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Tumour-specific PI3K inhibition via nanoparticle-targeted delivery in head and neck squamous cell carcinoma. Nat Commun 2017; 8:14292. [PMID: 28194032 PMCID: PMC5316830 DOI: 10.1038/ncomms14292] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 12/14/2016] [Indexed: 02/08/2023] Open
Abstract
Alterations in PIK3CA, the gene encoding the p110α subunit of phosphatidylinositol 3-kinase (PI3Kα), are frequent in head and neck squamous cell carcinomas. Inhibitors of PI3Kα show promising activity in various cancer types, but their use is curtailed by dose-limiting side effects such as hyperglycaemia. In the present study, we explore the efficacy, specificity and safety of the targeted delivery of BYL719, a PI3Kα inhibitor currently in clinical development in solid tumours. By encapsulating BYL719 into P-selectin-targeted nanoparticles, we achieve specific accumulation of BYL719 in the tumour milieu. This results in tumour growth inhibition and radiosensitization despite the use of a sevenfold lower dose of BYL719 compared with oral administration. Furthermore, the nanoparticles abrogate acute and chronic metabolic side effects normally observed after BYL719 treatment. These findings offer a novel strategy that could potentially enhance the efficacy of PI3Kα inhibitors while mitigating dose-limiting toxicity in patients with head and neck squamous cell carcinomas. Head and neck squamous cell carcinomas (HNSCC) often harbour PIK3CA mutations but PI3Kα inhibitors can cause some side effects. Here, the authors develop P-selectin targeted nanoparticles to enhance tumour-specific delivery of a PI3Kα inhibitor to HNSCC PDX and orthotopic xenograft models.
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Graus-Nunes F, Marinho TDS, Barbosa-da-Silva S, Aguila MB, Mandarim-de-Lacerda CA, Souza-Mello V. Differential effects of angiotensin receptor blockers on pancreatic islet remodelling and glucose homeostasis in diet-induced obese mice. Mol Cell Endocrinol 2017; 439:54-64. [PMID: 27780713 DOI: 10.1016/j.mce.2016.10.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 10/21/2016] [Accepted: 10/21/2016] [Indexed: 02/07/2023]
Abstract
Obesity leads to adverse endocrine pancreas remodelling, reduced islet lifespan and early type 2 diabetes onset. AT1R blockade shows beneficial pleiotropic effects. This study sought to compare the effects of losartan and telmisartan on pancreatic islets remodelling and glucose homeostasis in diet-induced obese mice. High-fat diet yielded overweight, insulin resistance, islet apoptosis and hypertrophy. Suitable insulin levels and preserved endocrine pancreas structure were correlated to adequate AKT-FOXO1 pathway functioning in losartan-treated animals. Conversely, telmisartan yielded enhanced PDX1 and GLP-1 islet expression along with greater GLP-1 levels, with the consequent better islet glucose sensing and uptake. Greater islet vascularisation coupled with reduced apoptosis and macrophage infiltration seems to underlie the beneficial findings in both treatments. In conclusion, these results provide compelling evidence that two antihypertensive drugs (telmisartan and losartan) ameliorate pancreatic islet structure, glucose handling, and vascularisation in obese mice. Although only telmisartan countered overweight, both drugs yielded reduced apoptosis and islet preservation, with translational potential.
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Affiliation(s)
- Francielle Graus-Nunes
- Laboratory of Morphometry, Metabolism and Cardiovascular Disease, Biomedical Centre, Institute of Biology, State University of Rio de Janeiro, Brazil
| | - Thatiany de Souza Marinho
- Laboratory of Morphometry, Metabolism and Cardiovascular Disease, Biomedical Centre, Institute of Biology, State University of Rio de Janeiro, Brazil
| | - Sandra Barbosa-da-Silva
- Laboratory of Morphometry, Metabolism and Cardiovascular Disease, Biomedical Centre, Institute of Biology, State University of Rio de Janeiro, Brazil
| | - Marcia Barbosa Aguila
- Laboratory of Morphometry, Metabolism and Cardiovascular Disease, Biomedical Centre, Institute of Biology, State University of Rio de Janeiro, Brazil
| | - Carlos Alberto Mandarim-de-Lacerda
- Laboratory of Morphometry, Metabolism and Cardiovascular Disease, Biomedical Centre, Institute of Biology, State University of Rio de Janeiro, Brazil
| | - Vanessa Souza-Mello
- Laboratory of Morphometry, Metabolism and Cardiovascular Disease, Biomedical Centre, Institute of Biology, State University of Rio de Janeiro, Brazil.
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53
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Bhattacharya S, McElhanon KE, Gushchina LV, Weisleder N. Role of phosphatidylinositol-4,5-bisphosphate 3-kinase signaling in vesicular trafficking. Life Sci 2016; 167:39-45. [PMID: 27760304 DOI: 10.1016/j.lfs.2016.10.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 10/13/2016] [Accepted: 10/14/2016] [Indexed: 02/07/2023]
Abstract
Phosphatidylinositol-4,5-bisphosphate 3-kinases (PI3Ks) are regulatory enzymes involved in the generation of lipid species that modulate cellular signaling pathways through downstream effectors to influence a variety of cellular functions. Years of intensive study of PI3Ks have produced a significant body of literature in many areas, including that PI3K can mediate intracellular vesicular trafficking and through these actions contribute to a number of important physiological functions. This review focuses on the crucial roles that PI3K and AKT, a major downstream partner of PI3K, play in the regulation of vesicle trafficking during various forms of vesicular endocytosis and exocytosis.
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Affiliation(s)
- Sayak Bhattacharya
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Kevin E McElhanon
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Liubov V Gushchina
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Noah Weisleder
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States.
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54
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Blandino-Rosano M, Scheys JO, Jimenez-Palomares M, Barbaresso R, Bender AS, Yanagiya A, Liu M, Rui L, Sonenberg N, Bernal-Mizrachi E. 4E-BP2/SH2B1/IRS2 Are Part of a Novel Feedback Loop That Controls β-Cell Mass. Diabetes 2016; 65:2235-48. [PMID: 27217487 PMCID: PMC4955981 DOI: 10.2337/db15-1443] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 05/09/2016] [Indexed: 01/08/2023]
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) regulates several biological processes, although the key downstream mechanisms responsible for these effects are poorly defined. Using mice with deletion of eukaryotic translation initiation factor 4E-binding protein 2 (4E-BP2), we determine that this downstream target is a major regulator of glucose homeostasis and β-cell mass, proliferation, and survival by increasing insulin receptor substrate 2 (IRS2) levels and identify a novel feedback mechanism by which mTORC1 signaling increases IRS2 levels. In this feedback loop, we show that 4E-BP2 deletion induces translation of the adaptor protein SH2B1 and promotes the formation of a complex with IRS2 and Janus kinase 2, preventing IRS2 ubiquitination. The changes in IRS2 levels result in increases in cell cycle progression, cell survival, and β-cell mass by increasing Akt signaling and reducing p27 levels. Importantly, 4E-BP2 deletion confers resistance to cytokine treatment in vitro. Our data identify SH2B1 as a major regulator of IRS2 stability, demonstrate a novel feedback mechanism linking mTORC1 signaling with IRS2, and identify 4E-BP2 as a major regulator of proliferation and survival of β-cells.
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Affiliation(s)
- Manuel Blandino-Rosano
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Joshua O Scheys
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Margarita Jimenez-Palomares
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Rebecca Barbaresso
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Aaron S Bender
- Diabetes, Obesity and Metabolism Institute, The Icahn School of Medicine at Mount Sinai, New York, NY
| | - Akiko Yanagiya
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Liangyou Rui
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Ernesto Bernal-Mizrachi
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI VA Ann Arbor Healthcare System, Ann Arbor, MI
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55
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Lakshmipathi J, Alvarez-Perez JC, Rosselot C, Casinelli GP, Stamateris RE, Rausell-Palamos F, O'Donnell CP, Vasavada RC, Scott DK, Alonso LC, Garcia-Ocaña A. PKCζ Is Essential for Pancreatic β-Cell Replication During Insulin Resistance by Regulating mTOR and Cyclin-D2. Diabetes 2016; 65:1283-96. [PMID: 26868297 PMCID: PMC4839210 DOI: 10.2337/db15-1398] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 02/06/2016] [Indexed: 12/23/2022]
Abstract
Adaptive β-cell replication occurs in response to increased metabolic demand during insulin resistance. The intracellular mediators of this compensatory response are poorly defined and their identification could provide significant targets for β-cell regeneration therapies. Here we show that glucose and insulin in vitro and insulin resistance in vivo activate protein kinase C ζ (PKCζ) in pancreatic islets and β-cells. PKCζ is required for glucose- and glucokinase activator-induced proliferation of rodent and human β-cells in vitro. Furthermore, either kinase-dead PKCζ expression (KD-PKCζ) or disruption of PKCζ in mouse β-cells blocks compensatory β-cell replication when acute hyperglycemia/hyperinsulinemia is induced. Importantly, KD-PKCζ inhibits insulin resistance-mediated mammalian target of rapamycin (mTOR) activation and cyclin-D2 upregulation independent of Akt activation. In summary, PKCζ activation is key for early compensatory β-cell replication in insulin resistance by regulating the downstream signals mTOR and cyclin-D2. This suggests that alterations in PKCζ expression or activity might contribute to inadequate β-cell mass expansion and β-cell failure leading to type 2 diabetes.
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Affiliation(s)
- Jayalakshmi Lakshmipathi
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Juan Carlos Alvarez-Perez
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Carolina Rosselot
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Gabriella P Casinelli
- Division of Pediatric Hematology/Oncology and Blood and Marrow Transplantation, Department of Pediatrics, Children's Hospital of Pittsburgh, Pittsburgh, PA
| | - Rachel E Stamateris
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Francisco Rausell-Palamos
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Christopher P O'Donnell
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
| | - Rupangi C Vasavada
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Donald K Scott
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Laura C Alonso
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Adolfo Garcia-Ocaña
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
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56
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Stamateris RE, Sharma RB, Kong Y, Ebrahimpour P, Panday D, Ranganath P, Zou B, Levitt H, Parambil NA, O'Donnell CP, García-Ocaña A, Alonso LC. Glucose Induces Mouse β-Cell Proliferation via IRS2, MTOR, and Cyclin D2 but Not the Insulin Receptor. Diabetes 2016; 65:981-95. [PMID: 26740601 PMCID: PMC5314707 DOI: 10.2337/db15-0529] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Accepted: 12/29/2015] [Indexed: 12/21/2022]
Abstract
An important goal in diabetes research is to understand the processes that trigger endogenous β-cell proliferation. Hyperglycemia induces β-cell replication, but the mechanism remains debated. A prime candidate is insulin, which acts locally through the insulin receptor. Having previously developed an in vivo mouse hyperglycemia model, we tested whether glucose induces β-cell proliferation through insulin signaling. By using mice lacking insulin signaling intermediate insulin receptor substrate 2 (IRS2), we confirmed that hyperglycemia-induced β-cell proliferation requires IRS2 both in vivo and ex vivo. Of note, insulin receptor activation was not required for glucose-induced proliferation, and insulin itself was not sufficient to drive replication. Glucose and insulin caused similar acute signaling in mouse islets, but chronic signaling differed markedly, with mammalian target of rapamycin (MTOR) and extracellular signal-related kinase (ERK) activation by glucose and AKT activation by insulin. MTOR but not ERK activation was required for glucose-induced proliferation. Cyclin D2 was necessary for glucose-induced β-cell proliferation. Cyclin D2 expression was reduced when either IRS2 or MTOR signaling was lost, and restoring cyclin D2 expression rescued the proliferation defect. Human islets shared many of these regulatory pathways. Taken together, these results support a model in which IRS2, MTOR, and cyclin D2, but not the insulin receptor, mediate glucose-induced proliferation.
