Therapeutic Potential of Exogenous Ketone Supplement Induced Ketosis in the Treatment of Psychiatric Disorders: Review of Current Literature

The Potential Effects of the Ketogenic Diet in the Prevention and Co-Treatment of Stress, Anxiety, Depression, Schizophrenia, and Bipolar Disorder: From the Basic Research to the Clinical Practice

BACKGROUND

The ketogenic diet (KD) has been highly developed in the past for the treatment of epileptic pathological states in children and adults. Recently, the current re-emergence in its popularity mainly focuses on the therapy of cardiometabolic diseases. The KD can also have anti-inflammatory and neuroprotective activities which may be applied to the prevention and/or co-treatment of a diverse range of psychiatric disorders.

PURPOSE

This is a comprehensive literature review that intends to critically collect and scrutinize the pre-existing research basis and clinical data of the potential advantageous impacts of a KD on stress, anxiety, depression, schizophrenia and bipolar disorder.

METHODS

This literature review was performed to thoroughly represent the existing research in this topic, as well as to find gaps in the international scientific community. In this aspect, we carefully investigated the ultimate scientific web databases, e.g., PubMed, Scopus, and Web of Science, to derive the currently available animal and clinical human surveys by using efficient and representative keywords.

RESULTS

Just in recent years, an increasing amount of animal and clinical human surveys have focused on investigating the possible impacts of the KD in the prevention and co-treatment of depression, anxiety, stress, schizophrenia, and bipolar disorder. Pre-existing basic research with animal studies has consistently demonstrated promising results of the KD, showing a propensity to ameliorate symptoms of depression, anxiety, stress, schizophrenia, and bipolar disorder. However, the translation of these findings to clinical settings presents a more complex issue. The majority of the currently available clinical surveys seem to be moderate, usually not controlled, and have mainly assessed the short-term effects of a KD. In addition, some clinical surveys appear to be characterized by enormous dropout rates and significant absence of compliance measurement, as well as an elevated amount of heterogeneity in their methodological design.

CONCLUSIONS

Although the currently available evidence seems promising, it is highly recommended to accomplish larger, long-term, randomized, double-blind, controlled clinical trials with a prospective design, in order to derive conclusive results as to whether KD could act as a potential preventative factor or even a co-treatment agent against stress, anxiety, depression, schizophrenia, and bipolar disorder. Basic research with animal studies is also recommended to examine the molecular mechanisms of KD against the above psychiatric diseases.

Targeting inflammasome complexes as a novel therapeutic strategy for mood disorders

INTRODUCTION

Inflammasome complexes, especially NLRP3, have gained great attention as a potential therapeutic target in mood disorders. NLRP3 triggers a caspase 1-dependent release of the inflammatory cytokines IL-1β and IL-18, and seems to interact with purinergic and kynurenine pathways, all of which are implicated in mood disorders development and progression.

AREAS COVERED

Emerging evidence supports NLRP3 inflammasome as a promising pharmacological target for mood disorders. We discussed the available evidence from animal models and human studies and provided a reflection on drawbacks and perspectives for this novel target.

EXPERT OPINION

Several studies have supported the involvement of NLRP3 inflammasome in MDD. However, most of the evidence comes from animal models. The role of NLRP3 inflammasome in BD as well as its anti-manic properties is not very clear and requires further exploration. There is evidence of anti-manic effects of P2×R7 antagonists associated with reduction in the brain levels of IL-1β and TNF-α in a murine model of mania. The involvement of other NLRP3 inflammasome expressing cells besides microglia, like astrocytes, and of other inflammasome complexes in mood disorders also deserves further investigation. Preclinical and clinical characterization of NLRP3 and other inflammasomes in mood disorders is needed before considering translational approaches, including clinical trials.

Prevalence of Diabetes, Ketosis, and Ketoacidosis and Their Correlation With Mortality in Critical COVID-19 Patients: A Single-Center Retrospective Study

Aim We aimed to find out the prevalence of diabetes, ketosis, and ketoacidosis in coronavirus disease 2019 (COVID-19) critically ill patients and to explore the clinical impact of the development of ketosis and ketoacidosis on the outcome of COVID-19 critically ill patients and identify them as potential risk factors for these patients. Methods We collected data on COVID-19 patients admitted to the intensive care unit (ICU) retrospectively. The study population will be classified into two groups based on the presence of diabetes or ketosis. Results The study comprises data on 253 ICU patients admitted with COVID-19 pneumonia. Two hundred patients (79.05%) had diabetes or prediabetes on admission. Seventy-six patients (30%) presented with ketosis. Nine patients had progressed to diabetic ketoacidosis during their ICU stay. Concerning the outcome, among 150 patients who died (59.3%), there was significantly higher mortality among the ketotic patients (69.7%) compared to nonketotic patients (54.8%) with a P-value < 0.027. We noted that the peak blood glucose level during ICU stay was statistically significantly higher in nonsurvivors (mean 345 mg/dl) compared to survivors (mean 298 mg/dl) with a P-value of 0.006. Our data showed that peak serum levels of lactate, procalcitonin (PCT), C-reactive protein, white blood cells (WBC), D dimer, and lactate dehydrogenase strongly positively correlated to the length of ICU stay. We used the ROC curve (receiver operating characteristic curve) to assess the relation between many laboratories and mortality. We noted that uncontrolled hyperglycemia and other laboratory variables are significant predictors of mortality of COVID-19 patients (e.g., peak blood glucose (P = 0.004), PCT (P = 0.047), and P < 0.001 of other laboratories (e.g. lactate, PH, WBC, D dimer, ferritin). Conclusion We reported a high prevalence of diabetes and ketosis among COVID-19 patients admitted to the ICU. Ketosis is associated with an increased mortality risk. Uncontrolled hyperglycemia is a significant predictor of mortality in critically ill COVID-19 patients.

Ketogenic therapy towards precision medicine for brain diseases

Precision nutrition and nutrigenomics are emerging in the development of therapies for multiple diseases. The ketogenic diet (KD) is the most widely used clinical diet, providing high fat, low carbohydrate, and adequate protein. KD produces ketones and alters the metabolism of patients. Growing evidence suggests that KD has therapeutic effects in a wide range of neuronal diseases including epilepsy, neurodegeneration, cancer, and metabolic disorders. Although KD is considered to be a low-side-effect diet treatment, its therapeutic mechanism has not yet been fully elucidated. Also, its induced keto-response among different populations has not been elucidated. Understanding the ketone metabolism in health and disease is critical for the development of KD-associated therapeutics and synergistic therapy under any physiological background. Here, we review the current advances and known heterogeneity of the KD response and discuss the prospects for KD therapy from a precision nutrition perspective.

Research progress in mitochondrial quality control in schizophrenia

Mitochondria are the main site of energy metabolism within cells, generating a substantial amount of ATP to supply energy to the human body. Research has shown that alterations in mitochondrial structure and function exist in individuals with schizophrenia, suggesting their potential impact on the onset of psychiatric disorders and clinical treatment efficacy. Therefore, understanding the research progress on the genetic mechanisms, pathological processes, image manifestations of schizophrenia and mitochondrial quality control, and summarizing the relevant evidence of mitochondrial-related targets as potential therapeutic targets for schizophrenia, can provide references for further research.

