scholarly journals Effect of intracellular alkalinization on pancreatic islet calcium uptake and insulin secretion

1986 ◽  
Vol 239 (1) ◽  
pp. 199-204 ◽  
Author(s):  
P Lindström ◽  
J Sehlin
Keyword(s):  
Insulin Secretion ◽  
Beta Cells ◽  
Calcium Uptake ◽  
Islet Cells ◽  
Cell Interior ◽  
Experimental Conditions ◽  
Bicarbonate Buffer ◽  
Stimulus Secretion Coupling ◽  
The Relationship ◽  
Intracellular Alkalinization

Microdissected beta-cell-rich pancreatic islets of ob/ob mice were used in studies of the relationship between intracellular pH (pHi) and 45Ca2+ uptake and insulin release. Stepwise increases in extracellular pH (pHo) from 6.80 to 8.00 resulted in a parallel, although less pronounced, elevation of pHi from 7.24 to 7.69. Experimental conditions that alkalinize the islet cell interior, i.e. addition of 5 mM-NH4+, sudden withdrawal of extracellular bicarbonate buffer or increase in pHo, induced insulin secretion in the absence of other types of secretory stimulation (1 mM-D-glucose). Intracellular acidification by lowering pHo below 7.40 or sudden addition of bicarbonate buffer did not induce insulin secretion. The removal of extracellular bicarbonate buffer, increase in pHo from 7.40 to 8.00, or the addition of 5 mM-L-5-hydroxytryptophan or 5 mM-NH4+, which all alkalinize the islet cells and induce insulin secretion, also increased the La3+-non-displaceable 45Ca2+ uptake in the presence of 1 mM-D-glucose. The results suggest that intracellular alkalinization in beta-cells can trigger insulin secretion. Taken together with the fact that D-glucose increases pHi in the islet cells, the results also point to the possibility that alkalinization may be a link in the stimulus-secretion coupling sequence in beta-cells.

scholarly journals A comparative study of amino acid consumption by rat islet cells and the clonal beta-cell line BRIN-BD11 - the functional significance of L-alanine

2003 ◽  
Vol 179 (3) ◽  
pp. 447-454 ◽  
Author(s):  
G Dixon ◽  
J Nolan ◽  
N McClenaghan ◽  
PR Flatt ◽  
P Newsholme
Keyword(s):  
Insulin Secretion ◽  
Beta Cell ◽  
Cell Line ◽  
Islet Cells ◽  
Beta Cell Line ◽  
Acid Consumption ◽  
Glutamine Consumption ◽  
Order Of Magnitude ◽  
Stimulus Secretion Coupling ◽  
Insulinotropic Effect

Evidence has been published that L -alanine may, under appropriate conditions, promote insulin secretion in normal rodent islets and various beta cell lines. Previous results utilising the clonal beta-cell line BRIN-BD11, demonstrated that alanine dramatically elevated insulin release by a mechanism requiring oxidative metabolism. We demonstrate in this paper that addition ofL -alanine had an insulinotropic effect in dispersed primary islet cells. Addition of D -glucose increasedL -alanine consumption in both BRIN-BD11 cells and primary islet cells.L -glutamine consumption in the BRIN-BD11 cell line and primary rat islets was also determined. The consumption rate was in line with that previously reported for cells of the immune system and other glutamine-utilising cells or tIssues. However,L -alanine consumption was at least an order of magnitude higher thanL -glutamine consumption. The metabolism ofL -alanine in the beta-cell may result in stimulation of insulin secretion via generation of metabolic stimulus secretion coupling factors such asL -glutamate.

Fluorescence-activated cell sorted rat islet cells and studies of the insulin secretory process

1996 ◽  
Vol 149 (1) ◽  
pp. 145-154 ◽  
Author(s):  
K Josefsen ◽  
J P Stenvang ◽  
H Kindmark ◽  
P-O Berggren ◽  
T Horn ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Beta Cells ◽  
Endocrine Cells ◽  
Islet Cells ◽  
Single Cells ◽  
Cell Types ◽  
Glucose Sensing ◽  
Secretory Process ◽  
Functional Coupling ◽  
Paracrine Interaction

