HIV-1 Tat-mediated protein transduction of Cu,Zn-superoxide dismutase into pancreatic β cells in vitro and in vivo

The regulation of insulin biosynthesis and secretion in pancreatic β-cells is essential for glucose homeostasis in humans. Previous findings point to the highly conserved, ubiquitously expressed serine/threonine kinase CK2 as having a negative regulatory impact on this regulation. In the cell culture model of rat pancreatic β-cells INS-1, insulin secretion is enhanced after CK2 inhibition. This enhancement is preceded by a rise in the cytosolic Ca2+ concentration. Here, we identified the serine residues S2362 and S2364 of the voltage-dependent calcium channel CaV2.1 as targets of CK2 phosphorylation. Furthermore, co-immunoprecipitation experiments revealed that CaV2.1 binds to CK2 in vitro and in vivo. CaV2.1 knockdown experiments showed that the increase in the intracellular Ca2+ concentration, followed by an enhanced insulin secretion upon CK2 inhibition, is due to a Ca2+ influx through CaV2.1 channels. In summary, our results point to a modulating role of CK2 in the CaV2.1-mediated exocytosis of insulin.

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Pannexin-2-deficiency sensitizes pancreatic β-cells to cytokine-induced apoptosis in vitro and impairs glucose tolerance in vivo

Molecular and Cellular Endocrinology ◽

10.1016/j.mce.2017.04.001 ◽

2017 ◽

Vol 448 ◽

pp. 108-121 ◽

Cited By ~ 3

Author(s):

Lukas A. Berchtold ◽

Michela Miani ◽

Thi A. Diep ◽

Andreas N. Madsen ◽

Valentina Cigliola ◽

...

Keyword(s):

Glucose Tolerance ◽

Β Cells ◽

Pancreatic Β Cells ◽

Induced Apoptosis

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Hyperinsulinemia promotes HMGB1 release leading to inflammation induced systemic insulin resistance: An interplay between pancreatic beta-cell and peripheral organs

10.1101/705103 ◽

2019 ◽

Author(s):

Abhinav Choubey ◽

Aditya K Kar ◽

Khyati Girdhar ◽

Tandrika Chattopadhyay ◽

Surbhi Dogra ◽

...

Keyword(s):

Insulin Resistance ◽

Pancreatic Beta Cell ◽

Underlying Mechanism ◽

Β Cells ◽

Pancreatic Β Cells ◽

Extracellular Milieu ◽

Peripheral Organs ◽

Systemic Insulin Resistance

SummaryInsulin resistance results from several pathophysiologic mechanisms, including chronic tissue inflammation and defective insulin signaling. Pancreatic β-cells hypersecretion (hyperinsulinemia), is a central hallmark of peripheral insulin resistance. However, the underlying mechanism by which hyperinsulinemia perpetuates towards the development of insulin resistance remains unclear and is still a bigger therapeutic challenge. Here, we found hyperinsulinemia triggers inflammation and insulin resistance by stimulating TLR4-driven inflammatory cascades. We show that hyperinsulinemia activates the TLR4 signaling through HMGB1, an endogenous TLR4 ligand emanating from hyperinsulinemia exposed immune cells and peripheral organs like adipose tissue and liver. Further, our observation suggests hyperinsulinemia ensuring hyperacetylation, nuclear-to-cytoplasmic shuttling and release of HMGB1 into the extracellular space. HMGB1 was also found to be elevated in serum of T2DM patients. We found that extracellular HMGB1 plays a crucial role to promote proinflammatory responses and provokes systemic insulin resistance. Importantly, in-vitro and in-vivo treatment with naltrexone, a TLR4 antagonist led to an anti-inflammatory phenotype with protection from hyperinsulinemia mediated insulin resistance. In-vitro treatment with naltrexone directly enhanced SIRT1 activity, blocked the release of HMGB1 into extracellular milieu, suppressed release of proinflammatory cytokines and ultimately led to insulin-sensitizing effects. These observations elucidate a regulatory network between pancreatic β-cells, macrophage and hepatocytes and assign an unexpected role of TLR4 - HMGB1 signaling axis in hyperinsulinemia mediated systemic insulin resistance.Graphical Abstract

