The Transcriptional Co-Regulator HCF-1 Is Required for INS-1 β-cell Glucose-Stimulated Insulin Secretion

AMPK (AMP-activated protein kinase) signalling plays a key role in whole-body energy homoeostasis, although its precise role in pancreatic β-cell function remains unclear. In the present stusy, we therefore investigated whether AMPK plays a critical function in β-cell glucose sensing and is required for the maintenance of normal glucose homoeostasis. Mice lacking AMPKα2 in β-cells and a population of hypothalamic neurons (RIPCreα2KO mice) and RIPCreα2KO mice lacking AMPKα1 (α1KORIPCreα2KO) globally were assessed for whole-body glucose homoeostasis and insulin secretion. Isolated pancreatic islets from these mice were assessed for glucose-stimulated insulin secretion and gene expression changes. Cultured β-cells were examined electrophysiologically for their electrical responsiveness to hypoglycaemia. RIPCreα2KO mice exhibited glucose intolerance and impaired GSIS (glucose-stimulated insulin secretion) and this was exacerbated in α1KORIPCreα2KO mice. Reduced glucose concentrations failed to completely suppress insulin secretion in islets from RIPCreα2KO and α1KORIPCreα2KO mice, and conversely GSIS was impaired. β-Cells lacking AMPKα2 or expressing a kinase-dead AMPKα2 failed to hyperpolarize in response to low glucose, although KATP (ATP-sensitive potassium) channel function was intact. We could detect no alteration of GLUT2 (glucose transporter 2), glucose uptake or glucokinase that could explain this glucose insensitivity. UCP2 (uncoupling protein 2) expression was reduced in RIPCreα2KO islets and the UCP2 inhibitor genipin suppressed low-glucose-mediated wild-type mouse β-cell hyperpolarization, mimicking the effect of AMPKα2 loss. These results show that AMPKα2 activity is necessary to maintain normal pancreatic β-cell glucose sensing, possibly by maintaining high β-cell levels of UCP2.

Download Full-text

Ontology of the apelinergic system in mouse pancreas during pregnancy and relationship with β-cell mass

Scientific Reports ◽

10.1038/s41598-021-94725-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Brenda Strutt ◽

Sandra Szlapinski ◽

Thineesha Gnaneswaran ◽

Sarah Donegan ◽

Jessica Hill ◽

...

Keyword(s):

Cell Proliferation ◽

Insulin Secretion ◽

Glucose Transporter ◽

Cell Mass ◽

Elevated Serum ◽

Pancreatic Β Cell ◽

Β Cells ◽

Β Cell ◽

Glucose Transporter 2 ◽

Glucose Stimulated Insulin Secretion

AbstractThe apelin receptor (Aplnr) and its ligands, Apelin and Apela, contribute to metabolic control. The insulin resistance associated with pregnancy is accommodated by an expansion of pancreatic β-cell mass (BCM) and increased insulin secretion, involving the proliferation of insulin-expressing, glucose transporter 2-low (Ins+Glut2LO) progenitor cells. We examined changes in the apelinergic system during normal mouse pregnancy and in pregnancies complicated by glucose intolerance with reduced BCM. Expression of Aplnr, Apelin and Apela was quantified in Ins+Glut2LO cells isolated from mouse pancreata and found to be significantly higher than in mature β-cells by DNA microarray and qPCR. Apelin was localized to most β-cells by immunohistochemistry although Aplnr was predominantly associated with Ins+Glut2LO cells. Aplnr-staining cells increased three- to four-fold during pregnancy being maximal at gestational days (GD) 9–12 but were significantly reduced in glucose intolerant mice. Apelin-13 increased β-cell proliferation in isolated mouse islets and INS1E cells, but not glucose-stimulated insulin secretion. Glucose intolerant pregnant mice had significantly elevated serum Apelin levels at GD 9 associated with an increased presence of placental IL-6. Placental expression of the apelinergic axis remained unaltered, however. Results show that the apelinergic system is highly expressed in pancreatic β-cell progenitors and may contribute to β-cell proliferation in pregnancy.

