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Marco HG, Glendinning S, Ventura T, Gäde G. The gonadotropin-releasing hormone (GnRH) superfamily across Pancrustacea/Tetraconata: A role in metabolism? Mol Cell Endocrinol 2024; 590:112238. [PMID: 38616035 DOI: 10.1016/j.mce.2024.112238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Accepted: 04/05/2024] [Indexed: 04/16/2024]
Affiliation(s)
- Heather G Marco
- Department of Biological Sciences, University of Cape Town, Rondebosch, 7701, South Africa.
| | - Susan Glendinning
- Centre for BioInnovation, University of the Sunshine Coast, Sippy Downs, Queensland, 4556, Australia; School of Science, Technology and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland, 4556, Australia
| | - Tomer Ventura
- Centre for BioInnovation, University of the Sunshine Coast, Sippy Downs, Queensland, 4556, Australia; School of Science, Technology and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland, 4556, Australia
| | - Gerd Gäde
- Department of Biological Sciences, University of Cape Town, Rondebosch, 7701, South Africa
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2
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Townsend LK, Steinberg GR. AMPK and the Endocrine Control of Metabolism. Endocr Rev 2023; 44:910-933. [PMID: 37115289 DOI: 10.1210/endrev/bnad012] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 03/10/2023] [Accepted: 04/24/2023] [Indexed: 04/29/2023]
Abstract
Complex multicellular organisms require a coordinated response from multiple tissues to maintain whole-body homeostasis in the face of energetic stressors such as fasting, cold, and exercise. It is also essential that energy is stored efficiently with feeding and the chronic nutrient surplus that occurs with obesity. Mammals have adapted several endocrine signals that regulate metabolism in response to changes in nutrient availability and energy demand. These include hormones altered by fasting and refeeding including insulin, glucagon, glucagon-like peptide-1, catecholamines, ghrelin, and fibroblast growth factor 21; adipokines such as leptin and adiponectin; cell stress-induced cytokines like tumor necrosis factor alpha and growth differentiating factor 15, and lastly exerkines such as interleukin-6 and irisin. Over the last 2 decades, it has become apparent that many of these endocrine factors control metabolism by regulating the activity of the AMPK (adenosine monophosphate-activated protein kinase). AMPK is a master regulator of nutrient homeostasis, phosphorylating over 100 distinct substrates that are critical for controlling autophagy, carbohydrate, fatty acid, cholesterol, and protein metabolism. In this review, we discuss how AMPK integrates endocrine signals to maintain energy balance in response to diverse homeostatic challenges. We also present some considerations with respect to experimental design which should enhance reproducibility and the fidelity of the conclusions.
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Affiliation(s)
- Logan K Townsend
- Centre for Metabolism Obesity and Diabetes Research, Hamilton, ON L8S 4L8, Canada
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Gregory R Steinberg
- Centre for Metabolism Obesity and Diabetes Research, Hamilton, ON L8S 4L8, Canada
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
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3
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Al-Abdulla R, Ferrero H, Boronat-Belda T, Soriano S, Quesada I, Alonso-Magdalena P. Exploring the Effects of Metabolism-Disrupting Chemicals on Pancreatic α-Cell Viability, Gene Expression and Function: A Screening Testing Approach. Int J Mol Sci 2023; 24:ijms24021044. [PMID: 36674557 PMCID: PMC9862653 DOI: 10.3390/ijms24021044] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/26/2022] [Accepted: 01/03/2023] [Indexed: 01/06/2023] Open
Abstract
Humans are constantly exposed to many environmental pollutants, some of which have been largely acknowledged as key factors in the development of metabolic disorders such as diabetes and obesity. These chemicals have been classified as endocrine-disrupting chemicals (EDCs) and, more recently, since they can interfere with metabolic functions, they have been renamed as metabolism-disrupting chemicals (MDCs). MDCs are present in many consumer products, including food packaging, personal care products, plastic bottles and containers, and detergents. The scientific literature has ever-increasingly focused on insulin-releasing pancreatic β-cells as one of the main targets for MDCs. Evidence highlights that these substances may disrupt glucose homeostasis by altering pancreatic β-cell physiology. However, their potential impact on glucagon-secreting pancreatic α-cells remains poorly known despite the essential role that this cellular type plays in controlling glucose metabolism. In the present study, we have selected seven paradigmatic MDCs representing major toxic classes, including bisphenols, phthalates, perfluorinated compounds, metals, and pesticides. By using an in vitro cell-based model, the pancreatic α-cell line αTC1-9, we have explored the effects of these compounds on pancreatic α-cell viability, gene expression, and secretion. We found that cell viability was moderately affected after bisphenol-A (BPA), bisphenol-F (BPF), and perfluorooctanesulfonic acid (PFOS) exposure, although cytotoxicity was relatively low. In addition, all bisphenols, as well as di(2-ethylhexyl) phthalate (DEHP) and cadmium chloride (CdCl2), promoted a marked decreased on glucagon secretion, together with changes in the expression of glucagon and/or transcription factors involved in cell function and identity, such as Foxo1 and Arx. Overall, our results indicated that most of the selected chemicals studied caused functional alterations in pancreatic α-cells. Moreover, we revealed, for the first time, their direct effects on key molecular aspects of pancreatic α-cell biology.
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Affiliation(s)
- Ruba Al-Abdulla
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, 03202 Elche, Spain
| | - Hilda Ferrero
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, 03202 Elche, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain
| | - Talía Boronat-Belda
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, 03202 Elche, Spain
| | - Sergi Soriano
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, 03202 Elche, Spain
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, 03690 Alicante, Spain
| | - Iván Quesada
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, 03202 Elche, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain
| | - Paloma Alonso-Magdalena
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, 03202 Elche, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain
- Correspondence:
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4
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De Iuliis A, Montinaro E, Fatati G, Plebani M, Colosimo C. Diabetes mellitus and Parkinson's disease: dangerous liaisons between insulin and dopamine. Neural Regen Res 2022; 17:523-533. [PMID: 34380882 PMCID: PMC8504381 DOI: 10.4103/1673-5374.320965] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/08/2021] [Accepted: 03/04/2021] [Indexed: 11/13/2022] Open
Abstract
The relationship between diabetes mellitus and Parkinson's disease has been described in several epidemiological studies over the 1960s to date. Molecular studies have shown the possible functional link between insulin and dopamine, as there is strong evidence demonstrating the action of dopamine in pancreatic islets, as well as the insulin effects on feeding and cognition through central nervous system mechanism, largely independent of glucose utilization. Therapies used for the treatment of type 2 diabetes mellitus appear to be promising candidates for symptomatic and/or disease-modifying action in neurodegenerative diseases including Parkinson's disease, while an old dopamine agonist, bromocriptine, has been repositioned for the type 2 diabetes mellitus treatment. This review will aim at reappraising the different studies that have highlighted the dangerous liaisons between diabetes mellitus and Parkinson's disease.
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Affiliation(s)
| | - Ennio Montinaro
- Department of Neurology, Santa Maria University Hospital, Terni, Italy
| | | | - Mario Plebani
- Department of Medicine-DiMED, University of Padova, Italy
- Department of Medicine-DiMED, University of Padova, Padova, Italy; Department of Laboratory Medicine-Hospital of Padova, Padova, Italy
| | - Carlo Colosimo
- Department of Neurology, Santa Maria University Hospital, Terni, Italy
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5
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Hughson BN. The Glucagon-Like Adipokinetic Hormone in Drosophila melanogaster - Biosynthesis and Secretion. Front Physiol 2021; 12:710652. [PMID: 35002748 PMCID: PMC8733639 DOI: 10.3389/fphys.2021.710652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 09/16/2021] [Indexed: 11/13/2022] Open
Abstract
Metabolic homeostasis requires the precise regulation of circulating sugar titers. In mammals, homeostatic control of circulating sugar titers requires the coordinated secretion and systemic activities of glucagon and insulin. Metabolic homeostasis is similarly regulated in Drosophila melanogaster through the glucagon-like adipokinetic hormone (AKH) and the Drosophila insulin-like peptides (DILPs). In flies and mammals, glucagon and AKH are biosynthesized in and secreted from specialized endocrine cells. KATP channels borne on these cells respond to fluctuations in circulating glucose titers and thereby regulate glucagon secretion. The influence of glucagon in the pathogenesis of type 2 diabetes mellitus is now recognized, and a crucial mechanism that regulates glucagon secretion was reported nearly a decade ago. Ongoing efforts to develop D. melanogaster models for metabolic syndrome must build upon this seminal work. These efforts make a critical review of AKH physiology timely. This review focuses on AKH biosynthesis and the regulation of glucose-responsive AKH secretion through changes in CC cell electrical activity. Future directions for AKH research in flies are discussed, including the development of models for hyperglucagonemia and epigenetic inheritance of acquired metabolic traits. Many avenues of AKH physiology remain to be explored and thus present great potential for improving the utility of D. melanogaster in metabolic research.
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Affiliation(s)
- Bryon N. Hughson
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
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Zhang C, Zhong T, Li Y, Li X, Yuan X, Liu L, Wu W, Wu J, Wu Y, Liang R, Xie X, Kang C, Liu Y, Lai Z, Xiao J, Tang Z, Jin R, Wang Y, Xiao Y, Zhang J, Li J, Liu Q, Sun Z, Zhong J. The hepatic AMPK-TET1-SIRT1 axis regulates glucose homeostasis. eLife 2021; 10:70672. [PMID: 34738906 PMCID: PMC8592569 DOI: 10.7554/elife.70672] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 11/04/2021] [Indexed: 11/13/2022] Open
Abstract
Ten-eleven translocation methylcytosine dioxygenase 1 (TET1) is involved in multiple biological functions in cell development, differentiation, and transcriptional regulation. Tet1 deficient mice display the defects of murine glucose metabolism. However, the role of TET1 in metabolic homeostasis keeps unknown. Here, our finding demonstrates that hepatic TET1 physically interacts with silent information regulator T1 (SIRT1) via its C-terminal and activates its deacetylase activity, further regulating the acetylation-dependent cellular translocalization of transcriptional factors PGC-1α and FOXO1, resulting in the activation of hepatic gluconeogenic gene expression that includes PPARGC1A, G6PC, and SLC2A4. Importantly, the hepatic gluconeogenic gene activation program induced by fasting is inhibited in Tet1 heterozygous mice livers. The adenosine 5'-monophosphate-activated protein kinase (AMPK) activators metformin or AICAR-two compounds that mimic fasting-elevate hepatic gluconeogenic gene expression dependent on in turn activation of the AMPK-TET1-SIRT1 axis. Collectively, our study identifies TET1 as a SIRT1 coactivator and demonstrates that the AMPK-TET1-SIRT1 axis represents a potential mechanism or therapeutic target for glucose metabolism or metabolic diseases.
