scholarly journals Transduction of MIN6 β Cells with TAT-Syntaxin SNARE Motif Inhibits Insulin Exocytosis in Biphasic Insulin Release in a Distinct Mechanism Analyzed by Evanescent Wave Microscopy

2002 ◽  
Vol 277 (52) ◽  
pp. 50805-50811 ◽  
Author(s):  
Mica Ohara-Imaizumi ◽  
Yoko Nakamichi ◽  
Chiyono Nishiwaki ◽  
Shinya Nagamatsu
Keyword(s):  
Insulin Release ◽  
Evanescent Wave ◽  
Β Cells ◽  
Biphasic Insulin ◽  
Distinct Mechanism ◽  
Snare Motif ◽  
Biphasic Insulin Release ◽  
Insulin Exocytosis

scholarly journals Imaging analysis reveals mechanistic differences between first- and second-phase insulin exocytosis

2007 ◽  
Vol 177 (4) ◽  
pp. 695-705 ◽  
Author(s):  
Mica Ohara-Imaizumi ◽  
Tomonori Fujiwara ◽  
Yoko Nakamichi ◽  
Tadashi Okamura ◽  
Yoshihiro Akimoto ◽  
...  
Keyword(s):  
Total Internal Reflection ◽  
Second Phase ◽  
Imaging Analysis ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Biphasic Insulin ◽  
Insulin Granules ◽  
Biphasic Insulin Release ◽  
Two Phases ◽  
Insulin Exocytosis

The mechanism of glucose-induced biphasic insulin release is unknown. We used total internal reflection fluorescence (TIRF) imaging analysis to reveal the process of first- and second-phase insulin exocytosis in pancreatic β cells. This analysis showed that previously docked insulin granules fused at the site of syntaxin (Synt)1A clusters during the first phase; however, the newcomers fused during the second phase external to the Synt1A clusters. To reveal the function of Synt1A in phasic insulin exocytosis, we generated Synt1A-knockout (Synt1A−/−) mice. Synt1A−/− β cells showed fewer previously docked granules with no fusion during the first phase; second-phase fusion from newcomers was preserved. Rescue experiments restoring Synt1A expression demonstrated restoration of granule docking status and fusion events. Inhibition of other syntaxins, Synt3 and Synt4, did not affect second-phase insulin exocytosis. We conclude that the first phase is Synt1A dependent but the second phase is not. This indicates that the two phases of insulin exocytosis differ spatially and mechanistically.

scholarly journals Defective calcium handling and insulin release in islets from diabetic Chinese hamsters

1979 ◽  
Vol 180 (1) ◽  
pp. 233-236 ◽  
Author(s):  
E G Siegel ◽  
C B Wollheim ◽  
G W Sharp ◽  
L Herberg ◽  
A E Renold
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Chinese Hamster ◽  
Calcium Handling ◽  
Biphasic Insulin ◽  
Chinese Hamsters ◽  
Diabetic Chinese Hamsters ◽  
Biphasic Insulin Release

In pancreatic islets from normal Chinese hamsters preloaded with 45Ca2+, glucose-induced biphasic insulin release was associated with increased 45Ca2+ efflux; islets from diabetic hamsters showed decreased insulin release and no increase in 45Ca2+ efflux. The lack of stimulated 45Ca2+ efflux persisted even when glucose-induced insulin release was potentiated by 3-isobutyl-1-methylxanthine. Since glucose-stimulated 45Ca2+ uptake by diabetic islets was not impaired, a defect in intracellular Ca2+ handling may be involved in the defective insulin release of the diabetic Chinese hamster.

Insulin exocytosis in Goto-Kakizaki rat β-cells subjected to long-term glinide or sulfonylurea treatment

2008 ◽  
Vol 412 (1) ◽  
pp. 93-101 ◽  
Author(s):  
Junko Kawai ◽  
Mica Ohara-Imaizumi ◽  
Yoko Nakamichi ◽  
Tadashi Okamura ◽  
Yoshihiro Akimoto ◽  
...  
Keyword(s):  
Insulin Release ◽  
Β Cells ◽  
Gk Rats ◽  
Insulin Granules ◽  
Long Term Treatment ◽  
Insulin Granule ◽  
Granule Motion ◽  
Insulin Exocytosis ◽  
First Phase Insulin Release

