1
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Lu J, Piper SJ, Zhao P, Miller LJ, Wootten D, Sexton PM. Targeting VIP and PACAP Receptor Signaling: New Insights into Designing Drugs for the PACAP Subfamily of Receptors. Int J Mol Sci 2022; 23:8069. [PMID: 35897648 PMCID: PMC9331257 DOI: 10.3390/ijms23158069] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/18/2022] [Accepted: 07/20/2022] [Indexed: 12/16/2022] Open
Abstract
Pituitary Adenylate Cyclase-Activating Peptide (PACAP) and Vasoactive Intestinal Peptide (VIP) are neuropeptides involved in a diverse array of physiological and pathological processes through activating the PACAP subfamily of class B1 G protein-coupled receptors (GPCRs): VIP receptor 1 (VPAC1R), VIP receptor 2 (VPAC2R), and PACAP type I receptor (PAC1R). VIP and PACAP share nearly 70% amino acid sequence identity, while their receptors PAC1R, VPAC1R, and VPAC2R share 60% homology in the transmembrane regions of the receptor. PACAP binds with high affinity to all three receptors, while VIP binds with high affinity to VPAC1R and VPAC2R, and has a thousand-fold lower affinity for PAC1R compared to PACAP. Due to the wide distribution of VIP and PACAP receptors in the body, potential therapeutic applications of drugs targeting these receptors, as well as expected undesired side effects, are numerous. Designing selective therapeutics targeting these receptors remains challenging due to their structural similarities. This review discusses recent discoveries on the molecular mechanisms involved in the selectivity and signaling of the PACAP subfamily of receptors, and future considerations for therapeutic targeting.
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Affiliation(s)
- Jessica Lu
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Sarah J Piper
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Peishen Zhao
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Laurence J Miller
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, USA
| | - Denise Wootten
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Patrick M Sexton
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
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2
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Rodgers RL. Glucagon, cyclic AMP, and hepatic glucose mobilization: A half‐century of uncertainty. Physiol Rep 2022; 10:e15263. [PMID: 35569125 PMCID: PMC9107925 DOI: 10.14814/phy2.15263] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/16/2022] [Accepted: 03/18/2022] [Indexed: 12/14/2022] Open
Abstract
For at least 50 years, the prevailing view has been that the adenylate cyclase (AC)/cyclic AMP (cAMP)/protein kinase A pathway is the predominant signal mediating the hepatic glucose‐mobilizing actions of glucagon. A wealth of evidence, however, supports the alternative, that the operative signal most of the time is the phospholipase C (PLC)/inositol‐phosphate (IP3)/calcium/calmodulin pathway. The evidence can be summarized as follows: (1) The consensus threshold glucagon concentration for activating AC ex vivo is 100 pM, but the statistical hepatic portal plasma glucagon concentration range, measured by RIA, is between 28 and 60 pM; (2) Within that physiological concentration range, glucagon stimulates the PLC/IP3 pathway and robustly increases glucose output without affecting the AC/cAMP pathway; (3) Activation of a latent, amplified AC/cAMP pathway at concentrations below 60 pM is very unlikely; and (4) Activation of the PLC/IP3 pathway at physiological concentrations produces intracellular effects that are similar to those produced by activation of the AC/cAMP pathway at concentrations above 100 pM, including elevated intracellular calcium and altered activities and expressions of key enzymes involved in glycogenolysis, gluconeogenesis, and glycogen synthesis. Under metabolically stressful conditions, as in the early neonate or exercising adult, plasma glucagon concentrations often exceed 100 pM, recruiting the AC/cAMP pathway and enhancing the activation of PLC/IP3 pathway to boost glucose output, adaptively meeting the elevated systemic glucose demand. Whether the AC/cAMP pathway is consistently activated in starvation or diabetes is not clear. Because the importance of glucagon in the pathogenesis of diabetes is becoming increasingly evident, it is even more urgent now to resolve lingering uncertainties and definitively establish glucagon’s true mechanism of glycemia regulation in health and disease.
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Affiliation(s)
- Robert L. Rodgers
- Department of Biomedical and Pharmaceutical Sciences College of Pharmacy University of Rhode Island Kingston Rhode Island USA
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3
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Chen CC, Hsu LW, Chen KD, Chiu KW, Chen CL, Huang KT. Emerging Roles of Calcium Signaling in the Development of Non-Alcoholic Fatty Liver Disease. Int J Mol Sci 2021; 23:ijms23010256. [PMID: 35008682 PMCID: PMC8745268 DOI: 10.3390/ijms23010256] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/22/2021] [Accepted: 12/22/2021] [Indexed: 01/10/2023] Open
Abstract
The liver plays a central role in energy metabolism. Dysregulated hepatic lipid metabolism is a major cause of non-alcoholic fatty liver disease (NAFLD), a chronic liver disorder closely linked to obesity and insulin resistance. NAFLD is rapidly emerging as a global health problem with currently no approved therapy. While early stages of NAFLD are often considered benign, the disease can progress to an advanced stage that involves chronic inflammation, with increased risk for developing end-stage disease including fibrosis and liver cancer. Hence, there is an urgent need to identify potential pharmacological targets. Ca2+ is an essential signaling molecule involved in a myriad of cellular processes. Intracellular Ca2+ is intricately compartmentalized, and the Ca2+ flow is tightly controlled by a network of Ca2+ transport and buffering proteins. Impaired Ca2+ signaling is strongly associated with endoplasmic reticulum stress, mitochondrial dysfunction and autophagic defects, all of which are etiological factors of NAFLD. In this review, we describe the recent advances that underscore the critical role of dysregulated Ca2+ homeostasis in lipid metabolic abnormalities and discuss the feasibility of targeting Ca2+ signaling as a potential therapeutic approach.
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Affiliation(s)
- Chien-Chih Chen
- Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan;
| | - Li-Wen Hsu
- Liver Transplantation Center, Department of Surgery, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan; (L.-W.H.); (K.-D.C.); (K.-W.C.); (C.-L.C.)
| | - Kuang-Den Chen
- Liver Transplantation Center, Department of Surgery, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan; (L.-W.H.); (K.-D.C.); (K.-W.C.); (C.-L.C.)
- Institute for Translational Research in Biomedicine, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan
| | - King-Wah Chiu
- Liver Transplantation Center, Department of Surgery, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan; (L.-W.H.); (K.-D.C.); (K.-W.C.); (C.-L.C.)
- Division of Hepato-Gastroenterology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan
| | - Chao-Long Chen
- Liver Transplantation Center, Department of Surgery, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan; (L.-W.H.); (K.-D.C.); (K.-W.C.); (C.-L.C.)
| | - Kuang-Tzu Huang
- Liver Transplantation Center, Department of Surgery, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan; (L.-W.H.); (K.-D.C.); (K.-W.C.); (C.-L.C.)
- Institute for Translational Research in Biomedicine, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 83301, Taiwan
- Correspondence: ; Tel.: +886-7-731-7123 (ext. 8193)
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4
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Alghamdi BS. The Effect of Short-Term Feeding of a High-Coconut Oil or High-Fat Diet on Neuroinflammation and the Performance of an Object-Place Task in Rats. Neurochem Res 2021; 46:287-298. [PMID: 33221998 DOI: 10.1007/s11064-020-03163-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 09/30/2020] [Accepted: 10/28/2020] [Indexed: 02/07/2023]
Abstract
The consumption of high-fat and high-sugar diets, in the form of junk food, and binge eating are now common. Increasing evidence suggests that a high-fat diet (HFD) can induce neuroinflammation and alter behavior. I aimed to study the effects of diets of differing fat content on neuroinflammation and spatial memory using an object-place (OP) task. Thirty-two adult male rats were allocated to four groups and fed a regular diet (Regular diet), a control diet (Control diet), an HFD (60% of calories from lard), or a high-coconut oil diet (HCOD; 60% of calories from coconut oil) for 3 days. Their water intake, food consumption, body mass, and metabolic variables were measured. HFD-fed rats showed significantly poorer performance on the OP task, as assessed using the discrimination index (- 0.208 ± 0.094), than the Regular (0.462 ± 0.078; P < 0.0001) and Control (0.379 ± 0.081; P = 0.0003) groups. However, no significant difference was observed in spatial memory between the HCOD and Regular groups. The concentrations of neuroinflammatory markers (interleukin [IL]-1β, IL-6, tumor necrosis factor α, and nuclear factor κB) were also measured in the hippocampus and prefrontal cortex. HFD-fed rats showed significantly higher levels of neuroinflammatory markers than the Regular and Control diet-fed groups. HCOD feeding did not induce neuroinflammation in the hippocampus and prefrontal cortex compared with the Regular and Control groups.
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Affiliation(s)
- Badrah Saeed Alghamdi
- Department of Physiology, Neuroscience Unit, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.
- Pre-Clinical Research Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.
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5
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Qiao A, Han S, Li X, Li Z, Zhao P, Dai A, Chang R, Tai L, Tan Q, Chu X, Ma L, Thorsen TS, Reedtz-Runge S, Yang D, Wang MW, Sexton PM, Wootten D, Sun F, Zhao Q, Wu B. Structural basis of G s and G i recognition by the human glucagon receptor. Science 2020; 367:1346-1352. [PMID: 32193322 DOI: 10.1126/science.aaz5346] [Citation(s) in RCA: 96] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 02/11/2020] [Indexed: 12/13/2022]
Abstract
Class B G protein-coupled receptors, an important class of therapeutic targets, signal mainly through the Gs class of heterotrimeric G proteins, although they do display some promiscuity in G protein binding. Using cryo-electron microscopy, we determined the structures of the human glucagon receptor (GCGR) bound to glucagon and distinct classes of heterotrimeric G proteins, Gs or Gi1 These two structures adopt a similar open binding cavity to accommodate Gs and Gi1 The Gs binding selectivity of GCGR is explained by a larger interaction interface, but there are specific interactions that affect Gi more than Gs binding. Conformational differences in the receptor intracellular loops were found to be key selectivity determinants. These distinctions in transducer engagement were supported by mutagenesis and functional studies.
