Oncology, and Tumor Immunology, Charité Universitätsmedizin Berlin, Berlin, Germany.,EBMT Transplant Complications Working Party, Paris, France.,Berlin Institute of Health, Berlin, Germany
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9
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What is the function of osteocalcin? J Oral Biosci 2020; 62:223-227. [PMID: 32535287 DOI: 10.1016/j.job.2020.05.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 05/28/2020] [Accepted: 05/29/2020] [Indexed: 01/16/2023]
Abstract
BACKGROUND Osteocalcin is the most abundant non-collagenous protein in bone and is specifically expressed in osteoblasts. Previous studies using osteocalcin-deficient (Ocn-/-) mice demonstrated that osteocalcin inhibits bone formation, and serum uncarboxylated osteocalcin functions as a hormone that improves glucose metabolism, induces testosterone synthesis in the testes, and maintains muscle mass. Furthermore, the relationship between serum osteocalcin and glucose metabolism or cardiovascular risk in humans has been reported. However, new Ocn-/- mice exhibited different phenotypes. HIGHLIGHT Bone volume, formation, and resorption were normal in the new Ocn-/- mice. The orientation of collagen fibers was parallel to the bone longitudinal direction and the size of apatite crystals was normal, but the c-axis of apatite crystals was random and bone strength was reduced in new Ocn-/- mice. Glucose metabolism, testosterone synthesis, and muscle mass were normal in new Ocn-/- mice. Exercise improved glucose metabolism and increased bone formation, leading to an increase in the serum osteocalcin level, which is a marker for bone formation. CONCLUSION Contrary to previous findings, new Ocn-/- mice revealed that osteocalcin has no function in the regulation of bone quantity, but instead, functions to direct the parallel alignment of the c-axis of apatite crystals with collagen fibrils. Moreover, it has no physiological function as a hormone that regulates glucose metabolism, testosterone synthesis, or muscle mass. These controversial phenotypes require further investigation. The relationship of serum osteocalcin with glucose metabolism or cardiovascular risk suggests the importance of exercise for their improvement.
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10
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Affiliation(s)
- Stavros C. Manolagas
- Division of Endocrinology and Metabolism, Center for Osteoporosis and Metabolic Bone Diseases, University of Arkansas for Medical Sciences, Arkansas, United States of America
- Central Arkansas Veterans Healthcare System, Little Rock, Arkansas, United States of America
- * E-mail:
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11
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Fowlkes JL, Clay Bunn R, Kalaitzoglou E, Ray P, Popescu I, Thrailkill KM. Postnatal loss of the insulin receptor in osteoprogenitor cells does not impart a metabolic phenotype. Sci Rep 2020; 10:8842. [PMID: 32483283 PMCID: PMC7264347 DOI: 10.1038/s41598-020-65717-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 05/07/2020] [Indexed: 11/09/2022] Open
Abstract
The relationship between osteoblast-specific insulin signaling, osteocalcin activation and gluco-metabolic homeostasis has proven to be complex and potentially inconsistent across animal-model systems and in humans. Moreover, the impact of postnatally acquired, osteoblast-specific insulin deficiency on the pancreas-to-skeleton-to-pancreas circuit has not been studied. To explore this relationship, we created a model of postnatal elimination of insulin signaling in osteoprogenitors. Osteoprogenitor-selective ablation of the insulin receptor was induced after ~10 weeks of age in IRl°x/lox/Osx-Cre+/- genotypic male and female mice (designated postnatal-OIRKO). At ~21 weeks of age, mice were then phenotypically and metabolically characterized. Postnatal-OIRKO mice demonstrated a significant reduction in circulating concentrations of undercarboxylated osteocalcin (ucOC), in both males and females compared with control littermates. However, no differences were observed between postnatal-OIRKO and control mice in: body composition (lean or fat mass); fasting serum insulin; HbA1c; glucose dynamics during glucose tolerance testing; or in pancreatic islet area or islet morphology, demonstrating that while ucOC is impacted by insulin signaling in osteoprogenitors, there appears to be little to no relationship between osteocalcin, or its derivative (ucOC), and glucose homeostasis in this model.
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Affiliation(s)
- John L Fowlkes
- University of Kentucky, Barnstable Brown Diabetes Center, Lexington, KY, USA. .,Department of Pediatrics, University of Kentucky College of Medicine, Lexington, KY, 40536, USA.
| | - R Clay Bunn
- University of Kentucky, Barnstable Brown Diabetes Center, Lexington, KY, USA.,Department of Pediatrics, University of Kentucky College of Medicine, Lexington, KY, 40536, USA
| | - Evangelia Kalaitzoglou
- University of Kentucky, Barnstable Brown Diabetes Center, Lexington, KY, USA.,Department of Pediatrics, University of Kentucky College of Medicine, Lexington, KY, 40536, USA
| | - Phil Ray
- University of Kentucky, Barnstable Brown Diabetes Center, Lexington, KY, USA
| | - Iuliana Popescu
- University of Kentucky, Barnstable Brown Diabetes Center, Lexington, KY, USA
| | - Kathryn M Thrailkill
- University of Kentucky, Barnstable Brown Diabetes Center, Lexington, KY, USA.,Department of Pediatrics, University of Kentucky College of Medicine, Lexington, KY, 40536, USA
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12
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Osteocalcin is necessary for the alignment of apatite crystallites, but not glucose metabolism, testosterone synthesis, or muscle mass. PLoS Genet 2020; 16:e1008586. [PMID: 32463816 PMCID: PMC7255595 DOI: 10.1371/journal.pgen.1008586] [Citation(s) in RCA: 101] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 12/29/2019] [Indexed: 01/08/2023] Open
Abstract
The strength of bone depends on bone quantity and quality. Osteocalcin (Ocn) is the most abundant noncollagenous protein in bone and is produced by osteoblasts. It has been previously claimed that Ocn inhibits bone formation and also functions as a hormone to regulate insulin secretion in the pancreas, testosterone synthesis in the testes, and muscle mass. We generated Ocn-deficient (Ocn–/–) mice by deleting Bglap and Bglap2. Analysis of Ocn–/–mice revealed that Ocn is not involved in the regulation of bone quantity, glucose metabolism, testosterone synthesis, or muscle mass. The orientation degree of collagen fibrils and size of biological apatite (BAp) crystallites in the c-axis were normal in the Ocn–/–bone. However, the crystallographic orientation of the BAp c-axis, which is normally parallel to collagen fibrils, was severely disrupted, resulting in reduced bone strength. These results demonstrate that Ocn is required for bone quality and strength by adjusting the alignment of BAp crystallites parallel to collagen fibrils; but it does not function as a hormone. The strength of bone depends on both its quantity and quality. Osteocalcin (Ocn) is the most abundant non-collagenous protein in bone, but its function remains unclear. Earlier studies by other investigators have suggested that Ocn decreases the quantity of bone by decreasing bone formation; and in addition it works as a hormone to regulate glucose metabolism, testosterone synthesis, and muscle mass in distant tissues. We have generated Ocn-deficient mice and show herein that Ocn is not required for bone formation. It is, however, required for optimal bone quality and strength. Specifically, we show that in the Ocn-deficient mice collagen fibers align normally, but apatite crystallites align randomly against collagen, resulting in disorganized mineralization and reduced bone strength. Furthermore, we show that glucose metabolism, testosterone synthesis, and muscle mass are normal in the Ocn-deficient mice. We conclude that Ocn acts in bone to optimize its quality and strength, but not quantity. And, in contrast to earlier claims, it does not work as a hormone to control glucose metabolism, testosterone synthesis, and muscle mass.
