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Ren L, Cui Q, Liu W, Wang L, Liao Y, Feng Y, Sun W, Yang Y, Zhang Z, Jin T, Prud'homme GJ, Zhang L, Li Y, Leng Y, Wang Q. Novel GLP-1 Analog Supaglutide Stimulates Insulin Secretion in Mouse and Human Islet Beta-Cells and Improves Glucose Homeostasis in Diabetic Mice. Front Physiol 2019; 10:930. [PMID: 31404283 PMCID: PMC6670290 DOI: 10.3389/fphys.2019.00930] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 07/09/2019] [Indexed: 12/11/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1), an incretin hormone plays an important role in regulating glucose homeostasis. The therapeutic use of native GLP-1 is inadequate due to its short in vivo half-life. We recently developed a novel GLP-1 mimetics supaglutide, and demonstrated that this formulation retained native GLP-1 biological activities and possessed long-lasting GLP-1 actions. In this study, we further examined its abilities in regulating blood glucose in diabetic mice. We found that supaglutide stimulated insulin secretion in both mouse and human islets in a dose-dependent fashion. Oral glucose tolerance test conducted in normal ICR mice showed that supaglutide significantly decreased postprandial glucose excursions in a dose-dependent fashion. In type 2 diabetic db/db mice, a single-dose injection of supaglutide significantly decreased blood glucose levels, and this efficacy was lasted for at least 72 h in a dose-dependent fashion. During a 4-weeks intervention course supaglutide (twice injections per week) dose-dependently and significantly decreased fasting and random blood glucose levels in hyperglycemic db/db mice. Supaglutide, at a dose of 1.2 mg/kg, significantly reduced serum fructosamine levels. This was associated with significant enlargement of beta-cell mass, increased pancreatic insulin content, and increased plasma insulin level. Notably, during the intervention course supaglutide significantly reduced body-weight gain in these obese diabetic mice, associated with reduced fat mass (but not the lean mass), improved lipid profile, i.e., declined serum triglyceride, and free fatty acid levels compared to the placebo control. These finding reveals that supaglutide exerts beneficial effects in regulating blood glucose and lipid homeostasis in diabetic db/db mice.
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Affiliation(s)
- Liwei Ren
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Qiaoli Cui
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Wenjuan Liu
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Liqian Wang
- Shanghai Yinuo Pharmaceutical Co., Ltd., Shanghai, China
| | - Yijing Liao
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Ying Feng
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Wanwan Sun
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Yehong Yang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Zhaoyun Zhang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Tianru Jin
- Division of Advanced Diagnostics, Toronto General Research Institute, University Health Network, Toronto, ON, Canada.,Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Gerald J Prud'homme
- Department of Laboratory Medicine and Pathobiology, Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada
| | - Lina Zhang
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Yiming Li
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Ying Leng
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Qinghua Wang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
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Okimura T, Jiang Z, Liang Y, Yamaguchi K, Oda T. Suppressive effect of ascophyllan HS on postprandial blood sugar level through the inhibition of α-glucosidase and stimulation of glucagon-like peptide-1 (GLP-1) secretion. Int J Biol Macromol 2019; 125:453-458. [PMID: 30537502 DOI: 10.1016/j.ijbiomac.2018.12.084] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 11/30/2018] [Accepted: 12/08/2018] [Indexed: 12/30/2022]
Abstract
A sulfated polysaccharide ascophyllan inhibited α-glucosidase in a concentration dependent manner, and >90% activity was inhibited at 1.0 mg/mL. The inhibitory activity was much higher than that of acarbose. No significant inhibitory effect of ascophyllan on α-amylase was observed up to 10.0 mg/mL. Ascophyllan HS, a commercially available ascophyllan preparation showed even higher inhibitory effect on α-glucosidase than ascophyllan. Interestingly, ascophyllan and ascophyllan HS induced the secretion of glucagon-like peptide-1 (GLP-1) from human intestinal NCI-H716 cell line in a concentration dependent manner (10-100 ng/mL). The oral glucose tolerance tests revealed that after continuous 8-week ingestion of ascophyllan HS at 100 mg/day, the glucose area under the curve values of the ascophyllan HS ingested group were significantly lower than placebo ingested group. Serum glycosylated hemoglobin (HbA1c) level in ascophyllan HS ingested group tended to decrease after 8-week ingestion, whereas no significant change was observed in placebo ingested group. This is the first report indicating that ascophyllan can induce the secretion of GLP-1 from human intestinal cell line (NCI-H716), besides the potent inhibitory effect on α-glucosidase. Furthermore, clinical trial suggested that ascophyllan HS may be a practically applicable blood glucose controlling agent in humans.
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Affiliation(s)
- Takasi Okimura
- Research and Development Division, Hayashikane Sangyo Co., Ltd., Shimonoseki, Yamaguchi 750-8608, Japan
| | - Zedong Jiang
- College of Food and Biological Engineering, Jimei University, Xiamen, Fujian 361021, China
| | - Yan Liang
- Graduate School of Fisheries Science and Environmental Studies, Nagasaki University, Nagasaki 852-8521, Japan
| | - Kenichi Yamaguchi
- Graduate School of Fisheries Science and Environmental Studies, Nagasaki University, Nagasaki 852-8521, Japan
| | - Tatsuya Oda
- Graduate School of Fisheries Science and Environmental Studies, Nagasaki University, Nagasaki 852-8521, Japan.
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Hasib A, Ng MT, Khan D, Gault VA, Flatt PR, Irwin N. Characterisation and antidiabetic utility of a novel hybrid peptide, exendin-4/gastrin/xenin-8-Gln. Eur J Pharmacol 2018; 834:126-135. [DOI: 10.1016/j.ejphar.2018.07.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 06/29/2018] [Accepted: 07/13/2018] [Indexed: 12/14/2022]
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Gupta A, Jelinek HF, Al-Aubaidy H. Glucagon like peptide-1 and its receptor agonists: Their roles in management of Type 2 diabetes mellitus. Diabetes Metab Syndr 2017; 11:225-230. [PMID: 27884496 DOI: 10.1016/j.dsx.2016.09.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 09/03/2016] [Indexed: 12/25/2022]
Abstract
This study summarizes major work which investigated the roles of glucagon like peptide-1 (GLP-1) and its receptor (GLP-1R); the use of GLP-1-R agonists and dipeptidyl peptidase 4 inhibitor in the management of type 2 diabetes mellitus. It focuses on the recent therapeutic development which has occurred in this field, and also discusses the potential treatments which can be discovered and implemented in the near future to design an effective therapy for type 2 diabetes mellitus.