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Affiliation(s)
- Anna Qiao
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shuo Han
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Xinmei Li
- University of Chinese Academy of Sciences, Beijing 100049, China.,National Laboratory of Biomacromolecules, National Center of Protein Science-Beijing, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhixin Li
- School of Pharmacy, Fudan University, Shanghai 201203, China
| | - Peishen Zhao
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Antao Dai
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Rulve Chang
- School of Pharmacy, Fudan University, Shanghai 201203, China
| | - Linhua Tai
- University of Chinese Academy of Sciences, Beijing 100049, China.,National Laboratory of Biomacromolecules, National Center of Protein Science-Beijing, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Qiuxiang Tan
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Xiaojing Chu
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Limin Ma
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | | | | | - Dehua Yang
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Ming-Wei Wang
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,University of Chinese Academy of Sciences, Beijing 100049, China.,School of Pharmacy, Fudan University, Shanghai 201203, China.,National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Patrick M Sexton
- School of Pharmacy, Fudan University, Shanghai 201203, China.,Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Denise Wootten
- School of Pharmacy, Fudan University, Shanghai 201203, China. .,Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Fei Sun
- University of Chinese Academy of Sciences, Beijing 100049, China. .,National Laboratory of Biomacromolecules, National Center of Protein Science-Beijing, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Qiang Zhao
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China. .,University of Chinese Academy of Sciences, Beijing 100049, China.,CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing 100101, China
| | - Beili Wu
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China. .,University of Chinese Academy of Sciences, Beijing 100049, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China.,CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing 100101, China
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6
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Mito K, Sato Y, Kobayashi T, Miyamoto K, Nitta E, Iwama A, Matsumoto M, Nakamura M, Sato K, Miyamoto T. The nicotinic acetylcholine receptor α7 subunit is an essential negative regulator of bone mass. Sci Rep 2017; 7:45597. [PMID: 28349965 PMCID: PMC5368561 DOI: 10.1038/srep45597] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 02/27/2017] [Indexed: 01/07/2023] Open
Abstract
The nicotinic receptor α7nAchR reportedly regulates vagal nerve targets in brain and cardiac tissue. Here we show that nAchR7−/− mice exhibit increased bone mass due to decreased osteoclast formation, accompanied by elevated osteoprotegerin/RANKL ratios in serum. Vagotomy in wild-type mice also significantly increased the serum osteoprotegerin/RANKL ratio, and elevated bone mass seen in nAchR7−/− mice was reversed in α7nAchR/osteoprotegerin-doubly-deficient mice. α7nAchR loss significantly increased TNFα expression in Mac1-positive macrophages, and TNFα increased the osteoprotegerin/RANKL ratio in osteoblasts. Targeting TNFα in nAchR7−/− mice normalized both serum osteoprotegerin/RANKL ratios and bone mass. Administration of nicotine, an α7nAchR ligand, to wild-type mice increased serum RANKL levels. Thus, vagal nerve stimulation of macrophages via α7nAchR regulates bone mass by modulating osteoclast formation.
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Affiliation(s)
- Kazuaki Mito
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Yuiko Sato
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.,Department of Musculoskeletal Reconstruction and Regeneration Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Tami Kobayashi
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.,Department of Musculoskeletal Reconstruction and Regeneration Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Kana Miyamoto
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Eriko Nitta
- Department of Cellular and Molecular Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohara, Chuo-ku, Chiba 260-8670, Japan
| | - Atsushi Iwama
- Department of Cellular and Molecular Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohara, Chuo-ku, Chiba 260-8670, Japan
| | - Morio Matsumoto
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Masaya Nakamura
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Kazuki Sato
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Takeshi Miyamoto
- Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.,Department of Advanced Therapy for Musculoskeletal Disorders, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan
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7
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Lannea coromandelica attenuates glucagon and oxyntomodulin mediated cAMP formation in HEK cells stably-expressing human glucagon receptor. J Herb Med 2015. [DOI: 10.1016/j.hermed.2015.06.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Interaction of Glucagon G-Protein Coupled Receptor with Known Natural Antidiabetic Compounds: Multiscoring In Silico Approach. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2015; 2015:497253. [PMID: 26236379 PMCID: PMC4508340 DOI: 10.1155/2015/497253] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 06/15/2015] [Indexed: 01/18/2023]
Abstract
Glucagon receptor (GCGR) is a secretin-like (class B) family of G-protein coupled receptors (GPCRs) in humans that plays an important role in elevating the glucose concentration in blood and has thus become one of the promising therapeutic targets for treatment of type 2 diabetes mellitus. GCGR based inhibitors for the treatment of type 2 diabetes are either glucagon neutralizers or small molecular antagonists. Management of diabetes without any side effects is still a challenge to the medical system, and the search for a new and effective natural GCGR antagonist is an important area for the treatment of type 2 diabetes. In the present study, a number of natural compounds containing antidiabetic properties were selected from the literature and their binding potential against GCGR was determined using molecular docking and other in silico approaches. Among all selected natural compounds, curcumin was found to be the most effective compound against GCGR followed by amorfrutin 1 and 4-hydroxyderricin. These compounds were rescored to confirm the accuracy of binding using another scoring function (x-score). The final conclusions were drawn based on the results obtained from the GOLD and x-score. Further experiments were conducted to identify the atomic level interactions of selected compounds with GCGR.
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9
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Marinho R, Mekary RA, Muñoz VR, Gomes RJ, Pauli JR, de Moura LP. Regulation of hepatic TRB3/Akt interaction induced by physical exercise and its effect on the hepatic glucose production in an insulin resistance state. Diabetol Metab Syndr 2015; 7:67. [PMID: 26288661 PMCID: PMC4539706 DOI: 10.1186/s13098-015-0064-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 08/10/2015] [Indexed: 02/07/2023] Open
Abstract
To maintain euglycemia in healthy organisms, hepatic glucose production is increased during fasting and decreased during the postprandial period. This whole process is supported by insulin levels. These responses are associated with the insulin signaling pathway and the reduction in the activity of key gluconeogenic enzymes, resulting in a decrease of hepatic glucose production. On the other hand, defects in the liver insulin signaling pathway might promote inadequate suppression of gluconeogenesis, leading to hyperglycemia during fasting and after meals. The hepatocyte nuclear factor 4, the transcription cofactor PGC1-α, and the transcription factor Foxo1 have fundamental roles in regulating gluconeogenesis. The loss of insulin action is associated with the production of pro-inflammatory biomolecules in obesity conditions. Among the molecular mechanisms involved, we emphasize in this review the participation of TRB3 protein (a mammalian homolog of Drosophila tribbles), which is able to inhibit Akt activity and, thereby, maintain Foxo1 activity in the nucleus of hepatocytes, inducing hyperglycemia. In contrast, physical exercise has been shown as an important tool to reduce insulin resistance in the liver by reducing the inflammatory process, including the inhibition of TRB3 and, therefore, suppressing gluconeogenesis. The understanding of these new mechanisms by which physical exercise regulates glucose homeostasis has critical importance for the understanding and prevention of diabetes.
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Affiliation(s)
- Rodolfo Marinho
- />São Paulo State University, UNESP, Rio Claro, SP Brazil
- />Faculty of Applied Science, University of Campinas (UNICAMP), Rua Pedro Zaccaria, 1300, Jardim Santa Luzia, Limeira, SP Brazil
| | - Rania A. Mekary
- />Department of Social and Administrative Sciences, MCPHS University, Boston, MA USA
- />Department of Nutrition, Harvard T. Chan School of Public Health, Boston, MA USA
| | - Vitor Rosetto Muñoz
- />Faculty of Applied Science, University of Campinas (UNICAMP), Rua Pedro Zaccaria, 1300, Jardim Santa Luzia, Limeira, SP Brazil
| | - Ricardo José Gomes
- />Department of Biosciences, São Paulo Federal University (UNIFESP), Santos, SP Brazil
| | - José Rodrigo Pauli
- />São Paulo State University, UNESP, Rio Claro, SP Brazil
- />Faculty of Applied Science, University of Campinas (UNICAMP), Rua Pedro Zaccaria, 1300, Jardim Santa Luzia, Limeira, SP Brazil
| | - Leandro Pereira de Moura
- />São Paulo State University, UNESP, Rio Claro, SP Brazil
- />Faculty of Applied Science, University of Campinas (UNICAMP), Rua Pedro Zaccaria, 1300, Jardim Santa Luzia, Limeira, SP Brazil
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10
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Ozcan L, Cristina de Souza J, Harari AA, Backs J, Olson EN, Tabas I. Activation of calcium/calmodulin-dependent protein kinase II in obesity mediates suppression of hepatic insulin signaling. Cell Metab 2013; 18:803-15. [PMID: 24268736 PMCID: PMC3863383 DOI: 10.1016/j.cmet.2013.10.011] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 09/07/2013] [Accepted: 10/11/2013] [Indexed: 01/12/2023]
Abstract
A hallmark of obesity is selective suppression of hepatic insulin signaling ("insulin resistance"), but critical gaps remain in our understanding of the molecular mechanisms. We now report a major role for hepatic CaMKII, a calcium-responsive kinase that is activated in obesity. Genetic targeting of hepatic CaMKII, its downstream mediator p38, or the p38 substrate and stabilizer MK2 enhances insulin-induced p-Akt in palmitate-treated hepatocytes and obese mouse liver, leading to metabolic improvement. The mechanism of improvement begins with induction of ATF6 and the ATF6 target p58(IPK), a chaperone that suppresses the PERK-p-eIF2α-ATF4 branch of the UPR. The result is a decrease in the ATF4 target TRB3, an inhibitor of insulin-induced p-Akt, leading to enhanced activation of Akt and its downstream metabolic mediators. These findings increase our understanding of the molecular mechanisms linking obesity to selective insulin resistance and suggest new therapeutic targets for type 2 diabetes and metabolic syndrome.
