scholarly journals Insulin secretion stimulated by l-arginine and its metabolite l-ornithine depends on Gαi2

2014 ◽  
Vol 307 (9) ◽  
pp. E800-E812 ◽  
Author(s):  
Veronika Leiss ◽  
Katarina Flockerzie ◽  
Ana Novakovic ◽  
Michaela Rath ◽  
Annika Schönsiegel ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Amino Acid ◽  
Metabolic Phenotype ◽  
Β Cells ◽  
Β Cell ◽  
Glucose Challenge ◽  
Intracellular Ca ◽  
Plasma Insulin Levels

Bordetella pertussis toxin (PTx), also known as islet-activating protein, induces insulin secretion by ADP-ribosylation of inhibitory G proteins. PTx-induced insulin secretion may result either from inactivation of Gαo proteins or from combined inactivation of Gαo, Gαi1, Gαi2, and Gαi3 isoforms. However, the specific role of Gαi2 in pancreatic β-cells still remains unknown. In global (Gαi2−/−) and β-cell-specific (Gαi2βcko) gene-targeted Gαi2 mouse models, we studied glucose homeostasis and islet functions. Insulin secretion experiments and intracellular Ca2+ measurements were used to characterize Gαi2 function in vitro. Gαi2−/− and Gαi2βcko mice showed an unexpected metabolic phenotype, i.e., significantly lower plasma insulin levels upon intraperitoneal glucose challenge in Gαi2−/− and Gαi2βcko mice, whereas plasma glucose concentrations were unchanged in Gαi2−/− but significantly increased in Gαi2βcko mice. These findings indicate a novel albeit unexpected role for Gαi2 in the expression, turnover, and/or release of insulin from islets. Detection of insulin secretion in isolated islets did not show differences in response to high (16 mM) glucose concentrations between control and β-cell-specific Gαi2-deficient mice. In contrast, the two- to threefold increase in insulin secretion evoked by l-arginine or l-ornithine (in the presence of 16 mM glucose) was significantly reduced in islets lacking Gαi2. In accord with a reduced level of insulin secretion, intracellular calcium concentrations induced by the agonistic amino acid l-arginine did not reach control levels in β-cells. The presented analysis of gene-targeted mice provides novel insights in the role of β-cell Gαi2 showing that amino acid-induced insulin-release depends on Gαi2.

scholarly journals Regulation of Insulin Secretion and β-Cell Mass by Activating Signal Cointegrator 2

2006 ◽  
Vol 26 (12) ◽  
pp. 4553-4563 ◽  
Author(s):  
Seon-Yong Yeom ◽  
Geun Hyang Kim ◽  
Chan Hee Kim ◽  
Heun Don Jung ◽  
So-Yeon Kim ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Endocrine Cells ◽  
Potential Role ◽  
Cell Mass ◽  
Dominant Negative ◽  
Transcriptional Coactivator ◽  
Β Cells ◽  
Β Cell ◽  
Islet Mass

ABSTRACT Activating signal cointegrator 2 (ASC-2) is a transcriptional coactivator of many nuclear receptors (NRs) and other transcription factors and contains two NR-interacting LXXLL motifs (NR boxes). In the pancreas, ASC-2 is expressed only in the endocrine cells of the islets of Langerhans, but not in the exocrine cells. Thus, we examined the potential role of ASC-2 in insulin secretion from pancreatic β-cells. Overexpressed ASC-2 increased glucose-elicited insulin secretion, whereas insulin secretion was decreased in islets from ASC-2+/− mice. DN1 and DN2 are two dominant-negative fragments of ASC-2 that contain NR boxes 1 and 2, respectively, and block the interactions of cognate NRs with the endogenous ASC-2. Primary rat islets ectopically expressing DN1 or DN2 exhibited decreased insulin secretion. Furthermore, relative to the wild type, ASC-2+/− mice showed reduced islet mass and number, which correlated with increased apoptosis and decreased proliferation of ASC-2+/− islets. These results suggest that ASC-2 regulates insulin secretion and β-cell survival and that the regulatory role of ASC-2 in insulin secretion appears to involve, at least in part, its interaction with NRs via its two NR boxes.

scholarly journals Deficiency of VCP-Interacting Membrane Selenoprotein (VIMP) Leads to G1 Cell Cycle Arrest and Cell Death in MIN6 Insulinoma Cells

