scholarly journals The connexin 43 regulator Rotigaptide reduces cytokine-induced cell death in human islets

2018 ◽  
Author(s):  
Seyed Mojtaba Ghiasi ◽  
Jakob Bondo Hansen ◽  
Dan Ploug Christensen ◽  
Thomas Mandrup-Poulsen
Keyword(s):  
Cell Death ◽  
Beta Cell ◽  
Connexin 43 ◽  
Cell Function ◽  
Protective Action ◽  
Human Islets ◽  
Mitochondrial Activity ◽  
No Production ◽  
Mrna Levels ◽  
Cell Defense

AbstarctBackgroundIntercellular communication mediated by cationic fluxes through the Connexin-family of gap-junctions regulates glucose-stimulated insulin-secretion and beta-cell defense against inflammatory stress. Rotigaptide (RG, ZP123) is a peptide analog that increases intercellular conductance in cardiac muscle-cells by prevention of dephosphorylation and thereby uncoupling of Connexin-43 (Cx43), possibly via action on unidentified protein phosphatases. For this reason, it is being studied in human arrhythmias. It is unknown if RG protects beta-cell function and viability against inflammatory or metabolic stress, a question of considerable translational interest for the treatment of beta-cell failure in diabetes.MethodsApoptosis was measured in human islets known to express Cx43, treated with RG or the control peptide ZP119 and exposed to glucolipotoxicity or IL-1b + IFNg. INS-1 cells shown to lack Cx43 were used to verify if RG protected human islet-cells via Cx43-coupling. To study mechanisms of action of Cx43-independent effects of RG, NO, IkBa degradation, mitochondrial activity, ROS and insulin mRNA levels were determined.ResultsRG reduced cytokine-induced apoptosis ~40% in human islets. In Cx43-deficient INS-1 cells this protective effect was markedly blunted as expected, but unexpectedly RG still modestly reduced apoptosis, and improved mitochondrial function, insulin-2 gene levels and accumulated insulin release. RG reduced NO production in Cx43-deficient INS-1 cells associated with reduced iNOS-expression, suggesting that RG blunts cytokine-induced NF-kB signaling in insulin-producing cells in a Cx43-independent manner.ConclusionRG reduces cytokine-induced cell-death in human islets. The protective action in Cx43-deficient INS-1 cells suggests a novel inhibitory mechanism of action of RG on NF-kB signaling.

scholarly journals The Connexin 43 Regulator Rotigaptide Reduces Cytokine-Induced Cell Death in Human Islets

2020 ◽  
Vol 21 (12) ◽  
pp. 4311 ◽  
Author(s):  
Seyed Mojtaba Ghiasi ◽  
Jakob Bondo Hansen ◽  
Dan Ploug Christensen ◽  
Björn Tyrberg ◽  
Thomas Mandrup-Poulsen
Keyword(s):  
Cell Death ◽  
Connexin 43 ◽  
Cell Function ◽  
Protective Action ◽  
Human Islets ◽  
Mitochondrial Activity ◽  
No Production ◽  
Mrna Levels ◽  
Independent Manner ◽  
Cell Defense

Background: Intercellular communication mediated by cationic fluxes through the Connexin family of gap junctions regulates glucose-stimulated insulin secretion and beta cell defense against inflammatory stress. Rotigaptide (RG, ZP123) is a peptide analog that increases intercellular conductance in cardiac muscle cells by the prevention of dephosphorylation and thereby uncoupling of Connexin-43 (Cx43), possibly via action on unidentified protein phosphatases. For this reason, it is being studied in human arrhythmias. It is unknown if RG protects islet cell function and viability against inflammatory or metabolic stress, a question of considerable translational interest for the treatment of diabetes. Methods: Apoptosis was measured in human islets shown to express Cx43, treated with RG or the control peptide ZP119 and exposed to glucolipotoxicity or IL-1β + IFNɣ. INS-1 cells shown to lack Cx43 were used to examine if RG protected human islet cells via Cx43 coupling. To study the mechanisms of action of Cx43-independent effects of RG, NO, IkBα degradation, mitochondrial activity, ROS, and insulin mRNA levels were determined. Results: RG reduced cytokine-induced apoptosis ~40% in human islets. In Cx43-deficient INS-1 cells, this protective effect was markedly blunted as expected, but unexpectedly, RG still modestly reduced apoptosis, and improved mitochondrial function, insulin-2 gene levels, and accumulated insulin release. RG reduced NO production in Cx43-deficient INS-1 cells associated with reduced iNOS expression, suggesting that RG blunts cytokine-induced NF-κB signaling in insulin-producing cells in a Cx43-independent manner. Conclusion: RG reduces cytokine-induced cell death in human islets. The protective action in Cx43-deficient INS-1 cells suggests a novel inhibitory mechanism of action of RG on NF-κB signaling.

