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Robertson RP. Antioxidants for Early Treatment of Type 2 Diabetes in Rodents and Humans: Lost in Translation? Diabetes 2024; 73:653-658. [PMID: 38387049 PMCID: PMC11043055 DOI: 10.2337/db23-0901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 02/13/2024] [Indexed: 02/24/2024]
Abstract
Reactive oxygen species (ROS) are formed by virtually all tissues. In normal concentrations they facilitate many physiologic activities, but in excess they cause oxidative stress and tissue damage. Local antioxidant enzyme synthesis in cells is regulated by the cytoplasmic KEAP-1/Nrf2 complex, which is stimulated by ROS, to release Nrf2 for entry into the nucleus, where it upregulates antioxidant gene expression. Major antioxidant enzymes include glutathione peroxidase (GPx), catalase (CAT), superoxide dismutases (SOD), hemoxygenases (HO), and peroxiredoxins (Prdx). Notably, the pancreatic islet β-cell does not express GPx or CAT, which puts it at greater risk for ROS damage caused by postprandial hyperglycemia. Experimentally, overexpression of GPx in β-cell lines and isolated islets, as well as in vivo studies using genetic models of type 2 diabetes (T2D), has demonstrated enhanced protection against hyperglycemia and oxidative stress. Oral treatment of diabetic rodents with ebselen, a GPx mimetic that is approved for human clinical use, reproduced these findings. Prdx detoxify hydrogen peroxide and reduce lipid peroxides. This suggests that pharmacologic development of more potent, β-cell-specific antioxidants could be valuable as a treatment for oxidative stress due to postprandial hyperglycemia in early T2D in humans. ARTICLE HIGHLIGHTS
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Affiliation(s)
- R. Paul Robertson
- Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, WA
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2
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Soukar I, Amarasinghe A, Pile LA. Coordination of cross-talk between metabolism and epigenetic regulation by the SIN3 complex. Enzymes 2023; 53:33-68. [PMID: 37748836 DOI: 10.1016/bs.enz.2023.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Post-translational modifications of histone proteins control the expression of genes. Metabolites from central and one-carbon metabolism act as donor moieties to modify histones and regulate gene expression. Thus, histone modification and gene regulation are connected to the metabolite status of the cell. Histone modifiers, such as the SIN3 complex, regulate genes involved in proliferation and metabolism. The SIN3 complex contains a histone deacetylase and a histone demethylase, which regulate the chromatin landscape and gene expression. In this chapter, we review the cross-talk between metabolic pathways that produce donor moieties, and epigenetic complexes regulating proliferation and metabolic genes. This cross-talk between gene regulation and metabolism is tightly controlled, and disruption of this cross-talk leads to metabolic diseases. We discuss promising therapeutics that directly regulate histone modifiers, and can affect the metabolic status of the cell, alleviating some metabolic diseases.
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Affiliation(s)
- Imad Soukar
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
| | - Anjalie Amarasinghe
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
| | - Lori A Pile
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States.
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3
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Pathophysiology of obesity and its associated diseases. Acta Pharm Sin B 2023. [DOI: 10.1016/j.apsb.2023.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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4
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Liu Y, Mu S, Chen W, Liu S, Cong Y, Liu J, Jia N. Saponins of Momordica charantia increase insulin secretion in INS-1 pancreatic β-cells via the PI3K/Akt/FoxO1 signaling pathway. ENDOCRINOL DIAB NUTR 2021; 68:329-337. [PMID: 34556263 DOI: 10.1016/j.endien.2021.08.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 05/06/2020] [Indexed: 11/16/2022]
Abstract
Saponins are the main bioactive substances with anti-hyperglycemic activities of Momordica charantia. This study aimed to verify the effects of M. charantia saponins on insulin secretion and explore the potential underlying mechanisms in INS-1 pancreatic β-cells. We injured INS-1 cells with 33.3mM glucose and then treated them with saponins. Saponins improved cell morphology and viability as demonstrated by inverted microscopy and CCK8 detection and significantly increased insulin secretion in a concentration-dependent manner as shown by ELISA. Thus, we obtained the optimal concentration for the subsequent experiments. Potential mechanisms were explored by immunofluorescence, western blotting, and RT-qPCR techniques. First, saponins increased the mRNA and protein levels of IRS-2 but decreased the serine 731 phosphorylation level of IRS-2. Moreover, saponins increased the phosphorylation of Akt protein and decreased the protein level of FoxO1, which were both reversed by the PI3K inhibitor ly294002. Furthermore, saponins increased the protein level of the downstream molecule and insulin initiating factor PDX-1, which was also reversed by ly294002. Saponins also increased Akt and PDX-1 mRNA and decreased FoxO1 mRNA, which were both reversed by ly294002. Saponins increased glucose-stimulated insulin secretion (GSIS) and intracellular insulin content, which were reversed by ly294002, as determined by ELISA. The immunofluorescence results also confirmed this tendency. In conclusion, our findings improve our understanding of the function of saponins in INS-1 pancreatic β-cells and suggest that saponins may increase insulin secretion via the PI3K/Akt/FoxO1 signaling pathway.
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Affiliation(s)
- Yufan Liu
- Traditional Chinese Medicine College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Shumin Mu
- Department of Endocrinology, Hospital Affiliated to Shandong Traditional Chinese Medicine University, Jinan, China.
| | - Wenbin Chen
- Scientific Center, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
| | - Shiyin Liu
- First Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Yuxuan Cong
- Department of Endocrinology, Weihai Hospital of Traditional Chinese Medicine, Weihai, China
| | - Jiajia Liu
- Department of Endocrinology, People's Hospital of Gaotang County, Liaocheng, China
| | - Ning Jia
- Department of Traditional Chinese Medicine, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
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Archana TM, Soumya K, James J, Sudhakaran S. Root extracts of Anacardium occidentale reduce hyperglycemia and oxidative stress in vitro. CLINICAL PHYTOSCIENCE 2021. [DOI: 10.1186/s40816-021-00293-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
Hyperglycemia is the hallmark of diabetes, and the associated oxidative stress is a major concern that invites an array of diabetic complications. The traditional practices of medicare are of great, current interest due to the high cost and side effects of conventional diabetic medications. The present in vitro study focuses on evaluating the potential of various A. occidentale root extracts for their antihyperglycemic and antioxidant potentials.
Materials and methods
The four different solvent extracts petroleum ether (PEAO), chloroform (CHAO), ethyl acetate (EAAO), and 80 % methanol (80 % MAO) of A. occidentale roots were evaluated for their total phenolic, flavonoid, and antioxidant capacity. Using MIN6 pancreatic β-cells, the cytotoxicity of the extracts was evaluated by MTT assay and the antidiabetic potential by quantifying the insulin levels by ELISA at a higher concentration of glucose. The effect of 80 % MAO on INS gene expression was determined by qRT PCR analysis.
Results
Among the four different solvent extracts of A. occidentale roots, 80 % MAO showed the highest concentration of phenolics (437.33 ± 0.03 µg GAE/mg), CHAO to be a rich source of flavonoids (46.04 ± 0.1 µg QE/mg) and with the highest total antioxidant capacity (1865.33 ± 0.09 µg AAE/ mg). Evaluation of the free radical scavenging and reducing properties of the extracts indicated 80 % MAO to exhibit the highest activity. The MTT assay revealed the least cytotoxicity of all four extracts. 80 % MAO enhanced INS up-regulation as well as insulin secretion even under high glucose concentration (27mM).
Conclusions
The present study demonstrated that the A. occidentale root extracts have effective antihyperglycemic and antioxidative properties, together with the potential of normalizing the insulin secretory system of β-cells. Above mentioned properties have to be studied further by identifying the active principles of A. occidentale root extracts and in vivo effects. The prospect of the present study is identifying drug leads for better management of diabetes from the A. occidentale root extracts.
Graphical abstract
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Saponins of Momordica charantia increase insulin secretion in INS-1 pancreatic β-cells via the PI3K/Akt/FoxO1 signaling pathway. ACTA ACUST UNITED AC 2020; 68:329-337. [PMID: 33069631 DOI: 10.1016/j.endinu.2020.05.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 05/06/2020] [Accepted: 05/06/2020] [Indexed: 12/20/2022]
Abstract
Saponins are the main bioactive substances with anti-hyperglycemic activities of Momordica charantia. This study aimed to verify the effects of M. charantia saponins on insulin secretion and explore the potential underlying mechanisms in INS-1 pancreatic β-cells. We injured INS-1 cells with 33.3mM glucose and then treated them with saponins. Saponins improved cell morphology and viability as demonstrated by inverted microscopy and CCK8 detection and significantly increased insulin secretion in a concentration-dependent manner as shown by ELISA. Thus, we obtained the optimal concentration for the subsequent experiments. Potential mechanisms were explored by immunofluorescence, western blotting, and RT-qPCR techniques. First, saponins increased the mRNA and protein levels of IRS-2 but decreased the serine 731 phosphorylation level of IRS-2. Moreover, saponins increased the phosphorylation of Akt protein and decreased the protein level of FoxO1, which were both reversed by the PI3K inhibitor ly294002. Furthermore, saponins increased the protein level of the downstream molecule and insulin initiating factor PDX-1, which was also reversed by ly294002. Saponins also increased Akt and PDX-1 mRNA and decreased FoxO1 mRNA, which were both reversed by ly294002. Saponins increased glucose-stimulated insulin secretion (GSIS) and intracellular insulin content, which were reversed by ly294002, as determined by ELISA. The immunofluorescence results also confirmed this tendency. In conclusion, our findings improve our understanding of the function of saponins in INS-1 pancreatic β-cells and suggest that saponins may increase insulin secretion via the PI3K/Akt/FoxO1 signaling pathway.
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7
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Apolipoprotein A-I primes beta cells to increase glucose stimulated insulin secretion. Biochim Biophys Acta Mol Basis Dis 2019; 1866:165613. [PMID: 31765698 DOI: 10.1016/j.bbadis.2019.165613] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 10/17/2019] [Accepted: 11/05/2019] [Indexed: 01/01/2023]
Abstract
The increase of plasma levels of high-density lipoproteins and Apolipoprotein A-I (ApoA-I), its main protein component, has been shown to have a positive action on glucose disposal in type 2 diabetic patients. The current study investigates the unexplored function of ApoA-I to prime beta cells for improved insulin secretion. INS-1E rat clonal beta cells as well as isolated murine islets were used to study the effect of ApoA-I on responsiveness of the beta cells to high glucose challenge. Confocal and transmission electron microscopy were used to dissect ApoA-I mechanisms of action. Chemical endocytosis blockers were used to understand the role of ApoA-I internalization in mediating its positive effect. Pre-incubation of beta cells and isolated murine islets with ApoA-I augmented glucose stimulated insulin secretion. This effect appeared to be due to an increased reservoir of insulin granules at the cell membrane, as confirmed by confocal and transmission electron microscopy. Moreover, ApoA-I induced pancreatic and duodenal homeobox 1 (PDX1) shuttling from the cytoplasm to the nucleus, with the subsequent increase in the proinsulin processing enzyme protein convertase 1 (PC1/3). Finally, the blockade of ApoA-I endocytosis in beta cells resulted in a loss of ApoA-I positive action on insulin secretion. The proposed mechanisms of the phenomenon here described include ApoA-I internalization into beta cells, PDX1 nuclear translocation, and increased levels of proinsulin processing enzymes. Altogether, these events lead to an increased number of insulin granules.