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Affiliation(s)
- Ankit Gupta
- School of Medicine, University of Tasmania, Hobart, Australia
| | - Herbert F Jelinek
- School of Community Health, Charles Sturt University, Albury, NSW, Australia
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Baker DJ, Atkinson AM, Wilkinson GP, Coope GJ, Charles AD, Leighton B. Characterization of the heterozygous glucokinase knockout mouse as a translational disease model for glucose control in type 2 diabetes. Br J Pharmacol 2014; 171:1629-41. [PMID: 24772483 DOI: 10.1111/bph.12498] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND AND PURPOSE The global heterozygous glucokinase (GK) knockout (gk(wt/del)) male mouse, fed on a high-fat (60% by energy) diet, has provided a robust and reproducible model of hyperglycaemia. This model could be highly relevant to some facets of human type 2 diabetes (T2D). We aimed to investigate the ability of standard therapeutic agents to lower blood glucose at translational doses, and to explore the glucose-lowering potential of novel glucokinase activators (GKAs) in this model. EXPERIMENTAL APPROACH We measured the ability of insulin, metformin, glipizide, exendin-4 and sitagliptin, after acute or repeat dose administration, to lower free-feeding glucose levels in gk(wt/del) mice. Further, we measured the ability of novel GKAs, GKA23, GKA71 and AZD6370 to control glucose either alone or in combination with some standard agents. KEY RESULTS A single dose of insulin (1 unit·kg(-1)), metformin (150, 300 mg·kg(-1)), glipizide (0.1, 0.3 mg·kg(-1)), exendin-4 (2, 20 μg·kg(-1)) and GKAs reduced free-feeding glucose levels. Sitagliptin (10 mg·kg(-1)), metformin (300 mg·kg(-1)) and AZD6370 (30, 400 mg·kg(-1)) reduced glucose excursions on repeat dosing. At a supra-therapeutic dose (400 mg·kg(-1)), AZD6370 also lowered basal levels of glucose without inducing hypoglycaemia. CONCLUSION AND IMPLICATIONS Standard glucose-lowering therapeutic agents demonstrated significant acute glucose lowering in male gk(wt/del) mice at doses corresponding to therapeutic free drug levels in man, suggesting the potential of these mice as a translatable model of human T2D. Novel GKAs also lowered glucose in this mouse model.
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Conlon JM, Mechkarska M, Lukic ML, Flatt PR. Potential therapeutic applications of multifunctional host-defense peptides from frog skin as anti-cancer, anti-viral, immunomodulatory, and anti-diabetic agents. Peptides 2014; 57:67-77. [PMID: 24793775 DOI: 10.1016/j.peptides.2014.04.019] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 04/24/2014] [Accepted: 04/24/2014] [Indexed: 12/14/2022]
Abstract
Frog skin constitutes a rich source of peptides with a wide range of biological properties. These include host-defense peptides with cytotoxic activities against bacteria, fungi, protozoa, viruses, and mammalian cells. Several hundred such peptides from diverse species have been described. Although attention has been focused mainly on antimicrobial activity, the therapeutic potential of frog skin peptides as anti-infective agents remains to be realized and no compound based upon their structures has yet been adopted in clinical practice. Consequently, alternative applications are being explored. Certain naturally occurring frog skin peptides, and analogs with improved therapeutic properties, show selective cytotoxicity against tumor cells and viruses and so have potential for development into anti-cancer and anti-viral agents. Some peptides display complex cytokine-mediated immunomodulatory properties. Effects on the production of both pro-inflammatory and anti-inflammatory cytokines by peritoneal macrophages and peripheral blood mononuclear cells have been observed so that clinical applications as anti-inflammatory, immunosuppressive, and immunostimulatory agents are possible. Several frog skin peptides, first identified on the basis of antimicrobial activity, have been shown to stimulate insulin release both in vitro and in vivo and so show potential as incretin-based therapies for treatment of patients with Type 2 diabetes mellitus. This review assesses the therapeutic possibilities of peptides from frogs belonging to the Ascaphidae, Alytidae, Pipidae, Dicroglossidae, Leptodactylidae, Hylidae, and Ranidae families that complement their potential role as anti-infectives for use against multidrug-resistant microorganisms.
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Affiliation(s)
- J Michael Conlon
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, 17666 Al Ain, United Arab Emirates; School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, Northern Ireland BT52 1SA, UK.
| | - Milena Mechkarska
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, 17666 Al Ain, United Arab Emirates
| | - Miodrag L Lukic
- Center for Molecular Medicine, Faculty of Medicine, University of Kragujevac, Kragujevac, Serbia
| | - Peter R Flatt
- School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, Northern Ireland BT52 1SA, UK
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Role of endogenous GLP-1 and GIP in beta cell compensatory responses to insulin resistance and cellular stress. PLoS One 2014; 9:e101005. [PMID: 24967820 PMCID: PMC4072716 DOI: 10.1371/journal.pone.0101005] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 06/02/2014] [Indexed: 12/15/2022] Open
Abstract
Role of GLP-1 and GIP in beta cell compensatory responses to beta cell attack and insulin resistance were examined in C57BL/6 mice lacking functional receptors for GLP-1 and GIP. Mice were treated with multiple low dose streptozotocin or hydrocortisone. Islet parameters were assessed by immunohistochemistry and hormone measurements were determined by specific enzyme linked immunoassays. Wild-type streptozotocin controls exhibited severe diabetes, irregularly shaped islets with lymphocytic infiltration, decreased Ki67/TUNEL ratio with decreased beta cell and increased alpha cell areas. GLP-1 and GIP were co-expressed with glucagon and numbers of alpha cells mainly expressing GLP-1 were increased. In contrast, hydrocortisone treatment and induction of insulin resistance increased islet numbers and area, with enhanced beta cell replication, elevated mass of beta and alpha cells, together with co-expression of GLP-1 and GIP with glucagon in islets. The metabolic responses to streptozotocin in GLP-1RKO and GIPRKO mice were broadly similar to C57BL/6 controls, although decreases in islet numbers and size were more severe. In contrast, both groups of mice lacking functional incretin receptors displayed substantially impaired islet adaptations to insulin resistance induced by hydrocortisone, including marked curtailment of expansion of islet area, beta cell mass and islet number. Our observations cannot be explained by simple changes in circulating incretin concentrations, suggesting that intra-islet GLP-1 and GIP make a significant contribution to islet adaptation, particularly expansion of beta cell mass and compensatory islet compensation to hydrocortisone and insulin resistance.