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Affiliation(s)
- Rachel E Stamateris
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Rohit B Sharma
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Yahui Kong
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Pantea Ebrahimpour
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Deepika Panday
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Pavana Ranganath
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Baobo Zou
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Helena Levitt
- Division of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | | | - Christopher P O'Donnell
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Adolfo García-Ocaña
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Disease, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Laura C Alonso
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
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57
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Gelam Honey Attenuates the Oxidative Stress-Induced Inflammatory Pathways in Pancreatic Hamster Cells. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2016; 2016:5843615. [PMID: 27034691 PMCID: PMC4808561 DOI: 10.1155/2016/5843615] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 08/23/2015] [Accepted: 10/01/2015] [Indexed: 01/22/2023]
Abstract
Purpose. Type 2 diabetes consists of progressive hyperglycemia and insulin resistance, which could result from glucose toxicity, inflammatory cytokines, and oxidative stress. In the present study we investigated the effect of Gelam honey and quercetin on the oxidative stress-induced inflammatory pathways and the proinflammatory cytokines. Methods. HIT-T15 cells were cultured and preincubated with the extract of Gelam honey (20, 40, 60, and 80 μg/mL), as well as quercetin (20, 40, 60, and 80 μM), prior to stimulation by 20 and 50 mM glucose. Results. HIT-T15 cells cultured under hyperglycemic condition showed a significant increase in the inflammatory pathways by phosphorylating JNK, IKK-β, and IRS-1 at Ser307 (p < 0.05). There was a significant decrease in the phosphorylation of Akt at Ser473 (p < 0.05). Pretreatment with Gelam honey and quercetin reduced the expression of phosphorylated JNK, IKK-β, and IRS-1, thereby significantly reducing the expression of proinflammatory cytokines like TNF-α, IL-6, and IL-1β (p < 0.05). At the same time there was a significant increase in the phosphorylated Akt showing the protective effects against inflammation and insulin resistance (p < 0.05). In conclusion, our data suggest the potential use of the extract from Gelam honey and quercetin in modulating the inflammation induced insulin signaling pathways.
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58
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The Potential Protective Action of Vitamin D in Hepatic Insulin Resistance and Pancreatic Islet Dysfunction in Type 2 Diabetes Mellitus. Nutrients 2016; 8:147. [PMID: 26959059 PMCID: PMC4808876 DOI: 10.3390/nu8030147] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 02/26/2016] [Accepted: 02/29/2016] [Indexed: 02/06/2023] Open
Abstract
Vitamin D deficiency (i.e., hypovitaminosis D) is associated with increased insulin resistance, impaired insulin secretion, and poorly controlled glucose homeostasis, and thus is correlated with the risk of metabolic diseases, including type 2 diabetes mellitus (T2DM). The liver plays key roles in glucose and lipid metabolism, and its dysregulation leads to abnormalities in hepatic glucose output and triglyceride accumulation. Meanwhile, the pancreatic islets are constituted in large part by insulin-secreting β cells. Consequently, islet dysfunction, such as occurs in T2DM, produces hyperglycemia. In this review, we provide a critical appraisal of the modulatory actions of vitamin D in hepatic insulin sensitivity and islet insulin secretion, and we discuss the potential roles of a local vitamin D signaling in regulating hepatic and pancreatic islet functions. This information provides a scientific basis for establishing the benefits of the maintenance, or dietary manipulation, of adequate vitamin D status in the prevention and management of obesity-induced T2DM and non-alcoholic fatty liver disease.
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59
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Liu H, Zheng J, Li RH. Clinical efficacy of 'Spleen-kidney-care' Yiqi Huayu and Jiangzhuo traditional Chinese medicine for the treatment of patients with diabetic nephropathy. Exp Ther Med 2015; 10:1096-1102. [PMID: 26622446 DOI: 10.3892/etm.2015.2627] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 08/19/2014] [Indexed: 12/28/2022] Open
Abstract
The aim of the present study was to investigate the effect of the traditional Chinese medicine (TCM), 'Spleen-kidney-care' Yiqi Huayu and Jiangzhuo decoction (SKC-YJ), as an adjuvant therapy in diabetic nephropathy (DN) treatment. In total, 72 patients with DN were randomly divided into control (n=54) and experimental (n=18) groups, with the latter administered SKC-YJ treatment. Indicators for determining the condition of the patients included the levels of proteinuria, blood glucose, glycosylated hemoglobin, blood lipids, blood viscosity and C-reactive protein, which were used to analyze the treatment protocols for DN. Following SKC-YJ treatment, the urinary albumin excretion rate, fasting blood glucose, 2 h-postprandial blood glucose, glycosylated hemoglobin, triglyceride, total cholesterol, blood viscosity, fibrinogen and C-reactive protein levels were detected in the two groups, and were all demonstrated to decrease significantly following treatment with SKC-YJ. Furthermore, the results revealed that SKC-YJ treatment exhibited no significant side-effects on the blood, liver and renal functions or gastrointestinal reactions. By contrast, SKC-YJ improved the symptoms of nausea, vomiting and diarrhea in the patients with DN, while showing no allergic reaction during the observation period. Therefore, SKC-YJ treatment was shown to significantly improve the clinical efficacy of DN treatment, illustrating novel roles for TCM in DN treatment.
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Affiliation(s)
- Hong Liu
- Department of Nephrology, Chongqing Hospital of Traditional Chinese Medicine, Chongqing 400021, P.R. China
| | - Jin Zheng
- Department of Nephrology, Chongqing Hospital of Traditional Chinese Medicine, Chongqing 400021, P.R. China
| | - Rong-Heng Li
- Cooperation Department of Chinese and Western Medicine, First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
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60
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Gao Y, Liao G, Xiang C, Yang X, Cheng X, Ou Y. Effects of phycocyanin on INS-1 pancreatic β-cell mediated by PI3K/Akt/FoxO1 signaling pathway. Int J Biol Macromol 2015; 83:185-94. [PMID: 26616456 DOI: 10.1016/j.ijbiomac.2015.11.054] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 10/22/2015] [Accepted: 11/20/2015] [Indexed: 01/09/2023]
Abstract
The level of methylglyoxal (MG), which is a side-product of metabolic pathways, particularly in glycolysis, is elevated in diabetes. Notably, the accumulation of MG causes a series of pathological changes. Phycocyanin (PC) has been demonstrated to show insulin-sensitizing effect, however, the underlying molecular mechanism remains elusive. The aim of this study was to investigate the protective effects of PC on INS-1 rat insulinoma β-cell against MG-induced cell dysfunction, as well as the underlying mechanisms. PC was preliminarily verified to time-dependently activate PI3-kinase (PI3K) pathway, but the PI3K-specific inhibitor Wortmannin blocked the effect of PC. Glucose-stimulated insulin secretion (GSIS) was impaired in MG-treated INS-1 cells. Furthermore, MG induced dephosphorylation of Akt and FoxO1, resulting in nuclear localization and transactivation of FoxO1. Nevertheless, these effects were all effectively attenuated by PC. The ameliorated insulin secretion was related to the changes of FoxO1 mediated by PC, which demonstrated by RNA interference. And, the dosage used in the above experiments did not affect β-cell viability and apoptosis, although long-term MG induced cell apoptosis and mitochondrial dysfunction. In conclusion, PC was capable to protect INS-1 pancreatic β-cell against MG-induced cell dysfunction through modulating PI3K/Akt pathway and the downstream FoxO1.
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Affiliation(s)
- Yingnv Gao
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China
| | - Gaoyong Liao
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China
| | - Chenxi Xiang
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China
| | - Xuegan Yang
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China
| | - Xiaodong Cheng
- Department of Integrative Biology & Pharmacology, The University of Texas Health Science Center, Houston, USA.
| | - Yu Ou
- School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China.
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61
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Li J, Li Q, Tang J, Xia F, Wu J, Zeng R. Quantitative Phosphoproteomics Revealed Glucose-Stimulated Responses of Islet Associated with Insulin Secretion. J Proteome Res 2015; 14:4635-46. [PMID: 26437020 DOI: 10.1021/acs.jproteome.5b00507] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
As central tissue of glucose homeostasis, islet has been an important focus of diabetes research. Phosphorylation plays pivotal roles in islet function, especially in islet glucose-stimulated insulin secretion. A systematic view on how phosphorylation networks were coordinately regulated in this process remains lacking, partially due to the limited amount of islets from an individual for a phosphoproteomic analysis. Here we optimized the in-tip and best-ratio phosphopeptide enrichment strategy and a SILAC-based workflow for processing rat islet samples. With limited islet lysates from each individual rat (20-47 μg), we identified 8539 phosphosites on 2487 proteins. Subsequent quantitative analyses uncovered that short-term (30 min) high glucose stimulation induced coordinate responses of islet phosphoproteome on multiple biological levels, including insulin secretion related pathways, cytoskeleton dynamics, protein processing in ER and Golgi, transcription and translation, and so on. Furthermore, three glucose-responsive phosphosites (Prkar1a pT75pS77 and Tagln2 pS163) from the data set were proved to be correlated with insulin secretion. Overall, we initially gave an in-depth map of islet phosphoproteome regulated by glucose on individual rat level. This was a significant addition to our knowledge about how phosphorylation networks responded in insulin secretion. Also, the list of changed phosphosites was a valuable resource for molecular researchers in diabetes field.
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Affiliation(s)
- Jiaming Li
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences , 320 Yueyang Road, Shanghai 200031, China
| | - Qingrun Li
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences , 320 Yueyang Road, Shanghai 200031, China
| | - Jiashu Tang
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences , 320 Yueyang Road, Shanghai 200031, China
| | - Fangying Xia
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences , 320 Yueyang Road, Shanghai 200031, China
| | - Jiarui Wu
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences , 320 Yueyang Road, Shanghai 200031, China.,Department of Life Sciences, ShanghaiTech University , 100 Haike Road, Shanghai 201210, China.,Shanghai Institutes for Advanced Study, Chinese Academy of Sciences , 99 Haike Road, Shanghai 201210, China
| | - Rong Zeng
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences , 320 Yueyang Road, Shanghai 200031, China.,Department of Life Sciences, ShanghaiTech University , 100 Haike Road, Shanghai 201210, China.,Shanghai Institutes for Advanced Study, Chinese Academy of Sciences , 99 Haike Road, Shanghai 201210, China
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62
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Specific and redundant roles of PKBα/AKT1 and PKBβ/AKT2 in human pancreatic islets. Exp Cell Res 2015; 338:82-8. [PMID: 26318486 DOI: 10.1016/j.yexcr.2015.08.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 07/16/2015] [Accepted: 08/20/2015] [Indexed: 01/09/2023]
Abstract
Protein kinase Bα (PKBα)/AKT1 and PKBβ/AKT2 are required for normal peripheral insulin action but their role in pancreatic β cells remains enigmatic as indicated by the relatively mild islet phenotype of mice with deficiency for either one of these two isoforms. In this study we have analysed proliferation, apoptosis, β cell size and glucose-stimulated insulin secretion in human islets overexpressing either PKBα or PKBβ. Our results reveal redundant and specific functions. Overexpression of either isoform resulted in increased β cell size, but insulin production and secretion remained unchanged. Proliferation and apoptosis of β cells were only significantly stimulated and inhibited, respectively, by PKBα/AKT1. Importantly, overexpression of PKBα/AKT1 in dissociated islets increased the ratio of β cells to non-β cells. These results confirm our previous findings obtained with rodent islets and strongly indicate that PKBα/AKT1 can regulate β cell mass also in human islets.
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Lee HJ, Choi YJ, Park SY, Kim JY, Won KC, Son JK, Kim YW. Hexane Extract of Orthosiphon stamineus Induces Insulin Expression and Prevents Glucotoxicity in INS-1 Cells. Diabetes Metab J 2015; 39:51-8. [PMID: 25729713 PMCID: PMC4342537 DOI: 10.4093/dmj.2015.39.1.51] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 06/02/2014] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Hyperglycemia, a characteristic feature of diabetes, induces glucotoxicity in pancreatic β-cells, resulting in further impairment of insulin secretion and worsening glycemic control. Thus, preservation of insulin secretory capacity is essential for the management of type 2 diabetes. In this study, we evaluated the ability of an Orthosiphon stamineus (OS) extract to prevent glucotoxicity in insulin-producing cells. METHODS We measured insulin mRNA expression and glucose-stimulated insulin secretion (GSIS) in OS-treated INS-1 cells after exposure to a high glucose (HG; 30 mM) concentration. RESULTS The hexane extract of OS elevated mRNA expression of insulin as well as pancreatic and duodenal homeobox-1 of INS-1 cells in a dose-dependent manner. The hexane OS extract also increased the levels of phosphorylated phosphatidylinositol 3-kinase (PI3K) in a concentration-dependent manner. Additionally, Akt phosphorylation was elevated by treatment with 100 and 200 µmol of the hexane OS extract. Three days of HG exposure suppressed insulin mRNA expression and GSIS; these expressions were restored by treatment with the hexane OS extract. HG elevated peroxide levels in the INS-1 cells. These levels were unaffected by OS treatment under both normal and hyperglycemic conditions. CONCLUSION Our results suggested that the hexane extract of OS elevates insulin mRNA expression and prevents glucotoxicity induced by a 3-day treatment with HG. This was associated with the activation of PI-3K and Akt.
