Inhibitory effect of UDP-glucose on cAMP generation and insulin secretion

Type-2 diabetes (T2D) is a global disease caused by the inability of pancreatic β-cells to secrete adequate insulin. However, the molecular mechanisms underlying the failure of β-cells to respond to glucose in T2D remains unknown. Here, we investigated the relative contribution of UDP-glucose (UDP-G), a P2Y14-specific agonist, in the regulation of insulin release using human isolated pancreatic islets and INS-1 cells. P2Y14 was expressed in both human and rodent pancreatic β-cells. Dose-dependent activation of P2Y14 by UDP-G suppressed glucose-stimulated insulin secretion (GSIS) and knockdown of P2Y14 abolished the UDP-G effect. 12-h pretreatment of human islets with pertussis-toxin (PTX) improved GSIS and prevented the inhibitory effect of UDP-G on GSIS. UDP-G on GSIS suppression was associated with suppression of cAMP in INS-1 cells. UDP-G decreased the reductive capacity of nondiabetic human islets cultured at 5 mm glucose for 72 h and exacerbated the negative effect of 20 mm glucose on the cell viability during culture period. T2D donor islets displayed a lower reductive capacity when cultured at 5 mm glucose for 72 h that was further decreased in the presence of 20 mm glucose and UDP-G. Presence of a nonmetabolizable cAMP analog during culture period counteracted the effect of glucose and UDP-G. Islet cultures at 20 mm glucose increased apoptosis, which was further amplified when UDP-G was present. UDP-G modulated glucose-induced proliferation of INS-1 cells. The data provide intriguing evidence for P2Y14 and UDP-G's role in the regulation of pancreatic β-cell function.

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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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Cytoprotective Effects of N-Acetylcysteine on Streptozotocin- Induced Oxidative Stress and Apoptosis in RIN-5F Pancreatic β-Cells

Cellular Physiology and Biochemistry ◽

10.1159/000495200 ◽

2018 ◽

Vol 51 (1) ◽

pp. 201-216 ◽

Cited By ~ 8

Author(s):

Arwa M.T. Al-Nahdi ◽

Annie John ◽

Haider Raza

Keyword(s):

Oxidative Stress ◽

Insulin Secretion ◽

Molecular Mechanisms ◽

Protective Action ◽

Mitochondrial Enzymes ◽

Partial Recovery ◽

Β Cells ◽

Pancreatic Β Cells ◽

Mitochondrial Energy Metabolism ◽

Mitochondrial Functions

Background/Aims: Numerous studies have reported overproduction of reactive oxygen species (ROS) and alterations in mitochondrial energy metabolism in the development of diabetes and its complications. The potential protective effects of N-acetylcysteine (NAC) in diabetes have been reported in many therapeutic studies. NAC has been shown to reduce oxidative stress and enhance redox potential in tissues protecting them against oxidative stress associated complications in diabetes. In the current study, we aimed to investigate the molecular mechanisms of the protective action of NAC on STZ-induced toxicity in insulin secreting Rin-5F pancreatic β-cells. Methods: Rin-5F cells were grown to 80% confluence and then treated with 10mM STZ for 24h in the presence or absence of 10mM NAC. After sub-cellular fractionation, oxidative stress, GSH-dependent metabolism and mitochondrial respiratory functions were studied using spectrophotometric, flow cytometric and Western blotting techniques. Results: Our results showed that STZ-induced oxidative stress and apoptosis caused inhibition in insulin secretion while NAC treatment restored the redox homeostasis, enhanced insulin secretion in control cells and prevented apoptosis in STZ-treated cells. Moreover, NAC attenuated the inhibition of mitochondrial functions induced by STZ through partial recovery of the mitochondrial enzymes and restoration of membrane potential. STZ-induced DNA damage and expression of apoptotic proteins were significantly inhibited in NAC-treated cells. Conclusion: Our results suggest that the cytoprotective action of NAC is mediated via suppression of oxidative stress and apoptosis and restoration of GSH homeostasis and mitochondrial bioenergetics. This study may, thus, help in better understanding the cellular defense mechanisms of pancreatic β-cells against STZ-induced cytotoxicity.