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Pathak V, Vasu S, Flatt PR, Irwin N. Effects of chronic exposure of clonal β-cells to elevated glucose and free fatty acids on incretin receptor gene expression and secretory responses to GIP and GLP-1. Diabetes Obes Metab 2014; 16:357-65. [PMID: 24164718 DOI: 10.1111/dom.12227] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 10/03/2013] [Accepted: 10/21/2013] [Indexed: 12/11/2022]
Abstract
AIM The incretin effect, mediated by glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), is impaired in type 2 diabetes. METHODS This study examines the effects of prolonged exposure to elevated glucose and free fatty acids in clonal BRIN BD11 cells on GIP and GLP-1 action. RESULTS Glucotoxic conditions (18 h) had no effect on GIP- or GLP-1-mediated insulinotropic responses. In contrast, 48 h glucotoxic culture impaired (p < 0.05 to p < 0.001) insulin release in response to GLP-1, and particularly GIP. Culture under lipotoxic conditions (18 h) impaired (p < 0.05 to p < 0.001) the insulin-releasing effect of GIP, but was without effect on GLP-1. However, 48 h lipotoxic culture compromised both GIP (p < 0.05 to p < 0.001) and GLP-1 (p < 0.05 to p < 0.01) insulin-releasing actions. Glucolipotoxic culture (18 h) completely annulled the insulinotropic action of GIP, whereas GLP-1 effects were similar to control. However, when glucolipotoxic culture was extended to 48 h, both GIP- and GLP-1-mediated effects were (p < 0.05 to p < 0.001) impaired. Assessment of cell viability, number and insulin content revealed detrimental (p < 0.05 to p < 0.001) effects under all culture conditions, barring 18 h glucotoxic and lipotoxic culture. Finally, GIP-R gene and protein expression was increased (p < 0.05 to p < 0.01) under glucotoxic culture, with decreased (p < 0.05 to p < 0.001) expression following glucolipotoxic culture. GLP-1-R gene expression followed a similar trend, but protein levels were generally reduced under all culture conditions. CONCLUSION The results indicate that impaired insulinotropic response to GIP and GLP-1 under diabetic milieu involves mechanisms beyond simple expression of respective receptors.
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Affiliation(s)
- V Pathak
- SAAD Centre for Pharmacy Diabetes, University of Ulster, Coleraine, UK
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9
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Gault VA, Bhat VK, Irwin N, Flatt PR. A novel glucagon-like peptide-1 (GLP-1)/glucagon hybrid peptide with triple-acting agonist activity at glucose-dependent insulinotropic polypeptide, GLP-1, and glucagon receptors and therapeutic potential in high fat-fed mice. J Biol Chem 2013; 288:35581-91. [PMID: 24165127 DOI: 10.1074/jbc.m113.512046] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon bind to related members of the same receptor superfamily and exert important effects on glucose homeostasis, insulin secretion, and energy regulation. The present study assessed the biological actions and therapeutic utility of novel GIP/glucagon/GLP-1 hybrid peptides. Nine novel peptides were synthesized and exhibited complete DPP-IV resistance and enhanced in vitro insulin secretion. The most promising peptide, [dA(2)]GLP-1/GcG, stimulated cAMP production in GIP, GLP-1, and glucagon receptor-transfected cells. Acute administration of [dA(2)]GLP-1/GcG in combination with glucose significantly lowered plasma glucose and increased plasma insulin in normal and obese diabetic (ob/ob) mice. Furthermore, [dA(2)]GLP-1/GcG elicited a protracted glucose-lowering and insulinotropic effect in high fat-fed mice. Twice daily administration of [dA(2)]GLP-1/GcG for 21 days decreased body weight and nonfasting plasma glucose and increased circulating plasma insulin concentrations in high fat-fed mice. Furthermore, [dA(2)]GLP-1/GcG significantly improved glucose tolerance and insulin sensitivity by day 21. Interestingly, locomotor activity was increased in [dA(2)]GLP-1/GcG mice, without appreciable changes in aspects of metabolic rate. Studies in knock-out mice confirmed the biological action of [dA(2)]GLP-1/GcG via multiple targets including GIP, GLP-1, and glucagon receptors. The data suggest significant promise for novel triple-acting hybrid peptides as therapeutic options for obesity and diabetes.
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Affiliation(s)
- Victor A Gault
- From the SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 1SA Northern Ireland, United Kingdom
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Zhang JF, Sha CJ, Sun Y, Gai YY, Sun JY, Han JB, Shao X, Sha CN, Li YX, Liu WH. Ultra-high-performance liquid chromatography for the determination of exenatide in monkey plasma by tandem quadrupole mass spectrometry. J Pharm Anal 2013; 3:235-240. [PMID: 29403823 PMCID: PMC5760979 DOI: 10.1016/j.jpha.2012.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 12/24/2012] [Indexed: 11/16/2022] Open
Abstract
A highly sensitive ultra-high-performance liquid chromatographic-tandem mass spectrometry (UPLC/MS/MS) method was developed for the quantification of the synthetic peptide drug of exenatide in monkey plasma. Sample preparation was carried out by solid-phase extraction (SPE), and bivalirudin was used as the internal standard (IS). An excellent chromatographic separation was obtained on a reversed-phase C18 column with a gradient elution. Detection utilized a Qtrap 5500 system operated in the positive ion mode with multiple reaction monitoring (MRM). The proposed method was validated by assessing the specificity, linearity, intra- and inter-day precision and accuracy, recovery, and stability. The method resulted in a linear calibration range of 0.10-30 ng/mL, extracting with only 50 μL monkey plasma aliquots. The intra- and inter-day precisions (as relative standard deviation) were less than 7.5% and 9.6%, respectively. The method could be successfully utilized for the pharmacokinetic study of exenatide in monkeys following a single subcutaneous injection of Byetta.