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Affiliation(s)
- Hae-Jung Lee
- Department of Pediatrics, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea
| | - Yoon-Jung Choi
- Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea
| | - So-Young Park
- Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea
| | - Jong-Yeon Kim
- Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea
| | - Kyu-Chang Won
- Department of Internal Medicine, Yeungnam University College of Medicine, Daegu, Korea
| | - Jong-Keun Son
- Yeungnam University College of Pharmacy, Gyeongsan, Korea
| | - Yong-Woon Kim
- Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea
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Gregg B, Elghazi L, Alejandro EU, Smith MR, Blandino-Rosano M, El-Gabri D, Cras-Méneur C, Bernal-Mizrachi E. Exposure of mouse embryonic pancreas to metformin enhances the number of pancreatic progenitors. Diabetologia 2014; 57:2566-75. [PMID: 25249235 PMCID: PMC4417192 DOI: 10.1007/s00125-014-3379-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 08/28/2014] [Indexed: 01/23/2023]
Abstract
AIMS/HYPOTHESIS Developing beta cells are vulnerable to nutrient environmental signals. Early developmental processes that alter the number of pancreatic progenitors can determine the number of beta cells present at birth. Metformin, the most widely used oral agent for treating diabetes, alters intracellular energy status in part by increasing AMP-activated protein kinase (AMPK) signalling. This study examined the effect of metformin on developing pancreas and beta cells. METHODS Pancreatic rudiments from CD-1 mice at embryonic day 13.0 (E13.0) were cultured with metformin, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR, an AMPK activator) or vehicle control in vitro. In another set of studies, pregnant C57BL/6 mice were treated with metformin throughout gestation. Embryonic (E14.0) and neonatal pancreases were then analysed for their morphometry. RESULTS In vitro metformin treatment led to an increase in the proliferation and number of pancreatic duodenal homeobox 1-positive (PDX1(+)) progenitors. These results were reproduced by in vitro culture of embryonic pancreas rudiments with AICAR, suggesting that AMPK activation was involved. Similarly, metformin administration to pregnant dams induced an increase in both PDX1(+) and neurogenin 3-positive progenitors in the embryonic pancreas at E14.0 and these changes resulted in an increased beta cell fraction in neonates. CONCLUSIONS/INTERPRETATION These results indicate that exposure to metformin during gestation modulates the early steps of beta cell development (prior to E14.0) towards an increase in the number of pancreatic and endocrine progenitors. These changes ultimately result in a higher beta cell fraction at birth. These findings are of clinical importance given that metformin is currently used for the treatment of gestational diabetes.
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Affiliation(s)
- Brigid Gregg
- Department of Pediatrics, Division of Endocrinology, Diabetes and Metabolism, University of Michigan, Ann Arbor, Michigan, USA
| | - Lynda Elghazi
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Emilyn U. Alejandro
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Michelle R. Smith
- Department of Pediatrics, Division of Endocrinology, Diabetes and Metabolism, University of Michigan, Ann Arbor, Michigan, USA
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Manuel Blandino-Rosano
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Deena El-Gabri
- Department of Pediatrics, Division of Endocrinology, Diabetes and Metabolism, University of Michigan, Ann Arbor, Michigan, USA
| | - Corentin Cras-Méneur
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Ernesto Bernal-Mizrachi
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
- VA Ann Arbor Healthcare System, Ann Arbor, Michigan
- Corresponding author: Dr. Ernesto Bernal-Mizrachi VA Ann Arbor Healthcare System, Ann Arbor, Michigan., Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan 48109-0678, USA., Phone: +1 (734) 615-0262, Fax: +1 (734) 936-6684,
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Bridges D, Saltiel AR. Phosphoinositides: Key modulators of energy metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:857-66. [PMID: 25463477 DOI: 10.1016/j.bbalip.2014.11.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/31/2014] [Accepted: 11/10/2014] [Indexed: 12/19/2022]
Abstract
Phosphoinositides are key players in many trafficking and signaling pathways. Recent advances regarding the synthesis, location and functions of these lipids have dramatically improved our understanding of how and when these lipids are generated and what their roles are in animal physiology. In particular, phosphoinositides play a central role in insulin signaling, and manipulation of PtdIns(3,4,5)P₃levels in particular, may be an important potential therapeutic target for the alleviation of insulin resistance associated with obesity and the metabolic syndrome. In this article we review the metabolism, regulation and functional roles of phosphoinositides in insulin signaling and the regulation of energy metabolism. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Dave Bridges
- Departments of Physiology and Pediatrics, University of Tennessee Health Science Center, Memphis, TN, USA; Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, TN, USA.
| | - Alan R Saltiel
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
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Ballon JS, Pajvani U, Freyberg Z, Leibel RL, Lieberman JA. Molecular pathophysiology of metabolic effects of antipsychotic medications. Trends Endocrinol Metab 2014; 25:593-600. [PMID: 25190097 DOI: 10.1016/j.tem.2014.07.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 07/21/2014] [Accepted: 07/23/2014] [Indexed: 11/23/2022]
Abstract
Antipsychotic medications are associated with major metabolic changes that contribute to medical morbidity and a significantly shortened life span. The mechanisms for these changes provide us with a broader understanding of central nervous and peripheral organ-mediated metabolic regulation. This paper reviews an extensive literature regarding putative mechanisms for effects of antipsychotic medications on weight regulation and glucose homeostasis as well as potential inherent metabolic risks of schizophrenia itself. We present a model suggesting that peripheral antipsychotic targets play a critical role in drug-induced weight gain and diabetes. We propose that a better understanding of these mechanisms will be crucial to developing improved treatments for serious mental illnesses as well as providing potentially novel therapeutic targets of metabolic disorders including diabetes.
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Affiliation(s)
- Jacob S Ballon
- Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Division of Experimental Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Utpal Pajvani
- Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Naomi Berrie Diabetes Institute, New York, NY 10032, USA
| | - Zachary Freyberg
- Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Rudolph L Leibel
- Naomi Berrie Diabetes Institute, New York, NY 10032, USA; Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Jeffrey A Lieberman
- Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Division of Experimental Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA.
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Cochran BJ, Bisoendial RJ, Hou L, Glaros EN, Rossy J, Thomas SR, Barter PJ, Rye KA. Apolipoprotein A-I increases insulin secretion and production from pancreatic β-cells via a G-protein-cAMP-PKA-FoxO1-dependent mechanism. Arterioscler Thromb Vasc Biol 2014; 34:2261-7. [PMID: 25147338 DOI: 10.1161/atvbaha.114.304131] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVE Therapeutic interventions that increase plasma levels of high-density lipoproteins and apolipoprotein A-I (apoA-I) A-I, the major high-density lipoprotein apolipoprotein, improve glycemic control in people with type 2 diabetes mellitus. High-density lipoproteins and apoA-I also enhance insulin synthesis and secretion in isolated pancreatic islets and clonal β-cell lines. This study identifies the signaling pathways that mediate these effects. APPROACH AND RESULTS Incubation with apoA-I increased cAMP accumulation in Ins-1E cells in a concentration-dependent manner. The increase in cAMP levels was inhibited by preincubating the cells with the cell-permeable, transmembrane adenylate cyclase inhibitor, 2'5' dideoxyadenosine, but not with KH7, which inhibits soluble adenylyl cyclases. Incubation of Ins-1E cells with apoA-I resulted in colocalization of ATP-binding cassette transporter A1 with the Gαs subunit of a heterotrimeric G-protein and a Gαs subunit-dependent increase in insulin secretion. Incubation of Ins-1E cells with apoA-I also increased protein kinase A phosphorylation and reduced the nuclear localization of forkhead box protein O1 (FoxO1). Preincubation of Ins-1E cells with the protein kinase A-specific inhibitors, H89 and PKI amide, prevented apoA-I from increasing insulin secretion and mediating the nuclear exclusion of FoxO1. Transfection of Ins-1E cells with a mutated FoxO1 that is restricted to the nucleus confirmed the requirement for FoxO1 nuclear exclusion by blocking insulin secretion in apoA-I-treated Ins-1E cells. ApoA-I also increased Irs1, Irs2, Ins1, Ins2, and Pdx1 mRNA levels. CONCLUSIONS ApoA-I increases insulin synthesis and secretion via a heterotrimeric G-protein-cAMP-protein kinase A-FoxO1-dependent mechanism that involves transmembrane adenylyl cyclases and increased transcription of key insulin response and β-cell survival genes.
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Affiliation(s)
- Blake J Cochran
- From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.)
| | - Radjesh J Bisoendial
- From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.)
| | - Liming Hou
- From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.)
| | - Elias N Glaros
- From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.)
| | - Jérémie Rossy
- From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.)
| | - Shane R Thomas
- From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.)
| | - Philip J Barter
- From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.)
| | - Kerry-Anne Rye
- From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.).
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Li L, Li X, Zhu Y, Zhang M, Yin D, Lu J, Liu F, Wang C, Jia W. Growth receptor binding protein 10 inhibits glucose-stimulated insulin release from pancreatic β-cells associated with suppression of the insulin/insulin-like growth factor-1 signalling pathway. Clin Exp Pharmacol Physiol 2014; 40:841-7. [PMID: 23937793 DOI: 10.1111/1440-1681.12160] [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] [Received: 03/02/2013] [Revised: 07/22/2013] [Accepted: 08/08/2013] [Indexed: 01/30/2023]
Abstract
Growth receptor binding protein 10 (Grb10) is an adaptor protein that interacts with the insulin receptor and insulin-like growth factor (IGF)-1 receptor. Overexpression of Grb10 in muscle cells and adipocytes inhibits insulin signalling, and transgenic mice overexpressing Grb10 exhibit impaired glucose tolerance. However, the roles of Grb10 in β-cells remain unknown. The aim of the present study was to explore the effect of Grb10 on β-cell function. The effects of Grb10 on glucose-stimulated insulin secretion (GSIS) and the insulin/IGF-1 signalling pathway were investigated in rat islets and/or dispersed islet cells with Grb10 overexpresion by adenovirus transfection. Protein expression was detected by western blot analysis. We found that Grb10 was expressed in both human and rat pancreas. Expression of Grb10 was increased in islets isolated from rats fed a high-fat plus high-sugar diet compared with islets isolated from rats fed normal chow diet, as well as in INS 832/13 cells exposed to high levels of glucose (20 mmol/L), palmitate (1 mmol/L) and interleukin-1β (50 U/mL). Overexpression of Grb10 in INS 832/13 cells or rat islets impaired GSIS compared with the respective control (all P < 0.05). Moreover, inhibition of GSIS by Grb10 overexpression was associated with a decrease in insulin- and IGF-1-induced Akt and extracellular signal-regulated kinase 1/2 phosphorylation. The results of the present study demonstrate that Grb10 is an important negative regulator of insulin/IGF-1 signalling in pancreatic β-cells and a potential target to improve β-cell function.
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Affiliation(s)
- Ling Li
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China; Diabetes Institute, Shanghai Jiao Tong University, Shanghai, China; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai, China
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69
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Jiang Q, Ding S, Wu J, Liu X, Wu Z. Norepinephrine stimulates mobilization of endothelial progenitor cells after limb ischemia. PLoS One 2014; 9:e101774. [PMID: 25007164 PMCID: PMC4090158 DOI: 10.1371/journal.pone.0101774] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 06/11/2014] [Indexed: 11/19/2022] Open
Abstract
Objective During several pathological processes such as cancer progression, thermal injury, wound healing and hindlimb ischemia, the mobilization of endothelial progenitor cells (EPCs) mobilization was enhanced with an increase of sympathetic nerve activity and norepinephrine (NE) secretion, yet the cellular and molecular mechanisms involved in the effects of NE on EPCs has less been investigated. Methods and Results EPCs from BMs, peripheral circulation and spleens, the VEGF concentration in BM, skeletal muscle, peripheral circulation and spleen and angiogenesis in ischemic gastrocnemius were quantified in mice with hindlimbs ischemia. Systemic treatment of NE significantly increased EPCs number in BM, peripheral circulation and spleen, VEGF concentration in BM and skeletal muscle and angiogenesis in ischemic gastrocnemius in mice with hind limb ischemia, but did not affair VEGF concentration in peripheral circulation and spleen. EPCs isolated from healthy adults were cultured with NE in vitro to evaluate proliferation potential, migration capacity and phosphorylations of Akt and eNOS signal moleculars. Treatment of NE induced a significant increase in number of EPCs in the S-phase in a dose-dependent manner, as well as migrative activity of EPCs in vitro (p<0.05). The co-treatment of Phentolamine, I127, LY294002 and L-NAME with NE blocked the effects of NE on EPCs proliferation and migration. Treatment with NE significantly increased phosphorylation of Akt and eNOS of EPCs. Addition of phentolamine and I127 attenuated the activation of Akt/eNOS pathway, but metoprolol could not. Pretreatment of mice with either Phentolamine or I127 significantly attenuated the effects of NE on EPCs in vivo, VEGF concentration in BM, skeletal muscle and angiogenesis in ischemic gastrocnemius, but Metoprolol did not. Conclusion These results unravel that sympathetic nervous system regulate EPCs mobilization and their pro-angiogenic capacity via α adrenoceptor, β 2 adrenoceptor and meanwhile Akt/eNOS signaling pathway.
