scholarly journals The LIM homeodomain protein ISL1 mediates the function of TCF7L2 in pancreatic beta cells

2018 ◽  
Vol 61 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Weijuan Shao ◽  
Vivian Szeto ◽  
Zhuolun Song ◽  
Lili Tian ◽  
Zhong-Ping Feng ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Wnt Pathway ◽  
Homeodomain Protein ◽  
Adenovirus Infection ◽  
Β Cell ◽  
Downstream Target ◽  
Cell Gene Expression ◽  
Mouse Islets ◽  
Cell Gene

Pancreatic β-cell Tcf7l2 deletion or its functional knockdown suggested the essential role of this Wnt pathway effector in controlling insulin secretion, glucose homeostasis and β-cell gene expression. As the LIM homeodomain protein ISL1 is a suggested Wnt pathway downstream target, we hypothesize that it mediates metabolic functions of TCF7L2. We aimed to determine the role of ISL1 in mediating the function of TCF7L2 and the incretin hormone GLP-1 in pancreatic β-cells. The effect of dominant negative TCF7L2 (TCF7L2DN) mediated Wnt pathway functional knockdown on Isl1 expression was determined in βTCFDN mouse islets and in the rat insulinoma cell line INS-1 832/13. Luciferase reporter assay and chromatin immunoprecipitation were utilized to determine whether Isl1 is a direct downstream target of Tcf7l2. TCF7L2DN adenovirus infection and siRNA-mediated Isl1 knockdown on β-cell gene expression were compared. Furthermore, Isl1 knockdown on GLP-1 stimulated β-catenin S675 phosphorylation and insulin secretion was determined. We found that TCF7L2DN repressed ISL1 levels in βTCFDN islets and the INS-1 832/13 cell line. Wnt stimulators enhanced Isl1 promoter activity and binding of TCF7L2 on Isl1 promoter. TCF7L2DN adenovirus infection and Isl1 knockdown generated similar repression on expression of β-cell genes, including the ones that encode GLUT2 and GLP-1 receptor. Either TCF7L2DN adenovirus infection or Isl1 knockdown attenuated GLP-1-stimulated β-catenin S675 phosphorylation in INS-1 832/13 cells or mouse islets and GLP-1 stimulated insulin secretion in INS-1 832/13 or MIN6 cells. Our observations support the existence of TCF7L2–ISL1 transcriptional network, and we suggest that this network also mediates β-cell function of GLP-1.

scholarly journals Cyanidin Stimulates Insulin Secretion and Pancreatic β-Cell Gene Expression through Activation of l-type Voltage-Dependent Ca2+ Channels

Nutrients ◽  
2017 ◽  
Vol 9 (8) ◽  
pp. 814 ◽  
Author(s):  
Tanyawan Suantawee ◽  
Sara Elazab ◽  
Walter Hsu ◽  
Shaomian Yao ◽  
Henrique Cheng ◽  
...  
Keyword(s):  
Gene Expression ◽  
Insulin Secretion ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Voltage Dependent ◽  
Cell Gene Expression ◽  
Cell Gene ◽  
Ca2 Channels

scholarly journals Regulation of Insulin Secretion and β-Cell Mass by Activating Signal Cointegrator 2

2006 ◽  
Vol 26 (12) ◽  
pp. 4553-4563 ◽  
Author(s):  
Seon-Yong Yeom ◽  
Geun Hyang Kim ◽  
Chan Hee Kim ◽  
Heun Don Jung ◽  
So-Yeon Kim ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Endocrine Cells ◽  
Potential Role ◽  
Cell Mass ◽  
Dominant Negative ◽  
Transcriptional Coactivator ◽  
Β Cells ◽  
Β Cell ◽  
Islet Mass

ABSTRACT Activating signal cointegrator 2 (ASC-2) is a transcriptional coactivator of many nuclear receptors (NRs) and other transcription factors and contains two NR-interacting LXXLL motifs (NR boxes). In the pancreas, ASC-2 is expressed only in the endocrine cells of the islets of Langerhans, but not in the exocrine cells. Thus, we examined the potential role of ASC-2 in insulin secretion from pancreatic β-cells. Overexpressed ASC-2 increased glucose-elicited insulin secretion, whereas insulin secretion was decreased in islets from ASC-2+/− mice. DN1 and DN2 are two dominant-negative fragments of ASC-2 that contain NR boxes 1 and 2, respectively, and block the interactions of cognate NRs with the endogenous ASC-2. Primary rat islets ectopically expressing DN1 or DN2 exhibited decreased insulin secretion. Furthermore, relative to the wild type, ASC-2+/− mice showed reduced islet mass and number, which correlated with increased apoptosis and decreased proliferation of ASC-2+/− islets. These results suggest that ASC-2 regulates insulin secretion and β-cell survival and that the regulatory role of ASC-2 in insulin secretion appears to involve, at least in part, its interaction with NRs via its two NR boxes.