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Affiliation(s)
- Jin-Feng Zhang
- School of Pharmacy, Yantai University, Yantai 264003, PR China
| | - Chun-Jie Sha
- State Key Laboratory of Long-acting and Targeting Drug Delivery System, Shandong Luye Pharmaceutical Co. Ltd., Yantai 264003, PR China
| | - Yu Sun
- School of Pharmacy, Yantai University, Yantai 264003, PR China
| | - Yun-Yun Gai
- State Key Laboratory of Long-acting and Targeting Drug Delivery System, Shandong Luye Pharmaceutical Co. Ltd., Yantai 264003, PR China
| | - Ji-Ye Sun
- State Key Laboratory of Long-acting and Targeting Drug Delivery System, Shandong Luye Pharmaceutical Co. Ltd., Yantai 264003, PR China
| | - Jiang-Bin Han
- State Key Laboratory of Long-acting and Targeting Drug Delivery System, Shandong Luye Pharmaceutical Co. Ltd., Yantai 264003, PR China
| | - Xin Shao
- State Key Laboratory of Long-acting and Targeting Drug Delivery System, Shandong Luye Pharmaceutical Co. Ltd., Yantai 264003, PR China
| | - Chun-Na Sha
- Rushan People's Hospital, Weihai 264200, PR China
| | - You-Xin Li
- State Key Laboratory of Long-acting and Targeting Drug Delivery System, Shandong Luye Pharmaceutical Co. Ltd., Yantai 264003, PR China
| | - Wan-Hui Liu
- School of Pharmacy, Yantai University, Yantai 264003, PR China
- State Key Laboratory of Long-acting and Targeting Drug Delivery System, Shandong Luye Pharmaceutical Co. Ltd., Yantai 264003, PR China
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Ojo OO, Abdel-Wahab YHA, Flatt PR, Conlon JM. Insulinotropic Actions of the Frog Skin Host-Defense Peptide Alyteserin-2a: A Structure-Activity Study. Chem Biol Drug Des 2013; 82:196-204. [DOI: 10.1111/cbdd.12151] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 03/24/2013] [Accepted: 04/07/2013] [Indexed: 11/26/2022]
Affiliation(s)
- Opeolu O. Ojo
- School of Biomedical Sciences; University of Ulster; Cromore Road; Coleraine; BT52 1SA; UK
| | | | - Peter R. Flatt
- School of Biomedical Sciences; University of Ulster; Cromore Road; Coleraine; BT52 1SA; UK
| | - J. Michael Conlon
- Department of Biochemistry; College of Medicine and Health Sciences; United Arab Emirates University; 17666; Al-Ain; United Arab Emirates
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Srinivasan D, Mechkarska M, Abdel-Wahab YH, Flatt PR, Conlon JM. Caerulein precursor fragment (CPF) peptides from the skin secretions of Xenopus laevis and Silurana epitropicalis are potent insulin-releasing agents. Biochimie 2013; 95:429-35. [DOI: 10.1016/j.biochi.2012.10.026] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 10/31/2012] [Indexed: 10/27/2022]
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13
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Ojo OO, Conlon JM, Flatt PR, Abdel-Wahab YHA. Frog skin peptides (tigerinin-1R, magainin-AM1, -AM2, CPF-AM1, and PGla-AM1) stimulate secretion of glucagon-like peptide 1 (GLP-1) by GLUTag cells. Biochem Biophys Res Commun 2013; 431:14-8. [PMID: 23291176 DOI: 10.1016/j.bbrc.2012.12.116] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 12/17/2012] [Indexed: 12/25/2022]
Abstract
Skin secretions of several frog species contain host-defense peptides with multiple biological activities including in vitro and in vivo insulin-releasing actions. This study investigates the effects of tigerinin-1R from Hoplobatrachus rugulosus (Dicroglossidae) and magainin-AM1, magainin-AM2, caerulein precursor fragment (CPF-AM1) and peptide glycine leucine amide (PGLa-AM1) from Xenopus amieti (Pipidae) on GLP-1 secretion from GLUTag cells. Tigerinin-1R showed the highest potency producing a significant (P<0.05) increase in GLP-1 release at a concentration of 0.1nM for the cyclic peptide and 0.3nM for the reduced form. All peptides from X. amieti significantly (P<0.05) stimulated GLP-1 release at concentrations ⩾300nM with magainin-AM2 exhibiting the greatest potency (minimum concentration producing a significant stimulation=1nM). The maximum stimulatory response (3.2-fold of basal rate, P<0.001) was produced by CPF-AM1 at a concentration of 3μM. No peptide stimulated release of the cytosolic enzyme, lactate dehydrogenase from GLUTag cells at concentrations up to 3μM indicating that the integrity of the plasma membrane had been preserved. The data indicate that frog skin peptides, by stimulating GLP-1 release as well as direct effects on insulin secretion, show therapeutic potential as agents for the treatment of type 2 diabetes.
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Affiliation(s)
- O O Ojo
- School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, UK
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Irwin N, Frizelle P, Montgomery IA, Moffett RC, O'Harte FPM, Flatt PR. Beneficial effects of the novel cholecystokinin agonist (pGlu-Gln)-CCK-8 in mouse models of obesity/diabetes. Diabetologia 2012; 55:2747-2758. [PMID: 22814764 DOI: 10.1007/s00125-012-2654-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 06/18/2012] [Indexed: 01/03/2023]
Abstract
AIMS/HYPOTHESIS Cholecystokinin (CCK) is a rapidly degraded gastrointestinal peptide that stimulates satiety and insulin secretion. We aimed to investigate the beneficial weight-lowering and metabolic effects of the novel N-terminally modified CCK analogue, (pGlu-Gln)-CCK-8. METHODS The biological actions of (pGlu-Gln)-CCK-8 were comprehensively evaluated in pancreatic clonal BRIN BD11 cells and in vivo in high-fat-fed and ob/ob mice. RESULTS (pGlu-Gln)-CCK-8 was completely resistant to enzymatic degradation and its satiating effects were significantly (p < 0.05 to p < 0.001) more potent than CCK-8. In BRIN-BD11 cells, (pGlu-Gln)-CCK-8 exhibited enhanced (p < 0.01 to p < 0.001) insulinotropic actions compared with CCK-8. When administered acutely to high-fat-fed or ob/ob mice, (pGlu-Gln)-CCK-8 improved glucose homeostasis. Sub-chronic twice daily injections of (pGlu-Gln)-CCK-8 in high-fat-fed mice for 28 days significantly decreased body weight (p < 0.05 to p < 0.001), accumulated food intake (p < 0.05 to p < 0.001), non-fasting glucose (p < 0.05) and triacylglycerol deposition in pancreatic (p < 0.01), adipose (p < 0.05) and liver (p < 0.001) tissue, and improved oral (p < 0.05) and i.p. (p < 0.05) glucose tolerance and insulin sensitivity (p < 0.001). Similar observations were noted in ob/ob mice given twice daily injections of (pGlu-Gln)-CCK-8. In addition, these beneficial effects were not reproduced by simple dietary restriction and were not associated with changes in energy expenditure. There was no evidence for development of tolerance to (pGlu-Gln)-CCK-8, and analysis of histology or blood-borne markers for pancreatic, liver and renal function in mice treated with (pGlu-Gln)-CCK-8 suggested little abnormal pathology. CONCLUSIONS/INTERPRETATION These studies emphasise the potential of (pGlu-Gln)-CCK-8 for the alleviation of obesity and insulin resistance.
