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Li M, Zhang R, Ge Q, Yue L, Ma D, Khattab F, Xie W, Cui Y, Gilon P, Zhao X, Li X, Cheng R. Chemerin as an Inducer of β Cell Proliferation Mediates Mitochondrial Homeostasis and Promotes β Cell Mass Expansion. Int J Mol Sci 2023; 24:ijms24119136. [PMID: 37298086 DOI: 10.3390/ijms24119136] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 05/16/2023] [Accepted: 05/19/2023] [Indexed: 06/12/2023] Open
Abstract
Loss of the β cell population is a crucial feature of type 2 diabetes. Restoring the β cell mass by stimulating β cell proliferation and preventing its apoptosis was proposed as a therapeutic approach to treating diabetes. Therefore, researchers have been increasingly interested in identifying exogenous factors that can stimulate β cell proliferation in situ and in vitro. Adipokine chemerin, which is secreted from adipose tissue and the liver, has been identified as a chemokine that plays a critical role in the regulation of metabolism. In this study, we demonstrate that chemerin as a circulating adipokine promotes β cell proliferation in vivo and in vitro. Chemerin serum levels and the expression of the main receptors within islets are highly regulated under a variety of challenging conditions, including obesity and type 2 diabetes. As compared to their littermates, mice overexpressing chemerin had a larger islet area and increased β cell mass with both a normal and high-fat diet. Moreover, in chemerin-overexpressed mice, we observed improved mitochondrial homeostasis and increased insulin synthesis. In summary, our findings confirm the potential role of chemerin as an inducer of β cell proliferation, and they provide novel insights into the helpful strategy to expand β cell population.
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Affiliation(s)
- Min Li
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Ruifan Zhang
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Qian Ge
- The First Clinical College, Chongqing Medical University, Chongqing 400016, China
| | - Lingzhi Yue
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Dan Ma
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Firas Khattab
- Pôle d'Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Wenhua Xie
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Yewei Cui
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Patrick Gilon
- Pôle d'Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Xueya Zhao
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Xi Li
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
| | - Rui Cheng
- Institute of Life Sciences, School of Basic Medicine, Chongqing Medical University, Chongqing 400016, China
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Reiterer M, Gilani A, Lo JC. Pancreatic Islets as a Target of Adipokines. Compr Physiol 2022; 12:4039-4065. [PMID: 35950650 DOI: 10.1002/cphy.c210044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Rising rates of obesity are intricately tied to the type 2 diabetes epidemic. The adipose tissues can play a central role in protection against or triggering metabolic diseases through the secretion of adipokines. Many adipokines may improve peripheral insulin sensitivity through a variety of mechanisms, thereby indirectly reducing the strain on beta cells and thus improving their viability and functionality. Such effects will not be the focus of this article. Rather, we will focus on adipocyte-secreted molecules that have a direct effect on pancreatic islets. By their nature, adipokines represent potential druggable targets that can reach the islets and improve beta-cell function or preserve beta cells in the face of metabolic stress. © 2022 American Physiological Society. Compr Physiol 12:1-27, 2022.
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Affiliation(s)
- Moritz Reiterer
- Division of Cardiology, Department of Medicine, Weill Center for Metabolic Health, Cardiovascular Research Institute, Weill Cornell Medicine, New York, New York, USA
| | - Ankit Gilani
- Division of Cardiology, Department of Medicine, Weill Center for Metabolic Health, Cardiovascular Research Institute, Weill Cornell Medicine, New York, New York, USA
| | - James C Lo
- Division of Cardiology, Department of Medicine, Weill Center for Metabolic Health, Cardiovascular Research Institute, Weill Cornell Medicine, New York, New York, USA
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Biondi G, Marrano N, Borrelli A, Rella M, Palma G, Calderoni I, Siciliano E, Lops P, Giorgino F, Natalicchio A. Adipose Tissue Secretion Pattern Influences β-Cell Wellness in the Transition from Obesity to Type 2 Diabetes. Int J Mol Sci 2022; 23:ijms23105522. [PMID: 35628332 PMCID: PMC9143684 DOI: 10.3390/ijms23105522] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 05/11/2022] [Accepted: 05/13/2022] [Indexed: 12/10/2022] Open
Abstract
The dysregulation of the β-cell functional mass, which is a reduction in the number of β-cells and their ability to secure adequate insulin secretion, represents a key mechanistic factor leading to the onset of type 2 diabetes (T2D). Obesity is recognised as a leading cause of β-cell loss and dysfunction and a risk factor for T2D. The natural history of β-cell failure in obesity-induced T2D can be divided into three steps: (1) β-cell compensatory hyperplasia and insulin hypersecretion, (2) insulin secretory dysfunction, and (3) loss of β-cell mass. Adipose tissue (AT) secretes many hormones/cytokines (adipokines) and fatty acids that can directly influence β-cell function and viability. As this secretory pattern is altered in obese and diabetic patients, it is expected that the cross-talk between AT and pancreatic β-cells could drive the maintenance of the β-cell integrity under physiological conditions and contribute to the reduction in the β-cell functional mass in a dysmetabolic state. In the current review, we summarise the evidence of the ability of the AT secretome to influence each step of β-cell failure, and attempt to draw a timeline of the alterations in the adipokine secretion pattern in the transition from obesity to T2D that reflects the progressive deterioration of the β-cell functional mass.
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Abstract
Leptin is a pluripotent peptide hormone produced mainly by adipocytes, as well as by other tissues such as the stomach. Leptin primarily acts on the central nervous system, particularly the hypothalamus, where this hormone regulates energy homeostasis and neuroendocrine function. Owing to this, disruption of leptin signaling has been linked with numerous pathological conditions. Recent studies have also highlighted the diverse roles of leptin in the digestive system including immune regulation, cell proliferation, tissue healing, and glucose metabolism. Of note, leptin acts differently under physiological and pathological conditions. Here, we review the current knowledge on the functions of leptin and its downstream signaling in the gastrointestinal tract and accessory digestive organs, with an emphasis on its physiological and pathological implications. We also discuss the current therapeutic uses of recombinant leptin, as well as its limitations.
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Affiliation(s)
- Min-Hyun Kim
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Hyeyoung Kim
- Department of Food and Nutrition, College of Human Ecology, Yonsei University, Seoul, Korea
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Schanton M, Maymó JL, Pérez-Pérez A, Sánchez-Margalet V, Varone CL. Involvement of leptin in the molecular physiology of the placenta. Reproduction 2017; 155:R1-R12. [PMID: 29018059 DOI: 10.1530/rep-17-0512] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 09/28/2017] [Accepted: 10/09/2017] [Indexed: 12/26/2022]
Abstract
Leptin is a homeostatic regulator in the placenta where it promotes proliferation, protein synthesis and the expression of tolerogenic maternal response molecules such as HLA-G. Leptin also exerts an anti-apoptotic action in placenta controlling the expression of p53 master cell cycle regulator under different stress conditions. On the other hand, leptin is an integrative target of different placental stimuli. The expression of leptin in placenta is regulated by hCG, insulin, steroids, hypoxia and many other growth hormones, suggesting that it might have an important endocrine function in the trophoblastic cells. The leptin expression is induced involving the cAMP/PKA or cAMP/Epac pathways which have profound actions upon human trophoblast function. The activation of PI3K and MAPK pathways also participates in the leptin expression. Estrogens play a central role during pregnancy, particularly 17β-estradiol upregulates the leptin expression in placental cells through genomic and non-genomic actions. The leptin promoter analysis reveals specific elements that are active in placental cells. The transcription factors CREB, AP1, Sp1, NFκB and the coactivator CBP are involved in the placental leptin expression. Moreover, placental leptin promoter is a target of epigenetic marks such as DNA methylation and histone acetylation that regulates not only the leptin expression in placenta during pregnancy but also determines the predisposition of acquiring adult metabolism diseases. Taken together, all these results allow a better understanding of leptin function and regulatory mechanisms of leptin expression in human placental trophoblasts, and support the importance of leptin during pregnancy and in programming adult health.
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Affiliation(s)
- Malena Schanton
- Departamento de Química BiológicaUniversidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina.,Universidad de Buenos AiresCONICET, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), Buenos Aires, Argentina
| | - Julieta L Maymó
- Departamento de Química BiológicaUniversidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina.,Universidad de Buenos AiresCONICET, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), Buenos Aires, Argentina
| | - Antonio Pérez-Pérez
- Departamento de Bioquímica Médica y Biología MolecularHospital Universitario Virgen Macarena, Facultad de Medicina, Universidad de Sevilla, Sevilla, España
| | - Víctor Sánchez-Margalet
- Departamento de Bioquímica Médica y Biología MolecularHospital Universitario Virgen Macarena, Facultad de Medicina, Universidad de Sevilla, Sevilla, España
| | - Cecilia L Varone
- Departamento de Química BiológicaUniversidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina .,Universidad de Buenos AiresCONICET, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), Buenos Aires, Argentina
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Sobrinho Santos EM, Guimarães TA, Santos HO, Cangussu LMB, de Jesus SF, Fraga CADC, Cardoso CM, Santos SHS, de Paula AMB, Gomez RS, Guimarães ALS, Farias LC. Leptin acts on neoplastic behavior and expression levels of genes related to hypoxia, angiogenesis, and invasiveness in oral squamous cell carcinoma. Tumour Biol 2017; 39:1010428317699130. [PMID: 28459203 DOI: 10.1177/1010428317699130] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Leptin, one of the main hormones controlling energy homeostasis, has been associated with different cancer types. In oral cancer, its effect is not well understood. We investigated, through in vitro and in vivo assays, whether leptin can affect the neoplastic behavior of oral squamous cell carcinoma. Expression of genes possibly linked to the leptin pathway was assessed in leptin-treated oral squamous cell carcinoma cells and also in tissue samples of oral squamous cell carcinoma and oral mucosa, including leptin, leptin receptor, hypoxia-inducible factor 1-alpha, E-cadherin, matrix metalloproteinase-2, matrix metalloproteinase-9, Col1A1, Ki67, and mir-210. Leptin treatment favored higher rates of cell proliferation and migration, and reduced apoptosis. Accordingly, leptin-treated oral squamous cell carcinoma cells show decreased messenger RNA caspase-3 expression, and increased levels of E-cadherin, Col1A1, matrix metalloproteinase-2, matrix metalloproteinase-9, and mir-210. In tissue samples, hypoxia-inducible factor 1-alpha messenger RNA and protein expression of leptin and leptin receptor were high in oral squamous cell carcinoma cases. Serum leptin levels were increased in first clinical stages of the disease. In animal model, oral squamous cell carcinoma-induced mice show higher leptin receptor expression, and serum leptin level was increased in dysplasia group. Our findings suggest that leptin seems to exert an effect on oral squamous cell carcinoma cells behavior and also on molecular markers related to cell proliferation, migration, and tumor angiogenesis.
