scholarly journals Slow oscillations of KATP conductance in mouse pancreatic islets provide support for electrical bursting driven by metabolic oscillations

2013 ◽  
Vol 305 (7) ◽  
pp. E805-E817 ◽  
Author(s):  
Jianhua Ren ◽  
Arthur Sherman ◽  
Richard Bertram ◽  
Paulette B. Goforth ◽  
Craig S. Nunemaker ◽  
...  
Keyword(s):  
Pancreatic Islets ◽  
Membrane Conductance ◽  
Calcium Oscillations ◽  
Free Calcium ◽  
Β Cells ◽  
Patch Clamp Technique ◽  
Slow Oscillations ◽  
Total Conductance ◽  
Mouse Pancreatic Islets ◽  
Metabolic Oscillations

We used the patch clamp technique in situ to test the hypothesis that slow oscillations in metabolism mediate slow electrical oscillations in mouse pancreatic islets by causing oscillations in KATP channel activity. Total conductance was measured over the course of slow bursting oscillations in surface β-cells of islets exposed to 11.1 mM glucose by either switching from current clamp to voltage clamp at different phases of the bursting cycle or by clamping the cells to −60 mV and running two-second voltage ramps from −120 to −50 mV every 20 s. The membrane conductance, calculated from the slopes of the ramp current-voltage curves, oscillated and was larger during the silent phase than during the active phase of the burst. The ramp conductance was sensitive to diazoxide, and the oscillatory component was reduced by sulfonylureas or by lowering extracellular glucose to 2.8 mM, suggesting that the oscillatory total conductance is due to oscillatory KATP channel conductance. We demonstrate that these results are consistent with the Dual Oscillator model, in which glycolytic oscillations drive slow electrical bursting, but not with other models in which metabolic oscillations are secondary to calcium oscillations. The simulations also confirm that oscillations in membrane conductance can be well estimated from measurements of slope conductance and distinguished from gap junction conductance. Furthermore, the oscillatory conductance was blocked by tolbutamide in isolated β-cells. The data, combined with insights from mathematical models, support a mechanism of slow (∼5 min) bursting driven by oscillations in metabolism, rather than by oscillations in the intracellular free calcium concentration.

scholarly journals Piezo1 channel activation mimics high glucose as a stimulator of insulin release

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Vijayalakshmi Deivasikamani ◽  
Savitha Dhayalan ◽  
Yilizila Abudushalamu ◽  
Romana Mughal ◽  
Asjad Visnagri ◽  
...  
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Cell Lines ◽  
High Glucose ◽  
Mammalian Cells ◽  
Cell Swelling ◽  
Β Cells ◽  
Β Cell ◽  
Intracellular Ca ◽  
Mouse Pancreatic Islets

AbstractGlucose and hypotonicity induced cell swelling stimulate insulin release from pancreatic β-cells but the mechanisms are poorly understood. Recently, Piezo1 was identified as a mechanically-activated nonselective Ca2+ permeable cationic channel in a range of mammalian cells. As cell swelling induced insulin release could be through stimulation of Ca2+ permeable stretch activated channels, we hypothesised a role for Piezo1 in cell swelling induced insulin release. Two rat β-cell lines (INS-1 and BRIN-BD11) and freshly-isolated mouse pancreatic islets were studied. Intracellular Ca2+ measurements were performed using the fura-2 Ca2+ indicator dye and ionic current was recorded by whole cell patch-clamp. Piezo1 agonist Yoda1, a competitive antagonist of Yoda1 (Dooku1) and an inactive analogue of Yoda1 (2e) were used as chemical probes. Piezo1 mRNA and insulin secretion were measured by RT-PCR and ELISA respectively. Piezo1 mRNA was detected in both β-cell lines and mouse islets. Yoda1 evoked Ca2+ entry was inhibited by Yoda1 antagonist Dooku1 as well as other Piezo1 inhibitors gadolinium and ruthenium red, and not mimicked by 2e. Yoda1, but not 2e, stimulated Dooku1-sensitive insulin release from β-cells and pancreatic islets. Hypotonicity and high glucose increased intracellular Ca2+ and enhanced Yoda1 Ca2+ influx responses. Yoda1 and hypotonicity induced insulin release were significantly inhibited by Piezo1 specific siRNA. Pancreatic islets from mice with haploinsufficiency of Piezo1 released less insulin upon exposure to Yoda1. The data show that Piezo1 channel agonist induces insulin release from β-cell lines and mouse pancreatic islets suggesting a role for Piezo1 in cell swelling induced insulin release. Hence Piezo1 agonists have the potential to be used as enhancers of insulin release.