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Selenoprotein P as a significant regulator of pancreatic β cell function

The Journal of Biochemistry ◽

10.1093/jb/mvz061 ◽

2019 ◽

Cited By ~ 1

Author(s):

Yoshiro Saito

Keyword(s):

Insulin Resistance ◽

Type 2 Diabetes ◽

Molecular Mechanisms ◽

Cell Function ◽

Insulin Signalling ◽

Selenoprotein P ◽

Β Cells ◽

Pancreatic Β Cells ◽

Β Cell Function

Abstract Selenoprotein P (SeP; encoded by SELENOP) is selenium (Se)-rich plasma protein that is mainly produced in the liver. SeP functions as a Se-transport protein to deliver Se from the liver to other tissues, such as the brain and testis. The protein plays a pivotal role in Se metabolism and antioxidative defense, and it has been identified as a ‘hepatokine’ that causes insulin resistance in type 2 diabetes. SeP levels are increased in type 2 diabetes patients, and excess SeP impairs insulin signalling, promoting insulin resistance. Furthermore, increased levels of SeP disturb the functioning of pancreatic β cells and inhibit insulin secretion. This review focuses on the biological function of SeP and the molecular mechanisms associated with the adverse effects of excess SeP on pancreatic β cells’ function, particularly with respect to redox reactions. Interactions between the liver and pancreas are also discussed.

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Tetracaine stimulates insulin secretion through the mobilization of Ca2+ from thapsigargin- and IP3-insensitive Ca2+ reservoir in pancreatic β-cells

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y00-010 ◽

2000 ◽

Vol 78 (6) ◽

pp. 462-468 ◽

Cited By ~ 1

Author(s):

José Roberto Bosqueiro ◽

Everardo Magalhães Carneiro ◽

Silvana Bordin ◽

Antonio Carlos Boschero

Keyword(s):

Insulin Secretion ◽

Pancreatic Islets ◽

Isolated Islets ◽

Inositol Triphosphate ◽

Free Medium ◽

Β Cells ◽

Pancreatic Β Cells ◽

Isolated Pancreatic Islets ◽

High Concentrations

The effect of tetracaine on 45Ca efflux, cytoplasmic Ca2+ concentration [Ca2+]i, and insulin secretion in isolated pancreatic islets and β-cells was studied. In the absence of external Ca2+, tetracaine (0.1-2.0 mM) increased the 45Ca efflux from isolated islets in a dose-dependant manner. Tetracaine did not affect the increase in 45Ca efflux caused by 50 mM K+ or by the association of carbachol (0.2 mM) and 50 mM K+. Tetracaine permanently increased the [Ca2+]i in isolated β-cells in Ca2+-free medium enriched with 2.8 mM glucose and 25 µM D-600 (methoxiverapamil). This effect was also observed in the presence of 10 mM caffeine or 1 µM thapsigargin. In the presence of 16.7 mM glucose, tetracaine transiently increased the insulin secretion from islets perfused in the absence and presence of external Ca2+. These data indicate that tetracaine mobilises Ca2+ from a thapsigargin-insensitive store and stimulates insulin secretion in the absence of extracellular Ca2+. The increase in 45Ca efflux caused by high concentrations of K+ and by carbachol indicates that tetracaine did not interfere with a cation or inositol triphosphate sensitive Ca2+ pool in β-cells.

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N-Type Ca2+-Channels in Murine Pancreatic β-Cells Are Inhibited by an Exclusive Coupling with Somatostatin Receptor Subtype 1

Endocrinology ◽

10.1210/en.2008-0883 ◽

2009 ◽

Vol 150 (2) ◽

pp. 741-748 ◽

Cited By ~ 12

Author(s):

Paul A. Smith

Keyword(s):