scholarly journals Functional Role of Serotonin in Insulin Secretion in a Diet-Induced Insulin-Resistant State

Endocrinology ◽  
2014 ◽  
Vol 156 (2) ◽  
pp. 444-452 ◽  
Author(s):  
Kyuho Kim ◽  
Chang-Myung Oh ◽  
Mica Ohara-Imaizumi ◽  
Sangkyu Park ◽  
Jun Namkung ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Pancreatic Islets ◽  
Cell Function ◽  
Β Cell ◽  
Pancreas Perfusion ◽  
Insulin Resistant ◽  
Β Cell Function ◽  
Resistant State ◽  
Insulin Resistant State

The physiological role of serotonin, or 5-hydroxytryptamine (5-HT), in pancreatic β-cell function was previously elucidated using a pregnant mouse model. During pregnancy, 5-HT increases β-cell proliferation and glucose-stimulated insulin secretion (GSIS) through the Gαq-coupled 5-HT2b receptor (Htr2b) and the 5-HT3 receptor (Htr3), a ligand-gated cation channel, respectively. However, the role of 5-HT in β-cell function in an insulin-resistant state has yet to be elucidated. Here, we characterized the metabolic phenotypes of β-cell-specific Htr2b−/− (Htr2b βKO), Htr3a−/− (Htr3a knock-out [KO]), and β-cell-specific tryptophan hydroxylase 1 (Tph1)−/− (Tph1 βKO) mice on a high-fat diet (HFD). Htr2b βKO, Htr3a KO, and Tph1 βKO mice exhibited normal glucose tolerance on a standard chow diet. After 6 weeks on an HFD, beginning at 4 weeks of age, both Htr3a KO and Tph1 βKO mice developed glucose intolerance, but Htr2b βKO mice remained normoglycemic. Pancreas perfusion assays revealed defective first-phase insulin secretion in Htr3a KO mice. GSIS was impaired in islets isolated from HFD-fed Htr3a KO and Tph1 βKO mice, and 5-HT treatment improved insulin secretion from Tph1 βKO islets but not from Htr3a KO islets. Tph1 and Htr3a gene expression in pancreatic islets was not affected by an HFD, and immunostaining could not detect 5-HT in pancreatic islets from mice fed an HFD. Taken together, these results demonstrate that basal 5-HT levels in β-cells play a role in GSIS through Htr3, which becomes more evident in a diet-induced insulin-resistant state.

scholarly journals A tumor-promoting role for soluble TβRIII in glioblastoma

2021 ◽  
Author(s):  
Isabel Burghardt ◽  
Judith Johanna Schroeder ◽  
Tobias Weiss ◽  
Dorothee Gramatzki ◽  
Michael Weller
Keyword(s):  
Endothelial Cells ◽  
Ex Vivo ◽  
Microvascular Endothelial Cells ◽  
Smad2 Phosphorylation ◽  
Cell Gene Expression ◽  
Microvascular Endothelial ◽  
Cell Gene ◽  
Mouse Glioma

