Ketone Administration for Seizure Disorders: History and Rationale for Ketone Esters and Metabolic Alternatives

A review of nutritional recommendations for scuba divers

BACKGROUND

Scuba diving is an increasingly popular activity that involves the use of specialized equipment and compressed air to breathe underwater. Scuba divers are subject to the physiological consequences of being immersed in a high-pressure environment, including, but not limited to, increased work of breathing and kinetic energy expenditure, decreased fluid absorption, and alteration of metabolism. Individual response to these environmental stressors may result in a differential risk of decompression sickness, a condition thought to result from excess nitrogen bubbles forming in a diver's tissues. While the mechanisms of decompression sickness are still largely unknown, it has been postulated that this response may further be influenced by the diver's health status. Nutritional intake has direct relevancy to inflammation status and oxidative stress resistance, both of which have been associated with increased decompression stress. While nutritional recommendations have been determined for saturation divers, these recommendations are likely overly robust for recreational divers, considering that the differences in time spent under pressure and the maximum depth could result nonequivalent energetic demands. Specific recommendations for recreational divers remain largely undefined.

METHODS

This narrative review will summarize existing nutritional recommendations and their justification for recreational divers, as well as identify gaps in research regarding connections between nutritional intake and the health and safety of divers.

RESULTS

Following recommendations made by the Institute of Medicine and the Naval Medical Research Institute of Bethesda, recreational divers are advised to consume ~170-210 kJ·kg-1 (40-50 kcal·kg-1) body mass, depending on their workload underwater, in a day consisting of 3 hours' worth of diving above 46 msw. Recommendations for macronutrient distribution for divers are to derive 50% of joules from carbohydrates and less than 30% of joules from fat. Protein consumption is recommended to reach a minimum of 1 g of protein·kg-1 of body mass a day to mitigate loss of appetite while meeting energetic requirements. All divers should take special care to hydrate themselves with an absolute minimum of 500 ml of fluid per hour for any dive longer than 3 hours, with more recent studies finding 0.69 liters of water two hours prior to diving is most effective to minimize bubble loads. While there is evidence that specialized diets may have specific applications in commercial or military diving, they are not advisable for the general recreational diving population considering the often extreme nature of these diets, and the lack of research on their effectiveness on a recreational diving population.

CONCLUSIONS

Established recommendations do not account for changes in temperature, scuba equipment, depth, dive time, work of breathing, breathing gas mix, or individual variation in metabolism. Individual recommendations may be more accurate when accounting for basal metabolic rate and physical activity outside of diving. However, more research is needed to validate these estimates against variation in dive profile and diver demographics.

Brain Metabolism in Health and Neurodegeneration: The Interplay Among Neurons and Astrocytes

The regulation of energy in the brain has garnered substantial attention in recent years due to its significant implications in various disorders and aging. The brain's energy metabolism is a dynamic and tightly regulated network that balances energy demand and supply by engaging complementary molecular pathways. The crosstalk among these pathways enables the system to switch its preferred fuel source based on substrate availability, activity levels, and cell state-related factors such as redox balance. Brain energy production relies on multi-cellular cooperation and is continuously supplied by fuel from the blood due to limited internal energy stores. Astrocytes, which interface with neurons and blood vessels, play a crucial role in coordinating the brain's metabolic activity, and their dysfunction can have detrimental effects on brain health. This review characterizes the major energy substrates (glucose, lactate, glycogen, ketones and lipids) in astrocyte metabolism and their role in brain health, focusing on recent developments in the field.

Putative Role of Adenosine A1 Receptors in Exogenous Ketone Supplements-Evoked Anti-Epileptic Effect

Approximately 30% of patients with epilepsy are drug-refractory. There is an urgent need to elucidate the exact pathophysiology of different types of epilepsies and the mechanisms of action of both antiseizure medication and metabolic therapies to treat patients more effectively and safely. For example, it has been demonstrated that exogenous ketone supplement (EKS)-generated therapeutic ketosis, as a metabolic therapy, may decrease epileptic activity in both animal models and humans, but its exact mechanism of action is unknown. However, it was demonstrated that therapeutic ketosis, among others, can increase adenosine level, which may enhance activity of A1 adenosine receptors (A1Rs) in the brain. It has also been demonstrated previously that adenosine has anti-epileptic effect through A1Rs in different models of epilepsies. Thus, it is possible that (i) therapeutic ketosis generated by the administration of EKSs may exert its anti-epileptic effect through, among other mechanisms, increased adenosine level and A1R activity and that (ii) the enhanced activity of A1Rs may be a necessary anti-epileptic mechanism evoked by EKS administration-generated ketosis. Moreover, EKSs can evoke and maintain ketosis without severe side effects. These results also suggest that the therapeutic application of EKS-generated ketosis may be a promising opportunity to treat different types of epilepsies. In this literature review, we specifically focus on the putative role of A1Rs in the anti-epileptic effect of EKS-induced ketosis.

Tracking the therapeutic efficacy of a ketone mono ester and β-hydroxybutyrate for ulcerative colitis in rats: New perspectives

Ulcerative colitis (UC) is an inflammatory condition that affects the colon's lining and increases the risk of colon cancer. Despite ongoing research, there is no identified cure for UC. The recognition of NLRP3 inflammasome activation in the pathogenesis of UC has gained widespread acceptance. Notably, the ketone body β-hydroxybutyrate inhibits NLRP3 demonstrating its anti-inflammatory properties. Additionally, BD-AcAc 2 is ketone mono ester that increases β-hydroxybutyrate blood levels. It has the potential to address the constraints associated with exogenous β-hydroxybutyrate as a therapeutic agent, including issues related to stability and short duration of action. However, the effects of β-hydroxybutyrate and BD-AcAc 2 on colitis have not been fully investigated. This study found that while both exogenous β-hydroxybutyrate and BD-AcAc 2 produced the same levels of plasma β-hydroxybutyrate, BD-AcAc 2 demonstrated superior effectiveness in mitigating dextran sodium sulfate-induced UC in rats. The mechanism of action involves modulating the NF-κB signaling, inhibiting the NLRP3 inflammasome, regulating antioxidant capacity, controlling tight junction protein expression and a potential to inhibit apoptosis and pyroptosis. Certainly, BD-AcAc 2's anti-inflammatory effects require more than just increasing plasma β-hydroxybutyrate levels and other factors contribute to its efficacy. Local ketone concentrations in the gastrointestinal tract, as well as the combined effect of specific ketone bodies, are likely to have contributed to the stronger protective effect observed with ketone mono ester ingestion in our experiment. As a result, further investigations are necessary to fully understand the mechanisms of BD-AcAc 2 and optimize its use.