Download Full-text

INS-1 cell glucose-stimulated insulin secretion is reduced by the downregulation of the 67 kDa laminin receptor

Journal of Tissue Engineering and Regenerative Medicine ◽

10.1002/term.1689 ◽

2013 ◽

Vol 9 (12) ◽

pp. 1376-1385 ◽

Cited By ~ 2

Author(s):

Georges Sabra ◽

Evan A. Dubiel ◽

Carina Kuehn ◽

Taoufik Khalfaoui ◽

Jean-François Beaulieu ◽

...

Keyword(s):

Insulin Secretion ◽

Laminin Receptor ◽

Glucose Stimulated Insulin Secretion ◽

Cell Glucose

Download Full-text

Bioactive Phytochemicals Isolated from Akebia quinata Enhances Glucose-Stimulated Insulin Secretion by Inducing PDX-1

Plants ◽

10.3390/plants9091087 ◽

2020 ◽

Vol 9 (9) ◽

pp. 1087

Author(s):

Dahae Lee ◽

Jin Su Lee ◽

Jurdas Sezirahiga ◽

Hak Cheol Kwon ◽

Dae Sik Jang ◽

...

Keyword(s):

Insulin Secretion ◽

Cell Function ◽

Experimental Studies ◽

Pancreatic Β Cell ◽

Β Cell ◽

Etoh Extract ◽

Chemical Structures ◽

Β Cell Function ◽

Glucose Stimulated Insulin Secretion ◽

Phosphoinositide 3 Kinase

Chocolate vine (Akebia quinata) is consumed as a fruit and is also used in traditional medicine. In order to identify the bioactive components of A. quinata, a phytosterol glucoside stigmasterol-3-O-β-d-glucoside (1), three triterpenoids maslinic acid (2), scutellaric acid (3), and hederagenin (4), and three triterpenoidal saponins akebia saponin PA (5), hederacoside C (6), and hederacolchiside F (7) were isolated from a 70% EtOH extract of the fruits of A. quinata (AKQU). The chemical structures of isolates 1–7 were determined by analyzing the 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data. Here, we evaluated the effects of AKQU and compounds 1–7 on insulin secretion using the INS-1 rat pancreatic β-cell line. Glucose-stimulated insulin secretion (GSIS) was evaluated in INS-1 cells using the GSIS assay. The expression levels of the proteins related to pancreatic β-cell function were detected by Western blotting. Among the isolates, stigmasterol-3-O-β-d-glucoside (1) exhibited strong GSIS activity and triggered the overexpression of pancreas/duodenum homeobox protein-1 (PDX-1), which is implicated in the regulation of pancreatic β-cell survival and function. Moreover, isolate 1 markedly induced the expression of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2), insulin receptor substrate-2 (IRS-2), phosphoinositide 3-kinase (PI3K), and Akt, which regulate the transcription of PDX-1. The results of our experimental studies indicated that stigmasterol-3-O-β-d-glucoside (1) isolated from the fruits of A. quinata can potentially enhance insulin secretion, and might alleviate the reduction in GSIS during the development of T2DM.

Download Full-text

L-Arginine prevents cereblon-mediated ubiquitination of glucokinase and stimulates glucose-6-phosphate production in pancreatic β-cells

Communications Biology ◽

10.1038/s42003-020-01226-3 ◽

2020 ◽

Vol 3 (1) ◽

Author(s):

Jaeyong Cho ◽

Yukio Horikawa ◽

Mayumi Enya ◽

Jun Takeda ◽

Yoichi Imai ◽

...

Keyword(s):

Insulin Secretion ◽

Ubiquitin Ligase ◽

E3 Ubiquitin Ligase ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Direct Stimulation ◽

Glucose Ratio ◽

Glucose Stimulated Insulin Secretion

Abstract We sought to determine a mechanism by which L-arginine increases glucose-stimulated insulin secretion (GSIS) in β-cells by finding a protein with affinity to L-arginine using arginine-immobilized magnetic nanobeads technology. Glucokinase (GCK), the key regulator of GSIS and a disease-causing gene of maturity-onset diabetes of the young type 2 (MODY2), was found to bind L-arginine. L-Arginine stimulated production of glucose-6-phosphate (G6P) and induced insulin secretion. We analyzed glucokinase mutants and identified three glutamate residues that mediate binding to L-arginine. One MODY2 patient with GCKE442* demonstrated lower C-peptide-to-glucose ratio after arginine administration. In β-cell line, GCKE442* reduced L-arginine-induced insulin secretion compared with GCKWT. In addition, we elucidated that the binding of arginine protects glucokinase from degradation by E3 ubiquitin ligase cereblon mediated ubiquitination. We conclude that L-arginine induces insulin secretion by increasing G6P production by glucokinase through direct stimulation and by prevention of degradation.