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Affiliation(s)
- Chunbo Zhang
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China.,School of Pharmacy, Nanchang University, Nanchang, China
| | - Tianyu Zhong
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Yuanyuan Li
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Xianfeng Li
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Xiaopeng Yuan
- School of Pharmacy, Nanchang University, Nanchang, China
| | - Linlin Liu
- Precision Medicine Center, First Affiliated Hospital of Gannan Medical University, Ganzhou, China
| | - Weilin Wu
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Jing Wu
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Ye Wu
- School of Pharmacy, Nanchang University, Nanchang, China
| | - Rui Liang
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Xinhua Xie
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Chuanchuan Kang
- Precision Medicine Center, First Affiliated Hospital of Gannan Medical University, Ganzhou, China
| | - Yuwen Liu
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Zhonghong Lai
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Jianbo Xiao
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Zhixian Tang
- Precision Medicine Center, First Affiliated Hospital of Gannan Medical University, Ganzhou, China
| | - Riqun Jin
- Precision Medicine Center, First Affiliated Hospital of Gannan Medical University, Ganzhou, China
| | - Yan Wang
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Yongwei Xiao
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Jin Zhang
- School of Basic Medical Sciences, Nanchang University, Nanchang, China
| | - Jian Li
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Qian Liu
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
| | - Zhongsheng Sun
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Jianing Zhong
- Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education, Gannan Medical University, Ganzhou, China
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Asadi F, Dhanvantari S. Pathways of Glucagon Secretion and Trafficking in the Pancreatic Alpha Cell: Novel Pathways, Proteins, and Targets for Hyperglucagonemia. Front Endocrinol (Lausanne) 2021; 12:726368. [PMID: 34659118 PMCID: PMC8511682 DOI: 10.3389/fendo.2021.726368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/13/2021] [Indexed: 12/15/2022] Open
Abstract
Patients with diabetes mellitus exhibit hyperglucagonemia, or excess glucagon secretion, which may be the underlying cause of the hyperglycemia of diabetes. Defective alpha cell secretory responses to glucose and paracrine effectors in both Type 1 and Type 2 diabetes may drive the development of hyperglucagonemia. Therefore, uncovering the mechanisms that regulate glucagon secretion from the pancreatic alpha cell is critical for developing improved treatments for diabetes. In this review, we focus on aspects of alpha cell biology for possible mechanisms for alpha cell dysfunction in diabetes: proglucagon processing, intrinsic and paracrine control of glucagon secretion, secretory granule dynamics, and alterations in intracellular trafficking. We explore possible clues gleaned from these studies in how inhibition of glucagon secretion can be targeted as a treatment for diabetes mellitus.
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada
- Program in Metabolism and Diabetes, Lawson Health Research Institute, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada
- Program in Metabolism and Diabetes, Lawson Health Research Institute, London, ON, Canada
- Imaging Research Program, Lawson Health Research Institute, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
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Nelson JM, Saunders CJ, Johnson EC. The Intrinsic Nutrient Sensing Adipokinetic Hormone Producing Cells Function in Modulation of Metabolism, Activity, and Stress. Int J Mol Sci 2021; 22:7515. [PMID: 34299134 PMCID: PMC8307046 DOI: 10.3390/ijms22147515] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/01/2021] [Accepted: 07/07/2021] [Indexed: 11/29/2022] Open
Abstract
All organisms confront the challenges of maintaining metabolic homeostasis in light of both variabilities in nutrient supplies and energetic costs of different physiologies and behaviors. While all cells are nutrient sensitive, only relative few cells within Metazoans are nutrient sensing cells. Nutrient sensing cells organize systemic behavioral and physiological responses to changing metabolic states. One group of cells present in the arthropods, is the adipokinetic hormone producing cells (APCs). APCs possess intrinsic nutrient sensors and receive contextual information regarding metabolic state through other endocrine connections. APCs express receptors for different hormones which modulate APC physiology and the secretion of the adipokinetic hormone (AKH). APCs are functionally similar to alpha cells in the mammalian pancreas and display a similar physiological organization. AKH release results in both hypertrehalosemia and hyperlipidemia through high affinity binding to the AKH receptor (AKHR). Another hallmark of AKH signaling is heightened locomotor activity, which accompanies starvation and is thought to enhance foraging. In this review, we discuss mechanisms of nutrient sensing and modulation of AKH release. Additionally, we compare the organization of AKH/AKHR signaling in different taxa. Lastly, we consider the signals that APCs integrate as well as recent experimental results that have expanded the functional repertoire of AKH signaling, further establishing this as both a metabolic and stress hormone.
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Affiliation(s)
- Jonathan M. Nelson
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (J.M.N.); (C.J.S.)
| | - Cecil J. Saunders
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (J.M.N.); (C.J.S.)
| | - Erik C. Johnson
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (J.M.N.); (C.J.S.)
- Center of Molecular Signaling, Wake Forest University, Winston-Salem, NC 27109, USA
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Ng XW, Chung YH, Piston DW. Intercellular Communication in the Islet of Langerhans in Health and Disease. Compr Physiol 2021; 11:2191-2225. [PMID: 34190340 PMCID: PMC8985231 DOI: 10.1002/cphy.c200026] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Blood glucose homeostasis requires proper function of pancreatic islets, which secrete insulin, glucagon, and somatostatin from the β-, α-, and δ-cells, respectively. Each islet cell type is equipped with intrinsic mechanisms for glucose sensing and secretory actions, but these intrinsic mechanisms alone cannot explain the observed secretory profiles from intact islets. Regulation of secretion involves interconnected mechanisms among and between islet cell types. Islet cells lose their normal functional signatures and secretory behaviors upon dispersal as compared to intact islets and in vivo. In dispersed islet cells, the glucose response of insulin secretion is attenuated from that seen from whole islets, coordinated oscillations in membrane potential and intracellular Ca2+ activity, as well as the two-phase insulin secretion profile, are missing, and glucagon secretion displays higher basal secretion profile and a reverse glucose-dependent response from that of intact islets. These observations highlight the critical roles of intercellular communication within the pancreatic islet, and how these communication pathways are crucial for proper hormonal and nonhormonal secretion and glucose homeostasis. Further, misregulated secretions of islet secretory products that arise from defective intercellular islet communication are implicated in diabetes. Intercellular communication within the islet environment comprises multiple mechanisms, including electrical synapses from gap junctional coupling, paracrine interactions among neighboring cells, and direct cell-to-cell contacts in the form of juxtacrine signaling. In this article, we describe the various mechanisms that contribute to proper islet function for each islet cell type and how intercellular islet communications are coordinated among the same and different islet cell types. © 2021 American Physiological Society. Compr Physiol 11:2191-2225, 2021.
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Affiliation(s)
- Xue W Ng
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - Yong H Chung
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
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10
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Role of cAMP in Double Switch of Glucagon Secretion. Cells 2021; 10:cells10040896. [PMID: 33919776 PMCID: PMC8070687 DOI: 10.3390/cells10040896] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/12/2021] [Accepted: 04/12/2021] [Indexed: 01/03/2023] Open
Abstract
Glucose metabolism plays a crucial role in modulating glucagon secretion in pancreatic alpha cells. However, the downstream effects of glucose metabolism and the activated signaling pathways influencing glucagon granule exocytosis are still obscure. We developed a computational alpha cell model, implementing metabolic pathways of glucose and free fatty acids (FFA) catabolism and an intrinsically activated cAMP signaling pathway. According to the model predictions, increased catabolic activity is able to suppress the cAMP signaling pathway, reducing exocytosis in a Ca2+-dependent and Ca2+ independent manner. The effect is synergistic to the pathway involving ATP-dependent closure of KATP channels and consequent reduction of Ca2+. We analyze the contribution of each pathway to glucagon secretion and show that both play decisive roles, providing a kind of "secure double switch". The cAMP-driven signaling switch plays a dominant role, while the ATP-driven metabolic switch is less favored. The ratio is approximately 60:40, according to the most recent experimental evidence.
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11
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Cruz AM, Partridge KM, Malekizadeh Y, Vlachaki Walker JM, Weightman Potter PG, Pye KR, Shaw SJ, Ellacott KLJ, Beall C. Brain Permeable AMP-Activated Protein Kinase Activator R481 Raises Glycaemia by Autonomic Nervous System Activation and Amplifies the Counterregulatory Response to Hypoglycaemia in Rats. Front Endocrinol (Lausanne) 2021; 12:697445. [PMID: 34975743 PMCID: PMC8718766 DOI: 10.3389/fendo.2021.697445] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 11/15/2021] [Indexed: 11/13/2022] Open
Abstract
AIM We evaluated the efficacy of a novel brain permeable "metformin-like" AMP-activated protein kinase activator, R481, in regulating glucose homeostasis. MATERIALS AND METHODS We used glucose sensing hypothalamic GT1-7 neuronal cells and pancreatic αTC1.9 α-cells to examine the effect of R481 on AMPK pathway activation and cellular metabolism. Glucose tolerance tests and hyperinsulinemic-euglycemic and hypoglycemic clamps were used in Sprague-Dawley rats to assess insulin sensitivity and hypoglycemia counterregulation, respectively. RESULTS In vitro, we demonstrate that R481 increased AMPK phosphorylation in GT1-7 and αTC1.9 cells. In Sprague-Dawley rats, R481 increased peak glucose levels during a glucose tolerance test, without altering insulin levels or glucose clearance. The effect of R481 to raise peak glucose levels was attenuated by allosteric brain permeable AMPK inhibitor SBI-0206965. This effect was also completely abolished by blockade of the autonomic nervous system using hexamethonium. During hypoglycemic clamp studies, R481 treated animals had a significantly lower glucose infusion rate compared to vehicle treated controls. Peak plasma glucagon levels were significantly higher in R481 treated rats with no change to plasma adrenaline levels. In vitro, R481 did not alter glucagon release from αTC1.9 cells, but increased glycolysis. Non brain permeable AMPK activator R419 enhanced AMPK activity in vitro in neuronal cells but did not alter glucose excursion in vivo. CONCLUSIONS These data demonstrate that peripheral administration of the brain permeable "metformin-like" AMPK activator R481 increases blood glucose by activation of the autonomic nervous system and amplifies the glucagon response to hypoglycemia in rats. Taken together, our data suggest that R481 amplifies the counterregulatory response to hypoglycemia by a central rather than a direct effect on the pancreatic α-cell. These data provide proof-of-concept that central AMPK could be a target for future drug development for prevention of hypoglycemia in diabetes.
