The anticonvulsant activity of acetone, the major ketone body in the ketogenic diet, is not dependent on its metabolites acetol, 1,2-propanediol, methylglyoxal, or pyruvic acid

Dietary Supplementation with Milk Lipids Leads to Suppression of Developmental and Behavioral Phenotypes of Hyperexcitable Drosophila Mutants

Dietary modifications often have a profound impact on the penetrance and expressivity of neurological phenotypes that are caused by genetic defects. Our previous studies in Drosophila melanogaster revealed that seizure-like phenotypes of gain-of-function voltage-gated sodium (Nav) channel mutants (paraShu, parabss1, and paraGEFS+), as well as other seizure-prone "bang-sensitive" mutants (eas and sda), were drastically suppressed by supplementation of a standard diet with milk whey. In the current study we sought to determine which components of milk whey are responsible for the diet-dependent suppression of their hyperexcitable phenotypes. Our systematic analysis reveals that supplementing the diet with a modest amount of milk lipids (0.26% w/v) mimics the effects of milk whey. We further found that a minor milk lipid component, α-linolenic acid, contributed to the diet-dependent suppression of adult paraShu phenotypes. Given that lipid supplementation during the larval stages effectively suppressed adult paraShu phenotypes, dietary lipids likely modify neural development to compensate for the defects caused by the mutations. Consistent with this notion, lipid feeding fully rescued abnormal dendrite development of class IV sensory neurons in paraShu larvae. Overall, our findings demonstrate that milk lipids are sufficient to ameliorate hyperexcitable phenotypes in Drosophila mutants, providing a foundation for future investigation of the molecular and cellular mechanisms by which dietary lipids modify genetically induced abnormalities in neural development, physiology, and behavior.

Anticonvulsant Profile of Selected Medium-Chain Fatty Acids (MCFAs) Co-Administered with Metformin in Mice in Acute and Chronic Treatment

In contrast to the other components of the medium-chain triglycerides ketogenic diet (MCT KD), i.e., caprylic acid (CA8), a comprehensive evaluation of caproic (CA6) and lauric acids' (CA12) properties in standard chemical and electrical seizure tests in mice has not yet been performed. We investigated their effects in maximal electroshock seizure threshold (MEST), 6 Hz seizure threshold and intravenous (i.v.) pentylenetetrazole (PTZ) seizure tests. Since ketone body production can be regulated by the activation of 5'AMP-activated protein kinase (AMPK), we hypothesized that metformin (an AMPK activator) enhance ketogenesis and would act synergistically with the fatty acids to inhibit convulsions. We assessed the effects of acute and chronic co-treatment with metformin and CA6/CA8 on seizures. CA6 and CA12 (p.o.) increased seizure threshold in the 6 Hz seizure test. CA6 at the highest tested dose (30 mmol/kg) developed toxicity in several mice, impaired motor performance and induced ketoacidosis. Acute and chronic co-treatment with metformin and CA6/CA8 did not affect seizure thresholds. Moreover, we observed the pro-convulsive effect of the acute co-administration of CA8 (5 mmol/kg) and metformin (100 mg/kg). Since this co-treatment was pro-convulsive, the safety profile and risk/benefit ratio of MCT KD and metformin concomitant therapy in epileptic patients should be further evaluated.

Dietary effects on antiseizure drug metabolism and management of epilepsy

In recent years, there has been growing interest in the influences of food-drug interactions on the metabolism of antiseizure medications (ASM) and the management of epilepsy. Studies have proven the effectiveness of the ketogenic diet (KD) in controlling refractory epilepsy. However, dietary interventions such as the KD or its variants may induce significant changes in serum drug concentrations which counteracts the anticonvulsive effects of ASMs, leading to an increased risk of developing seizures. Interactions with enzymes within the cytochrome P450 system may also explain the dietary influences on serum concentrations of antiseizure drugs. The bioavailability of ASMs is also affected by several foods and nutritional supplements. Nevertheless, more studies are warranted to explore the mechanisms underlying food-drug interactions and the risks and benefits of combined drug-diet therapy.

Molecular Mechanisms Underlying the Bioactive Properties of a Ketogenic Diet

The consumption of a high-fat, low-carbohydrate diet (ketogenic diet) has diverse effects on health and is expected to have therapeutic value in neurological disorders, metabolic syndrome, and cancer. Recent studies have shown that a ketogenic diet not only pronouncedly shifts the cellular metabolism to pseudo-starvation, but also exerts a variety of physiological functions on various organs through metabolites that act as energy substrates, signaling molecules, and epigenetic modifiers. In this review, we highlight the latest findings on the molecular mechanisms of a ketogenic diet and speculate on the significance of these functions in the context of the epigenome and microbiome. Unraveling the molecular basis of the bioactive effects of a ketogenic diet should provide solid evidence for its clinical application in a variety of diseases including cancer.

Ketone Supplementation: Meeting the Needs of the Brain in an Energy Crisis

Diverse neurological disorders are associated with a deficit in brain energy metabolism, often characterized by acute or chronic glucose hypometabolism. Ketones serve as the brain's only significant alternative fuel and can even become the primary fuel in conditions of limited glucose availability. Thus, dietary supplementation with exogenous ketones represents a promising novel therapeutic strategy to help meet the energetic needs of the brain in an energy crisis. Preliminary evidence suggests ketosis induced by exogenous ketones may attenuate damage or improve cognitive and motor performance in neurological conditions such as seizure disorders, mild cognitive impairment, Alzheimer's disease, and neurotrauma.

Exogenous ketone ester delays CNS oxygen toxicity without impairing cognitive and motor performance in male Sprague-Dawley rats

Hyperbaric oxygen (HBO2) is breathing >1 atmosphere absolute (ATA; 101.3 kPa) O2 and is used in HBO2 therapy and undersea medicine. What limits the use of HBO2 is the risk of developing central nervous system (CNS) oxygen toxicity (CNS-OT). A promising therapy for delaying CNS-OT is ketone metabolic therapy either through diet or exogenous ketone ester (KE) supplement. Previous studies indicate that KE induces ketosis and delays the onset of CNS-OT; however, the effects of exogeneous KE on cognition and performance are understudied. Accordingly, we tested the hypothesis that oral gavage with 7.5 g/kg induces ketosis and increases the latency time to seizure (LSz) without impairing cognition and performance. A single oral dose of 7.5 g/kg KE increases systemic β-hydroxybutyrate (BHB) levels within 0.5 h and remains elevated for 4 h. Male rats were separated into three groups: control (no gavage), water-gavage, or KE-gavage, and were subjected to behavioral testing while breathing 1 ATA (101.3 kPa) of air. Testing included the following: DigiGait (DG), light/dark (LD), open field (OF), and novel object recognition (NOR). There were no adverse effects of KE on gait or motor performance (DG), cognition (NOR), and anxiety (LD, OF). In fact, KE had an anxiolytic effect (OF, LD). The LSz during exposure to 5 ATA (506.6 kPa) O2 (≤90 min) increased 307% in KE-treated rats compared with control rats. In addition, KE prevented seizures in some animals. We conclude that 7.5 g/kg is an optimal dose of KE in the male Sprague-Dawley rat model of CNS-OT.