2018 ◽  
Vol 51 (5) ◽  
pp. 2185-2197 ◽  
Author(s):  
Lili Men ◽  
Juan Sun ◽  
Decheng Ren
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Insulin Secretion ◽  
Cell Apoptosis ◽  
Β Cells ◽  
Β Cell ◽  
Cycle Arrest ◽  
G1 Cell Cycle Arrest ◽  
Insulinoma Cells

Background/Aims: VCP-interacting membrane selenoprotein (VIMP), an ER resident selenoprotein, is highly expressed in β-cells, however, the role of VIMP in β-cells has not been characterized. In this study, we studied the relationship between VIMP deficiency and β-cell survival in MIN6 insulinoma cells. Methods: To determine the role of VIMP in β-cells, lentiviral VIMP shRNAs were used to knock down (KD) expression of VIMP in MIN6 cells. Cell death was quantified by propidium iodide (PI) staining followed by flow cytometric analyses using a FACS Caliber and FlowJo software. Cell apoptosis and proliferation were determined by TUNEL assay and Ki67 staining, respectively. Cell cycle was analyzed after PI staining. Results: The results show that 1) VIMP suppression induces β-cell apoptosis, which is associated with a decrease in Bcl-xL, and the β-cell apoptosis induced by VIMP suppression can be inhibited by overexpression of Bcl-xL; 2) VIMP knockdown (KD) decreases cell proliferation and G1 cell cycle arrest by accumulating p27 and decreasing E2F1; 3) VIMP KD suppresses unfolded protein response (UPR) activation by regulating the IRE1α and PERK pathways; 4) VIMP KD increases insulin secretion. Conclusion: These results suggest that VIMP may function as a novel regulator to modulate β-cell survival, proliferation, cell cycle, UPR and insulin secretion in MIN6 cells.

Modeling of Ca2+ flux in pancreatic β-cells: role of the plasma membrane and intracellular stores

2003 ◽  
Vol 285 (1) ◽  
pp. E138-E154 ◽  
Author(s):  
Leonid E. Fridlyand ◽  
Natalia Tamarina ◽  
Louis H. Philipson
Keyword(s):  
Plasma Membrane ◽  
Calcium Oscillations ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Ionic Flux ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Uptake And Release

We have developed a detailed mathematical model of ionic flux in β-cells that includes the most essential channels and pumps in the plasma membrane. This model is coupled to equations describing Ca2+, inositol 1,4,5-trisphosphate (IP3), ATP, and Na+ homeostasis, including the uptake and release of Ca2+ by the endoplasmic reticulum (ER). In our model, metabolically derived ATP activates inward Ca2+ flux by regulation of ATP-sensitive K+ channels and depolarization of the plasma membrane. Results from the simulations support the hypothesis that intracellular Na+ and Ca2+ in the ER can be the main variables driving both fast (2–7 osc/min) and slow intracellular Ca2+ concentration oscillations (0.3–0.9 osc/min) and that the effect of IP3 on Ca2+ leak from the ER contributes to the pattern of slow calcium oscillations. Simulations also show that filling the ER Ca2+ stores leads to faster electrical bursting and Ca2+ oscillations. Specific Ca2+ oscillations in isolated β-cell lines can also be simulated.

scholarly journals β cell-specific deletion of HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase causes overt diabetes due to reduction of β cell mass and impaired insulin secretion

2020 ◽  
Author(s):  
Ada Admin ◽  
Shoko Takei ◽  
Shuichi Nagashima ◽  
Akihito Takei ◽  
Daisuke Yamamuro ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Coenzyme A ◽  
Cell Mass ◽  
Bzip Transcription Factor ◽  
Β Cells ◽  
Β Cell ◽  
Embryonic Pancreas ◽  
Endocrine Progenitors ◽  
Coenzyme A Reductase

Inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), statins, which are used to prevent cardiovascular diseases, are associated with a modest increase in the risk of new-onset diabetes mellitus. To investigate the role of HMGCR in the development of β cells and glucose homeostasis, we deleted <i>Hmgcr</i> in a β cell-specific manner by using the Cre-loxP technique. Mice lacking <i>Hmgcr</i> in β cells (β-KO) exhibited hypoinsulinemic hyperglycemia as early as postnatal day 9 (P9) due to decreases in both β cell mass and insulin secretion. Ki67 positive cells were reduced in β-KO mice at P9, thus β cell mass reduction was caused by proliferation disorder immediately after birth. The mRNA expression of <i>neurogenin3 (Ngn3)</i>, which is transiently expressed in endocrine progenitors of the embryonic pancreas, was maintained despite a striking reduction in the expression of β cell-associated genes, such as <i>insulin</i>, <i>Pancreatic and duodenal homeobox 1</i> <i>(Pdx1)</i> and <i>MAF BZIP transcription factor A (</i><i>Mafa)</i> in the islets from β-KO mice. Histological analyses revealed dysmorphic islets with markedly reduced numbers of β cells, some of which were also positive for glucagon. In conclusion, HMGCR plays critical roles not only in insulin secretion but also in the development of β cells in mice.

