scholarly journals Glucose-dependent activation, activity, and deactivation of beta cell networks in acute mouse pancreas tissue slices

2020 ◽  
Author(s):  
Jurij Dolenšek ◽  
Maša Skelin Klemen ◽  
Marko Gosak ◽  
Lidija Križančić-Bombek ◽  
Viljem Pohorec ◽  
...  
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Insulin Release ◽  
Glucose Concentration ◽  
Calcium Oscillations ◽  
Tissue Slices ◽  
Mouse Pancreas ◽  
Network Parameters ◽  
Cell Networks ◽  
Glucose Dependence

AbstractGlucose progressively stimulates insulin release over a wide range of concentrations. However, the nutrient coding underlying activation, activity, and deactivation of beta cells affecting insulin release remains only partially described. Experimental data indicate that nutrient sensing in coupled beta cells in islets is predominantly a collective trait, overriding to a large extent functional differences between cells. However, some degree of heterogeneity between coupled beta cells may play important roles. To further elucidate glucose-dependent modalities in coupled beta cells, the degree of functional heterogeneity, and uncover the emergent collective operations, we combined acute mouse pancreas tissue slices with functional multicellular calcium imaging. We recorded beta cell calcium responses from threshold (7 mM) to supraphysiological (16 mM) glucose concentrations with high spatial and temporal resolution. This enabled the analysis of both classical physiological parameters and complex network parameters, as well as their comparison at the level of individual cells. The activation profile displayed two major glucose concentration-dependent features, shortening of delays to initial activation, and shortening of delays until half activation with increasing glucose concentration. Inversely, during deactivation both delays to initial deactivation and until half deactivation were progressively longer with increasing glucose concentration. The plateau activity with fast calcium oscillations expressed two types of glucose-dependence. Physiological concentrations mostly affected the frequency of oscillations, whereas supraphysiological concentrations progressively prolonged the duration of oscillations. Most of the measured functional network parameters also showed clear glucose-dependence. In conclusion, we propose novel understanding for glucose-dependent coding properties in beta cell networks, and its deciphering may have repercussions for our understanding of the normal physiology of glucose homeostasis as well as of disturbances of metabolic homeostasis, such as diabetes mellitus.

scholarly journals Glucose-dependent activation, activity, and deactivation of beta cell networks in acute mouse pancreas tissue slices

2021 ◽  
Author(s):  
Andraz Stozer ◽  
Maša Skelin Klemen ◽  
Marko Gosak ◽  
Lidija Križančić Bombek ◽  
Viljem Pohorec ◽  
...  
Keyword(s):  
Beta Cell ◽  
Common Ground ◽  
Calcium Oscillations ◽  
Tissue Slices ◽  
Mouse Pancreas ◽  
Functional Connections ◽  
Wide Range ◽  
Network Properties ◽  
Beta Cell Heterogeneity ◽  
Cell Networks

Many details of glucose-stimulated intracellular calcium changes in beta cells during activation, activity, and deactivation, as well as their concentration-dependence, remain to be analyzed. Classical physiological experiments indicated that in islets, functional differences between individual cells are largely attenuated, but recent findings suggest considerable intercellular heterogeneity, with some cells possibly coordinating the collective responses. To address the above with an emphasis on heterogeneity and describing the relations between classical physiological and functional network properties, we performed functional multicellular calcium imaging in mouse pancreas tissue slices over a wide range of glucose concentrations. During activation, delays to activation of cells and any-cell-to-first-responder delays shortened, and the sizes of simultaneously responding clusters increased with increasing glucose. Exactly the opposite characterized deactivation. The frequency of fast calcium oscillations during activity increased with increasing glucose up to 12 mM glucose, beyond which oscillation duration became longer, resulting in a homogenous increase in active time. In terms of functional connectivity, islets progressed from a very segregated network to a single large functional unit with increasing glucose. A comparison between classical physiological and network parameters revealed that the first-responders during activation had longer active times during plateau and the most active cells during the plateau tended to deactivate later. Cells with the most functional connections tended to activate sooner, have longer active times, and deactivate later. Our findings provide a common ground for recent differing views on beta cell heterogeneity and an important baseline for future studies of stimulus-secretion and intercellular coupling.