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Yaribeygi H, Noroozadeh A, Mohammadi MT, Johnston TP, Sahebkar A. Crocin Improves Oxidative Stress by Potentiating Intrinsic Anti-Oxidant Defense Systems in Pancreatic Cells During Uncontrolled Hyperglycemia. J Pharmacopuncture 2019; 22:83-89. [PMID: 31338247 PMCID: PMC6645341 DOI: 10.3831/kpi.2019.22.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 11/01/2018] [Accepted: 05/09/2019] [Indexed: 01/20/2023] Open
Abstract
Introduction Oxidative stress (OS) during uncontrolled hyperglycemia has a pivotal role in pancreatic dysfunction. Our study aimed to demonstrate that crocin can potentiate anti-oxidant defense systems of pancreatic cells to improve oxidative stress. Methods Male Wistar rats were divided randomly into four groups: a normal group, a normal-treated group, a diabetic group and a diabetic-treated group (n = 6 rats per group). Diabetes was induced by a single dose of streptozotocin (45 mg/kg/IV). The treated groups received crocin daily for 8 weeks (40 mg/kg/IP). At the end of the experiment, rats were sacrificed and pancreas tissue was obtained. Subsequently, the concentrations of malondialdehyde (MDA), nitrate and glutathione as well as the enzymatic activities of catalase and superoxide dismutase (SOD) were determined in all animals. Data were analyzed by two-way ANOVA with appropriate post hoc testing and a probability value of P < 0.05 was considered to represent a statistically significant difference in mean values. Results Uncontrolled hyperglycemia weakened the anti-oxidant system by decreasing SOD and catalase enzyme activity in pancreatic tissues and induced OS by increasing the MDA content in diabetic non-treated animals. Crocin potentiated the anti-oxidant defense system by increasing the activity of both SOD and catalase, and improved OS by diminishing MDA production in pancreatic cells of rats contained in the diabetic-treated group. Conclusion Based on our results, it is concluded that uncontrolled hyperglycemia can weaken the anti-oxidant defense system and cause the development of OS. Also, crocin can improve OS in pancreatic cells by potentiating the anti-oxidant defense system.
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Affiliation(s)
- Habib Yaribeygi
- Health Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran.,Chronic Kidney Diseases Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Ali Noroozadeh
- Department of Physiology and Biophysics, School of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Mohammad Taghi Mohammadi
- Department of Physiology and Biophysics, School of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Thomas P Johnston
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, Kansas City, Missouri, United States
| | - Amirhossein Sahebkar
- Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran.,School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran
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9
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Tang C, Yeung LSN, Koulajian K, Zhang L, Tai K, Volchuk A, Giacca A. Glucose-Induced β-Cell Dysfunction In Vivo: Evidence for a Causal Role of C-jun N-terminal Kinase Pathway. Endocrinology 2018; 159:3643-3654. [PMID: 30215691 PMCID: PMC6195676 DOI: 10.1210/en.2018-00566] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 08/26/2018] [Indexed: 11/19/2022]
Abstract
Prolonged elevation of glucose can adversely affect β-cell function. Oxidative stress, which has been implicated in glucose-induced β-cell dysfunction, can activate c-jun N-terminal kinase (JNK). However, whether JNK is causal in glucose-induced β-cell dysfunction in vivo is unclear. Therefore, we aimed at investigating the causal role of JNK activation in in vivo models of glucose-induced β-cell dysfunction. Glucose-induced β-cell dysfunction was investigated in the presence or absence of JNK inhibition. JNK inhibition was achieved using either (i) the JNK-specific inhibitor SP600125 or (ii) JNK-1-null mice. (i) Rats or mice were infused intravenously with saline or glucose with or without SP600125. (ii) JNK-1 null mice and their littermate wild-type controls were infused intravenously with saline or glucose. Following the glucose infusion periods in rats and mice, β-cell function was assessed in isolated islets or in vivo using hyperglycemic clamps. Forty-eight-hour hyperglycemia at ~20 mM in rats or 96-hour hyperglycemia at ~13 mM in mice impaired β-cell function in isolated islets and in vivo. Inhibition of JNK using either SP600125 or JNK-1-null mice prevented glucose-induced β-cell dysfunction in isolated islets and in vivo. Islets of JNK-1-null mice exposed to hyperglycemia in vivo showed an increase in Pdx-1 and insulin 2 mRNA, whereas islets of wild-type mice did not. Together, these data show that JNK pathway is involved in glucose-induced β-cell dysfunction in vivo and is thus a potential therapeutic target for type 2 diabetes.
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Affiliation(s)
- Christine Tang
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Lucy Shu Nga Yeung
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Khajag Koulajian
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Liling Zhang
- Division of Cellular and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Kevin Tai
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Allen Volchuk
- Keenan Research Centre for Biomedical Science, St. Michael Hospital, Toronto, Ontario, Canada
| | - Adria Giacca
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Institute of Medical Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Banting and Best Diabetes Centre, University of Toronto, Toronto, Ontario, Canada
- Correspondence: Adria Giacca, MD, Medical Sciences Building, 3336-1 King’s College Circle, Toronto, Ontario M5S 1A8, Canada. E-mail:
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Rehman K, Akash MSH. Mechanism of Generation of Oxidative Stress and Pathophysiology of Type 2 Diabetes Mellitus: How Are They Interlinked? J Cell Biochem 2017; 118:3577-3585. [PMID: 28460155 DOI: 10.1002/jcb.26097] [Citation(s) in RCA: 293] [Impact Index Per Article: 41.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 04/26/2017] [Indexed: 12/14/2022]
Abstract
Oxidative stress has been considered as a major hallmark for the pathogenesis and development of type 2 diabetes mellitus (T2DM), but still it is debatable whether it is a mere aggregation of inflammatory-induced responses or clinical entity that underlies with various pathophysiological factors. In this regard, the latest studies have shown the increasing trends for the involvement of reactive oxygen species (ROS) and oxidative stress in the pathogenesis and development of T2DM. ROS are highly reactive species and almost all cellular components are chemically changed due to the influence of ROS that ultimately results in the production of lipid peroxidation. Lipid peroxidation is a major causative factor for the development of oxidative stress that leads to overt T2DM and its associated micro- and macro-vascular complications. In this article, we have briefly described the role of various causative factors, transcriptional and metabolic pathways which are responsible to increase the production of oxidative stress, a most pivotal factor for the pathogenesis and development of T2DM. Therefore, we conclude that measurement of oxidative stress biomarkers may be one of the optional tool for the diagnosis and prediction of T2DM. Moreover, the key findings described in this article also provides a new conceptual framework for forthcoming investigations on the role of oxidative stress in pathogenesis of T2DM and drug discovery. J. Cell. Biochem. 118: 3577-3585, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Kanwal Rehman
- Institute of Pharmacy, Physiology and Pharmacology, University of Agriculture, Faisalabad, Pakistan
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11
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Guo LX, Liu JH, Zheng XX, Yin ZY, Kosaraju J, Tam KY. Geniposide improves insulin production and reduces apoptosis in high glucose-induced glucotoxic insulinoma cells. Eur J Pharm Sci 2017; 110:70-76. [PMID: 28363490 DOI: 10.1016/j.ejps.2017.03.038] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 03/26/2017] [Accepted: 03/27/2017] [Indexed: 12/26/2022]
Abstract
Our previous work revealed that in the pancreatic β cell line, geniposide modulated ATP production and glucose-stimulated insulin secretion (GSIS) induced by the acute stimulation of high glucose concentration. However, the effects of geniposide on functional impairment and the mass of β-cells exposed to elevated levels of glucose remains unknown. In the present study, impaired GSIS and restrained proliferation were observed in the prolonged culture of insulinoma INS-1 cells with 33mM of glucose (high glucose). Our results indicate that the glucose-induced impairment of insulin release was significantly reverted by the inclusion of 1 or 10μM of geniposide. Moreover, induction of the phosphorylation of AMP-activated protein kinase (AMPK) was observed, which promoted the utilization of nutrient stores for energy production. AMPK phosphorylation was enhanced by an increased number of INS-1 cells, and the increased expression of AMPK downstream target heme oxygenase 1 (HO-1), under high glucose concentration. Furthermore, geniposide protected rat insulinoma cells from apoptosis in high-glucose concentrations. We have shown that these effects were associated with an increased apoptosis-related Bcl-2/BAX protein ratio. In conclusion, geniposide dose dependently improves β-cell function and increases the proliferation of β-cells exposed to prolonged hyperglycemia.
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Affiliation(s)
- L X Guo
- Chongqing Key Lab of Natural Medicine Research, Chongqing Technology and Business University, Chongqing 400067, China.
| | - J H Liu
- Chongqing Key Lab of Natural Medicine Research, Chongqing Technology and Business University, Chongqing 400067, China; College of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing 400050, China
| | - X X Zheng
- Chongqing Key Lab of Natural Medicine Research, Chongqing Technology and Business University, Chongqing 400067, China
| | - Z Y Yin
- Chongqing Key Lab of Natural Medicine Research, Chongqing Technology and Business University, Chongqing 400067, China
| | - J Kosaraju
- Faculty of Health Sciences, University of Macau, Taipa, Macau, China
| | - K Y Tam
- Faculty of Health Sciences, University of Macau, Taipa, Macau, China
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Yamamoto Y, Miyatsuka T, Sasaki S, Miyashita K, Kubo F, Shimo N, Takebe S, Watada H, Kaneto H, Matsuoka TA, Shimomura I. Preserving expression of Pdx1 improves β-cell failure in diabetic mice. Biochem Biophys Res Commun 2016; 483:418-424. [PMID: 28017717 DOI: 10.1016/j.bbrc.2016.12.128] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 12/19/2016] [Indexed: 02/01/2023]
Abstract
Pdx1, a β-cell-specific transcription factor, has been shown to play a crucial role in maintaining β-cell function through transactivation of β-cell-related genes. In addition, it has been reported that the expression levels of Pdx1 are compromised under diabetic conditions in human and rodent models. We therefore aimed to clarify the possible beneficial role of Pdx1 against β-cell failure and generated the transgenic mouse that expressed Pdx1 conditionally and specifically in β cells (βPdx1) and crossed these mice with Ins2Akita diabetic mice. Whereas Pdx1 mRNA levels were reduced in Ins2Akita mice compared with their non-diabetic littermates, the mRNA levels of Pdx1 were significantly recovered in the islets of βPdx1; Ins2Akita mice. The βPdx1; Ins2Akita mice exhibited significantly improved glucose tolerance, compared with control Ins2Akita littermates, accompanied by increased insulin secretion after glucose loading. Furthermore, histological examination demonstrated that βPdx1; Ins2Akita mice had improved localization of SLC2A2 (GLUT2), and quantitative RT-PCR showed the recovered expression of Mafa and Gck mRNAs in the islets of βPdx1; Ins2Akita mice. These findings suggest that the sustained expression of Pdx1 improves β-cell failure in Ins2Akita mice, at least partially through the preserving expression of β-cell-specific genes as well as improved localization of GLUT2.