Abstract Purpose Members of the transforming growth factor (TGF)-β superfamily play a key role in the regulation of the malignant phenotype of glioblastoma by promoting invasiveness, angiogenesis, immunosuppression, and maintaining stem cell-like properties. Betaglycan, a TGF-β coreceptor also known as TGF-β receptor III (TβRIII), interacts with members of the TGF-β superfamily and acts as membrane-associated or shed molecule. Shed, soluble TβRIII (sTβRIII) is produced upon ectodomain cleavage of the membrane-bound form. Elucidating the role of TβRIII may improve our understanding of TGF-β pathway activity in glioblastoma Methods Protein levels of TβRIII were determined by immunohistochemical analyses and ex vivo single-cell gene expression profiling of glioblastoma tissue respectively. In vitro, TβRIII levels were assessed investigating long-term glioma cell lines (LTCs), cultured human brain-derived microvascular endothelial cells (hCMECs), glioblastoma-derived microvascular endothelial cells, and glioma-initiating cell lines (GICs). The impact of TβRIII on TGF-β signaling was investigated, and results were validated in a xenograft mouse glioma model Results Immunohistochemistry and ex vivo single-cell gene expression profiling of glioblastoma tissue showed that TβRIII was expressed in the tumor tissue, predominantly in the vascular compartment. We confirmed this pattern of TβRIII expression in vitro. Specifically, we detected sTβRIII in glioblastoma-derived microvascular endothelial cells. STβRIII facilitated TGF-β-induced Smad2 phosphorylation in vitro and overexpression of sTβRIII in a xenograft mouse glioma model led to increased levels of Smad2 phosphorylation, increased tumor volume, and decreased survival Conclusions These data shed light on the potential tumor-promoting role of extracellular shed TβRIII which may be released by glioblastoma endothelium with high sTβRIII levels.

scholarly journals Deficiency of VCP-Interacting Membrane Selenoprotein (VIMP) Leads to G1 Cell Cycle Arrest and Cell Death in MIN6 Insulinoma Cells

2018 ◽  
Vol 51 (5) ◽  
pp. 2185-2197 ◽  
Author(s):  
Lili Men ◽  
Juan Sun ◽  
Decheng Ren
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Insulin Secretion ◽  
Cell Apoptosis ◽  
Β Cells ◽  
Β Cell ◽  
Cycle Arrest ◽  
G1 Cell Cycle Arrest ◽  
Insulinoma Cells

Background/Aims: VCP-interacting membrane selenoprotein (VIMP), an ER resident selenoprotein, is highly expressed in β-cells, however, the role of VIMP in β-cells has not been characterized. In this study, we studied the relationship between VIMP deficiency and β-cell survival in MIN6 insulinoma cells. Methods: To determine the role of VIMP in β-cells, lentiviral VIMP shRNAs were used to knock down (KD) expression of VIMP in MIN6 cells. Cell death was quantified by propidium iodide (PI) staining followed by flow cytometric analyses using a FACS Caliber and FlowJo software. Cell apoptosis and proliferation were determined by TUNEL assay and Ki67 staining, respectively. Cell cycle was analyzed after PI staining. Results: The results show that 1) VIMP suppression induces β-cell apoptosis, which is associated with a decrease in Bcl-xL, and the β-cell apoptosis induced by VIMP suppression can be inhibited by overexpression of Bcl-xL; 2) VIMP knockdown (KD) decreases cell proliferation and G1 cell cycle arrest by accumulating p27 and decreasing E2F1; 3) VIMP KD suppresses unfolded protein response (UPR) activation by regulating the IRE1α and PERK pathways; 4) VIMP KD increases insulin secretion. Conclusion: These results suggest that VIMP may function as a novel regulator to modulate β-cell survival, proliferation, cell cycle, UPR and insulin secretion in MIN6 cells.

scholarly journals Reducing Glucokinase Activity Restores Endogenous Pulsatility and Enhances Insulin Secretion in Islets From db/db Mice

Endocrinology ◽  
2018 ◽  
Vol 159 (11) ◽  
pp. 3747-3760 ◽  
Author(s):  
Ishrat Jahan ◽  
Kathryn L Corbin ◽  
Avery M Bogart ◽  
Nicholas B Whitticar ◽  
Christopher D Waters ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Insulin Release ◽  
Opposite Effect ◽  
Glucose Sensing ◽  
Β Cell ◽  
Left Shift ◽  
Low Glucose ◽  
Mouse Islets ◽  
Secretion Rates

Abstract An early sign of islet failure in type 2 diabetes (T2D) is the loss of normal patterns of pulsatile insulin release. Disruptions in pulsatility are associated with a left shift in glucose sensing that can cause excessive insulin release in low glucose (relative hyperinsulinemia, a hallmark of early T2D) and β-cell exhaustion, leading to inadequate insulin release during hyperglycemia. Our hypothesis was that reducing excessive glucokinase activity in diabetic islets would improve their function. Isolated mouse islets were exposed to glucose and varying concentrations of the glucokinase inhibitor d-mannoheptulose (MH) to examine changes in intracellular calcium ([Ca2+]i) and insulin secretion. Acutely exposing islets from control CD-1 mice to MH in high glucose (20 mM) dose dependently reduced the size of [Ca2+]i oscillations detected by fura-2 acetoxymethyl. Glucokinase activation in low glucose (3 mM) had the opposite effect. We then treated islets from male and female db/db mice (age, 4 to 8 weeks) and heterozygous controls overnight with 0 to 10 mM MH to determine that 1 mM MH produced optimal oscillations. We then used 1 mM MH overnight to measure [Ca2+]i and insulin simultaneously in db/db islets. MH restored oscillations and increased insulin secretion. Insulin secretion rates correlated with MH-induced increases in amplitude of [Ca2+]i oscillations (R2 = 0.57, P < 0.01, n = 10) but not with mean [Ca2+]i levels in islets (R2 = 0.05, not significant). Our findings show that correcting glucose sensing can restore proper pulsatility to diabetic islets and improved pulsatility correlates with enhanced insulin secretion.