NLRP3 inflammatory pathway. Can we unlock depression?

Depression holds the title of the largest contributor to worldwide disability, with the numbers expected to continue growing. Currently, there are neither reliable biomarkers for the diagnosis of the disease nor are the current medications sufficient for a lasting response in nearly half of patients. In this comprehensive review, we analyze the previously established pathophysiological models of the disease and how the interplay between NLRP3 inflammasome activation and depression might offer a unifying perspective. Adopting this inflammatory theory, we explain how NLRP3 inflammasome activation emerges as a pivotal contributor to depressive inflammation, substantiated by compelling evidence from both human studies and animal models. This inflammation is found in the central nervous system (CNS) neurons, astrocytes, and microglial cells. Remarkably, dysregulation of the NLRP3 inflammasome extends beyond the CNS boundaries and permeates into the enteric and peripheral immune systems, thereby altering the microbiota-gut-brain axis. The integrity of the brain blood barrier (BBB) and intestinal epithelial barrier (IEB) is also compromised by this inflammation. By emphasizing the central role of NLRP3 inflammasome activation in depression and its far-reaching implications, we go over each area with potential modulating mechanisms within the inflammasome pathway in hopes of finding new targets for more effective management of this debilitating condition.

A Potential Role for the Ketogenic Diet in Alzheimer's Disease Treatment: Exploring Pre-Clinical and Clinical Evidence

Given the remarkable progress in global health and overall quality of life, the significant rise in life expectancy has become intertwined with the surging occurrence of neurodegenerative disorders (NDs). This emerging trend is poised to pose a substantial challenge to the fields of medicine and public health in the years ahead. In this context, Alzheimer's disease (AD) is regarded as an ND that causes recent memory loss, motor impairment and cognitive deficits. AD is the most common cause of dementia in the elderly and its development is linked to multifactorial interactions between the environment, genetics, aging and lifestyle. The pathological hallmarks in AD are the accumulation of β-amyloid peptide (Aβ), the hyperphosphorylation of tau protein, neurotoxic events and impaired glucose metabolism. Due to pharmacological limitations and in view of the prevailing glycemic hypometabolism, the ketogenic diet (KD) emerges as a promising non-pharmacological possibility for managing AD, an approach that has already demonstrated efficacy in addressing other disorders, notably epilepsy. The KD consists of a food regimen in which carbohydrate intake is discouraged at the expense of increased lipid consumption, inducing metabolic ketosis whereby the main source of energy becomes ketone bodies instead of glucose. Thus, under these dietary conditions, neuronal death via lack of energy would be decreased, inasmuch as the metabolism of lipids is not impaired in AD. In this way, the clinical picture of patients with AD would potentially improve via the slowing down of symptoms and delaying of the progression of the disease. Hence, this review aims to explore the rationale behind utilizing the KD in AD treatment while emphasizing the metabolic interplay between the KD and the improvement of AD indicators, drawing insights from both preclinical and clinical investigations. Via a comprehensive examination of the studies detailed in this review, it is evident that the KD emerges as a promising alternative for managing AD. Moreover, its efficacy is notably enhanced when dietary composition is modified, thereby opening up innovative avenues for decreasing the progression of AD.

Molecular Mechanisms of Neuroprotection by Ketone Bodies and Ketogenic Diet in Cerebral Ischemia and Neurodegenerative Diseases

Ketone bodies (KBs), such as acetoacetate and β-hydroxybutyrate, serve as crucial alternative energy sources during glucose deficiency. KBs, generated through ketogenesis in the liver, are metabolized into acetyl-CoA in extrahepatic tissues, entering the tricarboxylic acid cycle and electron transport chain for ATP production. Reduced glucose metabolism and mitochondrial dysfunction correlate with increased neuronal death and brain damage during cerebral ischemia and neurodegeneration. Both KBs and the ketogenic diet (KD) demonstrate neuroprotective effects by orchestrating various cellular processes through metabolic and signaling functions. They enhance mitochondrial function, mitigate oxidative stress and apoptosis, and regulate epigenetic and post-translational modifications of histones and non-histone proteins. Additionally, KBs and KD contribute to reducing neuroinflammation and modulating autophagy, neurotransmission systems, and gut microbiome. This review aims to explore the current understanding of the molecular mechanisms underpinning the neuroprotective effects of KBs and KD against brain damage in cerebral ischemia and neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease.

β-hydroxybutyrate administration improves liver injury and metabolic abnormality in postnatal growth retardation piglets

Abnormal hepatic energy metabolism limits the growth and development of piglets. We hypothesized that β-hydroxybutyrate (BHB) might improve the growth performance of piglets by maintaining hepatic caloric homeostasis. A total of 30 litters of newborn piglets were tracked, and 30 postnatal growth retardation (PGR) piglets and 40 healthy piglets were selected to treat with normal saline with or without BHB (25 mg/kg/days) at 7-d-old. At the age of 42 days, 8 piglets in each group were sacrificed, and serum and liver were collected. Compared with the healthy-control group piglets, PGR piglets showed lower body weight (BW) and liver weight (p < 0.05), and exhibited liver injury and higher inflammatory response. The contents of serum and hepatic BHB were lower (p < 0.05), and gene expression related to hepatic ketone body production were down-regulated in PGR piglets (p < 0.05). While BHB treatment increased BW and serum BHB levels, but decreased hepatic BHB levels in PGR piglets (p < 0.05). BHB alleviated the liver injury by inhibiting the apoptosis and inflammation in liver of PGR piglets (p < 0.05). Compared with the healthy-control group piglets, liver glycogen content and serum triglyceride level of PGR piglets were increased (p < 0.05), liver gluconeogenesis gene and lipogenesis gene expression were increased (p < 0.05), and liver NAD+ level was decreased (p < 0.05). BHB supplementation increased the ATP levels in serum and liver (p < 0.05), whereas decreased the serum glucose, cholesterol, triglyceride and high-density lipoprotein cholesterol levels and glucose and lipid metabolism in liver of PGR piglets (p < 0.05). Therefore, BHB treatment might alleviate the liver injury and inflammation, and improve hepatic energy metabolism by regulating glucose and lipid metabolism, thereby improving the growth performance of PGR piglets.