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Affiliation(s)
- Yuichi Yamamoto
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan
| | - Takeshi Miyatsuka
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan; Department of Metabolism and Endocrinology, Juntendo University, Graduate School of Medicine, Tokyo, Japan.
| | - Shugo Sasaki
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan
| | - Kazuyuki Miyashita
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan
| | - Fumiyo Kubo
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan
| | - Naoki Shimo
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan
| | - Satomi Takebe
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan
| | - Hirotaka Watada
- Department of Metabolism and Endocrinology, Juntendo University, Graduate School of Medicine, Tokyo, Japan
| | - Hideaki Kaneto
- Department of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School, Okayama, Japan
| | - Taka-Aki Matsuoka
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan
| | - Iichiro Shimomura
- Department of Metabolic Medicine, Osaka University, Graduate School of Medicine, Osaka, Japan
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The glutathione mimic ebselen inhibits oxidative stress but not endoplasmic reticulum stress in endothelial cells. Life Sci 2015; 134:9-15. [PMID: 26006036 DOI: 10.1016/j.lfs.2015.05.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 04/01/2015] [Accepted: 05/01/2015] [Indexed: 12/14/2022]
Abstract
AIMS Reactive oxygen species are associated with cardiovascular disease, diabetes, and atherosclerosis, yet the use of antioxidants in clinical trials has been ineffective at improving outcomes. In endothelial cells, high-dextrose-induced oxidative stress and endoplasmic reticulum stress promote endothelial dysfunction leading to the recruitment and activation of peripheral blood lymphocytes and the breakdown of barrier function. Ebselen, a glutathione peroxidase 1 (GPX1) mimic, has been shown to improve β-cell function in diabetes and prevent atherosclerosis. MAIN METHODS To determine if ebselen inhibits both oxidative stress and endoplasmic reticulum (ER) stress in endothelial cells, we examined its effects in human umbilical vein endothelial cells (HUVEC) and human coronary artery endothelial cells (HCAEC) with and without high-dextrose. Oxidative stress and ER stress were measured by 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-A]pyrazin-3-one hydrochloride chemiluminescence and ER stress alkaline phosphatase assays, respectively. GPX1 over-expression and knockdown were performed by transfecting cells with a GPX1 expression construct or a GPX1-specific siRNA, respectively. KEY FINDINGS Ebselen inhibited dextrose-induced oxidative stress but not ER stress in both HUVEC and HCAEC. Ebselen also had no effect on tunicamycin-induced ER stress in HCAEC. Furthermore, augmentation of GPX1 activity directly by sodium selenite supplementation or transfection of a GPX1 expression plasmid decreased dextrose-induced oxidative stress but not ER stress, while GPX1 knockout enhanced oxidative stress but had no effect on ER stress. SIGNIFICANCE These results suggest that ebselen targets only oxidative stress but not ER stress.
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14
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Koh G, Yang EJ, Kim JY, Hyun J, Yoo S, Lee SA. Intracellular glutathione production, but not protein glycation, underlies the protective effects of captopril against 2-deoxy-D-ribose-induced β-cell damage. Mol Med Rep 2015; 12:5314-20. [PMID: 26151175 DOI: 10.3892/mmr.2015.4047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 06/22/2015] [Indexed: 11/06/2022] Open
Abstract
Our previous study reported that both oxidative stress and protein glycation were the principal mechanisms underlying 2‑deoxy‑D‑ribose (dRib)‑induced pancreatic β‑cell damage. The aim of the present study was to investigate the effects of captopril on dRib‑induced damage in pancreatic β‑cells, as well as to determine the mechanisms underlying these effects. Treatment with dRib increased the levels of cytotoxicity, apoptosis, and intracellular reactive oxygen species in Syrian hamster insulinoma HIT‑T15 cells; however, pretreatment with captopril significantly inhibited the effects of dRib. The intracellular levels of reduced and oxidized glutathione were depleted following treatment with dRib; however, these levels were restored following HIT‑T15 cell treatment with captopril. In rat islets, dRib stimulation suppressed the mRNA expression levels of insulin, and pancreatic and duodenal homeobox 1, as well as insulin content; however, these effects were dose‑dependently reversed by treatment with captopril. Treatment with buthionine sulfoximine, an inhibitor of intracellular glutathione biosynthesis, inhibited the protective effects of captopril on dRib‑mediated glutathione depletion and cytotoxicity in HIT‑T15 cells. Following incubation with albumin, dRib increased the formation of dicarbonyl and advanced glycation end products. Treatment with captopril did not inhibit the dRib‑induced increase in production of dicarbonyl and advanced glycation end products. In conclusion, treatment with captopril reversed dRib‑induced oxidative damage and suppression of insulin expression in β‑cells. The mechanism underlying the protective effects of captopril may involve increased intracellular glutathione production, rather than protein glycation.
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Affiliation(s)
- Gwanpyo Koh
- Department of Internal Medicine, Jeju National University School of Medicine, Jeju‑si, Jeju 690‑767, Republic of Korea
| | - Eun-Jin Yang
- Department of Internal Medicine, Jeju National University School of Medicine, Jeju‑si, Jeju 690‑767, Republic of Korea
| | - Ji Young Kim
- Department of Internal Medicine, Jeju National University Hospital, Jeju‑si, Jeju 690‑767, Republic of Korea
| | - Jonghoon Hyun
- Department of Internal Medicine, Jeju National University School of Medicine, Jeju‑si, Jeju 690‑767, Republic of Korea
| | - Soyeon Yoo
- Department of Internal Medicine, Jeju National University Hospital, Jeju‑si, Jeju 690‑767, Republic of Korea
| | - Sang Ah Lee
- Department of Internal Medicine, Jeju National University School of Medicine, Jeju‑si, Jeju 690‑767, Republic of Korea
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15
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Puri S, Folias AE, Hebrok M. Plasticity and dedifferentiation within the pancreas: development, homeostasis, and disease. Cell Stem Cell 2014; 16:18-31. [PMID: 25465113 DOI: 10.1016/j.stem.2014.11.001] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cellular identity is established by genetic, epigenetic, and environmental factors that regulate organogenesis and tissue homeostasis. Although some flexibility in fate potential is beneficial to overall organ health, dramatic changes in cellular identity can have disastrous consequences. Emerging data within the field of pancreas biology are revising current beliefs about how cellular identity is shaped by developmental and environmental cues under homeostasis and stress conditions. Here, we discuss the changes occurring in cellular states upon fate modulation and address how our understanding of the nature of this fluidity is shaping therapeutic approaches to pancreatic disorders such as diabetes and cancer.
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Affiliation(s)
- Sapna Puri
- Diabetes Center, Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Alexandra E Folias
- Diabetes Center, Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Matthias Hebrok
- Diabetes Center, Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
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16
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Ito R, Tsujihata Y, Matsuda-Nagasumi K, Mori I, Negoro N, Takeuchi K. TAK-875, a GPR40/FFAR1 agonist, in combination with metformin prevents progression of diabetes and β-cell dysfunction in Zucker diabetic fatty rats. Br J Pharmacol 2014; 170:568-80. [PMID: 23848179 DOI: 10.1111/bph.12297] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 06/20/2013] [Accepted: 07/03/2013] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND AND PURPOSE TAK-875, a selective GPCR40/free fatty acid receptor 1 agonist, improves glycaemic control by increasing glucose-dependent insulin secretion. Metformin is a first-line drug for treatment of type 2 diabetes that improves peripheral insulin resistance. Based on complementary mechanism of action, combining these agents is expected to enhance glycaemic control. Here, we evaluated the chronic effects of TAK-875 monotherapy and combination therapy with metformin in diabetic rats. EXPERIMENTAL APPROACH Long-term effects on glycaemic control and β-cell function were evaluated using Zucker diabetic fatty (ZDF) rats, which develop diabetes with hyperlipidaemia and progressive β-cell dysfunction. KEY RESULTS Single doses of TAK-875 (3-10 mg·kg(-1) ) and metformin (50-150 mg·kg(-1) ) significantly improved both postprandial and fasting hyperglycaemia, and additive improvements were observed in their combination. Six-week treatment with TAK-875 (10 mg·kg(-1) , b.i.d.) significantly decreased glycosylated Hb (GHb) by 1.7%, and the effect was additively enhanced by combination with metformin (50 mg·kg(-1) , q.d.; GHb: -2.4%). This improvement in glycaemic control in the combination group was accompanied by significant 3.2-fold increase in fasting plasma insulin levels. Pancreatic insulin content was maintained at a level comparable to that in normal rats by combination treatment (vehicle: 26, combination: 67.1; normal lean: 69.1 ng·mg(-1) pancreas) without affecting pancreatic glucagon content. Immunohistochemical analyses revealed normal morphology, enhanced pancreas duodenum homeobox-1 expression and increased PCNA-positive cells in islets of the combination group. CONCLUSION AND IMPLICATIONS Our results indicate that combination therapy with TAK-875 and metformin could be a valuable strategy for glycaemic control and β-cell preservation in type 2 diabetes.
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Affiliation(s)
- R Ito
- Cardiovascular and Metabolic Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Kanagawa, Japan
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17
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Pdx1 maintains β cell identity and function by repressing an α cell program. Cell Metab 2014; 19:259-71. [PMID: 24506867 PMCID: PMC3950964 DOI: 10.1016/j.cmet.2013.12.002] [Citation(s) in RCA: 287] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 07/10/2013] [Accepted: 11/19/2013] [Indexed: 12/13/2022]
Abstract
Pdx1 is a homeobox-containing transcription factor that plays a key role in pancreatic development and adult β cell function. In this study, we traced the fate of adult β cells after Pdx1 deletion. As expected, β-cell-specific removal of Pdx1 resulted in severe hyperglycemia within days. Surprisingly, a large fraction of Pdx1-deleted cells rapidly acquired ultrastructural and physiological features of α cells, indicating that a robust cellular reprogramming had occurred. Reprogrammed cells exhibited a global transcriptional shift that included derepression of the α cell transcription factor MafB, resulting in a transcriptional profile that closely resembled that of α cells. These findings indicate that Pdx1 acts as a master regulator of β cell fate by simultaneously activating genes essential for β cell identity and repressing those associated with α cell identity. We discuss the significance of these findings in the context of the emerging notion that loss of β cell identity contributes to the pathogenesis of type 2 diabetes.