Ketone Bodies Inhibit the Opening of Acid-Sensing Ion Channels (ASICs) in Rat Hippocampal Excitatory Neurons in vitro

Objectives: Despite the long-term efficacy of antiepileptic drug treatments, frequent attacks of drug-resistant epilepsy necessitate the development of new antiepileptic drug therapy targets. The ketogenic diet is a high-fat, low-carbohydrate diet that has been shown to be effective in treating drug-resistant epilepsy, although the mechanism is yet unclear. In the ketogenic diet, excess fat is metabolized into ketone bodies (including acetoacetic acid, β-hydroxybutyric acid, and acetone). The present study explored the effect of ketone bodies on acid-sensing ion channels and provided a theoretical basis for the study of new targets of antiepileptic drugs based on “ketone body-acid sensing ion channels.”

Methods: In this study, rat primary cultured hippocampal neurons were used. The effects of acetoacetic acid, β-hydroxybutyric acid, and acetone on the open state of acid-sensing ion channels of hippocampal neurons were investigated by the patch-clamp technique.

Results: At pH 6.0, the addition of acetoacetic acid, β-hydroxybutyric acid, and acetone in the extracellular solution markedly weakened the currents of acid-sensing ion channels. The three ketone bodies significantly inhibited the opening of the acid-sensing ion channels on the surface of the hippocampal neurons, and 92, 47, and 77%, respectively.

Conclusions: Ketone bodies significantly inhibit the opening of acid-sensing ion channels. However, a new target for antiepileptic drugs on acid-sensing ion channels is yet to be investigated.

Ketogenic diet versus ketoacidosis: what determines the influence of ketone bodies on neurons?

Glucose is the main energy substrate for neurons, however, at certain conditions, e.g. in starvation, these cells could also use ketone bodies. This approach is used in clinical conditions as the ketogenic diet. The ketogenic diet is actually a biochemical model of fasting. It includes replacing carbohydrates by fats in daily meal. Synthesis of ketone bodies β-hydroxubutirate, acetoacetate and acetone begins once glycogen stores have depleted in the liver. The ketogenic diet can be used to treat clinical conditions, primarily epilepsy. The mechanism of neuroprotective action of ketogenic diet is not very clear. It is shown that ketone bodies influence neurons at three different levels, namely, metabolic, signaling and epigenetic levels. Ketone bodies are not always neuroprotective. Sometimes they can be toxic for the brain. Ketoacidosis which is a very dangerous complication of diabetes mellitus or alcoholism can be taken as an example. The exact mechanism of how neuroprotective properties of ketone bodies reverse to neurotoxic is yet to be established.

The Anticonvulsant Effects of Ketogenic Diet on Epileptic Seizures and Potential Mechanisms

Background:

Epilepsy is a syndrome of brain dysfunction induced by the aberrant excitability of certain neurons. Despite advances in surgical technique and anti-epileptic drug in recent years, recurrent epileptic seizures remain intractable and lead to a serious morbidity in the world. The ketogenic diet refers to a high-fat, low-carbohydrate and adequate-protein diet.Currently, its beneficial effects on epileptic seizure reduction have been well established. However, the detailed mechanisms underlying the anti-epileptic effects of ketogenic diet are still poorly understood. In this article, the possible roles of ketogenic diet on epilepsy were discussed.

Methods:

Data was obtained from the websites including Web of Science, Medline, Pubmed,Scopus, based on these keywords: “Ketogenic diet” and “epilepsy”.

Results:

As shown in both clinical and basic studies, the therapeutic effects of ketogenic diet might involve neuronal metabolism, neurotransmitter function, neuronal membrane potential and neuron protection against ROS.

Conclusion:

In this review, we systematically reviewed the effects and possible mechanisms of ketogenic diet on epilepsy, which may optimize the therapeutic strategies against epilepsy.

Breath profiles of children on ketogenic therapy

Ketogenic diets (KDs) were initially introduced to clinical practices as alimentary approaches with the aim to control drug-resistant epilepsies. Over the decades, a large and growing body of research has addressed the antiseizure effect of various KDs, and worked out KD-based dietary regimens, including their acting factors and modes of action. KDs have also appeared in weight loss therapies. Therapy control, particularly at initiation, happens through regular blood analysis and control of urine ketone levels. However, there is a lack of fast, reliable, and preferably non-invasive methods to accomplish this. The detection of exhaled breath constituents may offer a solution. The exhaled breath contains hundreds of volatile organic compounds (VOCs), which can be modified by diet. VOC detection technology has resulted in low-cost sensors that can facilitate the self-monitoring of patients in the future if reliable breath markers are available. Therefore, it is of interest to investigate the composition of exhaled breath in children on KDs. Twenty-two pediatric patients between 4 and 18 years of age were recruited in this study. Eleven of them received a KD and suffered from epilepsy, with the exception of one child, who was admitted to a weight-reduction therapy. The control group involved 11 patients with neurological disorders but not on KD. Breath volatiles were analyzed using gas chromatography mass spectrometry (GC-MS) after preconcentration of the analytes on needle traps (NTs). We found that the breath concentrations of a number of VOCs, namely acetaldehyde, acetone, 2-methylfuran, methyl-vinyl-ketone, and 2-pentanone were significantly elevated in the breath of children on a KD in comparison to their control counterparts. Interestingly, breath ethanol was lower in patients on a KD than in non-KD patients. Association studies revealed an interrelationship among (i) lipid parameters and ketone bodies, (ii) methacrolein, methyl-vinyl-ketone, and high-density lipoprotein, as well as (iii) methyl-vinyl-ketone, acetone, and 2-pentanone, thus raising the possibility of a common metabolic source. The duration of diet was positively and negatively associated with breath acetone and breath ethanol, respectively. Some of the changes were linked to β-oxidation, but there are uncertainties in regard to metabolic sources of other metabolites. Lipid peroxidation and alteration of intestinal microbial composition may also be involved in the changes of VOC profiles during KD. Since lipids used for metabolism during KD originate from external sources, the processes occurring cannot simply be compared to and deduced from changes appearing in starvation; however, lipid mobilization is also evident in starvation. To find reliable and sensitive VOC markers that are linked to the respective ketogenic regimen, further investigations are needed to reveal the metabolic background.

Do ketone bodies mediate the anti-seizure effects of the ketogenic diet?

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.