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Jørgensen CV, Bräuner‐Osborne H. Pharmacology and physiological function of the orphan GPRC6A receptor. Basic Clin Pharmacol Toxicol 2020; 126 Suppl 6:77-87. [DOI: 10.1111/bcpt.13397] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/11/2020] [Accepted: 02/11/2020] [Indexed: 12/17/2022]
Affiliation(s)
- Christinna V. Jørgensen
- Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Hans Bräuner‐Osborne
- Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
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Park D, Gu H, Baek JH, Baek K. Undercarboxylated osteocalcin downregulates pancreatic lipase expression in an ATF4-dependent manner in pancreatic acinar cells. Bone 2019; 127:220-227. [PMID: 31216497 DOI: 10.1016/j.bone.2019.06.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 04/17/2019] [Accepted: 06/13/2019] [Indexed: 10/26/2022]
Abstract
Osteocalcin is an osteoblast-specific secreted protein that has been associated with endocrine roles in multiple aspects of energy metabolism. We examined whether undercarboxylated osteocalcin (ucOC) downregulates pancreatic lipase (PNLIP) expression in pancreatic acinar cells and then identified the downstream signaling pathway involved. We previously demonstrated that β adrenergic blockade attenuates body weight/fat mass gain in high-fat diet-fed mice and that this effect is associated with decreased PNLIP expression in pancreatic acinar cells. In the present study, we first confirmed that the serum ucOC level is inversely correlated with PNLIP expression, i.e., mice exhibiting high serum levels of ucOC showed low PNLIP levels in the pancreas. In in vitro experiments using primary pancreatic acinar and 266-6 cells, ucOC downregulated PNLIP expression. cAMP/PKA signaling inhibitors significantly reversed ucOC-induced downregulation of PNLIP expression. ucOC promoted the phosphorylation of cAMP response element-binding protein 2 (ATF4). Overexpression of ATF4 significantly suppressed PNLIP expression. Knockdown of ATF4 by siRNA reversed the ucOC-induced downregulation of PNLIP expression. A luciferase reporter assay showed that ucOC suppressed PNLIP promoter transactivation. Chromatin immunoprecipitation and a luciferase reporter assay demonstrated that ATF4 directly bound to the CRE on the mouse PNLIP promoter and suppressed PNLIP transactivation. Knockdown of G-protein coupled receptor 6A (Gprc6a), a candidate receptor for mediating the response to ucOC in the bone-pancreas endocrine loop, by siRNA reversed the downregulating effect of ucOC on PNLIP expression. Taken together, ucOC downregulates pancreatic lipase expression in a cAMP/protein kinase A/ATF4-dependent manner. Gprc6a is a potential osteocalcin-sensing receptor that regulates PNLIP expression in pancreatic acinar cells.
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Affiliation(s)
- Danbi Park
- Department of Pharmacology, College of Dentistry and Research Institute of Oral Science, Gangneung-Wonju National University, Gangwondo 25457, Republic of Korea
| | - Hanna Gu
- Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 08826, Republic of Korea
| | - Jeong-Hwa Baek
- Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 08826, Republic of Korea.
| | - Kyunghwa Baek
- Department of Pharmacology, College of Dentistry and Research Institute of Oral Science, Gangneung-Wonju National University, Gangwondo 25457, Republic of Korea.
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Hypoglycemic and Toxic Effect of Morus mesozygia Leaf Extract on the Liver and Kidneys of Alloxan-Induced Hyperglycemic Wistar Rats. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2019; 2019:6712178. [PMID: 32030095 PMCID: PMC6770302 DOI: 10.1155/2019/6712178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 08/20/2019] [Accepted: 08/28/2019] [Indexed: 01/30/2023]
Abstract
Purpose We investigated the hypoglycemic and toxic effect of Morus mesozygia leaf extract on the liver and kidneys of alloxan-induced hyperglycemic wistar rats. Method Phytochemical analysis was done. Diabetes was induced by the use of alloxan monohydrate in six groups of rats, i.e., 200 mg/kg, 400 mg/kg, 800 mg/kg, glibenclamide, normal saline, and normal control group. Blood glucose was measured at the time of inoculation, then at 1, 2, 3, and 4 hours after. After 14 days, rats were killed under anesthesia; blood collected for measurement of total protein, albumin, TAGs, cholesterol, AST, ALT, urea, and creatinine; and whole tissue of liver and kidneys used for histological studies. Results The extract possessed antidiabetic effects between 400 mg/kg and 800 mg/kg doses, which we attributed to the presence of flavonoids, tannins, terpenoids, and amino acids. There was a drop in total protein and albumin with no statistical significance (P ≥ 0.05). The changes in levels of ALT, TAGs, cholesterol, AST, creatinine, and urea were not statistically different from the standard diabetic drug. The extract was protective against histological damage as there were no significant lesions suggestive of toxicities in the liver and kidneys at doses below 800 mg/kg. Conclusion We established credible evidence that Morus mesozygia leaf extract has hypoglycemic effects between 400 mg/kg and 800 mg/kg and that it is safe on the liver and kidneys of wistar rats at doses less than 800 mg/kg.
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Metabolic and skeletal homeostasis are maintained in full locus GPRC6A knockout mice. Sci Rep 2019; 9:5995. [PMID: 30979912 PMCID: PMC6461682 DOI: 10.1038/s41598-019-41921-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 03/20/2019] [Indexed: 11/08/2022] Open
Abstract
The G protein-coupled receptor class C, group 6, subtype A (GPRC6A) is suggested to have a physiological function in glucose and bone metabolism, although the precise role lacks consensus due to varying findings in different knockout (KO) mouse models and inconsistent findings on the role of osteocalcin, a proposed GPRC6A agonist. We have further characterized a full locus GPRC6A KO model with respect to energy metabolism, including a long-term high-dose glucocorticoid metabolic challenge. Additionally, we analyzed the microarchitecture of tibiae from young, middle-aged and aged GPRC6A KO mice and wildtype (WT) littermates. Compared to WT, vehicle-treated KO mice presented with normal body composition, unaltered insulin sensitivity and basal serum insulin and glucose levels. Corticosterone (CS) treatment resulted in insulin resistance, abnormal fat accrual, loss of lean mass and suppression of serum osteocalcin levels in both genotypes. Interestingly, serum osteocalcin and skeletal osteocalcin mRNA levels were significantly lower in vehicle-treated GPRC6A KO mice compared to WT animals. However, WT and KO age groups did not differ in long bone mass and structure assessed by micro-computed tomography. We conclude that GPRC6A is not involved in glucose metabolism under normal physiological conditions, nor does it mediate glucocorticoid-induced dysmetabolism in mice. Moreover, GPRC6A does not appear to possess a direct, non-compensable role in long bone microarchitecture under standard conditions.
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Riddy DM, Delerive P, Summers RJ, Sexton PM, Langmead CJ. G Protein–Coupled Receptors Targeting Insulin Resistance, Obesity, and Type 2 Diabetes Mellitus. Pharmacol Rev 2017; 70:39-67. [DOI: 10.1124/pr.117.014373] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 09/13/2017] [Indexed: 12/18/2022] Open
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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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Clemmensen C, Jørgensen CV, Smajilovic S, Bräuner-Osborne H. Robust GLP-1 secretion by basic L-amino acids does not require the GPRC6A receptor. Diabetes Obes Metab 2017; 19:599-603. [PMID: 27943578 DOI: 10.1111/dom.12845] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 12/05/2016] [Accepted: 12/06/2016] [Indexed: 01/15/2023]
Abstract
The G protein-coupled receptor GPRC6A (GPCR, Class C, group 6, subtype A) has been proposed to be a sensor for basic L-amino acids that are hypothesized to translate ingestive behaviour to endocrine information. However, the contribution of the GPRC6A receptor to L-amino acid-induced glucagon-like peptide 1 (GLP-1) secretion is unclear. Therefore, to discover whether the GPRC6A receptor is indispensible for amino acid-induced secretion of GLP-1, we treated, with oral gavage, GPRC6A knock-out (KO) and wild-type (WT) littermate mice with GPRC6A ligands (L-arginine and L-ornithine) and assessed GLP-1 levels in circulation. We found that oral administration of both L-arginine and L-ornithine significantly increased total plasma GLP-1 levels to a similar level in GPRC6A KO and WT mice 15 minutes after gavage (both amino acids) and accumulated up to 60 minutes after gavage (L-arginine). Conversely, GLP-1 secretion at the 30- and 60-minute time points in the KO mice was attenuated and did not reach statistical significance. In summary, these data confirm that L-arginine is a potent GLP-1 secretagogue and show that the main effect occurs independently of GPRC6A. In addition, this is the first study to show that also L-ornithine powerfully elicits GLP-1 release in vivo.
