scholarly journals Glucose Effects on Beta-Cell Growth and Survival Require Activation of Insulin Receptors and Insulin Receptor Substrate 2

2009 ◽  
Vol 29 (11) ◽  
pp. 3219-3228 ◽  
Author(s):  
Anke Assmann ◽  
Kohjiro Ueki ◽  
Jonathon N. Winnay ◽  
Takahashi Kadowaki ◽  
Rohit N. Kulkarni
Keyword(s):  
Insulin Receptor ◽  
Signaling Pathway ◽  
Cell Lines ◽  
Insulin Signaling ◽  
Insulin Receptors ◽  
Insulin Signaling Pathway ◽  
Insulin Receptor Substrate ◽  
Β Cells ◽  
Β Cell ◽  
Growth And Survival

ABSTRACT Insulin and insulin-like growth factor I (IGF-I) are ubiquitous hormones that regulate growth and metabolism of most mammalian cells, including pancreatic β-cells. In addition to being an insulin secretagogue, glucose regulates proliferation and survival of β-cells. However, it is unclear whether the latter effects of glucose occur secondary to autocrine activation of insulin signaling proteins by secreted insulin. To examine this possibility we studied the effects of exogenous glucose or insulin in β-cell lines completely lacking either insulin receptors (βIRKO) or insulin receptor substrate 2 (βIRS2KO). Exogenous addition of either insulin or glucose activated proteins in the insulin signaling pathway in control β-cell lines with the effects of insulin peaking earlier than glucose. Insulin stimulation of βIRKO and βIRS2KO cells led to blunted activation of phosphatidylinositol 3-kinase and Akt kinase, while surprisingly, glucose failed to activate either kinase but phosphorylated extracellular signal-regulated kinase. Control β-cells exhibited low expression of IGF-1 receptors compared to compensatory upregulation in βIRKO cells. The signaling data support the slow growth and reduced DNA and protein synthesis in βIRKO and βIRS2KO cells in response to glucose stimulation. Together, these studies provide compelling evidence that the growth and survival effects of glucose on β-cells require activation of proteins in the insulin signaling pathway.

scholarly journals Altered Insulin Receptor Substrate 1 Phosphorylation in Blood Neuron-Derived Extracellular Vesicles From Patients With Parkinson’s Disease

2020 ◽  
Vol 8 ◽  
Author(s):  
Szu-Yi Chou ◽  
Lung Chan ◽  
Chen-Chih Chung ◽  
Jing-Yuan Chiu ◽  
Yi-Chen Hsieh ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Insulin Receptor ◽  
Signaling Pathway ◽  
Extracellular Vesicles ◽  
Insulin Signaling ◽  
Clinical Manifestations ◽  
Insulin Signaling Pathway ◽  
Insulin Receptor Substrate ◽  
Neuronal Markers

IntroductionDiabetes increases the risk of Parkinson’s disease (PD). The phosphorylation of type 1 insulin receptor substrate (IRS-1) determines the function of insulin signaling pathway. Extracellular vesicles (EVs) are emerging as biomarkers of human diseases. The present study investigated whether PD patients exert altered phosphorylation IRS-1 (p-IRS-1) inside the blood neuron-derived extracellular vesicles (NDEVs).Research Design and MethodsIn total, there were 94 patients with PD and 63 healthy controls recruited and their clinical manifestations were evaluated. Blood NDEVs were isolated using the immunoprecipitation method, and Western blot analysis was conducted to assess total IRS-1, p-IRS-1, and downstream substrates level in blood NDEVs. Statistical analysis was performed using SPSS 19.0, and p < 0.05 was considered significant.ResultsThe isolated blood EVs were validated according to the presence of CD63 and HSP70, nanoparticle tracking analysis and transmission electron microscopy. NDEVs were positive with neuronal markers. PD patients exerted significantly higher level of p-IRS-1S312 in blood NDEVs than controls. In addition, the p-IRS-1S312 levels in blood NDEVs was positively associated with the severity of tremor in PD patients after adjusting of age, sex, hemoglobin A1c, and body mass index (BMI).ConclusionPD patients exerted altered p-IRS-1S312 in the blood NDEVs, and also correlated with the severity of tremor. These findings suggested the association between dysfunctional insulin signaling pathway with PD. The role of altered p-IRS-1S312 in blood NDEVs as a segregating biomarker of PD required further cohort study to assess the association with the progression of PD.