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Affiliation(s)
- Eliane Macedo Sobrinho Santos
- 1 Department of Dentistry, Universidade Estadual de Montes Claros, Montes Claros, Brazil.,2 Instituto Federal do Norte de Minas Gerais-Campus Araçuaí, Montes Claros, Brazil
| | | | | | | | | | | | | | - Sérgio Henrique Souza Santos
- 4 Institute of Agricultural Sciences, Food Engineering College, Universidade Federal de Minas Gerais (UFMG), Montes Claros, Minas Gerais, Brazil
| | | | - Ricardo Santiago Gomez
- 5 Department of Oral Surgery and Pathology, School of Dentistry, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, Brazil
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Sunflower Oil but Not Fish Oil Resembles Positive Effects of Virgin Olive Oil on Aged Pancreas after Life-Long Coenzyme Q Addition. Int J Mol Sci 2015; 16:23425-45. [PMID: 26426013 PMCID: PMC4632707 DOI: 10.3390/ijms161023425] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/21/2015] [Accepted: 09/22/2015] [Indexed: 12/15/2022] Open
Abstract
An adequate pancreatic structure is necessary for optimal organ function. Structural changes are critical in the development of age-related pancreatic disorders. In this context, it has been reported that different pancreatic compartments from rats were affected according to the fat composition consumed. Since there is a close relationship between mitochondria, oxidative stress and aging, an experimental approach has been developed to gain more insight into this process in the pancreas. A low dosage of coenzyme Q was administered life-long in rats in order to try to prevent pancreatic aging-related alterations associated to some dietary fat sources. According to that, three groups of rats were fed normocaloric diets containing Coenzyme Q (CoQ) for two years, where virgin olive, sunflower, or fish oil was included as unique fat source. Pancreatic samples for microscopy and blood samples were collected at the moment of euthanasia. The main finding is that CoQ supplementation gives different results according to fat used in diet. When sunflower oil was the main fat in the diet, CoQ supplementation seems to improve endocrine pancreas structure and in particular β-cell mass resembling positive effects of virgin olive oil. Conversely, CoQ intake does not seem to improve the structural alterations of exocrine compartment previously observed in fish oil fed rats. Therefore CoQ may improve pancreatic alterations associated to the chronic intake of some dietary fat sources.
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Abstract
INTRODUCTION Leptin, a 16 kDa anti-obesity hormone, exhibits various physiological properties. Interestingly, skin wound healing was proven to delay in leptin-deficient ob/ob mice. However, little is known on the mechanisms of this phenomenon. In this study, we attempted to elucidate a role of leptin in wound healing of skin. METHODS Immunohistochemical analysis was performed to confirm the expression of the leptin receptor (Ob-R) in human and mouse skin. Leptin was topically administered to chemical wounds created in mouse back skin along with sustained-release absorbable hydrogel. The process of wound repair was histologically observed and the area of ulceration was measured over time. The effect of leptin on the proliferation, differentiation and migration of human epidermal keratinocytes was investigated. RESULTS Ob-R was expressed in epidermal cells of human and mouse skin. Topical administration of leptin significantly promoted wound healing. Histological analysis showed more blood vessels in the dermal connective tissues in the leptin-treated group. The proliferation, differentiation/function and migration of human epidermal keratinocytes were enhanced by exogenous leptin. CONCLUSION Topically administered leptin was proven to promote wound healing in the skin by accelerating proliferation, differentiation/function and migration of epidermal keratinocytes and enhancing angiogenesis around the wounded area. These results strongly suggest that topical administration of leptin may be useful as a treatment to promote wound healing in the skin.
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Masjkur J, Arps-Forker C, Poser SW, Nikolakopoulou P, Toutouna L, Chenna R, Chavakis T, Chatzigeorgiou A, Chen LS, Dubrovska A, Choudhary P, Uphues I, Mark M, Bornstein SR, Androutsellis-Theotokis A. Hes3 is expressed in the adult pancreatic islet and regulates gene expression, cell growth, and insulin release. J Biol Chem 2014; 289:35503-16. [PMID: 25371201 DOI: 10.1074/jbc.m114.590687] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The transcription factor Hes3 is a component of a signaling pathway that supports the growth of neural stem cells with profound consequences in neurodegenerative disease models. Here we explored whether Hes3 also regulates pancreatic islet cells. We showed that Hes3 is expressed in human and rodent pancreatic islets. In mouse islets it co-localizes with alpha and beta cell markers. We employed the mouse insulinoma cell line MIN6 to perform in vitro characterization and functional studies in conditions known to modulate Hes3 based upon our previous work using neural stem cell cultures. In these conditions, cells showed elevated Hes3 expression and nuclear localization, grew efficiently, and showed higher evoked insulin release responses, compared with serum-containing conditions. They also exhibited higher expression of the transcription factor Pdx1 and insulin. Furthermore, they were responsive to pharmacological treatments with the GLP-1 analog Exendin-4, which increased nuclear Hes3 localization. We employed a transfection approach to address specific functions of Hes3. Hes3 RNA interference opposed cell growth and affected gene expression as revealed by DNA microarrays. Western blotting and PCR approaches specifically showed that Hes3 RNA interference opposes the expression of Pdx1 and insulin. Hes3 overexpression (using a Hes3-GFP fusion construct) confirmed a role of Hes3 in regulating Pdx1 expression. Hes3 RNA interference reduced evoked insulin release. Mice lacking Hes3 exhibited increased islet damage by streptozotocin. These data suggest roles of Hes3 in pancreatic islet function.
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Affiliation(s)
| | | | | | | | | | - Ramu Chenna
- the Applied Bioinformatics Group, BioInnovations Zentrum, University of Dresden, 01307 Dresden, Germany
| | - Triantafyllos Chavakis
- the Department of Clinical Pathobiochemistry, Institute for Clinical Chemistry and Laboratory Medicine and
| | - Antonios Chatzigeorgiou
- the Department of Clinical Pathobiochemistry, Institute for Clinical Chemistry and Laboratory Medicine and
| | - Lan-Sun Chen
- the Department of Clinical Pathobiochemistry, Institute for Clinical Chemistry and Laboratory Medicine and
| | - Anna Dubrovska
- Department of Medicine, OncoRay National Center for Radiation Research in Oncology, Medical Faculty Carl Gustav Carus, Dresden University of Technology, 01307 Dresden, Germany
| | - Pratik Choudhary
- the Diabetes Research Group, King's College London, London SE5 9RS, United Kingdom
| | - Ingo Uphues
- the Department of CardioMetabolic Diseases Research, Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach, Germany, and
| | - Michael Mark
- the Department of CardioMetabolic Diseases Research, Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach, Germany, and
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Umeki H, Tokuyama R, Ide S, Okubo M, Tadokoro S, Tezuka M, Tatehara S, Satomura K. Leptin promotes wound healing in the oral mucosa. PLoS One 2014; 9:e101984. [PMID: 25033454 PMCID: PMC4102470 DOI: 10.1371/journal.pone.0101984] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 06/13/2014] [Indexed: 01/02/2023] Open
Abstract
INTRODUCTION Leptin, a 16 kDa circulating anti-obesity hormone, exhibits many physiological properties. Recently, leptin was isolated from saliva; however, its function in the oral cavity is still unclear. In this study, we investigated the physiological role of leptin in the oral cavity by focusing on its effect on wound healing in the oral mucosa. METHODS Immunohistochemical analysis was used to examine the expression of the leptin receptor (Ob-R) in human/rabbit oral mucosa. To investigate the effect of leptin on wound healing in the oral mucosa, chemical wounds were created in rabbit oral mucosa, and leptin was topically administered to the wound. The process of wound repair was histologically observed and quantitatively analyzed by measuring the area of ulceration and the duration required for complete healing. The effect of leptin on the proliferation, differentiation and migration of human oral mucosal epithelial cells (RT7 cells) was investigated using crystal violet staining, reverse transcription polymerase chain reaction (RT-PCR) and a wound healing assay, respectively. RESULTS Ob-R was expressed in spinous/granular cells in the epithelial tissue and vascular endothelial cells in the subepithelial connective tissue of the oral mucosa. Topical administration of leptin significantly promoted wound healing and shortened the duration required for complete healing. Histological analysis of gingival tissue beneath the ulceration showed a denser distribution of blood vessels in the leptin-treated group. Although the proliferation and differentiation of RT7 cells were not affected by leptin, the migration of these cells was accelerated in the presence of leptin. CONCLUSION Topically administered leptin was shown to promote wound healing in the oral mucosa by accelerating epithelial cell migration and enhancing angiogenesis around the wounded area. These results strongly suggest that topical administration of leptin may be useful as a treatment to promote wound healing in the oral mucosa.
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Affiliation(s)
- Hirochika Umeki
- Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Yokohama, Kanagawa, Japan
| | - Reiko Tokuyama
- Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Yokohama, Kanagawa, Japan
| | - Shinji Ide
- Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Yokohama, Kanagawa, Japan
| | - Mitsuru Okubo
- Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Yokohama, Kanagawa, Japan
| | - Susumu Tadokoro
- Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Yokohama, Kanagawa, Japan
| | - Mitsuki Tezuka
- Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Yokohama, Kanagawa, Japan
| | - Seiko Tatehara
- Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Yokohama, Kanagawa, Japan
| | - Kazuhito Satomura
- Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Yokohama, Kanagawa, Japan
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Procaccini C, De Rosa V, Galgani M, Carbone F, La Rocca C, Formisano L, Matarese G. Role of adipokines signaling in the modulation of T cells function. Front Immunol 2013; 4:332. [PMID: 24151494 PMCID: PMC3799205 DOI: 10.3389/fimmu.2013.00332] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 10/01/2013] [Indexed: 12/15/2022] Open
Abstract
The field that links immunity and metabolism is rapidly expanding. Apparently non-immunological disorders such as obesity and type 2 diabetes have been linked to immune dysregulation, suggesting that metabolic alterations can be induced by or be consequence of an altered self-immune tolerance. In this context, adipose tissue produces and releases a variety of pro-inflammatory and anti-inflammatory factors, termed "adipokines," which can be considered as the bridge between obesity-related exogenous factors, such as nutrition and lifestyle, and the molecular events leading to metabolic syndrome, inflammatory, and/or autoimmune conditions. In obesity, increased production of most adipokines impacts on multiple functions such as appetite and energy balance, modulation of immune responses, insulin sensitivity, angiogenesis, blood pressure, lipid metabolism, and so on. This report aims to discuss some of the recent topics of adipocytokine research and their related signaling pathways, that may be of particular importance as could lead to effective therapeutic strategies for obesity-associated diseases.
