Resveratrol Potentiates Glucose-stimulated Insulin Secretion in INS-1E β-Cells and Human Islets through a SIRT1-dependent Mechanism

Glucose-stimulated insulin secretion (GSIS) is central to normal control of metabolic fuel homeostasis, and its impairment is a key element of β-cell failure in type 2 diabetes. Glucose exerts its effects on insulin secretion via its metabolism in β-cells to generate stimulus/secretion coupling factors, including a rise in the ATP/ADP ratio, which serves to suppress ATP-sensitive K+ (KATP) channels and activate voltage-gated Ca2+ channels, leading to stimulation of insulin granule exocytosis. Whereas this KATP channel-dependent mechanism of GSIS has been broadly accepted for more than 30 years, it has become increasingly apparent that it does not fully describe the effects of glucose on insulin secretion. More recent studies have demonstrated an important role for cyclic pathways of pyruvate metabolism in control of insulin secretion. Three cycles occur in islet β-cells: the pyruvate/malate, pyruvate/citrate, and pyruvate/isocitrate cycles. This review discusses recent work on the role of each of these pathways in control of insulin secretion and builds a case for the particular relevance of byproducts of the pyruvate/isocitrate cycle, NADPH and α-ketoglutarate, in control of GSIS.

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Perilipin Is Present in Islets of Langerhans and Protects against Lipotoxicity When Overexpressed in the β-Cell Line INS-1

Endocrinology ◽

10.1210/en.2008-0913 ◽

2009 ◽

Vol 150 (7) ◽

pp. 3049-3057 ◽

Cited By ~ 20

Author(s):

Jörgen Borg ◽

Cecilia Klint ◽

Nils Wierup ◽

Kristoffer Ström ◽

Sara Larsson ◽

...

Keyword(s):

Insulin Secretion ◽

Cell Line ◽

Islets Of Langerhans ◽

Prolonged Exposure ◽

Human Islets ◽

Lipid Storage ◽

Β Cells ◽

Β Cell ◽

Glucose Stimulated Insulin Secretion ◽

In Cells

Lipids have been shown to play a dual role in pancreatic β-cells: a lipid-derived signal appears to be necessary for glucose-stimulated insulin secretion, whereas lipid accumulation causes impaired insulin secretion and apoptosis. The ability of the protein perilipin to regulate lipolysis prompted an investigation of the presence of perilipin in the islets of Langerhans. In this study evidence is presented for perilipin expression in rat, mouse, and human islets of Langerhans as well as the rat clonal β-cell line INS-1. In rat and mouse islets, perilipin was verified to be present in β-cells. To examine whether the development of lipotoxicity could be prevented by manipulating the conditions for lipid storage in the β-cell, INS-1 cells with adenoviral-mediated overexpression of perilipin were exposed to lipotoxic conditions for 72 h. In cells exposed to palmitate, perilipin overexpression caused increased accumulation of triacylglycerols and decreased lipolysis compared with control cells. Whereas glucose-stimulated insulin secretion was retained after palmitate exposure in cells overexpressing perilipin, it was completely abolished in control β-cells. Thus, overexpression of perilipin appears to confer protection against the development of β-cell dysfunction after prolonged exposure to palmitate by promoting lipid storage and limiting lipolysis.

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Dopamine-Mediated Autocrine Inhibitory Circuit Regulating Human Insulin Secretion in Vitro

Molecular Endocrinology ◽

10.1210/me.2012-1101 ◽

2012 ◽

Vol 26 (10) ◽

pp. 1757-1772 ◽

Cited By ~ 43

Author(s):

Norman Simpson ◽

Antonella Maffei ◽

Matthew Freeby ◽

Steven Burroughs ◽

Zachary Freyberg ◽

...

