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Elevated Glucagon-like Peptide-1 and a Th2 Shift May Support Reduced Prevalence of Thoracic Aortic Aneurysm in Patients with Diabetes. J Cardiovasc Dev Dis 2021; 8:jcdd8110143. [PMID: 34821696 PMCID: PMC8618274 DOI: 10.3390/jcdd8110143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 10/22/2021] [Accepted: 10/25/2021] [Indexed: 11/17/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1) regulates processes involved in the pathophysiology of thoracic aortic aneurysms (TAAs), including inflammation, while protecting against aortic aneurysms in animal models. Type 2 diabetes (T2D) involves altered GLP-1 signaling due to pathology and/or therapy and is associated with reduced prevalence of TAAs. We aimed to assess whether T2D alters the inflammatory profile/proteolytic activity, possible correlations to elevated fasting GLP-1 (F-GLP-1), and its relevance for TAA. F-GLP-1, pro-inflammatory T helper 1 (Th1) cytokines, Th2 cytokines, C-reactive protein, and matrix metalloproteinase-2 activity (MMP-2) were analyzed in surgical patients with aortic valve pathology with/without T2D and without T2D but with TAA. Patients with T2D displayed an increase in the relative systemic expression of interleukin 6 and tumor necrosis factor α and a clear trend towards reduced levels of interferon γ (IFNγ). In addition, a positive association between GLP-1 and the plasma interleukin 4 (IL-4)/IFNγ ratio was detected. TAA was associated with significantly lower plasma levels of the Th2 cytokines IL-4 and interleukin 5. Plasma MMP-2 activity did not differ between groups. We conclude that T2D involved a Th2 shift, which associates with elevated F-GLP-1 and may-considering Th1 bias in TAA-contribute to reduced prevalence of TAA in T2D.
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Tanday N, Moffett RC, Gault VA, Flatt PR, Irwin N. Enzymatically stable analogue of the gut-derived peptide xenin on beta-cell transdifferentiation in high fat fed and insulin-deficient Ins1 Cre/+ ;Rosa26-eYFP mice. Diabetes Metab Res Rev 2021; 37:e3384. [PMID: 32662136 DOI: 10.1002/dmrr.3384] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 05/25/2020] [Accepted: 07/06/2020] [Indexed: 12/22/2022]
Abstract
BACKGROUND The antidiabetic effects of the gut hormone xenin include augmenting insulin secretion and positively affecting pancreatic islet architecture. METHODS The current study has further probed pancreatic effects through sub-chronic administration of the long-acting xenin analogue, xenin-25[Lys13 PAL], in both high fat fed (HFF) and streptozotocin (STZ)-induced insulin-deficient Ins1Cre/+ ;Rosa26-eYFP transgenic mice. Parallel effects on metabolic control and pancreatic islet morphology, including islet beta-cell lineage tracing were also assessed. RESULTS Xenin-25[Lys13 PAL] treatment reversed body weight loss induced by STZ, increased plasma insulin and decreased blood glucose levels. There were less obvious effects on these parameters in HFF mice, but all xenin-25[Lys13 PAL] treated mice exhibited decreased pancreatic alpha-cell areas and circulating glucagon. Xenin-25[Lys13 PAL] treatment fully, or partially, returned overall islet and beta-cell areas in STZ- and HFF mice to those of lean control animals, respectively, and was consistently associated with decreased beta-cell apoptosis. Interestingly, xenin-25[Lys13 PAL] also increased beta-cell proliferation and decreased alpha-cell apoptosis in STZ mice, with reduced alpha-cell growth noted in HFF mice. Lineage tracing studies revealed that xenin-25[Lys13 PAL] reduced the number of insulin positive pancreatic islet cells that lost their beta-cell identity, in keeping with a decreased transition of insulin positive to glucagon positive cells. These beneficial effects on islet cell differentiation were linked to maintained expression of Pdx1 within beta-cells. Xenin-25[Lys13 PAL] treatment was also associated with increased numbers of smaller sized islets in both models. CONCLUSIONS Benefits of xenin-25[Lys13 PAL] on diabetes includes positive modulation of islet cell differentiation, in addition to promoting beta-cell growth and survival.