268 THE EFFECTS OF METFORMIN ON THE INSULIN SIGNALING PATHWAY ON PORCINE GRANULOSA LUTEIN CELLS IN A PRIMARY CULTURE SYSTEM

2007 ◽  
Vol 19 (1) ◽  
pp. 250
Author(s):  
M. S. Hossein ◽  
M. S. Lee ◽  
W. S. Hwang
Keyword(s):  
Insulin Receptor ◽  
Signaling Pathway ◽  
Granulosa Cells ◽  
Insulin Signaling ◽  
Luciferase Activity ◽  
Insulin Signaling Pathway ◽  
Nuclear Factor ◽  
Activator Protein 1 ◽  
Activator Protein ◽  
Nuclear Factor Kb

Metformin (N,N22-dimethylbiguanide) is an oral antihyperglycaemic drug which increases insulin-stimulated glucose uptake as an insulin sensitizing agent (ISA) and has direct effects on ovarian steroidogenesis in human. To investigate the effects of metformin on the insulin signaling pathway on porcine granulosa lutein cells in a primary culture system, we examined mRNA expressions of porcine insulin receptor, insulin-like growth factor-1 receptor, and insulin receptor substrate-1; expressions of downstream targets (Raf, MEK1/2, ERK, PDK1, mTOR, p70, and nuclear factor kB) of the insulin receptor signaling pathway; the luciferase activity of transcription factors activator protein 1; and nuclear factor kB. Granulosa cells were plated in DMEM and 10% fetal bovine serum at a density of 3.5 � 107 in a T-25 tissue culture flask and cultured for 48 h at 37�C in a humidified atmosphere of 5% CO2 and 95% air. Then, porcine granulosa lutein cells (pGLs) were cultured in a serum-free DMEM as a control group or supplemented with 10-5 M metformin, 100 ng mL-1 of insulin, or both for 24 h. The monolayer was collected for RT-PCR and western blot analysis. For transient transfections, porcine granulosa cells were plated in DMEM and 10% FBS at a concentration of 2.5 � 106/well in 24-well culture dishes for 16 h and then transfected with plasmid constructs using FuGene6 Transfection Reagent. Reporter vectors used in these studies were AP-1-luc and NF-κ B-luc. Cells were treated post-transfection with 10-5 M metformin, 100 ng mL-1 insulin, or both for 48 h. The luciferase activity was assayed using the dual luciferase assay kit with a Microlumat LB 96 P luminometer. Metformin with insulin significantly increased mRNA expressions of insulin receptor, insulin-like growth factor-1 receptor, and insulin receptor substrate-1, whereas metformin alone had no significant effect on the expression of genes. Metformin alone and with insulin significantly increased expressions of downstream targets of the insulin receptor signaling pathway except MEK2. Metformin with insulin significantly elicited an induction of luciferase activity in the transfection of activator protein 1 and nuclear factor kB reporter, whereas metformin alone did not. Metformin induced expressions of target molecules in the insulin signaling pathway but had no effect on the luciferase activity of activator protein 1 and nuclear factor kB in porcine granulosa lutein cells. Metformin with insulin increased the luciferase activity of activator protein 1. These results suggest that metformin with insulin could change the function of ovarian granulosa cells induced by activator protein 1 activity.

scholarly journals Sphingomyelinase has an insulin-like effect on glucose transporter translocation in adipocytes

1998 ◽  
Vol 274 (5) ◽  
pp. R1446-R1453 ◽  
Author(s):  
T. S. David ◽  
P. A. Ortiz ◽  
T. R. Smith ◽  
J. Turinsky
Keyword(s):  
Plasma Membrane ◽  
Insulin Receptor ◽  
Glucose Uptake ◽  
Signaling Pathway ◽  
Insulin Signaling ◽  
Glucose Transporter ◽  
Insulin Signaling Pathway ◽  
Glut 1 ◽  
Glut 4 ◽  
Glut 4 Translocation

Rat epididymal adipocytes were incubated with 0, 0.1, and 1 mU sphingomyelinase/ml for 30 or 60 min, and glucose uptake and GLUT-1 and GLUT-4 translocation were assessed. Adipocytes exposed to 1 mU sphingomyelinase/ml exhibited a 173% increase in glucose uptake. Sphingomyelinase had no effect on the abundance of GLUT-1 in the plasma membrane of adipocytes. In contrast, 1 mU sphingomyelinase/ml increased plasma membrane content of GLUT-4 by 120% and produced a simultaneous decrease in GLUT-4 abundance in the low-density microsomal fraction. Sphingomyelinase had no effect on tyrosine phosphorylation of either the insulin receptor β-subunit or the insulin receptor substrate-1, a signaling molecule in the insulin signaling pathway. It is concluded that the incubation of adipocytes with sphingomyelinase results in insulin-like translocation of GLUT-4 to the plasma membrane and that this translocation does not occur via the activation of the initial components of the insulin signaling pathway.

scholarly journals Altered function of insulin receptor substrate-1–deficient mouse islets and cultured β-cell lines

1999 ◽  
Vol 104 (12) ◽  
pp. R69-R75 ◽  
Author(s):  
Rohit N. Kulkarni ◽  
Jonathon N. Winnay ◽  
Molly Daniels ◽  
Jens C. Brüning ◽  
Sarah N. Flier ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Cell Lines ◽  
Insulin Receptor Substrate ◽  
Deficient Mouse ◽  
Β Cell ◽  
Insulin Receptor Substrate 1 ◽  
Mouse Islets

scholarly journals Differential Mitogenic Signaling in Insulin Receptor-Deficient Fetal Pancreatic β-Cells

