Sergei S. Likhodii

Anticonvulsant properties of acetone, a brain ketone elevated by the ketogenic diet

The ketogenic diet (KD), a treatment for drug‐resistant epilepsy, elevates brain acetone. Acetone has been shown to suppress experimental seizures. Whether elevation of acetone is the basis of the anticonvulsant effects of the KD and whether acetone, like the KD, antagonizes many different types of seizures, however, is unknown. This study investigated the spectrum of the anticonvulsant effects of acetone in animal seizure models. Rats were injected with acetone intraperitoneally. Dose–response effects were measured in four different models: (1) the maximal electroshock test, which models human tonic‐clonic seizures; (2) the subcutaneous pentylenetetrazole test, which models human typical absence seizures; (3) the amygdala kindling test, which models human complex partial seizures with secondary generalization; and (4) the AY‐9944 test, which models chronic atypical absence seizures, a component of the Lennox–Gastaut syndrome. Acetone suppressed seizures in all of the models, with the following ED50s (expressed in mmol/kg): maximal electroshock, 6.6; pentylenetetrazole, 9.7; generalized kindled seizures, 13.1; focal kindled seizures, 26.5; AY‐9944, 4.0. Acetone appears to have a broad spectrum of anticonvulsant effects. These effects parallel the effects of the KD. Elevation of brain acetone therefore may account for the efficacy of the KD in intractable epilepsy. Ann Neurol 2003

Dietary fat, ketosis, and Seizure resistance in rats on the ketogenic diet

Summary: Purpose: Fat is the major component of the ketogenic diet (KD), yet no studies have examined whether the type of fat used in the diet can be optimized to provide additional benefits. The purpose of the present experiments was to compare the efficiency of different fats in inducing ketosis and affording seizure resistance.

The MCT Ketogenic Diet: Effects on Animal Seizure Models

Male Wistar rat pups were weaned at 20 days of age and placed on either a control diet or a ketogenic diet containing medium-chain triglyceride (MCT) oil. After 10 days on the diets, they were subjected to one of four seizure tests-maximal electric shock, threshold electroconvulsive shock, threshold pentylenetetrazol, or maximal pentylenetetrazol. After testing, subjects were sacrificed and blood samples were analyzed for beta-hydroxybutyrate concentration. It was found that the MCT diet produced blood levels of beta-hydroxybutyrate that were comparable to or higher than those commonly reported in clinical studies. However, no anticonvulsant effects were seen in any of the seizure tests. In fact, the tests involving maximal seizures actually showed proconvulsant effects. It appears that clinical levels of ketones may be present in the bloodstream without suppressing seizures.

Carbenoxolone does not cross the blood brain barrier: an HPLC study

BackgroundCarbenoxolone (CBX) is a widely used gap junctional blocker. Considering several reports indicating that transient gap junctional blockade could be a favourable intervention following injuries to central nervous tissue, and some current enthusiasm in studies using systemic injections of CBX, it is imperative to consider the penetration of CBX into central nervous tissue after systemic administrations. So far, only very indirect evidence suggests that CBX penetrates into the central nervous system after systemic administrations. We thus determined the amounts of CBX present in the blood and the cerebrospinal fluid of rats after intraperitoneal administration, using high performance liquid chromatographyResultsCBX was found in the blood of the animals, up to 90 minutes post-injection. However, the cerebrospinal fluid concentration of CBX was negligible.ConclusionThus, we conclude that, most likely, CBX does not penetrate the blood brain barrier and therefore recommend careful consideration in the manner of administration, when a central effect is desired.

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.