Eu- or hypoglycemic ketosis and ketoacidosis in children: a review

The last decade has been characterized by exciting findings on eu- or hypoglycemic ketosis and ketoacidosis. This review emphasizes the following five key points: 1. Since the traditional nitroprusside-glycine dipstick test for urinary ketones is often falsely negative, the blood determination of β-hydroxybutyrate, the predominant ketone body, is currently advised for a comprehensive assessment of ketone body status; 2. Fasting and infections predispose to relevant ketosis and ketoacidosis especially in newborns, infants, children 7 years or less of age, and pregnant, parturient, or lactating women; 3. Several forms of carbohydrate restriction (typically less than 20% of the daily caloric intake) are employed to induce ketosis. These ketogenic diets have achieved great interest as antiepileptic treatment, in the management of excessive body weight, diabetes mellitus, and in sport training; 4. Intermittent fasting is more and more popular because it might benefit against cardiovascular diseases, cancers, neurologic disorders, and aging; 5. Gliflozins, a new group of oral antidiabetics inhibiting the renal sodium-glucose transporter 2, are an emerging cause of eu- or hypoglycemic ketosis and ketoacidosis. In conclusion, the role of ketone bodies is increasingly recognized in several clinical conditions. In the context of acid-base balance evaluation, it is advisable to routinely integrate both the assessment of lactic acid and β-hydroxybutyrate.

1,3-Butanediol Administration Increases β-Hydroxybutyrate Plasma Levels and Affects Redox Homeostasis, Endoplasmic Reticulum Stress, and Adipokine Production in Rat Gonadal Adipose Tissue

Ketone bodies (KBs) are an alternative energy source under starvation and play multiple roles as signaling molecules regulating energy and metabolic homeostasis. The mechanism by which KBs influence visceral white adipose tissue physiology is only partially known, and our study aimed to shed light on the effects they exert on such tissue. To this aim, we administered 1,3-butanediol (BD) to rats since it rapidly enhances β-hydroxybutyrate serum levels, and we evaluated the effect it induces within 3 h or after 14 days of treatment. After 14 days of treatment, rats showed a decrease in body weight gain, energy intake, gonadal-WAT (gWAT) weight, and adipocyte size compared to the control. BD exerted a pronounced antioxidant effect and directed redox homeostasis toward reductive stress, already evident within 3 h after its administration. BD lowered tissue ROS levels and oxidative damage to lipids and proteins and enhanced tissue soluble and enzymatic antioxidant capacity as well as nuclear erythroid factor-2 protein levels. BD also reduced specific mitochondrial maximal oxidative capacity and induced endoplasmic reticulum stress as well as interrelated processes, leading to changes in the level of adipokines/cytokines involved in inflammation, macrophage infiltration into gWAT, adipocyte differentiation, and lipolysis.

(R,R)-BD-AcAc2 Mitigates Chronic Colitis in Rats: A Promising Multi-Pronged Approach Modulating Inflammasome Activity, Autophagy, and Pyroptosis

Ulcerative colitis is a chronic and incurable form of inflammatory bowel disease that can increase the risk of colitis-associated cancer and mortality. Limited treatment options are available for this condition, and the existing ones often come with non-tolerable adverse effects. This study is the first to examine the potential benefits of consuming (R,R)-BD-AcAc2, a type of ketone ester (KE), and intermittent fasting in treating chronic colitis induced by dextran sodium sulfate (DSS) in rats. We selected both protocols to enhance the levels of β-hydroxybutyrate, mimicking a state of nutritional ketosis and early ketosis, respectively. Our findings revealed that only the former protocol, consuming the KE, improved disease activity and the macroscopic and microscopic features of the colon while reducing inflammation scores. Additionally, the KE counteracted the DSS-induced decrease in the percentage of weight change, reduced the colonic weight-to-length ratio, and increased the survival rate of DSS-insulted rats. KE also showed potential antioxidant activities and improved the gut microbiome composition. Moreover, consuming KE increased the levels of tight junction proteins that protect against leaky gut and exhibited anti-inflammatory properties by reducing proinflammatory cytokine production. These effects were attributed to inhibiting NFκB and NLRP3 inflammasome activation and restraining pyroptosis and apoptosis while enhancing autophagy as revealed by reduced p62 and increased BECN1. Furthermore, the KE may have a positive impact on maintaining a healthy microbiome. To conclude, the potential clinical implications of our findings are promising, as (R,R)-BD-AcAc2 has a greater safety profile and can be easily translated to human subjects.

