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Bisht S, Singh MF. The triggering pathway, the metabolic amplifying pathway, and cellular transduction in regulation of glucose-dependent biphasic insulin secretion. Arch Physiol Biochem 2024:1-12. [PMID: 38196246 DOI: 10.1080/13813455.2023.2299920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 12/16/2023] [Indexed: 01/11/2024]
Abstract
Introduction: Insulin secretion is a highly regulated process critical for maintaining glucose homeostasis. This abstract explores the intricate interplay between three essential pathways: The Triggering Pathway, The Metabolic Amplifying Pathway, and Cellular Transduction, in orchestrating glucose-dependent biphasic insulin secretion.Mechanism: During the triggering pathway, glucose metabolism in pancreatic beta-cells leads to ATP production, closing ATP-sensitive potassium channels and initiating insulin exocytosis. The metabolic amplifying pathway enhances insulin secretion via key metabolites like NADH and glutamate, enhancing calcium influx and insulin granule exocytosis. Additionally, the cellular transduction pathway involves G-protein coupled receptors and cyclic AMP, modulating insulin secretion.Result and Conclusion: These interconnected pathways ensure a dynamic insulin response to fluctuating glucose levels, with the initial rapid phase and the subsequent sustained phase. Understanding these pathways' complexities provides crucial insights into insulin dysregulation in diabetes and highlights potential therapeutic targets to restore glucose-dependent insulin secretion.
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Affiliation(s)
- Shradha Bisht
- Amity Institute of Pharmacy, Amity University, Lucknow, Uttar Pradesh, India
| | - Mamta F Singh
- School of Pharmaceutical Sciences, SBS University, Balawala, Uttarakhand, India
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Jin L, Dang H, Wu J, Yuan L, Chen X, Yao J. Weizmannia coagulans BC2000 Plus Ellagic Acid Inhibits High-Fat-Induced Insulin Resistance by Remodeling the Gut Microbiota and Activating the Hepatic Autophagy Pathway in Mice. Nutrients 2022; 14:4206. [PMID: 36235858 PMCID: PMC9572659 DOI: 10.3390/nu14194206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 09/27/2022] [Accepted: 10/07/2022] [Indexed: 11/05/2022] Open
Abstract
(1) Background: Ellagic acid (EA) acts as a product of gut microbiota transformation to prevent insulin resistance, which is limited by high-fat diet (HFD)-induced dysbiosis. The aim of this study was to investigate the synergistic effects and mechanisms of supplementation with the probiotic Weizmannia coagulans (W. coagulans) on the prevention of insulin resistance by EA; (2) Methods: C57BL/6J mice were divided into five groups (n = 10/group): low-fat-diet group, high-fat-diet group, EA intervention group, EA + W. coagulans BC77 group, and EA + W. coagulans BC2000 group; (3) Result: W. coagulans BC2000 showed a synergistic effect on EA's lowering insulin resistance index and inhibiting high-fat diet-induced endotoxemia. The combined effect of BC2000 and EA activated the autophagy pathway in the mouse liver, a urolithin-like effect. This was associated with altered β-diversity of gut microbiota and increased Eggerthellaceae, a potential EA-converting family. Ellagic acid treatment alone and the combined use of ellagic acid and W. coagulans BC77 failed to activate the hepatic autophagy pathway; (4) Conclusions: W. coagulans BC2000 can assist EA in its role of preventing insulin resistance. This study provides a basis for the development of EA-rich functional food supplemented with W. coagulans BC2000.
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Affiliation(s)
- Long Jin
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
- Probiotics Institute, Hefei 230031, China
| | - Hongyang Dang
- College Life Science & Technology, Xinjiang University, Urumqi 830046, China
- Institute of Nutrition and Health, Qingdao University, Qingdao 266021, China
| | - Jinyong Wu
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Lixia Yuan
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Xiangsong Chen
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Jianming Yao
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
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Deng Q, Chen J. Potential Therapeutic Effect of All-Trans Retinoic Acid on Atherosclerosis. Biomolecules 2022; 12:869. [PMID: 35883425 PMCID: PMC9312697 DOI: 10.3390/biom12070869] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Revised: 06/08/2022] [Accepted: 06/22/2022] [Indexed: 11/16/2022] Open
Abstract
Atherosclerosis is a major risk factor for myocardial infarction and ischemic stroke, which are the leading cause of death worldwide. All-trans retinoic acid (ATRA) is a natural derivative of essential vitamin A. Numerous studies have shown that ATRA plays an important role in cell proliferation, cell apoptosis, cell differentiation, and embryonic development. All-trans retinoic acid (ATRA) is a ligand of retinoic acid receptors that regulates various biological processes by activating retinoic acid signals. In this paper, the metabolic processes of ATRA were reviewed, with emphasis on the effects of ATRA on inflammatory cells involved in the process of atherosclerosis.
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Affiliation(s)
| | - Jixiang Chen
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China;
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Effects and Underlying Mechanisms of Bioactive Compounds on Type 2 Diabetes Mellitus and Alzheimer's Disease. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2019; 2019:8165707. [PMID: 30800211 PMCID: PMC6360036 DOI: 10.1155/2019/8165707] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 10/15/2018] [Accepted: 10/24/2018] [Indexed: 01/11/2023]
Abstract
Type 2 diabetes mellitus is a complicated metabolic disorder characterized by hyperglycemia and glucose intolerance. Alzheimer's disease is a progressive brain disorder characterized by a chronic loss of cognitive and behavioral function. Considering the shared characteristics of both diseases, common therapeutic and preventive agents may be effective. Bioactive compounds such as polyphenols, vitamins, and carotenoids found in vegetables and fruits can have antioxidant and anti-inflammatory effects. These effects make them suitable candidates for the prevention or treatment of diabetes and Alzheimer's disease. Increasing evidence from cell or animal models suggest that bioactive compounds may have direct effects on decreasing hyperglycemia, enhancing insulin secretion, and preventing formation of amyloid plaques. The possible underlying molecular mechanisms are described in this review. More studies are needed to establish the clinical effects of bioactive compounds.
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Maternal vitamin A deficiency during pregnancy affects vascularized islet development. J Nutr Biochem 2016; 36:51-59. [DOI: 10.1016/j.jnutbio.2016.07.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 06/08/2016] [Accepted: 07/05/2016] [Indexed: 02/03/2023]
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Retinoids have therapeutic action in type 2 diabetes. Nutrition 2016; 32:898-903. [PMID: 27134203 DOI: 10.1016/j.nut.2016.02.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 12/22/2015] [Accepted: 02/02/2016] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Uncontrolled diabetes is associated with a compromised antioxidant state of the body. Consequentially, the reactive oxygen species generated lead to oxidative insult and associated complications. Based on this paradigm, exogenous antioxidant supplementation is thought to exert a therapeutic role in type 2 diabetes (T2-D) biology. METHODS In the present study, the effect of vitamin A supplementation was assessed on disease progression in T2-D BALB/c mice. Animals were divided into three groups. With the exception of control, the mice in remaining groups were induced with experimental T2-D. After a 15-day treatment protocol, the mice were sacrificed and various parameters were analyzed. RESULTS The treated group evidenced a considerable improvement in total antioxidant potential and glycemic control. A therapeutic effect on beta cell degeneration as compared to the diabetic group was also found. CONCLUSIONS The study illustrates the antihyperglycemic and antioxidant potential of vitamin A in vivo, which has potential to serve as a dietary intervention in T2-D.