scholarly journals Rapid non-genomic regulation of Ca2+ signals and insulin secretion by PPARα ligands in mouse pancreatic islets of Langerhans

2008 ◽  
Vol 200 (2) ◽  
pp. 127-138 ◽  
Author(s):  
Ana B Ropero ◽  
Pablo Juan-Picó ◽  
Alex Rafacho ◽  
Esther Fuentes ◽  
F Javier Bermúdez-Silva ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Islets Of Langerhans ◽  
Mitochondrial Function ◽  
Lipoprotein Metabolism ◽  
Calcium Oscillations ◽  
Ros Generation ◽  
Β Cells ◽  
Pancreatic Islets Of Langerhans ◽  
Mouse Pancreatic Islets

PPARα is a ligand-activated transcription factor belonging to the nuclear receptor superfamily. PPARα is involved in the regulation of in vivo triglyceride levels, presumably through its effects on fatty acid and lipoprotein metabolism. Some nuclear receptors have been involved in rapid effects mediated by non-genomic mechanisms. In this paper, we report the rapid non-genomic effects of PPARα ligands on the intracellular calcium concentration ([Ca2+]i), mitochondrial function, reactive oxygen species (ROS) generation, and secretion of insulin in freshly isolated mouse islets of Langerhans. The hypolipidemic fibrate PPARα agonist WY-14 643 decreased the glucose-induced calcium oscillations in intact islets. This effect was mimicked by the synthetic agonist GW7647 and the endogenous agonist oleylethanolamide. The WY-14 643 action was rapid in onset (5 min) and was still produced in the presence of protein and mRNA synthesis inhibitors, cycloheximide, and actinomycin-d. This suggests that it is independent of gene transcription. In addition, WY-14 623 impaired mitochondrial function, increased ROS formation and decreased insulin release. PPARα is present in β-cells, mainly in the cytosol and nucleus, with a small subpopulation localized in the plasma membrane. However, the presence of the PPARα ligand effects in mice bearing a disrupted Pparα gene raises the possibility that the rapid effects of the agonists in pancreatic β-cells are independent of the receptor. We conclude that PPARα agonists produce a decrease in glucose-induced [Ca2+]i signals and insulin secretion in β-cells through a rapid, non-genomic mechanism.

Sustained exposure of toxically damaged mouse pancreatic islets to high glucose does not increase β-cell dysfunction

1989 ◽  
Vol 123 (1) ◽  
pp. 47-51 ◽  
Author(s):  
D. L. Eizirik ◽  
S. Sandler
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
High Glucose ◽  
Β Cells ◽  
Β Cell ◽  
Glucose Stimulation ◽  
Cell Dysfunction ◽  
Mouse Pancreatic Islets ◽  
Insulin Secretory Response

ABSTRACT The aim of this study was to clarify whether prolonged in-vitro exposure of either normal or damaged β cells to a high glucose environment can be toxic to these cells. For this purpose NMRI mice were injected intravenously with a diabetogenic dose of streptozotocin (SZ; 160 mg/kg) or vehicle alone (controls). Their islets were isolated 15 min after the injection and subsequently maintained in culture for 21 days in the presence of 11·1 or 28 mmol glucose/l. After this period, during acute glucose stimulation, the control islets showed a marked increase in their insulin release in response to a high glucose stimulus. In the SZ-exposed islets there was a decrease in DNA and insulin contents, and a deficient insulin secretory response to glucose. However, in the SZ-damaged islets as well as in the control islets, culture with 28 mmol glucose/l compared with 11·1 mmol glucose/l did not impair islet retrieval after culture, islet DNA content or glucose-induced insulin release. Thus, the degree of damage was similar in the SZ-treated islets cultured at the two concentrations of glucose. These results suggest that glucose is not toxic to normal or damaged mouse pancreatic islets over a prolonged period in tissue culture. Journal of Endocrinology (1989) 123, 47–51

scholarly journals GPRC6A Mediates the Effects of l-Arginine on Insulin Secretion in Mouse Pancreatic Islets

