A role for polyamines in stimulus-secretion coupling in the pancreatic β-cell

1984 ◽  
Vol 4 (10) ◽  
pp. 869-877 ◽  
Author(s):  
P. J. Bungay ◽  
J. M. Potter ◽  
M. Griffin
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Intracellular Concentration ◽  
Secretory Process ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Rapid Synthesis ◽  
Stimulus Secretion Coupling ◽  
Significant Change

Measurement of the content of polyamines in pancreatic islets indicated that no significant change in their concentration took place during glucose-stimulated insulin release. The finding, together with the absence of any effect of α-difluoromethylornithine on glucosestimulated insulin release suggested that rapid synthesis of polyamines is not involved in stimulus-secretion coupling in the β-cell. The concentration of polyamines found in islets were high enough for them to act as substrates for the Ca2+-dependent islet transglutaminase during insulin release. This was further demonstrated by the ability of islet transglutaminase to incorporate [14C]putrescine into proteins from islet homogenates and by the demonstration of an increase in the covalent incorporation of [14C]putrescine into the proteins of intact islets following their challenge with glucose. Unlike monoamine substrates of transglutaminase, putrescine failed to effectively inhibit insulin release when its intracellular concentration was increased. A role for polyamines in the secretory process through their incorporation into islet proteins is suggested.

EFFECT OF FASTING ON 32P TRANSLOCATIONS IN PRE-LABELLED PANCREATIC ISLETS

1978 ◽  
Vol 88 (3) ◽  
pp. 545-555 ◽  
Author(s):  
Kjell Asplund ◽  
Norbert Freinkel
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Β Cell ◽  
Early Step ◽  
Phosphate Release ◽  
Insulin Secretagogues ◽  
Stimulus Secretion Coupling ◽  
The Right ◽  
Fasted Rats

ABSTRACT The rapid, short-lived efflux of inorganic 32P-orthophosphate that occurs when pre-labelled pancreatic islets are exposed to nutrient insulin secretagogues (the "phosphate flush") has been proposed to reflect some early step in β-cell secretory activation. In the present study, glucose-initiated phosphate efflux was studied during fasting. Pancreatic islets were isolated from fed and 48-h fasted rats by collagenase digestion. After pre-labelling with 32P-orthophosphate and basal perifusion with 0.5 mg/ml glucose, tissue analyses disclosed similar stores of radioactivity in the two groups of islets. Stimulatory perifusion with glucose at this time failed to promote insulin release from islets which had been secured from fasted donors although the "phosphate flush" was preserved. However, the characteristics of phosphate efflux were altered. Maximal glucose-induced phosphate release was greater with islets from fasted animals whereas phosphate release in response to low level stimulation with glucose was diminished. Accordingly, the dose-response curve for glucose-initiated phosphate efflux in islets from fasted rats was displaced to the right and compatible with a decreased sensitivity to glucose at the activation site for the "phosphate flush." Thus, while glucose is unable to enhance insulin release in vitro after fasting, glucose still elicits increased phosphate efflux. However, the phenomenon appears to be attended by an impaired responsiveness to activation by glucose, supporting the contention that some early step in the sequence of stimulus secretion coupling in the β-cell may be obtunded after food deprivation.

The agouti gene product stimulates pancreatic β-cell Ca2+ signaling and insulin release

1999 ◽  
Vol 1 (1) ◽  
pp. 11-19 ◽  
Author(s):  
B. Z. XUE ◽  
W. O. WILKISON ◽  
R. L. MYNATT ◽  
N. MOUSTAID ◽  
M. GOLDMAN ◽  
...  
Keyword(s):  
Gene Product ◽  
Insulin Release ◽  
Fold Increase ◽  
Cell Types ◽  
Human Pancreas ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Agouti Protein ◽  
Intracellular Ca ◽  
Agouti Gene

Xue, B. Z., W. O. Wilkison, R. L. Mynatt, N. Moustaid, M. Goldman, and M. B. Zemel. The agouti gene product stimulates pancreatic β-cell Ca2+ signaling and insulin release. Physiol. Genomics 1: 11-19, 1999.—Ubiquitous expression of the mouse agouti gene results in obesity and hyperinsulinemia. Human agouti is expressed in adipose tissue, and we found recombinant agouti protein to stimulate lipogenesis in adipocytes in a Ca2+-dependent fashion. However, adipocyte-specific agouti transgenic mice only became obese in the presence of hyperinsulinemia. Because intracellular Ca2+ concentration ([Ca2+]i) is a primary signal for insulin release, and we have shown agouti protein to increase [Ca2+]i in several cell types, we examined the effects of agouti on [Ca2+]i and insulin release. We demonstrated the expression of agouti in human pancreas and generated recombinant agouti to study its effects on Ca2+ signaling and insulin release. Agouti (100 nM) stimulated Ca2+ influx, [Ca2+]i increase, and a marked stimulation of insulin release in two β-cell lines (RIN-5F and HIT-T15; P < 0.05). Agouti exerted comparable effects in isolated human pancreatic islets and β-cells, with a 5-fold increase in Ca2+ influx ( P < 0.001) and a 2.2-fold increase in insulin release ( P < 0.01). These data suggest a potential role for agouti in the development of hyperinsulinemia in humans.