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Affiliation(s)
- Christoffer Clemmensen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, Munich, Germany
| | - Christinna V Jørgensen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Sanela Smajilovic
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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Jacobsen SE, Ammendrup-Johnsen I, Jansen AM, Gether U, Madsen KL, Bräuner-Osborne H. The GPRC6A receptor displays constitutive internalization and sorting to the slow recycling pathway. J Biol Chem 2017; 292:6910-6926. [PMID: 28280242 DOI: 10.1074/jbc.m116.762385] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 02/27/2017] [Indexed: 11/06/2022] Open
Abstract
The class C G protein-coupled receptor GPRC6A is a putative nutrient-sensing receptor and represents a possible new drug target in metabolic disorders. However, the specific physiological role of this receptor has yet to be identified, and the mechanisms regulating its activity and cell surface availability also remain enigmatic. In the present study, we investigated the trafficking properties of GPRC6A by use of both a classical antibody feeding internalization assay in which cells were visualized using confocal microscopy and a novel internalization assay that is based on real-time measurements of fluorescence resonance energy transfer. Both assays revealed that GPRC6A predominantly undergoes constitutive internalization, whereas the agonist-induced effects were imperceptible. Moreover, postendocytic sorting was investigated by assessing the co-localization of internalized GPRC6A with selected Rab protein markers. Internalized GPRC6A was mainly co-localized with the early endosome marker Rab5 and the long loop recycling endosome marker Rab11 and to a much lesser extent with the late endosome marker Rab7. This suggests that upon agonist-independent internalization, GPRC6A is recycled via the Rab11-positive slow recycling pathway, which may be responsible for ensuring a persistent pool of GPRC6A receptors at the cell surface despite chronic agonist exposure. Distinct trafficking pathways have been reported for several of the class C receptors, and our results thus substantiate that non-canonical trafficking mechanisms are a common feature for the nutrient-sensing class C family that ensure functional receptors in the cell membrane despite prolonged agonist exposure.
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Affiliation(s)
- Stine Engesgaard Jacobsen
- From the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark and
| | - Ina Ammendrup-Johnsen
- Molecular Neuropharmacology Laboratory, Lundbeck Foundation Center for Biomembranes in Nanomedicine, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Anna Mai Jansen
- Molecular Neuropharmacology Laboratory, Lundbeck Foundation Center for Biomembranes in Nanomedicine, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Ulrik Gether
- Molecular Neuropharmacology Laboratory, Lundbeck Foundation Center for Biomembranes in Nanomedicine, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Kenneth Lindegaard Madsen
- Molecular Neuropharmacology Laboratory, Lundbeck Foundation Center for Biomembranes in Nanomedicine, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- From the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark and
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21
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Leach K, Gregory KJ. Molecular insights into allosteric modulation of Class C G protein-coupled receptors. Pharmacol Res 2017; 116:105-118. [DOI: 10.1016/j.phrs.2016.12.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 11/18/2016] [Accepted: 12/07/2016] [Indexed: 12/23/2022]
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Fernandes TAP, Gonçalves LML, Brito JAA. Relationships between Bone Turnover and Energy Metabolism. J Diabetes Res 2017; 2017:9021314. [PMID: 28695134 PMCID: PMC5485508 DOI: 10.1155/2017/9021314] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/12/2017] [Accepted: 05/22/2017] [Indexed: 12/31/2022] Open
Abstract
It is well established that diabetes can be detrimental to bone health, and its chronic complications have been associated with an increased risk of osteoporotic fracture. However, there is growing evidence that the skeleton plays a key role in a whole-organism approach to physiology. The hypothesis that bone may be involved in the regulation of physiological functions, such as insulin sensitivity and energy metabolism, has been suggested. Given the roles of insulin, adipokines, and osteocalcin in these pathways, the need for a more integrative conceptual approach to physiology is emphasized. Recent findings suggest that bone plays an important role in regulating intermediary metabolism, being possibly both a target of diabetic complications and a potential pathophysiologic factor in the disease itself. Understanding the relationships between bone turnover and glucose metabolism is important in order to develop treatments that might reestablish energy metabolism and bone health. This review describes new insights relating bone turnover and energy metabolism that have been reported in the literature.
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Affiliation(s)
- Tânia A. P. Fernandes
- Instituto Superior de Ciências da Saúde Egas Moniz (ISCSEM), Campus Universitário-Quinta da Granja, 2829-511 Monte de Caparica, Portugal
- Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Campus Universitário-Quinta da Granja, 2829-511 Monte de Caparica, Portugal
- Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Rua de Jorge Viterbo Ferreira, No. 228, 4050-313 Porto, Portugal
- *Tânia A. P. Fernandes:
| | - Luísa M. L. Gonçalves
- Instituto Superior de Ciências da Saúde Egas Moniz (ISCSEM), Campus Universitário-Quinta da Granja, 2829-511 Monte de Caparica, Portugal
- Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Campus Universitário-Quinta da Granja, 2829-511 Monte de Caparica, Portugal
| | - José A. A. Brito
- Instituto Superior de Ciências da Saúde Egas Moniz (ISCSEM), Campus Universitário-Quinta da Granja, 2829-511 Monte de Caparica, Portugal
- Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Campus Universitário-Quinta da Granja, 2829-511 Monte de Caparica, Portugal
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Pi M, Nishimoto SK, Quarles LD. GPRC6A: Jack of all metabolism (or master of none). Mol Metab 2016; 6:185-193. [PMID: 28180060 PMCID: PMC5279936 DOI: 10.1016/j.molmet.2016.12.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 12/05/2016] [Accepted: 12/15/2016] [Indexed: 01/06/2023] Open
Abstract
Background GPRC6A, a widely expressed G-protein coupled receptor, is proposed to be a master regulator of complex endocrine networks and metabolic processes. GPRC6A is activated by multiple ligands, including osteocalcin (Ocn), testosterone (T), basic amino acids, and various cations. Scope of Review We review the controversy surrounding GPRC6A functions. In mice, GPRC6A is proposed to integrate metabolic functions through the coordinated secretion of hormones, including insulin, GLP-1, T, and IL-6, and direct effects of this receptor to control glucose and fat metabolism in the liver, skeletal muscle, and fat. Loss-of-GPRC6A results in metabolic syndrome (MetS), and activation of GPRC6A stimulates proliferation of β-cells, increases peripheral insulin sensitivity, and protects against high fat diet (HFD) induced metabolic abnormalities in most mouse models. Bone, cardiovascular, immune, and skin functions of GPRC6A have also been identified in mice. Expression of GPRC6A is increased in prostate cancer (PCa) cells, and inhibition of GPRC6A attenuates PCa progression in mouse models. The function of GPRC6A in humans, however, is not clear. During evolution, a unique polymorphism of GPRC6A emerged mainly in humans of Asian and European decent that has been proposed to alter membrane trafficking and function. In contrast, the ancestral allele found in all other species is retained in 1%, 15%, and 40% of people of Asian, European and African descent, respectively, suggesting GPRC6A gene variants may contribute to the racial disparities in the risk of developing MetS and PCa. Major Conclusions If the regulatory functions of GPRC6A identified in mice translate to humans, and polymorphisms in GPRC6A are found to predict racial disparities in human diseases, GPRC6A may be a new gene target to predict, prevent, and treat MetS, PCa, and other disorders impacted by GPRC6A.