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Affiliation(s)
- Lale Ozcan
- Department of Medicine, Columbia University, New York, NY 10032, USA.
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11
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Trakada G, Steiropoulos P, Zarogoulidis P, Nena E, Papanas N, Maltezos E, Bouros D. A fatty meal aggravates apnea and increases sleep in patients with obstructive sleep apnea. Sleep Breath 2013; 18:53-8. [DOI: 10.1007/s11325-013-0847-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 02/14/2013] [Accepted: 04/01/2013] [Indexed: 01/23/2023]
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12
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Cho YM, Merchant CE, Kieffer TJ. Targeting the glucagon receptor family for diabetes and obesity therapy. Pharmacol Ther 2012; 135:247-78. [DOI: 10.1016/j.pharmthera.2012.05.009] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 05/15/2012] [Indexed: 12/11/2022]
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13
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Peng IC, Chen Z, Sun W, Li YS, Marin TL, Hsu PH, Su MI, Cui X, Pan S, Lytle CY, Johnson DA, Blaeser F, Chatila T, Shyy JYJ. Glucagon regulates ACC activity in adipocytes through the CAMKKβ/AMPK pathway. Am J Physiol Endocrinol Metab 2012; 302:E1560-8. [PMID: 22454291 PMCID: PMC3378158 DOI: 10.1152/ajpendo.00504.2011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucagon is important for regulating lipid metabolism in part through its inhibition of fatty acid synthesis in adipocytes. Acetyl-CoA carboxylase 1 (ACC1) is the rate-limiting enzyme for fatty acid synthesis. Glucagon has been proposed to activate cAMP-dependent protein kinase A (PKA), which phosphorylates ACC1 to attenuate the lipogenic activity of ACC1. Because AMP-activated protein kinase (AMPK) also inhibits fatty acid synthesis by phosphorylation of ACC1, we examined the involvement of AMPK and its upstream kinase in the glucagon-elicited signaling in adipocytes in vitro and in vivo. LC-MS-MS analysis suggested that ACC1 was phosphorylated only at Ser(79), an AMPK-specific site, in glucagon-treated adipocytes. Pharmacological inhibitors and siRNA knockdown of AMPK or PKA in adipocytes demonstrate that glucagon regulates ACC1 and ACC2 activity through AMPK but not PKA. By using Ca(2+)/calmodulin-dependent protein kinase kinase-β knockout (CaMKKβ(-/-)) mice and cultured adipocytes, we further show that glucagon activates the CaMKKβ/AMPK/ACC cascade. Additionally, fasting increases the phosphorylation of AMPK and ACC in CaMKKβ(+/+) but not CaMKKβ(-/-) mice. These results indicate that CaMKKβ/AMPK signaling is an important molecular component in regulating lipid metabolism in adipocytes responding to glucagon and could be a therapeutic target for the dysregulation of energy storage.
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Affiliation(s)
- I-Chen Peng
- Division of Biomedical Sciences, University of California, Riverside, 92521, USA
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Ozcan L, Wong CC, Li G, Xu T, Pajvani U, Park SKR, Wronska A, Chen BX, Marks AR, Fukamizu A, Backs J, Singer HA, Yates JR, Accili D, Tabas I. Calcium signaling through CaMKII regulates hepatic glucose production in fasting and obesity. Cell Metab 2012; 15:739-51. [PMID: 22503562 PMCID: PMC3348356 DOI: 10.1016/j.cmet.2012.03.002] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Revised: 01/20/2012] [Accepted: 03/05/2012] [Indexed: 12/31/2022]
Abstract
Hepatic glucose production (HGP) is crucial for glucose homeostasis, but the underlying mechanisms have not been fully elucidated. Here, we show that a calcium-sensing enzyme, CaMKII, is activated in a calcium- and IP3R-dependent manner by cAMP and glucagon in primary hepatocytes and by glucagon and fasting in vivo. Genetic deficiency or inhibition of CaMKII blocks nuclear translocation of FoxO1 by affecting its phosphorylation, impairs fasting- and glucagon/cAMP-induced glycogenolysis and gluconeogenesis, and lowers blood glucose levels, while constitutively active CaMKII has the opposite effects. Importantly, the suppressive effect of CaMKII deficiency on glucose metabolism is abrogated by transduction with constitutively nuclear FoxO1, indicating that the effect of CaMKII deficiency requires nuclear exclusion of FoxO1. This same pathway is also involved in excessive HGP in the setting of obesity. These results reveal a calcium-mediated signaling pathway involved in FoxO1 nuclear localization and hepatic glucose homeostasis.
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Affiliation(s)
- Lale Ozcan
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Catherine C.L. Wong
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Gang Li
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Tao Xu
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Utpal Pajvani
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Sung Kyu Robin Park
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Anetta Wronska
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Bi-Xing Chen
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Andrew R. Marks
- Department of Medicine, Columbia University, New York, NY 10032, USA
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Akiyoshi Fukamizu
- Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Japan
| | - Johannes Backs
- Department of Internal Medicine III, University of Heidelberg, Heidelberg, Germany
| | - Harold A. Singer
- Center for Cardiovascular Sciences, Albany Medical College, Albany, NY 12208 USA
| | - John R. Yates
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Domenico Accili
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Ira Tabas
- Department of Medicine, Columbia University, New York, NY 10032, USA
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
- Department of Pathology & Cell Biology, Columbia University, New York, NY 10032, USA
- Correspondence:
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15
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Malekinejad H, Rahmani F, Valivande-Azar S, Taheri-Broujerdi M, Bazargani-Gilani B. Long-term administration of Silymarin augments proinflammatory mediators in the hippocampus of rats: evidence for antioxidant and pro-oxidant effects. Hum Exp Toxicol 2012; 31:921-30. [PMID: 22354081 DOI: 10.1177/0960327112436405] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Silymarin (SMN) is used as an antioxidant complex to attenuate the pro-oxidant effects of toxic agents. This study was designed to investigate the impact of a long-term administration of SMN on proinflammatory mediators, oxidative stress biomarkers and on the levels of interleukin-1β (IL-1β) transcript in the hippocampus. A total of 40 adult male Wistar rats were assigned into control and test groups. Animals in the test group were subdivided into four subgroups according to the following treatment profile: carbon tetrachloride (CCl(4), 0.5 ml/kg), SMN 25, SMN 50 and SMN 100 (mg/kg). The animals received the compounds by gastric gavage. Following the 8-week treatment period, animals in the CCl(4) group showed body weight loss, while the test groups except SMN 100 revealed a significant (p < 0.05) positive body weight gain. The levels of nitric oxide (NO) and malondialdehyde (MDA) as pro-oxidant and lipid peroxidation index, respectively, increased in CCl(4)- and SMN 100-treated groups, while SMN at lower dose levels did not alter the NO and MDA content. The concentration of total thiol molecules increased in the SMN 50 group and showed a remarkable decrease in CCl(4) and SMN 100 groups. Animals treated with CCl(4) or SMN 100 showed an upregulation of IL-1β, while animals in SMN 25 and SMN 50 groups showed a slight downregulation of expression of IL-1β at the messenger RNA level. These findings suggest that SMN at higher dosage level might exert pro-oxidant effect as an increase in the level of MDA and proinflammatory mediators such as NO, and upregulation of IL-1β in the hippocampus were shown.
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Affiliation(s)
- H Malekinejad
- Department of Pharmacology and Toxicology, Urmia University, Urmia, Iran.
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A natural inactivating mutant of human glucagon receptor exhibits multiple abnormalities in processing and signaling. ACTA ACUST UNITED AC 2011; 58:258-66. [PMID: 21680267 DOI: 10.1016/j.endonu.2011.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 04/12/2011] [Accepted: 04/20/2011] [Indexed: 11/21/2022]
Abstract
BACKGROUND AND AIM To elucidate the pathogenetic mechanisms of a mutant P86S glucagon receptor (GCGR) in causing a novel human disease (Mahvash disease). MATERIAL AND METHOD Enhanced green fluorescent protein (EGFP)-tagged WT and P86S GCGR were expressed in HEK 293 or H1299 cells either transiently or stably. Receptor localization and internalization, and cell apoptosis were studied by fluorescence microscopy, and calcium signaling by Rhod-3 labeling. Gene expression was assayed by RT-PCR or Western blot. Cell fate was determined by live cell imaging. RESULTS Unlike WT GCGR, P86S was partially localized to the plasma membrane and partially in the cytoplasm as previously reported and did not undergo internalization upon glucagon treatment. P86S did not elicit calcium response after treatment with 1 μM glucagon. Cells transiently expressing P86S exhibited more apoptosis than those expressing WT GCGR (18.3% vs 2.1%, P<0.05) but the X-box binding protein 1 mRNA cleavage, a marker of endoplasmic reticulum (ER) stress, was not evident, suggesting that the apoptosis did not result from ER stress. Cells stably expressing P86S did not exhibit apoptosis and a quarter of them harbored a novel inclusion body-like circular structure that was marked by P86S and ER residential proteins. These circular ER bodies were not seen in cells expressing WT GCGR or transiently expressing P86S and were not affected by treatment with proteasome inhibitor or microtubule depolymerizer, suggesting that they do not represent aggresome structures. The circular ER bodies could fuse and split to form new bodies. CONCLUSION The naturally-occurring P86S mutant GCGR exhibits abnormal receptor internalization and calcium mobilization, and causes apoptosis. The novel dynamic circular ER bodies may be adaptive in nature to nullify the toxic effects on P86S. These findings provide further insights into the pathogenetic mechanisms of Mahvash disease.