Sulfonylurea and glinide drugs display different effects on insulin granule motion in single β-cells in vitro. We therefore investigated the different effects that these drugs manifest towards insulin release in an in vivo long-term treatment model. Diabetic GK (Goto-Kakizaki) rats were treated with nateglinide, glibenclamide or insulin for 6 weeks. Insulin granule motion in single β-cells and the expression of SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins were then analysed. Perifusion studies showed that decreased first-phase insulin release was partially recovered when GK rats were treated with nateglinide or insulin for 6 weeks, whereas no first-phase release occurred with glibenclamide treatment. In accord with the perifusion results, TIRF (total internal reflection fluorescence) imaging of insulin exocytosis showed restoration of the decreased number of docked insulin granules and the fusion events from them during first-phase release for nateglinide or insulin, but not glibenclamide, treatment; electron microscopy results confirmed the TIRF microscopy data. Relative to vehicle-treated GK β-cells, an increased number of SNARE clusters were evident in nateglinide- or insulin-treated cells; a lesser increase was observed in glibenclamide-treated cells. Immunostaining for insulin showed that nateglinide treatment better preserved pancreatic islet morphology than did glibenclamide treatment. However, direct exposure of GK β-cells to these drugs could not restore the decreased first-phase insulin release nor the reduced numbers of docked insulin granules. We conclude that treatment of GK rats with nateglinide and glibenclamide varies in long-term effects on β-cell functions; nateglinide treatment appears overall to be more beneficial.

scholarly journals Doc2b serves as a scaffolding platform for concurrent binding of multiple Munc18 isoforms in pancreatic islet β-cells

2014 ◽  
Vol 464 (2) ◽  
pp. 251-258 ◽  
Author(s):  
Latha Ramalingam ◽  
Jingping Lu ◽  
Andy Hudmon ◽  
Debbie C. Thurmond
Keyword(s):  
Present Article ◽  
Pancreatic Islet ◽  
Macromolecular Complex ◽  
Β Cells ◽  
New Model ◽  
Biphasic Insulin ◽  
Insulin Exocytosis

In the present article, we describe a novel macromolecular complex composed of Munc18c, Doc2b and Munc18-1 in β-cells. These data provide the basis for a new model wherein Doc2b scaffolding may facilitate the transient Munc18–SNARE associations occurring during biphasic insulin exocytosis.

Development of the biphasic response to glucose in fetal and neonatal rat pancreas

1988 ◽  
Vol 254 (2) ◽  
pp. E167-E174 ◽  
Author(s):  
R. L. Hole ◽  
M. C. Pian-Smith ◽  
G. W. Sharp
Keyword(s):  
Beta Cell ◽  
Insulin Release ◽  
Neonatal Rat ◽  
Biphasic Response ◽  
Rat Pancreas ◽  
K Channels ◽  
Fetal Pancreas ◽  
Biphasic Insulin ◽  
Biphasic Insulin Release ◽  
Ca2 Channels

A study on the development of biphasic insulin release and sensitivity to inhibitors has been performed using perifused rat pancreas at 19.5 days of gestation (3 days before birth) and at 3 days after birth. In the fetal pancreas, 16.7 mM glucose caused a marked stimulation of insulin release that did not, however, manifest a biphasic response and was not inhibited by verapamil, a Ca2+ channel blocker. This suggested that the immature response was due to either a lack of voltage-dependent Ca2+ channels or their failure to open in response to glucose. Depolarizing concentrations of KCl stimulated insulin release, which was inhibited by verapamil, demonstrating that functional Ca2+ channels were present. In the presence of 16.7 mM glucose, quinine, which blocks glucose-sensitive k+ channels, potentiated the response of the fetal pancreas that now became sensitive to verapamil, demonstrating that functional K+ channels were also present in the fetal pancreatic beta-cell. The immaturity of the response is not due specifically to a defect in glucose metabolism; rather the metabolism of nutrient secretagogues fails to couple with the K+ channel in the fetal islet and thus fails to depolarize the beta-cell membrane. Three days after birth the pattern of response to high glucose is biphasic. Insulin release in fetal pancreas was inhibited by epinephrine and somatostatin.