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Affiliation(s)
- Neil Tanday
- SAAD Centre for Pharmacy and Diabetes, Ulster University, Coleraine, Northern Ireland, UK
| | - R Charlotte Moffett
- SAAD Centre for Pharmacy and Diabetes, Ulster University, Coleraine, Northern Ireland, UK
| | - Victor A Gault
- SAAD Centre for Pharmacy and Diabetes, Ulster University, Coleraine, Northern Ireland, UK
| | - Peter R Flatt
- SAAD Centre for Pharmacy and Diabetes, Ulster University, Coleraine, Northern Ireland, UK
| | - Nigel Irwin
- SAAD Centre for Pharmacy and Diabetes, Ulster University, Coleraine, Northern Ireland, UK
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Abstract
Type 1 diabetes is characterized by selective loss of beta cells and insulin secretion, which significantly impact glucose homeostasis. However, this progressive disease is also associated with dysfunction of the alpha cell component of the islet, which can exacerbate hyperglycemia due to paradoxical hyperglucagonemia or lead to severe hypoglycemia as a result of failed counterregulation. In this review, the physiology of alpha cell secretion and the potential mechanisms underlying alpha cell dysfunction in type 1 diabetes will be explored. Because type 1 diabetes is a progressive disease, a synthesized timeline of aberrant alpha cell function will be presented as an attempt to delineate the natural history of type 1 diabetes with respect to the alpha cell.
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Affiliation(s)
- Gina L C Yosten
- Department of Pharmacology and Physiology, Saint Louis University School of Medicine, 1402 S. Grand Blvd, Saint Louis, MO 63104, United States.
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Huang WQ, Guo JH, Zhang XH, Yu MK, Chung YW, Ruan YC, Chan HC. Glucose-Sensitive CFTR Suppresses Glucagon Secretion by Potentiating KATP Channels in Pancreatic Islet α Cells. Endocrinology 2017; 158:3188-3199. [PMID: 28977595 DOI: 10.1210/en.2017-00282] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 07/18/2017] [Indexed: 12/14/2022]
Abstract
The secretion of glucagon by islet α cells is normally suppressed by high blood glucose, but this suppressibility is impaired in patients with diabetes or cystic fibrosis (CF), a disease caused by mutations in the gene encoding CF transmembrane conductance regulator (CFTR), a cyclic adenosine monophosphate-activated Cl- channel. However, precisely how glucose regulates glucagon release remains controversial. Here we report that elevated glucagon secretion, together with increased glucose-induced membrane depolarization and Ca2+ response, is found in CFTR mutant (DF508) mice/islets compared with the wild-type. Overexpression of CFTR in AlphaTC1-9 cells results in membrane hyperpolarization and reduced glucagon release, which can be reversed by CFTR inhibition. CFTR is found to potentiate the adenosine triphosphate-sensitive K+ (KATP) channel because membrane depolarization and whole-cell currents sensitive to KATP blockers are significantly greater in wild-type/CFTR-overexpressed α cells compared with that in DF508/non-overexpressed cells. KATP knockdown also reverses the suppressive effect of CFTR overexpression on glucagon secretion. The results reveal that by potentiating KATP channels, CFTR acts as a glucose-sensing negative regulator of glucagon secretion in α cells, a defect of which may contribute to glucose intolerance in CF and other types of diabetes.
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Affiliation(s)
- Wen Qing Huang
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong
| | - Jing Hui Guo
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong
- Department of Pathophysiology, Key Laboratory of State Administration of Traditional Chinese Medicine of the People's Republic of China, School of Medicine, Jinan University, Guangzhou 510632, People's Republic of China
| | - Xiao Hu Zhang
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong
- Sichuan University-The Chinese University of Hong Kong Joint Laboratory for Reproductive Medicine, Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Mei Kuen Yu
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong
| | - Yiu Wa Chung
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong
| | - Ye Chun Ruan
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong
- Interdisciplinary Division of Biomedical Engineering, the Hong Kong Polytechnic University, Hong Kong, Hong Kong
| | - Hsiao Chang Chan
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong
- Sichuan University-The Chinese University of Hong Kong Joint Laboratory for Reproductive Medicine, Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu 610041, People's Republic of China