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Abstract
Retinoids (vitamin A and its natural and synthetic analogs) are required by most tissues for maintaining the normal health of the tissue. This is certainly true for the pancreas. The recent literature is convincing that retinoids are needed by the adult to assure normal pancreatic endocrine functions, especially those of the α- and β-cells. It is also well established that retinoids are required to insure normal pancreas development in utero, including the development of the endocrine pancreas. The actions of retinoids for maintaining normal pancreatic islet functions has drawn considerable research interest from investigators interested in understanding and treating metabolic disease. Pancreatic retinoids are also of interest to investigators studying the origins of pancreatic disease, including the development of pancreatic fibrosis and its sequelae. This research interest is focused on pancreatic stellate cells (PSCs) which store retinoids and possess the metabolic machinery needed to metabolize retinoids. The literature on pancreatic disease and retinoids suggests that there is an association between impairments in pancreatic retinoid storage and metabolism and the development of pancreatic disease. These topics will be considered in this review.
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Affiliation(s)
- Pierre-Jacques Brun
- 1 Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA ; 2 Institute of Molecular Biosciences, Mahidol University, Nakhon Pathom, Thailand
| | - Nuttaporn Wongsiriroj
- 1 Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA ; 2 Institute of Molecular Biosciences, Mahidol University, Nakhon Pathom, Thailand
| | - William S Blaner
- 1 Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA ; 2 Institute of Molecular Biosciences, Mahidol University, Nakhon Pathom, Thailand
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All-Trans Retinoic Acid Induces TGF-β2 in Intestinal Epithelial Cells via RhoA- and p38α MAPK-Mediated Activation of the Transcription Factor ATF2. PLoS One 2015. [PMID: 26225425 PMCID: PMC4520553 DOI: 10.1371/journal.pone.0134003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Objective We have shown previously that preterm infants are at risk of necrotizing enterocolitis (NEC), an inflammatory bowel necrosis typically seen in infants born prior to 32 weeks’ gestation, because of the developmental deficiency of transforming growth factor (TGF)-β2 in the intestine. The present study was designed to investigate all-trans retinoic acid (atRA) as an inducer of TGF-β2 in intestinal epithelial cells (IECs) and to elucidate the involved signaling mechanisms. Methods AtRA effects on intestinal epithelium were investigated using IEC6 cells. TGF-β2 expression was measured using reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and Western blots. Signaling pathways were investigated using Western blots, transiently-transfected/transduced cells, kinase arrays, chromatin immunoprecipitation, and selective small molecule inhibitors. Results AtRA-treatment of IEC6 cells selectively increased TGF-β2 mRNA and protein expression in a time- and dose-dependent fashion, and increased the activity of the TGF-β2 promoter. AtRA effects were mediated via RhoA GTPase, Rho-associated, coiled-coil-containing protein kinase 1 (ROCK1), p38α MAPK, and activating transcription factor (ATF)-2. AtRA increased phospho-ATF2 binding to the TGF-β2 promoter and increased histone H2B acetylation in the TGF-β2 nucleosome, which is typically associated with transcriptional activation. Conclusions AtRA induces TGF-β2 expression in IECs via RhoA- and p38α MAPK-mediated activation of the transcription factor ATF2. Further studies are needed to investigate the role of atRA as a protective/therapeutic agent in gut mucosal inflammation.
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Iqbal S, Naseem I. Role of vitamin A in type 2 diabetes mellitus biology: Effects of intervention therapy in a deficient state. Nutrition 2015; 31:901-7. [DOI: 10.1016/j.nut.2014.12.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 12/06/2014] [Accepted: 12/11/2014] [Indexed: 12/11/2022]
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Brun PJ, Grijalva A, Rausch R, Watson E, Yuen JJ, Das BC, Shudo K, Kagechika H, Leibel RL, Blaner WS. Retinoic acid receptor signaling is required to maintain glucose-stimulated insulin secretion and β-cell mass. FASEB J 2015; 29. [PMID: 25389133 PMCID: PMC4314234 DOI: 10.1096/fj.14-256743 10.1096/fj.14-256743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Retinoic acid signaling is required for maintaining a range of cellular processes, including cell differentiation, proliferation, and apoptosis. We investigated the actions of all-trans-retinoic acid (atRA) signaling in pancreatic β-cells of adult mice. atRA signaling was ablated in β-cells by overexpressing a dominant-negative retinoic acid receptor (RAR)-α mutant (RARdn) using an inducible Cre-Lox system under the control of the pancreas duodenal homeobox gene promoter. Our studies establish that hypomorphism for RAR in β-cells leads to an age-dependent decrease in plasma insulin in the fed state and in response to a glucose challenge. Glucose-stimulated insulin secretion was also impaired in islets isolated from mice expressing RARdn. Among genes that are atRA responsive, Glut2 and Gck mRNA levels were decreased in isolated islets from RARdn-expressing mice. Histologic analyses of RARdn-expressing pancreata revealed a decrease in β-cell mass and insulin per β-cell 1 mo after induction of the RARdn. Our results indicate that atRA signaling mediated by RARs is required in the adult pancreas for maintaining both β-cell function and mass, and provide insights into molecular mechanisms underlying these actions.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - William S. Blaner
- Correspondence: Department of Medicine, College of Physicians and Surgeons, Columbia University, 630 W. 168th Street, New York, NY 10032, USA. E-mail:
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Gene Expression Profile of NF-κB, Nrf2, Glycolytic, and p53 Pathways During the SH-SY5Y Neuronal Differentiation Mediated by Retinoic Acid. Mol Neurobiol 2014; 53:423-435. [PMID: 25465239 DOI: 10.1007/s12035-014-8998-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 11/12/2014] [Indexed: 01/17/2023]
Abstract
SH-SY5Y cells, a neuroblastoma cell line that is a well-established model system to study the initial phases of neuronal differentiation, have been used in studies to elucidate the mechanisms of neuronal differentiation. In the present study, we investigated alterations of gene expression in SH-SY5Y cells during neuronal differentiation mediated by retinoic acid (RA) treatment. We evaluated important pathways involving nuclear factor kappa B (NF-κB), nuclear E2-related factor 2 (Nrf2), glycolytic, and p53 during neuronal differentiation. We also investigated the involvement of reactive oxygen species (ROS) in modulating the gene expression profile of those pathways by antioxidant co-treatment with Trolox®, a hydrophilic analogue of α-tocopherol. We found that RA treatment increases levels of gene expression of NF-κB, glycolytic, and antioxidant pathway genes during neuronal differentiation of SH-SY5Y cells. We also found that ROS production induced by RA treatment in SH-SY5Y cells is involved in gene expression profile alterations, chiefly in NF-κB, and glycolytic pathways. Antioxidant co-treatment with Trolox® reversed the effects mediated by RA NF-κB, and glycolytic pathways gene expression. Interestingly, co-treatment with Trolox® did not reverse the effects in antioxidant gene expression mediated by RA in SH-SY5Y. To confirm neuronal differentiation, we quantified endogenous levels of tyrosine hydroxylase, a recognized marker of neuronal differentiation. Our data suggest that during neuronal differentiation mediated by RA, changes in profile gene expression of important pathways occur. These alterations are in part mediated by ROS production. Therefore, our results reinforce the importance in understanding the mechanism by which RA induces neuronal differentiation in SH-SY5Y cells, principally due this model being commonly used as a neuronal cell model in studies of neuronal pathologies.