Ketogenic Diet and Ketone Bodies as Clinical Support for the Treatment of SARS-CoV-2-Review of the Evidence

One of the proposed nutritional therapies to support drug therapy in COVID-19 is the use of a ketogenic diet (KD) or ketone bodies. In this review, we summarized the evidence from tissue, animal, and human models and looked at the mechanisms of action of KD/ketone bodies against COVID-19. KD/ketone bodies were shown to be effective at the stage of virus entry into the host cell. The use of β-hydroxybutyrate (BHB), by preventing the metabolic reprogramming associated with COVID-19 infection and improving mitochondrial function, reduced glycolysis in CD4+ lymphocytes and improved respiratory chain function, and could provide an alternative carbon source for oxidative phosphorylation (OXPHOS). Through multiple mechanisms, the use of KD/ketone bodies supported the host immune response. In animal models, KD resulted in protection against weight loss and hypoxemia, faster recovery, reduced lung injury, and resulted in better survival of young mice. In humans, KD increased survival, reduced the need for hospitalization for COVID-19, and showed a protective role against metabolic abnormalities after COVID-19. It appears that the use of KD and ketone bodies may be considered as a clinical nutritional intervention to assist in the treatment of COVID-19, despite the fact that numerous studies indicate that SARS-CoV-2 infection alone may induce ketoacidosis. However, the use of such an intervention requires strong scientific validation.

Antiseizure medication reduction and withdrawal in children with drug-resistant epilepsy after starting the ketogenic diet

AIM

To investigate the rate of successful withdrawal of antiseizure medication (ASM) after starting the ketogenic diet in children and identify predictive factors.

METHOD

We retrospectively reviewed data of children with epilepsy, who were treated with the ketogenic diet for 6 months or longer at our institution, over a 5-year period. We defined successful withdrawal of one or more medications as a time period of 3 months or more off this medication without restarting it or starting a new agent. Predictive clinical factors were investigated using binary multivariable logistic regression.

RESULTS

Seventy-one children were included (28 females, 43 males; median age at seizure onset 5 months, median age at diet initiation 58.5 months, median duration of ketogenic diet 27.7 months). Reduction of one or more ASMs was attempted in 54 out of 71 (76%) children and was successful in 34 out of 54 (63%), including discontinuation of all ASMs in 13. Younger age at the start of the ketogenic diet was associated with higher odds of successful ASM withdrawal. ASM withdrawal was successful in 11 out of 19 children with less than 50% seizure reduction at 3 months.

INTERPRETATION

Reduction of ASM was achieved in two-thirds of patients after the start of the ketogenic diet, where attempted, and can be successful even with little or unchanged seizure frequency while on the diet.

Does the ketogenic ratio matter when using ketogenic diet therapy in pediatric epilepsy?

The ketogenic diet (KD) is a widely used therapeutic option for individuals with medically refractory epilepsy. As the diet's name implies, ketosis is a historically important component of the diet, but it is not well understood how important ketosis is for seizure control. The ketogenic ratio is defined as the ratio of fat to carbohydrate plus protein by weight in the diet (grams). Traditionally, the classic KD contains a 4:1 ratio, and a very high proportion of fat in the diet. The classic KD, with its high proportion of fat and limited carbohydrate intake can be restrictive for patients with epilepsy. Recently, there is experience with use of lower ketogenic ratios and less-restrictive diets such as the modified Atkins diet and the low glycemic index treatment. In this narrative review, we examine the role of ketosis and ketogenic ratios in determining the efficacy of the KD in children with epilepsy.

Analysis of the efficacy and safety of inpatient and outpatient initiation of KD for the treatment of pediatric refractory epilepsy using generalized estimating equations

Objective

To compare the efficacy and safety of inpatient and outpatient initiation ketogenic diet (KD) protocol of pediatric refractory epilepsy.

Methods

Eligible children with refractory epilepsy were randomly assigned to receive KD with inpatient and outpatient initiation. The generalized estimation equation (GEE) model was used to analyze the longitudinal variables of seizure reduction, ketone body, weight, height, body mass index (BMI), and BMI Z-score at different follow-up times between the two groups.

Results

Between January 2013 and December 2021, 78 and 112 patients were assigned to outpatient and inpatient KD initiation groups, respectively. There were no statistical differences between the two groups based on baseline demographics and clinical characteristics (all Ps > 0.05). The GEE model indicated that the rate of reduction of seizures≥50% in the outpatient initiation group was higher than that of the inpatient initiation group (p = 0.049). A negative correlation was observed between the seizure reduction and blood ketone body at 1, 6, and 12 months (all Ps < 0.05). There were no significant differences in height, weight, BMI, and BMI Z-score between the two groups over the 12-month period by the GEE models (all Ps > 0.05). Adverse events were reported by 31 patients (43.05%) in the outpatient KD initiation group and 46 patients (42.20%) in the inpatient KD initiation group, but these differences were not statistically significant (p = 0.909).

Conclusion

Our study shows that outpatient KD initiation is a safe and effective treatment for children with refractory epilepsy.

Exploring the role of ketone bodies in the diagnosis and treatment of psychiatric disorders

In recent times, advances in the field of metabolomics have shed greater light on the role of metabolic disturbances in neuropsychiatric conditions. The following review explores the role of ketone bodies and ketosis in both the diagnosis and treatment of three major psychiatric disorders: major depressive disorder, anxiety disorders, and schizophrenia. Distinction is made between the potential therapeutic effects of the ketogenic diet and exogenous ketone preparations, as exogenous ketones in particular offer a standardized, reproducible manner for inducing ketosis. Compelling associations between symptoms of mental distress and dysregulation in central nervous system ketone metabolism have been demonstrated in preclinical studies with putative neuroprotective effects of ketone bodies being elucidated, including effects on inflammasomes and the promotion of neurogenesis in the central nervous system. Despite emerging pre-clinical data, clinical research on ketone body effectiveness as a treatment option for psychiatric disorders remains lacking. This gap in understanding warrants further investigating, especially considering that safe and acceptable ways of inducing ketosis are readily available.

Acetoacetate and β-hydroxybutyrate reduce mouse embryo viability via differential metabolic and epigenetic mechanisms

RESEARCH QUESTION

Does the ketone acetoacetate (AcAc) alone, or combined with β-hydroxybutyrate (βOHB), impact mouse embryo development, metabolism, histone acetylation and viability?