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Solini A, Sebastiani G, Nigi L, Santini E, Rossi C, Dotta F. Dapagliflozin modulates glucagon secretion in an SGLT2-independent manner in murine alpha cells. DIABETES & METABOLISM 2017; 43:512-520. [PMID: 28499695 DOI: 10.1016/j.diabet.2017.04.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 03/28/2017] [Accepted: 04/13/2017] [Indexed: 12/20/2022]
Abstract
AIM SGLT2 inhibitors reduce renal glucose uptake through an insulin-independent mechanism. They also increase glucagon concentration, although the extent to which this is due to a direct effect on pancreatic alpha cells remains unclear. METHODS In the present work, αTC1 cells treated with the SGLT2 inhibitor dapagliflozin (Dapa) were analyzed for glucose transporters, molecular mediators of hormone secretion, glucagon and GLP-1 release, and the effects of somatostatin. Data were validated in murine and human pancreatic islets. RESULTS SLC5A2 (the SGLT2-encoding gene) was nearly undetectable in αTC1 cells, not even by a digital PCR technique using different probes. In contrast, SLC5A1 (the SGLT1-encoding gene) was constitutively abundant in αTC1 cells and in islets, and increased with Dapa. This was associated with greater glucagon release, preceded by increased expression of preproglucagon and HNF4α. Looking at the candidate intracellular signalling pathway, reduced PASK and increased AMPK-α2 expression were also detected. GLUT1 and GLUT2, as well as regulators of glucagon release and alpha-cell phenotype (chromogranin A, paired box 6, proprotein convertase 1/2, synaptophysin), were unaffected by Dapa, as were GLP-1 receptor expression and GLP-1 release. Low glucose did not influence the stimulatory effect of Dapa on glucagon release, but was instead almost fully reverted by SLC5A1 silencing. When the effect of Dapa on AMPK and PASK, emerging regulators of lipid and glucose metabolism, was tested, upregulated AMPK-α2 appeared to be involved in molecular signalling. CONCLUSION Our study has shown that, in αTC1 cells, Dapa acutely upregulates SGLT1 expression and increases glucagon release through an SGLT1-dependent mechanism, with SGLT2 expression virtually undetectable. These results suggest the involvement of SGLT1 in modulating glucagon increases following SGLT2 inhibition.
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Affiliation(s)
- A Solini
- Department of surgical, medical, molecular and critical area pathology, university of Pisa, Via Roma 67, 56126 Pisa, Italy.
| | - G Sebastiani
- Department of medicine, surgery and neuroscience, university of Siena and Fondazione Umberto di Mario-Toscana life science, Viale Bracci 18, 53100 Siena, Italy
| | - L Nigi
- Department of medicine, surgery and neuroscience, university of Siena and Fondazione Umberto di Mario-Toscana life science, Viale Bracci 18, 53100 Siena, Italy
| | - E Santini
- Department of clinical and experimental medicine, university of Pisa, Pisa, Italy
| | - C Rossi
- Department of clinical and experimental medicine, university of Pisa, Pisa, Italy
| | - F Dotta
- Department of medicine, surgery and neuroscience, university of Siena and Fondazione Umberto di Mario-Toscana life science, Viale Bracci 18, 53100 Siena, Italy.
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Abstract
OBJECTIVES Mechanisms of toxicity and cell damage were investigated in novel clonal human pancreatic beta cell line, 1.1B4, after exposure to streptozotocin, alloxan, ninhydrin, and hydrogen peroxide. METHODS Viability, DNA damage, insulin secretion/content, [Ca]i, and glucokinase/hexokinase, mRNA expression were measured by MTT assay, comet assay, radioimmunoassay, fluorometric imaging plate reader, enzyme-coupled photometry, and real-time polymerase chain reaction, respectively. RESULTS Chemicals significantly reduced 1.1B4 cell viability in a time/concentration-dependent manner. Chronic 18-hour exposure decreased cellular insulin, glucokinase, and hexokinase activities. Chemicals decreased transcription of INS, GCK, PCSK1, PCSK2, and GJA1 (involved in secretory function). Insulin release and [Ca]i responses to nutrients and membrane-depolarizing agents were impaired. Streptozotocin and alloxan up-regulated transcription of genes, SOD1 and SOD2 (antioxidant enzymes). Ninhydrin and hydrogen peroxide up-regulated SOD2 transcription, whereas alloxan and hydrogen peroxide increased CAT transcription. Chemicals induced DNA damage, apoptosis, and increased caspase 3/7 activity. Streptozotocin and alloxan decreased transcription of BCL2 while increasing transcription of BAX. Chemicals did not affect transcription of HSPA4 and HSPA5 and nitrite production. CONCLUSIONS 1.1B4 cells represent a useful model of human beta cells. Chemicals impaired 1.1B4 cell secretory function and activated antioxidant defense and apoptotic pathways without activating endoplasmic reticulum stress response/nitrosative stress.