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Brun PJ, Grijalva A, Rausch R, Watson E, Yuen JJ, Das BC, Shudo K, Kagechika H, Leibel RL, Blaner WS. Retinoic acid receptor signaling is required to maintain glucose-stimulated insulin secretion and β-cell mass. FASEB J 2014; 29:671-83. [PMID: 25389133 DOI: 10.1096/fj.14-256743] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Retinoic acid signaling is required for maintaining a range of cellular processes, including cell differentiation, proliferation, and apoptosis. We investigated the actions of all-trans-retinoic acid (atRA) signaling in pancreatic β-cells of adult mice. atRA signaling was ablated in β-cells by overexpressing a dominant-negative retinoic acid receptor (RAR)-α mutant (RARdn) using an inducible Cre-Lox system under the control of the pancreas duodenal homeobox gene promoter. Our studies establish that hypomorphism for RAR in β-cells leads to an age-dependent decrease in plasma insulin in the fed state and in response to a glucose challenge. Glucose-stimulated insulin secretion was also impaired in islets isolated from mice expressing RARdn. Among genes that are atRA responsive, Glut2 and Gck mRNA levels were decreased in isolated islets from RARdn-expressing mice. Histologic analyses of RARdn-expressing pancreata revealed a decrease in β-cell mass and insulin per β-cell 1 mo after induction of the RARdn. Our results indicate that atRA signaling mediated by RARs is required in the adult pancreas for maintaining both β-cell function and mass, and provide insights into molecular mechanisms underlying these actions.
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Affiliation(s)
- Pierre-Jacques Brun
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Ambar Grijalva
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Richard Rausch
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Elizabeth Watson
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Jason J Yuen
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Bhaskar C Das
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Koichi Shudo
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Hiroyuki Kagechika
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Rudolph L Leibel
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - William S Blaner
- Departments of *Medicine and Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY USA; Department of Medicine, The University of Kansas Medical Center, Kansas City, KS, USA; Research Foundation Itsuu Laboratory, Tokyo, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
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Chen W, Chen G. The Roles of Vitamin A in the Regulation of Carbohydrate, Lipid, and Protein Metabolism. J Clin Med 2014; 3:453-79. [PMID: 26237385 PMCID: PMC4449691 DOI: 10.3390/jcm3020453] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 03/06/2014] [Accepted: 03/14/2014] [Indexed: 02/07/2023] Open
Abstract
Currently, two-thirds of American adults are overweight or obese. This high prevalence of overweight/obesity negatively affects the health of the population, as obese individuals tend to develop several chronic diseases, such as type 2 diabetes and cardiovascular diseases. Due to obesity's impact on health, medical costs, and longevity, the rise in the number of obese people has become a public health concern. Both genetic and environmental/dietary factors play a role in the development of metabolic diseases. Intuitively, it seems to be obvious to link over-nutrition to the development of obesity and other metabolic diseases. However, the underlying mechanisms are still unclear. Dietary nutrients not only provide energy derived from macronutrients, but also factors such as micronutrients with regulatory roles. How micronutrients, such as vitamin A (VA; retinol), regulate macronutrient homeostasis is still an ongoing research topic. As an essential micronutrient, VA plays a key role in the general health of an individual. This review summarizes recent research progress regarding VA's role in carbohydrate, lipid, and protein metabolism. Due to the large amount of information regarding VA functions, this review focusses on metabolism in metabolic active organs and tissues. Additionally, some perspectives for future studies will be provided.
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Affiliation(s)
- Wei Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN 37996, USA.
| | - Guoxun Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN 37996, USA.
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Bisphenol A impairs hepatic glucose sensing in C57BL/6 male mice. PLoS One 2013; 8:e69991. [PMID: 23922885 PMCID: PMC3726717 DOI: 10.1371/journal.pone.0069991] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 06/18/2013] [Indexed: 01/23/2023] Open
Abstract
AIMS/HYPOTHESIS Glucose sensing (eg. glucokinase activity) becomes impaired in the development of type 2 diabetes, the etiology of which is unclear. Estrogen can stimulate glucokinase activity, whereas the pervasive environmental pollutant bisphenol A (BPA) can inhibit estrogen action, hence we aimed to determine the effect of BPA on glucokinase activity directly. METHODS To evaluate a potential acute effect on hepatic glucokinase activity, BPA in water (n = 5) vs. water alone (n = 5) was administered at the EPA's purported "safe dose" (50 µg/kg) by gavage to lean 6-month old male C57BL/6 mice. Two hours later, animals were euthanized and hepatic glucokinase activity measured over glucose levels from 1-20 mmol/l in liver homogenate. To determine the effect of chronic BPA exposure on hepatic glucokinase activity, lean 6-month old male C57BL/6 mice were provided with water (n = 15) or water with 1.75 mM BPA (∼50 µg/kg/day; n = 14) for 2 weeks. Following the 2-week exposure, animals were euthanized and glucokinase activity measured as above. RESULTS Hepatic glucokinase activity was signficantly suppressed after 2 hours in animals given an oral BPA bolus compared to those who received only water (p = 0.002-0.029 at glucose 5-20 mmol/l; overall treatment effect p<0.001). Exposure to BPA over 2 weeks also suppressed hepatic glucokinase activity in exposed vs. unexposed mice (overall treatment effect, p = 0.003). In both experiments, the Hill coefficient was higher and Vmax lower in mice treated with BPA. CONCLUSIONS/INTERPRETATION Both acute and chronic exposure to BPA significantly impair hepatic glucokinase activity and function. These findings identify a potential mechanism for how BPA may increase risk for diabetes.