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Affiliation(s)
- Ana M Cruz
- Institute of Biomedical and Clinical Sciences, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Katie M Partridge
- Institute of Biomedical and Clinical Sciences, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Yasaman Malekizadeh
- Institute of Biomedical and Clinical Sciences, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Julia M Vlachaki Walker
- Institute of Biomedical and Clinical Sciences, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Paul G Weightman Potter
- Institute of Biomedical and Clinical Sciences, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Katherine R Pye
- Institute of Biomedical and Clinical Sciences, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Simon J Shaw
- Rigel Pharmaceuticals Inc., South San Francisco, CA, United States
| | - Kate L J Ellacott
- Institute of Biomedical and Clinical Sciences, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Craig Beall
- Institute of Biomedical and Clinical Sciences, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
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12
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Mechanisms of the Regulation and Dysregulation of Glucagon Secretion. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2020; 2020:3089139. [PMID: 32774668 PMCID: PMC7396046 DOI: 10.1155/2020/3089139] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 07/11/2020] [Indexed: 02/06/2023]
Abstract
Glucagon, a hormone secreted by pancreatic alpha cells, contributes to the maintenance of normal blood glucose concentration by inducing hepatic glucose production in response to declining blood glucose. However, glucagon hypersecretion contributes to the pathogenesis of type 2 diabetes. Moreover, diabetes is associated with relative glucagon undersecretion at low blood glucose and oversecretion at normal and high blood glucose. The mechanisms of such alpha cell dysfunctions are not well understood. This article reviews the genesis of alpha cell dysfunctions during the pathogenesis of type 2 diabetes and after the onset of type 1 and type 2 diabetes. It unravels a signaling pathway that contributes to glucose- or hydrogen peroxide-induced glucagon secretion, whose overstimulation contributes to glucagon dysregulation, partly through oxidative stress and reduced ATP synthesis. The signaling pathway involves phosphatidylinositol-3-kinase, protein kinase B, protein kinase C delta, non-receptor tyrosine kinase Src, and phospholipase C gamma-1. This knowledge will be useful in the design of new antidiabetic agents or regimens.
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Kim KH, Lee IS, Park JY, Kim Y, An EJ, Jang HJ. Cucurbitacin B Induces Hypoglycemic Effect in Diabetic Mice by Regulation of AMP-Activated Protein Kinase Alpha and Glucagon-Like Peptide-1 via Bitter Taste Receptor Signaling. Front Pharmacol 2018; 9:1071. [PMID: 30298009 PMCID: PMC6161541 DOI: 10.3389/fphar.2018.01071] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 09/04/2018] [Indexed: 12/13/2022] Open
Abstract
Taste receptors exist in several organs from tongue to colon and have diverse functions dependent on specific cell type. In enteroendocrine L-cells, stimulation of taste receptor signaling induces incretin hormones. Among incretin hormones, glucagon-like peptide-1 (GLP-1) induces insulinotropic action by activating GLP-1 receptor of pancreatic β-cells. However, GLP-1 mimetic medicines have reported clinical side effects, such as autoimmune hepatitis, acute kidney injury, pancreatitis, and pancreatic cancer. Here, we hypothesized that if natural components in ethnomedicines can activate agonistic action of taste receptor; they may stimulate GLP-1 and therefore, could be developed as safe and applicable medicines to type 2 diabetes mellitus (T2DM) with minimal side effects. Cucurbitacin B (CuB) is composed of triterpenoid structure and its structural character, that represents bitterness, can stimulate AMP-activated protein kinase (AMPK) pathway. CuB ameliorated hyperglycemia by activating intestinal AMPK levels and by inducing plasma GLP-1 and insulin release in diabetic mice. This hypoglycemic action was decreased in dorsomorphin-injected mice and α-gustducin null mice. Moreover, systemic inhibition study in differentiated NCI-H716 cell line showed that CuB-mediated GLP-1 secretion was involved in activation of AMPK through α-gustducin and Gβγ-signaling of taste receptors. In summary, we conclude that, CuB represents novel hypoglycemic agents by activation of AMPK and stimulation of GLP-1 in differentiated enteroendocrine L-cells. These results suggest that taste receptor signaling-based therapeutic agents within tremendously diverse ethnomedicines, could be applied to developing therapeutics for T2DM patients.
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Affiliation(s)
- Kang-Hoon Kim
- Department of Science in Korean Medicine, Graduate School, Kyung Hee University, Seoul, South Korea.,Department of Biochemistry, Graduate School, Kyung Hee University, Seoul, South Korea
| | - In-Seung Lee
- Department of Science in Korean Medicine, Graduate School, Kyung Hee University, Seoul, South Korea.,Department of Biochemistry, Graduate School, Kyung Hee University, Seoul, South Korea
| | - Ji Young Park
- Department of Science in Korean Medicine, Graduate School, Kyung Hee University, Seoul, South Korea.,Department of Biochemistry, Graduate School, Kyung Hee University, Seoul, South Korea
| | - Yumi Kim
- Department of Science in Korean Medicine, Graduate School, Kyung Hee University, Seoul, South Korea.,Department of Biochemistry, Graduate School, Kyung Hee University, Seoul, South Korea
| | - Eun-Jin An
- Department of Science in Korean Medicine, Graduate School, Kyung Hee University, Seoul, South Korea.,Department of Biochemistry, Graduate School, Kyung Hee University, Seoul, South Korea
| | - Hyeung-Jin Jang
- Department of Science in Korean Medicine, Graduate School, Kyung Hee University, Seoul, South Korea.,Department of Biochemistry, Graduate School, Kyung Hee University, Seoul, South Korea
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14
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Gelin L, Li J, Corbin KL, Jahan I, Nunemaker CS. Metformin Inhibits Mouse Islet Insulin Secretion and Alters Intracellular Calcium in a Concentration-Dependent and Duration-Dependent Manner near the Circulating Range. J Diabetes Res 2018; 2018:9163052. [PMID: 29862303 PMCID: PMC5971297 DOI: 10.1155/2018/9163052] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/25/2017] [Accepted: 01/17/2018] [Indexed: 12/23/2022] Open
Abstract
Metformin is considered the first-line treatment for type 2 diabetes. While metformin primarily increases insulin sensitivity, evidence also suggests that metformin affects the activity of insulin-secreting pancreatic islets. This study was designed to systematically examine the direct effects of metformin by measuring insulin secretion and the kinetics of the calcium response to glucose stimulation in isolated mouse islets using varying concentrations (20 μM, 200 μM, and 1 mM) and durations (~1, 2, and 3 days) of metformin exposure. We observed both concentration- and duration-dependent inhibitory effects of metformin. Concentrations as little as 20 μM (nearing circulating therapeutic levels) were sufficient to reduce insulin secretion following 3-day treatment. Concentrations of 200 μM and 1 mM produced more pronounced effects more rapidly. With 1 mM metformin, islets showed severe impairments in calcium handling, inhibition of insulin secretion, and increased cell death. No stimulatory effects of metformin were observed for any experimental endpoint. We conclude that the direct effects of metformin on islets are inhibitory at near-physiological concentrations. Beneficial effects of metformin observed on islets under various stressors may occur by "resting" fatigued cellular processes. However, metformin may have unintended consequences on normally functioning islets within the circulating range that require further evaluation.
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Affiliation(s)
- Lindor Gelin
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Jiewen Li
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Kathryn L. Corbin
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Ishrat Jahan
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Craig S. Nunemaker
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
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15
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Tengholm A, Gylfe E. cAMP signalling in insulin and glucagon secretion. Diabetes Obes Metab 2017; 19 Suppl 1:42-53. [PMID: 28466587 DOI: 10.1111/dom.12993] [Citation(s) in RCA: 130] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 04/24/2017] [Accepted: 04/26/2017] [Indexed: 01/24/2023]
Abstract
The "second messenger" archetype cAMP is one of the most important cellular signalling molecules with central functions including the regulation of insulin and glucagon secretion from the pancreatic β- and α-cells, respectively. cAMP is generally considered as an amplifier of insulin secretion triggered by Ca2+ elevation in the β-cells. Both messengers are also positive modulators of glucagon release from α-cells, but in this case cAMP may be the important regulator and Ca2+ have a more permissive role. The actions of cAMP are mediated by protein kinase A (PKA) and the guanine nucleotide exchange factor Epac. The present review focuses on how cAMP is regulated by nutrients, hormones and neural factors in β- and α-cells via adenylyl cyclase-catalysed generation and phosphodiesterase-mediated degradation. We will also discuss how PKA and Epac affect ion fluxes and the secretory machinery to transduce the stimulatory effects on insulin and glucagon secretion. Finally, we will briefly describe disturbances of the cAMP system associated with diabetes and how cAMP signalling can be targeted to normalize hypo- and hypersecretion of insulin and glucagon, respectively, in diabetic patients.