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Affiliation(s)
- Claudio Procaccini
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Salerno, Salerno, Italy
- Laboratorio di Immunologia, Istituto di Endocrinologia e Oncologia Sperimentale, Consiglio Nazionale delle Ricerche (IEOS-CNR), Napoli, Italy
| | - Veronica De Rosa
- Laboratorio di Immunologia, Istituto di Endocrinologia e Oncologia Sperimentale, Consiglio Nazionale delle Ricerche (IEOS-CNR), Napoli, Italy
- Unità di Neuroimmunologia, IRCCS Fondazione Santa Lucia, Roma, Italy
| | - Mario Galgani
- Laboratorio di Immunologia, Istituto di Endocrinologia e Oncologia Sperimentale, Consiglio Nazionale delle Ricerche (IEOS-CNR), Napoli, Italy
| | - Fortunata Carbone
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Salerno, Salerno, Italy
- Laboratorio di Immunologia, Istituto di Endocrinologia e Oncologia Sperimentale, Consiglio Nazionale delle Ricerche (IEOS-CNR), Napoli, Italy
| | - Claudia La Rocca
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Salerno, Salerno, Italy
- Laboratorio di Immunologia, Istituto di Endocrinologia e Oncologia Sperimentale, Consiglio Nazionale delle Ricerche (IEOS-CNR), Napoli, Italy
| | - Luigi Formisano
- Department of Biological, Geological and Environmental Sciences, Division of Pharmacology, University of Sannio, Benevento, Italy
| | - Giuseppe Matarese
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Salerno, Salerno, Italy
- IRCCS MultiMedica, Milano, Italy
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Han D, Yamamoto Y, Munesue S, Motoyoshi S, Saito H, Win MTT, Watanabe T, Tsuneyama K, Yamamoto H. Induction of receptor for advanced glycation end products by insufficient leptin action triggers pancreatic β-cell failure in type 2 diabetes. Genes Cells 2013; 18:302-14. [PMID: 23410183 DOI: 10.1111/gtc.12036] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 12/18/2012] [Indexed: 12/31/2022]
Abstract
Glucolipotoxicity, which is exerted by free fatty acids (FFA) and prolonged hyperglycemia, is implicated in pancreatic β-cell failure in diabetes. Pattern recognition receptors such as receptor for advanced glycation end products (RAGE) and toll-like receptors 2 and 4 could mediate danger signals in β-cells. We examined whether RAGE contributes to β-cell failure in a type 2 diabetes mouse model. Pancreatic islets were isolated from ob/ob, db/db, diet-induced obesity (DIO), RAGE-null (RAGE(-/-) ), and RAGE(+/+) wild-type (WT) control mice and dispersed into single cells for flow cytometry. RAGE expression was detected in insulin-positive β-cells of ob/ob and db/db mice, but not of WT, DIO, or RAGE(-/-) mice: thus, inadequate leptin receptor signaling and RAGE expression may be linked. Compared with RAGE(+/+) db/db mice, RAGE(-/-) db/db mice showed higher β-cell number and mass with less apoptosis as well as glucose tolerance with higher insulin secretion without any differences in serum levels of FFA and adiponectin. Palmitate or oleate pretreatment combined with a leptin antagonist induced RAGE expression, AGE-elicited apoptosis, and impaired glucose-stimulated insulin secretion by advanced glycation end products (AGE) in MIN6 cells. FFA elevation with concomitant AGE formation during prolonged hyperglycemia could cause β-cell damage through insufficient leptin action and subsequent RAGE induction in type 2 diabetes.
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Affiliation(s)
- Dong Han
- Department of Biochemistry and Molecular Vascular Biology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, 920-8640, Japan
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Pijet M, Pijet B, Litwiniuk A, Pajak B, Gajkowska B, Orzechowski A. Leptin impairs myogenesis in C2C12 cells through JAK/STAT and MEK signaling pathways. Cytokine 2013. [DOI: 10.1016/j.cyto.2012.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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14
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Abstract
β-Cell failure coupled with insulin resistance is a key factor in the development of type 2 diabetes. Changes in circulating levels of adipokines, factors released from adipose tissue, form a significant link between excessive adiposity in obesity and both aforementioned factors. In this review, we consider the published evidence for the role of individual adipokines on the function, proliferation, death and failure of β-cells, focusing on those reported to have the most significant effects (leptin, adiponectin, tumour necrosis factor α, resistin, visfatin, dipeptidyl peptidase IV and apelin). It is apparent that some adipokines have beneficial effects whereas others have detrimental properties; the overall contribution to β-cell failure of changed concentrations of adipokines in the blood of obese pre-diabetic subjects will be highly dependent on the balance between these effects and the interactions between the adipokines, which act on the β-cell via a number of intersecting intracellular signalling pathways. We emphasise the importance, and comparative dearth, of studies into the combined effects of adipokines on β-cells.
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Affiliation(s)
- Simon J Dunmore
- Diabetes and Metabolic Disease Research Group, Research Institute in Healthcare Science, University of Wolverhampton, Wolverhampton WV1 1LY, UK.
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15
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Araújo TG, Oliveira AG, Carvalho BM, Guadagnini D, Protzek AOP, Carvalheira JBC, Boschero AC, Saad MJA. Hepatocyte growth factor plays a key role in insulin resistance-associated compensatory mechanisms. Endocrinology 2012; 153:5760-9. [PMID: 23024263 DOI: 10.1210/en.2012-1496] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Insulin resistance is present in obesity and in type 2 diabetes and is associated with islet cell hyperplasia and hyperinsulinemia, but the driving forces behind this compensatory mechanism are incompletely understood. Previous data have suggested the involvement of an unknown circulating insulin resistance-related β-cell growth factor. In this context, looking for candidates to be a circulating factor, we realized that hepatocyte growth factor (HGF) is a strong candidate as a link between insulin resistance and increased mass of islets/hyperinsulinemia. Our approach aimed to show a possible cause-effect relationship between increase in circulating HGF levels and compensatory islet hyperplasia/hyperinsulinemia by showing the strength of the association, whether or not is a dose-dependent response, the temporality, consistency, plausibility, and reversibility of the association. In this regard, our data showed: 1) a strong and consistent correlation between HGF and the compensatory mechanism in three animal models of insulin resistance; 2) HGF increases β-cell mass in a dose-dependent manner; 3) blocking HGF shuts down the compensatory mechanisms; and 4) an increase in HGF levels seems to precede the compensatory response associated with insulin resistance, indicating that these events occur in a sequential mode. Additionally, blockages of HGF receptor (Met) worsen the impaired insulin-induced insulin signaling in liver of diet-induced obesity rats. Overall, our data indicate that HGF is a growth factor playing a key role in islet mass increase and hyperinsulinemia in diet-induced obesity rats and suggest that the HGF-Met axis may have a role on insulin signaling in the liver.
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Affiliation(s)
- Tiago G Araújo
- Department of Internal Medicine, State University of Campinas, Campinas, 13081-970 São Paulo, Brazil
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16
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Chetboun M, Abitbol G, Rozenberg K, Rozenfeld H, Deutsch A, Sampson SR, Rosenzweig T. Maintenance of redox state and pancreatic beta-cell function: role of leptin and adiponectin. J Cell Biochem 2012; 113:1966-76. [PMID: 22253064 DOI: 10.1002/jcb.24065] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Whereas oxidative stress is linked to cellular damage, reactive oxygen species (ROS) are also believed to be involved in the propagation of signaling pathways. Studies on the role of ROS in pancreatic beta-cell physiology, in contrast to pathophysiology, have not yet been reported. In this study we investigate the importance of maintaining cellular redox state on pancreatic beta-cell function and viability, and the effects of leptin and adiponectin on this balance. Experiments were conducted on RINm and MIN6 pancreatic beta-cells. Leptin (1-100 ng/ml) and adiponectin (1-100 nM) increased ROS accumulation, as was determined by DCFDA fluorescence. Using specific inhibitors, we found that the increase in ROS levels was mediated by NADPH oxidase (Nox), but not by AMP kinase (AMPK) or phosphatidyl inositol 3 kinase (PI3K). Leptin and adiponectin increased beta-cell number as detected by the XTT method, but did not affect apoptosis, indicating that the increased cell number results from increased proliferation. The adipokines-induced increase in viability is ROS dependent as this effect was abolished by N-acetyl-L-cysteine (NAC) or PEG-catalase. In addition, insulin secretion was found to be regulated by alterations in redox state, but not by adipokines. Finally, the effects of the various treatments on activity and mRNA expression of several antioxidant enzymes were determined. Both leptin and adiponectin reduced mRNA levels of superoxide dismutase (SOD)1. Adiponectin also decreased SOD activity and increased catalase and glutathione peroxidase (GPx) activities in the presence of H2O2. The results of this study show that leptin and adiponectin, by inducing a physiological increase in ROS levels, may be positive regulators of beta-cell mass.
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Affiliation(s)
- Moria Chetboun
- Department of Molecular Biology, Ariel University Center of Samaria, Ariel, Israel
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17
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Marroquí L, Gonzalez A, Ñeco P, Caballero-Garrido E, Vieira E, Ripoll C, Nadal A, Quesada I. Role of leptin in the pancreatic β-cell: effects and signaling pathways. J Mol Endocrinol 2012; 49:R9-17. [PMID: 22448029 DOI: 10.1530/jme-12-0025] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Leptin plays an important role in the control of food intake, energy expenditure, metabolism, and body weight. This hormone also has a key function in the regulation of glucose homeostasis. Although leptin acts through central and peripheral mechanisms to modulate glucose metabolism, the pancreatic β-cell of the endocrine pancreas is a critical target of leptin actions. Leptin receptors are present in the β-cell, and their activation directly inhibits insulin secretion from these endocrine cells. The effects of leptin on insulin occur also in the long term, since this hormone inhibits insulin gene expression as well. Additionally, β-cell mass can be affected by leptin through changes in proliferation, apoptosis, or cell size. All these different functions in the β-cell are triggered by leptin as a result of the large diversity of signaling pathways that this hormone is able to activate in the endocrine pancreas. Therefore, leptin can participate in glucose homeostasis owing to different levels of modulation of the pancreatic β-cell population. Furthermore, it has been proposed that alterations in this level of regulation could contribute to the impairment of β-cell function in obesity states. In the present review, we will discuss all these issues with special emphasis on the effects and pathways of leptin signaling in the pancreatic β-cell.