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Affiliation(s)
- Min Pi
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Satoru Kenneth Nishimoto
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - L Darryl Quarles
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
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Jørgensen S, Have CT, Underwood CR, Johansen LD, Wellendorph P, Gjesing AP, Jørgensen CV, Quan S, Rui G, Inoue A, Linneberg A, Grarup N, Jun W, Pedersen O, Hansen T, Bräuner-Osborne H. Genetic Variations in the Human G Protein-coupled Receptor Class C, Group 6, Member A (GPRC6A) Control Cell Surface Expression and Function. J Biol Chem 2016; 292:1524-1534. [PMID: 27986810 DOI: 10.1074/jbc.m116.756577] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 12/14/2016] [Indexed: 12/30/2022] Open
Abstract
GPRC6A is a G protein-coupled receptor activated by l-amino acids, which, based on analyses of knock-out mice, has been suggested to have physiological functions in metabolism and testicular function. The human ortholog is, however, mostly retained intracellularly in contrast to the cell surface-expressed murine and goldfish orthologs. The latter orthologs are Gq-coupled and lead to intracellular accumulation of inositol phosphates and calcium release. In the present study we cloned the bonobo chimpanzee GPRC6A receptor, which is 99% identical to the human receptor, and show that it is cell surface-expressed and functional. By analyses of chimeric human/mouse and human/bonobo receptors, bonobo receptor mutants, and the single nucleotide polymorphism database at NCBI, we identify an insertion/deletion variation in the third intracellular loop responsible for the intracellular retention and lack of function of the human ortholog. Genetic analyses of the 1000 genome database and the Inter99 cohort of 6,000 Danes establish the distribution of genotypes among ethnic groups, showing that the cell surface-expressed and functional variant is much more prevalent in the African population than in European and Asian populations and that this variant is partly linked with a stop codon early in the receptor sequence (rs6907580, amino acid position 57). In conclusion, our data solve a more than decade-old question of why the cloned human GPRC6A receptor is not cell surface-expressed and functional and provide a genetic framework to study human phenotypic traits in large genome sequencing projects linked with physiological measurement and biomarkers.
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Affiliation(s)
- Stine Jørgensen
- From the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Christian Theil Have
- the Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Christina Rye Underwood
- From the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Lars Dan Johansen
- From the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Petrine Wellendorph
- From the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Anette Prior Gjesing
- the Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Christinna V Jørgensen
- From the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Shi Quan
- BGI-Shenzhen, Shenzhen 518083, China
| | - Gao Rui
- BGI-Shenzhen, Shenzhen 518083, China
| | - Asuka Inoue
- the Laboratory of Molecular and Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.,the Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology, Kawaguchi, Saitama 332-0012, Japan
| | - Allan Linneberg
- the Research Centre for Prevention and Health, Capital Region of Denmark, DK-2600 Glostrup, Denmark.,the Department of Clinical Experimental Research, Rigshospitalet, DK-2100 Copenhagen, Denmark, and.,the Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Niels Grarup
- the Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Wang Jun
- BGI-Shenzhen, Shenzhen 518083, China
| | - Oluf Pedersen
- the Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Torben Hansen
- the Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- From the Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark,
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25
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Hinton PS. Role of reduced insulin-stimulated bone blood flow in the pathogenesis of metabolic insulin resistance and diabetic bone fragility. Med Hypotheses 2016; 93:81-6. [DOI: 10.1016/j.mehy.2016.05.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 04/28/2016] [Accepted: 05/11/2016] [Indexed: 01/22/2023]
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26
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Li J, Zhang H, Yang C, Li Y, Dai Z. An overview of osteocalcin progress. J Bone Miner Metab 2016; 34:367-79. [PMID: 26747614 DOI: 10.1007/s00774-015-0734-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 12/22/2015] [Indexed: 12/20/2022]
Abstract
An increasing amount of data indicate that osteocalcin is an endocrine hormone which regulates energy metabolism, male fertility and brain development. However, the detailed functions and mechanism of osteocalcin are not well understood and conflicting results have been obtained from researchers worldwide. In the present review, we summarize the progress of osteocalcin studies over the past 40 years, focusing on the structure of carboxylated and undercarboxylated osteocalcin, new functions and putative receptors, the role of osteocalcin in bone remodeling, specific expression and regulation in osteoblasts, and new indices for clinical studies. The complexity of osteocalcin in completely, uncompletely and non-carboxylated forms may account for the discrepancies in its tertiary structure and clinical results. Moreover, the extensive expression of osteocalcin and its putative receptor GPRC6A imply that there are new physiological functions and mechanisms of action of osteocalcin to be explored. New discoveries related to osteocalcin function will assist its potential clinical application and physiological theory, but comprehensive investigations are required.
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Affiliation(s)
- Jinqiao Li
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, P.O.Box 1053-23#, No. 26, Beijing Road, Haidian District, Beijing, 100094, China
| | - Hongyu Zhang
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, P.O.Box 1053-23#, No. 26, Beijing Road, Haidian District, Beijing, 100094, China
| | - Chao Yang
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, P.O.Box 1053-23#, No. 26, Beijing Road, Haidian District, Beijing, 100094, China
| | - Yinghui Li
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, P.O.Box 1053-23#, No. 26, Beijing Road, Haidian District, Beijing, 100094, China
| | - Zhongquan Dai
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, P.O.Box 1053-23#, No. 26, Beijing Road, Haidian District, Beijing, 100094, China.
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27
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Alamshah A, McGavigan AK, Spreckley E, Kinsey-Jones JS, Amin A, Tough IR, O'Hara HC, Moolla A, Banks K, France R, Hyberg G, Norton M, Cheong W, Lehmann A, Bloom SR, Cox HM, Murphy KG. L-arginine promotes gut hormone release and reduces food intake in rodents. Diabetes Obes Metab 2016; 18:508-18. [PMID: 26863991 PMCID: PMC4982043 DOI: 10.1111/dom.12644] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 01/31/2016] [Accepted: 02/07/2016] [Indexed: 12/14/2022]
Abstract
AIMS To investigate the anorectic effect of L-arginine (L-Arg) in rodents. METHODS We investigated the effects of L-Arg on food intake, and the role of the anorectic gut hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), the G-protein-coupled receptor family C group 6 member A (GPRC6A) and the vagus nerve in mediating these effects in rodents. RESULTS Oral gavage of L-Arg reduced food intake in rodents, and chronically reduced cumulative food intake in diet-induced obese mice. Lack of the GPRC6A in mice and subdiaphragmatic vagal deafferentation in rats did not influence these anorectic effects. L-Arg stimulated GLP-1 and PYY release in vitro and in vivo. Pharmacological blockade of GLP-1 and PYY receptors did not influence the anorectic effect of L-Arg. L-Arg-mediated PYY release modulated net ion transport across the gut mucosa. Intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) administration of L-Arg suppressed food intake in rats. CONCLUSIONS L-Arg reduced food intake and stimulated gut hormone release in rodents. The anorectic effect of L-Arg is unlikely to be mediated by GLP-1 and PYY, does not require GPRC6A signalling and is not mediated via the vagus. I.c.v. and i.p. administration of L-Arg suppressed food intake in rats, suggesting that L-Arg may act on the brain to influence food intake. Further work is required to determine the mechanisms by which L-Arg suppresses food intake and its utility in the treatment of obesity.