Effects of pharmacological inhibition of NADPH oxidase or iNOS on pro-inflammatory cytokine, palmitic acid or H2O2-induced mouse islet or clonal pancreatic β-cell dysfunction

2010 ◽  
Vol 30 (6) ◽  
pp. 445-453 ◽  
Author(s):  
Marta Michalska ◽  
Gabriele Wolf ◽  
Reinhard Walther ◽  
Philip Newsholme
Keyword(s):  
Fatty Acids ◽  
Insulin Secretion ◽  
Nadph Oxidase ◽  
Inflammatory Cytokine ◽  
Pancreatic Β Cell ◽  
Β Cells ◽  
Β Cell ◽  
Cell Dysfunction ◽  
Mouse Islets ◽  
Pro Inflammatory Cytokines

Various pancreatic β-cell stressors including cytokines and saturated fatty acids are known to induce oxidative stress, which results in metabolic disturbances and a reduction in insulin secretion. However, the key mechanisms underlying dysfunction are unknown. We investigated the effects of prolonged exposure (24 h) to pro-inflammatory cytokines, H2O2 or PA (palmitic acid) on β-cell insulin secretion, ATP, the NADPH oxidase (nicotinamide adenine dinucleotide phosphate oxidase) component p47phox and iNOS (inducible nitric oxide synthase) levels using primary mouse islets or clonal rat BRIN-BD11 β-cells. Addition of a pro-inflammatory cytokine mixture [IL-1β (interleukin-1β), TNF-α (tumour necrosis factor-α) and IFN-γ (interferon-γ)] or H2O2 (at sub-lethal concentrations) inhibited chronic (24 h) levels of insulin release by at least 50% (from islets and BRIN-BD11 cells), while addition of the saturated fatty acid palmitate inhibited acute (20 min) stimulated levels of insulin release from mouse islets. H2O2 decreased ATP levels in the cell line, but elevated p47phox and iNOS levels as did cytokine addition. Similar effects were observed in mouse islets with respect to elevation of p47phox and iNOS levels. Addition of antioxidants SOD (superoxide dismutase), Cat (catalase) and NAC (N-acetylcysteine) attenuated H2O2 or the saturated fatty acid palmitate-dependent effects, but not cytokine-induced dysfunction. However, specific chemical inhibitors of NADPH oxidase and/or iNOS appear to significantly attenuate the effects of cytokines, H2O2 or fatty acids in islets. While pro-inflammatory cytokines are known to increase p47phox and iNOS levels in β-cells, we now report that H2O2 can increase levels of the latter two proteins, suggesting a key role for positive-feedback redox sensitive regulation of β-cell dysfunction.

Abstract 1924: Carriers of Loss-of-Function Mutations in ABCA1 Display Pancreatic Beta Cell Dysfunction

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Menno Vergeer ◽  
Liam R Brunham ◽  
Joris Koetsveld ◽  
Janine K Kruit ◽  
C B Verchere ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Insulin Sensitivity ◽  
Plasma Glucose ◽  
Sensitivity Index ◽  
Loss Of Function ◽  
Β Cell ◽  
C Peptide ◽  
Cell Dysfunction ◽  
Time Interaction