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Affiliation(s)
- Laura Marroquí
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas-CIBERDEM, Elche, Spain
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18
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Domínguez-Bendala J, Inverardi L, Ricordi C. Regeneration of pancreatic beta-cell mass for the treatment of diabetes. Expert Opin Biol Ther 2012; 12:731-41. [DOI: 10.1517/14712598.2012.679654] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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19
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Tarabra E, Pelengaris S, Khan M. A simple matter of life and death-the trials of postnatal Beta-cell mass regulation. Int J Endocrinol 2012; 2012:516718. [PMID: 22577380 PMCID: PMC3346985 DOI: 10.1155/2012/516718] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 12/31/2011] [Indexed: 12/17/2022] Open
Abstract
Pancreatic beta-cells, which secrete the hormone insulin, are the key arbiters of glucose homeostasis. Defective beta-cell numbers and/or function underlie essentially all major forms of diabetes and must be restored if diabetes is to be cured. Thus, the identification of the molecular regulators of beta-cell mass and a better understanding of the processes of beta-cell differentiation and proliferation may provide further insight for the development of new therapeutic targets for diabetes. This review will focus on the principal hormones and nutrients, as well as downstream signalling pathways regulating beta-cell mass in the adult. Furthermore, we will also address more recently appreciated regulators of beta-cell mass, such as microRNAs.
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Affiliation(s)
- Elena Tarabra
- School of Life Sciences, Warwick University, Gibbet Hill Road, Coventry CV4 7AL, UK
- *Elena Tarabra:
| | - Stella Pelengaris
- School of Life Sciences, Warwick University, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Michael Khan
- School of Life Sciences, Warwick University, Gibbet Hill Road, Coventry CV4 7AL, UK
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20
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Lee YH, Magkos F, Mantzoros CS, Kang ES. Effects of leptin and adiponectin on pancreatic β-cell function. Metabolism 2011; 60:1664-72. [PMID: 21632069 DOI: 10.1016/j.metabol.2011.04.008] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 03/24/2011] [Accepted: 04/18/2011] [Indexed: 02/09/2023]
Abstract
Leptin and adiponectin are hormones secreted from adipocytes that have important roles in metabolism and energy homeostasis. This review evaluates the effects of leptin and adiponectin on β-cell function by analyzing and compiling results from human clinical trials and epidemiologic studies as well as in vitro and in vivo experiments. Leptin has been shown to inhibit ectopic fat accumulation and thereby prevent β-cell dysfunction and protect the β-cell from cytokine- and fatty acid-induced apoptosis. However, leptin suppresses insulin gene expression and secretion as well as glucose transport into the β-cell. Adiponectin stimulates insulin secretion by enhancing exocytosis of insulin granules and upregulating the expression of the insulin gene; however, this effect depends on the prevailing glucose concentration and status of insulin resistance. In addition, adiponectin has antiapoptotic properties in β-cells. Available evidence concerning the role of these adipokines on insulin secretion, insulin gene expression, and apoptosis is not always entirely consistent; and many fundamental questions remain to be answered by future studies.
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Affiliation(s)
- Yong-ho Lee
- Department of Internal Medicine, Yonsei University College of Medicine, Seoul, South Korea
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21
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Liu Y, Lv L, Xiao W, Gong C, Yin J, Wang D, Sheng H. Leptin activates STAT3 and ERK1/2 pathways and induces endometrial cancer cell proliferation. ACTA ACUST UNITED AC 2011; 31:365. [PMID: 21671179 DOI: 10.1007/s11596-011-0382-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Indexed: 01/06/2023]
Abstract
Obesity is an established risk factor for endometrial cancer. Leptin, a secreted protein of the ob gene by white adipose tissue, plays an important role in the regulation of food intake and energy consumption in the brain and acts as a potential growth stimulator in normal and neoplastic cancer cells. However, a direct role for leptin in endometrial cancer has not been demonstrated. In the present study, the effect of leptin on the proliferation of Ishikawa endometrial cancer cells was investigated as well as the possible mechanism(s) underlying this action in endometrial cancers which express both short and long isoforms of leptin receptors. The expression of leptin receptor (ObRb) in Ishikawa cells was detected by RT-PCR and Western blotting. The cells after serum starvation, were treated by leptin with various concentrations (0, 10, 50, 100, 150 ng/mL) for different durations (6, 12, 24 h). The effect of leptin treatment on cell proliferation was examined by MTT assay. Meanwhile, inhibitory effect of Janus tyrosine kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) inhibitor AG490 or extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor PD98059 on the proliferation of Ishikawa cells induced by leptin was also studied. Ishikawa cells were treated with 100 ng/mL leptin for various periods (0, 20, 40, 60 min), and the levels of STAT3 phosphorylation and ERK1/2 phosphorylation were examined by Western blotting. The results showed that leptin induced the phosphorylation of STAT3 and the activation of ERK1/2 in a time- and dose-dependent manner in the Ishikawa endometrial cancer cells. Blocking STAT3 phosphorylation with the inhibitor AG490, or blocking ERK1/2 activation by the specific ERK1/2 kinase inhibitor, PD98059, abolished leptin-induced proliferation of Ishikawa cells. In addition, leptin was found to potently induce the invasion of endometrial cancer cells in a Matrigel invasion assay. Leptin-stimulated invasion was effectively blocked by pharmacological inhibitors of STAT3 (AG490) and ERK1/2 kinase (PD98059). These results suggested that leptin promotes endometrial cancer growth and invasiveness by activating STAT3 and ERK1/2 signaling pathways and therefore blocking its action at the receptor level can be a rational therapeutic strategy.
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Affiliation(s)
- Yi Liu
- Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
| | - Liqun Lv
- Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Wei Xiao
- Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Cheng Gong
- Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Jie Yin
- Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Donghua Wang
- Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Hui Sheng
- Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
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22
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Cammisotto PG, Levy E, Bukowiecki LJ, Bendayan M. Cross-talk between adipose and gastric leptins for the control of food intake and energy metabolism. ACTA ACUST UNITED AC 2010; 45:143-200. [PMID: 20621336 DOI: 10.1016/j.proghi.2010.06.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/06/2010] [Indexed: 12/25/2022]
Abstract
The understanding of the regulation of food intake has become increasingly complex. More than 20 hormones, both orexigenic and anorexigenic, have been identified. After crossing the blood-brain barrier, they reach their main site of action located in several hypothalamic areas and interact to balance satiety and hunger. One of the most significant advances in this matter has been the discovery of leptin. This hormone plays fundamental roles in the control of appetite and in regulating energy expenditure. In accordance with the lipostatic theory stated by Kennedy in 1953, leptin was originally discovered in white adipose tissue. Its expression by other tissues was later established. Among them, the gastric mucosa has been shown to secrete large amounts of leptin. Both the adipose and the gastric tissues share similar characteristics in the synthesis and storage of leptin in granules, in the formation of a complex with the soluble receptor and a secretion modulated by hormones and energy substrates. However while adipose tissue secretes leptin in a slow constitutive endocrine way, the gastric mucosa releases leptin in a rapid regulated exocrine fashion into the gastric juice. Exocrine-secreted leptin survives the extreme hydrolytic conditions of the gastric juice and reach the duodenal lumen in an intact active form. Scrutiny into transport mechanisms revealed that a significant amount of the exocrine leptin crosses the intestinal wall by active transcytosis. Leptin receptors, expressed on the luminal and basal membrane of intestinal epithelial cells, are involved in the control of nutrient absorption by enterocytes, mucus secretion by goblet cells and motility, among other processes, and this control is indeed different depending upon luminal or basal stimulus. Gastric leptin after transcytosis reaches the central nervous system, to control food intake. Studies using the Caco-2, the human intestinal cell line, in vitro allowed analysis of the mechanisms of leptin actions on the intestinal mucosa, identification of the mechanisms of leptin transcytosis and understanding the modulation of leptin receptors by nutrients and hormones. Exocrine-secreted gastric leptin thus participates in a physiological axis independent in terms of time and regulation from that of adipose tissue to rapidly control food intake and nutrient absorption. Adipocytes and gastric epithelial cells are two cell types the metabolism of which is closely linked to food intake and energy storage. The coordinated secretion of adipose and gastric leptins ensures proper management of food processing and energy storage.
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Affiliation(s)
- Philippe G Cammisotto
- Department of Pathology and Cell Biology, University of Montreal, 2900 Boulevard Edouard-Montpetit, Montreal, QC, Canada.
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23
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Pérez-Pérez A, Gambino Y, Maymó J, Goberna R, Fabiani F, Varone C, Sánchez-Margalet V. MAPK and PI3K activities are required for leptin stimulation of protein synthesis in human trophoblastic cells. Biochem Biophys Res Commun 2010; 396:956-60. [DOI: 10.1016/j.bbrc.2010.05.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 05/06/2010] [Indexed: 11/28/2022]
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Abstract
OBJECTIVE To investigate the action of palmitate on insulin receptor (IR) signaling pathway in rat pancreatic islets. The following proteins were studied: IR substrate-1 and -2 (IRS1 and IRS2), phosphatidylinositol 3-kinase, extracellular signal-regulated protein kinase-1 and -2 (ERK1/2), and signal transducer and activator of transcription 3 (STAT3). METHODS Immunoblotting and immunoprecipitation assays were used to evaluate the phosphorylation states of IRS1 and IRS2 (tyrosine [Tyr]), ERK1/2 (threonine 202 [Thr202]/Tyr204), and STAT3 (serine [Ser727]). RESULTS The exposure of rat pancreatic islets to 0.1-mmol/L palmitate for up to 30 minutes produced a significant increase of Tyr phosphorylation in IRS2 but not in IRS1. The association of phosphatidylinositol 3-kinase with IRS2 was also upregulated by palmitate. Exposure to 5.6-mmol/L glucose caused a gradual decrease in ERK1/2 (Thr202/Tyr204) and STAT3 (serine [Ser727]) phosphorylations after 30-minute incubation. The addition of palmitate (0.1 mmol/L), associated with 5.6-mmol/L glucose, abolished these latter effects of glucose after 15-minute incubation. CONCLUSIONS Palmitate at physiological concentration associated with 5.6-mmol/L glucose activates IR signaling pathway in pancreatic beta cells.
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25
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Procaccini C, Lourenco EV, Matarese G, La Cava A. Leptin signaling: A key pathway in immune responses. ACTA ACUST UNITED AC 2009; 4:22-30. [PMID: 19774101 DOI: 10.2174/157436209787048711] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Leptin is a hormone whose central role is to regulate endocrine functions and to control energy expenditure. After the discovery that leptin can also have pro-inflammatory effects, several studies have tried to address - at the molecular level - the pathways involved in leptin-induced modulation of the immune functions in normal and pathologic conditions. The signaling events influenced by leptin after its binding to the leptin receptor have been under scrutiny in the past few years, and considerable experimental work has elucidated the consequences of leptin effects on immune cells. This review examines the biochemistry, function and regulation of leptin signaling in view of possible intervention on this molecule for a better management and therapy of immune-mediated diseases.