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Affiliation(s)
- Qijun Jiang
- Department of Cardiology, Wuhan General Hospital of Guangzhou Military, Wuhan, Hubei, China
- Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Shifang Ding
- Department of Cardiology, Wuhan General Hospital of Guangzhou Military, Wuhan, Hubei, China
- * E-mail:
| | - Jianxiang Wu
- Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Xing Liu
- Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Zonggui Wu
- Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
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Bhatnagar S, Soni MS, Wrighton LS, Hebert AS, Zhou AS, Paul PK, Gregg T, Rabaglia ME, Keller MP, Coon JJ, Attie AD. Phosphorylation and degradation of tomosyn-2 de-represses insulin secretion. J Biol Chem 2014; 289:25276-86. [PMID: 25002582 DOI: 10.1074/jbc.m114.575985] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The abundance and functional activity of proteins involved in the formation of the SNARE complex are tightly regulated for efficient exocytosis. Tomosyn proteins are negative regulators of exocytosis. Tomosyn causes an attenuation of insulin secretion by limiting the formation of the SNARE complex. We hypothesized that glucose-dependent stimulation of insulin secretion from β-cells must involve reversing the inhibitory action of tomosyn. Here, we show that glucose increases tomosyn protein turnover. Within 1 h of exposure to 15 mM glucose, ~50% of tomosyn was degraded. The degradation of tomosyn in response to high glucose was blocked by inhibitors of the proteasomal pathway. Using (32)P labeling and mass spectrometry, we showed that tomosyn-2 is phosphorylated in response to high glucose, phorbol esters, and analogs of cAMP, all key insulin secretagogues. We identified 11 phosphorylation sites in tomosyn-2. Site-directed mutagenesis was used to generate phosphomimetic (Ser → Asp) and loss-of-function (Ser → Ala) mutants. The Ser → Asp mutant had enhanced protein turnover compared with the Ser → Ala mutant and wild type tomosyn-2. Additionally, the Ser → Asp tomosyn-2 mutant was ineffective at inhibiting insulin secretion. Using a proteomic screen for tomosyn-2-binding proteins, we identified Hrd-1, an E3-ubiquitin ligase. We showed that tomosyn-2 ubiquitination is increased by Hrd-1, and knockdown of Hrd-1 by short hairpin RNA resulted in increased abundance in tomosyn-2 protein levels. Taken together, our results reveal a mechanism by which enhanced phosphorylation of a negative regulator of secretion, tomosyn-2, in response to insulin secretagogues targets it to degradation by the Hrd-1 E3-ubiquitin ligase.
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Affiliation(s)
| | | | | | - Alexander S Hebert
- Chemistry and Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706
| | | | | | | | | | | | - Joshua J Coon
- Chemistry and Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706
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Rachdi L, Kariyawasam D, Aïello V, Herault Y, Janel N, Delabar JM, Polak M, Scharfmann R. Dyrk1A induces pancreatic β cell mass expansion and improves glucose tolerance. Cell Cycle 2014; 13:2221-9. [PMID: 24870561 PMCID: PMC4111677 DOI: 10.4161/cc.29250] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 05/15/2014] [Accepted: 05/15/2014] [Indexed: 01/27/2023] Open
Abstract
Type 2 diabetes is caused by a limited capacity of insulin-producing pancreatic β cells to increase their mass and function in response to insulin resistance. The signaling pathways that positively regulate functional β cell mass have not been fully elucidated. DYRK1A (also called minibrain/MNB) is a member of the dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) family. A significant amount of data implicates DYRK1A in brain growth and Down syndrome, and recent data indicate that Dyrk1A haploinsufficient mice have a low functional β cell mass. Here we ask whether Dyrk1A upregulation could be a way to increase functional β cell mass. We used mice overexpressing Dyrk1A under the control of its own regulatory sequences (mBACTgDyrk1A). These mice exhibit decreased glucose levels and hyperinsulinemia in the fasting state. Improved glucose tolerance is observed in these mice as early as 4 weeks of age. Upregulation of Dyrk1A in β cells induces expansion of β cell mass through increased proliferation and cell size. Importantly, mBACTgDyrk1A mice are protected against high-fat-diet-induced β cell failure through increase in β cell mass and insulin sensitivity. These studies show the crucial role of the DYRK1A pathway in the regulation of β cell mass and carbohydrate metabolism in vivo. Activating the DYRK1A pathway could thus represent an innovative way to increase functional β cell mass.
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Affiliation(s)
- Latif Rachdi
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
| | - Dulanjalee Kariyawasam
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
- Hôpital Universitaire Necker Enfants Malades; Endocrinologie Gynécologie Diabétologie Pédiatriques; IMAGINE Institute; Paris, France
| | - Virginie Aïello
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
| | - Yann Herault
- Institut de Génétique et de Biologie Moléculaire et Cellulaire; Translational Medicine and Neuroscience Program; IGBMC; CNRS; INSERM; Université de Strasbourg; UMR7104, UMR964, and Institut Clinique de la Souris; ICS; GIE CERBM; Illkirch, France
| | - Nathalie Janel
- Sorbonne Paris Cité; Unité de Biologie Fonctionnelle et Adaptative (BFA); CNRS UMR 8251; Paris Diderot University; Paris, France
| | - Jean-Maurice Delabar
- Sorbonne Paris Cité; Unité de Biologie Fonctionnelle et Adaptative (BFA); CNRS UMR 8251; Paris Diderot University; Paris, France
| | - Michel Polak
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
- Hôpital Universitaire Necker Enfants Malades; Endocrinologie Gynécologie Diabétologie Pédiatriques; IMAGINE Institute; Paris, France
| | - Raphaël Scharfmann
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
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Dadi PK, Vierra NC, Ustione A, Piston DW, Colbran RJ, Jacobson DA. Inhibition of pancreatic β-cell Ca2+/calmodulin-dependent protein kinase II reduces glucose-stimulated calcium influx and insulin secretion, impairing glucose tolerance. J Biol Chem 2014; 289:12435-45. [PMID: 24627477 DOI: 10.1074/jbc.m114.562587] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells is caused by Ca(2+) entry via voltage-dependent Ca(2+) channels. CaMKII is a key mediator and feedback regulator of Ca(2+) signaling in many tissues, but its role in β-cells is poorly understood, especially in vivo. Here, we report that mice with conditional inhibition of CaMKII in β-cells show significantly impaired glucose tolerance due to decreased GSIS. Moreover, β-cell CaMKII inhibition dramatically exacerbates glucose intolerance following exposure to a high fat diet. The impairment of islet GSIS by β-cell CaMKII inhibition is not accompanied by changes in either glucose metabolism or the activities of KATP and voltage-gated potassium channels. However, glucose-stimulated Ca(2+) entry via voltage-dependent Ca(2+) channels is reduced in islet β-cells with CaMKII inhibition, as well as in primary wild-type β-cells treated with a peptide inhibitor of CaMKII. The levels of basal β-cell cytoplasmic Ca(2+) and of endoplasmic reticulum Ca(2+) stores are also decreased by CaMKII inhibition. In addition, CaMKII inhibition suppresses glucose-stimulated action potential firing frequency. These results reveal that CaMKII is a Ca(2+) sensor with a key role as a feed-forward stimulator of β-cell Ca(2+) signals that enhance GSIS under physiological and pathological conditions.
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Affiliation(s)
- Prasanna K Dadi
- From the Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232
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73
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Vetere A, Choudhary A, Burns SM, Wagner BK. Targeting the pancreatic β-cell to treat diabetes. Nat Rev Drug Discov 2014; 13:278-89. [PMID: 24525781 DOI: 10.1038/nrd4231] [Citation(s) in RCA: 200] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Diabetes is a leading cause of morbidity and mortality worldwide, and predicted to affect over 500 million people by 2030. However, this growing burden of disease has not been met with a comparable expansion in therapeutic options. The appreciation of the pancreatic β-cell as a central player in the pathogenesis of both type 1 and type 2 diabetes has renewed focus on ways to improve glucose homeostasis by preserving, expanding and improving the function of this key cell type. Here, we provide an overview of the latest developments in this field, with an emphasis on the most promising strategies identified to date for treating diabetes by targeting the β-cell.
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Affiliation(s)
- Amedeo Vetere
- Chemical Biology Program, Center for the Science of Therapeutics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Amit Choudhary
- 1] Chemical Biology Program, Center for the Science of Therapeutics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA. [2] Society of Fellows, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Sean M Burns
- Medical & Population Genetics Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Bridget K Wagner
- Chemical Biology Program, Center for the Science of Therapeutics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
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74
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Jiang H, Torregrossa AC, Potts A, Pierini D, Aranke M, Garg HK, Bryan NS. Dietary nitrite improves insulin signaling through GLUT4 translocation. Free Radic Biol Med 2014; 67:51-7. [PMID: 24157451 DOI: 10.1016/j.freeradbiomed.2013.10.809] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 10/14/2013] [Accepted: 10/15/2013] [Indexed: 01/31/2023]
Abstract
Diabetes mellitus type 2 is a syndrome of disordered metabolism with inappropriate hyperglycemia owing to a reduction in the biological effectiveness of insulin. Type 2 diabetes is associated with an impaired nitric oxide (NO) pathway that probably serves as the key link between metabolic disorders and cardiovascular disease. Insulin-mediated translocation of GLUT4 involves the PI3K/Akt kinase signal cascade that results in activation of endothelial NO synthase (eNOS). eNOS is dysfunctional during diabetes. We hypothesize that loss of eNOS-derived NO terminates the signaling cascade and therefore cannot activate GLUT4 translocation and that dietary nitrite may repair this pathway. In this study, we administered 50mg/L sodium nitrite to db/db diabetic mice for 4 weeks. After 4 weeks treatment, the db/db mice experienced less weight gain, improved fasting glucose levels, and reduced insulin levels. Cell culture experiments using CHO-HIRc-myc-GLUT4eGFP cell lines stably expressing insulin receptor and myc-GLUT4eGFP protein, as well as L6 skeletal muscle cells stably expressing rat GLUT4 with a Myc epitope (L6-GLUT4myc), showed that NO, nitrite, and GSNO stimulate GLUT4 translocation independent of insulin, which is inhibited by NEM. Collectively our data suggest that nitrite improves insulin signaling through restoration of NO-dependent nitrosation of GLUT4 signaling translocation. These data suggest that NO-mediated nitrosation of GLUT4 by nitrite or other nitrosating agents is necessary and sufficient for GLUT4 translocation in target tissue. Description of this pathway may justify a high-nitrate/nitrite diet along with the glycemic index to provide a safe and nutritional regimen for the management and treatment of diabetes.
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Affiliation(s)
- Hong Jiang
- Texas Therapeutics Institute, Brown Foundation Institute of Molecular Medicine, Health Science Center, Houston, TX 77030, USA
| | - Ashley C Torregrossa
- Texas Therapeutics Institute, Brown Foundation Institute of Molecular Medicine, Health Science Center, Houston, TX 77030, USA
| | - Amy Potts
- Texas Therapeutics Institute, Brown Foundation Institute of Molecular Medicine, Health Science Center, Houston, TX 77030, USA
| | - Dan Pierini
- California State University at Fullerton, Fullerton, CA 92831, USA
| | - Mayank Aranke
- The University of Texas at Austin, Austin, TX 78712, USA
| | - Harsha K Garg
- Texas Therapeutics Institute, Brown Foundation Institute of Molecular Medicine, Health Science Center, Houston, TX 77030, USA
| | - Nathan S Bryan
- Texas Therapeutics Institute, Brown Foundation Institute of Molecular Medicine, Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, The University of Texas at Houston, Houston, TX 77030, USA.
