The protective effect of the ketogenic diet on traumatic brain injury-induced cell death in juvenile rats

Exogenous ketone therapy does not protect brain tissue after moderate-sized intracerebral hemorrhage despite signs of early neurological benefit

Ketone bodies, or ketones, are an alternative energy source and have several nonmetabolic signaling actions, such as inhibiting inflammation. Because of this, exogenous ketone supplementation has been used to help treat various diseases. β-hydroxybutyrate (βHB) is the major ketone body that has reduced neurological injury and brain edema in animal models of ischemic stroke and traumatic brain injury. However, the therapeutic potential of βHB in intracerebral hemorrhage (ICH) has not yet been determined. Here we investigated the effects of exogenous βHB treatment following ICH on inflammation, edema, injury size, and functional outcomes. To do this, we administered 250 mg/kg of βHB (subcutaneously every 12 hours) starting 2 hours after collagenase-induced ICH in rats over 3 experiments. First, we observed that βHB-treated rats had significant reductions in transcript expression of pro-inflammatory markers Il1b (p = 0.0210), Tnfa (p = 0.0108), and Mcp1 (p = 0.0473) 3 days post-ICH. Second, βHB significantly improved neurological deficits measured by the neurological deficit scale on day 3 (p = 0.0416) in another cohort of rats, despite no treatment effect on edema (p = 0.2110). To test whether the effects of acute βHB treatment (for 7 days post-ICH) were chronically sustained, the third experiment used serial behavioural testing which confirmed that βHB significantly improved neurological deficit scores (p = 0.0459) 3 days post-ICH. These effects were not sustained at 7, 14, and 28 days post-ICH (all p≥0.1546). Similarly, βHB treatment did not yield differences in forelimb use asymmetry (all p>0.45) or brain lesion volume (p = 0.3381), the primary endpoint of this study. Thus, our studies show that an acute βHB treatment post-ICH can provide some early signs of functional benefit without evidence of lasting effects or neuroprotection. However, it remains to be tested whether other βHB dosing regimens may favorably affect these and other neurological, behavioral, and biochemical parameters, particularly given the early signals of reduced striatal inflammation.

Ketone Bodies after Cardiac Arrest: A Narrative Review and the Rationale for Use

Cardiac arrest survivors suffer the repercussions of anoxic brain injury, a critical factor influencing long-term prognosis. This injury is characterised by profound and enduring metabolic impairment. Ketone bodies, an alternative energetic resource in physiological states such as exercise, fasting, and extended starvation, are avidly taken up and used by the brain. Both the ketogenic diet and exogenous ketone supplementation have been associated with neuroprotective effects across a spectrum of conditions. These include refractory epilepsy, neurodegenerative disorders, cognitive impairment, focal cerebral ischemia, and traumatic brain injuries. Beyond this, ketone bodies possess a plethora of attributes that appear to be particularly favourable after cardiac arrest. These encompass anti-inflammatory effects, the attenuation of oxidative stress, the improvement of mitochondrial function, a glucose-sparing effect, and the enhancement of cardiac function. The aim of this manuscript is to appraise pertinent scientific literature on the topic through a narrative review. We aim to encapsulate the existing evidence and underscore the potential therapeutic value of ketone bodies in the context of cardiac arrest to provide a rationale for their use in forthcoming translational research efforts.

Non-pharmacological interventions for traumatic brain injury

Heterogeneity and variability of symptoms due to the type, site, age, sex, and severity of injury make each case of traumatic brain injury (TBI) unique. Considering this, a universal treatment strategy may not be fruitful in managing outcomes after TBI. Most of the pharmacological therapies for TBI aim at modifying a particular pathway or molecular process in the sequelae of secondary injury rather than a holistic approach. On the other hand, non-pharmacological interventions such as hypothermia, hyperbaric oxygen, preconditioning with dietary adaptations, exercise, environmental enrichment, deep brain stimulation, decompressive craniectomy, probiotic use, gene therapy, music therapy, and stem cell therapy can promote healing by modulating multiple neuroprotective mechanisms. In this review, we discussed the major non-pharmacological interventions that are being tested in animal models of TBI as well as in clinical trials. We evaluated the functional outcomes of various interventions with an emphasis on the links between molecular mechanisms and outcomes after TBI.

Ketogenic diet for mood disorders from animal models to clinical application

Mood disorders such as major depressive disorder (MDD) and bipolar disorder (BD) are often resistant to current pharmacological treatment. Therefore, various alternative therapeutic approaches including diets are, therefore, under investigation. Ketogenic diet (KD) is effective for treatment-resistant epilepsy and metabolic diseases, however, only a few clinical studies suggest its beneficial effect also for mental disorders. Animal models are a useful tool to uncover the underlying mechanisms of therapeutic effects. Women have a twice-higher prevalence of mood disorders but very little is known about sex differences in nutritional psychiatry. In this review, we aim to summarize current knowledge of the sex-specific effects of KD in mood disorders. Ketone bodies improve mitochondrial functions and suppress oxidative stress, inducing neuroprotective and anti-inflammatory effects which are both beneficial for mental health. Limited data also suggest KD-induced improvement of monoaminergic circuits and hypothalamus-pituitary-adrenal axis-the key pathophysiological pathways of mood disorders. Gut microbiome is an important mediator of the beneficial and detrimental effects of diet on brain functioning and mental health. Gut microbiota composition is affected in mood disorders but its role in the therapeutic effects of different diets, including KD, remains poorly understood. Still little is known about sex differences in the effects of KD on mental health as well as on metabolism and body weight. Some animal studies used both sexes but did not find differences in behavior, body weight loss or gut microbiota composition. More studies, both on a preclinical and clinical level, are needed to better understand sex-specific effects of KD on mental health.

Ketogenic Diet for Neonatal Hypoxic-Ischemic Encephalopathy

The prevalence of neonatal hypoxic-ischemic encephalopathy (HIE), a devastating neurological injury, is increasing; thus, effective treatments and preventions are urgently needed. The underlying pathology of HIE remains unclear; recent research has focused on elucidating key features of the disease. A variety of diseases can be alleviated by consuming a ketogenic diet (KD) despite differences in pathogenesis and features, given the common mechanisms of KD-induced effects. Dietary modification is the most translatable, cost-efficient, and safest approach to treat acute or chronic neurological disorders and reduces reliance on pharmaceutical treatments. Evidence suggests that the KD can exert beneficial effects in animal models and in humans with brain injuries. The efficacy of the KD in preventing neuronal damage, motor alterations, and cognitive decline varies. Moreover, the KD may provide an alternative source of energy, enhance mitochondrial function, and reduce the expression of inflammatory and apoptotic mediators. Thus, this diet has attracted interest as a potential therapy for HIE. This review examined the role of the KD in HIE treatment and described the mechanisms by which ketone bodies (KBs) exert effects under pathological conditions and protect against brain damage; the evidence supports the implementation of dietary interventions as a therapeutic strategy for HIE. Future research should aim to elucidate the underlying mechanisms of the KD in patients with HIE and determine whether the effect of the KD on clinical outcomes can be reproduced in humans.