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17
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Affiliation(s)
- Rao N. Jaladanki
- University of Maryland School of Medicine and Baltimore Veterans Affairs Medical Center
| | - Jian-Ying Wang
- University of Maryland School of Medicine and Baltimore Veterans Affairs Medical Center
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18
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Abstract
Objective To determine if resistance to weight gain is associated with alterations in sleep/wake states and orexin receptor gene expression. Design Three-month old obesity susceptible Sprague-Dawley (SD) and obesity resistant (OR) rats were fed standard rodent chow. Sleep/wake cycle was measured by radiotelemetry and orexin receptor profiles in sleep/wake regulatory areas of the brain were quantified by quantitative RT-PCR. Subjects Adult male obesity susceptible SD and selectively-bred OR rats. Measurements Body weight, food intake, energy efficiency, percent time spent in active wake, quiet wake, slow-wave sleep (SWS), rapid eye movement (REM) sleep, number and mean duration of sleep/wake episodes, number of stage transitions, SWS sleep delta power and orexin receptor mRNA levels were measured. Results Obesity resistant rats weighed significantly less and had lower energy efficiency than SD rats. Food intake was not different between SD and OR rats. Time spent in quiet wake was similar between groups, and therefore active wake and quiet wake were combined and are referred to as ‘wakefulness’. Obesity resistant rats spent significantly more time in wakefulness and less time in SWS compared to SD rats during the 24 h recording period. Relative to SD rats, OR rats had significantly fewer sleep/wake episodes and the duration of the episodes were prolonged, indicating less fragmented sleep. Further, OR rats had fewer transitions between sleep stages, which indicates that OR rats were behaviorally more stable and had more consolidated sleep than obesity susceptible SD rats. Obesity resistant rats exhibited lower delta power during SWS sleep, indicating a lower sleep drive. Our results demonstrated greater orexin receptor gene expression in sleep regulatory brain areas in OR rats. Conclusion These results demonstrate that prolonged wakefulness, better sleep quality, lower sleep drive and greater orexin signaling may confer protection against obesity.
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19
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Xu Y, Xie X. Glucagon receptor mediates calcium signaling by coupling to G alpha q/11 and G alpha i/o in HEK293 cells. J Recept Signal Transduct Res 2010; 29:318-25. [PMID: 19903011 DOI: 10.3109/10799890903295150] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucagon induces intracellular Ca(2+) ([Ca(2+)](i)) elevation by stimulating glucagon receptor (GCGR). Such [Ca(2+)](i) signaling plays important physiological roles, including glycogenolysis and glycolysis in liver cells and the survival of beta-cells. Previous studies indicated that phospholipase C (PLC) might be involved in glucagon-mediated [Ca(2+)](i) response. Other studies also debated whether cAMP accumulation mediated by GCGR/G alpha(s) coupling contributes to [Ca(2+)](i) elevation. But the exact mechanisms remain uncertain. In the present study, we found that glucagon induces [Ca(2+)](i) elevation in HEK293 cells expressing GCGR. Removing extracellular Ca(2+) did not affect glucagon-stimulated [Ca(2+)](i) response. But depleting the intracellular Ca(2+) store by thapsigargin completely inhibited glucagon-induced [Ca(2+)](i) response. Experiments with forskolin and adenylyl cyclase inhibitor revealed that cAMP is not the cause of [Ca(2+)](i) response. Further studies with G alpha(q/11) RNAi and pertussis toxin (PTX) indicated that both G alpha(q/11) and G alpha(i/o) are involved. Combination of G alpha(q/11) RNAi and G alpha(i/o) inhibition almost completely abolished glucagon-induced [Ca(2+)](i) signaling.
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Affiliation(s)
- Yazhen Xu
- State Key Laboratory for Drug Research, National Center for Drug Screening, Shanghai, China
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20
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Karwatsky J, Ma L, Dong F, Zha X. Cholesterol efflux to apoA-I in ABCA1-expressing cells is regulated by Ca2+-dependent calcineurin signaling. J Lipid Res 2009; 51:1144-56. [PMID: 19965585 DOI: 10.1194/jlr.m003145] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ATP-binding cassette transporter A1 (ABCA1) is required for the lipidation of apolipoprotein A-I (apoA-I), although molecular mechanisms supporting this process remain poorly defined. In this study, we focused on the role of cytosolic Ca(2+) and its signaling and found that cytosolic Ca(2+) was required for cholesterol efflux to apoA-I. Removing extracellular Ca(2+) or chelating cytosolic Ca(2+) were equally inhibitory for apoA-I lipidation. We provide evidence that apoA-I induced Ca(2+) influx from the medium. We further demonstrate that calcineurin activity, the downstream target of Ca(2+) influx, was essential; inhibition of calcineurin activity by cyclosporine A or FK506 completely abolished apoA-I lipidation. Furthermore, calcineurin inhibition abolished apoA-I binding and diminished JAK2 phosphorylation, an established signaling event for cholesterol efflux to apoA-I. Finally, we demonstrate that neither Ca(2+) manipulation nor calcineurin inhibition influenced ABCA1's capacity to release microparticles or to remodel the plasma membrane. We conclude that this Ca(2+)-dependent calcineurin/JAK2 pathway is specifically responsible for apoA-I lipidation without directly modifying ABCA1 activity.
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Affiliation(s)
- Joel Karwatsky
- Ottawa Hospital Research Institute and Department of Biochemistry Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8L6, Canada
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21
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Gelling RW, Vuguin PM, Du XQ, Cui L, Rømer J, Pederson RA, Leiser M, Sørensen H, Holst JJ, Fledelius C, Johansen PB, Fleischer N, McIntosh CHS, Nishimura E, Charron MJ. Pancreatic beta-cell overexpression of the glucagon receptor gene results in enhanced beta-cell function and mass. Am J Physiol Endocrinol Metab 2009; 297:E695-707. [PMID: 19602585 PMCID: PMC2739695 DOI: 10.1152/ajpendo.00082.2009] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In addition to its primary role in regulating glucose production from the liver, glucagon has many other actions, reflected by the wide tissue distribution of the glucagon receptor (Gcgr). To investigate the role of glucagon in the regulation of insulin secretion and whole body glucose homeostasis in vivo, we generated mice overexpressing the Gcgr specifically on pancreatic beta-cells (RIP-Gcgr). In vivo and in vitro insulin secretion in response to glucagon and glucose was increased 1.7- to 3.9-fold in RIP-Gcgr mice compared with controls. Consistent with the observed increase in insulin release in response to glucagon and glucose, the glucose excursion resulting from both a glucagon challenge and intraperitoneal glucose tolerance test (IPGTT) was significantly reduced in RIP-Gcgr mice compared with controls. However, RIP-Gcgr mice display similar glucose responses to an insulin challenge. beta-Cell mass and pancreatic insulin content were also increased (20 and 50%, respectively) in RIP-Gcgr mice compared with controls. When fed a high-fat diet (HFD), both control and RIP-Gcgr mice developed similar degrees of obesity and insulin resistance. However, the severity of both fasting hyperglycemia and impaired glucose tolerance (IGT) were reduced in RIP-Gcgr mice compared with controls. Furthermore, the insulin response of RIP-Gcgr mice to an IPGTT was twice that of controls when fed the HFD. These data indicate that increased pancreatic beta-cell expression of the Gcgr increased insulin secretion, pancreatic insulin content, beta-cell mass, and, when mice were fed a HFD, partially protected against hyperglycemia and IGT.
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Affiliation(s)
- Richard W Gelling
- Department of Biochemistry, Pediatric Endocrinology, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, New York, Bronx, NY 10461, USA
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22
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Alquicer G, Kodrík D, Krishnan N, Večeřa J, Socha R. Activation of insect anti-oxidative mechanisms by mammalian glucagon. Comp Biochem Physiol B Biochem Mol Biol 2009; 152:226-33. [DOI: 10.1016/j.cbpb.2008.11.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 11/27/2008] [Accepted: 11/28/2008] [Indexed: 10/21/2022]
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23
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Striker GE, Praddaude F, Alcazar O, Cousins SW, Marin-Castaño ME. Regulation of angiotensin II receptors and extracellular matrix turnover in human retinal pigment epithelium: role of angiotensin II. Am J Physiol Cell Physiol 2008; 295:C1633-46. [PMID: 18923060 PMCID: PMC2603567 DOI: 10.1152/ajpcell.00092.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Accepted: 10/11/2008] [Indexed: 11/22/2022]
Abstract
The early stage of age-related macular degeneration (AMD) is characterized by the formation of subretinal pigment epithelium (RPE) deposits as a result of the dysregulation in the turnover of extracellular matrix (ECM) molecules. However, the mechanism involved remains unclear. Hypertension (HTN) is an important risk factor for AMD, and angiotensin II (ANG II) is the most important hormone associated with HTN. However, the relevance of ANG II receptors and ANG II effects on RPE have not been investigated yet. Therefore, the expression and regulation of ANG II receptors as well as the ECM turnover were studied in human RPE. ANG II receptors were expressed and upregulated by ANG II in human RPE. This regulation resulted in functional receptor expression, since an increase in intracellular concentration of calcium was observed upon ANG II stimulation. ANG II also increased matrix metalloproteinase (MMP)-2 activity and MMP-14 at the mRNA and protein levels as well as type IV collagen degradation. These ANG II effects were abolished in the presence of the ANG II receptor subtype 1 (AT1) receptor antagonist candesartan. In contrast, ANG II decreased type IV collagen via both AT1 and AT2 receptors, suggesting a synergistic effect of the two receptor subtypes. In conclusion, we have confirmed the presence of ANG II receptors in human RPE and their regulation by ANG II as well as the regulation of ECM molecules via ANG II receptors. Our data support the hypothesis that ANG II may exert biological function in RPE through ANG II receptors and that ANG II may cause dysregulation of molecules that play a major role in the turnover of ECM in RPE basement membrane and Bruch's membrane, suggesting a pathogenic mechanism to explain the link between HTN and AMD.