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Affiliation(s)
- Claudio Procaccini
- Department of Medicine, University of California Los Angeles, Los Angeles, California 90095
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26
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Attig L, Djiane J, Gertler A, Rampin O, Larcher T, Boukthir S, Anton PM, Madec JY, Gourdou I, Abdennebi-Najar L. Study of hypothalamic leptin receptor expression in low-birth-weight piglets and effects of leptin supplementation on neonatal growth and development. Am J Physiol Endocrinol Metab 2008; 295:E1117-25. [PMID: 18780769 DOI: 10.1152/ajpendo.90542.2008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Low birth weight resulting from intrauterine growth retardation (IUGR) is a risk factor for further development of metabolic diseases. The pig appears to reproduce nearly all of the phenotypic pathological consequences of human IUGR and is likely to be more relevant than rodents in studies of neonatal development. In the present work, we characterized the model of low-birth-weight piglets with particular attention to the hypothalamic leptin-sensitive system, and we tested whether postnatal leptin supplementation can reverse the precocious signs of adverse metabolic programming. Our results demonstrated that 1) IUGR piglets present altered postnatal growth and increased adiposity; 2) IUGR piglets exhibit abnormal hypothalamic distribution of leptin receptors that may be linked to further disturbance in food-intake behavior; and 3) postnatal leptin administration can partially reverse the IUGR phenotype by correcting growth rate, body composition, and development of several organs involved in metabolic regulation. We conclude that IUGR may be characterized by altered leptin receptor distribution within the hypothalamic structures involved in metabolic regulation and that leptin supplementation can partially reverse the IUGR phenotype. These results open interesting therapeutic perspectives in physiopathology for the correction of defects observed in IUGR.
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Affiliation(s)
- L Attig
- Université Paris-Sud, Institut National de la Recherche Agronomique, Unité Mixte de Recherche (UMR) 1197, Neurobiologie de l'Olfaction et de la Prise Alimentaire, Jouy-en-Josas.
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27
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Pérez-Pérez A, Maymó J, Dueñas JL, Goberna R, Calvo JC, Varone C, Sánchez-Margalet V. Leptin prevents apoptosis of trophoblastic cells by activation of MAPK pathway. Arch Biochem Biophys 2008; 477:390-5. [DOI: 10.1016/j.abb.2008.06.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Revised: 06/13/2008] [Accepted: 06/14/2008] [Indexed: 10/21/2022]
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28
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Liapakis I, Anagnostoulis S, Karayiannakis A, Korkolis D, Lambropoulou M, Matarasso A, Simopoulos C. Burn wound angiogenesis is increased by exogenously administered recombinant leptin in rats. Acta Cir Bras 2008; 23:118-24. [DOI: 10.1590/s0102-86502008000200002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 12/18/2007] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND: Leptin is a potent direct angiogenic factor that stimulates endothelial cell migration and activation in vitro and angiogenesis in vivo. In addition, leptin has been discussed to play an important role in angiogenesis, as it promotes the formation of new blood vessels. PURPOSE: The effect of exogenously administered leptin on the healing process of a full tissue burn wound model. METHODS: Sixty-three Sprague-Dawley male rats were used. Full tissue burn wound was created by electrocautery. The width of the pin was 0.3 cm; its length was 2 cm and was used at the "cut" modulation. Rats were divided into seven groups of nine animals each. Burn wounds were injected with murine recombinant leptin and the rats were sacrificed 3, 7 and 9 days after surgery. Every group had obtained three animals for the three different days of sacrifice. Three different leptin doses of 250 pg/ml, 500 pg/ml and 1000 pg/ml were used in different animal groups (A, B and C). For every one of the three leptin doses used, another animal group was evaluated by using the combined injection of leptin and antileptin (A1, B1, and C1), in order to study the inhibitory effect to the leptin factor. Nine rats were served as controls. These were injected with 0.3 ml water for injection solution and sacrificed at the same time intervals. After sacrifice of the animals, the skin was grossly determined by its appearance, colour and texture. Full thickness burn wounds were dissected for histological examination. A qualitative analysis of angiogenesis in the burn wound was conducted following a standard hematoxylin and eosin stain. The wound tissue samples from each experimental group underwent immunohistochemical evaluation of microvessel density by endothelial cell staining with mouse anti-rat CD 34 monoclonal antibody. RESULTS: The most impressive growth of new blood vessels appeared seven and nine days after treatment with the highest leptin doses. There were no significant differences in microvessel density between the seventh and the ninth postoperative day among different groups treated with leptin. All wounds from the control group, as well as those from animal groups treated with the combined injection of leptin and antileptin did not develop any new vessels. CONCLUSION: Exogenous administration of recombinant leptin increases early tissue angiogenesis in the burn wound level of an experimental animal model.
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Affiliation(s)
| | | | | | | | | | - Alan Matarasso
- Albert Einstein College of Medicine/Montefiore Medical Center
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29
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Fernández-Riejos P, Goberna R, Sánchez-Margalet V. Leptin promotes cell survival and activates Jurkat T lymphocytes by stimulation of mitogen-activated protein kinase. Clin Exp Immunol 2008; 151:505-18. [PMID: 18234059 DOI: 10.1111/j.1365-2249.2007.03563.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Leptin (Ob) is a non-glycosylated peptide hormone that regulates energy homeostasis centrally, but also has systemic effects including the regulation of the immune function. We have reported previously that leptin activates human peripheral blood lymphocytes co-stimulated with phytohaemagglutinin (PHA) (4 microg/ml), which prevented the employment of pharmacological inhibitors of signalling pathways. In the present study, we used Jurkat T cells that responded to leptin with minimal PHA co-stimulation (0.25 microg/ml). The long isoform of leptin receptor is expressed on Jurkat T cells and upon leptin stimulation, the expression of early activation marker CD69 increases in a dose-dependent manner (0.1-10 nM). We have also found that leptin activates receptor-associated kinases of the Janus family-signal transucers and activators of transcription (JAK-STAT), mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PI3K) signalling pathways. Moreover, we sought to study the possible effect of leptin on cell survival and apoptosis of Jurkat T cells by culture in serum-free conditions. We have assayed the early phases of apoptosis by flow cytometric detection of fluorescein isothiocyanate (FITC)-labelled annexin V simultaneously with dye exclusion of propidium iodide (PI). As well, we have assayed the activation level of caspase-3 by inmunoblot with a specific antibody that recognizes active caspase-3. We have found that leptin inhibits the apoptotic process dose-dependently. By using pharmacological inhibitors, we have found that the stimulatory and anti-apoptotic effects of leptin in Jurkat T cells are dependent on MAPK activation, rather than the PI3K pathway, providing new data regarding the mechanism of action of leptin in T cells, which may be useful to understand more clearly the association between nutritional status and the immune function.
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Affiliation(s)
- P Fernández-Riejos
- Department of Clinical Biochemistry, Virgen Macarena University Hospital, Medical School University of Seville, Seville, Spain
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30
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The actions of leptin on survival and hydrogen peroxide toxicity in primary mixed glial cells of rat. Biologia (Bratisl) 2007. [DOI: 10.2478/s11756-007-0148-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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31
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Simopoulou T, Malizos KN, Iliopoulos D, Stefanou N, Papatheodorou L, Ioannou M, Tsezou A. Differential expression of leptin and leptin's receptor isoform (Ob-Rb) mRNA between advanced and minimally affected osteoarthritic cartilage; effect on cartilage metabolism. Osteoarthritis Cartilage 2007; 15:872-83. [PMID: 17350295 DOI: 10.1016/j.joca.2007.01.018] [Citation(s) in RCA: 190] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2006] [Accepted: 01/23/2007] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To investigate leptin's effect on cartilage metabolism and the pathophysiology of osteoarthritis (OA). METHODS Messenger RNA (mRNA) expression and protein levels of leptin and leptin's receptor isoforms were measured by real-time reverse transcription-PCR and Western blot in osteoarthritic and normal cartilage. Osteoarthritic cartilage samples were obtained from two locations of the knee (n=11) and hip (n=6); from the main defective area (advanced OA) and from adjacent macroscopically and histological intact regions (minimal OA). Paired serum and synovial fluid (SF) leptin levels were measured. The effect of leptin was evaluated on chondrocyte proliferation, IL-1beta (interleukin-1beta), NO and metalloproteinases 9 and 13 (MMP-9, MMP-13) protein expression. RESULTS Leptin's and leptin's receptor (Ob-Rb) expression levels were significantly increased in advanced OA cartilage compared to minimal. Leptin was significantly increased in SF than serum samples. Also, leptin had a detrimental effect on chondrocyte proliferation and induced IL-1beta production and MMP-9 and MMP-13 protein expression. Furthermore, leptin's mRNA expression in advanced OA cartilage was significantly correlated with BMI of the patients. CONCLUSION The increased leptin levels in SF point toward a local effect of leptin in articular cartilage, while the observed intrajoint differences of leptin and Ob-Rb mRNA expression may be related to the grade of cartilage destruction. The observed production of IL-1beta, MMP-9 and MMP-13 by chondrocytes after leptin treatment indicates a pro-inflammatory and catabolic role of leptin on cartilage metabolism. Furthermore, the observed correlation of leptin's mRNA expression with BMI suggests that leptin may be a metabolic link between obesity and OA.
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Affiliation(s)
- T Simopoulou
- Department of Biology, University of Thessalia, Medical School, Larissa, Greece
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Leptin induces inflammation-related genes in RINm5F insulinoma cells. BMC Mol Biol 2007; 8:41. [PMID: 17521427 PMCID: PMC1890559 DOI: 10.1186/1471-2199-8-41] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Accepted: 05/23/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Leptin acts not only on hypothalamic centers to control food intake but has additional functions in peripheral tissues, e.g. inhibition of insulin secretion from pancreatic islets. The leptin receptor (LEPRb) is a class I cytokine receptor that mediates activation of STAT transcription factors. In this study, we characterise the regulation of inflammation-related genes by leptin in insulinoma cells and compare the effect of transcriptional regulation by leptin with that of other cytokines. RESULTS We have used RINm5F insulinoma cells as a model system for a peripheral target cell of leptin. Six transcripts encoding inflammation-related proteins were found to be upregulated by activation of LEPRb, namely lipocalin-2, pancreatitis-associated protein, preprotachykinin-1, fibrinogen-beta, tissue-type plasminogen activator (tPA) and manganese-dependent superoxide dismutase (MnSOD). Four of these transcripts (fibrinogen-beta, lipocalin-2, tPA, MnSOD) were also induced by the proinflammatory cytokine interleukin-1beta (IL-1beta). Interferon-gamma alone had no effect on the leptin-induced transcripts but enhanced the upregulation by IL-1beta of lipocalin-2, tPA and MnSOD mRNA levels. Experiments with LEPRb point mutants revealed that the upregulation of the inflammation-related genes depended on the presence of tyrosine-1138 which mediates the activation of the transcription factors STAT1 and STAT3. Reporter gene assays showed that leptin induced the expression of preprotachykinin-1 and lipocalin-2 on the level of promoter regulation. Finally, leptin treatment increased caspase 3-like proteolytic activity in RINm5F cells. CONCLUSION The present data show that leptin induces a cytokine-like transcriptional response in RINm5F cells, consistent with the proposed function of leptin as a modulator of immune and inflammatory responses.