Ketogenic diets and the nervous system: a scoping review of neurological outcomes from nutritional ketosis in animal studies

OBJECTIVES

Ketogenic diets have reported efficacy for neurological dysfunctions; however, there are limited published human clinical trials elucidating the mechanisms by which nutritional ketosis produces therapeutic effects. The purpose of this present study was to investigate animal models that report variations in nervous system function by changing from a standard animal diet to a ketogenic diet, synthesise these into broad themes, and compare these with mechanisms reported as targets in pain neuroscience to inform human chronic pain trials.

METHODS

An electronic search of seven databases was conducted in July 2020. Two independent reviewers screened studies for eligibility, and descriptive outcomes relating to nervous system function were extracted for a thematic analysis, then synthesised into broad themes.

RESULTS

In total, 170 studies from eighteen different disease models were identified and grouped into fourteen broad themes: alterations in cellular energetics and metabolism, biochemical, cortical excitability, epigenetic regulation, mitochondrial function, neuroinflammation, neuroplasticity, neuroprotection, neurotransmitter function, nociception, redox balance, signalling pathways, synaptic transmission and vascular supply.

DISCUSSION

The mechanisms presented centred around the reduction of inflammation and oxidative stress as well as a reduction in nervous system excitability. Given the multiple potential mechanisms presented, it is likely that many of these are involved synergistically and undergo adaptive processes within the human body, and controlled animal models that limit the investigation to a particular pathway in isolation may reach differing conclusions. Attention is required when translating this information to human chronic pain populations owing to the limitations outlined from the animal research.

Ketogenic Diet: An Effective Treatment Approach for Neurodegenerative Diseases

This review discusses the effects and mechanisms of a ketogenic diet on neurodegenerative diseases on the basis of available evidence. A ketogenic diet refers to a high-fat, mediumprotein, and low-carbohydrate diet that leads to a metabolic shift to ketosis. This review systematically summarizes the scientific literature supporting this effective treatment approach for neurodegenerative diseases, including effects on mitochondrial function, oxidative stress, neuronal apoptosis, neuroinflammation, and the microbiota-gut-brain axis. It also highlights the clinical evidence for the effects of the ketogenic diet in the treatment of Alzheimer's disease, Parkinson's disease, and motor neuron disease. Finally, it discusses the common adverse effects of ketogenic therapy. Although the complete mechanism of the ketogenic diet in the treatment of neurodegenerative diseases remains to be elucidated, its clinical efficacy has attracted many new followers. The ketogenic diet is a good candidate for adjuvant therapy, but its specific applicability depends on the type and the degree of the disease.

A Novel Ketone-Supplemented Diet Improves Recognition Memory and Hippocampal Mitochondrial Efficiency in Healthy Adult Mice

Mitochondrial dysfunction and cognitive impairment are common symptoms in many neurologic and psychiatric disorders, as well as nonpathological aging. Ketones have been suggested as therapeutic for their efficacy in epilepsy and other brain pathologies such as Alzheimer's disease and major depressive disorder. However, their effects on cognitive function in healthy individuals is less established. Here, we explored the mitochondrial and performative outcomes of a novel eight-week ketone-supplemented ketogenic (KETO) diet in healthy adult male and female mice. In a novel object recognition test, KETO mice spent more time with the novel, compared to familiar, object, indicating an improvement in recognition memory. High-resolution respirometry on permeabilized hippocampal tissue returned significant reductions in mitochondrial O2 consumption. No changes in ATP production were observed, yielding a significantly higher ATP:O2 ratio, a measure of mitochondrial efficiency. Together, these findings demonstrate the KETO diet improves hippocampal mitochondrial efficiency. They add to a growing body of evidence that suggests ketones and ketogenic diets are neuroprotective and metabolically and cognitively relevant, even in healthy adults. They also suggest that ketogenic lifestyle changes may be effective strategies for protecting against cognitive decline associated with aging and disease.

Western and ketogenic diets in neurological disorders: can you tell the difference?

The prevalence of obesity tripled worldwide between 1975 and 2016, and it is projected that half of the US population will be overweight by 2030. The obesity pandemic is attributed, in part, to the increasing consumption of the high-fat, high-carbohydrate Western diet, which predisposes to the development of the metabolic syndrome and correlates with decreased cognitive performance. In contrast, the high-fat, low-carbohydrate ketogenic diet has potential therapeutic roles and has been used to manage intractable seizures since the early 1920s. The brain accounts for 25% of total body glucose metabolism and, as a result, is especially susceptible to changes in the types of nutrients consumed. Here, we discuss the principles of brain metabolism with a focus on the distinct effects of the Western and ketogenic diets on the progression of neurological diseases such as epilepsy, Parkinson's disease, Alzheimer's disease, and traumatic brain injury, highlighting the need to further explore the potential therapeutic effects of the ketogenic diet and the importance of standardizing dietary formulations to assure the reproducibility of clinical trials.

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.

Ketogenic Diet as a potential treatment for traumatic brain injury in mice

Traumatic brain injury (TBI) is a brain dysfunction without present treatment. Previous studies have shown that animals fed ketogenic diet (KD) perform better in learning tasks than those fed standard diet (SD) following brain injury. The goal of this study was to examine whether KD is a neuroprotective in TBI mouse model. We utilized a closed head injury model to induce TBI in mice, followed by up to 30 days of KD/SD. Elevated levels of ketone bodies were confirmed in the blood following KD. Cognitive and behavioral performance was assessed post injury and molecular and cellular changes were assessed within the temporal cortex and hippocampus. Y-maze and Novel Object Recognition tasks indicated that mTBI mice maintained on KD displayed better cognitive abilities than mTBI mice maintained on SD. Mice maintained on SD post-injury demonstrated SIRT1 reduction when compared with uninjured and KD groups. In addition, KD management attenuated mTBI-induced astrocyte reactivity in the dentate gyrus and decreased degeneration of neurons in the dentate gyrus and in the cortex. These results support accumulating evidence that KD may be an effective approach to increase the brain’s resistance to damage and suggest a potential new therapeutic strategy for treating TBI.