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Affiliation(s)
- Gary E Striker
- Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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24
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Striker GE, Praddaude F, Alcazar O, Cousins SW, Marin-Castaño ME. Regulation of angiotensin II receptors and extracellular matrix turnover in human retinal pigment epithelium: role of angiotensin II. Am J Physiol Cell Physiol 2008. [PMID: 18923060 DOI: 10.1152/ajpcell.00092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The early stage of age-related macular degeneration (AMD) is characterized by the formation of subretinal pigment epithelium (RPE) deposits as a result of the dysregulation in the turnover of extracellular matrix (ECM) molecules. However, the mechanism involved remains unclear. Hypertension (HTN) is an important risk factor for AMD, and angiotensin II (ANG II) is the most important hormone associated with HTN. However, the relevance of ANG II receptors and ANG II effects on RPE have not been investigated yet. Therefore, the expression and regulation of ANG II receptors as well as the ECM turnover were studied in human RPE. ANG II receptors were expressed and upregulated by ANG II in human RPE. This regulation resulted in functional receptor expression, since an increase in intracellular concentration of calcium was observed upon ANG II stimulation. ANG II also increased matrix metalloproteinase (MMP)-2 activity and MMP-14 at the mRNA and protein levels as well as type IV collagen degradation. These ANG II effects were abolished in the presence of the ANG II receptor subtype 1 (AT1) receptor antagonist candesartan. In contrast, ANG II decreased type IV collagen via both AT1 and AT2 receptors, suggesting a synergistic effect of the two receptor subtypes. In conclusion, we have confirmed the presence of ANG II receptors in human RPE and their regulation by ANG II as well as the regulation of ECM molecules via ANG II receptors. Our data support the hypothesis that ANG II may exert biological function in RPE through ANG II receptors and that ANG II may cause dysregulation of molecules that play a major role in the turnover of ECM in RPE basement membrane and Bruch's membrane, suggesting a pathogenic mechanism to explain the link between HTN and AMD.
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Affiliation(s)
- Gary E Striker
- Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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25
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Li XC, Zhuo JL. Targeting glucagon receptor signalling in treating metabolic syndrome and renal injury in Type 2 diabetes: theory versus promise. Clin Sci (Lond) 2007; 113:183-93. [PMID: 17623014 PMCID: PMC2277524 DOI: 10.1042/cs20070040] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Pancreatic bi-hormones insulin and glucagon are the Yin and Yang in the regulation of glucose metabolism and homoeostasis. Insulin is synthesized primarily by pancreatic beta-cells and is released in response to an increase in blood glucose levels (hyperglycaemia). By contrast, glucagon is synthesized by pancreatic alpha-cells and is released in response to a decrease in blood glucose (hypoglycaemia). The principal role of glucagon is to counter the actions of insulin on blood glucose homoeostasis, but it also has diverse non-hyperglycaemic actions. Although Type 1 diabetes is caused by insulin deficiency (insulin-dependent) and can be corrected by insulin replacement, Type 2 diabetes is a multifactorial disease and its treatment is not dependent on insulin therapy alone. Type 2 diabetes in humans is characterized by increased insulin resistance, increased fasting blood glucose, impaired glucose tolerance and the development of glomerular hyperfiltration and microalbuminuria, ultimately leading to diabetic nephropathy and end-stage renal disease. Clinical studies have suggested that an inappropriate increase in hyperglycaemic glucagon (hyperglucagonaemia) over hypoglycaemic insulin (not insulin deficiency until advanced stages) plays an important role in the pathogenesis of Type 2 diabetes. However, for decades, research efforts and resources have been devoted overwhelmingly to studying the role of insulin and insulin-replacement therapy. By contrast, the implication of glucagon and its receptor signalling in the development of Type 2 diabetic metabolic syndromes and end-organ injury has received little attention. The aim of this review is to examine the evidence as to whether glucagon and its receptor signalling play any role(s) in the pathogenesis of Type 2 diabetic renal injury, and to explore whether targeting glucagon receptor signalling remains only a theoretical antidiabetic strategy in Type 2 diabetes or may realize its promise in the future.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA
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26
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Yi PL, Lin CP, Tsai CH, Lin JG, Chang FC. The involvement of serotonin receptors in suanzaorentang-induced sleep alteration. J Biomed Sci 2007; 14:829-40. [PMID: 17657585 DOI: 10.1007/s11373-007-9197-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Accepted: 07/12/2007] [Indexed: 11/27/2022] Open
Abstract
Sedative-hypnotic medications, including benzodiazepines and non-benzodiazepines, are usually prescribed for the insomniac patients; however, the addiction, dependence and adverse effects of those medications have drawn much attention. In contrast, suanzaorentang, a traditional Chinese herb remedy, has been efficiently used for insomnia relief in China, although its mechanism remains unclear. This study was designed to further elucidate the underlying mechanism of suanzaorentang on sleep regulation. One ingredient of suanzaorentang, zizyphi spinosi semen, exhibits binding affinity for serotonin (5-hydroxytryptamine, 5-HT) receptors, 5-HT(1A) and 5-HT(2), and for GABA receptors. Our previous results have implicated that GABA(A) receptors, but not GABA(B), mediate suanzaorentang-induced sleep alteration. In current study we further elucidated the involvement of serotonin. We found that high dose of suanzaorentang (4 g/kg/2 ml) significantly increased non-rapid eye movement sleep (NREMS) when comparing to that obtained after administering starch placebo, although placebo at dose of 4 g/kg also enhanced NREMS comparing with that obtained from baseline recording. Rapid eye movement sleep (REMS) was not altered. Administration of either 5-HT(1A) antagonist (NAN-190), 5-HT(2) antagonist (ketanserin) or 5-HT(3 )antagonist (3-(4-Allylpiperazin-1-yl)-2-quinoxalinecarbonitrile) blocked suanzaorentang-induced NREMS increase. These results implicate the hypnotic effect of suanzaorentang and its effects may be mediated through serotonergic activation, in addition to GABAergic system.
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Affiliation(s)
- Pei-Lu Yi
- Department of Medical Technology, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli, Taiwan
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27
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Buchanan JB, Johnson RW. Regulation of food intake by inflammatory cytokines in the brain. Neuroendocrinology 2007; 86:183-90. [PMID: 17823502 DOI: 10.1159/000108280] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Accepted: 12/11/2007] [Indexed: 11/19/2022]
Abstract
A number of inflammatory cytokines are synthesized and released after activation of the immune system. In addition to other biological effects, these cytokines can potently inhibit food intake. Cytokine-mediated inhibition of food intake is of particular importance because excessive production of peripheral inflammatory cytokines is often associated with the cachexia-anorexia syndrome seen in some chronic diseases. The weight loss in cachexia is associated with an increase in morbidity and mortality. Understanding how cytokines regulate food intake may be crucial in enhancing quality of life and facilitating recovery in patients exhibiting cachexia. This review describes the main inflammatory cytokines that influence food intake and explores how peripheral cytokines communicate with hypothalamic nuclei to influence feeding.
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Affiliation(s)
- Jessica B Buchanan
- Laboratory of Integrative Immunology and Behaviour, Division of Nutritional Sciences, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
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28
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Yi PL, Tsai CH, Chen YC, Chang FC. Gamma-aminobutyric acid (GABA) receptor mediates suanzaorentang, a traditional Chinese herb remedy, -induced sleep alteration. J Biomed Sci 2006; 14:285-97. [PMID: 17151826 DOI: 10.1007/s11373-006-9137-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 10/26/2006] [Indexed: 11/26/2022] Open
Abstract
The sedative-hypnotic medications, including benzodiazepines and non-benzodiazepines, are the most common treatments for insomnia. However, concerns regarding patterns of inappropriate use, dependence and adverse effects have led to caution in prescribing those sedative-hypnotic medications. On the other hand, a traditional Chinese herb remedy, suanzaorentang, has been efficiently and widely used in clinic for insomnia relief without severe side effects in Asia. Although suanzaorentang has been reported to improve sleep disruption in insomniac patients, its mechanism is still unclear. The present study was designed to elucidate the effects of oral administration of suanzaorentang on physiological sleep-wake architectures and its underlying mechanism in rats. We found that oral administration of suanzaorentang at the beginning of the dark onset dose-dependently increased non-rapid eye movement sleep (NREMS) during the dark period, but had no significant effect on rapid eye movement sleep (REMS). Our results also indicated that intracerebroventricular (ICV) administration of gamma-aminobutyric acid (GABA) receptor type A antagonist, bicuculline, significantly blocked suanzaorentang-induced enhancement in NREMS during the dark period, but GABA(B) receptor antagonist, 2-hydroxysaclofen had no effect. These results implicated that this traditional Chinese herb remedy, suanzaorentang increases spontaneous sleep activity and its effects may be mediated through the GABA(A) receptors, but not GABA(B) receptors.