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Brun PJ, Yang KJZ, Lee SA, Yuen JJ, Blaner WS. Retinoids: Potent regulators of metabolism. Biofactors 2013; 39:151-63. [PMID: 23281051 PMCID: PMC3620893 DOI: 10.1002/biof.1056] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 09/13/2012] [Indexed: 12/18/2022]
Abstract
Retinoids (vitamin A and its analogs) are highly potent regulators of cell differentiation, cell proliferation, and apoptosis. Because of these activities, retinoids have been most extensively studied in the contexts of embryonic development and of proliferative diseases, especially cancer and skin disease. Recently, there has been considerable new research interest focused on gaining understanding of the roles that retinoids and/or retinoid-related proteins may have in the development of metabolic diseases, primarily obesity, diabetes, and dyslipidemia. This review will summarize recent advances that have been made in these areas, focusing on the role of retinoids in modulating adipogenesis, the roles of retinoids and retinoid-related proteins as signaling molecules linking obesity with the development of type II diabetes, the roles of retinoids in pancreatic β-cell biology/insulin secretion, and the actions of retinoids in hepatic steatosis.
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Affiliation(s)
- Pierre-Jacques Brun
- Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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Farhangi MA, Keshavarz SA, Eshraghian M, Ostadrahimi A, Saboor-Yaraghi AA. Vitamin a supplementation, serum lipids, liver enzymes and C-reactive protein concentrations in obese women of reproductive age. Ann Clin Biochem 2012; 50:25-30. [DOI: 10.1258/acb.2012.012096] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Background High-dose vitamin A influences glucose and lipid profile; however, the possible effects of moderate doses (25,000 IU/d) are conflicting. We aimed to compare the effect of vitamin A supplementation on several anthropometric and biochemical variables between obese and non-obese women. Methods This study was performed on 84 women among whom 56 were obese (body mass index [BMI] 30-35 kg/m2) and 28 were non-obese (BMI 18.5-24.9 kg/m2). Obese women were randomly divided into two groups: one group received 25,000 IU/d retinyl palmitate and another group received placebo. The third group was age-matched non-obese women who received 25,000 IU/d retinyl palmitate. At baseline and four months after intervention, fasting blood glucose (FBG), lipid profile, C-reactive protein (CRP) and liver enzymes were evaluated. Results Baseline concentrations of serum FBG and triglyceride in the obese vitamin A-treated group were significantly higher compared with the other groups (P = 0.004 and 0.007, respectively). A significant increase in serum FBG (P = 0.026), total cholesterol (TC) (P = 0.004) and low-density lipoprotein cholesterol (LDL-C) (P = 0.016) in the non-obese group and a significant decrease in serum high-density lipoprotein cholesterol (HDL-C) (P = 0.001) in the obese group was observed. Serum CRP increased significantly in the obese vitamin A-treated group (P = 0.03) and serum aspartate transaminase increased significantly in the obese and non-obese groups after vitamin A supplementation (P = 0.008 and 0.001, respectively). Conclusions Treatment with 25,000 IU/d vitamin A induced a mild elevation in serum lipids, CRP and liver enzymes in obese and non-obese women. Considering the other information about possible side-effects of excess vitamin A, use of vitamin A in this dose and duration should be considered with caution.
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Affiliation(s)
- Mahdieh Abbasalizad Farhangi
- Department of Community Nutrition, Faculty of Health and Nutrition, Tabriz University of Medical Sciences, 51666-14711 Tabriz
| | | | - Mohammadreza Eshraghian
- Department of Biostatistics and Epidemiology, Faculty of Public Health, Tehran University of Medical Sciences, 14155-6446 Tehran
| | - Alireza Ostadrahimi
- Nutrition Research Center, Faculty of Health and Nutrition, Tabriz University of Medical Sciences, 51666-14711 Tabriz, Iran
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17
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Zhao S, Li R, Li Y, Chen W, Zhang Y, Chen G. Roles of vitamin A status and retinoids in glucose and fatty acid metabolism. Biochem Cell Biol 2012; 90:142-52. [PMID: 22292422 DOI: 10.1139/o11-079] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The rising prevalence of metabolic diseases, such as obesity and diabetes, has become a public health concern. Vitamin A (VA, retinol) is an essential micronutrient for a variety of physiological processes, such as tissue differentiation, immunity, and vision. However, its role in glucose and lipid metabolism has not been clearly defined. VA activities are mediated by the metabolite of retinol catabolism, retinoic acid, which activates the retinoic acid receptor and retinoid X receptor (RXR). Since RXR is an obligate heterodimeric partner for many nuclear receptors involved in metabolism, it is reasonable to assume that VA status and retinoids contribute to glucose and lipid homeostasis. To date, the impacts of VA and retinoids on energy metabolism in animals and humans have been demonstrated in some basic and clinical investigations. This review summarizes the effects of VA status and retinoid treatments on metabolism of the liver, adipocytes, pancreatic β-cells, and skeletal muscle. It proposes a mechanism by which the dietary and hormonal signals converge on the promoter of sterol regulatory element-binding protein 1c gene to induce its expression, and in turn, the expression of lipogenic genes in hepatocytes. Future research projects relevant to the VA's roles in metabolic diseases are also discussed.
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Affiliation(s)
- Shi Zhao
- The Diabetes Center, Wuhan Central Hospital, Wuhan, Hubei 430014, China
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18
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Xun Z, Lee DY, Lim J, Canaria CA, Barnebey A, Yanonne SM, McMurray CT. Retinoic acid-induced differentiation increases the rate of oxygen consumption and enhances the spare respiratory capacity of mitochondria in SH-SY5Y cells. Mech Ageing Dev 2012; 133:176-85. [PMID: 22336883 DOI: 10.1016/j.mad.2012.01.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 12/22/2011] [Accepted: 01/29/2012] [Indexed: 01/15/2023]
Abstract
Retinoic acid (RA) is used in differentiation therapy to treat a variety of cancers including neuroblastoma. The contributing factors for its therapeutic efficacy are poorly understood. However, mitochondria (MT) have been implicated as key effectors in RA-mediated differentiation process. Here we utilize the SH-SY5Y human neuroblastoma cell line as a model to examine how RA influences MT during the differentiation process. We find that RA confers an approximately sixfold increase in the oxygen consumption rate while the rate of glycolysis modestly increases. RA treatment does not increase the number of MT or cause measurable changes in the composition of the electron transport chain. Rather, RA treatment significantly increases the mitochondrial spare respiratory capacity. We propose a competition model for the therapeutic effects of RA. Specifically, the high metabolic rate in differentiated cells limits the availability of metabolic nutrients for use by the undifferentiated cells and suppresses their growth. Thus, RA treatment provides a selective advantage for the differentiated state.
