Glucose Regulation of β-Cell KATP Channels: It Is Time for a New Model!

Diabetes, Год журнала: 2024, Номер 73(6), С. 856 - 863

Опубликована: Апрель 19, 2024

An agreed-upon consensus model of glucose-stimulated insulin secretion from healthy β-cells is essential for understanding diabetes pathophysiology. Since the discovery KATP channel in 1984, an oxidative phosphorylation (OxPhos)–driven rise ATP has been assumed to close channels initiate secretion. This lacks any evidence, genetic or otherwise, that mitochondria possess bioenergetics raise ATP/ADP ratio triggering threshold, and conflicts with evidence demonstrating OxPhos dispensable It also conflates stoichiometric yield thermodynamics, overestimates by failing account established features β-cell metabolism, such as leak, anaplerosis, cataplerosis, NADPH production subtract efficiency mitochondrial production. We have proposed alternative model, based on spatial bioenergetic specializations which glycolysis initiates The this includes 1) high control strength over secretion; 2) active at correct time explain closure; 3) plasma membrane–associated glycolytic enzymes channels; 4) pyruvate kinase favorable bioenergetics, relative OxPhos, raising ATP/ADP; 5) stalls before membrane depolarization increases after. Although several key experiments remain evaluate 1984 purely circumstantial must be rescued causal, mechanistic if it endure.

Язык: Английский

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Pyruvate kinase modulates the link between β‐cell fructose metabolism and insulin secretion

The FASEB Journal, Год журнала: 2025, Номер 39(7)

Опубликована: Март 28, 2025

Abstract The intricate link between glucose metabolism, ATP production, and glucose‐stimulated insulin secretion (GIIS) in pancreatic β‐cells has been well established. However, the effects of other digestible monosaccharides on this mechanism remain unclear. This study examined interaction intracellular fructose metabolism GIIS using MIN6‐K8 β‐cell lines mouse islets. Fructose at millimolar concentrations potentiated presence stimulatory levels (8.8 mM) glucose. potentiation was dependent sweet taste receptor‐activated phospholipase Cβ2 (PLCβ2) signaling. Concurrently, metabolic tracing 13 C‐labeled conjunction with biochemical analyses demonstrated that blunted glucose‐induced increase ATP/ADP ratio. Mechanistically, is substantially converted to 1‐phosphate (F1P) expense ATP. F1P directly inhibited PKM2 (pyruvate kinase M2), thereby reducing later glycolytic flux used for production. Remarkably, F1P‐mediated inhibition counteracted by TEPP‐46, a small‐molecule activator. TEPP‐46 restored ratio, leading enhancement fructose‐potentiated cells, normal islets, fructose‐unresponsive diabetic These findings reveal an antagonistic interplay β‐cells, highlighting as crucial regulator broadening our understanding relationship fuel secretion.

Язык: Английский

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Do We Need a New Hypothesis for KATP Closure in β-Cells? Distinguishing the Baby From the Bathwater

Diabetes, Год журнала: 2024, Номер 73(6), С. 844 - 848

Опубликована: Апрель 19, 2024

Язык: Английский

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The Synergistic Impact of Glycolysis, Mitochondrial OxPhos, and PEP Cycling on ATP Production in Beta Cells

International Journal of Molecular Sciences, Год журнала: 2025, Номер 26(4), С. 1454 - 1454

Опубликована: Фев. 10, 2025

Pancreatic beta cells regulate insulin secretion in response to glucose by generating ATP, which modulates ATP-sensitive potassium channels (KATP) channel activity and Ca2+ dynamics. We present a model of ATP production pancreatic cells, focusing on dynamics within the bulk cytosol, submembrane region, microdomains near KATP channels. is generated through glycolysis, mitochondrial oxidative phosphorylation (OxPhos), glycolytic pyruvate kinase-mediated phosphoenolpyruvate (PEP) production, supported PEP cycling between mitochondria cytosol. The examines relation oscillations, elucidating their interdependent Our findings demonstrate that both OxPhos PEP-mediated contribute substantially cellular levels. Specifically, glycolysis are crucial for initial (first-phase) increase subplasmalemmal effectively “filling up” pool cells. In second phase, coordinated pathways enables cost-effective fine-tuning levels, with localized effects microdomains. This addresses clarifies recent debate regarding mechanisms sufficient concentrations achieved close glucose-stimulated offering novel insights into regulation energy activity.