Dose-Dependent Beneficial Effect of Ketone Supplement-Evoked Ketosis on Anxiety Level in Female WAG/Rij Rats: Sometimes Less Is More

While one-third of the population can be affected by anxiety disorders during their lifetime, our knowledge of the pathophysiology of these disorders is far from complete. Previously, it has been demonstrated in male animals that exogenous ketone supplement-evoked ketosis can decrease anxiety levels in preclinical rodent models, such as Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. Thus, in this study, we investigated whether intragastric gavage of the exogenous ketone supplement KEMCT (mix of 1,3-butanediol-acetoacetate diester/ketone ester/KE and medium-chain triglyceride/MCT oil in 1:1 ratio) for 7 days can alter the anxiety levels of female WAG/Rij rats using the light-dark box (LDB) test. We demonstrated that a lower dose of KEMCT (3 g/kg/day) increased blood R-βHB (R-β-hydroxybutyrate) levels and significantly decreased anxiety levels (e.g., increased the time spent in the light compartment) in female WAG/Rij rats on the seventh day of administration. Although the higher KEMCT dose (5 g/kg/day) increased blood R-βHB levels more effectively, compared with the lower KEMCT dose, anxiety levels did not improve significantly. We conclude that ketone supplementation might be an effective strategy to induce anxiolytic effects not only in male but also in female WAG/Rij rats. However, these results suggest that the optimal level may be moderately, not highly, elevated blood R-βHB levels when the goal is to alleviate symptoms of anxiety. More studies are needed to understand the exact mechanism of action of ketone supplementation on anxiety levels and to investigate their use in other animal models and humans for the treatment of anxiety disorders and other mental health conditions.

Ketogenic-Mimicking Diet as a Therapeutic Modality for Bipolar Disorder: Biomechanistic Rationale and Protocol for a Pilot Clinical Trial

There is growing interest in the investigation of ketogenic diets as a potential therapy for bipolar disorder. The overlapping pharmacotherapies utilized for both bipolar disorder and seizures suggest that a mechanistic overlap may exist between these conditions, with fasting and the ketogenic diet representing the most time-proven therapies for seizure control. Recently, preliminary evidence has begun to emerge supporting a potential role for ketogenic diets in treating bipolar disorder. Notably, some patients may struggle to initiate a strict diet in the midst of a mood episode or significant life stressors. The key question addressed by this pilot clinical trial protocol is if benefits can be achieved with a less restrictive diet, as this would allow such an intervention to be accessible for more patients. Recent development of so-called ketone esters, that once ingested is converted to natural ketone bodies, combined with low glycemic index dietary changes has the potential to mimic two foundational components of therapeutic ketosis: high levels of ketones and minimal spiking of glucose/insulin. This pilot clinical trial protocol thus aims to investigate the effect of a 'ketogenic-mimicking diet' (combining supplementation of ketone esters with a low glycemic index dietary intervention) on neural network stability, mood, and biomarker outcomes in the setting of bipolar disorder. Positive findings obtained via this pilot clinical trial protocol may support future target engagement studies of ketogenic-mimicking diets or related ketogenic interventions. A lack of positive findings, in contrast, may justify a focus on more strict dietary interventions for future research.

Exploring the key factors of schizophrenia relapse by integrating LC-MS/1H NMR metabolomics and weighted correlation network analysis

BACKGROUND

Lack of comprehending key factors of schizophrenia relapse has impeded its effective treatment, indicating that the mechanism clarification and available intervention of schizophrenia relapse required further amelioration.

METHOD

Based on the integration of LC-MS and ¹H NMR metabolomics, a weighted correlation network was established to screen pivotal factors of accelerating schizophrenia relapse. Then, the cluster most correlated with schizophrenia relapse was explored, and the biological function of cluster was investigated. Next, the key biomarker related to schizophrenia relapse was obtained through multiple algorithms. Moreover, the Lilikoi algorithm and correlation analysis were implemented to reveal the association between key biomarker and schizophrenia relapse.

RESULT

Results showed that 458 different forms of metabolites were identified for structuring the weighted correlation network. The module-trait correlation indicated that the turquoise module was the most highly correlated with schizophrenia relapse. Further, network analysis revealed that, in turquoise module, cluster 1 composed of 139 metabolites (involved in lipid metabolism and energy metabolism) was the most important subnetwork relevant to schizophrenia relapse. Finally, phenylalanylphenylalanine was recommended as the key biomarker related to schizophrenia relapse. Moreover, the correlation analysis indicated that phenylalanylphenylalanine might affect the progression of schizophrenia by intervening in energy metabolism.

CONCLUSION

In summary, critical factors of schizophrenia relapse have been revealed in our research, expounding the schizophrenia progression more systemically, which could shed some light on improving the intervention of schizophrenia relapse.

Short- and long-term cognitive and metabolic effects of medium-chain triglyceride supplementation in rats

Medium-chain triglycerides (MCT) possess neuroprotective properties. However, the long-term metabolic consequences of supplementing a regular diet with cognition-enhancing doses of MCT are largely unknown. We studied the effects of chronic (28 days) supplementation of regular diet with different doses of MCT oil (1, 3, or 6 g/kg/day) or water (control) on working memory (Y-maze), behavior in the Open Field, spatial learning (Morris water maze), and weight of internal organs in male Wistar 2.5-m.o. Rats. In a separate experiment, we evaluated acute (single gavage) and chronic (28 days) effects of MCT or lard supplementation (3 g/kg) on blood biochemical parameters. MCT-1 and MCT-3 doses improved working memory in YM. In MWM, MCT-6 treatment improved spatial memory. Chronic MCT-1 or MCT-3 treatment did not affect internal organ weight, while MCT-6 dose increased liver weight and the brown/white adipose tissue ratio. Acutely, MCT administration elevated blood β-hydroxybutyrate and malondialdehyde levels. Chronic MCT administration (3 g/kg) did not affect the blood levels of glucose, lactate, pyruvate, acetoacetate, β-hydroxybutyrate, total and HDL cholesterol, triglycerides, malondialdehyde, and aspartate transaminase and alanine transaminase activities. Therefore, daily supplementation of standard feed with MCT resulted in mild intermittent ketosis. It improved working memory at lower concentrations without significant adverse side effects. At higher concentrations, it improved long-term spatial memory but also resulted in organ weight changes and is likely unsafe. These results highlight the importance of monitoring the metabolic effects of MCT supplementation alongside cognitive assessment in future studies of MCT's neuroprotective properties.

A bibliometric analysis of the global trends and hotspots for the ketogenic diet based on CiteSpace

The ketogenic diet (KD) is a potential nutritional therapy that is frequently utilized in various conditions. More and more studies are being done on KD in recent years. However, as far as we know, few studies have made an effort to offer a thorough synthesis and assessment of this topic. This paper aims to do a rigorous and thorough evaluation of the knowledge structure, development trend, and research hotspot of scientific outputs connected to KD. The bibliographic records connected to KD from January 1, 2001 to April 22, 2022 were collected using the core collection database of Web of Science. The complex data input, that consisted of the amount of publications, journals, authors, institutions, countries, keywords and cited references, was generated and analyzed visually using CiteSpace. A total of 2676 literatures on the KD were published between 2001 and 2022. The most KD-related publications were found in Epilepsia and Epilepsia Research. The authors with the most KD-related papers are Kossoff EH and Rho J. The United States is the country with the most publications, and Johns Hopkins University, Johns Hopkins University Hospital, and Johns Hopkins Medical Institutions are the institutions with the most articles. The high frequency keywords are "KD," "ketone body," "children," "efficacy," "weight loss," "low carbohydrate diet," "metabolism," "epilepsy," "beta hydroxybutyrate," and "modified atkins diet." The 2018 study by Kossoff EH on epilepsia and the 2017 study by Puchalska P on ketone body metabolism earned 127 and 114 citations, respectively. The results of this bibliometric analysis provide information on the state and trends in KD and may be used by researchers to pinpoint hot issues and discover new areas of study.

