scholarly journals Targeting of astrocytic glucose metabolism by beta-hydroxybutyrate

2016 ◽  
Vol 36 (10) ◽  
pp. 1813-1822 ◽  
Author(s):  
Rocío Valdebenito ◽  
Iván Ruminot ◽  
Pamela Garrido-Gerter ◽  
Ignacio Fernández-Moncada ◽  
Linda Forero-Quintero ◽  
...  
Keyword(s):  
Neuronal Excitability ◽  
Ketone Bodies ◽  
Neuroprotective Effect ◽  
Hippocampal Slices ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Glucose Consumption ◽  
Intermittent Fasting ◽  
Ketogenic Diets ◽  
Beta Hydroxybutyrate

The effectiveness of ketogenic diets and intermittent fasting against neurological disorders has brought interest to the effects of ketone bodies on brain cells. These compounds are known to modify the metabolism of neurons, but little is known about their effect on astrocytes, cells that control the supply of glucose to neurons and also modulate neuronal excitability through the glycolytic production of lactate. Here we have used genetically-encoded Förster Resonance Energy Transfer nanosensors for glucose, pyruvate and ATP to characterize astrocytic energy metabolism at cellular resolution. Our results show that the ketone body beta-hydroxybutyrate strongly inhibited astrocytic glucose consumption in mouse astrocytes in mixed cultures, in organotypic hippocampal slices and in acute hippocampal slices prepared from ketotic mice, while blunting the stimulation of glycolysis by physiological and pathophysiological stimuli. The inhibition of glycolysis was paralleled by an increased ability of astrocytic mitochondria to metabolize pyruvate. These results support the emerging notion that astrocytes contribute to the neuroprotective effect of ketone bodies.

scholarly journals Fluorescence changes reveal kinetic steps of muscarinic receptor–mediated modulation of phosphoinositides and Kv7.2/7.3 K+ channels

2009 ◽  
Vol 133 (4) ◽  
pp. 347-359 ◽  
Author(s):  
Jill B. Jensen ◽  
John S. Lyssand ◽  
Chris Hague ◽  
Bertil Hille
Keyword(s):  
Muscarinic Receptor ◽  
Neuronal Excitability ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Signaling Cascades ◽  
M Current ◽  
M1 Muscarinic ◽  
Rate Limiting ◽  
G Protein Coupled ◽  
Kinetics Of

G protein–coupled receptors initiate signaling cascades. M1 muscarinic receptor (M1R) activation couples through Gαq to stimulate phospholipase C (PLC), which cleaves phosphatidylinositol 4,5-bisphosphate (PIP2). Depletion of PIP2 closes PIP2-requiring Kv7.2/7.3 potassium channels (M current), thereby increasing neuronal excitability. This modulation of M current is relatively slow (6.4 s to reach within 1/e of the steady-state value). To identify the rate-limiting steps, we investigated the kinetics of each step using pairwise optical interactions likely to represent fluorescence resonance energy transfer for M1R activation, M1R/Gβ interaction, Gαq/Gβ separation, Gαq/PLC interaction, and PIP2 hydrolysis. Electrophysiology was used to monitor channel closure. Time constants for M1R activation (<100 ms) and M1R/Gβ interaction (200 ms) are both fast, suggesting that neither of them is rate limiting during muscarinic suppression of M current. Gαq/Gβ separation and Gαq/PLC interaction have intermediate 1/e times (2.9 and 1.7 s, respectively), and PIP2 hydrolysis (6.7 s) occurs on the timescale of M current suppression. Overexpression of PLC accelerates the rate of M current suppression threefold (to 2.0 s) to become nearly contemporaneous with Gαq/PLC interaction. Evidently, channel release of PIP2 and closure are rapid, and the availability of active PLC limits the rate of M current suppression.

scholarly journals Oxygen and seizure dynamics: I. Experiments

2014 ◽  
Vol 112 (2) ◽  
pp. 205-212 ◽  
Author(s):  
Justin Ingram ◽  
Chunfeng Zhang ◽  
John R. Cressman ◽  
Anupam Hazra ◽  
Yina Wei ◽  
...  
Keyword(s):  
Epileptiform Activity ◽  
Hippocampal Slices ◽  
Measurement Techniques ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Critical Factor ◽  
Seizure Onset ◽  
Cellular Excitability ◽  
Oxygen Dynamics ◽  
Polarographic Measurement

