In Vivo and In Vitro Glucose-Induced Biphasic Insulin Secretion in the Mouse: Pattern and Role of Cytoplasmic Ca2+ and Amplification Signals in  -Cells

Numerous evidence demonstrates that dynein is crucial for organization of microtubules (MTs) into radial arrays, but its exact function in this process is unclear. Here, we studied the role of cytoplasmic dynein in MT radial array formation in the absence of the centrosome. We found that dynein is a potent MT nucleator in vitro and that stimulation of dynein activity in cytoplasmic fragments of melanophores induces nucleation-dependent formation of MT radial array in the absence of the centrosome. This new property of dynein, in combination with its known role as an MT motor that is essential for MT array organization in the absence and presence of the centrosome, makes it a unique molecule whose activity is necessary and sufficient for the formation and maintenance of MT radial arrays in cells.

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A possible role of plasma glutathione in glucose-mediated insulin secretion: in vitro and in vivo studies in rats

Diabetologia ◽

10.1007/bf00264910 ◽

1989 ◽

Vol 32 (11) ◽

Cited By ~ 13

Author(s):

H.P.T. Ammon ◽

S. Klumpp ◽

A. Fu� ◽

E.J. Verspohl ◽

H. Jaeschke ◽

...

Keyword(s):

Insulin Secretion ◽

In Vivo Studies ◽

Plasma Glutathione ◽

Insulin Secretion In Vitro

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Role of adrenoceptors in vitro and in vivo in the effects of lithium on blood glucose levels and insulin secretion in the rat

British Journal of Pharmacology ◽

10.1111/j.1476-5381.1990.tb15796.x ◽

1990 ◽

Vol 100 (2) ◽

pp. 283-288 ◽

Cited By ~ 7

Author(s):

T. Fontela ◽

O. García Hermida ◽

J. Gómez-Acebo

Keyword(s):

Insulin Secretion ◽

Blood Glucose ◽

Glucose Levels ◽

Blood Glucose Levels

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Transgenic overexpression of intraislet ghrelin does not affect insulin secretion or glucose metabolism in vivo

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00341.2011 ◽

2012 ◽

Vol 302 (4) ◽

pp. E403-E408 ◽

Cited By ~ 8

Author(s):

Mika Bando ◽

Hiroshi Iwakura ◽

Hiroyuki Ariyasu ◽

Hiroshi Hosoda ◽

Go Yamada ◽

...

Keyword(s):

Insulin Secretion ◽

Glucose Metabolism ◽

Medium Chain Triglyceride ◽

Physiological Role ◽

Standard Diet ◽

Entry Site ◽

Insulin Secretion In Vivo

Whereas ghrelin is produced primarily in the stomach, a small amount of it is produced in pancreatic islets. Although exogenous administration of ghrelin suppresses insulin secretion in vitro or in vivo, the role of intraislet ghrelin in the regulation of insulin secretion in vivo remains unclear. To understand the physiological role of intraislet ghrelin in insulin secretion and glucose metabolism, we developed a transgenic (Tg) mouse model, rat insulin II promoter ghrelin-internal ribosomal entry site-ghrelin O-acyl transferase (RIP-GG) Tg mice, in which mouse ghrelin cDNA and ghrelin O-acyltransferase are overexpressed under the control of the rat insulin II promoter. Although pancreatic desacyl ghrelin levels were elevated in RIP-GG Tg mice, pancreatic ghrelin levels were not altered in animals on a standard diet. However, when Tg mice were fed a medium-chain triglyceride-rich diet (MCTD), pancreatic ghrelin levels were elevated to ∼16 times that seen in control animals. It seems likely that the gastric ghrelin cells possess specific machinery to provide the octanoyl acid necessary for ghrelin acylation but that this machinery is absent from pancreatic β-cells. Despite the overexpression of ghrelin, plasma ghrelin levels in the portal veins of RIP-GG Tg mice were unchanged from control levels. Glucose tolerance, insulin secretion, and islet architecture in RIP-GG Tg mice were not significantly different even when the mice were fed a MCTD. These results indicate that intraislet ghrelin does not play a major role in the regulation of insulin secretion in vivo.

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Impaired hyperphosphorylation of rotavirus NSP5 in cells depleted of casein kinase 1α is associated with the formation of viroplasms with altered morphology and a moderate decrease in virus replication

Journal of General Virology ◽

10.1099/vir.0.82922-0 ◽

2007 ◽

Vol 88 (10) ◽

pp. 2800-2810 ◽

Cited By ~ 22

Author(s):

Michela Campagna ◽

Mauricio Budini ◽

Francesca Arnoldi ◽

Ulrich Desselberger ◽

Jorge E. Allende ◽

...