The effects of a 6-week controlled, hypocaloric ketogenic diet, with and without exogenous ketone salts, on cognitive performance and mood states in overweight and obese adults

Background

Ketogenic diets are a commonly used weight loss method, but little is known how variations in sodium content and ketones influence cognition and mood during the early keto-adaptation period.

Objectives

To investigate the effects of an exogenous ketone salt (KS) as part of a hypocaloric KD on mood and cognitive outcomes in overweight and obese adults. A secondary objective was to evaluate changes in biochemical markers associated with inflammatory and cognitive responses.

Materials and methods

Adults who were overweight or obese participated in a 6-week controlled-feeding intervention comparing hypocaloric diets (∼75% of energy expenditure). KD groups received twice daily ketone salt (KD + KS; n = 12) or a flavor-matched placebo, free of minerals (KD + PL; n = 13). A separate group of age and BMI matched adults were later assigned to an isoenergetic low-fat diet (LFD; n = 12) as comparison to KD. Mood was assessed by shortened Profile of Mood States and Visual Analog Mood Scale surveys. Cognitive function was determined by the Automated Neuropsychological Assessment Metrics mental test battery.

Results

Both KD groups achieved nutritional ketosis. Fasting serum glucose decreased in both KD groups, whereas glucose was unaffected in the LFD. Insulin decreased at week 2 and remained lower in all groups. At week 2, depression scores in the KD + PL group were higher compared to KD + KS. Performance in the math processing and go/no-go cognitive tests were lower for KD + PL and LFD participants, respectively, compared to KD + KS. Serum leptin levels decreased for all groups throughout the study but were higher for KD + KS group at week 6. Serum TNF-α steadily increased for LFD participants, reaching significance at week 6.

Conclusion

During a short-term hypocaloric diet, no indication of a consistent decline in mood or cognitive function were seen in participants following either KD, despite KD + PL being relatively low in sodium. WK2 scores of “anger” and “depression” were higher in the LFD and KD + PL groups, suggesting that KS may attenuate negative mood parameters during the early intervention stages.

Supplementation of Regular Diet With Medium-Chain Triglycerides for Procognitive Effects: A Narrative Review

It is now widely accepted that ketosis (a physiological state characterized by elevated plasma ketone body levels) possesses a wide range of neuroprotective effects. There is a growing interest in the use of ketogenic supplements, including medium-chain triglycerides (MCT), to achieve intermittent ketosis without adhering to a strict ketogenic diet. MCT supplementation is an inexpensive and simple ketogenic intervention, proven to benefit both individuals with normal cognition and those suffering from mild cognitive impairment, Alzheimer's disease, and other cognitive disorders. The commonly accepted paradigm underlying MCT supplementation trials is that the benefits stem from ketogenesis and that MCT supplementation is safe. However, medium-chain fatty acids (MCFAs) may also exert effects in the brain directly. Moreover, MCFAs, long-chain fatty acids, and glucose participate in mutually intertwined metabolic pathways. Therefore, the metabolic effects must be considered if the desired procognitive effects require administering MCT in doses larger than 1 g/kg. This review summarizes currently available research on the procognitive effects of using MCTs as a supplement to regular feed/diet without concomitant reduction of carbohydrate intake and focuses on the revealed mechanisms linked to particular MCT metabolites (ketone bodies, MCFAs), highlighting open questions and potential considerations.

Schizophrenia: a disorder of broken brain bioenergetics

A substantial and diverse body of literature suggests that the pathophysiology of schizophrenia is related to deficits of bioenergetic function. While antipsychotics are an effective therapy for the management of positive psychotic symptoms, they are not efficacious for the complete schizophrenia symptom profile, such as the negative and cognitive symptoms. In this review, we discuss the relationship between dysfunction of various metabolic pathways across different brain regions in relation to schizophrenia. We contend that several bioenergetic subprocesses are affected across the brain and such deficits are a core feature of the illness. We provide an overview of central perturbations of insulin signaling, glycolysis, pentose-phosphate pathway, tricarboxylic acid cycle, and oxidative phosphorylation in schizophrenia. Importantly, we discuss pharmacologic and nonpharmacologic interventions that target these pathways and how such interventions may be exploited to improve the symptoms of schizophrenia.

SARS-CoV-2 Infections, Impaired Tissue, and Metabolic Health: Pathophysiology and Potential Therapeutics

The SARS-CoV-2 enters the human airways and comes into contact with the mucous membranes lining the mouth, nose, and eyes. The virus enters the healthy cells and uses cell machinery to make several copies of the virus. Critically ill patients infected with SARS-CoV-2 may have damaged lungs, air sacs, lining, and walls. Since COVID-19 causes cytokine storm, it damages the alveolar cells of the lungs and fills them with fluid, making it harder to exchange oxygen and carbon dioxide. The SARS-CoV-2 infection causes a range of complications, including mild to critical breathing difficulties. It has been observed that older people suffering from health conditions like cardiomyopathies, nephropathies, metabolic syndrome, and diabetes instigate severe symptoms. Many people who died due to COVID-19 had impaired metabolic health [IMH], characterized by hypertension, dyslipidemia, and hyperglycemia, i.e., diabetes, cardiovascular system, and renal diseases making their retrieval challenging. Jeopardy stresses for increased mortality from COVID-19 include older age, COPD, ischemic heart disease, diabetes mellitus, and immunosuppression. However, no targeted therapies are available as of now. Almost two-thirds of diagnosed coronavirus patients had cardiovascular diseases and diabetes, out of which 37% were under 60. The NHS audit revealed that with a higher expression of ACE-2 receptors, viral particles could easily bind their protein spikes and get inside the cells, finally causing COVID-19 infection. Hence, people with IMH are more prone to COVID-19 and, ultimately, comorbidities. This review provides enormous information about tissue [lungs, heart and kidneys] damage, pathophysiological changes, and impaired metabolic health of SARS-CoV-2 infected patients. Moreover, it also designates the possible therapeutic targets of COVID-19 and drugs which can be used against these targets.

An integrated pathological research for precise diagnosis of schizophrenia combining LC-MS/1H NMR metabolomics and transcriptomics

BACKGROUND

Lack of clinically specific biomarkers has impeded the precise diagnosis of schizophrenia, meanwhile, limited comprehending of pathogenesis for schizophrenia has restricted the effective treatment.

METHOD

An integrated multi-omic approach, combining metabolomic platform (LC-MS and ¹H NMR) and transcriptomic platform, was established to differentiate healthy subjects from schizophrenia patients. Based on filtered metabolites and genes, characteristic spectrums were further built. Then, representative metabolites and genes were screened out through Boruta algorithm. Moreover, characteristic diagnostic formulas were established via LASSO regression analysis.

RESULT

As a result, 86 differential metabolites (in line with amino acid metabolism, etc.) and 189 differential expression genes (involving in amino acid metabolic process, etc.) were obtained as potential biomarkers for schizophrenia. The latent interaction between metabolites with genes, such as HMGCLL1 with energy metabolism, etc., was further studied through the analysis of pathway-based integration. Moreover, fine predictive ability was attributed to characteristic metabolomic/transcriptomic diagnostic spectrums/formulas.