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Thioredoxin-mimetic peptide CB3 lowers MAPKinase activity in the Zucker rat brain. Redox Biol 2014; 2:447-56. [PMID: 24624334 PMCID: PMC3949098 DOI: 10.1016/j.redox.2013.12.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 12/20/2013] [Indexed: 02/07/2023] Open
Abstract
Diabetes is a high risk factor for dementia. High glucose may be a risk factor for dementia even among persons without diabetes, and in transgenic animals it has been shown to cause a potentiation of indices that are pre-symptomatic of Alzheimer's disease. To further elucidate the underlying mechanisms linking inflammatory events elicited in the brain during oxidative stress and diabetes, we monitored the activation of mitogen-activated kinsase (MAPKs), c-jun NH2-terminal kinase (JNK), p38 MAP kinases (p38MAPK), and extracellular activating kinsae1/2 (ERK1/2) and the anti-inflammatory effects of the thioredoxin mimetic (TxM) peptides, Ac-Cys-Pro-Cys-amide (CB3) and Ac-Cys-Gly-Pro-Cys-amide (CB4) in the brain of male leptin-receptor-deficient Zucker diabetic fatty (ZDF) rats and human neuroblastoma SH-SY5Y cells. Daily i.p. injection of CB3 to ZDF rats inhibited the phosphorylation of JNK and p38MAPK, and prevented the expression of thioredoxin-interacting-protein (TXNIP/TBP-2) in ZDF rat brain. Although plasma glucose/insulin remained high, CB3 also increased the phosphorylation of AMP-ribose activating kinase (AMPK) and inhibited p70S6K kinase in the brain. Both CB3 and CB4 reversed apoptosis induced by inhibiting thioredoxin reductase as monitored by decreasing caspase 3 cleavage and PARP dissociation in SH-SY5Y cells. The decrease in JNK and p38MAPK activity in the absence of a change in plasma glucose implies a decrease in oxidative or neuroinflammatory stress in the ZDF rat brain. CB3 not only attenuated MAPK phosphorylation and activated AMPK in the brain, but it also diminished apoptotic markers, most likely acting via the MAPK–AMPK–mTOR pathway. These results were correlated with CB3 and CB4 inhibiting inflammation progression and protection from oxidative stress induced apoptosis in human neuronal cells. We suggest that by attenuating neuro-inflammatory processes in the brain Trx1 mimetic peptides could become beneficial for preventing neurological disorders associated with diabetes. Thioredoxin mimeitics peptides (TXM) lower apoptosis in the brain of ZDF rat. TxM peptides prevent TXNIP/TBP-2 expression in the brain of ZDF rat. TxM peptides could become beneficial for preventing diabetes associated neurological disorders.
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Mahadevan J, Parazzoli S, Oseid E, Hertzel AV, Bernlohr DA, Vallerie SN, Liu CQ, Lopez M, Harmon JS, Robertson RP. Ebselen treatment prevents islet apoptosis, maintains intranuclear Pdx-1 and MafA levels, and preserves β-cell mass and function in ZDF rats. Diabetes 2013; 62:3582-8. [PMID: 23801580 PMCID: PMC3781455 DOI: 10.2337/db13-0357] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We reported earlier that β-cell-specific overexpression of glutathione peroxidase (GPx)-1 significantly ameliorated hyperglycemia in diabetic db/db mice and prevented glucotoxicity-induced deterioration of β-cell mass and function. We have now ascertained whether early treatment of Zucker diabetic fatty (ZDF) rats with ebselen, an oral GPx mimetic, will prevent β-cell deterioration. No other antihyperglycemic treatment was given. Ebselen ameliorated fasting hyperglycemia, sustained nonfasting insulin levels, lowered nonfasting glucose levels, and lowered HbA1c levels with no effects on body weight. Ebselen doubled β-cell mass, prevented apoptosis, prevented expression of oxidative stress markers, and enhanced intranuclear localization of pancreatic and duodenal homeobox (Pdx)-1 and v-maf musculoaponeurotic fibrosarcoma oncogene family, protein A (MafA), two critical insulin transcription factors. Minimal β-cell replication was observed in both groups. These findings indicate that prevention of oxidative stress is the mechanism whereby ebselen prevents apoptosis and preserves intranuclear Pdx-1 and MafA, which, in turn, is a likely explanation for the beneficial effects of ebselen on β-cell mass and function. Since ebselen is an oral antioxidant currently used in clinical trials, it is a novel therapeutic candidate to ameliorate fasting hyperglycemia and further deterioration of β-cell mass and function in humans undergoing the onset of type 2 diabetes.
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Affiliation(s)
- Jana Mahadevan
- Pacific Northwest Diabetes Research Institute and Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, Washington
| | - Susan Parazzoli
- Pacific Northwest Diabetes Research Institute and Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, Washington
| | - Elizabeth Oseid
- Pacific Northwest Diabetes Research Institute and Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, Washington
| | - Ann V. Hertzel
- Department of Biochemistry and Molecular Biology, University of Minnesota, Minneapolis, Minnesota
| | - David A. Bernlohr
- Department of Biochemistry and Molecular Biology, University of Minnesota, Minneapolis, Minnesota
| | - Sara N. Vallerie
- Pacific Northwest Diabetes Research Institute and Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, Washington
| | - Chang-qin Liu
- Pacific Northwest Diabetes Research Institute and Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, Washington
| | - Melissa Lopez
- Pacific Northwest Diabetes Research Institute and Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, Washington
| | - Jamie S. Harmon
- Pacific Northwest Diabetes Research Institute and Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, Washington
| | - R. Paul Robertson
- Pacific Northwest Diabetes Research Institute and Division of Metabolism, Endocrinology, and Nutrition, University of Washington, Seattle, Washington
- Department of Biochemistry and Molecular Biology, University of Minnesota, Minneapolis, Minnesota
- Corresponding author: R. Paul Robertson,
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Arunachalam S, Tirupathi Pichiah PB, Achiraman S. Doxorubicin treatment inhibits PPARγ and may induce lipotoxicity by mimicking a type 2 diabetes-like condition in rodent models. FEBS Lett 2012; 587:105-10. [PMID: 23219922 DOI: 10.1016/j.febslet.2012.11.019] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Revised: 10/16/2012] [Accepted: 11/16/2012] [Indexed: 01/04/2023]
Abstract
Doxorubicin-treated animals show elevated serum triglyceride and blood glucose levels. Adipocytes play an important role in buffering blood glucose and lipids. A raise in serum lipid level triggers adipogenesis in order to increase the lipid absorption capacity of adipose tissue. Doxorubicin inhibits adipogenesis through the down-regulation of PPARγ, a crucial component of the lipid metabolic pathway which controls the expression of glucose and fatty acid transporters. Doxorubicin-mediated down-regulation of PPARγ inhibits blood glucose and lipid clearance thereby causing hyperglycemia and hyperlipidemia resulting in lipotoxicity, glucotoxicity, inflammation and insulin resistance. Therefore we hypothesize that doxorubicin treatment could mimic a type 2 diabetic condition.
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Affiliation(s)
- Sankarganesh Arunachalam
- Department of Environmental Biotechnology, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India
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21
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Stojanovic I, Saksida T, Timotijevic G, Sandler S, Stosic-Grujicic S. Macrophage migration inhibitory factor (MIF) enhances palmitic acid- and glucose-induced murine beta cell dysfunction and destruction in vitro. Growth Factors 2012; 30:385-93. [PMID: 23137174 DOI: 10.3109/08977194.2012.734506] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Although several reports suggest a potentially deleterious role of macrophage migration inhibitory factor (MIF) in type 2 diabetes (T2D) pathology, it is still unclear how this pro-inflammatory cytokine acts on pancreatic beta cells. The aim of the present study was to evaluate MIF effects on murine beta cells in the in vitro settings mimicking T2D-associated conditions. Results indicate that recombinant MIF further increased apoptosis of pancreatic islets or MIN6 cells upon exposure to palmitic acid or glucose. This was accompanied by upregulation of several pro-apoptotic molecules. Furthermore, MIF potentiated nutrient-induced islet cell dysfunction, as revealed by lower glucose oxidation rate, ATP content, and depolarized mitochondrial membrane. The final outcome was potentiation of mitochondrial apoptotic pathway. The observed upregulation of nutrient-induced islet cell dysfunction and apoptosis by MIF implicates that silencing MIF may be beneficial for maintaining integrity of endocrine pancreas in obesity-associated T2D.
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Affiliation(s)
- Ivana Stojanovic
- Department of Immunology, Institute for Biological Research "Sinisa Stankovic", University of Belgrade, Serbia.
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22
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Thamizhiniyan V, Vijayaraghavan K, Subramanian SP. Gossypin, a flavonol glucoside protects pancreatic beta-cells from glucotoxicity in streptozotocin-induced experimental diabetes in rats. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.bionut.2012.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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23
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Delghingaro-Augusto V, Décary S, Peyot ML, Latour MG, Lamontagne J, Paradis-Isler N, Lacharité-Lemieux M, Akakpo H, Birot O, Nolan CJ, Prentki M, Bergeron R. Voluntary running exercise prevents β-cell failure in susceptible islets of the Zucker diabetic fatty rat. Am J Physiol Endocrinol Metab 2012; 302:E254-64. [PMID: 22045312 DOI: 10.1152/ajpendo.00360.2011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Physical activity improves glycemic control in type 2 diabetes (T2D), but its contribution to preserving β-cell function is uncertain. We evaluated the role of physical activity on β-cell secretory function and glycerolipid/fatty acid (GL/FA) cycling in male Zucker diabetic fatty (ZDF) rats. Six-week-old ZDF rats engaged in voluntary running for 6 wk (ZDF-A). Inactive Zucker lean and ZDF (ZDF-I) rats served as controls. ZDF-I rats displayed progressive hyperglycemia with β-cell failure evidenced by falling insulinemia and reduced insulin secretion to oral glucose. Isolated ZDF-I rat islets showed reduced glucose-stimulated insulin secretion expressed per islet and per islet protein. They were also characterized by loss of the glucose regulation of fatty acid oxidation and GL/FA cycling, reduced mRNA expression of key β-cell genes, and severe reduction of insulin stores. Physical activity prevented diabetes in ZDF rats through sustaining β-cell compensation to insulin resistance shown in vivo and in vitro. Surprisingly, ZDF-A islets had persistent defects in fatty acid oxidation, GL/FA cycling, and β-cell gene expression. ZDF-A islets, however, had preserved islet insulin mRNA and insulin stores compared with ZDF-I rats. Physical activity did not prevent hyperphagia, dyslipidemia, or obesity in ZDF rats. In conclusion, islets of ZDF rats have a susceptibility to failure that is possibly due to altered β-cell fatty acid metabolism. Depletion of pancreatic islet insulin stores is a major contributor to islet failure in this T2D model, preventable by physical activity.