DESIGN

Pronucleate mouse oocytes were cultured in vitro in G1/G2 media supplemented with ketones (AcAc or AcAc + βOHB) at concentrations representing those in maternal serum during pregnancy (0.04 mmol/l AcAc, 0.1 mmol/l βOHB), standard diet consumption (0.1 mmol/l AcAc, 0.25 mmol/l βOHB), ketogenic diet consumption (0.8 mmol/l AcAc, 2 mmol/l βOHB) and diabetic ketoacidosis (2 mmol/l AcAc, 4 mmol/l βOHB). Day 5 blastocysts were assessed for cell allocation, glucose metabolism and histone acetylation. Day 4 blastocysts exposed to 0.8 mmol/l AcAc + 2 mmol/l βOHB were transferred to standard-fed recipient females, and E14.5 fetal and placental development assessed.

RESULTS

Exposure to 2 mmol/l AcAc or 0.8 mmol/l AcAc + 2 mmol/l βOHB did not impair blastocyst development, but significantly increased glucose consumption (P = 0.001 each), lowered glycolytic flux (P = 0.01, P < 0.001) and elevated trophectoderm (TE) histone 3 lysine 27 acetylation (H3K27ac; P < 0.001 each) compared with unexposed controls. Preimplantation AcAc + βOHB exposure reduced post-implantation fetal development by 25% (P = 0.037), and delayed female-specific fetal limb development (P = 0.019) and estimated fetal age (P = 0.019) compared with controls.

CONCLUSION

Preimplantation exposure to ketones affects underlying metabolism and histone acetylation in blastocysts that are associated with persistent, female-specific perturbations in fetal development. A periconceptional diet that elevates ketone concentrations may impair human embryonic viability.

D-beta-hydroxybutyrate protects against microglial activation in lipopolysaccharide-treated mice and BV-2 cells

Microglial activation is a key event in neuroinflammation, which, in turn, is a central process in neurological disorders. In this study, we investigated the protective effects of D-beta-hydroxybutyrate (BHB) against microglial activation in lipopolysaccharide (LPS)-treated mice and BV-2 cells. The effects of BHB in mice were assessed using behavioral testing, morphological analysis and immunofluorescence labeling for the microglial marker ionizing calcium-binding adaptor molecule 1 (IBA-1) and the inflammatory cytokine interleukin-6 (IL-6) in the hippocampus. Moreover, we examined the levels of the inflammatory IL-6 and tumor necrosis factor-α (TNF-α), as well as those of the neuroprotective brain-derived neurotrophic factor (BDNF) and transforming growth factor-β (TGF-β) in the brain. In addition, we examined the effects of BHB on IL-6, TNF-α, BDNF, TGF-β, reactive oxygen species (ROS) level and cell viability in LPS-stimulated BV-2 cells. BHB treatments attenuated behavioral abnormalities, reduced the number of IBA-1-positive cells and the intensity of IL-6 fluorescence in the hippocampus, with amelioration of microglia morphological changes in the LPS-treated mice. Furthermore, BHB inhibited IL-6 and TNF-α generation, but promoted BDNF and TGF-β production in the brain of LPS-treated mice. In vitro, BHB inhibited IL-6 and TNF-α generation, increased BDNF and TGF-β production, reduced ROS level, ameliorated morphological changes and elevated cell viability of LPS-stimulated BV-2 cells. Together, our findings suggest that BHB exerts protective effects against microglial activation in vitro and in vivo, thereby reducing neuroinflammation.

Emerging Nutrition Approaches to Support the Mind and Muscle for Healthy Aging

This narrative review highlights recent advances and ongoing trials using nutrition approaches for healthy aging. Focus will be placed on nutrition therapies that target cognition ("the mind") and mobility ("the muscle"), both critical components to maintaining a high quality of life for older adults. For "the mind," two seemingly incongruent therapies are being investigated to improve cognition-the MIND diet (high in carbohydrates and anti-oxidant fruits and vegetables) and the ketogenic diet (low in carbohydrates, high in fats). For "the muscle," a focus on protein and energy intake has dominated the literature, yet a recent clinical trial supports the use of whole-grains as a tool to improve whole-body protein turnover-a primary regulator of lean body mass and muscle. Finally, emerging data and clinical trials on caloric restriction have solidified this strategy as the only nutritional approach to slow intrinsic factors of whole-body aging, which may positively impact both "the mind" and "the muscle."

Insights into the Cellular Interactions and Molecular Mechanisms of Ketogenic Diet for Comprehensive Management of Epilepsy

A high-fat diet with appropriate protein and low carbohydrate content, widely known as the ketogenic diet (KD), is considered as an effective non-pharmacotherapeutic treatment option for certain types of epilepsies. Several preclinical and clinical studies have been carried out to elucidate its mechanism of antiepileptic action. Ketone bodies produced after KD's breakdown interact with cellular excito-inhibitory processes and inhibit abnormal neuronal firing. The generated ketone bodies decrease glutamate release by inhibiting the vesicular glutamate transporter 1 and alter the transmembrane potential by hyperpolarization. Apart from their effect on the well-known pathogenic mechanisms of epilepsy, some recent studies have shown the interaction of KD metabolites with novel neuronal targets, particularly adenosine receptors, adenosine triphosphate-sensitive potassium channel, mammalian target of rapamycin, histone deacetylase, hydroxycarboxylic acid receptors, and the NLR family pyrin domain containing 3 inflammasomes to suppress seizures. The role of KD in augmenting gut microbiota as a potential mechanism for epileptic seizure suppression has been established. Furthermore, some recent findings also support the beneficial effect of KD against epilepsy- associated comorbidities. Despite several advantages of the KD in epilepsy management, its use is also associated with a wide range of side effects. Hypoglycemia, excessive ketosis, acidosis, renal stones, cardiomyopathies, and other metabolic disturbances are the primary adverse effects observed with the use of KD. However, in some recent studies, modified KD has been tested with lesser side effects and better tolerability. The present review discusses the molecular mechanism of KD and its role in managing epilepsy and its associated comorbidities.