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Affiliation(s)
- Zhiyin Xun
- Lawrence Berkeley National Laboratory, Life Sciences Division, 1 Cyclotron Rd., Berkeley, CA 94720, USA
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19
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Miyazaki S, Taniguchi H, Moritoh Y, Tashiro F, Yamamoto T, Yamato E, Ikegami H, Ozato K, Miyazaki JI. Nuclear hormone retinoid X receptor (RXR) negatively regulates the glucose-stimulated insulin secretion of pancreatic ß-cells. Diabetes 2010; 59:2854-61. [PMID: 20798333 PMCID: PMC2963544 DOI: 10.2337/db09-1897] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Retinoid X receptors (RXRs) are members of the nuclear hormone receptor superfamily and are thought to be key regulators in differentiation, cellular growth, and gene expression. Although several experiments using pancreatic β-cell lines have shown that the ligands of nuclear hormone receptors modulate insulin secretion, it is not clear whether RXRs have any role in insulin secretion. RESEARCH DESIGN AND METHODS To elucidate the function of RXRs in pancreatic β-cells, we generated a double-transgenic mouse in which a dominant-negative form of RXRβ was inducibly expressed in pancreatic β-cells using the Tet-On system. We also established a pancreatic β-cell line from an insulinoma caused by the β-cell-specific expression of simian virus 40 T antigen in the above transgenic mouse. RESULTS In the transgenic mouse, expression of the dominant-negative RXR enhanced the insulin secretion with high glucose stimulation. In the pancreatic β-cell line, the suppression of RXRs also enhanced glucose-stimulated insulin secretion at a high glucose concentration, while 9-cis-retinoic acid, an RXR agonist, repressed it. High-density oligonucleotide microarray analysis showed that expression of the dominant-negative RXR affected the expression levels of a number of genes, some of which have been implicated in the function and/or differentiation of β-cells. CONCLUSIONS These results suggest that endogenous RXR negatively regulates the glucose-stimulated insulin secretion. Given these findings, we propose that the modulation of endogenous RXR in β-cells may be a new therapeutic approach for improving impaired insulin secretion in type 2 diabetes.
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Affiliation(s)
- Satsuki Miyazaki
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hidenori Taniguchi
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yusuke Moritoh
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Fumi Tashiro
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Tsunehiko Yamamoto
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Eiji Yamato
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hiroshi Ikegami
- Department of Endocrinology, Metabolism and Diabetes, Kinki University School of Medicine, Osaka, Japan
| | - Keiko Ozato
- Section on Molecular Genetics of Immunity, Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Jun-ichi Miyazaki
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
- Corresponding author: Jun-ichi Miyazaki,
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20
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Kim JY, Song EH, Lee HJ, Oh YK, Park YS, Park JW, Kim BJ, Kim DJ, Lee I, Song J, Kim WH. Chronic ethanol consumption-induced pancreatic {beta}-cell dysfunction and apoptosis through glucokinase nitration and its down-regulation. J Biol Chem 2010; 285:37251-62. [PMID: 20855893 DOI: 10.1074/jbc.m110.142315] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Chronic ethanol consumption is known as an independent risk factor for type 2 diabetes, which is characterized by impaired glucose homeostasis and insulin resistance; however, there is a great deal of controversy concerning the relationships between alcohol consumption and the development of type 2 diabetes. We investigated the effects of chronic ethanol consumption on pancreatic β-cell dysfunction and whether generated peroxynitrite participates in the impaired glucose homeostasis. Here we show that chronic ethanol feeding decreases the ability of pancreatic β-cells to mediate insulin secretion and ATP production in coordination with the decrease of glucokinase, Glut2, and insulin expression. Specific blockade of ATF3 using siRNA or C-terminally deleted ATF3(ΔC) attenuated ethanol-induced pancreatic β-cell apoptosis or dysfunction and restored the down-regulation of glucokinase (GCK), insulin, and pancreatic duodenal homeobox-1 induced by ethanol. GCK inactivation and down-regulation were predominantly mediated by ethanol metabolism-generated peroxynitrite, which were suppressed by the peroxynitrite scavengers N(γ)-monomethyl-L-arginine, uric acid, and deferoxamine but not by the S-nitrosylation inhibitor DTT, indicating that tyrosine nitration is the predominant modification associated with GCK down-regulation and inactivation rather than S-nitrosylation of cysteine. Tyrosine nitration of GCK prevented its association with pBad, and GCK translocation into the mitochondria results in subsequent proteasomal degradation of GCK following ubiquitination. This study identified a novel and efficient pathway by which chronic ethanol consumption may induce GCK down-regulation and inactivation by inducing tyrosine nitration of GCK, resulting in pancreatic β-cell apoptosis and dysfunction. Peroxynitrite-induced ATF3 may also serve as a potent upstream regulator of GCK down-regulation and β-cell apoptosis.
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Affiliation(s)
- Ji Yeon Kim
- Divisions of Metabolic Diseases, National Institutes of Health, Eunpyeong-gu, Seoul 122-701, Korea
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21
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Muraoka T, Murao K, Imachi H, Yu X, Li J, Wong NC, Ishida T. PREB regulates transcription of pancreatic glucokinase in response to glucose and cAMP. J Cell Mol Med 2010; 13:2386-2395. [PMID: 19267880 DOI: 10.1111/j.1582-4934.2008.00469.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Prolactin regulatory element binding (PREB) is a transcription factor that regulates prolactin promoter activity in rat anterior pituitary. The PREB protein is not only expressed in the anterior pituitary but also in the pancreas. We have recently reported that in pancreatic beta-cells, PREB regulates the transcription of the insulin gene in response to glucose stimulation. In the current study, we have examined the role of PREB in regulating glucokinase (GK) in pancreatic beta-cells. To analyse the effects of PREB on GK gene transcription, we employed a reporter gene assay. In the cells expressing or with knocked down PREB, GK expression was determined. GK expression was regulated by glucose and cAMP, and both glucose and cAMP stimulated the expression of PREB in a dose-dependent manner. Conversely, overexpression of PREB using a PREB-expressing adenovirus increased the expression of the GK protein. GK enzymatic activity was also significantly increased in the cells that stably expressed PREB. In addition, PREB induced GK promoter activity. Chromatin immunoprecipitation (ChIP) analyses showed that PREB mediated its transcriptional effect by binding to the PREB-responsive cis-element of the GK promoter. Finally, we used siRNA to inhibit PREB expression in cells and demonstrated that the knockdown of PREB attenuated the effects of glucose and cAMP on GK expression. Our data show that in pancreatic -cells, PREB regulates the transcription of the GK gene in response to glucose and cAMP.