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75
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Yang KT, Bayan JA, Zeng N, Aggarwal R, He L, Peng Z, Kassa A, Kim M, Luo Z, Shi Z, Medina V, Boddupally K, Stiles BL. Adult-onset deletion of Pten increases islet mass and beta cell proliferation in mice. Diabetologia 2014; 57:352-61. [PMID: 24162585 PMCID: PMC3918745 DOI: 10.1007/s00125-013-3085-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 09/27/2013] [Indexed: 12/31/2022]
Abstract
AIMS/HYPOTHESIS Adult beta cells have a diminished ability to proliferate. Phosphatase and tensin homologue (PTEN) is a lipid phosphatase that antagonises the function of the mitogenic phosphatidylinositol 3-kinase (PI3K) pathway. The objective of this study was to understand the role of PTEN and PI3K signalling in the maintenance of beta cells postnatally. METHODS We developed a Pten (lox/lox); Rosa26 (lacZ); RIP-CreER (+) model that permitted us to induce Pten deletion by treatment with tamoxifen in mature animals. We evaluated islet mass and function as well as beta cell proliferation in 3- and 12-month-old mice treated with tamoxifen (Pten deleted) vs mice treated with vehicle (Pten control). RESULTS Deletion of Pten in juvenile (3-month-old) beta cells significantly induced their proliferation and increased islet mass. The expansion of islet mass occurred concomitantly with the enhanced ability of the Pten-deleted mice to maintain euglycaemia in response to streptozotocin treatment. In older mice (>12 months of age), deletion of Pten similarly increased islet mass and beta cell proliferation. This novel finding suggests that PTEN-regulated mechanisms may override the age-onset diminished ability of beta cells to respond to mitogenic stimulation. We also found that proteins regulating G1/S cell-cycle transition, such as cyclin D1, cyclin D2, p27 and p16, were altered when PTEN was lost, suggesting that they may play a role in PTEN/PI3K-regulated beta cell proliferation in adult tissue. CONCLUSIONS/INTERPRETATION The signals regulated by the PTEN/PI3K pathway are important for postnatal maintenance of beta cells and regulation of their proliferation in adult tissues.
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Affiliation(s)
- Kai-Ting Yang
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA, USA
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76
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Veras K, Almeida FN, Nachbar RT, de Jesus DS, Camporez JP, Carpinelli AR, Goedecke JH, de Oliveira Carvalho CR. DHEA supplementation in ovariectomized rats reduces impaired glucose-stimulated insulin secretion induced by a high-fat diet. FEBS Open Bio 2014; 4:141-6. [PMID: 24490138 PMCID: PMC3907747 DOI: 10.1016/j.fob.2014.01.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 12/28/2013] [Accepted: 01/13/2014] [Indexed: 12/16/2022] Open
Abstract
Dehydroepiandrosterone (DHEA) and the dehydroepiandrosterone sulfate (DHEA-S) are steroids produced mainly by the adrenal cortex. There is evidence from both human and animal models suggesting beneficial effects of these steroids for obesity, diabetes mellitus, hypertension, and osteoporosis, conditions associated with the post-menopausal period. Accordingly, we hypothesized that DHEA supplementation in ovariectomized (OVX) female rats fed a high-fat diet would maintain glucose-induced insulin secretion (GSIS) and pancreatic islet function. OVX resulted in a 30% enlargement of the pancreatic islets area compared to the control rats, which was accompanied by a 50% reduction in the phosphorylation of AKT protein in the pancreatic islets. However, a short-term high-fat diet induced insulin resistance, accompanied by impaired GSIS in isolated pancreatic islets. These effects were reversed by DHEA treatment, with improved insulin sensitivity to levels similar to the control group, and with increased serine phosphorylation of the AKT protein. These data confirm the protective effect of DHEA on the endocrine pancreas in a situation of diet-induced overweight and low estrogen concentrations, a phenotype similar to that of the post-menopausal period. Dehydroepiandrosterone (DHEA) is a physiological precursor of androgens and estrogens. Ovariectomized rats fed a high-fat diet showed insulin resistance and impaired glucose-induced insulin secretion. These effects were reversed by DHEA treatment, with improved insulin secretion and sensitivity.
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Key Words
- DHEA, dehydroepiandrosterone
- DHEA-S, dehydroepiandrosterone sulfate
- GSIS, glucose-induced insulin secretion
- GTT, glucose tolerance test
- HFD, high-fat diet
- High fat diet
- Insulin secretion
- Insulin sensitivity
- Kitt, glucose disappearance rate
- Menopause
- OHL, ovariectomized rats fed HFD
- OHLD, ovariectomized rats fed a HFD and treated with DHEA
- OVX, ovariectomized rats
- PI, propidium iodide
- PI3K, phosphatidylinositol-3-kinase
- PI3K-PDK1-Akt, PI3K-3-phosphoinositide dependent kinase-Akt
- Pancreatic islets
- SDS–PAGE, sodium dodecyl sulfate poly-acrylamide electrophoresis
- SHAM, sham-operated rats
- SHL, sham rats fed a HFD
- p-Akt/Akt
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Affiliation(s)
- Katherine Veras
- Department of Physiology and Biophysics, ICB 1, USP, São Paulo, SP, Brazil
| | | | | | | | | | | | - Julia H Goedecke
- South African Medical Research Council and Department of Human Biology, University of Cape Town, Cape Town, South Africa
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Abstract
Fractalkine is a chemokine, which has been shown to play important roles in metabolic disease in both animal models and humans. Fractalkine is a key player in the accumulation of atherosclerotic plaques, and fractalkine receptor (CX3CR1) mutations have been implicated in obesity. Serum fractalkine levels have been found to be elevated in type 2 diabetic patients, but the role of fractalkine signaling on the pancreatic β cell was unclear. Recently published findings in April 2013 issue of the journal Cell by Lee and Olefsky et al. have implicated fractalkine in β-cell insulin secretion. They demonstrate that Cx3cr1 knockout mice have impaired glucose tolerance resulting from decreased insulin secretion. In addition, fractalkine administration improved glucose tolerance and induced insulin secretion. This modulation of insulin secretion was proposed to result from an increase in intracellular calcium and potentiation of insulin secretion, which occurs in a Gαi and MEK-dependent manner. They also found that Cx3cr1 knockout animals had transcriptional repression of genes important for β-cell function, specifically NeuroD, via induction of ICER-1. One important issue that remains unresolved is how CX3CR1 signaling regulates the potentiation of calcium influx and the distal events in insulin exocytosis. Finally, testing the effects of fractalkine treatment on proliferation and survival in vivo during regenerative conditions would be critical to determine the potential use of this chemokine in diabetes. While these exciting results open the possibility for new therapeutics, there are some concerns about a potential risk for exacerbation of atherosclerosis.
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Affiliation(s)
- Brigid Gregg
- Department of Pediatrics and Communicable Diseases; Division of Endocrinology, Diabetes, and Metabolism; University of Michigan; Ann Arbor, MI USA
| | - Carey N Lumeng
- Department of Pediatrics and Communicable Diseases; University of Michigan; Ann Arbor, MI USA
| | - Ernesto Bernal-Mizrachi
- Division of Metabolism, Endocrinology, and Diabetes; University of Michigan; Brehm Center for Diabetes Research; VA Ann Arbor Healthcare System; Ann Arbor, MI USA
- Correspondence to: Ernesto Bernal-Mizrachi,
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Tsui S, Dai W, Lu L. CCCTC-binding factor mediates effects of glucose on beta cell survival. Cell Prolif 2013; 47:28-37. [PMID: 24354619 DOI: 10.1111/cpr.12085] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 10/07/2013] [Indexed: 12/17/2022] Open
Abstract
OBJECTIVES Pancreatic islet β-cell survival is paramount for regulation of insulin activity and for maintaining glucose homeostasis. Recently, Pax6 has been shown to be essential for many vital functions in β-cells, although many molecular mechanisms of its homeostasis in β-cells remain unclear. The present study investigates novel effects of glucose- and insulin-induced CCCTC-binding factor (CTCF) activity on Pax6 gene expression as well as for subsequent effects of insulin-activated signalling pathways, on β-cell proliferation. MATERIALS AND METHODS Pancreatic β-TC-1-6 cells were cultured in DMEM and stimulated with high concentrations of glucose (5-125 mm); cell viability was assessed by MTT assay. Effects of CTCF on Pax6 were evaluated in the high glucose-induced environment and CTCF/Erk-suppressed cells, by promoter reporter and western blotting analyses. RESULTS Increases in glucose and insulin concentrations upregulated CTCF and consequently downregulated Pax6 in β-cell survival and proliferation. Knocking-down CTCF directly affected Pax6 transcription through CTCF binding and blocked the response to glucose. Altered Erk activity mediated effects of CTCF on controlling Pax6 expression, which partially regulated β-cell proliferation. CONCLUSIONS CTCF functioned as a molecular mediator between insulin-induced upstream Erk signalling and Pax6 expression in these pancreatic β-cells. This pathway may contribute to regulation of β-cell survival and proliferation.
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Affiliation(s)
- S Tsui
- Department of Medicine, David Geffen School of Medicine University of California Los Angeles, Torrance, CA, 90502, USA
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Zeng N, Yang KT, Bayan JA, He L, Aggarwal R, Stiles JW, Hou X, Medina V, Abad D, Palian BM, Al-Abdullah I, Kandeel F, Johnson DL, Stiles BL. PTEN controls β-cell regeneration in aged mice by regulating cell cycle inhibitor p16ink4a. Aging Cell 2013; 12:1000-11. [PMID: 23826727 DOI: 10.1111/acel.12132] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/17/2013] [Indexed: 12/31/2022] Open
Abstract
Tissue regeneration diminishes with age, concurrent with declining hormone levels including growth factors such as insulin-like growth factor-1 (IGF-1). We investigated the molecular basis for such decline in pancreatic β-cells where loss of proliferation occurs early in age and is proposed to contribute to the pathogenesis of diabetes. We studied the regeneration capacity of β-cells in mouse model where PI3K/AKT pathway downstream of insulin/IGF-1 signaling is upregulated by genetic deletion of Pten (phosphatase and tensin homologue deleted on chromosome 10) specifically in insulin-producing cells. In this model, PTEN loss prevents the decline in proliferation capacity in aged β-cells and restores the ability of aged β-cells to respond to injury-induced regeneration. Using several animal and cell models where we can manipulate PTEN expression, we found that PTEN blocks cell cycle re-entry through a novel pathway leading to an increase in p16(ink4a), a cell cycle inhibitor characterized for its role in cellular senescence/aging. A downregulation in p16(ink4a) occurs when PTEN is lost as a result of cyclin D1 induction and the activation of E2F transcription factors. The activation of E2F transcriptional factors leads to methylation of p16(ink4a) promoter, an event that is mediated by the upregulation of polycomb protein, Ezh2. These analyses establish a novel PTEN/cyclin D1/E2F/Ezh2/p16(ink4a) signaling network responsible for the aging process and provide specific evidence for a molecular paradigm that explain how decline in growth factor signals such as IGF-1 (through PTEN/PI3K signaling) may control regeneration and the lack thereof in aging cells.