Exogenous Ketones and Lactate as a Potential Therapeutic Intervention for Brain Injury and Neurodegenerative Conditions

Metabolic dysfunction is a ubiquitous underlying feature of many neurological conditions including acute traumatic brain injuries and chronic neurodegenerative conditions. A central problem in neurological patients, in particular those with traumatic brain injuries, is an impairment in the utilization of glucose, which is the predominant metabolic substrate in a normally functioning brain. In such patients, alternative substrates including ketone bodies and lactate become important metabolic candidates for maintaining brain function. While the potential neuroprotective benefits of ketosis have been recognized for up to almost a century, the majority of work has focused on the use of ketogenic diets to induce such a state, which is inappropriate in cases of acute disease due to the prolonged periods of time (i.e., weeks to months) required for the effects of a ketogenic diet to be seen. The following review seeks to explore the neuroprotective effects of exogenous ketone and lactate preparations, which have more recently become commercially available and are able to induce a deep ketogenic response in a fraction of the time. The rapid response of exogenous preparations makes their use as a therapeutic adjunct more feasible from a clinical perspective in both acute and chronic neurological conditions. Potentially, their ability to globally moderate long-term, occult brain dysfunction may also be relevant in reducing lifetime risks of certain neurodegenerative conditions. In particular, this review explores the association between traumatic brain injury and contusion-related dementia, assessing metabolic parallels and highlighting the potential role of exogenous ketone and lactate therapies.

The metabolic basis of epilepsy

The brain is a highly energy-demanding organ and requires bioenergetic adaptability to balance normal activity with pathophysiological fuelling of spontaneous recurrent seizures, the hallmark feature of the epilepsies. Recurrent or prolonged seizures have long been known to permanently alter neuronal circuitry and to cause excitotoxic injury and aberrant inflammation. Furthermore, pathological changes in bioenergetics and metabolism are considered downstream consequences of epileptic seizures that begin at the synaptic level. However, as we highlight in this Review, evidence is also emerging that primary derangements in cellular or mitochondrial metabolism can result in seizure genesis and lead to spontaneous recurrent seizures. Basic and translational research indicates that the relationships between brain metabolism and epileptic seizures are complex and bidirectional, producing a vicious cycle that compounds the deleterious consequences of seizures. Metabolism-based treatments such as the high-fat, antiseizure ketogenic diet have become mainstream, and metabolic substrates and enzymes have become attractive molecular targets for seizure prevention and recovery. Moreover, given that metabolism is crucial for epigenetic as well as inflammatory changes, the idea that epileptogenesis can be both negatively and positively influenced by metabolic changes is rapidly gaining ground. Here, we review evidence that supports both pathophysiological and therapeutic roles for brain metabolism in epilepsy.

The Effect of the Ketogenic Diet on Adiponectin, Omentin and Vaspin in Children with Drug-Resistant Epilepsy

Background: Changes in adipokine secretion may be involved in the anti-epileptic effect of a ketogenic diet (KD) in drug-resistant epilepsy (DRE). Objectives: The assessment of the influence of KD on serum adiponectin, omentin-1, and vaspin in children with DRE. Methods: Anthropometric measurements (weight, height, BMI, and waist-to-hip circumference ratio) were performed in 72 children aged 3–9 years, divided into 3 groups: 24 children with DRE treated with KD, 26—treated with valproic acid (VPA), and a control group of 22 children. Biochemical tests included fasting glucose, insulin, beta-hydroxybutyric acid, lipid profile, aminotransferases activities, and blood gasometry. Serum levels of adiponectin, omentin-1 and vaspin were assayed using commercially available ELISA tests. Results: Serum levels of adiponectin and omentin-1 in the KD group were significantly higher and vaspin—lower in comparison to patients receiving VPA and the control group. In all examined children, serum adiponectin and omentin-1 correlated negatively with WHR and serum triglycerides, insulin, fasting glucose, and HOMA-IR. Vaspin levels correlated negatively with serum triglycerides and positively with body weight, BMI, fasting glucose, insulin, and HOMA-IR. Conclusion: One of the potential mechanisms of KD in children with drug-resistant epilepsy may be a modulation of metabolically beneficial and anti-inflammatory adipokine levels.

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 Supplements in Athletic Contexts: Past, Present, and Future

The ketone bodies acetoacetate (AcAc) and β-hydroxybutyrate (βHB) have pleiotropic effects in multiple organs including brain, heart, and skeletal muscle by serving as an alternative substrate for energy provision, and by modulating inflammation, oxidative stress, catabolic processes, and gene expression. Of particular relevance to athletes are the metabolic actions of ketone bodies to alter substrate utilisation through attenuating glucose utilisation in peripheral tissues, anti-lipolytic effects on adipose tissue, and attenuation of proteolysis in skeletal muscle. There has been long-standing interest in the development of ingestible forms of ketone bodies that has recently resulted in the commercial availability of exogenous ketone supplements (EKS). These supplements in the form of ketone salts and ketone esters, in addition to ketogenic compounds such as 1,3-butanediol and medium chain triglycerides, facilitate an acute transient increase in circulating AcAc and βHB concentrations, which has been termed 'acute nutritional ketosis' or 'intermittent exogenous ketosis'. Some studies have suggested beneficial effects of EKS to endurance performance, recovery, and overreaching, although many studies have failed to observe benefits of acute nutritional ketosis on performance or recovery. The present review explores the rationale and historical development of EKS, the mechanistic basis for their proposed effects, both positive and negative, and evidence to date for their effects on exercise performance and recovery outcomes before concluding with a discussion of methodological considerations and future directions in this field.