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Affiliation(s)
- Tomie Muraoka
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan
| | - Koji Murao
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan
| | - Hitomi Imachi
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan
| | - Xiao Yu
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan
| | - Junhua Li
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan
| | - Norman Cw Wong
- Departments of Medicine and Biochemistry & Molecular Biology, Faculty of Medicine, University of Calgary, Health Sciences Center, Calgary, Alberta, Canada
| | - Toshihiko Ishida
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan
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22
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Chen G, Zhang Y, Lu D, Li NQ, Ross AC. Retinoids synergize with insulin to induce hepatic Gck expression. Biochem J 2009; 419:645-53. [PMID: 19173678 PMCID: PMC3789248 DOI: 10.1042/bj20082368] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hepatic GK (glucokinase) plays a key role in maintaining glucose homoeostasis. Many stimuli regulate GK activity by controlling its gene transcription. We hypothesized that endogenous lipophilic molecules modulate hepatic Gck expression. Lipophilic molecules were extracted from rat livers, saponified and re-constituted as an LE (lipophilic extract). LE synergized with insulin to induce primary hepatocyte, but not beta-cell, Gck expression in an SREBP-1c (sterol-regulatory-element-binding protein-1c)-independent manner. The dramatic induction of Gck mRNA resulted in a significant increase in GK activity. Subsequently, the active molecules were identified as retinol and retinal by MS after the purification of the active LE fractions. Retinoids synergized with insulin to induce Gck expression by the activation of both RAR [RA (retinoic acid) receptor] and RXR (retinoid X receptor). Inhibition of RAR activation completely abolished the effect of retinal. The hepatic GK specific activity and Gck mRNA levels of Zucker lean rats fed with a VAD [VA (vitamin A)-deficient] diet were significantly lower than those of rats fed with VAS (VA-sufficient) diet. Additionally, the hepatic Gck mRNA expression of Sprague-Dawley rats fed with a VAD diet was lower than that of rats fed with VA-marginal, -adequate or -supplemented diets. The reduced expression of Gck mRNA was increased after an intraperitoneal dose of RA in VAD rats. Furthermore, an intravenous injection of RA rapidly raised hepatic Gck expression in rats fed with a VAS control diet. Understanding the underlying mechanism that mediates the synergy may be helpful for developing a treatment strategy for patients with diabetes.
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Affiliation(s)
- Guoxun Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN 37996, U.S.A.
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23
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Yoshida K, Murao K, Imachi H, Cao WM, Yu X, Li J, Ahmed RAM, Kitanaka N, Wong NCW, Unterman TG, Magnuson MA, Ishida T. Pancreatic glucokinase is activated by insulin-like growth factor-I. Endocrinology 2007; 148:2904-13. [PMID: 17317782 DOI: 10.1210/en.2006-1149] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Glucokinase (GK) plays a key role in the regulation of glucose use and glucose-stimulated insulin secretion in pancreatic islet cells. Gene targeting of the IGF-I receptor down-regulated pancreatic islet GK activity. That finding prompted us to examine the potential mechanism that may control GK gene activity using an islet cell line, INS-1, known to express IGF-I receptor. Exposure of these cells to IGF-I induced GK protein expression and activity of the enzyme in a dose-dependent manner. In addition, IGF-I induced activity of a reporter construct containing the GK promoter in parallel with the effect on endogenous GK mRNA levels. The stimulatory effect of IGF-I on GK promoter activity was abrogated by wortmannin and LY294002, specific inhibitors of phosphatidylinositol 3-kinase. Exposure of cells to IGF-I elicited a rapid phosphorylation of Akt and FoxO1, a known target of Akt signaling. Constitutively active Akt stimulates the activity of the GK promoter, and a dominant-negative mutant of Akt or mutagenesis of a FoxO1 response element in the GK promoter abolished the ability of IGF-I to stimulate the promoter activity. Furthermore, cell knockdown of FoxO1 with small interfering RNA disrupted the effect of IGF-I on GK expression. These results demonstrate that the phosphatidylinositol 3-kinase/Akt/FoxO1 pathway contributes to the regulation of GK gene expression in response to IGF-I stimulation.
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Affiliation(s)
- Kazuya Yoshida
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, 1750-1 Miki-cho, Kita-gun, Kagawa 761-0793, Japan
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24
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Zitzer H, Wente W, Brenner MB, Sewing S, Buschard K, Gromada J, Efanov AM. Sterol regulatory element-binding protein 1 mediates liver X receptor-beta-induced increases in insulin secretion and insulin messenger ribonucleic acid levels. Endocrinology 2006; 147:3898-905. [PMID: 16644917 DOI: 10.1210/en.2005-1483] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Liver X receptors (LXRalpha and LXRbeta) regulate glucose and lipid metabolism. Pancreatic beta-cells and INS-1E insulinoma cells express only the LXRbeta isoform. Activation of LXRbeta with the synthetic agonist T0901317 increased glucose-induced insulin secretion and insulin content, whereas deletion of the receptor in LXRbeta knockout mice severely blunted insulin secretion. Analysis of gene expression in LXR agonist-treated INS-1E cells and islets from LXRbeta-deficient mice revealed that LXRbeta positively regulated expression of ATP-binding cassette transporter A1 (ABCA1), sterol regulatory element-binding protein 1 (SREBP-1), insulin, PDX-1, glucokinase, and glucose transporter 2 (Glut2). Down-regulation of SREBP-1 expression with the specific small interfering RNA blocked basal and LXRbeta-induced expression of pancreatic duodenal homeobox 1 (PDX-1), insulin, and Glut2 genes. SREBP-1 small interfering RNA also prevented an increase in insulin secretion and insulin content induced by T0901317. Moreover, 5-(tetradecyloxy)-2-furoic acid, an inhibitor of the SREBP-1 target gene acetyl-coenzyme A carboxylase, blocked T0901317-induced stimulation of insulin secretion. In conclusion, activation of LXRbeta in pancreatic beta-cells increases insulin secretion and insulin mRNA expression via SREBP-1-regulated pathway. These data support the role of LXRbeta, SREBP-1, and cataplerosis/anaplerosis pathways in the control of insulin secretion in pancreatic beta-cells.
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Affiliation(s)
- Heike Zitzer
- Lilly Research Laboratories, Essener Bogen 7, D-22419 Hamburg, Germany
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25
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Colakoglu N, Kukner A, Oner J, Sonmez MF, Oner H, Ozan E. Effects of high dose retinoic acid on TGF-β2 expression during pancreatic organogenesis. J Mol Histol 2006; 36:413-8. [PMID: 16479313 DOI: 10.1007/s10735-005-9013-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Accepted: 12/13/2005] [Indexed: 10/25/2022]
Abstract
The aim of this study was to investigate the effects of excess all-trans retinoic acid, a vitamin A metabolite, on pancreatic organogenesis and TGF-beta2 expression during prenatal development in rats. First group of animals used as control while a single dose of 60 mg/kg all-trans retinoic acid was ingested by the mothers, at day 8 of gestation (before the neurulation period) in group II and at day 12 of gestation (after the neurulation period) in group III, and all embryos were sacrificed at day 18 of gestation. TGF-beta2 expression was detected in the capsule, acini and Langerhans islets in the control group. In the pancreas of group II, dilatation and congestion of interlobular vessels were observed. Langerhans islet structures were completely absent. Moreover acinar TGF-beta2 immune reactivity was not determined. In group III, acinar expression of TGF-beta2 in acid was similar to that in the controls but their Langerhans islets TGF-beta2 immune reactivity was significantly less than the controls. In view of the present findings we suggest that TGF-beta2 plays important role in pancreatic morphogenesis and administration of excess all-trans retinoic acid before neurulation inhibit TGF-beta2 expression disrupted pancreatic morphogenesis particularly Langerhans islets. However, its administration after neurulation had less adverse affect on pancreatic organogenesis and TGF-beta2 immune reactivity.