The ketogenic diet affects the social behavior of young male rats

The positive effects of the ketogenic diet (KD) on social behavior have been recently reported in patients and rodent models of autism spectrum disorder (ASD). Given the beneficial effects of the KD on epilepsy, mitochondrial function, carbohydrate metabolism, and inflammation, treatment based on the KD has the potential to reduce some of the ASD-associated symptoms, including abnormal social interactions. It is not known whether the KD influences sociability by reducing the pathological processes underlying ASD or through some independent mechanism. The aim of the present study was to evaluate the influence of the KD on the social behavior of rats. Four-week-old Long-Evans males were treated with the KD for 4 subsequent weeks. Afterwards, behavioral tests were performed in order to evaluate sociability, locomotor activity, working memory, and anxiety-related behaviors. Additionally we performed the social interaction test in animals that were receiving β-hydroxybutyrate or acetone. We have observed that rats fed with the KD showed increased social exploration in three different experimental settings. We did not observe any changes in the level of social interactions in animals treated with exogenous ketone bodies. The results did not show any difference in mobility or anxiety-related behaviors or working memory between the animals fed with the KD or standard rodent chow. In conclusion, we showed that the KD affects the social behavior of wild-type young adult male rats, which was not associated with other behavioral changes.

The ATP-sensitive K channel is seizure protective and required for effective dietary therapy in a model of mitochondrial encephalomyopathy

Effective therapies are lacking for mitochondrial encephalomyopathies (MEs). MEs are devastating diseases that predominantly affect the energy-demanding tissues of the nervous system and muscle, causing symptoms such as seizures, cardiomyopathy, and neuro- and muscular degeneration. Even common anti-epileptic drugs which are frequently successful in ameliorating seizures in other diseases tend to have a lower success rate in ME, highlighting the need for novel drug targets, especially those that may couple metabolic sensitivity to neuronal excitability. Furthermore, alternative epilepsy therapies such as dietary modification are gaining in clinical popularity but have not been thoroughly studied in ME. Using the Drosophila ATP6¹ model of ME, we have studied dietary therapy throughout disease progression and found that it is highly effective against the seizures of ME, especially a high fat/ketogenic diet, and that the benefits are dependent upon a functional K_ATP channel complex. Further experiments with K_ATP show that it is seizure-protective in this model, and that pharmacological promotion of its open state also ameliorates seizures. These studies represent important steps forward in the development of novel therapies for a class of diseases that is notoriously difficult to treat, and lay the foundation for mechanistic studies of currently existing therapies in the context of metabolic disease.

Mechanisms of Action of Antiseizure Drugs and the Ketogenic Diet

Antiseizure drugs (ASDs), also termed antiepileptic drugs, are the main form of symptomatic treatment for people with epilepsy, but not all patients become free of seizures. The ketogenic diet is one treatment option for drug-resistant patients. Both types of therapy exert their clinical effects through interactions with one or more of a diverse set of molecular targets in the brain. ASDs act by modulation of voltage-gated ion channels, including sodium, calcium, and potassium channels; by enhancement of γ-aminobutyric acid (GABA)-mediated inhibition through effects on GABAA receptors, the GABA transporter 1 (GAT1) GABA uptake transporter, or GABA transaminase; through interactions with elements of the synaptic release machinery, including synaptic vesicle 2A (SV2A) and α2δ; or by blockade of ionotropic glutamate receptors, including α-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors. The ketogenic diet leads to increases in circulating ketones, which may contribute to the efficacy in treating pharmacoresistant seizures. Production in the brain of inhibitory mediators, such as adenosine, or ion channel modulators, such as polyunsaturated fatty acids, may also play a role. Metabolic effects, including diversion from glycolysis, are a further postulated mechanism. For some ASDs and the ketogenic diet, effects on multiple targets may contribute to activity. Better understanding of the ketogenic diet will inform the development of improved drug therapies to treat refractory seizures.

Effects of exogenous ketone supplementation on blood ketone, glucose, triglyceride, and lipoprotein levels in Sprague-Dawley rats

Background

Nutritional ketosis induced by the ketogenic diet (KD) has therapeutic applications for many disease states. We hypothesized that oral administration of exogenous ketone supplements could produce sustained nutritional ketosis (>0.5 mM) without carbohydrate restriction.

Methods

We tested the effects of 28-day administration of five ketone supplements on blood glucose, ketones, and lipids in male Sprague–Dawley rats. The supplements included: 1,3-butanediol (BD), a sodium/potassium β-hydroxybutyrate (βHB) mineral salt (BMS), medium chain triglyceride oil (MCT), BMS + MCT 1:1 mixture, and 1,3 butanediol acetoacetate diester (KE). Rats received a daily 5–10 g/kg dose of their respective ketone supplement via intragastric gavage during treatment. Weekly whole blood samples were taken for analysis of glucose and βHB at baseline and, 0.5, 1, 4, 8, and 12 h post-gavage, or until βHB returned to baseline. At 28 days, triglycerides, total cholesterol and high-density lipoprotein (HDL) were measured.

Results

Exogenous ketone supplementation caused a rapid and sustained elevation of βHB, reduction of glucose, and little change to lipid biomarkers compared to control animals.

Conclusions

This study demonstrates the efficacy and tolerability of oral exogenous ketone supplementation in inducing nutritional ketosis independent of dietary restriction.

A randomised trial of a medium-chain TAG diet as treatment for dogs with idiopathic epilepsy

Despite appropriate antiepileptic drug treatment, approximately one-third of humans and dogs with epilepsy continue experiencing seizures, emphasising the importance for new treatment strategies to improve the quality of life of people or dogs with epilepsy. A 6-month prospective, randomised, double-blinded, placebo-controlled cross-over dietary trial was designed to compare a ketogenic medium-chain TAG diet (MCTD) with a standardised placebo diet in chronically antiepileptic drug-treated dogs with idiopathic epilepsy. Dogs were fed either MCTD or placebo diet for 3 months followed by a subsequent respective switch of diet for a further 3 months. Seizure frequency, clinical and laboratory data were collected and evaluated for twenty-one dogs completing the study. Seizure frequency was significantly lower when dogs were fed the MCTD (2·31/month, 0-9·89/month) in comparison with the placebo diet (2·67/month, 0·33-22·92/month, P=0·020); three dogs achieved seizure freedom, seven additional dogs had ≥50 % reduction in seizure frequency, five had an overall <50 % reduction in seizures (38·87 %, 35·68-43·27 %) and six showed no response. Seizure day frequency were also significantly lower when dogs were fed the MCTD (1·63/month, 0-7·58/month) in comparison with the placebo diet (1·69/month, 0·33-13·82/month, P=0·022). Consumption of the MCTD also resulted in significant elevation of blood β-hydroxybutyrate concentrations in comparison with placebo diet (0·071 (sd 0·035) v. 0·053 (sd 0·028) mmol/l, P=0·028). There were no significant changes in serum concentrations of glucose (P=0·903), phenobarbital (P=0·422), potassium bromide (P=0·404) and weight (P=0·300) between diet groups. In conclusion, the data show antiepileptic properties associated with ketogenic diets and provide evidence for the efficacy of the MCTD used in this study as a therapeutic option for epilepsy treatment.

