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Role of ATP and Pi in the mechanism of insulin secretion in the mouse insulinoma betaTC3 cell line.

ABSTRACT: Understanding the biochemical events associated with glucose-stimulated insulin secretion by pancreatic beta cells is of importance in gaining insight into both the pathophysiology of diabetes and the development of tissue-engineered bioartificial pancreatic substitutes. We have investigated the effects of glucose concentration on the bioenergetic status and on the metabolic and secretory functions exhibited by mouse insulinoma betaTC3 cells entrapped in calcium alginate/poly-L-lysine/alginate (APA) beads. Cells entrapped in APA beads constitute a possible implantable bioartificial pancreas for the long-term treatment of insulin-dependent diabetes mellitus. Our results show that, in entrapped betaTC3 cells, the oxygen consumption rate and the intracellular nucleotide triphosphate levels are unaffected by a step change in glucose concentration from 16 mM to 0 mM for 4.5 h and then back to 16 mM. The intracellular Pi level and the ammonia production rate were doubled, while insulin secretion was decreased 10-fold, upon switching from 16 mM to 0 mM glucose. The implications of these findings in the context of pancreatic beta cell biochemistry and the mechanism of the 'Fuel Hypothesis' are discussed.

SUBMITTER: Papas KK

PROVIDER: S-EPMC1218736 | biostudies-other | 1997 Sep

REPOSITORIES: biostudies-other

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Selenomethionine modulates insulin secretion in the MIN6-K8 mouse insulinoma cell line.

Project description:Selenium is an essential trace element of interest for its potential role in glucose homeostasis. The present study investigated the impact of selenium supplementation as selenomethionine (SeMet) on insulin secretion in MIN6-K8 cells, a pancreatic β-cell model. We found that SeMet enhanced percent glucose-induced insulin secretion, while also increasing tolbutamide- and KCl-induced percent insulin secretion. RNA-sequencing showed that SeMet supplementation altered expression of several selenoproteins, including glutathione peroxidase 3 (Gpx3) and selenoprotein P (SelP). Targeted knockdown of Gpx3 increased both percent and total insulin release, while SelP knockdown increased insulin content and insulin release. Collectively, these studies support a putative role for selenium and selenoproteins in the regulation of insulin secretion, glucose homeostasis, and diabetes risk.

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Selenomethionine Modulates Insulin Secretion in the MIN6-K8 Mouse Insulinoma Cell Line

Project description:Selenium is an essential trace element that has gained interest for its potential role in glucose homeostasis. The purpose of the present study was to investigate the impact of selenium supplementation as selenomethionine (SeMet) on insulin secretion in MIN6-K8 cells, a model of pancreatic -cells. We found that 40 μM and 80 μM SeMet significantly enhanced percent insulin secretion at low (2.8 mM), intermediate (11.7 mM), and high (16.7 mM) glucose stimulation. SeMet also increased tolbutamide- or KCl-induced percent insulin secretion at 40 μM and 80 μM. Ca2+ influx was only reduced with 80 μM SeMet. RNA-sequencing showed that 40 μM SeMet supplementation upregulated expression of selenoprotein H (SelH) and thioredoxin reductase 1 (Txnrd 1) and downregulated expression of glutathione peroxidase 3 (Gpx3), selenoprotein O (SelO), and selenoprotein P (SelP). Gpx3 knockdown increased both percent and total insulin release with high glucose stimulation. SelP knockdown increased insulin release at high glucose. In conclusion, high SeMet supplementation augments insulin secretion, while reductions in Gpx3 and SelP expression, from SeMet supplementation or via silencing, augment -cell function in the MIN6-K8 cell line. These studies support a putative role for selenium and selenoproteins in the regulation of glucose homeostasis and diabetes risk.

2024-03-13 | GSE183775 | GEO

RyR2/IRBIT regulates insulin gene transcript, insulin content, and secretion in the insulinoma cell line INS-1.