Nitric oxide donor SIN-1 inhibits insulin release

1996 ◽  
Vol 271 (4) ◽  
pp. C1098-C1102 ◽  
Author(s):  
A. Sjoholm
Keyword(s):  
Nitric Oxide ◽  
Diabetes Mellitus ◽  
Protein Kinase C ◽  
Insulin Secretion ◽  
Protein Kinase ◽  
Beta Cell ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
Kinase C ◽  
Stimulus Secretion Coupling

Preceding the onset of insulin-dependent diabetes mellitus, pancreatic islets are infiltrated by macrophages secreting interleukin-1 beta, which exerts cytotoxic and inhibitory actions on islet beta-cell insulin secretion through induction of nitric oxide (NO) synthesis. The influence of the NO donor 3-morpholinosydnonimine (SIN-1) on insulin secretion from isolated pancreatic islets in response to various secretagogues was investigated. Stimulation of insulin release evoked by glucose, phospholipase C activation with carbachol, and protein kinase C activation with phorbol ester were obtained by SIN-1, whereas the response to adenylyl cyclase activation or K(+)-induced depolarization was not affected. It is concluded that enzymes involved in glucose catabolism, phospholipase C or protein kinase C, may be targeted by NO. Reversal of SIN-1 inhibition of glucose-stimulated insulin release by dithiothreitol suggests that NO may inhibit insulin secretion partly by S-nitrosylation of thiol residues in key proteins in the stimulus-secretion coupling. These adverse effects of NO on the beta-cell stimulus-secretion coupling may be of importance for the development of the impaired insulin secretion characterizing diabetes mellitus.

scholarly journals Effect of perchlorate on calcium uptake and insulin secretion in mouse pancreatic islets

1987 ◽  
Vol 248 (1) ◽  
pp. 109-115 ◽  
Author(s):  
J Sehlin
Keyword(s):  
Insulin Secretion ◽  
Beta Cell ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
Glucose Oxidation ◽  
Calcium Uptake ◽  
Maximum Effect ◽  
Mouse Pancreatic Islets ◽  
Stimulus Secretion Coupling ◽  
Ca2 Channels

Microdissected beta-cell-rich pancreatic islets of non-inbred ob/ob mice were used in studies of how perchlorate (CIO4-) affects stimulus-secretion coupling in beta-cells. CIO4- at 16 mM potentiated D-glucose-induced insulin release, without inducing secretion at non-stimulatory glucose concentrations. The potentiation mainly applied to the first phase of stimulated insulin release. In the presence of 20 mM-glucose, the half-maximum effect of CIO4- was reached at 5.5 mM and maximum effect at 12 mM of the anion. The potentiation was reversible and inhibitable by D-mannoheptulose (20 mM) or Ca2+ deficiency. CIO4- at 1-8 mM did not affect glucose oxidation. The effects on secretion were paralleled by a potentiation of glucose-induced 45Ca2+ influx during 3 min. K+-induced insulin secretion and 45Ca2+ uptake were potentiated by 8-16 mM-CIO4-. The spontaneous inactivation of K+-induced (20.9 mM-K+) insulin release was delayed by 8 mM-CIO4-. The anion potentiated the 45Ca2+ uptake induced by glibenclamide, which is known to depolarize the beta-cell. Insulin release was not affected by 1-10 mM-trichloroacetate. It is suggested that CIO4- stimulates the beta-cell by affecting the gating of voltage-controlled Ca2+ channels.

Life and death decisions of the pancreatic β-cell: the role of fatty acids

2006 ◽  
Vol 112 (1) ◽  
pp. 27-42 ◽  
Author(s):  
Philip Newsholme ◽  
Deirdre Keane ◽  
Hannah J. Welters ◽  
Noel G. Morgan
Keyword(s):  
Fatty Acids ◽  
Insulin Release ◽  
Chronic Exposure ◽  
Cell Function ◽  
Pancreatic Β Cell ◽  
Β Cells ◽  
Β Cell ◽  
Endogenous Fatty Acid ◽  
Gene And Protein Expression ◽  
Β Cell Function