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Affiliation(s)
- Viviane Delghingaro-Augusto
- Molecular Nutrition Unit and The Montreal Diabetes Research Center, Research Center of the University of Montreal Hospital Center,University of Montreal, Quebec, Canada
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24
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Zhang Y, Liu D. Flavonol kaempferol improves chronic hyperglycemia-impaired pancreatic beta-cell viability and insulin secretory function. Eur J Pharmacol 2011; 670:325-32. [PMID: 21914439 DOI: 10.1016/j.ejphar.2011.08.011] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Revised: 07/22/2011] [Accepted: 08/17/2011] [Indexed: 01/04/2023]
Abstract
Considerable evidence shows that chronic hyperglycemia can cause pancreatic beta-cell dysfunction, which contributes to progressive deterioration of glucose homeostasis and overt diabetes. In the present study, we found that kaempferol, a flavonol compound present in various Chinese medicinal herbs, has cytoprotective effects on cultured clonal beta-cells and pancreatic human islets. Kaempferol treatment dose-dependently promoted viability, inhibited cellular apoptosis, and reduced caspase-3 activity in beta-cells and human islets exposed to chronic high glucose, with 10 μM kaempferol exerting the maximum effect. In addition, kaempferol treatment improved the expression of anti-apoptotic proteins Akt and Bcl-2 that was significantly reduced in beta-cells and human islets chronically exposed to hyperglycemia. Furthermore, exposure of beta-cells and human islets to kaempferol restored high glucose-attenuated intracellular cAMP and ATP production. Inhibition of protein kinase A or Akt activation ablated the anti-apoptotic effect of kaempferol. These cytoprotective effects of kaempferol were associated with improved insulin secretory function and synthesis in beta-cells and human islets. These findings provide evidence that kaempferol may be a naturally occurring anti-diabetic compound by protecting pancreatic beta-cell survival and function in a hostile environment that would otherwise lead to type 2 diabetes.
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Affiliation(s)
- Yanling Zhang
- Faculty of Life Science, Northwestern Polytechnical University, Xi'an, 710072, China
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25
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Abstract
Increasing evidences have suggested that oxidative stress plays a major role in the pathogenesis of diabetes mellitus (DM). Oxidative stress also appears to be the pathogenic factor in underlying diabetic complications. Reactive oxygen species (ROS) are generated by environmental factors, such as ionizing radiation and chemical carcinogens, and also by endogenous processes, including energy metabolism in mitochondria. ROS produced either endogenously or exogenously can attack lipids, proteins and nucleic acids simultaneously in living cells. There are many potential mechanisms whereby excess glucose metabolites traveling along these pathways might promote the development of DM complication and cause pancreatic β cell damage. However, all these pathways have in common the formation of ROS, that, in excess and over time, causes chronic oxidative stress, which in turn causes defective insulin gene expression and insulin secretion as well as increased apoptosis. Various methods for determining biomarkers of cellular oxidative stress have been developed, and some have been proposed for sensitive assessment of antioxidant defense and oxidative damage in diabetes and its complications. However, their clinical utility is limited by less than optimal standardization techniques and the lack of sufficient large-sized, multi-marker prospective trials.
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Affiliation(s)
- Hui Yang
- Department of Laboratory Medicine, China-Japan Friendship Hospital, Ministry of Health, Beijing, PR China
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26
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Babu A, Mehta A, Guerrero P, Chen Z, Meyer PM, Koh CK, Roberts R, Schaider J, Fogelfeld L. Safe and simple emergency department discharge therapy for patients with type 2 diabetes mellitus and severe hyperglycemia. Endocr Pract 2010; 15:696-704. [PMID: 19625243 DOI: 10.4158/ep09117.orr] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVE To investigate the safety and effectiveness of 2 simple discharge regimens for use in patients with type 2 diabetes mellitus (DM2) and severe hyperglycemia, who present to the emergency department (ED) and do not need to be admitted. METHODS We conducted an 8-week, open-label, randomized controlled trial in 77 adult patients with DM2 and blood glucose levels of 300 to 700 mg/dL seen in a public hospital ED. Patients were randomly assigned to receive glipizide XL, 10 mg orally daily (G group), versus glipizide XL, 10 mg orally daily, plus insulin glargine, 10 U daily (G+G group). The primary outcome was to maintain safe fasting glucose and random glucose levels of <350 and <500 mg/dL up to 4 weeks and <300 and <400 mg/dL, respectively, thereafter and to have no return ED visits (responders). RESULTS Baseline characteristics were similar between the 2 treatment groups. The primary outcome was achieved in 87% of patients in both treatment groups. The enrollment mean blood glucose values of 440 and 467 mg/dL in the G and G+G groups, respectively, declined by the end of week 1 to 298 and 289 mg/dL and by week 8 to 140 and 135 mg/dL, respectively. Homeostasis model assessment of beta-cell function and early insulin response improved 7-fold and 4-fold, respectively, in responders at the end of the 8-week study. CONCLUSION Sulfonylurea with and without use of a small dose of insulin glargine rapidly improved blood glucose levels and beta-cell function in patients with DM2. Use of sulfonylurea alone once daily can be considered a safe discharge regimen for such patients and an effective bridge between ED intervention and subsequent follow-up.
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Affiliation(s)
- Ambika Babu
- Department of Endocrinology and Metabolism, John H. Stroger Jr. Hospital of Cook County and Rush University Medical Center, Chicago, Illinois, USA.
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27
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Abstract
Type 1 diabetes (T1D) develops as a consequence of abnormal responses against several self-antigens, eventually leading to the autoimmune attack and destruction of the insulin-producing beta cells in the pancreas. In this issue of Laboratory Investigation, Li et al propose the transcription factor Pancreatic and duodenal homeobox 1 (PDX-1) as a T1D autoantigen by demonstrating autoreactivity to this pancreas-specific protein in both the NOD mouse model and patients with T1D. Because of the known roles of PDX-1 in pancreatic development as well as beta cell maintenance and function, targeting of PDX-1 expressing cells may result in the elimination of not only beta cells but also the progenitor cells required for regeneration of insulin-producing cells.
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Brand CL, Galsgaard ED, Tornehave D, Rømer J, Gotfredsen CF, Wassermann K, Knudsen LB, Vølund A, Sturis J. Synergistic effect of the human GLP-1 analogue liraglutide and a dual PPARalpha/gamma agonist on glycaemic control in Zucker diabetic fatty rats. Diabetes Obes Metab 2009; 11:795-803. [PMID: 19519868 DOI: 10.1111/j.1463-1326.2009.01049.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM/HYPOTHESIS Combination therapies are increasingly common in the clinical management of type 2 diabetes. We investigated to what extent combined treatment with the human glucagon-like peptide-1 (GLP-1) analogue liraglutide and the dual PPARalpha/gamma agonist ragaglitazar would improve glycaemic control in overtly diabetic Zucker diabetic fatty (ZDF) rats. METHODS Ninety overtly diabetic male ZDF rats were stratified into groups with matched haemoglobin A1c (HbA1c) (9.0+/-0.1%). Liraglutide (15 and 50 microg/kg subcutaneously twice daily), ragaglitazar (1 and 3 mg/kg perorally once daily) and their vehicles were studied as monotherapy and in combination in a 3x3 factorial design. RESULTS After 4-week treatment, synergistic effects on HbA1c, non-fasting morning blood glucose (BG) and/or 24-h BG profiles were observed with three of the four combinations. The relationship between plasma insulin and BG in combination-treated animals approached that of historical lean ZDF rats representing normal glucose homeostasis, suggesting that insulin secretion and insulin sensitivity were markedly improved. Increased insulin immunostaining in islets further supports the improved beta-cell function and/or insulin sensitivity in combination-treated animals. The synergistic effect on glycaemic control was found without a similar synergistic increase in beta-cell mass in the combination groups. CONCLUSIONS/INTERPRETATION Our data demonstrate that combination treatment with a human GLP-1 analogue and a dual PPARalpha/gamma agonist through distinct mechanism of actions synergistically improves glycaemic control in the ZDF rat.
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Affiliation(s)
- C L Brand
- Research and Development, Novo Nordisk A/S, Maaloev, Denmark
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29
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Won JC, Rhee BD, Ko KS. Glucose-responsive gene expression system for gene therapy. Adv Drug Deliv Rev 2009; 61:633-40. [PMID: 19394377 DOI: 10.1016/j.addr.2009.03.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Accepted: 03/25/2009] [Indexed: 12/30/2022]
Abstract
Regulation of gene expression by glucose is an important mechanism for mammals in adapting to their nutritional environment. Glucose, the primary fuel for most cells, modulates gene expression that is crucial in the cellular adaptation to glycemic variation. Transcription of the genes for insulin and glycolytic and lipogenic enzymes is stimulated by glucose in pancreatic beta-cells and liver. Recent findings further support the key role of the carbohydrate-responsive element binding protein in the regulation of glycolytic and lipogenic genes by glucose and dietary carbohydrates. Herein, we review the transcriptional regulation of glucose-responsive genes, and recent advances in the gene therapy using glucose-responsive gene expression for diabetes.
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Affiliation(s)
- Jong Chul Won
- Department of Internal Medicine, Sanggye Paik Hospital, Mitochondrial Research Group, Inje University College of Medicine, Seoul, Republic of Korea
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Ariyama Y, Tanaka Y, Shimizu H, Shimomura K, Okada S, Saito T, Yamada E, Oyadomari S, Mori M, Mori M. The role of CHOP messenger RNA expression in the link between oxidative stress and apoptosis. Metabolism 2008; 57:1625-35. [PMID: 19013284 DOI: 10.1016/j.metabol.2008.06.019] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Accepted: 06/09/2008] [Indexed: 12/20/2022]
Abstract
Low expression of antioxidant enzymes makes pancreatic beta-cells susceptible to cell damage by oxidative stress. Pancreatic beta-cell loss caused by endoplasmic reticulum stress is associated with the onset of diabetes mellitus. The present studies were undertaken to investigate a possible involvement of proapoptotic gene CHOP in pancreatic beta-cells damage by oxidative stress. The induction of CHOP messenger RNA and apoptosis were investigated in betaHC-9 cells after the oxidative stress by hydrogen peroxide and ribose. Latter was examined after the suppression of CHOP by small interfering RNA. For in vivo study, the pancreatic beta-cells were examined in CHOP-knockout (KO) mice after multiple low-dose streptozotocin (MLDS) administration. In betaHC-9 cells, both hydrogen peroxide and ribose obviously increased apoptotic cells, accompanied with enhanced CHOP messenger RNA expression. However, the number of apoptotic cells by those stimulations was significantly reduced by the addition of small interfering RNA against CHOP. In vivo study also showed that CHOP-KO mice were less susceptible to diabetes after MLDS administration. Although the oxidative stress marker level was similar to that of MLDS-treated wild type, the pancreatic beta-cell area was maintained in CHOP-KO mice. The present studies showed that CHOP should be important in pancreatic beta-cell injury by oxidative stress and indicate that CHOP may play a role in the development of pancreatic beta-cell damage on the onset of diabetes mellitus.