Ketogenic diet reduces early mortality following traumatic brain injury in Drosophila via the PPARγ ortholog Eip75B

Traumatic brain injury (TBI) is a common neurological disorder whose outcomes vary widely depending on a variety of environmental factors, including diet. Using a Drosophila melanogaster TBI model that reproduces key aspects of TBI in humans, we previously found that the diet consumed immediately following a primary brain injury has a substantial effect on the incidence of mortality within 24 h (early mortality). Flies that receive equivalent primary injuries have a higher incidence of early mortality when fed high-carbohydrate diets versus water. Here, we report that flies fed high-fat ketogenic diet (KD) following TBI exhibited early mortality that was equivalent to that of flies fed water and that flies protected from early mortality by KD continued to show survival benefits weeks later. KD also has beneficial effects in mammalian TBI models, indicating that the mechanism of action of KD is evolutionarily conserved. To probe the mechanism, we examined the effect of KD in flies mutant for Eip75B, an ortholog of the transcription factor PPARγ (peroxisome proliferator-activated receptor gamma) that contributes to the mechanism of action of KD and has neuroprotective effects in mammalian TBI models. We found that the incidence of early mortality of Eip75B mutant flies was higher when they were fed KD than when they were fed water following TBI. These data indicate that Eip75B/PPARγ is necessary for the beneficial effects of KD following TBI. In summary, this work provides the first evidence that KD activates PPARγ to reduce deleterious outcomes of TBI and it demonstrates the utility of the fly TBI model for dissecting molecular pathways that contribute to heterogeneity in TBI outcomes.

Dietary nutrition for neurological disease therapy: Current status and future directions

Adequate food intake and relative abundance of dietary nutrients have undisputed effects on the brain function. There is now substantial evidence that dietary nutrition aids in the prevention and remediation of neurologic symptoms in diverse pathological conditions. The newly described influences of dietary factors on the alterations of mitochondrial dysfunction, epigenetic modification and neuroinflammation are important mechanisms that are responsible for the action of nutrients on the brain health. In this review, we discuss the state of evidence supporting that distinct dietary interventions including dietary supplement and dietary restriction have the ability to tackle neurological disorders using Alzheimer's disease, Parkinson's disease, stroke, epilepsy, traumatic brain injury, amyotrophic lateral sclerosis, Huntington's disease and multiple sclerosis as examples. Additionally, it is also highlighting that diverse potential mechanisms such as metabolic control, epigenetic modification, neuroinflammation and gut-brain axis are of utmost importance for nutrient supply to the risk of neurologic condition and therapeutic response. Finally, we also highlight the novel concept that dietary nutrient intervention reshapes metabolism-epigenetics-immunity cycle to remediate brain dysfunction. Targeting metabolism-epigenetics-immunity network will delineate a new blueprint for combating neurological weaknesses.

Intermittent fasting in paediatric critical illness: The properties and potential beneficial effects of an overnight fast in the PICU

Although evidence for the superiority of continuous feeding over intermittent feeding is lacking, in most paediatric intensive care units (PICU) artificial feeding is administered continuously for 24 h per day. Until now, studies in PICU on intermittent feeding have primarily focused on surrogate endpoints such as nutritional intake and gastro-intestinal complaints and none have studied the effects of an extended fasting period. Intermittent fasting has been proven to have many health benefits in both animal and human studies. The observed beneficial effects are based on multiple metabolic and endocrine changes that are presumed crucial in critical illness as well. One key element is the transition to ketone body metabolism, which, among others, contributes to the stimulation of several cellular pathways involved in stress resistance (neuro)plasticity and mitochondrial biogenesis, and might help preserve brain function. Secondly, the fasting state stimulates the activation of autophagy, a process that is crucial for cellular function and integrity. Of the different intermittent fasting strategies investigated, time-restricted feeding with a daily extended fasting period appears most feasible in the PICU. Moreover, planning the fasting period overnight could help maintain the circadian rhythm. Although not investigated, such an overnight intermittent fasting strategy might improve the metabolic profile, feeding tolerance and perhaps even have beneficial effects on tissue repair, reperfusion injury, muscle weakness, and the immune response. Future studies should investigate practical implications in critically ill children and the optimal duration of the fasting periods, which might be affected by the severity of illness and by age.

The second phase of brain trauma can be controlled by nutraceuticals that suppress DAMP-mediated microglial activation

INTRODUCTION

A delayed second wave of brain trauma is mediated in large part by microglia that are activated to a pro-inflammatory M1 phenotype by DAMP proteins released by dying neurons. These microglia can promote apoptosis or necrosis in neighboring neurons by producing a range of pro-inflammatory cytokines and the deadly oxidant peroxynitrite. This second wave could therefore be mitigated with agents that blunt the post-traumatic M1 activation of microglia and that preferentially promote a pro-healing M2 phenotype.

AREAS COVERED

The literature on nutraceuticals that might have clinical potential in this regard.

EXPERT OPINION

The chief signaling pathway whereby DAMPs promote M1 microglial activation involves activation of toll-like receptor 4 (TLR4), NADPH oxidase, NF-kappaB, and the stress activated kinases JNK and p38. The green tea catechin EGCG can suppress TLR4 expression. Phycocyanobilin can inhibit NOX2-dependent NADPH oxidase, ferulate and melatonin can oppose pro-inflammatory signal modulation by NADPH oxidase-derived oxidants. Long-chain omega-3 fatty acids, the soy isoflavone genistein, the AMPK activator berberine, glucosamine, and ketone bodies can down-regulate NF-kappaB activation. Vitamin D activity can oppose JNK/p38 activation. A sophisticated program of nutraceutical supplementation may have important potential for mitigating the second phase of neuronal death and aiding subsequent healing.

Systematic Review - Neuroprotection of ketosis in acute injury of the mammalian central nervous system: A meta-analysis

To evaluate the neuroprotection exerted by ketosis against acute damage of the mammalian central nervous system (CNS). Search engines were interrogated to identify experimental studies comparing the mitigating effect of ketosis (intervention) versus non-ketosis (control) on acute CNS damage. Primary endpoint was a reduction in mortality. Secondary endpoints were a reduction in neuronal damage and dysfunction, and an 'aggregated advantage' (composite of all primary and secondary endpoints). Hedges' g was the effect measure. Subgroup analyses evaluated the modulatory effect of age, insult type, and injury site. Meta-regression evaluated timing, type, and magnitude of intervention as predictors of neuroprotection. The selected publications were 49 experimental murine studies (period 1979-2020). The intervention reduced mortality (g 2.45, SE 0.48, p < .01), neuronal damage (g 1.96, SE 0.23, p < .01) and dysfunction (g 0.99, SE 0.10, p < .01). Reduction of mortality was particularly pronounced in the adult subgroup (g 2.71, SE 0.57, p < .01). The aggregated advantage of ketosis was stronger in the pediatric (g 3.98, SE 0.71, p < .01), brain (g 1.96, SE 0.18, p < .01), and ischemic insult (g 2.20, SE 0.23, p < .01) subgroups. Only the magnitude of intervention was a predictor of neuroprotection (g 0.07, SE 0.03, p 0.01 per every mmol/L increase in ketone levels). Ketosis exerts a potent neuroprotection against acute damage to the mammalian CNS in terms of reduction of mortality, of neuronal damage and dysfunction. Hematic levels of ketones are directly proportional to the effect size of neuroprotection.

