M-Channel Activation Contributes to the Anticonvulsant Action of the Ketone Body β-Hydroxybutyrate.

Ketogenic diets are effective therapies for refractory epilepsy, yet the underlying mechanisms are incompletely understood. The anticonvulsant efficacy of ketogenic diets correlates positively to the serum concentration of β-hydroxybutyrate (BHB), the primary ketone body generated by ketosis. Voltage-gated potassium channels generated by KCNQ2-5 subunits, especially KCNQ2/3 heteromers, generate the M-current, a therapeutic target for synthetic anticonvulsants. Here, we report that BHB directly activates KCNQ2/3 channels (EC50 = 0.7 µM), via a highly conserved S5 tryptophan (W265) on KCNQ3. BHB was also acutely effective as an anticonvulsant in the pentylene tetrazole (PTZ) seizure assay in mice. Strikingly, coadministration of γ-amino-β-hydroxybutyric acid, a high-affinity KCNQ2/3 partial agonist that also acts via KCNQ3-W265, similarly reduced the efficacy of BHB in KCNQ2/3 channel activation in vitro and in the PTZ seizure assay in vivo. Our results uncover a novel, unexpected molecular basis for anticonvulsant effects of the major ketone body induced by ketosis. SIGNIFICANCE STATEMENT: Ketogenic diets are used to treat refractory epilepsy but the therapeutic mechanism is not fully understood. Here, we show that clinically relevant concentrations of β-hydroxybutyrate, the primary ketone body generated during ketogenesis, activates KCNQ2/3 potassium channels by binding to a specific site on KCNQ3, an effect known to reduce neuronal excitability. We provide evidence using a mouse chemoconvulsant model that KCNQ2/3 activation contributes to the antiepileptic action of β-hydroxybutyrate.