Endocrinology ◽  
2006 ◽  
Vol 147 (4) ◽  
pp. 1959-1968 ◽  
Author(s):  
C. Guillen ◽  
P. Navarro ◽  
M. Robledo ◽  
A. M. Valverde ◽  
M. Benito
Keyword(s):  
Insulin Receptor ◽  
Cell Lines ◽  
Cell Mass ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Phosphatidylinositol 3 Kinase ◽  
Β Cells ◽  
Β Cell ◽  
Phosphatidylinositol 3

Insulin receptor (IR) may play an essential role in the development of β-cell mass in the mouse pancreas. To further define the function of this signaling system in β-cell development, we generated IR-deficient β-cell lines. Fetal pancreata were dissected from mice harboring a floxed allele of the insulin receptor (IRLoxP) and used to isolate islets. These islets were infected with a retrovirus to express simian virus 40 large T antigen, a strategy for establishing β-cell lines (β-IRLoxP). Subsequently, these cells were infected with adenovirus encoding cre recombinase to delete insulin receptor (β-IR−/−). β-Cells expressed insulin and Pdx-1 mRNA in response to glucose. In β-IRLoxP β-cells, p44/p42 MAPK and phosphatidylinositol 3 kinase pathways, mammalian target of rapamycin (mTOR), and p70S6K phosphorylation and β-cell proliferation were stimulated in response to insulin. Wortmannin or PD98059 had no effect on insulin-mediated mTOR/p70S6K signaling and the corresponding mitogenic response. However, the presence of both inhibitors totally impaired these signaling pathways and mitogenesis in response to insulin. Rapamycin completely blocked insulin-activated mTOR/p70S6K signaling and mitogenesis. Interestingly, in β-IR−/− β-cells, glucose failed to stimulate phosphatidylinositol 3 kinase activity but induced p44/p42 MAPKs and mTOR/p70S6K phosphorylation and β-cell mitogenesis. PD98059, but not wortmannin, inhibited glucose-induced mTOR/p70S6K signaling and mitogenesis in those cells. Finally, rapamycin blocked glucose-mediated mitogenesis of β-IR−/− cells. In conclusion, independently of glucose, insulin can mediate mitogenesis in fetal pancreatic β-cell lines. However, in the absence of the insulin receptor, glucose induces β-cell mitogenesis.

scholarly journals Insulin and secretagogues differentially regulate fluid-phase pinocytosis in insulin-secreting β-cells

1996 ◽  
Vol 318 (2) ◽  
pp. 623-629 ◽  
Author(s):  
Gang XU ◽  
Jennie HOWLAND ◽  
Paul L ROTHENBERG
Keyword(s):  
T Cells ◽  
Cell Surface ◽  
Insulin Receptor ◽  
Cell Line ◽  
Chinese Hamster Ovary Cells ◽  
Insulin Receptors ◽  
Fluid Phase ◽  
Β Cells ◽  
Β Cell ◽  
Basal Rate

The physiological role of the β-cell insulin receptor is unknown. To evaluate a candidate function, the insulin regulation of fluid-phase pinocytosis was investigated in a clonal insulinoma cell line (βTC6-F7) and, for comparison, also in Chinese hamster ovary cells transfected with the human insulin receptor (CHO-T cells). In CHO-T cells, the net rate of fluid-phase pinocytosis was rapidly increased 3–4-fold over the basal rate by 100 nM insulin, with half-maximal stimulation at 2 nM insulin, as assayed by cellular uptake of horseradish peroxidase from the medium. Wortmannin, an inhibitor of phosphatidylinositol (PI)-3-kinase, blocked insulin-stimulated pinocytosis with an IC50 of 7.5 nM without affecting the basal rate of pinocytosis. In insulin-secreting βTC6-F7 cells, the secretagogues glucose and carbachol (at maximally effective concentrations of 15 mM and 0.5 mM respectively) augmented fluid-phase pinocytosis 1.65-fold over the basal rate. Wortmannin also inhibited secretagogue-stimulated pinocytosis in these β-cells with an IC50 of 7 nM but did not affect the basal rate of pinocytosis measured in the absence of secretagogues. Wortmannin did not influence either basal or secretagogue-induced insulin secretion. Although these βTC6-F7 cells have cell-surface insulin receptors, adding exogenous insulin or insulin-like growth factor 1 did not affect their rate of fluid-phase pinocytosis, either in the absence or presence of secretagogues. From these observations, we conclude that: (1) in both insulin-secreting β-cells and in conventional, insulin-responsive CHO-T cells, a common, wortmannin-sensitive reaction, which probably involves PI-3-kinase, regulates fluid-phase pinocytosis; (2) the insulin-receptor signal transduction pathway is dissociated from the regulation of fluid-phase pinocytosis in the insulin-secreting β-cell line we studied; and (3) the enhancement of fluid-phase pinocytosis associated with secretagogue-induced insulin release in βTC6-F7 cells is not attributable to autocrine activation of β-cell surface insulin receptors.

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