Endocrinology ◽  
2012 ◽  
Vol 153 (10) ◽  
pp. 4608-4615 ◽  
Author(s):  
Min Pi ◽  
Yunpeng Wu ◽  
Nataliya I Lenchik ◽  
Ivan Gerling ◽  
L. Darryl Quarles
Keyword(s):  
Insulin Secretion ◽  
Pancreatic Islets ◽  
Ex Vivo ◽  
Β Cells ◽  
Direct Role ◽  
Mouse Pancreatic Islets ◽  
Islet Size ◽  
G Protein Coupled ◽  
Stimulation Of

Abstract l-Arginine (l-Arg) is an insulin secretagogue, but the molecular mechanism whereby it stimulates insulin secretion from β-cells is not known. The possibility that l-Arg regulates insulin secretion through a G protein-coupled receptor (GPCR)-mediated mechanism is suggested by the high expression of the nutrient receptor GPCR family C group 6 member A (GPRC6A) in the pancreas and TC-6 β-cells and the finding that Gprc6a−/]minus] mice have abnormalities in glucose homeostasis. To test the direct role of GPRC6A in regulating insulin secretion, we evaluated the response of pancreatic islets derived from Gprc6a−/]minus] mice to l-Arg. We found that the islet size and insulin content were decreased in pancreatic islets from Gprac6a−/]minus] mice. These alterations were selective for β-cells, because there were no abnormalities in serum glucagon levels or glucagon content of islets derived from Gprac6a−/]minus] mice. Significant reduction was observed in both the pancreatic ERK response to l-Arg administration to Gprc6a−/]minus] mice in vivo and l-Arg-induced insulin secretion and production ex vivo in islets isolated from Gprc6a−/]minus] mice. l-Arg stimulation of cAMP accumulation in isolated islets isolated from Gprc6a−/]minus] mice was also diminished. These findings suggest that l-Arg stimulation of insulin secretion in β-cells is mediated, at least in part, through GPRC6A activation of cAMP pathways.

Synchronization and entrainment of cytoplasmic Ca2+ oscillations in cell clusters prepared from single or multiple mouse pancreatic islets

2004 ◽  
Vol 287 (2) ◽  
pp. E340-E347 ◽  
Author(s):  
Milos Zarkovic ◽  
Jean-Claude Henquin
Keyword(s):  
Pancreatic Islets ◽  
Islet Cells ◽  
Single Pulse ◽  
External Signal ◽  
Β Cells ◽  
Mouse Islet ◽  
Mouse Pancreatic Islets ◽  
The Difference ◽  
External Signals ◽  
Sufficient Strength

In contrast to pancreatic islets, isolated β-cells stimulated by glucose display irregular and asynchronous increases in cytoplasmic Ca2+ concentration ([Ca2+]i). Here, clusters of 5–30 cells were prepared from a single mouse islet or from pools of islets, loaded with fura-2, and studied with a camera-based system. [Ca2+]i oscillations were compared in pairs of clusters by computing the difference in period and a synchronization index λ. During perifusion with 12 mM glucose, the clusters exhibited regular [Ca2+]i oscillations that were quasi-perfectly synchronized (Δ period of 1.4% and index λ close to 1.0) between cells of each cluster. In contrast, separate clusters were not synchronized, even when prepared from one single islet. Pairs of clusters neighboring on the same coverslip were not better synchronized than pairs of clusters examined separately (distinct coverslips). We next attempted to synchronize clusters perifused with 12 mM glucose by applying external signals. A single pulse of 20 mM glucose, 10 mM amino acids, or 10 μM tolbutamide transiently altered [Ca2+]i oscillations but did not reset the clusters to oscillate synchronously. On a background of 12 mM glucose, repetitive applications (1 min/5 min) of 10 μM tolbutamide, but not of 20 mM glucose, synchronized separate clusters. Our results identify a level of β-cell heterogeneity intermediate between single β-cells and the whole islet. They do not support the idea that substances released by islet cells serve as paracrine synchronizers. However, synchronization can be achieved by an external signal, if this signal has a sufficient strength to overwhelm the intrinsic rhythm of glucose-induced oscillations and is repetitively applied.