A ketogenic diet protects DBA/1 and Scn1aR1407X/+ mice against seizure-induced respiratory arrest independent of ketosis

Patients with uncontrolled epilepsy have a high risk of sudden unexpected death in epilepsy (SUDEP). Seizure-induced respiratory arrest (S-IRA) is thought to be the determining cause of death in many cases of SUDEP. The goal of the present study was to use Scn1aR1407X/+ (Dravet Syndrome, DS) and DBA/1 mice to determine: (1) the effect of a ketogenic diet (KD) on S-IRA and (2) the relationship between serum ketones and the protective effect of a KD. Ketogenic diet treatment significantly decreased spontaneous seizure-induced mortality in DS mice compared to control (8% vs 39%, p = 0.0021). This protective effect was not abolished when ketosis was prevented by supplementing the KD with glucose (10% mortality, p = 0.0007). In DBA/1 mice, the latency to onset of S-IRA due to audiogenic seizures was delayed from 7.6 to 20.8 seconds by a KD on treatment day (TD) 7 compared to control (p < 0.0001), an effect that was reversed on TD14 when mice were crossed over to a control diet on TD7. β-Hydroxybutyrate (BHB) levels were significantly decreased in DBA/1 mice on a KD supplemented with glucose (p = 0.0038), but the protective effect was maintained. Our findings show that a KD decreases SUDEP in DS mice and increases the latency to audiogenic S-IRA in DBA/1 mice. In both mouse models, a KD was protective against S-IRA. This effect may be due in part to specific dietary components rather than generation of ketone bodies.

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.

Metabolism-based therapies for epilepsy: new directions for future cures

OBJECTIVE

Thousands of years after dietary therapy was proposed to treat seizures, how alterations in metabolism relates to epilepsy remains unclear, and metabolism-based therapies are not always effective.

METHODS

We consider the state of the science in metabolism-based therapies for epilepsy across the research lifecycle from basic to translational to clinical studies.

RESULTS

This analysis creates a conceptual framework for creative, rigorous, and transparent research to benefit people with epilepsy through the understanding and modification of metabolism.

INTERPRETATION

Despite intensive past efforts to evaluate metabolism-based therapies for epilepsy, distinct ways of framing a problem offer the chance to engage different mindsets and new (or newly applied) technologies. A comprehensive, creative, and inclusive problem-directed research agenda is needed, with a renewed and stringent adherence to rigor and transparency across all levels of investigation.

The Efficacy of Ketogenic Therapies in the Clinical Management of People with Neurodegenerative Disease: A Systematic Review

Ketone bodies have potential disease-modifying activity that represent a novel therapeutic approach for neurodegenerative diseases (NDD). The aim of this systematic review was to summarize and evaluate the evidence for the application of ketogenic therapies (dietary or exogenous ketogenic agents) for NDD and provide recommendations for future research. Eight databases were electronically searched for articles reporting on controlled trials (≥4 wk duration) that induced ketosis or elevated serum ketone concentrations in people with NDD. Of 4498 records identified, 17 articles met the inclusion criteria with a total of 979 participants including studies on mild cognitive impairment (MCI; n = 6), multiple sclerosis (n = 4), Alzheimer's disease (n = 5), Parkinson's disease (n = 1), and MCI secondary to Parkinson's disease (n = 1). Of 17 studies, 7 were randomized double-blind placebo-controlled trials. Most studies used dietary interventions (n = 9), followed by medium-chain triglycerides (n = 7) and a fasting protocol (n = 1). Generally, trials were 6 wk in duration and assessed cognition as the primary outcome. Studies were heterogeneous in type and severity of NDD, interventions used, and outcomes assessed. Overall, 3/17 studies carried a low risk of bias. Based on available evidence, exogenous ketogenic agents may be more feasible than dietary interventions in NDD from a compliance and adherence perspective; more research is required to confirm this. Recommendations for future research include improving exogenous formulations to reduce adverse effects, exploring interindividual factors affecting response-to-treatment, and establishing a "minimum required dose" for clinically meaningful improvements in disease-specific symptoms, such as cognition or motor function.

Applications of Ketogenic Diets in Patients with Headache: Clinical Recommendations

Headaches are among the most prevalent and disabling neurologic disorders and there are several unmet needs as current pharmacological options are inadequate in treating patients with chronic headache, and a growing interest focuses on nutritional approaches as non-pharmacological treatments. Among these, the largest body of evidence supports the use of the ketogenic diet (KD). Exactly 100 years ago, KD was first used to treat drug-resistant epilepsy, but subsequent applications of this diet also involved other neurological disorders. Evidence of KD effectiveness in migraine emerged in 1928, but in the last several year's different groups of researchers and clinicians began utilizing this therapeutic option to treat patients with drug-resistant migraine, cluster headache, and/or headache comorbid with metabolic syndrome. Here we describe the existing evidence supporting the potential benefits of KDs in the management of headaches, explore the potential mechanisms of action involved in the efficacy in-depth, and synthesize results of working meetings of an Italian panel of experts on this topic. The aim of the working group was to create a clinical recommendation on indications and optimal clinical practice to treat patients with headaches using KDs. The results we present here are designed to advance the knowledge and application of KDs in the treatment of headaches.

The protective effects of 1,3-butanediol acetoacetate diester on decompression sickness in rats