Role of HCA2 in Regulating Intestinal Homeostasis and Suppressing Colon Carcinogenesis

Hydroxycarboxylic acid receptor 2 (HCA₂) is vital for sensing intermediates of metabolism, including β-hydroxybutyrate and butyrate. It also regulates profound anti-inflammatory effects in various tissues, indicating that HCA₂ may serve as an essential therapeutic target for mediating inflammation-associated diseases. Butyrate and niacin, endogenous and exogenous ligands of HCA₂, have been reported to play an essential role in maintaining intestinal homeostasis. HCA₂, predominantly expressed in diverse immune cells, is also present in intestinal epithelial cells (IECs), where it regulates the intricate communication network between diet, microbiota, and immune cells. This review summarizes the physiological role of HCA₂ in intestinal homeostasis and its pathological role in intestinal inflammation and cancer.

The ketone ester, 3-hydroxybutyl-3-hydroxybutyrate, attenuates neurobehavioral deficits and improves neuropathology following controlled cortical impact in male rats

Traumatic brain injury (TBI) is a leading cause of human death and disability with no effective therapy to fully prevent long-term neurological deficits in surviving patients. Ketone ester supplementation is protective in animal models of neurodegeneration, but its efficacy against TBI pathophysiology is unknown. Here, we assessed the neuroprotective effect of the ketone monoester, 3-hydroxybutyl-3-hydroxybutyrate, (KE) in male Sprague Dawley rats (n=32). TBI was induced using the controlled cortical impact (CCI) with Sham animals not receiving the brain impact. KE was administered daily by oral gavage (0.5 ml/kg/day) and provided ad libitum at 0.3% (v/v) in the drinking water. KE supplementation started immediately after TBI and lasted for the duration of the study. Motor and sensory deficits were assessed using the Neurobehavioral Severity Scale-Revised (NSS-R) at four weeks post-injury. The NSS-R total score in CCI + KE (1.2 ± 0.4) was significantly lower than in CCI + water (4.4 ± 0.5). Similarly, the NSS-R motor scores in CCI + KE (0.6 ± 0.7) were significantly lower than CCI + water (2.9 ± 1.5). Although the NSS-R sensory score in the CCI + KE group (0.5 ± 0.2) was significantly lower compared to CCI + water (1.8 ± 0.4), no difference was observed between CCI + water and Sham + water (1.0 ± 0.2) groups. The lesion volume was smaller in the CCI + KE (10 ± 3 mm³) compared to CCI + water (47 ± 11 mm³; p < 0.001). KE significantly decreased Iba1⁺ stained areas in the cortex and hippocampus, and GFAP⁺ stained areas in all brain regions analyzed - prefrontal cortex, hippocampus, cortex, amygdala (p < 0.01). In summary, our results indicate that KE can protect against TBI-induced morphological and functional deficits when administered immediately after an insult.

Ketogenic diet, neuroprotection, and antiepileptogenesis

High fat, low carbohydrate ketogenic diets (KD) have been in use for the treatment of epilepsy for almost a hundred years. Remarkably, seizures that are resistant to conventional anti-seizure drugs can in many cases be controlled by the KD therapy, and it has been shown that many patients with epilepsy become seizure free even after discontinuation of the diet. These findings suggest that KD combine anti-seizure effects with disease modifying effects. In addition to the treatment of epilepsy, KDs are now widely used for the treatment of a wide range of conditions including weight reduction, diabetes, and cancer. The reason for the success of metabolic therapies is based on the synergism of at least a dozen different mechanisms through which KDs provide beneficial activities. Among the newest findings are epigenetic mechanisms (DNA methylation and histone acetylation) through which KD exerts long-lasting disease modifying effects. Here we review mechanisms through which KD can affect neuroprotection in the brain, and how a combination of those mechanisms with epigenetic alterations can attenuate and possibly reverse the development of epilepsy.

Nutritional interventions to improve neurophysiological impairments following traumatic brain injury: A systematic review

Traumatic brain injury (TBI) accounts for significant global health burden. Effects of TBI can become chronic even following mild injury. There is a need to develop effective therapies to attenuate the damaging effects of TBI and improve recovery outcomes. This literature review using a priori criteria (PROSPERO; CRD42018100623) summarized 43 studies between January 1998 and July 2019 that investigated nutritional interventions (NUT) delivered with the objective of altering neurophysiological (NP) outcomes following TBI. Risk of bias was assessed for included studies, and NP outcomes recorded. The systematic search resulted in 43 of 3,748 identified studies met inclusion criteria. No studies evaluated the effect of a NUT on NP outcomes of TBI in humans. Biomarkers of morphological changes and apoptosis, oxidative stress, and plasticity, neurogenesis, and neurotransmission were the most evaluated NP outcomes across the 43 studies that used 2,897 animals. The risk of bias was unclear in all reviewed studies due to poorly detailed methodology sections. Taking these limitations into account, anti-oxidants, branched chain amino acids, and ω-3 polyunsaturated fatty acids have shown the most promising pre-clinical results for altering NP outcomes following TBI. Refinement of pre-clinical methodologies used to evaluate effects of interventions on secondary damage of TBI would improve the likelihood of translation to clinical populations.

The Ketogenic Diet in the Treatment of Post-concussion Syndrome-A Feasibility Study

Concussion is the most common form of mild traumatic brain injury (mTBI). Although most patients' symptoms resolve within a month, patients with post-concussion syndrome (PCS) may continue to experience symptoms for years and have limited treatment options. This pilot study assessed the feasibility and symptom-related effects of a ketogenic diet (KD) in patients with PCS symptoms. The Ketogenic Diet in Post-Concussion Syndrome (KD-PCS) was a single-arm trial of a 2-month KD high in non-starchy vegetables and supplemented with medium-chain triglyceride (MCT) oil. Macronutrient targets were ≥70% fat, ≤10% carbohydrate, and the remainder as protein as energy. We assessed feasibility by daily self-reported measure of urine acetoacetate and collection of 3-day food records and serum beta-hydroxybutyrate at multiple timepoints. We assessed symptoms by administering the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) and Modified Balance Error Scoring System (M-BESS) at baseline and month 2 and the Post-Concussion Symptom Scale (PCSS) at baseline, month 1, and month 2. Fourteen participants enrolled in the KD-PCS. Twelve participants completed the study and 11 implemented the KD (73% fat, 9% carbohydrate, and 18% protein) and achieved ketosis. One participant complained of MCT-related diarrhea that resolved and another reported nausea and fatigue that resulted in withdrawal from the study. Among compliant participants, the visual memory domain of the ImPACT improved by 12 points (p = 0.02) and PCSS scores improved by 9 points, although not statistically significant. This pilot trial suggests that the KD is a feasible experimental treatment for PCS and justifies further study of its efficacy.