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Affiliation(s)
- Ni Zeng
- Pharmacology and Pharmaceutical Sciences; School of Pharmacy; University of Southern California; Los Angeles CA 90089 USA
| | - Kai-Ting Yang
- Department of Biochemistry; Keck School of Medicine; University of Southern California; Los Angeles CA 90033 USA
| | - Jennifer-Ann Bayan
- Pharmacology and Pharmaceutical Sciences; School of Pharmacy; University of Southern California; Los Angeles CA 90089 USA
| | - Lina He
- Pharmacology and Pharmaceutical Sciences; School of Pharmacy; University of Southern California; Los Angeles CA 90089 USA
| | - Richa Aggarwal
- Pharmacology and Pharmaceutical Sciences; School of Pharmacy; University of Southern California; Los Angeles CA 90089 USA
| | - Joseph W. Stiles
- Pharmacology and Pharmaceutical Sciences; School of Pharmacy; University of Southern California; Los Angeles CA 90089 USA
| | - Xiaogang Hou
- Pharmacology and Pharmaceutical Sciences; School of Pharmacy; University of Southern California; Los Angeles CA 90089 USA
| | - Vivian Medina
- Pharmacology and Pharmaceutical Sciences; School of Pharmacy; University of Southern California; Los Angeles CA 90089 USA
| | - Danny Abad
- Islet Transplant Center; City of Hope; Duarte CA 91010 USA
| | - Beth M. Palian
- Department of Biochemistry; Keck School of Medicine; University of Southern California; Los Angeles CA 90033 USA
| | | | - Fouad Kandeel
- Islet Transplant Center; City of Hope; Duarte CA 91010 USA
| | - Deborah L. Johnson
- Department of Biochemistry; Keck School of Medicine; University of Southern California; Los Angeles CA 90033 USA
| | - Bangyan L. Stiles
- Pharmacology and Pharmaceutical Sciences; School of Pharmacy; University of Southern California; Los Angeles CA 90089 USA
- Department of Pathology; Keck School of Medicine; University of Southern California; Los Angeles CA 90033 USA
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Berestovsky N, Zhou W, Nagrath D, Nakhleh L. Modeling integrated cellular machinery using hybrid Petri-Boolean networks. PLoS Comput Biol 2013; 9:e1003306. [PMID: 24244124 PMCID: PMC3820535 DOI: 10.1371/journal.pcbi.1003306] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 09/12/2013] [Indexed: 12/31/2022] Open
Abstract
The behavior and phenotypic changes of cells are governed by a cellular circuitry that represents a set of biochemical reactions. Based on biological functions, this circuitry is divided into three types of networks, each encoding for a major biological process: signal transduction, transcription regulation, and metabolism. This division has generally enabled taming computational complexity dealing with the entire system, allowed for using modeling techniques that are specific to each of the components, and achieved separation of the different time scales at which reactions in each of the three networks occur. Nonetheless, with this division comes loss of information and power needed to elucidate certain cellular phenomena. Within the cell, these three types of networks work in tandem, and each produces signals and/or substances that are used by the others to process information and operate normally. Therefore, computational techniques for modeling integrated cellular machinery are needed. In this work, we propose an integrated hybrid model (IHM) that combines Petri nets and Boolean networks to model integrated cellular networks. Coupled with a stochastic simulation mechanism, the model simulates the dynamics of the integrated network, and can be perturbed to generate testable hypotheses. Our model is qualitative and is mostly built upon knowledge from the literature and requires fine-tuning of very few parameters. We validated our model on two systems: the transcriptional regulation of glucose metabolism in human cells, and cellular osmoregulation in S. cerevisiae. The model produced results that are in very good agreement with experimental data, and produces valid hypotheses. The abstract nature of our model and the ease of its construction makes it a very good candidate for modeling integrated networks from qualitative data. The results it produces can guide the practitioner to zoom into components and interconnections and investigate them using such more detailed mathematical models.
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Affiliation(s)
- Natalie Berestovsky
- Department of Computer Science, Rice University, Houston, Texas, United States of America
| | - Wanding Zhou
- Department of Bioengineering, Rice University, Houston, Texas, United States of America
| | - Deepak Nagrath
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States of America
| | - Luay Nakhleh
- Department of Computer Science, Rice University, Houston, Texas, United States of America
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Puddu A, Sanguineti R, Mach F, Dallegri F, Viviani GL, Montecucco F. Update on the protective molecular pathways improving pancreatic beta-cell dysfunction. Mediators Inflamm 2013; 2013:750540. [PMID: 23737653 PMCID: PMC3659509 DOI: 10.1155/2013/750540] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 04/10/2013] [Indexed: 12/16/2022] Open
Abstract
The primary function of pancreatic beta-cells is to produce and release insulin in response to increment in extracellular glucose concentrations, thus maintaining glucose homeostasis. Deficient beta-cell function can have profound metabolic consequences, leading to the development of hyperglycemia and, ultimately, diabetes mellitus. Therefore, strategies targeting the maintenance of the normal function and protecting pancreatic beta-cells from injury or death might be crucial in the treatment of diabetes. This narrative review will update evidence from the recently identified molecular regulators preserving beta-cell mass and function recovery in order to suggest potential therapeutic targets against diabetes. This review will also highlight the relevance for novel molecular pathways potentially improving beta-cell dysfunction.
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Affiliation(s)
- Alessandra Puddu
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Roberta Sanguineti
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
| | - François Mach
- Division of Cardiology, Geneva University Hospitals, Faculty of Medicine, Foundation for Medical Researches, Avenue de la Roseraie 64, 1211 Geneva 4, Switzerland
| | - Franco Dallegri
- First Medical Clinic, Laboratory of Phagocyte Physiopathology and Inflammation, Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Giorgio Luciano Viviani
- Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Fabrizio Montecucco
- Division of Cardiology, Geneva University Hospitals, Faculty of Medicine, Foundation for Medical Researches, Avenue de la Roseraie 64, 1211 Geneva 4, Switzerland
- First Medical Clinic, Laboratory of Phagocyte Physiopathology and Inflammation, Department of Internal Medicine, University of Genoa, Viale Benedetto XV 6, 16132 Genova, Italy
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Osman MA, Sarkar FH, Rodriguez-Boulan E. A molecular rheostat at the interface of cancer and diabetes. Biochim Biophys Acta Rev Cancer 2013; 1836:166-76. [PMID: 23639840 DOI: 10.1016/j.bbcan.2013.04.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 04/23/2013] [Indexed: 12/17/2022]
Abstract
Epidemiology studies revealed the connection between several types of cancer and type 2 diabetes (T2D) and suggested that T2D is both a symptom and a risk factor of pancreatic cancer. High level of circulating insulin (hyperinsulinemia) in obesity has been implicated in promoting aggressive types of cancers. Insulin resistance, a symptom of T2D, pressures pancreatic β-cells to increase insulin secretion, leading to hyperinsulinemia, which in turn leads to a gradual loss of functional β-cell mass, thus indicating a fine balance and interplay between β-cell function and mass. While the mechanisms of these connections are unclear, the mTORC1-Akt signaling pathway has been implicated in controlling β-cell function and mass, and in mediating the link of cancer and T2D. However, incomplete understating of how the pathway is regulated and how it integrates body metabolism has hindered its efficacy as a clinical target. The IQ motif containing GTPase activating protein 1 (IQGAP1)-Exocyst axis is a growth factor- and nutrient-sensor that couples cell growth and division. Here we discuss how IQGAP1-Exocyst, through differential interactions with Rho-type of small guanosine triphosphatases (GTPases), acts as a rheostat that modulates the mTORC1-Akt and MAPK signals, and integrates β-cell function and mass with insulin signaling, thus providing a molecular mechanism for cancer initiation in diabetes. Delineating this regulatory pathway may have the potential of contributing to optimizing the efficacy and selectivity of future therapies for cancer and diabetes.
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Affiliation(s)
- Mahasin A Osman
- Warren Alpert Medical School, Division of Biology and Medicine, Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI 02912, USA.
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Hou GJ, Li CN, Liu SN, Huan Y, Liu Q, Sun SJ, Li LY, Hou SC, Shen ZF. Long-term treatment with EXf, a peptide analog of Exendin-4, improves β-cell function and survival in diabetic KKAy mice. Peptides 2013; 40:123-32. [PMID: 23353893 DOI: 10.1016/j.peptides.2013.01.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 01/15/2013] [Accepted: 01/15/2013] [Indexed: 12/31/2022]
Abstract
EXf is a C-terminally truncated fragment of Exendin-4 with two amino acid substitutions. Previous studies showed that EXf controls plasma glucose level acting as a glucagon-like peptide 1 (GLP-1) receptor agonist. The purpose of this study was to evaluate the effects of EXf on β-cell function and survival in diabetic KKAy mice. EXf treatment significantly improved the glucose intolerance and reduced non-fasting and fasting plasma glucose levels, as well as plasma triglyceride levels in diabetic KKAy mice. In hyperglycemic clamp test, EXf-treated mice displayed an increased glucose infusion rate and first-phase insulin secretion. Treatment with EXf also led to a significant restoration of islet morphology, an increase in Ki67 expression in β-cells, and a reduction in the number of TUNEL positive β-cells. In the pancreas, comparative transcription analysis showed up-regulation of Akt1. The up-regulation of phosphorylated Akt1 was confirmed by Western blot, and changes in the protein levels of members of the Akt1 pathway, such as PI3K, Bim, Bcl-2, Bax, Caspase-3, and Caspase-9, PDX-1, were observed as well. Therefore, EXf treatment could improve β-cell function and survival in diabetic KKAy mice, likely as a result of islet morphology restoration, stimulation of β-cell proliferation, and inhibition of β-cell apoptosis.
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Affiliation(s)
- Guo-jiang Hou
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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Batumalaie K, Zaman Safi S, Mohd Yusof K, Shah Ismail I, Devi Sekaran S, Qvist R. Effect of gelam honey on the oxidative stress-induced signaling pathways in pancreatic hamster cells. Int J Endocrinol 2013; 2013:367312. [PMID: 24324490 PMCID: PMC3845241 DOI: 10.1155/2013/367312] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 09/21/2013] [Accepted: 10/05/2013] [Indexed: 12/27/2022] Open
Abstract
Background. Oxidative stress induced by reactive oxygen and nitrogen species is critically involved in the impairment of β -cell function during the development of diabetes. Methods. HIT-T15 cells were cultured in 5% CO2 and then preincubated with Gelam honey extracts (20, 40, 60, and 80 µg/mL) as well as quercetin (20, 40, 60, and 80 µM), prior to stimulation by 20 and 50 mM of glucose. Cell lysate was collected to determine the effect of honey extracts and quercetin on the stress activated NF- κ B, MAPK pathways, and the Akt (ser473) activated insulin signaling pathway. Results. HIT-T15 cells cultured under hyperglycemic conditions demonstrated insulin resistance with a significant increase in the levels of MAPK, NF- κ B, and IRS-1 serine phosphorylation (ser307); however, Akt expression and insulin contents are significantly decreased. Pretreatment with quercetin and Gelam honey extract improved insulin resistance and insulin content by reducing the expression of MAPK, NF- κ B, and IRS-1 serine phosphorylation (ser307) and increasing the expression of Akt significantly. Conclusion. Gelam honey-induced differential expression of MAPK, NF- κ B, IRS-1 (ser307), and Akt in HIT-T15 cells shows that Gelam honey exerts protective effects against diabetes- and hyperglycemia-induced oxidative stress by improving insulin content and insulin resistance.
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Affiliation(s)
- Kalaivani Batumalaie
- Department of Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
- *Kalaivani Batumalaie:
| | - Sher Zaman Safi
- Department of Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Kamaruddin Mohd Yusof
- Department of Molecular Biology and Genetics, Faculty of Arts and Science, Canik Basari University, Samsun, Turkey
| | - Ikram Shah Ismail
- Department of Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Shamala Devi Sekaran
- Department of Microbiology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Rajes Qvist
- Department of Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
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86
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Zhang J, Zhang N, Liu M, Li X, Zhou L, Huang W, Xu Z, Liu J, Musi N, DeFronzo RA, Cunningham JM, Zhou Z, Lu XY, Liu F. Disruption of growth factor receptor-binding protein 10 in the pancreas enhances β-cell proliferation and protects mice from streptozotocin-induced β-cell apoptosis. Diabetes 2012; 61:3189-98. [PMID: 22923474 PMCID: PMC3501856 DOI: 10.2337/db12-0249] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Defects in insulin secretion and reduction in β-cell mass are associated with type 2 diabetes in humans, and understanding the basis for these dysfunctions may reveal strategies for diabetes therapy. In this study, we show that pancreas-specific knockout of growth factor receptor-binding protein 10 (Grb10), which is highly expressed in pancreas and islets, leads to elevated insulin/IGF-1 signaling in islets, enhanced β-cell mass and insulin content, and increased insulin secretion in mice. Pancreas-specific disruption of Grb10 expression also improved glucose tolerance in mice fed with a high-fat diet and protected mice from streptozotocin-induced β-cell apoptosis and body weight loss. Our study has identified Grb10 as an important regulator of β-cell proliferation and demonstrated that reducing the expression level of Grb10 could provide a novel means to increase β-cell mass and reduce β-cell apoptosis. This is critical for effective therapeutic treatment of both type 1 and 2 diabetes.