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Affiliation(s)
- Yasuyo Ariyama
- Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
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31
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Pipeleers D, Chintinne M, Denys B, Martens G, Keymeulen B, Gorus F. Restoring a functional beta-cell mass in diabetes. Diabetes Obes Metab 2008; 10 Suppl 4:54-62. [PMID: 18834433 DOI: 10.1111/j.1463-1326.2008.00941.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Type 1 and type 2 diabetes have often been presented as disease forms that profoundly differ in the presence and pathogenic significance of a reduced beta-cell mass. We review evidence indicating that the beta-cell mass in type 1 diabetes is usually not decreased by at least 90% at clinical onset, and remains often detectable for years after diagnosis at age above 15 years. Clinical and experimental evidence also exists for a reduced beta-cell mass in type 2 diabetes where it can be the cause for and/or the consequence of dysregulated beta-cell functions. With beta-cell mass defined as number of beta-cells, these views face the limitation of insufficient data and methods for human organs. Because beta-cells can occur under different phenotypes that vary with age and with environmental conditions, we propose to use the term functional beta-cell mass as an assessment of a beta-cell population by the number of beta-cells and their phenotype or functional state. Assays exist to measure functional beta-cell mass in isolated preparations. We selected a glucose-clamp test to evaluate functional beta-cell mass in type 1 patients at clinical onset and in type 1 recipients following intraportal islet cell transplantation. Comparison of the data with those in non-diabetic controls helps targeting and monitoring of therapeutic interventions.
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Affiliation(s)
- D Pipeleers
- Diabetes Research Center, Brussels Free University-VUB, JDRF Center for Beta Cell Therapy in Diabetes, Brussels, Belgium.
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32
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The sensitivity of pancreatic β-cells to mitochondrial injuries triggered by lipotoxicity and oxidative stress. Biochem Soc Trans 2008; 36:930-4. [DOI: 10.1042/bst0360930] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Pancreatic β-cells are essential for the maintenance of glucose homoeostasis, and dysfunction of these insulin-secreting cells results in the development of diabetes. In the course of events leading from obesity to Type 2 diabetes, several mechanisms are currently envisaged. Among them, lipids and oxidative stress are considered as toxic candidates for the β-cell. The cellular link between fatty acids and ROS (reactive oxygen species) is essentially the mitochondrion, a key organelle for the control of insulin secretion. Mitochondria are the main source of ROS and are also the primary target of oxidative attacks. The present review presents the current knowledge of lipotoxicity related to oxidative stress in the context of mitochondrial function in the β-cell.
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Abstract
Production and secretion of insulin from the β-cells of the pancreas is very crucial in maintaining normoglycaemia. This is achieved by tight regulation of insulin synthesis and exocytosis from the β-cells in response to changes in blood glucose levels. The synthesis of insulin is regulated by blood glucose levels at the transcriptional and post-transcriptional levels. Although many transcription factors have been implicated in the regulation of insulin gene transcription, three β-cell-specific transcriptional regulators, Pdx-1 (pancreatic and duodenal homeobox-1), NeuroD1 (neurogenic differentiation 1) and MafA (V-maf musculoaponeurotic fibrosarcoma oncogene homologue A), have been demonstrated to play a crucial role in glucose induction of insulin gene transcription and pancreatic β-cell function. These three transcription factors activate insulin gene expression in a co-ordinated and synergistic manner in response to increasing glucose levels. It has been shown that changes in glucose concentrations modulate the function of these β-cell transcription factors at multiple levels. These include changes in expression levels, subcellular localization, DNA-binding activity, transactivation capability and interaction with other proteins. Furthermore, all three transcription factors are able to induce insulin gene expression when expressed in non-β-cells, including liver and intestinal cells. The present review summarizes the recent findings on how glucose modulates the function of the β-cell transcription factors Pdx-1, NeuroD1 and MafA, and thereby tightly regulates insulin synthesis in accordance with blood glucose levels.
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Abstract
Glucotoxicity, lipotoxicity, and glucolipotoxicity are secondary phenomena that are proposed to play a role in all forms of type 2 diabetes. The underlying concept is that once the primary pathogenesis of diabetes is established, probably involving both genetic and environmental forces, hyperglycemia and very commonly hyperlipidemia ensue and thereafter exert additional damaging or toxic effects on the beta-cell. In addition to their contribution to the deterioration of beta-cell function after the onset of the disease, elevations of plasma fatty acid levels that often accompany insulin resistance may, as glucose levels begin to rise outside of the normal range, also play a pathogenic role in the early stages of the disease. Because hyperglycemia is a prerequisite for lipotoxicity to occur, the term glucolipotoxicity, rather than lipotoxicity, is more appropriate to describe deleterious effects of lipids on beta-cell function. In vitro and in vivo evidence supporting the concept of glucotoxicity is presented first, as well as a description of the underlying mechanisms with an emphasis on the role of oxidative stress. Second, we discuss the functional manifestations of glucolipotoxicity on insulin secretion, insulin gene expression, and beta-cell death, and the role of glucose in the mechanisms of glucolipotoxicity. Finally, we attempt to define the role of these phenomena in the natural history of beta-cell compensation, decompensation, and failure during the course of type 2 diabetes.
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Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, CR-CHUM, Technopole Angus, 2901 Rachel Est, Montreal, Quebec, Canada H1W 4A4.
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35
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Yamamoto M, Yamato E, Toyoda SI, Tashiro F, Ikegami H, Yodoi J, Miyazaki JI. Transgenic expression of antioxidant protein thioredoxin in pancreatic beta cells prevents progression of type 2 diabetes mellitus. Antioxid Redox Signal 2008; 10:43-9. [PMID: 17949261 DOI: 10.1089/ars.2007.1586] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The authors previously established a transgenic mouse line in the type 1 diabetes model, NOD mouse, in which thioredoxin (TRX), a redox protein, is overexpressed in pancreatic beta cells, and found that TRX overexpression slows the progression of type 1 diabetes. Recent reports on type 2 diabetes suggest that oxidative stress also degrades the function of beta cells. To elucidate whether TRX overexpression can prevent progressive beta cell failure from oxidative stress in type 2 diabetes, the authors transferred the TRX transgene from the NOD mouse onto a mouse model of type 2 diabetes, the db/db mouse. The progression of hyperglycemia and the reduction of body weight gain and insulin content of the db/db mouse were significantly suppressed by the TRX expression. Furthermore, TRX suppressed the reduction of Pdx-1 and MafA expression in the beta cells, which may be one of the cellular mechanisms for protecting beta cells from losing their insulin-secreting capacity. These results showed that TRX can protect beta cells from destruction not only in type 1 but also in type 2 diabetes, and that they provide evidence that oxidative stress plays a crucial role in the deterioration of beta cell function during the progression of type 2 diabetes.
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Affiliation(s)
- Mayu Yamamoto
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
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36
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Tang C, Han P, Oprescu AI, Lee SC, Gyulkhandanyan AV, Chan GNY, Wheeler MB, Giacca A. Evidence for a role of superoxide generation in glucose-induced beta-cell dysfunction in vivo. Diabetes 2007; 56:2722-31. [PMID: 17682092 DOI: 10.2337/db07-0279] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Prolonged elevation of glucose can adversely affect beta-cell function. In vitro studies have linked glucose-induced beta-cell dysfunction to oxidative stress; however, whether oxidative stress plays a role in vivo is unclear. Therefore, our objective was to investigate the role of oxidative stress in an in vivo model of glucose-induced beta-cell dysfunction. RESEARCH DESIGN AND METHODS Wistar rats were infused intravenously with glucose for 48 h to achieve 20 mmol/l hyperglycemia with/without co-infusion of one of the following antioxidants: taurine (2-amino ethanesulfonic acid) (TAU), an aldehyde scavenger; N-acetylcysteine (NAC), a precursor of glutathione; or tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (TPO), a superoxide dismutase mimetic. This was followed by islet isolation or hyperglycemic clamp. RESULTS A 48-h glucose infusion decreased glucose-stimulated insulin secretion (GSIS) and elevated reactive oxygen species (ROS), total superoxide, and mitochondrial superoxide in freshly isolated islets. TPO prevented the increase in total and mitochondrial superoxide and the beta-cell dysfunction induced by high glucose. However, TAU and NAC, despite completely normalizing H(2)DCF-DA (dihydro-dichlorofluorescein diacetate)-measured ROS, did not prevent the increase in superoxide and the decrease in beta-cell function induced by high glucose. TPO but not TAU also prevented beta-cell dysfunction induced by less extreme hyperglycemia (15 mmol/l) for a longer period of time (96 h). To further investigate whether TPO is effective in vivo, a hyperglycemic clamp was performed. Similar to the findings in isolated islets, prolonged glucose elevation (20 mmol/l for 48 h) decreased beta-cell function as assessed by the disposition index (insulin secretion adjusted for insulin sensitivity), and co-infusion of TPO with glucose completely restored beta-cell function. CONCLUSIONS These findings implicate superoxide generation in beta-cell dysfunction induced by prolonged hyperglycemia.
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Affiliation(s)
- Christine Tang
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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37
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Patterson S, Scullion SMJ, McCluskey JT, Flatt PR, McClenaghan NH. Prolonged exposure to homocysteine results in diminished but reversible pancreatic beta-cell responsiveness to insulinotropic agents. Diabetes Metab Res Rev 2007; 23:324-34. [PMID: 17089371 DOI: 10.1002/dmrr.699] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Plasma homocysteine levels may be elevated in poorly controlled diabetes with pre-existing vascular complications and/or nephropathy. Since homocysteine has detrimental effects on a wide diversity of cell types, the present study examined the effects of long-term homocysteine exposure on the secretory function of clonal BRIN-BD11 beta-cells. METHODS Acute insulin secretory function, cellular insulin content and viability of BRIN-BD11 cells were assessed following long-term (18 h) exposure to homocysteine in culture. RT-PCR and Western blot analysis were used to determine the expression of key beta-cell genes and proteins. Cells were cultured for a further 18 h without homocysteine to determine any long-lasting effects. RESULTS Homocysteine (250-1000 micromol/L) exposure reduced insulin secretion at both moderate (5.6 mmol/L) and stimulatory (16.7 mmol/L) glucose by 48-63%. Similarly, insulin secretory responsiveness to stimulatory concentrations of alanine, arginine, 2-ketoisocaproate, tolbutamide, KCl, elevated Ca2+, forskolin and PMA, GLP-1, GIP and CCK-8 were reduced by 11-62% following culture with 100-250 micromol/L homocysteine. These inhibitory effects could not simply be attributed to changes in cellular insulin content, cell viability, H2O2 generation or any obvious alterations of gene/protein expression for insulin, glucokinase, GLUT2, VDCC, or Kir6.2 and SUR1. Additional culture for 18 h in standard culture media after homocysteine exposure restored secretory responsiveness to all agents tested. CONCLUSION These findings suggest that long-term exposure to high homocysteine levels causes a reversible impairment of pancreatic beta-cell insulinotropic pathways. The in vivo actions of hyperhomocysteinaemia on islet cell function merit investigation.