Download Full-text

The adaptor protein APPL2 controls glucose-stimulated insulin secretion via F-actin remodeling in pancreatic β-cells

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2016997117 ◽

2020 ◽

Vol 117 (45) ◽

pp. 28307-28315

Author(s):

Baile Wang ◽

Huige Lin ◽

Xiaomu Li ◽

Wenqi Lu ◽

Jae Bum Kim ◽

...

Keyword(s):

Insulin Secretion ◽

Pancreatic Islets ◽

Adaptor Protein ◽

Hek293 Cells ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Actin Remodeling ◽

Actin Depolymerization ◽

Glucose Stimulated Insulin Secretion

Filamentous actin (F-actin) cytoskeletal remodeling is critical for glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells, and its dysregulation causes type 2 diabetes. The adaptor protein APPL1 promotes first-phase GSIS by up-regulating solubleN-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein expression. However, whether APPL2 (a close homology of APPL1 with the same domain organization) plays a role in β-cell functions is unknown. Here, we show that APPL2 enhances GSIS by promoting F-actin remodeling via the small GTPase Rac1 in pancreatic β-cells. β-cell specific abrogation of APPL2 impaired GSIS, leading to glucose intolerance in mice. APPL2 deficiency largely abolished glucose-induced first- and second-phase insulin secretion in pancreatic islets. Real-time live-cell imaging and phalloidin staining revealed that APPL2 deficiency abolished glucose-induced F-actin depolymerization in pancreatic islets. Likewise, knockdown of APPL2 expression impaired glucose-stimulated F-actin depolymerization and subsequent insulin secretion in INS-1E cells, which were attributable to the impairment of Ras-related C3 botulinum toxin substrate 1 (Rac1) activation. Treatment with the F-actin depolymerization chemical compounds or overexpression of gelsolin (a F-actin remodeling protein) rescued APPL2 deficiency-induced defective GSIS. In addition, APPL2 interacted with Rac GTPase activating protein 1 (RacGAP1) in a glucose-dependent manner via the bin/amphiphysin/rvs-pleckstrin homology (BAR-PH) domain of APPL2 in INS-1E cells and HEK293 cells. Concomitant knockdown of RacGAP1 expression reverted APPL2 deficiency-induced defective GSIS, F-actin remodeling, and Rac1 activation in INS-1E cells. Our data indicate that APPL2 interacts with RacGAP1 and suppresses its negative action on Rac1 activity and F-actin depolymerization thereby enhancing GSIS in pancreatic β-cells.

Download Full-text

Investigation of Ultrasound-Mediated Intracellular Ca2+ Oscillations in HIT-T15 Pancreatic β-Cell Line

Cells ◽

10.3390/cells9051129 ◽

2020 ◽

Vol 9 (5) ◽

pp. 1129

Author(s):

Chi Woo Yoon ◽

Nan Sook Lee ◽

Kweon Mo Koo ◽

Sunho Moon ◽

Kyosuk Goo ◽

...

Keyword(s):