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Downregulation of lncRNA TUG1 Affects Apoptosis and Insulin Secretion in Mouse Pancreatic β Cells

Cellular Physiology and Biochemistry ◽

10.1159/000373999 ◽

2015 ◽

Vol 35 (5) ◽

pp. 1892-1904 ◽

Cited By ~ 68

Author(s):

Dan-dan Yin ◽

Er-bao Zhang ◽

Liang-hui You ◽

Ning Wang ◽

Lin-tao Wang ◽

...

Keyword(s):

Insulin Secretion ◽

Cell Function ◽

Annexin V ◽

Pancreatic Tissue ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Lncrna Tug1

Background: Increasing evidence indicates that long noncoding RNAs (IncRNAs) perform specific biological functions in diverse processes. Recent studies have reported that IncRNAs may be involved in β cell function. The aim of this study was to characterize the role of IncRNA TUG1 in mouse pancreatic β cell functioning both in vitro and in vivo. Methods: qRT-PCR analyses were performed to detect the expression of lncRNA TUG1 in different tissues. RNAi, MTT, TUNEL and Annexin V-FITC assays and western blot, GSIS, ELISA and immunochemistry analyses were performed to detect the effect of lncRNA TUG1 on cell apoptosis and insulin secretion in vitro and in vivo. Results: lncRNA TUG1 was highly expressed in pancreatic tissue compared with other organ tissues, and expression was dynamically regulated by glucose in Nit-1 cells. Knockdown of lncRNA TUG1 expression resulted in an increased apoptosis ratio and decreased insulin secretion in β cells both in vitro and in vivo . Immunochemistry analyses suggested decreased relative islet area after treatment with lncRNA TUG1 siRNA. Conclusion: Downregulation of lncRNA TUG1 expression affected apoptosis and insulin secretion in pancreatic β cells in vitro and in vivo. lncRNA TUG1 may represent a factor that regulates the function of pancreatic β cells.

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Protection of pancreatic β-cells by exendin-4 may involve the reduction of endoplasmic reticulum stress; in vivo and in vitro studies

Journal of Endocrinology ◽

10.1677/joe-06-0148 ◽

2007 ◽

Vol 193 (1) ◽

pp. 65-74 ◽

Cited By ~ 70

Author(s):

Shin Tsunekawa ◽

Naoki Yamamoto ◽

Katsura Tsukamoto ◽

Yuji Itoh ◽

Yukiko Kaneko ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Er Stress ◽

Islet Cells ◽

Binding Protein ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells

The aim of this study was to investigate the in vivo and in vitro effects of exendin-4, a potent glucagon-like peptide 1 agonist, on the protection of the pancreatic β-cells against their cell death. In in vivo experiments, we used β-cell-specific calmodulin-overexpressing mice where massive apoptosis takes place in their β-cells, and we examined the effects of chronic treatment with exendin-4. Chronic and s.c. administration of exendin-4 reduced hyperglycemia. The treatment caused significant increases of the insulin contents of the pancreas and islets, and retained the insulin-positive area. Dispersed transgenic islet cells lived only shortly, and several endoplasmic reticulum (ER) stress-related molecules such as immunoglobulin-binding protein (Bip), inositol-requiring enzyme-1α, X-box-binding protein-1 (XBP-1), RNA-activated protein kinase-like endoplasmic reticulum kinase, activating transcription factor-4, and C/EBP-homologous protein (CHOP) were more expressed in the transgenic islets. We also found that the spliced form of XBP-1, a marker of ER stress, was also increased in β-cell-specific calmodulin-overexpressing transgenic islets. In the quantitative real-time PCR analyses, the expression levels of Bip and CHOP were reduced in the islets from the transgenic mice treated with exendin-4. These findings suggest that excess of ER stress occurs in the transgenic β-cells, and the suppression of ER stress and resultant protection against cell death may be involved in the anti-diabetic effects of exendin-4.