Abstract Studies of individual cell types in the islets of Langerhans are complicated by the cells' functional coupling by gap junctions and paracrine interaction. Access to purified alpha and beta cells is therefore desirable. We present a simplified and optimized method for fluorescence-activated cell sorting of endocrine pancreatic rat islets. For dispersion of the islets, dispase was superior to trypsin, as the number of vital single cells was higher (1·1 ± 0·1 × 103 vs 0·6 ± 0·1 × 103/islet, P<0·05). The purity of the sorted cells was 96·7 ± 1·2% for the non-beta cells and 97·8 ± 0·6% for the beta cells (numbers in percentages of endocrine cells). In culture, isolated beta cells, non-beta cells and mixtures of beta and non-beta cells formed aggregates, but not at low temperature (4 °C) and not in medium with low serum content (2%). Finally, in pure beta cell aggregates, glucose stimulated changes in cytoplasmic free Ca2+ concentration although both glucose- and arginine-induced insulin secretion was much reduced. We conclude that alpha cells are necessary for insulin secretion but not for glucose sensing. Journal of Endocrinology (1996) 149, 145–154

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.

cAMP-secretion coupling is impaired in diabetic GK/Par rat β-cells: a defect counteracted by GLP-1

2011 ◽  
Vol 301 (5) ◽  
pp. E797-E806 ◽  
Author(s):  
Manuel Dolz ◽  
Jamileh Movassat ◽  
Danielle Bailbé ◽  
Hervé Le Stunff ◽  
Marie-Hélène Giroix ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Insulin Release ◽  
Camp Accumulation ◽  
Camp Content ◽  
Camp Generation ◽  
Stimulus Secretion Coupling ◽  
Glucagon Like Peptide 1 ◽  
The Relationship

cAMP-raising agents with glucagon-like peptide-1 (GLP-1) as the first in class, exhibit multiple actions that are beneficial for the treatment of type 2 diabetic (T2D) patients, including improvement of glucose-induced insulin secretion (GIIS). To gain additional insight into the role of cAMP in the disturbed stimulus-secretion coupling within the diabetic β-cell, we examined more thoroughly the relationship between changes in islet cAMP concentration and insulin release in the GK/Par rat model of T2D. Basal cAMP content in GK/Par islets was significantly higher, whereas their basal insulin release was not significantly different from that of Wistar (W) islets. Even in the presence of IBMX or GLP-1, their insulin release did not significantly change despite further enhanced cAMP accumulation in both cases. The high basal cAMP level most likely reflects an increased cAMP generation in GK/Par compared with W islets since 1) forskolin dose-dependently induced an exaggerated cAMP accumulation; 2) adenylyl cyclase (AC)2, AC3, and Gsα proteins were overexpressed; 3) IBMX-activated cAMP accumulation was less efficient and PDE-3B and PDE-1C mRNA were decreased. Moreover, the GK/Par insulin release apparatus appears less sensitive to cAMP, since GK/Par islets released less insulin at submaximal cAMP levels and required five times more cAMP to reach a maximal secretion rate no longer different from W. GLP-1 was able to reactivate GK/Par insulin secretion so that GIIS became indistinguishable from that of W. The exaggerated cAMP production is instrumental, since GLP-1-induced GIIS reactivation was lost in the presence the AC blocker 2′,5′-dideoxyadenosine. This GLP-1 effect takes place in the absence of any improvement of the [Ca2+]i response and correlates with activation of the cAMP-dependent PKA-dependent pathway.

scholarly journals The stimulus-secretion coupling of glucose-induced insulin release. Effect of exogenous pyruvate on islet function

1978 ◽  
Vol 176 (1) ◽  
pp. 217-232 ◽  
Author(s):  
A Sener ◽  
S Kawazu ◽  
J C Hutton ◽  
A C Boschero ◽  
G Devis ◽  
...  
Keyword(s):  
Insulin Release ◽  
Islet Cells ◽  
Close Correlation ◽  
Net Generation ◽  
Isolated Pancreatic Islets ◽  
Pyruvate Oxidation ◽  
Net Uptake ◽  
Sigmoidal Curve ◽  
Stimulus Secretion Coupling ◽  
The Relationship