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Affiliation(s)
- N Irwin
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK.
| | - P Frizelle
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK
| | - I A Montgomery
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK
| | - R C Moffett
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK
| | - F P M O'Harte
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK
| | - P R Flatt
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK
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15
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Hematopoietic, CNS and skeletal muscle stem cells as drug targets: opportunities, progress and challenges. Future Med Chem 2012; 4:615-23. [DOI: 10.4155/fmc.12.5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Lineage-committed stem and progenitor cells are currently targeted by a handful of medicines, mainly to treat conditions involving the immune and hematopoietic systems. Knowledge of new stem and progenitor cell populations in the body is accumulating at a rapid pace and a new era of targeting resident stem cell populations for therapeutic ends is coming into focus. Small-molecule regulators of body-resident stem and progenitor cell assess are now a reality both in the clinic and as promising new drugs in the development pipeline. This review will explore the current state of the art with an emphasis on emerging concepts and experimental systems in the therapeutic regulation of endogenous stem and progenitor cell populations.
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Effect of dietary coconut kernel protein on the liver and pancreas of alloxan-induced diabetic rats: comparison with l-arginine and glibenclamide. MEDITERRANEAN JOURNAL OF NUTRITION AND METABOLISM 2012. [DOI: 10.1007/s12349-012-0090-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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17
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Administration of an acylated GLP-1 and GIP preparation provides added beneficial glucose-lowering and insulinotropic actions over single incretins in mice with Type 2 diabetes and obesity. Clin Sci (Lond) 2011; 121:107-17. [PMID: 21332446 DOI: 10.1042/cs20110006] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The present study examined the glucose-lowering and insulinotropic properties of acylated GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) peptides in Type 2 diabetes and obesity. GLP-1, GIP, Liraglutide, N-AcGIP(Lys(37)Myr) (N-acetylGIP with myristic acid conjugated at Lys(37)), a simple combination of both peptides and a Lira-AcGIP preparation [overnight preparation of Liraglutide and N-AcGIP(Lys(37)Myr)] were incubated with DPP-IV (dipeptidyl peptidase-IV) to assess peptide stability, and BRIN-BD11 cells were used to evaluate cAMP production and insulin secretion. Acute glucose-lowering and insulinotropic actions were evaluated in Swiss TO mice. Subchronic studies on glucose homoeostasis, insulin secretion, food intake and bodyweight were evaluated in ob/ob mice. Liraglutide, N-AcGIP(Lys(37)Myr), a simple combination of both peptides and the Lira-AcGIP preparation demonstrated improved DPP-IV resistance (P<0.001), while stimulating cAMP production and insulin secretion (1.4-2-fold; P<0.001). The Lira-AcGIP preparation was more potent at lowering plasma glucose (20-51% reduction; P<0.05-P<0.001) and stimulating insulin secretion (1.5-1.8-fold; P<0.05-P<0.001) compared with Liraglutide and N-AcGIP(Lys(37)Myr) or a simple peptide combination. Daily administration of the Lira-AcGIP preparation to ob/ob mice lowered bodyweight (7-9%; P<0.05), food intake (23%; P<0.05) and plasma glucose (46% reduction; P<0.001), while increasing plasma insulin (1.5-1.6-fold; P<0.001). The Lira-AcGIP preparation enhanced glucose tolerance, insulin response to glucose and insulin content (P<0.05-P<0.001). These findings demonstrate that a combined preparation of the acylated GLP-1 and GIP peptides Liraglutide and N-AcGIP(Lys(37)Myr) markedly improved glucose-lowering and insulinotropic properties in diabetic obesity compared with either incretin mimetic given individually.
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Abstract
The increasing prevalence, variable pathogenesis, progressive natural history, and complications of type 2 diabetes emphasise the urgent need for new treatment strategies. Longacting (eg, once weekly) agonists of the glucagon-like-peptide-1 receptor are advanced in development, and they improve prandial insulin secretion, reduce excess glucagon production, and promote satiety. Trials of inhibitors of dipeptidyl peptidase 4, which enhance the effect of endogenous incretin hormones, are also nearing completion. Novel approaches to glycaemic regulation include use of inhibitors of the sodium-glucose cotransporter 2, which increase renal glucose elimination, and inhibitors of 11β-hydroxysteroid dehydrogenase 1, which reduce the glucocorticoid effects in liver and fat. Insulin-releasing glucokinase activators and pancreatic-G-protein-coupled fatty-acid-receptor agonists, glucagon-receptor antagonists, and metabolic inhibitors of hepatic glucose output are being assessed. Early proof of principle has been shown for compounds that enhance and partly mimic insulin action and replicate some effects of bariatric surgery.
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Affiliation(s)
- Abd A Tahrani
- Centre of Endocrinology, Diabetes and Metabolism, University of Birmingham, Birmingham, UK
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19
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Rafferty EP, Wylie AR, Elliott CT, Chevallier OP, Grieve DJ, Green BD. In Vitro and In Vivo Effects of Natural Putative Secretagogues of Glucagon-Like Peptide-1 (GLP-1). Sci Pharm 2011; 79:615-21. [PMID: 21886907 PMCID: PMC3163370 DOI: 10.3797/scipharm.1104-16] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 06/09/2011] [Indexed: 11/22/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1) is an intestinal hormone with well-established glucose-lowering activity. The in vitro and in vivo actions of natural putative secretagogues of GLP-1 were investigated. The acute GLP-1 releasing activity of olive leaf extract (OLE), glutamine (GLN), alpha casein (ACAS), beta casein (BCAS) and chlorogenic acid (CGA) were assessed in STC-1 cells and C57BL/6 mice. All compounds except ACAS significantly increased acute in vitro GLP-1 secretion (66–386%; P<0.05–0.001). Oral gavage of OLE and GLN modestly increased plasma GLP-1 concentrations (48% and 41%, respectively), but did not lower glycaemic excursions. OLE and GLN are potent stimulators of GLP-1 secretion both in vitro and in vivo and chronic studies should assess their suitability as nutritional therapies for type 2 diabetes.