Project description:The role of ER Ca2+ release via ryanodine receptors (RyR) in pancreatic β-cell function is not well defined. Deletion of RyR2 from the rat insulinoma INS-1 (RyR2KO) enhanced IP3 receptor activity stimulated by 7.5 mM glucose, coincident with reduced levels of the protein IP3 Receptor Binding protein released with Inositol 1,4,5 Trisphosphate (IRBIT). Insulin content, basal (2.5 mM glucose) and 7.5 mM glucose-stimulated insulin secretion were reduced in RyR2KO and IRBITKO cells compared to controls. INS2 mRNA levels were reduced in both RyR2KO and IRBITKO cells, but INS1 mRNA levels were specifically decreased in RyR2KO cells. Nuclear localization of S-adenosylhomocysteinase (AHCY) was increased in RyR2KO and IRBITKO cells. DNA methylation of the INS1 and INS2 gene promotor regions was very low, and not different among RyR2KO, IRBITKO, and controls, but exon 2 of the INS1 and INS2 genes was more extensively methylated in RyR2KO and IRBITKO cells. Exploratory proteomic analysis revealed that deletion of RyR2 or IRBIT resulted in differential regulation of 314 and 137 proteins, respectively, with 41 in common. These results suggest that RyR2 regulates IRBIT levels and activity in INS-1 cells, and together maintain insulin content and secretion, and regulate the proteome, perhaps via DNA methylation.

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Selenomethionine Modulates Insulin Secretion in the MIN6-K8 Mouse Insulinoma Cell Line

Project description:Selenomethionine Modulates Insulin Secretion in the MIN6-K8 Mouse Insulinoma Cell Line

| PRJNA761990 | ENA

Chronic reduction of the cytosolic or mitochondrial NAD(P)-malic enzyme does not affect insulin secretion in a rat insulinoma cell line.

Project description:The cytosolic malic enzyme (ME1) has been suggested to augment insulin secretion via the malate-pyruvate and/or citrate-pyruvate shuttles, through the production of NADPH or other metabolites. We used selectable vectors expressing short hairpin RNA (shRNA) to stably decrease Me1 mRNA levels by 80-86% and ME1 enzyme activity by 78-86% with either of two shRNAs in the INS-1 832/13 insulinoma cell line. Contrary to published short term ME1 knockdown experiments, our long term targeted cells showed normal insulin secretion in response to glucose or to glutamine plus 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid. We found no increase in the mRNAs and enzyme activities of the cytosolic isocitrate dehydrogenase or glucose-6-phosphate dehydrogenase, which also produce cytosolic NADPH. There was no compensatory induction of the mRNAs for the mitochondrial malic enzymes Me2 or Me3. Interferon pathway genes induced in preliminary small interfering RNA experiments were not induced in the long term shRNA experiments. We repeated our study with an improved vector containing Tol2 transposition sequences to produce a higher rate of stable transferents and shortened time to testing, but this did not alter the results. We similarly used stably expressed shRNA to reduce mitochondrial NAD(P)-malic enzyme (Me2) mRNA by up to 95%, with severely decreased ME2 protein and a 90% decrease in enzyme activity. Insulin release to glucose or glutamine plus 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid remained normal. The maintenance of robust insulin secretion after lowering expression of either one of these malic enzymes is consistent with the redundancy of pathways of pyruvate cycling and/or cytosolic NADPH production in insulinoma cells.

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Menaquinone-4 Amplified Glucose-Stimulated Insulin Secretion in Isolated Mouse Pancreatic Islets and INS-1 Rat Insulinoma Cells.