Insulin Secretion ◽

Somatostatin Receptor ◽

Inhibitory Effect ◽

Receptor Subtype ◽

Receptor Subtypes ◽

Β Cells ◽

Pancreatic Β Cells ◽

Somatostatin Receptor Subtypes ◽

Perforated Patch Clamp ◽

Ca2 Channels

Somatostatin (SRIF) is a well-established inhibitor of insulin secretion, an effect in part mediated by a direct inhibition of voltage-operated Ca2+-channels. However, the identity of the somatostatin receptor subtypes (SSTRs) and voltage-operated Ca2+-channels involved in this process are unknown. Whole-cell perforated patch-clamp methods were applied to the murine pancreatic β-cell line, MIN6, to explore the molecular pharmacology of this problem. SRIF-14 inhibited voltage-gated Ca2+ currents (ICa2+) by 19 ± 3% (n=24) with a pEC50 = 9.05 (95% confidence limits 9–9.1). This action was mimicked solely by 100 nm CH-275, a selective agonist at the somatostatin type 1 receptor (SSTR1), but not by 100 nm BIM-23027, L-362855, or NNC-269100; agonists selective for the other four SSTRs known to exist in MIN6. The inhibition of ICa2+ produced by SRIF and CH-275 was insensitive to pertussis toxin but was reversed by a prepulse to +100 mV. The inhibition of ICa2+ by SRIF-14 was unaffected by 20 μm nifedipine, an inhibitor of L-type Ca2+ channels. Application of the specific N-type Ca2+ channel (Cav2.2) inhibitor ω-conotoxin GV1A at 100 nm mimicked, and as a consequence abolished, the inhibitory effect of SRIF-14 on ICa2+. SRIF selectively inhibits N-type Ca2+-channels in murine pancreatic β-cells via exclusive coupling with SSTR1. These findings help explain how SSTR1 activation can inhibit insulin secretion in pancreatic β-cells and suggest a possible new therapeutic lead for treatment of hyperinsulinemia. In pancreatic β-cells, somatostatin selectively inhibits N-type, but not other, Ca2+-channels via a direct and exclusive coupling with somatostatin receptor subtype 1.

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Resveratrol and curcumin enhance pancreatic β-cell function by inhibiting phosphodiesterase activity

Journal of Endocrinology ◽

10.1530/joe-14-0335 ◽

2014 ◽

Vol 223 (2) ◽

pp. 107-117 ◽

Cited By ~ 53

Author(s):

Michael Rouse ◽

Antoine Younès ◽

Josephine M Egan

Keyword(s):

Insulin Secretion ◽

Cell Lines ◽

Cell Function ◽

Human Islets ◽

Dependent Manner ◽

Pancreatic Β Cell ◽

Β Cells ◽

Β Cell ◽

Pde Inhibitors ◽

Β Cell Function

Resveratrol (RES) and curcumin (CUR) are polyphenols that are found in fruits and turmeric, and possess medicinal properties that are beneficial in various diseases, such as heart disease, cancer, and type 2 diabetes mellitus (T2DM). Results from recent studies have indicated that their therapeutic properties can be attributed to their anti-inflammatory effects. Owing to reports stating that they protect against β-cell dysfunction, we studied their mechanism(s) of action in β-cells. In T2DM, cAMP plays a critical role in glucose- and incretin-stimulated insulin secretion as well as overall pancreatic β-cell health. A potential therapeutic target in the management of T2DM lies in regulating the activity of phosphodiesterases (PDEs), which degrade cAMP. Both RES and CUR have been reported to act as PDE inhibitors in various cell types, but it remains unknown if they do so in pancreatic β-cells. In our current study, we found that both RES (0.1–10 μmol/l) and CUR (1–100 pmol/l)-regulated insulin secretion under glucose-stimulated conditions. Additionally, treating β-cell lines and human islets with these polyphenols led to increased intracellular cAMP levels in a manner similar to 3-isobutyl-1-methylxanthine, a classic PDE inhibitor. When we investigated the effects of RES and CUR on PDEs, we found that treatment significantly downregulated the mRNA expression of most of the 11 PDE isozymes, including PDE3B, PDE8A, and PDE10A, which have been linked previously to regulation of insulin secretion in islets. Furthermore, RES and CUR inhibited PDE activity in a dose-dependent manner in β-cell lines and human islets. Collectively, we demonstrate a novel role for natural-occurring polyphenols as PDE inhibitors that enhance pancreatic β-cell function.