scholarly journals Diabetic Kinome Inhibitors—A New Opportunity for β-Cells Restoration

2021 ◽  
Vol 22 (16) ◽  
pp. 9083
Author(s):  
Barbara Pucelik ◽  
Agata Barzowska ◽  
Janusz M. Dąbrowski ◽  
Anna Czarna
Keyword(s):  
High Throughput Screening ◽  
Human Life ◽  
Treatment Strategies ◽  
Current Treatment ◽  
Binding Modes ◽  
Β Cells ◽  
Β Cell ◽  
And Function

Diabetes, and several diseases related to diabetes, including cancer, cardiovascular diseases and neurological disorders, represent one of the major ongoing threats to human life, becoming a true pandemic of the 21st century. Current treatment strategies for diabetes mainly involve promoting β-cell differentiation, and one of the most widely studied targets for β-cell regeneration is DYRK1A kinase, a member of the DYRK family. DYRK1A has been characterized as a key regulator of cell growth, differentiation, and signal transduction in various organisms, while further roles and substrates are the subjects of extensive investigation. The targets of interest in this review are implicated in the regulation of β-cells through DYRK1A inhibition—through driving their transition from highly inefficient and death-prone populations into efficient and sufficient precursors of islet regeneration. Increasing evidence for the role of DYRK1A in diabetes progression and β-cell proliferation expands the potential for pharmaceutical applications of DYRK1A inhibitors. The variety of new compounds and binding modes, determined by crystal structure and in vitro studies, may lead to new strategies for diabetes treatment. This review provides recent insights into the initial self-activation of DYRK1A by tyrosine autophosphorylation. Moreover, the importance of developing novel DYRK1A inhibitors and their implications for the treatment of diabetes are thoroughly discussed. The evolving understanding of DYRK kinase structure and function and emerging high-throughput screening technologies have been described. As a final point of this work, we intend to promote the term “diabetic kinome” as part of scientific terminology to emphasize the role of the synergistic action of multiple kinases in governing the molecular processes that underlie this particular group of diseases.

scholarly journals Local activation of focal adhesion kinase orchestrates the positioning of presynaptic scaffold proteins and Ca2+ channel function to control glucose dependent insulin secretion.

2021 ◽  
Author(s):  
Nicole Hallahan ◽  
Kylie Deng ◽  
Dillon Jevon ◽  
Krish Kumar ◽  
Jason Tong ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Focal Adhesion Kinase ◽  
Focal Adhesion ◽  
Cell Structure ◽  
Scaffold Proteins ◽  
Β Cells ◽  
Β Cell ◽  
Local Activation ◽  
Pancreatic Slice

A developing understanding suggests that spatial compartmentalisation of components the glucose stimulus?secretion pathway in pancreatic β cells are critical in controlling insulin secretion. To investigate the mechanisms, we have developed live-cell sub-cellular imaging methods using the organotypic pancreatic slice. We demonstrate that the organotypic pancreatic slice, when compared with isolated islets, preserves intact β cell structure, and enhances glucose dependent Ca2+ responses and insulin secretion. Using the slice technique, we have discovered the essential role of local activation of integrins and the downstream component, focal adhesion kinase, in regulating β cells. Integrins and focal adhesion kinase are exclusively activated at the β cell capillary interface and using in situ and in vitro models we show their activation both positions presynaptic scaffold proteins, like ELKS and liprin, and regulates glucose dependent Ca2+ responses and insulin secretion. We conclude that focal adhesion kinase orchestrates the final steps of glucose dependent insulin secretion within the restricted domain where β cells contact the islet capillaries.

scholarly journals Perilipin2 down-regulation in β cells impairs insulin secretion under nutritional stress and damages mitochondria