CONCLUSION

The functional relationships of filtered metabolites and genes were studied, which could elaborate the pathological process of schizophrenia more systemically, supplying more precise information on mechanism description and diagnostic evidence of schizophrenia.

Astrocyte Bioenergetics and Major Psychiatric Disorders

Ongoing research continues to add new elements to the emerging picture of involvement of astrocyte energy metabolism in the pathophysiology of major psychiatric disorders, including schizophrenia, mood disorders, and addictions. This review outlines what is known about the energy metabolism in astrocytes, the most numerous cell type in the brain, and summarizes the recent work on how specific perturbations of astrocyte bioenergetics may contribute to the neuropsychiatric conditions. The role of astrocyte energy metabolism in mental health and disease is reviewed on the organism, organ, and cell level. Data arising from genomic, metabolomic, in vitro, and neurobehavioral studies is critically analyzed to suggest future directions in research and possible metabolism-focused therapeutic interventions.

β-hydroxybutyrate as an Anti-Aging Metabolite

The ketone bodies, especially β-hydroxybutyrate (β-HB), derive from fatty acid oxidation and alternatively serve as a fuel source for peripheral tissues including the brain, heart, and skeletal muscle. β-HB is currently considered not solely an energy substrate for maintaining metabolic homeostasis but also acts as a signaling molecule of modulating lipolysis, oxidative stress, and neuroprotection. Besides, it serves as an epigenetic regulator in terms of histone methylation, acetylation, β-hydroxybutyrylation to delay various age-related diseases. In addition, studies support endogenous β-HB administration or exogenous supplementation as effective strategies to induce a metabolic state of nutritional ketosis. The purpose of this review article is to provide an overview of β-HB metabolism and its relationship and application in age-related diseases. Future studies are needed to reveal whether β-HB has the potential to serve as adjunctive nutritional therapy for aging.

β-hydroxybutyrate as an Anti-Aging Metabolite

The ketone bodies, especially β-hydroxybutyrate (β-HB), derive from fatty acid oxidation and alternatively serve as a fuel source for peripheral tissues including the brain, heart, and skeletal muscle. β-HB is currently considered not solely an energy substrate for maintaining metabolic homeostasis but also acts as a signaling molecule of modulating lipolysis, oxidative stress, and neuroprotection. Besides, it serves as an epigenetic regulator in terms of histone methylation, acetylation, β-hydroxybutyrylation to delay various age-related diseases. In addition, studies support endogenous β-HB administration or exogenous supplementation as effective strategies to induce a metabolic state of nutritional ketosis. The purpose of this review article is to provide an overview of β-HB metabolism and its relationship and application in age-related diseases. Future studies are needed to reveal whether β-HB has the potential to serve as adjunctive nutritional therapy for aging.

β-hydroxybutyrate as an Anti-Aging Metabolite

The ketone bodies, especially β-hydroxybutyrate (β-HB), derive from fatty acid oxidation and alternatively serve as a fuel source for peripheral tissues including the brain, heart, and skeletal muscle. β-HB is currently considered not solely an energy substrate for maintaining metabolic homeostasis but also acts as a signaling molecule of modulating lipolysis, oxidative stress, and neuroprotection. Besides, it serves as an epigenetic regulator in terms of histone methylation, acetylation, β-hydroxybutyrylation to delay various age-related diseases. In addition, studies support endogenous β-HB administration or exogenous supplementation as effective strategies to induce a metabolic state of nutritional ketosis. The purpose of this review article is to provide an overview of β-HB metabolism and its relationship and application in age-related diseases. Future studies are needed to reveal whether β-HB has the potential to serve as adjunctive nutritional therapy for aging.

On the nutritional and therapeutic effects of ketone body D-β-hydroxybutyrate

Abstract

d-β-hydroxybutyrate (d-3HB), a monomer of microbial polyhydroxybutyrate (PHB), is also a natural ketone body produced during carbohydrate deprivation to provide energy to the body cells, heart, and brain. In recent years, increasing evidence demonstrates that d-3HB can induce pleiotropic effects on the human body which are highly beneficial for improving physical and metabolic health. Conventional ketogenic diet (KD) or exogenous ketone salts (KS) and esters (KE) have been used to increase serum d-3HB level. However, strict adaptation to the KD was often associated with poor patient compliance, while the ingestion of KS caused gastrointestinal distresses due to excessive consumption of minerals. As for ingestion of KE, subsequent degradation is required before releasing d-3HB for absorption, making these methods somewhat inferior. This review provides novel insights into a biologically synthesized d-3HB (d-3-hydroxybutyric acid) which can induce a faster increase in plasma d-3HB compared to the use of KD, KS, or KE. It also emphasizes on the most recent applications of d-3HB in different fields, including its use in improving exercise performance and in treating metabolic or age-related diseases. Ketones may become a fourth micro-nutrient that is necessary to the human body along with carbohydrates, proteins, and fats. Indeed, d-3HB being a small molecule with multiple signaling pathways within the body exhibits paramount importance in mitigating metabolic and age-related diseases. Nevertheless, specific dose–response relationships and safety margins of using d-3HB remain to be elucidated with more research.

Key points

• d-3HB induces pleiotropic effects on physical and metabolic health.

• Exogenous ketone supplements are more effective than ketogenic diet.

• d-3HB as a ketone supplement has long-term healthy impact.

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.

Slow but Steady-The Responsiveness of Sympathoadrenal System to a Hypoglycemic Challenge in Ketogenic Diet-Fed Rats

The sympathoadrenal counterregulatory response to hypoglycemia is critical for individuals with type 1 diabetes due to impaired ability to produce glucagon. Ketogenic diets (KD) are an increasingly popular diabetes management tool; however, the effects of KD on the sympathoadrenal response are largely unknown. Here, we determined the effects of KD-induced ketosis on the sympathoadrenal response to a single insulin-induced hypoglycemic challenge. We investigated how a 3 week KD feeding regimen affected the main components of the sympathoadrenal counterregulatory response: adrenal sympathetic nerve activity (ASNA), adrenal gland activity, plasma epinephrine, and brainstem glucose-responsive C1 neuronal activation in anesthetized, nondiabetic male Sprague-Dawley rats. Rats on KD had similar blood glucose (BG) levels and elevated ketone body β-hydroxybutyrate (BHB) levels compared to the control Chow diet group. All KD rats responded to hypoglycemia with a robust increase in ASNA, which was initiated at significantly lower BG levels compared to Chow-fed rats. The delay in hypoglycemia-induced ASNA increase was concurrent with rapid disappearance of BHB from cerebral and peripheral circulation. Adrenal gland activity paralleled epinephrine and ASNA response. Overall, KD-induced ketosis was associated with initiation of the sympathoadrenal response at lower blood glucose levels; however, the magnitude of the response was not diminished.

