[Ca2+]i regulates trafficking of Cav1.3 (α1D Ca2+ channel) in insulin-secreting cells

2004 ◽  
Vol 286 (2) ◽  
pp. C213-C221 ◽  
Author(s):  
Luping Huang ◽  
Arin Bhattacharjee ◽  
James T. Taylor ◽  
Min Zhang ◽  
Brian M. Keyser ◽  
...  
Keyword(s):  
Surface Proteins ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Glucose Stimulation ◽  
Channel Trafficking ◽  
Insulin Secreting Cells ◽  
High Concentrations ◽  
The Relationship ◽  
Insulin Secretory Response

Chronic exposure of pancreatic β-cells to high concentrations of glucose impairs the insulin secretory response to further glucose stimulation. This phenomenon is referred to as glucose desensitization. It has been shown that glucose desensitization is associated with abnormal elevation of β-cell basal intracellular free Ca2+ concentration ([Ca2+]i). We have investigated the relationship between the basal intracellular free Ca2+ and the L-type (Cav1.3) Ca2+ channel translocation in insulin-secreting cells. Glucose stimulation or membrane depolarization induced a nifedipine-sensitive Ca2+ influx, which was attenuated when the basal [Ca2+]i was elevated. Using voltage-clamp techniques, we found that changing [Ca2+]i could regulate the amplitude of the Ca2+ current. This effect was attenuated by drugs that interfere with the cytoskeleton. Immunofluorescent labeling of Cav1.3 showed an increase in the cytoplasmic distribution of the channels under high [Ca2+]i conditions by deconvolution microscopy. The [Ca2+]i-dependent translocation of Cav1.3 channel was also demonstrated by Western blot analysis of biotinylation/NeutrAvidin-bead-eluted surface proteins in cells preincubated at various [Ca2+]i. These results suggest that Cav1.3 channel trafficking is involved in glucose desensitization of pancreatic β-cells.

scholarly journals SIRT6 protects against palmitate-induced pancreatic β-cell dysfunction and apoptosis

2016 ◽  
Vol 231 (2) ◽  
pp. 159-165 ◽  
Author(s):  
Xiwen Xiong ◽  
Xupeng Sun ◽  
Qingzhi Wang ◽  
Xinlai Qian ◽  
Yang Zhang ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Mrna Levels ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Glucose Stimulation ◽  
Cell Dysfunction ◽  
High Concentrations ◽  
Glucose Stimulated Insulin Secretion

Chronic exposure of pancreatic β-cells to abnormally elevated levels of free fatty acids can lead to β-cell dysfunction and even apoptosis, contributing to type 2 diabetes pathogenesis. In pancreatic β-cells, sirtuin 6 (SIRT6) has been shown to regulate insulin secretion in response to glucose stimulation. However, the roles played by SIRT6 in β-cells in response to lipotoxicity remain poorly understood. Our data indicated that SIRT6 protein and mRNA levels were reduced in islets from diabetic and aged mice. High concentrations of palmitate (PA) also led to a decrease in SIRT6 expression in MIN6 β-cells and resulted in cell dysfunction and apoptosis. Knockdown of Sirt6 caused an increase in cell apoptosis and impairment in insulin secretion in response to glucose in MIN6 cells even in the absence of PA exposure. Furthermore, overexpression of SIRT6 alleviated the palmitate-induced lipotoxicity with improved cell viability and increased glucose-stimulated insulin secretion. In summary, our data suggest that SIRT6 can protect against palmitate-induced β-cell dysfunction and apoptosis.