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Affiliation(s)
- Jingjing Zhang
- From the Metabolic Syndrome Research Center, Diabetes Center, Institute of Metabolism and Endocrinology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China; the
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
| | - Ning Zhang
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
| | - Meilian Liu
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
| | - Xiuling Li
- Department of Hematology/Oncology, St. Jude Children’s Research Hospital, Memphis, Tennessee; and the
| | - Lijun Zhou
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
| | - Wei Huang
- From the Metabolic Syndrome Research Center, Diabetes Center, Institute of Metabolism and Endocrinology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China; the
| | - Zhipeng Xu
- From the Metabolic Syndrome Research Center, Diabetes Center, Institute of Metabolism and Endocrinology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China; the
| | - Jing Liu
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
| | - Nicolas Musi
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
| | - Ralph A. DeFronzo
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
| | - John M. Cunningham
- Department of Hematology/Oncology, St. Jude Children’s Research Hospital, Memphis, Tennessee; and the
| | - Zhiguang Zhou
- From the Metabolic Syndrome Research Center, Diabetes Center, Institute of Metabolism and Endocrinology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China; the
- Key Laboratory of Diabetes Immunology, Ministry of Education, Diabetes Center, Institute of Metabolism and Endocrinology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Xin-Yun Lu
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
| | - Feng Liu
- From the Metabolic Syndrome Research Center, Diabetes Center, Institute of Metabolism and Endocrinology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China; the
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; the
- Corresponding author: Feng Liu,
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87
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Kim HS, Tian L, Lin S, Cha JH, Jung HS, Park KS, Moon WK. Magnetic labeling of pancreaticβ-cells modulates the glucose- and insulin-induced phosphorylation of ERK1/2 and AKT. CONTRAST MEDIA & MOLECULAR IMAGING 2012; 8:20-6. [DOI: 10.1002/cmmi.1490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Hoe Suk Kim
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
- Institute of Radiation Medicine, Medical Research Center; Seoul National University; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Lianji Tian
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
- Department of Biomedical Science, College of Medicine; Seoul National University; Seoul, 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Shunmei Lin
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Joo Hee Cha
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Hye Seung Jung
- Department of Internal Medicine; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Kyong Soo Park
- Department of Internal Medicine; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Woo Kyung Moon
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
- Institute of Radiation Medicine, Medical Research Center; Seoul National University; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
- Department of Biomedical Science, College of Medicine; Seoul National University; Seoul, 101 Daehangno, Jongno-gu Seoul 110-744 Korea
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88
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Goldfine AB, Kulkarni RN. Modulation of β-cell function: a translational journey from the bench to the bedside. Diabetes Obes Metab 2012; 14 Suppl 3:152-60. [PMID: 22928576 DOI: 10.1111/j.1463-1326.2012.01647.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Both decreased insulin secretion and action contribute to the pathogenesis of type 2 diabetes (T2D) in humans. The insulin receptor and insulin signalling proteins are present in the rodent and human β-cell and modulate cell growth and function. Insulin receptors and insulin signalling proteins in β-cells are critical for compensatory islet growth in response to insulin resistance. Rodents with tissue-specific knockout of the insulin receptor in the β-cell (βIRKO) show reduced first-phase glucose-stimulated insulin secretion (GSIS) and with aging develop glucose intolerance and diabetes, phenotypically similar to the process seen in human T2D. Expression of multiple insulin signalling proteins is reduced in islets of patients with T2D. Insulin potentiates GSIS in isolated human β-cells. Recent studies in humans in vivo show that pre-exposure to insulin increases GSIS, and this effect is diminished in persons with insulin resistance or T2D. β-Cell function correlates to whole-body insulin sensitivity. Together, these findings suggest that pancreatic β-cell dysfunction could be caused by a defect in insulin signalling within β-cell, and β-cell insulin resistance may lead to a loss of β-cell function and/or mass, contributing to the pathophysiology of T2D.
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Affiliation(s)
- A B Goldfine
- Section of Clinical Research, Joslin Diabetes Center, Boston, MA 02215, USA.
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89
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Kulkarni RN, Mizrachi EB, Ocana AG, Stewart AF. Human β-cell proliferation and intracellular signaling: driving in the dark without a road map. Diabetes 2012; 61:2205-13. [PMID: 22751699 PMCID: PMC3425429 DOI: 10.2337/db12-0018] [Citation(s) in RCA: 190] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A major goal in diabetes research is to find ways to enhance the mass and function of insulin secreting β-cells in the endocrine pancreas to prevent and/or delay the onset or even reverse overt diabetes. In this Perspectives in Diabetes article, we highlight the contrast between the relatively large body of information that is available in regard to signaling pathways, proteins, and mechanisms that together provide a road map for efforts to regenerate β-cells in rodents versus the scant information in human β-cells. To reverse the state of ignorance regarding human β-cell signaling, we suggest a series of questions for consideration by the scientific community to construct a human β-cell proliferation road map. The hope is that the knowledge from the new studies will allow the community to move faster towards developing therapeutic approaches to enhance human β-cell mass in the long-term goal of preventing and/or curing type 1 and type 2 diabetes.
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Affiliation(s)
- Rohit N. Kulkarni
- Islet Cell Biology and Regenerative Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
- Department of Medicine, Harvard Medical School, Boston, Massachusetts
- Corresponding authors: Rohit N. Kulkarni, , and Andrew F. Stewart,
| | - Ernesto-Bernal Mizrachi
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Adolfo Garcia Ocana
- Division of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Andrew F. Stewart
- Division of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Corresponding authors: Rohit N. Kulkarni, , and Andrew F. Stewart,
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90
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Geraedts MCP, Takahashi T, Vigues S, Markwardt ML, Nkobena A, Cockerham RE, Hajnal A, Dotson CD, Rizzo MA, Munger SD. Transformation of postingestive glucose responses after deletion of sweet taste receptor subunits or gastric bypass surgery. Am J Physiol Endocrinol Metab 2012; 303:E464-74. [PMID: 22669246 PMCID: PMC3423100 DOI: 10.1152/ajpendo.00163.2012] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The glucose-dependent secretion of the insulinotropic hormone glucagon-like peptide-1 (GLP-1) is a critical step in the regulation of glucose homeostasis. Two molecular mechanisms have separately been suggested as the primary mediator of intestinal glucose-stimulated GLP-1 secretion (GSGS): one is a metabotropic mechanism requiring the sweet taste receptor type 2 (T1R2) + type 3 (T1R3) while the second is a metabolic mechanism requiring ATP-sensitive K(+) (K(ATP)) channels. By quantifying sugar-stimulated hormone secretion in receptor knockout mice and in rats receiving Roux-en-Y gastric bypass (RYGB), we found that both of these mechanisms contribute to GSGS; however, the mechanisms exhibit different selectivity, regulation, and localization. T1R3(-/-) mice showed impaired glucose and insulin homeostasis during an oral glucose challenge as well as slowed insulin granule exocytosis from isolated pancreatic islets. Glucose, fructose, and sucralose evoked GLP-1 secretion from T1R3(+/+), but not T1R3(-/-), ileum explants; this secretion was not mimicked by the K(ATP) channel blocker glibenclamide. T1R2(-/-) mice showed normal glycemic control and partial small intestine GSGS, suggesting that T1R3 can mediate GSGS without T1R2. Robust GSGS that was K(ATP) channel-dependent and glucose-specific emerged in the large intestine of T1R3(-/-) mice and RYGB rats in association with elevated fecal carbohydrate throughout the distal gut. Our results demonstrate that the small and large intestines utilize distinct mechanisms for GSGS and suggest novel large intestine targets that could mimic the improved glycemic control seen after RYGB.
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Affiliation(s)
- Maartje C P Geraedts
- Division of Endocrinology, Diabetes, and Nutrition, Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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91
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Meng ZX, Yin Y, Lv JH, Sha M, Lin Y, Gao L, Zhu YX, Sun YJ, Han X. Aberrant activation of liver X receptors impairs pancreatic beta cell function through upregulation of sterol regulatory element-binding protein 1c in mouse islets and rodent cell lines. Diabetologia 2012; 55:1733-44. [PMID: 22415588 DOI: 10.1007/s00125-012-2516-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 02/10/2012] [Indexed: 10/28/2022]
Abstract
AIMS/HYPOTHESIS Liver X receptors (LXR) are important transcriptional regulators of lipid and glucose metabolism. Our previous report demonstrated that LXR activation inhibited pancreatic beta cell proliferation through cell cycle arrest. Here we explore the role of LXR activation in beta cell insulin secretion and the underlying mechanism that might be involved. METHODS Mouse pancreatic islets or insulin-secreting MIN6 cells were exposed to the LXR agonist, T0901317, and insulin secretion, glucose and fatty acid oxidation, and lipogenic gene expression were assessed. The unsaturated fatty acid eicosapentaenoic acid and the dominant negative sterol regulatory element binding protein 1c (SREBP1c) were used to inhibit endogenous SREBP1c and evaluate the involvement of SREBP1c in beta cell dysfunction induced by LXR activation. RESULTS Treatment with the LXR agonist decreased beta cell glucose sensitivity and impaired glucose-stimulated insulin secretion in vivo and in vitro. This was accompanied by derangements of beta cell glucose oxygen consumption, glucose oxidation, ATP production and intracellular voltage-gated calcium channel flux. LXR activation also regulated the expression of lipid metabolism-related genes such as Fas, Acc (also known as Acaca) and Cpt1a, and led to intracellular lipid accumulation. Further studies revealed that inhibition of SREBP1c abolished LXR activation-induced lipid accumulation and improved beta cell glucose metabolism, ATP production and insulin secretion. CONCLUSIONS/INTERPRETATION Our data reveal that aberrant activation of LXR reproduced the phenomenon of beta cell dysfunction in the development of type 2 diabetes in vitro and in vivo. Upregulation of SREBP1c production and the lipotoxicity mediated by it played a central role in this process.
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Affiliation(s)
- Z X Meng
- Department of Biochemistry and Molecular Biology, Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, 140 Hanzhong Road, Nanjing 210029, People's Republic of China
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92
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Apolipoprotein A-IV improves glucose homeostasis by enhancing insulin secretion. Proc Natl Acad Sci U S A 2012; 109:9641-6. [PMID: 22619326 DOI: 10.1073/pnas.1201433109] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Apolipoprotein A-IV (apoA-IV) is secreted by the small intestine in response to fat absorption. Here we demonstrate a potential role for apoA-IV in regulating glucose homeostasis. ApoA-IV-treated isolated pancreatic islets had enhanced insulin secretion under conditions of high glucose but not of low glucose, suggesting a direct effect of apoA-IV to enhance glucose-stimulated insulin release. This enhancement involves cAMP at a level distal to Ca(2+) influx into the β cells. Knockout of apoA-IV results in compromised insulin secretion and impaired glucose tolerance compared with WT mice. Challenging apoA-IV(-/-) mice with a high-fat diet led to fasting hyperglycemia and more severe glucose intolerance associated with defective insulin secretion than occurred in WT mice. Administration of exogenous apoA-IV to apoA-IV(-/-) mice improved glucose tolerance by enhancing insulin secretion in mice fed either chow or a high-fat diet. Finally, we demonstrate that exogenous apoA-IV injection decreases blood glucose levels and stimulates a transient increase in insulin secretion in KKAy diabetic mice. These results suggest that apoA-IV may provide a therapeutic target for the regulation of glucose-stimulated insulin secretion and treatment of diabetes.
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93
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APPL1 potentiates insulin secretion in pancreatic β cells by enhancing protein kinase Akt-dependent expression of SNARE proteins in mice. Proc Natl Acad Sci U S A 2012; 109:8919-24. [PMID: 22566644 DOI: 10.1073/pnas.1202435109] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Insulin resistance and defective insulin secretion are the two major features of type 2 diabetes. The adapter protein APPL1 is an obligatory molecule in regulating peripheral insulin sensitivity, but its role in insulin secretion remains elusive. Here, we show that APPL1 expression in pancreatic β cells is markedly decreased in several mouse models of obesity and diabetes. APPL1 knockout mice exhibit glucose intolerance and impaired glucose-stimulated insulin secretion (GSIS), whereas transgenic expression of APPL1 prevents high-fat diet (HFD)-induced glucose intolerance partly by enhancing GSIS. In both pancreatic islets and rat β cells, APPL1 deficiency causes a marked reduction in expression of the exocytotic machinery SNARE proteins (syntaxin-1, synaptosomal-associated protein 25, and vesicle-associated membrane protein 2) and an obvious decrease in the number of exocytotic events. Such changes are accompanied by diminished insulin-stimulated Akt activation. Furthermore, the defective GSIS and reduced expression of SNARE proteins in APPL1-deficient β cells can be rescued by adenovirus-mediated expression of APPL1 or constitutively active Akt. These findings demonstrate that APPL1 couples insulin-stimulated Akt activation to GSIS by promoting the expression of the core exocytotic machinery involved in exocytosis and also suggest that reduced APPL1 expression in pancreatic islets may serve as a pathological link that couples insulin resistance to β-cell dysfunction in type 2 diabetes.
