SMAD2 disruption in mouse pancreatic beta cells leads to islet hyperplasia and impaired insulin secretion due to the attenuation of ATP-sensitive K+ channel activity

Background. Mutations in human KLF11 may lead to the development of maturity-onset diabetes of the young 7 (MODY7). This occurs due to impaired insulin synthesis in the pancreas. To date, the clinical and functional characteristics of the novel KLF11 mutation c.1061G > T have not yet been reported. Methods. Whole-exon sequencing was used to screen the proband and family members with clinical suspicion of the KLF11 variant. Luciferase reporter assays were used to investigate whether the KLF11 variant binds to the insulin promoter. Real-time PCR, western blotting, and glucose-stimulated insulin secretion (GSIS) analysis were used to analyze the KLF11 variant that regulates insulin expression and insulin secretion activity in beta cell lines. The Freestyle Libre H (Abbott Diabetes Care Ltd) was used to dynamically monitor the proband daily blood glucose levels. Results. Mutation screening for the whole exon genes identified a heterozygous KLF11 (c.1061G > T) variant in the proband, her mother, and her maternal grandfather. Cell-based luciferase reporter assays using wild-type and mutant transgenes revealed that the KLF11 (c.1061G > T) variant had impaired insulin promoter regulation activity. Moreover, this variant was found to impair insulin expression and insulin secretion in pancreatic beta cells. The proband had better blood glucose control without staple food intake ( p < 0.05 ). Conclusions. Herein, for the first time, we report a novel KLF11 (c.1061G > T) monogenic mutation associated with MODY7. This variant has impaired insulin promoter regulation activity and impairs insulin expression and secretion in pancreatic beta cells. Therefore, administering oral antidiabetic drugs along with dietary intervention may benefit the proband.

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The structure and function of the ATP-sensitive K+ channel in insulin-secreting pancreatic beta-cells

Journal of Molecular Endocrinology ◽

10.1677/jme.0.0220113 ◽

1999 ◽

Vol 22 (2) ◽

pp. 113-123 ◽

Cited By ~ 97

Author(s):

T Miki ◽

K Nagashima ◽

S Seino

Keyword(s):

Molecular Structure ◽

Insulin Secretion ◽

Beta Cell ◽

Beta Cells ◽

Katp Channel ◽

Pancreatic Beta Cells ◽

Pancreatic Beta Cell ◽

Molecular Genetic ◽

Katp Channels ◽

K Channel

ATP-sensitive K+ channels (KATP channels) play important roles in many cellular functions by coupling cell metabolism to electrical activity. The KATP channels in pancreatic beta-cells are thought to be critical in the regulation of glucose-induced and sulfonylurea-induced insulin secretion. Until recently, however, the molecular structure of the KATP channel was not known. Cloning members of the novel inwardly rectifying K+ channel subfamily Kir6.0 (Kir6.1 and Kir6.2) and the sulfonylurea receptors (SUR1 and SUR2) has clarified the molecular structure of KATP channels. The pancreatic beta-cell KATP channel comprises two subunits: a Kir6.2 subunit and an SUR1 subunit. Molecular biological and molecular genetic studies have provided insights into the physiological and pathophysiological roles of the pancreatic beta-cell KATP channel in insulin secretion.

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Mechanisms of Impaired Glucose Tolerance and Insulin Secretion during Isoflurane Anesthesia

Anesthesiology ◽

10.1097/aln.0b013e3181bbcb0d ◽

2009 ◽

Vol 111 (5) ◽

pp. 1044-1051 ◽

Cited By ~ 34

Author(s):

Katsuya Tanaka ◽

Takashi Kawano ◽

Takehito Tomino ◽

Hiroaki Kawano ◽

Tsuyoshi Okada ◽

...

Keyword(s):

Insulin Secretion ◽

Patch Clamp ◽

Glucose Tolerance ◽

Potassium Channel ◽

Beta Cells ◽

Mechanism Of Action ◽

Pancreatic Beta Cells ◽

Glucose Utilization ◽

Channel Activity ◽

Potassium Channel Activity

Background Volatile anesthetics impair insulin secretion and glucose utilization; however, the precise mechanism of action that underlies these effects is unknown. The authors hypothesized that isoflurane inhibits glucose-induced inhibition of adenosine triphosphate-sensitive potassium channel activity in pancreatic beta cells, which could result in impaired insulin secretion and glucose tolerance. Methods Intravenous glucose tolerance tests were performed on 28 male Japanese White rabbits anesthetized with sodium pentobarbital. Glibenclamide (50 microg/kg + 33.5 microg x kg x h) or vehicle was administered 75 min before intravenous administration of 0.6 g/kg glucose. Half of the animals (n = 7) in the vehicle and glibenclamide groups received isoflurane at 1.0 minimum alveolar concentration 30 min before administration of glucose, and the other half received a vehicle control. Hemodynamics, blood glucose, and plasma insulin were measured. A cell-attached patch clamp configuration was used to record single channel currents in the pancreas from male Swiss-Webster mice. Results Isoflurane alone or a combination of isoflurane and glibenclamide inhibited the insulinogenic index to a greater extent than in the vehicle and glibenclamide groups. In the patch clamp experiments, channel activity was significantly decreased as the glucose concentration was increased from 0 to 10 mm. The subsequent application of 0.5 mm isoflurane reversed the effects of glucose on channel activity. Conclusion These results show that isoflurane impairs insulin secretion and glucose utilization. The mechanism of action responsible for these effects may involve a decrease in glucose-induced inhibition of adenosine triphosphate-sensitive potassium channel activity in pancreatic beta cells.