Anaplerotic input is sufficient to induce time-dependent potentiation of insulin release in rat pancreatic islets

2004 ◽  
Vol 287 (5) ◽  
pp. E828-E833 ◽  
Author(s):  
Subhadra C. Gunawardana ◽  
Yi-Jia Liu ◽  
Michael J. MacDonald ◽  
Susanne G. Straub ◽  
Geoffrey W. G. Sharp
Keyword(s):  
Insulin Release ◽  
Tricarboxylic Acid Cycle ◽  
Acid Methyl Ester ◽  
Time Dependent ◽  
Second Phase ◽  
Acetyl Coa ◽  
Atp Production ◽  
Biphasic Insulin ◽  
Intracellular Ca ◽  
Biphasic Insulin Release

Nutrients that induce biphasic insulin release, such as glucose and leucine, provide acetyl-CoA and anaplerotic input in the β-cell. The first phase of release requires increased ATP production leading to increased intracellular Ca2+ concentration ([Ca2+]i). The second phase requires increased [Ca2+]i and anaplerosis. There is strong evidence to indicate that the second phase is due to augmentation of Ca2+-stimulated release via the KATP channel-independent pathway. To test whether the phenomenon of time-dependent potentiation (TDP) has similar properties to the ATP-sensitive K+ channel-independent pathway, we monitored the ability of different agents that provide acetyl-CoA and anaplerotic input or both of these inputs to induce TDP. The results show that anaplerotic input is sufficient to induce TDP. Interestingly, among the agents tested, the nonsecretagogue glutamine, the nonhydrolyzable analog of leucine aminobicyclo[2.2.1]heptane-2-carboxylic acid, and succinic acid methyl ester all induced TDP, and all significantly increased α-ketoglutarate levels in the islets. In conclusion, anaplerosis that enhances the supply and utilization of α-ketoglutarate in the tricarboxylic acid cycle appears to play an essential role in the generation of TDP.

Adrenergic Modification of Glucose-Induced Biphasic Insulin Release from Perifused Rat Pancreas

1971 ◽  
Vol 1 (4) ◽  
pp. 216-224 ◽  
Author(s):  
Ian M. Burr ◽  
Luc Balant ◽  
Werner Stauffacher ◽  
Albert E. Renold
Keyword(s):  
Insulin Release ◽  
Rat Pancreas ◽  
Biphasic Insulin ◽  
Biphasic Insulin Release

Effects of Caffeine and Acetylcholine on Glucose-Stimulated Insulin Release from Islet Transplants in Mice

1997 ◽  
Vol 6 (1) ◽  
pp. 33-37 ◽  
Author(s):  
Chun-Liang Shi
Keyword(s):  
Insulin Secretion ◽  
Intracellular Calcium ◽  
Insulin Release ◽  
Cholinergic Receptors ◽  
Mouse Islet ◽  
Kidney Capsule ◽  
Biphasic Insulin ◽  
Biphasic Insulin Release ◽  
Islet Transplants

In mouse islet grafts under the kidney capsule, the potentiating responsiveness to acetylcholine was markedly attenuated after a few weeks. The question arose as to whether transplanted islets show an decreased responsiveness to potentiators in general. The effect of caffeine on glucose-induced insulin secretion was, therefore, examined. Intrastrain transplantation was performed in NMRI and BALB/c mice, and islet grafts were removed and perifused in vitro after 3 and 12 wk. In grafts from both NMRI and BALB/c mice, 16.7 mmol/L glucose induced a biphasic insulin release. When 1 or 5 mmol/L caffeine was included in the perifusion medium, there was a marked potentiation of the glucose-induced insulin release that was at least as responsiveness as fresh untransplanted islets. In the absence of caffeine, 3-wk-old BALB/c grafts reacted less strongly to acetylcholine than did untransplanted islets. The addition of 1 mmol/L caffeine did not enhance the potentiating effect of acetylcholine, whether in untransplanted or transplanted islets. Rather, the interaction between caffeine and acetylcholine appeared negative. We concluded that the glucose-induced insulin secretion exhibits a diminished potentiatory responsiveness to acetylcholine but not to caffeine. The displacement and denervation of transplanted islets is likely to affect either the cholinergic receptors or their mediated influence on intracellular calcium. Copyright © 1997 Elsevier Science Inc.

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