scholarly journals microRNA-375 regulates glucose metabolism-related signaling for insulin secretion

2020 ◽  
Vol 244 (1) ◽  
pp. 189-200 ◽  
Author(s):  
Olivier Dumortier ◽  
Gaia Fabris ◽  
Didier F Pisani ◽  
Virginie Casamento ◽  
Nadine Gautier ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Glucose Metabolism ◽  
Beta Cell ◽  
Beta Cells ◽  
Cell Function ◽  
Islet Cells ◽  
Lactate Production ◽  
Human Islets ◽  
Pyruvate Dehydrogenase Kinase ◽  
Mrna Levels

Enhanced beta cell glycolytic and oxidative metabolism are necessary for glucose-induced insulin secretion. While several microRNAs modulate beta cell homeostasis, miR-375 stands out as it is highly expressed in beta cells where it regulates beta cell function, proliferation and differentiation. As glucose metabolism is central in all aspects of beta cell functioning, we investigated the role of miR-375 in this process using human and rat islets; the latter being an appropriate model for in-depth investigation. We used forced expression and repression of mR-375 in rat and human primary islet cells followed by analysis of insulin secretion and metabolism. Additionally, miR-375 expression and glucose-induced insulin secretion were compared in islets from rats at different developmental ages. We found that overexpressing of miR-375 in rat and human islet cells blunted insulin secretion in response to glucose but not to α-ketoisocaproate or KCl. Further, miR-375 reduced O2 consumption related to glycolysis and pyruvate metabolism, but not in response to α-ketoisocaproate. Concomitantly, lactate production was augmented suggesting that glucose-derived pyruvate is shifted away from mitochondria. Forced miR-375 expression in rat or human islets increased mRNA levels of pyruvate dehydrogenase kinase-4, but decreased those of pyruvate carboxylase and malate dehydrogenase1. Finally, reduced miR-375 expression was associated with maturation of fetal rat beta cells and acquisition of glucose-induced insulin secretion function. Altogether our findings identify miR-375 as an efficacious regulator of beta cell glucose metabolism and of insulin secretion, and could be determinant to functional beta cell developmental maturation.

scholarly journals Alginate Microencapsulation of Human Islets Does Not Increase Susceptibility to Acute Hypoxia

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
I. K. Hals ◽  
A. M. Rokstad ◽  
B. L. Strand ◽  
J. Oberholzer ◽  
V. Grill
Keyword(s):  
Cell Death ◽  
Oxygen Consumption ◽  
Beta Cell ◽  
Islet Transplantation ◽  
Oxygen Supply ◽  
Acute Hypoxia ◽  
Human Islets ◽  
Culture Conditions ◽  
Positive Finding ◽  
Potential Use

Islet transplantation in diabetes is hampered by the need of life-long immunosuppression. Encapsulation provides partial immunoprotection but could possibly limit oxygen supply, a factor that may enhance hypoxia-induced beta cell death in the early posttransplantation period. Here we tested susceptibility of alginate microencapsulated human islets to experimental hypoxia (0.1–0.3% O2for 8 h, followed by reoxygenation) on viability and functional parameters. Hypoxia reduced viability as measured by MTT by33.8±3.5% in encapsulated and42.9±5.2% in nonencapsulated islets (P<0.2). Nonencapsulated islets released 37.7% (median) more HMGB1 compared to encapsulated islets after hypoxic culture conditions (P<0.001). Glucose-induced insulin release was marginally affected by hypoxia. Basal oxygen consumption was equally reduced in encapsulated and nonencapsulated islets, by22.0±6.1% versus24.8±5.7%. Among 27 tested cytokines/chemokines, hypoxia increased the secretion of IL-6 and IL-8/CXCL8 in both groups of islets, whereas an increase of MCP-1/CCL2 was seen only with nonencapsulated islets.Conclusion. Alginate microencapsulation of human islets does not increase susceptibility to acute hypoxia. This is a positive finding in relation to potential use of encapsulation for islet transplantation.

scholarly journals Silymarin Protects Pancreatic β-Cells against Cytokine-Mediated Toxicity: Implication of c-Jun NH2-Terminal Kinase and Janus Kinase/Signal Transducer and Activator of Transcription Pathways