Acute anticonvulsant effects of capric acid in seizure tests in mice

Capric acid (CA10) is a 10-carbon medium-chain fatty acid abundant in the medium-chain triglyceride ketogenic diet (MCT KD). The purpose of this study was to characterize acute anticonvulsant effects of CA10 across several seizure tests in mice. Anticonvulsant effects of orally (p.o.) administered CA10 were assessed in the maximal electroshock seizure threshold (MEST), 6-Hz seizure threshold, and intravenous pentylenetetrazole (i.v. PTZ) seizure tests in mice. Acute effects of CA10 on motor coordination were assessed in the grip and chimney tests. Plasma and brain concentrations of CA10 were measured. Co-administration studies with CA10 and another abundant medium-chain fatty acid, caprylic acid (CA8) were performed. CA10 showed significant and dose-dependent anticonvulsant properties by increasing seizure thresholds in the 6-Hz and MEST seizure tests; it was ineffective in the i.v. PTZ seizure test. At higher doses than those effective in the 6-Hz and MEST seizure tests, CA10 impaired motor performance in the grip and chimney tests. An enhanced anticonvulsant response in the 6-Hz seizure test was produced when CA8 and CA10 were co-administered. An acute p.o. administration of CA10 resulted in dose-proportional increases in its plasma and brain concentrations. CA10 exerted acute anticonvulsant effects at doses that produce plasma exposures comparable to those reported in epileptic patients on the MCT KD. An enhanced anticonvulsant effect is observed when CA10 and the other main constituent of the MCT KD, CA8, were co-administered. Thus, acute anticonvulsant properties of CA10 and CA8 may influence the overall clinical efficacy of the MCT KD.

Neurobiochemical mechanisms of a ketogenic diet in refractory epilepsy

A ketogenic diet is an important therapy used in the control of drug-refractory seizures. Many studies have shown that children and adolescents following ketogenic diets exhibit an over 50% reduction in seizure frequency, which is considered to be clinically relevant. These benefits are based on a diet containing high fat (approximately 90% fat) for 24 months. This dietary model was proposed in the 1920s and has produced variable clinical responses. Previous studies have shown that the mechanisms underlying seizure control involve ketone bodies, which are produced by fatty acid oxidation. Although the pathways involved in the ketogenic diet are not entirely clear, the main effects of the production of ketone bodies appear to be neurotransmitter modulation and antioxidant effects on the brain. This review highlights the impacts of the ketogenic diet on the modulation of neurotransmitters, levels of biogenic monoamines and protective antioxidant mechanisms of neurons. In addition, future perspectives are proposed.

Neuroactive peptides as putative mediators of antiepileptic ketogenic diets

Various ketogenic diet (KD) therapies, including classic KD, medium chain triglyceride administration, low glycemic index treatment, and a modified Atkins diet, have been suggested as useful in patients affected by pharmacoresistant epilepsy. A common goal of these approaches is to achieve an adequate decrease in the plasma glucose level combined with ketogenesis, in order to mimic the metabolic state of fasting. Although several metabolic hypotheses have been advanced to explain the anticonvulsant effect of KDs, including changes in the plasma levels of ketone bodies, polyunsaturated fatty acids, and brain pH, direct modulation of neurotransmitter release, especially purinergic (i.e., adenosine) and γ-aminobutyric acidergic neurotransmission, was also postulated. Neuropeptides and peptide hormones are potent modulators of synaptic activity, and their levels are regulated by metabolic states. This is the case for neuroactive peptides such as neuropeptide Y, galanin, cholecystokinin, and peptide hormones such as leptin, adiponectin, and growth hormone-releasing peptides (GHRPs). In particular, the GHRP ghrelin and its related peptide des-acyl ghrelin are well-known controllers of energy homeostasis, food intake, and lipid metabolism. Notably, ghrelin has also been shown to regulate the neuronal excitability and epileptic activation of neuronal networks. Several lines of evidence suggest that GHRPs are upregulated in response to starvation and, particularly, in patients affected by anorexia and cachexia, all conditions in which also ketone bodies are upregulated. Moreover, starvation and anorexia nervosa are accompanied by changes in other peptide hormones such as adiponectin, which has received less attention. Adipocytokines such as adiponectin have also been involved in modulating epileptic activity. Thus, neuroactive peptides whose plasma levels and activity change in the presence of ketogenesis might be potential candidates for elucidating the neurohormonal mechanisms involved in the beneficial effects of KDs. In this review, we summarize the current evidence for altered regulation of the synthesis of neuropeptides and peripheral hormones in response to KDs, and we try to define a possible role for specific neuroactive peptides in mediating the antiepileptic properties of diet-induced ketogenesis.

Fasting in mood disorders: neurobiology and effectiveness. A review of the literature

Clinicians have found that fasting was frequently accompanied by an increased level of vigilance and a mood improvement, a subjective feeling of well-being, and sometimes of euphoria. Therapeutic fasting, following an established protocol, is safe and well tolerated. We aim in this article to explore the biological mechanisms activated during fasting that could have an effect on brain function with particular focus on mood (we do not discuss here the mechanisms regulating eating behavior) and to provide a comprehensive review on the potential positive impact of therapeutic fasting on mood. We explored Medline, Web of Science and PsycInfo according to the PRISMA criteria (Preferred Reporting Items for Systematic reviews and Meta-Analysis). The initial research paradigm was: [(fasting OR caloric restriction) AND (mental health OR depressive disorders OR mood OR anxiety)]. Many neurobiological mechanisms have been proposed to explain fasting effects on mood, such as changes in neurotransmitters, quality of sleep, and synthesis of neurotrophic factors. Many clinical observations relate an early (between day 2 and day 7) effect of fasting on depressive symptoms with an improvement in mood, alertness and a sense of tranquility reported by patients. The persistence of mood improvement over time remains to be determined.

How does the ketogenic diet work? Four potential mechanisms

The ketogenic diet and its newer variants are clinically useful in treating epilepsy. They can also have antiepileptogenic properties and can eventually have a role in treating other neurologic and nonneurologic conditions. Despite being nearly a century old, identifying the molecular underpinnings of the ketogenic diet has been challenging. However, recent studies provide experimental evidence for 4 distinct mechanisms that could contribute to the antiseizure and other beneficial effects of these diets. These mechanisms include carbohydrate reduction, activation of adenosine triphosphate (ATP)-sensitive potassium channels by mitochondrial metabolism, inhibition of the mammalian target of rapamycin pathway, and inhibition of glutamatergic excitatory synaptic transmission.

Therapeutic ketosis with ketone ester delays central nervous system oxygen toxicity seizures in rats

Central nervous system oxygen toxicity (CNS-OT) seizures occur with little or no warning, and no effective mitigation strategy has been identified. Ketogenic diets (KD) elevate blood ketones and have successfully treated drug-resistant epilepsy. We hypothesized that a ketone ester given orally as R,S-1,3-butanediol acetoacetate diester (BD-AcAc(2)) would delay CNS-OT seizures in rats breathing hyperbaric oxygen (HBO(2)). Adult male rats (n = 60) were implanted with radiotelemetry units to measure electroencephalogram (EEG). One week postsurgery, rats were administered a single oral dose of BD-AcAc(2), 1,3-butanediol (BD), or water 30 min before being placed into a hyperbaric chamber and pressurized to 5 atmospheres absolute (ATA) O2. Latency to seizure (LS) was measured from the time maximum pressure was reached until the onset of increased EEG activity and tonic-clonic contractions. Blood was drawn at room pressure from an arterial catheter in an additional 18 animals that were administered the same compounds, and levels of glucose, pH, Po(2), Pco(2), β-hydroxybutyrate (BHB), acetoacetate (AcAc), and acetone were analyzed. BD-AcAc(2) caused a rapid (30 min) and sustained (>4 h) elevation of BHB (>3 mM) and AcAc (>3 mM), which exceeded values reported with a KD or starvation. BD-AcAc(2) increased LS by 574 ± 116% compared with control (water) and was due to the effect of AcAc and acetone but not BHB. BD produced ketosis in rats by elevating BHB (>5 mM), but AcAc and acetone remained low or undetectable. BD did not increase LS. In conclusion, acute oral administration of BD-AcAc(2) produced sustained ketosis and significantly delayed CNS-OT seizures by elevating AcAc and acetone.