Ketogenic Diet Provided During Three Months Increases KCC2 Expression but Not NKCC1 in the Rat Dentate Gyrus

Ketogenic diet, a high fat and low carbohydrate diet, has been used as a non-pharmacological treatment in refractory epilepsy since 1920. In recent years, it has demonstrated to be effective in the treatment of numerous neurological and non-neurological diseases. Some neurological and neuropsychiatric disorders are known to be caused by gamma-aminobutyric acid (GABA)-mediated neurotransmission dysfunction. The strength and polarity of GABA-mediated neurotransmission are determined by the intracellular chloride concentration, which in turn is regulated by cation-chloride cotransporters NKCC1 and KCC2. Currently, it is unknown if the effect of ketogenic diet is due to the modulation of these cotransporters. Thus, we analyzed the effect of a ketogenic diet on the cation-chloride cotransporters expression in the dentate gyrus. We estimated the total number of NKCC1 immunoreactive (NKCC1-IR) neuronal and glial cells by stereology and determined KCC2 labeling intensity by densitometry in the molecular and granule layers as well as in the hilus of dentate gyrus of rats fed with normal or ketogenic diet for 3 months. The results indicated that ketogenic diet provided during 3 months increased KCC2 expression, but not NKCC1 in the dentate gyrus of the rat. The significant increase of KCC2 expression could explain, at least in part, the beneficial effect of ketogenic diet in the diseases where the GABAergic system is altered by increasing its inhibitory efficiency.

Application of ketogenic diets for pediatric neurocritical care

In this review, we summarize the general mechanisms of the ketogenic diet, and the application of a ketogenic diet in pediatric intensive care units for the neurological disorders of children and young infants. A ketogenic diet is a high-fat, low-carbohydrate, adequate-protein diet. It can alter the primary cerebral energy metabolism from glucose to ketone bodies, which involves multiple mechanisms of antiepileptic action, antiepileptogenic properties, neuro-protection, antioxidant and anti-inflammatory effects, and it is potentially a disease-modifying intervention. Although a ketogenic diet is typically used for the chronic stage of pharmacoresistant of epilepsy, recent studies have shown its efficacy in patients with the acute stage of refractory/super-refractory status epilepticus. The application of a ketogenic diet in pediatric intensive care units is a challenge because of the critical status of the patients, who are often in a coma or have a nothing by mouth order. Moreover, a ketogenic diet needs to be started early and sometimes through parenteral administration in patients with critical conditions such as refractory status epilepticus or febrile infection-related epilepsy syndrome. Animal models and some case reports have shown that the neuro-protective effects of a ketogenic diet can be extended to other emergent neurological diseases, such as traumatic brain injury and ischemic stroke.

Therapeutic alternative of the ketogenic Mediterranean diet to improve mitochondrial activity in Amyotrophic Lateral Sclerosis (ALS): A Comprehensive Review

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease which is pathogenically based on the mitochondrial alteration of motor neurons, causing progressive neuron death. While ALS is characterized by enormous oxidative stress, the Mediterranean diet has been seen to have high antioxidant power. Therefore, the aim of this study is to determine how the Mediterranean diet can improve mitochondrial activity, establishing the specific nutrients and, in addition, observing the pathogenic mechanisms related to the disease that would achieve this improvement. To this end, a comprehensive review of the literature was performed using PubMed. KBs have been observed to have a neuroprotective effect to improve energy balance, increasing survival and the number of motor neurons. This ketogenesis can be achieved after following a Mediterranean diet which is associated with great benefits in other neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and ALS. These benefits are due to the high antioxidant power especially based on polyphenols contained mainly in olive oil, wine, nuts, or berries. In short, KBs could be considered as a promising option to treat ALS, representing an alternative source to glucose in motor neurons by providing neuroprotection. In addition, treatment results can be improved as ketogenesis can be achieved (increase in KBs) by following a Mediterranean diet, thanks to the high antioxidant properties which, at the same time, would improve the high oxidative stress that characterizes the disease.

Dietary Supplementation With the Ketogenic Diet Metabolite Beta-Hydroxybutyrate Ameliorates Post-TBI Aggression in Young-Adult Male Drosophila

Traumatic brain injury (TBI), caused by repeated concussive head trauma can induce chronic traumatic encephalopathy (CTE), a neurodegenerative disease featuring behavioral symptoms ranging from cognitive deficits to elevated aggression. In a Drosophila model, we used a high-impact trauma device (Katzenberger et al., 2013, 2015) to induce TBI-like symptoms and to study post-TBI behavioral outcomes. Following TBI, aggression in banged male flies was significantly elevated as compared with that in unbanged flies. These increases in aggressive behavior were not the result of basal motility changes, as measured by a negative geotaxis assay. In addition, the increase in post-TBI aggression appeared to be specific to concussive trauma: neither cold exposure nor electric shock-two alternate types of trauma-significantly elevated aggressive behavior in male-male pairs. Various forms of dietary therapy, especially the high-fat, low-carbohydrate ketogenic diet (KD), have recently been explored for a wide variety of neuropathies. We thus hypothesized that putatively neuroprotective dietary interventions might be able to suppress post-traumatic elevations in aggressive behavior in animals subjected to head-trauma-inducing strikes, or "bangs". We supplemented a normal high-carbohydrate Drosophila diet with the KD metabolite beta-hydroxybutyrate (β-HB)-a ketone body (KB). Banged flies raised on a KB-supplemented diet exhibited a marked reduction in aggression, whereas aggression in unbanged flies was equivalent whether dieted with KB supplements or not. Pharmacological blockade of the ATP-sensitive potassium (KATP) channel abrogated KB effects reducing post-TBI aggression while pharmacological activation mimicked them, suggesting a mechanism by which KBs act in this model. KBs did not significantly extend lifespan in banged flies, but markedly extended lifespan in unbanged flies. We have thus developed a functional model for the study of post-TBI elevations of aggression. Further, we conclude that dietary interventions may be a fruitful avenue for further exploration of treatments for TBI- and CTE-related cognitive-behavioral symptoms.

Potential for diet to prevent and remediate cognitive deficits in neurological disorders

The pathophysiology of many neurological disorders involves oxidative stress, neuroinflammation, and mitochondrial dysfunction. There is now substantial evidence that diet can decrease these forms of pathophysiology, and an emerging body of literature relatedly suggests that diet can also prevent or even remediate the cognitive deficits observed in neurological disorders that exhibit such pathology (eg, Alzheimer's disease, multiple sclerosis, age-related cognitive decline, epilepsy). The current review summarizes the emerging evidence in relation to whole diets prominent in the scientific literature-ketogenic, caloric restriction, high polyphenol, and Mediterranean diets-and provides a discussion of the possible underlying neurophysiological mechanisms.