Inert gas bubbles are widely accepted as the causative factor of decompression sickness (DCS), resulting in gas embolism and systemic inflammatory responses. The anticonvulsive ketone ester 1,3-butanediol acetoacetate diester (BD-AcAc₂) was reported to have the characteristics of increasing blood oxygen partial pressure (ppO₂) and anti-inflammation and was thought to have the potential to reduce bubble formation and alleviate the pathological process of DCS. This study aims to investigate the potential protection of BD-AcAc₂ against DCS in a rat model. A single dose of BD-AcAc₂ was administered orally to adult male rats (5 g/kg body wt), followed by pharmacokinetic analysis or simulated air dives. After decompression, signs of DCS were monitored, and blood was sampled for biochemical measurements. Blood ketosis peaked at 2 h and lasted for more than 4 h. The incidence of DCS was decreased and postponed significantly in rats treated with BD-AcAc₂ compared with those treated with saline (P < 0.05). Although BD-AcAc₂ failed to reduce bubble load (P > 0.05), it showed an obvious decreasing trend. BD-AcAc₂ significantly increased blood ppO₂ and ameliorated oxidative and inflammatory responses, represented by increased plasma malondialdehyde (MDA), IL-1, IL-6, and TNF-α and decreased glutathione thiol (P < 0.05) levels, whereas blood pH remained unchanged (P > 0.05). These results suggest that BD-AcAc₂ exerted beneficial effects on DCS rats mainly related to increasing ppO₂ and anti-inflammatory and antioxidant properties. Together with its capacity for delaying central nervous system (CNS) oxygen toxicity seizures, BD-AcAc₂ might be an ideal drug candidate for DCS prevention and treatment.NEW & NOTEWORTHY This is the first study exploring the effects of BD-AcAc₂ on DCS prevention, and it was proven to be an efficient and simple method. The role of BD-AcAc₂ in increasing ppO₂, anti-inflammatory and antioxidant properties was thought to be the critical mechanism in DCS prevention.

Consequences of NaCT/SLC13A5/mINDY deficiency: good versus evil, separated only by the blood-brain barrier

NaCT/SLC13A5 is a Na⁺-coupled transporter for citrate in hepatocytes, neurons, and testes. It is also called mINDY (mammalian ortholog of ‘I'm Not Dead Yet’ in Drosophila). Deletion of Slc13a5 in mice leads to an advantageous phenotype, protecting against diet-induced obesity, and diabetes. In contrast, loss-of-function mutations in SLC13A5 in humans cause a severe disease, EIEE25/DEE25 (early infantile epileptic encephalopathy-25/developmental epileptic encephalopathy-25). The difference between mice and humans in the consequences of the transporter deficiency is intriguing but probably explainable by the species-specific differences in the functional features of the transporter. Mouse Slc13a5 is a low-capacity transporter, whereas human SLC13A5 is a high-capacity transporter, thus leading to quantitative differences in citrate entry into cells via the transporter. These findings raise doubts as to the utility of mouse models to evaluate NaCT biology in humans. NaCT-mediated citrate entry in the liver impacts fatty acid and cholesterol synthesis, fatty acid oxidation, glycolysis, and gluconeogenesis; in neurons, this process is essential for the synthesis of the neurotransmitters glutamate, GABA, and acetylcholine. Thus, SLC13A5 deficiency protects against obesity and diabetes based on what the transporter does in hepatocytes, but leads to severe brain deficits based on what the transporter does in neurons. These beneficial versus detrimental effects of SLC13A5 deficiency are separable only by the blood-brain barrier. Can we harness the beneficial effects of SLC13A5 deficiency without the detrimental effects? In theory, this should be feasible with selective inhibitors of NaCT, which work only in the liver and do not get across the blood-brain barrier.

Exogenous ketone salts inhibit superoxide production in the rat caudal solitary complex during exposure to normobaric and hyperbaric hyperoxia

The use of hyperbaric oxygen (HBO₂) in hyperbaric and undersea medicine is limited by the risk of seizures [i.e., central nervous system (CNS) oxygen toxicity, CNS-OT] resulting from increased production of reactive oxygen species (ROS) in the CNS. Importantly, ketone supplementation has been shown to delay onset of CNS-OT in rats by ∼600% in comparison with control groups (D'Agostino DP, Pilla R, Held HE, Landon CS, Puchowicz M, Brunengraber H, Ari C, Arnold P, Dean JB. Am J Physiol Regu Integr Comp Physiol 304: R829-R836, 2013). We have tested the hypothesis that ketone body supplementation inhibits ROS production during exposure to hyperoxygenation in rat brainstem cells. We measured the rate of cellular superoxide ([Formula: see text]) production in the caudal solitary complex (cSC) in rat brain slices using a fluorogenic dye, dihydroethidium (DHE), during exposure to control O₂ (0.4 ATA) followed by 1-2 h of normobaric oxygen (NBO₂) (0.95 ATA) and HBO₂ (1.95, and 4.95 ATA) hyperoxia, with and without a 50:50 mixture of ketone salts (KS) dl-β-hydroxybutyrate + acetoacetate. All levels of hyperoxia tested stimulated [Formula: see text] production similarly in cSC cells and coexposure to 5 mM KS during hyperoxia significantly blunted the rate of increase in DHE fluorescence intensity during exposure to hyperoxia. Not all cells tested produced [Formula: see text] at the same rate during exposure to control O₂ and hyperoxygenation; cells that increased [Formula: see text] production by >25% during hyperoxia in comparison with baseline were inhibited by KS, whereas cells that did not reach that threshold during hyperoxia were unaffected by KS. These findings support the hypothesis that ketone supplementation decreases the steady-state concentrations of superoxide produced during exposure to NBO₂ and HBO₂ hyperoxia.NEW & NOTEWORTHY Exposure of rat medullary tissue slices to levels of O₂ that mimic those that cause seizures in rats stimulates cellular superoxide ([Formula: see text]) production to varying degrees. Cellular [Formula: see text] generation in the caudal solitary complex is variable during exposure to control O₂ and hyperoxia and significantly decreases during ketone supplementation. Our findings support the theory that ketone supplementation delays onset of central nervous system oxygen toxicity in mammals, in part, by decreasing [Formula: see text] production in O₂-sensitive neurons.