The reactivity of α-oxoaldehyde with reactive oxygen species in diabetes complications

The reactions of three α-oxoaldehydes (methylglyoxal, glyoxal, and pyruvic acid) with hydroxyl radicals generated by sonolysis of water were investigated using an electron spin resonance (electron paramagnetic resonance) spin-trapping method, and their reaction kinetics were investigated. It is apparent from our experimental results that methylglyoxal exhibits the highest reactivity of the three α-oxoaldehydes. These α-oxoaldehydes can react with hydroxyl radicals faster than other well-known antioxidants can. The reactivity of hydroxyl radicals is higher than that of hydrogen peroxides.

Glyoxalase 1 and its substrate methylglyoxal are novel regulators of seizure susceptibility

PURPOSE

Epilepsy is a complex disease characterized by a predisposition toward seizures. There are numerous barriers to the successful treatment of epilepsy. For instance, current antiepileptic drugs have adverse side effects and variable efficacies. Furthermore, the pathophysiologic basis of epilepsy remains largely elusive. Therefore, investigating novel genes and biologic processes underlying epilepsy may provide valuable insight and enable the development of new therapeutic agents. We previously identified methylglyoxal (MG) as an endogenous γ-aminobutyric acid (GABAA ) receptor agonist. Here, we investigated the role of MG and its catabolic enzyme, glyoxalase 1 (GLO1), in seizures.

METHODS

We pretreated mice with MG before seizure induction with picrotoxin or pilocarpine and then assessed seizures behaviorally or by electroencephalography (EEG). We then investigated the role of GLO1 in seizures by treating mice with a pharmacologic inhibitor of GLO1 before seizure induction with pilocarpine and measured subsequent seizure phenotypes. Next, we explored the genetic relationship between Glo1 expression and seizures. We analyzed seizure phenotypes among C57BL/6J × DBA/2J (BXD) recombinant inbred (RI) mice with differential Glo1 expression. Lastly, we investigated a causal role for Glo1 in seizures by administering pilocarpine to transgenic (Tg) mice that overexpress Glo1.

KEY FINDINGS

Pretreatment with MG attenuated pharmacologically-induced seizures at both the behavioral and EEG levels. GLO1 inhibition, which increases MG concentration in vivo, also attenuated seizures. Among BXD RI mice, high Glo1 expression was correlated with increased seizure susceptibility. Tg mice overexpressing Glo1 displayed reduced MG concentration in the brain and increased seizure severity.

SIGNIFICANCE

These data identify MG as an endogenous regulator of seizures. Similarly, inhibition of GLO1 attenuates seizures, suggesting that this may be a novel therapeutic approach for epilepsy. Furthermore, this system may represent an endogenous negative feedback loop whereby high metabolic activity increases inhibitory tone via local accumulation of MG. Finally, Glo1 may contribute to the genetic architecture of epilepsy, as Glo1 expression regulates both MG concentration and seizure severity.

Combination treatment of epilepsy with ketogenic diet and concurrent pharmacological inhibition of cytochrome P450 2E1

While most epileptic patients respond to treatment with existing antiepileptic drugs, there remains a considerable number of patients in whom these drugs do not suffice. Such patients, particularly children, are often treated using the ketogenic diet. This diet imposes a strict limit on carbohydrates; while providing for adequate protein, most of the calories are supplied as triacylglycerol, much of which is metabolized to ketone bodies. Animal experiments have provided evidence that the anticonvulsant effect of the ketogenic diet is mediated by acetone and correlates with blood acetone levels. Acetone can be converted in vivo to glucose via acetol and pyruvate; the initial conversion to acetol is catalyzed by cytochrome P450 2E1 (CYP2E1). When CYP2E1 knockout mice are subjected to starvation to induce ketogenesis, they develop blood acetone levels much higher than those observed in wild-type mice. Similarly, pharmacological inhibition of CYP2E1 significantly increases blood acetone levels in rat and man. Taken together, these observations suggest that pharmacological inhibition of CYP2E1 has the potential to significantly increase the antiepileptic effect of the ketogenic diet. With patients that respond insufficiently to the diet alone, increased acetone levels may improve response. With patients who respond sufficiently to the diet, CYP2E1 inhibitors might allow a relaxation of the fairly severe diet regimen and so improve compliance and quality of life. An existing inhibitor of CYP2E1 is the drug disulfiram. This drug also inhibits the enzyme aldehyde dehydrogenase, which functions in alcohol degradation, and in this capacity has long been used in the treatment of alcohol addiction. Disulfiram inhibits CYP2E1 at conventional therapeutic dosages and increases blood acetone levels in humans and animals. It should therefore be a viable candidate for the proposed drug/diet combination treatment.

Hypothalamic hormones and metabolism

The ketogenic diet is an effective treatment for medically intractable epilepsy and may have antiepileptogenic, neuroprotective, and antitumor properties. While on a ketogenic diet, the body obtains most of its calories from fat rather than carbohydrates. This dramatic change in caloric composition results in a unique metabolic state. In turn, these changes in caloric composition and metabolism alter some of the neurohormones that participate in the complex neuronal network regulating energy homeostasis. Two observed changes are an increase in serum leptin and a decrease in serum insulin. These opposing changes in leptin and insulin are unique compared to other metabolic stimuli and may modify the activity of several cell signaling cascades including phosphoinositidyl-3 kinase (PI3K), adenosine monophosphate activated protein kinase (AMPK), and mammalian target of rapamycin (mTOR). These cell signaling pathways may mediate the anticonvulsant and other beneficial effects of the diet, though the neurohormonal changes induced by the ketogenic diet and the physiological consequences of these changes remain poorly characterized.

Ketone bodies in epilepsy

Seizures that are resistant to standard medications remain a major clinical problem. One underutilized option for patients with medication-resistant seizures is the high-fat, low-carbohydrate ketogenic diet. The diet received its name based on the observation that patients consuming this diet produce ketone bodies (e.g., acetoacetate, β-hydroxybutyrate, and acetone). Although the exact mechanisms of the diet are unknown, ketone bodies have been hypothesized to contribute to the anticonvulsant and antiepileptic effects. In this review, anticonvulsant properties of ketone bodies and the ketogenic diet are discussed (including GABAergic and glutamatergic effects). Because of the importance of ketone body metabolism in the early stages of life, the effects of ketone bodies on developing neurons in vitro also are discussed. Understanding how ketone bodies exert their effects will help optimize their use in treating epilepsy and other neurological disorders.