Dysregulated Glucose Metabolism as a Therapeutic Target to Reduce Post-traumatic Epilepsy

Traumatic brain injury (TBI) is a significant cause of disability worldwide and can lead to post-traumatic epilepsy. Multiple molecular, cellular, and network pathologies occur following injury which may contribute to epileptogenesis. Efforts to identify mechanisms of disease progression and biomarkers which predict clinical outcomes have focused heavily on metabolic changes. Advances in imaging approaches, combined with well-established biochemical methodologies, have revealed a complex landscape of metabolic changes that occur acutely after TBI and then evolve in the days to weeks after. Based on this rich clinical and preclinical data, combined with the success of metabolic therapies like the ketogenic diet in treating epilepsy, interest has grown in determining whether manipulating metabolic activity following TBI may have therapeutic value to prevent post-traumatic epileptogenesis. Here, we focus on changes in glucose utilization and glycolytic activity in the brain following TBI and during seizures. We review relevant literature and outline potential paths forward to utilize glycolytic inhibitors as a disease-modifying therapy for post-traumatic epilepsy.

Ketogenic Diets for Adult Neurological Disorders

The current review highlights the evidence supporting the use of ketogenic diet therapies in the management of a growing number of neurological disorders in adults. An overview of the scientific literature supporting posited mechanisms of therapeutic efficacy is presented including effects on neurotransmission, oxidative stress, and neuro-inflammation. The clinical evidence supporting ketogenic diet use in the management of adult epilepsy, malignant glioma, Alzheimer's disease, migraine headache, motor neuron disease, and other neurologic disorders is highlighted and reviewed. Lastly, common adverse effects of ketogenic therapy in adults, including gastrointestinal symptoms, weight loss, and transient dyslipidemia are discussed.

Coordination of GPR40 and Ketogenesis Signaling by Medium Chain Fatty Acids Regulates Beta Cell Function

Diabetes prevalence increases with age, and β-cell dysfunction contributes to the incidence of the disease. Dietary lipids have been recognized as contributory factors in the development and progression of the disease. Unlike long chain triglycerides, medium chain triglycerides (MCT) increase fat burning in animal and human subjects as well as serum C-peptide in type 2 diabetes patients. We evaluated the beneficial effects of MCT on β-cells in vivo and in vitro. MCT improved glycemia in aged rats via β-cell function assessed by measuring insulin secretion and content. In β-cells, medium chain fatty acid (MCFA)-C10 activated fatty acid receptor 1 FFAR1/GPR40, while MCFA-C8 induced mitochondrial ketogenesis and the C8:C10 mixture improved β cell function. We showed that GPR40 signaling positively impacts ketone body production in β-cells, and chronic treatment with β-hydroxybutyrate (BHB) improves β-cell function. We also showed that BHB and MCFA help β-cells recover from lipotoxic stress by improving mitochondrial function and increasing the expression of genes involved in β-cell function and insulin biogenesis, such as Glut2, MafA, and NeuroD1 in primary human islets. MCFA offers a therapeutic advantage in the preservation of β-cell function as part of a preventative strategy against diabetes in at risk populations.

Neuroprotective effect of berberine agonist against impairment of learning and memory skills in severe traumatic brain injury via Sirt1/p38 MAPK expression

Berberine has multiple clinical applications, including the treatment of tumors, diabetes, cardiovascular diseases, hyperlipidemia, inflammation, bacterial and viral infections, cerebral ischemic injuries, mental diseases, Alzheimer's disease and osteoporosis. In the present study, the neuroprotective effect of berberine agonist rescue learning and memory in severe traumatic brain injury (TBI), and the possible mechanism underlying these observations was explored. The protective effect of berberine agonist significantly recovered learning and memory skills, attenuated brain edema and inhibited matrix metalloproteinase‑3 and ‑9 protein expression in mice with severe TBI. Berberine agonist significantly reduced inflammation, oxidative stress and apoptosis levels in mice with severe TBI. Berberine agonist promoted choline acetyltransferase activity and inhibited the activity of acetylcholinesterase. Collectively, results of the present study revealed that the neuroprotective effect of berberine agonist rescues learning and memory skills in severe TBI.

The ketogenic diet as a treatment for traumatic brain injury: a scoping review

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide. The ketogenic diet (KD) has been identified as a potential therapy to enhance recovery after TBI. The purpose of this study is to complete a scoping review and synthesize the evidence regarding the KD and its therapeutic effects in TBI. The methodological framework of Arksey and O'Malley was employed. Databases searched include Medline, EMBASE, CCRCT, CINAHL and WebOfScience. Two reviewers independently screened titles, abstracts and full texts in a two-step screening protocol to determine inclusion. Abstracted data included study setting and therapeutic mechanism. The KD was demonstrated to reduce cerebral oedema, apoptosis, improve cerebral metabolism and behavioural outcomes in rodent TBIs. Additionally, the KD affected rodent TBIs in an age-dependent manner. Due to a lack of relevant outcome measures, the human trials did not establish much evidence with respect to the KD as a treatment for TBI; only its safety was established. The KD is an effective treatment for TBI recovery in rats and shows potential in humans. Future research should aim to better elucidate the KD's mechanisms of action in human TBIs and determine if the KD's effectiveness on clinical outcomes can be reproduced in humans.

Metabolic Dysfunctions in Amyotrophic Lateral Sclerosis Pathogenesis and Potential Metabolic Treatments

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease primarily characterized by loss of motor neurons in brain and spinal cord. The death of motor neurons leads to denervation of muscle which in turn causes muscle weakness and paralysis, decreased respiratory function and eventually death. Growing evidence indicates disturbances in energy metabolism in patients with ALS and animal models of ALS, which are likely to contribute to disease progression. Particularly, defects in glucose metabolism and mitochondrial dysfunction limit the availability of ATP to CNS tissues and muscle. Several metabolic approaches improving mitochondrial function have been investigated in vitro and in vivo and showed varying effects in ALS. The effects of metabolic approaches in ALS models encompass delays in onset of motor symptoms, protection of motor neurons and extension of survival, which signifies an important role of metabolism in the pathogenesis of the disease. There is now an urgent need to test metabolic approaches in controlled clinical trials. In addition, more detailed studies to better characterize the abnormalities in energy metabolism in patients with ALS and ALS models are necessary to develop metabolically targeted effective therapies that can slow the progression of the disease and prolong life for patients with ALS.