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Turner SM, Roy S, Sul HS, Neese RA, Murphy EJ, Samandi W, Roohk DJ, Hellerstein MK. Dissociation between adipose tissue fluxes and lipogenic gene expression in ob/ob mice. Am J Physiol Endocrinol Metab 2007; 292:E1101-9. [PMID: 17164440 PMCID: PMC2895312 DOI: 10.1152/ajpendo.00309.2005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent evidence has been presented that expression of lipogenic genes is downregulated in adipose tissue of ob/ob mice as well as in human obesity, suggesting a functionally lipoatrophic state. Using (2)H(2)O labeling, we measured three adipose tissue biosynthetic processes concurrently: triglyceride (TG) synthesis, palmitate de novo lipogenesis (DNL), and cell proliferation (adipogenesis). To determine the effect of the ob/ob mutation (leptin deficiency) on these parameters, adipose dynamics were compared in ob/ob, leptin-treated ob/ob, food-restricted ob/ob, and lean control mice. Adipose tissue fluxes for TG synthesis, de novo lipogenesis (DNL), and adipogenesis were dramatically increased in ob/ob mice compared with lean controls. Low-dose leptin treatment (2 microg/day) via miniosmotic pump suppressed all fluxes to control levels or below. Food restriction in ob/ob mice only modestly reduced DNL, with no change in TG synthesis or adipogenesis. Measurement of mRNA levels in age-matched ob/ob mice showed generally normal expression levels for most of the selected lipid anabolic genes, and leptin treatment had, with few exceptions, only modest effects on their expression. We conclude that leptin deficiency per se results in marked elevations in flux through diverse lipid anabolic pathways in adipose tissue (DNL, TG synthesis, and cell proliferation), independent of food intake, but that gene expression fails to reflect these changes in flux.
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Affiliation(s)
- S M Turner
- Department of Nutritional Sciences & Toxicology, University of California, Berkeley, CA 94720, USA.
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Alexandraki K, Piperi C, Kalofoutis C, Singh J, Alaveras A, Kalofoutis A. Inflammatory process in type 2 diabetes: The role of cytokines. Ann N Y Acad Sci 2007; 1084:89-117. [PMID: 17151295 DOI: 10.1196/annals.1372.039] [Citation(s) in RCA: 211] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Population-based studies have shown strong relationship between inflammatory markers and metabolic disturbances, obesity, and atherosclerosis, whereas inflammation has been considered as a "common soil" between these clinical entities and type 2 diabetes (T2D). The accumulation of macrophages in adipose tissue (AT), the common origin of macrophages and adipocytes, the prevalent presence of peripheral mononuclear cells, and apoptotic beta cells by themselves seem to be the sources of inflammation present in T2D, since they generate the mediators of the inflammatory processes, namely cytokines. The main cytokines involved in the pathogenesis of T2D are interleukin-1beta (IL-1beta), with an action similar to the one present in type 1 diabetes, tumor necrosis factor-alpha (TNF-alpha), and IL-6, considered as the main regulators of inflammation, leptin, more recently introduced, and several others, such as monocyte chemoattractant protein-1, resistin, adiponectin, with either deleterious or beneficial effects in diabetic pathogenesis. The characterization of these molecules targeted diabetes treatment beyond the classical interventions with lifestyle changes and pharmaceutical agents, and toward the determination of specific molecular pathways that lead to low grade chronic inflammatory state mainly due to an immune system's unbalance.
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Affiliation(s)
- Krystallenia Alexandraki
- Laboratory of Biological Chemistry, University of Athens Medical School, M. Asias 75, Goudi 11527, Athens, Greece
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35
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Posser T, de Aguiar CBNM, Garcez RC, Rossi FM, Oliveira CS, Trentin AG, Neto VM, Leal RB. Exposure of C6 glioma cells to Pb(II) increases the phosphorylation of p38MAPK and JNK1/2 but not of ERK1/2. Arch Toxicol 2007; 81:407-14. [PMID: 17333127 DOI: 10.1007/s00204-007-0177-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Accepted: 01/09/2007] [Indexed: 01/05/2023]
Abstract
Pb(II) is a neurotoxic pollutant that produces permanent cognitive deficits in children. Pb(II) can modulate cell signaling pathways and cell viability in a variety of cell types. However, these actions are not well demonstrated on glial cells, which represent an important target for metals into the central nervous system. The present work was undertaken to determine the ability of Pb(II) in modulating the activity of mitogen activated protein kinases (MAPKs) in cultures of C6 rat glioma cells, a useful functional model for the study of astrocytes. Additionally, cell viability was analyzed by measurement of MTT reduction. Cells were exposed to lead acetate 0.1, 1, 10 microM for 24 and 48 h. MAPKs activation - in particular ERK1/2, p38(MAPK) and JNK1/2 - were analyzed by western blotting. Results showed that 10 microM Pb(II) treatment for 24 h caused a discrete stimulation of p38(MAPK) phosphorylation. However, 1 and 10 microM Pb(II) treatment for 48 h provoked a significant stimulation in the phosphorylation state of p38(MAPK) and JNK1/2. The phosphorylation state of ERK1/2 was not modified by any Pb(II) treatment. Moreover, data indicate that at 48 h treatment even 1 microM Pb(II) can be cytotoxic, causing impairment on cell viability. Therefore, depending on a long incubation period, a significant concomitant activation of p38(MAPK) and JNK1/2 by Pb(II) took place in parallel with the impairment of C6 glioma cells viability.
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Affiliation(s)
- Thaís Posser
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040-900, Brazil
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36
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Desruisseaux MS, Trujillo ME, Tanowitz HB, Scherer PE. Adipocyte, adipose tissue, and infectious disease. Infect Immun 2006; 75:1066-78. [PMID: 17118983 PMCID: PMC1828569 DOI: 10.1128/iai.01455-06] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Mahalia S Desruisseaux
- Department of Pathology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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37
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Jackerott M, Møldrup A, Thams P, Galsgaard ED, Knudsen J, Lee YC, Nielsen JH. STAT5 activity in pancreatic beta-cells influences the severity of diabetes in animal models of type 1 and 2 diabetes. Diabetes 2006; 55:2705-12. [PMID: 17003334 DOI: 10.2337/db06-0244] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Pancreatic beta-cell growth and survival and insulin production are stimulated by growth hormone and prolactin through activation of the transcription factor signal transducer and activator of transcription (STAT)5. To assess the role of STAT5 activity in beta-cells in vivo, we generated transgenic mice that expressed a dominant-negative mutant of STAT5a (DNSTAT5) or constitutive active mutant of STAT5b (CASTAT5) under control of the rat insulin 1 promoter (RIP). When subjected to a high-fat diet, RIP-DNSTAT5 mice showed higher body weight, increased plasma glucose levels, and impairment of glucose tolerance, whereas RIP-CASTAT5 mice were more glucose tolerant and less hyperleptinemic than wild-type mice. Although the pancreatic insulin content and relative beta-cell area were increased in high-fat diet-fed RIP-DNSTAT5 mice compared with wild-type or RIP-CASTAT5 mice, RIP-DNSTAT5 mice showed reduced beta-cell proliferation at 6 months of age. The inhibitory effect of high-fat diet or leptin on insulin secretion was diminished in isolated islets from RIP-DNSTAT5 mice compared with wild-type islets. Upon multiple low-dose streptozotocin treatment, RIP-DNSTAT5 mice exhibited higher plasma glucose levels, lower plasma insulin levels, and lower pancreatic insulin content than wild-type mice, whereas RIP-CASTAT5 mice maintained higher levels of plasma insulin. In conclusion, our results indicate that STAT5 activity in beta-cells influences the susceptibility to experimentally induced type 1 and type 2 diabetes.
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Affiliation(s)
- Malene Jackerott
- Department of Medical Biochemistry and Genetics, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.
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Ogunwobi O, Mutungi G, Beales ILP. Leptin stimulates proliferation and inhibits apoptosis in Barrett's esophageal adenocarcinoma cells by cyclooxygenase-2-dependent, prostaglandin-E2-mediated transactivation of the epidermal growth factor receptor and c-Jun NH2-terminal kinase activation. Endocrinology 2006; 147:4505-16. [PMID: 16740977 DOI: 10.1210/en.2006-0224] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Obesity is an important risk factor for esophageal adenocarcinoma (EAC), and elevated serum leptin is characteristic of obesity. We hypothesized that leptin may have biological effects in promoting esophageal adenocarcinoma and examined the effects of leptin on the OE33 Barrett's-derived EAC line. Proliferation was assessed by dimethylthiazoldiphenyltetra-zoliumbromide and 5-bromo-2'-deoxyuridine incorporation assays and apoptosis by ELISA of intracellular nucleosomes. Intracellular signaling was examined using specific pharmacological inhibitors and direct detection of phosphorylated active kinases. Expression of the long and short leptin receptors by OE33 cells was confirmed by RT-PCR, Western blotting and immunocytochemistry. Leptin stimulated OE33 cell proliferation in a dose-dependent manner and inhibited apoptosis. These effects were dependent on cyclooxygenase (COX)-2 and replicated by adding prostaglandin E2 (PGE2). The effects of PGE2 and leptin were abolished by the EP-4 antagonist AH23848. ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and Janus tyrosine kinase (JAK)-2 were activated upstream of COX-2 induction, whereas the epidermal growth factor receptor and c-Jun NH2-terminal kinase (JNK) were downstream of COX-2. The activation of ERK and Akt but not p38 MAPK was JAK2 dependent. PGE2 stimulated phosphorylation of JNK in an EGF receptor-dependent manner, and activation of the epidermal growth factor receptor required protein kinase C, src, and matrix metalloproteinase activities. We conclude that leptin stimulates cell proliferation and inhibits apoptosis in OAC cells via ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and JAK2-dependent activation of COX-2 and PGE2 production. Subsequent PGE2-mediated transactivation of the epidermal growth factor receptor and JNK activation are essential to the leptin effects. These effects may contribute to the greatly increased risk of esophageal adenocarcinoma in obesity.