Keyword(s):

Insulin Secretion ◽

Secretory Granules ◽

Human Islets ◽

Negative Regulator ◽

Β Cells ◽

Regulatory Circuit ◽

Glucose Stimulated Insulin Secretion ◽

Insulin Secretion In Vitro

Abstract We describe a negative feedback autocrine regulatory circuit for glucose-stimulated insulin secretion in purified human islets in vitro. Using chronoamperometry and in vitro glucose-stimulated insulin secretion measurements, evidence is provided that dopamine (DA), which is loaded into insulin-containing secretory granules by vesicular monoamine transporter type 2 in human β-cells, is released in response to glucose stimulation. DA then acts as a negative regulator of insulin secretion via its action on D2R, which are also expressed on β-cells. We found that antagonism of receptors participating in islet DA signaling generally drive increased glucose-stimulated insulin secretion. These in vitro observations may represent correlates of the in vivo metabolic changes associated with the use of atypical antipsychotics, such as increased adiposity.

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Intracrine testosterone activation in human pancreatic β cells stimulates insulin secretion.

10.2337/figshare.12841109 ◽

2020 ◽

Author(s):

Ada Admin ◽

Weiwei Xu ◽

Lina Schiffer ◽

M.M. Fahd Qadir ◽

Yanqing Zhang ◽

...

Keyword(s):

Insulin Secretion ◽

Aromatase Inhibitor ◽

Cell Function ◽

Human Islets ◽

Human Pancreas ◽

Β Cells ◽

Male And Female ◽

Β Cell Function ◽

17Β Estradiol ◽

Glucose Stimulated Insulin Secretion

Testosterone (T) affects β cell function in men and women. T is a pro-hormone that undergoes intracrine conversion in target tissues to the potent androgen dihydrotestosterone (DHT) via the enzyme 5α-reductase (5α-R), or to the active estrogen 17β-estradiol (E2) via the aromatase enzyme. Using male and female human pancreas sections, we show that the 5α-R type1 isoform (SRD5A1) and aromatase are expressed in male and female β cells. We show that cultured male and female human islets exposed to T produce DHT and downstream metabolites. In these islets, exposure to the 5α-R inhibitors finasteride and dutasteride inhibited T conversion into DHT. We did not detect T conversion into E2 from female islets. However, we detected T conversion into E2 in islets from one out of four male donors. In this donor, exposure to the aromatase inhibitor anastrozole inhibited E2 production. Notably, in cultured male and female islets, T enhanced glucose-stimulated insulin secretion (GSIS). In these islets, exposure to 5α-R inhibitors or the aromatase inhibitor both inhibited T enhancement of GSIS. In conclusion, male and female human islets convert T into DHT and E2 via the intracrine activities of SRD5A1 and aromatase. This process is necessary for T enhancement of GSIS.<b></b>

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P-Rex1 Mediates Glucose-Stimulated Rac1 Activation and Insulin Secretion in Pancreatic β-Cells

Cellular Physiology and Biochemistry ◽

10.33594/000000310 ◽

2020 ◽

Vol 54 (6) ◽

pp. 1218-1230

Keyword(s):

Insulin Secretion ◽

Cell Types ◽

Human Islets ◽

Pi3 Kinase ◽

Membrane Extraction ◽

Limited Information ◽

Β Cells ◽

Downstream Signaling ◽

Published Evidence ◽

Glucose Stimulated Insulin Secretion

Background/Aims: Despite the published evidence implicating phosphoinositide 3-kinase (PI3-kinase) in the regulation of islet function, limited information is available on the putative contributory roles of its downstream signaling steps, including the phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 1 (P-Rex1) signaling pathway in the islet β-cell. Therefore, we investigated potential roles for P-Rex1 in glucose-stimulated Rac1 activation and insulin secretion in insulin-secreting (INS-1 832/13) β-cells. Methods: Glucose-stimulated Insulin secretion (GSIS) was quantified by ELISA. Expression of endogenous P-Rex1 and RhoG was suppressed by siRNA transfection using the DharmaFect1 reagent. Total membrane and cytosolic fractions were isolated using the Mem-PER Plus Membrane Extraction Kit. The degree of activation of Rac1 was determined by the pull-down assay. Results: P-Rex1 is expressed in INS-1 832/13 cells, normal rat islets and human islets. siRNA-mediated knockdown of P-Rex1 attenuated glucose-induced Rac1 activation, membrane association and insulin secretion. RhoG, which has been implicated in PI3-kinase-mediated Rac1 activation in other cell types, appears not to contribute to GSIS since the siRNA-mediated knockdown of RhoG failed to exert significant effects on GSIS. LY294002, a known inhibitor of PI3-kinase, potentiated GSIS without affecting glucose-induced Rac1 activation. Conclusion: Based on these findings, we conclude that P-Rex1 plays a novel regulatory role in glucose-induced Rac1 activation and insulin secretion.