2020 ◽  
Author(s):  
Akansha Mishra ◽  
Siming Liu ◽  
Joseph Promes ◽  
Mikako Harata ◽  
William Sivitz ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Cell Function ◽  
Islet Cells ◽  
Cell Metabolism ◽  
Nutritional Stress ◽  
Β Cells ◽  
Β Cell ◽  
Down Regulation

Perilipin 2 (PLIN2) is the lipid droplet (LD) protein in β cells that increases under nutritional stress. Down-regulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects β cell function under nutritional stress, PLIN2 was down-regulated in mouse β cells, INS1 cells, and human islet cells. β cell specific deletion of PLIN2 in mice on a high fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Down-regulation of PLIN2 in INS1 cells blunted GSIS after 24 h incubation with 0.2 mM palmitic acids. Down-regulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Down-regulation of PLIN2 decreased specific OXPHOS proteins in all three models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2 deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in β cells have an important role in preserving insulin secretion, β cell metabolism and mitochondrial function under nutritional stress.

scholarly journals Emerging role of testosterone in pancreatic β cell function and insulin secretion

2019 ◽  
Vol 240 (3) ◽  
pp. R97-R105 ◽  
Author(s):  
Weiwei Xu ◽  
Jamie Morford ◽  
Franck Mauvais-Jarvis
Keyword(s):  
Insulin Secretion ◽  
Metabolic Regulation ◽  
Cell Function ◽  
Visceral Obesity ◽  
Β Cells ◽  
Β Cell ◽  
Β Cell Function ◽  
Glucagon Like Peptide 1 ◽  
Glucose Stimulated Insulin Secretion

One of the most sexually dimorphic aspects of metabolic regulation is the bidirectional modulation of glucose homeostasis by testosterone in male and females. Severe testosterone deficiency predisposes men to type 2 diabetes (T2D), while in contrast, androgen excess predisposes women to hyperglycemia. The role of androgen deficiency and excess in promoting visceral obesity and insulin resistance in men and women respectively is well established. However, although it is established that hyperglycemia requires β cell dysfunction to develop, the role of testosterone in β cell function is less understood. This review discusses recent evidence that the androgen receptor (AR) is present in male and female β cells. In males, testosterone action on AR in β cells enhances glucose-stimulated insulin secretion by potentiating the insulinotropic action of glucagon-like peptide-1. In females, excess testosterone action via AR in β cells promotes insulin hypersecretion leading to oxidative injury, which in turn predisposes to T2D.

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

2015 ◽  
Vol 35 (5) ◽  
pp. 1892-1904 ◽  
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.

scholarly journals Metformin Preserves β-Cell Compensation in Insulin Secretion and Mass Expansion in Prediabetic Nile Rats

2021 ◽  
Vol 22 (1) ◽  
pp. 421
Author(s):  
Hui Huang ◽  
Bradi R. Lorenz ◽  
Paula Horn Zelmanovitz ◽  
Catherine B. Chan
Keyword(s):  
Insulin Secretion ◽  
Cell Function ◽  
Cell Mass ◽  
Metformin Treatment ◽  
Β Cells ◽  
Β Cell ◽  
Β Cell Function ◽  
Glucose Output ◽  
Mass Expansion

Prediabetes is a high-risk condition for type 2 diabetes (T2D). Pancreatic β-cells adapt to impaired glucose regulation in prediabetes by increasing insulin secretion and β-cell mass expansion. In people with prediabetes, metformin has been shown to prevent prediabetes conversion to diabetes. However, emerging evidence indicates that metformin has negative effects on β-cell function and survival. Our previous study established the Nile rat (NR) as a model for prediabetes, recapitulating characteristics of human β-cell compensation in function and mass expansion. In this study, we investigated the action of metformin on β-cells in vivo and in vitro. A 7-week metformin treatment improved glucose tolerance by reducing hepatic glucose output and enhancing insulin secretion. Although high-dose metformin inhibited β-cell glucose-stimulated insulin secretion in vitro, stimulation of β-cell insulin secretion was preserved in metformin-treated NRs via an indirect mechanism. Moreover, β-cells in NRs receiving metformin exhibited increased endoplasmic reticulum (ER) chaperones and alleviated apoptotic unfold protein response (UPR) without changes in the expression of cell identity genes. Additionally, metformin did not suppress β-cell mass compensation or proliferation. Taken together, despite the conflicting role indicated by in vitro studies, administration of metformin does not exert a negative effect on β-cell function or cell mass and, instead, early metformin treatment may help protect β-cells from exhaustion and decompensation.

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