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Affiliation(s)
- Neriman Colakoglu
- Histology and Embryology Department, Medical Faculty, Firat University, Elazig, Turkey.
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26
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Efanov AM, Sewing S, Bokvist K, Gromada J. Liver X receptor activation stimulates insulin secretion via modulation of glucose and lipid metabolism in pancreatic beta-cells. Diabetes 2004; 53 Suppl 3:S75-8. [PMID: 15561926 DOI: 10.2337/diabetes.53.suppl_3.s75] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Liver X receptors (LXRs) alpha and beta, transcription factors of a nuclear hormone receptor family, are expressed in pancreatic islets as well as glucagon-secreting and insulin-secreting cell lines. Culture of pancreatic islets or insulin-secreting MIN6 cells with a LXR specific agonist T0901317 caused an increase in glucose-dependent insulin secretion and islet insulin content. The stimulatory effect of T0901317 on insulin secretion was observed only after >72 h of islet culture with the compound. In MIN6 cells, T0901317 increased protein expression of lipogenic enzymes, fatty acid synthase, and acetyl-CoA carboxylase. LXR activation also produced an increase in glucokinase protein and pyruvate carboxylase (PC) activity levels. The PC inhibitor phenylacetic acid abolished the increase in insulin secretion in cells treated with T0901317. The results suggest that LXRs can control insulin secretion and biosynthesis via regulation of glucose and lipid metabolism in pancreatic beta-cells.
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Affiliation(s)
- Alexander M Efanov
- Lilly Research Laboratories, Essener Strasse 93, D-22419 Hamburg, Germany.
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27
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Erasmus C, Penny C, Kramer B. Retinoic acid increases the length and volume density of ducts in the rat embryonic pancreas. Dev Growth Differ 2003; 45:199-207. [PMID: 12752507 DOI: 10.1034/j.1600-0854.2004.00685.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In this study, the role of all-trans retinoic acid (RA) on the proliferation of rat embryonic pancreas ducts and on the proportion of insulin cells was investigated. All-trans RA (10-6 m) was added to Ham's F12.ITS serum-free medium in which 12.5 day rat dorsal pancreatic buds were cultured on Matrigel. Control explants were cultured on Matrigel in Ham's F12.ITS alone or in Ham's F12.ITS containing ethanol (the diluent for RA). After a 7 day culture period, explants were incubated with bromodeoxyuridine (BrdU) for assessment of cell proliferation. Explants were processed for both morphometry and immunocytochemistry. The length density and volume density of the pancreatic ducts were assessed using an image analysis system. Cells positive for insulin, BrdU and glucagon were localized on adjacent serial sections. RA treatment caused a statistically significant increase in the volume density (P < 0.007) and length density (P < 0.008) of the ducts, as well as a 1.2-fold increase (P < 0.0001) in the proportion of insulin to glucagon cells, compared to both control groups. Few insulin cells were BrdU positive, indicating that cells had a low proliferation rate. The increased proportion of insulin cells may relate to the increased volume density and length density of the ducts in RA-treated explants. It is suggested that RA stimulated the production of additional progenitor cells and not proliferation of existing insulin cells.
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Affiliation(s)
- Carene Erasmus
- Embryonic Differentiation and Development Research Program, School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, South Africa.
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Tulachan SS, Doi R, Kawaguchi Y, Tsuji S, Nakajima S, Masui T, Koizumi M, Toyoda E, Mori T, Ito D, Kami K, Fujimoto K, Imamura M. All-trans retinoic acid induces differentiation of ducts and endocrine cells by mesenchymal/epithelial interactions in embryonic pancreas. Diabetes 2003; 52:76-84. [PMID: 12502496 DOI: 10.2337/diabetes.52.1.76] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Retinoids during the embryonic period act as a mesenchymal inducer in many organs, including kidney, lung, central nervous system, and gut. Retinoic acid (RA) demonstrates insulinotropic effects in adult pancreas, but only a limited study has elucidated its role in pancreatic organogenesis. In this study, we have analyzed the existence of RA-signaling machinery in embryonic pancreas and evaluated its role using in vitro tissue culture experiments. Here we show the presence of endogenous retinaldehyde dehydrogenase 2 (RALDH2), the most effective RA-synthesizing enzyme, RA-binding proteins, and RA receptors (RARs) in embryonic pancreatic tissue. RALDH2 is expressed exclusively in the mesenchyme. Exogenously added all-trans-retinoic acid (atRA) in tissue culture experiments stimulated differentiation of endocrine and duct cells and promoted apoptotic cell death of acinar tissue. Furthermore, we demonstrate that atRA upregulates the PDX-1 expression. Taken together, our data suggest that atRA-mediated mesenchymal/epithelial interactions play an important role in determining the cell fate of epithelial cells via regulation of the PDX-1 gene, leading to the proper formation of the endocrine versus exocrine component during pancreatic organogenesis.
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Affiliation(s)
- Sidhartha Singh Tulachan
- Department of Surgery and Surgical Basic Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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29
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Abstract
Glucokinase (GK) serves as glucose sensor in pancreatic beta-cells and in other glucose sensor cells in the body. Biochemical genetic studies have characterized many activating and inactivating GK mutants that have been discovered in patients with hyperinsulinemic hypoglycemia or diabetes, all inherited as autosomal dominant traits. Mathematical modeling of the kinetic data of recombinant human wild-type and mutant GK accurately predicts the effects of GK mutations on the threshold of glucose-stimulated insulin release and glucose homeostasis. Structure/function studies of the enzyme suggest the existence of a hitherto unknown allosteric activator site of the enzyme that has significant implications for the physiological chemistry of GK-containing cells, particularly the pancreatic beta-cells. Glucose is the preeminent positive regulator of beta-cell GK expression and involves molecular mechanisms that are still to be elucidated in detail, but seem to have a specific requirement for increased glucose metabolism. Pharmaceutical chemists, motivated by the clear tenets of the GK glucose-sensor paradigm, have searched for and have discovered a novel class of GK activator molecules. The therapeutic application of this basic discovery offers a new principle for drug therapy of diabetes.