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Affiliation(s)
- Olorunseun Ogunwobi
- Biomedical Research Centre, School of Medicine, Health Policy, and Practice, University of East Anglia, Norwich NR4 7TJ, United Kingdom
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39
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Beales ILP, Ogunwobi O. Glycine-extended gastrin inhibits apoptosis in colon cancer cells via separate activation of Akt and JNK pathways. Mol Cell Endocrinol 2006; 247:140-9. [PMID: 16442704 DOI: 10.1016/j.mce.2005.12.050] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 12/07/2005] [Accepted: 12/20/2005] [Indexed: 01/12/2023]
Abstract
Glycine-extended gastrin (G-Gly) is produced by colon cancers and has growth promoting and anti-apoptotic effects in the colonic epithelium. We have examined the anti-apoptotic effects of G-Gly and the signal transduction pathways involved. G-Gly stimulated HT-29 cell proliferation in a concentration dependent manner and inhibited serum-starvation and celecoxib-induced apoptosis. Inhibition of signalling via c-Jun NH2-terminal kinase (JNK) with SP600125 or PI3-kinase/Akt with LY294002 abolished the effects of G-Gly. G-Gly significantly increased phosphorylation of both JNK and Akt. The JAK2 inhibitor AG490 abolished the anti-apoptotic effect of G-Gly and inhibited phosphorylation of Akt but not of JNK. G-Gly stimulated tyrosine phosphorylation of JAK2. G-Gly-increased activation of AP-1 was JNK-dependant and activation of STAT3 was JAK2-dependant. We conclude that G-Gly promotes growth and inhibits apoptosis in colon cancer cells. These effects are mediated via the JAK2, PI3-kinase/Akt and JNK pathways. Activation of JAK2 is upstream of Akt but not of JNK.
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Affiliation(s)
- Ian L P Beales
- Gastroenterology Unit, Norfolk and Norwich University Hospital, Norwich NR4 7UZ, United Kingdom.
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40
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Zhao T, Hou M, Xia M, Wang Q, Zhu H, Xiao Y, Tang Z, Ma J, Ling W. Globular adiponectin decreases leptin-induced tumor necrosis factor-alpha expression by murine macrophages: involvement of cAMP-PKA and MAPK pathways. Cell Immunol 2006; 238:19-30. [PMID: 16438946 DOI: 10.1016/j.cellimm.2005.12.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 12/05/2005] [Accepted: 12/08/2005] [Indexed: 10/25/2022]
Abstract
Several lines of evidence have supported a link between obesity and inflammation. The present study investigated the capacity of leptin and globular adiponectin to affect tumor necrosis factor alpha (TNF-alpha) production in murine peritoneal macrophages. Leptin stimulated TNF-alpha production at mRNA as well as protein levels in a dose- and time-dependent manner. Intracellular cAMP concentration was increased and protein kinase A (PKA) was activated with the treatment of leptin, subsequently downstream MAPK signal proteins, ERK1/2 and p38, were phosphorylated. Specific inhibitors for the signal proteins, Rp cAMPS, H89, PD98059, and U0126, or SB203580, suppressed the signaling pathway and TNF-alpha expression. Although gAd partially increased cAMP concentration and PKA activity, it directly reduced leptin-induced ERK1/2 and p38 MAPK phosphorylation thus inhibiting TNF-alpha production. In conclusion, leptin promotes inflammation by stimulating TNF-alpha production, which is mediated by cAMP-PKA-ERK1/2 and p38 MAPK pathways. gAd inhibited leptin-induced TNF-alpha production through suppressing phosphorylation of ERK1/2 and p38 pathways.
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Affiliation(s)
- Ting Zhao
- Department of Nutrition, School of Public Health, Zhongshan University (Northern Campus), Guangzhou, Guangdong Province, PR China
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41
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Irving AJ, Wallace L, Durakoglugil D, Harvey J. Leptin enhances NR2B-mediated N-methyl-D-aspartate responses via a mitogen-activated protein kinase-dependent process in cerebellar granule cells. Neuroscience 2006; 138:1137-48. [PMID: 16413128 PMCID: PMC1613257 DOI: 10.1016/j.neuroscience.2005.11.042] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Revised: 11/10/2005] [Accepted: 11/20/2005] [Indexed: 10/25/2022]
Abstract
It is well documented that the hormone leptin regulates energy balance via its actions in the hypothalamus. However, evidence is accumulating that leptin plays a key role in numerous CNS functions. Indeed, leptin receptors are expressed in many extrahypothalamic brain regions, with high levels found in the hippocampus and cerebellum. In the hippocampus leptin has been shown to facilitate N-methyl-D-aspartate receptor function and modulate synaptic plasticity. A role for leptin in cerebellar function is also indicated as leptin-deficient rodents display reduced mobility that is unrelated to obesity. Here we show that leptin receptor immunolabeling can be detected in cultured cerebellar granule cells, being expressed at the somatic plasma membrane and also concentrated at synapses. Furthermore, leptin facilitated NR2B N-methyl-D-aspartate receptor-mediated Ca2+ influx in cerebellar granule cells via a mitogen-activated protein kinase-dependent pathway. These findings provide the first direct evidence for a cellular action of leptin in cerebellar neurons. In addition, given that N-methyl-D-aspartate receptor activity in the cerebellum is crucial for normal locomotor function, these data also have important implications for the potential role of leptin in the control of movement.
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Affiliation(s)
- A J Irving
- Neurosciences Institute, Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
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42
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Tsukiyama S, Matsushita M, Matsumoto S, Morita T, Kobayashi S, Tamura H, Kamachi H, Ozaki M, Todo S. Transduction of Exogenous Constitutively Activated Stat3 into Dispersed Islets Induces Proliferation of Rat Pancreatic β-cells. ACTA ACUST UNITED AC 2006; 12:131-40. [PMID: 16499450 DOI: 10.1089/ten.2006.12.131] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In vitro proliferation of functional islet mass/beta-cells by transduction of cell cycle regulatory genes has not been well documented due to the lack of either an effective method for gene transduction to islets or effective genes for beta-cell proliferation. Signal transducers and activators of transcription- 3 (Stat3) are among the most important molecules for cell proliferation and for cell antiapoptosis. In this study, adenovirus-mediated gene transduction was performed on dispersed islet cells, and reaggregated islet mass functions, such as capabilities for reaggregation, proliferation, and glucose- stimulated insulin secretion (GSIS), were evaluated. The constitutively activated form of Stat3 (Stat3-C) was effectively transduced to most of the islet cells, even at a low density of adenovirus vector. There was no difference in the spontaneous reaggregation capability between Stat3-C transduced and control islet cells. BrdU incorporation in Stat3-C-transduced islet cells was significantly higher (2.8-fold) than that in the control cells, and it was significantly elevated (4-fold) by the addition of HGF in culture media. GSIS in Stat3-C-transduced islet cells was preserved to the level in controls by 5 days in culture. The results indicated that gene transduction into islet cells could be enhanced by first dispersing the cells. Stat3-C induced cell proliferation of beta-cells without loss of insulin secretion activity at the glucose challenge, and HGF enhanced the beta-cell proliferative activity of Stat3-C.
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Affiliation(s)
- Shusaku Tsukiyama
- First Department of Surgery, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan
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Abstract
It is well documented that the hormone leptin signals information regarding the status of fat stores to hypothalamic nuclei, which in turn control feeding behaviour and body weight. However, leptin and its receptor are widely expressed in many extra-hypothalamic brain regions, including hippocampus, brain stem and cerebellum. Moreover, evidence is accumulating that leptin has other neuronal functions that are unrelated to its effects on energy homeostasis. Indeed a role for leptin in neuronal development has been suggested as leptin-deficient rodents display abnormal brain development and leptin actively participates in the development of the hypothalamus. In the hippocampus, leptin is a potential cognitive enhancer as genetically obese rodents with dysfunctional leptin receptors display impairments in hippocampal synaptic plasticity. Moreover, direct administration of leptin into the hippocampus can facilitate hippocampal LTP (long-term potentiation) in vivo and improve memory processing in mice. At the cellular level, we have also shown that leptin has the capacity to convert short-term potentiation into LTP. Here, we review the data that leptin influences hippocampal synaptic plasticity via enhancing NMDA (N-methyl-D-aspartate) receptor function. We also provide evidence that rapid trafficking of NMDA receptors to the plasma membrane may underlie the effects of leptin on excitatory synaptic strength.
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44
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Shin HJ, Oh J, Kang SM, Lee JH, Shin MJ, Hwang KC, Jang Y, Chung JH. Leptin induces hypertrophy via p38 mitogen-activated protein kinase in rat vascular smooth muscle cells. Biochem Biophys Res Commun 2005; 329:18-24. [PMID: 15721267 DOI: 10.1016/j.bbrc.2004.12.195] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Indexed: 11/30/2022]
Abstract
The hypertrophy of vascular smooth muscle cells (VSMCs) is critical in vascular remodeling associated with hypertension, atherosclerosis, and restenosis. Recently, leptin has appeared to play a pivotal role in vascular remodeling. However, the mechanism by which leptin induces hypertrophy in vascular smooth muscle cells is still unknown. We studied the role of leptin as a potential hypertrophic factor in rat VSMCs. In the present study, leptin significantly increased [(3)H]leucine incorporation and the total protein/DNA ratio in VSMCs. The maximal hypertrophic effect was at 100ng/ml of leptin. Leptin induced phosphorylation and activation of p38 mitogen-activated protein (p38 MAP) kinase and of signal transducers and activators of transcription 3 in a concentration- and time-dependent manner. A p38 MAP kinase inhibitor SB203580 significantly inhibited leptin-induced hypertrophy, AG490 (a JAK2 inhibitor) partially inhibited it, and other MAP kinase inhibitors, PD98059 (an ERK inhibitor) and SP600125 (a JNK inhibitor), had no effect. These results indicate that leptin directly stimulates cellular hypertrophy via p38 MAP kinase in rat VSMCs.
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MESH Headings
- Animals
- Anthracenes/pharmacology
- Aorta/metabolism
- Arteriosclerosis
- Blotting, Western
- Cells, Cultured
- DNA/metabolism
- DNA-Binding Proteins/metabolism
- Dose-Response Relationship, Drug
- Electrophoresis, Polyacrylamide Gel
- Enzyme Activation
- Enzyme Inhibitors/pharmacology
- Flavonoids/pharmacology
- Hypertrophy
- Leptin/metabolism
- Leucine/metabolism
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/pathology
- Myocytes, Smooth Muscle/cytology
- Myocytes, Smooth Muscle/metabolism
- Phosphorylation
- Rats
- Rats, Sprague-Dawley
- STAT3 Transcription Factor
- Time Factors
- Trans-Activators/metabolism
- Tyrphostins/pharmacology
- p38 Mitogen-Activated Protein Kinases/metabolism
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Affiliation(s)
- Hye-Jin Shin
- Yonsei Research Institute of Aging Science, Yonsei University, Seoul 120-749, Republic of Korea
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45
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Luther MJ, Davies E, Muller D, Harrison M, Bone AJ, Persaud SJ, Jones PM. Cell-to-cell contact influences proliferative marker expression and apoptosis in MIN6 cells grown in islet-like structures. Am J Physiol Endocrinol Metab 2005; 288:E502-9. [PMID: 15479950 DOI: 10.1152/ajpendo.00424.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cell-to-cell interactions play an important role in the development and maintenance of the beta-cell phenotype. Here, we have investigated whether E-cadherin plays a role in regulating the growth of insulin-secreting MIN6 cells configured as three-dimensional islet-like clusters (pseudoislets). Pseudoislets form by cell aggregation rather than by proliferation from individual cells and attain the size of primary mouse islets after approximately 7 days of maintenance in culture. E-cadherin is known to mediate homotypic cell adhesion between beta-cells and has also been implicated in a number of cellular processes, including proliferation, apoptosis, and differentiation. E-cadherin and its associated intracellular elements, alpha- and beta-catenin, were upregulated in MIN6 pseudoislets. Pseudoislet formation was associated with an increased expression of cyclin-dependent kinase inhibitors and a concomitant downregulation of Ki67, suggesting an overall reduction in cellular proliferation. However, measurements of 5-bromo-2'-deoxyuridine incorporation revealed that there were no differences in the rate of MIN6 cell proliferation whether they were configured as monolayers or as pseudoislets, which is likely to be a result of their being a transformed cell line. Cells within pseudoislets were not necrotic, but apoptosis appeared to be upregulated in the islet-like structures. However, no differential expression of Fas and FasL was detected in monolayers and pseudoislets. These results suggest that cell-to-cell interactions within islet-like structures may initiate antiproliferative and proapoptotic signals.