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Intracrine testosterone activation in human pancreatic β cells stimulates insulin secretion.

10.2337/figshare.12841109.v1 ◽

2020 ◽

Author(s):

Ada Admin ◽

Weiwei Xu ◽

Lina Schiffer ◽

M.M. Fahd Qadir ◽

Yanqing Zhang ◽

...

Keyword(s):

Insulin Secretion ◽

Aromatase Inhibitor ◽

Cell Function ◽

Human Islets ◽

Human Pancreas ◽

Β Cells ◽

Male And Female ◽

Β Cell Function ◽

17Β Estradiol ◽

Glucose Stimulated Insulin Secretion

Testosterone (T) affects β cell function in men and women. T is a pro-hormone that undergoes intracrine conversion in target tissues to the potent androgen dihydrotestosterone (DHT) via the enzyme 5α-reductase (5α-R), or to the active estrogen 17β-estradiol (E2) via the aromatase enzyme. Using male and female human pancreas sections, we show that the 5α-R type1 isoform (SRD5A1) and aromatase are expressed in male and female β cells. We show that cultured male and female human islets exposed to T produce DHT and downstream metabolites. In these islets, exposure to the 5α-R inhibitors finasteride and dutasteride inhibited T conversion into DHT. We did not detect T conversion into E2 from female islets. However, we detected T conversion into E2 in islets from one out of four male donors. In this donor, exposure to the aromatase inhibitor anastrozole inhibited E2 production. Notably, in cultured male and female islets, T enhanced glucose-stimulated insulin secretion (GSIS). In these islets, exposure to 5α-R inhibitors or the aromatase inhibitor both inhibited T enhancement of GSIS. In conclusion, male and female human islets convert T into DHT and E2 via the intracrine activities of SRD5A1 and aromatase. This process is necessary for T enhancement of GSIS.<b></b>

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Multivalent activation of GLP-1 and sulfonylurea receptors modulates β-cell second-messenger signaling and insulin secretion

AJP Cell Physiology ◽

10.1152/ajpcell.00209.2018 ◽

2019 ◽

Vol 316 (1) ◽

pp. C48-C56

Author(s):

Nathaniel J. Hart ◽

Craig Weber ◽

Klearchos K. Papas ◽

Sean W. Limesand ◽

Josef Vagner ◽

...

Keyword(s):

Insulin Secretion ◽

Single Molecule ◽

Human Islets ◽

Intracellular Camp ◽

Dependent Manner ◽

Β Cells ◽

Β Cell ◽

Surface Receptors ◽

Glucagon Like Peptide 1 ◽

Glucose Stimulated Insulin Secretion

Linking two pharmacophores that bind different cell surface receptors into a single molecule can enhance cell-targeting specificity to cells that express the complementary receptor pair. In this report, we developed and tested a synthetic multivalent ligand consisting of glucagon-like peptide-1 (GLP-1) linked to glibenclamide (Glb) (GLP-1/Glb) for signaling efficacy in β-cells. Expression of receptors for these ligands, as a combination, is relatively specific to the β-cell in the pancreas. The multivalent GLP-1/Glb increased both intracellular cAMP and Ca2+, although Ca2+ responses were significantly depressed compared with the monomeric Glb. Moreover, GLP-1/Glb increased glucose-stimulated insulin secretion in a dose-dependent manner. However, unlike the combined monomers, GLP-1/Glb did not augment insulin secretion at nonstimulatory glucose concentrations in INS 832/13 β-cells or human islets of Langerhans. These data suggest that linking two binding elements, such as GLP-1 and Glb, into a single bivalent ligand can provide a unique functional agent targeted to β-cells.