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Affiliation(s)
- Eamon P Rafferty
- School of Biological Sciences, Queen's University Belfast, BT9 5AG, Northern Ireland, United Kingdom
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20
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Zahid OK, Mechkarska M, Ojo OO, Abdel-Wahab YHA, Flatt PR, Meetani MA, Conlon JM. Caerulein-and xenopsin-related peptides with insulin-releasing activities from skin secretions of the clawed frogs, Xenopus borealis and Xenopus amieti (Pipidae). Gen Comp Endocrinol 2011; 172:314-20. [PMID: 21458457 DOI: 10.1016/j.ygcen.2011.03.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2010] [Revised: 03/19/2011] [Accepted: 03/23/2011] [Indexed: 11/27/2022]
Abstract
Caerulein-related peptides were identified in norepinephrine-stimulated skin secretions of the tetraploid frog Xenopus borealis and the octoploid frog Xenopus amieti using negative ion electrospray mass spectrometry and their primary structures determined by positive ion tandem (MS/MS) mass spectrometry. X. borealis caerulein-B1 (pGlu-Gln-Asp-Tyr(SO(3))-Gly-Thr-Gly-Trp-Met-Asp-Phe.NH2) contains an additional Gly(5) residue compared with X. laevis caerulein and caerulein-B2 (pGlu-Asp-Tyr(SO(3))-Thr-Gly-Trp-Met-Asp-Phe.NH2) contains a Gln(2) deletion. X. amieti caerulein was identical to the X. laevis peptide. In addition, xenopsin, identical to the peptide from X. laevis, together with xenopsin-AM2 (pGlu-Gly-Arg-Arg-Pro-Trp-Ile- Leu) that contains the substitution Lys(3)→Arg were isolated from X. amieti secretions. X. borealis caerulein-B1, and X. amieti xenopsin and xenopsin-AM2 produced significant (P<0.05) and concentration-dependent stimulations of insulin release from the rat BRIN-BD11 clonal β cell line at concentrations ⩾30nM. The peptides did not stimulate the release of lactate dehydrogenase at concentrations up to 3μM demonstrating that the integrity of the plasma membrane had been preserved. While their precise biological role is unclear, the caerulein- and xenopsin-related peptides may constitute a component of the animal's chemical defenses against predators.
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Affiliation(s)
- Osama K Zahid
- Departmentof Chemistry, Faculty of Science, United Arab Emirates University, Al-Ain, United Arab Emirates
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21
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Rafferty EP, Wylie AR, Hand KH, Elliott CE, Grieve DJ, Green BD. Investigating the effects of physiological bile acids on GLP-1 secretion and glucose tolerance in normal and GLP-1R-/- mice. Biol Chem 2011; 392:539-46. [DOI: 10.1515/bc.2011.050] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Abstract
Physiological secretion of bile acids has previously been linked to the regulation of blood glucose. GLP-1 is an intestinal peptide hormone with important glucose-lowering actions, such as stimulation of insulin secretion and inhibition of glucagon secretion. In this investigation, we assessed the ability of several bile acid compounds to secrete GLP-1 in vitro in STC-1 cells. Bile acids stimulated GLP-1 secretion from 3.3- to 6.2-fold but some were associated with cytolytic effects. Glycocholic and taurocholic acids were selected for in vivo studies in normal and GLP-1R-/- mice. Oral glucose tolerance tests revealed that glycocholic acid did not affect glucose excursions. However, taurocholic acid reduced glucose excursions by 40% in normal mice and by 27% in GLP-1R-/- mice, and plasma GLP-1 concentrations were significantly elevated 30 min post-gavage. Additional studies used incretin receptor antagonists to probe involvement of GLP-1 and GIP in taurocholic acid-induced glucose lowering. The findings suggest that bile acids partially aid glucose regulation by physiologically enhancing nutrient-induced GLP-1 secretion. However, GLP-1 secretion appears to be only part of the glucose-lowering mechanism and our studies indicate that the other major incretin GIP is not involved.
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22
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Mechkarska M, Ojo OO, Meetani MA, Coquet L, Jouenne T, Abdel-Wahab YHA, Flatt PR, King JD, Conlon JM. Peptidomic analysis of skin secretions from the bullfrog Lithobates catesbeianus (Ranidae) identifies multiple peptides with potent insulin-releasing activity. Peptides 2011; 32:203-8. [PMID: 21087647 DOI: 10.1016/j.peptides.2010.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 11/01/2010] [Accepted: 11/01/2010] [Indexed: 11/16/2022]
Abstract
Using a combination of reversed-phase HPLC and electrospray mass spectrometry, peptidomic analysis of norepinephrine-stimulated skin secretions of the American bullfrog Lithobates catesbeianus Shaw, 1802 led to the identification and characterization of five newly described peptides (ranatuerin-1CBb, ranatuerin-2CBc, and -CBd, palustrin-2CBa, and temporin-CBf) together with seven peptides previously isolated on the basis of their antimicrobial activity (ranatuerin-1CBa, ranatuerin-2CBa, brevinin-1CBa, and -1CBb, temporin-CBa, -CBb, and -CBd). The abilities of the most abundant of the purified peptides to stimulate the release of insulin from the rat BRIN-BD11 clonal β cell line were evaluated. Ranatuerin-2CBd (GFLDIIKNLGKTFAGHMLDKIRCTIGTCPPSP) was the most potent peptide producing a significant stimulation of insulin release (119% of basal rate, P<0.01) from BRIN-BD11 cells at a concentration of 30nM, with a maximum response (236% of basal rate, P<0.001) at a concentration of 3μM. Ranatuerin-2CBd did not stimulate release of the cytosolic enzyme, lactate dehydrogenase at concentrations up to 3μM, indicating that the integrity of the plasma membrane had been preserved. Brevinin-1CBb (FLPFIARLAAKVFPSIICSVTKKC) produced the maximum stimulation of insulin release (285% of basal rate, P<0.001 at 3μM) but the peptide was cytotoxic at this concentration.