Anti-inflammatory effects of the hydroxycarboxylic acid receptor 2

The hydroxycarboxylic acid receptors (HCA1-3) are a family of G-protein-coupled receptors that are critical for sensing endogenous intermediates of metabolism. All three receptors are predominantly expressed on adipocytes and mediate anti-lipolytic effects. In addition to adipocytes, HCA2 is highly expressed on immune cells, including macrophages, monocytes, neutrophils and dermal dendritic cells, among other cell types. The endogenous ligand for HCA2 is beta-hydroxybutyrate (β-OHB), a ketone body produced by the liver through β-oxidation when an individual is in a negative energy balance. Recent studies demonstrate that HCA2 mediates profound anti-inflammatory effects in a variety of tissues, indicating that HCA2 may be an important therapeutic target for treating inflammatory disease processes. This review summarizes the roles of HCA2 on inflammation in a number of tissues and clinical states.

Metabolic Response of Pediatric Traumatic Brain Injury

Traumatic brain injury (TBI) in the pediatric brain presents unique challenges as the complex cascades of metabolic and biochemical responses to TBI are further complicated ongoing maturational changes of the developing brain. TBIs of all severities have been shown to significantly alter metabolism and hormones which impair the ability of the brain to process glucose for cellular energy. Under these conditions, the brain's primary fuel (glucose) becomes a less favorable fuel and the ability of the younger brain to revert to ketone metabolism can an advantage. This review addresses the potential of alternative substrate metabolic intervention as a logical pediatric TBI neuroprotective strategy.

Alpha lipoic acid inhibits neural apoptosis via a mitochondrial pathway in rats following traumatic brain injury

Alpha lipoic acid (ALA) is a powerful antioxidant that has proven protective effects against brain damage following a traumatic brain injury (TBI) in rats. However, the molecular mechanisms underlying these effects are not well understood. This study investigated the effect of ALA on neural apoptosis and the potential mechanism of these effects in the weight-drop model of TBI in male Sprague-Dawley rats that were treated with ALA (20 or 100 mg/kg) or vehicle via intragastric administration 30 min after TBI. Brain samples were collected 48 h later for analysis. ALA treatment resulted in a downregulation of caspase-3 expression, reduced the number of positive cells in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay and improved neuronal survival. Furthermore, the level of malondialdehyde and glutathione peroxidase activity were restored, while Bcl-2-associated X protein translocation to mitochondria and cytochrome c release into the cytosol were reduced by ALA treatment. These results demonstrate that ALA improves neurological outcome in rats by protecting neural cell against apoptosis via a mechanism that involves the mitochondria following TBI.

Nutritional or pharmacological activation of HCA(2) ameliorates neuroinflammation

Neuroinflammation is a pathology common to many neurological diseases, including multiple sclerosis (MS) and stroke. However, therapeutic attempts to modulate neuroinflammation have proved difficult. Neuroinflammatory cells express HCA2, a receptor for the endogenous neuroprotective ketone body β-hydroxybutyrate (BHB) as well as for the drugs dimethyl fumarate (DMF) and nicotinic acid, which have established efficacy in the treatment of MS and experimental stroke, respectively. This review summarizes the evidence that HCA2 is involved in the therapeutic effects of DMF, nicotinic acid, and ketone bodies in reducing neuroinflammation. Furthermore, we discuss the mechanisms underlying the beneficial effects of HCA2 activation in neuroinflammatory diseases and the therapeutic potential of recently developed synthetic ligands of HCA2.

Ketogenic diets, mitochondria, and neurological diseases

The ketogenic diet (KD) is a broad-spectrum therapy for medically intractable epilepsy and is receiving growing attention as a potential treatment for neurological disorders arising in part from bioenergetic dysregulation. The high-fat/low-carbohydrate "classic KD", as well as dietary variations such as the medium-chain triglyceride diet, the modified Atkins diet, the low-glycemic index treatment, and caloric restriction, enhance cellular metabolic and mitochondrial function. Hence, the broad neuroprotective properties of such therapies may stem from improved cellular metabolism. Data from clinical and preclinical studies indicate that these diets restrict glycolysis and increase fatty acid oxidation, actions which result in ketosis, replenishment of the TCA cycle (i.e., anaplerosis), restoration of neurotransmitter and ion channel function, and enhanced mitochondrial respiration. Further, there is mounting evidence that the KD and its variants can impact key signaling pathways that evolved to sense the energetic state of the cell, and that help maintain cellular homeostasis. These pathways, which include PPARs, AMP-activated kinase, mammalian target of rapamycin, and the sirtuins, have all been recently implicated in the neuroprotective effects of the KD. Further research in this area may lead to future therapeutic strategies aimed at mimicking the pleiotropic neuroprotective effects of the KD.

The collective therapeutic potential of cerebral ketone metabolism in traumatic brain injury

The postinjury period of glucose metabolic depression is accompanied by adenosine triphosphate decreases, increased flux of glucose through the pentose phosphate pathway, free radical production, activation of poly-ADP ribose polymerase via DNA damage, and inhibition of glyceraldehyde dehydrogenase (a key glycolytic enzyme) via depletion of the cytosolic NAD pool. Under these post-brain injury conditions of impaired glycolytic metabolism, glucose becomes a less favorable energy substrate. Ketone bodies are the only known natural alternative substrate to glucose for cerebral energy metabolism. While it has been demonstrated that other fuels (pyruvate, lactate, and acetyl-L-carnitine) can be metabolized by the brain, ketones are the only endogenous fuel that can contribute significantly to cerebral metabolism. Preclinical studies employing both pre- and postinjury implementation of the ketogenic diet have demonstrated improved structural and functional outcome in traumatic brain injury (TBI) models, mild TBI/concussion models, and spinal cord injury. Further clinical studies are required to determine the optimal method to induce cerebral ketone metabolism in the postinjury brain, and to validate the neuroprotective benefits of ketogenic therapy in humans.

The pathophysiology of traumatic brain injury at a glance

Traumatic brain injury (TBI) is defined as an impact, penetration or rapid movement of the brain within the skull that results in altered mental state. TBI occurs more than any other disease, including breast cancer, AIDS, Parkinson's disease and multiple sclerosis, and affects all age groups and both genders. In the US and Europe, the magnitude of this epidemic has drawn national attention owing to the publicity received by injured athletes and military personnel. This increased public awareness has uncovered a number of unanswered questions concerning TBI, and we are increasingly aware of the lack of treatment options for a crisis that affects millions. Although each case of TBI is unique and affected individuals display different degrees of injury, different regional patterns of injury and different recovery profiles, this review and accompanying poster aim to illustrate some of the common underlying neurochemical and metabolic responses to TBI. Recognition of these recurrent features could allow elucidation of potential therapeutic targets for early intervention.