We utilized a novel ratiometric nanoquantum dot fluorescence resonance energy transfer (NQD-FRET) optical sensor to quantitatively measure oxygen dynamics from single cell microdomains during hypoxic episodes as well as during 4-aminopyridine (4-AP)-induced spontaneous seizure-like events in rat hippocampal slices. Coupling oxygen sensing with electrical recordings, we found the greatest reduction in the O2 concentration ([O2]) in the densely packed cell body stratum (st.) pyramidale layer of the CA1 and differential layer-specific O2 dynamics between the st. pyramidale and st. oriens layers. These hypoxic decrements occurred up to several seconds before seizure onset could be electrically measured extracellularly. Without 4-AP, we quantified a narrow range of [O2], similar to the endogenous hypoxia found before epileptiform activity, which permits a quiescent network to enter into a seizure-like state. We demonstrated layer-specific patterns of O2 utilization accompanying layer-specific neuronal interplay in seizure. None of the oxygen overshoot artifacts seen with polarographic measurement techniques were observed. We therefore conclude that endogenously generated hypoxia may be more than just a consequence of increased cellular excitability but an influential and critical factor for orchestrating network dynamics associated with epileptiform activity.

scholarly journals Ketone Bodies in the Brain Beyond Fuel Metabolism: From Excitability to Gene Expression and Cell Signaling

2021 ◽  
Vol 14 ◽  
Author(s):  
Darío García-Rodríguez ◽  
Alfredo Giménez-Cassina
Keyword(s):  
Gene Expression ◽  
Neuronal Excitability ◽  
Ketone Bodies ◽  
Biological Effects ◽  
Epileptic Seizures ◽  
Ketogenic Diets ◽  
Infantile Seizures ◽  
Neuronal Physiology ◽  
The Impact ◽  
The Brain

Ketone bodies are metabolites that replace glucose as the main fuel of the brain in situations of glucose scarcity, including prolonged fasting, extenuating exercise, or pathological conditions such as diabetes. Beyond their role as an alternative fuel for the brain, the impact of ketone bodies on neuronal physiology has been highlighted by the use of the so-called “ketogenic diets,” which were proposed about a century ago to treat infantile seizures. These diets mimic fasting by reducing drastically the intake of carbohydrates and proteins and replacing them with fat, thus promoting ketogenesis. The fact that ketogenic diets have such a profound effect on epileptic seizures points to complex biological effects of ketone bodies in addition to their role as a source of ATP. In this review, we specifically focus on the ability of ketone bodies to regulate neuronal excitability and their effects on gene expression to respond to oxidative stress. Finally, we also discuss their capacity as signaling molecules in brain cells.

Ketogenic Diet in a Hippocampal Slice

2016 ◽  
Author(s):  
Masahito Kawamura
Keyword(s):  
Ketogenic Diet ◽  
Hippocampal Slice ◽  
Ketone Bodies ◽  
Hippocampal Slices ◽  
Patch Clamp Technique ◽  
Ketogenic Diets ◽  
Whole Cell Patch Clamp ◽  
Electrophysiological Recordings

The hippocampus is thought to be a good experimental model for investigating epileptogenesis in and/or antiepileptic therapy for temporal lobe epilepsy. The hippocampus is also a useful target for researching the ketogenic diet. This chapter focuses on electrophysiological recordings using hippocampal slices and introduces their use for studying the anticonvulsant effects underlying ketogenic diets. The major difficulty in using hippocampal slices is the inability to precisely reproduce the in vivo condition of ketogenic diet feeding in this in vitro preparation. Three different approaches are reported to reproduce diet effects in the hippocampal slices: (1) direct application of ketone bodies, (2) mimicking the ketogenic diet condition with whole-cell patch-clamp technique, and (3) hippocampal slices from ketogenic diet–fed animals. Significant results have been found with each of these methods. These three approaches are useful tools to elucidate the underlying anticonvulsant mechanisms of the ketogenic diet.