Voltage-dependent entry and generation of slow Ca2+ oscillations in glucose-stimulated pancreatic β-cells

1999 ◽  
Vol 276 (3) ◽  
pp. E512-E518 ◽  
Author(s):  
Staffan Dryselius ◽  
Eva Grapengiesser ◽  
Bo Hellman ◽  
Erik Gylfe
Keyword(s):  
Pancreatic Islets ◽  
Glucose Concentration ◽  
Similar Relationship ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Slow Oscillations ◽  
Voltage Dependent ◽  
Individual Mouse

The role of voltage-dependent Ca2+ entry for glucose generation of slow oscillations of the cytoplasmic Ca2+ concentration ([Ca2+]i) was evaluated in individual mouse pancreatic β-cells. Like depolarization with K+, a rise of the glucose concentration resulted in an enhanced influx of Mn2+, which was inhibited by nifedipine. This antagonist of L-type Ca2+ channels also blocked the slow oscillations of [Ca2+]iinduced by glucose. The slow oscillations occurred in synchrony with variations in Mn2+ influx and bursts of action currents, with the elevation of [Ca2+]ibeing proportional to the frequency of the action currents. A similar relationship was obtained when Ca2+ was replaced with Sr2+. Occasionally, the slow [Ca2+]ioscillations were superimposed with pronounced spikes temporarily arresting the action currents. It is concluded that the glucose-induced slow oscillations of [Ca2+]iare caused by periodic depolarization with Ca2+ influx through L-type channels. Ca2+ spiking, due to intracellular mobilization, may be important for chopping the slow oscillations of [Ca2+]iinto shorter ones characterizing β-cells situated in pancreatic islets.

Heat-shock treatment of mouse pancreatic islets results in a partial loss of islet cells but no remaining functional impairment among the surviving β cells

1988 ◽  
Vol 1 (1) ◽  
pp. 27-31 ◽  
Author(s):  
M. Welsh ◽  
D. L. Eizirik ◽  
E. Strandell
Keyword(s):  
Heat Shock ◽  
Heat Shock Proteins ◽  
Pancreatic Islets ◽  
Cell Function ◽  
Islet Cells ◽  
Β Cells ◽  
Insulin Synthesis ◽  
Mouse Pancreatic Islets ◽  
Β Cell Function ◽  
Shock Proteins

ABSTRACT To elucidate the role of thermal stress on the function of pancreatic β cells, isolated mouse pancreatic islets were incubated for 30 min at 42°C. This resulted in decreased glucose-stimulated insulin secretion, inhibited total protein and pro-insulin synthesis and the induction of heat-shock proteins with molecular weights of 64 and 88 kDa. Six days later, the islets exposed to heat shock showed a lower DNA content, indicating islet cell death. However, the insulin secretory response and rates of oxygen consumption in the presence of glucose were normal. It is suggested that the induction of heat-shock proteins does not permanently impair β-cell function, but rather protects these cells from lasting damage.

Piezo1 channel agonist mimics high glucose as a stimulator of insulin release

2018 ◽  
Author(s):  
Vijayalakshmi Deivasikamani ◽  
Savitha Dhayalan ◽  
Romana Mughal ◽  
Asjad Visnagri ◽  
Kevin Cuthbertson ◽  
...  
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Cell Lines ◽  
High Glucose ◽  
Ruthenium Red ◽  
Cell Swelling ◽  
Β Cells ◽  
Β Cell ◽  
Intracellular Ca ◽  
Mouse Pancreatic Islets