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Affiliation(s)
- Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Erik Gylfe
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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16
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Lazo-de-la-Vega-Monroy ML, Larrieta E, Tixi-Verdugo W, Ramírez-Mondragón R, Hernández-Araiza I, German MS, Fernandez-Mejia C. Effects of dietary biotin supplementation on glucagon production, secretion, and action. Nutrition 2017; 43-44:47-53. [PMID: 28935144 DOI: 10.1016/j.nut.2017.06.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 05/27/2017] [Accepted: 06/04/2017] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Despite increasing evidence that pharmacologic concentrations of biotin modify glucose metabolism, to our knowledge there have not been any studies addressing the effects of biotin supplementation on glucagon production and secretion, considering glucagon is one of the major hormones in maintaining glucose homeostasis. The aim of this study was to investigate the effects of dietary biotin supplementation on glucagon expression, secretion, and action. METHODS Male BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet (1.76 or 97.7 mg biotin/kg diet) for 8 wk postweaning. Glucagon gene mRNA expression was measured by the real-time polymerase chain reaction. Glucagon secretion was assessed in isolated islets and by glucagon concentration in plasma. Glucagon action was evaluated by glucagon tolerance tests, phosphoenolpyruvate carboxykinase (Pck1) mRNA expression, and glycogen degradation. RESULTS Compared with the control group, glucagon mRNA and secretion were increased from the islets of the biotin-supplemented group. Fasting plasma glucagon levels were higher, but no differences between the groups were observed in nonfasting glucagon levels. Despite the elevated fasting glucagon levels, no differences were found in fasting blood glucose concentrations, fasting/fasting-refeeding glucagon tolerance tests, glycogen content and degradation, or mRNA expression of the hepatic gluconeogenic rate-limiting enzyme, Pck1. CONCLUSIONS These results demonstrated that dietary biotin supplementation increased glucagon expression and secretion without affecting fasting blood glucose concentrations or glucagon tolerance and provided new insights into the effect of biotin supplementation on glucagon production and action.
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Affiliation(s)
- Maria-Luisa Lazo-de-la-Vega-Monroy
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico; Division of Health Sciences, Department of Medical Sciences, University of Guanajuato, Guanajuato, Mexico
| | - Elena Larrieta
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico; Department of Gastroentrology, Salvador Zubirán National Institute of Health Sciences and Nutrition, Mexico City, Mexico
| | - Wilma Tixi-Verdugo
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico
| | - Rafael Ramírez-Mondragón
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico
| | - Ileana Hernández-Araiza
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico
| | - Michael S German
- Diabetes Center/Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, California, USA
| | - Cristina Fernandez-Mejia
- Unit of Genetics of Nutrition, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Nacional de Pediatría, Mexico City, Mexico.
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17
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Solini A, Sebastiani G, Nigi L, Santini E, Rossi C, Dotta F. Dapagliflozin modulates glucagon secretion in an SGLT2-independent manner in murine alpha cells. DIABETES & METABOLISM 2017; 43:512-520. [PMID: 28499695 DOI: 10.1016/j.diabet.2017.04.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 03/28/2017] [Accepted: 04/13/2017] [Indexed: 12/20/2022]
Abstract
AIM SGLT2 inhibitors reduce renal glucose uptake through an insulin-independent mechanism. They also increase glucagon concentration, although the extent to which this is due to a direct effect on pancreatic alpha cells remains unclear. METHODS In the present work, αTC1 cells treated with the SGLT2 inhibitor dapagliflozin (Dapa) were analyzed for glucose transporters, molecular mediators of hormone secretion, glucagon and GLP-1 release, and the effects of somatostatin. Data were validated in murine and human pancreatic islets. RESULTS SLC5A2 (the SGLT2-encoding gene) was nearly undetectable in αTC1 cells, not even by a digital PCR technique using different probes. In contrast, SLC5A1 (the SGLT1-encoding gene) was constitutively abundant in αTC1 cells and in islets, and increased with Dapa. This was associated with greater glucagon release, preceded by increased expression of preproglucagon and HNF4α. Looking at the candidate intracellular signalling pathway, reduced PASK and increased AMPK-α2 expression were also detected. GLUT1 and GLUT2, as well as regulators of glucagon release and alpha-cell phenotype (chromogranin A, paired box 6, proprotein convertase 1/2, synaptophysin), were unaffected by Dapa, as were GLP-1 receptor expression and GLP-1 release. Low glucose did not influence the stimulatory effect of Dapa on glucagon release, but was instead almost fully reverted by SLC5A1 silencing. When the effect of Dapa on AMPK and PASK, emerging regulators of lipid and glucose metabolism, was tested, upregulated AMPK-α2 appeared to be involved in molecular signalling. CONCLUSION Our study has shown that, in αTC1 cells, Dapa acutely upregulates SGLT1 expression and increases glucagon release through an SGLT1-dependent mechanism, with SGLT2 expression virtually undetectable. These results suggest the involvement of SGLT1 in modulating glucagon increases following SGLT2 inhibition.
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Affiliation(s)
- A Solini
- Department of surgical, medical, molecular and critical area pathology, university of Pisa, Via Roma 67, 56126 Pisa, Italy.
| | - G Sebastiani
- Department of medicine, surgery and neuroscience, university of Siena and Fondazione Umberto di Mario-Toscana life science, Viale Bracci 18, 53100 Siena, Italy
| | - L Nigi
- Department of medicine, surgery and neuroscience, university of Siena and Fondazione Umberto di Mario-Toscana life science, Viale Bracci 18, 53100 Siena, Italy
| | - E Santini
- Department of clinical and experimental medicine, university of Pisa, Pisa, Italy
| | - C Rossi
- Department of clinical and experimental medicine, university of Pisa, Pisa, Italy
| | - F Dotta
- Department of medicine, surgery and neuroscience, university of Siena and Fondazione Umberto di Mario-Toscana life science, Viale Bracci 18, 53100 Siena, Italy.
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18
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Almaça J, Molina J, Menegaz D, Pronin AN, Tamayo A, Slepak V, Berggren PO, Caicedo A. Human Beta Cells Produce and Release Serotonin to Inhibit Glucagon Secretion from Alpha Cells. Cell Rep 2016; 17:3281-3291. [PMID: 28009296 PMCID: PMC5217294 DOI: 10.1016/j.celrep.2016.11.072] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 10/24/2016] [Accepted: 11/23/2016] [Indexed: 12/11/2022] Open
Abstract
In the pancreatic islet, serotonin is an autocrine signal increasing beta cell mass during metabolic challenges such as those associated with pregnancy or high-fat diet. It is still unclear whether serotonin is relevant for regular islet physiology and hormone secretion. Here, we show that human beta cells produce and secrete serotonin when stimulated with increases in glucose concentration. Serotonin secretion from beta cells decreases cyclic AMP (cAMP) levels in neighboring alpha cells via 5-HT1F receptors and inhibits glucagon secretion. Without serotonergic input, alpha cells lose their ability to regulate glucagon secretion in response to changes in glucose concentration, suggesting that diminished serotonergic control of alpha cells can cause glucose blindness and the uncontrolled glucagon secretion associated with diabetes. Supporting this model, pharmacological activation of 5-HT1F receptors reduces glucagon secretion and has hypoglycemic effects in diabetic mice. Thus, modulation of serotonin signaling in the islet represents a drug intervention opportunity.
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Affiliation(s)
- Joana Almaça
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | - Judith Molina
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Danusa Menegaz
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Alexey N Pronin
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Alejandro Tamayo
- Diabetes Research Institute, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Vladlen Slepak
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; Program in Neuroscience, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Per-Olof Berggren
- Diabetes Research Institute, University of Miami Miller School of Medicine, Miami, FL 33136, USA; Rolf Luft Research Center for Diabetes & Endocrinology, Karolinska Institutet, Stockholm SE-17177, Sweden; Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Alejandro Caicedo
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA; Program in Neuroscience, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
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19
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Zaitseva II, Zaitsev SV, Berggren PO. The imidazoline compound RX871024 promotes insulinoma cell death independent of AMP-activated protein kinase inhibition. Invest New Drugs 2016; 34:522-9. [DOI: 10.1007/s10637-016-0362-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 05/18/2016] [Indexed: 11/29/2022]
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20
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Gylfe E. Glucose control of glucagon secretion-'There's a brand-new gimmick every year'. Ups J Med Sci 2016; 121:120-32. [PMID: 27044660 PMCID: PMC4900067 DOI: 10.3109/03009734.2016.1154905] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 02/10/2016] [Accepted: 02/11/2016] [Indexed: 11/13/2022] Open
Abstract
Glucagon from the pancreatic α-cells is a major blood glucose-regulating hormone whose most important role is to prevent hypoglycaemia that can be life-threatening due to the brain's strong dependence on glucose as energy source. Lack of blood glucose-lowering insulin after malfunction or autoimmune destruction of the pancreatic β-cells is the recognized cause of diabetes, but recent evidence indicates that diabetic hyperglycaemia would not develop unless lack of insulin was accompanied by hypersecretion of glucagon. Glucagon release has therefore become an increasingly important target in diabetes management. Despite decades of research, an understanding of how glucagon secretion is regulated remains elusive, and fundamentally different mechanisms continue to be proposed. The autonomous nervous system is an important determinant of glucagon release, but it is clear that secretion is also directly regulated within the pancreatic islets. The present review focuses on pancreatic islet mechanisms involved in glucose regulation of glucagon release. It will be argued that α-cell-intrinsic processes are most important for regulation of glucagon release during recovery from hypoglycaemia and that paracrine inhibition by somatostatin from the δ-cells shapes pulsatile glucagon release in hyperglycaemia. The electrically coupled β-cells ultimately determine islet hormone pulsatility by releasing synchronizing factors that affect the α- and δ-cells.
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Affiliation(s)
- Erik Gylfe
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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21
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Sayers SR, Reimann F, Gribble FM, Parker H, Zac-Varghese S, Bloom SR, Foretz M, Viollet B, Rutter GA. Proglucagon Promoter Cre-Mediated AMPK Deletion in Mice Increases Circulating GLP-1 Levels and Oral Glucose Tolerance. PLoS One 2016; 11:e0149549. [PMID: 27010458 PMCID: PMC4806996 DOI: 10.1371/journal.pone.0149549] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/02/2016] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Enteroendocrine L-cells synthesise and release the gut hormone glucagon-like peptide-1 (GLP-1) in response to food transit. Deletion of the tumour suppressor kinase LKB1 from proglucagon-expressing cells leads to the generation of intestinal polyps but no change in circulating GLP-1 levels. Here, we explore the role of the downstream kinase AMP-activated protein kinase (AMPK) in these cells. METHOD Loss of AMPK from proglucagon-expressing cells was achieved using a preproglucagon promoter-driven Cre (iGluCre) to catalyse recombination of floxed alleles of AMPKα1 and α2. Oral and intraperitoneal glucose tolerance were measured using standard protocols. L-cell mass was measured by immunocytochemistry. Hormone and peptide levels were measured by electrochemical-based luminescence detection or radioimmunoassay. RESULTS Recombination with iGluCre led to efficient deletion of AMPK from intestinal L- and pancreatic alpha-cells. In contrast to mice rendered null for LKB1 using the same strategy, mice deleted for AMPK displayed an increase (WT: 0.05 ± 0.01, KO: 0.09±0.02%, p<0.01) in L-cell mass and elevated plasma fasting (WT: 5.62 ± 0.800 pg/ml, KO: 14.5 ± 1.870, p<0.01) and fed (WT: 15.7 ± 1.48pg/ml, KO: 22.0 ± 6.62, p<0.01) GLP-1 levels. Oral, but not intraperitoneal, glucose tolerance was significantly improved by AMPK deletion, whilst insulin and glucagon levels were unchanged despite an increase in alpha to beta cell ratio (WT: 0.23 ± 0.02, KO: 0.33 ± 0.03, p<0.01). CONCLUSION AMPK restricts L-cell growth and GLP-1 secretion to suppress glucose tolerance. Targeted inhibition of AMPK in L-cells may thus provide a new therapeutic strategy in some forms of type 2 diabetes.