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Affiliation(s)
- Milena Mechkarska
- Department of Biochemistry, United Arab Emirates University, 17666 Al-Ain, United Arab Emirates
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23
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Renal glucose reabsorption inhibitors to treat diabetes. Trends Pharmacol Sci 2011; 32:63-71. [PMID: 21211857 DOI: 10.1016/j.tips.2010.11.011] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 11/24/2010] [Accepted: 11/29/2010] [Indexed: 12/18/2022]
Abstract
Current therapies to reduce hyperglycaemia in type 2 diabetes mellitus (T2DM) mostly involve insulin-dependent mechanisms and lose their effectiveness as pancreatic β-cell function declines. In the kidney, filtered glucose is reabsorbed mainly via the high-capacity, low-affinity sodium glucose cotransporter-2 (SGLT2) at the luminal surface of cells lining the first segment of the proximal tubules. Selective inhibitors of SGLT2 reduce glucose reabsorption, causing excess glucose to be eliminated in the urine; this decreases plasma glucose. In T2DM, the glucosuria produced by SGLT2 inhibitors is associated with weight loss, and mild osmotic diuresis might assist a reduction in blood pressure. The mechanism is independent of insulin and carries a low risk of hypoglycaemia. This review examines the potential of SGLT2 inhibitors as a novel approach to the treatment of hyperglycaemia in T2DM.
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Riedel MJ, Kieffer TJ. Treatment of diabetes with glucagon-like peptide-1 gene therapy. Expert Opin Biol Ther 2010; 10:1681-92. [PMID: 21029027 DOI: 10.1517/14712598.2010.532786] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
IMPORTANCE OF THE FIELD Glucagon-like peptide (GLP)-1 receptor agonists are in widespread clinical use for the treatment of diabetes. While effective, these peptides require frequent injections to maintain efficacy. Therefore, alternative delivery methods including gene therapy are currently being evaluated. AREAS COVERED IN THIS REVIEW Here, we review the biology of GLP-1, evidence supporting the clinical use of the native peptide as well as synthetic GLP-1 receptor agonists, and the rationale for their delivery by gene therapy. We then review progress made in the field of GLP-1 gene therapy for both type 1 and type 2 diabetes. WHAT THE READER WILL GAIN Efforts to improve the biological half-life of GLP-1 receptor agonists are discussed. We focus on the development of both viral and non-viral gene delivery methods, highlighting vector designs and the strengths and weaknesses of these approaches. We also discuss the utility of targeting regulated GLP-1 production to tissues including the liver, muscle, islet and gut. TAKE HOME MESSAGE GLP-1 is a natural peptide possessing several actions that effectively combat diabetes. Current delivery methods for GLP-1-based drugs are cumbersome and do not recapitulate the normal secretion pattern of the native hormone. Gene therapy offers a useful method for directing long-term production and secretion of the native peptide. Targeted production of GLP-1 using tissue-specific promoters and delivery methods may improve therapeutic efficacy, while also eliminating the burden of frequent injections.
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Affiliation(s)
- Michael J Riedel
- University of British Columbia, Department of Cellular and Physiological Sciences, Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
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25
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Porter DW, Kerr BD, Flatt PR, Holscher C, Gault VA. Four weeks administration of Liraglutide improves memory and learning as well as glycaemic control in mice with high fat dietary-induced obesity and insulin resistance. Diabetes Obes Metab 2010; 12:891-9. [PMID: 20920042 DOI: 10.1111/j.1463-1326.2010.01259.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
AIM Liraglutide is a long-acting glucagon-like peptide-1 (GLP-1) mimetic which is a treatment option for type 2 diabetes. GLP-1 peptides, including Liraglutide, cross the blood-brain barrier and may additionally act to improve brain function. The present study tested the hypothesis that, in addition to its antihyperglycaemic actions, peripheral administration of Liraglutide exerts positive actions on cognitive function in mice with high fat dietary-induced obesity and insulin resistance. METHODS Young Swiss TO mice maintained on high fat diet for 20 weeks received twice-daily injections of Liraglutide (200 µg/kg bw; sc) or saline vehicle over 28 days. An additional group of mice on standard diet received twice-daily saline injections. Energy intake, bodyweight, non-fasting plasma glucose and insulin concentrations were monitored at regular intervals. Glucose tolerance, open field assessment, object recognition testing and electrophysiological long-term potentiation (LTP) were performed at termination of the study. RESULTS Liraglutide treatment resulted in significant time-dependent reduction in bodyweight and energy intake, whilst improving non-fasting glucose and normalizing glucose tolerance. Although Liraglutide did not alter general behaviour, treated mice exhibited marked increase in recognition index (RI) during object recognition testing, indicative of enhanced learning and memory ability. Furthermore, Liraglutide rescued the deleterious effects of high fat diet on hippocampal LTP of neurotransmission following both chronic and direct intracerebroventricular (icv) administration. CONCLUSION Liraglutide administered peripherally not only improves metabolic parameters but exerts additional beneficial effects on cognitive function and hippocampal synaptic plasticity. Whether therapy with GLP-1 mimetics has similar effects in humans with type 2 diabetes needs to be established.
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Affiliation(s)
- D W Porter
- The SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, Northern Ireland, UK
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26
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Kerr BD, Flatt PR, Gault VA. Effects of γ-glutamyl linker on DPP-IV resistance, duration of action and biological efficacy of acylated glucagon-like peptide-1. Biochem Pharmacol 2010; 80:396-401. [DOI: 10.1016/j.bcp.2010.04.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 04/01/2010] [Accepted: 04/15/2010] [Indexed: 11/16/2022]
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Bailey CJ, Green BD, Flatt PR. Fixed-dose combination therapy for type 2 diabetes: sitagliptin plus pioglitazone. Expert Opin Investig Drugs 2010; 19:1017-25. [DOI: 10.1517/13543784.2010.505235] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Grieve DJ, Cassidy RS, Green BD. Emerging cardiovascular actions of the incretin hormone glucagon-like peptide-1: potential therapeutic benefits beyond glycaemic control? Br J Pharmacol 2010; 157:1340-51. [PMID: 19681866 DOI: 10.1111/j.1476-5381.2009.00376.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1) is an incretin hormone secreted by the small intestine in response to nutrient ingestion. It has wide-ranging effects on glucose metabolism, including stimulation of insulin release, inhibition of glucagon secretion, reduction of gastric emptying and augmentation of satiety. Importantly, the insulinotropic actions of GLP-1 are uniquely dependent on ambient glucose concentrations, and it is this particular characteristic which has led to its recent emergence as a treatment for type 2 diabetes. Although the major physiological function of GLP-1 appears to be in relation to glycaemic control, there is growing evidence to suggest that it may also play an important role in the cardiovascular system. GLP-1 receptors (GLP-1Rs) are expressed in the heart and vasculature of both rodents and humans, and recent studies have demonstrated that GLP-1R agonists have wide-ranging cardiovascular actions, such as modulation of heart rate, blood pressure, vascular tone and myocardial contractility. Importantly, it appears that these agents may also have beneficial effects in the setting of cardiovascular disease (CVD). For example, GLP-1 has been found to exert cardioprotective actions in experimental models of dilated cardiomyopathy, hypertensive heart failure and myocardial infarction (MI). Preliminary clinical studies also indicate that GLP-1 infusion may improve cardiac contractile function in chronic heart failure patients with and without diabetes, and in MI patients after successful angioplasty. This review will discuss the current understanding of GLP-1 biology, examine its emerging cardiovascular actions in both health and disease and explore the potential use of GLP-1 as a novel treatment for CVD.