Traumatic brain injury and diet

Increasing attention is being paid to nutritional and metabolic management of traumatic brain injury patients. The gross metabolic changes that occur after injury have been found to be influenced by both macronutrients, that is, dietary ratios of fat, carbohydrates, and protein, and micronutrients, for example, vitamins and minerals. Alterations in diet and nutritional strategies have been shown to decrease both morbidity and mortality after injury. Despite this knowledge, defining optimal nutritional support following traumatic brain injury continues to be an ongoing challenge.

Caprylic triglyceride as a novel therapeutic approach to effectively improve the performance and attenuate the symptoms due to the motor neuron loss in ALS disease

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of motor neurons causing progressive muscle weakness, paralysis, and finally death. ALS patients suffer from asthenia and their progressive weakness negatively impacts quality of life, limiting their daily activities. They have impaired energy balance linked to lower activity of mitochondrial electron transport chain enzymes in ALS spinal cord, suggesting that improving mitochondrial function may present a therapeutic approach for ALS. When fed a ketogenic diet, the G93A ALS mouse shows a significant increase in serum ketones as well as a significantly slower progression of weakness and lower mortality rate. In this study, we treated SOD1-G93A mice with caprylic triglyceride, a medium chain triglyceride that is metabolized into ketone bodies and can serve as an alternate energy substrate for neuronal metabolism. Treatment with caprylic triglyceride attenuated progression of weakness and protected spinal cord motor neuron loss in SOD1-G93A transgenic animals, significantly improving their performance even though there was no significant benefit regarding the survival of the ALS transgenic animals. We found that caprylic triglyceride significantly promoted the mitochondrial oxygen consumption rate in vivo. Our results demonstrated that caprylic triglyceride alleviates ALS-type motor impairment through restoration of energy metabolism in SOD1-G93A ALS mice, especially during the overt stage of the disease. These data indicate the feasibility of using caprylic acid as an easily administered treatment with a high impact on the quality of life of ALS patients.

The ketogenic diet as a treatment paradigm for diverse neurological disorders

Dietary and metabolic therapies have been attempted in a wide variety of neurological diseases, including epilepsy, headache, neurotrauma, Alzheimer disease, Parkinson disease, sleep disorders, brain cancer, autism, pain, and multiple sclerosis. The impetus for using various diets to treat - or at least ameliorate symptoms of - these disorders stems from both a lack of effectiveness of pharmacological therapies, and also the intrinsic appeal of implementing a more "natural" treatment. The enormous spectrum of pathophysiological mechanisms underlying the aforementioned diseases would suggest a degree of complexity that cannot be impacted universally by any single dietary treatment. Yet, it is conceivable that alterations in certain dietary constituents could affect the course and impact the outcome of these brain disorders. Further, it is possible that a final common neurometabolic pathway might be influenced by a variety of dietary interventions. The most notable example of a dietary treatment with proven efficacy against a neurological condition is the high-fat, low-carbohydrate ketogenic diet (KD) used in patients with medically intractable epilepsy. While the mechanisms through which the KD works remain unclear, there is now compelling evidence that its efficacy is likely related to the normalization of aberrant energy metabolism. The concept that many neurological conditions are linked pathophysiologically to energy dysregulation could well provide a common research and experimental therapeutics platform, from which the course of several neurological diseases could be favorably influenced by dietary means. Here we provide an overview of studies using the KD in a wide panoply of neurologic disorders in which neuroprotection is an essential component.

The nervous system and metabolic dysregulation: emerging evidence converges on ketogenic diet therapy

A link between metabolism and brain function is clear. Since ancient times, epileptic seizures were noted as treatable with fasting, and historical observations of the therapeutic benefits of fasting on epilepsy were confirmed nearly 100 years ago. Shortly thereafter a high fat, low-carbohydrate ketogenic diet (KD) debuted as a therapy to reduce seizures. This strict regimen could mimic the metabolic effects of fasting while allowing adequate caloric intake for ongoing energy demands. Today, KD therapy, which forces predominantly ketone-based rather than glucose-based metabolism, is now well-established as highly successful in reducing seizures. Cellular metabolic dysfunction in the nervous system has been recognized as existing side-by-side with nervous system disorders - although often with much less obvious cause-and-effect as the relationship between fasting and seizures. Rekindled interest in metabolic and dietary therapies for brain disorders complements new insight into their mechanisms and broader implications. Here we describe the emerging relationship between a KD and adenosine as a way to reset brain metabolism and neuronal activity and disrupt a cycle of dysfunction. We also provide an overview of the effects of a KD on cognition and recent data on the effects of a KD on pain, and explore the relative time course quantified among hallmark metabolic changes, altered neuron function and altered animal behavior assessed after diet administration. We predict continued applications of metabolic therapies in treating dysfunction including and beyond the nervous system.

Cerebral ketone metabolism during development and injury

Cerebral metabolism of ketones is a normal part of the process of brain development. While the mature brain relies on glucose as a primary fuel source, metabolism of ketone bodies remains an alternative energy source under conditions of starvation. The neuroprotective properties of brain ketone metabolism make this alternative substrate a viable therapeutic option for various pathologies. Since the ability to revert to utilizing ketones as an alternative substrate is greatest in the younger post-weaned brain, this particular therapeutic approach remains an untapped resource particularly for pediatric pathological conditions.

A ketogenic diet reduces long-term potentiation in the dentate gyrus of freely behaving rats

Ketogenic diets are very low in carbohydrates and can reduce epileptic seizures significantly. This dietary therapy is particularly effective in pediatric and drug-resistant epilepsy. Hypothesized anticonvulsant mechanisms of ketogenic diets focus on increased inhibition and/or decreased excitability/excitation. Either of these consequences might not only reduce seizures, but also could affect normal brain function and synaptic plasticity. Here, we characterized effects of a ketogenic diet on hippocampal long-term potentiation, a widely studied form of synaptic plasticity. Adult male rats were placed on a control or ketogenic diet for 3 wk before recording. To maintain the most physiological conditions possible, we assessed synaptic transmission and plasticity using chronic in vivo recordings in freely behaving animals. Rats underwent stereotaxic surgery to chronically implant a recording electrode in the hippocampal dentate gyrus and a stimulating electrode in the perforant path; they recovered for 1 wk. After habituation and stable baseline recording, 5-Hz theta-burst stimulation was delivered to induce long-term potentiation. All animals showed successful plasticity, demonstrating that potentiation was not blocked by the ketogenic diet. Compared with rats fed a control diet, rats fed a ketogenic diet demonstrated significantly diminished long-term potentiation. This decreased potentiation lasted for at least 48 h. Reduced potentiation in ketogenic diet-fed rats is consistent with a general increase in neuronal inhibition (or decrease in excitability) and decreased seizure susceptibility. A better understanding of the effects of ketogenic diets on synaptic plasticity and learning is important, as diet-based therapy is often prescribed to children with epilepsy.