Both stimulatory and detrimental effects of NEFAs (non-esterified fatty acids) on pancreatic β-cells have been recognized. Acute exposure of the pancreatic β-cell to high glucose concentrations and/or saturated NEFAs results in a substantial increase in insulin release, whereas chronic exposure results in desensitization and suppression of secretion, followed by induction of apoptosis. Some unsaturated NEFAs also promote insulin release acutely, but they are less toxic to β-cells during chronic exposure and can even exert positive protective effects. Therefore changes in the levels of NEFAs are likely to be important for the regulation of β-cell function and viability under physiological conditions. In addition, the switching between endogenous fatty acid synthesis or oxidation in the β-cell, together with alterations in neutral lipid accumulation, may have critical implications for β-cell function and integrity. Long-chain acyl-CoA (formed from either endogenously synthesized or exogenous fatty acids) controls several aspects of β-cell function, including activation of specific isoenzymes of PKC (protein kinase C), modulation of ion channels, protein acylation, ceramide formation and/or NO-mediated apoptosis, and transcription factor activity. In this review, we describe the effects of exogenous and endogenous fatty acids on β-cell metabolism and gene and protein expression, and have explored the outcomes with respect to insulin secretion and β-cell integrity.

Interleukin 10 inhibits insulin release from and nitric oxide production in rat pancreatic islets

1996 ◽  
Vol 135 (3) ◽  
pp. 374-378 ◽  
Author(s):  
Renato Laffranchi ◽  
Giatgen A Spinas
Keyword(s):  
Nitric Oxide ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
Interleukin 10 ◽  
Interleukin 1Β ◽  
Nitric Oxide Production ◽  
Β Cell ◽  
Cell Dysfunction ◽  
Rat Pancreatic Islets ◽  
Oxide Production

Laffranchi R, Spinas GA. Interleukin 10 inhibits insulin release from and nitric oxide production in rat pancreatic islets. Eur J Endocrinol 1996;135:374–8. ISSN 0804–4643 Interleukin 10 was found to prevent cytokine-induced nitric oxide production in murine macrophages. Because, in rat islets, interleukin 1β induces β-cell dysfunction, mainly due to overproduction of nitric oxide, we studied if this effect could be counteracted by interleukin 10. Rat pancreatic islets were cultured for 24 h in the presence or absence of 0.02–20 ng/ml recombinant human interleukin 10. Interleukin 10 dose-dependently inhibited insulin secretion with maximal inhibition (27 ±4%, p < 0.05) at 2 ng/ml without impairment of islet cell viability. However, incubation of pancreatic islets with interleukin 10 resulted in a 61.5% decrease of nitric oxide production. Co-incubation of islets with interleukin 10 (2 ng/ml) and recombinant human interleukin 1β (0.15 ng/ml) resulted in a more pronounced suppression of basal insulin release than with interleukin 1β alone (55 ± 3.6% vs 44 ± 3.6% with interleukin 1β alone, p < 0.05) but did not reduce interleukin 1β-stimulated NO production or reverse the effect of interleukin 1β on cell viability. Thus, in pancreatic islets interleukin 10 is not capable of counteracting the interleukin 1β-induced β-cell dysfunction, but rather enhances the inhibitory effect of interleukin 1β by a different mechanism. Renato Laffranchi, Division of Endocrinology and Metabolism, Department of Internal Medicine, University Hospital, Rämistrasse 100, CH-8091 Zürich, Switzerland

The Stimulus-Secretion Coupling of Amino Acid-induced Insulin Release: Secretory and Oxidative Response of Pancreatic Islets to L-Asparagine

Diabetes ◽  
1984 ◽  
Vol 33 (5) ◽  
pp. 464-469 ◽  
Author(s):  
F. Malaisse-Lagae ◽  
M. Welsh ◽  
P. Lebrun ◽  
A. Herchuelz ◽  
A. Sener ◽  
...  
Keyword(s):  
Amino Acid ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
Oxidative Response ◽  
Stimulus Secretion Coupling

scholarly journals Evidence for the participation of calmodulin in stimulus–secretion coupling in the pancreatic β-cell

1980 ◽  
Vol 192 (3) ◽  
pp. 919-927 ◽  
Author(s):  
Juan J. Gagliardino ◽  
Donna E. Harrison ◽  
Michael R. Christie ◽  
Elma E. Gagliardino ◽  
Stephen J. H. Ashcroft
Keyword(s):  
Insulin Release ◽  
Kinase Inhibitor ◽  
Potent Inhibitor ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Β Cell ◽  
Batch Type ◽  
Dependent Inhibition ◽  
Stimulus Secretion Coupling ◽  
Rat Islets Of Langerhans