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Affiliation(s)
- Steven Patterson
- Diabetes Research Group, School of Biomedical Sciences, University of Ulster, Coleraine, N Ireland, UK.
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38
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Robertson RP, Harmon JS. Pancreatic islet beta-cell and oxidative stress: the importance of glutathione peroxidase. FEBS Lett 2007; 581:3743-8. [PMID: 17433304 PMCID: PMC2762945 DOI: 10.1016/j.febslet.2007.03.087] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 03/31/2007] [Indexed: 01/09/2023]
Abstract
Pancreatic beta-cell function continuously deteriorates in type 2 diabetes despite optimal treatment regimens, which has been attributed to hyperglycemia itself via formation of excess levels of reactive oxygen species (ROS). Glutathione peroxidase GPx), by virtue of its ability to catabolize both H(2)O(2) and lipid peroxides, is uniquely positioned to protect tissues from ROS. The level of this antioxidant in beta cells is extremely low and overexpression of GPx in islets provides enhanced protection against oxidative stress. This suggests that GPx mimetics may represent a valuable ancillary treatment that could add a novel layer of protection for the beta-cell.
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Affiliation(s)
- R Paul Robertson
- Pacific Northwest Research Institute, University of Washington, 720 Broadway, Seattle, WA 98122, United States.
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39
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Jang WG, Kim EJ, Park KG, Park YB, Choi HS, Kim HJ, Kim YD, Kim KS, Lee KU, Lee IK. Glucocorticoid receptor mediated repression of human insulin gene expression is regulated by PGC-1α. Biochem Biophys Res Commun 2007; 352:716-21. [PMID: 17150186 DOI: 10.1016/j.bbrc.2006.11.074] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Accepted: 11/15/2006] [Indexed: 11/20/2022]
Abstract
Transcriptional regulation of the insulin gene plays a critical role in maintenance of pancreatic beta cell function in response to various stimuli. Here, we used INS-1 cells to test the hypothesis that PGC-1alpha regulates human insulin gene transcription by modulating glucocorticoid (GR) binding to the insulin gene promoter. Analysis of the human insulin promoter region revealed that the suppressive region regulated by GR and PGC-1alpha is localized from -362 to -257 bp. To locate the GR binding site in the human insulin promoter region, EMSAs were performed with candidate GR binding sequences and confirmed that a palindromic region (Palin, -284 to -274 bp) specifically interacts with GR. We also found that the Palin-binding activity of GR is increased in the presence of PGC-1alpha. These findings suggest that PGC-1alpha elevates the binding of GR to Palin and thereby enhances the GR-mediated inhibition of human insulin transcription.
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Affiliation(s)
- Won Gu Jang
- Department of Genetic Engineering, Kyungpook National University, Daegu, Republic of Korea
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40
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Robertson RP, Harmon JS. Diabetes, glucose toxicity, and oxidative stress: A case of double jeopardy for the pancreatic islet beta cell. Free Radic Biol Med 2006; 41:177-84. [PMID: 16814095 DOI: 10.1016/j.freeradbiomed.2005.04.030] [Citation(s) in RCA: 222] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Accepted: 04/06/2005] [Indexed: 12/16/2022]
Abstract
Diabetes is commonly referred to in terms of type 1 and type 2. Both forms involve pancreatic islet beta-cell abnormalities, characterized by death in type 1 and accelerated apoptosis in type 2. The resultant chronic hyperglycemia leads to chronic oxidative stress for all tissues because glucose in abnormally high concentrations forms reactive oxygen species. It has been repeatedly emphasized that this can lead to oxidative damage in the classical secondary targets of diabetes, such as eyes, kidneys, nerves, and blood vessels. However, it has been much less appreciated that the beta cell itself is also a prime target, a case of double jeopardy. This situation is all the more pernicious because islets contain among the lowest levels of antioxidant enzyme activities compared to other tissues. This adverse effect of high glucose concentrations is referred to as glucose toxicity. A major manifestation of glucose toxicity in the beta cell is defective insulin gene expression, diminished insulin content, and defective insulin secretion. The molecular mechanisms involve the development of decreased levels of two very important insulin promoter transcription factors, PDX-1 and MafA. Studies with animal models of type 2 diabetes have established that pharmacologic protection against oxidative stress ameliorates the severity of diabetes progression. Translational research with humans is now under way to ascertain whether this protection can be provided to patients experiencing inadequate glycemic control.
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Affiliation(s)
- R Paul Robertson
- Department of Medicine and Department of Pharmacology, Pacific Northwest Research Institute, 720 Broadway, Seattle, WA 98122, USA.
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41
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Poitout V, Hagman D, Stein R, Artner I, Robertson RP, Harmon JS. Regulation of the insulin gene by glucose and fatty acids. J Nutr 2006; 136:873-6. [PMID: 16549443 PMCID: PMC1853259 DOI: 10.1093/jn/136.4.873] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The insulin gene is expressed almost exclusively in pancreatic beta-cells. Metabolic regulation of insulin gene expression enables the beta-cell to maintain adequate stores of intracellular insulin to sustain the secretory demand. Glucose is the major physiologic regulator of insulin gene expression; it coordinately controls the recruitment of transcription factors [e.g., pancreatic/duodenal homeobox-1 (PDX-1), mammalian homologue of avian MafA/L-Maf (MafA), Beta2/Neuro D (B2), the rate of transcription, and the stability of insulin mRNA. However, chronically elevated levels of glucose (glucotoxicity) and lipids (lipotoxicity) also contribute to the worsening of beta-cell function in type 2 diabetes, in part via inhibition of insulin gene expression. The mechanisms of glucotoxicity, which involve decreased binding activities of PDX-1 and MafA and increased activity of C/EBPbeta, are mediated by high-glucose-induced generation of oxidative stress. On the other hand, lipotoxicity is mediated by de novo ceramide synthesis and involves inhibition of PDX-1 nuclear translocation and MafA gene expression. Glucotoxicity and lipotoxicity have common targets, which makes their combination particularly harmful to insulin gene expression and beta-cell function in type 2 diabetes.
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Affiliation(s)
- Vincent Poitout
- Department of Medicine, University of Montréal, Montréal, QC, Canada.
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42
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Xu ZK, Chen NG, Ma CY, Meng ZX, Sun YJ, Han X. Role of peroxisome proliferator-activated receptor gamma in glucose-induced insulin secretion. Acta Biochim Biophys Sin (Shanghai) 2006; 38:1-7. [PMID: 16395520 DOI: 10.1111/j.1745-7270.2006.00128.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Peroxisome proliferator-activated receptor (PPAR) isoforms (alpha and gamma) are known to be expressed in pancreatic islets as well as in insulin-producing cell lines. Ligands of PPAR have been shown to enhance glucose-induced insulin secretion in rat pancreatic islets. However, their effect on insulin secretion is still unclear. To understand the molecular mechanism by which PPARgamma exerts its effect on glucose-induced insulin secretion, we examined the endogenous activity of PPAR isoforms, and studied the PPARgamma function and its target gene expression in INS-1 cells. We found that: (1) endogenous PPARg was activated in a ligand-dependent manner in INS-1 cells; (2) overexpression of PPARgamma in the absence of PPARgamma ligands enhanced glucose-induced insulin secretion, which indicates that the increased glucose-induced insulin secretion is a PPARgamma-mediated event; (3) the addition of both PPARgamma and retinoid X receptor (RXR) ligands showed a synergistic effect on the augmentation of reporter activity, suggesting that the hetero-dimerization of PPARgamma and RXR is required for the regulation of the target genes; (4) PPARs upregulated both the glucose transporter 2 (GLUT2) and Cb1-associated protein (CAP) genes in INS-1 cells. Our findings suggest an important mechanistic pathway in which PPARgamma enhances glucose-induced insulin secretion by activating the expression of GLUT2 and CAP genes in a ligand-dependent manner.
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Affiliation(s)
- Ze-Kuan Xu
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 210029, China
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43
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Masiello P. Animal models of type 2 diabetes with reduced pancreatic beta-cell mass. Int J Biochem Cell Biol 2005; 38:873-93. [PMID: 16253543 DOI: 10.1016/j.biocel.2005.09.007] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2005] [Revised: 09/02/2005] [Accepted: 09/08/2005] [Indexed: 12/31/2022]
Abstract
Type 2 diabetes is increasingly viewed as a disease of insulin deficiency due not only to intrinsic pancreatic beta-cell dysfunction but also to reduction of beta-cell mass. It is likely that, in diabetes-prone subjects, the regulated beta-cell turnover that adapts cell mass to body's insulin requirements is impaired, presumably on a genetic basis. We still have a limited knowledge of how and when this derangement occurs and what might be the most effective therapeutic strategy to preserve beta-cell mass. The animal models of type 2 diabetes with reduced beta-cell mass described in this review can be extremely helpful (a) to have insight into the mechanisms underlying the defective growth or accelerated loss of beta-cells leading to the beta-cell mass reduction; (b) to investigate in prospective studies the mechanisms of compensatory adaptation and subsequent failure of a reduced beta-cell mass. Furthermore, these models are of invaluable importance to test the effectiveness of potential therapeutic agents that either stimulate beta-cell growth or inhibit beta-cell death.
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Affiliation(s)
- Pellegrino Masiello
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, University of Pisa, Scuola Medica, Italy.
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Abstract
The increasing worldwide incidence of diabetes in adults constitutes a global public health burden. It is predicted that by 2025, India, China and the United States will have the largest number of people with diabetes. According to the 2003 estimates of the International Diabetes Federation, the diabetes mellitus prevalence in the USA is 8.0% and approximately 90-95% of diabetic Americans have type 2 diabetes - about 16 million people. Type 2 diabetes is a complex, heterogeneous, polygenic disease characterized mainly by insulin resistance and pancreatic beta-cell dysfunction. Appropriate experimental models are essential tools for understanding the molecular basis, pathogenesis of the vascular and neural lesions, actions of therapeutic agents and genetic or environmental influences that increase the risks of type 2 diabetes. Among the animal models available, those developed in rodents have been studied most thoroughly for reasons such as short generation time, inherited hyperglycaemia and/or obesity in certain strains and economic considerations. In this article, we review the current status of most commonly used rodent diabetic models developed spontaneously, through means of genetic engineering or artificial manipulation. In addition to these models, the Psammomys obesus, rhesus monkeys and many other species are studied intensively and reviewed by Shafrir, Bailey and Flatt and Hansen.