AMPA Induces NO-Dependent cGMP Signals in Hippocampal and Cortical Neurons via L-Type Voltage-Gated Calcium Channels

2019 ◽  
Vol 30 (4) ◽  
pp. 2128-2143 ◽  
Author(s):  
Jan Giesen ◽  
Ernst-Martin Füchtbauer ◽  
Annette Füchtbauer ◽  
Klaus Funke ◽  
Doris Koesling ◽  
...  
Keyword(s):  
Calcium Channels ◽  
Cortical Neurons ◽  
Calcium Influx ◽  
Hippocampal Slices ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Acute Hippocampal Slices ◽  
The Impact

Abstract The nitric oxide (NO)/cGMP signaling cascade has an established role in synaptic plasticity. However, with conventional methods, the underlying cGMP signals were barely detectable. Here, we set out to confirm the well-known NMDA-induced cGMP increases, to test the impact of AMPA on those signals, and to identify the relevant phosphodiesterases (PDEs) using a more sensitive fluorescence resonance energy transfer (FRET)-based method. Therefore, a “knock-in” mouse was generated that expresses a FRET-based cGMP indicator (cGi-500) allowing detection of cGMP concentrations between 100 nM and 3 μM. Measurements were performed in cultured hippocampal and cortical neurons as well as acute hippocampal slices. In hippocampal and cortical neurons, NMDA elicited cGMP signals half as high as the ones elicited by exogenous NO. Interestingly, AMPA increased cGMP independently of NMDA receptors and dependent on NO synthase (NOS) activation. NMDA- and AMPA-induced cGMP signals were not additive indicating that both pathways converge on the level of NOS. Accordingly, the same PDEs, PDE1 and PDE2, were responsible for degradation of NMDA- as well as AMPA-induced cGMP signals. Mechanistically, AMPAR induced calcium influx through L-type voltage-gated calcium channels leading to NOS and finally NO-sensitive guanylyl cyclase activation. Our results demonstrate that in addition to NMDA also AMPA triggers endogenous NO formation and hence cGMP production.

Distribution of phospholipids around gramicidin and D-.beta.-hydroxybutyrate dehydrogenase as measured by resonance energy transfer

Biochemistry ◽  
1988 ◽  
Vol 27 (6) ◽  
pp. 2033-2039 ◽  
Author(s):  
Suke Wang ◽  
Earl Martin ◽  
Joseph Cimino ◽  
Geneva Omann ◽  
Michael Glaser
Keyword(s):  
Energy Transfer ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Beta Hydroxybutyrate

Structural dynamics of P-type ATPase ion pumps

2019 ◽  
Vol 47 (5) ◽  
pp. 1247-1257 ◽  
Author(s):  
Mateusz Dyla ◽  
Sara Basse Hansen ◽  
Poul Nissen ◽  
Magnus Kjaergaard
Keyword(s):  
Structural Dynamics ◽  
Single Molecule ◽  
New Technologies ◽  
Atp Hydrolysis ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Time Resolved ◽  
Dynamics Simulations ◽  
Types Of Information ◽  
P Type

Abstract P-type ATPases transport ions across biological membranes against concentration gradients and are essential for all cells. They use the energy from ATP hydrolysis to propel large intramolecular movements, which drive vectorial transport of ions. Tight coordination of the motions of the pump is required to couple the two spatially distant processes of ion binding and ATP hydrolysis. Here, we review our current understanding of the structural dynamics of P-type ATPases, focusing primarily on Ca2+ pumps. We integrate different types of information that report on structural dynamics, primarily time-resolved fluorescence experiments including single-molecule Förster resonance energy transfer and molecular dynamics simulations, and interpret them in the framework provided by the numerous crystal structures of sarco/endoplasmic reticulum Ca2+-ATPase. We discuss the challenges in characterizing the dynamics of membrane pumps, and the likely impact of new technologies on the field.

Quantum Dot Bioconjugates as Energy Donors in Fluorescence Resonance Energy Transfer Assays

2003 ◽  
Vol 773 ◽  
Author(s):  
Aaron R. Clapp ◽  
Igor L. Medintz ◽  
J. Matthew Mauro ◽  
Hedi Mattoussi
Keyword(s):  
Energy Transfer ◽  
Quantum Dot ◽  
Organic Dyes ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Genetically Engineered ◽  
Molar Ratio ◽  
Binding Assays ◽  
Specific Sequence ◽  
Donor Acceptor

AbstractLuminescent CdSe-ZnS core-shell quantum dot (QD) bioconjugates were used as energy donors in fluorescent resonance energy transfer (FRET) binding assays. The QDs were coated with saturating amounts of genetically engineered maltose binding protein (MBP) using a noncovalent immobilization process, and Cy3 organic dyes covalently attached at a specific sequence to MBP were used as energy acceptor molecules. Energy transfer efficiency was measured as a function of the MBP-Cy3/QD molar ratio for two different donor fluorescence emissions (different QD core sizes). Apparent donor-acceptor distances were determined from these FRET studies, and the measured distances are consistent with QD-protein conjugate dimensions previously determined from structural studies.

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