Anticonvulsant profile of caprylic acid, a main constituent of the medium-chain triglyceride (MCT) ketogenic diet, in mice

The purpose of the present study was to evaluate the acute anticonvulsant effects of caprylic acid (CA), the main constituent of the medium-chain triglyceride ketogenic diet (MCT KD), in seizure tests typically used in screening for potential antiepileptic drugs in mice. Pharmacodynamic and pharmacokinetic interactions between CA and valproate (VPA) were also investigated. CA (p.o.) and VPA (i.p.) were administered 30 min before testing. Acute effects on motor coordination were assessed in the chimney test. Total plasma and brain concentrations of CA and VPA, when administered alone or in combination, were determined by high performance liquid chromatography. CA (10-30 mmol/kg) increased the threshold for i.v. pentylenetetrazole-induced myoclonic and clonic convulsions, but not tonic convulsions. CA (5-30 mmol/kg) increased the threshold for 6-Hz psychomotor seizures but was ineffective in the maximal electroshock seizure threshold test. CA (10-60 mmol/kg p.o.) impaired motor performance in the chimney test (TD(50) value, 58.4 mmol/kg). Increasing doses of CA (5-30 mmol/kg) produced proportional increases in plasma and brain exposure with constant brain/plasma partitioning. CA increased anticonvulsant potency of VPA in the maximal electroshock seizure and 6-Hz seizure tests. Co-administration of CA and VPA had no effect on brain and plasma concentrations of either compound. In summary, CA exerts acute anticonvulsant effects and potentiates the anticonvulsant effect of VPA at doses that result in plasma exposures comparable to those reported in epileptic patients on the MCT KD. Thus, this acute anticonvulsant property of CA may benefit and add to the overall clinical efficacy of the MCT KD.

Neuron-restrictive silencer factor is not required for the antiepileptic effect of the ketogenic diet

PURPOSE

The ketogenic diet (KD) has been used as an effective antiepileptic treatment for nearly a century. Inhibition of glycolysis and increased levels of ketone bodies are both known to contribute to the antiepileptic effects of the KD. Neuron-restrictive silencer factor (NRSF), also known as RE-1 silencing transcription factor (REST), is implicated in the antiepileptic effects of the glycolytic inhibitor 2-deoxy-d-glucose (2DG). Glycolytic inhibition is a common feature of the KD and 2DG treatment, leading to the hypothesis that NRSF might also be involved in the antiepileptic effect of the KD. To test this hypothesis, the present study was designed to investigate the role of NRSF in the antiepileptic effect of 2DG, the KD, and acetone in vivo.

METHODS

Kindling was used as a model to test the antiepileptic effects of 2DG, the KD, and acetone on control and NRSF conditional knockout mice (NRSF-cKO; from the intercross of CamKIIα-iCre and NRSF exon 2 floxed mice). After recovery from electrode implantation, adult mice were stimulated twice a day at afterdischarge threshold (ADT) current intensity. In the 2DG- (500 mg/kg) and acetone- (10 mmol/kg) treated groups, drugs were injected intraperitoneally 20 min before each stimulus. In the 2DG group, mice were pretreated with intraperitoneal injections for 3 days in addition to the injections administered before the regular kindling stimulation. In the KD group, mice were fed the KD instead of a control diet until the end of stimulations.

KEY FINDINGS

Compared with control mice, the antiepileptic effect of 2DG was abolished in NRSF-cKO mice, indicating that NRSF is required for the antiepileptic effect of 2DG. In the KD-fed group, kindling development was retarded in both control and NRSF-cKO mice. In the acetone-treated group, inhibition of kindling-induced epileptogenesis was observed in both control and NRSF-cKO mice, similar to the action of the KD.

SIGNIFICANCE

These findings imply that NRSF repression complex is not essential for the antiepileptic effect of the ketogenic diet.

Diet composition modifies the toxicity of repeated soman exposure in rats

It was previously demonstrated that diet potently modulates the toxic effects of an acute lethal dose of the nerve agent soman. The current investigation was undertaken to examine the influence of diet on the cumulative toxicity of repeated soman administration. Rats were fed one of four distinct diets (standard, choline-enriched, glucose-enriched, or ketogenic) for four weeks prior to and throughout a repeated soman dosing and recovery regimen. Each diet group included animals exposed to an equivalent volume of saline that served as negative controls. In exposure Week 1, animals received three consecutive daily doses of 0.4 LD(50) soman. In exposure Week 2, animals received four consecutive daily doses of 0.5 LD(50) soman. In exposure Week 3, animals received five consecutive daily doses of 0.5 LD(50) soman. Week 4 constituted a post-exposure recovery evaluation. Throughout the experiment, behavioral function was assessed by a discriminated avoidance test that required intact sensory and motor function. Survival and body weight changes were recorded daily. Differences in toxicity as a function of diet composition became apparent during the first week. Specifically, rats fed the glucose-enriched diet showed pronounced intoxication during Week 1, resulting in imperfect survival, weight loss, and deteriorated avoidance performance relative to all other groups. All rats fed the glucose-enriched diet died by the end of exposure Week 2. In contrast, only 10% of animals fed the standard diet died by the end of Week 2. Also in Week 2, weight loss and disrupted avoidance performance were apparent for all groups except for those fed the ketogenic diet. This differential effect of diet composition became even more striking in Week 3 when survival in the standard and choline diet groups approximated 50%, whereas survival equaled 90% in the ketogenic diet group. Avoidance performance and weight loss measures corroborated the differential toxicity observed across diet groups. Upon cessation of soman exposure during the final week, recovery of weight and avoidance performance in survivors was comparable across diet groups. These results systematically replicate previous findings demonstrating that diet composition exacerbates or attenuates toxicity in rodents exposed acutely to organophosphorus compounds.

Diet composition exacerbates or attenuates soman toxicity in rats: implied metabolic control of nerve agent toxicity

To evaluate the role of diet composition on nerve agent toxicity, rats were fed four distinct diets ad libitum for 28 d prior to challenge with 110 μg/kg (1.0 LD(50), sc) soman. The four diets used were a standard rodent diet, a choline-enriched diet, a glucose-enriched diet, and a ketogenic diet. Body weight was recorded throughout the study. Toxic signs and survival were evaluated at key times for up to 72 h following soman exposure. Additionally, acquisition of discriminated shuttlebox avoidance performance was characterized beginning 24h after soman challenge and across the next 8 d (six behavioral sessions). Prior to exposure, body weight was highest in the standard diet group and lowest in the ketogenic diet group. Upon exposure, differences in soman toxicity as a function of diet became apparent within the first hour, with mortality in the glucose-enriched diet group reaching 80% and exceeding all other groups (in which mortality ranged from 0 to 6%). At 72 h after exposure, mortality was 100% in the glucose-enriched diet group, and survival approximated 50% in the standard and choline-enriched diet groups, but equaled 87% in the ketogenic diet group. Body weight loss was significantly reduced in the ketogenic and choline-enriched diet groups, relative to the standard diet group. At 1 and 4h after exposure, rats in the ketogenic diet group had significantly lower toxic sign scores than all other groups. The ketogenic diet group performed significantly better than the standard diet group on two measures of active avoidance performance. The exacerbated soman toxicity observed in the glucose-enriched diet group coupled with the attenuated soman toxicity observed in the ketogenic diet group implicates glucose availability in the toxic effects of soman. This increased glucose availability may enhance acetylcholine synthesis and/or utilization, thereby exacerbating peripheral and central soman toxicity.

