Objective Ketone bodies (KB) are products of fatty acid oxidation and serve as essential fuels during fasting or treatment with the high-fat anti-seizure ketogenic diet (KD). Despite growing evidence that KB exert broad neuroprotective effects, their role in seizure control has not been firmly demonstrated. The major goal of this study was to demonstrate the direct anti-seizure effects of KB and to identify an underlying target mechanism. Methods We studied the effects of both the KD and KB in spontaneously epileptic Kcna1-null mice using a combination of behavioral, planar multi-electrode, and standard cellular electophysiological techniques. Thresholds for mitochondrial permeability transition (mPT) were determined in acutely isolated brain mitochondria. Results KB alone were sufficient to: (1) exert anti-seizure effects in Kcna1-null mice; (2) restore intrinsic impairment of hippocampal long-term potentiation (LTP) and spatial learning-memory defects in Kcna1-null mutants; and (3) raise the threshold for calcium-induced mPT in acutely prepared mitochondria from hippocampi of Kcna1-null animals. Targeted deletion of the cyclophilin D (CypD) subunit of the mPT complex abrogated the effects of KB on mPT, and in vivo pharmacological inhibition and activation of mPT were found to mirror and reverse, respectively, the anti-seizure effects of the KD in Kcna1-null mice. Interpretation The present data reveal the first direct link between mPT and seizure control, and provide a potential mechanistic explanation for the KD. Given that mPT is increasingly being implicated in diverse neurological disorders, our results suggest that metabolism-based treatments and/or metabolic substrates might represent a worthy paradigm for therapeutic development.

Ketone bodies (KB) have been shown to prevent neurodegeneration in models of Parkinson's and Alzheimer's diseases, but the mechanisms underlying these effects remain unclear. One possibility is that KB may exert antioxidant activity. In the current study, we explored the effects of KB on rat neocortical neurons exposed to hydrogen peroxide (H 2 O 2 ) or diamide -a thiol oxidant and activator of mitochondrial permeability transition (mPT). We found that: (i) KB completely blocked large inward currents induced by either H 2 O 2 or diamide; (ii) KB significantly decreased the number of propidium iodide-labeled cells in neocortical slices after exposure to H 2 O 2 or diamide; (iii) KB significantly decreased reactive oxygen species (ROS) levels in dissociated neurons and in isolated neocortical mitochondria; (iv) the electrophysiological effects of KB in neurons exposed to H 2 O 2 or diamide were mimicked by bongkrekic acid and cyclosporin A, known inhibitors of mPT, as well as by catalase and DLdithiothreitol, known antioxidants; (v) diamide alone did not significantly alter basal ROS levels in neurons, supporting previous studies indicating that diamide-induced neuronal injury may be mediated by mPT opening; and (vi) KB significantly increased the threshold for calcium-induced mPT in isolated mitochondria. Taken together, our data suggest that KB may prevent mPT and oxidative injury in neocortical neurons, most likely by decreasing mitochondrial ROS production.

Although the mechanisms underlying the anti-seizure effects of the high-fat ketogenic diet (KD) remain unclear, a long-standing question has been whether ketone bodies (i.e., β-hydroxybutyrate, acetoacetate and acetone), either alone or in combination, contribute mechanistically. The traditional belief has been that while ketone bodies reflect enhanced fatty acid oxidation and a general shift toward intermediary metabolism, they are not likely to be the key mediators of the KD's clinical effects, as blood levels of β-hydroxybutyrate do not correlate consistently with improved seizure control. Against this unresolved backdrop, new data support ketone bodies as having anti-seizure actions. Specifically, β-hydroxybutyrate has been shown to interact with multiple novel molecular targets such as histone deacetylases, hydroxycarboxylic acid receptors on immune cells, and the NLRP3 inflammasome. Clearly, as a diet-based therapy is expected to render a broad array of biochemical, molecular, and cellular changes, no single mechanism can explain how the KD works. Specific metabolic substrates or enzymes are only a few of many important factors influenced by the KD that can collectively influence brain hyperexcitability and hypersynchrony. This review summarizes recent novel experimental findings supporting the anti-seizure and neuroprotective properties of ketone bodies.

Summary Individuals with poorly controlled epilepsy have a higher risk for Sudden Unexpected Death in Epilepsy (SUDEP). With approximately one third of people with epilepsy not achieving adequate seizure control with current anti-seizure drugs, there is a critical need to identify treatments that reduce risk factors for SUDEP. The Kcna1-null mutant mouse lacking the potassium channel Kv1.1alpha subunit model risk factors and terminal events associated with SUDEP. In the current study, we demonstrate the progressive nature of epilepsy and sudden death in this model (mean age of mortality, postnatal day (P) 42.8 ± 1.3) and tested the hypothesis that long-term treatment with the ketogenic diet (KD) will prolong the life of Kcna1-null mice. We found that the KD postpones disease progression by delaying the onset of severe seizures and increases the lifespan of these mutant mice by 47%. Future studies are needed to determine the mechanisms underlying the KD effects on longevity.