The Implication of Physiological Ketosis on The Cognitive Brain: A Narrative Review

Dietary Influence on Drug Efficacy: A Comprehensive Review of Ketogenic Diet-Pharmacotherapy Interactions

It is widely acknowledged that the ketogenic diet (KD) has positive physiological effects as well as therapeutic benefits, particularly in the treatment of chronic diseases. Maintaining nutritional ketosis is of utmost importance in the KD, as it provides numerous health advantages such as an enhanced lipid profile, heightened insulin sensitivity, decreased blood glucose levels, and the modulation of diverse neurotransmitters. Nevertheless, the integration of the KD with pharmacotherapeutic regimens necessitates careful consideration. Due to changes in their absorption, distribution, metabolism, or elimination, the KD can impact the pharmacokinetics of various medications, including anti-diabetic, anti-epileptic, and cardiovascular drugs. Furthermore, the KD, which is characterised by the intake of meals rich in fats, has the potential to impact the pharmacokinetics of specific medications with high lipophilicity, hence enhancing their absorption and bioavailability. However, the pharmacodynamic aspects of the KD, in conjunction with various pharmaceutical interventions, can provide either advantageous or detrimental synergistic outcomes. Therefore, it is important to consider the pharmacokinetic and pharmacodynamic interactions that may arise between the KD and various drugs. This assessment is essential not only for ensuring patients' compliance with treatment but also for optimising the overall therapeutic outcome, particularly by mitigating adverse reactions. This highlights the significance and necessity of tailoring pharmacological and dietetic therapies in order to enhance the effectiveness and safety of this comprehensive approach to managing chronic diseases.

Perspective: The Impact of Fasting and Caloric Restriction on Neurodegenerative Diseases in Humans

Neurodegenerative diseases (NDs) are characterized by the progressive functional and structural denaturation of neurons in the central and peripheral nervous systems. Despite the wide range of genetic predispositions, the increased emergence of these disorders has been associated with a variety of modifiable risk factors, including lifestyle factors. Diet has been shown to influence cognitive alterations in the elderly population with age-related brain pathologies, and specific dietary interventions might, therefore, confer preservatory protection to neural structures. Although Mediterranean and ketogenic diets have been studied, no clear guidelines have been implemented for the prevention or treatment of ND in clinical practice. Murine models have shown that intermittent fasting and caloric restriction (CR) can counteract disease processes in various age-related disorders, including NDs. The objective of this perspective is to provide a comprehensive, comparative overview of the available primary intervention studies on fasting and CR in humans with ND and to elucidate possible links between the mechanisms underlying the effects of fasting, CR, and the neuropathology of ND. We also included all currently available studies in older adults (with and without mild cognitive impairment) in which the primary endpoint was cognitive function to provide further insights into the feasibility and outcomes of such interventions. Overall, we conclude that nutritional intervention trials focusing on fasting and CR in humans with ND have been neglected, and more high-quality studies, including longitudinal clinical intervention trials, are urgently needed to elucidate the underlying immune-metabolic mechanisms in diet and ND.

A randomized feasibility trial of the modified Atkins diet in older adults with mild cognitive impairment due to Alzheimer's disease

Background

Alzheimer's disease (AD) is increasing in prevalence, but effective treatments for its cognitive impairment remain severely limited. This study investigates the impact of ketone body production through dietary manipulation on memory in persons with mild cognitive impairment due to early AD and explores potential mechanisms of action.

Methods

We conducted a 12-week, parallel-group, controlled feasibility trial of a ketogenic diet, the modified Atkins diet (MAD), compared to a control diet in patients with cognitive impairments attributed to AD. We administered neuropsychological assessments, including memory tests, and collected blood samples at baseline and after 12 weeks of intervention. We performed untargeted lipidomic and targeted metabolomic analyses on plasma samples to detect changes over time.

Results

A total of 839 individuals were screened to yield 38 randomized participants, with 20 assigned to receive MAD and 18 assigned to receive a control diet. Due to attrition, only 13 in the MAD arm and nine in the control arm were assessed for the primary endpoint, with two participants meeting ketosis levels used to define MAD adherence criteria. The average change from baseline in the Memory Composite Score was 1.37 (95% CI: -0.87, 4.90) points higher in the MAD group compared to the control group. The effect size of the intervention on baseline MAD change was moderate (Cohen's D = 0.57, 95% CI: -0.67, 1.33). In the 15 participants (nine MAD, six control) assessed for lipidomic and metabolomic-lipidomics and metabolomics, 13 metabolites and 10 lipids showed significant changes from baseline to 12 weeks, including triacylglycerols (TAGs, 50:5, 52:5, and 52:6), sphingomyelins (SM, 44:3, 46:0, 46:3, and 48:1), acetoacetate, fatty acylcarnitines, glycerol-3-phosphate, and hydroxy fatty acids.

Conclusions

Attrition was greatest between baseline and week 6. All participants retained at week 6 completed the study. Despite low rates of adherence by criteria defined a priori, lipidomic and metabolomic analyses indicate significant changes from baseline in circulating lipids and metabolites between MAD and control participants at 12-week postrandomization, and MAD participants showed greater, albeit nonsignificant, improvement in memory.