Tetraethylammonium modifies gap junctions between pancreatic beta-cells

1981 ◽  
Vol 240 (3) ◽  
pp. C116-C120 ◽  
Author(s):  
M. S. Sheppard ◽  
P. Meda
Keyword(s):  
Beta Cell ◽  
Gap Junctions ◽  
Beta Cells ◽  
Insulin Release ◽  
Pancreatic Beta Cells ◽  
Freeze Fracture ◽  
Potassium Conductance ◽  
Median Number ◽  
Rat Islets Of Langerhans ◽  
Gap Junctional

Gap junctions between pancreatic beta-cells were quantitatively assessed in freeze-fracture replicas of isolated rat islets of Langerhans incubated for 90 min with or without the potassium conductance blocker tetraethylammonium (TEA). The results show that TEA increases the median number of particles per beta-cell gap junction but not the frequency of gap junctions at both nonstimulating and threshold-stimulating concentrations of glucose. TEA increased the relative gap junctional area at both concentrations of glucose. TEA had no effect on insulin release at a basal concentration of glucose but potentiated that release at the threshold glucose level. Thus TEA modifies beta-cell gap junctions independently of its effect on insulin release. However, the junctional changes observed were greater when insulin release was also elevated.

Role of Ca2+ in impaired insulin release from islets of diabetic (C57BL/KsJ-db/db) mice

1980 ◽  
Vol 239 (2) ◽  
pp. E132-E138
Author(s):  
E. G. Siegel ◽  
C. B. Wollheim ◽  
G. W. Sharp ◽  
L. Herberg ◽  
A. E. Renold
Keyword(s):  
Tissue Culture ◽  
Beta Cell ◽  
Insulin Release ◽  
Glucose Concentration ◽  
Insulin Response ◽  
Isolated Islets ◽  
Diabetic Mice ◽  
Impaired Insulin ◽  
Insulin Response To Glucose

The involvement of Ca2+ in the impaired insulin release of diabetic C57BL/KsJ-db/db mice was studied. Twenty-week-old severely hyperglycemic mice were compared to nondiabetic C57BL/KsJ mice as controls. Collagenase-isolated islets were maintained for 46 h in tissue culture allowing for equilibration at the same glucose concentration (8.3) mM). The insulin content of both types of islets was similar. In control islets preloaded during culture with 45Ca2+ glucose-induced insulin release was associated with increased 45Ca2+ effux. Islets from diabetic mice showed markedly reduced insulin response to glucose and a smaller increase in 45Ca2+ efflux. Because insulin release was strikingly potentiated by 3-isobutyl-1-methylxanthine (IBMX), even more than in control islets, there was no generalized release defect. In both types of islets, IBMX potentiation was accompanied by a further enhanced 45Ca2+ efflux, possibly suggesting that cAMP effects are associated with increased cytosol Ca2+% concentrations. As Ca2+ uptake was stimulated by glucose in both types of islets, a defect may lie in the mechanism by which glucose uses cellulr calcium to raise cytosol Ca2+ in the beta-cell of these diabetic mice.

scholarly journals Effects of protein kinase C activation on the regulation of the stimulus-secretion coupling in pancreatic β-cells

1989 ◽  
Vol 264 (1) ◽  
pp. 207-215 ◽  
Author(s):  
P Arkhammar ◽  
T Nilsson ◽  
M Welsh ◽  
N Welsh ◽  
P O Berggren
Keyword(s):  
Protein Kinase C ◽  
Membrane Potential ◽  
Protein Kinase ◽  
Beta Cells ◽  
Insulin Release ◽  
Phorbol Ester ◽  
Glucose Concentration ◽  
Secretory Response ◽  
Kinase C ◽  
Pkc Activation