1. In isolated pancreatic islets, pyruvate causes a shift to the left of the sigmoidal curve relating the rate of insulin release to the ambient glucose concentration. The magnitude of this effect is related to the concentration of pyruvate (5–90 mM) and, at a 30 mM concentration, is equivalent to that evoked by 2 mM-glucose. Pyruvate also enhances insulin release in the presence of fructose, leucine and 4-methyl-2-oxopentanoate. 2. In the presence of glucose 8 mM), the secretory response to pyruvate is an immediate process, displaying a biphasic pattern. 3. The insulinotropic action of pyruvate coincides with an inhibition of 45Ca efflux and a stimulation of 45Ca net uptake. The relationship between 45Ca uptake and insulin release displays its usual pattern in the presence of pyruvate. 4. Exogenous pyruvate rapidly accumulates in the islets in amounts close to those derived from the metabolism of glucose. The oxidation of [2-14C]pyruvate represents 64% of the rate of [1-14C]pyruvate decarboxylation and, at a 30 mM concentration, is comparable with that of 8 mM-[U-14C]glucose. 5. When corrected for the conversion of pyruvate into lactate, the oxidation of 30 mM-pyruvate corresponds to a net generation of about 314 pmol of reducing equivalents/120 min per islet. 6. Pyruvate does not affect the rate of glycolysis, but inhibits the oxidation of glucose. Glucose does not affect pyruvate oxidation. 7. Pyruvate (30 mM) does not affect the concentration of ATP, ADP and AMP in the islet cells. 8. Pyruvate (30 mM) increases the concentration of reduced nicotinamide nucleotides in the presence but not in the absence of glucose. A close correlation is seen between the concentration of reduced nicotinamide nucleotides and the net uptake of 45Ca. Menadione inhibits the effect of pyruvate on insulin release, without altering its rate of oxidation. 9. Pyruvate, like glucose, modestly stimulates lipogenesis. 10. Pyruvate, in contrast with glucose, markedly inhibits the oxidation of endogenous nutrients. The latter effect accounts for the apparent discrepancy between the rate of pyruvate oxidation and the magnitude of its insulinotropic action. 11. Dichloroacetate fails to affect glucose oxidation and glucose-stimulated insulin release. 12. It is concluded that the effect of pyruvate to stimulate insulin release depends on its ability to increase the concentration of reduced nicotinamide nucleotides in the islet cells.

Correlation between Ca2+-ATPase activity of rat islet cells and insulin secretion

1992 ◽  
Vol 134 (2) ◽  
pp. 221-225 ◽  
Author(s):  
C. M. Gronda ◽  
G. B. Diaz ◽  
J. P. F. C. Rossi ◽  
J. J. Gagliardino
Keyword(s):  
Enzyme Activity ◽  
Insulin Secretion ◽  
Ionic Strength ◽  
Atpase Activity ◽  
Islet Cells ◽  
Experimental Conditions ◽  
Physiological Regulation ◽  
Enhancing Effect ◽  
Cellular Targets ◽  
Low Ionic Strength

ABSTRACT Using medium with a low ionic strength, a low concentration of Ca2+ and Mg2+ and devoid of K+, we have measured Ca2+-ATPase activity in the homogenates of rat islets preincubated for 3 min with several hormones in the presence of 3·3 mmol glucose/l. Insulin secretion was also measured in islets incubated for 5 min under identical experimental conditions. Islets preincubated with glucose (3·3 mmol/l) and glucagon (1·4 μmol/l) plus theophylline (10 mmol/l), ACTH (0·11 nmol/l), bovine GH (0·46 μmol/l), prolactin (0·2 μmol/l) or tri-iodothyronine (1·0 nmol/l) have significantly lower Ca2+-ATPase activity than those preincubated with only 3·3 mmol glucose/l. All these hormones increased the release of insulin significantly. Dexamethasone (0·1 μmol/l) and somatostatin (1·2 μmol/l) enhanced the Ca2+-ATPase activity while adrenaline (10 μmol/l) did not produce any significant effect on the activity of the enzyme. These hormones decreased the release of insulin significantly. These results demonstrated that islet Ca2+-ATPase activity was modulated by the hormones tested. Their inhibitory or enhancing effect seemed to be related to their effect on insulin secretion; i.e. those which stimulated the secretion of insulin inhibited the activity of the enzyme and vice versa. Hence, their effect on insulin secretion may be due, in part, to their effect on enzyme activity and consequently on the concentration of cytosolic Ca2+. These results reinforce the assumption that Ca2+-ATPase activity participates in the physiological regulation of insulin secretion, being one of the cellular targets for several agents which affect this process. Journal of Endocrinology (1992) 134, 221–225

scholarly journals The LXR Ligand T0901317 Acutely Inhibits Insulin Secretion by Affecting Mitochondrial Metabolism