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Targeted delivery of antisense oligonucleotides to pancreatic β-cells

Science Advances ◽

10.1126/sciadv.aat3386 ◽

2018 ◽

Vol 4 (10) ◽

pp. eaat3386 ◽

Cited By ~ 41

Author(s):

C. Ämmälä ◽

W. J. Drury ◽

L. Knerr ◽

I. Ahlstedt ◽

P. Stillemark-Billton ◽

...

Keyword(s):

Targeted Delivery ◽

Target Genes ◽

Cell Types ◽

Cell Type Specificity ◽

Β Cells ◽

Pancreatic Β Cells ◽

Glucagon Like Peptide 1 ◽

Novel Therapeutic

Antisense oligonucleotide (ASO) silencing of the expression of disease-associated genes is an attractive novel therapeutic approach, but treatments are limited by the ability to deliver ASOs to cells and tissues. Following systemic administration, ASOs preferentially accumulate in liver and kidney. Among the cell types refractory to ASO uptake is the pancreatic insulin-secreting β-cell. Here, we show that conjugation of ASOs to a ligand of the glucagon-like peptide-1 receptor (GLP1R) can productively deliver ASO cargo to pancreatic β-cells both in vitro and in vivo. Ligand-conjugated ASOs silenced target genes in pancreatic islets at doses that did not affect target gene expression in liver or other tissues, indicating enhanced tissue and cell type specificity. This finding has potential to broaden the use of ASO technology, opening up novel therapeutic opportunities, and presents an innovative approach for targeted delivery of ASOs to additional cell types.

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CK2 acts as a potent negative regulator of receptor-mediated insulin release in vitro and in vivo

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1519430112 ◽

2015 ◽

Vol 112 (49) ◽

pp. E6818-E6824 ◽

Cited By ~ 17

Author(s):

Mario Rossi ◽

Inigo Ruiz de Azua ◽

Luiz F. Barella ◽

Wataru Sakamoto ◽

Lu Zhu ◽

...

Keyword(s):

Insulin Release ◽

Cell Activity ◽

Negative Regulator ◽

Whole Body ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Release In Vitro

G protein-coupled receptors (GPCRs) regulate virtually all physiological functions including the release of insulin from pancreatic β-cells. β-Cell M3 muscarinic receptors (M3Rs) are known to play an essential role in facilitating insulin release and maintaining proper whole-body glucose homeostasis. As is the case with other GPCRs, M3R activity is regulated by phosphorylation by various kinases, including GPCR kinases and casein kinase 2 (CK2). At present, it remains unknown which of these various kinases are physiologically relevant for the regulation of β-cell activity. In the present study, we demonstrate that inhibition of CK2 in pancreatic β-cells, knockdown of CK2α expression, or genetic deletion of CK2α in β-cells of mutant mice selectively augmented M3R-stimulated insulin release in vitro and in vivo. In vitro studies showed that this effect was associated with an M3R-mediated increase in intracellular calcium levels. Treatment of mouse pancreatic islets with CX4945, a highly selective CK2 inhibitor, greatly reduced agonist-induced phosphorylation of β-cell M3Rs, indicative of CK2-mediated M3R phosphorylation. We also showed that inhibition of CK2 greatly enhanced M3R-stimulated insulin secretion in human islets. Finally, CX4945 treatment protected mice against diet-induced hyperglycemia and glucose intolerance in an M3R-dependent fashion. Our data demonstrate, for the first time to our knowledge, the physiological relevance of CK2 phosphorylation of a GPCR and suggest the novel concept that kinases acting on β-cell GPCRs may represent novel therapeutic targets.

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