Effects of protein kinase C (PKC) activation on the insulin-secretory process were investigated, by using beta-cell-rich suspensions obtained from pancreatic islets of obese-hyperglycaemic mice. The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), which is known to activate PKC directly, the muscarinic-receptor agonist carbamoylcholine and high glucose concentration enhanced the phosphorylation of a specific 80 kDa PKC substrate in the beta-cells. At a non-stimulatory glucose concentration, 10 nM-TPA increased insulin release, although there were no changes in either the cytoplasmic free Ca2+ concentration ([Ca2+]i) or membrane potential, as measured with the fluorescent indicators quin-2 and bisoxonol respectively. At a stimulatory glucose concentration TPA caused a lowering in [Ca2+]i, whereas membrane potential was unaffected. Despite the decrease in [Ca2+]i, there was a large stimulation of insulin release. Addition of TPA lowered [Ca2+]i also in beta-cells stimulated by tolbutamide or high K+, although to a lesser extent than in those stimulated by glucose. There was no effect of TPA on either Ca2+ buffering or the ability of Ins(1,4,5)P3 to release Ca2+ in permeabilized beta-cells. However, the phorbol ester inhibited the rise in [Ca2+]i in response to carbamoylcholine, which stimulates the formation of InsP3, in intact beta-cells. Down-regulation of PKC influenced neither glucose-induced insulin release nor the increase in [Ca2+]i. Hence, although PKC activation is of no major importance in glucose-stimulated insulin release, this enzyme can serve as a modulator of the glucose-induced insulin-secretory response. Such a modulation involves mechanisms promoting both amplification of the secretory response and lowering of [Ca2+]i.

scholarly journals Neuron-enriched RNA-binding Proteins Regulate Pancreatic Beta Cell Function and Survival

2017 ◽  
Vol 292 (8) ◽  
pp. 3466-3480 ◽  
Author(s):  
Jonàs Juan-Mateu ◽  
Tatiana H. Rech ◽  
Olatz Villate ◽  
Esther Lizarraga-Mollinedo ◽  
Anna Wendt ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Beta Cell ◽  
Beta Cells ◽  
Insulin Release ◽  
Beta Cell Function ◽  
Rna Binding ◽  
Cell Function ◽  
Rna Binding Proteins ◽  
Pancreatic Beta Cell ◽  
Splicing Regulators

Pancreatic beta cell failure is the central event leading to diabetes. Beta cells share many phenotypic traits with neurons, and proper beta cell function relies on the activation of several neuron-like transcription programs. Regulation of gene expression by alternative splicing plays a pivotal role in brain, where it affects neuronal development, function, and disease. The role of alternative splicing in beta cells remains unclear, but recent data indicate that splicing alterations modulated by both inflammation and susceptibility genes for diabetes contribute to beta cell dysfunction and death. Here we used RNA sequencing to compare the expression of splicing-regulatory RNA-binding proteins in human islets, brain, and other human tissues, and we identified a cluster of splicing regulators that are expressed in both beta cells and brain. Four of them, namely Elavl4, Nova2, Rbox1, and Rbfox2, were selected for subsequent functional studies in insulin-producing rat INS-1E, human EndoC-βH1 cells, and in primary rat beta cells. Silencing of Elavl4 and Nova2 increased beta cell apoptosis, whereas silencing of Rbfox1 and Rbfox2 increased insulin content and secretion. Interestingly, Rbfox1 silencing modulates the splicing of the actin-remodeling protein gelsolin, increasing gelsolin expression and leading to faster glucose-induced actin depolymerization and increased insulin release. Taken together, these findings indicate that beta cells share common splicing regulators and programs with neurons. These splicing regulators play key roles in insulin release and beta cell survival, and their dysfunction may contribute to the loss of functional beta cell mass in diabetes.

scholarly journals β-cells operate collectively to help maintain glucose homeostasis