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MESH Headings
- Animals
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Type 2/drug therapy
- Diabetes Mellitus, Type 2/metabolism
- Disease Models, Animal
- Hypoglycemic Agents/therapeutic use
- Mice
- Mice, Inbred C57BL
- Mice, Inbred Strains
- Rats
- Rats, Inbred OLETF
- Rats, Inbred SHR
- Rats, Inbred Strains
- Rats, Sprague-Dawley
- Rats, Zucker
- Streptozocin
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Affiliation(s)
- Desu Chen
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, PR China
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45
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Wargent E, Stocker C, Augstein P, Heinke P, Meyer A, Hoffmann T, Subramanian A, Sennitt MV, Demuth HU, Arch JRS, Cawthorne MA. Improvement of glucose tolerance in Zucker diabetic fatty rats by long-term treatment with the dipeptidyl peptidase inhibitor P32/98: comparison with and combination with rosiglitazone. Diabetes Obes Metab 2005; 7:170-81. [PMID: 15715890 DOI: 10.1111/j.1463-1326.2004.00383.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM The aim of this study was to investigate the effect of long-term treatment with the dipeptidyl peptidase inhibitor P32/98 and its combination with rosiglitazone on blood glucose control and islet of Langerhans histology in male Zucker diabetic fatty (ZDF) rats, when treatment begins before or after the development of overt diabetes. METHODS ZDF rats were treated with P32/98 from the age of 9, 12 or 15 weeks. Rosiglitazone maleate was given to a separate group from the age of 13 weeks. P32/98 was given to all of these rosiglitazone-treated rats from 16 weeks of age. Rosiglitazone maleate was also given from 16 weeks of age to half the rats that were given P32/98 from 9 weeks of age. The compounds were given by oral gavage until the rats were 14 weeks old and then in the diet. The experiment was terminated at the age of 20-21 weeks. Blood glucose, plasma insulin and oral glucose tolerance were measured at intervals; islet histology was assessed terminally. RESULTS P32/98 improved glucose tolerance after both single and multiple doses when treatment started at 9 weeks of age, also after the third week of treatment when treatment began at 12 or 15 weeks of age. P32/98 reduced daytime blood glucose when treatment began at 12 weeks. Treatment with rosiglitazone increased food intake and body weight, and after 2 weeks, reduced daytime blood glucose, water intake and the area under the glucose tolerance curve. A single dose of P32/98 markedly improved glucose tolerance in rosiglitazone-treated rats. When treatment had begun at 9 weeks of age, P32/98 stimulated insulin secretion in some glucose tolerance tests. Neither P32/98 nor rosiglitazone affected pancreatic insulin content, nor did they have clear effects on islet histology. CONCLUSION P32/98 elicited a sustained improvement in glucose tolerance in both prediabetic and diabetic ZDF rats. The effects of P32/98 on glucose and insulin were similar to those of rosiglitazone, and in contrast to rosiglitazone, P32/98 did not increase food intake or body weight. However, neither compound was especially effective at improving diabetes in ZDF rats when treatment began at 9, 12 or 15 (P32/98) or 13 (rosiglitazone) weeks of age.
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Affiliation(s)
- E Wargent
- Clore Laboratory, University of Buckingham, Buckingham, UK
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46
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Alemzadeh R, Tushaus KM. Modulation of adipoinsular axis in prediabetic zucker diabetic fatty rats by diazoxide. Endocrinology 2004; 145:5476-84. [PMID: 15319354 DOI: 10.1210/en.2003-1523] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dysregulation of the adipoinsular axis in male obese Zucker diabetic fatty (ZDF; fa/fa) rats, a model of type 2 diabetes, results in chronic hyperinsulinemia and increased de novo lipogenesis in islets, leading to beta-cell failure and diabetes. Diazoxide (DZ; 150 mg/kg.d), an inhibitor of insulin secretion, was administered to prediabetic ZDF animals for 8 wk as a strategy for prevention of diabetes. DZ reduced food intake (P < 0.02) and rate of weight gain only in ZDF rats (P < 0.01). Plasma insulin response to glucose load was attenuated in DZ-Zucker lean rats (ZL; P < 0.01), whereas DZ-ZDF had higher insulin response to glucose than controls (P < 0.001). DZ improved hemoglobin A1c (P < 0.001) and glucose tolerance in ZDF (P < 0.001), but deteriorated hemoglobin A1c in ZL rats (P < 0.02) despite normal tolerance in the fasted state. DZ lowered plasma leptin (P < 0.001), free fatty acid, and triglyceride (P < 0.001) levels, but increased adiponectin levels (P < 0.02) only in ZDF rats. DZ enhanced beta3-adrenoreceptor mRNA (P < 0.005) and adenylate cyclase activity (P < 0.01) in adipose tissue from ZDF rats only, whereas it enhanced islet beta3- adrenergic receptor mRNA (P < 0.005) but paradoxically decreased islet adenylate cyclase activity (P < 0.005) in these animals. Islet fatty acid synthase mRNA (P < 0.03), acyl coenzyme A carboxylase mRNA (P < 0.01), uncoupling protein-2 mRNA (P < 0.01), and triglyceride content (P < 0.005) were only decreased in DZ-ZDF rats, whereas islet insulin mRNA and insulin content were increased in DZ-ZDF (P < 0.01) and DZ-ZL rats (P < 0.03). DZ-induced beta-cell rest improved the lipid profile, enhanced the metabolic efficiency of insulin, and prevented beta-cell dysfunction and diabetes in diabetes-prone animals. This therapeutic strategy may be beneficial in preventing beta-cell failure and progression to diabetes in humans.
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Affiliation(s)
- Ramin Alemzadeh
- Department of Pediatrics, Section of Endocrinology and Metabolism, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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Soto C, Mena R, Luna J, Cerbón M, Larrieta E, Vital P, Uría E, Sánchez M, Recoba R, Barrón H, Favari L, Lara A. Silymarin induces recovery of pancreatic function after alloxan damage in rats. Life Sci 2004; 75:2167-80. [PMID: 15325843 DOI: 10.1016/j.lfs.2004.04.019] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2003] [Accepted: 04/07/2004] [Indexed: 11/30/2022]
Abstract
Alloxan has been widely used to produce experimental diabetes mellitus syndrome. This compound causes necrosis of pancreatic beta-cells and, as is well known, induces oxidant free radicals which play a relevant role in the etiology and pathogenesis of both experimental and human diabetes mellitus. Previously we have reported hypoglycemic and antilipoperoxidative actions of silymarin in serum and pancreatic tissue respectively. The aim of this study was to test whether silymarin could reduce the hyperglycemia and revert the pancreatic damage in alloxan treated rats, tested with silymarin in two protocols: using both compounds simultaneously for four or eight doses, or using the compound 20 days after alloxan administration for 9 weeks. Serum glucose and insulin were determined, and pancreatic fragments were used for histology and insulin immunohistochemistry. Pancreatic islets were isolated to assess insulin and Pdx1 mRNA expression by RT-PCR. Our results showed that 72 hours after alloxan administration, serum glucose increased and serum insulin decreased significantly, whereas pancreatic tissue presented morphological abnormalities such as islet shrinkage, necrotic areas, loss of cell organization, widespread lipoid deposits throughout the exocrine tissue, and loss of beta cells, but insulin and glucagon immunoreactivity was scattered if any. In contrast the pancreatic tissue and both insulin and glucose serum levels of rats treated with silymarin were similar to those of control animals. In addition, insulin and glucagon immunoreactive cells patterns in Langerhans islets were also normal, and normal insulin and Pdx1 mRNA expression patterns were detected during pancreatic recovery in Langerhans islets. The overall results suggest that silymarin induces pancreatic function recovery demonstrated by insulin and glucagon expression protein and normoglycemia after alloxan pancreatic damage in rats.
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Affiliation(s)
- C Soto
- Department of Biological Systems, Metropolitan Autonomous University, Mexico.
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Robertson RP. Chronic oxidative stress as a central mechanism for glucose toxicity in pancreatic islet beta cells in diabetes. J Biol Chem 2004; 279:42351-4. [PMID: 15258147 DOI: 10.1074/jbc.r400019200] [Citation(s) in RCA: 708] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- R Paul Robertson
- Pacific Northwest Research Institute, Seattle, Washington 98122, USA.
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Melloul D. Transcription Factors in Islet Development and Physiology: Role of PDX-1 in Beta-Cell Function. Ann N Y Acad Sci 2004; 1014:28-37. [PMID: 15153417 DOI: 10.1196/annals.1294.003] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Differentiation of early foregut endoderm into pancreatic endocrine and exocrine cells depends on a cascade of gene activation events controlled by various transcription factors. The first molecular marker identified that specifies the early pancreatic epithelium is the homeodomain-containing transcription factor PDX-1. Its absence in mice and humans during development leads to agenesis of the pancreas. Later, it becomes restricted primarily to beta cells where it regulates the expression of beta cell-specific genes, and, most importantly, mediates the glucose effect on insulin gene transcription. Although exposure of beta cells to high glucose concentrations for relatively short periods stimulates insulin gene expression, chronic exposure has adverse effects on many beta-cell functions, including insulin gene transcription. These events appear to correlate with pdx-1 gene expression and its ability to bind the insulin gene. We consider that loss of PDX-1 function or altered pdx-1 gene expression due to mutations or functional impairment of transcription factors controlling its expression can lead to diabetes.
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Affiliation(s)
- Danielle Melloul
- Department of Endocrinology and Metabolism, The Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
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50
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Martín MA, Fernández E, Pascual-Leone AM, Escrivá F, Alvarez C. Protein calorie restriction has opposite effects on glucose metabolism and insulin gene expression in fetal and adult rat endocrine pancreas. Am J Physiol Endocrinol Metab 2004; 286:E542-50. [PMID: 14665443 DOI: 10.1152/ajpendo.00242.2003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We previously demonstrated that fetuses from undernourished pregnant rats exhibited increased beta-cell mass and hyperinsulinemia, whereas keeping food restriction until adult age caused reduced beta-cell mass, hypoinsulinemia, and decreased insulin secretion. Because these alterations can be related to insulin availability, we have now investigated early and long-term effects of protein calorie food restriction on insulin mRNA levels as well as the possible mechanisms that could modulate the endogenous insulin mRNA content. We used fetuses at 21.5 days of gestation proceeding from food-restricted rats during the last week of pregnancy and 70-day-old rats undernourished from day 14 of gestation until adult age and with respective controls. Insulin mRNA levels, glucose transporters, and total glycolysis and mitochondrial oxidative fluxes were evaluated. We additionally analyzed undernutrition effects on signals implicated in glucose-mediated insulin gene expression, especially pancreatic duodenal homeobox-1 (PDX-1), stress-activated protein kinase-2 (p38/SAPK2), and phosphatidylinositol 3-kinase. Undernourished fetuses showed increased insulin mRNA, oxidative glucose metabolism, and p38/SAPK2 levels, whereas undernutrition until adult age provoked a decrease in insulin gene expression, oxidative glucose metabolism, and PDX-1 levels. The results indicate that food restriction caused changes in insulin gene expression and content leading to alterations in glucose-stimulated insulin secretion. The molecular events, increased p38/SAPK2 levels in fetuses and decreased PDX-1 levels in adults, seem to be the responsible for the altered insulin mRNA expression. Moreover, because PDX-1 activation appears to be regulated by glucose-derived metabolite(s), the altered glucose oxidation caused by undernutrition could in some manner affect insulin mRNA expression.
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Affiliation(s)
- M A Martín
- Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad Complutense, Ciudad Universitaria, 28040 Madrid, Spain
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