1. The ability of a range of phenothiazines to inhibit activation of brain phosphodiesterase by purified calmodulin was studied. Trifluoperazine, prochlorperazine and 8-hydroxyprochlorperazine produced equipotent dose-dependent inhibition with half-maximum inhibition at 12μm. When tested at 10 or 50μm, 7-hydroxyprochlorperazine was a similarly potent inhibitor. However, trifluoperazine-5-oxide and N-methyl-2-(trifluoromethyl)phenothiazine were ineffective at concentrations up to 50μm, and produced only a modest inhibition at 100μm. 2. The same phenothiazines were tested for their ability to inhibit activation of brain phosphodiesterase by boiled extracts of rat islets of Langerhans. At a concentration of 20μm, 70–80% inhibition was observed with trifluoperazine, prochlorperazine, 7-hydroxyprochlorperazine or 8-hydroxyprochlorperazine, whereas trifluoperazine-5-oxide and N-methyl-2-(trifluoromethyl)phenothiazine were less effective. 3. The effect of these phenothiazines on insulin release from pancreatic islets was studied in batch-type incubations. Insulin release stimulated by glucose (20mm) was markedly inhibited by 10μm-trifluoperazine or -prochlorperazine and further inhibited at a concentration of 20μm. 8-Hydroxyprochlorperazine (20μm) was also a potent inhibitor but 7-hydroxyprochlorperazine (20μm) elicited only a modest inhibition of glucose-stimulated insulin release; no inhibition was observed with trifluoperazine-5-oxide or N-methyl-2-(trifluoromethyl)phenothiazine. 4. Trifluoperazine (20μm) markedly inhibited insulin release stimulated by leucine or 4-methyl-2-oxopentanoate in the absence of glucose, and both trifluoperazine and prochlorperazine (20μm) decreased insulin release stimulated by glibenclamide in the presence of 3.3mm-glucose. 5. None of the phenothiazines affected basal insulin release in the presence of 2mm-glucose. 6. Trifluoperazine (20μm) did not inhibit islet glucose utilization nor the incorporation of [3H]leucine into (pro)insulin or total islet protein. 7. Islet extracts catalysed the incorporation of 32P from [γ-32P]ATP into endogenous protein substrates. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis resolved several phosphorylated bands, but incorporation was slight. However, calmodulin in the presence of Ca2+ greatly enhanced incorporation: the predominant phosphorylated band had an estimated mol.wt. of 55000. This enhanced incorporation was abolished by trifluoperazine, but not by cyclic AMP-dependent protein kinase inhibitor protein. 8. These results suggest that islet phosphodiesterase-stimulating activity is similar to, although not necessarily identical with, calmodulin from skeletal muscle; that islet calmodulin may play an important role in Ca2+-dependent stimulus–secretion coupling in the β-cell; and that calmodulin may exert part at least of its effect on secretion via phosphorylation of endogenous islet proteins.

scholarly journals MKP-1 mediates glucocorticoid-induced ERK1/2 dephosphorylation and reduction in pancreatic β-cell proliferation in islets from early lactating mothers

2010 ◽  
Vol 299 (6) ◽  
pp. E1006-E1015 ◽  
Author(s):  
José E. Nicoletti-Carvalho ◽  
Camilo Lellis-Santos ◽  
Tatiana S. Yamanaka ◽  
Tatiane C. Nogueira ◽  
Luciana C. Caperuto ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Pancreatic Islets ◽  
Chromatin Immunoprecipitation ◽  
Protein Phosphatase ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Chromatin Immunoprecipitation Assay ◽  
Isolated Pancreatic Islets ◽  
Immunoprecipitation Assay ◽  
Lactating Mothers

Maternal pancreatic islets undergo a robust increase of mass and proliferation during pregnancy, which allows a compensation of gestational insulin resistance. Studies have described that this adaptation switches to a low proliferative status after the delivery. The mechanisms underlying this reversal are unknown, but the action of glucocorticoids (GCs) is believed to play an important role because GCs counteract the pregnancy-like effects of PRL on isolated pancreatic islets maintained in cell culture. Here, we demonstrate that ERK1/2 phosphorylation (phospho-ERK1/2) is increased in maternal rat islets isolated on the 19th day of pregnancy. Phospho-ERK1/2 status on the 3rd day after delivery (L3) rapidly turns to values lower than that found in virgin control rats (CTL). MKP-1, a protein phosphatase able to dephosphorylate ERK1/2, is increased in islets from L3 rats. Chromatin immunoprecipitation assay revealed that binding of glucocorticoid receptor (GR) to MKP-1 promoter is also increased in islets from L3 rats. In addition, dexamethasone (DEX) reduced phospho-ERK1/2 and increased MKP-1 expression in RINm5F and MIN-6 cells. Inhibition of transduction with cycloheximide and inhibition of phosphatases with orthovanadate efficiently blocked DEX-induced downregulation of phospho-ERK1/2. In addition, specific knockdown of MKP-1 with siRNA suppressed the downregulation of phospho-ERK1/2 and the reduction of proliferation induced by DEX. Altogether, our results indicate that downregulation of phospho-ERK1/2 is associated with reduction in proliferation found in islets of early lactating mothers. This mechanism is probably mediated by GC-induced MKP-1 expression.

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