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Nitric oxide opens ATP-sensitive K+ channels through suppression of phosphofructokinase activity and inhibits glucose-induced insulin release in pancreatic beta cells.

The Journal of General Physiology ◽

10.1085/jgp.104.6.1079 ◽

1994 ◽

Vol 104 (6) ◽

pp. 1079-1098 ◽

Cited By ~ 56

Author(s):

Y Tsuura ◽

H Ishida ◽

S Hayashi ◽

K Sakamoto ◽

M Horie ◽

...

Keyword(s):

Nitric Oxide ◽

Insulin Secretion ◽

Beta Cells ◽

Katp Channel ◽

Pancreatic Beta Cells ◽

Katp Channels ◽

Channel Activity ◽

K Channels ◽

Intracellular Mechanism ◽

Phosphofructokinase Activity

Nitric oxide (NO) is known to be a potent messenger in the intracellular signal transduction system in many tissues. In pancreatic beta cells, NO has been reported to be formed from L-arginine through NO synthase. To elucidate the effect of NO on insulin secretion and to investigate the intracellular mechanism of its effect, we have used sodium nitroprusside (SNP) as a NO donor. SNP inhibited glucose-induced insulin secretion in a dose-dependent manner, and its effect was reversed by hemoglobin, a known NO scavenger. However, glyceraldehyde-induced insulin secretion was not affected by SNP. Since the closure of ATP-sensitive K+ channels (KATP channel) has been established as a key step in glucose-induced insulin secretion, we have directly assessed the effect of SNP on KATP channel activity using the patch clamp technique. The KATP channel activity reduced by glucose was found to be reversibly activated by the addition of SNP, and this activation was able to be similarly reproduced by applying S-Nitroso-N-acetyl-DL-penicillamine (SNAP), another NO generator. Furthermore, these activating effects were completely eliminated by hemoglobin, in accordance with the reversibility in inhibition of glucose-induced insulin release. However, SNP could not affect the KATP channel suppression by ATP applied to the inside of the plasma membrane. The activation of the KATP channel by NO, therefore, seems to be due to the decreased ATP production attributable to impairment of glucose metabolism in beta cells. Since SNP exhibited no effect on glyceraldehyde-induced KATP channel inhibition, NO may disturb a glycolytic step before glyceraldehyde-3-phosphate. The KATP channel activation by 2-deoxyglucose through presumable ATP consumption due to its phosphorylation by glucokinase was, however, not affected even in the presence of SNP. But in the permeabilized beta cells made by exposure to a low concentration (0.02 U/ml) of streptolysin O (open cell-attached configuration), SNP reopens KATP channels which have been eliminated by fructose-6-phosphate, while this effect was not observed in the KATP channels inhibited by fructose-1,6-bisphosphate. On the other hand, in rat ventricular myocyte KATP channels were not activated by SNP even under a low concentration of glucose. From these observations, the inhibition of phosphofructokinase activity is probably the site responsible for the impairment of glucose metabolism induced by NO in pancreatic beta cells. NO, therefore, seems to be a factor in the deterioration of glucose-induced insulin secretion from pancreatic beta cells through a unique intracellular mechanism.

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Oxidized LDL Downregulates ABCA1 Expression via MEK/ERK/LXR Pathway in INS-1 Cells

Nutrients ◽

10.3390/nu13093017 ◽

2021 ◽

Vol 13 (9) ◽

pp. 3017

Author(s):

Jingya Lyu ◽

Kensaku Fukunaga ◽

Hitomi Imachi ◽

Seisuke Sato ◽

Toshihiro Kobayashi ◽

...

Keyword(s):

Insulin Secretion ◽

Pancreatic Beta Cells ◽

Oxidized Ldl ◽

Specific Inhibitor ◽

Density Lipoprotein ◽

Dependent Manner ◽

Cholesterol Accumulation ◽

Impaired Insulin Secretion ◽

Abca1 Expression ◽

Impaired Insulin

Impaired insulin secretion is one of the main causes of type 2 diabetes. Cholesterol accumulation-induced lipotoxicity contributes to impaired insulin secretion in pancreatic beta cells. However, the detailed mechanism in this process remains unclear. In this study, we proved that oxidized low-density lipoprotein (OxLDL) reduced insulin content, decreased PDX-1 expression, and impaired glucose-stimulated insulin secretion (GSIS) in INS-1 cells, which were rescued by addition of high-density lipoprotein (HDL). OxLDL receptors and cholesterol content were increased by OxLDL. Consistently, OxLDL suppressed cholesterol transporter ABCA1 expression and transcription in a dose-dependent and time-dependent manner. Inhibition of MEK by its specific inhibitor, PD98059, altered the effect of OxLDL on ABCA1 transcription and activation of ERK. Next, chromatin immunoprecipitation assay demonstrated that liver X receptor (LXR) could directly bind to ABCA1 promoter and this binding was inhibited by OxLDL. Furthermore, OxLDL decreased the nuclear LXR expression, which was prevented by HDL. LXR-enhanced ABCA1 transcription was suppressed by OxLDL, and the effect was cancelled by mutation of the LXR-binding sites. In summary, our study shows that OxLDL down-regulates ABCA1 expression by MEK/ERK/LXR pathway, leading to cholesterol accumulation in INS-1 cells, which may result in impaired insulin synthesis and GSIS.

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