Project description:Vitamin K2 is indispensable for blood coagulation and bone metabolism. Menaquinone-4 (MK-4) is the predominant homolog of vitamin K2, which is present in large amounts in the pancreas, although its function is unclear. Meanwhile, β-cell dysfunction following insulin secretion has been found to decrease in patients with type 2 diabetes mellitus. To elucidate the physiological function of MK-4 in pancreatic β-cells, we studied the effects of MK-4 treatment on isolated mouse pancreatic islets and rat INS-1 cells. Glucose-stimulated insulin secretion significantly increased in isolated islets and INS-1 cells treated with MK-4. It was further clarified that MK-4 enhanced cAMP levels, accompanied by the regulation of the exchange protein directly activated by the cAMP 2 (Epac2)-dependent pathway but not the protein kinase A (PKA)-dependent pathway. A novel function of MK-4 on glucose-stimulated insulin secretion was found, suggesting that MK-4 might act as a potent amplifier of the incretin effect. This study therefore presents a novel potential therapeutic approach for impaired insulinotropic effects.

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RyR2/IRBIT regulates insulin gene transcription, insulin content, and secretion in the insulinoma cell line INS-1

Project description:The role of ER Ca2+ release via ryanodine receptors (RyR) in pancreatic B-cell function is not well defined. Deletion of RyR2 from the rat insulinoma INS-1 enhanced the Ca2+ integral (AUC) stimulated by glucose, and reduced levels of the protein IRBIT (AHCYL1). Deletion of IRBIT increased the Ca2+ AUC in response to glucose via enhanced IP3 receptor activity. Insulin content, basal and glucose-stimulated insulin secretion (GSIS), and INS2 mRNA levels were reduced in both RyR2KO and IRBITKO cells. Nuclear localization of S-adenosylhomocysteinase (AHCY) was increased in RyR2KO and IRBITKO cells, and exon 2 of the INS1 and INS2 genes was more extensively methylated in RyR2KO and IRBITKO cells. Deletion of RyR2 or IRBIT resulted in differential regulation of 314 and 137 proteins, respectively, with 41 in common. We conclude that RyR2 regulates IRBIT levels in INS-1 cells, and together regulate insulin content, GSIS, and the proteome, perhaps via DNA methylation.

2021-11-10 | MSV000088344 | MassIVE

Functional Analysis of Novel Candidate Regulators of Insulin Secretion in the MIN6 Mouse Pancreatic β Cell Line.

Project description:Elucidating the regulation of glucose-stimulated insulin secretion (GSIS) in pancreatic β cells is important for understanding and treating diabetes. The pancreatic β cell line, MIN6, retains GSIS but gradually loses it in long-term culture. The MIN6 subclone, MIN6c4, exhibits well-regulated GSIS even after prolonged culture. We previously used DNA microarray analysis to compare gene expression in the parental MIN6 cells and MIN6c4 cells and identified several differentially regulated genes that may be involved in maintaining GSIS. Here we investigated the potential roles of six of these genes in GSIS: Tmem59l (Transmembrane protein 59 like), Scgn (Secretagogin), Gucy2c (Guanylate cyclase 2c), Slc29a4 (Solute carrier family 29, member 4), Cdhr1 (Cadherin-related family member 1), and Celsr2 (Cadherin EGF LAG seven-pass G-type receptor 2). These genes were knocked down in MIN6c4 cells using lentivirus vectors expressing gene-specific short hairpin RNAs (shRNAs), and the effects of the knockdown on insulin expression and secretion were analyzed. Suppression of Tmem59l, Scgn, and Gucy2c expression resulted in significantly decreased glucose- and/or KCl-stimulated insulin secretion from MIN6c4 cells, while the suppression of Slc29a4 expression resulted in increased insulin secretion. Tmem59l overexpression rescued the phenotype of the Tmem59l knockdown MIN6c4 cells, and immunostaining analysis indicated that the TMEM59L protein colocalized with insulin and GM130, a Golgi complex marker, in MIN6 cells. Collectively, our findings suggested that the proteins encoded by Tmem59l, Scgn, Gucy2c, and Slc29a4 play important roles in regulating GSIS. Detailed studies of these proteins and their functions are expected to provide new insights into the molecular mechanisms involved in insulin secretion.

| S-EPMC4795703 | biostudies-literature

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