AbstractObjectiveGlucose and hypotonicity induced cell swelling stimulate insulin release from pancreatic β-cells but the mechanisms are poorly understood. Recently, Piezo1 was identified as a mechanically-activated nonselective Ca2+ permeable cationic channel in a range of mammalian cells. As cell swelling induced insulin release could be through stimulation of Ca2+ permeable stretch activated channels, we hypothesised a role for Piezo1 in cell swelling induced insulin release.MethodsTwo rat β-cell lines (INS-1 and BRIN-BD11) and freshly-isolated mouse pancreatic islets were studied. Intracellular Ca2+ measurements were performed using the fura-2 Ca2+ indicator dye. Piezo1 agonist Yoda1, a competitive antagonist of Yoda1 (Dooku1) and an inactive analogue of Yoda1 (2e) were used as chemical probes. Piezo1 mRNA and insulin secretion were measured by RT-PCR and ELISA respectively.ResultsPiezo1 mRNA was detected in both β-cell lines and mouse islets. Yoda1 evoked Ca2+ entry which was inhibited by Yoda1 antagonist Dooku1 as well as other Piezo1 inhibitors gadolinium and ruthenium red, and not mimicked by 2e. Yoda1, but not 2e, stimulated Dooku1-sensitive insulin release from β-cells and pancreatic islets. Hypotonicity and high glucose increased intracellular Ca2+ and enhanced Yoda1 Ca2+ influx responses. Pre-treatment with ruthenium red significantly reduced hypotonicity induced insulin release from β-cells and pancreatic islets.ConclusionThe data show that Piezo1 channel agonist induces insulin release from β-cell lines and mouse pancreatic islets suggesting a role for Piezo1 in cell swelling induced insulin release. Hence Piezo1 agonists have a potential to be used as enhancers of insulin release.

scholarly journals Inhibition of the malate–aspartate shuttle in mouse pancreatic islets abolishes glucagon secretion without affecting insulin secretion

2015 ◽  
Vol 468 (1) ◽  
pp. 49-63 ◽  
Author(s):  
Jelena A. Stamenkovic ◽  
Lotta E. Andersson ◽  
Alice E. Adriaenssens ◽  
Annika Bagge ◽  
Vladimir V. Sharoyko ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Insulin Secretion ◽  
Pancreatic Islets ◽  
Glucagon Secretion ◽  
Nutrient Sensing ◽  
Β Cells ◽  
Mouse Pancreatic Islets ◽  
Glucagon And Insulin ◽  
Malate Aspartate Shuttle

Secretion of both glucagon and insulin is perturbed in Type 2 diabetes (T2D). In the present study, we identify a difference in mitochondrial shuttling between α- and β-cells that adjusts nutrient sensing and which potentially could be employed to specifically target secretion of either hormone.

IONIC EFFECTS ON THE UPTAKE OF CHLOROMERCURIBENZENE-p-SULPHONIC ACID BY PANCREATIC ISLETS

1977 ◽  
Vol 86 (3) ◽  
pp. 552-560 ◽  
Author(s):  
Monica Söderberg ◽  
Inge-Bert Täljedal
Keyword(s):  
Pancreatic Islets ◽  
Islet Cell ◽  
Choline Chloride ◽  
Inorganic Ions ◽  
Sulphonic Acid ◽  
Cell Uptake ◽  
Β Cells ◽  
Sulphydryl Groups ◽  
Microdissected Pancreatic Islets ◽  
Ionic Effects

ABSTRACT Effects of inorganic ions on the uptake of chloromercuribenzene-p-sulphonic acid (CMBS) were studied in microdissected pancreatic islets of non-inbred ob/ob-mice. Na2SO4 stimulated the total islet cell uptake of CMBS but decreased the amount of CMBS remaining in islets after brief washing with L-cysteine. CaCl2 stimulated both the total and the cysteine-non-displaceable uptake; the stimulatory effect of CaCl2 on the cysteine-non-displaceable CMBS uptake was counteracted by Na2SO4. NaCl, KCl or choline chloride had no significant effect on the total islet cell uptake of CMBS, whereas LiCl was stimulatory. It is concluded that β-cells resemble erythrocytes in having a permeation path for CMBS that is inhibited by SO42−. By analogy with existing models of the erythrocyte membrane, it is suggested that the SO42−-sensitive path leads to sulphydryl groups controlling monovalent cationic permeability in β-cells.

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