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Affiliation(s)
- David J Grieve
- Centre for Vision and Vascular Science, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, UK.
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Glucagon-like peptide-1 analogues enhance synaptic plasticity in the brain: a link between diabetes and Alzheimer's disease. Eur J Pharmacol 2009; 630:158-62. [PMID: 20035739 DOI: 10.1016/j.ejphar.2009.12.023] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2009] [Revised: 11/25/2009] [Accepted: 12/15/2009] [Indexed: 01/27/2023]
Abstract
Type 2 diabetes has been identified as a risk factor for patients with Alzheimer's disease. Insulin signalling is often impaired in Alzheimer's disease, contributing to the neurodegenerative process. One potential strategy to help prevent this is the normalisation of insulin signalling in the brain. Therefore, the present study was designed to test the effects of novel enzyme-resistant analogues of the insulin-releasing incretin hormone, glucagon-like peptide 1 (GLP-1). The effects of Liraglutide (Victoza) and other novel GLP-1 analogues were tested on synaptic plasticity (LTP) in area CA1 of the hippocampus. At a dose of 15nmol in 5microl i.c.v., Liraglutide (P<0.005), Asp(7)GLP-1 (P<0.001), N-glyc-GLP-1 (P<0.01), and Pro(9)GLP-1 (P<0.001). In contrast, the GLP-1 receptor antagonist exendin(9-39)amide impaired LTP (P<0.001). Co-injection of exendin(9-39) and Liraglutide showed no effect on LTP. These results clearly demonstrate that Liraglutide and other GLP-1 analogues elicit effects on neurotransmission in the brain. Furthermore, GLP-1 peptides are not only effective in modulating insulin-release and achieving glycaemic control in type 2 diabetes, but are also effective in modulating synaptic plasticity. These findings are consistent with our previous observations that the novel analogue (Val(8))GLP-1 enhances LTP and reverses the impairments of LTP induced by beta-amyoid fragments. Therefore, the drug effects seen here could potentially ameliorate the impairments in neuronal communication and cognitive processes observed in Alzheimer's disease.
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30
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Irwin N, Flatt PR, Patterson S, Green BD. Insulin-releasing and metabolic effects of small molecule GLP-1 receptor agonist 6,7-dichloro-2-methylsulfonyl-3-N-tert-butylaminoquinoxaline. Eur J Pharmacol 2009; 628:268-73. [PMID: 19917278 DOI: 10.1016/j.ejphar.2009.11.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2009] [Revised: 10/07/2009] [Accepted: 11/10/2009] [Indexed: 02/06/2023]
Abstract
Much recent attention has focused on the GLP-1 receptor as a potential target for antidiabetic drugs. Enzyme resistant GLP-1 mimetics such as exenatide are now employed for the treatment of type 2 diabetes, but must be administered by injection. The present study has examined and compared the in vitro and in vivo metabolic actions of a small molecule GLP-1 receptor agonist 6,7-dichloro-2-methylsulfonyl-3-N-tert-butylaminoquinoxaline (DMB), with native GLP-1, exenatide and liraglutide. DMB significantly stimulated in vitro insulin secretion from BRIN-BD11 cells but with decreased molar potency compared to native GLP-1 or related mimetics. Administration of DMB in combination with glucose to mice significantly (P<0.05) decreased the overall glucose excursion compared to controls. Exenatide and liraglutide evoked similar (P<0.001) reductions of the overall glycaemic excursion, but were significantly (P<0.001 and P<0.05; respectively) more effective than DMB. These observations were associated with prominently (P<0.05) enhanced glucose-mediated insulin release by exenatide and liraglutide, but not by DMB. Combined injection of DMB with either liraglutide or exenatide did not substantially improve glucose-lowering or insulin-releasing responses. However, administration of DMB in combination with exendin(9-39) did not impair its glucoregulatory actions. These results provide evidence to support the development and potential use of low molecular weight GLP-1 receptor agonists for the treatment of type 2 diabetes.
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Affiliation(s)
- Nigel Irwin
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences Research Institute, University of Ulster, Coleraine, United Kingdom.
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31
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Abstract
Many patients with type 2 diabetes are obese (diabesity), and the two conditions together impose a particularly complex therapeutic challenge. Several differently acting agents are often required at the same time, encouraging development of more single-tablet combinations. Longer-acting (once daily and once weekly) injected agonists of glucagon-like peptide-1 are due to provide additional options to stimulate insulin secretion with weight loss and minimal risk of hypoglycemia. Further, dipeptidyl peptidase-4 inhibitors ("weight-neutral" insulinotropic agents) are also expected. Sodium-glucose cotransporter 2 inhibitors offer a new option to reduce hyperglycemia and facilitate weight loss by increasing the elimination of glucose in the urine. Selective peroxisome proliferator-activated receptor modulators are being studied to produce compounds with desired effects. Many other agents with antidiabetic and antiobesity activity are progressing in clinical development.
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Affiliation(s)
- Clifford J Bailey
- Life and Health Sciences, Aston University, Aston Street, Aston Triangle, Birmingham B4 7ET, UK.
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32
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Abstract
In obese patients bariatric surgery is increasing in popularity as a strategy to promote, and maintain, weight loss. In obese type 2 diabetes bypass, bariatric surgery improves glycaemic control — often to a greater extent than would be anticipated by weight loss alone. Surgical bypass procedures appear to initially offer a greater glucose-lowering effect than surgical restriction procedures. This review considers the rationale for bariatric surgery as a treatment for diabesity and the implications of the different procedures on the secretion and action of enteral hormones.
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Affiliation(s)
- Peter R Flatt
- School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK
| | - Caroline Day
- Diabetes Research Group, Aston University, Birmingham, UK
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