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MESH Headings
- Animals
- Appetite Depressants/administration & dosage
- Appetite Depressants/adverse effects
- Appetite Depressants/pharmacology
- Appetite Depressants/therapeutic use
- Arginine/administration & dosage
- Arginine/adverse effects
- Arginine/therapeutic use
- Cells, Cultured
- Dietary Supplements/adverse effects
- Energy Intake/drug effects
- Energy Metabolism/drug effects
- Gastrointestinal Agents/administration & dosage
- Gastrointestinal Agents/adverse effects
- Gastrointestinal Agents/pharmacology
- Gastrointestinal Agents/therapeutic use
- Glucagon-Like Peptide 1/agonists
- Glucagon-Like Peptide 1/blood
- Glucagon-Like Peptide 1/metabolism
- In Vitro Techniques
- Injections, Intraperitoneal
- Injections, Intraventricular
- Intestinal Mucosa/cytology
- Intestinal Mucosa/drug effects
- Intestinal Mucosa/metabolism
- Intestinal Mucosa/pathology
- Male
- Mice, Inbred C57BL
- Mice, Knockout
- Obesity/diet therapy
- Obesity/drug therapy
- Obesity/metabolism
- Obesity/pathology
- Peptide YY/agonists
- Peptide YY/blood
- Peptide YY/metabolism
- Random Allocation
- Rats, Wistar
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/antagonists & inhibitors
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Weight Loss/drug effects
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Affiliation(s)
- A Alamshah
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - A K McGavigan
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - E Spreckley
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - J S Kinsey-Jones
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - A Amin
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - I R Tough
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - H C O'Hara
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - A Moolla
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - K Banks
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - R France
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - G Hyberg
- AstraZeneca R&D, Mölndal, Sweden
| | - M Norton
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - W Cheong
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - A Lehmann
- AstraZeneca R&D, Mölndal, Sweden
- Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - S R Bloom
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
| | - H M Cox
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - K G Murphy
- Section of Endocrinology and Investigative Medicine, Department of Medicine, Imperial College London, London, UK
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28
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Pi M, Kapoor K, Ye R, Nishimoto SK, Smith JC, Baudry J, Quarles LD. Evidence for Osteocalcin Binding and Activation of GPRC6A in β-Cells. Endocrinology 2016; 157:1866-80. [PMID: 27007074 PMCID: PMC4870875 DOI: 10.1210/en.2015-2010] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The possibility that G protein-coupled receptor family C member A (GPRC6A) is the osteocalcin (Ocn)-sensing G protein-coupled receptor that directly regulates pancreatic β-cell functions is controversial. In the current study, we found that Ocn and an Ocn-derived C-terminal hexapeptide directly activate GPRC6A-dependent ERK signaling in vitro. Computational models probe the structural basis of Ocn binding to GPRC6A and predict that the C-terminal hexapeptide docks to the extracellular side of the transmembrane domain of GPRC6A. Consistent with the modeling, mutations in the computationally identified binding pocket of GPRC6A reduced Ocn and C-terminal hexapeptide activation of this receptor. In addition, selective deletion of Gprc6a in β-cells (Gprc6a(β)(-cell-cko)) by crossing Gprc6a(flox/flox) mice with Ins2-Cre mice resulted in reduced pancreatic weight, islet number, insulin protein content, and insulin message expression. Both islet size and β-cell proliferation were reduced in Gprc6a(β)(-cell-cko) compared with control mice. Gprc6a(β)(-cell-cko) exhibited abnormal glucose tolerance, but normal insulin sensitivity. Islets isolated from Gprc6a(β)(-cell-cko) mice showed reduced insulin simulation index in response to Ocn. These data establish the structural basis for Ocn direct activation of GPRC6A and confirm a role for GPRC6A in regulating β-cell proliferation and insulin secretion.
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Affiliation(s)
- Min Pi
- Departments of Medicine (M.P., R.Y., L.D.Q.) and Microbiology, Immunology and Biochemistry (S.K.N.), University of Tennessee Health Science Center, Memphis, Tennessee 38163; University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics (K.K., J.C.S., J.B.), Oak Ridge, Tennessee 37830; and Department of Biochemistry and Cellular and Molecular Biology (J.C.S.), University of Tennessee, Knoxville, Tennessee 37996
| | - Karan Kapoor
- Departments of Medicine (M.P., R.Y., L.D.Q.) and Microbiology, Immunology and Biochemistry (S.K.N.), University of Tennessee Health Science Center, Memphis, Tennessee 38163; University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics (K.K., J.C.S., J.B.), Oak Ridge, Tennessee 37830; and Department of Biochemistry and Cellular and Molecular Biology (J.C.S.), University of Tennessee, Knoxville, Tennessee 37996
| | - Ruisong Ye
- Departments of Medicine (M.P., R.Y., L.D.Q.) and Microbiology, Immunology and Biochemistry (S.K.N.), University of Tennessee Health Science Center, Memphis, Tennessee 38163; University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics (K.K., J.C.S., J.B.), Oak Ridge, Tennessee 37830; and Department of Biochemistry and Cellular and Molecular Biology (J.C.S.), University of Tennessee, Knoxville, Tennessee 37996
| | - Satoru Kenneth Nishimoto
- Departments of Medicine (M.P., R.Y., L.D.Q.) and Microbiology, Immunology and Biochemistry (S.K.N.), University of Tennessee Health Science Center, Memphis, Tennessee 38163; University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics (K.K., J.C.S., J.B.), Oak Ridge, Tennessee 37830; and Department of Biochemistry and Cellular and Molecular Biology (J.C.S.), University of Tennessee, Knoxville, Tennessee 37996
| | - Jeremy C Smith
- Departments of Medicine (M.P., R.Y., L.D.Q.) and Microbiology, Immunology and Biochemistry (S.K.N.), University of Tennessee Health Science Center, Memphis, Tennessee 38163; University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics (K.K., J.C.S., J.B.), Oak Ridge, Tennessee 37830; and Department of Biochemistry and Cellular and Molecular Biology (J.C.S.), University of Tennessee, Knoxville, Tennessee 37996
| | - Jerome Baudry
- Departments of Medicine (M.P., R.Y., L.D.Q.) and Microbiology, Immunology and Biochemistry (S.K.N.), University of Tennessee Health Science Center, Memphis, Tennessee 38163; University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics (K.K., J.C.S., J.B.), Oak Ridge, Tennessee 37830; and Department of Biochemistry and Cellular and Molecular Biology (J.C.S.), University of Tennessee, Knoxville, Tennessee 37996
| | - Leigh Darryl Quarles
- Departments of Medicine (M.P., R.Y., L.D.Q.) and Microbiology, Immunology and Biochemistry (S.K.N.), University of Tennessee Health Science Center, Memphis, Tennessee 38163; University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics (K.K., J.C.S., J.B.), Oak Ridge, Tennessee 37830; and Department of Biochemistry and Cellular and Molecular Biology (J.C.S.), University of Tennessee, Knoxville, Tennessee 37996
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29
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Rueda P, Harley E, Lu Y, Stewart GD, Fabb S, Diepenhorst N, Cremers B, Rouillon MH, Wehrle I, Geant A, Lamarche G, Leach K, Charman WN, Christopoulos A, Summers RJ, Sexton PM, Langmead CJ. Murine GPRC6A Mediates Cellular Responses to L-Amino Acids, but Not Osteocalcin Variants. PLoS One 2016; 11:e0146846. [PMID: 26785252 PMCID: PMC4718634 DOI: 10.1371/journal.pone.0146846] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 12/21/2015] [Indexed: 12/13/2022] Open
Abstract
Phenotyping of Gprc6a KO mice has shown that this promiscuous class C G protein coupled receptor is variously involved in regulation of metabolism, inflammation and endocrine function. Such effects are described as mediated by extracellular calcium, L-amino acids, the bone-derived peptide osteocalcin (OCN) and the male hormone testosterone, introducing the concept of a bone-energy-metabolism-reproduction functional crosstalk mediated by GPRC6A. However, whilst the calcium and L-amino acid-sensing properties of GPRC6A are well established, verification of activity of osteocalcin at both human and mouse GPRC6A in vitro has proven somewhat elusive. This study characterises the in vitro pharmacology of mouse GPRC6A in response to its putative ligands in both recombinant and endogenous GPRC6A-expressing cells. Using cell signalling, and glucagon-like peptide (GLP)-1 and insulin release assays, our results confirm that basic L-amino acids act as agonists of the murine GPRC6A receptor in both recombinant cells and immortalised entero-endocrine and pancreatic β-cells. In contrast, our studies do not support a role for OCN as a direct ligand for mouse GPRC6A, suggesting that the reported in vivo effects of OCN that require GPRC6A may be indirect, rather than via direct activation of the receptor.