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Abstract
Glucagon-like peptide-1 (GLP-1) is a peptide hormone, released from intestinal L-cells in response to hormonal, neural and nutrient stimuli. In addition to potentiation of meal-stimulated insulin secretion, GLP-1 signalling exerts numerous pleiotropic effects on various tissues, regulating energy absorption and disposal, as well as cell proliferation and survival. In Type 2 Diabetes (T2D) reduced plasma levels of GLP-1 have been observed, and plasma levels of GLP-1, as well as reduced numbers of GLP-1 producing cells, have been correlated to obesity and insulin resistance. Increasing endogenous secretion of GLP-1 by selective targeting of the molecular mechanisms regulating secretion from the L-cell has been the focus of much recent research. An additional and promising strategy for enhancing endogenous secretion may be to increase the L-cell mass in the intestinal epithelium, but the mechanisms that regulate the growth, survival and function of these cells are largely unknown. We recently showed that prolonged exposure to high concentrations of the fatty acid palmitate induced lipotoxic effects, similar to those operative in insulin-producing cells, in an in vitro model of GLP-1-producing cells. The mechanisms inducing this lipototoxicity involved increased production of reactive oxygen species (ROS). In this review, regulation of GLP-1-secreting cells is discussed, with a focus on the mechanisms underlying GLP-1 secretion, long-term regulation of growth, differentiation and survival under normal as well as diabetic conditions of hypernutrition.
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Srinivasan DK, Ojo OO, Owolabi BO, Conlon JM, Flatt PR, Abdel-Wahab YHA. [I10W]tigerinin-1R enhances both insulin sensitivity and pancreatic beta cell function and decreases adiposity and plasma triglycerides in high-fat mice. Acta Diabetol 2016; 53:303-15. [PMID: 26138324 DOI: 10.1007/s00592-015-0783-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 05/31/2015] [Indexed: 12/11/2022]
Abstract
AIMS We have previously described the insulinotropic activities of [I10W]tigerinin-1R (RVCSAIPLPWCH.NH2) in vitro. In this study, we investigated the effects of the peptide on nutrient homoeostasis in mice with diet-induced obesity and insulin resistance. METHODS Male NIH Swiss mice were maintained on a high-fat diet for 12 weeks prior to the study. Twice-daily intraperitoneal injections of [I10W]tigerinin-1R (75 nmol/kg body weight) were administered for 28 days. Body weight, energy intake, body fat content, and plasma concentrations of triglyceride, cholesterol, non-fasting glucose and insulin were monitored. Effects of the peptide on glycaemic control were measured by glucose tolerance and insulin sensitivity tests. Pancreatic hormone content and insulin secretory responses of islets isolated from treated and untreated mice were examined. Immunohistochemical analysis was performed to study possible changes in islet morphology. RESULTS Administration of [I10W]tigerinin-1R to high-fat-fed mice produced significant (P < 0.05) decreases in plasma glucose, glucagon and triglyceride concentrations and an increase in plasma insulin compared to high-fat-fed controls. No changes in body weight or energy intake were observed with peptide treatment, but glycaemic control was significantly improved in response to oral or intraperitoneal glucose. Insulin sensitivity and secretory responses of islets to established insulin secretagogues were also significantly improved in peptide-treated mice. Total body fat, pancreatic insulin and glucagon contents, islet, beta and alpha cell areas were all significantly decreased in treated mice. CONCLUSIONS This study shows that [I10W]tigerinin-1R improves insulin sensitivity, islet function and glycaemic control in high-fat-fed mice and has potential as a template for development of novel anti-diabetic agents.
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Affiliation(s)
- Dinesh K Srinivasan
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 1SA, Northern Ireland, UK
| | - Opeolu O Ojo
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 1SA, Northern Ireland, UK
| | - Bosede O Owolabi
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 1SA, Northern Ireland, UK
| | - J Michael Conlon
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 1SA, Northern Ireland, UK
| | - Peter R Flatt
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 1SA, Northern Ireland, UK
| | - Yasser H A Abdel-Wahab
- SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 1SA, Northern Ireland, UK.
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Vasu S, Moffett RC, McClenaghan NH, Flatt PR. Differential molecular and cellular responses of GLP-1 secreting L-cells and pancreatic alpha cells to glucotoxicity and lipotoxicity. Exp Cell Res 2015; 336:100-8. [DOI: 10.1016/j.yexcr.2015.05.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 05/25/2015] [Accepted: 05/26/2015] [Indexed: 12/25/2022]
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