Enhancement of Ketone Supplements-Evoked Effect on Absence Epileptic Activity by Co-Administration of Uridine in Wistar Albino Glaxo Rijswijk Rats

Both uridine and exogenous ketone supplements decreased the number of spike-wave discharges (SWDs) in a rat model of human absence epilepsy Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. It has been suggested that alleviating influence of both uridine and ketone supplements on absence epileptic activity may be modulated by A₁ type adenosine receptors (A₁Rs). The first aim was to determine whether intraperitoneal (i.p.) administration of a specific A₁R antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 0.2 mg/kg) and a selective adenosine A_2A receptor antagonist (7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo [1,5-c]pyrimidine) (SCH 58261; 0.5 mg/kg) have a modulatory influence on i.p. 1000 mg/kg uridine-evoked effects on SWD number in WAG/Rij rats. The second aim was to assess efficacy of a sub-effective dose of uridine (i.p. 250 mg/kg) combined with beta-hydroxybutyrate salt + medium chain triglyceride (KSMCT; 2.5 g/kg, gavage) on absence epilepsy. DPCPX completely abolished the i.p. 1000 mg/kg uridine-evoked alleviating effect on SWD number whereas SCH 58261 was ineffective, confirming the A₁R mechanism. Moreover, the sub-effective dose of uridine markedly enhanced the effect of KSMCT (2.5 g/kg, gavage) on absence epileptic activity. These results demonstrate the anti-epilepsy benefits of co-administrating uridine and exogenous ketone supplements as a means to treat absence epilepsy.

Ketone Body, 3-Hydroxybutyrate: Minor Metabolite - Major Medical Manifestations

Ketone bodies - 3-hydroxybutyrate (3-OHB), acetoacetate, and acetone - are ancient, evolutionarily preserved, small fuel substrates, which uniquely can substitute and alternate with glucose under conditions of fuel and food deficiency. Once canonized as a noxious, toxic pathogen leading to ketoacidosis in patients with diabetes, it is now becoming increasingly clear that 3-OHB possesses a large number of beneficial, life-preserving effects in the fields of clinical science and medicine. 3-OHB, the most prominent ketone body, binds to specific hydroxyl-carboxylic acid receptors and inhibits histone deacetylase enzymes, free fatty acid receptors, and the NOD-like receptor protein 3 inflammasome, tentatively inhibiting lipolysis, inflammation, oxidative stress, cancer growth, angiogenesis, and atherosclerosis, and perhaps contributing to the increased longevity associated with exercise and caloric restriction. Clinically ketone bodies/ketogenic diets have for a long time been used to reduce the incidence of seizures in epilepsy and may have a role in the treatment of other neurological diseases such as dementia. 3-OHB also acts to preserve muscle protein during systemic inflammation and is an important component of the metabolic defense against insulin-induced hypoglycemia. Most recently, a number of studies have reported that 3-OHB dramatically increases myocardial blood flow and cardiac output in control subjects and patients with heart failure. At the moment, scientific interest in ketone bodies, in particular 3-OHB, is in a hectic transit and, hopefully, future, much needed, controlled clinical studies will reveal and determine to which extent the diverse biological manifestations of 3-OHB should be introduced medically.

The contribution of ketone bodies to glycolytic inhibition for the treatment of adult and pediatric glioblastoma

PURPOSE

Glioblastoma (GBM) remains one of the most lethal primary brain tumors in children and adults. Targeting tumor metabolism has emerged as a promising-targeted therapeutic strategy for GBM and characteristically resistant GBM stem-like cells (GSCs).

METHODS

Gene expression data was obtained from the online patient-histology database, GlioVis. GSC mitochondria morphology was examined by TEM. Cell viability and effect on GSC self-renewal was determined via MTS assay and neurosphere assay, respectively. Proteins were evaluated by Western Blot.

RESULTS

Enzymes necessary for ketone catabolism (BDH1, OXCT1 and ACAT1) are significantly downregulated in adult and pediatric GBM. GSC mitochondrial ultrastructure suggested defects in oxidative phosphorylation. Treatment of both GBM and GSC cell lines resulted in dose-dependent decreases in viability in response to glycolytic inhibitor 2-deoxy-D-glucose (2-DG), and ketone body Acetoacetate (AA), but not β-hydroxybutyrate (βHB). AA induced apoptosis was confirmed by western blot analysis, indicating robust caspase activation and PARP cleavage. AA reduced neurosphere formation at concentrations as low as 1 mM. Combined treatment of low dose 2-DG (50 μM) with AA resulted in more cell death than either treatment alone. The effect was greater than additive at low concentrations of AA, reducing viability approximately 50% at 1 mM AA. AA was found to directly upregulate mitochondrial uncoupling protein 2 (UCP2), which may explain this potential drug synergism via multi-faceted inhibition of the glycolytic pathway.

CONCLUSION

Targeting the metabolic pathway of GBM via glycolytic inhibition in conjunction with ketogenic diet or exogenous ketone body supplementation warrants further investigation as a promising adjunctive treatment to conventional therapy.

β-hydroxybutyrate Impedes the Progression of Alzheimer's Disease and Atherosclerosis in ApoE-Deficient Mice

β-hydroxybutyrate (β-OHB) has been shown to exert an anti-inflammatory activity. Apolipoprotein-E (ApoE) is strongly associated with atherosclerosis and Alzheimer's disease (AD). This study aimed to explore the therapeutic effect of β-OHB in the brain and the aorta of high-fat diet (HFD)-fed ApoE-deficient mice. We found in Apo-E deficient mice that β-OHB attenuated lipid deposition in the choroid plexus (ChP) and decreased amyloid plaque in the substantia nigra pars compacta. We also found decreased CD68-positive macroglia infiltration of the ChP in β-OHB-treated ApoE-deficient mice. β-OHB treatment ameliorated IgG extravasation into the hippocampal region of the brain. In vitro study using ChP mice cell line revealed that β-OHB attenuated oxidized low-density lipoprotein-induced ApoE-specific differentially expressed inflammatory ChP genes. Treatment with β-OHB reduced aortic plaque formation without affecting blood lipid profiles and decreased serum production of resistin, a well-established risk factor for both AD and atherosclerosis. Thus, the current study suggests and describes the therapeutic potential of β-OHB for the treatment of AD and atherosclerosis.