Role of A-type potassium currents in excitability, network synchronicity, and epilepsy

A range of ionic currents have been suggested to be involved in distinct aspects of epileptogenesis. Based on pharmacological and genetic studies, potassium currents have been implicated, in particular the transient A-type potassium current (K(A)). Epileptogenic activity comprises a rich repertoire of characteristics, one of which is synchronized activity of principal cells as revealed by occurrences of for instance fast ripples. Synchronized activity of this kind is particularly efficient in driving target cells into spiking. In the recipient cell, this synchronized input generates large brief compound excitatory postsynaptic potentials (EPSPs). The fast activation and inactivation of K(A) lead us to hypothesize a potential role in suppression of such EPSPs. In this work, using computational modeling, we have studied the activation of K(A) by synaptic inputs of different levels of synchronicity. We find that K(A) participates particularly in suppressing inputs of high synchronicity. We also show that the selective suppression stems from the current's ability to become activated by potentials with high slopes. We further show that K(A) suppresses input mimicking the activity of a fast ripple. Finally, we show that the degree of selectivity of K(A) can be modified by changes to its kinetic parameters, changes of the type that are produced by the modulatory action of KChIPs and DPPs. We suggest that the wealth of modulators affecting K(A) might be explained by a need to control cellular excitability in general and suppression of responses to synchronicity in particular. Wealso suggest that compounds changing K(A)-kinetics may be used to pharmacologically improve epileptic status.

Cerebral hemodynamic responses to seizure in the mouse brain: simultaneous near-infrared spectroscopy-electroencephalography study

We applied near-infrared spectroscopy (NIRS) and electroencephalography (EEG) simultaneously on the mouse brain and investigated the hemodynamic response to epileptic episodes under pharmacologically driven seizure. gamma-butyrolactone (GBL) and 4-aminopyridine (4-AP) were applied to induce absence and tonic-clonic seizures, respectively. The epileptic episodes were identified from the single-channel EEG, and the corresponding hemodynamic changes in different regions of the brain were characterized by multichannel frequency-domain NIRS. Our results are the following: (i) the oxyhemoglobin level increases in the case of GBL-treated mice but not 4-AP-treated mice compared to the predrug state; (ii) the dominant response to each absence seizure is a decrease in deoxyhemolobin; (iii) the phase shift between oxy- and deoxyhemoglobin reduces in GBL-treated mice but no 4-AP-treated mice; and (iv) the spatial correlation of hemodynamics increased significantly in 4-AP-treated mice but not in GBL-treated mice. Our results shows that spatiotemporal tracking of cerebral hemodynamics using NIRS can be successfully applied to the mouse brain in conjunction with electrophysiological recording, which will support the study of molecular, cellular, and network origin of neurovascular coupling in vivo.

A flexible microelectrode for mouse EEG

Electroencephalography (EEG) of the mouse brain offers the advantage to monitor brain states in freely moving conditions under genetic or molecular manipulation. We present a novel, flexible, and biocompatible microfabricated electrode based on polyimide to record a multi-channel EEG from a mouse. Our microelectrode has 32 recording electrodes, including two ground electrodes. The connectors for the signal transmission are carefully affixed to the microelectrode. The overall weight of the microelectrode does not exceed 150 mg, including connectors. The implantation of the microelectrodes does not require invasive surgery and the mouse can be easily discharged from the wires when it is not being recorded. Simultaneous measurements with the microelectrode and a conventional screw electrode show that the microelectrode successfully collects the broad band EEG signals from the skull.

Methyl ethyl ketone blocks status epilepticus induced by lithium-pilocarpine in rats

BACKGROUND AND PURPOSE

A ketogenic diet has been used successfully to treat patients with intractable epilepsy, although the mechanism is unknown. Acetone has been shown to have an anticonvulsive effect in various animal models. The main purpose of this study was to determine whether other ketones, 2-butanone (methyl ethyl ketone: MEK) and 3-pentanone (diethyl ketone: DEK), also show anticonvulsive effects in lithium-pilocarpine (Li-pilocarpine)-induced status epilepticus (SE) in rats.

EXPERIMENTAL APPROACH

Anticonvulsive effects of MEK and DEK in Li-pilocarpine SE rats were measured by behavioural scoring. Anti-seizure effects of MEK were also evaluated using electroencephalography (EEG). Neuroprotective effect of MEK was investigated by haematoxylin and eosin staining 4 weeks after the treatment with pilocarpine.

KEY RESULTS

Acetone, MEK and DEK showed anticonvulsant effects in Li-pilocarpine-induced SE rats. Treatment with MEK twice (8 mmol.kg(-1) and 5 mmol.kg(-1)) almost completely blocked spontaneous recurrent cortical seizure EEG up to 4 weeks after the administration of pilocarpine. MEK also showed strong neuroprotective effects in Li-pilocarpine-treated rats 4 weeks following the administration of pilocarpine. Significant neural cell death occurred in the hippocampus of Li-pilocarpine SE rats, especially in the CA1 and CA3 subfields. In contrast, normal histological characteristics were observed in these regions in the MEK-pretreated rats.

CONCLUSIONS AND IMPLICATIONS

Both MEK and DEK showed strong anticonvulsive effects in Li-pilocarpine-induced SE rats. They also inhibited continuous recurrent seizure and neural damage in hippocampal region for 4 weeks after the treatment with pilocarpine. These findings appear to be of value in the investigation of epilepsy.

Hypometabolism as a therapeutic target in Alzheimer's disease

The pathology of Alzheimer's disease (AD) is characterized by cerebral atrophy in frontal, temporal, and parietal regions, with senile plaques, dystrophic neurites, and neurofibrillar tangles within defined areas of the brain. Another characteristic of AD is regional hypometabolism in the brain. This decline in cerebral glucose metabolism occurs before pathology and symptoms manifest, continues as symptoms progress, and is more severe than that of normal aging. Ketone bodies are an efficient alternative fuel for cells that are unable to metabolize glucose or are 'starved' of glucose. AC-1202 is designed to elevate serum ketone levels safely. We previously showed that treatment with AC-1202 in patients with mild-to-moderate AD improves memory and cognition. Treatment outcomes were influenced by apolipoprotein E genotype status. These data suggest that AC-1202 may be an effective treatment for cognitive dysfunction by providing an alternative substrate for use by glucose-compromised neurons.