Modulation of beta-hydroxybutyrate in traumatic brain injury

PURPOSE OF REVIEW

Traumatic brain injury (TBI) is a significant public health concern with substantial morbidity and mortality rates in the United States. Current management strategies primarily focus on symptomatic approaches and prevention of secondary complications. However, recent research highlights the potential role of ketone bodies, particularly beta-hydroxybutyrate (BHB), in modulating cellular processes involved in TBI. This article reviews the metabolism of BHB, its effect in TBI, and its potential therapeutic impact in TBI.

RECENT FINDINGS

BHB can be produced endogenously through fasting or administered exogenously through ketogenic diets, and oral or intravenous supplements. Studies suggest that BHB may offer several benefits in TBI, including reducing oxidative stress, inflammation, controlling excitotoxicity, promoting mitochondrial respiration, and supporting brain regeneration. Various strategies to modulate BHB levels are discussed, with exogenous ketone preparations emerging as a rapid and effective option.

SUMMARY

BHB offers potential therapeutic advantages in the comprehensive approach to improve outcomes for TBI patients. However, careful consideration of safety and efficacy is essential when incorporating it into TBI treatment protocols. The timing, dosage, and long-term effects of ketone use in TBI patients require further investigation to fully understand its potential benefits and limitations.

Molecular Study of the Protective Effect of a Low-Carbohydrate, High-Fat Diet against Brain Insulin Resistance in an Animal Model of Metabolic Syndrome

Brain insulin resistance is linked to metabolic syndrome (MetS). A low-carbohydrate, high-fat (LCHF) diet has been proposed to have a protective effect. Therefore, this study aimed to investigate the brain insulin resistance markers in a rat animal model of MetS and the protective effects of the LCHF diet. Four groups of male rats (10/group) were created. Group I (Control) was fed a regular diet. Groups II-IV were injected with dexamethasone (DEX) to induce MetS. Group II received DEX with a regular diet. Group III (DEX + LCHF) rates were fed a low-carbohydrate, high-fat diet, while Group IV (DEX + HCLF) rats were fed a high-carbohydrate, low-fat (HCLF) diet. At the end of the four-week experiment, HOMA-IR was calculated. Moreover, cerebral gene expression analysis of S-100B, BDNF, TNF-α, IGF-1, IGF-1 R, IGFBP-2, IGFBP-5, Bax, Bcl-2, and caspase-3 was carried out. In the DEX group, rats showed a significant increase in the HOMA-IR and a decrease in the gene expression of IGF-1, IGF-1 R, IGFBP-2, IGFBP-5, BDNF, and Bcl2, with a concomitant rise in S100B, TNF-α, Bax, and caspase-3. The LCHF diet group showed a significantly opposite effect on all parameters. In conclusion, MetS is associated with dysregulated cerebral gene expression of BDNF, S100B, and TNF-α and disturbed IGF-1 signaling, with increased apoptosis and neuroinflammation. Moreover, the LCHF diet showed a protective effect, as evidenced by preservation of the investigated biochemical and molecular parameters.

Enzymatic Synthesis of Ascorbic Acid-Ketone Body Hybrids

Molecular hybrids obtained by connecting two or more bioactive molecules through a metabolizable linker are used as multi-target drugs for the therapy of multifactorial diseases. Ascorbic acid, as well as the ketone bodies acetoacetate and (R)-3-hydroxybutyrate, are bioactive molecules that have common fields of application in the treatment and prevention of neurodegenerative diseases and cardiac injuries as well. In spite of this, the preparation of ascorbic acid ketone body hybrids is uncovered by the literature. Herein, we report the lipase-catalyzed condensation of methyl acetoacetate with ascorbic acid, which affords the 6-O-acetoacetyl ascorbic acid in quantitative yield. The same approach, employing the methyl (R)-3-hydroxybutyrate in place of the methyl acetoacetate, allows the preparation of the 6-O-(R)-3-hydroxybutyryl ascorbic acid in 57% yield. A better result (90% overall yield) is achieved through the lipase-catalyzed coupling of ascorbic acid with methyl (R)-3-O-methoxymethyl-3-hydroxybutyrate followed by the cleavage of the MOM protecting group. The two novel products are fully characterized and additional information on the antioxidant activity of the new products is also given.