Background The ATP Binding Cassette transporter A1 (ABCA1) transports free cholesterol to nascent high-density lipoproteins (HDL) and maintains plasma HDL levels. In mice, ABCA1 is essential in regulating intracellular cholesterol homeostasis and insulin secretion in the β cell. The role of ABCA1 in human glucose metabolism is unclear. Objective and methods To assess the effects of ABCA1 dysfunction on glucose homeostasis in humans , we matched heterozygous carriers of disruptive mutations in ABCA1 and non-carriers for age, gender and BMI and performed oral glucose tolerance tests (OGTT; 9 vs. 8 respectively) and hyperglycemic clamping experiments (6 vs. 6). Results Carriers had lower HDL-C levels than non-carriers (0.58 ± 0.3 vs. 1.46 ± 0.4 mmol/L, p=0.001) but LDL-C did not differ (3.4 ± 1.0 vs. 2.8 ± 0.8 mmol/L, p=0.21). Fasting plasma glucose was not different (5.2 ± 1.5 vs. 5.0 ± 0.4 mmol/L). Glucose curves after OGTT were significantly higher in carriers than in non-carriers (genotype * time interaction, p=0.005; plasma glucose at t=60 min 9.0 ± 3.0 mmol/L vs. 6.0 ± 1.4 mmol/L respectively, p=0.02). During hyperglycemic clamps, carriers showed a lower first phase insulin and C-peptide response than non-carriers (genotype * time interaction, p<0.05 and p<0.01 respectively; insulin at t=5 min 164±118 vs. 352 ±141 pmol/L, p<0.05; C-peptide at t=5 min 1033 ± 628 vs. 1942 ± 723 pmol/L, p<0.05) but no difference in insulin sensitivity index (0.0216 ± 0.012 mg kg −1 . min −1 . pM −1 for carriers and 0.0197 ± 0.005 mg kg −1 . min −1 . pM −1 for non-carriers; p=0.73). Disposition index - a measure of β cell function, adjusted for insulin sensitivity - was lower in carriers than in non-carriers (1037 ± 610 vs. 2718 ± 1524; p<0.05). Non-carriers responded to an arginine stimulus with an increase in C-peptide levels (from 3558 ± 1240 pM to 6817 ± 1665 pM; p<0.005), whereas in carriers this increase did not reach statistical significance (from 3727 ± 1843 pM to 5480 ± 1757 pM; p=0.12). Conclusion Carriers of loss-of-function mutations in ABCA1 show impaired insulin secretion without insulin resistance, resulting in glucose intolerance. Our data confirm previous studies in mice and provide evidence for a role of ABCA1 in β cell dysfunction and the pathophysiology of diabetes mellitus in man.

Glucagonotropic and Glucagonostatic Effects of KATP Channel Closure and Potassium Depolarization

Endocrinology ◽  
2020 ◽  
Vol 162 (1) ◽  
Author(s):  
Eike Früh ◽  
Christin Elgert ◽  
Frank Eggert ◽  
Stephan Scherneck ◽  
Ingo Rustenbeck
Keyword(s):  
Insulin Secretion ◽  
Beta Cells ◽  
Katp Channel ◽  
Glucagon Secretion ◽  
Alpha Cells ◽  
High Potassium ◽  
Intrinsic Signal ◽  
Mouse Islets ◽  
Glucagon And Insulin

Abstract The role of depolarization in the inverse glucose-dependence of glucagon secretion was investigated by comparing the effects of KATP channel block and of high potassium. The secretion of glucagon and insulin by perifused mouse islets was simultaneously measured. Lowering glucose raised glucagon secretion before it decreased insulin secretion, suggesting an alpha cell–intrinsic signal recognition. Raising glucose affected glucagon and insulin secretion at the same time. However, depolarization by tolbutamide, gliclazide, or 15 mM KCl increased insulin secretion before the glucagon secretion receded. In contrast to the robust depolarizing effect of arginine and KCl (15 and 40 mM) on single alpha cells, tolbutamide was of variable efficacy. Only when applied before other depolarizing agents had tolbutamide a consistent depolarizing effect and regularly increased the cytosolic Ca2+ concentration. When tested on inside-out patches tolbutamide was as effective on alpha cells as on beta cells. In the presence of 1 µM clonidine, to separate insulinotropic from glucagonotropic effects, both 500 µM tolbutamide and 30 µM gliclazide increased glucagon secretion significantly, but transiently. The additional presence of 15 or 40 mM KCl in contrast led to a marked and lasting increase of the glucagon secretion. The glucagon secretion by SUR1 knockout islets was not increased by tolbutamide, whereas 40 mM KCl was of unchanged efficiency. In conclusion a strong and sustained depolarization is compatible with a marked and lasting glucagon secretion. KATP channel closure in alpha cells is less readily achieved than in beta cells, which may explain the moderate and transient glucagonotropic effect.

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