Glucose regulates glucokinase activity in cultured islets from rat pancreas.

Liang, Yin; Najafi, Habiba; Matschinsky, Franz M.

doi:10.1016/s0021-9258(17)44841-1

Cited by 91 publications

(4 citation statements)

References 20 publications

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“…37,38 Because 2 mM glucose is below the threshold for GCK activation, 39,40 we considered this to be indicative of the low-activity, likely "open", state; 25 mM glucose, while higher than the highest level β-cells ever experience in vivo, is commonly used to induce maximal GCK enzymatic activity in living cells. 41,42 As expected, the change in FRET is significantly higher for the 25 mM glucose-treated cells than for cells in 2 mM glucose. Representative images of the anisotropy values show increased levels of activation in cells treated with 25 mM glucose (Figure 5B).…”

Section: ■ Resultssupporting

confidence: 77%

Nitric Oxide Activates β-Cell Glucokinase by Promoting Formation of the “Glucose-Activated” State

et al. 2018

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The release of insulin from the pancreas is tightly controlled by glucokinase (GCK) activity that couples β-cell metabolism to changes in blood sugar. Despite having only a single glucose-binding site, GCK displays positive glucose cooperativity. Ex vivo structural studies have identified several potential protein conformations with varying levels of enzymatic activity, yet it is unclear how living cells regulate GCK cooperativity. To better understand the cellular regulation of GCK activation, we developed a homotransfer Förster resonance energy transfer (FRET) GCK biosensor and used polarization microscopy to eliminate fluorescence crosstalk from FRET quantification and improve the signal-to-noise ratio. This approach enhanced sensor contrast compared to that seen with the heterotransfer FRET GCK reporter and allowed observation of individual GCK states using an automated method to analyze FRET data at the pixel level. Mutations known to activate and inhibit GCK activity produced distinct anisotropy distributions, suggesting that at least two conformational states exist in living cells. A high glucose level activated the biosensor in a manner consistent with GCK's enzymology. Interestingly, glucose-free conditions did not affect GCK biosensor FRET, indicating that there is a single low-activity state, which is counter to proposed structural models of GCK cooperativity. Under low-glucose conditions, application of chemical NO donors efficiently shifted GCK to the more active conformation. Notably, GCK activation by mutation, a high glucose level, a pharmacological GCK activator, or S-nitrosylation all shared the same FRET distribution. These data suggest a simplified model for GCK activation in living cells, where post-translational modification of GCK by S-nitrosylation facilitates a single conformational transition that enhances GCK enzymatic activity.

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Section: ■ Resultssupporting

confidence: 77%

Nitric Oxide Activates β-Cell Glucokinase by Promoting Formation of the “Glucose-Activated” State

et al. 2018

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“…Glucose phosphorylation by glucokinase (GCK) is normally a rate-limiting step in glucose metabolism and a central regulator of glucose-stimulated insulin secretion (GSIS) ( 14 ), and absence of GCK is expected to reduce glucose flux in β-cells and as a consequence, decrease insulin secretion and increase blood glucose levels ( 15 ). Sustained catalytic activation of β-cell GCK has been proposed as a potential cause of the compensatory increase in glucose sensitivity in early stages of the type 2 diabetes ( 16 , 17 ), but the same overstimulation of β-cell metabolism is also proposed as a culprit in subsequent “exhaustion” and loss of β-cell mass ( 18 – 20 ). We previously demonstrated increased glucose metabolism, as reflected in increased NAD(P)H autofluorescence and mitochondrial depolarization, in islets from K ATP -GOF diabetic mice ( 21 ).…”

Section: Introductionmentioning

confidence: 99%

Genetic Reduction of Glucose Metabolism Preserves Functional β-Cell Mass in KATP-Induced Neonatal Diabetes

et al. 2022

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Beta-cell failure and loss of β-cell mass are key events in diabetes progression. Although insulin hypersecretion in early stages has been implicated in β-cell exhaustion/failure, loss of β-cell mass still occurs in KATP-gain-of-function (GOF) mouse models of human neonatal diabetes, in the absence of insulin secretion. Thus, we hypothesize that hyperglycemia-induced increased β-cell metabolism is responsible for β-cell failure, and that reducing glucose metabolism will prevent loss of β-cell mass. To test this, KATP-GOF mice were crossed with mice carrying β-cell specific glucokinase haploinsuficincy (GCK+/−), to genetically reduce glucose metabolism. As expected, both KATP-GOF and KATP-GOF/GCK+/− mice showed lack of glucose-stimulated insulin secretion. However, KATP-GOF/GCK+/− mice demonstrated markedly reduced blood glucose, delayed diabetes progression, and improved glucose tolerance compared to KATP-GOF mice. In addition, decreased plasma insulin and content, increased proinsulin and augmented plasma glucagon observed in KATP-GOF mice were normalized to control levels in KATP-GOF/GCK+/− mice. Strikingly, KATP-GOF/GCK+/− mice demonstrated preserved β-cell mass and identity, compared to the marked decrease in β-cell identity and increased dedifferentiation observed in KATP-GOF mice. Moreover KATP-GOF/GCK+/− mice demonstrated restoration of body-weight, and liver and brown/white adipose tissue mass and function, and normalization of physical activity and metabolic efficiency compared to KATP-GOF mice. These results demonstrate that decreasing β-cell glucose signaling can prevent glucotoxicity-induced loss of insulin content and β-cell failure independently of compensatory insulin hypersecretion and β-cell exhaustion.

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“…Triglyceride content and the activity of the pyruvate dehydrogenase complex (PDHc) in the isolated islets were determined according to the methodology described by Briaud et al [20] and Zhou et al [21], respectively. Glucokinase (GK) and hexokinase (HK) were measured in the citosolic fraction of isolated islets by fluorometric assay [22,23] as the conversion of NAD + to NADH by exogenous glucose-6-phosphate dehydrogenase. More details of the methodologies have been described elsewhere [12,13].…”

Section: Methodsmentioning

confidence: 99%

Dietary fish oil normalized glucose-stimulated insulin secretion in isolated pancreatic islets of dyslipemic rats through mechanisms involving glucose phosphorylation, peroxisome proliferator-activated receptor γ and uncoupling protein 2

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Chicco

Lombardo

2013

Prostaglandins, Leukotrienes and Essential Fatty Acids

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Glucose regulates glucokinase activity in cultured islets from rat pancreas.

Cited by 91 publications

References 20 publications

Nitric Oxide Activates β-Cell Glucokinase by Promoting Formation of the “Glucose-Activated” State

Nitric Oxide Activates β-Cell Glucokinase by Promoting Formation of the “Glucose-Activated” State

Genetic Reduction of Glucose Metabolism Preserves Functional β-Cell Mass in KATP-Induced Neonatal Diabetes

Dietary fish oil normalized glucose-stimulated insulin secretion in isolated pancreatic islets of dyslipemic rats through mechanisms involving glucose phosphorylation, peroxisome proliferator-activated receptor γ and uncoupling protein 2

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