Endocrinology ◽  
2017 ◽  
Vol 158 (7) ◽  
pp. 2145-2154 ◽  
Author(s):  
Jonas Maczewsky ◽  
Jelena Sikimic ◽  
Cita Bauer ◽  
Peter Krippeit-Drews ◽  
Carmen Wolke ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Membrane Potential ◽  
Blood Glucose Concentration ◽  
Mitochondrial Metabolism ◽  
Cell Physiology ◽  
Acute Effects ◽  
Β Cells ◽  
Β Cell ◽  
Experimental Conditions ◽  
Stimulus Secretion Coupling

Abstract The role of liver X receptor (LXR) in pancreatic β-cell physiology and pathophysiology is still unclear. It has been postulated that chronic LXR activation in β-cells induces lipotoxicity, a key step in the development of β-cell dysfunction, which accompanies type 2 diabetes mellitus. In most of these studies, the LXR ligand T0901317 has been administered chronically in the micromolar range to study the significance of LXR activation. In the current study, we have evaluated acute effects of T0901317 on stimulus-secretion coupling of β-cells. We found that 10 µM T0901317 completely suppressed oscillations of the cytosolic Ca2+ concentration induced by 15 mM glucose. Obviously, this effect was due to inhibition of mitochondrial metabolism. T0901317 markedly depolarized the mitochondrial membrane potential, thus inhibiting adenosine triphosphate (ATP) production and reducing the cytosolic ATP concentration. This led in turn to a huge increase in KATP current and hyperpolarization of the cell membrane potential. Eventually, T0901317 inhibited glucose-induced insulin secretion. These effects were rapid in on-set and not compatible with the activation of a nuclear receptor. In vivo, T0901317 acutely increased the blood glucose concentration after intraperitoneal application. In summary, these data clearly demonstrate that T0901317 exerts acute effects on stimulus-secretion coupling. This observation questions the chronic use of T0901317 and limits the interpretation of results obtained under these experimental conditions.

scholarly journals Exogenous Ghrelin Increases Plasma Insulin Level in Diabetic Rats

Biomolecules ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 633 ◽  
Author(s):  
Haba Elabadlah ◽  
Rasheed Hameed ◽  
Crystal D’Souza ◽  
Sahar Mohsin ◽  
Ernest A. Adeghate
Keyword(s):  
Body Weight ◽  
Insulin Secretion ◽  
Amino Acid ◽  
Beta Cell ◽  
Beta Cells ◽  
Islet Cells ◽  
Insulin Level ◽  
Diabetic Rats ◽  
Pancreatic Islet Cells ◽  
Beta Cell Line

Ghrelin, a 28-amino acid peptide, is a strong growth hormone secretagogue and a regulator of food intake. In addition, ghrelin is thought to play a role in insulin secretion and in glucose homeostasis. A lot of contradictory data have been reported in the literature regarding the co-localization of ghrelin with other hormones in the islet of Langerhans, its role in insulin secretion and attenuation of type 2 diabetes mellitus. In this study, we investigate the effect of chronic ghrelin treatment on glucose, body weight and insulin level in normal and streptozotocin-induced diabetic male Wistar rats. We have also examined the distribution pattern and co-localization of ghrelin with insulin in pancreatic islet cells using immunohistochemistry and immune-electron microscopy and the ability of ghrelin to stimulate insulin release from the CRL11065 beta cell line. Control, non-diabetic groups received intraperitoneal injection of normal saline, while treated groups received intraperitoneal injection of 5 µg/kg body weight of ghrelin (amino acid chain 24–51) on a daily basis for a duration of four weeks. Our results show that the administration of ghrelin increases the number of insulin-secreting beta cells and serum insulin level in both normal and diabetic rats. We also demonstrated that ghrelin co-localizes with insulin in pancreatic islet cells and that the pattern of ghrelin distribution is altered after the onset of diabetes. Moreover, ghrelin at a dose of 10−6 M and 10−12 M increased insulin release from the CRL11065 beta cell line. In summary, ghrelin co-localizes with insulin in the secretory granules of pancreatic beta cells and enhances insulin production.

scholarly journals Diffusion of metabolites across gap junctions mediates metabolic coordination of β-islet cells

2020 ◽  
Author(s):  
Vishnu P. Rao ◽  
Megan A. Rizzo
Keyword(s):  
Insulin Secretion ◽  
Gap Junctions ◽  
Beta Cells ◽  
Calcium Influx ◽  
Islet Cells ◽  
Metabolic Coupling ◽  
Heterogeneous Expression ◽  
Low Glucose ◽  
Junctional Activity ◽  
Gap Junctional

