Neuronal inhibition and seizure suppression by acetoacetate and its analog, 2-phenylbutyrate

Atsushi Kadowaki, Nagisa Sada, Narinobu Juge, Ayaka Wakasa, Yoshinori Moriyama, Tsuyoshi Inoue

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Objective: The ketogenic diet is clinically used to treat drug-resistant epilepsy. The diet treatment markedly increases ketone bodies (acetoacetate and β-hydroxybutyrate), which work as energy metabolites in the brain. Here, we investigated effects of acetoacetate on voltage-dependent Ca2+ channels (VDCCs) in pyramidal cells of the hippocampus. We further explored an acetoacetate analog that inhibited VDCCs in pyramidal cells, reduced excitatory postsynaptic currents (EPSCs), and suppressed seizures in vivo. Methods: The effects of acetoacetate and its analogs on VDCCs and EPSCs were evaluated using patch-clamp recordings from CA1 pyramidal cells of mouse hippocampal slices. The in vivo effects of these reagents were also evaluated using a chronic seizure model induced by intrahippocampal injection of kainate. Results: Acetoacetate inhibited VDCCs in pyramidal cells of hippocampal slices, and reduced EPSCs in slices exhibiting epileptiform activity. More potent EPSC inhibitors were then explored by modifying the chemical structure of acetoacetate, and 2-phenylbutyrate was identified as an acetoacetate analog that inhibited VDCCs and EPSCs more potently. Although acetoacetate is known to inhibit vesicular glutamate transporters (VGLUTs), 2-phenylbutyrate did not inhibit VGLUTs, showing that 2-phenylbutyrate is an acetoacetate analog that preferably inhibits VDCCs. In addition, 2-phenylbutyrate markedly reduced EPSCs in slices exhibiting epileptiform activity, and suppressed hippocampal seizures in vivo in a mouse model of epilepsy. The in vivo antiseizure effects of 2-phenylbutyrate were more potent than those of acetoacetate. Finally, intraperitoneal 2-phenylbutyrate was delivered to the brain, and its brain concentration reached the level enough to reduce EPSCs. Significance: These results demonstrate that 2-phenylbutyrate is an acetoacetate analog that inhibits VDCCs and EPSCs in pyramidal cells, suppresses hippocampal seizures in vivo, and has brain penetration ability. Thus 2-phenylbutyrate provides a useful chemical structure as a lead compound to develop new antiseizure drugs originating from ketone bodies.

Original languageEnglish
Pages (from-to)845-857
Number of pages13
JournalEpilepsia
Volume58
Issue number5
DOIs
Publication statusPublished - May 1 2017

Fingerprint

Phenylbutyrates
Excitatory Postsynaptic Potentials
Seizures
Pyramidal Cells
Vesicular Glutamate Transport Protein 2
Ketone Bodies
Brain
acetoacetic acid
Ketogenic Diet
Hydroxybutyrates
Kainic Acid

Keywords

  • Antiseizure effect
  • Hippocampus
  • Ketogenic diet
  • Ketone body analog
  • Voltage-dependent Ca channel

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

Cite this

Neuronal inhibition and seizure suppression by acetoacetate and its analog, 2-phenylbutyrate. / Kadowaki, Atsushi; Sada, Nagisa; Juge, Narinobu; Wakasa, Ayaka; Moriyama, Yoshinori; Inoue, Tsuyoshi.

In: Epilepsia, Vol. 58, No. 5, 01.05.2017, p. 845-857.

Research output: Contribution to journalArticle

Kadowaki, Atsushi ; Sada, Nagisa ; Juge, Narinobu ; Wakasa, Ayaka ; Moriyama, Yoshinori ; Inoue, Tsuyoshi. / Neuronal inhibition and seizure suppression by acetoacetate and its analog, 2-phenylbutyrate. In: Epilepsia. 2017 ; Vol. 58, No. 5. pp. 845-857.
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AU - Moriyama, Yoshinori

AU - Inoue, Tsuyoshi

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N2 - Objective: The ketogenic diet is clinically used to treat drug-resistant epilepsy. The diet treatment markedly increases ketone bodies (acetoacetate and β-hydroxybutyrate), which work as energy metabolites in the brain. Here, we investigated effects of acetoacetate on voltage-dependent Ca2+ channels (VDCCs) in pyramidal cells of the hippocampus. We further explored an acetoacetate analog that inhibited VDCCs in pyramidal cells, reduced excitatory postsynaptic currents (EPSCs), and suppressed seizures in vivo. Methods: The effects of acetoacetate and its analogs on VDCCs and EPSCs were evaluated using patch-clamp recordings from CA1 pyramidal cells of mouse hippocampal slices. The in vivo effects of these reagents were also evaluated using a chronic seizure model induced by intrahippocampal injection of kainate. Results: Acetoacetate inhibited VDCCs in pyramidal cells of hippocampal slices, and reduced EPSCs in slices exhibiting epileptiform activity. More potent EPSC inhibitors were then explored by modifying the chemical structure of acetoacetate, and 2-phenylbutyrate was identified as an acetoacetate analog that inhibited VDCCs and EPSCs more potently. Although acetoacetate is known to inhibit vesicular glutamate transporters (VGLUTs), 2-phenylbutyrate did not inhibit VGLUTs, showing that 2-phenylbutyrate is an acetoacetate analog that preferably inhibits VDCCs. In addition, 2-phenylbutyrate markedly reduced EPSCs in slices exhibiting epileptiform activity, and suppressed hippocampal seizures in vivo in a mouse model of epilepsy. The in vivo antiseizure effects of 2-phenylbutyrate were more potent than those of acetoacetate. Finally, intraperitoneal 2-phenylbutyrate was delivered to the brain, and its brain concentration reached the level enough to reduce EPSCs. Significance: These results demonstrate that 2-phenylbutyrate is an acetoacetate analog that inhibits VDCCs and EPSCs in pyramidal cells, suppresses hippocampal seizures in vivo, and has brain penetration ability. Thus 2-phenylbutyrate provides a useful chemical structure as a lead compound to develop new antiseizure drugs originating from ketone bodies.

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