Язык: Английский

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ER calcium stores contribute to glucose-induced Ca2+ waves and intercellular connectivity in mouse pancreatic islets

bioRxiv (Cold Spring Harbor Laboratory), Год журнала: 2025, Номер unknown

Опубликована: Март 14, 2025

Abstract Defective insulin secretion is a hallmark of diabetes mellitus. Glucose-induced Ca 2+ oscillations are critical for the stimulation secretion, though mechanisms through which these propagate across islet poorly understood. Here, we use beta cell-targeted GCaMP6f to explore role endoplasmic reticulum (ER) mobilization in response submaximal (11mM) and hyperglycemic (25mM) glucose concentrations. Inhibition inositol 1,4,5 trisphosphate (IP 3 ) receptors, other ion channels, with 2-aminoethoxydiphenyl borate (2-APB) had minimal effects on initial peak or intercellular connectivity provoked by 11mM glucose. However, 2-APB lowered subsequent glucose-induced cytosolic increases at both 11 25mM Unexpectedly, activation IP receptors muscarinic acetylcholine receptor agonist carbachol impact elicited mM glucose, but waves 25 were more coordinated. To determine whether ER calcium was sufficient initiate next blocked sarco(endo)plasmic ATPase (SERCA) pumps thapsigargin, whilst preventing plasma membrane depolarization K ATP -channel opener, diazoxide. Under conditions, an increase followed secondary that slowly subsided. The application alongside diazoxide still enhanced dynamics, this activity uncoordinated cells connected. Our results show plays relatively minor initiation propagation On hand, stores required transition sustained waves. Highlights IP3R inhibition perturbs islets store insufficient generate cell GRAPHICAL ABSTRACT

Язык: Английский

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Exploration of individual beta cell function over time in vivo: effects of hyperglycemia and glucagon-like peptide-1 receptor (GLP1R) agonism

bioRxiv (Cold Spring Harbor Laboratory), Год журнала: 2025, Номер unknown

Опубликована: Апрель 5, 2025

The coordinated function of beta cells within the pancreatic islet is required for normal regulation insulin secretion and partly controlled by specialized "leader" highly connected "hub" beta-cell subpopulations. Whether these subpopulations are functionally stable in vivo remains unclear. Here, we establish an approach to monitor Ca 2+ dynamics individual over time, after engraftment into anterior eye chamber, where continuous blood perfusion near innervation pertain. Under normoglycemic conditions, network dynamics, behavior leaders hubs, remain at least seven days. Hyperglycemia, resulting from high-fat diet feeding or loss a host Gck allele, caused engrafted islets display incomplete abortive waves overall connectivity was diminished. Whereas hub cell numbers were lowered profoundly both disease models, largely persisted. Treatment with GLP1R agonist Exendin-4 led recovery islet-wide re-emergence minutes, effects incretin mimetic being more marked than those observed analogous treatments vitro . Similar observations made using 3-dimensional imaging across whole islet. Our findings thus suggest that incretins may act directly indirectly on vivo. described provide broad applicability exploration time living animal.

Язык: Английский

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What do stimulated beta cells have in common with cancer cells?

Biosystems, Год журнала: 2024, Номер 242, С. 105257 - 105257

Опубликована: Июнь 12, 2024

This study investigates the metabolic parallels between stimulated pancreatic beta cells and cancer cells, focusing on glucose glutamine metabolism. Addressing significant public health challenges of Type 2 Diabetes (T2D) cancer, we aim to deepen our understanding mechanisms driving insulin secretion cellular proliferation. Our analysis anaplerotic cycles role NADPH in biosynthesis elucidates their vital functions both processes. Additionally, point out that cell types share an antioxidative response mediated by Nrf2 signaling pathway, glutathione synthesis, UCP2 upregulation. Notably, facilitates transfer C4 metabolites, enhancing reductive TCA cycle Furthermore, observe hypoxic responses are transient post-stimulation but persistent cells. By synthesizing these insights, research may suggest novel therapeutic targets for T2D, highlighting shared strategies comparative not only illuminates complexity conditions also emphasizes crucial pathways function survival, offering fresh perspectives tackling T2D challenges.

Язык: Английский

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Pyruvate kinase modulates the link between β-cell fructose metabolism and insulin secretion