AbstractLoss of oscillatory insulin secretion is an early marker of type II diabetes. In an individual beta-cell, insulin secretion is triggered by glucose metabolism, which leads to membrane depolarization and calcium influx. Islet β-cells display coordinated secretion; however, it is unclear how the heterogeneous population of insulin-secreting beta cells coordinate their response to glucose. The mechanisms underlying both electrical and calcium synchronicity are well explored. Even so, the mechanism governing metabolic coordination is unclear given key glycolytic enzymes’ heterogeneous expression. To understand how islet cells coordinate their metabolic activity, a microfluidic applicator delivered glucose stimulation to spatially defined areas of isolated mouse islets. We measured metabolic responses using NADH/NADPH (or NAD(P)H) autofluorescence and calcium changes using Fluo-4 fluorescence. Glucose stimulated a rise in NAD(P)H even in islet areas unexposed to the treatment, suggesting metabolic coordination. A gap junction inhibitor blocked the coordinated NAD(P)H rise in the low-glucose areas. Additionally, metabolic communication did not occur in immortalized β-cell clusters known to lack gap junctions, demonstrating their importance for metabolic coupling. Metabolic communication also preceded glucose-stimulated rises in intracellular calcium. Further, pharmacological blockade of calcium influx did not disrupt NAD(P)H rises in untreated regions. These data suggest that metabolic coordination between islet beta-cells relies on gap-junctional activity and precedes synchronous electrical and calcium activity.

scholarly journals Inhibition of insulin secretion via distinct signaling pathways in alpha2-adrenoceptor knockout mice

2003 ◽  
pp. 343-350 ◽  
Author(s):  
M Peterhoff ◽  
A Sieg ◽  
M Brede ◽  
CM Chao ◽  
L Hein ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Adenylyl Cyclase ◽  
Signaling Pathways ◽  
Beta Cells ◽  
Intracellular Signaling ◽  
Islet Cells ◽  
Inhibitory Effect ◽  
Receptor Subtypes ◽  
Mouse Islets ◽  
Alpha2 Adrenoceptor

OBJECTIVE: Adrenaline inhibits insulin secretion through activation of alpha(2)-adrenoceptors (ARs). These receptors are linked to pertussis toxin-sensitive G proteins. Agonist binding leads to inhibition of adenylyl cyclase, inhibition of Ca(2+) channels and activation of K(+) channels. Recently, three distinct subtypes of alpha(2)-AR were described, alpha(2A)-AR, alpha(2B)-AR and alpha(2C)-AR. At present, it is unknown which of these alpha(2)-AR subtype(s) may regulate insulin secretion. We used mice deficient in alpha(2)-ARs to analyze the coupling and role of individual alpha(2)-AR subtypes in insulin-secreting beta cells. METHODS: The inhibitory effect of adrenaline on insulin secretion was measured in freshly isolated and cultured wild type (wt) and alpha(2)-AR knockout (KO) mouse islets in order to examine the receptor subtypes which mediate adrenaline-induced inhibition of insulin secretion. Adenylyl cyclase activity was measured in isolated cultured islets. Membrane potential was measured using the amphotericin B permeabilized patch clamp method in isolated and cultured single islet cells. RESULTS: In wt, alpha(2A)- and alpha(2C)-AR KO mouse islets, adrenaline, 1 microM/L, inhibited secretion by 83, 80 and 100% respectively. In contrast, in alpha(2A/2C)-AR double KO mouse islets, adrenaline had no effect on stimulated secretion indicating that both alpha(2A)-AR and alpha(2C)-AR, but not alpha(2B)-AR, are functionally expressed in mouse islets. Surprisingly, glucose (16.7 mM/L)-induced secretion in the presence of 1 microM/L forskolin was greatly impaired in alpha(2A)-AR KO islets. However, when cAMP levels were increased further by the combination of forskolin (5 microM/L) and 3-isobutyl-1-methylxanthine (100 microM/L), secretion was stimulated 2.7-fold (8.5-fold in wt islets). Adrenaline lowered the concentration of cAMP in wt and alpha(2C)-AR KO mouse islets by 74%. Adrenaline also hyperpolarized wt and alpha(2C)-AR KO beta cells. In contrast, adrenaline did not inhibit adenylyl cyclase in islets of alpha(2A)-AR KO mice, nor did it hyperpolarize alpha(2A)-AR KO beta cells. CONCLUSION: Adrenaline inhibits insulin release through alpha(2A)- and alpha(2C)-ARs via distinct intracellular signaling pathways.

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