Dietary ketosis improves circadian dysfunction as well as motor symptoms in the BACHD mouse model of Huntington's disease

Disturbances in sleep/wake cycles are common among patients with neurodegenerative diseases including Huntington's disease (HD) and represent an appealing target for chrono-nutrition-based interventions. In the present work, we sought to determine whether a low-carbohydrate, high-fat diet would ameliorate the symptoms and delay disease progression in the BACHD mouse model of HD. Adult WT and BACHD male mice were fed a normal or a ketogenic diet (KD) for 3 months. The KD evoked a robust rhythm in serum levels of β-hydroxybutyrate and dramatic changes in the microbiome of male WT and BACHD mice. NanoString analysis revealed transcriptional changes driven by the KD in the striatum of both WT and BACHD mice. Disturbances in sleep/wake cycles have been reported in mouse models of HD and are common among HD patients. Having established that the KD had effects on both the WT and mutant mice, we examined its impact on sleep/wake cycles. KD increased daytime sleep and improved the timing of sleep onset, while other sleep parameters were not altered. In addition, KD improved activity rhythms, including rhythmic power, and reduced inappropriate daytime activity and onset variability. Importantly, KD improved motor performance on the rotarod and challenging beam tests. It is worth emphasizing that HD is a genetically caused disease with no known cure. Life-style changes that not only improve the quality of life but also delay disease progression for HD patients are greatly needed. Our study demonstrates the therapeutic potential of diet-based treatment strategies in a pre-clinical model of HD.

Metabolic and Cellular Compartments of Acetyl-CoA in the Healthy and Diseased Brain

The human brain is characterised by the most diverse morphological, metabolic and functional structure among all body tissues. This is due to the existence of diverse neurons secreting various neurotransmitters and mutually modulating their own activity through thousands of pre- and postsynaptic interconnections in each neuron. Astroglial, microglial and oligodendroglial cells and neurons reciprocally regulate the metabolism of key energy substrates, thereby exerting several neuroprotective, neurotoxic and regulatory effects on neuronal viability and neurotransmitter functions. Maintenance of the pool of mitochondrial acetyl-CoA derived from glycolytic glucose metabolism is a key factor for neuronal survival. Thus, acetyl-CoA is regarded as a direct energy precursor through the TCA cycle and respiratory chain, thereby affecting brain cell viability. It is also used for hundreds of acetylation reactions, including N-acetyl aspartate synthesis in neuronal mitochondria, acetylcholine synthesis in cholinergic neurons, as well as divergent acetylations of several proteins, peptides, histones and low-molecular-weight species in all cellular compartments. Therefore, acetyl-CoA should be considered as the central point of metabolism maintaining equilibrium between anabolic and catabolic pathways in the brain. This review presents data supporting this thesis.

The Evolution of Ketosis: Potential Impact on Clinical Conditions

Ketone bodies are small compounds derived from fatty acids that behave as an alternative mitochondrial energy source when insulin levels are low, such as during fasting or strenuous exercise. In addition to the metabolic function of ketone bodies, they also have several signaling functions separate from energy production. In this perspective, we review the main current data referring to ketone bodies in correlation with nutrition and metabolic pathways as well as to the signaling functions and the potential impact on clinical conditions. Data were selected following eligibility criteria accordingly to the reviewed topic. We used a set of electronic databases (Medline/PubMed, Scopus, Web of Sciences (WOS), Cochrane Library) for a systematic search until July 2022 using MeSH keywords/terms (i.e., ketone bodies, BHB, acetoacetate, inflammation, antioxidant, etc.). The literature data reported in this review need confirmation with consistent clinical trials that might validate the results obtained in in vitro and in vivo in animal models. However, the data on exogenous ketone consumption and the effect on the ketone bodies’ brain uptake and metabolism might spur the research to define the acute and chronic effects of ketone bodies in humans and pursue the possible implication in the prevention and treatment of human diseases. Therefore, additional studies are required to examine the potential systemic and metabolic consequences of ketone bodies.

Acetoacetate Improves Memory in Alzheimer's Mice via Promoting Brain-Derived Neurotrophic Factor and Inhibiting Inflammation

The ketone bodies, especially the β-hydroxybutyrate, had been shown to modulate the function of the central nervous system and prevent the pathological progression of Alzheimer's disease (AD). However, little is known about the role of acetoacetate in the AD brain. Thus, we intraventricularly injected acetoacetate into familial AD mice (APPSWE) for 14 days and monitored their memory and biochemical changes. During the behavior test, acetoacetate at 100 mg/kg led to significant improvement in both Y-maze and novel object recognition tests (NORTs) (both P < .05), indicating ameliorating spatial and recognition memory, respectively. Biomedical tests revealed two mechanisms were involved. Firstly, acetoacetate inhibited the GPR43-pERK pathway, which led to apparent inhibition in tumor necrosis factor-α and Interleukin-6 expression in the hippocampus in a concentration-dependent manner. Secondarily, acetoacetate stimulated the expression of hippocampal brain-derived neurotrophic factor (BDNF). We concluded that acetoacetate could ameliorate AD symptoms and exhibited promising features as a therapeutic for AD.

The emerging role of the microbiome in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia and can be influenced by genetic and environmental factors. Recent studies suggest that the intestinal microbiota is altered in AD patients when compared to healthy individuals and may play a role in disease onset and progression. Aging is the greatest risk factor for AD, and age-related changes in the microbiota can affect processes that contribute to cognitive decline. The microbiota may affect AD by modulating peripheral and central immunity or by secreting factors that influence neurogenesis or neuronal cell death. Finally, probiotic and dietary interventions that target the microbiome may have therapeutic potential to prevent or treat AD.