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Oxytocin signal contributes to the adaptative growth of islets during gestation

Endocrine Connections ◽

10.1530/ec-21-0043 ◽

2021 ◽

Author(s):

Ping Gu ◽

Yuege Lin ◽

Qi Wan ◽

Dongming Su ◽

Qun Shu

Keyword(s):

Insulin Secretion ◽

Pregnant Women ◽

Cell Function ◽

Pancreatic Β Cell ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Cell Adaptation ◽

Β Cell Function ◽

Insulinoma Cells

Background: Increased insulin production and secretion by pancreatic β-cells are important for ensuring the high insulin demand during gestation. However, the underlying mechanism of β-cell adaptation during gestation or in gestational diabetes mellitus (GDM) remains unclear. Oxytocin is an important physiological hormone in gestation and delivery, and it also contributes to the maintenance of β-cell function. The aim of this study was to investigate the role of oxytocin in β-cell adaptation during pregnancy. Methods: The relationship between the blood oxytocin level and pancreatic β-cell function in patients with GDM and healthy pregnant women was investigated. Gestating and non-gestating mice were used to evaluate the in vivo effect of oxytocin signal on β-cells during pregnancy. In vitro experiments were performed on INS-1 insulinoma cells. Results: The blood oxytocin levels were lower in patients with GDM than in healthy pregnant women and were associated with impaired pancreatic β-cell function. Acute administration of oxytocin increased insulin secretion in both gestating and non-gestating mice. A three-week oxytocin treatment promoted the proliferation of pancreatic β-cells and increased the β-cell mass in gestating but not non-gestating mice. Antagonism of oxytocin receptors by atosiban impaired insulin secretion and induced GDM in gestating but not non-gestating mice. Oxytocin enhanced glucose-stimulated insulin secretion, activated the mitogen-activated protein kinase pathway, and promoted cell proliferation in INS-1 cells. Conclusions: These findings provide strong evidence that oxytocin is needed for β-cell adaptation during pregnancy to maintain β-cell function, and lack of oxytocin could be associated with the risk of GDM.

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Increased expression of GAD65 and GABA in pancreatic β-cells impairs first-phase insulin secretion

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2000.279.3.e684 ◽

2000 ◽

Vol 279 (3) ◽

pp. E684-E694 ◽

Cited By ~ 44

Author(s):

Yuguang Shi ◽

Jamil Kanaani ◽

Virginie Menard-Rose ◽

Yan Hui Ma ◽

Pi-Yun Chang ◽

...

Keyword(s):

Insulin Secretion ◽

Glucose Tolerance ◽

Cell Function ◽

Normal Glucose Tolerance ◽

Negative Regulator ◽

Β Cells ◽

Pancreatic Β Cells ◽

Pancreas Perfusion ◽

First Phase Insulin Secretion

The functional role of glutamate decarboxylase (GAD) and its product GABA in pancreatic islets has remained elusive. Mouse β-cells express the larger isoform GAD67, whereas human islets express only the smaller isoform GAD65. We have generated two lines of transgenic mice expressing human GAD65 in pancreatic β-cells (RIP7-hGAD65, Lines 1 and 2) to study the effect that GABA generated by this isoform has on islet cell function. The ascending order of hGAD65 expression and/or activity in β-cells was Line 1 heterozygotes < Line 2 heterozygotes < Line 1 homozygotes. Line 1 heterozygotes have normal glucose tolerance, whereas Line 1 homozygotes and Line 2 heterozygotes exhibit impaired glucose tolerance and inhibition of insulin secretion in vivo in response to glucose. In addition, fasting levels of blood glucose are elevated and insulin is decreased in Line 1 homozygotes. Pancreas perfusion experiments suggest that GABA generated by GAD65 may function as a negative regulator of first-phase insulin secretion in response to glucose by affecting a step proximal to or at the KATP +channel.

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Downregulation of lncRNA TUG1 Affects Apoptosis and Insulin Secretion in Mouse Pancreatic β Cells

Cellular Physiology and Biochemistry ◽

10.1159/000373999 ◽

2015 ◽

Vol 35 (5) ◽

pp. 1892-1904 ◽

Cited By ~ 68

Author(s):

Dan-dan Yin ◽

Er-bao Zhang ◽

Liang-hui You ◽

Ning Wang ◽

Lin-tao Wang ◽

...