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Affiliation(s)
- Pei-Lu Yi
- Department of Medical Technology, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli, Taiwan
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Aromataris EC, Roberts ML, Barritt GJ, Rychkov GY. Glucagon activates Ca2+ and Cl- channels in rat hepatocytes. J Physiol 2006; 573:611-25. [PMID: 16581855 PMCID: PMC1779747 DOI: 10.1113/jphysiol.2006.109819] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Glucagon is one of the major hormonal regulators of glucose metabolism, counteracting the hepatic effects of insulin when the concentration of glucose in the bloodstream falls below a certain level. Glucagon also regulates bile flow, hepatocellular volume and membrane potential of hepatocytes. It is clear that changes in cell volume and membrane potential cannot occur without significant ion fluxes across the plasma membrane. The effects of glucagon on membrane currents in hepatocytes, however, are not well understood. Here we show, by patch-clamping of rat hepatocytes, that glucagon activates two types of currents: a small inwardly rectifying Ca2+ current with characteristics similar to those of the store-operated Ca2+ current and a larger outwardly rectifying Cl- current similar to that activated by cell swelling. We show that the mechanism of glucagon action on membrane conductance involves phospholipase C and adenylyl cyclase. Contribution of the adenylyl cyclase-dependent pathway to activation of the currents depended on Epac (exchange protein directly activated by cAMP), but not on protein kinase A. The activation of Ca2+ and Cl- channels is likely to play a key role in the mechanisms by which glucagon regulates hepatocyte metabolism and volume.
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Affiliation(s)
- Edoardo C Aromataris
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia 5005, Australia
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Li XC, Carretero OA, Zhuo JL. Cross-talk between angiotensin II and glucagon receptor signaling mediates phosphorylation of mitogen-activated protein kinases ERK 1/2 in rat glomerular mesangial cells. Biochem Pharmacol 2006; 71:1711-9. [PMID: 16643859 PMCID: PMC2276839 DOI: 10.1016/j.bcp.2006.03.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 03/16/2006] [Accepted: 03/16/2006] [Indexed: 12/26/2022]
Abstract
We have recently shown that the pancreatic hormone glucagon-induced phosphorylation of mitogen-activated protein (MAP) kinase ERK 1/2 as well as growth and proliferation of rat glomerular mesangial cells (MCs) via activation of cAMP-dependent protein kinase A (PKA)- and phospholipase C (PLC)/Ca2+-mediated signaling pathways. Since circulating glucagon and tissue angiotensin II (Ang II) levels are inappropriately elevated in type 2 diabetes, we tested the hypothesis that glucagon induces phosphorylation of ERK 1/2 in MCs by interacting with Ang II receptor signaling. Stimulation of MCs by glucagon (10 nM) induced a marked increase in intracellular [Ca2+]i that was abolished by [Des-His1, Glu9]-glucagon (1 microM), a selective glucagon receptor antagonist. Both glucagon and Ang II-induced ERK 1/2 phosphorylation (glucagon: 214+/-14%; Ang II: 174+/-16%; p<0.001 versus control), and these responses were inhibited by the AT1 receptor blocker losartan (glucagon + losartan: 77+/-14%; Ang II + losartan: 84+/-18%; p<0.01 versus glucagon or Ang II) and the AT2 receptor blocker PD 123319 (glucagon + PD: 78+/-7%; Ang II + PD: 87+/-7%; p<0.01 versus glucagon or Ang II). Inhibition of cAMP-dependent PKA with H89 (1 microM) or PLC with U73122 (1 microM) also markedly attenuated the phosphorylation of ERK 1/2 induced by glucagon (glucagon + U73122: 109+/-15%; glucagon + H89: 113+/-16%; p<0.01 versus glucagon) or Ang II (Ang II + U73122: 111+/-13%; Ang II + H89: 86+/-10%; p<0.01 versus Ang II). Wortmannin (1 microM), a selective PI 3-kinase inhibitor, also blocked glucagon- or Ang II-induced ERK 1/2 phosphorylation. These results suggest that AT1 receptor-activated cAMP-dependent PKA, PLC and PI 3-kinase signaling is involved in glucagon-induced MAP kinase ERK 1/2 phosphorylation in MCs. The inhibitory effect of PD 123319 on glucagon-induced ERK 1/2 phosphorylation further suggests that AT2 receptors also play a similar role in this response.
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Affiliation(s)
- Xiao C. Li
- Laboratory of Receptor and Signal Transduction, Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA
| | - Oscar A. Carretero
- Laboratory of Receptor and Signal Transduction, Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA
| | - Jia L. Zhuo
- Laboratory of Receptor and Signal Transduction, Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
- * Corresponding author at: Laboratory of Receptor and Signal Transduction, Division of Hypertension and Vascular Research, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, USA. Tel.: +1 313 916 4958; fax: +1 313 916 1479. E-mail address: (J.L. Zhuo)
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Li XC, Carretero OA, Shao Y, Zhuo JL. Glucagon receptor-mediated extracellular signal-regulated kinase 1/2 phosphorylation in rat mesangial cells: role of protein kinase A and phospholipase C. Hypertension 2006; 47:580-5. [PMID: 16391176 PMCID: PMC2367309 DOI: 10.1161/01.hyp.0000197946.81754.0a] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Glucagon, a major insulin counterregulatory hormone, binds to specific Gs protein-coupled receptors to activate glycogenolytic and gluconeogenic pathways, causing blood glucose levels to increase. Inappropriate increases in serum glucagon play a critical role in the development of insulin resistance and target organ damage in type 2 diabetes. We tested the hypotheses that: (1) glucagon induces proliferation of rat glomerular mesangial cells through glucagon receptor-activated phosphorylation of mitogen-activated protein kinase extracellular signal-regulated kinase 1/2 (p-ERK 1/2); and (2) this phosphorylation involves activation of cAMP-dependent protein kinase A (PKA) and phospholipase C (PLC)/[Ca2+]i signaling pathways. In rat mesangial cells, glucagon (1 nM) stimulated [3H]-thymidine incorporation by 96% (P<0.01). This proliferative effect was blocked by the specific glucagon receptor antagonist [Des-His1-Glu9] glucagon (1 micromol/L; P<0.01), a mitogen-activated protein kinase/ERK kinase inhibitor PD98059 (10 micromol/L; P<0.01), a PLC inhibitor U73122 (1 micromol/L; P<0.01), or a PKA inhibitor H-89 (1 micromol/L; P<0.01). The proliferation was associated with a 2-fold increase in p-ERK 1/2 that peaked 5 minutes after glucagon stimulation (P<0.01) and also was blocked by [Des-His1-Glu9] glucagon. Total ERK 1/2 was not affected by glucagon. Pretreating of mesangial cells with U73122 or H89 significantly attenuated ERK 1/2 phosphorylation induced by glucagon. We believe that these are the first data showing that glucagon activates specific receptors to induce ERK 1/2 phosphorylation and thereby increase mesangial cell proliferation and that this effect of glucagon involves both PLC/[Ca2+]i- and cAMP-dependent PKA-activated signaling cascades.
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Affiliation(s)
- Xiao C Li
- Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA
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Martin B, Lopez de Maturana R, Brenneman R, Walent T, Mattson MP, Maudsley S. Class II G protein-coupled receptors and their ligands in neuronal function and protection. Neuromolecular Med 2005; 7:3-36. [PMID: 16052036 PMCID: PMC2636744 DOI: 10.1385/nmm:7:1-2:003] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2005] [Accepted: 01/26/2005] [Indexed: 12/20/2022]
Abstract
G protein-coupled receptors (GPCRs) play pivotal roles in regulating the function and plasticity of neuronal circuits in the nervous system. Among the myriad of GPCRs expressed in neural cells, class II GPCRs which couples predominantly to the Gs-adenylate cyclase-cAMP signaling pathway, have recently received considerable attention for their involvement in regulating neuronal survival. Neuropeptides that activate class II GPCRs include secretin, glucagon-like peptides (GLP-1 and GLP-2), growth hormone-releasing hormone (GHRH), pituitary adenylate cyclase activating peptide (PACAP), corticotropin-releasing hormone (CRH), vasoactive intestinal peptide (VIP), parathyroid hormone (PTH), and calcitonin-related peptides. Studies of patients and animal and cell culture models, have revealed possible roles for class II GPCRs signaling in the pathogenesis of several prominent neurodegenerative conditions including stroke, Alzheimer's, Parkinson's, and Huntington's diseases. Many of the peptides that activate class II GPCRs promote neuron survival by increasing the resistance of the cells to oxidative, metabolic, and excitotoxic injury. A better understanding of the cellular and molecular mechanisms by which class II GPCRs signaling modulates neuronal survival and plasticity will likely lead to novel therapeutic interventions for neurodegenerative disorders.
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Affiliation(s)
- Bronwen Martin
- Laboratory of Neurosciences, National Institute on Ageing Intramural Research Program, Gerontology Research Center, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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Fischer L, Haag-Diergarten S, Scharrer E, Lutz TA. Leukotriene and purinergic receptors are involved in the hyperpolarizing effect of glucagon in liver cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1669:26-33. [PMID: 15842996 DOI: 10.1016/j.bbamem.2005.01.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Revised: 11/15/2004] [Accepted: 01/19/2005] [Indexed: 12/24/2022]
Abstract
The pancreatic hormone glucagon hyperpolarizes the liver cell membrane. In the present study, we investigated the cellular signalling pathway of glucagon-induced hyperpolarization of liver cells by using the conventional microelectrode method. The membrane potential was recorded in superficial liver cells of superfused mouse liver slices. In the presence of the K+ channel blockers tetraethylammonium (TEA, 1 mmol/l) and Ba2+ (BaCl2, 5 mmol/l) and the blocker of the Na+/K+ ATPase, ouabain (1 mmol/l), no glucagon-induced hyperpolarization was observed confirming previous findings. The hyperpolarizing effect of glucagon was abolished by the leukotriene B4 receptor antagonist CP 195543 (0.1 mmol/l) and the purinergic receptor antagonist PPADS (5 micromol/l). ATPgammaS (10 micromol/l), a non-hydrolyzable ATP analogue, induced a hyperpolarization of the liver cell membrane similar to glucagon. U 73122 (1 micromol/l), a blocker of phospholipase C, prevented both the glucagon- and ATPgammaS-induced hyperpolarization. These findings suggest that glucagon affects the hepatic membrane potential partly by inducing the formation and release of leukotrienes and release of ATP acting on purinergic receptors of the liver cell membrane.