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Affiliation(s)
- Franz M Matschinsky
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
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Blumentrath J, Neye H, Verspohl EJ. Effects of retinoids and thiazolidinediones on proliferation, insulin release, insulin mRNA, GLUT 2 transporter protein and mRNA of INS-1 cells. Cell Biochem Funct 2001; 19:159-69. [PMID: 11494305 DOI: 10.1002/cbf.907] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Both 9-cis-retinoic acid (9cRA) and all-trans-retinoic acid (ATRA) are active metabolites of vitamin A (retinol). There exists an interaction between retinoid receptors and peroxisome proliferator-activated receptors (PPARgamma). To define their functions in an insulin secreting system the effects of ATRA, 9cRA and the PPARgamma agonist rosiglitazone on cell proliferation, insulin release and glucose transporter (GLUT) 2 of INS-1 cells were tested. Retinoic acid receptor (RAR-alpha and -gamma) and retinoid X receptor (RXR-alpha and -beta) proteins are present (immunoblots). Both 9cRA and ATRA inhibit INS-1 cell proliferation ([3H]-thymidine assay) in a concentration dependent manner. Both 9cRA and ATRA increased insulin release, but only ATRA ralsed the GLUT 2 mRNA in a bell-shaped concentration response curve after 48 h. The insulinotropic effect of one compound is not significantly superimposed by the other indicating that the same binding sites are used by 9cRA and ATRA. The acute and chronic effects of the PPARgamma agonist rosiglitazone on insulin release were additionally determined since glitazones act as transcription factors together with RXR agonists. At high concentrations (100 microM) rosiglitazone inhibited glucose (8.3 mM) stimulated insulin secretion (acute experiment over 60 min). Insulin secretion, however, was increased during a 24 h treatment at a concentration of 10 microM and again inhibited at 100 microM. Changes in preproinsulin mRNA expression were not observed. Rosiglitazone (100 microM) increased GLUT 2 mRNA paralleled by an increase of GLUT 2 protein, but only after 24 h of treatment. This data indicate that RAR and RXR mediate insulin release. The changes in GLUT 2 have no direct impact on insulin release; the inhibition seen at high concentrations of either compound is possibly the result of the observed inhibition of cell proliferation. Effects of rosiglitazone on preproinsulin mRNA and GLUT 2 (mRNA and protein) do not play a role in modulating insulin secretion. With the presence of an RXR receptor agonist the effect of rosiglitazone on insulin release becomes stimulatory. Thus the effects of RAR-, RXR agonists and rosiglitazone depend on their concentrations, the duration of their presence and are due to specific interactions.
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Affiliation(s)
- J Blumentrath
- Department of Pharmacology, Institute of Pharmaceutical Chemistry, University of Münster, Hittorfstr. 58-62, 48149 Münster
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Player AN, Shen LP, Kenny D, Antao VP, Kolberg JA. Single-copy gene detection using branched DNA (bDNA) in situ hybridization. J Histochem Cytochem 2001; 49:603-12. [PMID: 11304798 DOI: 10.1177/002215540104900507] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We have developed a branched DNA in situ hybridization (bDNA ISH) method for detection of human papillomavirus (HPV) DNA in whole cells. Using human cervical cancer cell lines with known copies of HPV DNA, we show that the bDNA ISH method is highly sensitive, detecting as few as one or two copies of HPV DNA per cell. By modifying sample pretreatment, viral mRNA or DNA sequences can be detected using the same set of oligonucleotide probes. In experiments performed on mixed populations of cells, the bDNA ISH method is highly specific and can distinguish cells with HPV-16 from cells with HPV-18 DNA. Furthermore, we demonstrate that the bDNA ISH method provides precise localization, yielding positive signals retained within the subcellular compartments in which the target nucleic acid sequences are localized. As an effective and convenient means for nucleic acid detection, the bDNA ISH method is applicable to the detection of cancers and infectious agents. (J Histochem Cytochem 49:603-611, 2001)
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Affiliation(s)
- A N Player
- Bayer Diagnostics, 4560 Horton Street, Emeryville, CA 94608-2916, USA
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Fernandez-Mejia C, Vega-Allende J, Rojas-Ochoa A, Rodriguez-Dorantes M, Romero-Navarro G, Matschinsky FM, Wang J, German MS. Cyclic adenosine 3',5'-monophosphate increases pancreatic glucokinase activity and gene expression. Endocrinology 2001; 142:1448-52. [PMID: 11250924 DOI: 10.1210/endo.142.4.8100] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Comparison of the pancreatic and hepatic glucokinase gene transcripts reveals tissue-specific control of expression and the existence of two distinct promoters in a single glucokinase gene. The existence of alternate promoters suggests that separate factors regulate glucokinase transcription in the two tissues. Hepatic glucokinase expression has been shown to be repressed by cAMP; however, in the pancreatic beta-cell it is unlikely that cAMP represses glucokinase activity, as cAMP is known to positively affect glucose-induced insulin secretion, a process that in mature islets requires pancreatic glucokinase activity. In this work we demonstrate that cAMP indeed has a stimulatory effect on pancreatic glucokinase. The cyclic nucleotide stimulates pancreatic glucokinase activity after 3-h incubation, and maximal effects are observed after 6 and 12 h of treatment. Using the bDNA assay, a sensitive signal amplification technique, we detected relative increases in glucokinase messenger RNA levels of 40.5 +/- 7.5% after 3-h incubation with cAMP. This stimulatory effect was increased to 106.3 +/- 22% after 6-h incubation and sustained up to 12 h of incubation. Inhibition of gene transcription by actinomycin D abolishes cAMP-induced glucokinase activity. In transfected fetal islets, cAMP increased the activity of the -1000 bp rat glucokinase promoter by 60 +/- 6%. These data demonstrate that cAMP has a stimulatory effect on pancreatic glucokinase gene expression and that the nucleotide has opposite effects on pancreatic and hepatic glucokinase, supporting the concept that glucokinase transcription in the liver and that in the beta-cell differ.
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Affiliation(s)
- C Fernandez-Mejia
- Nutritional Genetics Unit, Biomedical Research Institute, National University of México, México City, C.P. 04530, México.
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Morimoto S, Fernandez-Mejia C, Romero-Navarro G, Morales-Peza N, Díaz-Sánchez V. Testosterone effect on insulin content, messenger ribonucleic acid levels, promoter activity, and secretion in the rat. Endocrinology 2001; 142:1442-7. [PMID: 11250923 DOI: 10.1210/endo.142.4.8069] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Coexistence of hyperinsulinemia and hyperandrogenism in women has been frequently described. Most of the studies addressing this issue have focused on the mechanisms by which insulin produces hyperandrogenism. In the present study, we analyzed the effects of testosterone in vivo and in vitro upon insulin gene expression and release in the rat. Our studies demonstrate that testosterone increases insulin messenger RNA (mRNA) levels in vitro as well as in vivo. In both prepuberal and intact adult rats, serum testosterone concentrations were positively correlated with insulin mRNA levels and insulin concentration in serum. Testosterone deprivation after gonadectomy decreased both insulin gene expression and serum insulin concentration. Insulin mRNA levels were partially restored after 3 days of testosterone administration and serum insulin was 80% and 27% above baseline values at 5 and 7 days posttreatment. Primary cultured pancreatic islets treated with the sexual steroid increased about 80% insulin mRNA, as well as protein, and release. In transfected islets, testosterone increased the activity of the -410 bp rat insulin promoter I by 154%. These data demonstrate that testosterone has a direct effect upon pancreatic islet function by favoring insulin gene expression and release.
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Affiliation(s)
- S Morimoto
- Department of Reproductive Biology, National Institute of Medical Sciences and Nutrition Salvador Zubiran, National University of México, Tlalpan 14000, D.F. México City, México
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