Beneficial Effects of Exogenous Ketogenic Supplements on Aging Processes and Age-Related Neurodegenerative Diseases

Life expectancy of humans has increased continuously up to the present days, but their health status (healthspan) was not enhanced by similar extent. To decrease enormous medical, economical and psychological burden that arise from this discrepancy, improvement of healthspan is needed that leads to delaying both aging processes and development of age-related diseases, thereby extending lifespan. Thus, development of new therapeutic tools to alleviate aging processes and related diseases and to increase life expectancy is a topic of increasing interest. It is widely accepted that ketosis (increased blood ketone body levels, e.g., β-hydroxybutyrate) can generate neuroprotective effects. Ketosis-evoked neuroprotective effects may lead to improvement in health status and delay both aging and the development of related diseases through improving mitochondrial function, antioxidant and anti-inflammatory effects, histone and non-histone acetylation, β-hydroxybutyrylation of histones, modulation of neurotransmitter systems and RNA functions. Administration of exogenous ketogenic supplements was proven to be an effective method to induce and maintain a healthy state of nutritional ketosis. Consequently, exogenous ketogenic supplements, such as ketone salts and ketone esters, may mitigate aging processes, delay the onset of age-associated diseases and extend lifespan through ketosis. The aim of this review is to summarize the main hallmarks of aging processes and certain signaling pathways in association with (putative) beneficial influences of exogenous ketogenic supplements-evoked ketosis on lifespan, aging processes, the most common age-related neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis), as well as impaired learning and memory functions.

Mitochondrial dysfunction as a critical event in the pathophysiology of bipolar disorder

The understanding of the pathophysiology of bipolar disorder (BD) remains modest, despite recent advances in neurobiological research. The mitochondrial dysfunction hypothesis of bipolar disorder has been corroborated by several studies involving postmortem brain analysis, neuroimaging, and specific biomarkers in both rodent models and humans. Evidence suggests that BD might be related to abnormal mitochondrial morphology and dynamics, neuroimmune dysfunction, and atypical mitochondrial metabolism and oxidative stress pathways. Mitochondrial dysfunction in mood disorders is also associated with abnormal Ca2+ levels, glutamate excitotoxicity, an imbalance between pro- and antiapoptotic proteins towards apoptosis, abnormal gene expression of electron transport chain complexes, and decreased ATP synthesis. This paper aims to review and discuss the implications of mitochondrial dysfunction in BD etiology and to explore mitochondria as a potential target for novel therapeutic agents.

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.

Age- and Sex-Dependent Modulation of Exogenous Ketone Supplement-Evoked Effects on Blood Glucose and Ketone Body Levels in Wistar Albino Glaxo Rijswijk Rats

In certain disease states, such as epilepsy, the elevation of blood ketone levels with ketogenic diets (KDs) has beneficial effects, while exogenous ketone supplements (EKSs) were shown to increase the level of blood ketone bodies (such as β-hydroxybutyrate, βHB) and decrease blood glucose levels without dietary restrictions. It has been suggested that ketone body and glucose utilization of the body may be modified by age and gender resulting in changes in blood βHB and glucose levels, but it was not investigated through several months yet. Thus, we investigated whether the effect of an EKS on blood βHB and glucose level is modulated by age and sex in Wistar Albino Glaxo Rijswijk (WAG/Rij) rats, a model animal of human absence epilepsy. We used KEMCT (1:1 mix of ketone ester/KE and medium-chain triglyceride/MCT oil) by oral gavage in female and male WAG/Rij rats. Animals were fed with standard diet, which was supplemented by KEMCT (2.5 g/kg) once per month by oral gavage for 17 months. One hour after KEMCT treatment, changes in blood R-beta-hydroxybutyrate (R-βHB) and glucose levels were measured. KEMCT gavage significantly increased blood R-βHB and decreased blood glucose levels, in both male and female rats, compared with the controls. In male rats, the KEMCT-induced increase in blood R-βHB levels was lower at the 7th and 8th months and higher at the 16th and 17th months, compared with the results at the 1st month. KEMCT-generated increase in R-βHB levels was higher in female rats, compared with male rats between the 2nd and 11th months, but older (between the 14th and 17th months) female rats showed lower levels than males. KEMCT gavage induced significantly lower glucose levels at the 4th, 9th, 10th, 12th, and 13th months in both sexes, but between the 14th and 17th months, only males showed significantly lower levels, compared with the results at the 1st month. KEMCT treatment induced lower blood glucose levels in female than in male rats between the 1st and 8th months, but higher glucose levels were measured in female rats at the 17th month than in males. These findings suggest that age and sex can modify the EKS-evoked effects on blood R-βHB and glucose concentrations.

Importance of lipids for upper motor neuron health and disease

Building evidence reveals the importance of maintaining lipid homeostasis for the health and function of neurons, and upper motor neurons (UMNs) are no exception. UMNs are critically important for the initiation and modulation of voluntary movement as they are responsible for conveying cerebral cortex' input to spinal cord targets. To maintain their unique cytoarchitecture with a prominent apical dendrite and a very long axon, UMNs require a stable cell membrane, a lipid bilayer. Lipids can act as building blocks for many biomolecules, and they also contribute to the production of energy. Therefore, UMNs require sustained control over the production, utilization and homeostasis of lipids. Perturbations of lipid homeostasis lead to UMN vulnerability and progressive degeneration in diseases such as hereditary spastic paraplegia (HSP) and primary lateral sclerosis (PLS). Here, we discuss the importance of lipids, especially for UMNs.

Potential Therapeutic Effects of Exogenous Ketone Supplementation for Type 2 Diabetes: A Review

Type 2 diabetes (T2D) is among the most prevalent non-communicable lifestyle diseases. We propose that overnutrition and low levels of physical activity can contribute to a vicious cycle of hyperglycemia, inflammation and oxidative stress, insulin resistance, and pancreatic β-cell dysfunction. The pathophysiological manifestations of T2D have a particular impact on the vasculature and individuals with T2D are at high risk of cardiovascular disease. Targeting aspects of the vicious cycle represent therapeutic approaches for improving T2D and protecting against cardiovascular complications. The recent advent of exogenous oral ketone supplements represents a novel, non-pharmacological approach to improving T2D pathophysiology and potentially protecting against cardiovascular disease risk. Herein, we review the emerging literature regarding the effects of exogenous ketone supplementation on metabolic control, inflammation, oxidative stress, and cardiovascular function in humans and highlight the potential application for breaking the vicious cycle of T2D pathophysiology.

COVID-19 infection may cause ketosis and ketoacidosis

The present study included 658 hospitalized patients with confirmed COVID-19. Forty-two (6.4%) out of 658 patients presented with ketosis on admission with no obvious fever or diarrhoea. They had a median (interquartile range [IQR]) age of 47.0 (38.0-70.3) years, and 16 (38.1%) were men. Patients with ketosis were younger (median age 47.0 vs. 58.0 years; P = 0.003) and had a greater prevalence of fatigue (31.0% vs. 10.6%; P < 0.001), diabetes (35.7% vs. 18.5%; P = 0.007) and digestive disorders (31.0% vs. 12.0%; P < 0.001). They had a longer median (IQR) length of hospital stay (19.0 [12.8-33.3] vs. 16.0 [10.0-24.0] days; P < 0.001) and a higher mortality rate (21.4% vs. 8.9%; P = 0.017). Three (20.0%) out of the 15 patients with diabetic ketosis developed acidosis, five patients (26.7%) with diabetic ketosis died, and one of these (25.0%) presented with acidosis. Two (7.4%) and four (14.3%) of the 27 non-diabetic ketotic patients developed severe acidosis and died, respectively, and one (25.0%) of these presented with acidosis. This suggests that COVID-19 infection caused ketosis or ketoacidosis, and induced diabetic ketoacidosis for those with diabetes. Ketosis increased the length of hospital stay and mortality. Meanwhile, diabetes increased the length of hospital stay for patients with ketosis but had no effect on their mortality.