Keyword(s):

Insulin Secretion ◽

Cell Function ◽

Annexin V ◽

Pancreatic Tissue ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Lncrna Tug1

Background: Increasing evidence indicates that long noncoding RNAs (IncRNAs) perform specific biological functions in diverse processes. Recent studies have reported that IncRNAs may be involved in β cell function. The aim of this study was to characterize the role of IncRNA TUG1 in mouse pancreatic β cell functioning both in vitro and in vivo. Methods: qRT-PCR analyses were performed to detect the expression of lncRNA TUG1 in different tissues. RNAi, MTT, TUNEL and Annexin V-FITC assays and western blot, GSIS, ELISA and immunochemistry analyses were performed to detect the effect of lncRNA TUG1 on cell apoptosis and insulin secretion in vitro and in vivo. Results: lncRNA TUG1 was highly expressed in pancreatic tissue compared with other organ tissues, and expression was dynamically regulated by glucose in Nit-1 cells. Knockdown of lncRNA TUG1 expression resulted in an increased apoptosis ratio and decreased insulin secretion in β cells both in vitro and in vivo . Immunochemistry analyses suggested decreased relative islet area after treatment with lncRNA TUG1 siRNA. Conclusion: Downregulation of lncRNA TUG1 expression affected apoptosis and insulin secretion in pancreatic β cells in vitro and in vivo. lncRNA TUG1 may represent a factor that regulates the function of pancreatic β cells.

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Structural finding of R/S-3,4-dihydro-2,2-dimethyl-6-halo-4-(substituted phenylaminocarbonylamino)-2H-1-benzopyrans as selective pancreatic β-cells KATP-pβ channel openers

Canadian Journal of Chemistry ◽

10.1139/v07-127 ◽

2007 ◽

Vol 85 (12) ◽

pp. 1053-1063 ◽

Cited By ~ 5

Author(s):

Sk. Mahasin Alam ◽

Soma Samanta ◽

Amit Kumar Halder ◽

Soumya Basu ◽

Tarun Jha

Keyword(s):

Insulin Secretion ◽

Negative Impact ◽

Inhibitory Effect ◽

Van Der Waals Interactions ◽

Β Cells ◽

Pancreatic Β Cells ◽

Qsar Study ◽

Water Partition Coefficient ◽

Qsar Models ◽

Leave One Out

R/S-3,4-Dihydro-2,2-dimethyl-6-halo-4-(substituted phenylaminocarbonyl-amino)-2H-1-benzopyrans are pancreatic β-cells potassium (KATP-pβ) channel openers with inhibitory effect on insulin secretion. To find the more active and effective benzopyrans as selective potassium (KATP-pβ) channel openers towards the pancreatic tissues, quantitative structure–activity relationships (QSAR) study was performed using E-state and R-state indices along with Wang–Ford charges, n-octanol/water partition coefficient, molar refractivity, and indicator parameters. QSAR models were developed by statistical techniques, e.g., multiple linear regression (MLR), principle component regression analysis (PCRA), and partial least squares (PLS) analysis. The generated equations were validated by the leave-one-out cross-validation method. The models show the importance of ETSA indices of atom numbers 16, 17, 18, 19, 21 as well as 22. The positive coefficient of S16, S17, S18, S19, S21, and S22 indicate that with the increase of the value of E-state indices, desired activity decreases. RTSA index is also important for the biological activity, and the atom numbers 16, 17, 18, 19, 20 and 22 are involved in van der Waals interactions. RTSA index also possesses negative impact on the inhibition of residual insulin secretion. Wang–Ford charges of some particular atoms are also important for the inhibition. Increase of n-octanol/water partition coefficients of compounds inhibit insulin secretion, and the presence of chlorine atom at m- and p- positions of the phenyl ring B is necessary for the inhibition of residual insulin secretion.Key words: benzopyran derivatives, potassium channel openers, PCRA, PLS, QSAR.

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