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Affiliation(s)
- Lisa Fischer
- Institute of Veterinary Physiology, Vetsuisse Faculty University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
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Jiao YB, Rui YC, Li TJ, Yang PY, Qiu Y. Expression of pro-inflammatory and anti-inflammatory cytokines in brain of atherosclerotic rats and effects of Ginkgo biloba extract. Acta Pharmacol Sin 2005; 26:835-9. [PMID: 15960890 DOI: 10.1111/j.1745-7254.2005.00106.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
AIM To study the protein and mRNA expressions of pro-inflammatory and anti-inflammatory cytokines in the brain of rats with atherosclerosis (AS) and the effects of Ginkgo biloba extract (GbE) on expressions of cytokines. METHODS The experimental model of AS in rats were established by intraperitioneal injection of vitamin D3 with high fat/cholesterol diet. GbE 100 mg/kg was administered to rats by ig. After 8 weeks, the expressions of IL-1beta, TNF-alpha, IL-10, and IL-10R in the brain tissues of AS rats were detected by enzyme-linked immunosorbant assay, immunohistochemistry, Western blotting, and reverse transcriptase polymerase chain reaction. RESULTS The protein and mRNA expressions of IL-1beta, TNF-alpha, and IL-10 in the brains were markedly higher in AS groups than that in control groups (6.11+/-0.15, 1.55+/-0.14, 0.54+/-0.04 ng/g wet weight vs 0.80+/-0.14, 0.33+/-0.09, and 0.33+/-0.02 ng/g wet weight, respectively). The protein and mRNA expressions of IL-1beta and TNF-alpha in the brains were markedly lower in GbE groups (3.82+/-0.54, 0.95+/-0.08 ng/g wet weight) than that in AS groups, the protein and mRNA expressions of IL-10 and IL-10R in the brains were markedly higher in GbE groups (0.85+/-0.06 ng/g wet weight) than that in AS groups. CONCLUSION GbE inhibited production of pro-inflammatory cytokines IL-1beta and TNF-alpha, but up-regulated the production of anti-inflammatory cytokines, IL-10 and IL-10R in brain, which might be related with its anti-AS actions.
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Affiliation(s)
- Ya-Bin Jiao
- Department of Pharmacology, School of Pharmacy, the Second Military Medical University, Shanghai 200433, China
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35
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Abstract
One paradox of hormonal regulation during exercise is the maintenance of glucose homeostasis after endurance training despite a lower increase in plasma glucagon. One explanation could be that liver sensitivity to glucagon is increased by endurance training. Glucagon exerts its effect through a 62 KDa glycoprotein receptor, member of the G protein-coupled receptor. To determine whether changes with exercise in glucagon sensitivity occurred at the level of the glucagon receptor (GR), binding characteristics of hepatic glucagon receptors were ascertained in rat purified plasma membranes. Saturation kinetics indicated no difference in the dissociation constant or affinity of glucagon receptor, but a significantly higher glucagon receptor binding density in liver in endurance trained compared to untrained animals. Along with endurance training, it appears that fasting also changes GR binding characteristics. In animals fasting 24 hrs, a significant increase in glucagon receptor density was also reported. Although the exact mechanism remains unknown, there is no doubt that the liver can adapt to physiological stress through modulation of GR binding characteristics to enhance the hepatic glucose production responsiveness to glucagon. Key words: glucagon sensitivity, liver, endurance training, rats
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Affiliation(s)
- Carole Lavoie
- Département des sciences de l'activité physique, Université du Québec à Trois-Rivieres, Case Postale 500, Trois-Rivieres, Québec, Canada
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36
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Qureshi SA, Rios Candelore M, Xie D, Yang X, Tota LM, Ding VDH, Li Z, Bansal A, Miller C, Cohen SM, Jiang G, Brady E, Saperstein R, Duffy JL, Tata JR, Chapman KT, Moller DE, Zhang BB. A novel glucagon receptor antagonist inhibits glucagon-mediated biological effects. Diabetes 2004; 53:3267-73. [PMID: 15561959 DOI: 10.2337/diabetes.53.12.3267] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucagon maintains glucose homeostasis during the fasting state by promoting hepatic gluconeogenesis and glycogenolysis. Hyperglucagonemia and/or an elevated glucagon-to-insulin ratio have been reported in diabetic patients and animals. Antagonizing the glucagon receptor is expected to result in reduced hepatic glucose overproduction, leading to overall glycemic control. Here we report the discovery and characterization of compound 1 (Cpd 1), a compound that inhibits binding of 125I-labeled glucagon to the human glucagon receptor with a half-maximal inhibitory concentration value of 181 +/- 10 nmol/l. In CHO cells overexpressing the human glucagon receptor, Cpd 1 increased the half-maximal effect for glucagon stimulation of adenylyl cyclase with a KDB of 81 +/- 11 nmol/l. In addition, Cpd 1 blocked glucagon-mediated glycogenolysis in primary human hepatocytes. In contrast, a structurally related analog (Cpd 2) was not effective in blocking glucagon-mediated biological effects. Real-time measurement of glycogen synthesis and breakdown in perfused mouse liver showed that Cpd 1 is capable of blocking glucagon-induced glycogenolysis in a dosage-dependent manner. Finally, when dosed in humanized mice, Cpd 1 blocked the rise of glucose levels observed after intraperitoneal administration of exogenous glucagon. Taken together, these data suggest that Cpd 1 is a potent glucagon receptor antagonist that has the capability to block the effects of glucagon in vivo.
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Affiliation(s)
- Sajjad A Qureshi
- Department of Metabolic Disorder and Molecular Endocrinology, Merck Research Laboratories, Rahway, New Jersey, USA.
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Feldkaemper MP, Burkhardt E, Schaeffel F. Localization and regulation of glucagon receptors in the chick eye and preproglucagon and glucagon receptor expression in the mouse eye. Exp Eye Res 2004; 79:321-9. [PMID: 15336494 DOI: 10.1016/j.exer.2004.04.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Accepted: 04/06/2004] [Indexed: 10/26/2022]
Abstract
Myopia is a condition in which the eye is too long for the focal length of cornea and lens. Analysis of the messengers that are released by the retina to control axial eye growth in the animal model of the chicken revealed that glucagon-immunoreactive amacrine cells are involved in the retinal image processing that controls the growth of the sclera. It was found that the amount of retinal glucagon mRNA increased during treatment with positive lenses and pharmacological studies supported the idea that glucagon may act as a stop signal for eye growth. Glucagon exerts its regulatory effects by binding to a single type of glucagon receptor. In this study, we have sequenced the chicken glucagon receptor and compared its DNA and amino acid sequence with the human and mouse homologues. After sequencing about 80% of the receptor, we found a homology between 79.4 and 75.6% on cDNA level. At the protein level, about 73% of the amino acids were identical. Moreover, the cellular localization and regulation of the glucagon receptor in the chick retina was studied. In situ hybridization studies showed that many cells in the ganglion cell layer and inner nuclear layer, and some cells in the outer nuclear layer, express the receptor mRNA. Injection of the glucagon agonist Lys17,18,Glu21-glucagon induced a down-regulation of glucagon receptor mRNA content. Since the mouse would be an attractive mammalian model to study the biochemical and genetic basis of myopia, and because recent studies have demonstrated that form deprivation myopia can be induced, the expression of preproglucagon and glucagon receptor genes were also studied in the mouse retina and were found to be expressed.
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Affiliation(s)
- Marita P Feldkaemper
- Section of Neurobiology of the Eye, University Eye Hospital Tuebingen, Calwerstrasse 7/1, 72076, Germany.
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38
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Walsh NA, Yusta B, DaCambra MP, Anini Y, Drucker DJ, Brubaker PL. Glucagon-like peptide-2 receptor activation in the rat intestinal mucosa. Endocrinology 2003; 144:4385-92. [PMID: 12960094 DOI: 10.1210/en.2003-0309] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Glucagon-like peptide-2 (GLP-2) increases small intestinal growth and function in rodents and human subjects. GLP-2 exerts its effects through a seven-transmembrane domain, G protein-coupled receptor (GLP-2R), stimulating cAMP generation and activating protein kinase A signaling in heterologous cell lines transfected with the GLP-2R. As intestinal cell lines expressing the GLP-2R have not been identified, we developed methods for studying GLP-2R signaling in the rat small intestinal mucosa in vitro. Isolated rat intestinal mucosal cells expressed mRNA transcripts for the GLP-2R, as well as for chromogranin A and beta-tubulin III, markers for enteroendocrine and neural cells, respectively. cAMP production in response to [Gly2]GLP-2, a degradation-resistant analog of GLP-2, was maximal at 10-11 m (268 +/- 93% of control, P < 0.001), with reduced cAMP accumulation observed at higher doses. The cAMP response was diminished by pretreatment with 10-9 m GLP-2, and was abolished by pretreatment with 10-6 m GLP-2 (P < 0.05), indicating receptor desensitization. GLP-2 treatment of isolated mucosal cells increased 3H-thymidine incorporation (to 128 +/- 8% of controls, P < 0.05), and this was prevented by inhibition of the protein kinase A pathway with H89. In contrast, GLP-2 did not affect p44/p42 MAPK phosphorylation or the levels of cytosolic calcium in the mucosal cell preparation. These results provide the first evidence that activation of the endogenous rat mucosal GLP-2 receptor is linked to activation of a cAMP/protein kinase A-dependent, growth-promoting pathway in vitro.