Keyword(s):

Cytoplasmic Inclusion ◽

Rna Replication ◽

Viral Rna ◽

Structural Protein ◽

Cytoplasmic Inclusion Bodies ◽

Replicative Cycle ◽

In Cells

The rotavirus (RV) non-structural protein 5, NSP5, is encoded by the smallest of the 11 genomic segments and localizes in ‘viroplasms’, cytoplasmic inclusion bodies in which viral RNA replication and packaging take place. NSP5 is essential for the replicative cycle of the virus because, in its absence, viroplasms are not formed and viral RNA replication and transcription do not occur. NSP5 is produced early in infection and undergoes a complex hyperphosphorylation process, leading to the formation of proteins differing in electrophoretic mobility. The role of hyperphosphorylation of NSP5 in the replicative cycle of rotavirus is unknown. Previous in vitro studies have suggested that the cellular kinase CK1α is responsible for the NSP5 hyperphosphorylation process. Here it is shown, by means of specific RNA interference, that in vivo, CK1α is the enzyme that initiates phosphorylation of NSP5. Lack of NSP5 hyperphosphorylation affected neither its interaction with the virus VP1 and NSP2 proteins normally found in viroplasms, nor the production of viral proteins. In contrast, the morphology of viroplasms was altered markedly in cells in which CK1α was depleted and a moderate decrease in the production of double-stranded RNA and infectious virus was observed. These data show that CK1α is the kinase that phosphorylates NSP5 in virus-infected cells and contribute to further understanding of the role of NSP5 in RV infection.

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Granule docking and cargo release in pancreatic β-cells

Biochemical Society Transactions ◽

10.1042/bst0360294 ◽

2008 ◽

Vol 36 (3) ◽

pp. 294-299 ◽

Cited By ~ 9

Author(s):

Sebastian Barg ◽

Anders Lindqvist ◽

Stefanie Obermüller

Keyword(s):

Insulin Secretion ◽

Live Cell Imaging ◽

Cell Imaging ◽

Fusion Pore ◽

Β Cells ◽

Pancreatic Β Cells ◽

Isolated Pancreatic Islets ◽

Biphasic Insulin ◽

Biphasic Insulin Secretion

Biphasic insulin secretion is required for proper insulin action and is observed not only in vivo, but also in isolated pancreatic islets and even single β-cells. Late events in the granule life cycle are thought to underlie this temporal pattern. In the last few years, we have therefore combined live cell imaging and electrophysiology to study insulin secretion at the level of individual granules, as they approach the plasma membrane, undergo exocytosis and finally release their insulin cargo. In the present paper, we review evidence for two emerging concepts that affect insulin secretion at the level of individual granules: (i) the existence of specialized sites where granules dock in preparation for exocytosis; and (ii) post-exocytotic regulation of cargo release by the fusion pore.

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MicroRNA-378-3p/5p suppresses the migration and invasiveness of oral squamous carcinoma cells by inhibiting KLK4 expression

Biochemistry and Cell Biology ◽

10.1139/bcb-2019-0017 ◽

2020 ◽

Vol 98 (2) ◽

pp. 154-163

Author(s):

Zhi Cui ◽

Shiqun Sun ◽

Qilin Liu ◽

Xuechun Zhou ◽

Siyu Gao ◽

...

Keyword(s):

Epithelial Mesenchymal Transition ◽

Squamous Carcinoma ◽

Effective Measure ◽

Mesenchymal Transition ◽

Squamous Carcinoma Cells ◽

Oral Squamous Carcinoma ◽

In Cells

Distant metastasis frequently occurs in oral squamous cell carcinoma (OSCC) and contributes to the adverse prognosis for patients with OSCC. However, the potential mechanisms behind the metastasis have not yet been clarified. This study investigated the role of miR-378 in the migration and invasiveness of OSCC in vitro and in vivo. According to our results, the migration and invasiveness of OSCC cells were increased in cells overexpressing miR-378, and reduced in cells where miR-378-3p/5p was silenced. In addition, overexpression of miR-378 suppressed the expressions and activities of matrix metalloproteinase 9 (MMP-9) and MMP-2. Epithelial–mesenchymal transition (EMT) was restrained by overexpression of miR-378, as evidenced by an increase in E-cadherin expression and decrease in N-cadherin and uPA expression. However, knockdown of miR-378-3p/5p produced the opposite results. Moreover, kallikrein-related peptidase 4 (KLK4) was confirmed to be a target gene of miR-378. Overexpression of KLK4 reversed the induced decrease in migration and invasiveness of cells overexpressing miR-378 by upregulating the levels of MMP-9, MMP-2, and N-cadherin, and downregulating the level of E-cadhrin. Finally, the number of metastasis nodules in the lung tissues of nude mice was reduced by overexpression of miR-378, whereas the number of metastases increased with knockdown of miR-378. Taken together, our results suggest that the miR-378–KLK4 axis is involved in the mechanisms behind the migration and invasiveness of OSCC cells. Targeting the miR-378–KLK4 axis may be an effective measure for treating OSCC.