Insulin Secretion ◽

Cell Line ◽

Purinergic Signaling ◽

Underlying Mechanism ◽

Resting Cells ◽

Pancreatic Β Cell ◽

Pulsed Ultrasound ◽

Β Cell ◽

Secretion Pathways ◽

Glucose Stimulated Insulin Secretion

In glucose-stimulated insulin secretion (GSIS) of pancreatic β-cells, the rise of free cytosolic Ca2+ concentration through voltage-gated calcium channels (VGCCs) triggers the exocytosis of insulin-containing granules. Recently, mechanically induced insulin secretion pathways were also reported, which utilize free cytosolic Ca2+ ions as a direct regulator of exocytosis. In this study, we aimed to investigate intracellular Ca2+ responses on the HIT-T15 pancreatic β-cell line upon low-intensity pulsed ultrasound (LIPUS) stimulation and found that ultrasound induces two distinct types of intracellular Ca2+ oscillation, fast-irregular and slow-periodic, from otherwise resting cells. Both Ca2+ patterns depend on the purinergic signaling activated by the rise of extracellular ATP or ADP concentration upon ultrasound stimulation, which facilitates the release through mechanosensitive hemichannels on the plasma membrane. Further study demonstrated that two subtypes of purinergic receptors, P2X and P2Y, are working in a competitive manner depending on the level of glucose in the cell media. The findings can serve as an essential groundwork providing an underlying mechanism for the development of a new therapeutic approach for diabetic conditions with further validation.

Download Full-text

Rice Bran Phenolic Extracts Modulate Insulin Secretion and Gene Expression Associated with β-Cell Function

Nutrients ◽

10.3390/nu12061889 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1889 ◽

Cited By ~ 1

Author(s):

Nancy Saji ◽

Nidhish Francis ◽

Lachlan J. Schwarz ◽

Christopher L. Blanchard ◽

Abishek B. Santhakumar

Keyword(s):

Insulin Secretion ◽

Rice Bran ◽

Cell Function ◽

Β Cell ◽

Free Radical Damage ◽

Glucose Transporter 2 ◽

Expression Of Genes ◽

Β Cell Function ◽

Glucose Stimulated Insulin Secretion ◽

Phenolic Extracts

Oxidative stress is known to modulate insulin secretion and initiate gene alterations resulting in impairment of β-cell function and type 2 diabetes mellitus (T2DM). Rice bran (RB) phenolic extracts contain bioactive properties that may target metabolic pathways associated with the pathogenesis of T2DM. This study aimed to examine the effect of stabilized RB phenolic extracts on the expression of genes associated with β-cell function such as glucose transporter 2 (Glut2), pancreatic and duodenal homeobox 1 (Pdx1), sirtuin 1 (Sirt1), mitochondrial transcription factor A (Tfam), and insulin 1 (Ins1) in addition to evaluating its impact on glucose-stimulated insulin secretion. It was observed that treatment with different concentrations of RB phenolic extracts (25-250 µg/mL) significantly increased the expression of Glut2, Pdx1, Sirt1, Tfam, and Ins1 genes and glucose-stimulated insulin secretion under both normal and high glucose conditions. RB phenolic extracts favourably modulated the expression of genes involved in β-cell dysfunction and insulin secretion via several mechanisms such as synergistic action of polyphenols targeting signalling molecules, decreasing free radical damage by its antioxidant activity, and stimulation of effectors or survival factors of insulin secretion.

Download Full-text

Improved glucose tolerance with DPPIV inhibition requires β‐cell SENP1 amplification of glucose‐stimulated insulin secretion

Physiological Reports ◽

10.14814/phy2.14420 ◽

2020 ◽

Vol 8 (8) ◽

Author(s):

Mourad Ferdaoussi ◽

Nancy Smith ◽

Haopeng Lin ◽

Austin Bautista ◽

Aliya F. Spigelman ◽

...

Keyword(s):

Insulin Secretion ◽

Glucose Tolerance ◽

Β Cell ◽

Glucose Stimulated Insulin Secretion

Download Full-text

Neuroligin-2-derived peptide-covered polyamidoamine-based (PAMAM) dendrimers enhance pancreatic β-cells' proliferation and functions

MedChemComm ◽

10.1039/c8md00419f ◽

2019 ◽

Vol 10 (2) ◽

pp. 280-293

Author(s):

Anna Munder ◽

Yoni Moskovitz ◽

Aviv Meir ◽

Shirin Kahremany ◽

Laura Levy ◽

...

Keyword(s):

Insulin Secretion ◽

Cellular Stress ◽

Pamam Dendrimers ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Cell Functions ◽

Functional Maturation ◽

Glucose Stimulated Insulin Secretion

The nanoscale composite improved β-cell functions in terms of rate of proliferation, glucose-stimulated insulin secretion, resistance to cellular stress and functional maturation.

Download Full-text