K_ATP channel activity and slow oscillations in pancreatic beta cells are regulated by mitochondrial ATP production

The Journal of Physiology, Год журнала: 2023, Номер 601(24), С. 5655 - 5667

Опубликована: Ноя. 20, 2023

Abstract Pancreatic beta cells secrete insulin in response to plasma glucose. The ATP‐sensitive potassium channel (K ATP ) links glucose metabolism islet electrical activity these by responding increased cytosolic [ATP]/[ADP]. It was recently proposed that pyruvate kinase (PK) close proximity cell K locally produces the inhibits activity. This proposal largely based on observation applying phosphoenolpyruvate (PEP) and ADP cytoplasmic side of excised inside‐out patches inhibited . To test relative contributions local vs. mitochondrial production, we recorded using mouse INS‐1 832/13 cells. In contrast prior reports, could not replicate inhibition PEP + ADP. However, when pH solutions corrected for addition PEP, strong observed as a result well‐known action protons inhibit cell‐attached recordings, perifusing either PK activator or an inhibitor had little no effect closure glucose, further suggesting is important regulator contrast, inhibitors robustly Finally, measuring [ATP]/[ADP] responses imposed calcium oscillations cells, found oxidative phosphorylation raise even at its nadir during burst silent phase, agreement with our mathematical model. These results indicate produced primary controller pancreatic image Key points Phosphoenolpyruvate plus adenosine diphosphate does patches. only if unbalanced. Modulating has minimal effects Mitochondrial inhibition, potentiates Although level falls phase oscillations, mitochondria can still produce enough via therefore main source

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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The mitochondrial enzyme pyruvate carboxylase restricts pancreatic β-cell senescence by blocking p53 activation

Proceedings of the National Academy of Sciences, Год журнала: 2024, Номер 121(44)

Опубликована: Окт. 22, 2024

Defective glucose-stimulated insulin secretion (GSIS) and β-cell senescence are hallmarks in diabetes. The mitochondrial enzyme pyruvate carboxylase (PC) has been shown to promote GSIS proliferation the clonal lines, yet its physiological relevance remains unknown. Here, we provide animal human data showing a role of PC protecting β-cells against maintaining under different pathological conditions. β-cell-specific deletion impaired induced mouse models either standard chow diet or prolonged high-fat feeding. Transcriptomic analysis indicated that p53-related cell cycle arrest activated PC-deficient islets. Overexpression inhibited hyperglycemia- aging-induced islets as well INS-1E β-cells, whereas knockdown provoked senescence. Mechanistically, interacted with MDM2 prevent degradation via binding motif, which turn restricts p53-dependent senescent program β-cells. On contrary, regulatory effects on tricarboxylic acid (TCA) anaplerotic flux p53-independent. We illuminate function controlling through MDM2–p53 axis.

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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NPC1 is required for postnatal islet β cell differentiation by maintaining mitochondria turnover

Theranostics, Год журнала: 2024, Номер 14(5), С. 2058 - 2074

Опубликована: Янв. 1, 2024

Rationale: NPC1 is a protein localized on the lysosome membrane regulating intracellular cholesterol transportation and maintaining normal function.GWAS studies have found that variants in T2D was pancreatic islet expression quantitative trait locus, suggesting potential role of pathophysiology.Methods: Two-week-old Npc1 -/-mice wild type littermates were employed to examine β cell morphology functional changes induced by loss Npc1.Single RNA sequencing conducted primary islets.Npc1 -/-Min6 line generated using CRISPR/Cas9 gene editing.Seahorse XF24 used analyze Min6 mitochondria respiration.Ultra-high-resolution imaging with Lattice SIM 2 electron microscope observe cells.Mitophagy Dye mt-Keima measure mitophagy.Results: In -/-mice, we survival mass expansion as well glucose insulin secretion 2-week-old mice reduced.Npc1 retarded postnatal differentiation growth impaired oxidative phosphorylation (OXPHOS) function increase mitochondrial superoxide production, which might be attributed autophagy flux particularly (mitophagy) dysfunctional null cells. Conclusion:Our study revealed played an important turnover, ensured establishment sufficient OXPHOS for cells maturation.

Язык: Английский

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The role of anaplerotic metabolism of glucose and glutamine in insulin secretion: A model approach

Biophysical Chemistry, Год журнала: 2024, Номер 311, С. 107270 - 107270

Опубликована: Май 23, 2024

We propose a detailed computational beta cell model that emphasizes the role of anaplerotic metabolism under glucose and glucose-glutamine stimulation. This goes beyond traditional focus on mitochondrial oxidative phosphorylation ATP-sensitive K+ channels, highlighting predominant generation ATP from phosphoenolpyruvate in vicinity KATP channels. It also underlines modulatory H2O2 as signaling molecule first phase glucose-stimulated insulin secretion. In second phase, critical pathways, activated by stimulation via pyruvate carboxylase glutamine glutamate dehydrogenase. particularly focuses production NADPH key enhancers The predictions are consistent with empirical data, complex interplay metabolic pathways emphasizing primary facilitating By delineating these crucial provides valuable insights into potential therapeutic targets for diabetes.