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Affiliation(s)
- Patricia Rueda
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | | | - Yao Lu
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Gregory D. Stewart
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Stewart Fabb
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Natalie Diepenhorst
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | | | | | | | - Anne Geant
- Institut de Recherches Servier, Suresnes, France
| | | | - Katie Leach
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - William N. Charman
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Arthur Christopoulos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Roger J. Summers
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Patrick M. Sexton
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Christopher J. Langmead
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
- * E-mail:
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30
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Johansson H, Boesgaard MW, Nørskov-Lauritsen L, Larsen I, Kuhne S, Gloriam DE, Bräuner-Osborne H, Sejer Pedersen D. Selective Allosteric Antagonists for the G Protein-Coupled Receptor GPRC6A Based on the 2-Phenylindole Privileged Structure Scaffold. J Med Chem 2015; 58:8938-51. [PMID: 26516782 DOI: 10.1021/acs.jmedchem.5b01254] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
G protein-coupled receptors (GPCRs) represent a biological target class of fundamental importance in drug therapy. The GPRC6A receptor is a newly deorphanized class C GPCR that we recently reported for the first allosteric antagonists based on the 2-arylindole privileged structure scaffold (e.g., 1-3). Herein, we present the first structure-activity relationship study for the 2-arylindole antagonist 3, comprising the design, synthesis, and pharmacological evaluation of a focused library of 3-substituted 2-arylindoles. In a FRET-based inositol monophosphate (IP1) assay we identified compounds 7, 13e, and 34b as antagonists at the GPRC6A receptor in the low micromolar range and show that 7 and 34b display >9-fold selectivity for the GPRC6A receptor over related GPCRs, making 7 and 34b the most potent and selective antagonists for the GPRC6A receptor reported to date.
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Affiliation(s)
- Henrik Johansson
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Jagtvej 162, 2100 Copenhagen, Denmark
| | - Michael Worch Boesgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Jagtvej 162, 2100 Copenhagen, Denmark
| | - Lenea Nørskov-Lauritsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Jagtvej 162, 2100 Copenhagen, Denmark
| | - Inna Larsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Jagtvej 162, 2100 Copenhagen, Denmark
| | - Sebastiaan Kuhne
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Jagtvej 162, 2100 Copenhagen, Denmark
| | - David E Gloriam
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Jagtvej 162, 2100 Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Jagtvej 162, 2100 Copenhagen, Denmark
| | - Daniel Sejer Pedersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Jagtvej 162, 2100 Copenhagen, Denmark
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31
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Arginine-induced insulin secretion in endoplasmic reticulum. Biochem Biophys Res Commun 2015; 466:717-22. [PMID: 26348775 DOI: 10.1016/j.bbrc.2015.09.006] [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] [Received: 08/27/2015] [Accepted: 09/03/2015] [Indexed: 01/31/2023]
Abstract
Arginine, a semi-essential amino acid, is known as one of the most strongest insulin secretagogues in a glucose-dependent manner, but major mechanism is unknown. Arginine induced insulin secretion in mice as well as β cell line, NIT-1, in which more than 90% of intracellular insulin is prionsulin without arginine cultivation. Arginine administration reduced prionsulin amount in 30 s, then insulin is secreted from NIT1 cells. These data indicated that the target factor(s) for arginine-induced insulin secretion located in endoplasmic reticulum (ER). We established the screening system for identifying the arginine mimetics. Brazilian propolis, not Chinese propolis, induced insulin secretion. To identify target factor(s) of arginine induced insulin secretion, our previous study was that nanobeads technology facilitated us to purify chemical-target factors. This time we chose the other way, proinsulin associating factor purification and arginine-immobilized agarose. Three proinsulin associating factors and 5 arginine interacting factors were identified. Among theses factors, Calnexin (CNX) was the only one factor, which belonged to both groups, suggesting that CNX might play a key role in arginine-induced insulin secretion in ER.
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32
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Kinsey-Jones JS, Alamshah A, McGavigan AK, Spreckley E, Banks K, Cereceda Monteoliva N, Norton M, Bewick GA, Murphy KG. GPRC6a is not required for the effects of a high-protein diet on body weight in mice. Obesity (Silver Spring) 2015; 23:1194-200. [PMID: 25958858 PMCID: PMC4692088 DOI: 10.1002/oby.21083] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 02/19/2015] [Indexed: 01/08/2023]
Abstract
OBJECTIVE The G-protein coupled receptor family C group 6 member A (GPRC6A) is activated by proteinogenic amino acids and may sense amino acids in the gastrointestinal tract and the brain. The study investigated whether GPRC6A was necessary for the effects of low- and high-protein diets on body weight and food intake in mice. METHODS The role of GPRC6A in mediating the effects of a low-protein diet on body weight was investigated in GPRC6a knockout (GPRC6a-KO) and wild-type (WT) mice fed a control diet (18% protein) or a low-protein diet (6% protein) for 9 days. The role of GPRC6A in mediating the effects of a high-protein diet on body weight was investigated in GPRC6a-KO and WT mice fed a control diet (18% protein) or a high-protein diet (50% protein) for 5 weeks. RESULTS A high-protein diet reduced body weight gain and food intake compared with a control diet in both WT and GPRC6a-KO mice. A low-protein diet decreased body weight gain in GPRC6a-KO mice. CONCLUSIONS GPRC6A was not necessary for the effects of a low- or high-protein diet on body weight and likely does not play a role in protein-induced satiety.
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Affiliation(s)
- James S Kinsey-Jones
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
| | - Amin Alamshah
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
| | - Anne K McGavigan
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
| | - Eleanor Spreckley
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
| | - Katherine Banks
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
| | - Nicholas Cereceda Monteoliva
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
| | - Mariana Norton
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
| | - Gavin A Bewick
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
- Division of Diabetes and Nutritional Sciences, King's College London, Guy's Campus, London, UK
| | - Kevin G Murphy
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
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33
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Brennan-Speranza TC, Conigrave AD. Osteocalcin: an osteoblast-derived polypeptide hormone that modulates whole body energy metabolism. Calcif Tissue Int 2015; 96:1-10. [PMID: 25416346 DOI: 10.1007/s00223-014-9931-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 11/11/2014] [Indexed: 02/07/2023]
Abstract
Osteocalcin is a bone-specific protein that is regularly used in the clinical setting as a serum marker of bone turnover. Recent evidence indicates that osteocalcin plays a previously unsuspected role in the control of energy metabolism. Thus, osteocalcin-deficient mice have a profoundly deranged metabolic phenotype that includes insulin resistance, glucose intolerance and abnormal fat deposition. Additionally, osteocalcin administration in mice improves insulin sensitivity and decreases fat pad mass and serum triglyceride levels. The role of osteocalcin in human macronutrient metabolism is less clear but recent studies report positive correlations between serum osteocalcin levels and established indices of metabolic health. Herein, we review key physiological functions of osteocalcin, focussing on the roles of osteocalcin in the modulation of macronutrient metabolism, male reproductive function and foetal brain development. We consider the implications of these findings for the coordination of metabolism with development and fertility. We also consider evidence that a Class C G-protein-coupled receptor from a subgroup known to mediate nutrient-sensing acts as the osteocalcin receptor.