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Affiliation(s)
- Sophie R. Sayers
- Department of Cell Biology and Functional Genomics, Imperial College London, London, W12 ONN, United Kingdom
| | - Frank Reimann
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom
| | - Fiona M. Gribble
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom
| | - Helen Parker
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom
| | - Sagen Zac-Varghese
- Department of Investigative Medicine, Imperial College London, London, W12 ONN, United Kingdom
| | - Stephen R. Bloom
- Department of Investigative Medicine, Imperial College London, London, W12 ONN, United Kingdom
| | - Marc Foretz
- INSERM, U1016, Institut Cochin, 75014 Paris, France
- CNRS, UMR8104, 75014 Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - Benoit Viollet
- INSERM, U1016, Institut Cochin, 75014 Paris, France
- CNRS, UMR8104, 75014 Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - Guy A. Rutter
- Department of Cell Biology and Functional Genomics, Imperial College London, London, W12 ONN, United Kingdom
- * E-mail:
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22
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Affiliation(s)
- Ivan Quesada
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Elche, Spain
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23
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Vieira E, Merino B, Quesada I. Role of the clock gene Rev-erbα in metabolism and in the endocrine pancreas. Diabetes Obes Metab 2015; 17 Suppl 1:106-14. [PMID: 26332975 DOI: 10.1111/dom.12522] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 05/01/2015] [Indexed: 01/08/2023]
Abstract
Several hormones are regulated by circadian rhythms to adjust the metabolism to the light/dark cycles and feeding/activity patterns throughout the day. Circadian rhythms are mainly governed by the central clock located in the suprachiasmatic nucleus but also by clocks present in peripheral organs, like the endocrine pancreas. Plasma glucose levels and the main pancreatic hormones insulin and glucagon also exhibit daily variations. Alterations in circadian rhythms are associated with metabolic disturbances and pathologies such as obesity and diabetes. The molecular components of central and peripheral clocks and their regulatory mechanisms are well established. Among the different clock genes, Rev-erbα is considered one of the key links between circadian rhythms and metabolism. Rev-erbα is a critical part of a negative feedback loop in the core circadian clock and modulates the clock oscillatory properties. In addition, Rev-erbα plays an important role in the regulation of lipid and glucose metabolism, thermogenesis, adipocyte and muscle differentiation as well as mitochondrial function. In the endocrine pancreas, Rev-erbα regulates insulin and glucagon secretion and pancreatic β-cell proliferation. In the present review, we discuss all these subjects and, particularly, the role of the clock gene Rev-erbα in the endocrine pancreas.
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Affiliation(s)
- E Vieira
- Department of Cell Biology and Genetic, State University of Maringá, Maringá, Brazil
| | - B Merino
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and Instituto de Bioingeniería, Universidad Miguel Hernandez, Elche, Spain
| | - I Quesada
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and Instituto de Bioingeniería, Universidad Miguel Hernandez, Elche, Spain
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24
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Li J, Yu Q, Ahooghalandari P, Gribble FM, Reimann F, Tengholm A, Gylfe E. Submembrane ATP and Ca2+ kinetics in α-cells: unexpected signaling for glucagon secretion. FASEB J 2015; 29:3379-88. [PMID: 25911612 PMCID: PMC4539996 DOI: 10.1096/fj.14-265918] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 04/16/2015] [Indexed: 11/11/2022]
Abstract
Cytoplasmic ATP and Ca(2+) are implicated in current models of glucose's control of glucagon and insulin secretion from pancreatic α- and β-cells, respectively, but little is known about ATP and its relation to Ca(2+) in α-cells. We therefore expressed the fluorescent ATP biosensor Perceval in mouse pancreatic islets and loaded them with a Ca(2+) indicator. With total internal reflection fluorescence microscopy, we recorded subplasma membrane concentrations of Ca(2+) and ATP ([Ca(2+)]pm; [ATP]pm) in superficial α- and β-cells of intact islets and related signaling to glucagon and insulin secretion by immunoassay. Consistent with ATP's controlling glucagon and insulin secretion during hypo- and hyperglycemia, respectively, the dose-response relationship for glucose-induced [ATP]pm generation was left shifted in α-cells compared to β-cells. Both cell types showed [Ca(2+)]pm and [ATP]pm oscillations in opposite phase, probably reflecting energy-consuming Ca(2+) transport. Although pulsatile insulin and glucagon release are in opposite phase, [Ca(2+)]pm synchronized in the same phase between α- and β-cells. This paradox can be explained by the overriding of Ca(2+) stimulation by paracrine inhibition, because somatostatin receptor blockade potently stimulated glucagon release with little effect on Ca(2+). The data indicate that an α-cell-intrinsic mechanism controls glucagon in hypoglycemia and that paracrine factors shape pulsatile secretion in hyperglycemia.
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Affiliation(s)
- Jia Li
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Qian Yu
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Parvin Ahooghalandari
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Fiona M Gribble
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Frank Reimann
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Anders Tengholm
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Erik Gylfe
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
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Sun G, da Silva Xavier G, Gorman T, Priest C, Solomou A, Hodson DJ, Foretz M, Viollet B, Herrera PL, Parker H, Reimann F, Gribble FM, Migrenne S, Magnan C, Marley A, Rutter GA. LKB1 and AMPKα1 are required in pancreatic alpha cells for the normal regulation of glucagon secretion and responses to hypoglycemia. Mol Metab 2015; 4:277-86. [PMID: 25830091 PMCID: PMC4354920 DOI: 10.1016/j.molmet.2015.01.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 01/14/2015] [Accepted: 01/17/2015] [Indexed: 10/24/2022] Open
Abstract
AIMS/HYPOTHESIS Glucagon release from pancreatic alpha cells is required for normal glucose homoeostasis and is dysregulated in both Type 1 and Type 2 diabetes. The tumour suppressor LKB1 (STK11) and the downstream kinase AMP-activated protein kinase (AMPK), modulate cellular metabolism and growth, and AMPK is an important target of the anti-hyperglycaemic agent metformin. While LKB1 and AMPK have emerged recently as regulators of beta cell mass and insulin secretion, the role of these enzymes in the control of glucagon production in vivo is unclear. METHODS Here, we ablated LKB1 (αLKB1KO), or the catalytic alpha subunits of AMPK (αAMPKdKO, -α1KO, -α2KO), selectively in ∼45% of alpha cells in mice by deleting the corresponding flox'd alleles with a preproglucagon promoter (PPG) Cre. RESULTS Blood glucose levels in male αLKB1KO mice were lower during intraperitoneal glucose, aminoimidazole carboxamide ribonucleotide (AICAR) or arginine tolerance tests, and glucose infusion rates were increased in hypoglycemic clamps (p < 0.01). αLKB1KO mice also displayed impaired hypoglycemia-induced glucagon release. Glucose infusion rates were also elevated (p < 0.001) in αAMPKα1 null mice, and hypoglycemia-induced plasma glucagon increases tended to be lower (p = 0.06). Glucagon secretion from isolated islets was sensitized to the inhibitory action of glucose in αLKB1KO, αAMPKdKO, and -α1KO, but not -α2KO islets. CONCLUSIONS/INTERPRETATION An LKB1-dependent signalling cassette, involving but not restricted to AMPKα1, is required in pancreatic alpha cells for the control of glucagon release by glucose.
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Affiliation(s)
- Gao Sun
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
| | - Gabriela da Silva Xavier
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
| | | | | | - Antonia Solomou
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
| | - David J. Hodson
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
| | - Marc Foretz
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris cité, Paris, France
| | - Benoit Viollet
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Sorbonne Paris cité, Paris, France
| | - Pedro-Luis Herrera
- Department of Genetic Medicine & Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Helen Parker
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, UK
| | - Frank Reimann
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, UK
| | - Fiona M. Gribble
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, UK
| | - Stephanie Migrenne
- University Paris Diderot-Paris 7-Unit of Functional and Adaptive Biology (BFA) EAC 7059C NRS, France
| | - Christophe Magnan
- University Paris Diderot-Paris 7-Unit of Functional and Adaptive Biology (BFA) EAC 7059C NRS, France
| | | | - Guy A. Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK
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Bessho M, Murase-Mishiba Y, Imagawa A, Terasaki J, Hanafusa T. Possible contribution of taurine to distorted glucagon secretion in intra-islet insulin deficiency: a metabolome analysis using a novel α-cell model of insulin-deficient diabetes. PLoS One 2014; 9:e113254. [PMID: 25393115 PMCID: PMC4231115 DOI: 10.1371/journal.pone.0113254] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 10/24/2014] [Indexed: 01/30/2023] Open
Abstract
Glycemic instability is a serious problem in patients with insulin-deficient diabetes, and it may be due in part to abnormal endogenous glucagon secretion. However, the intracellular metabolic mechanism(s) involved in the aberrant glucagon response under the condition of insulin deficiency has not yet been elucidated. To investigate the metabolic traits that underlie the distortion of glucagon secretion under insulin deficient conditions, we generated an αTC1-6 cell line with stable knockdown of the insulin receptor (IRKD), i.e., an in vitro α-cell model for insulin-deficient diabetes, which exhibits an abnormal glucagon response to glucose. A comprehensive metabolomic analysis of the IRKD αTC1-6 cells (IRKD cells) revealed some candidate metabolites whose levels differed markedly compared to those in control αTC1-6 cells, but also which could affect the glucagon release in IRKD cells. Of these candidates, taurine was remarkably increased in the IRKD cells and was identified as a stimulator of glucagon in αTC1-6 cells. Taurine also paradoxically exaggerated the glucagon secretion at a high glucose concentration in IRKD cells and islets with IRKD. These results indicate that the metabolic alterations induced by IRKD in α-cells, especially the increase of taurine, may lead to the distorted glucagon response in IRKD cells, suggesting the importance of taurine in the paradoxical glucagon response and the resultant glucose instability in insulin-deficient diabetes.