Endocrinology ◽  
2005 ◽  
Vol 146 (1) ◽  
pp. 175-185 ◽  
Author(s):  
Takeru Matsuda ◽  
Kevin Ferreri ◽  
Ivan Todorov ◽  
Yoshikazu Kuroda ◽  
Craig V. Smith ◽  
...  
Keyword(s):  
Cell Death ◽  
Human Islets ◽  
Janus Kinase ◽  
Time Dependent ◽  
No Production ◽  
Rinm5f Cells ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Ifn Γ

Silymarin is a polyphenolic flavonoid that has a strong antioxidant activity and exhibits anticarcinogenic, antiinflammatory, and cytoprotective effects. Although its hepatoprotective effect has been well documented, the effect of silymarin on pancreatic β-cells is largely unknown. In this study, the effect of silymarin on IL-1β and/or interferon (IFN)-γ-induced β-cell damage was investigated using RINm5F cells and human islets. IL-1β and/or IFN-γ induced cell death in a time-dependent manner in RINm5F cells. The time-dependent increase in cytokine-induced cell death appeared to correlate with the time-dependent nitric oxide (NO) production. Silymarin dose-dependently inhibited both cytokine-induced NO production and cell death in RINm5F cells. Treatment of human islets with a combination of IL-1β and IFN-γ (IL-1β+IFN-γ), for 48 h and 5 d, resulted in an increase of NO production and the impairment of glucose-stimulated insulin secretion, respectively. Silymarin prevented IL-1β+IFN-γ-induced NO production and β-cell dysfunction in human islets. These cytoprotective effects of silymarin appeared to be mediated through the suppression of c-Jun NH2-terminal kinase and Janus kinase/signal transducer and activator of transcription pathways. Our data show a direct cytoprotective effect of silymarin in pancreatic β-cells and suggest that silymarin may be therapeutically beneficial for type 1 diabetes.

scholarly journals The diabetes-linked transcription factor PAX4 promotes β-cell proliferation and survival in rat and human islets

2004 ◽  
Vol 167 (6) ◽  
pp. 1123-1135 ◽  
Author(s):  
Thierry Brun ◽  
Isobel Franklin ◽  
Luc St-Onge ◽  
Anna Biason-Lauber ◽  
Eugene J. Schoenle ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Transcription Factor ◽  
Cell Function ◽  
Fold Increase ◽  
Human Islets ◽  
Mrna Levels ◽  
Phosphatidylinositol 3 Kinase ◽  
Β Cell ◽  
Atp Production ◽  
Adult Rat

The mechanism by which the β-cell transcription factor Pax4 influences cell function/mass was studied in rat and human islets of Langerhans. Pax4 transcripts were detected in adult rat islets, and levels were induced by the mitogens activin A and betacellulin. Wortmannin suppressed betacellulin-induced Pax4 expression, implicating the phosphatidylinositol 3-kinase signaling pathway. Adenoviral overexpression of Pax4 caused a 3.5-fold increase in β-cell proliferation with a concomitant 1.9-, 4-, and 5-fold increase in Bcl-xL (antiapoptotic), c-myc, and Id2 mRNA levels, respectively. Accordingly, Pax4 transactivated the Bcl-xL and c-myc promoters, whereas its diabetes-linked mutant was less efficient. Bcl-xL activity resulted in altered mitochondrial calcium levels and ATP production, explaining impaired glucose-induced insulin secretion in transduced islets. Infection of human islets with an inducible adenoviral Pax4 construct caused proliferation and protection against cytokine-evoked apoptosis, whereas the mutant was less effective. We propose that Pax4 is implicated in β-cell plasticity through the activation of c-myc and potentially protected from apoptosis through Bcl-xL gene expression.

scholarly journals Unbiased profiling of the human proinsulin biosynthetic interaction network reveals a role for peroxiredoxin 4 in proinsulin folding

2020 ◽  
Author(s):  
Ada Admin ◽  
Duc T. Tran ◽  
Anita Pottekat ◽  
Saiful A. Mir ◽  
Salvatore Loguercio ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Beta Cell ◽  
Secretory Pathway ◽  
Cell Function ◽  
Affinity Purification ◽  
Interaction Network ◽  
Human Islets ◽  
Cell Protein ◽  
Insulin Biosynthesis ◽  
Human Proinsulin