2019 ◽  
Author(s):  
Boris Podobnik ◽  
Dean Korošak ◽  
Maša Skelin Klemen ◽  
Andraž Stožer ◽  
Jurij Dolenšek ◽  
...  
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Glucose Homeostasis ◽  
Cell Activity ◽  
Cell Communication ◽  
Calcium Oscillations ◽  
Homeostatic Function ◽  
Entire Cell ◽  
Collective Phenomenon ◽  
Gap Junctional

Residing in the islets of Langerhans in the pancreas, beta cells contribute to glucose homeostasis by managing the body’s insulin supply. A circulating hypothesis has been that healthy beta cells heavily engage in cell-to-cell communication to perform their homeostatic function. We provide strong evidence in favor of this hypothesis in the form of (i) a dynamical network model that faithfully mimics fast calcium oscillations in response to above-threshold glucose stimulation and (ii) empirical data analysis that reveals a qualitative shift in the cross-correlation structure of measured signals below and above the threshold glucose concentration. Combined together, these results point to a glucose-induced transition in beta-cell activity thanks to increasing coordination through gap-junctional signaling and paracrine interactions. The model further suggests how the conservation of entire cell-cell conductance, observed in coupled but not uncoupled beta cells, emerges as a collective phenomenon. An overall implication is that improving the ability to monitor beta-cell signaling should offer means to better understand the pathogenesis of diabetes mellitus.

scholarly journals The Relationship between Membrane Potential and Calcium Dynamics in Glucose-Stimulated Beta Cell Syncytium in Acute Mouse Pancreas Tissue Slices

PLoS ONE ◽  
2013 ◽  
Vol 8 (12) ◽  
pp. e82374 ◽  
Author(s):  
Jurij Dolenšek ◽  
Andraž Stožer ◽  
Maša Skelin Klemen ◽  
Evan W. Miller ◽  
Marjan Slak Rupnik
Keyword(s):  
Membrane Potential ◽  
Beta Cell ◽  
Calcium Dynamics ◽  
Tissue Slices ◽  
Mouse Pancreas ◽  
The Relationship

The bimodal effect of interleukin 1 on rat pancreatic beta-cells – stimulation followed by inhibition – depends upon dose, duration of exposure, and ambient glucose concentration

1988 ◽  
Vol 119 (2) ◽  
pp. 307-311 ◽  
Author(s):  
Giatgen A. Spinas ◽  
Jerry P. Palmer ◽  
Thomas Mandrup-Poulsen ◽  
Henrik Andersen ◽  
Jens Høiriis Nielsen ◽  
...  
Keyword(s):  
Beta Cells ◽  
Insulin Release ◽  
Glucose Concentration ◽  
Pancreatic Beta Cells ◽  
Cell Function ◽  
Interleukin 1 ◽  
Glucose Levels ◽  
Lower Glucose ◽  
In Vivo Effects

Abstract. To investigate the hypothesis that interleukin 1 initially stimulates and then suppresses beta-cell function and that this sequential effect is directly related to interleukin 1 dose, duration of exposure, and ambient glucose concentration, insulin release was measured from cultured newborn rat islets exposed for 6 h to 6 days to interleukin 1 at doses ranging from 20 to 2000 ng/l at glucose concentrations of 3.3, 5.5 and 11 mmol/l. After 6 h of exposure and at all three glucose levels, all doses of interleukin 1 stimulated insulin release, maximal stimulation (370% of control) being observed at 5.5 mmol/l glucose and 100 ng/l interleukin 1. In contrast, after 6 days, all doses of interleukin 1 were inhibitory irrespective of glucose level, maximal inhibition (90%) being observed at 11 mmol/l glucose and 2000 ng/l interleukin 1. At 24 and 48 h of exposure, the biphasic effect of interleukin 1 was observed: lower doses of interleukin 1 at lower glucose concentrations at 24 h being more stimulatory with transition to inhibition directly related to higher glucose levels, higher interleukin 1 doses, and longer exposure. After 48 h, 200 ng/l of interleukin 1 increased insulin release to 220% at 3.3 mmol/l glucose, but at 11 mmol/l glucose a 60% suppression was seen. On the basis of these data we suggest that interleukin l's effect on beta-cells is bimodal: stimulation followed by inhibition. Increasing interleukin 1 dose and ambient glucose concentration shift this response to the left. Experimental results will, and in vivo effects may, depend upon these three variables.