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Affiliation(s)
- Tara C Brennan-Speranza
- Discipline of Physiology & Bosch Institute, School of Medical Sciences, University of Sydney, Sydney, NSW, 2006, Australia,
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34
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Ferron M, Lacombe J. Regulation of energy metabolism by the skeleton: Osteocalcin and beyond. Arch Biochem Biophys 2014; 561:137-46. [DOI: 10.1016/j.abb.2014.05.022] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 05/19/2014] [Accepted: 05/22/2014] [Indexed: 12/30/2022]
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35
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Leiss V, Flockerzie K, Novakovic A, Rath M, Schönsiegel A, Birnbaumer L, Schürmann A, Harteneck C, Nürnberg B. Insulin secretion stimulated by L-arginine and its metabolite L-ornithine depends on Gα(i2). Am J Physiol Endocrinol Metab 2014; 307:E800-12. [PMID: 25205820 PMCID: PMC4216945 DOI: 10.1152/ajpendo.00337.2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bordetella pertussis toxin (PTx), also known as islet-activating protein, induces insulin secretion by ADP-ribosylation of inhibitory G proteins. PTx-induced insulin secretion may result either from inactivation of Gα(o) proteins or from combined inactivation of Gα(o), Gα(i1), Gα(i2), and Gα(i3) isoforms. However, the specific role of Gα(i2) in pancreatic β-cells still remains unknown. In global (Gα(i2)(-/-)) and β-cell-specific (Gα(i2)(βcko)) gene-targeted Gα(i2) mouse models, we studied glucose homeostasis and islet functions. Insulin secretion experiments and intracellular Ca²⁺ measurements were used to characterize Gα(i2) function in vitro. Gα(i2)(-/-) and Gα(i2)(βcko) mice showed an unexpected metabolic phenotype, i.e., significantly lower plasma insulin levels upon intraperitoneal glucose challenge in Gα(i2)(-/-) and Gα(i2)(βcko) mice, whereas plasma glucose concentrations were unchanged in Gα(i2)(-/-) but significantly increased in Gα(i2)(βcko) mice. These findings indicate a novel albeit unexpected role for Gα(i2) in the expression, turnover, and/or release of insulin from islets. Detection of insulin secretion in isolated islets did not show differences in response to high (16 mM) glucose concentrations between control and β-cell-specific Gα(i2)-deficient mice. In contrast, the two- to threefold increase in insulin secretion evoked by L-arginine or L-ornithine (in the presence of 16 mM glucose) was significantly reduced in islets lacking Gα(i2). In accord with a reduced level of insulin secretion, intracellular calcium concentrations induced by the agonistic amino acid L-arginine did not reach control levels in β-cells. The presented analysis of gene-targeted mice provides novel insights in the role of β-cell Gα(i2) showing that amino acid-induced insulin-release depends on Gα(i2).
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MESH Headings
- Animals
- Arginine/metabolism
- Blood Glucose/analysis
- Calcium Signaling
- Crosses, Genetic
- Down-Regulation
- Fluorescent Antibody Technique
- GTP-Binding Protein alpha Subunit, Gi2/agonists
- GTP-Binding Protein alpha Subunit, Gi2/genetics
- GTP-Binding Protein alpha Subunit, Gi2/metabolism
- GTP-Binding Protein alpha Subunits, Gi-Go/agonists
- GTP-Binding Protein alpha Subunits, Gi-Go/genetics
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Hyperglycemia/blood
- Hyperglycemia/metabolism
- Hyperglycemia/prevention & control
- Hypoglycemia/blood
- Hypoglycemia/metabolism
- Hypoglycemia/prevention & control
- Insulin/blood
- Insulin/metabolism
- Insulin Secretion
- Islets of Langerhans/cytology
- Islets of Langerhans/metabolism
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Ornithine/blood
- Ornithine/metabolism
- Specific Pathogen-Free Organisms
- Tissue Culture Techniques
- Up-Regulation
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Affiliation(s)
- Veronika Leiss
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Katarina Flockerzie
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Ana Novakovic
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Michaela Rath
- Department of Experimental Diabetology, German Institute of Human Nutrition, Potsdam-Rehbrücke, Nuthetal, Germany
| | - Annika Schönsiegel
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Lutz Birnbaumer
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health/Department of Health and Human Services, Durham, North Carolina
| | - Annette Schürmann
- Department of Experimental Diabetology, German Institute of Human Nutrition, Potsdam-Rehbrücke, Nuthetal, Germany
| | - Christian Harteneck
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany
| | - Bernd Nürnberg
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, and Interfaculty Center of Pharmacogenomics and Drug Research, University of Tübingen, Tübingen, Germany;
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Clemmensen C, Smajilovic S, Wellendorph P, Bräuner-Osborne H. The GPCR, class C, group 6, subtype A (GPRC6A) receptor: from cloning to physiological function. Br J Pharmacol 2014; 171:1129-41. [PMID: 24032653 DOI: 10.1111/bph.12365] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 07/25/2013] [Accepted: 08/26/2013] [Indexed: 12/16/2022] Open
Abstract
GPRC6A (GPCR, class C, group 6, subtype A) is a class C GPCR that has been cloned from human, mouse and rat. Several groups have shown that the receptor is activated by a range of basic and small aliphatic L-α-amino acids of which L-arginine, L-lysine and L-ornithine are the most potent compounds with EC50 values in the mid-micromolar range. In addition, several groups have shown that the receptor is either directly activated or positively modulated by divalent cations such as Ca(2+) albeit in concentrations above 5 mM, which is above the physiological concentration in most tissues. More recently, the peptide osteocalcin and the steroid testosterone have also been suggested to be endogenous GPRC6A agonists. The receptor is widely expressed in all three species which, along with the omnipresence of the amino acids and divalent cation ligands, suggest that the receptor could be involved in a broad range of physiological functions. So far, this has mainly been addressed by analyses of genetically modified mice where the GPRC6A receptor has been ablated. Although there has been some discrepancies among results reported from different groups, there is increasing evidence that the receptor is involved in regulation of inflammation, metabolism and endocrine functions. GPRC6A could thus be an interesting target for new drugs in these therapeutic areas.
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Affiliation(s)
- C Clemmensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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37
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Tao YX, Liang XF. G Protein-Coupled Receptors as Regulators of Glucose Homeostasis and Therapeutic Targets for Diabetes Mellitus. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:1-21. [DOI: 10.1016/b978-0-12-800101-1.00001-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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38
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Clemmensen C, Smajilovic S, Smith EP, Woods SC, Bräuner-Osborne H, Seeley RJ, D'Alessio DA, Ryan KK. Oral L-arginine stimulates GLP-1 secretion to improve glucose tolerance in male mice. Endocrinology 2013; 154:3978-83. [PMID: 23959939 PMCID: PMC3800753 DOI: 10.1210/en.2013-1529] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Pharmacological and surgical interventions that increase glucagon-like peptide 1 (GLP-1) action are effective to improve glucose homeostasis in type 2 diabetes mellitus. In light of this, nutritional strategies to enhance postprandial GLP-1 secretion, particularly in the context of diet-induced obesity, may provide an alternative therapeutic approach. Importantly, recent evidence suggests the amino acid L-arginine, a well-known insulin secretagogue, can also stimulate release of GLP-1 from isolated rat intestine. Here we tested the hypothesis that oral L-arginine acts as a GLP-1 secretagogue in vivo, to augment postprandial insulin secretion and improve glucose tolerance. To test this, we administered L-arginine or vehicle by oral gavage, immediately prior to an oral glucose tolerance test in lean and diet-induced obese mice. In both lean and obese mice oral L-arginine increased plasma GLP-1 and insulin and substantially improved glucose clearance. To directly assess the contribution of GLP-1 receptor (GLP-1R)-signaling to these improvements, L-arginine was given to Glp1r knockout mice and their wild-type littermates. In this experiment oral l-arginine significantly augmented insulin secretion and improved glucose clearance in WT mice, but not in Glp1r knockout littermates. Taken together these findings identify L-arginine as a GLP-1 secretagogue in vivo and demonstrate that improvement of glucose tolerance by oral L-arginine depends on GLP-1R-signaling. These findings raise the intriguing possibility that L-arginine-based nutritional and/or pharmaceutical therapies may benefit glucose tolerance by improving the postprandial GLP-1 response in obese individuals.