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EphrinB1 modulates glutamatergic inputs into POMC neurons and controls glucose homeostasis

10.1101/2020.02.10.941765 ◽

2020 ◽

Author(s):

Manon Gervais ◽

Alexandre Picard ◽

Bernard Thorens ◽

Sophie Croizier

Keyword(s):

Insulin Secretion ◽

Glucose Homeostasis ◽

Synapse Formation ◽

Brain Regions ◽

Excitatory Input ◽

Nerve Activity ◽

Input Amount

AbstractProopiomelanocortin (POMC) neurons are major regulators of energy balance and glucose homeostasis. In addition to being regulated by hormones and nutrients, POMC neurons are controlled by glutamatergic input originating from multiple brain regions. However, the factors involved in the formation of glutamatergic inputs and how they contribute to bodily functions remain largely unknown. Here, we show that during the development of glutamatergic inputs, POMC neurons exhibit enriched expression of the Efnb1 (EphrinB1) and Efnb2 (EphrinB2) genes, which are known to control excitatory synapse formation. In vitro silencing and in vivo loss of Efnb1 or Efnb2 in POMC neurons decreases the amount of glutamatergic inputs into these neurons. We found that mice lacking Efnb1 in POMC neurons display impaired glucose tolerance due to blunted vagus nerve activity and decreased insulin secretion. However, mice lacking Efnb2 in POMC neurons showed no deregulation of insulin secretion and only mild alterations in feeding behavior and gluconeogenesis. Collectively, our data demonstrate the role of ephrins in controlling excitatory input amount into POMC neurons and show an isotype-specific role of ephrins on the regulation of glucose homeostasis and feeding.

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l-cysteine reversibly inhibits glucose-induced biphasic insulin secretion and ATP production by inactivating PKM2

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1417197112 ◽

2015 ◽

Vol 112 (10) ◽

pp. E1067-E1076 ◽

Cited By ~ 30

Author(s):

Daiki Nakatsu ◽

Yuta Horiuchi ◽

Fumi Kano ◽

Yoshiyuki Noguchi ◽

Taichi Sugawara ◽

...

Keyword(s):

Insulin Secretion ◽

Min6 Cells ◽

Atp Production ◽

Insulin Synthesis ◽

Subunit Dissociation ◽

Flight Mass Spectrometry ◽

Biphasic Insulin ◽

Biphasic Insulin Secretion ◽

Glucose Stimulated Insulin Secretion

Increase in the concentration of plasma l-cysteine is closely associated with defective insulin secretion from pancreatic β-cells, which results in type 2 diabetes (T2D). In this study, we investigated the effects of prolonged l-cysteine treatment on glucose-stimulated insulin secretion (GSIS) from mouse insulinoma 6 (MIN6) cells and from mouse pancreatic islets, and found that the treatment reversibly inhibited glucose-induced ATP production and resulting GSIS without affecting proinsulin and insulin synthesis. Comprehensive metabolic analyses using capillary electrophoresis time-of-flight mass spectrometry showed that prolonged l-cysteine treatment decreased the levels of pyruvate and its downstream metabolites. In addition, methyl pyruvate, a membrane-permeable form of pyruvate, rescued l-cysteine–induced inhibition of GSIS. Based on these results, we found that both in vitro and in MIN6 cells, l-cysteine specifically inhibited the activity of pyruvate kinase muscle isoform 2 (PKM2), an isoform of pyruvate kinases that catalyze the conversion of phosphoenolpyruvate to pyruvate. l-cysteine also induced PKM2 subunit dissociation (tetramers to dimers/monomers) in cells, which resulted in impaired glucose-induced ATP production for GSIS. DASA-10 (NCGC00181061, a substituted N,N′-diarylsulfonamide), a specific activator for PKM2, restored the tetramer formation and the activity of PKM2, glucose-induced ATP production, and biphasic insulin secretion in l-cysteine–treated cells. Collectively, our results demonstrate that impaired insulin secretion due to exposure to l-cysteine resulted from its direct binding and inactivation of PKM2 and suggest that PKM2 is a potential therapeutic target for T2D.

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