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

ISLET CONTENTS OF CYCLIC 3′,5′-GUANOSINE MONOPHOSPHATE UNDER CONDITIONS WHICH AFFECT THE CYCLIC 3′,5′-ADENOSINE MONOPHOSPHATE

1977 ◽  
Vol 86 (2) ◽  
pp. 344-354 ◽  
Author(s):  
Eva Gagerman ◽  
Bo Hellman
Keyword(s):  
Turnover Rate ◽  
Phosphodiesterase Inhibitor ◽  
Dry Weight ◽  
Adenosine Monophosphate ◽  
Guanosine Monophosphate ◽  
Simple Pattern ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
High Concentrations

ABSTRACT The sensitivity of the radioimmunoassay for cGMP was considerably increased by previous 2′-O-succinylation of the nucleotide. The basal content of cGMP in β-cell-rich pancreatic islets isolated from ob/ob-mice was similar to that of cAMP, i. e. about 3 μmoles per kg dry weight. Extracellular Ca2+ was a prerequisite for maintaining this amount of cGMP. The islet cGMP differed from cAMP in being only slightly enhanced or not affected at all when the islets were exposed to high concentrations of glucose, the sulphydryl reagents chloromercuribenzene-p-sulphonic acid and iodoacetamide, or the potent phosphodiesterase inhibitor 3-isobutyl-l-methylxanthine. The data obtained suggest that the turnover rate for cGMP is much slower than that for cAMP in the pancreatic β-cells. The interrelationships between the two cyclic nucleotides do not seem to fit into a simple pattern of antagonism.

The sensitivity of pancreatic β-cells to mitochondrial injuries triggered by lipotoxicity and oxidative stress

2008 ◽  
Vol 36 (5) ◽  
pp. 930-934 ◽  
Author(s):  
Ning Li ◽  
Francesca Frigerio ◽  
Pierre Maechler
Keyword(s):  
Oxidative Stress ◽  
Current Knowledge ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Primary Target ◽  
Glucose Homoeostasis ◽  
Insulin Secreting Cells ◽  
And Oxidative Stress

Pancreatic β-cells are essential for the maintenance of glucose homoeostasis, and dysfunction of these insulin-secreting cells results in the development of diabetes. In the course of events leading from obesity to Type 2 diabetes, several mechanisms are currently envisaged. Among them, lipids and oxidative stress are considered as toxic candidates for the β-cell. The cellular link between fatty acids and ROS (reactive oxygen species) is essentially the mitochondrion, a key organelle for the control of insulin secretion. Mitochondria are the main source of ROS and are also the primary target of oxidative attacks. The present review presents the current knowledge of lipotoxicity related to oxidative stress in the context of mitochondrial function in the β-cell.

scholarly journals Inhibition of calpain blocks pancreatic β-cell spreading and insulin secretion

2005 ◽  
Vol 289 (2) ◽  
pp. E313-E321 ◽  
Author(s):  
Géraldine Parnaud ◽  
Eva Hammar ◽  
Dominique G. Rouiller ◽  
Domenico Bosco
Keyword(s):  
Insulin Secretion ◽  
Cell Attachment ◽  
Cell Spreading ◽  
Cysteine Proteases ◽  
Secretory Response ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Insulin Secretory Response ◽  
Calpain Inhibitors

In addition to promoting insulin secretion, an increase in cytosolic Ca2+ triggered by glucose has been shown to be crucial for spreading of β-cells attached on extracellular matrix (804G matrix). Calpains are Ca2+-dependent cysteine proteases involved in an extended spectrum of cellular responses, including cytoskeletal rearrangements and vesicular trafficking. The present work aimed to assess whether calpain is also implicated in the process of Ca2+-induced insulin secretion and spreading of rat pancreatic β-cells. The results indicate calpain dependency of β-cell spreading on 804G matrix. Indeed, treatment with three distinct calpain inhibitors (N-Ac-Leu-Leu-norleucinal, calpeptin, and ethyl(+)-(2S,3S)-3-[(S)-3-methyl-1-(3-methylbutylcarbamoyl)butyl-carbamoyl]-2-ox-iranecarboxylate) inhibited cell spreading induced by glucose and KCl, whereas cell attachment was not significantly modified. Calpain inhibitors also suppressed glucose- and KCl-stimulated insulin secretion without affecting insulin synthesis. Washing the inhibitor out of the cell culture restored spreading on 804G matrix and insulin secretory response after 24 h. In addition, incubation with calpeptin did not affect insulin secretory response to mastoparan that acts on exocytosis downstream of intracellular calcium [Ca2+]i. Finally, calpeptin was shown to affect the [Ca2+]i response to glucose but not to KCl. In summary, the results show that inhibition of calpain blocks spreading and insulin secretion of primary pancreatic β-cells. It is therefore suggested that calpain could be a mediator of Ca2+-induced-insulin secretion and β-cell spreading.