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Affiliation(s)
- Natalie A Walsh
- Department of Physiology, University of Toronto, Toronto, Canada M5S 1A8
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Abstract
A 29-amino acid polypeptide hormone, glucagon has been one of the most prolific models in the study of hormone action. The key biologic function of glucagon is to counterbalance the actions of insulin and maintain a normal level of serum glucose. Diabetes mellitus can thus be considered a bihormonal disorder with an excess of glucagon contributing to the hyperglycemic state. The effects of glucagon are mediated by the glucagon receptor, which is itself a prototypical member of a distinct category called family B receptors within the G protein-coupled superfamily of seven-helical transmembrane receptors (GPCRs). At the structural level, the peptide ligands of family B receptors are highly homologous, in particular in the N-terminal region of the molecules. The mechanism by which highly homologous peptide ligands selectively recognize their receptors involves distinct molecular interactions that are gradually being elucidated. This review focuses on structural determinants of the glucagon receptor that are important for its activity with respect to interaction with its ligand and G proteins. Information about the glucagon receptor is presented within the context of what is known about other members of the family B GPCRs.
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Affiliation(s)
- Cecilia G Unson
- The Rockefeller University, 1230 York Avenue, Box 294, New York, NY 10021, USA.
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40
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Mayo KE, Miller LJ, Bataille D, Dalle S, Göke B, Thorens B, Drucker DJ. International Union of Pharmacology. XXXV. The glucagon receptor family. Pharmacol Rev 2003; 55:167-94. [PMID: 12615957 DOI: 10.1124/pr.55.1.6] [Citation(s) in RCA: 332] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Peptide hormones within the secretin-glucagon family are expressed in endocrine cells of the pancreas and gastrointestinal epithelium and in specialized neurons in the brain, and subserve multiple biological functions, including regulation of growth, nutrient intake, and transit within the gut, and digestion, energy absorption, and energy assimilation. Glucagon, glucagon-like peptide-1, glucagon-like peptide-2, glucose-dependent insulinotropic peptide, growth hormone-releasing hormone and secretin are structurally related peptides that exert their actions through unique members of a structurally related G protein-coupled receptor class 2 family. This review discusses advances in our understanding of how these peptides exert their biological activities, with a focus on the biological actions and structural features of the cognate receptors. The receptors have been named after their parent and only physiologically relevant ligand, in line with the recommendations of the International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR).
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Affiliation(s)
- Kelly E Mayo
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois, USA
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Kramer JM, Beatty JA, Plowey ED, Waldrop TG. Exercise and hypertension: a model for central neural plasticity. Clin Exp Pharmacol Physiol 2002; 29:122-6. [PMID: 11906470 DOI: 10.1046/j.1440-1681.2002.03610.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Physical movement is accompanied by coordinated changes in respiratory and cardiovascular activity proportional to the metabolic demands of the locomotor task. Cardiorespiratory changes include increases in ventilation, blood pressure and heart rate, as well as altered regional sympathetic nerve activity and blood flow. 2. The posterior hypothalamic area, a periventricular region in the caudal-most diencephalon, has been shown to play a role in mediating the coupling of locomotion and cardiorespiratory activity. Stimulation of this brain region produces locomotor behaviour and simultaneous increases in cardiorespiratory activity that are independent of peripheral feedback from contracting muscles. Posterior hypothalamic neurons are also activated by exercise and exercise-related stimuli, such as muscle contraction. 3. In spontaneously hypertensive rats (SHR), a deficiency in the inhibitory GABA neurotransmitter system within the posterior hypothalamic area contributes to tonically elevated levels of arterial blood pressure. We previously identified a reduction in the GABA synthesizing enzyme glutamic acid decarboxylase (GAD) within the posterior hypothalamus of SHR. 4. We have recently demonstrated that exercise can upregulate GABA-mediated caudal hypothalamic control of cardiovascular function in SHR. Similarly, exercise increases GAD gene transcript levels in the posterior hypothalamus. Thus, we have identified a model to study exercise-related central neural plasticity in GABAergic neurotransmitter function. Moreover, we suggest that exercise may increase cardiovascular health through changing central neural regulation of blood pressure.
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Affiliation(s)
- Jeffery M Kramer
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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Short AD, Taylor CW. Parathyroid hormone controls the size of the intracellular Ca(2+) stores available to receptors linked to inositol trisphosphate formation. J Biol Chem 2000; 275:1807-13. [PMID: 10636879 DOI: 10.1074/jbc.275.3.1807] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In HEK 293 cells stably expressing type 1 parathyroid (PTH) receptors, PTH stimulated release of intracellular Ca(2+) stores in only 27% of cells, whereas 96% of cells responded to carbachol. However, in almost all cells PTH potentiated the response to carbachol by about 3-fold. Responses to carbachol did not desensitize, but only the first challenge in Ca(2+)-free medium caused an increase in [Ca(2+)](i), indicating that the carbachol-sensitive Ca(2+) stores had been emptied. Subsequent addition of PTH also failed to increase [Ca(2+)](i), but when it was followed by carbachol there was a substantial increase in [Ca(2+)](i). A similar potentiation was observed between ATP and PTH but not between carbachol and ATP. Intracellular heparin inhibited responses to carbachol and PTH, and pretreatment with ATP and carbachol abolished responses to PTH, suggesting that the effects of PTH involve inositol trisphosphate (IP(3)) receptors. PTH neither stimulated detectable IP(3) formation nor affected the amount formed in response to ATP or carbachol. PTH stimulated cyclic AMP formation, but this was not the means whereby PTH potentiated Ca(2+) signals. We suggest that PTH may regulate Ca(2+) mobilization by facilitating translocation of Ca(2+) between discrete intracellular stores and that it thereby regulates the size of the Ca(2+) pool available to receptors linked to IP(3) formation.
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Affiliation(s)
- A D Short
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1QJ, United Kingdom
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Yusta B, Somwar R, Wang F, Munroe D, Grinstein S, Klip A, Drucker DJ. Identification of glucagon-like peptide-2 (GLP-2)-activated signaling pathways in baby hamster kidney fibroblasts expressing the rat GLP-2 receptor. J Biol Chem 1999; 274:30459-67. [PMID: 10521425 DOI: 10.1074/jbc.274.43.30459] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Glucagon-like peptide-2 (GLP-2) promotes the expansion of the intestinal epithelium through stimulation of the GLP-2 receptor, a recently identified member of the glucagon-secretin G protein-coupled receptor superfamily. Although activation of G protein-coupled receptors may lead to stimulation of cell growth, the mechanisms transducing the GLP-2 signal to mitogenic proliferation remain unknown. We now report studies of GLP-2R signaling in baby hamster kidney (BHK) cells expressing a transfected rat GLP-2 receptor (BHK-GLP-2R cells). GLP-2, but not glucagon or GLP-1, increased the levels of cAMP and activated both cAMP-response element- and AP-1-dependent transcriptional activity in a dose-dependent manner. The activation of AP-1-luciferase activity was protein kinase A (PKA) -dependent and markedly diminished in the presence of a dominant negative inhibitor of PKA. Although GLP-2 stimulated the expression of c-fos, c-jun, junB, and zif268, and transiently increased p70 S6 kinase in quiescent BHK-GLP-2R cells, GLP-2 also inhibited extracellular signal-regulated kinase 1/2 and reduced serum-stimulated Elk-1 activity. Furthermore, no rise in intracellular calcium was observed following GLP-2 exposure in BHK-GLP-2R cells. Although GLP-2 stimulated both cAMP accumulation and cell proliferation, 8-bromo-cyclic AMP alone did not promote cell proliferation. These findings suggest that the GLP-2R may be coupled to activation of mitogenic signaling in heterologous cell types independent of PKA via as yet unidentified downstream mediators of GLP-2 action in vivo.
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Affiliation(s)
- B Yusta
- Department of Medicine, The Toronto General Hospital, University of Toronto, Toronto, Ontario M5G 2C4, Canada
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Kushikata T, Fang J, Krueger JM. Interleukin-10 inhibits spontaneous sleep in rabbits. J Interferon Cytokine Res 1999; 19:1025-30. [PMID: 10505745 DOI: 10.1089/107999099313244] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022] Open
Abstract
Proinflammatory cytokines, including interleukin-1beta(IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) are involved in sleep regulation. IL-10 is an anti-inflammatory cytokine that inhibits proinflammatory cytokine production. We hypothesized that IL-10 could attenuate sleep. Thirty-one male rabbits were used. Three doses of IL-10 (5 ng, 50 ng, and 250 ng) were injected intracerebroventricularly during the rest (light) period. One dose of IL-10 (250 ng) was injected during the active (dark) cycle. Appropriate time-matched control injections of saline were given to the same rabbits on different days. The two highest doses of IL-10 significantly inhibited spontaneous nonrapid eye movement sleep if IL-10 was given during the light cycle. The highest dose of IL-10 (250 ng) also significantly decreased rapid eye movement sleep. IL-10 administered at dark onset had no effect on sleep. The sleep inhibitory properties of IL-10 provide additional evidence for the hypothesis that a brain cytokine network is involved in regulation of physiologic sleep.
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Affiliation(s)
- T Kushikata
- Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman 99164-6520, USA
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