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39
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Jacobsen SE, Nørskov-Lauritsen L, Thomsen ARB, Smajilovic S, Wellendorph P, Larsson NHP, Lehmann A, Bhatia VK, Bräuner-Osborne H. Delineation of the GPRC6A receptor signaling pathways using a mammalian cell line stably expressing the receptor. J Pharmacol Exp Ther 2013; 347:298-309. [PMID: 24008333 PMCID: PMC11047948 DOI: 10.1124/jpet.113.206276] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 09/05/2013] [Indexed: 11/22/2022] Open
Abstract
The GPRC6A receptor is a recently "deorphanized" class C G protein-coupled receptor. We and others have shown that this receptor is coactivated by basic l-α-amino acids and divalent cations, whereas other groups have also suggested osteocalcin and testosterone to be agonists. Likewise, the GPRC6A receptor has been suggested to couple to multiple G protein classes albeit via indirect methods. Thus, the exact ligand preferences and signaling pathways are yet to be elucidated. In the present study, we generated a Chinese hamster ovary (CHO) cell line that stably expresses mouse GPRC6A. In an effort to establish fully the signaling properties of the receptor, we tested representatives of four previously reported GPRC6A agonist classes for activity in the Gq, Gs, Gi, and extracellular-signal regulated kinase signaling pathways. Our results confirm that GPRC6A is activated by basic l-α-amino acids and divalent cations, and for the first time, we conclusively show that these responses are mediated through the Gq pathway. We were not able to confirm previously published data demonstrating Gi- and Gs-mediated signaling; neither could we detect agonistic activity of testosterone and osteocalcin. Generation of the stable CHO cell line with robust receptor responsiveness and optimization of the highly sensitive homogeneous time resolved fluorescence technology allow fast assessment of Gq activation without previous manipulations like cotransfection of mutated G proteins. This cell-based assay system for GPRC6A is thus useful in high-throughput screening for novel pharmacological tool compounds, which are necessary to unravel the physiologic function of the receptor.
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Affiliation(s)
- Stine Engesgaard Jacobsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (S.E.J., L.N.-L., A.R.B.T., S.S., P.W., V.K.B., H.B.-O.); and AstraZeneca, Mölndal, Sweden (N.H.P.L., A.L.)
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40
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Wauson EM, Lorente-Rodríguez A, Cobb MH. Minireview: Nutrient sensing by G protein-coupled receptors. Mol Endocrinol 2013; 27:1188-97. [PMID: 23820899 DOI: 10.1210/me.2013-1100] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are membrane proteins that recognize molecules in the extracellular milieu and transmit signals inside cells to regulate their behaviors. Ligands for many GPCRs are hormones or neurotransmitters that direct coordinated, stereotyped adaptive responses. Ligands for other GPCRs provide information to cells about the extracellular environment. Such information facilitates context-specific decision making that may be cell autonomous. Among ligands that are important for cellular decisions are amino acids, required for continued protein synthesis, as metabolic starting materials and energy sources. Amino acids are detected by a number of class C GPCRs. One cluster of amino acid-sensing class C GPCRs includes umami and sweet taste receptors, GPRC6A, and the calcium-sensing receptor. We have recently found that the umami taste receptor heterodimer T1R1/T1R3 is a sensor of amino acid availability that regulates the activity of the mammalian target of rapamycin. This review focuses on an array of findings on sensing amino acids and sweet molecules outside of neurons by this cluster of class C GPCRs and some of the physiologic processes regulated by them.
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Affiliation(s)
- Eric M Wauson
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041, USA
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41
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Córdoba-Chacón J, Gahete MD, Pozo-Salas AI, Castaño JP, Kineman RD, Luque RM. Endogenous somatostatin is critical in regulating the acute effects of L-arginine on growth hormone and insulin release in mice. Endocrinology 2013; 154:2393-8. [PMID: 23696563 PMCID: PMC3689276 DOI: 10.1210/en.2013-1136] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
l-arginine (l-Arg) rapidly stimulates GH and insulin release in vivo. It has been hypothesized that l-Arg stimulates GH release by lowering hypothalamic somatostatin (SST) tone. l-Arg may also act directly at the pituitary to stimulate GH release. Moreover, l-Arg has a direct stimulatory effect on β-cells, which is thought to be blunted by the release of SST from pancreatic δ-cells. To confirm the role of endogenous SST on l-Arg-induced GH and insulin release, wild-type (WT) and SST-knockout (SST-KO) mice were injected with l-Arg (ip; 0.8 g/kg), and pre-/post-injection GH, insulin, and glucose levels were measured. In WT mice, l-Arg evoked a 6-fold increase in circulating GH. However, there was only a modest increase in GH levels in WT pituitary cell cultures treated with l-Arg. In contrast, l-Arg failed to increase GH in SST-KO beyond their already elevated levels. These results further support the hypothesis that the primary mechanism by which l-Arg acutely increases GH in vivo is by lowering hypothalamic SST input to the pituitary and not via direct pituitary effects. Additionally, l-Arg induced a clear first-phase insulin secretion in WT mice, but not in SST-KO. However, SST-KO, but not WT mice, displayed a robust and sustained second-phase insulin release. These results further support a role for endogenous SST in regulating l-Arg-mediated insulin release.
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42
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Clemmensen C, Pehmøller C, Klein AB, Ratner C, Wojtaszewski JFP, Bräuner-Osborne H. Enhanced voluntary wheel running in GPRC6A receptor knockout mice. Physiol Behav 2013; 118:144-51. [PMID: 23680430 DOI: 10.1016/j.physbeh.2013.05.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 03/22/2013] [Accepted: 05/06/2013] [Indexed: 01/30/2023]
Abstract
GPRC6A is an amino acid-sensing receptor highly expressed in the brain and in skeletal muscle. Although recent evidence suggests that genetically engineered GPRC6A receptor knockout (KO) mice are susceptible to develop subtle endocrine and metabolic disturbances, the underlying disruptions in energy metabolism are largely unexplored. Based on GPRC6A's expression pattern and ligand preferences, we hypothesize that the receptor may impact energy metabolism via regulating physical activity levels. Thus, in the present study, we exposed GPRC6A receptor KO mice and their wild-type (WT) littermates to voluntary wheel running and forced treadmill exercise. Moreover, we assessed energy expenditure in the basal state, and evaluated the effects of wheel running on food intake, body composition, and a range of exercise-induced central and peripheral biomarkers. We found that adaptation to voluntary wheel running is affected by GPRC6A, as ablation of the receptor significantly enhances wheel running in KO relative to WT mice. Both genotypes responded to voluntary exercise by increasing food intake and improving body composition to a similar degree. In conclusion, these data demonstrate that the GPRC6A receptor is involved in regulating exercise behaviour. Future studies are highly warranted to delineate the underlying molecular details and to assess if these findings hold any translational value.
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Affiliation(s)
- Christoffer Clemmensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
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Oya M, Kitaguchi T, Pais R, Reimann F, Gribble F, Tsuboi T. The G protein-coupled receptor family C group 6 subtype A (GPRC6A) receptor is involved in amino acid-induced glucagon-like peptide-1 secretion from GLUTag cells. J Biol Chem 2012; 288:4513-21. [PMID: 23269670 DOI: 10.1074/jbc.m112.402677] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Although amino acids are dietary nutrients that evoke the secretion of glucagon-like peptide 1 (GLP-1) from intestinal L cells, the precise molecular mechanism(s) by which amino acids regulate GLP-1 secretion from intestinal L cells remains unknown. Here, we show that the G protein-coupled receptor (GPCR), family C group 6 subtype A (GPRC6A), is involved in amino acid-induced GLP-1 secretion from the intestinal L cell line GLUTag. Application of l-ornithine caused an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in GLUTag cells. Application of a GPRC6A receptor antagonist, a phospholipase C inhibitor, or an IP(3) receptor antagonist significantly suppressed the l-ornithine-induced [Ca(2+)](i) increase. We found that the increase in [Ca(2+)](i) stimulated by l-ornithine correlated with GLP-1 secretion and that l-ornithine stimulation increased exocytosis in a dose-dependent manner. Furthermore, depletion of endogenous GPRC6A by a specific small interfering RNA (siRNA) inhibited the l-ornithine-induced [Ca(2+)](i) increase and GLP-1 secretion. Taken together, these findings suggest that the GPRC6A receptor functions as an amino acid sensor in GLUTag cells that promotes GLP-1 secretion.
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Affiliation(s)
- Manami Oya
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
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