scholarly journals Dual Mode of Action of Acetylcholine on Cytosolic Calcium Oscillations in Pancreatic Beta and Acinar Cells In Situ

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1580
Author(s):  
Nastja Sluga ◽  
Sandra Postić ◽  
Srdjan Sarikas ◽  
Ya-Chi Huang ◽  
Andraž Stožer ◽  
...  
Keyword(s):  
Beta Cells ◽  
Acinar Cells ◽  
Cell Types ◽  
Cytosolic Calcium ◽  
Calcium Oscillations ◽  
The Body ◽  
Cholinergic Innervation ◽  
Oscillatory Activity ◽  
Tissue Slices

Cholinergic innervation in the pancreas controls both the release of digestive enzymes to support the intestinal digestion and absorption, as well as insulin release to promote nutrient use in the cells of the body. The effects of muscarinic receptor stimulation are described in detail for endocrine beta cells and exocrine acinar cells separately. Here we describe morphological and functional criteria to separate these two cell types in situ in tissue slices and simultaneously measure their response to ACh stimulation on cytosolic Ca2+ oscillations [Ca2+]c in stimulatory glucose conditions. Our results show that both cell types respond to glucose directly in the concentration range compatible with the glucose transporters they express. The physiological ACh concentration increases the frequency of glucose stimulated [Ca2+]c oscillations in both cell types and synchronizes [Ca2+]c oscillations in acinar cells. The supraphysiological ACh concentration further increases the oscillation frequency on the level of individual beta cells, inhibits the synchronization between these cells, and abolishes oscillatory activity in acinar cells. We discuss possible mechanisms leading to the observed phenomena.

Modulation of calciumflux influences interleukin 1 β effects on insulin release from isolated islets of Langerhans

1989 ◽  
Vol 121 (3) ◽  
pp. 447-455 ◽  
Author(s):  
Steffen Helqvist ◽  
Pierre Bouchelouche ◽  
Henrik Ullits Andersen ◽  
Jørn Nerup
Keyword(s):  
Cell Membrane ◽  
Beta Cell ◽  
Beta Cells ◽  
Insulin Release ◽  
Interleukin 1 ◽  
Calcium Ionophore ◽  
Calcium Flux ◽  
Rat Islets ◽  
Mouse Islets ◽  
Isolated Rat

Abstract. The controlled flux of calcium across the cell membrane is intimately linked to the release of insulin from pancreatic beta-cells, but the uncontrolled influx of calcium is a common final denominator of cell death. Because interleukin 1 has been shown to be cytotoxic to beta-cells in isolated rat islets of Langerhans and since interleukin 1 has a calcium ionophore effect on other cell types, this study was designed to test whether alterations of the calcium flux across the beta-cell membrane would influence the effects of interleukin 1 on isolated rat and mouse islets. Further, the cytosolic free Ca2+ concentration was measured by the fura-2 method in rat islets during acute interleukin 1 exposure. Treatment with 10 μmol/l of verapamil (a potent blocker of the voltage-dependent calcium channel) tended to suppress the inhibitory effect of interleukin 1 on insulin release from rat islets, suggesting protection against cytotoxicity. Conversely, a stimulatory effect of interleukin 1 on mouse islets during 6 days of exposure to interleukin 1 was turned into inhibition by high extracellular calcium concentration. Interleukin 1 did not have any acute effect on cytosolic free Ca2+ concentration. In conclusion, interleukin 1 has no specific calcium ionophore effect on beta-cells, but alterations of the calcium flux across the beta-cell membrane influence the functional effects of interleukin 1, suggesting interference with cell function and toxicity, which would likely be accompanied by an uncontrolled influx of calcium.

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