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Regulation and functional effects of ZNT8 in human pancreatic islets

Journal of Endocrinology ◽

10.1530/joe-12-0071 ◽

2012 ◽

Vol 214 (2) ◽

pp. 225-232 ◽

Cited By ~ 21

Author(s):

Bruno Lefebvre ◽

Brigitte Vandewalle ◽

Anne-Sophie Balavoine ◽

Gurvan Queniat ◽

Ericka Moerman ◽

...

Keyword(s):

Cell Death ◽

Insulin Secretion ◽

Metabolic Stress ◽

Human Islets ◽

Β Cells ◽

Prediabetic State ◽

Zinc Depletion ◽

Packaging Efficiency ◽

Glucose Stimulated Insulin Secretion

Zinc ions are essential for the formation of insulin crystals in pancreatic β cells, thereby contributing to packaging efficiency of stored insulin. Zinc fluxes are regulated through the SLC30A (zinc transporter, ZNT) family. Here, we investigated the effect of metabolic stress associated with the prediabetic state (zinc depletion, glucotoxicity, and lipotoxicity) on ZNT expression and human pancreatic islet function. Both zinc depletion and lipotoxicity (but not glucotoxicity) downregulatedZNT8(SLC30A8) expression and altered the glucose-stimulated insulin secretion index (GSIS).ZNT8overexpression in human islets protected them from the decrease in GSIS induced by tetrakis-(2-pyridylmethyl) ethylenediamine and palmitate but not from cell death. In addition, zinc supplementation decreased palmitate-induced human islet cell death without restoring GSIS. Altogether, we showed thatZNT8expression responds to variation in zinc and lipid levels in human β cells, with repercussions on insulin secretion. Prospects for increasingZNT8expression and/or activity may prove beneficial in type 2 diabetes in humans.

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Regulation of cAMP accumulation and activity by distinct phosphodiesterase subtypes in INS-1 cells and human pancreatic β-cells

10.1101/593418 ◽

2019 ◽

Author(s):

Evan P.S. Pratt ◽

Kyle E. Harvey ◽

Amy E. Salyer ◽

Shiqi Tang ◽

Gregory H. Hockerman

Keyword(s):

Insulin Secretion ◽

Cell Function ◽

Human Islets ◽

Pde4 Inhibitor ◽

Β Cells ◽

Pancreatic Β Cells ◽

Creb Phosphorylation ◽

Glucose Stimulated Insulin Secretion ◽

Camp Levels

AbstractPancreatic β-cells express multiple phosphodiesterase (PDE) subtypes, but the specific roles for each in β-cell function, particularly in humans, is not clear. We evaluated the cellular role of PDE1, PDE3, and PDE4 activity in the rat insulinoma cell line INS-1 and in primary human β-cells using subtype-selective PDE inhibitors. Using a genetically encoded, FRET-based cAMP sensor, we found that the PDE1 inhibitor 8MM-IBMX and the PDE4 inhibitor rolipram elevated cAMP levels above baseline in the absence and presence of 18 mM glucose in INS-1 cells. Inhibition of PDE1 or PDE4 potentiated glucose-stimulated insulin secretion in INS-1 cells. In contrast, the inhibition of PDE3 with cilostamide had little effect on cAMP levels or glucose-stimulated insulin secretion. PDE1 inhibition, but not PDE3 of PDE4 inhibition, reduced palmitate-induced caspase-3/7 activation, and enhanced CREB phosphorylation in INS-1 cells. In human β-cells, only PDE3 or PDE4 inhibition increased cAMP levels in 1.7 mM glucose, but PDE1, PDE3, or PDE4 inhibition potentiated cAMP levels in 16.7 mM glucose. Inhibition of PDE1 or PDE4 increased cAMP levels to a greater extent in 16.7 mM glucose than in 1.7 mM glucose in human β-cells. In contrast, elevation of cAMP levels by PDE3 inhibition was not different at these glucose concentrations. PDE1 inhibition also potentiated insulin secretion from human islets, suggesting that the role of PDE1 may be conserved between INS-1 cells and human pancreatic β-cells. Our results suggest that inhibition of PDE1 may be a useful strategy to potentiate glucose-stimulated insulin secretion, and to protect β-cells from the toxic effects of excess fatty acids.

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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.

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