scholarly journals Granular detail of β cell structures for insulin secretion

2021 ◽  
Vol 220 (2) ◽  
Author(s):  
Jonathan S. Bogan
Keyword(s):  
Insulin Secretion ◽  
Secretory Granule ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Glucose Stimulation ◽  
Granule Exocytosis ◽  
Cell Biol ◽  
Cell Structures ◽  
Insulin Secretory Granule

Pancreatic β cells secrete insulin in response to increased glucose concentrations. Müller et al. (2021. J. Cell Biol. https://doi.org/10.1083/jcb.202010039) use 3D FIB-SEM to study the architecture of these cells and to elucidate how glucose stimulation remodels microtubules to control insulin secretory granule exocytosis.

scholarly journals Glucagon Potentiates Insulin Secretion Via β-Cell GCGR at Physiological Concentrations of Glucose

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2495
Author(s):  
Yulin Zhang ◽  
Chengsheng Han ◽  
Wenzhen Zhu ◽  
Guoyi Yang ◽  
Xiaohong Peng ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
High Glucose ◽  
Critical Role ◽  
Β Cells ◽  
Β Cell ◽  
Glucose Stimulation ◽  
Primary Mouse ◽  
High Concentrations ◽  
Glucose Stimulated Insulin Secretion ◽  
Glucagon Receptors

Incretin-potentiated glucose-stimulated insulin secretion (GSIS) is critical to maintaining euglycemia, of which GLP-1 receptor (GLP-1R) on β-cells plays an indispensable role. Recently, α-cell-derived glucagon but not intestine-derived GLP-1 has been proposed as the critical hormone that potentiates GSIS via GLP-1R. However, the function of glucagon receptors (GCGR) on β-cells remains elusive. Here, using GCGR or GLP-1R antagonists, in combination with glucagon, to treat single β-cells, α-β cell clusters and isolated islets, we found that glucagon potentiates insulin secretion via β-cell GCGR at physiological but not high concentrations of glucose. Furthermore, we transfected primary mouse β-cells with RAB-ICUE (a genetically encoded cAMP fluorescence indicator) to monitor cAMP level after glucose stimulation and GCGR activation. Using specific inhibitors of different adenylyl cyclase (AC) family members, we revealed that high glucose concentration or GCGR activation independently evoked cAMP elevation via AC5 in β-cells, thus high glucose stimulation bypassed GCGR in promoting insulin secretion. Additionally, we generated β-cell-specific GCGR knockout mice which glucose intolerance was more severe when fed a high-fat diet (HFD). We further found that β-cell GCGR activation promoted GSIS more than GLP-1R in HFD, indicating the critical role of GCGR in maintaining glucose homeostasis during nutrient overload.

scholarly journals Targeting Mitochondrial Calcium Uptake with the Natural Flavonol Kaempferol, to Promote Metabolism/Secretion Coupling in Pancreatic β-cells

Nutrients ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 538 ◽  
Author(s):  
Flavien Bermont ◽  
Aurelie Hermant ◽  
Romy Benninga ◽  
Christian Chabert ◽  
Guillaume Jacot ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Calcium Uptake ◽  
Cell Function ◽  
Intervention Strategy ◽  
Mitochondrial Calcium ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Insulin Secreting Cells ◽  
Mitochondrial Calcium Uptake