The Western diet: a blind spot of eating disorder research?-a narrative review and recommendations for treatment and research

Over the last 50 years, in parallel with the obesity epidemic, the prevalence of eating disorders has increased and presentations have changed. In this narrative review, we consider recent research exploring the implications of changing patterns of food consumption on metabolic and neurobiological pathways, a hitherto neglected area in eating disorder research. One of the major changes over this time has been the introduction of ultra-processed (NOVA-4) foods, which are gradually replacing unprocessed and minimally processed foods. This has resulted in the increased intake of various sugars and food additives worldwide, which has important metabolic consequences: triggering insulin and glucose response, stimulating appetite, and affecting multiple endocrine and neurobiological pathways, as well as the microbiome. A paradigm shift is needed in the conceptual framework by which the vulnerability to, and maintenance of, different eating disorders may be understood, by integrating recent knowledge of the individual metabolic responses to modern highly processed foods into existing psychological models. This could stimulate research and improve treatment outcomes.

Exogenous Ketone Supplements Improved Motor Performance in Preclinical Rodent Models

Nutritional ketosis has been proven effective for neurometabolic conditions and disorders linked to metabolic dysregulation. While inducing nutritional ketosis, ketogenic diet (KD) can improve motor performance in the context of certain disease states, but it is unknown whether exogenous ketone supplements—alternatives to KDs—may have similar effects. Therefore, we investigated the effect of ketone supplements on motor performance, using accelerating rotarod test and on postexercise blood glucose and R-beta-hydroxybutyrate (R-βHB) levels in rodent models with and without pathology. The effect of KD, butanediol (BD), ketone-ester (KE), ketone-salt (KS), and their combination (KE + KS: KEKS) or mixtures with medium chain triglyceride (MCT) (KE + MCT: KEMCT; KS + MCT: KSMCT) was tested in Sprague-Dawley (SPD) and WAG/Rij (WR) rats and in GLUT-1 Deficiency Syndrome (G1D) mice. Motor performance was enhanced by KEMCT acutely, KE and KS subchronically in SPD rats, by KEKS and KEMCT groups in WR rats, and by KE chronically in G1D mice. We demonstrated that exogenous ketone supplementation improved motor performance to various degrees in rodent models, while effectively elevated R-βHB and in some cases offsets postexercise blood glucose elevations. Our results suggest that improvement of motor performance varies depending on the strain of rodents, specific ketone formulation, age, and exposure frequency.

In vitro human colonic microbiota utilises D-β-hydroxybutyrate to increase butyrogenesis

The ketone body D-β-hydroxybutyrate (DBHB) has gained attention owing to its cellular signalling function; however, its effect on the human colonic microbiota remains unclear. Here, DBHB dynamics in the human colon were investigated using an in vitro colonic microbiota model, which maintained most of the operational taxonomic units detected in the original faeces. Over 54% of 0.41% (w/v) DBHB was metabolised by microbiota models originating from seven faecal samples after 30 h of fermentation (regarded as DBHB utilisers); however, <19% of DBHB was metabolised by microbiota models from five faecal samples (regarded as non-utilisers of DBHB). In utilisers, DBHB administration increased the relative abundance of the genus Coprococcus, correlated with increased butyrogenesis. Increased butyrogenesis was not observed in DBHB non-utilisers. Based on PICRUSt analysis, the relative abundance of β-hydroxybutyrate dehydrogenase was maintained in microbiota models from DBHB utilisers following DBHB administration; however, it decreased in microbiota models from non-utilisers. After 21 h of fermentation, the intracellular glutamate concentration, which is indicative of growth, showed a positive correlation with DBHB utilisation (R² = 0.70). Human colonic microbiotas with high growth activity demonstrate efficient utilisation of DBHB for increased butyrate production, which affords health benefits.

Why a d-β-hydroxybutyrate monoester?

Much of the world's prominent and burdensome chronic diseases, such as diabetes, Alzheimer's, and heart disease, are caused by impaired metabolism. By acting as both an efficient fuel and a powerful signalling molecule, the natural ketone body, d-β-hydroxybutyrate (βHB), may help circumvent the metabolic malfunctions that aggravate some diseases. Historically, dietary interventions that elevate βHB production by the liver, such as high-fat diets and partial starvation, have been used to treat chronic disease with varying degrees of success, owing to the potential downsides of such diets. The recent development of an ingestible βHB monoester provides a new tool to quickly and accurately raise blood ketone concentration, opening a myriad of potential health applications. The βHB monoester is a salt-free βHB precursor that yields only the biologically active d-isoform of the metabolite, the pharmacokinetics of which have been studied, as has safety for human consumption in athletes and healthy volunteers. This review describes fundamental concepts of endogenous and exogenous ketone body metabolism, the differences between the βHB monoester and other exogenous ketones and summarises the disease-specific biochemical and physiological rationales behind its clinical use in diabetes, neurodegenerative diseases, heart failure, sepsis related muscle atrophy, migraine, and epilepsy. We also address the limitations of using the βHB monoester as an adjunctive nutritional therapy and areas of uncertainty that could guide future research.

Case-Control Study of the Effects of Gut Microbiota Composition on Neurotransmitter Metabolic Pathways in Children With Attention Deficit Hyperactivity Disorder

Background

Attention-deficit/hyperactivity disorder (ADHD) is a neuropsychiatric condition that may be related to an imbalance of neural transmitters. The gut microbiota is the largest ecosystem in the human body, and the brain-gut axis theory proposes that the gut microbiome can affect brain function in multiple ways. The purpose of this study was to explore the gut microbiota in children with ADHD and assess the possible role of the gut microbiota in disease pathogenesis to open new avenues for ADHD treatment.

Methods

A case-control design was used. We enrolled 17 children aged 6-12 years with ADHD who were treated in the Pediatric Outpatient Department of the First Medical Center of the Chinese PLA General Hospital from January to June, 2019. Seventeen children aged 6-12 years were selected as the healthy control (HC) group. Fecal samples of cases and controls were analyzed by shotgun metagenomics sequencing. Alpha diversity and the differences in the relative abundances of bacteria were compared between the two groups. Functional annotations were performed for the microbiota genes and metabolic pathways were analyzed using the Kyoto Encyclopedia of Genes and Genomes (KEGG).