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Affiliation(s)
- Megumi Bessho
- Department of Internal Medicine (I), Osaka Medical College, Osaka, Japan
| | | | - Akihisa Imagawa
- Department of Internal Medicine (I), Osaka Medical College, Osaka, Japan; Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Jungo Terasaki
- Department of Internal Medicine (I), Osaka Medical College, Osaka, Japan
| | - Toshiaki Hanafusa
- Department of Internal Medicine (I), Osaka Medical College, Osaka, Japan
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Watts M, Sherman A. Modeling the pancreatic α-cell: dual mechanisms of glucose suppression of glucagon secretion. Biophys J 2014; 106:741-51. [PMID: 24507615 DOI: 10.1016/j.bpj.2013.11.4504] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 11/21/2013] [Accepted: 11/26/2013] [Indexed: 12/11/2022] Open
Abstract
The mechanism by which glucose induces insulin secretion in β-cells is fairly well understood. Despite years of research, however, the mechanism of glucagon secretion in α-cells is still not well established. It has been proposed that glucose regulates glucagon secretion by decreasing the conductance of either outward ATP-dependent potassium channels (K(ATP)) or an inward store-operated current (SOC). We have developed a mathematical model based on mouse data to test these hypotheses and found that both mechanisms are possible. Glucose metabolism closes K(ATP) channels, which depolarizes the cell but paradoxically reduces calcium influx by inactivating voltage-dependent calcium and sodium channels and decreases secretion. Glucose metabolism also activates SERCA pumps, which fills the endoplasmic reticulum and hyperpolarizes the cells by reducing the inward current through SOC channels and again suppresses glucagon secretion. We find further that the two mechanisms can combine to account for the nonmonotonic dependence of secretion on glucose observed in some studies, an effect that cannot be obtained with either mechanism alone.
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Affiliation(s)
- Margaret Watts
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Arthur Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.
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28
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Zac-Varghese S, Trapp S, Richards P, Sayers S, Sun G, Bloom SR, Reimann F, Gribble FM, Rutter GA. The Peutz-Jeghers kinase LKB1 suppresses polyp growth from intestinal cells of a proglucagon-expressing lineage in mice. Dis Model Mech 2014; 7:1275-86. [PMID: 25190708 PMCID: PMC4213731 DOI: 10.1242/dmm.014720] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Liver kinase B1 (LKB1; also known as STK11) is a serine/threonine kinase and tumour suppressor that is mutated in Peutz-Jeghers syndrome (PJS), a premalignant syndrome associated with the development of gastrointestinal polyps. Proglucagon-expressing enteroendocrine cells are involved in the control of glucose homeostasis and the regulation of appetite through the secretion of gut hormones such as glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY). To determine the role of LKB1 in these cells, we bred mice bearing floxed alleles of Lkb1 against animals carrying Cre recombinase under proglucagon promoter control. These mice (GluLKB1KO) were viable and displayed near-normal growth rates and glucose homeostasis. However, they developed large polyps at the gastro-duodenal junction, and displayed premature mortality (death from 120 days of age). Histological analysis of the polyps demonstrated that they had a PJS-like appearance with an arborising smooth-muscle core. Circulating GLP-1 levels were normal in GluLKB1KO mice and the polyps expressed low levels of the peptide, similar to levels in the neighbouring duodenum. Lineage tracing using a Rosa26tdRFP transgene revealed, unexpectedly, that enterocytes within the polyps were derived from non-proglucagon-expressing precursors, whereas connective tissue was largely derived from proglucagon-expressing precursors. Developmental studies in wild-type mice suggested that a subpopulation of proglucagon-expressing cells undergo epithelial-mesenchymal transition (EMT) to become smooth-muscle-like cells. Thus, it is likely that polyps in the GluLKB1KO mice developed from a unique population of smooth-muscle-like cells derived from a proglucagon-expressing precursor. The loss of LKB1 within this subpopulation seems to be sufficient to drive tumorigenesis.
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Affiliation(s)
- Sagen Zac-Varghese
- Department of Investigative Medicine, Imperial College London, London, W12 ONN, UK
| | - Stefan Trapp
- Department of Surgery and Cancer, Imperial College London, London, W12 ONN, UK
| | - Paul Richards
- Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge, CB2 0XY, UK
| | - Sophie Sayers
- Department of Cell Biology, Imperial College London, London, W12 ONN, UK
| | - Gao Sun
- Department of Cell Biology, Imperial College London, London, W12 ONN, UK
| | - Stephen R Bloom
- Department of Investigative Medicine, Imperial College London, London, W12 ONN, UK
| | - Frank Reimann
- Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge, CB2 0XY, UK
| | - Fiona M Gribble
- Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge, CB2 0XY, UK
| | - Guy A Rutter
- Department of Cell Biology, Imperial College London, London, W12 ONN, UK.
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Abstract
Glucose homeostasis is precisely regulated by glucagon and insulin, which are released by pancreatic α- and β-cells, respectively. While β-cells have been the focus of intense research, less is known about α-cell function and the actions of glucagon. In recent years, the study of this endocrine cell type has experienced a renewed drive. The present review contains a summary of established concepts as well as new information about the regulation of α-cells by glucose, amino acids, fatty acids and other nutrients, focusing especially on glucagon release, glucagon synthesis and α-cell survival. We have also discussed the role of glucagon in glucose homeostasis and in energy and lipid metabolism as well as its potential as a modulator of food intake and body weight. In addition to the well-established action on the liver, we discuss the effects of glucagon in other organs, where the glucagon receptor is expressed. These tissues include the heart, kidneys, adipose tissue, brain, small intestine and the gustatory epithelium. Alterations in α-cell function and abnormal glucagon concentrations are present in diabetes and are thought to aggravate the hyperglycaemic state of diabetic patients. In this respect, several experimental approaches in diabetic models have shown important beneficial results in improving hyperglycaemia after the modulation of glucagon secretion or action. Moreover, glucagon receptor agonism has also been used as a therapeutic strategy to treat obesity.
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30
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Abstract
Glucagon secreted by pancreatic α-cells is the major hyperglycemic hormone correcting acute hypoglycaemia (glucose counterregulation). In diabetes the glucagon response to hypoglycaemia becomes compromised and chronic hyperglucagonemia appears. There is increasing awareness that glucagon excess may underlie important manifestations of diabetes. However opinions differ widely how glucose controls glucagon secretion. The autonomous nervous system plays an important role in the glucagon response to hypoglycaemia. But it is clear that glucose controls glucagon secretion also by mechanisms involving direct effects on α-cells or indirect effects via paracrine factors released from non-α-cells within the pancreatic islets. The present review discusses these mechanisms and argues that different regulatory processes are involved in a glucose concentration-dependent manner. Direct glucose effects on the α-cell and autocrine mechanisms are probably most significant for the glucagon response to hypoglycaemia. During hyperglycaemia, when secretion from β- and δ-cells is stimulated, paracrine inhibitory factors generate pulsatile glucagon release in opposite phase to pulsatile release of insulin and somatostatin. High concentrations of glucose have also stimulatory effects on glucagon secretion that tend to balance and even exceed the inhibitory influence. The latter actions might underlie the paradoxical hyperglucagonemia that aggravates hyperglycaemia in persons with diabetes.
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Affiliation(s)
- Erik Gylfe
- Department of Medical Cell Biology, Uppsala University, BMC Box 571, SE-751 23, Uppsala, Sweden.
| | - Patrick Gilon
- Pôle d'Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
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31
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Vieira E, Marroquí L, Figueroa ALC, Merino B, Fernandez-Ruiz R, Nadal A, Burris TP, Gomis R, Quesada I. Involvement of the clock gene Rev-erb alpha in the regulation of glucagon secretion in pancreatic alpha-cells. PLoS One 2013; 8:e69939. [PMID: 23936124 PMCID: PMC3723646 DOI: 10.1371/journal.pone.0069939] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 06/13/2013] [Indexed: 11/19/2022] Open
Abstract
Disruption of pancreatic clock genes impairs pancreatic beta-cell function, leading to the onset of diabetes. Despite the importance of pancreatic alpha-cells in the regulation of glucose homeostasis and in diabetes pathophysiology, nothing is known about the role of clock genes in these cells. Here, we identify the clock gene Rev-erb alpha as a new intracellular regulator of glucagon secretion. Rev-erb alpha down-regulation by siRNA (60–70% inhibition) in alphaTC1-9 cells inhibited low-glucose induced glucagon secretion (p<0.05) and led to a decrease in key genes of the exocytotic machinery. The Rev-erb alpha agonist GSK4112 increased glucagon secretion (1.6 fold) and intracellular calcium signals in alphaTC1-9 cells and mouse primary alpha-cells, whereas the Rev-erb alpha antagonist SR8278 produced the opposite effect. At 0.5 mM glucose, alphaTC1-9 cells exhibited intrinsic circadian Rev-erb alpha expression oscillations that were inhibited by 11 mM glucose. In mouse primary alpha-cells, glucose induced similar effects (p<0.001). High glucose inhibited key genes controlled by AMPK such as Nampt, Sirt1 and PGC-1 alpha in alphaTC1-9 cells (p<0.05). AMPK activation by metformin completely reversed the inhibitory effect of glucose on Nampt-Sirt1-PGC-1 alpha and Rev-erb alpha. Nampt inhibition decreased Sirt1, PGC-1 alpha and Rev-erb alpha mRNA expression (p<0.01) and glucagon release (p<0.05). These findings identify Rev-erb alpha as a new intracellular regulator of glucagon secretion via AMPK/Nampt/Sirt1 pathway.