Lipid and fatty acid profiles in rats consuming different high-fat ketogenic diets

High-fat ketogenic diets are used to treat intractable seizures in children, but little is known of the mechanism by which these diets work or whether fats rich in n−3 polyunsaturates might be beneficial. Tissue lipid and fatty acid profiles were determined in rats consuming very high fat (80 weight%), low-carbohydrate ketogenic diets containing either medium-chain triglyceride, flaxseed oil, butter, or an equal combination of these three fat sources. Ketogenic diets containing butter markedly raised liver triglyceride but had no effect on plasma cholesterol. Unlike the other fats, flaxseed oil in the ketogenic diet did not raise brain cholesterol. Brain total and free fatty acid profiles remained similar in all groups, but there was an increase in the proportion of arachidonate in brain total lipids in the medium-chain triglyceride group, while the two groups consuming flaxseed oil had significantly lower arachidonate in brain, liver, and plasma. The very high dietary intake of α-linolenate in the flaxseed group did not change docosahexaenoate levels in the brain. Our previous report based on these diets showed that although ketosis is higher in rats consuming a ketogenic diet based on medium-chain triglyceride oil, seizure resistance in the pentylenetetrazol model is not clearly related to the degree of ketosis achieved. In combination with our present data from the same seizure study, it appears that ketogenic diets with widely differing effects on tissue lipids and fatty acid profiles can confer a similar amount of seizure protection.

The Ketogenic Diet: Proposed Mechanisms of Action

SummaryThe ketogenic diet is a high-fat, low-carbohydrate diet used to treat drug-resistant seizures, especially in children. A number of possible mechanisms of action have been proposed to explain the anticonvulsant effects of the diet. Four of these hypothetical mechanisms are discussed in the present article: the pH hypothesis, the metabolic hypotheses, the amino acid hypothesis, and the ketone hypothesis.

A Comparison of the Ability of a 4:1 Ketogenic Diet and a 6.3:1 Ketogenic Diet to Elevate Seizure Thresholds in Adult and Young Rats

Summary:  Purpose: The pentylenetetrazol (PTZ) infusion test was used to compare seizure thresholds in adult and young rats fed either a 4:1 ketogenic diet (KD) or a 6.3:1 KD. We hypothesized that both KDs would significantly elevate seizure thresholds and that the 4:1 KD would serve as a better model of the KD used clinically.

Effect of the ketogenic diet on the activity level of Wistar rats.

Children, adolescents, and adults with epilepsy often also show symptoms associated with attention-deficit/hyperactivity disorder (ADHD). The ketogenic diet, which is administered to children with epilepsy refractory to drug therapy, seems to improve behavior in individuals with symptoms of ADHD. The basis for this improvement is unknown, although it seems to be unrelated to seizure control. The present research was designed to investigate the effect of two ketogenic diets on the behavior of normal adult male rats. Two experiments were conducted. In experiment 1, 36 subjects were placed on one of three diets: a control diet, a 6.3:1 ketogenic diet, and a 4:1 ketogenic diet. In experiment 2, 20 subjects were placed either on a control diet or on a 4:1 ketogenic diet. The activity level of each subject was measured using an open field test. Time spent immobile, grooming, and in exploratory behavior was measured for 600 s. Subjects were tested once before initiation of the diets and once while on the diets. No significant group differences were found in activity level before initiation of the diets. After initiation of the diets, subjects in both ketogenic groups showed a significantly lower activity level than the rats on the control diet. The ketogenic diet decreases activity level in an animal model. This behavioral change may relate to the improved behavior seen when children with symptoms of ADHD are placed on the diet.

Acetone as an Anticonvulsant

Recent interest in the anticonvulsant effects of acetone has stemmed from studies related to the ketogenic diet (KD). The KD, a high‐fat diet used to treat drug‐resistant seizures, raises blood and brain levels of three ketones: beta‐hydroxybutyrate, acetoacetate, and acetone. An obvious question is whether these ketones have anticonvulsant properties. We found that neither beta‐hydroxybutyrate nor acetoacetate has proven to be anticonvulsant. Acetone, however, is clearly anticonvulsant at physiological, and near‐physiological, nontoxic concentrations. Despite knowledge of acetones anticonvulsant properties since the 1930s, acetone had never been characterized using the standard animal seizure tests. In our recent experiments, acetone was found to be active in animal models of tonic–clonic seizures, typical absence seizures, complex partial seizures, and atypical absence seizures associated with Lennox–Gastaut syndrome. Therapeutic indices are either comparable or better than that of valproate, a standard broad‐spectrum anticonvulsant. A number of acetone‐like molecules have also been tested, and these also show good potency up to a “cutoff” point of nine carbons contained in the side chain. Above this number, potency disappears, suggesting the possibility of a receptor for acetone and its analogs.