Язык: Английский

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Short-Term Inhibition of Translation by Cycloheximide Concurrently Affects Mitochondrial Function and Insulin Secretion in Islets from Female Mice

International Journal of Molecular Sciences, Год журнала: 2023, Номер 24(20), С. 15464 - 15464

Опубликована: Окт. 23, 2023

Since glucose stimulates protein biosynthesis in beta cells concomitantly with the stimulation of insulin release, possible interaction both processes was explored. The inhibited by 10 μM cycloheximide (CHX) 60 min prior to perifused, freshly isolated or 22 h-cultured NMRI mouse islets. CHX reduced insulinotropic effect 25 mM 500 tolbutamide fresh but not cultured In islets second phase even enhanced. and strongly content proinsulin, insulin, moderately diminished [Ca2+]i increase during stimulation. oxygen consumption rate (OCR) about 50% higher than that at basal significantly increased tolbutamide. fresh, cultured, glucose-induced OCR changes NAD(P)H- FAD-autofluorescence. It is concluded short-term exposure interferes signal function mitochondria, which have different working conditions interference may be an off-target result from cytosolic synthesis mitochondrial proteins.

Язык: Английский

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Pancreatic islets undergo functional and morphological adaptation during development of Barth Syndrome

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

Опубликована: Июль 2, 2024

Abstract Barth syndrome is a multisystem genetic disorder caused by mutation in TAFAZZIN , gene that encodes phospholipid:lysophospholipid transacylase important for cardiolipin remodeling. Syndrome patients suffer from number of symptoms including early heart failure, fatigue, and systemic metabolic alterations, hypoglycemia. The endocrine pancreas central to glucose homeostasis, however, the impact defective remodeling on pancreatic islet function consequences metabolism unclear. Surprisingly, mouse model with global knockdown, we observed improved tolerance compared wildtype littermates. We show secretory are robustly maintained through various compensatory mechanisms increased uptake mitochondrial volume. Transcriptomics analyses revealed expression genes encoding proteins involved N-acetylglucosamine synthesis protein O -linked N-acetylglucosaminylation. These pathways might provide molecular mechanism coupling changes volume regulation.

Язык: Английский

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Analysis of beta-cell maturity and mitochondrial morphology in juvenile non-human primates exposed to maternal Western-style diet during development

Frontiers in Endocrinology, Год журнала: 2024, Номер 15

Опубликована: Июль 24, 2024

Introduction Using a non-human primate (NHP) model of maternal Western-style diet (mWSD) feeding during pregnancy and lactation, we previously reported altered offspring beta:alpha cell ratio in vivo insulin hyper-secretion ex vivo. Mitochondria are known to maintain beta-cell function by producing ATP for secretion. In response nutrient stress, the mitochondrial network within beta cells undergoes morphological changes respiration metabolic adaptability. Given that dynamics have also been associated with cellular fate transitions, assessed whether mWSD exposure was markers maturity and/or morphology might explain islet phenotype. Methods We evaluated expression identity/maturity (NKX6.1, MAFB, UCN3) via florescence microscopy islets Japanese macaque pre-adolescent (1 year old) peri-adolescent (3-year-old) born dams fed either control or WSD lactation weaned onto WSD. Mitochondrial NHP analyzed 2D transmission electron 3D using super resolution deconvolve network. Results There no difference percent expressing key from WSD-fed at 1 3 years age; however, WSD-exposed old showed increased levels NKX6.1 per age. Regardless diet, found be primarily short fragmented both ages NHP; overall volume utero lactational consumption may increase fragmentation. Discussion Despite having clear developmental effects on secretory glucose, this does not appear mediated general, more suggests greater ability flexibility.

Язык: Английский

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The Proton Leak of the Inner Mitochondrial Membrane Is Enlarged in Freshly Isolated Pancreatic Islets

Biomedicines, Год журнала: 2024, Номер 12(8), С. 1747 - 1747

Опубликована: Авг. 2, 2024

In a number of investigations on the mechanism metabolic amplification insulin secretion, differences between response freshly isolated islets and cultured for one day have been observed. Since no trivial explanation like insufficient numbers viable cells after cell culture could be found, more thorough investigation into mechanisms responsible difference was made, concentrating function mitochondria as site where metabolism nutrient stimulators secretion forms signals impacting transport fusion granules. Using combinations inhibitors oxidative phosphorylation, we come to conclusion that mitochondrial membrane potential is lower exchange reducing equivalents faster in than islets. The significantly higher rate oxygen consumption fresh (13 vs. 8 pmol/min/islet) not caused by different activity F1F0-ATPase, but larger proton leak. These observations raise questions whether leak physiologically regulated pathway its size reflects working condition within pancreas.

Язык: Английский

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