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MESH Headings
- AMP-Activated Protein Kinases/genetics
- AMP-Activated Protein Kinases/metabolism
- Animals
- Cell Line
- Circadian Rhythm/genetics
- Cytokines/genetics
- Cytokines/metabolism
- Gene Expression Regulation
- Glucagon/genetics
- Glucagon/metabolism
- Glucagon-Secreting Cells/cytology
- Glucagon-Secreting Cells/drug effects
- Glucagon-Secreting Cells/metabolism
- Glucose/metabolism
- Glucose/pharmacology
- Glycine/analogs & derivatives
- Glycine/pharmacology
- Isoquinolines/pharmacology
- Metformin/pharmacology
- Mice
- Nicotinamide Phosphoribosyltransferase/genetics
- Nicotinamide Phosphoribosyltransferase/metabolism
- Nuclear Receptor Subfamily 1, Group D, Member 1/agonists
- Nuclear Receptor Subfamily 1, Group D, Member 1/antagonists & inhibitors
- Nuclear Receptor Subfamily 1, Group D, Member 1/genetics
- Nuclear Receptor Subfamily 1, Group D, Member 1/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Signal Transduction
- Sirtuin 1/genetics
- Sirtuin 1/metabolism
- Thiophenes/pharmacology
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Affiliation(s)
- Elaine Vieira
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- * E-mail: (EV); (IQ)
| | - Laura Marroquí
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Ana Lucia C. Figueroa
- Diabetes and Obesity Laboratory, Institut d'investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Beatriz Merino
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Rebeca Fernandez-Ruiz
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- Diabetes and Obesity Laboratory, Institut d'investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Angel Nadal
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Thomas P. Burris
- Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Ramon Gomis
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- Diabetes and Obesity Laboratory, Institut d'investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
- Endocrinology and Diabetes Unit, Hospital Clinic, Universitat de Barcelona, Barcelona, Spain
| | - Ivan Quesada
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- * E-mail: (EV); (IQ)
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AMPK is involved in the regulation of incretin receptors expression in pancreatic islets under a low glucose concentration. PLoS One 2013; 8:e64633. [PMID: 23717642 PMCID: PMC3661597 DOI: 10.1371/journal.pone.0064633] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 04/17/2013] [Indexed: 01/09/2023] Open
Abstract
The precise role of AMP-activated protein kinase (AMPK), a target of metformin, in pancreatic β cells remains controversial, even though metformin was recently shown to enhance the expression of incretin receptors (GLP-1 and GIP receptors) in pancreatic β cells. In this study, we investigated the effect of AMPK in the regulation of incretin receptors expression in pancreatic islets. The phosphorylation of AMPK in the mouse islets was decreased by increasing glucose concentrations. We showed the expression of incretin receptors in bell-shaped response to glucose; Expression of the incretin receptors in the isolated islets showed higher levels under a medium glucose concentration (11.1 mM) than that under a low glucose concentration (2.8 mM), but was suppressed under a high glucose concentration (22.2 mM). Both treatment with an AMPK inhibitor and DN-AMPK expression produced a significant increase of the incretin receptors expression under a low glucose concentration. By contrast, in hyperglycemic db/db islets, the enhancing effect of the AMPK inhibitor on the expression of incretin receptors was diminished under a low glucose concentration. Taken together, AMPK is involved in the regulation of incretin receptors expression in pancreatic islets under a low glucose concentration.
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Cheng-Xue R, Gómez-Ruiz A, Antoine N, Noël LA, Chae HY, Ravier MA, Chimienti F, Schuit FC, Gilon P. Tolbutamide controls glucagon release from mouse islets differently than glucose: involvement of K(ATP) channels from both α-cells and δ-cells. Diabetes 2013; 62:1612-22. [PMID: 23382449 PMCID: PMC3636641 DOI: 10.2337/db12-0347] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We evaluated the role of ATP-sensitive K⁺ (K(ATP)) channels, somatostatin, and Zn²⁺ in the control of glucagon secretion from mouse islets. Switching from 1 to 7 mmol/L glucose inhibited glucagon release. Diazoxide did not reverse the glucagonostatic effect of glucose. Tolbutamide decreased glucagon secretion at 1 mmol/L glucose (G1) but stimulated it at 7 mmol/L glucose (G7). The reduced glucagon secretion produced by high concentrations of tolbutamide or diazoxide, or disruption of K(ATP) channels (Sur1(-/-) mice) at G1 could be inhibited further by G7. Removal of the somatostatin paracrine influence (Sst(-/-) mice or pretreatement with pertussis toxin) strongly increased glucagon release, did not prevent the glucagonostatic effect of G7, and unmasked a marked glucagonotropic effect of tolbutamide. Glucose inhibited glucagon release in the absence of functional K(ATP) channels and somatostatin signaling. Knockout of the Zn²⁺ transporter ZnT8 (ZnT8(-/-) mice) did not prevent the glucagonostatic effect of glucose. In conclusion, glucose can inhibit glucagon release independently of Zn²⁺, K(ATP) channels, and somatostatin. Closure of K(ATP) channels controls glucagon secretion by two mechanisms, a direct stimulation of α-cells and an indirect inhibition via somatostatin released from δ-cells. The net effect on glucagon release results from a balance between both effects.
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Affiliation(s)
- Rui Cheng-Xue
- Pôle d’Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Ana Gómez-Ruiz
- Pôle d’Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Nancy Antoine
- Pôle d’Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Laura A. Noël
- Pôle d’Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Hee-Young Chae
- Pôle d’Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Magalie A. Ravier
- Institut de Génomique Fonctionnelle, CNRS UMR-5203, INSERM U661, Universités de Montpellier 1 et 2, Montpellier, France
| | | | - Frans C. Schuit
- Gene Expression Unit, Department of Molecular and Cellular Medicine, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Patrick Gilon
- Pôle d’Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
- Corresponding author: Patrick Gilon,
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34
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Affiliation(s)
- Erik Gylfe
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
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35
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Chen X, Hermansen K, Jeppesen PB. Impact of glucagon-like peptide-1 (7-36) amide, isosteviol and 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside on leucine-mediated α-cell dysfunction. Diabetes Obes Metab 2012; 14:1020-31. [PMID: 22747908 DOI: 10.1111/j.1463-1326.2012.01633.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 03/30/2012] [Accepted: 06/03/2012] [Indexed: 01/09/2023]
Abstract
AIM To investigate the acute and chronic effects of l-leucine on pancreatic α-cell function in vitro. Furthermore, we wanted to explore if glucagon-like peptide-1 (GLP-1), isosteviol (ISV) and 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR) counteract changes in α-cell function induced by chronic exposure to leucine. METHODS Isolated mice islets were incubated with 10 mM leucine for 2 or 72 h. We investigated glucagon and insulin secretion at 2 mM and 16.7 mM glucose. In addition, we cultured clonal α-TC1-6 cells with 5 mM leucine, 5 mM leucine plus GLP-1 (10(-6) M), or ISV (10(-6) M) or AICAR (10(-5) M) at high glucose for 72 h. We measured the glucagon secretion, cholesterol (CHO) and triglyceride (TG) content, cell proliferation as well as gene expression. RESULTS Ten millimolar of leucine for 2 h significantly stimulated glucagon and insulin secretion both at 2 and 16.7 mM glucose in mice islets. After 72 h incubation with 10 mM leucine the glucagon secretion was enhanced at both 2 and 16.7 mM glucose, whereas the glucose-stimulated insulin secretion (16.7 mM glucose) was inhibited. Chronic exposure to 5 mM leucine increased glucagon secretion, CHO and TG content, cell proliferation and Pcsk2 (p < 0.001), MafB (p < 0.05), Gcg (p < 0.001), Prkaa1 (p < 0.01), Hmgcr (p < 0.001), Srebf2 (p < 0.001), Acaca (p < 0.001), Mtor (p < 0.05) mRNA expression in clonal α-TC1-6 cells. While GLP-1 was cable of reducing glucagon hypersecretion and Pcsk2 (p < 0.05) mRNA expression. ISV and AICAR had no effect on leucine-induced glucagon hypersecretion. CONCLUSIONS Long-term exposure to leucine induces hypersecretion of glucagon secretion, that is, aminoacidotoxicity and influences some key genes of pancreatic α-cells. Interestingly, GLP-1 counteracts the leucine-induced α-cell dysfunction.
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Affiliation(s)
- X Chen
- Department of Medicine and Endocrinology, Aarhus University Hospital, Aarhus C, Denmark
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36
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Gaisano HY, Macdonald PE, Vranic M. Glucagon secretion and signaling in the development of diabetes. Front Physiol 2012; 3:349. [PMID: 22969729 PMCID: PMC3432929 DOI: 10.3389/fphys.2012.00349] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 08/10/2012] [Indexed: 12/19/2022] Open
Abstract
Normal release of glucagon from pancreatic islet α-cells promotes glucose mobilization, which counteracts the hypoglycemic actions of insulin, thereby ensuring glucose homeostasis. In treatment of diabetes aimed at rigorously reducing hyperglycemia to avoid chronic complications, the resulting hypoglycemia triggering glucagon release from α-cells is frequently impaired, with ensuing hypoglycemic complications. This review integrates the physiology of glucagon secretion regulating glucose homeostasis in vivo to single α-cell signaling, and how both become perturbed in diabetes. α-cells within the social milieu of the islet micro-organ are regulated not only by intrinsic signaling events but also by paracrine regulation, particularly by adjacent insulin-secreting β-cells and somatostatin-secreting δ-cells. We discuss the intrinsic α-cell signaling events, including glucose sensing and ion channel regulation leading to glucagon secretion. We then discuss the complex crosstalk between the islet cells and the breakdown of this crosstalk in diabetes contributing to the dysregulated glucagon secretion. Whereas, there are many secretory products released by β- and δ-cells that become deficient or excess in diabetes, we discuss the major ones, including the better known insulin and lesser known somatostatin, which act as putative paracrine on/off switches that very finely regulate α-cell secretory responses in health and diabetes. Of note in several type 1 diabetes (T1D) rodent models, blockade of excess somatostatin actions on α-cell could normalize glucagon secretion sufficient to attain normoglycemia in response to hypoglycemic assaults. There has been slow progress in fully elucidating the pathophysiology of the α-cell in diabetes because of the small number of α-cells within an islet and the islet mass becomes severely reduced and inflamed in diabetes. These limitations are just now being surmounted by new approaches.