Results

There was no significant difference in the alpha diversity of gut microbiota between the ADHD and HC groups. Compared with HCs, Faecalibacterium and Veillonellaceae were significantly reduced in children with ADHD (P < 0.05), Odoribacter and Enterococcus were significantly increased [linear discriminant analysis (LDA) > 2]. At the species level, Faecalibacterium prausnitzii, Lachnospiraceae bacterium, and Ruminococcus gnavus were significantly reduced in the ADHD group (P < 0.05), while Bacteroides caccae, Odoribacter splanchnicus, Paraprevotella xylaniphila, and Veillonella parvula were increased (P < 0.05). Metabolic pathway analysis revealed significant between-group differences in the metabolic pathways of neurotransmitters (e.g., serotonin and dopamine) (P < 0.05).

Conclusion

Composition differences of gut microbiota in subjects with ADHD may contribute to brain-gut axis alterations and affect neurotransmitter levels, which could contribute to ADHD symptoms.

Induced Ketosis as a Treatment for Neuroprogressive Disorders: Food for Thought?

Induced ketosis (or ketone body ingestion) can ameliorate several changes associated with neuroprogressive disorders, including schizophrenia, bipolar disorder, and major depressive disorder. Thus, the effects of glucose hypometabolism can be bypassed through the entry of beta-hydroxybutyrate, providing an alternative source of energy to glucose. The weight of evidence suggests that induced ketosis reduces levels of oxidative stress, mitochondrial dysfunction, and inflammation-core features of the above disorders. There are also data to suggest that induced ketosis may be able to target other molecules and signaling pathways whose levels and/or activity are also known to be abnormal in at least some patients suffering from these illnesses such as peroxisome proliferator-activated receptors, increased activity of the Kelch-like ECH-associated protein/nuclear factor erythroid 2-related factor 2, Sirtuin-1 nuclear factor-κB p65, and nicotinamide adenine dinucleotide (NAD). This review explains the mechanisms by which induced ketosis might reduce mitochondrial dysfunction, inflammation, and oxidative stress in neuropsychiatric disorders and ameliorate abnormal levels of molecules and signaling pathways that also appear to contribute to the pathophysiology of these illnesses. This review also examines safety data relating to induced ketosis over the long term and discusses the design of future studies.

Inhibition of adenosine A1 receptors abolished the nutritional ketosis-evoked delay in the onset of isoflurane-induced anesthesia in Wistar Albino Glaxo Rijswijk rats

Background

It has been demonstrated that administration of exogenous ketone supplement ketone salt (KS) and ketone ester (KE) increased blood ketone level and delayed the onset of isoflurane-induced anesthesia in different rodent models, such as Wistar Albino Glaxo Rijswijk (WAG/Rij) rats. The modulatory effect of adenosinergic system may have a role in the ketone supplementation-evoked effects on isoflurane-generated anesthesia. Thus, we investigated whether adenosine receptor antagonists can modulate the effect of exogenous ketone supplements on the onset of akinesia induced by isoflurane.

Methods

To investigate the effect of exogenous ketone supplements on anesthetic induction we used ketone supplement KE, KS, KEKS (1:1 mix of KE and KS), KSMCT and KEMCT (1:1 mix of KS and KE with medium chain triglyceride/MCT oil, respectively) in WAG/Rij rats. Animals were fed with standard diet (SD), which was supplemented by oral gavage of different ketone supplements (2.5 g/kg/day) for 1 week. After 7 days, isoflurane (3%) was administered for 5 min and the time until onset of isoflurane-induced anesthesia (time until immobility; light phase of anesthesia: loss of consciousness without movement) was measured. Changes in levels of blood β-hydroxybutyrate (βHB), blood glucose and body weight of animals were also recorded. To investigate the putative effects of adenosine receptors on ketone supplements-evoked influence on isoflurane-induced anesthesia we used a specific adenosine A1 receptor antagonist DPCPX (intraperitoneally/i.p. 0.2 mg/kg) and a selective adenosine A2A receptor antagonist SCH 58261 (i.p. 0.5 mg/kg) alone as well as in combination with KEKS.

Results

Significant increases were demonstrated in both blood βHB levels and the number of seconds required before isoflurane-induced anesthesia (immobility) after the final treatment by all exogenous ketone supplements. Moreover, this effect of exogenous ketone supplements positively correlated with blood βHB levels. It was also demonstrated that DPCPX completely abolished the effect of KEKS on isoflurane-induced anesthesia (time until immobility), but not SCH 58261.

Conclusions

These findings strengthen our previous suggestion that exogenous ketone supplements may modulate the isoflurane-induced onset of anesthesia (immobility), likely through A1Rs.

Targeting Mitochondrial Dysfunction for Bipolar Disorder

People with bipolar disorder (BD) all too often have suboptimal long-term outcomes with existing treatment options. They experience relapsing episodes of depression and mania and also have interepisodic mood and anxiety symptoms. We need to have a better understanding of the pathophysiology of BD if we are to make progress in improving these outcomes. This chapter will focus on the critical role of mitochondria in human functioning, oxidative stress, and the biological mechanisms of mitochondria in BD. Additionally, this chapter will present the evidence that, at least for some people, BD is a product of mitochondrial dysregulation. We review the modulators of mitochondria, the connection between current BD medication treatments and mitochondria, and additional medications that have theoretical potential to treat BD.

Ketosis and bipolar disorder: controlled analytic study of online reports

BACKGROUND

Members of online bipolar disorder forums often report experiences of mood-stabilisation on the ketogenic diet, which has traditionally been used in the treatment of epilepsy. We examined the nature and extent of such reports.

AIMS

To investigate associations between a ketogenic diet and mood stabilisation among individuals with bipolar disorder.

METHOD

We undertook an observational analytic study of free-text comments in online forums about mood effects of dietary interventions (ketogenic, omega-3 enriched or vegetarian) classified by a priori categories of change in mood stabilisation in 274 people with bipolar disorder.

RESULTS

There were 141 (85.5%) free-text comments on ketogenic diets that reported a positive impact on mood stabilisation. Reports of significant mood stabilisation or remission of symptoms over a period were substantially higher for a ketogenic diet than for other diets (93/165, 56.4%, 95% CI 48.4-64.1) v. 14/94, 14.9%, 95% CI 8.4-23.7), odds ratio 7.4, 95% CI 3.8-14.1, P < 0.0001), many with detailed reports of the improvements experienced and several lasting for extended periods (months to years). Other reported associations included fewer episodes of depression (in 41.2%, 95% CI 30.6-52.4 of individuals); improved clarity of thought and speech (28.2%, 95% CI 19.0-39.0); increased energy (25.9, 95% CI 17.0-36.5); and weight loss (25.9%, 95% CI 17.0-36.5).

CONCLUSIONS

Despite the inherent limitations of the observational data based on self-reports posted online, the association strength and reports of sustained benefit support a hypothesis of a ketogenic diet being associated with beneficial effects on mood stabilisation. Caution should be exercised in interpreting this data until a controlled trial can be carried out to examine this hypothesis. These preliminary observations are generally consistent with a mitochondrial dysfunction component to bipolar disorder aetiology with ketones bypassing a block between glycolysis and the tricarboxylic acid cycle.

DECLARATION OF INTEREST

None.