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Affiliation(s)
- Melanie J Luther
- Beta-Cell Development and Function Group, Division of Reproductive Health, Endocrinology and Development, Hodgkin Bldg., King's College London, Guy's Campus, London Bridge, London SE1 1UL, UK
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46
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Uchida T, Nakamura T, Hashimoto N, Matsuda T, Kotani K, Sakaue H, Kido Y, Hayashi Y, Nakayama KI, White MF, Kasuga M. Deletion of Cdkn1b ameliorates hyperglycemia by maintaining compensatory hyperinsulinemia in diabetic mice. Nat Med 2005; 11:175-82. [PMID: 15685168 DOI: 10.1038/nm1187] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Accepted: 01/04/2005] [Indexed: 12/31/2022]
Abstract
The protein p27(Kip1) regulates cell cycle progression in mammals by inhibiting the activity of cyclin-dependent kinases (CDKs). Here we show that p27(Kip1) progressively accumulates in the nucleus of pancreatic beta cells in mice that lack either insulin receptor substrate 2 (Irs2(-/-)) or the long form of the leptin receptor (Lepr(-/-) or db/db). Deletion of the gene encoding p27(Kip1) (Cdkn1b) ameliorated hyperglycemia in these animal models of type 2 diabetes mellitus by increasing islet mass and maintaining compensatory hyperinsulinemia, effects that were attributable predominantly to stimulation of pancreatic beta-cell proliferation. Thus, p27(Kip1) contributes to beta-cell failure during the development of type 2 diabetes in Irs2(-/-) and Lepr(-/-) mice and represents a potential new target for the treatment of this condition.
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Affiliation(s)
- Tohru Uchida
- Division of Diabetes and Digestive and Kidney Diseases, Department of Clinical Molecular Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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Craig J, Zhu H, Dyce PW, Petrik J, Li J. Leptin enhances oocyte nuclear and cytoplasmic maturation via the mitogen-activated protein kinase pathway. Endocrinology 2004; 145:5355-63. [PMID: 15284194 DOI: 10.1210/en.2004-0783] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Recent studies have suggested that leptin has a central role in female reproduction, including ovarian function. The leptin receptor (Ob-R) has six isoforms and can signal through either the MAPK or the Janus-activated kinase/signal transducer and activator of transcription signal-transduction pathway, depending on the isoform. Expression of Ob-R has been reported in human and mouse oocytes; however, the physiological role of leptin during follicular development and oocyte maturation is largely unknown. In the current study, expression of Ob-R during oocyte growth and maturation was investigated in porcine oocytes from small, medium, and large follicles and in oocytes in the germinal vesicle (GV), GV breakdown, and metaphase II (MII) stages at both the mRNA and protein levels. The proportion of oocytes expressing Ob-R was maximal in oocytes from medium follicles and at the GV breakdown stage (P < 0.05), whereas the proportion of oocytes expressing the long isoform, Ob-Rb, was found to be consistently low throughout growth and maturation. When included in oocyte maturation medium, leptin significantly increased the proportion of oocytes reaching MII (P < 0.01), elevated cyclin B1 protein content in MII-stage oocytes (P < 0.05), and enhanced embryo developmental potential (P < 0.05), suggesting that leptin plays a role in both nuclear and cytoplasmic maturation. During oocyte maturation, leptin increased phosphorylated MAPK content by 2.8-fold (P < 0.05), and leptin-stimulated oocyte maturation was blocked when leptin-induced MAPK phosphorylation was suppressed by a specific MAPK activation inhibitor, U0126 (P < 0.01), demonstrating that leptin enhances nuclear maturation via activation of the MAPK pathway.
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Affiliation(s)
- Jesse Craig
- Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada
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Zhang L, Fu Z, Binkley C, Giordano T, Burant CF, Logsdon CD, Simeone DM. Raf kinase inhibitory protein inhibits beta-cell proliferation. Surgery 2004; 136:708-15. [PMID: 15349122 DOI: 10.1016/j.surg.2003.12.013] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Raf-1 kinase inhibitory protein (RKIP) was recently identified as a physiologic endogenous inhibitor of the extracellular signal-regulated kinase (ERK) pathway. The expression and role of RKIP within the pancreas are unknown. METHODS RKIP expression in normal pancreas and human insulinomas was examined by using paraffin-embedded sections. Co-localization of RKIP within islet cell subtypes was performed by using double immunofluorescence staining with antibodies directed toward RKIP and endocrine markers. To examine the role of RKIP in beta-cell proliferation, stable expression of sense (ss) and antisense (as) RKIP was established in HIT-T15 beta cells. The effect of RKIP on the ERK-signaling pathway in beta cells was determined by Western blotting with the use of phospho-specific antibodies directed against mitogen-activated protein kinase kinase (MEK) and ERK. The role of RKIP in beta-cell proliferation was assessed by using MTS assay and FACS analysis. RESULTS RKIP was expressed only within pancreatic islet cells. Immunofluorescent double staining revealed that RKIP was expressed in most beta cells and a subset of pancreatic polypeptide-expressing cells. Based on the known function of RKIP, we hypothesized that RKIP expression would be downregulated in insulinomas: 8 of 9 human insulinomas demonstrated no RKIP staining, with decreased expression in 1 of 9 insulinomas. Studies using asRKIP and ssRKIP demonstrated that RKIP blocked activation of MEK and ERK by Raf-1 in beta cells. We also showed that RKIP inhibited beta-cell proliferation by altering cell cycle distribution, rather than by promoting apoptosis. CONCLUSIONS RKIP is important in beta-cell proliferation, and its downregulation may play a role in islet neoplasia.
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Affiliation(s)
- Lizhi Zhang
- Department of Surgery, University of Michigan Medical School, Ann Arbor, Mich, USA
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Yin N, Wang D, Zhang H, Yi X, Sun X, Shi B, Wu H, Wu G, Wang X, Shang Y. Molecular mechanisms involved in the growth stimulation of breast cancer cells by leptin. Cancer Res 2004; 64:5870-5. [PMID: 15313931 DOI: 10.1158/0008-5472.can-04-0655] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Obesity is a risk factor for breast cancer in postmenopausal women. Leptin, an adipocyte-derived cytokine, elicits proliferative effects in some cell types and potentially stimulates the growth of mammary epithelium. Here we show that leptin induced time- and dose-dependent signal transducer and activator of transcription 3 (STAT3) phosphorylation and extracellular signal-regulated kinase (ERK) 1/2 kinase activation in breast carcinoma cells. Blocking STAT3 phosphorylation with a specific inhibitor, AG490, abolished leptin-induced proliferation of MCF-7 cells, whereas blocking ERK1/2 activation by a specific ERK1/2 kinase inhibitor, U0126, did not result in any significant changes in leptin-induced cell proliferation. Our experiments also showed that one member of the p160 family of steroid receptor coactivators, steroid receptor coactivator (SRC)-1, but not glucocorticoid receptor interacting protein 1 (GRIP1) or amplified in breast cancer 1 (AIB1), also functioned in gene transactivation in response to leptin treatment. Glutathione S-transferase pull-down experiments showed that SRC-1 physically interacted with the activation domain of STAT3 and that chromatin immunoprecipitation experiments detected the occupancy of SRC-1, but not GRIP1 or AIB1, on the promoter of STAT3 target genes. Our experiments collectively showed that SRC-1 is involved in STAT3 signaling pathway that is implicated in leptin-stimulated cell growth.
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Affiliation(s)
- Na Yin
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing, China
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Kinsella JM, Laidlaw HA, Tang T, Harvey J, Sutherland C, Ashford MLJ. The aminoguanidine carboxylate BVT.12777 activates ATP-sensitive K+ channels in the rat insulinoma cell line, CRI-G1. BMC Pharmacol 2004; 4:17. [PMID: 15329154 PMCID: PMC516774 DOI: 10.1186/1471-2210-4-17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2004] [Accepted: 08/24/2004] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND 3-guanidinopropionic acid derivatives reduce body weight in obese, diabetic mice. We have assessed whether one of these analogues, the aminoguanidine carboxylate BVT.12777, opens KATP channels in rat insulinoma cells, by the same mechanism as leptin. RESULTS BVT.12777 hyperpolarized CRI-G1 rat insulinoma cells by activation of KATP channels. In contrast, BVT.12777 did not activate heterologously expressed pancreatic beta-cell KATP subunits directly. Although BVT.12777 stimulated phosphorylation of MAPK and STAT3, there was no effect on enzymes downstream of PI3K. Activation of KATP in CRI-G1 cells by BVT.12777 was not dependent on MAPK or PI3K activity. Confocal imaging showed that BVT.12777 induced a re-organization of cellular actin. Furthermore, the activation of KATP by BVT.12777 in CRI-G1 cells was demonstrated to be dependent on actin cytoskeletal dynamics, similar to that observed for leptin. CONCLUSIONS This study shows that BVT.12777, like leptin, activates KATP channels in insulinoma cells. Unlike leptin, BVT.12777 activates KATP channels in a PI3K-independent manner, but, like leptin, channel activation is dependent on actin cytoskeleton remodelling. Thus, BVT.12777 appears to act as a leptin mimetic, at least with respect to KATP channel activation, and may bypass up-stream signalling components of the leptin pathway.
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Affiliation(s)
- Jackie M Kinsella
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - Hilary A Laidlaw
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - Teresa Tang
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - Jenni Harvey
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - Calum Sutherland
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - Michael LJ Ashford
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
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