Pharmacodynamic and pharmacokinetic interactions between common antiepileptic drugs and acetone, the chief anticonvulsant ketone body elevated in the ketogenic diet in mice

PURPOSE

Acetone is the principal ketone body elevated in the ketogenic diet (KD), with demonstrated robust anticonvulsant properties across a variety of seizure tests and models of epilepsy. Because the majority of patients continue to receive antiepileptic drugs (AEDs) during KD treatment, interactions between acetone and AEDs may have important clinical implications. Therefore, we investigated whether acetone could affect the anticonvulsant activity and pharmacokinetic properties of several AEDs against maximal electroshock (MES)-induced seizures in mice.

METHODS

Effects of acetone given in subthreshold doses were tested on the anticonvulsant effects of carbamazepine (CBZ), lamotrigine (LTG), oxcarbazepine (OXC), phenobarbital (PB), phenytoin (PHT), topiramate (TPM) and valproate (VPA) against MES-induced seizures in mice. In addition, acute adverse effects of acetone-AEDs combinations were assessed in the chimney test (motor performance) and passive avoidance task (long-term memory). Pharmacokinetic interactions between acetone and AEDs were also studied in the mouse brain tissue.

RESULTS

Acetone (5 or 7.5 mmol/kg, intraperitoneally [i.p.]) enhanced the anticonvulsant activity of CBZ, LTG, PB, and VPA against MES-induced seizures; effects of OXC, PHT, and TPM were not changed. Acetone (7.5 mmol/kg) did not enhance the acute adverse-effect profiles of the studied AEDs. Acetone (5 or 7.5 mmol/kg, i.p.) did not affect total brain concentrations of the studied AEDs. In contrast, VPA, CBZ, LTG, OXC, and TPM significantly decreased the concentration of free acetone in the brain; PB and PHT had no effect.

CONCLUSIONS

Acetone enhances the anticonvulsant effects of several AEDs such as VPA, CBZ, LTG, and PB without affecting their pharmacokinetic and side-effect profiles.

Methylglyoxal production in vascular smooth muscle cells from different metabolic precursors

Methylglyoxal (MG), a metabolic by-product, reacts with certain proteins to yield irreversible advanced glycation end products (AGEs) and increases oxidative stress that causes the pathophysiological changes in diabetes, hypertension, and aging. Although MG production from glucose has been well documented, the contribution of other intermediates of different metabolic pathways to MG formation is far less known. Our aim was to determine and compare the formation of MG, MG-induced AGE, N(epsilon)-carboxyethyl-lysine (CEL), inducible nitric oxide synthase (iNOS), nitric oxide, and peroxynitrite from different metabolic precursors in cultured rat aortic vascular smooth muscle cells (VSMCs). High-performance liquid chromatography was used to determine MG levels, whereas nitrite + nitrate, indicators of nitric oxide production, and peroxynitrite levels were measured with specific assay kits. The CEL and iNOS were detected using immunocytochemistry. There was a concentration-dependent increase in MG levels in VSMCs after 3-hour incubation with 5, 15, and 25 mmol/L of D-glucose, fructose, or aminoacetone. Aminoacetone produced a 7-fold increase in MG levels above the basal value followed by fructose (3.9-fold), D-glucose (3.5-fold), acetol (2.8-fold), and sucrose (2.3-fold) after a 3-hour incubation with 25 mmol/L of each precursor. L-Glucose, 3-O-methylglucose, and mannitol had no effect on MG production. All precursors, except l-glucose, 3-O-methylglucose and mannitol, increased CEL. Aminoacetone, D-glucose, and fructose significantly increased iNOS, nitrite/nitrate, and peroxynitrite levels. In conclusion, aminoacetone is the most potent precursor of MG production in VSMCs, followed by fructose and d-glucose. This could have important implications in relation to high dietary fructose and protein intake.

Are purines mediators of the anticonvulsant/neuroprotective effects of ketogenic diets?

Abnormal neuronal signaling caused by metabolic changes characterizes several neurological disorders, and in some instances metabolic interventions provide therapeutic benefits. Indeed, altering metabolism either by fasting or by maintaining a low-carbohydrate (ketogenic) diet might reduce epileptic seizures and offer neuroprotection in part because the diet increases mitochondrial biogenesis and brain energy levels. Here we focus on a novel hypothesis that a ketogenic diet-induced change in energy metabolism increases levels of ATP and adenosine, purines that are critically involved in neuron-glia interactions, neuromodulation and synaptic plasticity. Enhancing brain bioenergetics (ATP) and increasing levels of adenosine, an endogenous anticonvulsant and neuroprotective molecule, might help with understanding and treating a variety of neurological disorders.

A ketogenic diet rescues the murine succinic semialdehyde dehydrogenase deficient phenotype

Succinic semialdehyde dehydrogenase (SSADH) deficiency is a heritable disorder of GABA degradation characterized by ataxia, psychomotor retardation and seizures. To date, there is no effective treatment for SSADH deficiency. We tested the hypothesis that a ketogenic diet (KD) would improve outcome in an animal model of SSADH deficiency, the SSADH knockout mouse (Aldh5a1-/-). Using a 4:1 ratio of fat to combined carbohydrate and protein KD we set out to compare the general phenotype, in vivo and in vitro electrophysiology and [35S]TBPS binding in both Aldh5a1-/- mice and control (Aldh5a1+/+) mice. We found that the KD prolonged the lifespan of mutant mice by >300% with normalization of ataxia, weight gain and EEG compared to mutants fed a control diet. Aldh5a1-/- mice showed significantly reduced mIPSC frequency in CA1 hippocampal neurons as well as significantly decreased [35S]TBPS binding in all brain areas examined. In KD fed mutants, mIPSC activity normalized and [35S]TBPS binding was restored in the cortex and hippocampus. The KD appears to reverse toward normal the perturbations seen in Aldh5a1-/- mice. Our data suggest that the KD may work in this model by restoring GABAergic inhibition. These data demonstrate a successful experimental treatment for murine SSADH deficiency using a KD, giving promise to the idea that the KD may be successful in the clinical treatment of SSADH deficiency.

The neuropharmacology of the ketogenic diet

The ketogenic diet is a valuable therapeutic approach for epilepsy, one in which most clinical experience has been with children. Although the mechanism by which the diet protects against seizures is unknown, there is evidence that it causes effects on intermediary metabolism that influence the dynamics of the major inhibitory and excitatory neurotransmitter systems in brain. The pattern of protection of the ketogenic diet in animal models of seizures is distinct from that of other anticonvulsants, suggesting that it has a unique mechanism of action. During consumption of the ketogenic diet, marked alterations in brain energy metabolism occur, with ketone bodies partly replacing glucose as fuel. Whether these metabolic changes contribute to acute seizure protection is unclear; however, the ketone body acetone has anticonvulsant activity and could play a role in the seizure protection afforded by the diet. In addition to acute seizure protection, the ketogenic diet provides protection against the development of spontaneous recurrent seizures in models of chronic epilepsy, and it has neuroprotective properties in diverse models of neurodegenerative disease.