bioRxiv (Cold Spring Harbor Laboratory), Год журнала: 2024, Номер unknown

Опубликована: Авг. 15, 2024

2 ABSTRACT Glucose triggers insulin secretion from pancreatic β-cells through intracellular glucose metabolism, ATP production, and closure of ATP-sensitive K + channels (K channels). Fructose also stimulates secretion, but the underlying mechanisms remain unclear. This study investigated contribution phospholipase C (PLC) signaling fructose metabolism to fructose-stimulated (FSIS) using MIN6-K8 clonal mouse islets. Fructose-induced PLC activation, assessed by inositol 1-phosphate accumulation, was reduced in fructose-unresponsive β-cell models, such as diabetic islets channel-deficient β-cells, suggesting that responsiveness is primarily determined signaling. Although FSIS dependent on Ca 2+ influx, ATP/ADP ratio unexpectedly lowered fructose, suppression hardly affected FSIS. Metabolic flux analysis revealed accumulation (F1P) suppressed pyruvate kinase (PK) activity, contributing depletion. Strikingly, a small-molecule PK activator, TEPP-46, antagonized F1P-mediated suppression, prevented drop ratio, restored cells, normal islets, These findings metabolic effects identified key regulator linking FSIS, thereby providing new insights into potential therapeutic targets for fructose-associated diseases. 1 GRAPHICAL Left: Fructose-stimulated driven sweet taste receptor (STR)-mediated β-cells. Meanwhile, does not promote because causes (F1P), which suppresses M2 (PKM2), lowering ratio. Right: A activator counteracted PKM2 inhibition, decrease, substantially enhanced Thus, has been

Язык: Английский

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Sex-dependent additive effects of dorzagliatin and incretin on insulin secretion in a novel mouse model ofGCK-MODY

bioRxiv (Cold Spring Harbor Laboratory), Год журнала: 2024, Номер unknown

Опубликована: Ноя. 11, 2024

Abstract Glucokinase (GK) catalyses the key regulatory step in glucose-stimulated insulin secretion. Correspondingly, hetero– and homozygous mutations human GCK cause maturity-onset diabetes of young (GCK-MODY) permanent neonatal (PNDM), respectively. To explore possible utility glucokinase activators (GKA) glucagon–like receptor-1 (GLP-1) agonists these diseases, we have developed a novel hypomorphic Gck allele mice encoding an aberrantly spliced mRNA deleted for exons 2 3. In islets from knock-in (Gck KI/KI ) mice, GK immunoreactivity was reduced by >85%, secretion eliminated. Homozygous were smaller than wildtype littermates displayed frank (fasting blood glucose >18 mmol/L; HbA1c ∼12%), ketosis nephropathy. Heterozygous KI/+ intolerant (HbA1c ∼5.5%). Abnormal Ca 2+ dynamics beta cell-beta cell connectivity completely reversed recently-developed GKA, dorzagliatin, which largely inactive mouse islets. The GLP-1 receptor agonist exendin-4 improved tolerance male action potentiated but not female mice. Sex-dependent additive effects agents also observed on vitro . Combined treatment with GKA incretin may thus be useful -MODY or -PNDM. Article Highlights a. deficiency can drive (GCK-MODY; heterozygotes (GCK-PNDM; homozygotes b. We describe where aberrant splicing lowers activity to ∼85%. use activator, c. Whereas heterozygous mutant are mildly hyperglycemic, survive adulthood. Dorzagliatin potentiates activation sex-dependently d. drugs some forms

Язык: Английский

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An INS-1 beta-cell proteome highlights the role of fatty acid biosynthesis in glucose-stimulated insulin secretion

bioRxiv (Cold Spring Harbor Laboratory), Год журнала: 2024, Номер unknown

Опубликована: Июль 13, 2024

Abstract Pancreatic beta cells secrete insulin as a response to rising glucose level, process known glucose-stimulated secretion (GSIS). In this study, we used liquid chromatography tandem mass spectrometry and data-independent acquisition acquire proteomes of rat pancreatic INS-1 832/13 that were short-term stimulated with concentrations ranging from 0 20 mM, quantifying the behavior 3703 proteins across 11 concentrations. Ensemble clustering proteome profiles revealed unique patterns expressed by cells. 237 proteins, amongst them associated vesicular SNARE interactions, protein export, showed an increase in abundance upon stimulation, whilst majority including those metabolic pathways such glycolysis, TCA cycle respiratory chain, did not respond Interestingly, observe enzymes participating fatty acid metabolism, responded distinctly, showing “switch-on” release starvation no further changes increasing levels. We speculate increased activity might either be part GSIS replenishing membrane lipids required for vesicle-mediated exocytosis and/or providing electron sink compensate catabolism. Significance Study high-throughput proteomics capture comprehensive 30 minutes post stimulation cell line. Our study provides insights into regulation cells, specifically highlighting early role biosynthesis. These findings suggest necessary shift focus electrochemical mechanisms understanding GSIS, paving way future research. As first document alterations initial phase our furthermore documents extent variability when obtaining data after short times, therefore highlights necessity well-controlled design biological replicates. The recorded set complements existing metabolomic transcriptomic studies, valuable resource subsequent investigations.

Язык: Английский

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