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94
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Abdelli S, Bonny C. JNK3 maintains expression of the insulin receptor substrate 2 (IRS2) in insulin-secreting cells: functional consequences for insulin signaling. PLoS One 2012; 7:e35997. [PMID: 22563476 PMCID: PMC3341388 DOI: 10.1371/journal.pone.0035997] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 03/26/2012] [Indexed: 12/20/2022] Open
Abstract
We have recently shown that silencing of the brain/islet specific c-Jun N-terminal Kinase3 (JNK3) isoform enhances both basal and cytokine-induced beta-cell apoptosis, whereas silencing of JNK1 or JNK2 has opposite effects. While it is known that JNK1 or JNK2 may promote apoptosis by inhibiting the activity of the pro-survival Akt pathway, the effect of JNK3 on Akt has not been documented. This study aims to determine the involvement of individual JNKs and specifically JNK3 in the regulation of the Akt signaling pathway in insulin-secreting cells. JNK3 silencing strongly decreases Insulin Receptor Substrate 2 (IRS2) protein expression, and blocks Akt2 but not Akt1 activation by insulin, while the silencing of JNK1 or JNK2 activates both Akt1 and Akt2. Concomitantly, the silencing of JNK1 or JNK2, but not of JNK3, potently phosphorylates the glycogen synthase kinase3 (GSK3β). JNK3 silencing also decreases the activity of the transcription factor Forkhead BoxO3A (FoxO3A) that is known to control IRS2 expression, in addition to increasing c-Jun levels that are known to inhibit insulin gene expression. In conclusion, we propose that JNK1/2 on one hand and JNK3 on the other hand, have opposite effects on insulin-signaling in insulin-secreting cells; JNK3 protects beta-cells from apoptosis and dysfunction mainly through maintenance of a normal IRS2 to Akt2 signaling pathway. It seems that JNK3 mediates its effects mainly at the transcriptional level, while JNK1 or JNK2 appear to mediate their pro-apoptotic effect in the cytoplasm.
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Affiliation(s)
- Saida Abdelli
- Service of Medical Genetics, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland
| | - Christophe Bonny
- Service of Medical Genetics, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland
- * E-mail:
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95
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Transient neonatal diabetes mellitus gene Zac1 impairs insulin secretion in mice through Rasgrf1. Mol Cell Biol 2012; 32:2549-60. [PMID: 22547676 DOI: 10.1128/mcb.06637-11] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The biallelic expression of the imprinted gene ZAC1/PLAGL1 underlies ≈ 60% of all cases of transient neonatal diabetes mellitus (TNDM) that present with low perinatal insulin secretion. Molecular targets of ZAC1 misexpression in pancreatic β cells are unknown. Here, we identified the guanine nucleotide exchange factor Rasgrf1 as a direct Zac1/Plagl1 target gene in murine β cells. Doubling Zac1 expression reduced Rasgrf1 expression, the stimulus-induced activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways, and, ultimately, insulin secretion. Normalizing Rasgrf1 expression reversed this phenotype. Moreover, the transplantation of Zac1-overexpressing β cells failed to reinstate euglycemia in experimental diabetic mice. In contrast, Zac1 expression did not interfere with the signaling of the glucagon-like peptide 1 receptor (GLP-1R), and the GLP-1 analog liraglutide improved hyperglycemia in transplanted experimental diabetic mice. This study unravels a mechanism contributing to insufficient perinatal insulin secretion in TNDM and raises new prospects for therapy.
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96
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Smillie KJ, Cousin MA. Akt/PKB controls the activity-dependent bulk endocytosis of synaptic vesicles. Traffic 2012; 13:1004-11. [PMID: 22487004 PMCID: PMC3488115 DOI: 10.1111/j.1600-0854.2012.01365.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 04/04/2012] [Accepted: 04/09/2012] [Indexed: 01/26/2023]
Abstract
Activity-dependent bulk endocytosis (ADBE) is the dominant SV endocytosis mode during intense neuronal activity. The dephosphorylation of Ser774 on dynamin I is essential for triggering of ADBE, as is its subsequent rephosphorylation by glycogen synthase kinase 3 (GSK3). We show that in primary cultures of cerebellar granule neurons the protein kinase Akt phosphorylates GSK3 during intense neuronal activity, ensuring that GSK3 is inactive during intense stimulation to aid dynamin I dephosphorylation. Furthermore, when a constitutively active form of Akt was overexpressed in primary neuronal cultures, ADBE was inhibited with no effect on clathrin-mediated endocytosis. Thus Akt has two major regulatory roles (i) to ensure efficient dynamin I dephosphorylation via acute activity-dependent inhibition of GSK3 and (ii) to negatively regulate ADBE when activated in the longer term. This is the first demonstration of a role for Akt in SV recycling and suggests a key role for this protein kinase in modulating synaptic strength during elevated neuronal activity.
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Affiliation(s)
- Karen J Smillie
- Membrane Biology Group, Centre for Integrative Physiology, George Square, University of Edinburgh, Edinburgh EH8 9XD, UK
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97
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Koh DS, Cho JH, Chen L. Paracrine interactions within islets of Langerhans. J Mol Neurosci 2012; 48:429-40. [PMID: 22528452 DOI: 10.1007/s12031-012-9752-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 03/12/2012] [Indexed: 01/05/2023]
Abstract
Glucose supply fluctuates between meal and fasting periods and its consumption by the body varies greatly depending on bodily metabolism. Pancreatic islets of Langerhans secrete various endocrine hormones including insulin and glucagon to keep blood glucose level relatively constant. Additionally, islet hormones regulate activity of neighboring cells as local autocrine or paracrine modulators. Moreover, islet cells release neurotransmitters such as glutamate and γ-aminobutyric acid (GABA) to gain more precise regulation of hormones release kinetics. Excitatory glutamate is co-released with glucagon from α-cells and activates glutamate receptors in the neighboring cells. GABA released from β-cells was shown to inhibit α-cells but to activate β-cells by acting GABA(A) receptors. This review summarizes the recent progress in understanding the paracrine/autocrine interactions in islets.
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Affiliation(s)
- Duk-Su Koh
- University of Washington, Seattle, WA, USA.
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98
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Xie J, Herbert TP. The role of mammalian target of rapamycin (mTOR) in the regulation of pancreatic β-cell mass: implications in the development of type-2 diabetes. Cell Mol Life Sci 2012; 69:1289-304. [PMID: 22068611 PMCID: PMC11114779 DOI: 10.1007/s00018-011-0874-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Revised: 10/20/2011] [Accepted: 10/20/2011] [Indexed: 12/22/2022]
Abstract
Type-2 diabetes mellitus (T2DM) is a disorder that is characterized by high blood glucose concentration in the context of insulin resistance and/or relative insulin deficiency. It causes metabolic changes that lead to the damage and functional impairment of organs and tissues resulting in increased morbidity and mortality. It is this form of diabetes whose prevalence is increasing at an alarming rate due to the 'obesity epidemic', as obesity is a key risk factor in the development of insulin resistance. However, the majority of individuals who have insulin resistance do not develop diabetes due to a compensatory increase in insulin secretion in response to an increase in insulin demand. This adaptive response is sustained by an increase in both β-cell function and mass. Importantly, there is increasing evidence that the Serine/Threonine kinase mammalian target of rapamycin (mTOR) plays a key role in the regulation of β-cell mass and therefore likely plays a critical role in β-cell adaptation. Therefore, the primary focus of this review is to summarize our current understanding of the role of mTOR in stimulating pancreatic β-cell mass and thus, in the prevention of type-2 diabetes.
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Affiliation(s)
- Jianling Xie
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
| | - Terence P. Herbert
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
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Lee SA, Jeong E, Kim EH, Shin MS, Hwang JY, Koh EH, Lee WJ, Park JY, Kim MS. Various oscillation patterns of serum fibroblast growth factor 21 concentrations in healthy volunteers. Diabetes Metab J 2012; 36:29-36. [PMID: 22363919 PMCID: PMC3283824 DOI: 10.4093/dmj.2012.36.1.29] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 09/07/2011] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Fibroblast growth factor 21 (FGF21) was originally identified as a paroxysm proliferator activated receptor-α target gene product and is a hormone involved in metabolic regulation. The purpose of this study was to investigate the diurnal variation of serum FGF21 concentration in obese and non-obese healthy volunteers. METHODS Blood samples were collected from five non-obese (body mass index [BMI] ≤23 kg/m(2)) and five obese (BMI ≥25 kg/m(2)) healthy young men every 30 to 60 minutes over 24 hours. Serum FGF21 concentrations were determined by radioimmunoassay. Anthropometric parameters, glucose, free fatty acid, insulin, leptin, and cortisol concentrations were also measured. RESULTS The serum FGF21 concentrations displayed various individual oscillation patterns. The oscillation frequency ranged between 6 and 12 times per day. The average duration of oscillation was 2.52 hours (range, 1.9 to 3.0 hours). The peaks and troughs of FGF21 oscillation showed no circadian rhythm. However, the oscillation frequency had a diurnal variation and was lower during the light-off period than during the light-on period (2.4 vs. 7.3 times, P<0.001). There was no difference in the total frequency or duration of oscillations between non-obese and obese subjects, but obese individuals had increased numbers of larger oscillations (amplitude ≥0.19 ng/mL). CONCLUSION Various oscillation patterns in serum FGF21 concentration were observed, and reduced oscillation frequencies were seen during sleep. The oscillation patterns of serum FGF21 concentration suggest that FGF21 may be secreted into systemic circulation in a pulsatile manner. Obesity appeared to affect the amplitude of oscillations of serum FGF21.
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Affiliation(s)
- Sang Ah Lee
- Department of Internal Medicine, Jeju National University School of Medicine, Jeju, Korea
| | - Eunheiu Jeong
- Department of Internal Medicine, Seoul Veterans Hospital, Seoul, Korea
| | - Eun Hee Kim
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Mi-Seon Shin
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Jenie Yoonoo Hwang
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Eun Hee Koh
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Woo Je Lee
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Joong-Yeol Park
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Min-Seon Kim
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
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Fiory F, Lombardi A, Miele C, Giudicelli J, Beguinot F, Van Obberghen E. Methylglyoxal impairs insulin signalling and insulin action on glucose-induced insulin secretion in the pancreatic beta cell line INS-1E. Diabetologia 2011; 54:2941-52. [PMID: 21861178 DOI: 10.1007/s00125-011-2280-8] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 07/18/2011] [Indexed: 12/13/2022]
Abstract
AIMS/HYPOTHESIS Chronic hyperglycaemia aggravates insulin resistance, at least in part, by increasing the formation of advanced glycation end-products (AGEs). Methylglyoxal (MGO) is the most reactive AGE precursor and its abnormal accumulation participates in damage in various tissues and organs. Here we investigated the ability of MGO to interfere with insulin signalling and to affect beta cell functions in the INS-1E beta cell line. METHODS INS-1E cells were incubated with MGO and then exposed to insulin or to glucose. Western blotting was used to study signalling pathways, and real-time PCR to analyse gene expression; insulin levels were determined by radioimmunoassay. RESULTS Non-cytotoxic MGO concentrations inhibited insulin-induced IRS tyrosine phosphorylation and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB) pathway activation independently from reactive oxygen species (ROS) production. Concomitantly, formation of AGE adducts on immunoprecipitated IRS was observed. Aminoguanidine reversed MGO inhibitory effects and the formation of AGE adducts on IRS. Further, the insulin- and glucose-induced expression of Ins1, Gck and Pdx1 mRNA was abolished by MGO. Finally, MGO blocked glucose-induced insulin secretion and PI3K/PKB pathway activation. These MGO effects were abolished by LiCl, which inhibits glycogen synthase kinase-3 (GSK-3). CONCLUSIONS/INTERPRETATION MGO exerted major damaging effects on INS-1E cells impairing both insulin action and secretion. An important actor in these noxious MGO effects appears to be GSK-3. In conclusion, MGO participates not only in the pathogenesis of the debilitating complications of type 2 diabetes, but also in worsening of the diabetic state by favouring beta cell failure.
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Affiliation(s)
- F Fiory
- Dipartimento di Biologia e Patologia Cellulare e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Università degli Studi di Napoli Federico II, Naples, Italy
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