Pancreatic β-cells secrete insulin to lower blood glucose, following a meal. Maintenance of β-cell function is essential to preventing type 2 diabetes. In pancreatic β-cells, mitochondrial matrix calcium is an activating signal for insulin secretion. Recently, the molecular identity of the mitochondrial calcium uniporter (MCU), the transporter that mediates mitochondrial calcium uptake, was revealed. Its role in pancreatic β-cell signal transduction modulation was clarified, opening new perspectives for intervention. Here, we investigated the effects of a mitochondrial Ca2+-targeted nutritional intervention strategy on metabolism/secretion coupling, in a model of pancreatic insulin-secreting cells (INS-1E). Acute treatment of INS-1E cells with the natural plant flavonoid and MCU activator kaempferol, at a low micromolar range, increased mitochondrial calcium rise during glucose stimulation, without affecting the expression level of the MCU and with no cytotoxicity. Enhanced mitochondrial calcium rises potentiated glucose-induced insulin secretion. Conversely, the MCU inhibitor mitoxantrone inhibited mitochondrial Ca2+ uptake and prevented both glucose-induced insulin secretion and kaempferol-potentiated effects. The kaempferol-dependent potentiation of insulin secretion was finally validated in a model of a standardized pancreatic human islet. We conclude that the plant product kaempferol activates metabolism/secretion coupling in insulin-secreting cells by modulating mitochondrial calcium uptake.

ATP-sensitive K+ channels and disease: from molecule to malady

2007 ◽  
Vol 293 (4) ◽  
pp. E880-E889 ◽  
Author(s):  
Frances M. Ashcroft
Keyword(s):  
Neonatal Diabetes ◽  
Channel Structure ◽  
Congenital Hyperinsulinism ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
American Physiological Society ◽  
And Function ◽  
The Relationship

This essay is based on a lecture given to the American Physiological Society in honor of Walter B. Cannon, an advocate of homeostasis. It focuses on the role of the ATP-sensitive potassium K+ (KATP) channel in glucose homeostasis and, in particular, on its role in insulin secretion from pancreatic β-cells. The β-cell KATP channel comprises pore-forming Kir6.2 and regulatory SUR1 subunits, and mutations in either type of subunit can result in too little or too much insulin release. Here, I review the latest information on the relationship between KATP channel structure and function, and consider how mutations in the KATP channel genes lead to neonatal diabetes or congenital hyperinsulinism.

Glucokinase activators: molecular tools for studying the physiology of insulin-secreting cells

2007 ◽  
Vol 35 (5) ◽  
pp. 1208-1210 ◽  
Author(s):  
D. Johnson ◽  
R.M. Shepherd ◽  
D. Gill ◽  
T. Gorman ◽  
D.M. Smith ◽  
...  
Keyword(s):  
Human Islets ◽  
Significant Advance ◽  
Cell Physiology ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Rate Limiting Step ◽  
Glucokinase Activators ◽  
Insulin Secreting Cells ◽  
Treatment Of Diabetes

GK (glucokinase) catalyses the phosphorylation of glucose to glucose 6-phosphate in glucosensitive cells. In pancreatic β-cells, this reaction is the rate-limiting step of insulin release. Recent work has led to the discovery of synthetic small-molecule activators of GK that stimulate β-cell physiology and subsequently enhance the glucose-dependent release of insulin. It is currently recognized that these compounds may represent a significant advance in the development of new agents in the treatment of diabetes. In addition, GKAs (GK activators) are emerging as reagents that are useful tools with which to probe the function of pancreatic β-cells and other glucosensitive cells. This includes providing insights into the physiology of the β-cell by helping to elucidate the kinetic cycle of GK, confirming the central role of glucose metabolism to the β-cell and highlighting subtle species-dependent differences in insulin secretion between rodent and human islets of Langerhans.

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