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Affiliation(s)
- Herbert Y Gaisano
- Departments of Medicine and Physiology, University of Toronto Toronto, ON, Canada
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Energy-dependent modulation of glucagon-like signaling in Drosophila via the AMP-activated protein kinase. Genetics 2012; 192:457-66. [PMID: 22798489 DOI: 10.1534/genetics.112.143610] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Adipokinetic hormone (AKH) is the equivalent of mammalian glucagon, as it is the primary insect hormone that causes energy mobilization. In Drosophila, current knowledge of the mechanisms regulating AKH signaling is limited. Here, we report that AMP-activated protein kinase (AMPK) is critical for normal AKH secretion during periods of metabolic challenges. Reduction of AMPK in AKH cells causes a suite of behavioral and physiological phenotypes resembling AKH cell ablations. Specifically, reduced AMPK function increases life span during starvation and delays starvation-induced hyperactivity. Neither AKH cell survival nor gene expression is significantly impacted by reduced AMPK function. AKH immunolabeling was significantly higher in animals with reduced AMPK function; this result is paralleled by genetic inhibition of synaptic release, suggesting that AMPK promotes AKH secretion. We observed reduced secretion in AKH cells bearing AMPK mutations employing a specific secretion reporter, confirming that AMPK functions in AKH secretion. Live-cell imaging of wild-type AKH neuroendocrine cells shows heightened excitability under reduced sugar levels, and this response was delayed and reduced in AMPK-deficient backgrounds. Furthermore, AMPK activation in AKH cells increases intracellular calcium levels in constant high sugar levels, suggesting that the underlying mechanism of AMPK action is modification of ionic currents. These results demonstrate that AMPK signaling is a critical feature that regulates AKH secretion, and, ultimately, metabolic homeostasis. The significance of these findings is that AMPK is important in the regulation of glucagon signaling, suggesting that the organization of metabolic networks is highly conserved and that AMPK plays a prominent role in these networks.
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Tan B, Li X, Yin Y, Wu Z, Liu C, Tekwe CD, Wu G. Regulatory roles for L-arginine in reducing white adipose tissue. FRONT BIOSCI-LANDMRK 2012; 17:2237-46. [PMID: 22652774 PMCID: PMC3422877 DOI: 10.2741/4047] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
As the nitrogenous precursor of nitric oxide, L-arginine regulates multiple metabolic pathways involved in the metabolism of fatty acids, glucose, amino acids, and proteins through cell signaling and gene expression. Specifically, arginine stimulates lipolysis and the expression of key genes responsible for activation of fatty acid oxidation to CO2 and water. The underlying mechanisms involve increases in the expression of peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1 alpha), mitochondrial biogenesis, and the growth of brown adipose tissue growth. Furthermore, arginine regulates adipocyte-muscle crosstalk and energy partitioning via the secretion of cytokines and hormones. In addition, arginine enhances AMP-activated protein kinase (AMPK) expression and activity, thereby modulating lipid metabolism and energy balance toward the loss of triacylglycerols. Growing evidence shows that dietary supplementation with arginine effectively reduces white adipose tissue in Zucker diabetic fatty rats, diet-induced obese rats, growing-finishing pigs, and obese patients with type II diabetes. Thus, arginine can be used to prevent and treat adiposity and the associated metabolic syndrome.
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Affiliation(s)
- Bi’e Tan
- Research Center of Healthy Breeding of Livestock and Poultry and Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, the Chinese Academy of Sciences, Changsha, Hunan, China 410125
| | - Xinguo Li
- Hunan Institute of Animal Husbandry and Veterinary Medicine, Changsha, Hunan, China 410131
| | - Yulong Yin
- Research Center of Healthy Breeding of Livestock and Poultry and Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, the Chinese Academy of Sciences, Changsha, Hunan, China 410125
| | - Zhenlong Wu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193
| | - Chuang Liu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193
| | - Carmen D. Tekwe
- Department of Statistics, Texas A and M University, College Station, TX, USA 77843-3143
| | - Guoyao Wu
- Research Center of Healthy Breeding of Livestock and Poultry and Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, the Chinese Academy of Sciences, Changsha, Hunan, China 410125
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193
- Department of Animal Science, Texas A&M University, College Station, TX, USA 77843-2471
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Verspohl EJ. Novel Pharmacological Approaches to the Treatment of Type 2 Diabetes. Pharmacol Rev 2012; 64:188-237. [DOI: 10.1124/pr.110.003319] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Current world literature. Curr Opin Organ Transplant 2011; 16:650-60. [PMID: 22068023 DOI: 10.1097/mot.0b013e32834dd969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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MacDonald PE, Rorsman P. Per-arnt-sim (PAS) domain kinase (PASK) as a regulator of glucagon secretion. Diabetologia 2011; 54:719-21. [PMID: 21327866 DOI: 10.1007/s00125-011-2072-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 01/19/2011] [Indexed: 12/21/2022]
Abstract
The physiological and pathophysiological regulation of glucagon secretion from pancreatic alpha cells remains a hotly debated topic. The mechanism(s) contributing to the glucose sensitivity of glucagon release and its impaired regulation in diabetes remain unclear. A paper in the current issue of Diabetologia by da Silva Xavier and colleagues (doi: 10.1007/s00125-010-2010-7 ) provides intriguing new insight into a metabolic sensing pathway mediated by the per-arnt-sim (PAS) domain kinase (PASK) that may contribute to both the paracrine and the intrinsic glucose regulation of alpha cells. Importantly, the authors show that PASK is decreased in islets from patients with type 2 diabetes, providing a potential mechanism for impaired suppression of glucagon by hyperglycaemia in this disease. Much work remains to be done to determine the exact role and mechanism of PASK in alpha and beta cells. Nevertheless, the present work introduces a new player in the metabolic regulation of glucagon secretion.
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Affiliation(s)
- P E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada.
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da Silva Xavier G, Farhan H, Kim H, Caxaria S, Johnson P, Hughes S, Bugliani M, Marselli L, Marchetti P, Birzele F, Sun G, Scharfmann R, Rutter J, Siniakowicz K, Weir G, Parker H, Reimann F, Gribble FM, Rutter GA. Per-arnt-sim (PAS) domain-containing protein kinase is downregulated in human islets in type 2 diabetes and regulates glucagon secretion. Diabetologia 2011; 54:819-27. [PMID: 21181396 PMCID: PMC3052475 DOI: 10.1007/s00125-010-2010-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Accepted: 11/12/2010] [Indexed: 10/27/2022]
Abstract
AIMS/HYPOTHESIS We assessed whether per-arnt-sim (PAS) domain-containing protein kinase (PASK) is involved in the regulation of glucagon secretion. METHODS mRNA levels were measured in islets by quantitative PCR and in pancreatic beta cells obtained by laser capture microdissection. Glucose tolerance, plasma hormone levels and islet hormone secretion were analysed in C57BL/6 Pask homozygote knockout mice (Pask-/-) and control littermates. Alpha-TC1-9 cells, human islets or cultured E13.5 rat pancreatic epithelia were transduced with anti-Pask or control small interfering RNAs, or with adenoviruses encoding enhanced green fluorescent protein or PASK. RESULTS PASK expression was significantly lower in islets from human type 2 diabetic than control participants. PASK mRNA was present in alpha and beta cells from mouse islets. In Pask-/- mice, fasted blood glucose and plasma glucagon levels were 25 ± 5% and 50 ± 8% (mean ± SE) higher, respectively, than in control mice. At inhibitory glucose concentrations (10 mmol/l), islets from Pask-/- mice secreted 2.04 ± 0.2-fold (p < 0.01) more glucagon and 2.63 ± 0.3-fold (p < 0.01) less insulin than wild-type islets. Glucose failed to inhibit glucagon secretion from PASK-depleted alpha-TC1-9 cells, whereas PASK overexpression inhibited glucagon secretion from these cells and human islets. Extracellular insulin (20 nmol/l) inhibited glucagon secretion from control and PASK-deficient alpha-TC1-9 cells. PASK-depleted alpha-TC1-9 cells and pancreatic embryonic explants displayed increased expression of the preproglucagon (Gcg) and AMP-activated protein kinase (AMPK)-alpha2 (Prkaa2) genes, implying a possible role for AMPK-alpha2 downstream of PASK in the control of glucagon gene expression and release. CONCLUSIONS/INTERPRETATION PASK is involved in the regulation of glucagon secretion by glucose and may be a useful target for the treatment of type 2 diabetes.
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Affiliation(s)
- G. da Silva Xavier
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ UK
| | - H. Farhan
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ UK
| | - H. Kim
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ UK
| | - S. Caxaria
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ UK
| | - P. Johnson
- Nuffield Department of Surgical Sciences, Oxford University, Oxford, UK
| | - S. Hughes
- Nuffield Department of Surgical Sciences, Oxford University, Oxford, UK
| | - M. Bugliani
- Dipartimento di Endocrinologia e Metabolismo, Unità Metabolica, Università di Pisa, Pisa, Italy
| | - L. Marselli
- Dipartimento di Endocrinologia e Metabolismo, Unità Metabolica, Università di Pisa, Pisa, Italy
| | - P. Marchetti
- Dipartimento di Endocrinologia e Metabolismo, Unità Metabolica, Università di Pisa, Pisa, Italy
| | - F. Birzele
- Boehringer Ingelheim Pharma, Target Discovery Research, Ingelheim, Germany
| | - G. Sun
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ UK
| | - R. Scharfmann
- INSERM U845, Centre de Recherche Croissance et Signalisation, Université Paris Descartes, Faculté de Médecine, Hôpital Necker, Paris, France
| | - J. Rutter
- Division of Endocrinology, University of Utah School of Medicine, Salt Lake, UT USA
| | - K. Siniakowicz
- Section on Islet Transplantation and Cell Biology, Research Division, Joslin Diabetes Center and the Department of Medicine, Harvard Medical School, Boston, MA USA
| | - G. Weir
- Section on Islet Transplantation and Cell Biology, Research Division, Joslin Diabetes Center and the Department of Medicine, Harvard Medical School, Boston, MA USA
| | - H. Parker
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, Addenbrooke’s Hospital, Cambridge, UK
| | - F. Reimann
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, Addenbrooke’s Hospital, Cambridge, UK
| | - F. M. Gribble
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, Addenbrooke’s Hospital, Cambridge, UK
| | - G. A. Rutter
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ UK
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