The beta cell protein synthetic machinery is dedicated to the production of mature insulin, which requires the proper folding and trafficking of its precursor, proinsulin. The complete network of proteins that mediate proinsulin folding and advancement through the secretory pathway, however, remains poorly defined. Here we used affinity purification and mass spectrometry to identify for the first time, the proinsulin biosynthetic interaction network in human islets. Stringent analysis established a central node of proinsulin interactions with ER folding factors, including chaperones and oxidoreductases, that is remarkably conserved in both sexes and across three ethnicities. The ER-localized peroxiredoxin PRDX4 was identified as a prominent proinsulin interacting protein. In beta cells, gene silencing of PRDX4 rendered proinsulin susceptible to misfolding, particularly in response to oxidative stress, while exogenous PRDX4 improved proinsulin folding. Moreover, proinsulin misfolding induced by oxidative stress or high glucose was accompanied by sulfonylation of PRDX4, a modification known to inactivate peroxiredoxins. Notably, islets from patients with Type II diabetes (T2D) exhibited significantly higher levels of sulfonylated PRDX4 than islets from healthy individuals. In conclusion, we have generated the first reference map of the human proinsulin interactome to identify critical factors controlling insulin biosynthesis, beta cell function, and T2D.

scholarly journals OR14-01 FSTL3 Neutralizing Antibodies Restore Function to Diabetic Mouse and Human Islets: A New Approach for Treating Diabetes

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Alan Schneyer ◽  
Melissa L Brown ◽  
Nolan Meyer ◽  
Alexa Lopez ◽  
Alden Richter
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
High Glucose ◽  
Beta Cell Function ◽  
Neutralizing Antibodies ◽  
Cell Function ◽  
Human Islets ◽  
Extracellular Proteins ◽  
Chow Diet ◽  
Human Diabetes

Abstract Activin, GDF11 and myostatin are structurally related members of the TGFbeta superfamily of growth factors with many biological roles in animal models and humans. Their actions are neutralized by extracellular proteins such as follistatin and follistatin like-3 (FSTL3). We have previously demonstrated that genetic inactivation of Fstl3 results in enlarged pancreatic islets containing increased numbers of beta cells that produce more insulin in response to glucose compared to wild type litter mates. We further discovered that at least some of these new beta cells arise via transdifferentiation from alpha cells. We also demonstrated that functional human islets from normal donors produce very high levels of activin. In contrast, activin biosynthesis is vastly reduced and FSTL3 synthesis is significantly increased in human islets from diabetic donors suggesting that activin is critical for normal insulin production. This was substantiated by direct treatment of human diabetic islets with activin which restored their response to glucose. These observations support the hypothesis that an FSTL3 neutralizing antibody would constitute a novel therapeutic approach to curing diabetes through restoring beta cell function as well as accelerating generation of new beta cells through transdifferentiation. To test this hypothesis, we produced a mouse monoclonal antibody that neutralized hFSTL3 (FP-101), thereby releasing bioactive activin, GDF11, and myostatin. We have now tested this antibody for biological activity in vitro on mouse and human islets. We used islets from high fat diet (HFD) treated mice to model diabetes-inducing effects of obesity as well as 24-hour incubation in hyperglycemic (33 mM glucose) medium to create human islets that lose responsiveness to high glucose as a model for human diabetes. In mouse islets we found that stimulation of normal (chow diet) islets by high glucose produced a stimulation index (SI) of 3.5 that was reduced to 2 in HFD islets. Treatment with activin, FP-101, or a commercial polyclonal antibody to mFSTL3 all increased response of HFD islets to elevated glucose and partially restored SI to normal levels. In human islets, hyperglycemia eliminated the normal (2.5 SI) response to high glucose while activin or FP-101 treatments dose-responsively restored this response. These results demonstrate that anti-FSTL3 therapy can restore function to compromised beta cells from mouse and human diabetes models. The observation that activin has the same action as anti-FSTL3 antibody indicates that FP-101 works through enhancing the activin signaling pathway. Finally, these results demonstrate that the FSTL3-activin pathway is an important regulator of beta cell function in humans as well as mice, supporting further development of this therapy as a diabetes treatment.

scholarly journals The diet-derived short chain fatty acid propionate improves beta-cell function in humans and stimulates insulin secretion from human islets in vitro

2016 ◽  
Vol 19 (2) ◽  
pp. 257-265 ◽  
Author(s):  
Attilio Pingitore ◽  
Edward S. Chambers ◽  
Thomas Hill ◽  
Inmaculada Ruz Maldonado ◽  
Bo Liu ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Fatty Acid ◽  
Beta Cell ◽  
Beta Cell Function ◽  
Short Chain Fatty Acid ◽  
Cell Function ◽  
Human Islets ◽  
Chain Fatty Acid ◽  
Short Chain
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